A new parallel resonant notch dc link voltage source PWM inverter topology to obtain zero switching loss high switching frequency dc-ac power conversion is proposed. Analysis and simulation results of the new topology for a three phase PWM inverter induction-motor drive are presented. Significant features of the proposed topology are use of conventional PWM techniques, low device voltage stresses (1.1p.u.), simple design and load independent operation of the resonant notch interface circuit.

A voltage source PWM converter with battery charging and AC/DC power conversion ability is proposed in this paper. The proposed voltage source PWM converter is independently controlled by active and reactive components and implemented by DSP controller. In UPS application the mathematical model of the voltage source PWM converter has been derived. Finally, the performance of the voltage source converter is shown and discussed through experimental results. (author). 8 refs., 8 figs.

This paper describes a control method of a three-phase voltage-source PWM-rectifier as it is used in dynamic 4Q-drives, which makes it possible to use this rectifier as a dynamic reactive power compensator for other loads too. An adaptive control system of the dc-link voltage, whose parameter values of the feedback filter and PI controller are changed in accordance with the value of the dc-voltage error, is introduced. The calculation method of load harmonic currents in the ac system is based on space vector equations of line voltages and currents. Measured results show the capability of the proposed control method. 5 refs, 9 figs

High performance solid-state volt-ampere reactive (VAR) compensators using three-phase pulse-width modulation (PWM) current-source and voltage-source inverters are proposed, analyzed and experimentally verified. The proposed VAR compensator topologies offer improved performance characteristics in terms of the size of the reactive components, generated current harmonic distortion, and control simplicity and flexibility. The configurations are based on PWM current-source inverters connected to a dc reactor and PWM voltage-source reactors connected to a dc capacitor. To improve system transient response, a current regulated synchronous compensator which operates at a constant switching frequency is presented. The advantages of this scheme include fast response time and reduced switching stresses. Control system simplifications are achieved in a power factor compensator that requires minimum sensing and no reactive power calculations. The system also reduces any line current harmonics generated by nonlinear loads and compensates for voltage unbalance in the ac source. A systematic and comprehensive design method for the power circult and control system is developed for each of the proposed schemes. 60 refs., 82 figs., 14 tabs.

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 is demonstrated by the simulations of a 6MW wind turbine's grid connection and experimentally verified via a smallscale prototype.

The technique of vector space decomposition control of voltage source inverter fed dual three-phase induction machines is presented in this paper. By vector space decomposition, the analytical modeling and control of the machine are accomplished in three two-dimensional orthogonal subspaces and the dynamics of the electromechanical energy conversion related and the nonelectromechanical energy conversion related machine variables are thereby totally decoupled. A space vector PWM technique is also developed based on the vector space decomposition to limit the 5th, 7th, 17th, 19th,... harmonic currents which in such a system would be otherwise difficult to control. The techniques developed in this paper can be generalized for the control of an induction machine with an arbitrary number of phases.

This paper presents a PWM ac-ac half-bridge circuit that, in the future, will be employed at the development of a stabilized voltage source. Principle of operation, theoretical analysis, design procedure is provided. The PWM ac-ac half-bridge have been validated by simulation and experimental results. (author) 5 refs., 12 figs.

This letter presents a multi-frequency proportional-resonant (MFPR) current controller developed for PWM voltage source converter (VSC) under the unbalanced supply voltage conditions. The delta operator is used in place of the shift operator for the implementation of MFPR by using a low-cost fixed-point DSP. The experimental results with an alternative control strategy validated the feasibility of the proposed MFPR current controller for the PWM VSC during voltage unbalance.

With the recent developments in semiconductors and control equipment, Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) has attracted the growing interest of researchers. The use of VSC technology and Pulse Width Modulation (PWM) has a number of potential advantages: short ...

Matlab SimPowerSystems is a modern design tool that allows scientists and engineers to rapidly and easily build models that simulate power systems. Not only can you draw the circuit topology rapidly, but your analysis of the circuit can include its interactions with mechanical, thermal, control, and other disciplines. The paper covers some case studies that provide detailed, realistic examples of how to use SimPowerSystems in power system analysis. The following types of studies is coverted on the paper: 1. Thyristor-Based Static Var Compensator: Study the steady-state and dynamic performance of a static var compensator (SVC) on a transmission system. 2. Transient Stability of a Power System with SVC and PSS: Study of the application of static var compensator (SVC) and power system stabilizers (PSS) to improve transient stability and power oscillation damping of the system. 3. GTO-Based STATCOM: Study the steady-state and dynamic performance of a static synchronous compensator (STATCOM) on a transmission system. 4. Control of load flow using UPFC: Study the steady-state and dynamic performance of a unified power flow controller (UPFC). 5. Chopper-Fed DC Motor Drive: Study of a DC motor drive with armature voltage controlled by a GTO thyristor chopper. 6. VSC-Based HVDC Link: Modeling of a forced-commutated Voltage-Sourced Converter high-voltage direct current (VSC-HVDC) transmission link. 7. Three-Phase Network with Electrical Machines: Simulation of a three-phase power system containing electrical machines and other three-phase models. 8. Variable-Frequency Induction Motor Drive: Study of a PWM inverter-driven variable-frequency AC induction motor in variable-voltage, variable-speed operation.

The most common solution for modern adjustable speed drives (ASD) is the use of induction motors (IM) fed by voltage-source inverters (VSI). The inverter generates a pulsewidth modulated (PWM) voltage, with values of about 6 kV/ dv/dt m s or even more. In three-leg inverters for three-phase applications the occurrence of common-mode voltage is inherent due to asymmetrical output pulses. As a result, for electromagnetic compatibility (EMC) reasons, in most applications shielded cables are used between the inverter and the motor, implying high installation costs. The present paper discusses the use of cheaper, unshielded cables. A new method for measuring electromagnetic interference (EMI) from unshielded cables is proposed and measurement results are presented. The level of EMI is evaluated in different situations: without an output filter, with a classical LC output filter and with an advanced output filter with DC link connection. It is concluded that, from an EMC point of view, unshielded cables can give very good performance provided that a common-mode (CM) output filter is used.

The zero-current-switching based three-phase voltage-source PWM inverter was proposed, and it was demonstrated in the driving experiment of an induction motor that the inverter is applicable to even loads with speed electromotive force. The inverter was featured by circuit configuration where the Y-connected LC resonant circuit was connected on the AC side of the inverter, and its neutral point was also connected with the neutral point of a DC capacitor. Even if the resonant frequency and Q of the resonant circuit were different for every phase, the inverter could be operated stably by controlling independently resonant current of each phase. Although the inverter could use the same voltage-resistant IGBT as conventional ones and could reduce switching loss remarkably, it had a demerit to increase conducting loss because of the superposition of load and resonant currents in switching elements. However, such conducting loss could be reduced by use of a switching element with low ON voltage drop, and the total efficiency of the inverter increased with its switching frequency. 6 refs., 14 figs., 1 tab.

This paper presents the application of the hysteresis band current controller (HBCC) technique to the three phase pulse width modulation (PWM) AC chopper used for the purpose of controlling the magnitude of the sinusoidal currents and voltages applied to an AC load. If the HBCC technique used in the inverters is directly employed in the three phase PWM AC chopper, it causes the AC chopper to fail to provide balanced three phase sinusoidal currents for a three phase AC load. In return, this situation leads some unavoidable and serious faults to occur in the hardware of the three phase PWM AC chopper. In respect to this case, the detailed analysis expressing the related faults is presented. Consequently, for the first time, a novel HBCC technique overcoming these faults is proposed for the t...

In electric vehicles (EVs), AC induction motors can provide variable speed at low cost. The most common method for controlling induction motors uses a 3-phase AC voltage-source inverter with sine-wave PWM (pulse width modulation). Because the motor`s speed and acceleration depend on amplitude as well as frequency, the inverter must produce sine waves of variable voltage and frequency. The authors describe how a single microcontroller can provide such control functions while generating PWM waveforms in which the modulation is sinusoidal.

The main purpose of this paper is the implementation of a new voltage source inverter referred to as boost inverter or boost dc-ac converter. The main attribute of the new inverter topology is the fact that it generates an ac output voltage larger than the dc input one, depending on the instantaneous duty cycle. The converter is controlled by pulse width modulation (PWM). A design example, simulation and experimental results are included in this paper. (author) 3 refs., 15 figs.

A Utility-interactive residential PV system adapted a novel single-phase composite PWM voltage source inverter (VSI) is proposed. The proposed system is equipped with PV array, battery storage, and a single-phase VSI, which has a new circuit configuration and PWM method. The VSI circuit consists of the normal single-phase bridge circuit and an additional arm. The two auxiliary self-turn-off devices for the arm adopt to a composite PWM control, which contributes to reduce the ripple in the AC output current. Also, the VSI has a LC series resonance circuit tuned to twice the utility frequency connected in parallel with the smoothing capacitor. The series resonance circuit absorbs the double-frequency AC components included in the DC pulsed current. Consequently, the smoothing capacitor is drastically reduced. It was found with the computer simulation and the experiment that the waveform of AC output current shows an ideal sine wave.

This paper deals with the design, the control and the simulation of a voltage balancing static converter for a three phases utility distribution. Unbalancing sources and compensator structures are studied and compared. The balancing method consists in injecting the load currents negative and zero sequence in opposite phase by means of a PWM voltage source inverter. The identification of the load currents negative sequence is based on the fluctuating active and reactive power computing allowing a transient state compensation. A general formulation is proposed allowing to relate the unbalance parameters to the inverter design. The compensation currents and the DC voltage loops are studied and carried out. Presented simulation results allow to validate control loops and to refine the theoretical study on the basis of a specification. This study has been supported by a research contract between the LEEI and the CENTRALP Automatismes company. Cet article traite du dimensionnement, du pilotage et de la simulation d'un convertisseur statique de rééquilibrage dynamique de la tension d'un réseau de distribution. Les sources de déséquilibre sont identifiées et les structures statiques de rééquilibrage sont décrites. Le principe du rééquilibrage consiste en une compensation des systèmes inverse et homopolaire de courants au moyen d'un onduleur de tension en modulation de largeur d'impulsion. L'identification du système inverse de courants repose sur le calcul des puissances active et réactive fluctuantes mises en jeu par la charge déséquilibrée, permettant une compensatiori en régime transitoire. Une formulation générale du dimensionnement du compensateur est proposée permettant de lier les paramètres caractéristiques du déséquilibre à la valeur des éléments constitutifs. L'asservissement des courants et la régulation de la tension de l'onduleur sont analysés. Les résultats de simulation ont permis de valider et d'affiner l'étude théorique sur la base d'un cahier des charges. Cette étude s'inscrit dans le cadre d'une opération contractuelle entre le LEEI et les Etablissements CENTRALP Automatismes.

Abstract in portuguese Este artigo propõe uma metodologia de projeto aprimorada para determinação dos componentes auxiliares para o conversor ZVT CC-CC PWM snubber assisted auxiliary switch. O procedimento de projeto proposto é baseado na redução das perdas de condução no circuito auxiliar. Isto é somente possível devido à localização do capacitor snubber de bloqueio, o qual é compartilhado por ambas as chaves ativas. Através do procedimento de projeto proposto o rendimento do co (more) nversor pode ser aumentado. Uma análise comparativa do rendimento é apresentada e os resultados experimentais, obtidos de protótipos de laboratório de 1 kW, 100 kHz, mostram uma melhoria relevante em relação ao rendimento apresentado pelo projeto original. Além disso, os resultados experimentais também confirmam que o projeto proposto para o conversor ZVT snubber assisted auxiliary switch torna-o competitivo em relação ao conversor ZVT PWM com fonte auxiliar de tensão constante (true PWM ZVS pole). Abstract in english This paper proposes an improved design to calculate the snubber auxiliary elements of ZVT DC-DC PWM converters with snubber assisted auxiliary switch. The proposed improved design guidelines are based on the reduction of the conduction losses through the auxiliary circuit. It is accomplished by the unique location of the turn-off snubber capacitor, which is shared by both active switches. By means of this improved design guidelines the converter efficiency can be increase (more) d. An efficiency comparative analysis is carried out and the experimental results, obtained from 1 kW, 100 kHz laboratory prototypes, show a relevant improvement in converter efficiency compared to the original converter design. In addition, experimental results also confirm that with the improved design the ZVT PWM converters with snubber assisted auxiliary switch can be competitive with ZVT PWM converters with constant auxiliary voltage source (True PWM ZVS pole).

This paper reports the control characteristics of the single-phase sinusoidal PWM voltage source inverter, taking as an example its application to a photovoltaic power generation system. The new circuit in the power generation system to be connected to the interconnected system can be controlled in a composite PWM mode, when provided with auxiliary arms in the main bridge circuit. This circuit is characterized by the diodes totally connected in antiparallel, instead of in series in the current source inverter system, with the filter circuit, which connects the middle points of the auxiliary arms, corresponding to that for reactances connected in parallel. The power generation system to be connected to commercial power supply needs a connecting reactor of sufficiently high capacity to make inverter output voltage compatible with that of the utility system. The voltage source inverter system needs a feedback control system for AC output current, in order to control variation of DC voltage resulting from variation of solar radiation. It is recommended that a storage battery is included in the voltage source inverter circuit, to control ignition angle optionally at a positive or negative level, thereby making the two-way inverter which can be also used to charge the battery. 7 tabs., 14 figs.

Electricite de France (EDF) has developed a clean 36 kW converter for the power supply of a food industry direct current tube heat exchanger: the converter generates a quasi-nil level of harmonics and a power factor of 0.95. It is composed of two conversion stages, a PWM-driven rectifier and a three-phase inverter

Abstract in portuguese Este trabalho desenvolve um procedimento de projeto sistemático para o controle das correntes de entrada e da tensão de saída de retificadores PWM trifásicos. Primeiramente é apresentado o modelo discreto em eixos síncronos dq do retificador PWM trifásico com filtro de entrada L, o qual leva em conta o tempo de processamento necessário para a implementação em tempo real. A operação do retificador com resposta de tempo mínimo é obtida utilizando o método de (more) desacoplamento por retroação de estados no domínio discreto, sem a necessidade de um controlador de corrente adicional no eixo d. Além disso, são desenvolvidos servos controladores de corrente e tensão a fim de garantir fator de deslocamento unitário e regulação de tensão no barramento CC respectivamente. Finalmente, resultados experimentais são apresentados, a fim de validar o procedimento proposto e verificar o desempenho do retificador PWM trifásico. Abstract in english This paper develops a systematic design procedure based on discrete decoupling by state feedback applied to three-phase PWM rectifiers. A discrete model for synchronous frame is developed for three-phase PWM rectifier with an L filter. This model takes into account the computational delays presents in the discrete implementation. Deadbeat response is obtaining without the requirement of a current controller in the axis d. Moreover, discrete servo controllers to ensure uni (more) t displacement power factor and regulated DC link voltage are developed. Finally, experimental results are presented to demonstrate the feasibility of the proposed procedure, algorithms and the performance of the overall system.

This paper presents a modeling, analysis and design of a PWM voltage source inverter (VSI) to be connected between a dc source and the ac grid. The control algorithm of the PWM-VSI applies the concept of the instantaneous p-q (real-imaginary) power theory and the converter dc source is supplied by a photovoltaic array (PC). The objective is to show that with an adequate control the converter can transfer the dc energy from PV array and improve the power factor of the electrical system. Some design considerations are also discussed. The feasibility of the proposed control method was verified by a digital simulation and measurements on a small prototype model. (author) 5 refs., 12 figs., 1 tab.

An optimized photovoltaic (PV) pumping system based on an induction motor driving a centrifugal pump was presented. Each component of the system was modelled separately. The system was designed to maximize the daily pumped water quantity through the optimization of every possible operating point. A natural PWM VS inverter was used to feed the motor. The PV array was coupled to an induction motor driving a monocellular centrifugal pump. Air-gap flux functioning was used to modify the PWM voltage source inverter. Results of the simulation were then compared with data from pumps working with a constant air-gap flux. The value obtained by the amount of water flow per day was the criterion used to evaluate the effectiveness of the algorithm. The influence of the cell temperature variation on the performance of the optimized system was also investigated. It was concluded that an increase in both daily pumped quantity and pump efficiency was achieved using the optimized system. 12 refs., 14 figs.

Grid connected wind turbines may produce flicker during continuous operation. In this paper flicker emission of grid connected wind turbines with doubly fed induction generators is investigated during continuous operation. A STATCOM using PWM voltage source converter (VSC) is connected in shunt to the point of common coupling (PCC) to relieve the flicker produced by grid connected wind turbines and the corresponding control scheme is described in detail. Simulation results show that STATCOM is an effective measure to mitigate the flicker level during continuous operation of grid connected wind turbines.

The paper proposes an induction motor vector-controlled drive system that exhibits some special features, namely, the bi-directional power flow capability, unity fundamental power factor and reduced harmonic injection into the ac mains. The systems consists of two independently controlled voltage source PWM converters, connecting the ac mains with a 5 Hp induction machine. A detailed theoretical analysis of converter control is first reviewed, followed by the construction of its PSpice subsystem is modeled using SIMNON language, that is later extended to the overall drive system simulation. Design aspects and extensive simulation results are presented. (author) 8 refs., 10 figs.

Induction motor driven by a voltage source PWM inverter was studied in torque pulsation reducing method. In the sine wave pattern PWM modulation, instantaneous torque of induction motor pulses with 6 times as many as the fundamental frequency. PWM modulation, added with a sine sigal wave of that 6th harmonic wave, was tried, during which trial the induction motor was calculated in current and instantaneous torque by a state variable method to study the torque in vanishing effect. In other words, torque wave form and current wave from were obtained in a sine wave pattern and compared/studied in a sine wave, added/modulated with a 6th harmonic wave. Next, torque form based on the pattern and torque from with the 6th harmonic wave taken into consideration were calculated. As a result, the PWM modulation method, to add/modulate the fundamental sine signal wave with the sine signal wave of 6th harmonic wave, was calculated in instantaneous torque and current of induction motor, with the conclusion for the 6th harmonic wave pulsation to be eliminated. 6 refs., 15 figs., 4 tabs.

Abstract in portuguese Este artigo propõe dois novos algoritmos de limitação para inversores de tensão trifásicos a quatro braços. Estes baseiam-se na limitação do vetor de comando dentro da região de operação linear do inversor. O primeiro algoritmo utiliza um elipsóide inscrito no dodecaedro definido pelas extremidades dos possíveis vetores de comutação do inversor, e o segundo é baseado nos planos limites desse poliedro. Uma descrição detalhada, abordando os principais pont (more) os requeridos para a implementação digital, da modulação space vector e dos algoritmos de limitação são apresentados. Ainda, as tensões de saída e as correntes nos indutores são dinamicamente reguladas, por meio de servo controladores MIMO em eixos síncronos dq0. Estes controladores são projetados usando a técnica do regulador linear quadrático discreto de regime permanente, o qual assegura estabilidade para o sistema em toda a faixa de operação. Além disso, para prover transições suaves entre os diferentes modos de operação do inversor, são propostos algoritmos MIMO não lineares para limitar a sobrecarga da ação integral, quando o vetor de comando for limitado, e atualizar dinamicamente as variáveis dos servo controladores. Finalmente, são apresentados resultados experimentais obtidos de um protótipo de 15 kVA, totalmente controlado por um DSP TMS320F241, para validar os algoritmos propostos e demostrar o desempenho do sistema como um todo. Abstract in english This paper proposes two novel limiting algorithms for three-phase four-leg voltage source inverters to constrain the command vector inside the dodecahedron defined by the boundaries of the inverter linear operating range. The first algorithm uses an inscribed ellipsoid on the dodecahedron, and the second one is based on the polyhedron boundary planes. A detailed description, with the key points required for a digital implementation of space vector and limiting algorithms, (more) is given. In addition, the output voltages and the inductors currents are dynamically regulated by means of MIMO servo controller in dq0 coordinates. These controllers are designed using optimal discrete linear quadratic regulator technique, which ensures stability for the system at all operating conditions. In order to provide smooth transitions among the different modes of operation, nonlinear MIMO anti-windup algorithms are proposed to dynamically update the controllers servo variables. Finally, experimental results on a 15 kVA PWM inverter fully controlled by a DSP controller, TMS320F241, has been used to validate the feasibility of the proposed algorithm and to demonstrate the performance of the overall system.

We present a three-phase PWM converter without ac voltage and ac current sensors. The phase angle used in the control system is adjusted by using a PLL controller without sensing ac voltage. To prevent over-current at startup, the initial phase angle of the source voltage is estimated from the shunt current using a novel strategy. Furthermore, the phase currents can be reconstructed from the shunt current without any modification of PWM pattern. To reduce the effect of current ripple, the shunt current is sampled twice for every phase in one PWM period and the sample timings are carefully adjusted. All of the proposed control schemes can be implemented using a single chip microprocessor (SH7046, Renesas Tech.). Simulation and experimental results with a 5-kW prototype confirmed that the schemes worked well.

This study focused on three simplified models, namely (1) one set of single-phase DC-DC converter, (2) two sets of parallel connection single-phase DC-DC converter, and (3) two sets of series connection single-phase DC-DC converter. The purposes are: (1) to propose the simplification conditions and procedures for the three-phase AC-DC converter; (2) propose a set of new simplification steps for modeling, and present the examples of different three-phase AC-DC circuit topologies, detailed discussion on the simplification steps for modeling of a three-phase AC-DC converter is offered, to help people simplify and analyze the simplified model easily; (3) according to three types of simplified modeling in the three-phase AC-DC converter, this study established a useful reference for the design and analysis of the control systems of the three-phase AC-DC converter simply; (4) to acquire PWM control strategy beforehand based on PFC-Controlled property; (5) to reduce the switching loss for the PWM control strategy of the simplified model; (6) to maintain the original circuit topology and verify that the theory can extensively apply the knowledge of single-phase DC-DC converter to the simplified modeling of three-phase AC-DC converter.   

This paper describes the design of a line conditioner for three phase ac-ac power conditioning. It is based on a three phase PWM ac-ac buck-boost converter. It has several advantages in terms of size, weight, efficiency and performance over state of the art line conditioners. Design specifications and relationships are presented. Analytical formulae for determining the efficiency of the line conditioner are presented. A controller design which features fast transient response is developed. Operation of the line conditioner in the presence of voltage sags and surges, load addition and rejection is illustrated by means of simulation. Experimental results verifying the operation of the power circuit are also presented.

A current controlled VSI-PWM rectifier and inverter with capacitor dc link is regarded as one of the most promising structures for three-phase to three-phase power conversion. This type of converter normally requires twelve switches for a rectifier and inverter composed of self turn-off switch such as a bi-polar transistor or IGBT with an antiparallel diode. In this paper, a new three-phase to three-phase converter for ac motor drives is proposed. The proposed converter employs only eight switches and has the capability of delivering sinusoidal input currents with unity power factor and bidirectional power flow. This paper describes the feasibility and the operational limitations of the proposed structure. A mathematical model of the system is derived using generalized modulation theory and experimental results for steady state and dynamic behavior are presented to verify the developed model.

The three-phase current link AC to AC power supply, a relatively new topology for AC power supply application, has several potential advantages such as smaller number of magnetic components, lower switching frequency and more rugged operation. Despite this, it has received very little attention by the researchers, and the majority of work found in the literature is confined to the application of voltage type converters in this area. This thesis presents a comprehensive systematic approach for steady state/dynamic analysis and design of three-phase current link AC to AC power supplies. Concept of PWM methods in three-phase current type converters (CTC) is explained and the associated constraints in PWM pattern generation are addressed. Several PWM techniques are described and their performance from different aspects are compared. A steady state analysis is presented based on the Fourier representation of PWM waveforms which allows an accurate prediction of the relationships between the fundamental/harmonic components of the waveforms and other system parameters. Expressions governing various steady state characteristics of the system are derived. A dynamic model using the concept of local average of signals is established. The agreement between the dynamic behavior of switching system and derived model is illustrated. Phenomenon of multiple crossing is explained and the necessary requirement for avoiding such a phenomenon is obtained. The concept of internal model controllers is introduced and its application in the inverter control system for achieving zero steady state error is described. A detailed design procedure is presented. Root-locus method is used to design the system controllers. The applicability of different models in different design problems is discussed. All s-domain designs are verified by time-domain simulations. Experiments are conducted on a 2 KVA, 60 Hz to 50 Hz power supply. A 32 bit DSP-base high performance controller is used to implement the control system. The predicted steady state and dynamic results as well as the time-domain simulations are experimentally verified.

For three-phase power inversion, the voltage control is realized by means of pulse width modulation (PWM) of the switching variables which represent the control signals for the individual phases of the inverter. Analysis of the harmonic power spectra of the three-phase voltage-controlled inverter with randomized lead-lag modes of operation is presented. In these modes, the pulses of switching variables are either leading- or lagging-edge modulated. The randomized PWM technique provides non-repetitive switching patterns which result in spreading of distinct harmonic power over a wider frequency range. The circuit description of the randomized PWM technique is presented and three kinds of inverter control functions are introduced for explaining the principle of randomized pulse width modulation. The randomized pulse position technique is also discussed and analyzed. Closed-form expressions are given which describe the output spectra of the power inverter. MATLAB plots are provided to verify the experimental results based on those of Trzynadlowski and Legowski (1989, 1990). Program listings for calculating the spectra of a single phase output of a voltage controlled inverter are included. 30 refs., 41 figs.

This paper presents a unified positive-and negative-sequence dual-dq dynamic model of wind-turbine driven doublyfed induction generator (DFIG) under unbalanced grid voltage conditions. Strategies for enhanced control and operation of a DFIG-used back-to-back (BTB) PWM voltage source converter (VSC) are proposed. The modified control design for the grid-side converter in the stationary ?? frames diminishes the amplitude of DC-link voltage ripples of twice the grid frequency, and the two proposed control targets for the rotor-side converter are alternatively achieved, which, as a result, improve the fault-ride through (FRT) capability of the DFIG based wind power generation systems during unbalanced network supply. A complete unbalanced control scheme with both grid-and rotor-side converters...

This paper examines ac motor shaft voltages and the resulting bearing currents when operated under pulse width modulation (PWM) voltage source inverters. The paper reviews the mechanical and electrical characteristics of the bearings and motor in relation to shaft voltages and bearing currents. A brief review of previous work is addressed, including the system model and experimental results. The theory of electric discharge machining (EDM) is presented, including component calculations of the system elements. The effect of system elements on shaft voltages and bearing currents are evaluated experimentally and the results compared to theory. A design calculation is proposed that provides the relative potential for EDM. Finally, the paper will present quantitative results on one solution to the shaft voltage and bearing current problem.

These days, a quiet induction motor is strongly demanded. Electromagnetic factor is main cause of vibration and acoustic noise of small induction motor. Electromagnetic forces and magnetostrictive forces are considered of origin of electromagnetic vibration and noise. In this paper, magnetostrictive vibration of ring of electrical steel sheets was simulated by mechanical Finite Element Method. Magnetostriction was assumed as external forces and they were added at each node of meshed ring. Resonant frequency and mode of ring were calculated. In steel sheet ring excited by PWM voltage source inverter, frequency spectrum of vibration of ring was measured and compared with calculated results. It was confirmed that these procedure simulated magnetostriction behavior of electrical steel sheets. Furthermore, electromagnetic forces of small induction motor was calculated and compared with magnetostriction data. It became clear that electromagnetic vibration was affected by the magnetostriction of steel. These results will be useful to reduce the acoustic noise and to develop quiet motors.

Abstract Since the mechanical power extracted from wind is proportional to the cube of the wind speed, the output of the wind turbine generator system fluctuates considerably due to wind speed variations. Therefore, high penetration of wind power to the power grid causes fluctuation of the grid frequency, which has adverse effects on power system stability and reliability. Since a superconducting magnetic energy storage (SMES) system has the ability to provide both active and reactive power simultaneously and quickly, the SMES system can be an effective tool to mitigate frequency fluctuations under such conditions. In the present study, a PWM voltage source converter and two-quadrant DC-DC-chopper-controlled SMES system is proposed, which can significantly decrease the voltage and output p...

In this paper, a simple control strategy for an optimal extraction of output power from grid connected variable speed wind energy conversion system (WECS) is presented. The system consists of a variable speed wind turbine coupled to a permanent magnet synchronous generator (PMSG) through a gear box, a diode bridge rectifier, a dc-to-dc boost converter and a current controlled voltage source inverter. The maximum power point tracker (MPPT) extracts maximum power from the wind turbine from cut-in to rated wind velocity by sensing only dc link power. The MPPT step and search algorithm in addition to the DC-DC and DC-AC converters PWM controllers are simulated using MATLAB-SIMULINK software. The obtained simulation results show that the objectives of extracting maximum power from the wind and ...

The paper presents a power generation system based on the cogeneration of heat and electricity with a novel high speed turbogenerator. The machine consists of a single stage steam turbine and a directly coupled permanent magnet synchronous generator in one constructional unit. A PWM IGBT rectifier is the load to the generator and a PWM IGBT three-phase four-wire inverter feeds the power into the low voltage mains. In order to increase the turbine efficiency at light load, variable speed operation of the turbogenerator is realized. Different control schemes for mains parallel operation and stand alone operation are presented. The control schemes allow for the use of a lookup table based control with a speed-power-characteristic or for the use of a maximum power point tracker. Measurement results from the successfully tested turbogenerator set are presented.

This paper proposes direct power control (DPC) for three-phase PWM rectifiers using a new switching table, without line voltage sensors. The instantaneous active and reactive powers, directly controlled by selecting the optimum state of the converter, are used as the PWM control variables instead of the phase line currents being used. The main goal of the control system is to maintain the dc-bus voltage at the required level, while input currents drawn from the power supply should be sinusoidal and in phase with respective phase voltages to satisfy the unity power factor (UPF) operation. Conventional PI and a designed fuzzy logic-based controller, in the dc-bus voltage control loop, have been used to provide active power command. A dSPACE based experimental system was developed to verify t...

Abstract in portuguese Este artigo apresenta uma metodologia sistematizada de projeto de filtros de saída de segunda ordem para inversores que sintetizam tensões senoidais através de modulação por largura de pulso (PWM) digital. O propósito desta metodologia é o de determinar os parâmetros do filtro que assegure a especificação da máxima taxa de distorção harmônica total (THD) admissível nas tensões de saída do inversor PWM, para cargas lineares e não-lineares. A metodologia p (more) roposta é discutida em detalhes, incluindo a descrição das etapas necessárias para a derivação do procedimento de projeto para diferentes topologias de inversores de tensão e o procedimento para obtenção das curvas necessárias para o projeto. Finalizando, são apresentados alguns exemplos de projeto para topologias de inversores monofásicos e trifásicos com saída a três fios e a quatro fios. Resultados experimentais são apresentados para demonstrar a validade da metodologia de projeto proposta. Abstract in english This paper presents a systematized methodology of second-order output filter for inverters that synthesize sinusoidal voltage waveforms through digital pulse-width modulation (PWM). The objective of this methodology is to determine the largest corner frequency of the filter that ensure the specification of the maximum total harmonic distortion (THD) admissible in the output voltages of the PWM inverter, for linear and non-linear loads. The proposed methodology is discusse (more) d in detail, including the description of the required steps for the derivation of the design procedure for different topologies of voltage inverters and the procedure to obtain the design curve. Finally, it is presented some design examples for single-phase, three-phase three-wire and three-phase four-wire filters topologies. Experimental results have been provided to demonstrate the validity of the proposed design methodology.

A new photovoltaics (PV) power generation system that used an active filter (AF) function was proposed. The AF was installed to condition reactive power and harmonic compensation as well as flicker and voltage regulation. A maximum point power tracking (MPPT) control system was used to stabilize the voltage source inverter (VSI) output current. A general dq transformation was used to compensate the negative components and the harmonics component. The output terminal of the PV array was connected to a smoothing capacitor interfacing the PV-AF inverter. A voltage source PWM converter was controlled with feedback loops of the output current of the inverter. Optimal values of the power inverter gains and filter constants were tuned to obtain responses. The PV system was simulated using real weather conditions. Results of the study demonstrated the stability and effectiveness of the proposed system. It was concluded that the PV-AF can also be used to provide harmonic damping throughout power distribution systems. 12 refs., 3 tabs., 9 figs.

The device for shielding a rectifier, switched in between current limiting reactors to a three phase alternating voltage source, contains a high voltage arc short circuiting unit whose power electrodes are switched in to the circuits of alternating and direct current of the rectifier. To increase the reliability, each reactor is made of two parts with inductively linked and matched, sequentially connected windings, whose common point in each phase is switched in to the power source. One extreme outlead is connected to the power electrode of the arc short circuiting device and the other, to the alternating current input of the rectifier.

This paper reports on the basic configuration of the railway static power conditioner (RPC), a static voltage compensator for AC electric railways. 20 MVA / 60 kV RPCs started commercial operation in 2002 at each substations on the newly extended Tohoku Shinkansen. The results of operational test indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, handle the exciting rush current of transformers, as well as compensate for harmonics. The voltage fluctuations on the three-phase side were succcessfully controlled by the RPCs.   

This paper presents the implementation of the OTA (Operational Transconductance Amplifier) & CCII (Second generation Current Conveyor)-based control system of active power filter (APF). The three-phase shunt PWM VSI-APF is used as the power circuit for simple control. This proposed control system using OTA & CCII-based circuits since it has the advantage of its adaptive control, real-time processing and it has wide bandwidth which can work with the high frequency power switches in order to eliminate the higher order of harmonics, moreover, it can be fabricated in one single chip by using CMOS technology. Theoretical analysis, design and simulation results are provided.

A topological approach to a utility-interactive inverter that treats the photovoltaic array as a current-source, rather than as a voltage-source is presented. The different characteristics resulting from this approach have certain advantages that apply to single-phase residential units as well as to three-phase high power units. Advantages include open-loop control of the ac current waveform, an array voltage that can extend from zero up to some maximum, and the use of an inductor as the dc energy storage element. Simulations showed that the switching frequency for an active-waveshaping inverter can actually be quite low (5 kHz or less) and still obtain a distortion level in the utility current of less than 5% THD. Finally, a 20 kW three-phase current-source converter is described.

Abstract in portuguese O objetivo deste trabalho é de que ele possa ser utilizado como tutorial da modulação space vector para profissionais da área de Eletrônica de Potência. Nesse sentido, este artigo apresenta uma abordagem unificada para a modulação space vector aplicada a inversores alimentados em tensão. Cinco inversores de tensão são apresentados para exemplificar a metodologia proposta, são eles: inversor monofásico em ponte completa, inversor trifásico a três fios de doi (more) s e três níveis, inversor trifásico a quatro fios de três e quatro braços. Para cada um dos inversores são apresentados os vetores de comutação, os planos de separação, os planos limites para operação na região linear, bem como algumas possíveis seqüências de comutação. Resultados experimentais são apresentados para validar a metodologia proposta. Abstract in english This paper presents a unified approach of the space vector modulation for voltage-source inverters. To demonstrate the proposed unified approach, five fundamental inverters topologies are analyzed, that are: single-phase full-bridge; three-phase three-wire; three-phase four-wire, three-phase four-leg and three-phase three-level inverters. Switching vectors, separation and boundary planes in the inverter output space as well as decomposition matrices and possible switching (more) sequences are derived for each one of these inverters. Experimental results are shown to validate the proposed approach.

The authors have already proposed a new power consolidation-inversion-control system for the Faraday type magnetohydrodynamic (MHD) generator. The d.c. power output from each electrode pair is at first inverted through the voltage source PWM inverter and the a.c. power outputs are then consolidated by the transformers. The authors' numerical simulation has already indicated that the system has an adequate performance as a fast active power controller. The system has the capability of controlling not only the active power but also the reactive power independently and simultaneously. In this paper, improvements are made on the power control system to realize the independent and simultaneous control of the active and the reactive power. To confirm numerically the performances of the improved system, simulations are carried out for the whole system, including the Faraday type MHD generator, the power consolidation-inversion-control system and the infinite bus. The calculations of the transient responses of the whole system show that the improved system can control rapidly and with stability the active and the reactive power independently and simultaneously. The system has an adequate performance as a power transmission circuit between the Faraday type MHD generator and the electric power system and also as an active and reactive power controller. (Author).

A novel fuel cell based inverter for residential systems was presented. The inverter consisted of an isolated ZVS current-fed half bridge DC-DC converter cascaded with a single phase quasi-resonant voltage source inverter. The 400 V DC output was converted to 220 V 50 Hz single-phase AC by means of a quasi-resonant PWM inverter stage. An output LC filter was used to produce a THD of AC waveform. The inverter stage was developed from a classical VSI inverter with an L-type full-wave resonant switch. The structure did not require any clamping circuit and was able to guarantee the stable oscillation of resonant links as well as the soft switching of the inverter only by using a discrete pulse width modulation of the inverter grid interface. This paper provided an analysis of the proposed topology of the inverter grid interface. The analysis was divided into 7 modes. Operation modes were based on the assumption that the currents were continuous, that all switching devices and resonant components were ideal. Transformer leakage inductance and magnetizing inductance were neglected. Four operating modes in each resonant cycle were considered, and solutions were presented for all modes. It was concluded that the inverter performed well in all the analyzed power ranges. 9 refs., 1 tab., 11 figs.

Power supplies used on the electric power environment test process for electronic products and audio-amplifiers are required to generate arbitrary ac voltage waveforms in the wide frequency range. Traditionally, analogue amplifier technologies have been used for those application even though those have the disadvantages of low-efficiency, bulky in volume, and heavy in weight. Recently, however, research on the arbitrary waveform power generator becomes to be attractive among power electronics engineers, because the audio amplifiers utilizes the D-Mode switching technologies have been move into the market. This paper presents an arbitrary ac power generator utilizes a novel instantaneous waveform control method for a single-phase voltage source PWM inverter. A remarkable feature of this control method is that an adaptive frequency band-pass filter based on a rotation frame transformation and a command generator on the rotation frame is used. The proposed method can suppress the resonance caused by the LC filter at the output line, and hence it enables to generate a rectangular voltage waveform without overshoot. The command generator generates both an instantaneous frame angle and accurate voltage commands on the rotating frame from one an analogue signal. The effectiveness of this method is verified through 500W experimental set-up.

A new mathematical model of the power circuit of a three-phase voltage source converter (VSC) was developed in the stationary and synchronous reference frames. The mathematical model was then used to analyze and synthesize the voltage and current control loops for the VSC. Analytical expressions were derived for calculating the gains and time constants of the current and voltage regulators. The mathematical model was used to control a 140-kW regenerative VSC. The synchronous reference frame model was used to define feedforward signals in the current regulators to eliminate the cross coupling between the d and q phases. It allowed the reduction of the current control loop to first-order plants and improved their tracking capability. The bandwidths of the current and voltage-control loops were found to be approximately 20 and 60 times (respectively) smaller than the sampling frequency. All control algorithms were implemented in a digital-signal processor. All results of the analysis were experimentally verified.

Abstract This paper presents a novel linearized model of a power system installed HVAC parallel-connected with a HVDC system based voltage source converter (VSC HVDC) in order to determine the most effective input to apply supplementary controller and design of phase compensator. The power system linearized model cannot be appropriate during the severe disturbances such as three phase faults. In this paper, a nonlinear model of a power system is obtained and in addition, an adaptive neural damping controller based neural identifier is proposed to improve stability and overcome the drawbacks of conventional phase compensator. Simulation results carried out by SIMULINK/MATLAB show the proposed strategy is most effective in comparison with phase compensator. Copyright 2010 John Wiley & Sons, ...

This paper presents a three-phase electric drive with a modified electronic smoothing inductor (MESI) having reduced size of passive components. The classical electronic smoothing inductor (ESI) is able to control a diode bridge output current and also reduce not only mains current harmonics but also output voltage ripple. ESI performs the function of an inductor that has controlled variable impedance. MESI requires active switches with lower ratings than ESI and has the same performance. In MESI, an active voltage source realized by a low-voltage switch-mode converter stage is inserted in series with DC-link capacitor. This increases power factor (PF) and reduces the total harmonic distortions (THDs) in current at mains. Input currents of the diode bridge which usually show high peak amplitudes are converted into a 120° rectangular shape which ideally results in a total PF of 0.955 and THDs of 31%, by electronic smoothing techniques.

Voltage source inverter (VSI) can produce single and three-phase (3P) AC voltages from a constant or variable DC voltage. There are many ways to control the VSI output voltage. Each control way produces some harmonics at the VSI output voltage. The space vector pulse width modulation (SVPWM) may be more effective than other modulation methods, e.g. harmonic injection, phase shifting, multi career pulse width modulation, in decreasing the low order harmonics (LOH). Different switching strategies (SSs) of power electronic devices in SVPWM have some specific advantages and disadvantages with regard to one another. In this paper, a comparative study between different SVPWM SSs is carried out by considering some objective functions such as total harmonic distortion (THD), power and switching lo...

This paper presents an excellent PWM method for power conversion circuits. The proposed method is called a Vector Frequency Modulation (VFM) in this paper. VFM does not belong to any conventional PWM methods. Although an idea of space voltage vector is employed in VFM, any traditional equations to calculate the periods of the voltage vectors are not used. The voltage vectors are classified into two groups, zero vectors and non-zero ones. Instead of the complicated equations, a very simple algorithm is employed in VFM. One vector period is fixed and the zero vectors are distributed among the non-zero vectors in the ratio determined by the command voltage or frequency. The behavior of VFM is performed in software and any modulation-wave oscillators, comparators and up-down counters are not needed. At first, a reversible chopper is modulated by VFM and a 2kW DC motor is driven by the chopper. The motor speed is regulated by modern control theory. Next, a three-phase inverter is modulated by VFM and a 2.2kW induction motor is driven by the inverter. Experimental results are shown to prove that VFM is actually useful for power conversion circuits.

The design of an ac propulsion system for an electric vehicle includes a three-phase induction motor, transistorized PWM inverter/battery charger, microprocessor-based controller, and two-speed automatic transaxle. This system was built and installed in a Mercury Lynx test bed vehicle as part of a Department of Energy propulsion system development program. An integral part of the inverter is a 4-kw battery charger which utilizes one of the bridge transistors. The overall inverter strategy for this configuration is discussed. The function of the microprocessor-based controller is described. Typical test results of the total vehicle and each of its major components are given, including system efficiencies and test track performance results.

Three phase rectifiers with switching frequencies of 500 kHz or more require high speed current controllers. At such high switching frequencies analog controllers as well as high speed digital signal processing (DSP) systems have limited performance. In this paper, two high speed current controller implementations using two different field-programmable gate arrays (FPGA) - one for switching frequencies up to 1 MHz and one for switching frequencies beyond 1 MHz - are presented to overcome this performance limitation. Starting with the digital system design all the blocks of the signal chain, containing analog-to-digital (A/D) interface, digital controller implementation using HW-multipliers and implementation of a novel high speed, high resolution pulse width modulation (PWM) are discussed and compared. Final measurements verify the performance of the controllers. (author)

This document presents the modeling of a wind turbine-generator system and developing a control scheme for maximum power extraction. The system comprises a low-power variable speed wind rotor coupled to a squirrel cage induction generator through gearbox. The generator delivers electrical energy to a DC load through a PWM three phase rectifier which control variables are duty cycle and the fundamental frequency of the modulated signal. The control scheme maintains constant relationship voltage/frequency in the stator of the generator to operate the machine with constant air gap flow at its nominal value, thereby decreasing electrical losses in the circuit of the stator and rotor. The controller is based on MPPT algorithms for determining the operating point the system and achieve the proper mechanical speed shaft. The performance is evaluated through simulations in MatlabRTM/simulink. and presents this type of control as a good alternative for handling low-power wind turbine-generator systems effectively and efficiently

In the following memoir, the author presents a description of the conception of a three phase PWM DC/AC inverter and its application in a Photovoltaic pumping system using an induction motor. The inverter, without a transformer, consists of a small number of fully integrated circuits and the output sinus-shaped signals are based on the Pulse Width Modulated technique.Its design was based on an analogue structure. In the power section a compact IGBT power module was used. This inverter is simple, it can easily be adapted to a different power and voltage range by simple changing the IGBTs power module. To assess its performances, the inverter was coupled to a Photovoltaic bore-hole submersible system with centrifugal and progressive cavity pumps. This memoir presents the results of the efficiency of the inverter itself and the efficiency of the pumping subsystem. The study ends in a possible technology transfer for production in developing countries. (author)

This paper is concerned with the design and implementation of current control of three-phase PWM rectifier based on predictive control strategy. The proposed predictive current control technique operates with constant switching frequency, using space-vector modulation (SVM). The main goal of the designed current control scheme is to maintain the dc-bus voltage at the required level and to achieve the unity power factor (UPF) operation of the converter. For this purpose, two predictive current control algorithms, in the sense of deadbeat control, are developed for direct controlling input current vector of the converter in the stationary a-b and rotating d-q reference frame, respectively. For both predictive current control algorithms, at the beginning of each switching period, the required...

This paper establishes an analytical model for a resonant snubber based soft-switching inverter. The model adopts loss separation method to evaluate losses in individual components. Because of symmetry of the inverter circuit, the developed model is suitable for both single-phase and three-phase inverters. A single-phase inverter was built and tested with a single-phase induction motor driving a fan load to verify the developed model. The equivalent single-phase induction motor model was curve-fitted from experiment. Analytical results showed reasonable agreement with experiment. The same efficiency evaluation method was then applied to the conventional hard-switching inverter, and the results were compared with that of the soft-switching inverter. The resonant snubber base soft-switching inverter shows substantial efficiency improvement over the hard switching PWM (pulse-width-modulation) inverter, especially in low speed operation.

Abstract in portuguese Este artigo propõe uma solução para a conexão direta de geradores de indução trifásicos em uma rede monofásica com regulação de vazão o que faz com que, a velocidade do gerador de indução se mantenha acima de sua velocidade síncrona. Para que a conexão entre gerador e rede monofásica seja satisfatória e para que os critérios de qualidade de energia sejam preservados, o controle do fluxo de energia, entre a rede monofásica e o conversor PWM trifásico, ? (more) ? realizado empregando a idéia de sistema interligado ajustando a defasagem e amplitude da tensão sintetizada pelo conversor em relação a tensão da rede monofásica de forma que o fator de potência na rede monofásica seja unitário. Em relação ao conversor de potência, espera-se que o mesmo produza tensões senoidais, com freqüência e amplitude fixas para que o gerador de indução opere balanceado. O artigo descreve a estratégia de controle do inversor, o critério de projeto dos controladores e apresenta alguns resultados experimentais. Abstract in english This paper proposes a solution for the direct connection of a three-phase induction generator to a single-phase feeder. This high power quality system is intended to be used in micro-hydro power plants applications with control of the water flow. It is employed to maintain the speed of the induction generator greater than its synchronous value. The difference between the generated power and the power consumed by the local load flows through the single-phase feeder. The po (more) wer flow control is provided by a three-phase PWM inverter that additionally guarantees the local power quality. A system with good power quality must have sinusoidal and constant amplitude voltages, fixed frequency operation, balanced induction generator voltages and currents, harmonics and reactive power compensation. The paper describes the inverter control strategy, presents design criteria of the controllers, and shows experimental results.

It is well known that the ability of the permanent magnet synchronous machine (PMSM) to operate over a wide constant power speed range (CPSR) is dependent upon the machine inductance [1,2,3,4,5]. Early approaches for extending CPSR operation included adding supplementary inductance in series with the motor [1] and the use of anti-parallel thyristor pairs in series with the motor-phase windings [5]. The increased inductance method is compatible with a voltage-source inverter (VSI) controlled by pulse-width modulation (PWM) which is called the conventional phase advance (CPA) method. The thyristor method has been called the dual mode inverter control (DMIC). Neither of these techniques has met with wide acceptance since they both add cost to the drive system and have not been shown to have an attractive cost/benefit ratio. Recently a method has been developed to use fractional-slot concentrated windings to significantly increase the machine inductance [6]. This latest approach has the potential to make the PMSM compatible with CPA without supplemental external inductance. If the performance of such drive is acceptable, then the method may make the PMSM an attractive option for traction applications requiring a wide CPSR. A 30 pole, 6 kW, 6000 maximum revolutions per minute (rpm) prototype of the fractional-slot PMSM design has been developed [7]. This machine has significantly more inductance than is typical of regular PMSMs. The prototype is to be delivered in late 2005 to the Oak Ridge National Laboratory (ORNL) for testing and development of a suitable controller. In advance of the test/control development effort, ORNL has used the PMSM models developed over a number of previous studies to study the steady-state performance of high-inductance PMSM machines with a view towards control issues. The detailed steady-state model developed includes all motor and inverter-loss mechanisms and will be useful in assessing the performance of the dynamic controller to be developed in future work. This report documents the results of this preliminary investigation.

Abstract in portuguese Com o avanço da tecnologia dos dispositivos semicondutores de potência os inversores de frequência atuam de forma importante em toda indústria. O inversor de frequência convencional contém elementos armazenadores de energia no seu elo de corrente contínua. Estes elementos armazenadores de energia são capacitores eletrolíticos e possibilitam manter a tensão do elo de corrente contínua constante. Entretanto, quanto maior sua capacitância maior é a distorção d (more) a corrente de entrada. Com a substituição do banco de capacitores eletrolíticos por um capacitor de filme, diminui-se a distorção nas correntes de entrada, porém distorções indesejadas aparecem na tensão do elo de corrente contínua e também nas correntes de saída. Estas distorções são compostas por componentes harmônicas de baixas frequências. O conversor em matriz trifásico-trifásico por sua vez, possibilita a transferência direta de energia da entrada (rede) diretamente para a saída (carga) sem a necessidade de elementos armazenadores de energia como acontece no inversor de frequência. Entretando o desbalanceamento das tensões da entrada afetam diretamente a forma de onda das tensões da saída. Dessa maneira, este trabalho propõe um método de controle de corrente do conversor em matriz e do inversor de frequência sem banco de capacitores do elo de corrente contínua com objetivo de compensar o desbalanceamento das tensões de saída do conversor em matriz e compensar também as componentes harmônicas de baixa frequência que aparecem nas correntes de saída do inversor de frequência. O método proposto utiliza um controlador do tipo PI e modulação por vetores espaciais para que a frequência de acionamento das chaves dos conversores seja constante. Abstract in english Voltage source three-phase inverter plays an important role in modern industry. The conventional voltage source inverter has a large electrolytic capacitor as energy store element in order to keep the DC-link voltage constant. However, a large electrolytic capacitor increases the input current distortion. Replacing the large electrolytic capacitor by a small film capacitor, the input current quality is improved but the DC-link voltage and the output currents are distorted (more) by low order harmonic components. The three phase to three phase matrix converter performs electric energy direct transfer from the input to the output with sinusoidal input current although the distortion and the unbalance of the input voltages affects directly the output of the matrix converter. This paper proposes a load current control method to the matrix converter and also to the voltage source inverter in absence of the dc-link capacitor in order to compensate the distortion caused by low order harmonics components in the output currents. The proposed load current control scheme employs just one PI controller and since that the space vector modulation is used in this control, the switching frequency of the converter is kept constant. Theorical foundation, simulations results and experimental results are presented.

In this paper, an interleaved active-power-filter concept with reduced size of passive components is discussed. The topology is composed of two pulsewidth-modulation interleaved voltage-source inverters connected together on the ac line and sharing the same dc-link capacitor. The advantages of the proposed approach are as follows: 1. significant reduction in the linkage inductors' size by decreasing the line-current ripple due to the interleaving; 2. reduction of the switching stress in the dc-link capacitor, due to the shared connection; and 3. more accurate compensation for high-power applications, because the power sharing allows one to use a higher switching frequency in each inverter. This paper analyzes the design of the passive components and gives a practical and low-cost solution for the minimization of the circulation currents between the inverters, by using common-mode coils. Several simulation results are discussed, and experimental results with a three-phase 10-kVA 400-V unit are obtained to validate the theoretical analysis. Udgivelsesdato: March

This paper presents a transformerless hybrid active filter that is integrated into medium-voltage adjustable-speed motor drives for fans, pumps, and compressors without regenerative braking. The authors have designed and constructed a three-phase experimental system rated at 400V and 15kW, which is a downscaled model from a feasible 6.6-kV 1-MW motor drive system. This system consists of the hybrid filter connecting a passive filter tuned to the 7th harmonic filter in series with an active filter that is based on a three-level diode-clamped PWM converter, as well as an adjustable-speed motor drive in which a diode rectifier is used as the front end. The hybrid filter is installed on the ac side of the diode rectifier with no line-frequency transformer. The downscaled system has been exclusively tested so as to confirm the overall compensating performance of the hybrid filter and the filtering performance of a switching-ripple filter for mitigating switching-ripple voltages produced by the active filter. Experimental results verify that the hybrid filter achieves harmonic compensation of the source current in all the operating regions from no-load to the rated-load conditions, and that the switching-ripple filter reduces the switching-ripple voltages as expected.

A three-phase transformerless power electronic conversion system is used as an interface between a photovoltaic (PV) array and the utility line. A high efficiency is obtained because a conventional power transformer is not applied and because of a high array voltage. A maximum power point tracker (MPPT) is used for optimal utilization of the PV-array, which results in a high yield of the system. The power electronic converter is based on the topology of a Pulse Width Modulated Current Source Inverter (PWM-CSI). The inverter is operated at a high switching frequency (20 kHz), so that waveforms with a low distortion are generated, while the power factor is near unity. On the ac side as well as on the dc side the harmonics and the ripple components are considered. Performance measurements on a 1kVA-prototype system show that the efficiency of the system increases from 65% at 20% load to 85% at full load. From 20% to full load, the power factor exceeds 0.95. 11 figs., 4 refs.

This paper describes analyses using a status space method to verify fundamental characteristics of a three-phase step-up/down current-source rectifier. The analytical results were compared with experimental results to clarify the practicability of the circuitry. The circuitry used insulated-gate bipolar transistors (IGBT) as switching elements, and the DC circuit had buck boost converters and buck converters connected longitudinally and used a PWM method. A simulation revealed that current flowing in the fly-back inductor is kept nearly constant, and the source current is controlled sinusoidally. The result of experiments on a circuit fabricated practically using IGBT showed a good agreement with the simulation result including from ripples to transient phenomena attributable to switching the self arc-extinguishing elements. It was found that low-order harmonics in the measurements and calculations have been suppressed to approximately 1% or lower. Measurements and theoretical values agreed approximately well with each other in static characteristics when modulation rates were varied, verifying that the step-up and down characteristics can be obtained as proposed in the circuitry. 8 refs., 9 figs.

NASA Glenn Research Center (GRC) has been involved in the research and development of high speed flywheel systems for small satellite energy storage and attitude control applications. One research and development area has been the minimization of the switching noise produced by the pulsed width modulated (PWM) inverter that drives the flywheel permanent magnet motor/generator (PM M/G). This noise can interfere with the flywheel M/G hardware and the system avionics hampering the full speed performance of the flywheel system. One way to attenuate the inverter switching noise is by placing an AC filter at the three phase output terminals of the inverter with the filter neutral point connected to the DC link (DC bus) midpoint capacitors. The main benefit of using an AC filter in this fashion is the significant reduction of the inverter s high dv/dt switching and its harmonics components. Additionally, common mode (CM) and differential mode (DM) voltages caused by the inverter s high dv/dt switching are also reduced. Several topologies of AC filters have been implemented and compared. One AC filter topology consists of a two-stage R-L-C low pass filter. The other topology consists of the same two-stage R-L-C low pass filter with a series connected trap filter (an inductor and capacitor connected in parallel). This paper presents the analysis, design and experimental results of these AC filter topologies and the comparison between the no filter case and conventional AC filter.

In this paper, the design of a distribution static compensator (DSTATCOM) based on cascaded transformer multilevel inverter is proposed. The topology requires controlling only a common dc storage capacitor. Two-level ramp-comparison current control method is extended for the multilevel inverter using phase-shifted multi-carrier PWM. The method provides equal switching stress and power handling for all the cascaded units. The net switching frequency increases while the ripple magnitude reduces using multilevel topology. These cause the feedforward gain to increase leading to a higher bandwidth of the control loop. An expression of the feedforward gain is derived for fixed switching frequency modulation of the inverter. It is shown that the use of proportional plus resonant controller with proposed multilevel modulation improves the tracking characteristics at fundamental frequency. A seven-level inverter based DSTATCOM is proposed for the application to the three-phase medium voltage distribution system and the results are shown through the PSCAD/EMTDC simulation. The proposed modulation and control scheme is validated through the experimental results that are obtained using the laboratory model of a single-phase, five-level inverter based DSTATCOM. (author)

This paper describes a nonlinear torque and stator flux controller for three phase induction motor (IM) drives on the basis of a space vector modulation (SVM) scheme. Using the IM fifth order model in a fixed 'ab' axis reference frame with stator currents (i{sub sa},i{sub sb}) and stator fluxes ({psi}{sub sa},{psi}{sub sb}) as state variables, a sliding mode (SM) torque and flux controller is designed first in order to track a linear reference model, which has the desired dynamic behaviors for the IM drive system. The SM controller generates the reference voltages (v{sub as}{sup *},v{sub bs}{sup *}) for a two level space vector modulation-pulse width modulation (SVM-PWM) inverter that feeds the motor. Then, the SM controller is combined with an adaptive input-output feedback linearization technique in order to preserve the system robustness with respect to stator and rotor resistances variations and uncertainties. Finally, simulations and comparative experimental results with the proposed control scheme are presented. (author)

In this paper, a new chaotic PWM inverter is proposed and implemented to reduce the conducted electromagnetic interference (EMI) in induction motor drives for electric vehicles. The key is to design a chaotic frequency modulator to modulate the switching frequency of the space vector PWM inverter. C...

This paper presents a new pulse width modulation (PWM) controller for unmanned aerial vehicle (UAV) precision sprayer for agriculture using a TL494 fix-frequency pulse width modulator together with a data acquisition board and developed software. The PWM controller was implemented through the guidan...

Space Vector Pulse Width Modulation (SVPWM) method is an advanced, computation intensive PWM method and possibly the best among all the PWM techniques for variable frequency drive applications. The SVPWM is an alternative method for the determination of switching pulse width and their position. The ...

We show the main results obtained when applying the average theory to Zero Average Dynamic control technique in a buck power converter with pulse-width modulation (PWM). In particular, we have obtained the bound values for output error and sliding surface. The PWM with centered and lateral pulse con...

The full-digital audio amplifiers have several merits such as a high power enabling a small size of the amplifier and digital implementation of the signal processing which allows desired precision of the processing except for the final stage switching amplifiers. Unfortunately, the pulse width modulation (PWM) causes signal distortions because of the non-linearity of the modulation from the viewpoint of the transient response. This paper proposes a compensation method of the PWM distortion with feedback approach. In the noise-shaping filter of the delta-sigma modulator to calculate the pulse codes for the PWM, the distortion caused by the PWM is evaluated and fed it back to compensate the distortion. Eventually the filter is implemented as a state-variable filter with non-linear feedback from the quantizer. The calculation of the filter elements is also described. By using proposed filters, PWM signals with small distortions and small floor noise can be obtained to realize high-fidelity audio amplifiers.

Two state-of-the-art variable-speed rotary compressors, of nominal one ton cooling capacity, were instrumented and tested in the laboratory. Both compressors were identical except for their respective variable-speed drive systems (i.e., motor and inverter). One compressor had an inverter driven induction motor (IDIM) drive, and the other had a permanent magnet electronically commutated motor drive (PM-ECM). The laboratory study evaluated the compressor`s efficiency under representative variable-speed conditions. Testing was conducted as a function of compressor drive frequency and of refrigerant condensing and evaporating conditions. Saturated refrigerant conditions, inlet superheat, and subcooling were controlled using a secondary refrigerant calorimeter. Spectrum analysis was conducted on the current input to one phase of the three- phase drive systems to measure motor speed and characterize harmonic content of the inverters. An optimal volt per Hz ratio was determined at 120-, 90-, 60-, and 30-Hz drive frequencies and at different load conditions for the rotary with induction motor as driven by a PWM inverter and also by a motor generator set (ideal induction motor drive). Variation of voltage input to the compressor had the largest effect at the lowest drive frequency (30Hz). A 5% variation about the optimal voltage at 30 Hz frequency caused a roughly 5% drop in compressor isentropic efficiency. Calorimeter data were used to develop modulating compressor and drive system performance maps. Performances of the two compressors were compared and the rotary with PM-ECM drive showed better efficiency trends at 30-Hz drive frequency. Above the 30-Hz drive frequency no clear advantage was observed for the PM-ECM vs the IDIM, possibly due to oversizing of the PM-ECM inverter.

This paper presents high-order harmonic resonance phenomena of voltage sourced converter (VSC). When a voltage sourced converter is connected to power system with cables, there is possibility that minute high-order harmonic voltages of a voltage sourced converter are magnified by a series resonance and a parallel resonance, and high-order harmonic resonance phenomena are found by this study. The cause of high-order harmonic resonance phenomena is investigated and figured out by the analysis using EMTP. In addition, it is verified that high-order harmonic resonance phenomena occur as a practical matter.

The superconducting Maglev system suspended by EDS intrinsically has negative magnetic damping. In order to improve the magnetic damping, we used a linear generator by controlling the power factor of the current in the linear genetator coils. We developed a PWM converter and a simulator ( using Micro Cap VI ) for this control. This paper describes how to control the PWM converter and subsequently the power factor and the result of confirmation of this control method through simulation and synthetic bench tests. We can now control the PWM converter and the power factor without affecting the output power.   

This paper deals with operating a high speed induction motor, with a double star stator winding shift by an angle of 30 deg C. This motor is supplied by an hysteresis current control voltage source inverter. (orig.)

Jun 25, 2003 ... When an external electric field is applied, the ions move according to the ... dc, high-voltage source feeds the desired voltage to the two electrodes. ... The following figure shows images of ethylene flames burning in air at ...

In 1998, Eltra, the Independent System operator and the Transmission company in western Denmark decided to investigate the use of the new HVDC Light technology for DC connection of wind power to Eltra's transmission grid. There is an increasing amount of wind farms that need to be connected to the AC transmission network. Offshore wind farms will be connected to the ac system via long submarine cables. Integration of offshore wind farms with HVDC transmission based on Voltage Source Converters (VSC), such as HVDC Light, is an advantage due to regulating properties of HVDC Light. The purpose with the Tjaereborg project was to demonstrate on a small scale the application of this new technology for connection of large-scale offshore wind farms. The project was realized on the existing wind farm at Tjaereborg close to Esbjerg on the west coast of Denmark. It was released and started in March 1999 and was taken over for tests and demonstration in December 2000. VSC with Pulse Width Modulation (PWM) can operate in all four quadrants of the PQ-plane, i.e. it can operate as rectifier or inverter at variable frequency and at the same time absorb or supply reactive power to the AC network. HVDC Light is suitable for connection of wind farms with induction generators, since the wind generators are decoupled from the AC network. In the wind farm, the HVDC Light can supply an AC voltage to a dead net at start up as well as collect the wind power and at the same time supply reactive power to the wind generators. It can also vary the frequency, getting the highest power economy from the wind farm. At the receiving end, the VSC delivers wind power to the AC network and independently regulates the AC network voltage. The co-operation between the HVDC Light and the windmills was tested by simulations prior to commissioning, mainly in EMTDC. During commissioning relevant test were repeated as applicable. Some disturbances were simulated, for minimizing system disturbances during commissioning. It may be mentioned that black start of the windmill as subsystem from the HVDC Light has been successfully demonstrated. The experience from both commissioning and operation so far shows that HVDC Light transmission based on VSC techniques is a promising concept for connecting large wind farms to ac systems. With the used concept of the HVDC rectifier working in the stiff voltage mode, the windmills just see the HVDC Light rectifier as a stiff ac network, as they are used to. Thus the introduction of HVDC Light does not introduce any new requirement on the windmills. However, at design of the windmills in the future, the dynamic speed increase at AC system faults must be considered. The reason is that the windmills will in the future not be allowed to trip at temporary AC system faults.

Institutional and governmental support on wind energy sources, together with the wind energy potential and improvement of wind energy conversion technology, has led to a fast development of wind power generation in recent years. The continuous increase of the wind power penetration level brings a result that wind power generation gradually becomes an important component of power generation in the grid, which makes the study on the wind power quality issues and the interaction between the wind turbines and the grid necessary and imperative. The research documented in this thesis examines power quality issues of grid-connected wind turbines and the interaction between wind turbines and the grid. The specific goal of the research has been to investigate flicker emission and mitigation of grid-connected wind turbines with doubly fed induction generators (DFIG) during continuous operation, and voltage recovery of such kind of grid-connected wind turbines after the clearance of a short circuit fault in the grid. As a basis of the research, a model of grid-connected wind turbines with DFIG is developed in the dedicated power system analysis tool PSCAD/EMTDC, which simulates the dynamics of the system from the turbine rotor, where the kinetic wind energy is converted to mechanical energy, to the grid connection point where the electric power is fed into the grid. The complete grid-connected wind turbine model includes the wind speed model, the aerodynamic model of the wind turbine, the mechanical model of the transmission system, models of the electrical components, namely the DFIG, PWM voltage source converters, transformer, capacitor, and the control system. The grid model and the electrical components of the wind turbine are built with standard electrical component models from PSCAD/EMTDC library. The wind model, the aerodynamic model, the mechanical model and the control system are built with custom components developed in PSCAD/EMTDC. Two control schemes are implemented in the developed grid-connectedwind turbine model: speed control and pitch control. The speed control scheme is composed by two vectorcontrol schemes designed respectively for the rotor-side and grid-side PWM voltage source converters. Cascade control is used in the vector-control schemes. Two design methods, poleplacement and internal model control, are applied for designing the PI-controllers in the vector-control schemes. The pitch control scheme is employed to regulate the aerodynamic power from the turbine. The performances of the control schemes, respectively current control loops, power control loops, DC-link voltage control loop and pitch control loop, are illustrated, which meet the design requirements. Simulation results show that the wind turbine is capable of providing satisfactory steady state and dynamic performances, which makes it possible that the wind turbine model can be applied to study the power quality issues of such kind of grid-connected wind turbines and their interaction with the grid. To evaluate the flicker levels produced by grid-connected wind turbines with DFIG, a flickermeter model is developed according to the IEC standard IEC 61000-4-15, which simulates the response of the lamp-eye-brain chain and provides on-line statistical analysis ofthe flicker signal and the final results. Based on the developed model of grid-connected wind turbines with DFIG and the flickermeter model, the flicker emission during continuous operation is studied. The influence factors that affect flicker emission of grid-connected DFIG wind turbines, such as wind characteristics (mean speed, turbulence intensity) and grid conditions (short circuit capacity, grid impedance angle) are analysed. The effects of the influence factors are compared with previous research results related to the fixed speed wind turbine. In particular, the effects of mean wind speed, turbulence intensity and grid impedance angle are different from that in the case of the fixed speed wind turbine. It is possible to regulate the reactive power flow on theconnection line so that the voltage fluctuation caused by the active power flow can be compensated by that caused by the reactive power flow. Based on this principle, two effective measures are proposed to mitigate the flicker levels produced by grid-connected wind turbines with DFIG, respectively by wind turbine output reactive power control and using STATCOM. Simulation results demonstrate that these two measures are effective for flicker mitigation regardless of mean wind speed, turbulence intensity and short circuit capacity ratio. The voltage recovery study is started with grid-connected wind turbines with dynamic slip control, which are simple, cost-effective, partially variable speed wind turbines, for gaining a good understanding of transient responses of induction generators in an external short-circuit situation. The model of a variable speed wind turbine with dynamic slip control in the simulation tool of PSCAD/EMTDC is presented, and the control schemes, respectively dynamic slip control andpitch control, are described. The transient process of grid-connected wind turbines after an external short-circuit fault is analyzed in detail. It is concluded from the analysis that increasing the electromagnetic torque or decreasing the aerodynamic torque helps to recover the voltage after the clearance of an external short-circuit fault. For the wind turbine with dynamic slip control, after the clearance of an external short-circuit fault, the electromagnetic torque may be strengthened by adjusting the generator slip, and the aerodynamic torque may be reduced by regulating the pitch angle, which helped to slow the rotor speed down and re-established the voltage at the wind turbine terminal. Simulation results demonstrate that pitch control, dynamic slip control and combined control are effective measures for voltage recovery of grid-connected wind turbines with dynamic slip control. An emergency pitch regulation scheme is developed and applied in the case of pitch control. Based on the acquired knowledge, the voltage recovery of grid-connected wind turbines with DFIG is studied. Two kinds of situations are studied which depend on whether the rotor protection devices in the DFIG are triggered or not. When the situation after an external short-circuit fault is not serious enough to trigger the rotor protection devices, the control schemes of the DFIG operated as normal and are capable of forcing the rotor speed down and re-establishing the voltage at the wind turbine terminal after the clearance of the short-circuit fault, which are demonstrated by simulation results. The performances of the wind turbine as well as the control schemes are illustrated in detail. If the situation after an external short-circuit fault is serious enough, the protection devices in the rotor circuit will be triggered which yields a result that the generator rotor is shortcircuited and the rotor-side converter is deactivated. In this situation, a control strategy is proposed to re-establish the voltage at the wind turbine terminal and restore the wind turbine's normal operation after the fault clearance, which is verified by simulations results. The control strategy, which takes advantage of the benefits of the rotor circuit protection device and the emergency pitch control scheme, are performed in three steps, respectively protection device activation, voltage recovery assisted by pitch control, and normal operation restoration of the wind turbine with DFIG.

evaluate the performance of a number of hlgh-speed PWM chips as a function ... addition, these devices show higher speed resulting from increased ... being conducted on devices and systems for use down to .... an adjustable clock for setting ...

The 12-step sensorless drive scheme requires an interval to detect the zero crossing of the back emf. The voltage regulating pulse-width modulation (PWM) is commonly used for the speed control of a motor. However, it induces the fluctuation of the back emf and makes the zero-crossing detection difficult. This paper proposes two digital approaches to the zero-crossing detection for the presence of the PWM. One approach is to vary the zero-crossing detecting period linearly with respect to the speed of the motor. The other is to detect the back emf only on the positive pulses of the PWM in order to avoid the fluctuation of the back emf. A digital filter is also incorporated in order to eliminate the noise generated by the PWM. Experiments show that both approaches have good performance for the speed control of the brushless dc motor.

Feb 23, 2006 ... The utilization of power electronics designed for and operated at low ... This would also result in reduced development time-and-effort and launch ... (PWM) controllers, and advanced commercial DC/DC converter modules.

Power Electronic Components, Circuits and Systems. 4. ... Provide a technology base for the development of lightweight electronic ... Integrate advanced components into mission-specific low temperature circuits .... PWM Control Circuits ...

A flywheel magnetic bearing (MB) pulse width modulated power amplifier (PWM) configuration is selected to minimize noise generated by the PWMs in the flywheel position sensor system. Two types of noise are addressed: beat frequency noise caused by variations in PWM switching frequencies, and demodulation noise caused by demodulation of high order harmonics of the switching voltage into the MB control band. Beat frequency noise is eliminated by synchronizing the PWM switch frequencies, and demodulation noise is minimized by selection of a switching frequency which does not have harmonics at the carrier frequency of the sensor. The recommended MB PWM system has five synchronized PWMs switching at a non-integer harmonic of the sensor carrier.

This paper sets forth the steady-state and dynamic performance characteristics of a novel stand-alone, single-phase induction generator scheme in which the load voltage and frequency are regulated using a full-bridge pulse-width modulation (PWM) DC/AC inverter. A battery feeding the PWM inverter supplies (receives) power to (from) the generator when load demand is greater (lesser) than the power supplied from the prime mover which could be diesel engine, wind or hydro.

The small-signal transfer functions of DC/DC switch-mode converters are defined in the frequency domain via a two-port model of the whole closed-loop system (i.e., power cell, error-amplifier, PWM modulator) and via a three-port model of the open-loop power cell plus PWM modulator. Applications of these functions in power-system design are shown. Measurement techniques are discussed in detail and relevant results are reported.

Abstract in spanish Se presenta un Emulador de turbinas eólicas para realizar pruebas de laboratorio sobre los bloques de generación, regulación y control de un sistema de generación con energía eólica de capacidad menor a 10kW. En el Emulador, un motor de inducción trifásico de 10 hp accionado por un inversor de voltaje controlado con un algoritmo de control directo de par reemplaza a la turbina eólica. El programa de interfaz permite definir las características de transferencia d (more) e la turbina eólica utilizando la relación velocidad del viento/par mecánico en el eje de salida y el patrón de viento aplicado a la turbina. El programa de control convierte estos datos en la demanda de par aplicada al actuador del motor AC, y mide la velocidad del eje del motor para cerrar el lazo de emulación. El Emulador permite realizar todas las pruebas electromecánicas, desde la caracterización del generador, hasta el ajuste de los controles y protecciones para un equipo que opere en una localización determinada. Las pruebas iniciales de Emulador fueron exitosas. Abstract in english This work presents a Wind Turbine Emulator able to perform laboratory tests on the generation, regulation and control blocks in a wind energy-driven electric generator system with less than 10 kW output. In the Wind Turbine Emulator a 10 hp three-phase induction motor driven by a voltage source inverter controlled by a direct torque control algorithm replaces the wind turbine. The interface program allows the user to define the wind turbine transfer characteristics using (more) the wind speed/mechanical torque in the output shaft relationship and the wind pattern applied to the turbine. The control program converts these data into the torque demand signals applied to the AC motor driver and measures the motor axis speed in order to close the emulation loop. The Emulator makes it possible to perform all the electromechanical tests from the generator characterization up to the control algorithms and protection settings final fine tuning to optimize system operation for operation at a particular location. The Emulator?s initial test results were successful, justifying continuing its development.

A harmonic injection PWM is proposed, which aims at minimization of the harmonics of the multiple power converter. The harmonic components of output voltage, output current and torque when a harmonic component is injected are analyzed in detail. A novel injection PWM is proposed, where the third harmonic is injected into the sinusoidal reference voltage, for which the amplitude and phase angle are actively controlled so that the harmonic components are reduced. First, the Fourier series of PWM voltage when a harmonic component is injected into the reference sine wave is derived and the relation between the components of voltage, current and torque are clarified. Next, the suitable amplitude and phase angle of the injected third harmonics to minimize the ripple torque are derived. The simulation results shows the effectiveness of the ripple torque reduction. It is further noted this PWM method is suitable for multiple inverter PWM control, where the switching frequency is relatively low because high power GTOs are used as switching devices. 14 refs., 10 figs., 3 tabs.

Electrical impedance tomography (EIT) utilizes electrodes placed on the surface of a body to determine the complex conductivity distribution within the body. EIT can be performed by applying currents through the electrodes and measuring the electrode voltages or by applying electrode voltages and measuring the currents. Techniques have also been developed for applying the desired currents using voltage sources. This paper describes a voltage source for use in applied-voltage EIT that includes the capability of measuring both the applied voltage and applied current. A calibration circuit and calibration algorithm are described which enables all voltage sources in an EIT system to be calibrated to a common standard. The calibration minimizes the impact of stray shunt impedance, passive component variability and active component non-ideality. Simulation data obtained using PSpice are used to demonstrate the effectiveness of the circuits and calibration algorithm. PMID:16636413

This paper describes a circuit analysis of a magnetic oscillation type sinusoidal inverter. The inverter is connected to an ac voltage source such as the line power, and can supply electric power easily to the ac voltage source. The inverter utilizes a magnetic oscillation circuit constructed with power transistors and a nonlinear magnetic core. In order to quantitative analysis, we present a simulation model of the magnetic oscillation circuit based on a general purpose circuit simulation program “SPICE”. The simulation results of the oscillation voltage and current waveforms agree well with experimental ones.   

In this report a class of isolated PDM and PWM DC-AC SICAMs is described, which introduce the audio reference only in the output stage. AC-DC power supply is implemented in its simplest form: diode rectifier followed by a medium-size charge-storage capacitor. Isolation from the AC mains is achieved using a high frequency (HF) transformer, receiving the HF voltage pulses from the input 'inverter' stage and transferring them to the output 'rectifier+inverter' stage, which can use either PDM or PWM. The latter stage is then interfaced to the load using an output low-pass filter. Each of the dedicated stages is discussed in detail. Measurements on the master/slave PWM DC-AC SICAM prototype are presented to help benchmarking the performance of this class of SICAMs and identify the advantages and drawbacks. (au)

This final report for the Swiss Federal Office of Energy (SFOE) presents the results of the third phase of a project aiming to develop controllers that use pulse-width modulation (PWM) to control domestic heat pumps. The first two phases of the project are briefly described, in which three versions of PWM heating control strategies were developed and successfully implemented in two commercially available heat pump controllers. The main goal of the project's third phase is described, which was to make a representative comparison between the three PWM approaches and conventional relay-type controllers with respect to comfort, energy efficiency, and costs under the same operating conditions. The work was carried out in the Measurement and Control Laboratory of the Swiss Federal Institute of Technology in Zurich, Switzerland. The results of the tests are presented and discussed. The report is concluded with recommendations for further work to be done in a fourth phase of the project.

Recently, a new family of AC-AC converters has been proposed for AC power conditioning. These converters are solid-state function equivalent to transformers with a continuously variable transformation ratio. Operating with the principle of pulse width modulated (PWM) control using gate turn-off switching devices like IGBTs have been shown to have significant performance advantages compared to older generation of thyristor based phase controlled converters. Although various techniques for realizing AC-AC power control using PWM control have been proposed in the past, few have seen wide application. This is seen to be primarily due to the complexity of the bi-directional switch requirements. In this paper, transient analysis and modeling of PWM AC-AC voltage converters with reduced number of...

In this paper, an analytical technique is presented for time domain analysis (transient and steady-state response) of perturbed PWM push-pull DC-DC converter using interesting corollary on Kharitonov?s theorem. The main advantage of the proposed analysis is that even though the transfer function model of a PWM push-pull DC-DC converter is perturbed, the complete analysis has been done on a linear transfer function model of a PWM push-pull DC-DC converter. The proposed analysis is verified using MATLAB simulation. This analysis will be very much useful to power electronics engineers, since the technique is very simple and computationally efficient and easily applicable in precise applications such as aerospace applications.

In this article, an integrated lab environment for the electrical engineering education is presented which includes hardware and software for the modeling, simulation and control of multilevel inverters. A five-level cascade inverter is designed and implemented which is an educational platform for the students to test different pulse width modulation (PWM) techniques and verify simulation results. The integrated environment is based on Matlab together with dSPACE. Sinusoidal PWM (SPWM) and Selected Harmonic Elimination PWM (SHEPWM) blocks are constructed in Matlab/Simulink and converted to C code using Matlab/Real-Time Workshop. C codes are sent to dSPACEs DS1103 digital signal processor (DSP) via dSPACE/Real-Time Interface software. Voltages with variable frequency and amplitude obtained ...

AIMS: This study aimed to characterize P-wave morphology (PWM) in leads V3-V6 during focal atrial tachycardia (AT) originating from the lower right atrium (RA), and to investigate the role of interatrial conduction (IAC) pathways in the formation of PWM.METHODS AND RESULTS: Twenty-eight consecutive patients with tachycardia foci in the lower RA underwent detailed atrial endocardial activation mapping and radiofrequency catheter ablation. P-wave configuration was analysed using standard 12-lead electrocardiogram. Atrial tachycardia originated from lower non-septal tricuspid annulus (LTA) (n = 11), coronary sinus ostium (CSo) (n = 11), lower crista terminalis (LCT) (n = 4), or lower free wall (n = 2). In leads V3-V6, PWM showed a negative pattern in at least two consecutive leads during AT originating from CSo (11/11) and LTA (9/11), with an associated sensitivity of 91%, specificity of 100%, positive predictive value (PPV) of 100%, and negative predictive value (NPV) of 75%. A positive PWM was observed in three of four ATs originating from LCT, with an associated sensitivity of 75%, specificity of 100%, PPV of 60%, and NPV of 96%. A negative PWM in V3-V6 was consistent with a preferential IAC through musculature in the vicinity of the CS and an activation of both atria in an antero-posterior direction. In contrast, a positive PWM was associated with the engagement of a posterior (non-CS-related) interatrial connection.CONCLUSION: Characteristic PWMs in V3-V6 may accurately differentiate the anatomic sites of AT from the low RA with high PPVs and NPVs. P-wave morphology in V3-V6 is likely to be influenced by the engagement of the preferential IAC. PMID:23054216

This paper presents a Pulse-Width Modulation (PWM) pre-emphasis technique which utilizes time-domain information processing to increase the data rate for a given bandwidth of interconnection. The PWM pre-emphasis method does not change the pulse amplitude as for conventional FIR pre-emphasis, but instead exploits timing resolution. This fits well with recent CMOS technology trends toward higher switching speeds and lower supply voltage. We discuss multiple-valued data transmission based on time-domain pre-emphasis techniques in consideration of higher-order channel effects. Also, a new data-dependent adaptive time-domain pre-emphasis technique is proposed to compensate for the data-dependent jitter.   

In this paper, a single-phase five-level PV inverter topology for grid-connected photovoltaic (PV) system with a novel PWM control scheme is presented. PWM signals were generated by comparing two reference signals identical to each other with an offset equivalent to the amplitude of the triangular carrier signal. A digital PI current control algorithm is implemented to keep the current injected into the grid sinusoidal and to have high dynamic performance with rapidly changing atmospheric conditions and low THD. This new configuration of the proposed inverter is implemented in a prototype.   

Analysis and modeling of common mode conducted ElectroMagnetic Interference (EMI) in the Radio Frequency (RF) range (10 KHZ--30MHZ) of a ZVT (DC-DC boost Zero Voltage Transition) PWM converter and a conventional PWM (DC-DC boost) converter are compared. Noise signal measurement is carried out by means of a LISN (Line Impedance Stabilization Network). To compute the noise spectrum of LISN output in RF range, direct simulation of equivalent noise circuits is implemented as well as an analysis in the frequency domain.

In this paper, a controller design for coreless linear synchronous motor is proposed. The designed controller is mainly composed of speed and current control, which are carried out by the high-speed digital signal processor(DSP). In addition the PWM inverter is controlled by space voltage PWM method. This system is implemented using by 32-bit DSP(TMS320C31), a high-integrated logic device(EPM940), and IPM(Intelligent Power Modules) for compact and powerful system design. The experimental results show the effective performance of controller for coreless linear synchronous motor. (author). 9 refs., 7 figs., 1 tab.

In this paper, vector control is applied to the PWM inverter fed permanent magnet synchronous motor (PMSM). Rotor based d and q coordinates system are used to decompose the stator currents into i{sub d} (flux component) and i{sub q} (torque component). The i{sub d} current is used for field weakening. This enables the PMSM to operate with constant power above rated speed. Furthermore, a speed control is made. The proposed current control strategy is described and analyzed. The implementation of the vector control on a prototype PWM inverter fed PMSM is considered and discussed. Experimental results are shown. (author) 7 refs., 8 figs.

...three-phase underground transmission line to transfer power from...0.06-mile-long, 115-kV, three-phase overhead transmission line. The applicant indicates...reliability; (2) the proposed transmission line will be located on...

The Capacitor Coupled Converter (Ccc) Is A Dc-Dc Converter Which Produce A Dc Source As The Output. It Has Two Input Terminals For Connection To A Dc Voltage Source, Two Output Terminals For Connection To A Load, And A Plurality Of Circuit Control Terminals For Receiving A Plurality Of Control Wavef...

denotes the zero matrix. ... phrase our theoretical problem as "Given an input DC voltage source, ... we assume knowledge of the capacitor voltages and inductor currents, and ... low-pam one, a higher switching frequency w i l l yield a smaller output ripple. However because the particular thyristor or transistor switch ...

This note describes a simple and effective method of stabilizing the temperature of a FET or other small device over the range 77/sup 0/K to room temperature. By driving a Zener diode from a constant voltage source, a self-heating effect is produced which increases sharply when the temperature falls below a preset value.

Jan 1, 1990 ... Analysis of Cavity-Backed Slot Antennas: FDTD. FEM 8~ ... Illustration of the effectiveness of the resistive voltage source . 46. C . .... are performed using both the hybrid FEM/h/lohI and the FDTD NEWS code. The ... has been applied to spectral methods to simulate open-space propagation problems.

Subsea power cables are a critical component of a voltage-source converter-high-voltage direct current (VSC-HVDC) transmission system in any offshore electrical power scheme. Subsea cables have complicated structures consisting of many different layers: conductor, insulation, sheath, and armor. Harm...

The paper gives an overview of HVAC and HVDC connection of wind farm to the grid, with an emphasis on Voltage Source Converter (VSC)-based HVDC for large wind farms requiring long distance cable connection. Flexible control capabilities of a VSC-based HVDC system enables smooth integration of wind f...

The performance of different current controller structures for Voltage Source Converters (VSC) under weak grid conditions caused by large grid impedance is investigated. The VSC is synchronized to the grid by a Phase Locked Loop (PLL). Current control techniques and PLL techniques for handling both ...

Indirect Current Control (ICC) of boost type Voltage Source Converters (VSCs) using separate compensation of line IZ voltage drop is presented. A separate bi-directional VSC is used to produce the compensation voltage. This simplifies the ICC regulator scheme as the power flow is controlled through single modulation index. Experimental verification is provided for bi-directional control of the power flow.

This paper presents the description and simulation of a new proposed arrangement of RLD/RCD snubber circuit used with pulse width modulated voltage source inverter. The new arrangement allows minimizing the number of active elements of RCD with 50%. This will help the designer to reduce the size of ...

A mercury switch W.E. 218-a, used in a discharge line type pulse generator has the disadvantage of generating multiple pulses when operated at high voltages. This disadvantage is overcome by the insertion of a second mercury switch between the line and the voltage source. (auth)

A nozzle for an electric dispersion reactor includes two coaxial cylindrical bodies, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

The voltage source described consists of a dynamo operated by hand and two series connections switched in parallel each of which consists of a rectifier and a storage capacitor. One of these storage capacitors supplies the high voltage for the counter tube and the other one is for delivering direct voltage to an audio-frequency amplifier. (Gmelin Inst)

This paper presents a direct AC/AC bi-directional power converter that can convert 220 V mains voltage to 110 V or vice versa in a single power conversion stage. The proposed converter makes use of four quadrant switches and high frequency PWM control to accomplish the desired voltage conversion at ...

In this paper, the investigation of the nonlinear dynamics of an adjustable speed switched reluctance motor (SRM) drive with voltage PWM regulation is carried out. The corresponding bifurcation diagrams and chaotic Poincare sections are presented. It shows that the system generally exhibits a period...

The 42 VY_20°/J28 V, 175 W, 50 kHz PWM buck dc/dc converter was operated both at room temperature ... output (load) current for continuous ... [2], to provide a design margin for the output ripple voltage .... devices such as the zero-voltage ...

Precise modulation of nozzle flow rates is a critical measure to achieve variable-rate spray applications. An electronic flow rate control system accommodating with microprocessors and pulse width modulation (PWM) controlled solenoid valves was designed to manipulate the output of spray nozzles inde...

The authors present a statistical approach to the analysis of random pulsewidth modulation (RPWM) methods which generate PWM signals by comparing a reference modulating function with random numbers or signals. Such an approach is used to analyze and optimize a new weighted RPWM (WRPWM) method and al...

When the speed of induction motor is varied by inverter for energy saving, the harmonics are induced in the course of frequency change. In the frequency changing devices for the generation of variable speed, the rectangular and PWM inverters are being used. And, while the harmonics of 6{+-}1 are induced in the rectangular inverter, the harmonics are varied according to the switching frequency in the PWM inverter. It was known that the amplitude of lower order harmonics is large in the rectangular inverter. However, in the PWM inverter, the amplitude of lower order harmonics is large at low frequency, the distortion rate of overall harmonics become lower at high switching frequency, and the order of generated harmonics become gradually higher. Whereas the response characteristics of rectangular inverter with harmonics become worse and affect negatively by pulsating frequency, the PWM inverter can be applied to the high precision control system with excellent response characteristics even though the switching frequency increases. (author). refs., figs., tabs.

In this paper a new Zero-Voltage-Transition (ZVT) PWM switching cell is presented. The proposed switching cell is composed of the normal hard-switched PWM cell (consisting of one active switch and one passive switch), plus an auxiliary circuit (consisting of one active switch and some reactive components). The auxiliary circuit is inactive during the ON and OFF intervals of the switches in the normal PWM switch. However, the transitions between the two states are controlled by the auxiliary circuit. Prior to turn-on, the voltage across the active switch in the PWM cell is forced to zero, thus the turn-on losses of the active switch are practically eliminated. At turn-off the auxiliary circuit behaves like a non-dissipative passive snubber reducing the turn-off losses to a great extent. Zero-Voltage-Transition switching technique almost eliminates switching losses. The active switch operates under ZVT conditions, the passive switch (diode) has a controlled reverse recovery, and the switch in the auxiliary circuit operates under Zero-Current-Switching (ZCS) conditions. (orig.) 6 refs.

The immune response to the group-specific carbohydrate of group A streptococci (A-CHO) provides an informative in vitro model for the investigation of several aspects of human anticarbohydrate immune responses. A-CHO-specific B cells can be polyclonally activated by pokeweed mitogen (PWM), and, spec...

Although Methanocaldococcus (Methanococcus) jannaschii was the first archaeon to have its genome sequenced, little is known about the promoters of its protein-coding genes. To expand our knowledge, we have experimentally identified 131 promoters for 107 protein-coding genes in this genome by mapping their transcription start sites. Compared to previously identified promoters, more than half of which are from genes for stable RNAs, the protein-coding gene promoters are qualitatively similar in overall sequence pattern, but statistically different at several positions due to greater variation among their sequences. Relative binding affinity for general transcription factors was measured for 12 of these promoters by competition electrophoretic mobility shift assays. These promoters bind the factors less tightly than do most tRNA gene promoters. When a position weight matrix (PWM) was constructed from the protein gene promoters, factor binding affinities correlated with corresponding promoter PWM scores. We show that the PWM based on our data more accurately predicts promoters in the genome and transcription start sites than could be done with the previously available data. We also introduce a PWM logo, which visually displays the implications of observing a given base at a position in a sequence. PMID:19359364

In this paper with the help of Matlab/Simulink and dSPACE, the Switch-Mode DC Converter is built in real-time to control the output voltage of the controller using PWM algorithm. First, the Simulink model of Switch-Mode DC Converter (i.e. Single-Pole and Two-Pole Converter Model) is built and, after...

An analog macromodel for the SG1525A PWM (pulse width modulator) that is compatible with SPICE2G.6 and PSPICE analog simulators has been developed. It exhibits no convergence problems, simulates realistic line and load responses, frequency response, output voltage levels, and has time domain capability. Model development and a comparison of macromodel performance with actual measurements will be discussed.

Presented is a fast control strategy to improve the transient response of a zero-voltage-transition pulse-width-modulation (PWM) boost converter. A prototype circuit based on the proposed control strategy was designed and constructed. Experimental results show that the proposed controller can reduce...

The effect of d-penicillamine (Pen) and mixtures of Pen and copper sulfate on the capacity of normal human peripheral blood mononuclear cells (PBM) to generate immunoglobulin-secreting cells (ISC) in response to the T-cell-dependent polyclonal B-cell activators pokeweed mitogen (PWM) and staphylococ...

A novel technique for efficiently extracting the maximum output power from a solar panel under varying meteorological conditions is presented. The methodology is based on connecting a pulse-width-modulated (PWM) dc/dc SEPIC or Cuk converter between a solar panel and a load or battery bus. The conver...

This paper presents a theoretical study and experimental results of using phase-shift technique to dilate the output spectrum of a five-level neutral-point-clamped (NPC) pulse width modulated (PWM) H-bridge inverter. It is shown that the output spectrum can be made to consist of the multiple of the ...

Applications in naval propulsion take a real interest in optimisation of energy conversion. This optimisation is particularly interesting in term of vibration mitigation and acoustic moderation. Some PWM methods allowing these improvements are presented and a new optimisation method acting both on vibration and noise is introduced. (authors)

In this paper, a chaotic Pulse width modulation (PWM) closed-loop induction motor drive is proposed and implemented to improve the electromagnetic compatibility (EMC) for electric propulsion. The key is to propose a chaotically amplitude-modulated frequency modulator (CAFM) to modulate the space vec...

This paper proposes and implements a new hybrid chaotic (HC) pulse width modulation (PWM) scheme for the reduction of electromagnetic interference (EMI) in alternating current (AC) motor drives. This scheme utilizes logistic mapping to simultaneously chaoize both the carrier frequency and the pulse ...

Random PWM (RPWM) techniques normally work well with high sampling frequency. When implemented in digital signal processors (DSP), performance of the RPWM schemes are limited by the speed of the processors. In this paper, the noise spectra of various DSP implemented RPWM techniques are presented. Th...

This paper presents the design of digital controls of PWM DC-DC converters on a digital signal processor (DSP) based platform. Three digital control approaches are being investigated: discretisation of analog control, digital proportional-integral-derivative (PID) control, and deadbeat control. Simu...

An embedded system is a special-purpose computer system designed to perform one or a few dedicated functions. Altera DSP Builder presents designers and users with an alternate approach when creating their systems by employing a blockset similar to that already used in Simulink. The application considered in this paper is the design of a Pulse Width Modulation (PWM) system for use in stereo vision. PWM can replace a digital-to-analogue converter to control audio speakers, LED intensity, motor speed, and servo position. Rather than the conventional HDL coding approach this Simulink approach provides an easy understanding platform to the PWM design. This paper includes a comparison between two approaches regarding resource usage and flexibility etc. Included is how DSP Builder manipulates an onboard clock signal, in order to create the control pulses to the 'raw' coding of a PWM generator in VHDL. Both methods were shown to a selection of people and their views on which version they would subsequently use in their relative fields is discussed.

A digital controller is designed and implemented by a Digital Signal Processor (DSP) to replace the Pulse Width Modulator (PWM) and error amplifier compensation network in a two wheeler forward converter. The DSP controller is designed in three approaches: a) Discretization of analog controller - th...

This paper analyses the proposed solutions in recent literature and presents a new architecture for the implementation of a power recycler for dc power supplies burn-in test. The proposed circuit is regulated by conventional integrated circuits: PWM and power factor controllers. Circuit operation, design characteristics, simulation and experimental results are provided in the paper. (author) 10 refs., 8 figs.

Flying Capacitor (FC) multilevel pulse width modulated (PWM) converters are an attractive choice due to the natural voltage balance property. During start-up of the converter, care has to be taken that the power switches are not exposed to voltage overstress due to uncharged capacitors. A flying cap...

To reduce the system imbalance, various types of specially-connected transformers have been adopted in Taiwan and abroad. Because three-phase transformer models are necessary for three-phase load flow simulation, specially-connected transformers which have been adopted so far are selected to derive three-phase models in this paper. These transformers include the single-phase connection, the V-V connection, the Wye-Delta connection, the Scott connection, the Le Blanc connection, and the Modified-Woodbridge connection. The three-phase models with the specially-connected transformers offered in this paper distinctly represent the HSR feeding system by means of the physical three-phase circuit and the symmetrical-component equivalent circuit. The three-phase model could be joined to the three-phase load flow program to exactly analyze the system imbalance in the future. The symmetrical-component equivalent circuit may also be used to derive the approximate unbalance-estimating formula.

In this article, stabilization methods of wind farms composed of fixed-speed wind turbines and variable-speed wind turbines are analyzed. A current-controlled voltage source converter scheme for a variable-speed wind turbine driving doubly fed induction generator is proposed. The proposed scheme is then compared with two other doubly fed induction generator control schemes to show the effectiveness of the proposed controller. Different types of symmetrical and unsymmetrical faults are analyzed considering wind farm recent grid codes. Though all of the schemes are able to stabilize the wind farms during transient conditions, the proposed current-controlled voltage source converter scheme offers the advantage of less intricacy of controller design, better performance during grid fault, and o...

A backside illuminated charge coupled device (CCD) is formed of a relatively thick high resistivity photon sensitive silicon substrate, with frontside electronic circuitry, and an optically transparent backside ohmic contact for applying a backside voltage which is at least sufficient to substantially fully deplete the substrate. A greater bias voltage which overdepletes the substrate may also be applied. One way of applying the bias voltage to the substrate is by physically connecting the voltage source to the ohmic contact. An alternate way of applying the bias voltage to the substrate is to physically connect the voltage source to the frontside of the substrate, at a point outside the depletion region. Thus both frontside and backside contacts can be used for backside biasing to fully deplete the substrate. Also, high resistivity gaps around the CCD channels and electrically floating channel stop regions can be provided in the CCD array around the CCD channels. The CCD array forms an imaging sensor useful in astronomy.

This paper presents about an example of circuit design and characteristics of inverter according to the variable capacitance of the DC voltage source separation capacitor used in ZVS-HB type high frequency resonant inverter. The soft switching technology known as ZVS is used to reduce turn off loss at switching. In the event the capacitance of the DC voltage source separation capacitor is varied, the analysis of inverter circuit has generally described by using normalized parameter and operating characteristics have been evaluated in terms of switching frequency and parameters. According to the calculated characteristics value, a method of the circuit designs and operating characteristic of the inverter is also presented in this paper. In addition, this paper proves the validity of theoretical analysis through the experiment. This proposed inverter shows that it can be practically used in future as power source system for the lighting equipment of discharge lamp, DC-DC converter etc. (author). 6 refs., 10 figs., 2 tabs.

To improve measurements of 10 V Zener based standards, we have designed a new transfer voltage source for use with 10 V Josephson arrays. The transfer voltage is compared, in turn, with that of the Zener standard and of the array. The use of two separate circuits should help to solve the problem of common ground connections and prevent noise from the Zener standard entering the array circuit. This transfer device can also be used for 10 V Josephson array comparisons.

A method and a circuit for controlling an ac machine comprises controlling a full bridge network of commutation switches which are connected between a multiphase voltage source and the phase windings to switch the phase windings between a parallel connection and a series connection while providing commutation discharge paths for electrical current resulting from inductance in the phase windings. This provides extra torque for starting a vehicle from lower battery current.

A photoconductive, high energy photon beam detector/monitor for detecting x-rays and gamma radiation, having a thin, disk-shaped diamond substrate with a first and second surface, and electrically conductive coatings, or electrodes, of a predetermined configuration or pattern, disposed on the surfaces of the substrate. A voltage source and a current amplifier is connected to the electrodes to provide a voltage bias to the electrodes and to amplify signals from the detector.

This paper describes basic fundamental requirements of the overall system design for offshore wind generation tied via HVdc cables to onshore grids. An approach for standardization when using voltage-source HVdc (VSC-HVdc) technology is proposed, supported by simulations demonstrating viability of the approach. The approach is based upon retaining existing wind generator design concepts and customizing the HVdc to achieve the most economical overall system, and to provide for the project to be realized with multiple vendor, operator, and regulatory entities. (orig.)

In this paper, the operation of shunt-connected Voltage Source Converters under unbalanced voltage conditions is investigated. The attention focuses on voltage dips, thus on transient operation. Three different current controllers for VSC with corresponding dc-link voltage controllers are described and implemented. The performance of the three controllers is evaluated by comparing the dc-link voltage when the converter is subject to different types of voltage dips. Both simulated and measured dips are considered.

In this paper, a new topology of cascaded multilevel inverter using a reduced number of switches, insulated gate driver circuits and voltage standing on switches is proposed. The proposed topology results in reduction of installation area and cost and has simplicity of control system. This structure consists of series connected sub-multilevel inverters blocks. Three algorithms for determination of magnitudes of dc voltage sources have been presented, too. Validity of the analysis has been proved by simulation and experimental results. (author)

This paper proposes a new double-connected 3-phase voltage source inverter with improved output voltage waveform. An auxiliary single-phase inverter injects a ripple voltage into the double-connected inverter to convert 12-step operation to 36-step operation. The KVA rating of the output phase-shifting transformer is reduced by employing a harmonic canceling reactor. The whole rectifier-inverter system including the proposed technique is introduced, and the experimental results are provided. (author). 6 refs., 6 figs., 2 tabs.

The magnetic analysis of stators of electrical motors is performed through an innovative 2D finite element formulation that takes into account the effects of eddy currents within the laminations by means of a generalized constitutive relationship also including vector hysteresis. This approach is applied to a deep estimation of magnetic flux distribution and magnetic losses in stator of induction motors supplied by high-frequency sinusoidal or six-step voltage sources.

A pyroelectric energy converter is described comprising: a capacitor formed of dielectric material having temperature dependent capacitance; means to subject the capacitor to a source of heat to vary thermal energy of the capacitor; and a means coupled to the capacitor to substantially reversibly apply charge thereto and to remove charge therefrom. The means to substantially reversibly apply charge to and remove charge from the capacitor comprises a continuously variable voltage source.

Reactive power compensation and harmonic reduction are two relevant research problems that exist in modern electric power systems. With the advancement of modern power electronics technology in both circuits and devices, new and better solutions are being proposed and applied to solve these two problems. To compensate reactive power, a cascading voltage source inverter with a Phase-Shift, Unipolar SPWM switching scheme is proposed. The main circuit of this inverter is composed of several identical voltage source H-bridge inverters connected in cascade form. Advantages of this scheme include use of identically rated storage capacitors, similarly rated switches and diodes, quick system response to load changes, and easily achievable redundancy. To solve the harmonic reduction problem, the flying capacitor multilevel voltage source inverter is adopted to construct a novel power line conditioner. The Phase Shift SPWM switching scheme is also employed to operate the switches of this inverter. As a result, it is possible to extend the new power line conditioner to distribution systems or industrial applications where voltage usually ranges from 4.16kV to 13.8kV. It is shown that the proposed power line conditioner not only balances the unbalanced load, but simultaneously compensates the reactive power as well.

A doubly fed induction generator (DFIG) is a variable speed induction machine. It is a standard, wound rotor induction machine with its stator windings directly connected to the grid and its rotor windings connected to the grid through a back-to-back AC/DC/AC PWM converter. The power generation of a DFIG includes power delivered from two paths, one from the stator to the grid and the other from the rotor, through the frequency converter, to the grid. The power production characteristics, therefore, depend not only on the induction machine but also on the two PWM converters as well as how they are controlled. This paper investigates power generation characteristics of a DFIG system through computer simulation. The specific features of the study are (1) a steady-state model of a DFIG system ...

A new closed-loop generalised scheme for an n-stage current-mode multiphase switched-capacitor converter (CMSC) is proposed by combining multiphase operation and pulse-width-modulation (PWM) control for step-up DC-DC conversion and output current regulation. The CMSC is composed of n-voltage doublers and one constant current source in series. The n-voltage doublers are in charge of boosting output voltage, and combined with multiphase operation to provide voltage gain of 2n at most. The current source is adopted mainly for supplying a constant current at the output terminal, and combined with PWM to reinforce output regulation as well as robustness to source/loading variation. The relevant theoretical analysis and design include: an n-stage CMSC model, steady-state/dynamic analysis, power ...

This paper presents a modification in pulse width modulation (PWM) scheme with unequal shoot-through distribution for the Z-source inverter (ZSI) which can minimize ripples in the current through the Z-source inductors as well as the voltage across the Z-source capacitors. For the same system parameters, the proposed control technique provides better voltage boost across the Z-source capacitor, DC-link, and also the AC output voltage than the traditional PWM. The ripples in the Z-network elements are found to be reduced by 75% in the proposed modulation scheme with optimum harmonic profile in the AC output. Since the Z-network requirement will be based on the ripple profile of the elements, the Z-network requirements can be greatly reduced. The effectiveness of the proposed modulation sche...

For the storage ring (SR) a stability of +-10 ppM is required for the main bending and focusing magnets; for the correction magnets, the requirements range from +-100 ppM for sextupole to 300 ppM for dipole magnets. The main dipole magnets are connected in series and energized from a 12-phase power supply. All other magnets have individual pulse-width-modulated (PWM) power supplies. The load of the 1436 PWM power supplies on the ac line is distributed as evenly as practicable. For the power supplies of the bending and focusing magnets of the injector synchrotron, stringent requirements are met for flat injection and ejection currents and for current tracking during acceleration.

Advances in speed control for motors in recent years, notably those in power electronics, have widened the range of application for several adjustable speed drive (ASD) types to include the smaller horsepower sizes. The DC motor drive, formerly in almost universal use for speed control, is being challenged by the high efficiency induction motor/pulse width modulation (PWM) drive; and for special small horsepower size applications, by the permanent magnet motor/PWM inverter drive or by the switched reluctance motor drive. The main characteristics of the several ASD types suitable for small horsepower size applications are discussed, as well as their unwanted side effects: poor power factor, harmonic distortion of the supply, acoustic noise, and electromagnetic interference. A procedure is recommended for determining which, if any, ASD to use.

Our aim was to investigate whether neurological impairment in Behcet's disease (BD) can be assessed by means of proton MRS and whether it can assist in prognosis. We used single-voxel MRS to measure metabolites in regions of normal-appearing pons, basal ganglia and periventricular white matter (PWM) in 32 patients with chronic BD patients with and without neurological deficits and 29 control subjects. Patients had significantly higher N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios in the basal ganglia than the controls. The Cho/Cr ratio in the PWM was also significantly higher in the patients. MRS enabled clear discrimination of patients and controls and also revealed spectral differences between non-neuro-Behcet's disease and neuro-Behcet's disease in the basal ganglia. MRS can be used to assess brain involvement in BD even if structural changes are absent. (orig.)

AC railway vehicles controlled by PWM line side converters inject harmonic current into the feeding overhead line. This causes problems such as resonance expansion which will lead to malfunctions or overcurrents at substations and electromagnetic interference with signalling systems. Normal active filters only shift the harmonic frequencies to a higher range. A novel harmonic compensator produces an exact counter mmf which becomes sinusoidal in the main transformer main flux then becomes sinusoidal. Experimental results from a small model of a Japanese AC railway vehicle are described. Especially, harmonic currents are very well suppressed in the 3-4 kHz frequency range that coincides with the signalling band. As a result, this novel harmonic compensator and its method appear promising for use in any 50 Hz, and 60 Hz fed PWM controlled AC railway traction system.   

More and more researchers have great concern on the issue of Common-mode voltage (CMV) in high voltage large power converter. A novel common-mode voltage suppression scheme based on zero-vector PWM strategy (ZVPWM) is present in this paper. Taking a diode-clamped five-level converter as example, the principle of zero vector PWM common-mode voltage (ZCMVPWM) suppression method is studied in detail. ZCMVPWM suppression strategy is including four important parts, which are locating the sector of reference voltage vector, locating the small triangular sub-sector of reference voltage vector, reference vector synthesis, and calculating the operating time of vector. The principles of four important pars are illustrated in detail and the corresponding MATLAB models are established. System simulation and experimental results are provided. It gives some consultation value for the development and research of multi-level converters.

Purpose - The purpose of this paper is to present, a novel boost-active clamp bridge single stage high-frequency zero voltage soft-switching-pulse width modulation (ZVS-PWM) inverter, which converts the utility frequency AC power into high-frequency AC power with an embedded controller. This single stage high-frequency inverter is composed of a single-phase diode bridge rectifier, a non-smoothing filter, a boost-active clamp bridge type ZVS-PWM high-frequency inverter, and an induction-heated load with planar type litz wire working coil assembly. Also, the paper discusses how to extend the soft-switching operation ranges and improve power conversion efficiency. Design/methodology/approach - The proposed converter is simulated and it is implemented using embedded controller. Findings - It w...

Based on the difference close-loop feedback technique and the difference pre-amp, a high efficiency PWM CMOS class-D audio power amplifier is proposed. A rail-to-rail PWM comparator with window function has been embedded in the class-D audio power amplifier. Design results based on the CSMC 0.5 mum CMOS process show that the max efficiency is 90%, the PSRR is -75 dB, the power supply voltage range is 2.5-5.5 V, the THD+N in 1 kHz input frequency is less than 0.20%, the quiescent current in no load is 2.8 mA, and the shutdown current is 0.5 muA. The active area of the class-D audio power amplifier is about 1.47 x 1.52 mm{sup 2}. With the good performance, the class-D audio power amplifier can be applied to several audio power systems.

Abstract This paper presents an effective PWM method for power conversion circuits. The proposed method is called Vector Frequency Modulation (VFM) in this paper. VFM is different from conventional PWM methods. Although VFM is based on the concept of the space voltage vector, all necessary calculations of the periods of the voltage vectors can be performed without using traditional equations. The voltage vectors are classified into two groups, zero vectors and nonzero vectors. Instead of the complicated equations, a very simple algorithm is employed in VFM. One vector period is fixed and the zero vectors are distributed among the nonzero vectors in the ratio determined by the command voltage or frequency. The action of VFM is performed in software, and no modulation-wave oscillators, compa...

This work presents the simulation of a shunt active filter using seven-level cascaded inverter. The ultimate objective is to bring out the influence of multiple carrier level shifted PWM techniques on the performance of a shunt active filter. Classical disposition PWM techniques such as PD, POD and APOD have been used to generate the gating signals for the inverter active switches. A comparison is presented to substantiate the effect of these techniques in filtering. The comparison is made from the perspective of reduction in THD of source currents after filtering. For compensation current extraction synchronous detection method has been used. The harmonic reduction is achieved in source currents as well as source voltages.

The high-power density PWM type 3-phase CVCF sinewave power conditioner was proposed which incorporates a new quasi-resonant DC link and single-phase high-frequency transformer link. It was featured by the advanced control system implementation with a precise instantaneous space voltage vector regulation scheme including DSP control strategy and ZVS-PWM controlled high-frequency inverter technique in place of conventional inverter-cycloconversion systems. The operating principle of the 3-phase sinewave modulated CVCF conditioner operated at zero-voltage turn-on/off switching modes was revealed in detail, and it was proven that the 3-phase cycloconverter with zero-voltage switching and time-sharing vector-distributed schemes efficiently operates without any conventional RCD snubber circuits. In addition, it was pointed out that the proposed 3-phase power conversion system with the high-frequency AC link is suitable for CVCF distributed power supplies. 13 refs., 13 figs.

There is a need for robust current control of a pulse width modulation (PWM) power amplifier whose transient response characteristics do not deteriorate with extensive load changes and/or direct-current power supply voltage changes. In this article, we propose a digital robust controller with bumpless mode switching to control the current of a PWM power amplifier to satisfy the demands and extend the range of an inductive load width. It is necessary to measure the value of the load in order to implement this bumpless mode switching automatically depending on the load range. Therefore, a method of estimating the inductive load is shown. The bumpless mode switching is automatically performed by estimating an inductive value without specifying the value of the inductive load beforehand. That ...

This paper presents a survey on single-phase soft-switching unity power factor rectifiers with reduced conduction losses. The reduced conduction losses are achieved by the employment of a single converter, instead of the typical configuration composed by a front end rectifier followed by a boost converter. Among several possible soft-switching topologies, two are selected for analysis and further experimentation. The first converter is a ZVS step-up converter, which features regulation by conventional PWM and instantaneous average line current control. The second one is a quasi-resonant ZCS step-up converter which features current-sense frequency control and soft commutation with no auxiliary switches. Experimental results for a 1,6 kW ZVS-PWM prototype operating at 70 kHz and a 830 W ZCS-FM converter are presented. (author) 8 refs., 15 figs.

The full-digital audio amplifiers are advantageous with the points of its high power efficiency and its possibility of high fidelity due to the digital signal processing. With the full-digital amplifier, class-D amplifiers are used to drive the load with PWM signals produced from the source signal. Unfortunately, the signals are distorted when the PCM signals are converted to the PWM signals because the pulse-width modulation is a nonlinear conversion from the viewpoint of transient responses. This paper proposes a way to compensate the distortion caused by the pulse-width modulation. A feedforward compensation approach is used because of the simplicity of implementation. The distortion components are estimated with the source signals and its time-derivative signals and used to cancel out them by subtracting them from the source signals. A numerical example with two-tone test is performed to show the effectiveness of the proposed method. The distortion compensation scheme used here may be applicative to other applications.

This paper presents a methodology for capacitor optimum determination in unbalanced distribution systems. The methodology aims to minimize losses of energy and power during the peak hours considering the capacitor costs. Restrictions were adopted for voltage limits representation and unbalancing between phases. A three phase modelling is presented, allowing the precise representation of the elements constituting the distribution systems. Tests are presented of a three phase system consisted of single, two and three phases, resulting in significant efficiency of the study methodology.

The leukoproliferative (LP) response of splenic leukocytes from the marine benthic fish English sole (Pleuronectes vetulus) stimulated with the mitogens lipopolysaccharide (LPS), convanavalin A (Con A), and pokeweed mitogen (PWM) was examined as a biomarker of immunotoxic effects. English sole were exposed to contaminants, either by injection of an organic-solvent extract of a sediment containing polycyclic aromatic compounds (PACs) or placed for up to 5 weeks on a reference sediment containing 0.15 to 1.5% (v/v) of the PAC-contaminated sediment. English sole either injected with the contaminated extract or held on PAC-contaminated sediment had an augmented response to Con A. The LP response to LPS showed no relationship to PAC exposure in laboratory-exposed fish, while PWM showed no consistent relationship to exposure to PACs. In a field study, English sole captured from an urban area in Puget Sound, Washington, USA, contaminated with PACs and other chemical contaminants had a significantly augmented LP response to Con A and PWM in comparison to the LP response in fish from a nonurban reference site. Fish from another nonurban site also had an augmented LP response to Con A, indicating that the elevation of the Con A LP response can also result from factors other than chemical contaminant exposure. In addition, English sole from this site also had an augmented LP response to LPS, whereas fish from urban sites did not exhibit an augmented LP response to LPS. Overall, the results demonstrated that although the LP response in splenic leukocytes of English sole to Con A was linked to contaminant exposure, the LP response to Con A did not exhibit high specificity as an indicator of chemical contaminant exposure. However, the concerted use of Con A, LPS, and PWM allowed for identification of apparent chemical contaminant-induced alterations of the LP response in English sole from an urban area of Puget Sound.

Low power industrial motor drives are dominated by the Induction motor, followed by Permanent Magnet, (PM) motors. This paper presents an efficiency comparison of these motors from measurements on six 100 W motors of comparable size, fed by VSI PWM DC-link inverters. The focus is on the PM motors as these seem to offer the highest efficiency at low power ratings. To set the PM motors in perspective, comparison is made to a 2 pole, 3 phase, Induction motor. (au)

Pulse Width Modulation (PWM) new techniques give better inverter output voltages. So, a potential difference is introduced between the inverter artificial reference point O and the machine neutral point N. This paper proposes a new parameter for the PWM modelling, to represent this O-N voltage variation in the inverter control. This potential difference imposes a system decomposition on the converter-machine set : each reference point is associated to own reference frame. Firstly, the standard case V_NO=0 is studied by the analysis tools. Then, the influence of a V_NO continuous value voltage is shown on the voltage harmonic spectrum and on the machine behaviour. Lastly, a study of PWM with third harmonic injection is realized and shows interest of the new PWM modelling for modern modulations, Les nouvelles techniques de modulation par largeur d'impulsion (MLI) permettent aux ensembles convertisseur-machine de disposer d'un meilleur rapport de tension. En fait, elles imposent une différence de potentiel entre le point de référence de l'onduleur, O, et le point neutre de la machine, N. Cet article propose une nouvelle modélisation de la MLI, avec un degré de liberté supplémentaire, pour prendre en compte cette variation de tension entre O et N (V_NO) dans la commande de l'onduleur. L'utilisation de V_No dans la boucle de commande de l'ensemble convertisseur-machine, nécessite alors la décomposition du système par l'intermédiaire de deux référentiels associés à chaque point de référence. Après avoir vérifié ces deux outils d'analyse dans le cas standard où V_NO = 0, nous étudions l'influence d'un V_NO de type continu sur le spectre des harmoniques de tension et sur le comportement de la machine. Enfin, une étude sur la MLI avec injection d'harmonique 3 valide l'intérêt de cette nouvelle approche quant à l'analyse de modulations moins classiques.

Switch-mode Power Converters are well known for emissions in the band of electromagnetic interference (EMI) interest. The spectrum shape depends on the type of modulator and its purpose. This paper gives design guidelines to choose the optimum topology depending on requirements of different applications. Spectral measurements on prototypes of a pulse width modulator (PWM), a -modulator and a hysteretic self-oscillating modulator are shown, which are verifying their simulations, with respect to different EMI challenges.

The paper summarizes our experiences of various electric driving of piezoelectric elements (piezoelectric membranes, actuators, piezoelectric ceramic transformers, etc.) with help of the fast digital electronic components - particularly the Field Programmable Gate Arrays (FPGA), eventually the Digital Signal Processor (DSP). These components are often used in the piezoelectric applications with the extreme rate requirements - e.g. the driving ultrasonic piezoceramic motors by Pulse-width modulation (PWM) signal or the controlled elasticity of the piezoelectric materials.

This paper presents a steady-state analysis considering the converters operation. The non-dissipative snubber associated with a forward converter provides the soft communication switching. The proposed approach allows building high frequency converters and their operation are described; the output voltage is controlled by a conventional pwm converter with a constant frequency. The complete operating principles, theoretical analysis, relevant equations, simulation and experimental data are also presented 5 refs., 9 figs.

This paper presents a dc link notching current inverter with zero-current switching for a current source motor drive. Notches in the link current allow front rectifier and inverter`s switches to commutate at zero-current crossing and synchronize with PWM strategy. The paper also discusses design considerations for the resonant elements and control strategies for having sinusoidal input/output voltages and currents. Simulation and experimental results corroborate theoretical analysis. (author) 7 refs., 17 figs.

This paper summarizes the multilevel power conversion technologies published in THE IEEJ TRANSACTIONS ON INDUSTRY APPLICATIONS and presented at IEEJ Technical Meetings on Semiconductor Power Converter or Japan Industry Applications Society Conferences (JIASC) as well as international conference proceedings and journals. This survey includes various types of circuit topologies from the first neutral-point clamped PWM converter to the hottest modular multilevel cascaded converters, and their applications. In addition, some new circuit topologies of multilevel converters for low voltage applications are also reported.   

The size of passive components in an adjustable speed drive can be reduced by using small dc-link capacitors. The EMI filter in the drive also consists of passive components. The size of the filter can be reduced by using a three-level inverter, which can have low output voltage distortion. However, the three-level inverter based on small dc-link capacitors requires a PWM strategy to maintain neutral-point voltage balance. In this paper, the common mode voltage, which is the determining factor for the EMI filter size, is analyzed for a virtual-vector-based PWM strategy. The common mode voltage, the shaft voltage, and the conducted emission for the small dc-link capacitor based three-level inverter are compared with that of the two-level inverter operated with space vector PWM strategy. Experimental results for the common mode voltage, the shaft voltage, and the conducted emission are presented. Results show that the conducted emission from the three-level inverter is lower than that of the two-level inverter.Thus, a three-level inverter requires a smaller EMI filter in motor drives with small dc-link capacitors.

The main purpose of applying soft switching techniques to DC-DC converters is to reduce the considerable switching losses of conventional PWM converters. There are two ways to use this benefit. One of them is to develop a converter with increased efficiency. The other one is to increase the switching frequency as to get smaller reactive components, which lets shrink the converter volume. Another reason to use soft switching techniques is the improved electromagnetic compatibility (EMC) compared with hard switching PWM converters. Most of this techniques provide softened current and voltage waveforms for the switches and diodes. In this report different techniques to reduce switching losses by using resonance are investigated. The characteristics of these techniques are compiled in tables for easier comparison. Most of the techniques are applied to a buck-type converter, simulated with parasitic effects and their key waveforms are presented. Because of the fast progress in semiconductor capabilities and the variety of applications for DC-DC converters as well as the resonant techniques it is not possible to give a final assignment of techniques and applications. To choose the best technique for every specific application it is necessary to compare all of them. And after this, the best soft switching solution must be compared with an optimized conventional PWM converter. (author) figs., tabs., 7 refs.

Hysteresis control, ramp comparison control, synchronous frame proportional integral (PI) control, and predictive control are the different classes of current control schemes for a PWM inverter-fed PMSM drive. The fundamental requirements for the current controller are the fast dynamic response, zero steady-state error, stable PWM inverter operation, and robustness against the variations of machine parameters. This paper presented a model reference adaptive control (MRAC) based current control technique for a PWM inverter-fed permanent magnet synchronous motor (PMSM) drive that was designed to improve current control performance. Although the predictive current control is known to give ideal transient and steady-state responses, its steady-state response may be degraded as a result of motor parameter variations, particularly at high speed operation. To overcome this problem, the disturbances caused by the parameter variations were estimated in this study using an MRAC technique. A feedforward manner was used to improve the steady-state control performance while retaining good dynamic performance. The asymptotic stability of the proposed control scheme was confirmed and the adaptation laws were derived by the Lyapunov stability theory. The proposed control scheme does not require the measurement of the phase voltage, unlike the conventional disturbance estimation scheme. It was concluded that a systematic design approach can be accomplished using the proposed scheme. The overall control system was implemented using DSP TMS320C31 and its effectiveness was verified through experiments. 14 refs., 1 tab., 8 figs.