Showing papers on "PWM rectifier published in 2006"

Control of permanent-magnet generators applied to variable-speed wind-energy systems connected to the grid

Abstract: Wind energy is a prominent area of application of variable-speed generators operating on the constant grid frequency. This paper describes the operation and control of one of these variable-speed wind generators: the direct driven permanent magnet synchronous generator (PMSG). This generator is connected to the power network by means of a fully controlled frequency converter, which consists of a pulsewidth-modulation (PWM) rectifier, an intermediate dc circuit, and a PWM inverter. The generator is controlled to obtain maximum power from the incident wind with maximum efficiency under different load conditions. Vector control of the grid-side inverter allows power factor regulation of the windmill. This paper shows the dynamic performance of the complete system. Different experimental tests in a 3-kW prototype have been carried out to verify the benefits of the proposed system.

Differential Mode Input Filter Design for a Three-Phase Buck-Type PWM Rectifier Based on Modeling of the EMC Test Receiver

Abstract: For a three-phase buck-type pulsewidth modulation rectifier input stage of a high-power telecommunications power supply module, a differential-mode (DM) electromagnetic compatibility (EMC) filter is designed for compliance to CISPR 22 Class B in the frequency range of 150 kHz-30 MHz. The design is based on a harmonic analysis of the rectifier input current and a mathematical model of the measurement procedure including the line impedance stabilization network (LISN) and the test receiver. Guidelines for a successful filter design are given, and components for a 5-kW rectifier prototype are selected. Furthermore, formulas for the estimation of the quasi-peak detector output based on the LISN output voltage spectrum are provided. The damping of filter resonances is optimized for a given attenuation in order to facilitate a higher stability margin for system control. Furthermore, the dependence of the filter input and output impedances and the attenuation characteristic on the inner mains impedance are discussed. As experimentally verified by using a three-phase common-/Differential-Mode separator, this procedure allows accurate prediction of the converter DM conducted emission levels and therefore could be employed in the design process of the rectifier system to ensure compliance to relevant EMC standards

Common mode EMC input filter design for a three-phase buck-type PWM rectifier system

Abstract: The EMC input filter design for a three-phase PWM rectifier is usually separated into the design of the differential (DM) and of the common mode (CM) stage. While for the DM filter part design rules and procedures are well-known and the parameters are easier to derive, the CM filter design is often based on trial-and-error methods and/or on the experience of the designer. In this work, a comprehensive design procedure for a CM EMC input filter is performed exemplarily for a three-phase three-switch buck-type PWM rectifier with an integrated boost output stage. A simplified model of the CM noise propagation is developed and the relevant parasitic impedances are identified. A capacitive connection from the star-point of the DM input filter to the capacitive centre point of the rectifier output voltage is proposed and the effect of this measure concerning CM EMC is verified. Finally, a two stage CM filter is designed and the compliance to the conducted emission requirements of CISPR 22 class A is verified through measurements on a 5 kW prototype.

Direct Power Control System of Three Phase Boost Type PWM Rectifiers

Abstract: This paper establishs the power control mathematical model of rectifier based on the mathematical model of three phase boost type PWM rectifier in synchronous dq coordinates. According to the power control mathematical model, the paper proposes a new design method of filter inductance in AC side , voltage and capacitance in DC side of main circuit for three phase boost type PWM rectifier by combining with the features of direct power control(DPC) system. Based on the models of rectifier, the control structure of rectifier DPC system and the design method of controller is obtained. Meanwhile, the paper discusses the influence of bridge loss and equivalent series resistance(ESR) of capacitor on rectifier. The design method is proved feasible by simulation and experiment and is available for reference in engineering.

The Delta-Rectifier: Analysis, Control and Operation

Abstract: The three-phase Delta-Rectifier is formed by a delta-connection of single-phase pulsewidth modulation (PWM) rectifier modules and has the advantage that it can provide full rated output power in the case of a mains phase loss. In this paper the Delta-Rectifier, implemented with a standard (two-level and/or three-level) boost converter, is analyzed based on an equivalent star connection. Analysis of the Delta-Rectifier shows a redundancy in the switching states concerning the input voltage formation. Furthermore, the Delta-Rectifier has reduced current ripple in the mains phase currents if the modulation is implemented with synchronized PWM. A disadvantage of two-level Delta-Rectifier is the higher voltage stress on the switching devices; however this is mitigated when the boost converter is implemented with a three-level topology as realized for a 10.5-kW laboratory prototype. The Delta-Rectifier concept is proposed based on theoretical considerations and is verified experimentally. The influence of non-idealities on the current ripple formation in the practical realization is analyzed and a high quality mains phase current is demonstrated

Study on Power Decoupling Control of Three Phase Voltage Source PWM Rectifiers

Abstract: This paper proposes a new power control strategy of three phase voltage source PWM rectifiers to solve the coupling between instantaneous active power and instantaneous reactive power. This strategy is obtained based on the power control math model of three phase voltage source PWM rectifiers in synchronous dq coordinates. A new power control switching table is set up according to new dividing of input voltage space and resultant voltage space vectors for improving the properties of system and saving complicated PWM modulation module. The switching functions is selected in new power control switching table according to the position of source voltage space vector and input voltage space vector of rectifier required. This paper gives a design method of system controller. The control strategy is proved feasible by simulink simulation with different loads.

Harmonic Mitigation in Wind Turbine Energy Conversion Systems

Abstract: Permanent magnet synchronous generators (PMSG applied to wind energy conversion system (WECS) using variable speed operation is being used more frequently i wind turbine application. Variable speed systems have several advantages over the traditional method of operating win turbines, such as the reduction of mechanical stress and a increase in energy capture. To allow the variable speed operation of the PMSG WECS a conventional three-phase bridge rectifier (BR) with a bulky capacitor associated with voltage source current controlled inverter (VS-CCI) is used This simple scheme introduces a high intensity low frequency current harmonic content into the PMSG and consequently increases the total loses in it. Subsequently, decreases the power capability of the system. This paper presents comparative simulation study between three different approaches applied to harmonic mitigation in PMSG WECS The studied techniques are: a) harmonic trap filters (HTF), b single-switch three-phase boost rectifier (PFC) and c) a three phase boost type PWM rectifier (PWMREC).

A new high power factor bidirectional hybrid three-phase rectifier

Abstract: This paper presents a new bidirectional hybrid three-phase rectifier suitable for medium and high power applications. The rectifier employs a three-phase diode bridge rectifier and a boost-type three-phase PWM rectifier. The proposed rectifier is capable of providing sinusoidal input currents with low harmonic distortion and DC output voltage regulation. The rectifier topology generation, the principle of operation, control scheme and simulation results are described in the paper.

Development of a New Mathematical Model of Three Phase PWM Boost Rectifier Under Unbalanced Supply Voltage Operating Conditions

Abstract: This paper proposes a new mathematical model of the three-phase PWM boost rectifier in the positive and negative synchronous rotating frames under the unbalanced operating conditions. A detailed analytical expression for dc link voltage has been presented, from which the presence of the even harmonic components in the dc output voltage and odd harmonic components in the ac input current can be deduced. A simple algorithm for the reference current calculation is proposed from the analytical point of view. The dual frame PI control scheme developed based on this model can maintain the dc output voltage almost constant and keep the supply side power factor close to unity under the unbalanced operating conditions. The feasibility of this dual rotating d-q frame control scheme is verified by experimental results on a 1.6 kVA three-phase PWM rectifier. The test results demonstrate that the control scheme based on the new mathematical model can reduce the even-order harmonics at the dc link voltage and the odd-order harmonics in the ac input current.

High Dinamic Control of a PWM Rectifier using Harmonic Elimination

Abstract: In this paper the problem of current control in high power converters using low frequency, precalculated switching patterns is addressed To overcome the problem of switching harmonics feeding through the current controllers a harmonic prediction and compensation method is devised The good performance of the method is tested extensively through simulation of an three level PWM rectifier modulated with a five angles selective harmonic elimination, resulting in 250 Hz switching frequency Finally, preliminary experimental results, controlling current in a passive R-L load are provides to confirm the implementation feasibility of the proposed technique

Modeling and Control of Three-phase Voltage Source PWM Rectifier

Abstract: This paper presents the state of the art in the field of three-phase voltage source PWM rectifier with reduced input harmonics and unity power factor The working principle, modeling procedure, corresponding control strategy as well as typical waveforms are introduced in detail which can provide some guidelines for engineers to analyze, design and implement

Analysis of pulse width modulation techniques for AC/DC line-side converters

Abstract: The paper presents the analysis of the modulation strategies for the AC/DC line-side converters. The application of the different modulation methods to the control system of the AC/DC converter has been presented. The operation of the AC/DC converter in different dynamic states strongly depends on the modulation method applied. The theoretical background of Hysteresis-Band Modulation, Carrier-Based Sinusoidal Modulation and Space-Vector Modulation has been presented. The issue of overmodulation has been discussed. Voltage Oriented Control of the AC/DC line-side converter has been chosen to examine the presented modulation methods. The influence of the discussed modulation methods on the line current distortion and the switching frequency has been examined. The simulation results of the presented techniques have been demonstrated and concluded.

Comparative study of three-phase PWM rectifiers for wind energy conversion

Abstract: This paper presents a study of alternative PWM rectifier topologies that can meet power conditioning requirements of induction as well as permanent-magnet synchronous generators for wind energy conversion. The studied topologies use three bidirectional switches in combination with a three-phase diode bridge, and are previously used only for unity power factor rectification. This paper first shows that these topologies can also operate with either leading or lagging input power factor, hence can be used to supply reactive power to induction and permanent-magnet synchronous generators while extracting active power from them. The topologies are further compared to the conventional six-switch PWM voltage-sourced converter (VSC) in terms of switching and conduction losses. Additionally, the common-mode voltage generated by these topologies under different modulation methods is analyzed and shown to be significantly lower than that generated by the conventional six-switch VSC.

A New Hybrid High Power Factor Three-Phase Unidirectional Rectifier

Abstract: This paper presents a new unidirectional hybrid three-phase rectifier composed by the parallel association of a single switch three-phase boost rectifier with a PWM three phase unidirectional rectifier. The objective to be reached is to reduce the harmonic content of input currents by processing a fraction of output active power with the PWM rectifier. The proposed structure allows to obtain a THD varying between 0 and 32%, just depending on the power processed by PWM three phase unidirectional rectifier. So, if the PWM rectifier is settled to process 45% of the total output power, the THD obtained is 0. Decreasing the PWM power to about 33% of the load power is possible to achieve the standards requirements. The rectifier topology conception, the principle of operation, control scheme and simulation results are also presented in this paper.

Research on the Technology of the Neutral-point Voltage Balance and Dual-loop Control Scheme for Three-level PWM Rectifier

Abstract: A mathematical model of the three-level PWM rectifier is set up.Compared with the model of DC motor,some similarities are established.Based on the state feedback decoupling,the dual close-loop control of DC motor is applied to three-level PWM rectifier.As a result,the three-level rectifier has favorable dynamic and steady state performance,sinusoidal input current and unity power factor.Besides,a method is proposed to control the neutral-point voltage charge unbalance,which is an inherent problem of three-level inverter.The redundant positive small vectors and negative small vectors are selected according to the direction information of input current of each phase as well as the ripple of neutral-point voltage.Finally,experimental results verify the feasibility and validity of dual-loop control system and neutral-point voltage control method.

Transient Modeling and Control of the Novel ZVS Z-Source Rectifier

Abstract: This paper presents the analysis of dynamic response of the ZVS Z-source rectifier and design of the closed-loop controllers for both the z-source rectifier and the z-network circuit. Due to the unique Z-network, the transient response is found to be challenging in controlling the ZVS Z-source rectifier. By combining the traditional PWM rectifier model and equivalent model of the z-network. The ZVS Z-Source rectifier model is proposed. Through detailed analysis, the controllers are designed to obtain the steady DC-link voltage and a sinusoidal AC voltage under linear loads.

Control of a DC generator based on a Hybrid Excitation Synchronous Machine connected to a PWM rectifier

Abstract: This paper deals with the control of an hybrid excitation synchronous generator which is used to supply an isolated grid for aircraft applications. This grid is supposed to be a 270 V DC bus. Thus, a rectifier is required between the machine and the DC bus. Two structures can be used: diode or PWM rectifier. Here, only the structure with a PWM rectifier is studied. With a such system, it is possible to use a vector control applied to the structure in order to obtain minimal copper losses in the machine. The controller is synthesized here using a methodology based on a graphical representation of the system and then it is validated by simulation

Study and control of two two‐level PWM rectifier—clamping bridge–seven‐level NPC VSI cascade: application to PMSM speed control

Abstract: In this paper, the authors present a study of the stability problem of the input DC voltages of the seven-level neutral point clamping (NPC) voltage source inverter (VSI). In the first part, they develop a knowledge model of this converter by using connection functions. In the second part, the authors propose a PWM strategy which uses six bipolar carriers to control this converter. In this part, the inverter is fed by constant input DC voltages. In the last part of this paper, the authors study the stability problem of the input DC voltages of the inverter. Thus, they study a cascade made up of two two-level PWM rectifier—seven-level NPC VSI. The results obtained show that the input DC voltages of the inverter are not stable but are better than the ones obtained with a cascade which uses one PWM rectifier. To improve the performance of the proposed cascade and stabilize the input DC voltages, the authors propose in this paper a solution which uses a clamping bridge. This study allows a solution to be found for the instability problem of the input DC voltages of the inverter. The results obtained with this solution confirm the good performances of the proposed solution. Copyright © 2005 John Wiley & Sons, Ltd.

Passive and Hybrid PFC Rectifiers

Abstract: The diode rectifier offers several desirable features such as a unity displacement-factor and a high efficiency with low complexity and high reliability, but the utility line-current is significantly distorted The traditional multi-pulse (eg, 12-pulse, 18-pulse and so on) PAM concept by means of multiple rectifier units and phase-shifting isolation-transformers is a well-known scheme to improve the input line-current waveform and reduce dc-current/voltage ripple Though, the necessity of the isolation-transformer is a great weak point especially for applications in low to medium power range To mitigate the problem, several investigations have been done The PWM rectifier is a modern and effective alternative, although it results in a higher initial cost, lower efficiency and EMI noise problems due to high frequency switchingTo solve the problem, we have two alternatives without PWM and are so called “Passive” schemes One is the multi-pulse/multi-phase scheme without the isolation transformer but with an autotransformer This scheme results in a simplified multi-pulse PAM rectifier The other is the Third-Harmonic-Current Injection and the expanded schemes Although these two schemes have been studied independently in most cases, new types of diode PFC rectifier obtained by combining the two schemes have been studied recently Additionally, further new topologies, so called “Hybrid” type, have been proposed very recently The rectifiers with the new concept consist of an autotransformer-connected double 3-phase bridge 12-pulse rectifier and a PWM dc-dc converter on the dc-side to perform the current injection The Hybrid rectifiers offer output voltage controllability and sinusoidal input currents similarly to the PWM rectifiersTo show the current trends and remaining possibilities of the Passive and Hybrid rectifiers, this paper gives a survey and historical review of the rectifiers Then, some new topologies in the category are investigated Simulation and experimental results of the rectifiers are described to explore the operating mechanism and to obtain hints to achieve new topologies

Improved feedforward control of three-phase voltage source PWM rectifier

Abstract: Since three-phase voltage source PWM rectifier is vulnerable to the disturbance of both load and grid voltage,an improved feedforward control strategy is proposed based on the power balance relationship between the input and output of rectifier,which is deduced according to the mathematic model of the rectifier.Feedforward signal includes the information of both grid voltage and DC side load.Power balance between the input and output can be maintained by adjusting AC side currents.Experiments have been done on the laboratory platform and results verify the effectiveness of the control strategy proposed.Robustness of the rectifier to the disturbance of both load and the grid voltage has been improved.

Modeling and Simulation of Three Phase High Power Factor PWM Rectifier

Abstract: Numerical simulation methodology based on high frequency mathematical model of high power factor PWM rectifier is proposed in this paper. And input to output transform function is deduced. With the help of input to output transform function, the design method of voltage regulator has been presented. The simulation for three-phase PWM rectifier is implemented with Runge-kutta, thus comprehensive simulation can be achieved with M file in MATLAB. Finally, the simulation results and experimental results are given. The complete agreement with the results of simulation and experiment manifests that the proposed simulation method in this paper is effective. Of course, the design period of three-phase high power factor PWM rectifier can be shortened by virtue of proposed simulation methodology.

Space vector modulation applied to three-phase three-switch two-level unidirectional PWM rectifier

Abstract: This work presents a methodology to apply space vector modulation to three-phase three-switch two-level Y-connected unidirectional PWM rectifier. Converter switching stages are analyzed to determine switches control signals for space vector modulation. A switching sequence is proposed to minimize the number of switches commutations. Rectifier models and vector control structure are also described. In order to validate the proposed modulation, experimental results are presented for a 20 kW prototype.

Advanced control of a boost AC-DC PWM rectifier for variable-speed induction generator

Abstract: This paper describes simple control structures for vector controlled stand-alone induction generator (IG) used to operate under variable speeds. Different control principles, indirect vector control and deadbeat current control, are developed for a voltage source PWM converter and the three-phase variable speed squirrel-cage IG to regulate DC-link and generator voltages with newly designed phase locked loop circuit. The required reactive power for the variable speed IG is supplied by means of the PWM converter and a capacitor bank to buildup the voltage of the IG without the need for a battery and to reduce the rating of the PWM converter with the need for only three sensors and to eliminate the harmonics generated by the PWM converter as well. These proposed schemes can be used efficiently for variable speed, wind energy conversion systems. The measurements of the IG systems at various speeds and loads are given and show that these systems are capable of good AC and DC voltages regulation.

A New Power Analysis Method of PWM Rectifier with Unbalanced Voltage Condition

Abstract: The thesis puts forward a new calculation method of tri-dimension instantaneous complex power based on coordinate conversion and symmetrical componentsAccording to the instantaneous complex power,system input power could be decomposed as 12 power components,such as:instantaneous active power、reactance capacity between the axes of q0,dq and d0,etcTwo kinds of control strategy that one aims to suppress negative-sequence current AC side,while the other aims to suppress the secondary harmonic of input AC side,are analyzed in the thesis based on analysis of instantaneous powerThe thesis has constructed a PWM rectifier simulation platform based on Saberr and has presented various waveforms of instantaneous active power,instantaneous reactance capacity,instantaneous power-factor and input current etcBy adopting different optimizing control algorithm in every unbalanced input caseThese provide a firm theory base for the power analysis and optimizing control of the three-phase PWM rectifier in the case of unbalanced input

Minimization of DC Reactor and Operation Characteristics of Direct-Power-Controlled Current-Source PWM Rectifier

Abstract: This paper describes a direct-power-controlled current-source PWM rectifier, and presents operation characteristics by using a 2-kW experimental setup. The key of the proposed strategy is a direct selection of switching modes on the basis of a relay control technique of instantaneous active and reactive power, using an optimum switching table. The main feature of the direct power control is high-speed response of the power control; hence inductance of the DC reactor can be reduced. Feasibility of the strategy is verified through experimental tests, using the prototype. Experimental results demonstrate that the inductance of the DC reactor can be reduced down to 0.7 mH in the prototype, achieving the 92.5-% maximum efficiency, 99.9-% maximum total input power factor, and 3.1-% total harmonic distortion of the input current. Furthermore, operation characteristics are examined under unbalanced power source condition.

Minimization of Smoothing Capacitor and Operation Characteristics under Unbalanced Power Source of Direct-Power-Controlled PWM Rectifier

Abstract: This paper describes direct power control of a PWM rectifier. The key of this strategy is a direct selection of switching modes on the basis of instantaneous errors of active and reactive power. In addition, this paper presents a theoretical analysis on relation between the instantaneous power and the switching modes, which is essential to compose a switching-mode table. The feature of this method is high-speed response owing to direct-instantaneous-power control with relay elements; hence a DC-bus smoothing capacitor can be minimized. Controllability of the proposed technique was examined through various experimental tests, and it was confirmed that the maximum total input power factor and efficiency were 99.6% and 96.6% over a load power range from 400 to 1600W, respectively. Moreover this paper discusses operation characteristics of the direct-power-controlled PWM rectifier, compared with a conventional subharmonic PWM rectifier, under unbalanced power source condition. Experimental data prove that the proposed technique achieves more than 95-% power factor and less than 6-% DC bus ripples.

Analysis and Control of the Output Instantaneous Power for Three Phase PWM Boost Rectifier Under Unbalanced Supply Voltage Conditions

Abstract: This paper proposes a new method to analyze the output instantaneous power of the three phase PWM boost rectifier under unbalanced supply voltage conditions An analytical expression for the output instantaneous power has been derived and presented, which provides the link between the output dc linkage voltage and the instantaneous output power Based on the mathematical model of the three phase PWM rectifier in the rotating synchronous frame, the physical concept of the output instantaneous power has been explained from the analytical point of view A direct relationship between the dc link voltage ripples and the second harmonic component in the instantaneous output power has been derived A simple cascaded PI control scheme has been developed for the dc output voltage control The controller ensures that the dc link voltage is maintained constant and the supply side power factor is kept close to unity under the unbalanced supply voltage operating conditions Simulation and experimental test results are provided on a 16 kVA laboratory based PWM rectifier to validate the proposed analysis and control scheme

Voltage Sag Compensation in High-Quality AC/DC Converters Using the Single-Phase DQ Theory

Abstract: Voltage sags are one of the most important power quality problems, affecting industrial and commercial customers. Industrial processes are particularly sensitive to relatively minor voltage sags. Utilities have been improved their fault-recovery capabilities, however it is still impossible to eliminate faults in the systems. Therefore, customers will have to improve the ride-through capability of the system equipment in their facilities. This paper presents the application of the single-phase DQ theory as a simple method to detect voltage sags in the AC mains obtaining the voltage peak value. This information can be used to achieve, by analytical manipulations, the input current adjusting during the sag, in order to maintain the load power constant. Applying the above considerations to a single-phase five-level PWM rectifier both objectives power factor correction in steady state and voltage sag compensation in transient state are gotten. Simulation and experimental results have been carried out in a 1 kVA, single-phase power converter.

Performance Comparison of Voltage Mode Control and Current Mode Control of a Three-Phase PWM Rectifier based on a Dual SISO Model

Abstract: The challenge in controlling a three-phase PWM rectifier mainly arises from the fact that the state-space-averaged model reported in literature has a multi-input multi-output (MIMO) non-linear structure and furthermore exhibits non-minimum phase feature Recently, a dual single-input single-output (SISO) model developed for the rectifier showed that the dynamics of the d-axis is similar to that of a traditional dc-dc boost converter This finding makes it possible to extend the control design and system analysis techniques of dc-dc converters to these rectifiers In this paper, the well-documented techniques in dc-dc converters namely, voltage and current-mode control techniques, are applied and investigated for a three phase rectifier The steady-state and transient performances for step changes in output voltage reference, dc load, and supply voltage are experimentally investigated and the results obtained with the two control methods are compared Experimental results suggest that better performance can be achieved with the current mode controller The results also further justify the validity of the dual SISO model

AC Current Sensorless Control of Three-Phase Three-Wire PWM rectifiers under the Unbalanced Source Voltage

Abstract: This paper proposes an AC current sensorless control strategy for a PWM rectifier under the unbalanced source voltage. In the unbalanced system, if we use the traditional control scheme, it will yield large input current harmonics and dc-link voltage ripples due to the effect of the negative components. Meanwhile, in the ordinary control methods, at least two current sensors are needed to test the phase current, which increases the system's cost and reliability. This paper's control objective is to balance the input current and minimize the dc-link voltage ripples of the three-phase three-wire boost rectifier without the AC current sensors in the case of the unbalanced situation. The control is implemented in the positive SRF, and notch filters will be applied. The two AC current sensors will be replaced by only one current sensor, which is expected to test the dc-link current. The feasibility of the method has been confirmed through computer simulations.