DEFF Research Database (Denmark)
Yu, Yifan; Konstantinou, Georgios; Townsend, Christopher D.
2017-01-01
The cascaded H-bridge (CHB) converter is becoming a promising candidate for use in next generation large-scale photovoltaic (PV) power plants. However, solar power generation in the three converter phase-legs can be significantly unbalanced, especially in a large geographically-dispersed plant...
DEFF Research Database (Denmark)
Ciobotaru, Mihai; Iov, Florin; Zanchetta, P.
2008-01-01
To pave the way to a sustainable energy future based on a larger share of Distributed Generation (DG), there is a clear need to prepare the European electricity system for the large-scale integration of both renewable and other distributed energy sources. Advanced power electronic converters for DG...... reference frame controller, based on proportional-resonant (PR) technique, for a multi-level H-bridge power converter for Universal and Flexible Power Management in Future Electricity Network. The proposed method is tested in terms of harmonic content in the Point of Common Coupling (PCC), voltage...
Battery pack state of charge balancing algorithm for cascaded H-Bridge multilevel converters
DEFF Research Database (Denmark)
Máthé, Lászlo; Burlacu, Paul Dan; Schaltz, Erik
2016-01-01
is not in linear relation with the State Of Charge (SOC) of the entire battery; thus, the balancing becomes more cumbersome. A method to balance the SOC of the battery packs in a system using cascaded H-Bridge is proposed in this paper. The method uses nearest level control followed by sorting and selection based...
Cascaded H-bridge multilevel inverter for renewable energy generation
Pandey, Ravikant; Nath Tripathi, Ravi; Hanamoto, Tsuyoshi
2016-04-01
In this paper cascaded H-bridge multilevel inverter (CHBMLI) has been investigated for the application of renewable energy generation. Energy sources like solar, wind, hydro, biomass or combination of these can be manipulated to obtain alternative sources for renewable energy generation. These renewable energy sources have different electrical characteristics like DC or AC level so it is challenging to use generated power by connecting to grid or load directly. The renewable energy source require specific power electronics converter as an interface for conditioning generated power .The multilevel inverter can be utilized for renewable energy sources in two different modes, the power generation mode (stand-alone mode), and compensator mode (statcom). The performance of the multilevel inverter has been compared with two level inverter. In power generation mode CHBMLI supplies the active and reactive power required by the different loads. For operation in compensator mode the indirect current control based on synchronous reference frame theory (SRFT) ensures the grid operating in unity power factor and compensate harmonics and reactive power.
DEFF Research Database (Denmark)
Ciobotaru, Mihai; Iov, Florin; Zanchetta, Pericle
2008-01-01
More "green" power provided by Distributed Generation will enter into the European electricity network in the near future. In order to control the power flow and to ensure proper and secure operation of this future grid, with an increased level of the renewable power, new power electronic convert...
DEFF Research Database (Denmark)
Iov, Florin; Bifaretti, Steffano; Zanchetta, Pericle
2008-01-01
The paper proposes a novel power conversion system for Universal and Flexible Power Management (UNIFLEX-PM) in Future Electricity Network. The structure is based on three AC-DC converters each one connected to a different grid, (representing the main grid and/or various distributed generation...... systems) on the AC side, and linked together at DC side by suitable DC isolation modules. Each port of the UNIFLEX-PM system employs a conversion structure based on a three-phase 7-level AC-DC cascaded converter. Effective and accurate power flow control is demonstrated through simulation in Matlab...... and Simulink environment on a simplified model based on a two-port structure and using a Stationery Reference Frame based control solution. Control of different Power flow profiles has been successfully tested in numerous network conditions such as voltage unbalance, frequency excursions and harmonic...
DEFF Research Database (Denmark)
Pouresmaeil, Edris; Montesinos-Miracle, Daniel; Gomis-Bellmunt, Oriol
2011-01-01
This paper presents a control strategy of multilevel converters for integration of renewable energy resources into power grid. The proposed technique provides compensation for active, reactive, and harmonic current components of grid-connected loads. A three-level H-bridge converter is proposed a...
A NOVEL CASCADED H- BRIDGE MULTILEVEL INVERTER BASED ON OPTIMAL PWM TECHNIQUE
MAHESWARI, A.; GNANAMBAL, I
2013-01-01
In this paper, a novel cascaded H- bridge multilevel inverter has been proposed using less number of switches. A standard cascaded multilevel inverter requires 4h number of switches for (2h + 1) levels whereas h is the number of dc sources. This proposed scheme allows less number of switches for the same level. A novel cascaded H- bridge multilevel inverter fed induction motor shows better performance due to fundamental frequency switching scheme using optimal PWM Technique (OPWM). High qual...
DEFF Research Database (Denmark)
Gong, Zheng; Dai, Peng; Wu, Xiaojie
2017-01-01
In recent years, voltage source multilevel converters are very popular in medium/high-voltage industrial applications, among which the NPC/H-Bridge converter is a popular solution to the medium/high-voltage drive systems. The conventional finite control set model predictive control (FCS-MPC) stra......In recent years, voltage source multilevel converters are very popular in medium/high-voltage industrial applications, among which the NPC/H-Bridge converter is a popular solution to the medium/high-voltage drive systems. The conventional finite control set model predictive control (FCS......-MPC) strategy is not practical for multilevel converters due to their substantial calculation requirements, especially under high number of voltage levels. To solve this problem, a hierarchical model predictive voltage control (HMPVC) strategy with referring to the implementation of g-h coordinate space vector...... calculation is significantly reduced and the advantages of the conventional FCS-MPC strategy are reserved. In addition, a HMPVC-based field oriented control scheme is applied to a drive system with the NPC/H-Bridge converter. Both steady-state and transient performances are evaluated by simulations...
Grid Connection of Wave Power Farm Using an N-Level Cascaded H-Bridge Multilevel Inverter
Directory of Open Access Journals (Sweden)
Rickard Ekström
2013-01-01
Full Text Available An N-level cascaded H-bridge multilevel inverter is proposed for grid connection of large wave power farms. The point-absorber wave energy converters are individually rectified and used as isolated DC-sources. The variable power characteristics of the wave energy converters are discussed, and a method of mitigating this issue is demonstrated. The complete power control system is given in detail and has been experimentally verified for a single-phase setup of the 9-level inverter. Theoretical expressions of the power sharing between multilevel cells are derived and show good correspondence with the experimental results.
Comprehensive Analysis of LCL Filter Interfaced Cascaded H-Bridge Multilevel Inverter-Based DSTATCOM
Directory of Open Access Journals (Sweden)
Ravikant Pandey
2017-03-01
Full Text Available Three-phase two-level voltage source converters are used for distribution static compensator (DSTATCOM applications and can be replaced by a multilevel inverter. In this paper, an LCL filter interfaced cascaded H-bridge multilevel inverter-based (CHBMLI DSTATCOM is simulated and its performance is analyzed considering the system parameters. The analysis considers factors including the switching frequency, modulation index, and filter parameters of a DSTATCOM system. The LCL filter design and analysis for the low switching frequency operation of CHBMLI is proposed in this paper. Phase shift pulse-width modulation is used for the generation of switching signals. The reference current is generated using synchronous reference frame theory (SRFT for reactive power and harmonic compensations. The simulation model of the CHBMLI-based DSTATCOM system is developed in MATLAB Simulink. The results are demonstrated for a linear/non-linear load under unbalanced conditions, considering the voltage sag and swell in the system due to a disturbance in the load.
Cascaded H-Bridge with Bidirectional Boost Converters for Energy Storage
DEFF Research Database (Denmark)
Trintis, Ionut; Munk-Nielsen, Stig; Teodorescu, Remus
2011-01-01
This paper presents the design and control of a cascaded H-bridge converter for energy storage with bidirectional boost converter as charge/discharge unit. The disadvantage of the second harmonic on the main energy storage unit as well as its voltage variation with the state of charge is solved...
Multilevel converters for 10 MW Wind Turbines
DEFF Research Database (Denmark)
Ma, Ke; Blaabjerg, Frede
2011-01-01
Several promising multi-level converter configurations for 10 MW Wind Turbines both with direct drive and one-stage gear box drive using Permanent Magnet Synchronous Generator (PMSG) are proposed, designed and compared. Reliability is a crucial indicator for large scale wind power converters......, therefore the evaluations are mainly focused on the power device thermal performances, which are closely related to the life time and cost of the converter. Simulation results of different converter candidates regarding the loss and junction temperature are presented and analyzed. It is concluded...... that the three-level and five-level H-bridge converter topologies both have potential to achieve improved thermal performances compared to the three-level Neutral-Point-Clamped converter topology in the wind power application....
Nguyen-Quang, N.; Stone, D. A.; Bingham, Chris; Foster, M. P.
2007-01-01
This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order...
Directory of Open Access Journals (Sweden)
MUDASIR AHMED MEMON
2017-01-01
Full Text Available In this paper, PSO (Particle Swarm Optimization based technique is proposed to derive optimized switching angles that minimizes the THD (Total Harmonic Distortion and reduces the effect of selected low order non-triple harmonics from the output of the multilevel inverter. Conventional harmonic elimination techniques have plenty of limitations, and other heuristic techniques also not provide the satisfactory results. In this paper, single phase symmetrical cascaded H-Bridge 11-Level multilevel inverter is considered, and proposed algorithm is utilized to obtain the optimized switching angles that reduced the effect of 5th, 7th, 11th and 13th non-triplen harmonics from the output voltage of the multilevel inverter. A simulation result indicates that this technique outperforms other methods in terms of minimizing THD and provides high-quality output voltage waveform.
Multilevel converters for industrial applications
Gonzalez, Sergio Alberto
2013-01-01
Modern semiconductor devices have reached high current and voltage levels, and their power-handling limits can be extended if they are used in multilevel converter configurations. To create high-performance and reliable control designs, however, engineers need in-depth understanding of the characteristics and operation of these topologies. Multilevel Converters for Industrial Applications presents a thorough and comprehensive analysis of multilevel converters with a common DC voltage source. The book offers a novel perspective to help readers understand the principles of the operation of volta
Energy Technology Data Exchange (ETDEWEB)
Xiao, B; Shen, K; Mei, J; Filho, F; Tolbert, L M
2012-09-15
A single-phase cascaded H-bridge multilevel inverter for a grid-connected photovoltaic (PV) system with nonactive power compensation is presented in this paper. To maximize the solar energy extraction of each PV string, an individual maximum power point tracking (MPPT) control scheme is applied, which allows the independent control of each dc-link voltage. A generalized nonactive power theory is applied to generate the nonactive current reference. Within the inverters™ capability, the local consumption of nonactive power is provided to realize power factor correction. A single-phase modular cascaded multilevel inverter prototype has been built. Each H-bridge is connected to a 195 W solar panel. Simulation and experimental results are presented to validate the proposed ideas.
A single leg switched PWM method for three-phase H-Bridge Voltage Source Converters
DEFF Research Database (Denmark)
Senturk, Osman Selcuk; Helle, Lars; Munk-Nielsen, Stig
2009-01-01
This paper proposes a single leg switched or a hybrid PWM (HPWM) method for three-phase three-level H-Bridge Voltage Source Converters (3L-HB-VSCs). By means of the proposed modulation, a 3L-HB-VSC can generate the same output as a three-level neutral point clamped (3L-NPC) VSC with phase...... disposition (PD) PWM provided that the outputs of 3L-HBVSC are isolated by transformers or connected to open winding machines. Thus, the proposed method is called PD-HPWM. Moreover, it is emphasized that 3L-HB-VSC with HPWM utilizes its switches similar to 3L-NPC-VSC. Compared to 3L-NPC-VSCs, 3L......-HB-VSCs (without neutral point clamping diodes) have simpler, more modular, and more reliable 2L circuit structure. Therefore, this method encourages the use of 3L-HB-VSCs in the applications utilizing transformers such as grid-side converters of multi-MW wind turbines. The proposed PWM method's performance...
DEFF Research Database (Denmark)
Abarzadeh, Mostafa; Madadi Kojabadi, Hossein; Deng, Fujin
2016-01-01
Static power converters have various applications, such as static ground power units (GPUs) for airplanes. This study proposes a new configuration of a static GPU based on a novel nine-level flying capacitor h-bridge active-neutral-point-clamped (FCHB_ANPC) converter. The main advantages of the p......Static power converters have various applications, such as static ground power units (GPUs) for airplanes. This study proposes a new configuration of a static GPU based on a novel nine-level flying capacitor h-bridge active-neutral-point-clamped (FCHB_ANPC) converter. The main advantages...... demonstrate the validity and feasibility of the proposed converter and the modulation method under various operating conditions....
Multilevel converters for power system applications
Energy Technology Data Exchange (ETDEWEB)
Lai, J.S.; Stovall, J.P. [Oak Ridge National Lab., TN (United States); Peng, F.Z. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States)
1995-09-01
Multilevel converters are emerging as a new breed of power converter options for power system applications. These converters are most suitable for high voltage high power applications because they connect devices in series without the need for component matching. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. To avoid voltage unbalance between different levels, several techniques have been proposed for different applications. Excluding magnetic-coupled converters, this paper introduces three multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded inverters with separate dc sources. The operation principle, features, constraints, and potential applications of these converters will be discussed.
Multilevel converters -- A new breed of power converters
Energy Technology Data Exchange (ETDEWEB)
Lai, J.S. [Oak Ridge National Lab., TN (United States). Engineering Technology Div.; Peng, F.Z. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States)
1995-09-01
Multilevel voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of dc capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate dc sources. The operating principle, features, constraints, and potential applications of these converters will be discussed.
Directory of Open Access Journals (Sweden)
Janardhan Kavali
2016-12-01
Full Text Available Multilevel inverters are becoming more popular in the power conversion systems for high power and power quality demanding applications. The MATLAB based simulation on SIMULINK platform is presented for the Single Phase five level cascaded H-bridge Multilevel Inverter (CHB-MLI topology with less number of switches and with different control schemes and Sinusoidal Pulse Width Modulation (SPWM schemes. A detailed comparison of various control schemes is presented in this paper with reference to Total Harmonic Distortion (THD in the output voltage and utilization factor of the power devices. It is observed that among all the control schemes, the THD is minimum in the Sinusoidal Pulse Width Modulation-Phase Disposition (SPWM-PD scheme with variable carrier wave magnitude.
Passive Reactor Compensated Cascaded H-Bridge Multilevel LC-StatCom
DEFF Research Database (Denmark)
Farivar, Glen; Townsend, Christopher David; Hredzak, Branislav
2017-01-01
The cascaded H-bridge (CHB) low-capacitance StatCom (LC-StatCom) has a limited operating area in the inductive region compared to a conventional StatCom's V–I characteristic. This limitation for operation in the inductive region is considered to be the biggest disadvantage of CHB LC......-StatCom. In this paper, the effect of adding parallel and series reactors on the LC-StatCom system's V–I characteristic is analyzed. Then, a new configuration, which fully compensates for the lost operating area of the LC-StatCom, is introduced. A scaled down single-phase seven-level laboratory prototype is used...
multilevel buck converter for automotive electrical load
African Journals Online (AJOL)
user
MULTILEVEL BUCK CONVERTER FOR AUTOMOTIVE ELECTRICAL LOAD. E. T. Yabefa1,* and D. Ebregbe2. 1ELECTRICAL DEPARTMENT, BAYELSA STATE COLLEGE OF ARTS & SCIENCE (BYCAS) YENAGOA, BAYELSA STATE NIGERIA. 2ELECTRICAL ENGINEERING DEPARTMENT, NIGER DELTA UNIVERSITY, ...
Multilevel-clamped multilevel converters (MLC^{2})
DEFF Research Database (Denmark)
Rodriguez, Pedro; Bellar, Maria Dias; Muñoz-Aguliar, Raúl Santiago
2012-01-01
This letter introduces a new series of multilevel (ML) converters based on the ML clamping concept. By applying this technique, a ML clamping unit (MCU) conveys additional levels for synthesizing the output waveforms of a diode-clampedML dc– ac power converter. The basic building block of the ML ...
Carrier Rotation Strategies for Equal Power Distributions in Cascaded H-Bridge Multilevel Inverters
Venkata Rao, Jagilinki; Mahesh, Aeidapu
2017-10-01
Multicarrier pulse width modulation (MC-PWM) techniques such as Level-shifted PWM (LS-PWM) and Phase-shifted PWM (PS-PWM) are the popular methods to control the output voltage of Multilevel Inverters (MLIs). The advantage of LS-PWM techniques over PS-PWMs is that they produce better harmonic profile, but the un-equal power distribution problem of LS-PWMs imposes limitation to their usage in high power and medium voltage applications. For achieving the equal conduction periods and to evenly distribute the power among different cells, carrier rotation should be employed in LS-PWM. This paper proposes two rotation schemes introduced to LS-PWM for producing the collective benefit of equal power distribution from PS-PWM and better harmonic profile from LS-PWM. MATALB/Simulink has been used to create simulation models and the experimental validations are performed by a hardware setup using dSPACE-DS1104 R&D Controller board. Furthermore, experimental results of device conduction periods, conduction losses of individual cells, total harmonic distortions (THDs) and fundamental output voltages have been measured. The effectiveness of proposed methods are verified by comparing the obtained results with traditional MC-PWM techniques.
Synchronous Control of Modular Multilevel Converters
DEFF Research Database (Denmark)
Oleschuk, Valentin; Blaabjerg, Frede; Bose, Bimal K.
2002-01-01
for each module and the composed voltage at the output of the converter. Multilevel output voltage of the converter has quarter-wave symmetry during the whole range including the zone of overmodulation. Both continuous and discontinuous versions of synchronous PWM, based on vector approach...
Multilevel push pull power converter
DEFF Research Database (Denmark)
2007-01-01
A power converter for converting an input voltage (Vin) into an output voltage (Vout), comprising a first supply potential and a second supply potential established by the input voltage, and at least one primary winding having two terminals, a center tap arranged between the two terminals...... and connected to the first supply potential, and at least one secondary winding magnetically coupled to the primary winding for providing at least one output voltage (Vout); and a first controllable switch connected between the second supply potential and one terminal of the primary winding and a second...... controllable switch connected between the second supply potential and the other terminal of the primary winding and a third controllable switch connected between the second supply potential and the one terminal of the primary winding and a fourth controllable switch connected between the second supply...
Implementation of Cascaded H-Bridge Multilevel Inverter using MATLAB-DSP (ezDSP28335) Interfacing
W. Razia Sultana; Sarat Kumar Sahoo; Hari Ohm Singh; Ankit Dubey
2014-01-01
This study demonstrates, the generation of triggering signals using SPWM technique for a seven level H-Bridge cascaded inverter with the help of MATLAB-DSP (ezDSP 28335) interfacing without using EPWM block and presents the final output of the inverter. The focus is mainly on hardware implementation of Cascaded H-Bridge MLI using MATLAB-DSP interfacing. Generation of triggering signals using MATLAB-DSP interfacing has been explained briefly. Use of GPIO block in SIMULINK model makes the trigg...
Generalized modular multilevel converter and modulation
DEFF Research Database (Denmark)
Liu, Hui; Loh, Poh Chiang; Blaabjerg, Frede
2014-01-01
Modular multilevel converter (MMC) has gained popularity recently with its modulation, capacitor voltage balancing and circulating current issues widely discussed. Contributing to this effort, a study is presented here to show how the MMC topology can be derived from the viewpoint of two series...... converters regulating a power grid. The generalized topology derived and notated as GMMC can then be altered to create various types of MMC, including the traditional topology that is presently well-known. This effort has not been previously discussed, and may smoothen the understanding of MMC operation...
Multilevel converters for large electric drives
Energy Technology Data Exchange (ETDEWEB)
Tolbert, L.M.; Peng, F.Z.
1997-11-01
Traditional two-level high frequency pulse width modulation (PWM) inverters for motor drives have several problems associated with their high frequency switching which produces common-mode voltage and high voltage change (dV/dt) rates to the motor windings. Multilevel inverters solve these problems because their devices can switch at a much lower frequency. Two different multilevel topologies are identified for use as a converter for electric drives, a cascade inverter with separate dc sources and a back-to-back diode clamped converter. The cascade inverter is a natural fit for large automotive all electric drives because of the high VA ratings possible and because it uses several levels of dc voltage sources which would be available from batteries or fuel cells. The back to back diode damped converter is ideal where a source of ac voltage is available such as a hybrid electric vehicle. Simulation and experimental results show the superiority of these two converters over PWM based drives.
Capacitor Monitoring for Modular Multilevel Converters
DEFF Research Database (Denmark)
Deng, Fujin; Liu, Dong; Wang, Yanbo
2017-01-01
The modular multilevel converter (MMC) is attractive for medium- or high-power applications because of the advantages of its high modularity, availability, and high power quality. Reliability is one of the most important challenges for the MMC consisting of a large number of submodules (SMs......). The capacitor monitoring in each SM of the MMC is an important issue, which would affect the performance of the MMC. This paper proposed an effective monitoring method for the capacitance in each SM of the MMC. The proposed method reveals the relationship between the arm average capacitance and the capacitance...
State of charge balancing after hot swap for cascaded H-bridge multilevel converters
DEFF Research Database (Denmark)
Mathe, Laszlo; Schaltz, Erik; Teodorescu, Remus
2017-01-01
battery module has different SoC than the other modules. In case the unbalance is large it takes long time to equalize the modules SoC. In this paper a method to minimize the time used for the balancing is proposed. The proposed method is an extension of the nearest level control with sorting...... and selection based balancing, thus, it can be implemented as an addition to the nearest level control method....
Modular Multilevel Converters: Control and Applications
Directory of Open Access Journals (Sweden)
Fernando Martinez-Rodrigo
2017-10-01
Full Text Available This review article is mainly oriented to the control and applications of modular multilevel converters (MMC. The main topologies of the switching modules are presented, for normal operation and for the elimination of DC faults. Methods to keep the capacitor voltage balanced are included. The voltage and current modulators, that are the most internal loops of control, are detailed. Voltage control and current control schemes are included which regulate DC link voltage and reactive power. The cases of unbalanced and distorted networks are analyzed, and schemes are proposed so that MMC contribute to improve the quality of the grid in these situations. The main applications in high voltage direct current (HVDC transmission along with other medium voltage (MV and low voltage (LV applications are included. Finally, the application to offshore wind farms is specifically analyzed.
MULTILEVEL CONVERTERS FOR MICROWELDING BASED ON M-ARY SYSTEM
Directory of Open Access Journals (Sweden)
Zhuikov V.
2012-12-01
Full Text Available Multilevel converter constructing and functioning principles are given. Two different approaches to increase efficiency are described. Both decisions are compared with typical applications, so advantages and drawbacks are specified.
A New Modular Multilevel Converter with Integrated Energy Storage
DEFF Research Database (Denmark)
Trintis, Ionut; Munk-Nielsen, Stig; Teodorescu, Remus
2011-01-01
This paper introduces a new modular converter with integrated energy storage based on the cascaded half-bridge modular multilevel converter with common DC bus. It represents a complete modular solution with power electronics and energy storage building blocks, for medium and high voltage...... in the future HVDC meshed grids. Its functionality and flexibility makes the converter independent on the energy storage unit characteristic. The converter concept with its basic functions and control schemes are described and evaluated in this paper....
DEFF Research Database (Denmark)
Najjar, Mohammad; Moeini, Amirhossein; Dowlatabadi, Mohammadkazem Bakhshizadeh
2016-01-01
/4 power quality standard, which has the strictest grid codes at medium voltage level, will also be met in the whole range of the modulation indices. In order to achieve this goal, symmetrical CHB with variable DC Links are employed, while the converter has a low number of switching transitions. In other...
Design of state observer for modular multilevel converter
DEFF Research Database (Denmark)
Liu, Hui; Ma, Ke; Loh, Poh Chiang
2015-01-01
Modular multilevel converter (MMC) is an attractive choice for transformer-less and filter-less high power conversion system due to its ability to upscale to high voltage levels by the use of semiconductors. The capacitor voltages on each converter cell are important variables to be monitored...
Neural Network Control of Asymmetrical Multilevel Converters
Directory of Open Access Journals (Sweden)
Patrice WIRA
2009-12-01
Full Text Available This paper proposes a neural implementation of a harmonic eliminationstrategy (HES to control a Uniform Step Asymmetrical Multilevel Inverter(USAMI. The mapping between the modulation rate and the requiredswitching angles is learned and approximated with a Multi-Layer Perceptron(MLP neural network. After learning, appropriate switching angles can bedetermined with the neural network leading to a low-computational-costneural controller which is well suited for real-time applications. Thistechnique can be applied to multilevel inverters with any number of levels. Asan example, a nine-level inverter and an eleven-level inverter are consideredand the optimum switching angles are calculated on-line. Comparisons to thewell-known sinusoidal pulse-width modulation (SPWM have been carriedout in order to evaluate the performance of the proposed approach. Simulationresults demonstrate the technical advantages of the proposed neuralimplementation over the conventional method (SPWM in eliminatingharmonics while controlling a nine-level and eleven-level USAMI. Thisneural approach is applied for the supply of an asynchronous machine andresults show that it ensures a highest quality torque by efficiently cancelingthe harmonics generated by the inverters.
Efficient modelling of a modular multilevel converter
DEFF Research Database (Denmark)
El-Khatib, Walid Ziad; Holbøll, Joachim; Rasmussen, Tonny Wederberg
2013-01-01
Looking at the near future, we see that offshore wind penetration into the electrical grid will continue increasing rapidly. Until very recently, the trend has been to place the offshore wind farms close to shore within the reach for transmission using HVAC cables but for larger distances HVDC...... are calculated for the converter. Time-domain simulations on a MMC HVDC test system are performed in the PSCAD/EMTDC software environment based on the new model. The results demonstrate that the modeled MMC-HVDC system with or without converter transformer is able to operate under specific fault conditions....
Device Loading of Modular Multilevel Converter in Wind Power
DEFF Research Database (Denmark)
Popova, L.; Ma, Ke; Blaabjerg, Frede
2015-01-01
Modular multilevel converter (MMC) is a recently emerged multilevel topology for high-voltage high-power applications. However, in wind power applications, to the best of the authors knowledge, the performance of the MMC has not been extensively investigated. In this paper, the application...... of the MMC to wind energy systems is studied. The converters used to connect the wind turbine to the grid, which have rated active powers of 2MW and 10MW, are proposed and investigated. The electrical losses and thermal loading of the power devices in the proposed converter solutions are analyzed based...... on the gird conditions/requirements for wind power. The efficiency of the MMC under different P/Q boundaries defined by grid codes is investigated and compared with two-level (2L) and three-level (3L) neutral point clamped converters. It is concluded that it is possible to use the MMC in wind power...
multilevel buck converter for automotive electrical load
African Journals Online (AJOL)
... from internal combustion engine (ICE). The mass production of the hybrid electric (HE) and the electric vehicle (EV) is still awaited due to subsystem inefficiencies. Increasing the efficiencies of the power converters within subsystems of these HEVs and EVs will increase the performance of the new transportation vehicles.
Modular Multilevel Converter Control Strategy with Fault Tolerance
DEFF Research Database (Denmark)
Teodorescu, Remus; Eni, Emanuel-Petre; Mathe, Laszlo
2013-01-01
The Modular Multilevel Converter (MMC) technology has recently emerged in VSC-HVDC applications where it demonstrated higher efficiency and fault tolerance compared to the classical 2-level topology. Due to the ability of MMC to connect to HV levels, MMC can be also used in transformerless STATCOM...
Control of Modular Multilevel Converter with reduced internal data exchange
DEFF Research Database (Denmark)
Máthé, Lászlo; Burlacu, Paul Dan; Teodorescu, Remus
2017-01-01
Modular Multilevel Converters (MMC) are penetrating due to their superior performances. Due to the modular structure of the converter, communication platform has to be established between the Sub-Modules (SM) and a Central Controller Unit (CCU). When the communication platform is designed...... for such an application, several key parameters have to be considered such as high speed data transfer with low propagation delay, data integrity, and ability for accurate synchronization. In order to minimize the data flow in the MMC a hierarchical control is proposed where a CCU calculates an identical reference...
DEFF Research Database (Denmark)
Ma, Ke; Muñoz-Aguilar, R. S.; Rodriguez, Pedro
2014-01-01
In this paper, a five-level multilevel-clamped multilevel converter (5L- MLC2) topology is analyzed based on a typical grid integration application for renewable energy system. The loss and thermal distributions of the power devices in different switching legs are investigated and illustrated und...... the clamping switching legs and the main switching legs; it also shows a good and consistent efficiency characteristic under different output power ranges when complying with the grid codes.......In this paper, a five-level multilevel-clamped multilevel converter (5L- MLC2) topology is analyzed based on a typical grid integration application for renewable energy system. The loss and thermal distributions of the power devices in different switching legs are investigated and illustrated under...... rated condition. Afterward, a loss and efficiency evaluation method is proposed and applied which takes into account various injected reactive power ranges regulated by the grid codes. It is concluded that the loss and thermal distributions of the 5L- MLC2 multilevel topology are unequal between...
A control method for voltage balancing in modular multilevel converters
DEFF Research Database (Denmark)
Deng, Fujin; Chen, Zhe
2014-01-01
The modular multilevel converter (MMC) is attractive for medium- or high-power applications because of the advantages of its high modularity, availability, and high power quality. The voltage balancing of the floating capacitors in the cascaded submodules of the MMC is a key issue. In this paper......, a voltage-balancing control method is proposed. This method uses the phase-shifted carrier-based pulsewidth modulation scheme to control high-frequency current components for capacitor voltage balancing in the MMC without measuring the arm currents. Simulations and experimental studies of the MMC were...
Nonlinear Control Structure of Grid Connected Modular Multilevel Converters
DEFF Research Database (Denmark)
Hajizadeh, Amin; Norum, Lars; Ahadpour Shal, Alireza
2017-01-01
This paper implements nonlinear control structure based on Adaptive Fuzzy Sliding Mode (AFSM) Current Control and Unscented Kalman Filter (UKF) to estimate the capacitor voltages from the measurement of arm currents of Modular Multilevel Converter (MMC). UKF use nonlinear unscented transforms...... in the prediction step in order to preserve the stochastic characteristics of a nonlinear system. In order to design adaptive robust control strategy and nonlinear observer, mathematical model of MMC using rotating d-q theory has been used. Digital time-domain simulation studies are carried out in the Matlab...
Insulation Coordination for a Modular Multilevel Converter Prototype
Christe, Alexandre; Coulinge, Émilien Luc Henri; Dujic, Drazen
2016-01-01
This paper provides a detailed overview of the dielectric design and insulation coordination applied to a medium voltage modular multilevel converter prototype. The complete system has ratings of 0.5 MVA and is designed for connection to a 10 kVdc supply with a system voltage of 6.6 kVac. The choice of air as insulating and cooling medium requires careful considerations regarding the clearance and creepage distances with respect to the selected materials. The design considerations from the su...
Fault Detection and Localization Method for Modular Multilevel Converters
DEFF Research Database (Denmark)
Deng, Fujin; Chen, Zhe; Khan, Mohammad Rezwan
2015-01-01
The modular multilevel converter (MMC) is attractive for medium- or high-power applications because of the advantages of its high modularity, availability, and high power quality. However, reliability is one of the most important issues for MMCs those are made of large number of power electronic...... submodules (SMs). This paper proposed an effective fault detection and localization method for MMCs. An MMC fault can be detected by comparing the measured state variables and the estimated state variables with a Kalman Filter. The fault localization is based on the failure characteristics of the SM...... in the MMC. The proposed method can be implemented with less computational intensity and complexity, even in case that multiple SMs faults occur in a short time interval. The proposed method is not only implemented in simulations with professional tool PSCAD/EMTDC, but also verified with a down-scale MMC...
A Comparison of Modulation Techniques for Modular Multilevel Converters
Directory of Open Access Journals (Sweden)
Miguel Moranchel
2016-12-01
Full Text Available This work presents a comparison of three different modulation techniques applied to modular multilevel converters (MMCs. The three modulation strategies studied in this paper are the phase-shifted sinusoidal pulse width modulation (PS-SPWM, the space-vector modulation (SVM and the nearest level modulation (NLM. This paper focuses on analysing the particularities and implementation of each modulation technique. The modulation technique largely defines the generated harmonic content, making this is a key point that must be studied in depth. The paper briefly describes the three modulation techniques and analyses the harmonics generated by each one of the methods. In addition, the paper presents and compares the digital implementation of the three modulation methods in a Field Programmable Gate Array (FPGA. The proposed approaches are validated using a real processing platform and experimentally evaluated in a real high-power six-level MMC.
A nine-level hybrid symmetric cascaded multilevel converter for ...
Indian Academy of Sciences (India)
Bridge (TCHB) power cell and one three-level H-bridge power cell with equal dc link voltages, and they are connected in cascade. Due to cascade connection and equal dc link voltage, the power shared by each power cell is nearly equal.
Comparative Study of Two Multilevel Converters for Envelope Amplifier
Directory of Open Access Journals (Sweden)
Miroslav Vasić
2010-06-01
Full Text Available Modern transmitters usually have to amplify and transmit signals with simultaneous envelope and phase modulation. Due to this property of the transmitted signal, linear power amplifiers (class A, B or AB are usually used as a solution for the power amplifier stage. These amplifiers have high linearity, but suffer from low efficiency when the transmitted signal has low peak-to-average power ratio. The Kahn envelope elimination and restoration (EER technique is used to enhance efficiency of RF transmitters, by combining highly efficient,nonlinear RF amplifier (class D or E with a highly efficient envelope amplifier in order to obtain linear and highly efficientRF amplifier. This paper compares two solutions for the envelope amplifier based on a combination of multilevel converter and linear regulator. The solutions are compared regarding their efficiency, size and weight. Both solutions can reproduce any signal with maximal spectral component of 2 MHz and give instantaneous maximal power of 50 W. The efficiency measurements show that when the signals with low average value are transmitted, the implemented prototypes have up to 20% higher efficiency than linear regulator that is used as a conventional solution.
DEFF Research Database (Denmark)
Konstantinou, Georgios; Ceballos, Salvador; Gabiola, Igor
2017-01-01
Testing and verification of high-level and low-level control, modulation, fault handling and converter co-ordination for modular multilevel converters (MMCs) requires development of experimental prototype converters. In this paper, we provide a a complete overview of the MMC-based experimental...
Multilevel Modular Converter for VSC-HVDC Transmission Applications: Control and Operational Aspects
DEFF Research Database (Denmark)
Gnanarathna, Udana N.; Gole, Aniruddha M.; Chaudhary, Sanjay Kumar
2010-01-01
Control methods for a new class of converter, the multilevel modular converter (MMC), recently introduced for HVDC transmission are discussed. The paper discusses converter-level controls including firing pulse generation and capacitor voltage balancing. It also covers higher level controls...
Space vector-based modeling and control of a modular multilevel converter in HVDC applications
DEFF Research Database (Denmark)
Bonavoglia, M.; Casadei, G.; Zarri, L.
2013-01-01
Modular multilevel converter (MMC) is an emerging multilevel topology for high-voltage applications that has been developed in recent years. In this paper, the modeling and the control of MMCs are restated in terms of space vectors, which may allow a deeper understanding of the converter behavior....... As a result, a control scheme for three-phase MMCs based on the previous theoretical analysis is presented. Numerical simulations are used to test its feasibility....
DEFF Research Database (Denmark)
Ghasemi, N.; Zare, F.; Boora, A.A.
2012-01-01
Multilevel converters, because of the benefits they attract in generating high quality output voltage, are used in several applications. Various modulation and control techniques are introduced by several researchers to control the output voltage of the multilevel converters like space vector...... on the output voltage quality by reducing its total harmonic distortion, which must take into consideration for some applications such as uninterruptable power supply, motor drive systems and piezoelectric transducer excitation. In order to verify the proposed modulation technique, MATLAB simulations...
Simulation and Analysis of a Grid Connected Multi-level Converter Topologies and their Comparison
Directory of Open Access Journals (Sweden)
Mohammad Shadab Mirza
2014-09-01
Full Text Available This paper presents simulation and analysis of a grid connected multi-level converter topologies. In this paper, converter circuit works as an inverter by controlling the switching angle (α. This paper, presents a MATLAB/SIMULINK model of multi-level converter topologies (topology1 & topology2. Topology1 is without transformer while topology2 with transformer. Both the topologies are simulated and analyzed for three level converters in order to reduce the total harmonic distortion (THD. A comparative study of topology1 and topology2 is also presented in this paper for different switching angles (α and battery voltages. The results have been tabulated and discussed.
DEFF Research Database (Denmark)
Irnawan, Roni; Silva, Filipe Miguel Faria da; Bak, Claus Leth
2017-01-01
This paper evaluates the modeling methods for a half-bridge modular multilevel converter (HB-MMC) based voltage-sourced converter (VSC) HVDC system for electromechanical transient (RMS) program. At first, the electrical and control system representation of the HB-MMC system in RMS program...
A single phase multilevel inverter as power converter for 3-phase ...
African Journals Online (AJOL)
A single phase multilevel inverter as power converter for 3-phase electric loads. ... m-phase maker was simulated using MATLAB and the results confirmed the excellent perfor-mance of the RBNPS. The listed advantages attained could be incorporated in the design and operation of a converter for an electric drive of a car.
Internal Balance during Low-Voltage-Ride-Through of the Modular Multilevel Converter STATCOM
Tsolaridis, Georgios; Kontos, E.; Chaudhary, Sanjay K.; Bauer, P.; Teodorescu, Remus
2017-01-01
Grid faults are common in power systems and can have a severe impact on the operation of the converters in the system. In this paper, the operation of a Modular Multilevel Converter (MMC)-based Static Synchronous Compensators (STATCOM) is investigated during grid faults. The study focuses on the
A new configuration for multilevel converters with diode clamped topology
DEFF Research Database (Denmark)
Nami, A.; Zare, F.; Ledwich, G.
2008-01-01
points in this type of converter is dc-voltage control. In this paper, a novel multi output dc-dc converter connected to a diode clamped topology is presented. This converter, for a given duty cycles, is able to regulate the capacitor voltage to provide an appropriate input voltage for NPC regardless...
Device loading of modular multilevel converter MMC in wind power application
DEFF Research Database (Denmark)
Popova, L.; Pyrhönen, J.; Ma, Ke
2014-01-01
Modular multilevel converter (MMC) is a recently emerged multilevel topology for high-voltage high-power applications. However, in wind power application the performance of the MMC has not been deeply investigated. In this paper the application of MMC in wind energy systems is studied....... The converters used to connect the wind turbine to the grid having the rated active powers of 2MW and 10MW are designed and investigated. Electrical losses and thermal loading of the power devices in the proposed converter solutions are analyzed. The efficiency of the MMC converter under different P/Q boundaries...... defined by grid codes is investigated and compared with two-level and three-level NPC converters. It is concluded that it is possible to use the MMC in wind power application and the losses are distributed evenly between the sub-modules of the MMC converter. However, inside a sub-module the losses...
Hybrid Modulation Scheme for Cascaded H-Bridge Inverter Cells ...
African Journals Online (AJOL)
This work proposes a switching technique for cascaded H-Bridge (CHB) cells. Single carrier Sinusoidal PWM (SCSPWM) scheme is employed in the generation of the gating signals. A sequential switching and base PWM circulation schemes are presented for this fundamental cascaded multilevel inverter topology.
Energy iteration model research of DCM Buck converter with multilevel pulse train technique
Qin, Ming; Li, Xiang
2017-08-01
According as the essence of switching converter is the nature of energy, the energy iteration model of the Multilevel Pulse Train (MPT) technique is studied in this paper. The energy iteration model of DCM Buck converter with MPT technique can reflect the control law and excellent transient performance of the MPT technique. The iteration relation of energy transfer in switching converter is discussed. The structure and operation principle of DCM Buck converter with MPT technique is introduced and the energy iteration model of this converter is set up. The energy tracks of MPT-control Buck converter and PT converter is researched and compared to show that the ratio of steady-state control pulse satisfies the expectation for the MPT technique and the MPT-controlled switching converter has much lower output voltage ripple than the PT converter.
A nine-level hybrid symmetric cascaded multilevel converter for ...
Indian Academy of Sciences (India)
Indrajit Sarkar
Therefore, due to this limitation of asymmetric or hybrid cascaded converters on input power quality, the use of these converters is popular for electric vehicle applications, and have limited industrial use [20]. Several attempts have been made to increase the number of output voltage levels of symmetric CHB–MLCs as well.
DEFF Research Database (Denmark)
Margheritini, Lucia; Victor, L.; Kofoed, Jens Peter
2009-01-01
In multi-level wave energy converters the water from incoming waves is stored in reservoirs one on top of the other. Prevision formula for the overtopping flow rates in the individual reservoirs is fundamental for dimensioning correctly the turbines and optimizing the device. Having a number...... words, the opening between two consecutive reservoirs. 13 different geometries have been tested in 2D irregular waves and a new formulation for prediction of overtopping in multilevel structures is presented....
Design and Control of Modular Multilevel Converter in an Active Front and Application
Asimakopoulos, Panagiotis; Prof Bongiorno, Massimo
2013-09-01
A proposed topology to operate as an Active Front End is the Modular Multilevel Converter. The Modular Multilevel Converter is a new solution in the field of medium and high power electronics. The converter's operation is based on the modular approach. It consists of modules, each one being a half-bridge connected in parallel to a capacitor. The special characteristic of this idea is that it is possible to build the sinusoidal waveform of the voltage by adding several modules in series in each phase-leg of the converter. An arm inductance is connected in series with the modules of every arm. In contrast to the two level voltage source converter, where the output phase voltage can be either plus or minus the half of the dc-link voltage, the MMC can change its output with steps equal to each module capacitor's voltage level.
DEFF Research Database (Denmark)
Dowlatabadi, Mohammadkazem Bakhshizadeh; Ma, Ke; Loh, Poh Chiang
2015-01-01
Modular Multilevel Converter (MMC) has recently become a popular multilevel topology for high-power applications. Conventionally, the circulating current between the legs of an MMC is an unwanted current that must be minimized in order to reduce the converter loading. In this paper the impacts...... of the circulating current in the MMC to the current ratings of power semiconductor devices are comprehensively studied. It is shown that by injecting some circulating current instead of completely eliminating it, the device peak current, average current and rms current can be improved. The conduction and switching...
Control of modular multilevel converters based on time-scale analysis and orthogonal functions
DEFF Research Database (Denmark)
Zarri, L.; Tani, A.; Mengoni, M.
2014-01-01
Modular multilevel converter (MMC) is a promising multilevel topology for high-voltage applications that has been developed in recent years. The control of MMCs has been analyzed in detail in many papers, showing that the converter capacitors can be kept charged and balanced by controlling...... current is still a complex task and cannot be fully tackled with traditional linear control techniques. In this paper a multiple time-scale analysis is proposed to determine an approximated model of the MMC that can be used to solve the control problem of the capacitor voltages. In addition, it is shown...
Modular Multi-level converter based HVDC System for Grid Connection of Offshore Wind Power Plant
DEFF Research Database (Denmark)
Gnanarathna, U.N.; Chaudhary, Sanjay Kumar; Gole, A.M.
2010-01-01
This paper explores the application of modular multi-level converters (MMC) as a means for harnessing the power from off-shore wind power plants. The MMC consists of a large number of simple voltage sourced converter (VSC) submodules that can be easily assembled into a converter for high......-voltage and high power. The paper shows that the MMC converter has a fast response and low harmonic content in comparison with a two-level VSC option. The paper discusses the modeling approach used, including a solution to the modeling challenge imposed by the very large number of switching devices in the MMC....
National Research Council Canada - National Science Library
Hou, Yanbin; Sun, Wanrong; Ren, Aifeng; Liu, Shuming
2016-01-01
...) and hybrid multilevel converter. Under the control of input signal, cascaded power converters with separate DC sources operate in PSM switch mode to directly generate high-voltage and high-power output...
Unifying and generating of space vector modulation sequences for multilevel converter
DEFF Research Database (Denmark)
Ma, Ke; Blaabjerg, Frede
2014-01-01
Space Vector Modulation (SVM) is a powerful method which enables some freedom to generate the modulation sequences and modify the performances of converter. However, in the multi-level converter structures, the number of switching state redundancies significantly increases, and the determination ...... on the discovered correlation and pattern, a general method for modulation sequences generating is proposed, and a series of new modulation sequences are deducted according to several easily applied rules.......Space Vector Modulation (SVM) is a powerful method which enables some freedom to generate the modulation sequences and modify the performances of converter. However, in the multi-level converter structures, the number of switching state redundancies significantly increases, and the determination...
Enhanced DC-Link Capacitor Voltage Balancing Control of DC–AC Multilevel Multileg Converters
DEFF Research Database (Denmark)
Busquets-Monge, Sergio; Maheshwari, Ram Krishan; Nicolas-Apruzzese, Joan
2015-01-01
This paper presents a capacitor voltage balancing control applicable to any multilevel dc–ac converter formed by a single set of series-connected capacitors implementing the dc link and semiconductor devices, such as the diode-clamped topology. The control is defined for any number of dc-link vol...
DEFF Research Database (Denmark)
Huang, Shaojun; Mathe, Laszlo; Teodorescu, Remus
2013-01-01
Two existing methods to implement resampling modulation technique for modular multilevel converter (MMC) (the sampling frequency is a multiple of the carrier frequency) are: the software solution (using a microcontroller) and the hardware solution (using FPGA). The former has a certain level...
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Máthé, Lászlo; Teodorescu, Remus
2016-01-01
With the aim to solve the unbalanced thermal behavior in the modular multilevel converter, introduced by mismatch in the submodule parameters, a thermal balancing control strategy is proposed here. The proposed solution ensures a balanced junction temperature for the power devices, while the bala...
Hexuple-Inverter Configuration for Multilevel Nine-Phase Symmetrical Open-Winding Converter
DEFF Research Database (Denmark)
Padmanaban, Sanjeevi Kumar; Bhaskar, Mahajan Sagar; Maroti, Pandav Kiran
2016-01-01
Hexuple-inverter configuration for multilevel nine-phase symmetrical open-winding ac converter is articulated in this work. Power modular unit consists of six classical three-phase voltage source inverters (VSI). Each VSI includes one bi-directional device (MOSFET/IGBT) per each phase and link...
DEFF Research Database (Denmark)
Farivar, Glen; Ghias, Amer M. Y. M.; Hredzak, Branislav
2017-01-01
This paper proposes a new method for measuring capacitor voltages in multilevel flying capacitor (FC) converters that requires only one voltage sensor per phase leg. Multiple dc voltage sensors traditionally used to measure the capacitor voltages are replaced with a single voltage sensor at the ac...
DEFF Research Database (Denmark)
Burlacu, Paul Dan; Mathe, Laszlo; Rejas, Marcos
2015-01-01
Modular Multilevel Converter (MMC) is very promising technology this days. It offers fault tolerant capabilities and ensures high efficiency with low output voltage harmonic content which results in need for smaller filter size. A disadvantage of the system is that the control becomes more...
Power Devices Loading in Multilevel Converters for 10 MW Wind Turbines
DEFF Research Database (Denmark)
Ma, Ke; Blaabjerg, Frede; Xu, Dehong
2011-01-01
Several promising multilevel converter solutions for 10 MW wind turbines using permanent magnet synchronous generators are proposed, designed and compared both with one-stage gear-box drive and direct drive systems. The current and loss distributions, as well as the utilization of power devices...
DEFF Research Database (Denmark)
Ma, Ke; Muñoz-Aguilar, S.; Rodriguez, P.
2012-01-01
In this paper a five-level Multi-Clamped Multilevel Converter (5L-MLC2) topology is analyzed based on a typical grid integration application for renewable energy generation system. The loss and thermal distribution of the power devices in different switching legs are investigated and illustrated...... under rated operation. Afterwards, a loss and efficiency evaluation method is proposed and applied which takes into account various reactive power operation boundaries regulated by the grid codes. It is concluded that the 5L-MLC2 multilevel topology shows a good and consistent efficiency characteristic...... under different output active powers when complying with the active/reactive power operation range regulated by e.g. the German grid codes....
Modular Multilevel Converter solutions with few Sub-Modules for wind power application
DEFF Research Database (Denmark)
Smirnova, Liudmila; Pyrhönen, Juha; Ma, Ke
2014-01-01
Modular Multilevel Converter (MMC) is a topology where series connection of Sub-Modules (SM) is used to achieve almost sinusoidal output voltage. The MMC converter with a large number of SMs is actively used in high voltage DC (HVDC) transmission systems where a bulky converter is not a difficult...... issue. In this paper the possibility to use a MMC with just a few SMs for wind power application with limited space in the nacelle is analysed. The current loading, electrical losses and thermal performance of the power devices in the converter solutions studied are analysed. It is shown that an MMC...... converter with full-bridge (FB) SMs has a more uniform loss and temperature distribution among the semiconductor devices than an MMC with half-bridge (HB) SMs. The reliability of the MMC converters is also investigated in terms of thermal loading....
DEFF Research Database (Denmark)
Dowlatabadi, Mohammadkazem Bakhshizadeh; Ma, Ke; Loh, Poh Chiang
2015-01-01
Modular Multilevel Converter (MMC) has recently become a popular multilevel topology for high-power applications, where the reliability performance is a crucial design consideration. In this paper the impacts of the circulating current in the MMC to the loss and thermal loading of power...... semiconductor devices are comprehensively investigated. Also a novel control strategy by utilizing the circulating current is proposed to enhance the reliability performance of MMC in order to limit the amplitude of thermal cycles. It is concluded that the circulating current may change the losses and thermal...
Converter DC/AC Multilevel of Three Cells: Modeling and Simulation
Directory of Open Access Journals (Sweden)
Julián Peláez-Restrepo
2013-11-01
Full Text Available This paper presents a three-cell converter DC / AC. Multilevel topologies are attracting attention in the industry, obtained as a ripple on the state variables much smaller, and reduces stress on the switching devices. The topology used in this work is known in the technical literature as floating capacitor multilevel inverter, which imposes the challenge of balancing the voltage across each cell switching using floating capacitors, besides obtaining a sinusoidal signal regulated. The paper presents the averaged model of the inverter, and results obtained through simulation.
Modular Multilevel Converters Based Variable Speed Wind Turbines for Grid Faults
DEFF Research Database (Denmark)
Deng, Fujin; Liu, Dong; Wang, Yanbo
2016-01-01
The modular multilevel converter (MMC) becomes attractive in the medium- and high-power application with high modularity. In this paper, the MMC is proposed to be applied in the variable speed wind turbine (VSWT) based on the full-scale back-to-back (BTB) power converter, where the generator......-side converter is the three-level neutral-point-clamped (NPC) converter and the grid-side converter is the three-phase MMC. A control strategy is also presented for the MMC based VSWT for the second-order harmonic current elimination. The proposed MMC based VSWT and control not only mitigate the voltage ripple...... of the proposed MMC based VSWT and control are conducted with a detailed PSCAD/EMTDC model, and the results show their effectiveness....
Optimized Thermal Management System of Modular Multilevel Converter for HVDC applications
DEFF Research Database (Denmark)
Hajizadeh, Amin
2017-01-01
The dynamical behavior of temperature is becoming a critical design consideration for the Modular Multilevel Converter (MMC). Investigation of an advanced control structure for Grid Connected-Modular Multilevel Converter (GC-MMC) is proposed in this paper. To achieve this goal, an non-linear model...... of MMC regarding considering of negative and positive sequence components with thermal dynamics has been presented. Then, due to existence of unbalance voltage faults in distribution grid, non-linarites and uncertainties in model, adaptive robust current controller which is composed of sliding mode...... and fuzzy control, is developed for GC-MMC. Finally, numerical results are given in order to show the dynamic performance of GC-MMC prototype under normal and unbalanced fault conditions. They illustrate the proposed current controllers could keep the MMC stable under different conditions and thermal...
A New Structure Based on Cascaded Multilevel Converter for Variable Speed Wind Turbine
DEFF Research Database (Denmark)
Deng, Fujin; Chen, Zhe
2010-01-01
An alternative structure for variable speed wind turbine, using multiple permanent magnet synchronous generators (PMSGs) drive-train configuration and cascaded multilevel converter is proposed in this paper. This study presents a power electronic solution for the wind turbine. A transformer......-less cascaded multilevel converter interface based on PMSGs is developed to synthesize a desired high ac sinusoidal output voltage. The benefits of high power and high ac voltage make this structure possible to be applied in the wind power generation. In addition, the bulky transformer could be omitted....... A simulation model of 10 MW variable speed wind turbine based on PMSGs developed in PSCAD/EMTDC is presented. The dynamic performance of grid-connected wind turbine is analyzed. Simulation results shows that the proposed structure may be attractive in wind power generation....
Design, Control and Application of Modular Multilevel Converters for HVDC Transmission Systems
DEFF Research Database (Denmark)
Sharifabadi, Kamran; Harnefors, Lennart; Nee, Hans-Peter
Design, Control and Application of Modular Multilevel Converters for HVDC Transmission Systems is a comprehensive guide to semiconductor technologies applicable for MMC design, component sizing control, modulation, and application of the MMC technology for HVDC transmission. Separated into three...... distinct parts, the first offers an overview of MMC technology, including information on converter component sizing, Control and Communication, Protection and Fault Management, and Generic Modelling and Simulation. The second covers the applications of MMC in offshore WPP, including planning, technical...... and economic requirements and optimization options, fault management, dynamic and transient stability. Finally, the third chapter explores the applications of MMC in HVDC transmission and Multi Terminal configurations, including Supergrids....
Design, control and application of modular multilevel converters for HVDC transmission systems
Sharifabadi, Kamran; Nee, Hans-Peter; Norrga, Staffan; Teodorescu, Remus
2016-01-01
Design, Control and Application of Modular Multilevel Converters for HVDC Transmission Systems is a comprehensive guide to semiconductor technologies applicable for MMC design, component sizing control, modulation, and application of the MMC technology for HVDC transmission. Separated into three distinct parts, the first offers an overview of MMC technology, including information on converter component sizing, Control and Communication, Protection and Fault Management, and Generic Modelling and Simulation. The second covers the applications of MMC in offshore WPP, including planning, technical and economic requirements and optimization options, fault management, dynamic and transient stability. Finally, the third chapter explores the applications of MMC in HVDC transmission and Multi Terminal configurations, including Supergrids.
DEFF Research Database (Denmark)
Rodriguez, Pedro; Busquets-Monge, Sergio; Blaabjerg, Frede
2011-01-01
This work presents the development of the space vector pulse width modulation (SVPWM) of a new multi-level converter topology. First, the proposed converter and its natural space vector diagram are presented. Secondly, a modified space vector diagram based on the virtual-vectors technique is shown...
DEFF Research Database (Denmark)
Bhaskar, Mahajan Sagar; Kulkarni, Rishi M.; Padmanaban, Sanjeevi Kumar
2016-01-01
In this paper hybrid non isolated/ non inverting Nx interleaved DC-DC multilevel Boost Converter for renewable energy applications is presented. The presented hybrid topology is derived from the conventional interleaved converter and the Nx Multilevel boost converter. In renewable energy....... The advantages of presenting topology of DC-DC converter are high voltage conversion, reduce ripple, low voltage stress, non inverting without utilizing the high duty and transformer. The main advantage of presented topology is more number of levels can be increased by adding capacitor and diode circuitry...
A Cascade Multilevel Converter of Switched Reluctance Motor and Its Control Timing Sequence
Directory of Open Access Journals (Sweden)
Runquan MENG
2014-04-01
Full Text Available A kind of cells cascaded multilevel converter of switched reluctance motor was proposed, which can be made up of low voltage power electronic devices and can be applied to drive high voltage switched reluctance motor. Based on introducing the main circuit topology, the operating modes and the voltage superposition law of proposed converter, the control strategy for the switched reluctance drive by the use of proposed converter was analyzed and a kind of corresponding control time sequence was established. By means of Matlab/Simulink simulation and actual system experiment, the system controlled under proposed timing sequence was validated to have good driving performance. In addition, the experiment result shows that the power converter has almost no harmonic pollution to the power source and has a high grid-side power factor because of employing phase-shifting transformer and multi-pulse rectifier in the input port, the threat against insulation of the motor winding decreased with the lessening of voltage gradient of the motor winding by making the winding voltage to vary in multi-level.
Internal balance during low-voltage-ride-through of the modular multilevel converter statcom
DEFF Research Database (Denmark)
Tsolaridis, Georgios; Kontos, Epameinondas; Chaudhary, Sanjay K.
2017-01-01
Grid faults are common in power systems and can have a severe impact on the operation of the converters in the system. In this paper, the operation of a Modular Multilevel Converter (MMC)-based Static Synchronous Compensators (STATCOM) is investigated during grid faults. The study focuses...... on the challenging internal control of the converter to allow the independent control of the energy levels of each arm, with the goal to maintain internal balancing of the MMC during contingencies. Extensive experimental results highlight the need for a sophisticated internal control. Moreover, the experimental...... analysis verifies that, by using the proposed control structure, the MMC can effectively ride through a fault on the AC side without tripping, while injecting the necessary positive and negative sequence reactive current levels according to the most recent grid codes....
Modeling, Development and Control of Multilevel Converters for Power System Application =
Vahedi, Hani
The main goal of this project is to develop a multilevel converter topology to be useful in power system applications. Although many topologies are introduced rapidly using a bunch of switches and isolated dc sources, having a single-dc-source multilevel inverter is still a matter of controversy. In fact, each isolated dc source means a bulky transformer and a rectifier that have their own losses and costs forcing the industries to avoid entering in this topic conveniently. On the other hand, multilevel inverters topologies with single-dc-source require associated controllers to regulate the dc capacitors voltages in order to have multilevel voltage waveform at the output. Thus, a complex controller would not interest investors properly. Consequently, developing a single-dc-source multilevel inverter topology along with a light and reliable voltage control is still a challenging topic to replace the 2-level inverters in the market effectively. The first effort in this project was devoted to the PUC7 inverter to design a simple and yet efficient controller. A new modelling is performed on the PUC7 inverter and it has been simplified to first order system. Afterwards, a nonlinear cascaded controller is designed and applied to regulate the capacitor voltage at 1/3 of the DC source amplitude and to generate 7 identical voltage levels at the output supplying different type of loads such as RL or rectifier harmonic ones. In next work, the PUC5 topology is proposed as a remedy to the PUC7 that requires a complicated controller to operate properly. The capacitor voltage is regulated at half of dc source amplitude to generate 5 voltage levels at the output. Although the 7-level voltage waveform is replaced by a 5-level one in PUC5 topology, it is shown that the PUC5 needs a very simple and reliable voltage balancing technique due to having some redundant switching states. Moreover, a sensor-less voltage balancing technique is designed and implemented on the PUC5 inverter
Debnath, Suman
The growing demand for wind power generation has pushed the capacity of wind turbines towards MW power levels. Higher capacity of the wind turbines necessitates operation of the generators and power electronic conversion systems at higher voltage/power levels. The power electronic conversion system of a wind energy conversion system (WECS) needs to meet the stringent requirements in terms of reliability, efficiency, scalability and ease of maintenance, power quality, and dv/dt stress on the generator/transformer. Although the multilevel converters including the neutral point clamped (NPC) converter and the active NPC converter meet most of the requirements, they fall short in reliability and scalability. Motivated by modularity/scalability feature of the modular multilevel converter (MMC), this research is to enable the MMC to meet all of the stringent requirements of the WECS by addressing their unique control challenges. This research presents systematic modeling and control of the MMC to enable it to be a potential converter topology for grid integration of full-scale WECSs. Based on the developed models, appropriate control systems for control of circulating current and capacitor voltages under fixed- and variable-frequency operations are proposed. Using the developed MMC models, a gradient-based cosimulation algorithm to optimize the gains of the developed control systems, is proposed. Performance/effectiveness of the developed models and the proposed control systems for the back-to-back MMC-based WECS are evaluated/verified based on simulations studies in the PSCAD/EMTDC software environment and experimental case studies on a laboratory-scale hardware prototype.
Review of fault diagnosis and fault-tolerant control for modular multilevel converter of HVDC
DEFF Research Database (Denmark)
Liu, Hui; Loh, Poh Chiang; Blaabjerg, Frede
2013-01-01
, several typical topologies of MMC-HVDC systems are presented. Then fault types such as capacitor voltage unbalance, unbalance between upper and lower arm voltage are analyzed and the corresponding fault detection and diagnosis approaches are explained. In addition, more attention is dedicated to control......This review focuses on faults in Modular Multilevel Converter (MMC) for use in high voltage direct current (HVDC) systems by analyzing the vulnerable spots and failure mechanism from device to system and illustrating the control & protection methods under failure condition. At the beginning...... strategies, when running in MMC faults or grid faults. This paper ends up with a discussion of other opportunities for future development....
Double-Carrier Phase-Disposition Pulse Width Modulation Method for Modular Multilevel Converters
DEFF Research Database (Denmark)
Zhou, Fayun; Luo, An; Li, Yan
2017-01-01
Modular multilevel converters (MMCs) have become one of the most attractive topologies for high-voltage and high-power applications. A double-carrier phase disposition pulse width modulation (DCPDPWM) method for MMCs is proposed in this paper. Only double triangular carriers with displacement angle...... are needed for DCPDPWM, one carrier for the upper arm and the other for the lower arm. Then, the theoretical analysis of DCPDPWM for MMCs is presented by using a double Fourier integral analysis method, and the Fourier series expression of phase voltage, line-to-line voltage and circulating current...
DEFF Research Database (Denmark)
Wang, Zhongxu; Wang, Huai; Zhang, Yi
2017-01-01
A novel switching power loss estimation method for modular multilevel converters (MMCs) with the nearest level modulation (NLM) is introduced in this paper. It focuses on the switching actions caused only by change of the inserted submodule (SM) number per arm, named as the essential switching...... transitions. Every essential switching action can be identified under the assumption of ideal sinusoidal arm voltage reference. The corresponding arm current value determining the switching energy can be obtained with the exclusive use of the exact time of the switching action. Effects of the modulation index...
A Novel Multilevel Quad-Inverter Configuration for Quasi Six-Phase Open-Winding Converter
DEFF Research Database (Denmark)
Padmanaban, Sanjeevi Kumar; Blaabjerg, Frede; Wheeler, Patrick
2016-01-01
of standard four three-phase voltage source inverter (VSI) and each connected to the open-end windings. Each VSIs are incorporated with one bi-directional switching device (MOSFET/IGBT) per phase and two capacitors with neutral point connected. Further, an original modified single carrier five......This paper developed a novel quad-inverter configuration for multilevel six-phase asymmetrical open-winding AC converter. Proposal found to be suited for (low-voltage/high-current) applications such as AC tractions and `More-Electric Aircraft' propulsion systems. Modular power circuit comprises...
Directory of Open Access Journals (Sweden)
Fei Chang
2015-01-01
Full Text Available The modular multilevel converter (MMC is an emerging voltage source converter topology suitable for multiterminal high voltage direct current transmission based on modular multilevel converter (MMC-MTDC. This paper presents fault characteristics of MMC-MTDC including submodule fault, DC line fault, and fault ride-through of wind farm integration. Meanwhile, the corresponding protection strategies are proposed. The correctness and effectiveness of the control strategies are verified by establishing a three-terminal MMC-MTDC system under the PSCAD/EMTDC electromagnetic transient simulation environment.
Directory of Open Access Journals (Sweden)
Ahmed Zama
2016-12-01
Full Text Available Thanks to scalability, performance and efficiency, the Modular Multilevel Converter (MMC, since its invention, becomes an attractive topology in industrial applications such as high voltage direct current (HVDC transmission system. However, modelling challenges related to the high number of switching elements in the MMC are highlighted when such systems are integrated into large simulated networks for stability or protection algorithms testing. In this work, a novel dynamic models for MMC is proposed. The proposed models are intended to simplify modeling challenges related to the high number of switching elements in the MMC. The models can be easily used to simulate the converter for stability analysis or protection algorithms for HVDC grids.
High Order Voltage and Current Harmonic Mitigation Using the Modular Multilevel Converter STATCOM
DEFF Research Database (Denmark)
Kontos, Epameinondas; Tsolaridis, Georgios; Teodorescu, Remus
2017-01-01
Due to the increase of power electronic-based loads, the maintenance of high power quality poses a challenge in modern power systems. To limit the total harmonic distortion in the line voltage and currents at the point of the common coupling (PCC), active power filters are commonly employed....... This paper investigates the use of the multilevel modular converter (MMC) for harmonics mitigation due to its high bandwidth compared with conventional converters. A selective harmonics detection method and a harmonics controller are implemented, while the output current controller of the MMC is tuned...... to selectively inject the necessary harmonic currents. Unlike previous studies, focus is laid on the experimental verification of the active filtering capability of the MMC. For this reason an MMC-based double-star STATCOM is developed and tested for two representative case studies, i.e., for grid currents...
Control of a Modular Multilevel Converter STATCOM under internal and external unbalances
DEFF Research Database (Denmark)
Tsolaridis, Georgios; Kontos, E.; Parikh, Harsh
2016-01-01
This paper develops a complete control scheme for the Modular Multilevel Converter (MMC) in a STATCOM application. The focus is laid on the internal balancing of the converter and its reliable operation under internal mismatches as well as under external unbalanced conditions. The leg energy...... and the simulation results verified the capability to provide maximum reactive power to the AC grid while maintaining internal balance through the individual control of each arm energy level....... controller ensures that the sum of the capacitor voltages of each phase are equal. An intuitive arm energy controller is also implemented which allows the decoupled control of the energy levels of every arm. The control performance of the STATCOM was evaluated under asymmetrical grid faults...
Wang, Lei; Fan, Youping; Zhang, Dai; Ge, Mengxin; Zou, Xianbin; Li, Jingjiao
2017-09-01
This paper proposes a method to simulate a back-to-back modular multilevel converter (MMC) HVDC transmission system. In this paper we utilize an equivalent networks to simulate the dynamic power system. Moreover, to account for the performance of converter station, core components of model of the converter station gives a basic model of simulation. The proposed method is applied to an equivalent real power system.
DEFF Research Database (Denmark)
Dowlatabadi, Mohammadkazem Bakhshizadeh; Najjar, Mohammad; Blaabjerg, Frede
2016-01-01
In this paper, a Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) method, which utilizes adjustable dc links, is presented for a Static Synchronous Compensator (STATCOM) based on Cascaded H-Bridge (CHB) multilevel converter. The proposed switching algorithm is able to fix...
DEFF Research Database (Denmark)
Bhaskar, Mahajan Sagar; Padmanaban, Sanjeevikumar; Fedák, Viliam
2017-01-01
; such as a photovoltaic (PV) system with a Multilevel Inverter (MLI), electrical drives, automotive, hybrid electric cars etc. The proposed topology is derived by attaching the Cockcroft Walton (CW) multiplier to an upper L-converter of the LL topology of XY family. The mode of operation of L-LMBC with mathematical...
Device Loading and Efficiency of Modular Multilevel Converter under Various Modulation Strategies
DEFF Research Database (Denmark)
Liu, Hui; Ma, Ke; Blaabjerg, Frede
2016-01-01
of the power devices in terms of power loss and thermal profiles, which are critical issues in terms of efficiency and reliability of the MMC. Special attention is given to the performance comparison of MMC under various modulation indexes as well as different switching frequencies when applying those......Modular Multilevel Converter (MMC) has been becoming a very important solution for high power and medium power applications, where the efficiency and reliability performance are crucial design considerations. In this paper, three widely used modulation methods for MMC, Phase Shift PWM (PSPWM......), Phase Disposition PWM (PDPWM) and Nearest Level Modulation (NLM), are comprehensively investigated to uncover the desired solution for high transmission efficiency and system reliability. An important part of this paper is also devoted to reveal the impact of modulation schemes on the loading stress...
DEFF Research Database (Denmark)
Zhang, Yi; Wang, Huai; Wang, Zhongxu
2017-01-01
Power cycling in semiconductor modules contributes to repetitive thermal-mechanical stresses, which in return accumulate as fatigue on the devices, and challenge the lifetime. Typically, lifetime models are expressed in number-of-cycles, within which the device can operate without failures under...... predefined conditions. In these lifetime models, thermal stresses (e.g., junction temperature variations) are commonly considered. However, the lifetime of power devices involves in crossdisciplinary knowledge. As a result, the lifetime prediction is affected by the selected lifetime model. In this regard......, this paper benchmarks the most commonly-employed lifetime models of power semiconductor devices for offshore Modular Multilevel Converters (MMC) based wind farms. The benchmarking reveals that the lifetime model selection has a significant impact on the lifetime estimation. The use of analytical lifetime...
System-on-chip implementation of embedded real-time simulator for modular multilevel converters
DEFF Research Database (Denmark)
Ricco, Mattia; Gheorghe, Marius-Radu; Máthé, Lászlo
2017-01-01
The aim of this paper is to present the implementation of an Embedded Real-Time Simulator (ERTS) for Modular Multilevel Converters (MMCs), using low-cost System-on-Chip (SoC) platform. In order to achieve new functionalities such as sensor-less control, monitoring, diagnostic and fault detection......, the MMC plant model can be implemented along with the controller. In MMC applications, the implementation of the RTS is particularly challenging due to the complex structure of the MMC and its stringent timing constraints, especially when the number of Sub-Modules (SMs) increases. In addition....... For these reasons, a Xilinx Zynq SoC platform is adopted; this device provides two hard-processors along with the programmable gate array. In this work, the MMC plant model and the MMC controller are implemented in the two available microcontrollers, whereas, all the modulators and interfaces can be implemented...
Fault-Tolerant Approach for Modular Multilevel Converters under Submodule Faults
DEFF Research Database (Denmark)
Deng, Fujin; Tian, Yanjun; Zhu, Rongwu
2016-01-01
The modular multilevel converter (MMC) is attractive for medium- or high-power applications because of the advantages of its high modularity, availability, and high power quality. The fault-tolerant operation is one of the important issues for the MMC. This paper proposed a fault-tolerant approach...... for the MMC under submodule (SM) faults. The characteristic of the MMC with arms containing different number of healthy SMs under faults is analyzed. Based on the characteristic, the proposed approach can effectively keep the MMC operation as normal under SM faults. It can effectively improve the MMC...... performance under SM faults but without the knowledge of the number of the faulty SMs in the arm, without extra demand on communication systems, which potentially increases the reliability. The time-domain simulation studies with the PSCAD/EMTDC are conducted and a down-scale MMC prototype is also tested...
Protection Scheme for Modular Multilevel Converters under Diode Open-Circuit Faults
DEFF Research Database (Denmark)
Deng, Fujin; Zhu, Rongwu; Liu, Dong
2018-01-01
The modular multilevel converter (MMC) is attractive for medium- or high-power applications because of the advantages of its high modularity, availability, and high power quality. Reliability is one of the most important challenges for the MMC consisting of a large number of power electronic...... devices. The diode open-circuit fault in the submodule (SM) is an important issue for the MMC, which would affect the performance of the MMC and disrupt the operation of the MMC. This paper analyzes the impact of diode open-circuit failures in the SMs on the performance of the MMC and proposes...... a protection scheme for the MMC under diode open-circuit faults. The proposed protection scheme not only can effectively eliminate the possible caused high voltage due to the diode open-circuit fault but also can quickly detect the faulty SMs, which effectively avoids the destruction and protects the MMC...
Voltage-Balancing Method for Modular Multilevel Converters Switched at Grid Frequency
DEFF Research Database (Denmark)
Deng, Fujin; Chen, Zhe
2015-01-01
The modular multilevel converter (MMC) becomes attractive for high-voltage and high-power applications due to its high modularity, availability, and power quality. The voltage balance issue of capacitors is very important in the MMC, and the balancing of the capacitor voltage is increasingly...... difficult as the switching frequency is reduced. In this paper, a voltage-balancing method is proposed for the MMC switched at grid frequency with reduced losses and does not rely on the arm current. By assigning the low-frequency pulses with different pulse widths, the capacitor charge transfer in the MMC...... can be controlled for keeping the capacitor voltage balancing in the MMC. Simulations and experimental studies of the MMC are conducted, and the results confirm the effectiveness of the proposed capacitor voltage-balancing method....
DEFF Research Database (Denmark)
Tanaka, Takaaki; Wang, Huai; Ma, Ke
2017-01-01
Static Synchronous Compensators (STATCOMs) are being applied for offshore wind power plants to satisfy the grid codes under both normal operation and grid fault conditions. This paper investigates the performances of Modular Multilevel Cascade Converters (MMCC) for the STATCOM application, with s...
DEFF Research Database (Denmark)
Tanaka, Takaaki; Wang, Huai; Ma, Ke
2017-01-01
Static Synchronous Compensators (STATCOMs) have been applied for offshore wind power plants to satisfy the grid codes under both normal operation and grid fault conditions. This paper investigates the performances of two types of Modular Multilevel Cascade Converters (MMCC) for STATCOM applicatio...
DEFF Research Database (Denmark)
Gan, Chun; Wu, Jianhua; Hu, Yihua
2017-01-01
This paper presents an integrated multilevel converter of switched reluctance motors (SRMs) fed by a modular front-end circuit for plug-in hybrid electric vehicle (PHEV) applications. Several operating modes can be achieved by changing the on-off states of the switches in the front-end circuit. I...
Directory of Open Access Journals (Sweden)
M.R. Banaei
2014-09-01
Full Text Available Multilevel inverters are suggested to obtain high quality output voltage. In this paper, a new hybrid configuration is proposed, obtained by cascading one four switches H-bridge cell with a family of multilevel inverters. In addition, by the use of specific sequence for value of DC sources named Fibonacci series, asymmetrical topology of proposed inverter is introduced. Main advantages are that proposed inverter has least Peak Inverse Voltage (PIV than other conventional multilevel converters in both symmetric and asymmetric modes. Also, this topology doubles the number of output levels using only one cascaded four switches H-bridge cell. The PCI-1716 DAQ using PC has been used to generate switching pulses in experimental results. For presenting valid performance of proposed configuration, simulation results carried out by MATLAB/SIMULINK software and the validity of the proposed multilevel inverter is verified by experimental results.
DEFF Research Database (Denmark)
Ma, Ke; Blaabjerg, Frede; Liserre, Marco
2013-01-01
As the power level of a single wind turbine is continuously pushed up even to 7 MW, the wind power generation systems are required to be more reliable and able to withstand extreme grid disturbances. Moreover, it is becoming a need that the wind power generation system should be more active...... devices in full-scale power converters, particularly during grid faults, may compromise the reliability performance and further increase the cost of the system. In this paper, three promising grid-side multilevel converter topologies for the next-generation 10-MW wind turbines are proposed and basically...
Directory of Open Access Journals (Sweden)
Rui Li
2016-12-01
Full Text Available The AC voltage control of a DC/DC converter based on the modular multilevel converter (MMC is considered under normal operation and during a local DC fault. By actively setting the AC voltage according to the two DC voltages of the DC/DC converter, the modulation index can be near unity, and the DC voltage is effectively utilized to output higher AC voltage. This significantly decreases submodule (SM capacitance and conduction losses of the DC/DC converter, yielding reduced capital cost, volume, and higher efficiency. Additionally, the AC voltage is limited in the controllable range of both the MMCs in the DC/DC converter; thus, over-modulation and uncontrolled currents are actively avoided. The AC voltage control of the DC/DC converter during local DC faults, i.e., standby operation, is also proposed, where only the MMC connected on the faulty cable is blocked, while the other MMC remains operational with zero AC voltage output. Thus, the capacitor voltages can be regulated at the rated value and the decrease of the SM capacitor voltages after the blocking of the DC/DC converter is avoided. Moreover, the fault can still be isolated as quickly as the conventional approach, where both MMCs are blocked and the DC/DC converter is not exposed to the risk of overcurrent. The proposed AC voltage control strategy is assessed in a three-terminal high-voltage direct current (HVDC system incorporating a DC/DC converter, and the simulation results confirm its feasibility.
DEFF Research Database (Denmark)
Bhaskar, Mahajan Sagar; Padmanaban, Sanjeevikumar; Blaabjerg, Frede
2016-01-01
In this treatise, 4Nx hybrid Non Inverting & Non Isolated (NI-NI) DC-DC interleaved multi-level boost converter (4Nx IMBC) for renewable energy applications is proposed. The proposed 4Nx IMBC is derived by coalescing the feature of 2Nx DC-DC Interleaved Multi-level Boost Converter (2Nx IMBC......), voltage-lift-switched-inductor-modified (VLSlm Cell) and Cockcroft Walton (CW) voltage multipliers. The 4Nx converter provides 4N times more conversion voltage ratio compared to conventional boost converter where N denotes the number of output stages of the 4Nx IMBC. To make renewable energy sources...
Sotoodeh, Pedram
This dissertation presents the design of a novel multi-level inverter with FACTS capability for small to mid-size (10-20kW) permanent-magnet wind installations using modular multi-level converter (MMC) topology. The aim of the work is to design a new type of inverter with D-STATCOM option to provide utilities with more control on active and reactive power transfer of distribution lines. The inverter is placed between the renewable energy source, specifically a wind turbine, and the distribution grid in order to fix the power factor of the grid at a target value, regardless of wind speed, by regulating active and reactive power required by the grid. The inverter is capable of controlling active and reactive power by controlling the phase angle and modulation index, respectively. The unique contribution of the proposed work is to combine the two concepts of inverter and D-STATCOM using a novel voltage source converter (VSC) multi-level topology in a single unit without additional cost. Simulations of the proposed inverter, with 5 and 11 levels, have been conducted in MATLAB/Simulink for two systems including 20 kW/kVAR and 250 W/VAR. To validate the simulation results, a scaled version (250 kW/kVAR) of the proposed inverter with 5 and 11 levels has been built and tested in the laboratory. Experimental results show that the reduced-scale 5- and 11-level inverter is able to fix PF of the grid as well as being compatible with IEEE standards. Furthermore, total cost of the prototype models, which is one of the major objectives of this research, is comparable with market prices.
DEFF Research Database (Denmark)
Ma, Ke; Blaabjerg, Frede; Liserre, Marco
2011-01-01
, and able to contribute to the grid recovery by injecting reactive current during grid faults. Consequently, the full-scale power converter solutions are becoming more and more popular to fulfill the growing challenges in the wind power application. Nevertheless, the loading of the power devices in full......-scale power converters, especially during grid faults may compromise the reliability performance and further increase the cost of the system. In this paper, three promising grid side multilevel converter topologies for the next generation 10 MW wind turbines are proposed and basically designed as case study......As the power level of a single wind turbine is continuously pushed up even to 7 MW, the wind power generation system are required to be more reliable, and able to withstand extreme grid disturbances. Moreover, it is becoming a need that the wind power generation system should be more active...
Fajingbesi, F. E.; Midi, N. S.; Khan, S.
2017-06-01
Green energy sources or renewable energy system generally utilize modular approach in their design. This sort of power sources are generally in DC form or in single cases AC. Due to high fluctuation in the natural origin of this energy (wind & solar) source they are stored as DC. DC power however are difficult to transfer over long distances hence DC to AC converters and storage system are very important in green energy system design. In this work we have designed a novel multilevel DC to AC converter that takes into account the modular design of green energy systems. A power conversion efficiency of 99% with reduced total harmonic distortion (THD) was recorded from our simulated system design.
Design of a Modular Multilevel Converter as an Active Front-End for a magnet supply application
Panagiotis, Asimakopoulos; Massimo, Bongiorno
2015-01-01
The aim of this work is to describe the general design procedure of a Modular Multilevel Converter (MMC) applied as an Active Front-End (AFE) for a magnet supply for beam accelerators. The dimensioning criteria for the converter and the dc-link capacitance are presented and the grid transformer requirements are set. Considering the converter design, the arm inductance calculation is based on the specifications for the arm-current ripple and the DC-link fault tolerance, but, also, on the limitation of the second harmonic and the second-order LC resonance of the arm current. The module capacitance value is evaluated by focusing on the required switching dynamics and the capacitor-voltage ripple according to a newly proposed graphical method. The loading of each semiconductor in the half bridge is calculated via simulation, indicating the unsymmetrical current distribution. It is concluded that the current distribution for each semiconductor depends on the mode of operation of the converter. The different criter...
A Cascade Multilevel Converter of Switched Reluctance Motor and Its Control Timing Sequence
National Research Council Canada - National Science Library
Runquan Meng; Min Wu
2014-01-01
... voltage switched reluctance motor. Based on introducing the main circuit topology, the operating modes and the voltage superposition law of proposed converter, the control strategy for the switched reluctance drive by the use...
Harmonic cancellation in a novel multilevel converter topology for the future smart grid
Moonen, Dominicus Johannes Guilielmus; Gagic, Mladen; Buesink, Frederik Johannes Karel; Ferreira, Jan; Leferink, Frank
2017-01-01
Increased switching speed of semiconductors are reducing losses, but increasing emissions. EMC compliance becomes increasingly difficult in power electronics. A reactive attitude is unwanted, often due to the possible increased costs of solutions. Converter topologies that can inherently reduce
DEFF Research Database (Denmark)
Liu, Hui; Ma, Ke; Loh, Poh Chiang
2015-01-01
Due to the possibility of putting a large number of modules consisting of switches and capacitors connected in series, the modular multilevel converter (MMC) can easily be scaled to high power and high voltage power conversion, which is an attractive feature for filter-less and transformer......-less design and helpful to achieve high efficiency. However, a significantly increased amount of sub-modules in a MMC may increase the requirements for sensors and also increase the risk of failures. As a result, fault detection and diagnosis of MMC sub-modules are of great importance for continuous operation...... and post-fault maintenance. Therefore, in this paper, an effective fault diagnosis technique for real-time diagnosis of the switching device faults covering both the open-circuit faults and the short-circuit faults in MMC sub-modules is proposed, in which the faulty phase and the fault type is detected...
DEFF Research Database (Denmark)
Zhang, Yi; Wang, Huai; Wang, Zhongxu
2017-01-01
The reliability aspect study of Modular Multilevel Converter (MMC) is of great interest in industry applications, such as offshore wind. Lifetime prediction of key components is an important tool to design MMC with fulfilled reliability specifications. While many efforts have been made...... and electrical power modeling methods on the estimated lifetime of IGBT modules in an MMC for offshore wind power application. In a 30 MW MMC case study, an annual wind speed profile with a resolution of 1 s/data, 10 minute/data, and 1 hour/data are considered, respectively. A method to re-generate higher...... used in the MMC, resulting in significant differences. The study serves as a first step to quantify the impact of mission profile modeling on lifetime prediction, and to provide a guideline on mission profile collection for the presented application....
DEFF Research Database (Denmark)
Deng, Fujin; Chen, Zhe
2015-01-01
The modular multilevel converter (MMC) becomes attractive for medium- or high-power applications because of the advantages of high modularity, availability, and power quality. One of the technical challenges associated with an MMC is the balancing of the capacitors' voltages. In this paper......, a voltage-balancing control method is proposed for the MMC under phase-shifted carrier-based pulsewidth modulation. The proposed voltage-balancing method uses the linearization method for pulse sorting without arm current measurement, which can control the capacitor charge transfer to balance the capacitor...... voltage in the MMC. In the proposed method, the voltagebalancing algorithm is implemented in each carrier wave period, which reduces the computational intensity and burden. In addition, the arm current can also be improved with the proposed method. The simulation studies with the professional tool PSCAD...
DEFF Research Database (Denmark)
Isidori, Andrea; Rossi, Fabio Mario; Blaabjerg, Frede
2012-01-01
. Furthermore, the increment of the wind roughness class causes a larger dispersion of the mean values and the variation of the junction temperatures, also affecting the lifetime of the converter. Hence, the cycles lifetime largely decreases considering variable wind speed profile. In fact, the results show...... the dynamics of the system using different kinds of modulation strategies and analyzing different wind load conditions dependent on roughness classes. It is concluded that 60° discontinuous PWM modulation strategies show better thermal performance and increase the estimated lifetime of the converter...
DEFF Research Database (Denmark)
Isidori, Andrea; Rossi, Fabio Mario; Blaabjerg, Frede
2014-01-01
of the converter. Furthermore, the increment of the wind roughness class causes a larger dispersion of the mean values and the variation of the junction temperatures, which also affect the lifetime of the converter. Hence, the cycle lifetime largely decreases considering the variable-wind-speed profile. In fact...... of the system using different kinds of modulation strategies and analyzing the different wind-load conditions that are dependent on roughness classes. This paper shows that the 60 ° discontinuous pulsewidth-modulation strategies allow better thermal performance and increase the estimated lifetime...
Impact of modulation strategies on power devices loading for 10 MW multilevel wind power converter
DEFF Research Database (Denmark)
Blaabjerg, Frede; Isidori, Andrea; Rossi, Fabio Mario
2012-01-01
the dynamics of the system using different kinds of modulation strategies, identifying which methods can improve the converter efficiency. It is concluded that 60° discontinuous PWM modulation strategies show less power losses in the semiconductor devices and will increase the overall efficiency......This paper focuses on the control and modulation of a three-level Neutral Point Clamped (3L-NPC) back-to-back full scale converter for a 10 MW direct-drive wind turbine, equipped with a Permanent Magnet Synchronous Generator (PMSG). Emphasis is oriented towards the investigation of the power losses...
Correct-by-design Control Synthesis for Multilevel Converters using State Space Decomposition
Directory of Open Access Journals (Sweden)
Gilles Feld
2014-07-01
Full Text Available High-power converters based on elementary switching cells are more and more used in the industry of power electronics owing to various advantages such as lower voltage stress and reduced power loss. However, the complexity of controlling such converters is a major challenge that the power manufacturing industry has to face with. The synthesis of industrial switching controllers relies today on heuristic rules and empiric simulation. The state of the system is not guaranteed to stay within the limits that are admissible for its correct electrical behavior. We show here how to apply a formal method in order to synthesize a correct-by-design control that guarantees that the power converter will always stay within a predefined safe zone of variations for its input parameters. The method is applied in order to synthesize a correct-by-design control for 5-level and 7-level power converters with a flying capacitor topology. We check the validity of our approach by numerical simulations for 5 and 7 levels. We also perform physical experimentations using a prototype built by SATIE laboratory for 5 levels.
A novel double quad-inverter configuration for multilevel twelve-phase open-winding converter
DEFF Research Database (Denmark)
Padmanaban, Sanjeevi Kumar; Blaabjerg, Frede; Wheeler, Patrick William
2016-01-01
numerical simulation software's (Matlab/PLECS) developments. Further, the results confirm the good agreement to the developed theoretical background. Proposed converter suits the need of low-voltage/high-current applications such as ac tractions and `More-Electric Aircraft' propulsion systems....
DEFF Research Database (Denmark)
Wang, Songcen; Teodorescu, Remus; Máthé, Lászlo
2015-01-01
This paper focuses on modeling and SOC (State of Charge) balancing control of lithium-ion battery energy storage system based on cascaded multilevel converter for both grid integration and electric vehicle propulsion applications. The equivalent electrical circuit model of lithium-ion battery...
Directory of Open Access Journals (Sweden)
Yanbin Hou
2016-01-01
Full Text Available Compared with conventional Class-A, Class-B, and Class-AB amplifiers, Class-D amplifier, also known as switching amplifier, employs pulse width modulation (PWM technology and solid-state switching devices, capable of achieving much higher efficiency. However, PWM-based switching amplifier is usually designed for low-voltage application, offering a maximum output voltage of several hundred Volts. Therefore, a step-up transformer is indispensably adopted in PWM-based Class-D amplifier to produce high-voltage output. In this paper, a switching amplifier without step-up transformer is developed based on digital pulse step modulation (PSM and hybrid multilevel converter. Under the control of input signal, cascaded power converters with separate DC sources operate in PSM switch mode to directly generate high-voltage and high-power output. The relevant topological structure, operating principle, and design scheme are introduced. Finally, a prototype system is built, which can provide power up to 1400 Watts and peak voltage up to ±1700 Volts. And the performance, including efficiency, linearity, and distortion, is evaluated by experimental tests.
DEFF Research Database (Denmark)
Padmanaban, Sanjeevi Kumar; Hontz, Michael R.; Khanna, Raghav
2016-01-01
This article presents the developments of a novel isolated/non-isolated quad inverter configuration for multilevel dual six-phase (twelve-phase) star-winding converter. The modular circuit consists of four standard voltage source inverters (VSIs). Each VSI is incorporated with one bi-directional ...... systems, electrical vehicles, AC tractions, and `More-Electric Aircraft' propulsion systems....... converter is numerically modeled using Matlab/PLECS simulation software and the predicted behavior of the system is analyzed and presented. Good agreement is obtained between these results and the theoretical analysis. Suitable applications for the converter include (low-voltage/high-current) medium power...
Directory of Open Access Journals (Sweden)
Junhong Song
2018-01-01
Full Text Available A flexible group battery energy storage system (FGBESS based on cascaded multilevel converters is attractive for renewable power generation applications because of its high modularity and high power quality. However, reliability is one of the most important issues and the system may suffer from great financial loss after fault occurs. In this paper, based on conventional fundamental phase shift compensation and third harmonic injection, a hybrid compensation fault-tolerant method is proposed to improve the post-fault performance in the FGBESS. By adjusting initial phase offset and amplitude of injected component, the optimal third harmonic injection is generated in an asymmetric system under each faulty operation. Meanwhile, the optimal redundancy solution under each fault condition is also elaborated comprehensively with a comparison of the presented three fault-tolerant strategies. This takes full advantage of battery utilization and minimizes the loss of energy capacity. Finally, the effectiveness and feasibility of the proposed methods are verified by results obtained from simulations and a 10 kW experimental platform.
Directory of Open Access Journals (Sweden)
Hui Liu
2015-07-01
Full Text Available Due to the possibility of putting a large number of modules consisting of switches and capacitors connected in series, the modular multilevel converter (MMC can easily be scaled to high power and high voltage power conversion, which is an attractive feature for filter-less and transformer-less design and helpful to achieve high efficiency. However, a significantly increased amount of sub-modules in a MMC may increase the requirements for sensors and also increase the risk of failures. As a result, fault detection and diagnosis of MMC sub-modules are of great importance for continuous operation and post-fault maintenance. Therefore, in this paper, an effective fault diagnosis technique for real-time diagnosis of the switching device faults covering both the open-circuit faults and the short-circuit faults in MMC sub-modules is proposed, in which the faulty phase and the fault type is detected by analyzing the difference among the three output load currents, while the localization of the faulty switches is achieved by comparing the estimation results by the adaptive observer. In contrast to other methods that use additional sensors or devices, the presented technique uses the measured phase currents only, which are already available for MMC control. In additional, its operation, effectiveness and robustness are confirmed by simulation results under different operating conditions and load conditions.
Directory of Open Access Journals (Sweden)
Wen Wu
2017-11-01
Full Text Available A modular multilevel converter (MMC is considered to be a promising topology for medium- or high-power applications. However, a significantly increased amount of sub-modules (SMs in each arm also increase the risk of failures. Focusing on the fault-tolerant operation issue for the MMC under SM faults, the operation characteristics of MMC with different numbers of faulty SMs in the arms are analyzed and summarized in this paper. Based on the characteristics, a novel circulating current-suppressing (CCS fault-tolerant control strategy comprised of a basic control unit (BCU and virtual resistance compensation control unit (VRCCU in two parts is proposed, which has three main features: (i it can suppress the multi-different frequency components of the circulating current under different SM fault types simultaneously; (ii it can help fast limiting of the transient fault current caused at the faulty SM bypassed moment; and (iii it does not need extra communication systems to acquire the information of the number of faulty SMs. Moreover, by analyzing the stability performance of the proposed controller using the Root-Locus criterion, the election principle of the value of virtual resistance is revealed. Finally, the efficiency of the control strategy is confirmed with the simulation and experiment studies under different fault conditions.
Directory of Open Access Journals (Sweden)
Imen Ouerdani
2017-03-01
Full Text Available This paper focuses on the carrier disposition Pulse Width Modulation (PWM strategies for Modular Multilevel Converters (MMC. The authors propose a new Phase Opposition Disposition PWM (PODPWM scheme applicable regardless of the converter’s sub-modules number. Moreover, a capacitor voltage sorting algorithm is synthesized aiming to ensure the converter’s balanced operation. Simulation results of a 3.6 MVA, 3-SM-MMC are presented and discussed. In addition, a Hardware In the Loop (HIL validation of the proposed PODPWM has been made using Field Programmable Gate Array (FPGA target. The actual power system (the 3-SM-MMC and the 3-phase RL load is then replaced by its real-time emulator. The latter is interfaced to the PODPWM control under test and both are implemented and run altogether in the same Xilinx XC7Z020 Zynq FPGA device. The obtained real-time HIL emulation results are presented and compared to the offline simulation results.
Energy Technology Data Exchange (ETDEWEB)
Wu, Jinn-Chang [Department of Microelectronic Engineering, National Kaohsiung Marine University, No. 142, Haijhuan Rd., Kaohsiung (China); Wu, Kuen-Der; Jou, Hurng-Liahng; Xiao, Shun-Tian [Department of Electrical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung (China)
2011-02-15
This paper proposes a three-phase three-wire hybrid power filter configured by a three-phase passive power filter and a three-phase diode-clamped multi-level power converter with a small power capacity of zero-sequence current loop connected in series to compensate for the harmonic currents of nonlinear load. The salient feature is that a small power capacity of zero-sequence current loop is applied to overcome the problem of balancing voltages of two DC capacitors for a diode-clamped multi-level power converter applying in the three-phase three-wire hybrid power filter. A laboratory prototype is developed to verify the performance of the proposed three-phase three-wire hybrid power filter. The experimental results have demonstrated the feasibility and practicality of the proposed three-phase three-wire hybrid power filter. (author)
DC-DC Type High-Frequency Link DC for Improved Power Quality of Cascaded Multilevel Inverter
Sadikin, Muhammad; Senjyu, Tomonobu; Yona, Atsushi
2013-06-01
Multilevel inverters are emerging as a new breed of power converter options for power system applications. Recent advances in power switching devices enabled the suitability of multilevel inverters for high voltage and high power applications because they are connecting several devices in series without the need of component matching. Usually, a transformerless battery energy storage system, based on a cascaded multilevel inverter, is used as a measure for voltage and frequency deviations. System can be reduced in size, weight, and cost of energy storage system. High-frequency link circuit topology is advantageous in realizing compact and light-weight power converters for uninterruptible power supply systems, new energy systems using photovoltaic-cells, fuel-cells and so on. This paper presents a DC-DC type high-frequency link DC (HFLDC) cascaded multilevel inverter. Each converter cell is implemented a control strategy for two H-bridge inverters that are controlled with the same multicarrier pulse width modulation (PWM) technique. The proposed cascaded multilevel inverter generates lower voltage total harmonic distortion (THD) in comparison with conventional cascaded multilevel inverter. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of the proposed cascaded multilevel inverter.
DEFF Research Database (Denmark)
Liu, Hui; Loh, Poh Chiang; Blaabjerg, Frede
2015-01-01
by employing wavelet transform under different fault conditions. Then the fuzzy logic rules are automatically trained based on the fuzzified fault features to diagnose the different faults. Neither additional sensor nor the capacitor voltages are needed in the proposed method. The high accuracy, good...... for continuous operation and post-fault maintenance. In this article, a fault diagnosis technique is proposed for the short circuit fault in a modular multi-level converter sub-module using the wavelet transform and adaptive neuro fuzzy inference system. The fault features are extracted from output phase voltage...
Kontos, E.
2018-01-01
High Voltage DC (HVDC) grids provide an efficient solution for the transmission of bulk power over long distances between the energy production and consumption centers. Up to now, most of the implemented dc connections are point-to-point, creating dc links to strengthen the existing, predominantly ac, electricity grid. However, to optimize the use of assets and energy harvest, multi-terminal HVdc grids are envisioned. Based on recent research and industrial trends, the Multilevel Modular Conv...
H-Bridge Inverter denganBoost-up Chopper sebagai Pengondisi DayaPhotovoltaic
Directory of Open Access Journals (Sweden)
Suroso Suroso
2011-02-01
Full Text Available This paper discusses anapplication of H-bridge inverter equipped with boost-up chopper circuits as photovoltaic power conditioner in stand-alone operation. First, the boost-up chopper circuits working to regulate the DCoutput voltage of photovoltaic with proportional-integral (PI controller is described. Then, the H-bridge inverter converting the DC output voltage of chopper circuits become AC voltage waveform is presented. The uni-polar sinusoidal pulse-width modulation technique (SPWM is appliedto the inverter circuits to produce sinusoidal output current waveform. The simulation results of the proposed photovoltaic system for different output voltages, and transient voltage wave forms are presented in the paper. The results show that the boost-up chopper circuits is effective to be appliedin the photovoltaic system to obtain stable DC output voltage of the photovoltaic, and AC voltage waveform generated bythe inverter circuits.
Directory of Open Access Journals (Sweden)
Douglas T. kureve
2017-07-01
Full Text Available This research work focuses on developing an amplitude modulation index based equation that can predict the harmonic content in the conventional seven-level cascaded H-bridge multilevel inverter CHBMLI at low switching frequency. A logic circuit using phase opposition disposition pulse width modulation PODPWM scheme is used for the seven-level CHBMLI. The multilevel inverter MLI is simulated for amplitude modulation indices from 0.10 to 0.26.The simulated and calculated results of the harmonic content in the output voltage at amplitude modulation index of 0.20 produce minimum values of 16.61 and 13.00 respectively. The harmonic content from the amplitude modulation equation on average deviates from the simulated result by 2.74 . Simulation results are obtained using MATLABSIMULINK software.
Cao, Dong
Due the energy crisis and increased oil price, renewable energy sources such as photovoltaic panel, wind turbine, or thermoelectric generation module, are used more and more widely for vehicle and grid-connected applications. However, the output of these renewable energy sources varies according to different solar radiation, wind speed, or temperature difference, a power converter interface is required for the vehicle or grid-connected applications. Thermoelectric generation (TEG) module as a renewable energy source for automotive industry is becoming very popular recently. Because of the inherent characteristics of TEG modules, a low input voltage, high input current and high voltage gain dc-dc converters are needed for the automotive load. Traditional high voltage gain dc-dc converters are not suitable for automotive application in terms of size and high temperature operation. Switched-capacitor dc-dc converters have to be used for this application. However, high voltage spike and EMI problems exist in traditional switched-capacitor dc-dc converters. Huge capacitor banks have to be utilized to reduce the voltage ripple and achieve high efficiency. A series of zero current switching (ZCS) or zero voltage switching switched-capacitor dc-dc converters have been proposed to overcome the aforementioned problems of the traditional switched-capacitor dc-dc converters. By using the proposed soft-switching strategy, high voltage spike is reduced, high EMI noise is restricted, and the huge capacitor bank is eliminated. High efficiency, high power density and high temperature switched-capacitor dc-dc converters could be made for the TEG interface in vehicle applications. Several prototypes have been made to validate the proposed circuit and confirm the circuit operation. In order to apply PV panel for grid-connected application, a low cost dc-ac inverter interface is required. From the use of transformer and safety concern, two different solutions can be implemented, non
DEFF Research Database (Denmark)
Deng, Fujin; Chen, Zhe
2015-01-01
The modular multilevel converter (MMC) is attractive for medium- and high-power applications because of its high modularity, availability, and power quality. In this paper, the current ripple on the dc link of the three-phase MMC derived from the phase-shifted carrier-based pulse-width modulation...... scheme is analyzed. A control strategy is proposed for the current ripple elimination. Through the regulation of the phase-shifted angles of the carrier waves in the three phases of the MMC, the current ripple on the dc link of the three-phase MMC can be effectively eliminated. Simulations...... and experimental studies of the MMC were conducted, and the results confirm the effectiveness of the proposed current ripple elimination control....
Cascades of alternating pitchfork and flip bifurcations in H-bridge inverters
Avrutin, Viktor; Zhusubaliyev, Zhanybai T.; Mosekilde, Erik
2017-04-01
Power electronic DC/AC converters (inverters) play an important role in modern power engineering. These systems are also of considerable theoretical interest because their dynamics is influenced by the presence of two vastly different forcing frequencies. As a consequence, inverter systems may be modeled in terms of piecewise smooth maps with an extremely high number of switching manifolds. We have recently shown that models of this type can demonstrate a complicated bifurcation structure associated with the occurrence of border collisions. Considering the example of a PWM H-bridge single-phase inverter, the present paper discusses a number of unusual phenomena that can occur in piecewise smooth maps with a very large number of switching manifolds. We show in particular how smooth (pitchfork and flip) bifurcations may form a macroscopic pattern that stretches across the overall bifurcation structure. We explain the observed bifurcation phenomena, show under which conditions they occur, and describe them quantitatively by means of an analytic approximation.
A Back-to-Back 2L-3L Grid Integration of a Marine Current Energy Converter
Directory of Open Access Journals (Sweden)
Senad Apelfröjd
2015-01-01
Full Text Available The paper proposes a back-to-back 2L-3L grid connection topology for a marine current energy converter. A prototype marine current energy converter has been deployed by a research group at Uppsala University. The concept behind the prototype revolves around a fixed pitch vertical axis turbine directly connected to a permanent magnet synchronous generator (PMSG. The proposed grid connection system utilizes a well known and proven two level voltage source converter generator-side combined with a three-level cascaded H-bridge (CHB multilevel converter grid-side. The multilevel converter brings benefits in terms of efficiency, power quality and DC-link utilization. The system is here presented for a single marine current energy converter but can easily be scaled up for clusters of marine current energy converters. Control schemes for both grid-side and generator-side voltage source converters are presented. The start-up, steady state and dynamic performance of the marine current energy converter are investigated and simulation results are presented in this paper.
DEFF Research Database (Denmark)
Gohil, Ghanshyamsinh Vijaysinh; Wang, Huai; Liserre, Marco
2014-01-01
A method to selectively control the amount of dc link voltage ripple by processing desired reactive power by a DC/DC converter in isolated AC/DC or AC/DC/AC system is proposed. The concept can reduce the dc link capacitors used for balancing the input and output power and thereby limiting the vol...
DEFF Research Database (Denmark)
Behrouzian, Ehsan; Bongiorno, Massimo; Teodorescu, Remus
2017-01-01
The purpose of this paper is to investigate the impact of switching harmonics on the instantaneous power distribution in the cells of a cascaded H-bridge-based STATCOM when using phase-shifted pulse width modulation. The case of high- and low-switching frequency for the converter cells...... control loops. It is also shown that the selected frequency modulation ratio affects the active power distribution among the cells. In particular, the selection of a noninteger frequency modulation ratio helps in providing a more uniform power distribution among cells of the same phase leg, thus...
Modeling and Analysis of the Common Mode Voltage in a Cascaded H-Bridge Electronic Power Transformer
Directory of Open Access Journals (Sweden)
Yun Yang
2017-09-01
Full Text Available Electronic power transformers (EPTs have been identified as emerging intelligent electronic devices in the future smart grid, e.g., the Energy Internet, especially in the application of renewable energy conversion and management. Considering that the EPT is directly connected to the medium-voltage grid, e.g., a10 kV distribution system, and its cascaded H-bridges structure, the common mode voltage (CMV issue will be more complex and severe. The CMV will threaten the insulation of the entire EPT device and even produce common mode current. This paper investigates the generated mechanism and characteristics of the CMV in a cascaded H-bridge EPT (CHB-EPT under both balanced and fault grid conditions. First, the CHB-EPT system is introduced. Then, a three-phase simplified circuit model of the high-voltage side of the EPT system is presented. Combined with a unipolar modulation strategy and carrier phase shifting technology by rigorous mathematical analysis and derivation, the EPT internal CMV and its characteristics are obtained. Moreover, the influence of the sinusoidal pulse width modulation dead time is considered and discussed based on analytical calculation. Finally, the simulation results are provided to verify the validity of the aforementioned model and the analysis results. The proposed theoretical analysis method is also suitable for other similar cascaded converters and can provide a useful theoretical guide for structural design and power density optimization.
DEFF Research Database (Denmark)
Gao, Congzhe; Jiang, Xinjian; Li, Yongdong
2013-01-01
used traditional method; therefore, the system performance improvement and cost reduction are expected. Based on the proposed DCM2C, a novel N +1-level cascade multilevel topology is proposed for a cascade active power filter (CS-APF). The simulation and experimental results from the CS-APF have...
Energy Technology Data Exchange (ETDEWEB)
Filho, Faete J [ORNL; Tolbert, Leon M [ORNL; Ozpineci, Burak [ORNL
2012-01-01
The work developed here proposes a methodology for calculating switching angles for varying DC sources in a multilevel cascaded H-bridges converter. In this approach the required fundamental is achieved, the lower harmonics are minimized, and the system can be implemented in real time with low memory requirements. Genetic algorithm (GA) is the stochastic search method to find the solution for the set of equations where the input voltages are the known variables and the switching angles are the unknown variables. With the dataset generated by GA, an artificial neural network (ANN) is trained to store the solutions without excessive memory storage requirements. This trained ANN then senses the voltage of each cell and produces the switching angles in order to regulate the fundamental at 120 V and eliminate or minimize the low order harmonics while operating in real time.
Directory of Open Access Journals (Sweden)
HAMEDANI, P.
2016-08-01
Full Text Available Multicarrier based PWM switching patterns are commonly utilized to control Cascaded H-bridge (CHB inverters. The main contribution of this paper is to comprehensively investigate the effect of various multicarrier based PWM techniques on harmonic content of the CHB multilevel inverter. In order to achieve this, both of the CHB output voltage and the input current at power grid side have been taken into account. In this work, various PWM modulations such as level shifted (LS, phase shifted (PS, hybrid, and rotative-LS (R-LS have been studied through both simulation and implementation of an experimental setup. By extracting the frequency spectrum and calculation of THD and WTHD indices, a quantitative comparative study of various multicarrier PWM techniques has been carried out. According to the results, the R-LS-PWM methods (i.e. R-PD, and two new proposed R-POD and R-APOD reduce the harmonic distortion of the input current while keeping the obvious advantage of LS-PWM modulation such as lower harmonic distortion of the output voltage. Specially, the proposed R-APOD-PWM modulation offers these preferable privileges at odd frequency ratio values.
Comparison of bipolar sub-modules for the alternate arm converter
DEFF Research Database (Denmark)
Wickramasinghe, Harith R.; Konstantinou, Georgios; Pou, Josep
2016-01-01
Research on dc-fault tolerant multilevel converters has gained noticeable attention over recent years. The alternate arm converter (AAC) is one of such emerging multilevel converter topologies, and a hybrid topology of the two-level converter and the modular multilevel converter (MMC). Bipolar su...... in the losses, construction, and application to the AAC, compared to FB-SM....
Wang, Kun; Fu, Rongguo; Wang, Guiyuan; Tran, HongCam; Chang, BenKang; Yang, Liu
2017-11-01
A transmission mode AlxGa1-x As / GaAs photocathode consisting of a composition-graded window layer and an exponential-doping emission layer is proposed to improve the performance of photon-enhanced thermionic emission (PETE) solar energy converters. The theoretical model with this complex photocathode is deduced based on one-dimensional continuity equations to analyze the characteristics of the device. It is found the multilevel built-in electric fields can effectively enhance the conversion efficiency and response of the entire spectrum in contrast to other photocathode structures. Because of less heterojunction interface recombination losses and greater transport capacity of photoelectrons toward emissive surface. Moreover, the effect of Al proportion variation in the window layer and the thickness of the window layer and emission layer on performance is discussed. The model would provide theoretical guidance for better performance of PETE device.
Tekwani, P. N.; Shah, M. T.
2017-07-01
This paper presents behaviour analysis and digital implementation of current error space phasor based hysteresis controller applied to three-phase three-level flying capacitor converter as front-end topology. The controller is self-adaptive in nature, and takes the converter from three-level to two-level mode of operation and vice versa, following various trajectories of sector change with the change in reference dc-link voltage demanded by the load. It keeps current error space phasor within the prescribed hexagonal boundary. During the contingencies, the proposed controller takes the converter in over modulation mode to meet the load demand, and once the need is satisfied, controller brings back the converter in normal operating range. Simulation results are presented to validate behaviour of controller to meet the said contingencies. Unity power factor is assured by proposed controller with low current harmonic distortion satisfying limits prescribed in IEEE 519-2014. Proposed controller is implemented using TMS320LF2407 16-bit fixed-point digital signal processor. Detailed analysis of numerical format to avoid overflow of sensed variables in processor, and per-unit model implementation in software are discussed and hardware results are presented at various stages of signal conditioning to validate the experimental setup. Control logic for the generation of reference currents is implemented in TMS320LF2407A using assembly language and experimental results are also presented for the same.
Tekwani, P. N.; Shah, M. T.
2017-10-01
This paper presents behaviour analysis and digital implementation of current error space phasor based hysteresis controller applied to three-phase three-level flying capacitor converter as front-end topology. The controller is self-adaptive in nature, and takes the converter from three-level to two-level mode of operation and vice versa, following various trajectories of sector change with the change in reference dc-link voltage demanded by the load. It keeps current error space phasor within the prescribed hexagonal boundary. During the contingencies, the proposed controller takes the converter in over modulation mode to meet the load demand, and once the need is satisfied, controller brings back the converter in normal operating range. Simulation results are presented to validate behaviour of controller to meet the said contingencies. Unity power factor is assured by proposed controller with low current harmonic distortion satisfying limits prescribed in IEEE 519-2014. Proposed controller is implemented using TMS320LF2407 16-bit fixed-point digital signal processor. Detailed analysis of numerical format to avoid overflow of sensed variables in processor, and per-unit model implementation in software are discussed and hardware results are presented at various stages of signal conditioning to validate the experimental setup. Control logic for the generation of reference currents is implemented in TMS320LF2407A using assembly language and experimental results are also presented for the same.
Inoue, Shigenori; Maharjan, Laxman; Asakura, Jun; Akagi, Hirofumi
Renewable energy sources such as wind turbine generators and photovoltaics are intermittent in nature, thus resulting in fluctuating electric power. Leveling of their electric power is indispensable to realize large-scale renewable energy sources, and to avoid severe power quality problems when they are interconnected into the grid. A battery energy storage system (BESS), combining batteries with a power converter and digital control, should be installed in the vicinity of an intermittent energy source. The fluctuating power is compensated by appropriately controlling an active power stored in, or released from, the battery. This paper describes a 6.6-kV transformerless battery energy storage system based on a cascade multilevel PWM (pulse-width-modulation) converter, with focus on a control method for active power and SOC (state-of-charge) balancing. A down-scaled 200-V, 10-kW, 3.6-kWh (13-MJ) laboratory model using nine NiMH (Nickel Metal Hydride) battery packs is designed, constructed, and tested to verify the viability and effectiveness of the 6.6-kV system.
National Research Council Canada - National Science Library
Muxuan Xiao; Qianming Xu; Honglin Ouyang
2017-01-01
.... In this paper, the relationship between phase-shifted pulse width modulation (PWM) and phase disposition PWM is analyzed, and then an improved hybrid modulation strategy is proposed for cascaded H-bridge...
Multilevel Inverters for Electric Vehicle Applications
Energy Technology Data Exchange (ETDEWEB)
Habetler, T.G.; Peng, F.Z.; Tolbert, L.M.
1998-10-22
This paper presents multilevel inverters as an application for all-electric vehicle (EV) and hybrid-electric vehicle (HEV) motor drives. Diode-clamped inverters and cascaded H-bridge inverters, (1) can generate near-sinusoidal voltages with only fundamental frequency switching; (2) have almost no electromagnetic interference (EMI) and common-mode voltage; and (3) make an EV more accessible/safer and open wiring possible for most of an EV'S power system. This paper explores the benefits and discusses control schemes of the cascade inverter for use as an EV motor drive or a parallel HEV drive and the diode-clamped inverter as a series HEV motor drive. Analytical, simulated, and experimental results show the superiority of these multilevel inverters for this new niche.
High-power converters and AC drives
Wu, Bin
2017-01-01
This new edition reflects the recent technological advancements in the MV drive industry, such as advanced multilevel converters and drive configurations. It includes three new chapters, Control of Synchronous Motor Drives, Transformerless MV Drives, and Matrix Converter Fed Drives. In addition, there are extensively revised chapters on Multilevel Voltage Source Inverters and Voltage Source Inverter-Fed Drives. This book includes a systematic analysis on a variety of high-power multilevel converters, illustrates important concepts with simulations and experiments, introduces various megawatt drives produced by world leading drive manufacturers, and addresses practical problems and their mitigations methods.
H-Bridge Transformerless Inverter with Common Ground for Single-Phase Solar-Photovoltaic System
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede
2017-01-01
IGBT's (RB-IGBT) and two MOSFET's), a capacitor and a small filter at the output stage. The proposed topology share a common ground with the grid and the PV source. A Unipolar Sinusoidal Pulse-Width Modulation (SPWM) technique is used to modulate the inverter to minimize switching loss, output current...... ripple and filter requirements. The main advantages of the new inverter topology are the elimination of the leakage current and ability to provide reactive power to the grid. Further, the peak of output ac voltage is equal to input dc-voltage (unlike NPC and ANPC type which requires two times of the peak......This paper proposes a new single-phase H-Bridge transformerless inverter with common ground for grid-connected photovoltaic systems (hereafter it is called ‘Siwakoti-H’ inverter). The inverter works on the principle of flying capacitor and consists of only four power switches (two reverse blocking...
multilevel buck converter for automotive electrical load
African Journals Online (AJOL)
user
oil for the production and fueling of these vehicles, with challenges of oil production shortage due to increased pipeline vandalism, and ... The mass production of the hybrid electric (HE) and the electric vehicle (EV) is still awaited due to ... Figure 1: Functional block diagram of EV propulsion system [4]. This followed the ...
DEFF Research Database (Denmark)
Bhaskar, Mahajan Sagar; Sanjeevikumar, Padmanaban; Wheeler, Patrick
2016-01-01
A New breed of a buck boost converter, named as the XY converter family is proposed in this article. In the XY family, 16 topologies are presented which are highly suitable for renewable energy applications which require a high ratio of DC-DC converter; such as a photovoltaic multilevel inverter...... system, high voltage automotive applications and industrial drives. Compared to the traditional boost converter and existing recent converters, the proposed XY converter family has the ability to provide a higher output voltage by using less number of power devices and reactive components. Other distinct...... features of the XY converter family are i) Single control switch ii) Provide negative output voltage iii) Non-isolated topologies iv) High conversion ratio without making the use of high duty cycle and v) modular structure. XY family is compared with the recent high step-up converters and the detailed...
Highly-Efficient and Modular Medium-Voltage Converters
2015-09-28
of the modular multilevel converter based on si and sic switching devices for medium/high-voltage applications," IEEE Trans. Electron Devices, vol...4. TITLE AND SUBTITLE Highly-Efficient and Modula Medium-Voltage Converters 6. AUTHOR(S) Maryam Saeedifard 7. PERFORMING ORGANIZATIC i NAME(S...improving the converter’s efficiency and power density. 15. SUBJECT TERMS Modular Multilevel Converters , DC-DC Conversion, DC-AC Conversion 16
Matalata, Hendi; Hamid, Muh. Imran
2016-01-01
Multilevel inverter is a converter which converts the DC power source into an AC power source with a voltage output of more than two levels. Conventional multilevel inverter topology for the three levels developed at this time generally uses four components of the power switch. In this paper presented a three-level multilevel inverter topology by reducing the power switch components into two pieces and named as the type of diode clamped multilevel inverter three level one phase. Simulation wi...
Trübenekr, Jakub
2009-01-01
The Bachelor Thesis examines Multilevel marketing (abbreviated as 'MLM') as a business sector. The first aim of this study is to analyse the system of MLM within the company Oriflame and to measure to what extent the success of MLM is dependent on the duration of the seller's involvement in MLM and on the type of individual's character. Additionally, the thesis investigates whether it is possible to attain financial independence within Oriflame. The second goal is to find out what is the publ...
Passivity-Based Control by Series/Parallel Damping of Single-Phase PWM Voltage Source Converter
del Puerto Flores, Dunstano; Scherpen, Jacqueline; Liserre, Marco; de Vries, Martijn M. J.; Kransse, Marco J.; Monopoli, Vito Giuseppe
This paper describes a detailed design procedure for passivity-based controllers developed using the Brayton-Moser (BM) framework. Several passivity-based feedback designs are presented for the voltage-source converter, specifically for the H-bridge converter, since nowadays it is one of the
Variable-speed wind power system with improved energy capture via multilevel conversion
Erickson, Robert W.; Al-Naseem, Osama A.; Fingersh, Lee Jay
2005-05-31
A system and method for efficiently capturing electrical energy from a variable-speed generator are disclosed. The system includes a matrix converter using full-bridge, multilevel switch cells, in which semiconductor devices are clamped to a known constant DC voltage of a capacitor. The multilevel matrix converter is capable of generating multilevel voltage wave waveform of arbitrary magnitude and frequencies. The matrix converter can be controlled by using space vector modulation.
Neutral Point Clamped Npc Type Multilevel Inverter
Directory of Open Access Journals (Sweden)
Purohit Sadanand Chandrashekhar
2015-08-01
Full Text Available Concept of the multilevel inverter is same as the other inverter which is to converts Direct current DC to Alternating current AC .The inverted current can be at any vital voltage and frequency with the use of pertinent transformers switching and control circuits. From the source like batteries solar panel wind turbine or fuel cell the inverter will convert the DC electricity to AC electricity. In this modern technology Power electronics is very important where it used in a great variety of product. With the high potential in high power for industry multilevel inverter will become most popular for so many applications.
Reliability Evaluation of a Single-phase H-bridge Inverter with Integrated Active Power Decoupling
DEFF Research Database (Denmark)
Tang, Junchaojie; Wang, Haoran; Ma, Siyuan
2016-01-01
Various power decoupling methods have been proposed recently to replace the DC-link Electrolytic Capacitors (E-caps) in single-phase conversion system, in order to extend the lifetime and improve the reliability of the DC-link. However, it is still an open question whether the converter level...... reliability becomes better or not, since additional components are introduced and the loading of the existing components may be changed. This paper aims to study the converter level reliability of a single-phase full-bridge inverter with two kinds of active power decoupling module and to compare...... it with the traditional passive DC-link solution. The converter level reliability is obtained by component level electro-thermal stress modeling, lifetime model, Weibull distribution, and Reliability Block Diagram (RBD) method. The results are demonstrated by a 2 kW single-phase inverter application....
Energy Technology Data Exchange (ETDEWEB)
Martin, J.P.; Pierfederici, S.; Meibody-Tabar, F.; Davat, B. [Institut National Polytechnique Lorraine, Green INPL CNRS-UPRESA 7037 (France)
2000-07-01
In order to increase the reliability of 3-phase PMSM, we propose to supply each phase separately by H-bridge YSI. When one phase is disconnected, the two supply phases allow the system to work at reduced power but high torque undulation appears. By modifying the current waveform of only one supplied phase of the PMSM, we show that it is possible to filter the torque undulations, and the motor can generate almost half of the rated torque. The performances of this supplying structure are compared to the one of double star PMSM, which allow achieving the same degree of reliability. (authors)
DEFF Research Database (Denmark)
Rahul, Arun; Pramanick, Sumit; Kaarthik, R. Sudharshan
2017-01-01
In this paper, a new space vector pulse width modulation method to extend the linear modulation range of a cascaded five level inverter topology with a single dc supply is presented. Using this method, the inverter can be controlled linearly and the peak phase fundamental output voltage...... of the inverter can be increased from 0.577 to 0.637Vdc without increasing the dc bus voltage and without exceeding the induction motor voltage rating. This new technique makes use of cascaded inverter pole voltage redundancy and property of the space vector structure for its operation. Using this, the induction...... motor drive can be operated till the full speed range (0-50 Hz) with the elimination of lower order harmonics in the phase voltage and phase current. The five-level topology presented in this paper is realized by cascading a two-level inverter and two full bridge modules with floating capacitors...
Energy Technology Data Exchange (ETDEWEB)
Liber, B.
1991-08-22
A catalytic converter is provided which is economical to manufacture and is not readily poisoned by contaminants in a gas stream such as would be encountered in the operation of an internal combustion engine, whereby an improved life expectancy of the unit can be achieved. The converter of the invention comprises a sintered porous body including molybdenum or a molybdenum-containing compound or a molybdenum complex. A method of forming a catlytic converter unit comprises forming a slurry including molybdenum or a molybdenum compound, forming the slurry into a sintered body member, and hardening or curing the same to form a self-sustaining body member. A method for treating an exhaust gas using the above catalytic converter is also disclosed. A preferred embodiment for an internal combustion engine is described. Examples of different catalytic compositions are included. 13 figs.
Directory of Open Access Journals (Sweden)
Manel Hammami
2017-12-01
Full Text Available The implementation of maximum power point tracking (MPPT schemes by the ripple correlation control (RCC algorithm is presented in this paper. A reference is made to single-phase single-stage multilevel photovoltaic (PV generation systems, when the inverter input variables (PV voltage and PV current have multiple low-frequency (ripple harmonics. The harmonic analysis is carried out with reference to a multilevel configuration consisting of an H-bridge inverter and level doubling network (LDN cell, leading to the multilevel inverter having double the output voltage levels as compared to the basic H-bridge inverter topology (i.e., five levels vs. three levels. The LDN cell is basically a half-bridge fed by a floating capacitor, with self-balancing voltage capability. The multilevel configuration introduces additional PV voltage and current low-frequency harmonics, perturbing the basic implementation of the RCC scheme (based on the second harmonic component, leading to malfunctioning. The proposed RCC algorithm employs the PV current and voltage harmonics at a specific frequency for the estimation of the voltage derivative of power dP/dV (or dI/dV, driving the PV operating point toward the maximum power point (MPP in a faster and more precise manner. The steady-state and transient performances of the proposed RCC-MPPT schemes have been preliminarily tested and compared using MATLAB/Simulink. Results have been verified by experimental tests considering the whole multilevel PV generation system, including real PV modules, multilevel insulated-gate bipolar transistor (IGBT inverters, and utility grids.
Medium Voltage Three-level Converters for the Grid Connection of aMulti-MW Wind Turbine
DEFF Research Database (Denmark)
Senturk, Osman Selcuk; Helle, Lars; Munk-Nielsen, Stig
2009-01-01
Three-level (3L) neutral point clamped (NPC), flying capacitor (FC), and H-bridge (HB) voltage source converters (VSCs) as a grid-side full-scale medium voltage (MV) converter are modeled, controlled, and simulated for the grid connection of a hypothetical 6MW wind turbine. Via the converter...... topological features and the simulation results demonstrating the converter performance, these three 3L-VSCs are discussed and compared in terms of power density and reliability, which can be considered as two of the most important criteria for the converters placed in wind turbine nacelles. Given the grid...
Medium voltage three-level converters for the grid connection of a multi-MW wind turbine
DEFF Research Database (Denmark)
Senturk, Osman Selcuk; Helle, Lars; Munk-Nielsen, Stig
2009-01-01
Three-level (3L) neutral point clamped (NPC), flying capacitor (FC), and H-bridge (HB) voltage source converters (VSCs) as a grid-side full-scale medium voltage (MV) converter are modeled, controlled, and simulated for the grid connection of a hypothetical 6MW wind turbine. Via the converter...... topological features and the simulation results demonstrating the converter performance, these three 3L-VSCs are discussed and compared in terms of power density and reliability, which can be considered as two of the most important criteria for the converters placed in wind turbine nacelles. Given the grid...
Design of current source DC/DC converter and inverter for 2kW fuel cell application
DEFF Research Database (Denmark)
Andreiciks, A.; Steiks, I.; Krievs, O.
2013-01-01
In order to use hydrogen fuel cell in domestic applications either as main power supply or backup power source, the low DC output voltage of the fuel cell has to be matched to the voltage level and frequency of the utility grid AC voltage. The interfacing power converter systems usually consist...... of a DC/DC converter and an inverter. In this paper a detailed simulation study of such interfacing converter system comprising a double inductor push-pull step-up DC/DC converter and a cascaded H-bridge inverter has been carried out and further confirmed with experimental results. The power converter...
Disain SPWM Multilevel Inverter Satu Fasa Lima Belas Level
Directory of Open Access Journals (Sweden)
Effendi Effendi
2016-08-01
Full Text Available Fifteen level single phase multilevel inverter is constructed using power circuit consist of 7 MOSFETs, seven independents DC sources, seven diodes, and an H-Bridge circuit. Switching method used in this MLI is sinusoidal pulse width modulation (SPWM multicarrier where the reference wave in the form of a sinusoidal wave. Multicarrier SPWM circuit is designed using electronic components such as Op-Amp that used as a comparator and some logic gates such as AND, OR and NOT gate to trigger S1, S2, S3, S4, S5, S6, S7, and H-Bridge circuit. Carrier waves used in this MLI modified from the triangle wave that having a frequency into carrier waves without frequency (DC sources where THD that generated into 5.502%. While methods that use frequency such as Phase Disposition PWM (PD PWM, Phase Shift PWM (PS-PWM, and Carrier Overlapping PWM (CO PWM that produces THD greater than the proposed method, this system was simulated using PSIM software.
Schinkel, Daniel; Nuijten, Petrus A.C.M.
2005-01-01
A data converter comprises a discrete- time sigma delta modulator e.g. for driving a Class-D power amplifier. The low-pass filter of the sigma delta modulator is modified by adding a suitably positioned pole to lower the oscillation frequency (limit cycle) of the sigma delta modulator in order to
Schinkel, Daniel
2005-01-01
A data converter comprises a discrete-time sigma delta modulator e.g. for driving a Class-D power amplifier. The low-pass filter of the sigma delta modulator is modified by adding a suitably positioned pole to lower the oscillation frequency (limit cycle) of the sigma delta modulator in order to
Schinkel, Daniel
2006-01-01
A data converter comprises a discrete-time sigma delta modulator e.g. for driving a Class-D power amplifier. The low-pass filter of the sigma delta modulator is modified by adding a suitably positioned pole to lower the oscillation frequency (limit cycle) of the sigma delta modulator in order to
DEFF Research Database (Denmark)
Kloch, Allan; Hansen, Peter Bukhave; Wolfson, David
1999-01-01
. It is predicted that jitter accumulation can be minimised by using a 9-10 dB ratio between the signal and CW power also assuring a high extinction ratio. Using this guideline simulations show that 20 cross-gain modulation converters can be cascaded at 10 Gbit/s with only ~20 ps of accumulated jitter...... and an extinction ratio of ~10 dB.The regenerative capabilities of the cross-phase converters are described and verified experimentally at 20 Gbit/s, where the noise redistribution and improvement of the signal-to-noise ratio clearly is demonstrated by controlling the input power to an EDFA. In a similar experiment...... at 2.5 Gbit/s, the regeneration causes a reduction of the required input power to an in-line EDFA of ~6 dB for a power penalty of 1 dB at a bit error rate of 10-9. If two converters are concatenated the power requirement is reduced ~8 dB. Obviously, the power reduction allows for longer spans between...
Multilevel ensemble Kalman filter
Chernov, Alexey
2016-01-06
This work embeds a multilevel Monte Carlo (MLMC) sampling strategy into the Monte Carlo step of the ensemble Kalman filter (EnKF). In terms of computational cost vs. approximation error the asymptotic performance of the multilevel ensemble Kalman filter (MLEnKF) is superior to the EnKF s.
Multilevel Mixture Factor Models
Varriale, Roberta; Vermunt, Jeroen K.
2012-01-01
Factor analysis is a statistical method for describing the associations among sets of observed variables in terms of a small number of underlying continuous latent variables. Various authors have proposed multilevel extensions of the factor model for the analysis of data sets with a hierarchical structure. These Multilevel Factor Models (MFMs)…
Grid Converters for Stationary Battery Energy Storage Systems
DEFF Research Database (Denmark)
Trintis, Ionut
to hours, rated at MW and MWh, battery energy storage systems are suitable and ecient solutions. Grid connection of the storage system can be done at dierent voltage levels, depending on the location and application scenario. For high power and energy ratings, increase in the battery and converter voltage...... was realized for a 100 kW active rectier to be used in a 6 kV battery energy storage test bench. In the second part, dierent solutions for power converters to interface energy storage units to medium voltage grid are given. A new modular multilevel converter concept is introduced, where the energy storage......-voltage 100 kW bidirectional grid converter, to be used in a high voltage battery energy storage test bench. The control structure proved to be stable without damping. The converter was tested in the test bench and the experimental results are presented. Multilevel converters are replacing the classical two...
Energy Technology Data Exchange (ETDEWEB)
Howson, R.E.
1988-08-23
This patent describes a convertible barge, comprising: a. a deck; b. modules positioned on the deck in end to end relation and at least some of which contain pipeline processing equipment. The modules being removably attached to the deck, each module comprising a floor, ceiling, and a pair of side walls extending longitudinally of the barge between the ends; and c. means defining a closable opening comprising a roll-up door in at least one end of the modules for passing a pipeline portion from the module to a respectively adjacent module as the pipeline is being processed, for sealing the module during storage and for providing passageways between the modules and a view of pipe laying operations during use. A method for converting a barge to a lay barge, comprising: a. positioning on a deck of the barge in end to end relation of modules each of which has a floor, ceiling, and a pair of sidewalls extending longitudinally of the barge between the ends; b. providing pipeline process stations in at least some of the modules; c. removably attaching the modules to the deck; and d. providing a roll-up door in at least one of the modules ends of each module for passing a pipeline portion from the module to a respectively adjacent module as the pipeline is being processed and for providing passageways between the modules and a view of pipe laying operations during use.
Analysis of Harmonic Injection to the Modulation of Multi-Level ...
African Journals Online (AJOL)
This paper explores the analysis of third and ninth harmonic injection to the modulation of a multilevel diode clamped converter (DCC) at a varying modulation index. The spectral distributions of the various multi-level waveforms obtained under normal modulation index of 0.8 and over modulation index of 1.15 were ...
Space Vector Pulse Width Modulation of a Multi-Level Diode ...
African Journals Online (AJOL)
Space Vector Pulse Width Modulation of a Multi-Level Diode Clamped Converter with Experimental Verification. ... This paper used generic on-time application method to realize the application time for the zero vector and two adjacent active vectors in determining the switching process of the multilevel DCC, quite unlike the ...
Multilevel ensemble Kalman filtering
Hoel, Hakon
2016-06-14
This work embeds a multilevel Monte Carlo sampling strategy into the Monte Carlo step of the ensemble Kalman filter (EnKF) in the setting of finite dimensional signal evolution and noisy discrete-time observations. The signal dynamics is assumed to be governed by a stochastic differential equation (SDE), and a hierarchy of time grids is introduced for multilevel numerical integration of that SDE. The resulting multilevel EnKF is proved to asymptotically outperform EnKF in terms of computational cost versus approximation accuracy. The theoretical results are illustrated numerically.
Fault diagnosis method based on FFT-RPCA-SVM for Cascaded-Multilevel Inverter.
Wang, Tianzhen; Qi, Jie; Xu, Hao; Wang, Yide; Liu, Lei; Gao, Diju
2016-01-01
Thanks to reduced switch stress, high quality of load wave, easy packaging and good extensibility, the cascaded H-bridge multilevel inverter is widely used in wind power system. To guarantee stable operation of system, a new fault diagnosis method, based on Fast Fourier Transform (FFT), Relative Principle Component Analysis (RPCA) and Support Vector Machine (SVM), is proposed for H-bridge multilevel inverter. To avoid the influence of load variation on fault diagnosis, the output voltages of the inverter is chosen as the fault characteristic signals. To shorten the time of diagnosis and improve the diagnostic accuracy, the main features of the fault characteristic signals are extracted by FFT. To further reduce the training time of SVM, the feature vector is reduced based on RPCA that can get a lower dimensional feature space. The fault classifier is constructed via SVM. An experimental prototype of the inverter is built to test the proposed method. Compared to other fault diagnosis methods, the experimental results demonstrate the high accuracy and efficiency of the proposed method. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.
Five-Level Converter with Low Switching Frequency Applied as DC Voltage Supply
DEFF Research Database (Denmark)
Rasmussen, Tonny Wederberg
1999-01-01
This paper describes the use of a multi-level converter as a DC supply. Equations for the converter will be deduced in the nondissipative case. The equations provide solutions to DC voltage and the angle of converter voltage. In addition the spectrum for the harmonics after the elimination...
1978-01-01
Air flotation technology used in NASA's Apollo program has found an interesting application in Hawaii's Aloha Stadium near Honolulu. The stadium's configuration can be changed, by moving entire 7,000-seat sections on a cushion of air, for best accommodation of spectators and participants at different types of events. In most stadiums, only a few hundred seats can be moved, by rolling sections on wheels or rails. At Aloha Stadium, 28,000 of the 50,000 seats can be repositioned for better spectator viewing and, additionally, for improved playing conditions. For example, a stadium designed primarily for football may compromise the baseball diamond by providing only a shallow outfield. Aloha's convertibility allows a full-size baseball field as well as optimum configurations for many other types of sports and special events. The photos show examples. The stadium owes its versatility to air flotation technology developed by General Motors. Its first large-scale application was movement of huge segments of the mammoth Saturn V moonbooster during assembly operations at Marshall Space Flight Center.
Multilevel Mixture Kalman Filter
Directory of Open Access Journals (Sweden)
Xiaodong Wang
2004-11-01
Full Text Available The mixture Kalman filter is a general sequential Monte Carlo technique for conditional linear dynamic systems. It generates samples of some indicator variables recursively based on sequential importance sampling (SIS and integrates out the linear and Gaussian state variables conditioned on these indicators. Due to the marginalization process, the complexity of the mixture Kalman filter is quite high if the dimension of the indicator sampling space is high. In this paper, we address this difficulty by developing a new Monte Carlo sampling scheme, namely, the multilevel mixture Kalman filter. The basic idea is to make use of the multilevel or hierarchical structure of the space from which the indicator variables take values. That is, we draw samples in a multilevel fashion, beginning with sampling from the highest-level sampling space and then draw samples from the associate subspace of the newly drawn samples in a lower-level sampling space, until reaching the desired sampling space. Such a multilevel sampling scheme can be used in conjunction with the delayed estimation method, such as the delayed-sample method, resulting in delayed multilevel mixture Kalman filter. Examples in wireless communication, specifically the coherent and noncoherent 16-QAM over flat-fading channels, are provided to demonstrate the performance of the proposed multilevel mixture Kalman filter.
Metal complex modified azo polymers for multilevel organic memories
Ma, Yong; Chen, Hong-Xia; Zhou, Feng; Li, Hua; Dong, Huilong; Li, You-Yong; Hu, Zhi-Jun; Xu, Qing-Feng; Lu, Jian-Mei
2015-04-01
Multilevel organic memories have attracted considerable interest due to their high capacity of data storage. Despite advances, the search for multilevel memory materials still remains a formidable challenge. Herein, we present a rational design and synthesis of a class of polymers containing an azobenzene-pyridine group (PAzo-py) and its derivatives, for multilevel organic memory storage. In this design, a metal complex (M(Phen)Cl2, M = Cu, Pd) is employed to modify the HOMO-LUMO energy levels of azo polymers, thereby converting the memory state from binary to ternary. More importantly, this approach enables modulating the energy levels of azo polymers by varying the coordination metal ions. This makes the achievement of high performance multilevel memories possible. The ability to tune the bandgap energy of azo polymers provides new exciting opportunities to develop new materials for high-density data storage.Multilevel organic memories have attracted considerable interest due to their high capacity of data storage. Despite advances, the search for multilevel memory materials still remains a formidable challenge. Herein, we present a rational design and synthesis of a class of polymers containing an azobenzene-pyridine group (PAzo-py) and its derivatives, for multilevel organic memory storage. In this design, a metal complex (M(Phen)Cl2, M = Cu, Pd) is employed to modify the HOMO-LUMO energy levels of azo polymers, thereby converting the memory state from binary to ternary. More importantly, this approach enables modulating the energy levels of azo polymers by varying the coordination metal ions. This makes the achievement of high performance multilevel memories possible. The ability to tune the bandgap energy of azo polymers provides new exciting opportunities to develop new materials for high-density data storage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00871a
A Comparative Modelling Study of PWM Control Techniques for Multilevel Cascaded Inverter
Directory of Open Access Journals (Sweden)
A. TAHRI
2005-01-01
Full Text Available The emergence of multilevel converters has been in increase since the last decade. These new types of converters are suitable for high voltage and high power application due to their ability to synthesize waveforms with better harmonic spectrum. Numerous topologies have been introduced and widely studied for utility and drive applications. Amongst these topologies, the multilevel cascaded inverter was introduced in Static Var compensation and drive systems. This paper investigates several control techniques applied to the Multilevel Cascaded Inverter in order to ensure an efficient voltage utilization and better harmonic spectrum. A modelling and control strategy of a single phase Multilevel Cascaded Inverter is also investigated. Computer simulation results using Matlab program are reported and discussed together with a comparative study of the different control techniques of multilevel cascaded inverter.Moreover, experimental results are carried out on a scaled down prototype to prove the effectiveness of the proposed analysis.
Multilevel corporate environmental responsibility.
Karassin, Orr; Bar-Haim, Aviad
2016-12-01
The multilevel empirical study of the antecedents of corporate social responsibility (CSR) has been identified as "the first knowledge gap" in CSR research. Based on an extensive literature review, the present study outlines a conceptual multilevel model of CSR, then designs and empirically validates an operational multilevel model of the principal driving factors affecting corporate environmental responsibility (CER), as a measure of CSR. Both conceptual and operational models incorporate three levels of analysis: institutional, organizational, and individual. The multilevel nature of the design allows for the assessment of the relative importance of the levels and of their components in the achievement of CER. Unweighted least squares (ULS) regression analysis reveals that the institutional-level variables have medium relationships with CER, some variables having a negative effect. The organizational level is revealed as having strong and positive significant relationships with CER, with organizational culture and managers' attitudes and behaviors as significant driving forces. The study demonstrates the importance of multilevel analysis in improving the understanding of CSR drivers, relative to single level models, even if the significance of specific drivers and levels may vary by context. Copyright © 2016 Elsevier Ltd. All rights reserved.
Practical Marginalized Multilevel Models
Griswold, Michael E.; Swihart, Bruce J.; Caffo, Brian S.; Zeger, Scott L.
2013-01-01
Clustered data analysis is characterized by the need to describe both systematic variation in a mean model and cluster-dependent random variation in an association model. Marginalized multilevel models embrace the robustness and interpretations of a marginal mean model, while retaining the likelihood inference capabilities and flexible dependence structures of a conditional association model. Although there has been increasing recognition of the attractiveness of marginalized multilevel models, there has been a gap in their practical application arising from a lack of readily available estimation procedures. We extend the marginalized multilevel model to allow for nonlinear functions in both the mean and association aspects. We then formulate marginal models through conditional specifications to facilitate estimation with mixed model computational solutions already in place. We illustrate the MMM and approximate MMM approaches on a cerebrovascular deficiency crossover trial using SAS and an epidemiological study on race and visual impairment using R. Datasets, SAS and R code are included as supplemental materials. PMID:24357884
Handbook of multilevel analysis
National Research Council Canada - National Science Library
Leeuw, Jan de; Meijer, Erik
2008-01-01
... appropriate and eﬃcient model-based methods have become available to deal with this issue, that we have come to appreciate the power that more complex models provide for describing the world and providing new insights. This book sets out to present some of the most recent developments in what has come to be known as multilevel modelling. An...
Nine Level Inverter with Boost Converter from Renewable Energy Source
Directory of Open Access Journals (Sweden)
Maruthu Pandiyan.R
2015-01-01
Full Text Available A new single phase nine level multilevel inverter is proposed. The input to the proposed nine level multilevel inverter is obtained from solar panel . The solar energy obtained from the solar panel is not constant and it varies with times. In order to maintain the constant voltage obtained from the solar panel the boost converter is used to maintain the constant output voltage using MPPT ( Perturb and observe algorithm algorithm. Then the buck boost converter output voltage is stored in the battery bank. Finally the battery energy is connected to the 9 level inverter circuits. The harmonics in the inverter is eliminated by using the fuzzy logic controller. The gate pulse for the multilevel inverter is given by the fuzzy logic controller which in turn reduces the harmonics in the inverter. Then the inverter output is connected to the grid are some application.
Indian Academy of Sciences (India)
The structures presented above are based on three—phase converter units. This is the nat- ural choice for three phase systems. However, implementations-based on single~phase converters of the voltage source type have been proposed, ﬁgure 11 (Lai & Peng 1996;. ' Peng & Lai 1996). Advantages include: (i) modularity ...
Directory of Open Access Journals (Sweden)
Mechouma Rabiaa
2014-01-01
Full Text Available In recent years, power demand of industrial applications has increased significantly reaching some megawatts. The use of multilevel converters for applications of medium and high powers is proposed as a solution to drawback semiconductor technology. A multilevel converter not only achieves high power ratings, but also enables the use of renewable energy sources. Renewable energy sources such as photovoltaic can be easily interfaced to a multilevel converter system for a high power application. This paper presents the simulation study in Matlab/Simulink of a grid connected photovoltaic three phase Neutral Point Clamped (NPC inverter with DC/DC boost converter for constant and variable solar radiation.
Law, Kody
2016-01-06
This talk will pertain to the filtering of partially observed diffusions, with discrete-time observations. It is assumed that only biased approximations of the diffusion can be obtained, for choice of an accuracy parameter indexed by l. A multilevel estimator is proposed, consisting of a telescopic sum of increment estimators associated to the successive levels. The work associated to O( 2) mean-square error between the multilevel estimator and average with respect to the filtering distribution is shown to scale optimally, for example as O( 2) for optimal rates of convergence of the underlying diffusion approximation. The method is illustrated on some toy examples as well as estimation of interest rate based on real S&P 500 stock price data.
Multilevel Interventions: Measurement and Measures
Charns, Martin P.; Alligood, Elaine C.; Benzer, Justin K.; Burgess, James F.; Mcintosh, Nathalie M.; Burness, Allison; Partin, Melissa R.; Clauser, Steven B.
2012-01-01
Background Multilevel intervention research holds the promise of more accurately representing real-life situations and, thus, with proper research design and measurement approaches, facilitating effective and efficient resolution of health-care system challenges. However, taking a multilevel approach to cancer care interventions creates both measurement challenges and opportunities. Methods One-thousand seventy two cancer care articles from 2005 to 2010 were reviewed to examine the state of measurement in the multilevel intervention cancer care literature. Ultimately, 234 multilevel articles, 40 involving cancer care interventions, were identified. Additionally, literature from health services, social psychology, and organizational behavior was reviewed to identify measures that might be useful in multilevel intervention research. Results The vast majority of measures used in multilevel cancer intervention studies were individual level measures. Group-, organization-, and community-level measures were rarely used. Discussion of the independence, validity, and reliability of measures was scant. Discussion Measurement issues may be especially complex when conducting multilevel intervention research. Measurement considerations that are associated with multilevel intervention research include those related to independence, reliability, validity, sample size, and power. Furthermore, multilevel intervention research requires identification of key constructs and measures by level and consideration of interactions within and across levels. Thus, multilevel intervention research benefits from thoughtful theory-driven planning and design, an interdisciplinary approach, and mixed methods measurement and analysis. PMID:22623598
Multilevel ensemble Kalman filtering
Hoel, Haakon
2016-01-08
The ensemble Kalman filter (EnKF) is a sequential filtering method that uses an ensemble of particle paths to estimate the means and covariances required by the Kalman filter by the use of sample moments, i.e., the Monte Carlo method. EnKF is often both robust and efficient, but its performance may suffer in settings where the computational cost of accurate simulations of particles is high. The multilevel Monte Carlo method (MLMC) is an extension of classical Monte Carlo methods which by sampling stochastic realizations on a hierarchy of resolutions may reduce the computational cost of moment approximations by orders of magnitude. In this work we have combined the ideas of MLMC and EnKF to construct the multilevel ensemble Kalman filter (MLEnKF) for the setting of finite dimensional state and observation spaces. The main ideas of this method is to compute particle paths on a hierarchy of resolutions and to apply multilevel estimators on the ensemble hierarchy of particles to compute Kalman filter means and covariances. Theoretical results and a numerical study of the performance gains of MLEnKF over EnKF will be presented. Some ideas on the extension of MLEnKF to settings with infinite dimensional state spaces will also be presented.
Five-Level Active-Neutral-Point-Clamped DC/DC Converter
DEFF Research Database (Denmark)
Liu, Dong; Deng, Fujin; Chen, Zhe
2016-01-01
Multi-level converters are getting more and more attentions because of their obvious merits such as lower voltage stress and harmonic, smaller size of output filters, and so on. In this paper, a five-level active-neutral-point-clamped (5L-ANPC) dc/dc converter is proposed for power transfer...
Triphase Cascaded Converters with Direct Synchronous Pulswidth Modulation
DEFF Research Database (Denmark)
Oleschuk, V.; Blaabjerg, Frede; Bose, B. K.
2002-01-01
A novel method of direct synchronous pulse-width modulation (PWM) is applied for control of modular multilevel converters consisting from three standard triphase inverter modules along with an 0.33 p.u. output transformer. The proposed method provides synchronisation of the voltage waveforms...... for both each module and the composed voltage at the output of the converter. Multilevel output voltage of the converter has quarter-wave symmetry during the whole range including the zone of overmodulation. Both continuous and discontinuous versions of synchronous PWM, based on a vector approach...... for determination of the pulse patterns, have been analysed and compared using simulations of the systems with low switching frequencies, which normally are used in high power systems....
Multilevel models applications using SAS
Wang, Jichuan; Fisher, James F
2011-01-01
This book covers a broad range of topics about multilevel modeling. The goal is to help readers to understand the basic concepts, theoretical frameworks, and application methods of multilevel modeling. It is at a level also accessible to non-mathematicians, focusing on the methods and applications of various multilevel models and using the widely used statistical software SAS®. Examples are drawn from analysis of real-world research data.
Utilizing zero-sequence switchings for reversible converters
Hsu, John S.; Su, Gui-Jia; Adams, Donald J.; Nagashima, James M.; Stancu, Constantin; Carlson, Douglas S.; Smith, Gregory S.
2004-12-14
A method for providing additional dc inputs or outputs (49, 59) from a dc-to-ac inverter (10) for controlling motor loads (60) comprises deriving zero-sequence components (V.sub.ao, V.sub.bo, and V.sub.co) from the inverter (10) through additional circuit branches with power switching devices (23, 44, 46), transforming the voltage between a high voltage and a low voltage using a transformer or motor (42, 50), converting the low voltage between ac and dc using a rectifier (41, 51) or an H-bridge (61), and providing at least one low voltage dc input or output (49, 59). The transformation of the ac voltage may be either single phase or three phase. Where less than a 100% duty cycle is acceptable, a two-phase modulation of the switching signals controlling the inverter (10) reduces switching losses in the inverter (10). A plurality of circuits for carrying out the invention are also disclosed.
A Grid-Connected Multilevel Current Source Inverter and Its Protection for Grid-Disconnection
Nimrod Vázquez; Luz del Carmen García; Claudia Hernández; Eslí Vázquez; Héctor López; Ilse Cervantes; Juan Iturria
2013-01-01
Traditionally DC-AC converters are considered with voltage source inverters (VSI); although less studied and discussed, it has started recently to be used current source inverters (CSI). Another possibility for DC/AC conversion is the multilevel configuration. This paper shows experimental operation and simulation analysis of a grid-connected multilevel current source inverter (MCSI), which includes a circuit for equipment safety reasons due to grid disconnections.
Characterizing Genuine Multilevel Entanglement
Kraft, Tristan; Ritz, Christina; Brunner, Nicolas; Huber, Marcus; Gühne, Otfried
2018-02-01
Entanglement of high-dimensional quantum systems has become increasingly important for quantum communication and experimental tests of nonlocality. However, many effects of high-dimensional entanglement can be simulated by using multiple copies of low-dimensional systems. We present a general theory to characterize those high-dimensional quantum states for which the correlations cannot simply be simulated by low-dimensional systems. Our approach leads to general criteria for detecting multilevel entanglement in multiparticle quantum states, which can be used to verify these phenomena experimentally.
DEFF Research Database (Denmark)
Bruni, Luis Emilio; Giorgi, Franco
2016-01-01
the importance of this fundamental difference in order to explain how levels, domains and orders of magnitude, on one hand, and synchronic and diachronic processes, on the other, contribute to the overall organization of every living being. To account for such multi-level organization, semiotic freedom...... is assumed to be a scalar property that endows living systems at different levels and domains with the capacity to ponder selectively the overall structural coherence and functional compatibility of their heterarchical processing, which is increasingly less conditioned by the underlying molecular determinism....
Wavelength converter technology
DEFF Research Database (Denmark)
Kloch, Allan; Hansen, Peter Bukhave; Poulsen, Henrik Nørskov
1999-01-01
Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on all-optical wavelength converter types based on semiconductor optical amplifiers.......Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on all-optical wavelength converter types based on semiconductor optical amplifiers....
Wavelength converter technology
DEFF Research Database (Denmark)
Kloch, Allan; Hansen, Peter Bukhave; Poulsen, Henrik Nørskov
1999-01-01
Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on air-optical wavelength converter types based on semiconductor optical amplifiers.......Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on air-optical wavelength converter types based on semiconductor optical amplifiers....
Technologies for converter topologies
Zhou, Yan; Zhang, Haiyu
2017-02-28
In some embodiments of the disclosed inverter topologies, an inverter may include a full bridge LLC resonant converter, a first boost converter, and a second boost converter. In such embodiments, the first and second boost converters operate in an interleaved manner. In other disclosed embodiments, the inverter may include a half-bridge inverter circuit, a resonant circuit, a capacitor divider circuit, and a transformer.
Power Converters for Accelerators
Visintini, R.
2015-06-15
Particle accelerators use a great variety of power converters for energizing their sub-systems; while the total number of power converters usually depends on the size of the accelerator or combination of accelerators (including the experimental setup), the characteristics of power converters depend on their loads and on the particle physics requirements: this paper aims to provide an overview of the magnet power converters in use in several facilities worldwide.
Multilevel Modeling of Social Segregation
Leckie, George; Pillinger, Rebecca; Jones, Kelvyn; Goldstein, Harvey
2012-01-01
The traditional approach to measuring segregation is based upon descriptive, non-model-based indices. A recently proposed alternative is multilevel modeling. The authors further develop the argument for a multilevel modeling approach by first describing and expanding upon its notable advantages, which include an ability to model segregation at a…
Power converters definitions, classification and converter topologies
Bordry, Frederick
2006-01-01
This paper introduces power conversion principles and defines the terminology. The concepts of sources and switches are defined and classified. From the basic laws of source interconnections, a generic method of power converter synthesis is presented. Some examples illustrate this systematic method. Finally, the notions of commutation cell and soft commutation are introduced and discussed.
Ali, Ahmed MA
2016-01-01
This book covers high speed data converters from the perspective of a leading high speed ADC designer and architect, with a strong emphasis on high speed Nyquist A/D converters. For our purposes, the term 'high speed' is defined as sampling rates that are greater than 10 MS/s.
Ferreira, J.A.
2014-01-01
Electrical power converter for converting electrical power of a power source connected or connectable at an input to electrical DC-power at an output, wherein between the input and the output a first circuit of submodules is provided, wherein said first circuit of submodules and the power source
Westra, Jan R.; Annema, Anne J.; van den Boom, Jeroen M.; Dijkmans, Eise C.
2001-01-01
A digital to analog converter (DAC) for converting a digital signal (DS) having a maximum voltage range which corresponds to a first supply voltage (UL) into an analog signal (UOUT) having a maximum voltage range which corresponds to a second supply voltage (UH). The first supply voltage (UL) is
Westra, Jan R.; Annema, Anne J.; van den Boom, Jeroen M.; Dijkmans, Eise C.
2006-01-01
A digital to analog converter (DAC) for converting a digital signal (DS) having a maximum voltage range which corresponds to a first supply voltage (UL) into an analog signal (UOUT) having a maximum voltage range which corresponds to a second supply voltage (UH). The first supply voltage (UL) is
A New Family of Multilevel Grid Connected Inverters Based on Packed U Cell Topology.
Pakdel, Majid; Jalilzadeh, Saeid
2017-09-29
In this paper a novel packed U cell (PUC) based multilevel grid connected inverter is proposed. Unlike the U cell arrangement which consists of two power switches and one capacitor, in the proposed converter topology a lower DC power supply from renewable energy resources such as photovoltaic arrays (PV) is used as a base power source. The proposed topology offers higher efficiency and lower cost using a small number of power switches and a lower DC power source which is supplied from renewable energy resources. Other capacitor voltages are extracted from the base lower DC power source using isolated DC-DC power converters. The operation principle of proposed transformerless multilevel grid connected inverter is analyzed theoretically. Operation of the proposed multilevel grid connected inverter is verified through simulation studies. An experimental prototype using STM32F407 discovery controller board is performed to verify the simulation results.
Multilevel turbulence simulations
Energy Technology Data Exchange (ETDEWEB)
Tziperman, E. [Princeton Univ., NJ (United States)
1994-12-31
The authors propose a novel method for the simulation of turbulent flows, that is motivated by and based on the Multigrid (MG) formalism. The method, called Multilevel Turbulence Simulations (MTS), is potentially more efficient and more accurate than LES. In many physical problems one is interested in the effects of the small scales on the larger ones, or in a typical realization of the flow, and not in the detailed time history of each small scale feature. MTS takes advantage of the fact that the detailed simulation of small scales is not needed at all times, in order to make the calculation significantly more efficient, while accurately accounting for the effects of the small scales on the larger scale of interest. In MTS, models of several resolutions are used to represent the turbulent flow. The model equations in each coarse level incorporate a closure term roughly corresponding to the tau correction in the MG formalism that accounts for the effects of the unresolvable scales on that grid. The finer resolution grids are used only a small portion of the simulation time in order to evaluate the closure terms for the coarser grids, while the coarse resolution grids are then used to accurately and efficiently calculate the evolution of the larger scales. The methods efficiency relative to direct simulations is of the order of the ratio of required integration time to the smallest eddies turnover time, potentially resulting in orders of magnitude improvement for a large class of turbulence problems.
space vector pulse width modulation of a multi-level diode clamped ...
African Journals Online (AJOL)
ES Obe
nique in most industrial drives and control applications. It also focuses on the step by step ... the zero vector and two adjacent active vectors in determining the switching pro- cess of the multilevel DCC, quite unlike the .... Table 1: Switching states of an n-level Diode clamped converter. Switching States. S1. S2 ... Sn−2. Sa−1.
space vector pulse width modulation of a multi-level diode clamped ...
African Journals Online (AJOL)
ES Obe
Abstract. This paper presents the analysis of a multi-level diode clamped converter (DCC) which is implemented using space-vector pulse width modulation (SVPWM) tech- nique, widely considered as the most efficient and easily applied modulation tech- nique in most industrial drives and control applications.
Directory of Open Access Journals (Sweden)
Zanxiang Nie
2017-01-01
Full Text Available Linear wave energy converters generate intrinsically intermittent power with variable frequency and amplitude. A composite energy storage system consisting of batteries and super capacitors has been developed and controlled by buck-boost converters. The purpose of the composite energy storage system is to handle the fluctuations and intermittent characteristics of the renewable source, and hence provide a steady output power. Linear wave energy converters working in conjunction with a system composed of various energy storage devices, is considered as a microsystem, which can function in a stand-alone or a grid connected mode. Simulation results have shown that by applying a boost H-bridge and a composite energy storage system more power could be extracted from linear wave energy converters. Simulation results have shown that the super capacitors charge and discharge often to handle the frequent power fluctuations, and the batteries charge and discharge slowly for handling the intermittent power of wave energy converters. Hardware systems have been constructed to control the linear wave energy converter and the composite energy storage system. The performance of the composite energy storage system has been verified in experiments by using electronics-based wave energy emulators.
Microminiature thermionic converters
King, Donald B.; Sadwick, Laurence P.; Wernsman, Bernard R.
2001-09-25
Microminiature thermionic converts (MTCs) having high energy-conversion efficiencies and variable operating temperatures. Methods of manufacturing those converters using semiconductor integrated circuit fabrication and micromachine manufacturing techniques are also disclosed. The MTCs of the invention incorporate cathode to anode spacing of about 1 micron or less and use cathode and anode materials having work functions ranging from about 1 eV to about 3 eV. Existing prior art thermionic converter technology has energy conversion efficiencies ranging from 5-15%. The MTCs of the present invention have maximum efficiencies of just under 30%, and thousands of the devices can be fabricated at modest costs.
Improving Power Converter Reliability
DEFF Research Database (Denmark)
Ghimire, Pramod; de Vega, Angel Ruiz; Beczkowski, Szymon
2014-01-01
The real-time junction temperature monitoring of a high-power insulated-gate bipolar transistor (IGBT) module is important to increase the overall reliability of power converters for industrial applications. This article proposes a new method to measure the on-state collector?emitter voltage...... of a high-power IGBT module during converter operation, which may play a vital role in improving the reliability of the power converters. The measured voltage is used to estimate the module average junction temperature of the high and low-voltage side of a half-bridge IGBT separately in every fundamental...
Comparison of multi-MW converters considering the determining factors in wind power application
DEFF Research Database (Denmark)
Ma, Ke; Liserre, Marco; Blaabjerg, Frede
2013-01-01
converters are normally targeted to the industrial drive applications, and they did not take into account the special requirements in the case of wind power. This paper tries to unify and compare several promising wind power converters by a series new model and perspective. The evaluation criteria...... to be unified for comparison. And the two-level low-voltage converter solution still shows cost advantage regarding power semiconductors, while some multi-level medium-voltage converter solutions can show better performance when complying with the grid codes....
Modeling for spatial multilevel structural data
Min, Suqin; He, Xiaoqun
2013-03-01
The traditional multilevel model assumed independence between groups. However, the datasets grouped by geographical units often has spatial dependence. The individual is influenced not only by its region but also by the adjacent regions, and level-2 residual distribution assumption of traditional multilevel model is violated. In order to deal with such spatial multilevel data, we introduce spatial statistics and spatial econometric models into multilevel model, and apply spatial parameters and adjacency matrix in traditional level-2 model to reflect the spatial autocorrelation. Spatial lag model express spatial effects. We build spatial multilevel model which consider both multilevel thinking and spatial correlation.
DEFF Research Database (Denmark)
Bhaskar, Mahajan Sagar; Padamanaban, Sanjeevi Kumar; Blaabjerg, Frede
2016-01-01
In this paper hybrid non isolated and non-invertingCockcroft-Walton multiplier based 2Nx InterleavedBoost converter (2Nx IBC) for renewable energy applications is presented. The presented hybrid boost converter topology is derived from non-inverting Nx Multilevel Boost Converter (Nx MBC......) and inverting Nx Multilevel Boost Converter (Nx MBC). In renewable energy applications, generated voltage needs to be stepped up with high conversion ratio using a DC-DC converter at voltage levels as per the application requirement. The advantages of the presentedtopology of interleaved converter are high...... voltage conversion ratio, reduce ripple, low voltage stress, non-inverting output voltage without utilizing the high duty cycle, coupled inductors and transformer. The main advantage of presented topology consists in increasing voltage gain by adding capacitor and diode into circuitry without disturbing...
Microsatellite CONVERT Input File
U.S. Geological Survey, Department of the Interior — Microsatellite data formatted for the software CONVERT, which includes dataset numerical IDs, sampling site names, and locus identifiers. Rows 291-294 provides...
Banic, C. V.; Eckhouse, S. A.; Kornbrust, F. J.; Lifman, K.; Peterson, J. L.; Rosati, R. W.; Young, D.
An advanced converter system for use in electrochemical energy storge was defined. Improved and experimental apparatus are designed to measure these characteristics and to enable better definition of the battery power conditioner interface. Improvement of energy storage system performance through modification of battery converter characteristics is investigated. Power conditioning based on fuel cell use was evaluated. It is concluded that this high switching frequency concept has the potential for significantly reducing the size and cost of battery plant power conditioners.
Energy Technology Data Exchange (ETDEWEB)
Armonies, Uwe; Dommaschk, Mike; Retzmann, Dietmar; Wuerflinger, Klaus [Siemens AG, Erlangen (Germany). Energy Sector E T PS
2011-07-01
HVDC transmission is now being used to integrate offshore Windparks to Grid and feed power into the centre of large Metropolitan areas. For these applications the Voltage-Sourced Converter (VSV) using Modular Multilevel Technology is replacing the Classic Line-Commutated Converters and even VSCs using 2 or 3-level topologies. Modular Multilevel Converters comprise the series connection of many single modules, each with high energy storage, giving an almost linear control capability. The control of each module and its semi-conductors must produce balanced module loading. The analysis of real pulse patterns and measured data shows that the loading can be calculated by using idealized currents and voltages, which take into account the actual imbalance. In addition to the MMC control the balance of the arm energy plays a decisive role. Besides balancing the individual capacitor voltages by MMC control it is critical to control the energy of the individual arms. The basic functionality of this control system is demonstrated with real step response measurements. (orig.)
Iordache, Octavian
2011-01-01
This book is devoted to modeling of multi-level complex systems, a challenging domain for engineers, researchers and entrepreneurs, confronted with the transition from learning and adaptability to evolvability and autonomy for technologies, devices and problem solving methods. Chapter 1 introduces the multi-scale and multi-level systems and highlights their presence in different domains of science and technology. Methodologies as, random systems, non-Archimedean analysis, category theory and specific techniques as model categorification and integrative closure, are presented in chapter 2. Chapters 3 and 4 describe polystochastic models, PSM, and their developments. Categorical formulation of integrative closure offers the general PSM framework which serves as a flexible guideline for a large variety of multi-level modeling problems. Focusing on chemical engineering, pharmaceutical and environmental case studies, the chapters 5 to 8 analyze mixing, turbulent dispersion and entropy production for multi-scale sy...
Solving Linear Fractional Multilevel Programs
Directory of Open Access Journals (Sweden)
Shifali Bhargava
2014-01-01
Full Text Available The linear fractional multilevel programming (LFMP problem has been studied and it has been proved that an optimal solution to this problem occurs at a boundary feasible extreme point. Hence the Kth-best algorithm can be proposed to solve the problem. This property can be applied to quasiconcave multilevel problems provided that the first (n - 1 level objective functions are explicitly quasimonotonic, otherwise it cannot be proved that there exists a boundary feasible extreme point that solves the LFMP problem. (original abstract
Multilevel security for relational databases
Faragallah, Osama S; El-Samie, Fathi E Abd
2014-01-01
Concepts of Database Security Database Concepts Relational Database Security Concepts Access Control in Relational Databases Discretionary Access Control Mandatory Access Control Role-Based Access Control Work Objectives Book Organization Basic Concept of Multilevel Database Security IntroductionMultilevel Database Relations Polyinstantiation Invisible Polyinstantiation Visible Polyinstantiation Types of Polyinstantiation Architectural Consideration
Sloupová, Petra
2010-01-01
This Bachelor's thesis deals with multilevel marketing (MLM) in practice. The number of companies based on multilevel marketing has been enormly increased during the last 20 years. The main conditions for the entrance into the serious MLM company are described in this thesis. The practical part of the Bacelor's thesis deals with people's opinion of multilevel marketing and about multilevel marketing in a company called Oriflame. Several problems were discovered in this company. In the conclus...
DEFF Research Database (Denmark)
Margheritini, Lucia; Vicinanza, Diego; Frigaard, Peter
2008-01-01
The SSG (Sea Slot-cone Generator) is a wave energy converter of the overtopping type. The structure consists of a number of reservoirs one on the top of each others above the mean water level, in which the water of incoming waves is stored temporary. In each reservoir, expressively designed low...... head hydroturbines are converting the potential energy of the stored water into power. A key to success for the SSG will be the low cost of the structure and its robustness. The construction of the pilot plant is scheduled and this paper aims to describe the concept of the SSG wave energy converter...... and the studies behind the process that leads to its construction. The pilot plant is an on-shore full scale module in 3 levels with an expected power production of 320 MWh/y in the North Sea. Location, wave climate and laboratory tests results will be used here to describe the pilot plant and its characteristics....
Multilevel algorithms for nonlinear optimization
Alexandrov, Natalia; Dennis, J. E., Jr.
1994-01-01
Multidisciplinary design optimization (MDO) gives rise to nonlinear optimization problems characterized by a large number of constraints that naturally occur in blocks. We propose a class of multilevel optimization methods motivated by the structure and number of constraints and by the expense of the derivative computations for MDO. The algorithms are an extension to the nonlinear programming problem of the successful class of local Brown-Brent algorithms for nonlinear equations. Our extensions allow the user to partition constraints into arbitrary blocks to fit the application, and they separately process each block and the objective function, restricted to certain subspaces. The methods use trust regions as a globalization strategy, and they have been shown to be globally convergent under reasonable assumptions. The multilevel algorithms can be applied to all classes of MDO formulations. Multilevel algorithms for solving nonlinear systems of equations are a special case of the multilevel optimization methods. In this case, they can be viewed as a trust-region globalization of the Brown-Brent class.
DEFF Research Database (Denmark)
Sørensen, P G; Rømer, F K; Cortes, D
1984-01-01
In order to evaluate bleomycin-associated lung damage in humans, lung function parameters and serum levels of the endothelial-bound angiotensin-converting enzyme (ACE) were determined by serial measurements in 11 patients who were treated for testicular cancer. None developed clinical or radiolog...
Monroe, Jr., James E.
1977-08-09
A thermionic device for converting nuclear energy into electrical energy comprising a tubular anode spaced from and surrounding a cylindrical cathode, the cathode having an outer emitting surface of ruthenium, and nuclear fuel on the inner cylindrical surface. The nuclear fuel is a ceramic composition of fissionable material in a metal matrix. An axial void is provided to collect and contain fission product gases.
Definition of Power Converters
Bordry, F
2015-01-01
The paper is intended to introduce power conversion principles and to define common terms in the domain. The concept s of sources and switches are defined and classified. From the basic laws of source interconnections, a generic method of power converter synthesis is presented. Some examples illustrate this systematic method. Finally, the commutation cell and soft commuta tion are introduced and discussedd.
An Electromagnetic Beam Converter
DEFF Research Database (Denmark)
2009-01-01
The present invention relates to an electromagnetic beam converter and a method for conversion of an input beam of electromagnetic radiation having a bell shaped intensity profile a(x,y) into an output beam having a prescribed target intensity profile l(x',y') based on a further development...
Multilevel Workflow System in the ATLAS Experiment
Borodin, M; The ATLAS collaboration; De, K; Golubkov, D; Klimentov, A; Maeno, T; Vaniachine, A
2014-01-01
The ATLAS experiment is scaling up Big Data processing for the next LHC run using a multilevel workflow system comprised of many layers. In Big Data processing ATLAS deals with datasets, not individual files. Similarly a task (comprised of many jobs) has become a unit of the ATLAS workflow in distributed computing, with about 0.8M tasks processed per year. In order to manage the diversity of LHC physics (exceeding 35K physics samples per year), the individual data processing tasks are organized into workflows. For example, the Monte Carlo workflow is composed of many steps: generate or configure hard-processes, hadronize signal and minimum-bias (pileup) events, simulate energy deposition in the ATLAS detector, digitize electronics response, simulate triggers, reconstruct data, convert the reconstructed data into ROOT ntuples for physics analysis, etc. Outputs are merged and/or filtered as necessary to optimize the chain. The bi-level workflow manager - ProdSys2 - generates actual workflow tasks and their jobs...
Multilevel Workflow System in the ATLAS Experiment
Borodin, M; The ATLAS collaboration; Golubkov, D; Klimentov, A; Maeno, T; Vaniachine, A
2015-01-01
The ATLAS experiment is scaling up Big Data processing for the next LHC run using a multilevel workflow system comprised of many layers. In Big Data processing ATLAS deals with datasets, not individual files. Similarly a task (comprised of many jobs) has become a unit of the ATLAS workflow in distributed computing, with about 0.8M tasks processed per year. In order to manage the diversity of LHC physics (exceeding 35K physics samples per year), the individual data processing tasks are organized into workflows. For example, the Monte Carlo workflow is composed of many steps: generate or configure hard-processes, hadronize signal and minimum-bias (pileup) events, simulate energy deposition in the ATLAS detector, digitize electronics response, simulate triggers, reconstruct data, convert the reconstructed data into ROOT ntuples for physics analysis, etc. Outputs are merged and/or filtered as necessary to optimize the chain. The bi-level workflow manager - ProdSys2 - generates actual workflow tasks and their jobs...
Cross-Regulation Assessment of DIDO Buck-Boost Converter for Renewable Energy Application
Directory of Open Access Journals (Sweden)
Deepak Elamalayil Soman
2017-06-01
Full Text Available When medium- or high-voltage power conversion is preferred for renewable energy sources, multilevel power converters have received much of the interest in this area as methods for enhancing the conversion efficiency and cost effectiveness. In such cases, multilevel, multi-input multi-output (MIMO configurations of DC-DC converters come to the scenario for integrating several sources together, especially considering the stringent regulatory needs and the requirement of multistage power conversion systems. Considering the above facts, a three-level dual input dual output (DIDO buck-boost converter, as the simplest form of MIMO converter, is proposed in this paper for DC-link voltage regulation. The capability of this converter for cross regulating the DC-link voltage is analyzed in detail to support a three-level neutral point clamped inverter-based grid connection in the future. The cross-regulation capability is examined under a new type of pulse delay control (PDC strategy and later compared with a three-level boost converter (TLBC. Compared to conventional boost converters, the high-voltage three-level buck boost converter (TLBBC with PDC exhibits a wide controllability range and cross regulation capability. These enhanced features are extremely important for better regulating variable output renewable energy sources such as solar, wind, wave, marine current, etc. The simulation and experimental results are provided to validate the claim.
Directory of Open Access Journals (Sweden)
T. Ajith Bosco Raj
2014-01-01
Full Text Available The main objective of this work is to study the behaviour of the solar PV systems and model the efficient Grid-connected solar power system. The DC-DC MPPT circuit using chaotic pulse width modulation has been designed to track maximum power from solar PV module. The conversion efficiency of the proposed MPPT system is increased when CPWM is used as a control scheme. This paper also proposes a simplified multilevel (seven level inverter for a grid-connected photovoltaic system. The primary goal of these systems is to increase the energy injected to the grid by keeping track of the maximum power point of the panel, by reducing the switching frequency, and by providing high reliability. The maximum power has been tracked experimentally. It is compared with parallel boost converter. Also this model is based on mathematical equations and is described through an equivalent circuit including a PV source with MPPT, a diode, a series resistor, a shunt resistor, and dual boost converter with active snubber circuit. This model can extract PV power and boost by using dual boost converter with active snubber. By using this method the overall system efficiency is improved thereby reducing the switching losses and cost.
Multilevel techniques for Reservoir Simulation
DEFF Research Database (Denmark)
Christensen, Max la Cour
The subject of this thesis is the development, application and study of novel multilevel methods for the acceleration and improvement of reservoir simulation techniques. The motivation for addressing this topic is a need for more accurate predictions of porous media flow and the ability to carry...... based on element-based Algebraic Multigrid (AMGe). In particular, an advanced AMGe technique with guaranteed approximation properties is used to construct a coarse multilevel hierarchy of Raviart-Thomas and L2 spaces for the Galerkin coarsening of a mixed formulation of the reservoir simulation...... equations. By experimentation it is found that the AMGe based upscaling technique provided very accurate results while reducing the computational time proportionally to the reduction in degrees of freedom. Furthermore, it is demonstrated that the AMGe coarse spaces (interpolation operators) can be used...
DEFF Research Database (Denmark)
Andresen, Markus; Ma, Ke; Liserre, Marco
2015-01-01
A Smart Transformer (ST) can cover an important managing role in the future electrical distribution grid. For the moment, the reliability and cost are not competitive with traditional transformers and create a barrier for its application. This work conduct detail designs and analysis...... for a promising modular ST solution, which is composed of Modular Multi-level converter, Quad Active Bridge DC-DC converters, and two-level voltage source converters. The focus is put on the loading conditions and thermal stress of power semiconductor devices in order to discover critical parts of the whole...
Asymmetric overlap and hysteresis current control of zero-current switched alternate arm converter
DEFF Research Database (Denmark)
Wickramasinghe, Harith R.; Konstantinou, Georgios; Pou, Josep
2016-01-01
The alternate arm converter (AAC) is a multilevel converter of the same family as the modular multilevel converter (MMC). Contrary to the MMC, the AAC offers dc-fault tolerant capabilities but requires complex submodule (SM) capacitor voltage/energy regulation and circulating current control....... Such control is also limited due to the small overlap period where both arms conduct and energy between the arms can be exchanged. This paper develops a double-band hysteresis-based circulating current control strategy by introducing an asymmetric overlap period control of the director switches (DSs......). The proposed controller ensures zero-current switching operation of the DSs, and increases the flexibility of SM capacitor voltage regulation owing to the asymmetric overlap period. It improves the performance of current control and energy regulation for the AAC at both near sweet-spot and non sweet...
The microminiature thermionic converter
King, Donald B.; Luke, James R.; Zavadil, Kevin R.
2001-02-01
A new generation of thermionic converter, the microminiature thermionic converter (MTC) has been fabrication using semiconductor integrated circuit (IC) fabrication methods and micromachining manufacturing (MM) techniques. The use of IC and MM techniques allows the fabrication of MTCs with micron scale cathode to anode spacing and with anode and cathode materials which will have work functions ranging from 1 eV to 2.5 eV. The use of small cathode to anode spacing and variable electrode work functions gives the MTC the potential to convert heat energy to relatively large current densities (up to 10s of Amps/cm2) at relatively high conversion efficiencies (~25%), well within the range of high end conventional electrical generation equipment. Tests of prototype MTCs have demonstrated energy conversion at several emitter and collector temperatures. Power generated by the prototype MTC is less than expected because of less than optimal emission characteristics encountered with the low work function materials used for the first MTC prototypes. Work is in progress to improve the thermionic emission characteristics of the low work function electrodes. .
Multilevel optimization algorithms and applications
Pardalos, Panos; Värbrand, Peter
1998-01-01
Researchers working with nonlinear programming often claim "the word is non linear" indicating that real applications require nonlinear modeling. The same is true for other areas such as multi-objective programming (there are always several goals in a real application), stochastic programming (all data is uncer tain and therefore stochastic models should be used), and so forth. In this spirit we claim: The word is multilevel. In many decision processes there is a hierarchy of decision makers, and decisions are made at different levels in this hierarchy. One way to handle such hierar chies is to focus on one level and include other levels' behaviors as assumptions. Multilevel programming is the research area that focuses on the whole hierar chy structure. In terms of modeling, the constraint domain associated with a multilevel programming problem is implicitly determined by a series of opti mization problems which must be solved in a predetermined sequence. If only two levels are considered, we have ...
Multilevel marketing společnosti Amway
Drozdková, Markéta
2010-01-01
This thesis analyses effectiveness and principles of multilevel marketing as a possible way of selling products and services. Theoretical part describes basis of marketing and direct selling, which is the basis of multilevel marketing. The thesis also states illegal forms of selling that misuse the advantages of multilevel marketing. Pracical part applies gained knowledge on Amway corporation and it atteds to operation of the company, which is evaluated by SWOT analysis.
Cycloidal Wave Energy Converter
Energy Technology Data Exchange (ETDEWEB)
Stefan G. Siegel, Ph.D.
2012-11-30
This program allowed further advancing the development of a novel type of wave energy converter, a Cycloidal Wave Energy Converter or CycWEC. A CycWEC consists of one or more hydrofoils rotating around a central shaft, and operates fully submerged beneath the water surface. It operates under feedback control sensing the incoming waves, and converts wave power to shaft power directly without any intermediate power take off system. Previous research consisting of numerical simulations and two dimensional small 1:300 scale wave flume experiments had indicated wave cancellation efficiencies beyond 95%. The present work was centered on construction and testing of a 1:10 scale model and conducting two testing campaigns in a three dimensional wave basin. These experiments allowed for the first time for direct measurement of electrical power generated as well as the interaction of the CycWEC in a three dimensional environment. The Atargis team successfully conducted two testing campaigns at the Texas A&M Offshore Technology Research Center and was able to demonstrate electricity generation. In addition, three dimensional wave diffraction results show the ability to achieve wave focusing, thus increasing the amount of wave power that can be extracted beyond what was expected from earlier two dimensional investigations. Numerical results showed wave cancellation efficiencies for irregular waves to be on par with results for regular waves over a wide range of wave lengths. Using the results from previous simulations and experiments a full scale prototype was designed and its performance in a North Atlantic wave climate of average 30kW/m of wave crest was estimated. A full scale WEC with a blade span of 150m will deliver a design power of 5MW at an estimated levelized cost of energy (LCOE) in the range of 10-17 US cents per kWh. Based on the new results achieved in the 1:10 scale experiments these estimates appear conservative and the likely performance at full scale will
Kazimierczuk, Marian K
2012-01-01
This book is devoted to resonant energy conversion in power electronics. It is a practical, systematic guide to the analysis and design of various dc-dc resonant inverters, high-frequency rectifiers, and dc-dc resonant converters that are building blocks of many of today's high-frequency energy processors. Designed to function as both a superior senior-to-graduate level textbook for electrical engineering courses and a valuable professional reference for practicing engineers, it provides students and engineers with a solid grasp of existing high-frequency technology, while acquainting them wit
Directory of Open Access Journals (Sweden)
MOALLEMI KHIAVI, A.
2015-08-01
Full Text Available Nowadays power converters play an important role in power system and industrial centers. One of the most important and widely used types of conversion is DC to AC conversion that is also called inverters. Generally inverters are divided to voltage source inverter (VSI and current source inverter (CSI. From another view the inverters are divided to two-level and multilevel types. The multilevel inverters are attractive because of their good output waveform quality. However, there has been less attention to multilevel current source inverter (MLCSI when compared with multilevel VSI. In this paper, a new topology for MLCSI is proposed. The proposed topology employs reduced number of switches to generate desired multilevel output current. The proposed MLCSI is capable of balancing the currents of the inductors that are used in the MLCSI structure. A multicarrier PWM based switching strategy is also proposed for the MLCSI. The simulation results using PSCAD/EMTDC as well as the experimental results from a single-phase 5-level CSI laboratory prototype demonstrate its validity.
Special Tests for the Power Electronic Converters of Wind Turbine Generators
DEFF Research Database (Denmark)
Helle, Lars; Senturk, Osman Selcuk; Teodorescu, Remus
2011-01-01
-side VSCs is used to estimate the switch junction temperatures through the simulation of wind turbine grid interface operation. A discussion of the power density and reliability of the grid-side VSCs with respect to press-pack switches, gate driver, and cooling plate is included. A test set-up for a single......Power electronic converters for wind turbines are characterized by high specific power density and high reliability. Special tests for such converters are performed in order to determine the power loss and thermal models, which are dependent of the load profile and converter structure. Two multi......-level medium-voltage source converter topologies, of the 3L-ANPC-VSC and 3L-HB-VSC type, are considered in the paper. Both converters employ press-pack IGBT-diode pairs and interface a 6 MW wind turbine to a medium voltage grid. The power loss and thermal model data applicable for both grid and generator...
The multilevel governance of migration and integration
Scholten, P.; Penninx, R.; Garcés–Mascareñas, B.; Penninx, R.
2016-01-01
This chapter focuses on migration and integration as multilevel policy issues and explores the consequences in terms of multilevel governance. Immigration policymaking has been characterized by continued struggle between national governments and the EU about the amount of discretion states have in
Power quality enhancement using cascaded multilevel inverter ...
African Journals Online (AJOL)
This paper investigates mitigation of current harmonics using different configuration of cascaded multilevel inverter based shunt hybrid active power filter (SHAPF) and to improve power quality of the system. The main objective of this paper is to develop and analyze the compensation characteristics of cascaded multilevel ...
Scalable Adaptive Multilevel Solvers for Multiphysics Problems
Energy Technology Data Exchange (ETDEWEB)
Xu, Jinchao [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mathematics
2014-11-26
In this project, we carried out many studies on adaptive and parallel multilevel methods for numerical modeling for various applications, including Magnetohydrodynamics (MHD) and complex fluids. We have made significant efforts and advances in adaptive multilevel methods of the multiphysics problems: multigrid methods, adaptive finite element methods, and applications.
Pedersen, F.
2008-09-01
The presented bidirectional DC/DC converter design concept is a further development of an already existing converter used for low battery voltage operation.For low battery voltage operation a high efficient low parts count DC/DC converter was developed, and used in a satellite for the battery charge and battery discharge function.The converter consists in a bidirectional, non regulating DC/DC converter connected to a discharge regulating Buck converter and a charge regulating Buck converter.The Bidirectional non regulating DC/DC converter performs with relatively high efficiency even at relatively high currents, which here means up to 35Amps.This performance was obtained through the use of power MOSFET's with on- resistances of only a few mille Ohms connected to a special transformer allowing paralleling several transistor stages on the low voltage side of the transformer. The design is patent protected. Synchronous rectification leads to high efficiency at the low battery voltages considered, which was in the range 2,7- 4,3 Volt DC.The converter performs with low switching losses as zero voltage zero current switching is implemented in all switching positions of the converter.Now, the drive power needed, to switch a relatively large number of low Ohm , hence high drive capacitance, power MOSFET's using conventional drive techniques would limit the overall conversion efficiency.Therefore a resonant drive consuming considerable less power than a conventional drive circuit was implemented in the converter.To the originally built and patent protected bidirectional non regulating DC/DC converter, is added the functionality of regulation.Hereby the need for additional converter stages in form of a Charge Buck regulator and a Discharge Buck regulator is eliminated.The bidirectional DC/DC converter can be used in connection with batteries, motors, etc, where the bidirectional feature, simple design and high performance may be useful.
Fluorescent radiation converter
Viehmann, W. (Inventor)
1981-01-01
A fluorescence radiation converter is described which includes a substantially undoped optically transparent substrate and a waveshifter coating deposited on at least one portion of the substrate for absorption of radiation and conversion of fluorescent radiation. The coating is formed to substantially 1000 g/liter of a solvent, 70 to 200 g/liter of an organic polymer, and 0.2 to 25 g/liter of at least one organic fluorescent dye. The incoming incident radiation impinges on the coating. Radiation is absorbed by the fluorescent dye and is re-emitted as a longer wavelength radiation. Radiation is trapped within the substrate and is totally internally reflected by the boundary surface. Emitted radiation leaves the substrate ends to be detected.
Electromagnetic wave energy converter
Bailey, R. L. (Inventor)
1973-01-01
Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive dc output power.
A multilevel nonvolatile magnetoelectric memory
Shen, Jianxin; Cong, Junzhuang; Shang, Dashan; Chai, Yisheng; Shen, Shipeng; Zhai, Kun; Sun, Young
2016-09-01
The coexistence and coupling between magnetization and electric polarization in multiferroic materials provide extra degrees of freedom for creating next-generation memory devices. A variety of concepts of multiferroic or magnetoelectric memories have been proposed and explored in the past decade. Here we propose a new principle to realize a multilevel nonvolatile memory based on the multiple states of the magnetoelectric coefficient (α) of multiferroics. Because the states of α depends on the relative orientation between magnetization and polarization, one can reach different levels of α by controlling the ratio of up and down ferroelectric domains with external electric fields. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure confirm that the states of α can be well controlled between positive and negative by applying selective electric fields. Consequently, two-level, four-level, and eight-level nonvolatile memory devices are demonstrated at room temperature. This kind of multilevel magnetoelectric memory retains all the advantages of ferroelectric random access memory but overcomes the drawback of destructive reading of polarization. In contrast, the reading of α is nondestructive and highly efficient in a parallel way, with an independent reading coil shared by all the memory cells.
Multilevel joint competing risk models
Karunarathna, G. H. S.; Sooriyarachchi, M. R.
2017-09-01
Joint modeling approaches are often encountered for different outcomes of competing risk time to event and count in many biomedical and epidemiology studies in the presence of cluster effect. Hospital length of stay (LOS) has been the widely used outcome measure in hospital utilization due to the benchmark measurement for measuring multiple terminations such as discharge, transferred, dead and patients who have not completed the event of interest at the follow up period (censored) during hospitalizations. Competing risk models provide a method of addressing such multiple destinations since classical time to event models yield biased results when there are multiple events. In this study, the concept of joint modeling has been applied to the dengue epidemiology in Sri Lanka, 2006-2008 to assess the relationship between different outcomes of LOS and platelet count of dengue patients with the district cluster effect. Two key approaches have been applied to build up the joint scenario. In the first approach, modeling each competing risk separately using the binary logistic model, treating all other events as censored under the multilevel discrete time to event model, while the platelet counts are assumed to follow a lognormal regression model. The second approach is based on the endogeneity effect in the multilevel competing risks and count model. Model parameters were estimated using maximum likelihood based on the Laplace approximation. Moreover, the study reveals that joint modeling approach yield more precise results compared to fitting two separate univariate models, in terms of AIC (Akaike Information Criterion).
Integrated power electronic converters and digital control
Emadi, Ali; Nie, Zhong
2009-01-01
Non-isolated DC-DC ConvertersBuck ConverterBoost ConverterBuck-Boost ConverterIsolated DC-DC ConvertersFlyback ConverterForward ConverterPush-Pull ConverterFull-Bridge ConverterHalf-Bridge ConverterPower Factor CorrectionConcept of PFCGeneral Classification of PFC CircuitsHigh Switching Frequency Topologies for PFCApplication of PFC in Advanced Motor DrivesIntegrated Switched-Mode Power ConvertersSwitched-Mode Power SuppliesThe Concept of Integrated ConverterDefinition of Integrated Switched-Mode Power Supplies (ISMPS)Boost-Type Integrated TopologiesGeneral Structure of Boost-Type Integrated T
Advanced power electronics converters PWM converters processing AC voltages
dos Santos, Euzeli
2014-01-01
This book covers power electronics, in depth, by presenting the basic principles and application details, which can be used both as a textbook and reference book. Introduces a new method to present power electronics converters called Power Blocks Geometry. Applicable for courses focusing on power electronics, power electronics converters, and advanced power converters. Offers a comprehensive set of simulation results to help understand the circuits presented throughout the book
Impedance source power electronic converters
Liu, Yushan; Ge, Baoming; Blaabjerg, Frede; Ellabban, Omar; Loh, Poh Chiang
2016-01-01
Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key features: Comprehensive analysis of the impedance source converter/inverter topologies, including typical topologies and derived topologies. Fully explains the design and control techniques of impedance source converters/inverters, including hardware design and control parameter design for corresponding control methods. Presents the latest power conversion solutions that aim to advance the role of pow...
Impedance Source Power Electronic Converters
DEFF Research Database (Denmark)
Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming
control methods. Presents the latest power conversion solutions that aim to advance the role of power electronics into industries and sustainable energy conversion systems. Compares impedance source converter/inverter applications in renewable energy power generation and electric vehicles as well......Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable...
Advanced Multilevel Monte Carlo Methods
Jasra, Ajay
2017-04-24
This article reviews the application of advanced Monte Carlo techniques in the context of Multilevel Monte Carlo (MLMC). MLMC is a strategy employed to compute expectations which can be biased in some sense, for instance, by using the discretization of a associated probability law. The MLMC approach works with a hierarchy of biased approximations which become progressively more accurate and more expensive. Using a telescoping representation of the most accurate approximation, the method is able to reduce the computational cost for a given level of error versus i.i.d. sampling from this latter approximation. All of these ideas originated for cases where exact sampling from couples in the hierarchy is possible. This article considers the case where such exact sampling is not currently possible. We consider Markov chain Monte Carlo and sequential Monte Carlo methods which have been introduced in the literature and we describe different strategies which facilitate the application of MLMC within these methods.
Adaptive Multilevel Monte Carlo Simulation
Hoel, H
2011-08-23
This work generalizes a multilevel forward Euler Monte Carlo method introduced in Michael B. Giles. (Michael Giles. Oper. Res. 56(3):607–617, 2008.) for the approximation of expected values depending on the solution to an Itô stochastic differential equation. The work (Michael Giles. Oper. Res. 56(3):607– 617, 2008.) proposed and analyzed a forward Euler multilevelMonte Carlo method based on a hierarchy of uniform time discretizations and control variates to reduce the computational effort required by a standard, single level, Forward Euler Monte Carlo method. This work introduces an adaptive hierarchy of non uniform time discretizations, generated by an adaptive algorithmintroduced in (AnnaDzougoutov et al. Raùl Tempone. Adaptive Monte Carlo algorithms for stopped diffusion. In Multiscale methods in science and engineering, volume 44 of Lect. Notes Comput. Sci. Eng., pages 59–88. Springer, Berlin, 2005; Kyoung-Sook Moon et al. Stoch. Anal. Appl. 23(3):511–558, 2005; Kyoung-Sook Moon et al. An adaptive algorithm for ordinary, stochastic and partial differential equations. In Recent advances in adaptive computation, volume 383 of Contemp. Math., pages 325–343. Amer. Math. Soc., Providence, RI, 2005.). This form of the adaptive algorithm generates stochastic, path dependent, time steps and is based on a posteriori error expansions first developed in (Anders Szepessy et al. Comm. Pure Appl. Math. 54(10):1169– 1214, 2001). Our numerical results for a stopped diffusion problem, exhibit savings in the computational cost to achieve an accuracy of ϑ(TOL),from(TOL−3), from using a single level version of the adaptive algorithm to ϑ(((TOL−1)log(TOL))2).
Advancing multilevel thinking and methods in HRM research
Renkema, Maarten; Meijerink, Jeroen Gerard; Bondarouk, Tatiana
2016-01-01
Purpose Despite the growing belief that multilevel research is necessary to advance HRM understanding, there remains a lack of multilevel thinking – the application of principles for multilevel theory building. The purpose of this paper is to propose a systematic approach for multilevel HRM
Multilevel Modulation formats for Optical Communication
DEFF Research Database (Denmark)
Jensen, Jesper Bevensee
2008-01-01
This thesis studies the use of multilevel modulation formats for optical communication systems. Multilevel modulation is an attractive method of increasing the spectral efficiency of optical communication systems. Various modulation formats employing phase modulation, amplitude modulation...... or a combination of the two have been studied. The use of polarization multiplexing (PolMux) to double the bit rate has also been investigated. The impact of transmission impairments such as chromatic dispersion, self phase modulation and cross phase modulation has been investigated. The feasibility of multilevel...... modulation for network oriented scenarios has been demonstrated....
Optimized Integrated Harmonic Filter Inductor for Dual-Converter-Fed Open-End Transformer Topology
DEFF Research Database (Denmark)
Gohil, Ghanshyamsinh Vijaysinh; Bede, Lorand; Teodorescu, Remus
2017-01-01
Many high power converter systems are often connected to the medium voltage network using a step-up transformer. In such systems, the converter-side windings of the transformer can be configured as an open-end and multi-level voltage waveforms can be achieved by feeding these open-end windings from...... in this paper, where the flux in the common part of the magnetic core is completely canceled out. As a result, the size of the magnetic component can be significantly reduced. A multi-objective design optimization is presented, where the energy loss and the volume are optimized. The optimization process takes...
Overview of power converter designs feasible for high voltage transformer-less wind turbine
DEFF Research Database (Denmark)
Sztykiel, Michal
2011-01-01
Many leading wind turbine manufacturers are pushing forward in variable-speed wind turbines, often exceeding 5 MW. Therefore, novel designs and concepts for optimal high power wind turbines appeared. One of the most promising concepts is the high voltage (10-35 kV) transformer-less topology. High...... topology along with an overview of most promising candidates for optimal full-scale power converter design. Study is carried with proposed and justified high voltage wind turbine application along with selection of existing and most promising multilevel power converter topologies, which could...
DEFF Research Database (Denmark)
Bhaskar, Mahajan Sagar; Padmanaban, Sanjeevikumar; Maroti, Pandav Kiran
2017-01-01
applications. The noticeable features of the proposed 2LC-Y converter topologies are: i) Only one power control switch and input source; ii) High negative output voltage with moderate duty ratio; iii) Low output current and minimal internal resistance; iv) Transformer-less converter topologies; v) High voltage......New members of XY converter family topologies are proposed in this treatise for a high-voltage/low-current renewable application. Based on the X Converter, the whole existing X-Y Converter family is categorized into four categories; L-Y, 2L-Y, 2LC-Y and 2LCm-Y converter. Four new 2LC-Y topologies...... (2LC-LVD, 2LC-2LVD, 2LC-2LCVD and 2LC-2LCmVD) converters are presented in this treatise which offer an effective solution for renewable applications requiring a very high voltage conversion ratio such as a Photovoltaic Multilevel Inverter (PV-MLI) system, hybrid electrical drives and automotive...
Impedance Source Power Electronic Converters
DEFF Research Database (Denmark)
Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming
control methods. Presents the latest power conversion solutions that aim to advance the role of power electronics into industries and sustainable energy conversion systems. Compares impedance source converter/inverter applications in renewable energy power generation and electric vehicles as well......Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable...... and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key...
Impedance Source Power Electronic Converters
DEFF Research Database (Denmark)
Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming
and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key......Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable...... control methods. Presents the latest power conversion solutions that aim to advance the role of power electronics into industries and sustainable energy conversion systems. Compares impedance source converter/inverter applications in renewable energy power generation and electric vehicles as well...
The Sage handbook of multilevel modeling
Scott, Marc A; Marx, Brian D
2013-01-01
Leading contributors combine practical pieces with overviews of the state of the art in the field, making this handbook essential reading for any student or researcher looking to apply multilevel techniques in their own research
Directory of Open Access Journals (Sweden)
Libing Wang
2014-01-01
Full Text Available In order to control the cascaded H-bridges (CHB converter with staircase modulation strategy in a real-time manner, a real-time and closed-loop control algorithm based on artificial neural network (ANN for three-phase CHB converter is proposed in this paper. It costs little computation time and memory. It has two steps. In the first step, hierarchical particle swarm optimizer with time-varying acceleration coefficient (HPSO-TVAC algorithm is employed to minimize the total harmonic distortion (THD and generate the optimal switching angles offline. In the second step, part of optimal switching angles are used to train an ANN and the well-designed ANN can generate optimal switching angles in a real-time manner. Compared with previous real-time algorithm, the proposed algorithm is suitable for a wider range of modulation index and results in a smaller THD and a lower calculation time. Furthermore, the well-designed ANN is embedded into a closed-loop control algorithm for CHB converter with variable direct voltage (DC sources. Simulation results demonstrate that the proposed closed-loop control algorithm is able to quickly stabilize load voltage and minimize the line current’s THD (<5% when subjecting the DC sources disturbance or load disturbance. In real design stage, a switching angle pulse generation scheme is proposed and experiment results verify its correctness.
Wang, Libing; Mao, Chengxiong; Wang, Dan; Lu, Jiming; Zhang, Junfeng; Chen, Xun
2014-01-01
In order to control the cascaded H-bridges (CHB) converter with staircase modulation strategy in a real-time manner, a real-time and closed-loop control algorithm based on artificial neural network (ANN) for three-phase CHB converter is proposed in this paper. It costs little computation time and memory. It has two steps. In the first step, hierarchical particle swarm optimizer with time-varying acceleration coefficient (HPSO-TVAC) algorithm is employed to minimize the total harmonic distortion (THD) and generate the optimal switching angles offline. In the second step, part of optimal switching angles are used to train an ANN and the well-designed ANN can generate optimal switching angles in a real-time manner. Compared with previous real-time algorithm, the proposed algorithm is suitable for a wider range of modulation index and results in a smaller THD and a lower calculation time. Furthermore, the well-designed ANN is embedded into a closed-loop control algorithm for CHB converter with variable direct voltage (DC) sources. Simulation results demonstrate that the proposed closed-loop control algorithm is able to quickly stabilize load voltage and minimize the line current's THD (switching angle pulse generation scheme is proposed and experiment results verify its correctness.
Wang, Libing; Mao, Chengxiong; Wang, Dan; Lu, Jiming; Zhang, Junfeng; Chen, Xun
2014-01-01
In order to control the cascaded H-bridges (CHB) converter with staircase modulation strategy in a real-time manner, a real-time and closed-loop control algorithm based on artificial neural network (ANN) for three-phase CHB converter is proposed in this paper. It costs little computation time and memory. It has two steps. In the first step, hierarchical particle swarm optimizer with time-varying acceleration coefficient (HPSO-TVAC) algorithm is employed to minimize the total harmonic distortion (THD) and generate the optimal switching angles offline. In the second step, part of optimal switching angles are used to train an ANN and the well-designed ANN can generate optimal switching angles in a real-time manner. Compared with previous real-time algorithm, the proposed algorithm is suitable for a wider range of modulation index and results in a smaller THD and a lower calculation time. Furthermore, the well-designed ANN is embedded into a closed-loop control algorithm for CHB converter with variable direct voltage (DC) sources. Simulation results demonstrate that the proposed closed-loop control algorithm is able to quickly stabilize load voltage and minimize the line current's THD (sources disturbance or load disturbance. In real design stage, a switching angle pulse generation scheme is proposed and experiment results verify its correctness. PMID:24772025
Cervical Laminoplasty for Multilevel Cervical Myelopathy
Directory of Open Access Journals (Sweden)
Murali Krishna Sayana
2011-01-01
Full Text Available Cervical spondylotic myelopathy can result from degenerative cervical spondylosis, herniated disk material, osteophytes, redundant ligamentum flavum, or ossification of the posterior longitudinal ligament. Surgical intervention for multi-level myelopathy aims to decompress the spinal cord and maintain stability of the cervical spine. Laminoplasty was major surgical advancement as laminectomy resulted in kyphosis and unsatisfactory outcomes. Hirabayashi popularised the expansive open door laminoplasty which was later modified several surgeons. Laminoplasty has changed the way surgeons approach multilevel cervical spondylotic myelopathy.
Radiation tolerant power converter controls
Todd, B; King, Q; Uznanski, S
2012-01-01
The Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is the world's most powerful particle collider. The LHC has several thousand magnets, both warm and super-conducting, which are supplied with current by power converters. Each converter is controlled by a purpose-built electronic module called a Function Generator Controller (FGC). The FGC allows remote control of the power converter and forms the central part of a closed-loop control system where the power converter voltage is set, based on the converter output current and magnet-circuit characteristics. Some power converters and FGCs are located in areas which are exposed to beam-induced radiation. There are numerous radiation induced effects, some of which lead to a loss of control of the power converter, having a direct impact upon the accelerator's availability. Following the first long shut down (LS1), the LHC will be able to run with higher intensity beams and higher beam energy. This is expected to lead to signifi...
New fault tolerant matrix converter
Energy Technology Data Exchange (ETDEWEB)
Ibarra, Edorta; Andreu, Jon; Kortabarria, Inigo; Ormaetxea, Enekoitz; Alegria, Inigo Martinez de; Martin, Jose Luis [Department of Electronics and Telecommunications, University of the Basque Country, Alameda de Urquijo s/n, E-48013 Bilbao (Spain); Ibanez, Pedro [TECNALIA, Energy Unit, Parque Tecnologico de Zamudio, E-48170 Bizkaia (Spain)
2011-02-15
The matrix converter (MC) presents a promising topology that will have to overcome certain barriers (protection systems, durability, the development of converters for real applications, etc.) in order to gain a foothold in the industry. In some applications, where continuous operation must be insured in the case of a system failure, improved reliability of the converter is of particular importance. In this sense, this article focuses on the study of a fault tolerant MC. The fault tolerance of a converter is characterized by its total or partial response in the case of a breakage of any of its components. Taking into consideration that virtually no work has been done on fault tolerant MCs, this paper describes the most important studies in this area. Moreover, a new method is proposed for detecting the breakage of MC semiconductors. Likewise, a new variation of SVM modulation with failure tolerance capacity is presented. This guarantees the continuous operation of the converter and the pseudo-optimum control of a PMSM. This paper also proposes a novel MC topology, which allows the flexible reconfiguration of this converter, when one or several of its semiconductors are damaged. In this way, the MC can continue operating at 100% of its performance without having to double its resources. In this way, it can be said that the solution described in this article represents a step forward towards the development of reliable matrix converters for real applications. (author)
Performance Comparison of Phase Shifted PWM and Sorting Method for Modular Multilevel Converters
DEFF Research Database (Denmark)
Haddioui, Marcos Rejas; Máthé, Lászlo; Burlacu, Paul Dan
2015-01-01
on keeping the capacitor voltage ripple under some limit, unnecessary switching events are eliminated leading to reduced switching losses. This paper presents a comparison between the steady-state performances in terms of output voltage THD and equivalent switching frequency of the Phase Shifted Carrier PWM...
Modular Multilevel Converter Modelling, Control and Analysis under Grid Frequency Deviations
DEFF Research Database (Denmark)
Sztykiel, Michal; Silva, Rodrigo Da; Teodorescu, Remus
2012-01-01
A tool for component sizing for MMCs has been developed and tested through simulations in PLECS. The steady-state behaviour under grid frequency deviations - interesting for offshore wind farm connections - has been analysed, providing insights in MMC characteristics and further testing...
Modular multilevel converter modelling, control and analysis under grid frequency deviations
DEFF Research Database (Denmark)
Sztykiel, Michal; da Silva, Rodrigo; Teodorescu, Remus
2013-01-01
A tool for component sizing for MMCs has been developed and tested through simulations in PLECS. The steady-state behaviour under grid frequency deviations — interesting for offshore wind farm connections — has been analysed, providing insights in MMC characteristics and further testing...
DEFF Research Database (Denmark)
Zhang, Yi; Wang, Huai; Wang, Zhongxu
2017-01-01
predefined conditions. In these lifetime models, thermal stresses (e.g., junction temperature variations) are commonly considered. However, the lifetime of power devices involves in crossdisciplinary knowledge. As a result, the lifetime prediction is affected by the selected lifetime model. In this regard...... models should be justified in terms of applicability, limitations, and underlying statistical properties....
Multistability and hidden attractors in a multilevel DC/DC converter
DEFF Research Database (Denmark)
Zhusubaliyev, Zhanybai T.; Mosekilde, Erik
2015-01-01
produce complicated structures of attracting and repelling states organized around the basic switching cycle. This leads us to suggest the existence of hidden attractors in such systems as well. In this case, the condition will be that the basin of attraction does not overlap with the fixed point...... that represents the basic switching cycle....
High Order Voltage and Current Harmonic Mitigation Using the Modular Multilevel Converter STATCOM
Kontos, E.; Tsolaridis, Georgios; Teodorescu, Remus; Bauer, P.
2017-01-01
Due to the increase of power electronic-based loads, the maintenance of high power quality poses a challenge in modern power systems. To limit the total harmonic distortion in the line voltage and currents at the point of the common coupling (PCC), active power filters are commonly employed. This
DEFF Research Database (Denmark)
Liu, Hui; Ma, Ke; Loh, Poh Chiang
2015-01-01
. As a result, a sensorless control method is proposed in this paper, which targets to improve the performances of MMC in respect to the above mentioned disadvantages: To decrease the cost and simplify the physical implementation, a state observer is proposed and designed to estimate both the capacitor voltages...
Multilevel Complex Networks and Systems
Caldarelli, Guido
2014-03-01
Network theory has been a powerful tool to model isolated complex systems. However, the classical approach does not take into account the interactions often present among different systems. Hence, the scientific community is nowadays concentrating the efforts on the foundations of new mathematical tools for understanding what happens when multiple networks interact. The case of economic and financial networks represents a paramount example of multilevel networks. In the case of trade, trade among countries the different levels can be described by the different granularity of the trading relations. Indeed, we have now data from the scale of consumers to that of the country level. In the case of financial institutions, we have a variety of levels at the same scale. For example one bank can appear in the interbank networks, ownership network and cds networks in which the same institution can take place. In both cases the systemically important vertices need to be determined by different procedures of centrality definition and community detection. In this talk I will present some specific cases of study related to these topics and present the regularities found. Acknowledged support from EU FET Project ``Multiplex'' 317532.
Multilevel sequential Monte Carlo samplers
Beskos, Alexandros
2016-08-29
In this article we consider the approximation of expectations w.r.t. probability distributions associated to the solution of partial differential equations (PDEs); this scenario appears routinely in Bayesian inverse problems. In practice, one often has to solve the associated PDE numerically, using, for instance finite element methods which depend on the step-size level . hL. In addition, the expectation cannot be computed analytically and one often resorts to Monte Carlo methods. In the context of this problem, it is known that the introduction of the multilevel Monte Carlo (MLMC) method can reduce the amount of computational effort to estimate expectations, for a given level of error. This is achieved via a telescoping identity associated to a Monte Carlo approximation of a sequence of probability distributions with discretization levels . âˆž>h0>h1â‹¯>hL. In many practical problems of interest, one cannot achieve an i.i.d. sampling of the associated sequence and a sequential Monte Carlo (SMC) version of the MLMC method is introduced to deal with this problem. It is shown that under appropriate assumptions, the attractive property of a reduction of the amount of computational effort to estimate expectations, for a given level of error, can be maintained within the SMC context. That is, relative to exact sampling and Monte Carlo for the distribution at the finest level . hL. The approach is numerically illustrated on a Bayesian inverse problem. Â© 2016 Elsevier B.V.
Impedance Source Power Electronic Converters
DEFF Research Database (Denmark)
Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming
and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key...... control methods. Presents the latest power conversion solutions that aim to advance the role of power electronics into industries and sustainable energy conversion systems. Compares impedance source converter/inverter applications in renewable energy power generation and electric vehicles as well...... as different industrial applications. Provides an overview of existing challenges, solutions and future trends. Supported by calculation examples, simulation models and results....
Conceptualising Multilevel Regulation in the EU: A Legal Translation of Multilevel Governance?
Chowdhury, Nupur; Wessel, Ramses A.
2012-01-01
How should we conceive of regulation in the European context? This paper attempts to answer this by developing multilevel regulation as a theoretical concept. The basic aim of the paper is to explore the difference and convergence between regulation and governance and develop multilevel governance
High-Voltage Converter for the Traction Application
Directory of Open Access Journals (Sweden)
Sergey Volskiy
2016-01-01
Full Text Available High-voltage converter employing IGCT switches (VDC=2800 V for traction application is presented. Such a power traction drive operates with an unstable input voltage over 2000⋯4000 V DC and with an output power up to 1200 kW. The original power circuit of the high-voltage converter is demonstrated. Development of the attractive approach to designing the low-loss snubber circuits of the high-frequency IGCT switches is proposed. It is established on the complex multilevel analysis of the transient phenomena and power losses. The essential characteristics of the critical parameters under transient modes and the relation between the snubber circuit parameters and the losses are discussed. Experimental results for the prototype demonstrate the properties of new power circuit. The test results confirm the proposed high-voltage converter performance capability as well as verifying the suitability of the conception for its use in the Russian suburban train power system and other high-voltage applications.
Paulkovich, J.
1979-01-01
Device will convert wind, water, tidal or wave energy into electrical or mechanical energy. Is comprised of windmill-like paddles or blades synchronously geared to orient themselves to wind direction for optimum energy extraction.
Henzler, Stephan
2010-01-01
This text covers the fundamentals of time-to-digital converters on analog and digital conversion principles. It includes a theoretical investigation into quantization, linearity, noise and variability, and it details a range of advanced TDC architectures.
Lewyn, L. L. (Inventor)
1965-01-01
An analog to digital converter circuit arrangement is reported that is suitable for use in ultra fast pulse height analysis. The circuit uses series connected tunnel diodes to quantize a voltage signal into discrete levels.
Laser system with wavelength converter
DEFF Research Database (Denmark)
2012-01-01
The present invention relates to an apparatus comprising a diode laser (10) providing radiation in a first wavelength interval, a radiation conversion unit (12) having an input and an output, the radiation converter configured to receive the radiation in the first wavelength interval from the diode...... laser at the input, the radiation conversion unit configured to convert the radiation in the first wavelength interval to radiation in a second wavelength interval and the output configured to output the converted radiation, the second wavelength interval having one end point outside the first...... wavelength interval. Further, the invention relates to a method of optically pumping a target laser (14) in a laser system, the laser system comprising a laser source providing radiation at a first frequency, the laser source being optically connected to an input of a frequency converter, the frequency...
Kim, Eun Sook; Cao, Chunhua
2015-01-01
Considering that group comparisons are common in social science, we examined two latent group mean testing methods when groups of interest were either at the between or within level of multilevel data: multiple-group multilevel confirmatory factor analysis (MG ML CFA) and multilevel multiple-indicators multiple-causes modeling (ML MIMIC). The performance of these methods were investigated through three Monte Carlo studies. In Studies 1 and 2, either factor variances or residual variances were manipulated to be heterogeneous between groups. In Study 3, which focused on within-level multiple-group analysis, six different model specifications were considered depending on how to model the intra-class group correlation (i.e., correlation between random effect factors for groups within cluster). The results of simulations generally supported the adequacy of MG ML CFA and ML MIMIC for multiple-group analysis with multilevel data. The two methods did not show any notable difference in the latent group mean testing across three studies. Finally, a demonstration with real data and guidelines in selecting an appropriate approach to multilevel multiple-group analysis are provided.
Radiation tolerant power converter controls
Todd, B.; Dinius, A.; King, Q.; Uznanski, S.
2012-11-01
The Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is the world's most powerful particle collider. The LHC has several thousand magnets, both warm and super-conducting, which are supplied with current by power converters. Each converter is controlled by a purpose-built electronic module called a Function Generator Controller (FGC). The FGC allows remote control of the power converter and forms the central part of a closed-loop control system where the power converter voltage is set, based on the converter output current and magnet-circuit characteristics. Some power converters and FGCs are located in areas which are exposed to beam-induced radiation. There are numerous radiation induced effects, some of which lead to a loss of control of the power converter, having a direct impact upon the accelerator's availability. Following the first long shut down (LS1), the LHC will be able to run with higher intensity beams and higher beam energy. This is expected to lead to significantly increased radiation induced effects in materials close to the accelerator, including the FGC. Recent radiation tests indicate that the current FGC would not be sufficiently reliable. A so-called FGClite is being designed to work reliably in the radiation environment in the post-LS1 era. This paper outlines the concepts of power converter controls for machines such as the LHC, introduces the risks related to radiation and a radiation tolerant project flow. The FGClite is then described, with its key concepts and challenges: aiming for high reliability in a radiation field.
Boron nitride converted carbon fiber
Rousseas, Michael; Mickelson, William; Zettl, Alexander K.
2016-04-05
This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.
Current status of converter steelmaking
Energy Technology Data Exchange (ETDEWEB)
Oghbasialasie, H.; Holappa, L.
1995-12-31
This literature work is mainly focusing on the mechanisms of modern converter steelmaking and related with the evaluation of converter technology applied during the last decades and further to the future. The history of steelmaking has been briefly reviewed from bloomeries and early-steelmaking processes to the progress of modern converter process. The pneumatic converter processes were developed in the 1850`s and thereafter the basis for the rapid growth of steel industries was established for the next 100 years. The world production of steel has not continuously grown but fluctuating quite much. It reached 723 Mt in 1994. The production is believed to grow the forecast for the year 2003 being approximately 800 Mt. Electric arc furnace production is estimated to reach 280 Mt by 2003, and BOFIOH will reach 520 Mt by 2003. The current status of the converter steelmaking process is briefly described both on its theoretical bases and practical technological progresses. Developments which significantly improve the process are briefly discussed. Several more recent developments such as combined oxygen blowing process, increased scrap melting, post combustion and hot metal pretreatment are discussed. The future progress will be in further development of these process characteristics as well as in eventual emerging of the continuous converter process. (author)
Energy Technology Data Exchange (ETDEWEB)
Aime, M.
2003-11-15
Thanks to the technological progress achieved in the field of power electronics, the use of static converters has spread to new applications. In particular, some applications such as active filtering or the supply of special AC machines require power converters having good dynamic performances. The subject of this thesis is to evaluate systematically the dynamic performances of multi-cell converters, and then to optimize these performances. This document is organized in four chapters. The first one summarizes the main multilevel converter structures, and some control strategies dedicated to these structures. The second chapter presents the evaluation criteria chosen to quantify the dynamic performances of static converters. These criteria are then used to compare the performances obtained with two different PWM strategies. An optimized strategy which results from a trade-off between the two former strategies is then introduced. The third chapter shows a new control strategy of multi-cell voltage source converters. This new strategy enables to control the peak current at a fixed switching frequency. The operation of this controller is explained, and the results obtained by digital simulations are presented and discussed. The fourth chapter deals with the experimental achievement of the peak current control. In particular, the implementation of the control algorithm within a FPGA is demonstrated. Finally, the conclusion of this thesis presents some orientations for further developments, in order to improve the current control strategy and to widen its field of applications. (author)
Wide-range 7-switch flying capacitor based dc-dc converter for point-of-load applications
Jain, Parth
In this thesis a dc-dc converter referred to as the 7-switch flying capacitor (7SFC) based multi-level buck converter intended for point-of-load applications is presented. The 7SFC operates with the principle of "transformability" which allows it to run in several switching modes when paired with a digital controller. The mode is selected based on input and output conditions by estimating the highest efficiency mode. The 7SFC converter utilizes a flying capacitor, which for certain modes allows for a large reduction in switching losses, especially when the converter is operated with high-input voltages. Compared to the conventional 2-phase interleaved buck converter, the 7SFC is able to reduce the size of the output inductors and capacitor by 33%. The 7SFC discrete prototype is able to achieve efficiencies greater than 90% over the majority of the operating range.
Simulation and Study of Multilevel Inverter System Fed By Photovoltaic Source
Directory of Open Access Journals (Sweden)
Ali Abdulrazzak Jasim
2018-01-01
Full Text Available This paper proposes a simulation of Photovoltaic energy used to supply an induction motor with acomparison of two types of inverters.In general, the greater number of motorswhich"are used incommercial and industrial applicationsare"induction motors. To use PV source to run the induction motor, an interface circuits are used which are a dc-dc"converter and an inverter, the PV cell has nonlinear behavior,"adc-dc converter is used along with Maximum Power Point Tracker controllerto improve theefficiency by boosting the output voltage of the PV module and to match the load demand."The dc output voltage of PV modulethen"converted to AC, two types of inverter are presented, A conventional Voltage Source Inverter system and multilevel inverter system which employselective harmonic eliminationmethod fed three phase induction motor, these two types of inverters are simulated using Matlab/Simulink and their results are presented. The FFT spectrum is presented of the output currents to analyze the harmonics reduction, which shows that the"multilevel inverter is better than VSI system"according to harmonics reduction and increment in output voltage and power.
Directory of Open Access Journals (Sweden)
Yanni Zhong
2017-03-01
Full Text Available Low-voltage direct-current (LVDC networks offer improved conductor utilisation on existing infrastructure and reduced conversion stages, which can lead to a simpler and more efficient distribution network. However, LVDC networks must continue to support AC loads, requiring efficient, low-distortion DC–AC converters. Additionally, increasing numbers of DC loads on the LVAC network require controlled, low-distortion, unity power factor AC-DC converters with large capacity, and bi-directional capability. An AC–DC/DC–AC converter design is therefore proposed in this study to minimise conversion loss and maximise power quality. Comparative analysis is performed for a conventional IGBT two-level converter, a SiC MOSFET two-level converter, a Si MOSFET modular multi-level converter (MMC and a GaN HEMT MMC, in terms of power loss, reliability, fault tolerance, converter cost and heatsink size. The analysis indicates that the five-level MMC with parallel-connected Si MOSFETs is an efficient, cost-effective converter for low-voltage converter applications. MMC converters suffer negligible switching loss, which enables reduced device switching without loss penalty from increased harmonics and filtering. Optimal extent of parallel-connection for MOSFETs in an MMC is investigated. Experimental results are presented to show the reduction in device stress and electromagnetic interference generating transients through the use of reduced switching and device parallel-connection.
The Simulation of DFIG Grid Side Converter
National Research Council Canada - National Science Library
LU Yan-Ling; LU Jian-qiang; BAO Jie
2017-01-01
Firstly，DFIG basic structure of grid side converter was analyzed according to basic principles of voltage converter, and a mathematical model of grid side converter was established in the three-phase...
Multilevel sequential Monte-Carlo samplers
Jasra, Ajay
2016-01-05
Multilevel Monte-Carlo methods provide a powerful computational technique for reducing the computational cost of estimating expectations for a given computational effort. They are particularly relevant for computational problems when approximate distributions are determined via a resolution parameter h, with h=0 giving the theoretical exact distribution (e.g. SDEs or inverse problems with PDEs). The method provides a benefit by coupling samples from successive resolutions, and estimating differences of successive expectations. We develop a methodology that brings Sequential Monte-Carlo (SMC) algorithms within the framework of the Multilevel idea, as SMC provides a natural set-up for coupling samples over different resolutions. We prove that the new algorithm indeed preserves the benefits of the multilevel principle, even if samples at all resolutions are now correlated.
Color error diffusion based on multilevel halftone
Zhu, Wenhua; Chen, Chun; Wang, Qiang; Bu, Jiajun
2014-07-01
We propose a multilevel halftone-based color error diffusion (ED) algorithm. Our algorithm aims to achieve a "blue noise" color halftone by exploiting the interchannel relationship of a separated color image. The method focuses on dot distribution and dot overlapping control to yield high quality results. It treats color ED as a multilevel halftone and employs an embedded multilevel ED algorithm to determine the number of color dots in the processing pixel. In the color rendering process, the most suitable colors are selected as output based on the sum of the input and the error diffused from the processed dot. Experimental results show that the proposed algorithm generates high-quality halftone images with "blue noise" characteristics. Comparisons with state-of-the-art methods using objective and subjective measures show that our method is superior, as it effectively avoids dot overlapping and preserves the details of the original image.
Commons in a Multi-level World
Directory of Open Access Journals (Sweden)
Fikret Berkes
2007-11-01
Full Text Available This special issue of the International Journal of the Commons considers a variety of conceptual perspectives and lessons from cases to deal with the problems of a globalized, multi-level world. It aims to contribute to extending and elaborating commons theory; understanding the issue of scale and institutional linkages; and understanding multi-level governance of a commons with state, private and civil society actors. The issue is based largely on papers presented at the 2006 Biennial Conference of IASC in Bali, Indonesia. Papers investigate partnerships, networks, and cross-scale institutional linkages in commons management, using a grassroots perspective, while taking into account multi-level governance. The issue includes both conceptual and case study papers (and those combining the two, providing examples from a range of geographical areas and resource types, and using interdisciplinary perspectives, in keeping with IASC ideals.
Modeling of asymmetrical boost converters
Directory of Open Access Journals (Sweden)
Eliana Isabel Arango Zuluaga
2014-01-01
Full Text Available The asymmetrical interleaved dual boost (AIDB is a fifth-order DC/DC converter designed to interface photovoltaic (PV panels. The AIDB produces small current harmonics to the PV panels, reducing the power losses caused by the converter operation. Moreover, the AIDB provides a large voltage conversion ratio, which is required to step-up the PV voltage to the large dc-link voltage used in grid-connected inverters. To reject irradiance and load disturbances, the AIDB must be operated in a closed-loop and a dynamic model is required. Given that the AIDB converter operates in Discontinuous Conduction Mode (DCM, classical modeling approaches based on Continuous Conduction Mode (CCM are not valid. Moreover, classical DCM modeling techniques are not suitable for the AIDB converter. Therefore, this paper develops a novel mathematical model for the AIDB converter, which is suitable for control-pur-poses. The proposed model is based on the calculation of a diode current that is typically disregarded. Moreover, because the traditional correction to the second duty cycle reported in literature is not effective, a new equation is designed. The model accuracy is contrasted with circuital simulations in time and frequency domains, obtaining satisfactory results. Finally, the usefulness of the model in control applications is illustrated with an application example.
Modeling of asymmetrical boost converters
Directory of Open Access Journals (Sweden)
Eliana Isabel Arango Zuluaga
2014-03-01
Full Text Available The asymmetrical interleaved dual boost (AIDB is a fifth-order DC/DC converter designed to interface photovoltaic (PV panels. The AIDB produces small current harmonics to the PV panels, reducing the power losses caused by the converter operation. Moreover, the AIDB provides a large voltage conversion ratio, which is required to step-up the PV voltage to the large dc-link voltage used in grid-connected inverters. To reject irradiance and load disturbances, the AIDB must be operated in a closed-loop and a dynamic model is required. Given that the AIDB converter operates in Discontinuous Conduction Mode (DCM, classical modeling approaches based on Continuous Conduction Mode (CCM are not valid. Moreover, classical DCM modeling techniques are not suitable for the AIDB converter. Therefore, this paper develops a novel mathematical model for the AIDB converter, which is suitable for control-pur-poses. The proposed model is based on the calculation of a diode current that is typically disregarded. Moreover, because the traditional correction to the second duty cycle reported in literature is not effective, a new equation is designed. The model accuracy is contrasted with circuital simulations in time and frequency domains, obtaining satisfactory results. Finally, the usefulness of the model in control applications is illustrated with an application example.
Mao, Mingxuan; Duan, Qichang; Zhang, Li; Chen, Hao; Hu, Bei; Duan, Pan
2017-08-24
The paper presents a novel two-stage particle swarm optimization (PSO) for the maximum power point tracking (MPPT) control of a PV system consisting of cascaded PV-converter modules, under partial shading conditions (PSCs). In this scheme, the grouping method of the shuffled frog leaping algorithm (SFLA) is incorporated with the basic PSO algorithm, ensuring fast and accurate searching of the global extremum. An adaptive speed factor is also introduced to improve its convergence speed. A PWM algorithm enabling permuted switching of the PV sources is applied. The method enables this PV system to achieve the maximum power generation for any number of PV and converter modules. Simulation studies of the proposed MPPT scheme are performed on a system having two chained PV buck-converter modules and a dc-ac H-bridge connected at its terminals for supplying an AC load. The results show that this type of PV system allows each module to achieve the maximum power generation according its illumination level without affecting the others, and the proposed new control method gives significantly higher power output compared with the conventional P&O and PSO methods.
Data analysis using regression and multilevel/hierarchical models
National Research Council Canada - National Science Library
Gelman, Andrew; Hill, Jennifer
2007-01-01
"Data Analysis Using Regression and Multilevel/Hierarchical Models is a comprehensive manual for the applied researcher who wants to perform data analysis using linear and nonlinear regression and multilevel models...
Multilevel transport solution of LWR reactor cores
Energy Technology Data Exchange (ETDEWEB)
Jose Ignacio Marquez Damian; Cassiano R.E. de Oliveira; HyeonKae Park
2008-09-01
This work presents a multilevel approach for the solution of the transport equation in typical LWR assemblies and core configurations. It is based on the second-order, even-parity formulation of the transport equation, which is solved within the framework provided by the finite element-spherical harmonics code EVENT. The performance of the new solver has been compared with that of the standard conjugate gradient solver for diffusion and transport problems on structured and unstruc-tured grids. Numerical results demonstrate the potential of the multilevel scheme for realistic reactor calculations.
The Boost Converter – Revisited
Directory of Open Access Journals (Sweden)
Barry W. Williams
2015-12-01
Full Text Available The dc-to-dc boost converter is a single-switch, single-inductor, switching circuit used to efficiently transform energy from one dc voltage level to a greater voltage level of the same relative polarity. For a specific resistive load range, as the duty cycle decreases, the boost converter inductor enters a discontinuous current mode of operation - the output load current having decreased to a definable level. This paper analyses the fact that a further reduction of load current, as the duty cycle decreases towards zero, will always result in the re-emergence of a continuous inductor current condition. Further, at the other load extreme, high-current, progressively for increasing load current, starting at low duty cycle conditions, the minimum inductor current always increases from a fixed normalised current level, for a specific load range. These and other hitherto unexplored boost converter properties are analysed and verified mathematically and with PSpice simulations.
DEFF Research Database (Denmark)
Margheritini, Lucia
between ventures and private investors, and to promote an accelerated shift from a technology to a market focus. This Thesis is presented as a collection of works published by the author on her research on the Sea wave Slot cone Generator wave energy converter. These include 1 accepted and 2 submitted...... from technology to market focus. This has been done by using the R&D steps for a specific wave energy converter as an example of best practice for wave energy development towards commercialization. The Sea wave Slot cone Generator (SSG) is a multilevel wave energy converter. Incoming waves overtop...... the consumption of fossil fuels and related greenhouse-gas emissions and to the development of Renewable Energy Sources (RES). Diversification of RES is fundamental in such a path to ensure sustainability. In this contest wave energy can provide great contribution, having its worldwide resource been estimated...
An Original Stepwise Multilevel Logistic Regression Analysis of Discriminatory Accuracy
DEFF Research Database (Denmark)
Merlo, Juan; Wagner, Philippe; Ghith, Nermin
2016-01-01
BACKGROUND AND AIM: Many multilevel logistic regression analyses of "neighbourhood and health" focus on interpreting measures of associations (e.g., odds ratio, OR). In contrast, multilevel analysis of variance is rarely considered. We propose an original stepwise analytical approach that disting......BACKGROUND AND AIM: Many multilevel logistic regression analyses of "neighbourhood and health" focus on interpreting measures of associations (e.g., odds ratio, OR). In contrast, multilevel analysis of variance is rarely considered. We propose an original stepwise analytical approach...
Simplified design of data converters
Lenk, John
1997-01-01
Simplified Design of Data Converters shows how to design and experiment with data converters, both analog-to-digital and digital to analog. The design approach here is the same one used in all of John Lenk's best-selling books on simplified and practical design. Throughout the book, design problems start with guidelines for selecting all components on a trial-value basis, assuming a specific design goal and set of conditions. Then, using the guideline values in experimental circuits, the desired results are produced by varying the experimental component values, if needed.If you are a w
Energy Technology Data Exchange (ETDEWEB)
Reass, W. A. (William A.); Apgar, S. E. (Sean E.); Baca, D. M. (David M.); Doss, James D.; Gonzales, J. (Jacqueline); Gribble, R. F. (Robert F.); Hardek, T. W. (Thomas W.); Lynch, M. T. (Michael T.); Rees, D. E. (Daniel E.); Tallerico, P. J. (Paul J.); Trujillo, P. B. (Pete B.); Anderson, D. E. (David E.); Heidenreich, D. A. (Dale A.); Hicks, J. D. (Jim D.); Leontiev, V. N.
2003-01-01
The Spallation Neutron Source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge National Laboratory. The accelerator requires 15 converter-modulator stations each providing between 9 and 11 MW pulses with up to a 1 .I MW average power. The converter-modulator can be described as a resonant 20 kHz polyphase boost inverter. Each converter modulator derives its buss voltage from a standard substation cast-core transformer. Each substation is followed by an SCR pre-regulator to accommodate voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage is provided by self-clearing metallized hazy polypropylene traction capacitors. These capacitors do not fail short, but clear any internal anomaly. Three 'H-Bridge' IGBT transistor networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are time-gated to generate the desired klystron pulse width. Pulse width modulation of the individual 20 lcHz pulses is utilized to provide regulated output waveforms with DSP based adaptive feedforward and feedback techniques. The boost transformer design utilizes nanocrystalline alloy that provides low core loss at design flux levels and switching frequencies. Capacitors are used on the transformer secondary networks to resonate the leakage inductance. The transformers are wound for a specific leakage inductance, not turns ratio. This design technique generates multiple secondary volts per turn as compared to the primary. With the appropriate tuning conditions, switching losses are minimized. The resonant topology has the added benefit of being deQed in a klystron fault condition, with little energy deposited in the arc. This obviates the need of crowbars or other related networks. A review of these design parameters, operational performance, production status, and OWL installation and performance to date will be presented.
Multilevel Dual Damascene copper interconnections
Lakshminarayanan, S.
Copper has been acknowledged as the interconnect material for future generations of ICs to overcome the bottlenecks on speed and reliability present with the current Al based wiring. A new set of challenges brought to the forefront when copper replaces aluminum, have to be met and resolved to make it a viable option. Unit step processes related to copper technology have been under development for the last few years. In this work, the application of copper as the interconnect material in multilevel structures with SiO2 as the interlevel dielectric has been explored, with emphasis on integration issues and complete process realization. Interconnect definition was achieved by the Dual Damascene approach using chemical mechanical polishing of oxide and copper. The choice of materials used as adhesion promoter/diffusion barrier included Ti, Ta and CVD TiN. Two different polish chemistries (NH4OH or HNO3 based) were used to form the interconnects. The diffusion barrier was removed during polishing (in the case of TiN) or by a post CMP etch (as with Ti or Ta). Copper surface passivation was performed using boron implantation and PECVD nitride encapsulation. The interlevel dielectric way composed of a multilayer stack of PECVD SiO2 and SixNy. A baseline process sequence which ensured the mechanical and thermal compatibility of the different unit steps was first created. A comprehensive test vehicle was designed and test structures were fabricated using the process flow developed. Suitable modifications were subsequently introduced in the sequence as and when processing problems were encountered. Electrical characterization was performed on the fabricated devices, interconnects, contacts and vias. The structures were subjected to thermal stressing to assess their stability and performance. The measurement of interconnect sheet resistances revealed lower copper loss due to dishing on samples polished using HNO3 based slurry. Interconnect resistances remained stable upto 400o
Brainard, John P [Albuquerque, NM; Christenson, Todd R [Albuquerque, NM
2009-11-03
A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.
Westra, Jan R.; Annema, Anne J.
2000-01-01
A digital to analog converter for a multibit digital input signal has a set of conversion elements for the positive signal excursions and a set of conversion elements for the negative signal excursions. In each set the conversion elements are selected according to a dynamic element matching
Westra, Jan R.; Annema, Anne J.
2006-01-01
A digital to analog converter for a multibit digital input signal has a set of conversion elements for the positive signal excursions and a set of conversion elements for the negative signal excursions. In each set the conversion elements are selected according to a dynamic element matching
XML Docbook to Mediawiki Converter
Directory of Open Access Journals (Sweden)
Maria Chiara Pievatolo
2013-05-01
Full Text Available A Perl script, based on the work of Stefano Selleri, to migrate XML-Docbook 4.X documents to Wiki markup. I added some lines to meet my need to convert my Kant translations from Docbook to MediaWiki. A sample of the output can be...
Multilevel Growth Mixture Models for Classifying Groups
Palardy, Gregory J.; Vermunt, Jeroen K.
2010-01-01
This article introduces a multilevel growth mixture model (MGMM) for classifying both the individuals and the groups they are nested in. Nine variations of the general model are described that differ in terms of categorical and continuous latent variable specification within and between groups. An application in the context of school effectiveness…
Multilevel models in international business research
Peterson, M.F.; Arregle, J-L.; Martin, Xavier
2012-01-01
Multiple-level (or mixed linear) modeling (MLM) can simultaneously test hypotheses at several levels of analysis (usually two or three), or control for confounding effects at one level while testing hypotheses at others. Advances in multi-level modeling allow increased precision in quantitative
Multilevel modelling and public health policy
Leyland, Alastair H.; Groenewegen, Peter P.
2003-01-01
Background: Multilevel modelling is a statistical technique that extends ordinary regression analysis to the situation where the data are hierarchical. Such data form an increasingly common evidence base for public health policy, and as such it is important that policy makers should be aware of this
Robust Algebraic Multilevel Methods and Algorithms
Kraus, Johannes
2009-01-01
This book deals with algorithms for the solution of linear systems of algebraic equations with large-scale sparse matrices, with a focus on problems that are obtained after discretization of partial differential equations using finite element methods. Provides a systematic presentation of the recent advances in robust algebraic multilevel methods. Can be used for advanced courses on the topic.
Cervical Laminoplasty for Multilevel Cervical Myelopathy
Murali Krishna Sayana; Hassan Jamil; Ashley Poynton
2011-01-01
Cervical spondylotic myelopathy can result from degenerative cervical spondylosis, herniated disk material, osteophytes, redundant ligamentum flavum, or ossification of the posterior longitudinal ligament. Surgical intervention for multi-level myelopathy aims to decompress the spinal cord and maintain stability of the cervical spine. Laminoplasty was major surgical advancement as laminectomy resulted in kyphosis and unsatisfactory outcomes. Hirabayashi popularised the expansive open door lami...
A Practical Guide to Multilevel Modeling
Peugh, James L.
2010-01-01
Collecting data from students within classrooms or schools, and collecting data from students on multiple occasions over time, are two common sampling methods used in educational research that often require multilevel modeling (MLM) data analysis techniques to avoid Type-1 errors. The purpose of this article is to clarify the seven major steps…
Frequency assignment for satellite multilevel SCPC systems
Lau, Yuk-Hong; Skellern, D. J.
1991-01-01
A method for searching the frequency assignment for satellite multilevel SCPC systems is proposed based on the method for the case of equal carrier systems. The quality of assignment improves significantly on published results. The method requires only very short computations times.
A multilevel evolutionary framework for sustainability analysis
Directory of Open Access Journals (Sweden)
Timothy M. Waring
2015-06-01
Full Text Available Sustainability theory can help achieve desirable social-ecological states by generalizing lessons across contexts and improving the design of sustainability interventions. To accomplish these goals, we argue that theory in sustainability science must (1 explain the emergence and persistence of social-ecological states, (2 account for endogenous cultural change, (3 incorporate cooperation dynamics, and (4 address the complexities of multilevel social-ecological interactions. We suggest that cultural evolutionary theory broadly, and cultural multilevel selection in particular, can improve on these fronts. We outline a multilevel evolutionary framework for describing social-ecological change and detail how multilevel cooperative dynamics can determine outcomes in environmental dilemmas. We show how this framework complements existing sustainability frameworks with a description of the emergence and persistence of sustainable institutions and behavior, a means to generalize causal patterns across social-ecological contexts, and a heuristic for designing and evaluating effective sustainability interventions. We support these assertions with case examples from developed and developing countries in which we track cooperative change at multiple levels of social organization as they impact social-ecological outcomes. Finally, we make suggestions for further theoretical development, empirical testing, and application.
The Economic Cost of Homosexuality: Multilevel Analyses
Baumle, Amanda K.; Poston, Dudley, Jr.
2011-01-01
This article builds on earlier studies that have examined "the economic cost of homosexuality," by using data from the 2000 U.S. Census and by employing multilevel analyses. Our findings indicate that partnered gay men experience a 12.5 percent earnings penalty compared to married heterosexual men, and a statistically insignificant earnings…
Communicative Skill and the Multilevel Language Classroom.
Rado, Marta
1984-01-01
Focuses on speech act theory and the demands of the multilevel language classroom, noting that special attention should be paid in language classes to what is meant, as distinct from what is said. Using the communicative approach to language teaching and crossing cultural boundaries, cross-cultural conversations are being developed that are…
Application of multilevel analysis approach in management theory
Directory of Open Access Journals (Sweden)
S. Morteza Ghayour
2013-12-01
Full Text Available Any phenomenon can be considered and analyzed in terms of different perspectives. In multilevel theorists view, structure or structures of the studied phenomenon are used to consider or to analyze it, completely. Level of analysis indicates the purpose of a researcher or theorist that is intended to be explained or justified, like individual, group or organizational levels and then they are generalized. Contrary to multilevel approach, the conventional approach of theorizing considers micro level or macro level. It cannot perform a simultaneous micro–macro level analysis. A multilevel approach characterized by inter-level and multilevel organizational view to organizational phenomena is an attempt to expand the boundaries of knowledge and provide a new plan. This study uses documentary studies to analyze the multi-level approach of theorizing, multilevel models and multilevel analysis.
DEFF Research Database (Denmark)
Gohil, Ghanshyamsinh Vijaysinh; Bede, Lorand; Teodorescu, Remus
2016-01-01
Many high power converter systems are often connected to the medium voltage network using a step-up transformer. In such systems, the converter-side windings of the transformer can be configured as an open-end and multi-level voltage waveforms can be achieved by feeding these open-end windings from...... the flux in the common part of the magnetic core is completely canceled out. As a result, the size of the magnetic component can be significantly reduced. A multi-objective design optimization is presented, where the energy loss and the volume are optimized. The optimization process takes into account...
Efficiency of Capacitively Loaded Converters
DEFF Research Database (Denmark)
Andersen, Thomas; Huang, Lina; Andersen, Michael A. E.
2012-01-01
This paper explores the characteristic of capacitance versus voltage for dielectric electro active polymer (DEAP) actuator, 2kV polypropylene film capacitor as well as 3kV X7R multi layer ceramic capacitor (MLCC) at the beginning. An energy efficiency for capacitively loaded converters...... is introduced as a definition of efficiency. The calculated and measured efficiency curves for charging DEAP actuator, polypropylene film capacitor and X7R MLCC are provided and compared. The attention has to be paid for the voltage dependent capacitive load, like X7R MLCC, when evaluating the charging...... efficiency of converter. Based on the capacitancevoltage curve, the correct capacitance should be chosen when calculating the stored energy; otherwise misleading optimistic efficiency can always be obtained. Actually, when DEAP actuator is not available at the early developing stage, the voltage independent...
Radiated EMI from power converters
Directory of Open Access Journals (Sweden)
Arnautovski-Toševa Vesna
2005-01-01
Full Text Available With the continuous increase of switching frequency together with the ongoing trend to higher complexity and functionality, power converters as a part of electronic systems have raised more and more electromagnetic energy pollution to the local system environment. In the same time, stringent demands are imposed on the designers of new circuits that electromagnetic interference (EMI has to be suppressed at its source before it is allowed to propagate into other circuits and systems. In this paper, the authors present a full-wave numerical method for calculation and simulation of electromagnetic field radiated by power converter circuitry. The main objective is to analyze the layout geometry in order to obtain competitive PCB layout that will enable suitably attenuated level of the radiated electric field to safe level. By this it would be possible to ensure reliable operation of the sensitive electronic components in the proximity.
Westra, Jan R.; Annema, Anne J.
2000-01-01
A digital to analog converter for a multibit digital input signal has a set of conversion elements for the positive signal excursions and a set of conversion elements for the negative signal excursions. In each set the conversion elements are selected according to a dynamic element matching algorithm. To improve the mismatch-noise shaping of these algorithms, excess conversion elements may be additionally selected.
DEFF Research Database (Denmark)
Boora, Arash A.; Nami, Alireza; Zare, Firuz
2010-01-01
The output voltage quality of some of the single-phase multilevel inverters can be improved when their dc-link voltages are regulated asymmetrically. Symmetrical and asymmetrical multilevel diode-clamped inverters have the problem of dc-link capacitor voltage balancing, especially when power factor...... of the load is close to unity. In this paper, a new single-inductor multi-output dc/dc converter is proposed that can control the dc-link voltages of a single-phase diode-clamped inverter asymmetrically to achieve voltage quality enhancement. The circuit of the presented converter is explained and the main...... that the proposed combination of introduced multioutput dc–dc converter and single-phase ADCI is a good candidate for power conversion in residential photovoltaic (PV) utilization....
Development of a Compact Matrix Converter
Directory of Open Access Journals (Sweden)
J. Bauer
2009-01-01
Full Text Available This paper deals with the development of a matrix converter. Matrix converters belong to the category of direct frequency converters. A converter does not contain DC-link and the output voltage is provided by direct switching of voltage from the input phases. This is enabled by 9 bidirectional switches, which are provided by anti-serial connection of 18 IGBT transistors. The absence of a DC-link is great advantage of the matrix converter, but it also increases the requirements on the converter control. For this reason a new prototype of a matrix converter is being developed with sophisticated modern components (FPGA, Power PC equipped in the control part of the converter. The converter will be used for testing new control algorithms and commutation methods.
Computerized simulation of converter process
Energy Technology Data Exchange (ETDEWEB)
Jalkanen, H.; Suomi, M.L.; Wallgren, M. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Metallurgy
1996-12-31
Converter process is essentially an oxidising refining process aiming in addition to (1) the primary refining action, decarburisation of high carbon iron melt, also to (2) maximal elimination of impurity elements, especially silicon, phosphorus and sulphur, (3) melting of substantial amounts of scrap using the extra heat released in oxidation reactions and (4) to exact final steel temperature control, optimal for further treatments. `Quantitative modelling of such a complex non-stationary chemical process as oxygen converting necessitates extensive formulation of chemical and thermal evolution of the process in connection with the technological properties of the reactor and the process control measures. A comprehensive converter simulation program like CONSIM-3. 1 and its preceding versions that is based on the theoretical and practical knowledge on the process can be used for (1) educating specialists and smelter personnel, (2) planning of the blowing programs, (3) developing and testing of process control systems and after some elaboration and restructuring (4) it can be integrated to static or dynamic process control systems. (orig.) SULA 2 Research Programme; 10 refs.
High efficiency thermionic converter studies
Huffman, F. N.; Sommer, A. H.; Balestra, C. L.; Briere, D. P.; Oettinger, P. E.
1976-01-01
The objective is to improve thermionic converter performance by means of reduced interelectrode losses, greater emitter capabilities, and lower collector work functions until the converter performance level is suitable for out-of-core space reactors and radioisotope generators. Electrode screening experiments have identified several promising collector materials. Back emission work function measurements of a ZnO collector in a thermionic diode have given values less than 1.3 eV. Diode tests were conducted over the range of temperatures of interest for space power applications. Enhanced mode converter experiments have included triodes operated in both the surface ionization and plasmatron modes. Pulsed triodes were studied as a function of pulse length, pulse potential, inert gas fill pressure, cesium pressure, spacing, emitter temperature and collector temperature. Current amplifications (i.e., mean output current/mean grid current) of several hundred were observed up to output current densities of one amp/sq cm. These data correspond to an equivalent arc drop less than 0.1 eV.
Simulation Results of Double Forward Converter
Directory of Open Access Journals (Sweden)
P. Vijaya KUMAR
2009-12-01
Full Text Available This work aims to find a better forward converter for DC to DC conversion.Simulation of double forward converter in SMPS system is discussed in this paper. Aforward converter with RCD snubber to synchronous rectifier and/or to current doubleris also discussed. The evolution of the forward converter is first reviewed in a tutorialfashion. Performance parameters are discussed including operating principle, voltageconversion ratio, efficiency, device stress, small-signal dynamics, noise and EMI. Itscircuit operation and its performance characteristics of the forward converter with RCDsnubber and double forward converter are described and the simulation results arepresented.
Multilevel resistive information storage and retrieval
Energy Technology Data Exchange (ETDEWEB)
Lohn, Andrew; Mickel, Patrick R.
2016-08-09
The present invention relates to resistive random-access memory (RRAM or ReRAM) systems, as well as methods of employing multiple state variables to form degenerate states in such memory systems. The methods herein allow for precise write and read steps to form multiple state variables, and these steps can be performed electrically. Such an approach allows for multilevel, high density memory systems with enhanced information storage capacity and simplified information retrieval.
Hochman, Jiří
2009-01-01
The Bachelor's thesis deals with multilevel marketing phenomenon which is on the rise in the Czech Republic recently. It tries to clarify why, and also shows the real problems and situations which meets interested persons. The second part is practical. It deals with company EFCZ. In this part are described several problems regarding the company. In the conclusion are recommended several steps which should be taken by the company to improve it's situation.
Automatic Multilevel Parallelization Using OpenMP
Directory of Open Access Journals (Sweden)
Haoqiang Jin
2003-01-01
Full Text Available In this paper we describe the extension of the CAPO parallelization support tool to support multilevel parallelism based on OpenMP directives. CAPO generates OpenMP directives with extensions supported by the NanosCompiler to allow for directive nesting and definition of thread groups. We report some results for several benchmark codes and one full application that have been parallelized using our system.
Multilevel Monte Carlo in Approximate Bayesian Computation
Jasra, Ajay
2017-02-13
In the following article we consider approximate Bayesian computation (ABC) inference. We introduce a method for numerically approximating ABC posteriors using the multilevel Monte Carlo (MLMC). A sequential Monte Carlo version of the approach is developed and it is shown under some assumptions that for a given level of mean square error, this method for ABC has a lower cost than i.i.d. sampling from the most accurate ABC approximation. Several numerical examples are given.
Automatic Synthesis of Multilevel Combinational Logic
DEFF Research Database (Denmark)
Andersen, Anders C.; Madsen, Jan; Madsen, J.R.
1989-01-01
This paper describes a system for the synthesis of multilevel combinational logic, transforming functional description into mask layout. The system includes a logic synthesis part, partly consisting of tools developed at Eindhoven University of Technology, which has been interfaced to the layout...... synthesis part in the CATOE-system, developed at the DesignCenter of Electronics Institute. The various steps in the transformation are presented together with a complete design example, implementing a multi-output combinational decoder function....
Directory of Open Access Journals (Sweden)
V. V. Konashchuk
2013-07-01
Full Text Available The article studies functioning of the scheme of transformation power through the converter wind-power installations during emergency operation. The main types of emergencies for this converter are considered. An approach to the calculation of short-circuit current of a synchronous generator and short-circuit current of an LC-circuit is presented. Protection elements (voltage limiters, fuses, fast current sensors are given for circuit protection and the reliability in emergency conditions is offered. Unlike classic circuit diagrams for wind-power installations, the circuit diagrams without multiplying gear for turbo-generator wind-рower installations have a self-stabilization effect of electromechanical system under optimal conditions in a wide range of a wind flow. In order to improve its effectiveness and implement an offline mode, you need to use converters to match the frequency of the generator voltage and that the frequency of network. Circuit diagrams of such converters have a complex structure, they contain a number of power supplies and rectifiers, capacitive storages, pulse converters and multi-level inverters.
Electromechanical converters for electric vehicles
Ambros, T.; Burduniuc, M.; Deaconu, S. I.; Rujanschi, N.
2018-01-01
The paper presents the analysis of various constructive schemes of synchronous electromechanical converters with permanent magnets fixed on the rotor and asynchronous with the short-circuit rotor. Various electrical stator winding schemes have also been compared, demonstrating the efficiency of copper utilization in toroidal windings. The electromagnetic calculus of the axial machine has particularities compared to the cylindrical machine, in the paper is presented the method of correlating the geometry of the cylindrical and axial machines. In this case the method and recommendations used in the design of such machines may be used.
Multilevel Ventilation: Theory and Simplified Mathematical Model
Directory of Open Access Journals (Sweden)
P. Torok
2008-01-01
Full Text Available Considering the issues of artificial ventilation (AV in non-homogenous pathological lung processes (acute lung injury, acute respiratory distress syndrome, pneumonia, etc., the authors created a mathematical model of multicompartment non-homogenous injured lungs that were ventilated by a new mode of AV, the so-called three-level ventilation. Multilevel ventilation was defined a type (modification of ALV whose basic ventilation level was produced by the modes CMV, PCV or PS (ASB and add-on level, and the so-called background ventilation was generated by the levels of PEEP and high PEEP (PEEPh with varying frequency and duration. Multi-level ventilation on 3 pressure levels was realized by the mathematical model as a combination of pressure-controlled ventilation (PCV and two levels of PEEP and PEEPh. The objective was to prove that in cases of considerably non-homogenous gas distribution in acute pathological disorders of lungs, gas entry into the so-called slow bronchoalveolar compartments could be improved by multilevel AV, without substabtially changing the volume of so-called fast compartments. Material and Method. Multi-level ventilation at 3 pressure levels was realized by the mathematical model as a combination of PCV and two levels of PEEP and PEEPh. Results. By comparing the single-level AV in the PCV mode with the so-called three-level ventilation defined as a combination of PCV+PEEPh/PEEP, the authors have discovered that the loading of slow compartments in the model was considerably improved by 50—60% as compared with the baseline values. In absolute terms, this difference was as many as 2—10 times of the volume. Conclusion. The mathematical model may demonstrate that the application of the so-called three-level AV causes considerable changes in gas distribution in the lung parenchyma disordered by a non-homogenous pathological process. The authors state that the proposed mathematical model requires clinical verification in order
OAM mode converter in twisted fibers
DEFF Research Database (Denmark)
Usuga Castaneda, Mario A.; Beltran-Mejia, Felipe; Cordeiro, Cristiano
2014-01-01
We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA.......We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA....
12 CFR 1.6 - Convertible securities.
2010-01-01
... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Convertible securities. 1.6 Section 1.6 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE TREASURY INVESTMENT SECURITIES § 1.6 Convertible securities. A national bank may not purchase securities convertible into stock at the option of...
Convertible Subspaces of Hessenberg-Type Matrices
Directory of Open Access Journals (Sweden)
Henrique F. da Cruz
2017-12-01
Full Text Available We describe subspaces of generalized Hessenberg matrices where the determinant is convertible into the permanent by affixing ± signs. An explicit characterization of convertible Hessenberg-type matrices is presented. We conclude that convertible matrices with the maximum number of nonzero entries can be reduced to a basic set.
Ecologically Optimal Solution of Power Semiconductors Converters
Directory of Open Access Journals (Sweden)
Pavol Spanik
2003-01-01
Full Text Available One of the relevant scientific programs of Department of Power Electrical Systems is research of ecologically optimal topologies main circuits of power converters. This paper presents some methods how to reduce unfavourable influences of power converters on the grid. The achieved results were applieed in praxis, especially in the power converters produced by Electrotechnical Research and Projecting Institute in Nova Dubnica.
A novel converter topology for TEM applications
Indian Academy of Sciences (India)
and energy levels of the TEM system, require special type of excitation technique. Power converters for ... This paper proposes a novel converter topology to meet these excitation current require- ments. A novel ... The converter control system is given a square wave current reference of required amplitude,. ON duration TS ...
Incentive systems in multi-level markets for virtual goods
Schmidt, A.U.
2005-01-01
As an alternative to rigid DRM measures, ways of marketing virtual goods through multi-level or networked marketing have raised some interest. This report is a first approach to multi-level markets for virtual goods from the viewpoint of theoretical economy. A generic, kinematic model for the monetary flow in multi-level markets, which quantitatively describes the incentives that buyers receive through resales revenues, is devised. Building on it, the competition of goods is examined in a dyn...
An investigation of multilevel refinement in routing and location problems
Rodney, Demane O'Neil
2008-01-01
Multilevel refinement is a collaborative hierarchical solution technique. The multilevel technique aims to enhance the solution process of optimisation problems by improving the asymptotic convergence in the quality of solutions produced by its underlying local search heuristics and/or improving the convergence rate of these heuristics. To these aims, the central methodologies of the multilevel technique are filtering solutions from the search space (via coarsening), reducing the amount of pr...
Hybrid thermionic-photovoltaic converter
Datas, A.
2016-04-01
A conceptual device for the direct conversion of heat into electricity is presented. This concept hybridizes thermionic (TI) and thermophotovoltaic (TPV) energy conversion in a single thermionic-photovoltaic (TIPV) solid-state device. This device transforms into electricity both the electron and photon fluxes emitted by an incandescent surface. This letter presents an idealized analysis of this device in order to determine its theoretical potential. According to this analysis, the key advantage of this converter, with respect to either TPV or TI, is the higher power density in an extended temperature range. For low temperatures, TIPV performs like TPV due to the negligible electron flux. On the contrary, for high temperatures, TIPV performs like TI due to the great enhancement of the electron flux, which overshadows the photon flux contribution. At the intermediate temperatures, ˜1650 K in the case of this particular study, I show that the power density potential of TIPV converter is twice as great as that of TPV and TI. The greatest impact concerns applications in which the temperature varies in a relatively wide range, for which averaged power density enhancement above 500% is attainable.
Hybrid thermionic-photovoltaic converter
Energy Technology Data Exchange (ETDEWEB)
Datas, A. [Instituto de Energía Solar, Universidad Politécnica de Madrid, 28040 Madrid (Spain)
2016-04-04
A conceptual device for the direct conversion of heat into electricity is presented. This concept hybridizes thermionic (TI) and thermophotovoltaic (TPV) energy conversion in a single thermionic-photovoltaic (TIPV) solid-state device. This device transforms into electricity both the electron and photon fluxes emitted by an incandescent surface. This letter presents an idealized analysis of this device in order to determine its theoretical potential. According to this analysis, the key advantage of this converter, with respect to either TPV or TI, is the higher power density in an extended temperature range. For low temperatures, TIPV performs like TPV due to the negligible electron flux. On the contrary, for high temperatures, TIPV performs like TI due to the great enhancement of the electron flux, which overshadows the photon flux contribution. At the intermediate temperatures, ∼1650 K in the case of this particular study, I show that the power density potential of TIPV converter is twice as great as that of TPV and TI. The greatest impact concerns applications in which the temperature varies in a relatively wide range, for which averaged power density enhancement above 500% is attainable.
Social Capital and Health: A Review of Prospective Multilevel Studies
National Research Council Canada - National Science Library
Murayama, Hiroshi; Fujiwara, Yoshinori; Kawachi, Ichiro
2012-01-01
Background: This article presents an overview of the concept of social capital, reviews prospective multilevel analytic studies of the association between social capital and health, and discusses intervention...
Converting pest insects into food
DEFF Research Database (Denmark)
Offenberg, Hans Joachim; Wiwatwittaya, Decha
2010-01-01
Canopy dwelling weaver ants (Oecophylla spp.) are used to control a variety of pests in a number of tropical tree crops. What is less familiar is the existence of commercial markets where these ants and their brood are sold for (i) human consumption, (ii) pet food or (iii) traditional medicine...... on management, 32-115 kg ant brood (mainly new queens) was harvested per ha per year without detrimental effect on colony survival and worker ant densities. This suggest that ant biocontrol and ant harvest can be sustainable integrated in plantations and double benefits derived. As ant production is fuelled...... by pest insects, problematic pests are converted into food and additional earnings. To assess the profitability of providing additional food for the ants, O. smaragdina food conversion efficiency (ECI) was estimated in the laboratory. This estimate suggests the feeding of weaver ants in ant farms...
High-Performance Data Converters
DEFF Research Database (Denmark)
Steensgaard-Madsen, Jesper
in a standard CMOS technology, they can be designed to yield 100 dB performance at 10 times oversampling. The proposed scaled-element mismatch-shaping D/A converters are well suited for use as the feedback stage in oversampled delta-sigma quantizers. It is, however, not easy to make full use of their potential...... this problem. This way, the delta-sigma quantizer's feedback signal is obtained by a multiple-stage quantization, where the loop quantizer (low-resolution and minimum-delay) implements only the last-stage quantization. Hence, high-speed, high-resolutiondelta-sigma quantization is feasible without using complex...... circuitry. An improved version of the MASH topology is also proposed. A delta-sigma quantizer is used to quantize the input signal into an oversampled digital representation of low-to-moderate resolution. The delta-sigma quantizer'struncation error is estimated either directly, or as the first...
Reliability of Wave Energy Converters
DEFF Research Database (Denmark)
Ambühl, Simon
There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs to become successful and more competitive to other renewable electricity sources, the consideration of the structural reliability of WECs is essential...... WEPTOS. Calibration of safety factors are performed for welded structures at theWavestar device including different control systems for harvesting energy from waves. In addition, a case study of different O&M strategies for WECs is discussed, and an example of reliability-based structural optimization....... Structural reliability considerations and optimizations impact operation and maintenance (O&M) costs as well as the initial investment costs. Furthermore, there is a control system for WEC applications which defines the harvested energy but also the loads onto the structure. Therefore, extreme loads but also...
Reliability of Wave Energy Converters
DEFF Research Database (Denmark)
Ambühl, Simon
There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs tobecome successful and more competitive to other renewable electricity sources,the consideration of the structural reliability of WECs is essential...... for welded structures at the Wavestar device includingdifferent control systems for harvesting energy from waves. In addition, a casestudy of different O&M strategies for WECs is discussed, and an example ofreliability-based structural optimization of the Wavestar foundation ispresented. The work performed.......Structural reliability considerations and optimizations impact operation andmaintenance (O&M) costs as well as the initial investment costs.Furthermore, there is a control system for WEC applications which defines theharvested energy but also the loads onto the structure. Therefore, extremeloads but also fatigue loads...
DEFF Research Database (Denmark)
Vicinanza, Diego; Margheritini, Lucia; Kofoed, Jens Peter
2012-01-01
The Sea-wave Slot-cone Generator concept (SSG) is a Wave Energy Converter based on the wave overtopping principle utilizing several reservoirs placed on top of each other, in which the energy of the incoming wave will be stored as potential energy. The water captured in the reservoirs will then run...... through turbines for electricity production. The system utilizes a wide spectrum of different wave conditions by means of multiple reservoirs, located at different levels above the still water level. Thereby, it obtains a high overall efficiency and it can be suitable for shoreline and breakwater...... at the Svaaheia site (Norway), Port of Hanstholm (Denmark) and Port of Garibaldi (Oregon, USA). In the last-mentioned two projects, the Sea-wave Slot-cone Generator technology is integrated into outer harbor breakwater and jetty reconstruction projects. Comprehensive studies have been performed in the last years...
Spinal deformity after multilevel osteoplastic laminotomy.
Raab, Peter; Juergen, Krauss; Gloger, Harald; Soerensen, Nils; Wild, Alexander
2008-06-01
Multilevel laminectomy in children has a significant rate of postoperative spinal deformity. To decrease the incidence of this complication, the use of osteoplastic laminotomy is advocated to minimise the risk of spinal deformity by preserving the normal architecture of the spine. In this retrospective study, a 10-year series of a paediatric population undergoing multilevel osteoplastic laminotomy is reviewed to determine the incidence, especially in contrast to laminectomies, and to identify factors that affect the occurrence of spinal column deformity. Seventy patients (mean age 4.2 years) underwent multilevel osteoplastic laminotomy for congenital anomalies or removal of spinal tumours. All patients had a clinical and radiographic examination preoperatively, 12 months postoperatively and at follow-up. Mean follow-up was 5.3 years (range 3-12.6 years). Nineteen patients (27%) had a new or progressive spinal deformity. There was an increased incidence in patients who had surgery for spinal tumours (Pspine (spine included (Pdeformity found a significantly higher (46%) compared to our study group. This study demonstrates that osteoplastic laminotomy was found to be very effective in decreasing the incidence of spinal deformities after spinal-canal surgery for spinal-cord tumours or congenital anomalies in children and adolescents. The choice of an anatomical reconstructive surgical technique such as osteoplastic laminotomy seems to be essential to minimise secondary problems due to the surgical technique itself. Nevertheless, growing patients should be followed up for several years after the initial operation for early detection and consequent management of any possible deformity of the spinal column.
Power analysis of trials with multilevel data
Moerbeek, Mirjam
2015-01-01
Power Analysis of Trials with Multilevel Data covers using power and sample size calculations to design trials that involve nested data structures. The book gives a thorough overview of power analysis that details terminology and notation, outlines key concepts of statistical power and power analysis, and explains why they are necessary in trial design. It guides you in performing power calculations with hierarchical data, which enables more effective trial design.The authors are leading experts in the field who recognize that power analysis has attracted attention from applied statisticians i
Agent Based Reasoning in Multilevel Flow Modeling
DEFF Research Database (Denmark)
Lind, Morten; Zhang, Xinxin
2012-01-01
to launch the MFM Workbench into an agent based environment, which can complement disadvantages of the original software. The agent-based MFM Workbench is centered on a concept called “Blackboard System” and use an event based mechanism to arrange the reasoning tasks. This design will support the new......Multilevel Flow Modeling (MFM) is a modeling method used for modeling complex industrial plant. Currently, MFM is supported with a standalone software tool called MFM Workbench, which is equipped with causal-relation analysis and other functionalities. The aim of this paper is to offer a new design...
An introduction to multilevel flow modeling
DEFF Research Database (Denmark)
Lind, Morten
2011-01-01
Multilevel Flow Modeling (MFM) is a methodology for functional modeling of industrial processes on several interconnected levels of means-end and part-whole abstractions. The basic idea of MFM is to represent an industrial plant as a system which provides the means required to serve purposes in i...... in detail by a water mill example. The overall reasoning capabilities of MFM and its basis in cause-effect relations are also explained. The appendix contains an overview of MFM concepts and their definitions....
Multilevel Flow Modeling of Domestic Heating Systems
DEFF Research Database (Denmark)
Hu, Junjie; Lind, Morten; You, Shi
2012-01-01
Multilevel Flow Modeling (MFM) is a well recognized methodology for functional modeling of complex systems which primarily focuses on the representation of their goals and functions. It has been successfully used in industrial process, e.g. nuclear power plant, chemical plants etc. to facilitate...... i.e. supplying and transferring thermal energy, it is off interest to use MFM to investigate similarities and differences between different implementations. In this paper, three typical domestic European heating systems, which differ from each other in the number of temperature sensors and auxiliary...
Consequence Reasoning in Multilevel Flow Modelling
DEFF Research Database (Denmark)
Zhang, Xinxin; Lind, Morten; Ravn, Ole
2013-01-01
Consequence reasoning is a major element for operation support system to assess the plant situations. The purpose of this paper is to elaborate how Multilevel Flow Models can be used to reason about consequences of disturbances in complex engineering systems. MFM is a modelling methodology...... syntax and gives detailed reasoning formulas for consequence reasoning. The reasoning formulas offers basis for developing rule-based system to perform consequence reasoning based on MFM, which can be used for alarm design, risk monitoring, and supervision and operation support system design....
Multilevel Simulation of Heterogeneous Reconfigurable Platforms
Directory of Open Access Journals (Sweden)
Damien Picard
2009-01-01
Full Text Available This paper presents a general system-level simulation and testing methodology for reconfigurable System-on-Chips, starting from behavioral specifications of system activities to multilevel simulations of accelerated tasks running on the reconfigurable circuit. The system is based on a common objectoriented environment that offers valuable debugging and probing facilities as well as integrated testing features. Our system brings these benefits to the hardware simulation, while enforcing validation through characterization tests and interoperability through on-demand mainstream tools connections. This framework has been partially developed in the scope of the EU Morpheus project and is used to validate our contribution to the spatial design task.
Multilevel Hybrid Chernoff Tau-Leap
Moraes, Alvaro
2015-01-07
Markovian pure jump processes can model many phenomena, e.g. chemical reactions at molecular level, protein transcription and translation, spread of epidemics diseases in small populations and in wireless communication networks, among many others. In this work [6] we present a novel multilevel algorithm for the Chernoff-based hybrid tauleap algorithm. This variance reduction technique allows us to: (a) control the global exit probability of any simulated trajectory, (b) obtain accurate and computable estimates for the expected value of any smooth observable of the process with minimal computational work.
Multilevel Hybrid Chernoff Tau-Leap
Moraes, Alvaro
2014-01-06
Markovian pure jump processes can model many phenomena, e.g. chemical reactions at molecular level, protein transcription and translation, spread of epidemics diseases in small populations and in wireless communication networks, among many others. In this work [6] we present a novel multilevel algorithm for the Chernoff-based hybrid tauleap algorithm. This variance reduction technique allows us to: (a) control the global exit probability of any simulated trajectory, (b) obtain accurate and computable estimates for the expected value of any smooth observable of the process with minimal computational work.
Multilevel Hybrid Chernoff Tau-Leap
Moraes, Alvaro
2016-01-06
Markovian pure jump processes can model many phenomena, e.g. chemical reactions at molecular level, protein transcription and translation, spread of epidemics diseases in small populations and in wireless communication networks, among many others. In this work [6] we present a novel multilevel algorithm for the Chernoff-based hybrid tauleap algorithm. This variance reduction technique allows us to: (a) control the global exit probability of any simulated trajectory, (b) obtain accurate and computable estimates for the expected value of any smooth observable of the process with minimal computational work.
Cluster bias: Testing measurement invariance in multilevel data
Jak, S.
2013-01-01
In this thesis we presented methods and procedures to test and account for measurement bias in multilevel data. Multilevel data are data with a clustered structure, for instance data of children grouped in classrooms, or data of employees in teams. For example, with data of children in classes, we
Multilevel Modeling: A Review of Methodological Issues and Applications
Dedrick, Robert F.; Ferron, John M.; Hess, Melinda R.; Hogarty, Kristine Y.; Kromrey, Jeffrey D.; Lang, Thomas R.; Niles, John D.; Lee, Reginald S.
2009-01-01
This study analyzed the reporting of multilevel modeling applications of a sample of 99 articles from 13 peer-reviewed journals in education and the social sciences. A checklist, derived from the methodological literature on multilevel modeling and focusing on the issues of model development and specification, data considerations, estimation, and…
Performance analysis of modified algorithm for finding multilevel association rules
Shrivastava, Arpna; Jain, R. C.
2013-01-01
Multilevel association rules explore the concept hierarchy at multiple levels which provides more specific information. Apriori algorithm explores the single level association rules. Many implementations are available of Apriori algorithm. Fast Apriori implementation is modified to develop new algorithm for finding multilevel association rules. In this study the performance of this new algorithm is analyzed in terms of running time in seconds.
Fast Multilevel Panel Method for Wind Turbine Rotor Flow Simulations
van Garrel, Arne; Venner, Cornelis H.; Hoeijmakers, Hendrik Willem Marie
2017-01-01
A fast multilevel integral transform method has been developed that enables the rapid analysis of unsteady inviscid flows around wind turbines rotors. A low order panel method is used and the new multi-level multi-integration cluster (MLMIC) method reduces the computational complexity for
Application of Multilevel Logistic Model to Identify Correlates of ...
African Journals Online (AJOL)
Implementation of multilevel model is becoming a common analytic technique over a wide range of disciplines including social and economic sciences. In this paper, an attempt has been made to assess the application of multilevel logistic model for the purpose of identifying the effect of household characteristics on poverty ...
Multilevel- marketing v České republice
Prudičová, Petra
2009-01-01
Graduation Theses concerns an analysis and evaluation, of how a multi-level marketing, functions in the Czech Republic. Explaining its ideals and principals, while it theoretically applies on a specific company, which is involved with multi-level marketing. The target is to introduce such system in an objective way and evaluate it in practice.
A Multilevel Analysis of Parental Discipline and Child Antisocial Behavior
Stoolmiller, Mike; Snyder, Jim
2004-01-01
We demonstrate graphical and analytical methods for multilevel (2- and 3-level) models using the analysis of observed microsocial interaction between parent-child dyads as an example. We also present multilevel path diagrams and argue that while not as compact as equations, path diagrams may communicate results better to a wider audience. The…
Multilevel Higher-Order Item Response Theory Models
Huang, Hung-Yu; Wang, Wen-Chung
2014-01-01
In the social sciences, latent traits often have a hierarchical structure, and data can be sampled from multiple levels. Both hierarchical latent traits and multilevel data can occur simultaneously. In this study, we developed a general class of item response theory models to accommodate both hierarchical latent traits and multilevel data. The…
Extensions of Mantel-Haenszel for Multilevel DIF Detection
French, Brian F.; Finch, W. Holmes
2013-01-01
Multilevel data structures are ubiquitous in the assessment of differential item functioning (DIF), particularly in large-scale testing programs. There are a handful of DIF procures for researchers to select from that appropriately account for multilevel data structures. However, little, if any, work has been completed to extend a popular DIF…
Matching Strategies for Observational Data with Multilevel Structure
Steiner, Peter M.
2011-01-01
Given the different possibilities of matching in the context of multilevel data and the lack of research on corresponding matching strategies, the author investigates two main research questions. The first research question investigates the advantages and disadvantages of different matching strategies that can be pursued with multilevel data…
Szczesniak, Pawel
2013-01-01
AC voltage frequency changes is one of the most important functions of solid state power converters. The most desirable features in frequency converters are the ability to generate load voltages with arbitrary amplitude and frequency, sinusoidal currents and voltages waveforms; the possibility of providing unity power factor for any load; and, finally, a simple and compact power circuit. Over the past decades, a number of different frequency converter topologies have appeared in the literature, but only the converters with either a voltage or current DC link are commonly used in industrial app
Multilevel Modeling of the Performance Variance
Directory of Open Access Journals (Sweden)
Alexandre Teixeira Dias
2012-12-01
Full Text Available Focusing on the identification of the role played by Industry on the relations between Corporate Strategic Factors and Performance, the hierarchical multilevel modeling method was adopted when measuring and analyzing the relations between the variables that comprise each level of analysis. The adequacy of the multilevel perspective to the study of the proposed relations was identified and the relative importance analysis point out to the lower relevance of industry as a moderator of the effects of corporate strategic factors on performance, when the latter was measured by means of return on assets, and that industry don‟t moderates the relations between corporate strategic factors and Tobin‟s Q. The main conclusions of the research are that the organizations choices in terms of corporate strategy presents a considerable influence and plays a key role on the determination of performance level, but that industry should be considered when analyzing the performance variation despite its role as a moderator or not of the relations between corporate strategic factors and performance.
Multilevel analysis in road safety research.
Dupont, Emmanuelle; Papadimitriou, Eleonora; Martensen, Heike; Yannis, George
2013-11-01
Hierarchical structures in road safety data are receiving increasing attention in the literature and multilevel (ML) models are proposed for appropriately handling the resulting dependences among the observations. However, so far no empirical synthesis exists of the actual added value of ML modelling techniques as compared to other modelling approaches. This paper summarizes the statistical and conceptual background and motivations for multilevel analyses in road safety research. It then provides a review of several ML analyses applied to aggregate and disaggregate (accident) data. In each case, the relevance of ML modelling techniques is assessed by examining whether ML model formulations (i) allow improving the fit of the model to the data, (ii) allow identifying and explaining random variation at specific levels of the hierarchy considered, and (iii) yield different (more correct) conclusions than single-level model formulations with respect to the significance of the parameter estimates. The evidence reviewed offers different conclusions depending on whether the analysis concerns aggregate data or disaggregate data. In the first case, the application of ML analysis techniques appears straightforward and relevant. The studies based on disaggregate accident data, on the other hand, offer mixed findings: computational problems can be encountered, and ML applications are not systematically necessary. The general recommendation concerning disaggregate accident data is to proceed to a preliminary investigation of the necessity of ML analyses and of the additional information to be expected from their application. Copyright © 2013 Elsevier Ltd. All rights reserved.
Multi-level spectral graph partitioning method
Talu, Muhammed Fatih
2017-09-01
In this article, a new method for multi-level and balanced division of non-directional graphs (MSGP) is introduced. Using the eigenvectors of the Laplacian matrix of graphs, the method has a spectral approach which has superiority over local methods (Kernighan-Lin and Fiduccia-Mattheyses) with a global division ability. Bisection, which is a spectral method, can divide the graph by using the Fiedler vector, while the recursive version of this method can divide into multiple levels. However, the spectral methods have two disadvantages: (1) high processing costs; (2) dividing the sub-graphs independently. With a better understanding of the eigenvectors of the whole graph, and by discovering the confidential information owned, MSGP can divide the graphs into balanced and multi-leveled without recursive processing. Inspired by Haar wavelets, it uses the eigenvectors with a binary heap tree. The comparison results in seven existing methods (some are community detection algorithms) on regular and irregular graphs which clearly demonstrate that MSGP works about 14,4 times faster than the others to produce a proper partitioning result.
Multilevel VLSI interconnection—an optimum approach?
Srikrishnan, K. V.; Totta, P. A.
1986-04-01
The wirability of circuit elements is a key ingredient in the success of the very large scale integration technology. Multilevel wiring eliminates the need to use extensive areas of the silicon surface simply for wiring channels. Increasing the number of wiring planes significantly improves the possibility of achieving the goals of the VLSI, i.e. the interconnection of the maximum number of devices in the smallest possible area. Extensive modeling has shown the need to optimize the wiring pitch, number of wiring planes and electrical properties of the materials used (e.g-low resistivity for conductors and low dielectric constant for insulators). The choice of the interconnection technology is also influenced by other factors. Some of these areas: cost and reliability objectives; in house expertise and practice; new process/equipment availability and a desire to maintain process commonality. The selected strategy is sometimes an optimum approach for an individual situation which is not universally optimum. In IBM, for example, two different but successful multilevel wiring technologies are being used extensively. The first is used for bipolar circuits; it is a three-level metallization design, with sputtered SiO2 as the insulator. The second, for FET devices, has two-levels of metal and polyimide as the insulator. Both technologies use area array input/output terminal connections and lift off line definition. The process/material set of each is reviewed to emphasize the mechanics of reaching an ``optimum'' solution for the individual applications.
Gadolinium sheet converter for neutron radiography
Energy Technology Data Exchange (ETDEWEB)
Lima, C.T.S. [Laboratorio de Neutrongrafia em Tempo Real (LNRTR/PEN/COPPE), Universidade Federal do Rio de Janeiro, Ilha do Fundao, Caixa Postal 68509, 21941-972 Rio de Janeiro, RJ (Brazil); Crispim, V.R. [Laboratorio de Neutrongrafia em Tempo Real (LNRTR/PEN/COPPE), Universidade Federal do Rio de Janeiro, Ilha do Fundao, Caixa Postal 68509, 21941-972 Rio de Janeiro, RJ (Brazil); PEN/COPPE-DNC/Escola Politecnica CT, Universidade Federal do Rio de Janeiro, Ilha do Fundao, Caixa Postal 68509, 21941-972 Rio de Janeiro, RJ (Brazil)], E-mail: verginia@con.ufrj.br; Santos, W.M.S. [Laboratorio de Colisao Atomica e Molecular (LACAM/IF), Universidade Federal do Rio de Janeiro, Ilha do Fundao, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ (Brazil)
2007-12-15
This work describes a methodology developed for the confection of gadolinium sheet converter for neutron radiography using the gadolinium chloride (GdCl{sub 3}) as material converter. Though manufactured at a relatively low cost, they are as good as the sheet converter on the market. Here, we present neutron radiography of the penetrameter, the edge spread function, the modulation transfer function and characteristic curves for each set sheet-AA400 Kodak film.
Ocean floor mounting of wave energy converters
Siegel, Stefan G
2015-01-20
A system for mounting a set of wave energy converters in the ocean includes a pole attached to a floor of an ocean and a slider mounted on the pole in a manner that permits the slider to move vertically along the pole and rotate about the pole. The wave energy converters can then be mounted on the slider to allow adjustment of the depth and orientation of the wave energy converters.
Commutation Processes in Multiresonant ZVS Bridge Converter
Directory of Open Access Journals (Sweden)
Miroslaw Luft
2008-01-01
Full Text Available The analysis of the multiresonant ZVS DC/DC bridge converter is presented. The control system of the converter is basedon the method of frequency control at the constant time of transistor turn-off with a phase shift. The operation of the circuit is givenand the operating range of the converter is defined where ZVS switching operation is assured. Control characteristics are given andthe converter’s efficiency is defined. The circuit’s operation is analysed on the basis of results of the converter simulation tests using Simplorer programme.
Conducted Emission Evaluation for Direct Matrix Converters
Nothofer, A.; Tarisciotti, L.; Greedy, S.; Empringham, L.; De Lillo, L.; Degano, M.
2016-05-01
Matrix converters have been recently proposed as an alternative solution to the standard back-to-back converter in aerospace applications. However, Electromagnetic Interference (EMI), in particular, conducted emissions represent a critical aspect for this converter family. Direct Matrix Converter (DMC) are usually modelled only at the normal operating frequency, but for the research presented in this paper, the model is modified in order to include a detailed high frequency description, which is of interest for conducted emission studies.This paper analyzes the performance of DMC, when different control and modulation techniques are used. Experimental results are shown to validate the simulation models.
Comparison of the Impedance-Source Networks for Two and Multilevel Buck-Boost Inverter Applications
DEFF Research Database (Denmark)
Husev, Oleksandr; Blaabjerg, Frede; Roncero-Clemente, Carlos
2016-01-01
described, which makes it difficult to choose the best option. Thus, the aim of this paper is to present a comprehensive analytical comparison of the impedance-source-based buck–boost inverters in terms of passive component count and semiconductor stress. Based on the waveform of the input current, i.......e., with or without a transformer, and with or without inductor coupling, the impedance-source converters are classified. The main criterion in our comprehensive comparison is the energy stored in the passive elements, which is considered both under constant and predefined high frequency current ripple...... in the inductors and the voltage ripple across the capacitors. Two-level and multilevel solutions are described. The conclusions provide a “one-stop” information source and a selection guide of impedance-source-based buck–boost inverters for different applications....
Perspectives on Multi-Level Dynamics
Atay, Fatihcan M; Blanchard, Philippe; Cessac, Bruno; Olbrich, Eckehard; Volchenkov, Dima
2016-01-01
As Physics did in previous centuries, there is currently a common dream of extracting generic laws of nature in economics, sociology, neuroscience, by focalising the description of phenomena to a minimal set of variables and parameters, linked together by causal equations of evolution whose structure may reveal hidden principles. This requires a huge reduction of dimensionality (number of degrees of freedom) and a change in the level of description. Beyond the mere necessity of developing accurate techniques affording this reduction, there is the question of the correspondence between the initial system and the reduced one. In this paper, we offer a perspective towards a common framework for discussing and understanding multi-level systems exhibiting structures at various spatial and temporal levels. We propose a common foundation and illustrate it with examples from different fields. We also point out the difficulties in constructing such a general setting and its limitations.
Multilevel Drift-Implicit Tau-Leap
Ben Hammouda, Chiheb
2016-01-06
The dynamics of biochemical reactive systems with small copy numbers of one or more reactant molecules is dominated by stochastic effects. For those systems, discrete state-space and stochastic simulation approaches were proved to be more relevant than continuous state-space and deterministic ones. In systems characterized by having simultaneously fast and slowtimescales, the existing discrete space-state stochastic path simulation methods such as the stochastic simulation algorithm (SSA) and the explicit tauleap method can be very slow. Implicit approximations were developed in the literature to improve numerical stability and provide efficient simulation algorithms for those systems. In this work, we propose an efficient Multilevel Monte Carlo method in the spirit of the work by Anderson and Higham (2012) that uses drift-implicit tau-leap approximations at levels where the explicit tauleap method is not applicable due to numerical stability issues. We present numerical examples that illustrate the performance of the proposed method.
Multilevel Monte Carlo Approaches for Numerical Homogenization
Efendiev, Yalchin R.
2015-10-01
In this article, we study the application of multilevel Monte Carlo (MLMC) approaches to numerical random homogenization. Our objective is to compute the expectation of some functionals of the homogenized coefficients, or of the homogenized solutions. This is accomplished within MLMC by considering different sizes of representative volumes (RVEs). Many inexpensive computations with the smallest RVE size are combined with fewer expensive computations performed on larger RVEs. Likewise, when it comes to homogenized solutions, different levels of coarse-grid meshes are used to solve the homogenized equation. We show that, by carefully selecting the number of realizations at each level, we can achieve a speed-up in the computations in comparison to a standard Monte Carlo method. Numerical results are presented for both one-dimensional and two-dimensional test-cases that illustrate the efficiency of the approach.
Multi-level coupled cluster theory
Energy Technology Data Exchange (ETDEWEB)
Myhre, Rolf H.; Koch, Henrik, E-mail: henrik.koch@ntnu.no [Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Department of Chemistry and the PULSE Institute, Stanford University, Stanford, California 94305 (United States); Sánchez de Merás, Alfredo M. J. [Institute of Molecular Science, University of Valencia, ES-46980 Paterna, Valencia (Spain)
2014-12-14
We present a general formalism where different levels of coupled cluster theory can be applied to different parts of the molecular system. The system is partitioned into subsystems by Cholesky decomposition of the one-electron Hartree-Fock density matrix. In this way the system can be divided across chemical bonds without discontinuities arising. The coupled cluster wave function is defined in terms of cluster operators for each part and these are determined from a set of coupled equations. The total wave function fulfills the Pauli-principle across all borders and levels of electron correlation. We develop the associated response theory for this multi-level coupled cluster theory and present proof of principle applications. The formalism is an essential tool in order to obtain size-intensive complexity in the calculation of local molecular properties.
DEFF Research Database (Denmark)
Ma, Ke; Blaabjerg, Frede
2014-01-01
The three-level neutral-point (NP)-clamped (3L-NPC) converter is a promising multilevel topology in the application of megawatt wind power generation systems. However, the growing requirements by grid codes may impose high stress and even give reliability problem to this converter topology....... This paper investigates the loss and thermal performances of a 10-MW 3L-NPC wind power inverter undergoing low-voltage ride-through (LVRT) operation. A series of new space vector modulation methods is then proposed to relocate the thermal loading among the power switching devices. It is concluded that...
Modeling and Simulation of Matrix Converter
DEFF Research Database (Denmark)
Liu, Fu-rong; Klumpner, Christian; Blaabjerg, Frede
2005-01-01
This paper discusses the modeling and simulation of matrix converter. Two models of matrix converter are presented: one is based on indirect space vector modulation and the other is based on power balance equation. The basis of these two models is• given and the process on modeling is introduced...
Reliability of Power Electronic Converter Systems
DEFF Research Database (Denmark)
The main aims of power electronic converter systems (PECS) are to control, convert, and condition electrical power flow from one form to another through the use of solid-state electronics. This book outlines current research into the scientific modeling, experimentation, and remedial measures for...
Time-Interleaved Analog to Digital Converters
Louwsma, S.M.; van Tuijl, Adrianus Johannes Maria; Nauta, Bram
2010-01-01
This book describes the research carried out by our PhD student Simon Louwsma at the University of Twente, The Netherlands in the field of high-speed Analogto- Digital (AD) converters. AD converters are crucial circuits for modern systems where information is stored or processed in digital form. Due
High Precision Current Measurement for Power Converters
Cerqueira Bastos, M
2015-01-01
The accurate measurement of power converter currents is essential to controlling and delivering stable and repeatable currents to magnets in particle accelerators. This paper reviews the most commonly used devices for the measurement of power converter currents and discusses test and calibration methods.
RF digital-to-analog converter
Conway, P.H.; Yu, D.U.L.
1995-02-28
A digital-to-analog converter is disclosed for producing an RF output signal proportional to a digital input word of N bits from an RF reference input, N being an integer greater or equal to 2. The converter comprises a plurality of power splitters, power combiners and a plurality of mixers or RF switches connected in a predetermined configuration. 18 figs.
Modelling and Control of Grid converter
DEFF Research Database (Denmark)
Teodorescu, Remus; Blaabjerg, Frede; Iov, Florin
The present report describes the work done in the Phase 1a during the research project "Modelling and Control of Grid Converter". The developed models for the plant and different control strategies for the grid converter are presented in detail. Simulation results under different operating...
Modelling and Control of Grid converter
DEFF Research Database (Denmark)
Iov, Florin; Teodorescu, Remus; Blaabjerg, Frede
The present report describes the work done in the Phase 1b during the research project "Modelling and Control of Grid Converter". The models used in simulations are presented in detail. Two control strategies for the grid converter are considered for investigations, namely the Adaptive Band...
Present trends in HVDC converter station design
Energy Technology Data Exchange (ETDEWEB)
Carlsson, Lennart; Asplund, Gunnar; Bjorklund, Hans; Flisberg, Gunnar [ABB Power Systems AB, Ludvika (Sweden)
1994-12-31
HVDC converter station technology has developed rapidly to satisfy increasing requirements during past 10 - 15 years, but there has not been any dramatic changes since thyristor valves were introduced in the mid 70s. This paper describes some recent and expected future developments, that will substantiality change and simplify future converter stations. (author) 4 refs., 7 figs.
DEFF Research Database (Denmark)
Forouzesh, Mojtaba; Siwakoti, Yam P.; Gorji, Saman A.
2017-01-01
on the general law and framework of the development of next-generation step-up dc-dc converters, this paper aims to comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage...
Evolutionary biosemiotics and multilevel construction networks.
Sharov, Alexei A
2016-12-01
In contrast to the traditional relational semiotics, biosemiotics decisively deviates towards dynamical aspects of signs at the evolutionary and developmental time scales. The analysis of sign dynamics requires constructivism (in a broad sense) to explain how new components such as subagents, sensors, effectors, and interpretation networks are produced by developing and evolving organisms. Semiotic networks that include signs, tools, and subagents are multilevel, and this feature supports the plasticity, robustness, and evolvability of organisms. The origin of life is described here as the emergence of simple self-constructing semiotic networks that progressively increased the diversity of their components and relations. Primitive organisms have no capacity to classify and track objects; thus, we need to admit the existence of proto-signs that directly regulate activities of agents without being associated with objects. However, object recognition and handling became possible in eukaryotic species with the development of extensive rewritable epigenetic memory as well as sensorial and effector capacities. Semiotic networks are based on sequential and recursive construction, where each step produces components (i.e., agents, scaffolds, signs, and resources) that are needed for the following steps of construction. Construction is not limited to repair and reproduction of what already exists or is unambiguously encoded, it also includes production of new components and behaviors via learning and evolution. A special case is the emergence of new levels of organization known as metasystem transition . Multilevel semiotic networks reshape the phenotype of organisms by combining a mosaic of features developed via learning and evolution of cooperating and/or conflicting subagents.
Transformer Isolated Buck-Boost Converters
Directory of Open Access Journals (Sweden)
Barry W. Williams
2016-12-01
Full Text Available Of the single-switch dc-to-dc converters, those with the buck-boost voltage transfer function offer most potential for transformer coupling, hence isolation, at the kilowatt level. This paper highlights the limitations of the traditional magnetic coupled, buck-boost topology. Then four split-capacitor transformer-coupled topologies (specifically the Cuk, sepic, zeta, and a new, converters with a common ac equivalent circuit are explored, that do not temporarily store core magnetic energy as does the traditional isolated buck-boost converter nor have a core dc magnetizing current bias, as with the sepic and zeta transformer coupled topologies. Core dc bias capacitive voltage compensation is a practical design constraint in three of the four topologies, while all four must cater for stray and leakage inductance effects. Simulations and experimental results for the new converter at 408W support the transformer-coupled, single-switch dc-to-dc converter concepts investigated.
Modelling, analyses and design of switching converters
Cuk, S. M.; Middlebrook, R. D.
1978-01-01
A state-space averaging method for modelling switching dc-to-dc converters for both continuous and discontinuous conduction mode is developed. In each case the starting point is the unified state-space representation, and the end result is a complete linear circuit model, for each conduction mode, which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small-signal). While the method is generally applicable to any switching converter, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model. The insights that emerge from the general state-space modelling approach lead to the design of new converter topologies through the study of generic properties of the cascade connection of basic buck and boost converters.
Periodic Control of Power Electronic Converters
DEFF Research Database (Denmark)
Zhou, Keliang; Danwei, Wang; Yang, Yongheng
Advanced power electronic converters convert, control and condition electricity. Power converters require control strategies for periodic signal compensation to assure good power quality and stable power system operation. This comprehensive text presents the most recent internal model principle...... based periodic control technology, which offers the perfect periodic control solution for power electronic conversion. It also provides complete analysis and synthesis methods for periodic control systems, and plenty of practical examples to demonstrate the validity of proposed periodic control...... technology for power converters. It proposes a unified framework for housing periodic control schemes for power converters, and provides a general proportional-integral-derivative control solution to periodic signal compensation in extensive engineering applications. Periodic Control of Power Electronic...
A review of Indirect Matrix Converter Topologies
Directory of Open Access Journals (Sweden)
Salem Rahmani
2015-08-01
Full Text Available Abstract—Matrix Converter (MC is a modern direct AC/AC electrical power converter without dc-link capacitor. MC is operated in four quadrant, assuring a control of the output voltage, amplitude and frequency. The matrix converter has recently attracted significant attention among researchers and it has become increasing attractive for applications of wind energy conversion, military power supplies, induction motor drives, etc. Recently, different MC topologies have been proposed and developed which have their own advantages and disadvantages. Matrix converter can be classified as direct and indirect structures. The direct one has been elaborated in previous work. In this paper the indirect MCs are reviewed. Different characteristics of the indirect MC topologies are mentioned to show the strengths and weaknesses of such converter topologies.
Switched Mode Four-Quadrant Converters
Thurel, Y
2015-01-01
This paper was originally presented at CAS-2004, and was slightly modified for CAS-2014. It presents a review of the key parameters that impact the design choices for a true four-quadrant power converter, in the range 1-10 kW, mainly based on switching mode converter topology. This paper will first describe the state-of-the-art for this power converter family, giving the drawbacks and advantages of different possible solutions. It will also present practical results obtained from the CERN-designed converter. It will finally give some important tips regarding critical phases like test one, when conducting a project dealing with this type of power converter.
single-phase dc phase dc-ac boost converter ac boost converter
African Journals Online (AJOL)
User
This paper describes a new power conversion circuit dc-dc boost converter. It boost converter. It boost converter. It comprises an H comprises an H. Change of load .... A full-wave rectified signal is used to produce an AC reference voltage v* o. The outer voltage loop generates the reference current command i* f. A common.
Energy Technology Data Exchange (ETDEWEB)
Ecklebe, Andreas
2009-05-22
The publication discusses a three- to two-phase matrix converter for contactless power transmission systems. Based on relevant publications, possible resonance setups for contactless power transmission systems are investigated to begin with. An analysis of relevant parameters shows the differences between the various setups, but it also shows that for an investigation focusing on the feeding converter, simple modelling of the three investigated resonance setups is possible with the aid of a serial oscillating circuit. In consequence, it should be possible to apply the results also to the matrix converter with other serially resonant loads. The second part of the investigation focuses on the matrix converter. After a theoretical description, a combination von high-frequency control - e.g. bulk pulsing - and low-frequency pulsing patterns for setting the harmonics level of the grid currents is presented. The similarity to a conventional H bridge circuit enables an assessment of commutation and the identification of the necessary inverter states. These are characterized in that a bidirectional connection between the input system and each output phase is available at any time. The functioning of the commutation and of the inverter as a whole is proved by simulation in a first step, in which also the dynamic switching characteristics of the power semiconductors is taken into account. Finally, the results of laboratory measurements are presented and compared with the theoretical results. The laboratory setup consists of the power section of the matrix converter with input filters and modular gate drivers, a DSP/FPGA control system, and a contactless power transmission system with a current inverter and load on the secondary side. The investigation thus provides information on the use of the three-to-two phase matrix converter as an interesting alternative for feeding of contactless power transmission systems and other serially resonant loads. (orig.) [German] Diese
Electromagnetic Compatibility of Matrix Converter System
Directory of Open Access Journals (Sweden)
S. Fligl
2006-12-01
Full Text Available The presented paper deals with matrix converters pulse width modulation strategies design with emphasis on the electromagnetic compatibility. Matrix converters provide an all-silicon solution to the problem of converting AC power from one frequency to another, offering almost all the features required of an ideal static frequency changer. They possess many advantages compared to the conventional voltage or current source inverters. A matrix converter does not require energy storage components as a bulky capacitor or an inductance in the DC-link, and enables the bi-directional power flow between the power supply and load. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. The perspective of matrix converters regarding EMC in comparison with other types of converters is brightly evident because it is no need to use any equipment for power factor correction and current and voltage harmonics reduction. Such converter with proper control is properly compatible both with the supply mains and with the supplied load. A special digital control system was developed for the realized experimental test bed which makes it possible to achieve greater throughput of the digital control system and its variability.
Underwater noise from a wave energy converter
DEFF Research Database (Denmark)
Tougaard, Jakob
A recent addition to the anthropogenic sources of underwater noise is offshore wave energy converters. Underwater noise was recorded from the Wavestar wave energy converter located at Hastholm, Denmark (57°7.73´N, 8°37.23´E). The Wavestar is a full-scale test and demonstration converter...... in full operation and start and stop of the converter. Median broad band (10 Hz – 20 kHz) sound pressure level (Leq) was 123 dB re. 1 Pa, irrespective of status of the wave energy converter (stopped, running or starting/stopping). The most pronounced peak in the third-octave spectrum was in the 160 Hz...... significant noise above ambient could be detected above the 250 Hz band. The absolute increase in noise above ambient was very small. L50 third-octave levels in the four bands with the converter running were thus only 1-2 dB above ambient L50 levels. The noise recorded 25 m from the wave energy converter...
Energy Technology Data Exchange (ETDEWEB)
Miranda Vidales, Homero
2007-06-15
Since 1980 the multilevel converters have been fundamental part in equipment of power electronics such as of velocity variators for induction motors. In the last decades the applications of these converters was extended to other functions such as electrical vehicles, energy transmission systems and network conditioners equipment. At present the multilevel converters have gained a very important space in applications of medium and high voltage thanks to their characteristics they present. Especially in network conditioners which are equipment of power electronics that are based on static converters. Among the main applications of the network conditioners are the compensation of harmonics in current and/or voltage, the generation of reactive power and the compensation of deviations in the magnitude of the voltage. The harmonic contamination in the electric net is one of the most severe problems and it is worth to mention that in the majority of the industrialized countries there is not any charge that penalizes the generation and harmonic propagation. Nevertheless, it is necessary to perform a study and to offer solutions that help reduce the effects caused by the generation of harmonics in current and/or voltage. A solution to this problem is the active filters that are found within the network conditioners, which help reduce the amount of harmonics that circulate in the electric network. Nevertheless in systems of medium and high voltage the use of this equipment becomes complicated since the power devices that compose the conventional converters (two levels) do not support simultaneously high levels of voltage and current. As a solution to these problems emerge the multilevel inverters. The multilevel inverters are equipment that operates with low levels of voltage in the DC sources and the semiconductor devices can commute at very low frequency delivering in the way out a wave form with very low harmonic distortion. A power active filter is designed for the
Multilevel inverter switching controller using a field programmable ...
African Journals Online (AJOL)
Conducted simulation and measurement results verified and validated the switching controller design functionality and requirement. Keywords: multilevel inverter, switching controller; FPGA, general purpose processor (GPP);digital signal processing (DSP); IGBT; Verilog, power consumption; harmonic elimination (SHE).
The Geography of International Strategy: a multi-level framework
D. van den Berghe (Douglas)
2001-01-01
textabstractThis article introduces a multi-level framework to structure and analyse FDI patterns. It is argued that three internationalisation strategies currently simultaneously shape the globalisation of Foreign Direct Investment (FDI): classical internationalisation, emerging
Multilevel Image Segmentation Based on an Improved Firefly Algorithm
Directory of Open Access Journals (Sweden)
Kai Chen
2016-01-01
Full Text Available Multilevel image segmentation is time-consuming and involves large computation. The firefly algorithm has been applied to enhancing the efficiency of multilevel image segmentation. However, in some cases, firefly algorithm is easily trapped into local optima. In this paper, an improved firefly algorithm (IFA is proposed to search multilevel thresholds. In IFA, in order to help fireflies escape from local optima and accelerate the convergence, two strategies (i.e., diversity enhancing strategy with Cauchy mutation and neighborhood strategy are proposed and adaptively chosen according to different stagnation stations. The proposed IFA is compared with three benchmark optimal algorithms, that is, Darwinian particle swarm optimization, hybrid differential evolution optimization, and firefly algorithm. The experimental results show that the proposed method can efficiently segment multilevel images and obtain better performance than the other three methods.
Adjusting for the Incidence of Measurement Errors in Multilevel ...
African Journals Online (AJOL)
-prone explanatory variables and adjusts for the incidence of these errors giving rise to more adequate multilevel models. 2.0 Methodology. 2.1. Data Structure. The illustrative data employed was drawn from an educational environment. There.
Multilevel Atomic Coherent States and Atomic Holomorphic Representation
Cao, Chang-Qi; Haake, Fritz
1996-01-01
The notion of atomic coherent states is extended to the case of multilevel atom collective. Based on atomic coherent states, a holomorphic representation for atom collective states and operators is defined. An example is given to illustrate its application.
Selective harmonic control for power converters
DEFF Research Database (Denmark)
Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede
2014-01-01
This paper proposes an Internal Model Principle (IMP) based Selective Harmonic Controller (SHC) for power converters. The proposed SHC offers an optimal control solution for power converters to mitigate power harmonics. It makes a good trade-off among cost, complexity and performance. It has high...... accuracy and fast transient response, and it is cost-effective, easy for real-time implementation, and compatible for design rules-of-thumb. An application on a three-phase PWM converter has confirmed the effectiveness of the proposed control scheme in terms of harmonic mitigation....
Reliability of Power Electronic Converter Systems
DEFF Research Database (Denmark)
for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power......-tolerant adjustable speed drive systems; mission profile oriented reliability design in wind turbine and photovoltaic systems; reliability of power conversion systems in photovoltaic applications; power supplies for computers; and high-power converters. Reliability of Power Electronic Converter Systems is essential...... reading for researchers, professionals and students working with power electronics and their applications, particularly those specializing in the development and application of power electronic converters and systems....
A Discrete Modeling Approach for Buck Converter
Zhaoxia, Leng; Qingfeng, Liu; Jinkun, Sun; Huamin, Wang
In this paper, a discrete modeling approach for Buck converters based on continuous condition mode (CCM) and discontinuous condition mode (DCM) was presented. The unified coefficient matrixes of discrete model were described by building a mathematical function and the calculation methods of the parameters in coefficient matrixes were given. The working states of Buck converter on various work conditions were described adopting one discrete equation. The validity of the proposed modeling approach was proved by contrasting the output of discrete model with the operation result of Buck converter system in Simulink.
Pseudolog Digital-to-Analog Converter
Gooder, S. T.
1986-01-01
Sensitivity decreases by 10 at beginning of each input decade. Method conceived to convert binary-coded data to suitable linear form for stripchart recording. Strip-chart recordings obtained from typical pressure readings in a vacuum system during pumpdown. In reading curve, BCD digital vacuum-gage output processed by analog-to-digital converter in such way that only reading digits (but not range) appear in output. In range and reading, range also converted to analog and placed as most significant digit.
Programmable Analog-To-Digital Converter
Kist, Edward H., Jr.
1993-01-01
High-speed analog-to-digital converter with programmable voltage steps that can be changed during operation. Allows concentration of converter resolution over specific portion of waveform. Particularly useful in digitizing wind-shear radar and lidar return signals, in digital oscilloscopes, and other applications in which desirable to increase digital resolution over specific area of waveform while accepting lower resolution over rest of waveform. Effective increase in dynamic range achieved without increase in number of analog-to-digital converter bits. Enabling faster analog-to-digital conversion.
Heatsink Design of High Power Converter
Energy Technology Data Exchange (ETDEWEB)
Kim, Chan Ki [Chungang University (Korea)
1999-04-01
Various ways of designing heat sink are available for commercial high power converters and among them, the method of air cooling is the most popular and practical method than any other ones. In this paper, a practical method of cooling high power converter, which includes a method of reducing noise and vibration caused by the fan and a method of estimating the gap and contact resistances existing between the thyristor and heat sink, is presented. Finally, the heat transfer analysis and implementation methods of heat sink for high power converter is presented. (author). 14 refs., 11 figs., 3 tabs.
Power Electronics Converters for Wind Turbine Systems
DEFF Research Database (Denmark)
Blaabjerg, Frede; Liserre, Marco; Ma, Ke
2012-01-01
The steady growth of installed wind power together with the upscaling of the single wind turbine power capability has pushed the research and development of power converters toward full-scale power conversion, lowered cost pr kW, increased power density, and also the need for higher reliability......, in the latter case with attention to series connection and parallel connection either electrical or magnetic ones (multiphase/windings machines/transformers). It is concluded that as the power level increases in wind turbines, medium-voltage power converters will be a dominant power converter configuration...
Shekhar, A.; Kontos, E.; Ramirez Elizondo, L.M.; Rodrigo Mor, A. R.; Bauer, P.
2017-01-01
It is anticipated that with the thrust towards use of clean energy resources such as electric vehicles, future distribution grids will face a steep increase in power demand, forcing the utility operators to invest in enhancing the power delivering capacity of the grid infrastructure. It is
Fault Diagnosis and Fault-tolerant Control of Modular Multi-level Converter High-voltage DC System
DEFF Research Database (Denmark)
Liu, Hui; Ma, Ke; Wang, Chao
2016-01-01
device fault, DC line faults as well as AC grid faults. Special attention is given to the comparison of the corresponding fault diagnosis and fault-tolerant control approaches. Further, focus is dedicated to control/protection strategies and topologies with fault ride-though capability for MMC...... of failures and lower the reliability of the MMC-HVDC system. Therefore, research on the fault diagnosis and fault-tolerant control of MMC-HVDC system is of great significance in order to enhance the reliability of the system. This paper provides a comprehensive review of fault diagnosis and fault handling...... strategies of MMC-HVDC systems for the most common faults happened in MMC-HVDC systems covering MMC faults, DC side faults as well as AC side faults. An important part of this paper is devoted to a discussion of the vulnerable spots as well as failure mechanism of the MMC-HVDC system covering switching...
Kontos, E.
2018-01-01
High Voltage DC (HVDC) grids provide an efficient solution for the transmission of bulk power over long distances between the energy production and consumption centers. Up to now, most of the implemented dc connections are point-to-point, creating dc links to strengthen the existing, predominantly
Reliability of power electronic converter systems
Chung, Henry Shu-hung; Blaabjerg, Frede; Pecht, Michael
2016-01-01
This book outlines current research into the scientific modeling, experimentation, and remedial measures for advancing the reliability, availability, system robustness, and maintainability of Power Electronic Converter Systems (PECS) at different levels of complexity.
State estimation for wave energy converters
Energy Technology Data Exchange (ETDEWEB)
Bacelli, Giorgio; Coe, Ryan Geoffrey
2017-04-01
This report gives a brief discussion and examples on the topic of state estimation for wave energy converters (WECs). These methods are intended for use to enable real-time closed loop control of WECs.
Load balancing multimodule switching power converters
Mclyman, W. T.; Wester, G. W.
1979-01-01
Regulating system individually adjusts duty cycles of modules so that all share load equally, thus, protects individual modules and their components from overload and increases reliability and life expectancy. Converters are alternative to high-power, single unit systems.
A three-port direct current converter
DEFF Research Database (Denmark)
2016-01-01
The three-port direct current converter comprising: at least one input direct current source; at least one storage battery; a primary side circuit; a secondary side circuit; a first single magnetic component shared by the primary side circuit and the secondary side circuit, wherein the primary side...... circuit comprises a connection between the at least one input direct current source and the at least one storage battery, the primary side circuit configured for operating as a buck converter; a second magnetic component serially coupled to the first single magnetic component, wherein the first and second...... magnetic components are configured to perform a voltage step-up, wherein the secondary side circuit comprises a connection between the at least one storage battery and at least one load, the secondary side configured for operating as a tapped boost converter; wherein the three-port direct current converter...
Catalytic converters as a source of platinum
Directory of Open Access Journals (Sweden)
A. Fornalczyk
2011-10-01
Full Text Available The increase of Platinum Group Metals demand in automotive industry is connected with growing amount of cars equipped with the catalytic converters. The paper presents the review of available technologies during recycling process. The possibility of removing platinum from the used catalytic converters applying pyrometallurgical and hyrdometallurgical methods were also investigated. Metals such as Cu, Pb, Ca, Mg, Cd were used in the pyrometallurgical research (catalytic converter was melted with Cu, Pb and Ca or Mg and Cd vapours were blown through the whole carrier. In hydrometallurgical research catalytic converters was dissolved in aqua regia. Analysis of Pt contents in the carrier before and after the process was performed by means of atomic absorption spectroscopy. Obtained result were discussed.
Third order digital-to-analog converter
Dotson, W. P.
1972-01-01
System, consisting of sample and hold digital-to-analog converter, clock circuit, sample delay circuit, initial condition circuit and interpolator circuit, improves accuracy of reconstructed analog signal without increasing sample rates.
(PFC) converters feeding brushless DC motor drive
African Journals Online (AJOL)
DR OKE
1Department of Electrical Engineering, Indian Institute of Technology Delhi, INDIA ... configurations of PFC converters feeding BLDC motor drive are presented as low ..... In future, it is expected for a continuing research in the quest of energy ...
Input-output rearrangement of isolated converters
DEFF Research Database (Denmark)
Madsen, Mickey Pierre; Kovacevic, Milovan; Mønster, Jakob Døllner
2015-01-01
This paper presents a new way of rearranging the input and output of isolated converters. The new arrangement posses several advantages, as increased voltage range, higher power handling capabilities, reduced voltage stress and improved efficiency, for applications where galvanic isolation...
Fast simulation techniques for switching converters
King, Roger J.
1987-01-01
Techniques for simulating a switching converter are examined. The state equations for the equivalent circuits, which represent the switching converter, are presented and explained. The uses of the Newton-Raphson iteration, low ripple approximation, half-cycle symmetry, and discrete time equations to compute the interval durations are described. An example is presented in which these methods are illustrated by applying them to a parallel-loaded resonant inverter with three equivalent circuits for its continuous mode of operation.
Solid-state power converter repeatability analysis
Dal Gobbo, Anthony; Aguglia, Davide
2015-01-01
This paper presents a method for evaluating power converter repeatability. The focus is on solid-state switch mode power converter for which the most problematic non-repeatability sources are the jitter of the drivers and of the switches leading to output voltage pulses bad repeatability. Both driver and switch turn-on and turn-off delay dispersion have been measured. These measurements confirm that the delay is Gaussian distributed and that the repeatability prediction method is valid.
Switching power converters medium and high power
Neacsu, Dorin O
2013-01-01
An examination of all of the multidisciplinary aspects of medium- and high-power converter systems, including basic power electronics, digital control and hardware, sensors, analog preprocessing of signals, protection devices and fault management, and pulse-width-modulation (PWM) algorithms, Switching Power Converters: Medium and High Power, Second Edition discusses the actual use of industrial technology and its related subassemblies and components, covering facets of implementation otherwise overlooked by theoretical textbooks. The updated Second Edition contains many new figures, as well as
Utilization of Nonlinear Converters for Audio Amplification
Iversen, Niels; Birch, Thomas; Knott, Arnold
2012-01-01
Class D ampliers ts the automotive demands quite well. The traditional buck-based amplier has reduced both the cost and size of ampliers. However the buck topology is not without its limitations. The maximum peak AC output voltage produced by the power stage is only equal the supply voltage. The introduction ofnon-linear converters for audio amplication defeats this limitation. A Cuk converter, designed to deliver an AC peak output voltage twice the supply voltage, is presented in this paper....
ANALOG-TO-DIGITAL DATA CONVERTER
Rodgers, G.W.; Althouse, J.E.; Anderson, D.P.; Bussey, G.R.; Minnear, L.H.
1960-09-01
Electrical apparatus is described, particularly useful in telemetry work, for converting analog signals into electrical pulses and recording them. An electronic editor commands the taking of signal readings at a frequency which varies according to linearity of the analog signal being converted. Readings of information signals are recorded, along with time base readings and serial numbering, if desired, on magnetic tape and the latter may be used to operate a computer or the like. Magnetic tape data may be transferred to punched cards.
Mitigation of EMI in a flyback converter
2013-01-01
M.Ing. (Electrical & Electronic Engineering Science) This study investigates the mitigation of conducted electromagnetic interference (EMI) in a flyback DC-DC converter. Without the use of filters, the maximum mitigation of EMI possible without significantly decreasing converter operating efficiency is investigated. The following parameters are found to influence EMI: · Switching speed: Decreasing switching speed (increasing rise and fall times of the MOSFET) effectively reduces both commo...
TOTAL HARMONIC DISTORTION ANALYSIS OF MATRIX CONVERTER
K. Kandan; Senthilkumar,K.; Dhivya, K.
2016-01-01
This paper deals with the validation and design analysis of Matrix converter for variable frequency using mathematical equations. The analysis was done using Venturini modulation algorithm. The PI controller is used for Matrix converter to reduce Total Harmonic Distortion (THD) in the output current. The comparative study is done for open loop and closed loop PI compensation in MATLAB-Simulink. Furthermore, the output waveforms are produced with significant reduction in the Total Harmonic Dis...
Multilevel Cross-Dependent Binary Longitudinal Data
Serban, Nicoleta
2013-10-16
We provide insights into new methodology for the analysis of multilevel binary data observed longitudinally, when the repeated longitudinal measurements are correlated. The proposed model is logistic functional regression conditioned on three latent processes describing the within- and between-variability, and describing the cross-dependence of the repeated longitudinal measurements. We estimate the model components without employing mixed-effects modeling but assuming an approximation to the logistic link function. The primary objectives of this article are to highlight the challenges in the estimation of the model components, to compare two approximations to the logistic regression function, linear and exponential, and to discuss their advantages and limitations. The linear approximation is computationally efficient whereas the exponential approximation applies for rare events functional data. Our methods are inspired by and applied to a scientific experiment on spectral backscatter from long range infrared light detection and ranging (LIDAR) data. The models are general and relevant to many new binary functional data sets, with or without dependence between repeated functional measurements.
Multilevel weighted least squares polynomial approximation
Haji-Ali, Abdul-Lateef
2017-06-30
Weighted least squares polynomial approximation uses random samples to determine projections of functions onto spaces of polynomials. It has been shown that, using an optimal distribution of sample locations, the number of samples required to achieve quasi-optimal approximation in a given polynomial subspace scales, up to a logarithmic factor, linearly in the dimension of this space. However, in many applications, the computation of samples includes a numerical discretization error. Thus, obtaining polynomial approximations with a single level method can become prohibitively expensive, as it requires a sufficiently large number of samples, each computed with a sufficiently small discretization error. As a solution to this problem, we propose a multilevel method that utilizes samples computed with different accuracies and is able to match the accuracy of single-level approximations with reduced computational cost. We derive complexity bounds under certain assumptions about polynomial approximability and sample work. Furthermore, we propose an adaptive algorithm for situations where such assumptions cannot be verified a priori. Finally, we provide an efficient algorithm for the sampling from optimal distributions and an analysis of computationally favorable alternative distributions. Numerical experiments underscore the practical applicability of our method.
Multilevel hybrid Chernoff tau-leap
Moraes, Alvaro
2015-04-08
In this work, we extend the hybrid Chernoff tau-leap method to the multilevel Monte Carlo (MLMC) setting. Inspired by the work of Anderson and Higham on the tau-leap MLMC method with uniform time steps, we develop a novel algorithm that is able to couple two hybrid Chernoff tau-leap paths at different levels. Using dual-weighted residual expansion techniques, we also develop a new way to estimate the variance of the difference of two consecutive levels and the bias. This is crucial because the computational work required to stabilize the coefficient of variation of the sample estimators of both quantities is often unaffordable for the deepest levels of the MLMC hierarchy. Our method bounds the global computational error to be below a prescribed tolerance, TOL, within a given confidence level. This is achieved with nearly optimal computational work. Indeed, the computational complexity of our method is of order O(TOL−2), the same as with an exact method, but with a smaller constant. Our numerical examples show substantial gains with respect to the previous single-level approach and the Stochastic Simulation Algorithm.
Dendritic growth model of multilevel marketing
Pang, James Christopher S.; Monterola, Christopher P.
2017-02-01
Biologically inspired dendritic network growth is utilized to model the evolving connections of a multilevel marketing (MLM) enterprise. Starting from agents at random spatial locations, a network is formed by minimizing a distance cost function controlled by a parameter, termed the balancing factor bf, that weighs the wiring and the path length costs of connection. The paradigm is compared to an actual MLM membership data and is shown to be successful in statistically capturing the membership distribution, better than the previously reported agent based preferential attachment or analytic branching process models. Moreover, it recovers the known empirical statistics of previously studied MLM, specifically: (i) a membership distribution characterized by the existence of peak levels indicating limited growth, and (ii) an income distribution obeying the 80 - 20 Pareto principle. Extensive types of income distributions from uniform to Pareto to a "winner-take-all" kind are also modeled by varying bf. Finally, the robustness of our dendritic growth paradigm to random agent removals is explored and its implications to MLM income distributions are discussed.
Soil moisture calibration of TDR multilevel probes
Directory of Open Access Journals (Sweden)
Serrarens Daniel
2000-01-01
Full Text Available Time domain reflectometry (TDR probes are increasingly used for field estimation of soil water content. The objective of this study was to evaluate the accuracy of the multilevel TDR probe under field conditions. For this purpose, eight such TDR probes were installed in small plots that were seeded with beans and sorghum. Data collection from the probes was such that soil moisture readings were automated and logged using a standalone field unit. Neutron probe measurements were used to calibrate the TDR probes. Soil-probe contact and soil compaction were critical to the accuracy of the TDR, especially when a number of TDR probes are combined for a single calibration curve. If each probe is calibrated individually, approximate measurement errors were between 0.005 and 0.015 m³ m-3. However, measurement errors doubled to approximately 0.025 to 0.03 m³ m-3, when TDR probes were combined to yield a single calibration curve.
Multilevel cross-dependent binary longitudinal data.
Serban, Nicoleta; Staicu, Ana-Maria; Carroll, Raymond J
2013-12-01
We provide insights into new methodology for the analysis of multilevel binary data observed longitudinally, when the repeated longitudinal measurements are correlated. The proposed model is logistic functional regression conditioned on three latent processes describing the within- and between-variability, and describing the cross-dependence of the repeated longitudinal measurements. We estimate the model components without employing mixed-effects modeling but assuming an approximation to the logistic link function. The primary objectives of this article are to highlight the challenges in the estimation of the model components, to compare two approximations to the logistic regression function, linear and exponential, and to discuss their advantages and limitations. The linear approximation is computationally efficient whereas the exponential approximation applies for rare events functional data. Our methods are inspired by and applied to a scientific experiment on spectral backscatter from long range infrared light detection and ranging (LIDAR) data. The models are general and relevant to many new binary functional data sets, with or without dependence between repeated functional measurements. © 2013, The International Biometric Society.
LHC Power Converters: A Precision Game
2001-01-01
The LHC test-bed, String 2, is close to commissioning and one important element to get a first chance to prove what it can do is the power converter system. In String 2 there are 16 converters, in the full LHC there will be almost 1800. This article takes a look at what is so special about the power converters for the LHC. The 13 000 Amps power converters with the watercooled cables going to the String 2 feedboxes. The LHC's superconducting magnets will be the pinnacle of high technology. But to work, they'll need the help of high-precision power converters to supply them with extremely stable DC current. Perfection will be the name of the game, with an accuracy of just 1-2 parts per million (ppm) required. LEP, for the sake of comparison, could live with 10-20 ppm. The LHC's power converters will be very different from those of LEP or the SPS since the new accelerator's magnets are mostly superconducting. That means that they require much higher currents at a lower voltage since superconductors have no re...
Adaptive electrothermal protection of power converters
Directory of Open Access Journals (Sweden)
Baraniuk G. A.
2017-06-01
Full Text Available Thermal management for power converters during normal operation and transient modes when electrical components are warmed up is an actual problem. This can be particularly important for converters with intermittent duty operation, e.g. power supplies for resistance welding. According to some research, nearly 60% of failures are temperature-induced, and for every 10°C temperature rise in operating environment the failure rate nearly doubles. In this paper, thermal motion of state equations eigenvalue is analysed. It is shown, that in semiconductor converters with an output smoothing filter it is appropriate to use thermal protection devices based on thermal normalisation of the converter filter and, while for cases when short circuits are possible it is appropriate to use a soft start system with thermal adaptation for soft start time factor. Based on these results, two systems of thermal protections operating for semiconductor power converters are introduced. Simulation of combined electromagnetic and thermal processes in buck converter operating with both thermal management systems in overlapping environments MATLAB/Simulink and PLECS showed the possibility to significantly reduce thermal shock on semiconductor components. Using the system of filter parameters normalisation decreases the temperature of the crystal from 210°C to 85°C, using the adaptive soft start system decreases the temperature from 180°C to 80°C. The simulation results are confirmed by tests on real devices.
Thermal Stress Analysis of Medium-Voltage Converters for Smart Transformers
DEFF Research Database (Denmark)
Andresen, Markus; Ma, Ke; De Carne, Giovanni
2017-01-01
A smart transformer (ST) can take over an important managing role in the future electrical distribution grid system and can provide many advanced grid services compared to the traditional transformer. However, the risk is that the advanced functionality is balanced out by a lower reliability....... To address this concern, this work conducts thermal stress analysis for a modular multilevel converter (MMC), which is a promising solution for the medium voltage stage of the ST. The focus is put on the mission profiles of the transformer and the impact on the thermal stress of power semiconductor devices....... Normal operation at different power levels and medium voltage grid faults in a feeder fed by a traditional transformer are considered as well as the electrical and the thermal stress of the disconnection and the reconnection procedures. For the validation, the thermal stress of one MMC cell is reproduced...
Introduction to multi-level community based culturally situated interventions.
Schensul, Jean J; Trickett, Edison
2009-06-01
This introduction to a special issue of the American Journal of Community Psychiatry is the result of a symposium at the Annual Meeting of the Society for Applied Anthropology, 2006, that brought together anthropologists and psychologists involved in community based collaborative intervention studies to examine critically the assumptions, processes and results of their multilevel interventions in local communities with local partners. The papers were an effort to examine context by offering a theoretical framework for the concept of "level" in intervention science, and advocating for "multi-level" approaches to social/behavioral change. They presented examples of ways in which interventions targeted social "levels" either simultaneously or sequentially by working together with communities across levels, and drawing on and co-constructing elements of local culture as components of the intervention. The papers raised a number of important issues, for example: (1) How are levels defined and how should collaborators be chosen; (2) does it matter at which level multilevel interventions begin; (3) do multilevel interventions have a greater effect on desired outcomes than level-specific interventions; (4) are multilevel interventions more sustainable; (5) are multilevel interventions cost effective to run, and evaluate; (6) how can theories of intervention be generated and adapted to each level of a multilevel intervention; (7) how should intervention activities at each level coordinate to facilitate community resident or target population empowerment? Many of these questions were only partially addressed in the papers presented at that time, and are more fully addressed in the theoretical papers, case studies and approach to evaluation included in this collection.
MULTILEVEL RECURRENT MODEL FOR HIERARCHICAL CONTROL OF COMPLEX REGIONAL SECURITY
Directory of Open Access Journals (Sweden)
Andrey V. Masloboev
2014-11-01
Full Text Available Subject of research. The research goal and scope are development of methods and software for mathematical and computer modeling of the regional security information support systems as multilevel hierarchical systems. Such systems are characterized by loosely formalization, multiple-aspect of descendent system processes and their interconnectivity, high level dynamics and uncertainty. The research methodology is based on functional-target approach and principles of multilevel hierarchical system theory. The work considers analysis and structural-algorithmic synthesis problem-solving of the multilevel computer-aided systems intended for management and decision-making information support in the field of regional security. Main results. A hierarchical control multilevel model of regional socio-economic system complex security has been developed. The model is based on functional-target approach and provides both formal statement and solving, and practical implementation of the automated information system structure and control algorithms synthesis problems of regional security management optimal in terms of specified criteria. An approach for intralevel and interlevel coordination problem-solving in the multilevel hierarchical systems has been proposed on the basis of model application. The coordination is provided at the expense of interconnection requirements satisfaction between the functioning quality indexes (objective functions, which are optimized by the different elements of multilevel systems. That gives the possibility for sufficient coherence reaching of the local decisions, being made on the different control levels, under decentralized decision-making and external environment high dynamics. Recurrent model application provides security control mathematical models formation of regional socioeconomic systems, functioning under uncertainty. Practical relevance. The model implementation makes it possible to automate synthesis realization of
Predicting Psychotherapy Dropouts: A Multilevel Approach.
Kegel, Alexander F; Flückiger, Christoph
2015-01-01
The role of therapeutic processes in predicting premature termination of psychotherapy has been a particular focus of recent research. The purpose of this study was to contrast outpatients who completed therapy and those who dropped out with respect to their self-reported in-session experiences of self-esteem, mastery, clarification and the therapeutic alliance. The 296 patients with mixed disorders were treated with an integrative form of cognitive-behavioural therapy without pre-determined time limit (M = 20.2 sessions). Multilevel analyses indicated that patients who did not completetreatment reported, on average, lower levels of self-esteem, mastery and clarification and lower ratings of their therapeutic alliance in treatment in contrast to patients who completed therapy. Patient-reported change in self-esteem experiences over the course of treatment turned out to be the strongest predictor of dropout from psychotherapy or successful completion. When dropout occurred before the average treatment length was reached, patients reported fewer clarifying experiences as early as the first session and their ratings of the therapeutic alliance were characterized by an absence of positive development. Both of these aspects seem to be involved in patients' decisions to leave treatment early. The findings underscore the importance of the therapeutic process in understanding the mechanisms behind treatment dropout. Analyses data from 296 patients at a private outpatient clinic in a routine practice setting (CBT). Completer/dropout definition: presence or absence of measurement battery at post-assessment. Focuses on change in therapy processes by investigating post-session reports. Finds that positive changes in self-esteem experiences is the most robust predictor of dropout, followed by ratings of clarification experiences and the global alliance. In line with recent dropout research, these process indicators might help to detect therapeutic situations that are
On the thermodynamics of multilevel evolution.
Tessera, Marc; Hoelzer, Guy A
2013-09-01
Biodiversity is hierarchically structured both phylogenetically and functionally. Phylogenetic hierarchy is understood as a product of branching organic evolution as described by Darwin. Ecosystem biologists understand some aspects of functional hierarchy, such as food web architecture, as a product of evolutionary ecology; but functional hierarchy extends to much lower scales of organization than those studied by ecologists. We argue that the more general use of the term "evolution" employed by physicists and applied to non-living systems connects directly to the narrow biological meaning. Physical evolution is best understood as a thermodynamic phenomenon, and this perspective comfortably includes all of biological evolution. We suggest four dynamical factors that build on each other in a hierarchical fashion and set the stage for the Darwinian evolution of biological systems: (1) the entropic erosion of structure; (2) the construction of dissipative systems; (3) the reproduction of growing systems and (4) the historical memory accrued to populations of reproductive agents by the acquisition of hereditary mechanisms. A particular level of evolution can underpin the emergence of higher levels, but evolutionary processes persist at each level in the hierarchy. We also argue that particular evolutionary processes can occur at any level of the hierarchy where they are not obstructed by material constraints. This theoretical framework provides an extensive basis for understanding natural selection as a multilevel process. The extensive literature on thermodynamics in turn provides an important advantage to this perspective on the evolution of higher levels of organization, such as the evolution of altruism that can accompany the emergence of social organization. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Isolated and soft-switched power converter
Peng, Fang Zheng; Adams, Donald Joe
2002-01-01
An isolated and soft-switched power converter is used for DC/DC and DC/DC/AC power conversion. The power converter includes two resonant tank circuits coupled back-to-back through an isolation transformer. Each resonant tank circuit includes a pair of resonant capacitors connected in series as a resonant leg, a pair of tank capacitors connected in series as a tank leg, and a pair of switching devices with anti-parallel clamping diodes coupled in series as resonant switches and clamping devices for the resonant leg. The power converter is well suited for DC/DC and DC/DC/AC power conversion applications in which high-voltage isolation, DC to DC voltage boost, bidirectional power flow, and a minimal number of conventional switching components are important design objectives. For example, the power converter is especially well suited to electric vehicle applications and load-side electric generation and storage systems, and other applications in which these objectives are important. The power converter may be used for many different applications, including electric vehicles, hybrid combustion/electric vehicles, fuel-cell powered vehicles with low-voltage starting, remote power sources utilizing low-voltage DC power sources, such as photovoltaics and others, electric power backup systems, and load-side electric storage and generation systems.
Understanding delta-sigma data converters
Pavan, Shanti; Temes, Gabor C
2017-01-01
This new edition introduces novel analysis and design techniques for delta-sigma (ΔΣ) converters in physical and conceptual terms, and includes new chapters that explore developments in the field over the last decade. This book explains the principles and operation of delta-sigma analog-to-digital converters (ADCs) in physical and conceptual terms in accordance with the most recent developments in the field. The interest of ΔΣ converter designers has shifted significantly over the past decade, due to many new applications for data converters at the far ends of the frequency spectrum. Continuous-time delta-sigma A/D converters with GHz clocks, of both lowpass and bandpass types, are required for wireless applications. At the other extreme, multiplexed ADCs with very narrow (sometimes 10 Hz wide) signal bandwidths, but very high accuracy are needed in the interfaces of biomedical and environmental sensors. To reflect the changing eeds of designers, the second edition includes significant new material on bo...
A resonant dc-dc power converter assembly
DEFF Research Database (Denmark)
2015-01-01
The present invention relates to a resonant DC-DC power converter assembly comprising a first resonant DC-DC power converter and a second resonant DC-DC power converter having identical circuit topologies. A first inductor of the first resonant DC-DC power converter and a second inductor of the s......The present invention relates to a resonant DC-DC power converter assembly comprising a first resonant DC-DC power converter and a second resonant DC-DC power converter having identical circuit topologies. A first inductor of the first resonant DC-DC power converter and a second inductor...
Bayesian Optimal Experimental Design Using Multilevel Monte Carlo
Ben Issaid, Chaouki
2015-01-07
Experimental design is very important since experiments are often resource-exhaustive and time-consuming. We carry out experimental design in the Bayesian framework. To measure the amount of information, which can be extracted from the data in an experiment, we use the expected information gain as the utility function, which specifically is the expected logarithmic ratio between the posterior and prior distributions. Optimizing this utility function enables us to design experiments that yield the most informative data for our purpose. One of the major difficulties in evaluating the expected information gain is that the integral is nested and can be high dimensional. We propose using Multilevel Monte Carlo techniques to accelerate the computation of the nested high dimensional integral. The advantages are twofold. First, the Multilevel Monte Carlo can significantly reduce the cost of the nested integral for a given tolerance, by using an optimal sample distribution among different sample averages of the inner integrals. Second, the Multilevel Monte Carlo method imposes less assumptions, such as the concentration of measures, required by Laplace method. We test our Multilevel Monte Carlo technique using a numerical example on the design of sensor deployment for a Darcy flow problem governed by one dimensional Laplace equation. We also compare the performance of the Multilevel Monte Carlo, Laplace approximation and direct double loop Monte Carlo.
Converters for Distributed Power Generation Systems
DEFF Research Database (Denmark)
Blaabjerg, Frede; Yang, Yongheng
2015-01-01
Power electronics technology has become the enabling technology for the integration of distributed power generation systems (DPGS) such as offshore wind turbine power systems and commercial photovoltaic power plants. Depending on the applications, a vast array of DPGS-based power converter...... presents an overview of the power converters for the DPGS, mainly based on wind turbine systems and photovoltaic systems, covering a wide range of applications. Moreover, the modulation schemes and interfacing power filters for the power converters are also exemplified. Finally, the general control...... topologies has been developed and more are coming into the market in order to achieve an efficient and reliable power conversion from the renewables. In addition, stringent demands from both the distribution system operators and the consumers have been imposed on the renewable-based DPGS. This article...
Data Converter for Multistandard Mobile Phones
DEFF Research Database (Denmark)
Yurttas, Aziz; Bruun, Erik; Jensen, Rasmus Glarborg
2004-01-01
This paper describes an analog to digital converter (ADC) for mobile communication systems using a direct down conversion architecture. The ADC can be programmed to meet the requirements of different communication standards, including GSM (Global System for Mobile communication) and WCDMA (Wideband...... Code Division Multiple Access). The ADC is realized with a pipeline ADC architecture for WCDMA and a Sigma-Delta architecture for GSM. In order to have an optimized area and power consumption, the basic building blocks (opamps) of the converters are shared between the two converter architectures....... The entire ADC consumes about 5.5 mW and occupies an active area of about 0.36 mm(2). A test circuit has been developed and fabricated and measurements show that both the required programmability and the required performance can be obtained using the proposed configurations....
Self-oscillating resonant power converter
DEFF Research Database (Denmark)
2014-01-01
The present invention relates to resonant power converters and inverters comprising a self-oscillating feedback loop coupled from a switch output to a control input of a switching network comprising one or more semiconductor switches. The self-oscillating feedback loop sets a switching frequency...... of the power converter and comprises a first intrinsic switch capacitance coupled between a switch output and a control input of the switching network and a first inductor. The first inductor is coupled in-between a first bias voltage source and the control input of the switching network and has...... a substantially fixed inductance. The first bias voltage source is configured to generate an adjustable bias voltage applied to the first inductor. The output voltage of the power converter is controlled in a flexible and rapid manner by controlling the adjustable bias voltage....
Metamaterial polarization converter analysis: limits of performance
DEFF Research Database (Denmark)
Markovich, Dmitry L.; Andryieuski, Andrei; Zalkovskij, Maksim
2013-01-01
In this paper, we analyze the theoretical limits of a metamaterial-based converter with orthogonal linear eigenpolarizations that allow linear-to-elliptical polarization transformation with any desired ellipticity and ellipse orientation. We employ the transmission line approach providing a needed...... level of the design generalization. Our analysis reveals that the maximal conversion efficiency for transmission through a single metamaterial layer is 50 %, while the realistic reflection configuration can give the conversion efficiency up to 90 %. We show that a double layer transmission converter...... and a single layer with a ground plane can have 100 % polarization conversion efficiency. We tested our conclusions numerically reaching the designated limits of efficiency using a simple metamaterial design. Our general analysis provides useful guidelines for the metamaterial polarization converter design...
Reliability of Power Electronic Converter Systems
DEFF Research Database (Denmark)
for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power...... electronic converter systems; anomaly detection and remaining-life prediction for power electronics; reliability of DC-link capacitors in power electronic converters; reliability of power electronics packaging; modeling for life-time prediction of power semiconductor modules; minimization of DC......-link capacitance in power electronic converter systems; wind turbine systems; smart control strategies for improved reliability of power electronics system; lifetime modelling; power module lifetime test and state monitoring; tools for performance and reliability analysis of power electronics systems; fault...
High Efficiency Reversible Fuel Cell Power Converter
DEFF Research Database (Denmark)
Pittini, Riccardo
The large scale integration of renewable energy sources requires suitable energy storage systems to balance energy production and demand in the electrical grid. Bidirectional fuel cells are an attractive technology for energy storage systems due to the high energy density of fuel. Compared...... to traditional unidirectional fuel cell, bidirectional fuel cells have increased operating voltage and current ranges. These characteristics increase the stresses on dc-dc and dc-ac converters in the electrical system, which require proper design and advanced optimization. This work is part of the PhD project...... entitled "High Efficiency Reversible Fuel Cell Power Converter" and it presents the design of a high efficiency dc-dc converter developed and optimized for bidirectional fuel cell applications. First, a brief overview of fuel cell and energy storage technologies is presented. Different system topologies...
Reliability of Power Electronic Converter Systems
DEFF Research Database (Denmark)
-link capacitance in power electronic converter systems; wind turbine systems; smart control strategies for improved reliability of power electronics system; lifetime modelling; power module lifetime test and state monitoring; tools for performance and reliability analysis of power electronics systems; fault......The main aims of power electronic converter systems (PECS) are to control, convert, and condition electrical power flow from one form to another through the use of solid-state electronics. This book outlines current research into the scientific modeling, experimentation, and remedial measures...... for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power...
Parametric pendulum based wave energy converter
Yurchenko, Daniil; Alevras, Panagiotis
2018-01-01
The paper investigates the dynamics of a novel wave energy converter based on the parametrically excited pendulum. The herein developed concept of the parametric pendulum allows reducing the influence of the gravity force thereby significantly improving the device performance at a regular sea state, which could not be achieved in the earlier proposed original point-absorber design. The suggested design of a wave energy converter achieves a dominant rotational motion without any additional mechanisms, like a gearbox, or any active control involvement. Presented numerical results of deterministic and stochastic modeling clearly reflect the advantage of the proposed design. A set of experimental results confirms the numerical findings and validates the new design of a parametric pendulum based wave energy converter. Power harvesting potential of the novel device is also presented.
Reliability of Power Electronic Converter Systems
DEFF Research Database (Denmark)
The main aims of power electronic converter systems (PECS) are to control, convert, and condition electrical power flow from one form to another through the use of solid-state electronics. This book outlines current research into the scientific modeling, experimentation, and remedial measures...... for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power......-link capacitance in power electronic converter systems; wind turbine systems; smart control strategies for improved reliability of power electronics system; lifetime modelling; power module lifetime test and state monitoring; tools for performance and reliability analysis of power electronics systems; fault...
Impedance coordinative control for cascaded converter in bidirectional application
DEFF Research Database (Denmark)
Tian, Yanjun; Loh, Poh Chiang; Deng, Fujin
2016-01-01
A two-stage cascaded converter is formed by connecting two sub-converters in series. Output impedance of one sub-converter will therefore interact with input impedance of the other sub-converter. Such interaction may affect the system dynamics and stability, especially when one sub-converter is c......A two-stage cascaded converter is formed by connecting two sub-converters in series. Output impedance of one sub-converter will therefore interact with input impedance of the other sub-converter. Such interaction may affect the system dynamics and stability, especially when one sub......-converter is constant-power-controlled, and hence has different impedance characteristics when its power reverses. To lessen such constant-power effects, a control scheme that can coordinate impedance behaviors of the two sub-converters is proposed. The idea is to reshape the lowfrequency negative impedance...
Hydrodynamic Performance of a Wave Energy Converter
Yang, Yingchen
2010-11-01
To harvest energy from ocean waves, a new wave energy converter (WEC) was proposed and tested in a wave tank. The WEC freely floats on the water surface and rides waves. It utilizes its wave-driven angular oscillation to convert the mechanical energy of waves into electricity. To gain the maximum possible angular oscillation of the WEC under specified wave conditions, both floatation of the WEC and wave interaction with the WEC play critical roles in a joint fashion. During the experiments, the submersion condition of the WEC and wave condition were varied. The results were analyzed in terms of the oscillation amplitude, stability, auto-orientation capability, and wave frequency dependency.
The Angiotensin-Converting-Enzyme-Induced Angioedema.
Bas, Murat
2017-02-01
The bradykinin B2 receptor antagonist icatibant is effective in angiotensin-converting enzyme inhibitor-induced angioedema. The drug is not approved officially for this indication and has to be administered in an emergency situation off-label. Corticosteroids or antihistamines do not seem to work in this condition. The effectiveness of C1-esterase-inhibitor in angiotensin-converting enzyme-induced angioedema must be verified in a double-blind study. Copyright Â© 2016 Elsevier Inc. All rights reserved.
Subramanian, K.; Kavitha, K. V. N.; Saravanan, K.
2017-11-01
A soft switched single switch isolated dc-dc conveys proposed in this paper. This converter works on the principle of zero current switching (zcs) and zero voltage switching (zvs). The circuit comprises lossless snubber with low rating. The switch works on zcs during turn on and zvs during turnoff. The diodes are based on zcs turn on and turnoff conditions. This paper presents the concept of soft switching and its applications to dc-dc converter. The losses due to soft switching and hard switching are compared.
Combination solar photovoltaic heat engine energy converter
Chubb, Donald L.
1987-01-01
A combination solar photovoltaic heat engine converter is proposed. Such a system is suitable for either terrestrial or space power applications. The combination system has a higher efficiency than either the photovoltaic array or the heat engine alone can attain. Advantages in concentrator and radiator area and receiver mass of the photovoltaic heat engine system over a heat-engine-only system are estimated. A mass and area comparison between the proposed space station organic Rankine power system and a combination PV-heat engine system is made. The critical problem for the proposed converter is the necessity for high temperature photovoltaic array operation. Estimates of the required photovoltaic temperature are presented.
A quadratic analog-to-digital converter
Harrison, D. C.; Staples, M. H.
1980-01-01
An analog-to-digital converter with a square root transfer function has been developed for use with a pair of CCD imaging detectors in the White Light Coronagraph/X-ray XUV Telescope experiment to be flown as part of the Internal Solar Polar Mission. It is shown that in background-noise-limited instrumentation systems a quadratic analog-to-digital converter will allow a maximum dynamic range with a fixed number of data bits. Low power dissipation, moderately fast conversion time, and reliability are achieved in the proposed design using standard components and avoiding nonlinear elements.
Electrodes For Alkali-Metal Thermoelectric Converters
Williams, Roger M.; Wheeler, Bob L.; Jeffries-Nakamura, Barbara; Lamb, James L.; Bankston, C. Perry; Cole, Terry
1989-01-01
Combination of thin, porous electrode and overlying collector grid reduces internal resistance of alkali-metal thermoelectric converter cell. Low resistance of new electrode and grid boosts power density nearly to 1 W/cm2 of electrode area at typical operating temperatures of 1,000 to 1,300 K. Conductive grid encircles electrode film on alumina tube. Bus wire runs along tube to collect electrical current from grid. Such converters used to transform solar, nuclear, and waste heat into electric power.
Converting ODM Metadata to FHIR Questionnaire Resources.
Doods, Justin; Neuhaus, Philipp; Dugas, Martin
2016-01-01
Interoperability between systems and data sharing between domains is becoming more and more important. The portal medical-data-models.org offers more than 5.300 UMLS annotated forms in CDISC ODM format in order to support interoperability, but several additional export formats are available. CDISC's ODM and HL7's framework FHIR Questionnaire resource were analyzed, a mapping between elements created and a converter implemented. The developed converter was integrated into the portal with FHIR Questionnaire XML or JSON download options. New FHIR applications can now use this large library of forms.
Directory of Open Access Journals (Sweden)
M. Akherraz
1997-12-01
Full Text Available This paper presents an in-depth analytical and experimental investigation of an indirect DC-DC converter. The DC-AC conversion is a full bridge based on IGBT power modules, and the AC-DC conversion is done via a high frequency AC link and a first diode bridge. The AC link, which consists of snubbing capacitors and a variable air-gap transformer, is analytically designed to fulfill Zero Voltage commutation requirement. The proposed converter is simulated using PSPICE and a prototype is designed built and tested in the laboratory. PSPICE simulation and experimental results are presented and compared.
Situational and Dispositional Factors that Predict Motivation: a Multilevel Study.
Pineda-Espejel, Heriberto Antonio; López-Walle, Jeanette; Tomás, Inés
2017-03-30
This study aimed to test a multilevel mediation model which examined the relationship between the perceived motivational climate created by coaches at team level and motivational regulations towards sport at individual level, as mediated by individual goal orientations. 211 university athletes from 20 teams training in different types of sport completed a battery of instruments that measured the variables included in the model. The statistics significance level was .05. Results of the multilevel mediation model revealed that the task-involving climate at team level positively predicted individual task orientation (γ01 = .77, p .05). The results are in line with previous research that have focused in the study of motivational climate at individual level, but the present study make a novel contribution by providing the perspective of a multilevel mediation model and thereby clarifying the phenomenon at team level.
On multi-level thinking and scientific understanding
McIntyre, Michael Edgeworth
2017-10-01
Professor Duzheng YE's name has been familiar to me ever since my postdoctoral years at MIT with Professors Jule CHARNEY and Norman PHILLIPS, back in the late 1960s. I had the enormous pleasure of meeting Professor YE personally in 1992 in Beijing. His concern to promote the very best science and to use it well, and his thinking on multi-level orderly human activities, reminds me not only of the communication skills we need as scientists but also of the multi-level nature of science itself. Here I want to say something (a) about what science is; (b) about why multi-level thinking—and taking more than one viewpoint—is so important for scientific as well as for other forms of understanding; and (c) about what is meant, at a deep level, by "scientific understanding" and trying to communicate it, not only with lay persons but also across professional disciplines. I hope that Professor YE would approve.
Multi-Level Sequential Pattern Mining Based on Prime Encoding
Lianglei, Sun; Yun, Li; Jiang, Yin
Encoding is not only to express the hierarchical relationship, but also to facilitate the identification of the relationship between different levels, which will directly affect the efficiency of the algorithm in the area of mining the multi-level sequential pattern. In this paper, we prove that one step of division operation can decide the parent-child relationship between different levels by using prime encoding and present PMSM algorithm and CROSS-PMSM algorithm which are based on prime encoding for mining multi-level sequential pattern and cross-level sequential pattern respectively. Experimental results show that the algorithm can effectively extract multi-level and cross-level sequential pattern from the sequence database.
Mathematical model comparing of the multi-level economics systems
Brykalov, S. M.; Kryanev, A. V.
2017-12-01
The mathematical model (scheme) of a multi-level comparison of the economic system, characterized by the system of indices, is worked out. In the mathematical model of the multi-level comparison of the economic systems, the indicators of peer review and forecasting of the economic system under consideration can be used. The model can take into account the uncertainty in the estimated values of the parameters or expert estimations. The model uses the multi-criteria approach based on the Pareto solutions.
Multilevel quadrature of elliptic PDEs with log-normal diffusion
Harbrecht, Helmut
2015-01-07
We apply multilevel quadrature methods for the moment computation of the solution of elliptic PDEs with lognormally distributed diffusion coefficients. The computation of the moments is a difficult task since they appear as high dimensional Bochner integrals over an unbounded domain. Each function evaluation corresponds to a deterministic elliptic boundary value problem which can be solved by finite elements on an appropriate level of refinement. The complexity is thus given by the number of quadrature points times the complexity for a single elliptic PDE solve. The multilevel idea is to reduce this complexity by combining quadrature methods with different accuracies with several spatial discretization levels in a sparse grid like fashion.