Showing papers on "PWM rectifier published in 2000"

Sensorless control strategies for PWM rectifier

Abstract: In this paper two different control strategies for a PWM rectifier without line voltage sensors are compared. The direct power control (DPC) which has no need for line voltage measurements is compared to the conventional voltage oriented control (VOC) strategy in rotating coordinates with a novel line voltage estimator. The steady-state performance of both strategies is compared with regards to voltage unbalance and pre-distorted grid. Furthermore, the use of discontinuous modulation is motivated in the classical control strategy and is analyzed along with the novel line voltage estimator. It is shown that the VOC strategy with line voltage estimator exhibits several advantages compared to DPC. Some simulations and experimental results verifying the comparison are presented.

A novel control method for three-phase PWM rectifiers using a single current sensor

Abstract: This paper proposes a control method for three-phase voltage-source PWM rectifiers using only a single current sensor in the DC-link. A PWM modulation strategy for reconstructing three phase currents from the DC-link current is given. When 3/spl phi/ input currents cannot be reconstructed, a method for modifying the switching state of the PWM rectifier and a method for the predictive state observer is proposed. Compensation of the 2 sampling delays is also included, and this method is combined with all of the experiments. Performance differences between the two methods in a typical voltage source PWM rectifier are investigated experimentally.

A vector controlled current-source PWM rectifier with a novel current damping method

Abstract: Three-phase current-type pulse width modulation (PWM) rectifiers are becoming increasingly popular as the front-end converter unit in power electronic systems due to tighter electromagnetic compatibility (EMC) regulations. In this paper the control of the current source PWM rectifier in the synchronously rotating reference frame is discussed. A control system is presented in which the active and reactive power are independently controlled with real and imaginary axis components of the supply current vector. A new damping method for supply current oscillations is introduced. The method operates in an open-loop manner and is very suitable for microcontroller implementation since the calculation power demand is low. Furthermore, it is shown that in the synchronously rotating coordinates, where the sinusoidal variables appear as DC quantities, the compensation of the reactive power drawn by the supply filter can be done very easily. The proposed control methods are realized using a single-chip Motorola MC68HC916Y1 microcontroller. The experimental tests show excellent performance in both steady state and transient conditions.

AC voltage and current sensorless control of three-phase PWM rectifiers

Abstract: In this paper, a novel control scheme of three-phase PWM rectifiers eliminating the AC voltage and current sensors is proposed. Both the phase angle and the magnitude of the source voltage are estimated by controlling the deviation between the rectifier current and its model current to be zero. The phase currents can be reconstructed from switching states of the PWM rectifier and the measured DC link currents. To eliminate the calculation time delay effect of the microprocessor, a predictive state observer is employed. The proposed control scheme reduces the system cost and improves its reliability. The feasibility of the proposed AC sensorless technique for PWM rectifiers has been verified through experiments using a high performance DSP chip.

PWM rectifier having de-coupled power factor and output current control loops

Abstract: A PWM rectifier wherein the switching bridge has m input filter capacitors, each connected at a terminal thereof, to the line side of the bridge. These terminals are used to connect an m-phase a.c. power supply (m>=1) having a per phase system inductance to the bridge. A current smoothing inductor is connected to the load side of the bridge and enables a load to be connected thereto. A switching pattern generator controls the switches in the switching bridge based on a reference output current. A first control loop is provided for determining an active portion of the reference output current based on a desired power level of the load and an m-phase voltage at the capacitor terminals. A second control loop is provided for determining a reactive portion of the reference output current based on the m-phase voltage at the capacitor terminals. The reactive portion of the current is selected so as to obtain a desired per phase power factor, such as unity, on the power supply. In this manner the output current and power factor control loops are independent of and not coupled to one another.

Control strategies for PWM rectifier/inverter-fed induction motors

Abstract: The paper reviews the technology status and control strategies developed for PWM rectifier/inverter-fed induction motor drives with emphasis for its similarities. A review includes: new PWM techniques, field oriented and direct torque control of induction motor (FOC and DTC), voltage oriented and direct power control of a PWM rectifier (VOC and DPC), and novel virtual flux (VF) based sensorless control of a PWM rectifier. Also, neural network and fuzzy logic based intelligent controllers for motion control have been discussed. Selected oscillograms are shown in order to illustrate properties of the described control strategies.

A three-phase voltage-type PWM rectifier with the function of an active power filter

Abstract: In recent years, harmonic pollution in electrical power systems due to nonlinear loads such as AC/DC power converters has become a serious problem. To eliminate or reduce harmonics in power systems, a number of methods have been developed and put into practice. Active power filters and PWM rectifiers are two typical examples of these methods. The active power filter and PWM rectifier have basically the same circuit configuration and can operate based on the same control principle. Therefore, one can design a power converter capable of both the active filter operation and PWM rectifier operation at the same time. Such a converter operates as a PWM rectifier to supply DC power to its own load and, at the same time, operates as an active filter to supply to the AC line a compensating current equal to the harmonic current produced by the nonlinear load connected to the same AC line. Here, a three-phase voltage-type PWM rectifier with the function of an active power filter is investigated.

Analysis and implementation of a three-level PWM rectifier/inverter

Abstract: A three-level pulse width modulation (PWM) technique for ac/dc/ac converter is proposed. Single-phase three-level rectifier based on double boost configuration with power factor correction is used in the input side. Three-phase three-level voltage source inverter based on diode clamped scheme is employed in order to reduce the harmonic content of the inverter output voltages. In the rectifier side, the hysteresis current controller is used to track the line current command in phase with the mains voltage. A capacitor voltage compensator is adopted to balance the neutral point voltage in order to maintain good quality voltage waveforms on the output of the inverter. In the inverter side, three-level PWM based on sine-triangular comparison is used to reduce the voltage harmonics. The major advantage of the adopted three-level scheme is that the blocking voltage of each power switch is clamping to half of dc-link voltage. The proposed control scheme is verified by the software simulation and experimental results based on a laboratory prototype.

A new concept for minimizing high-frequency common-mode EMI of three-phase PWM rectifier systems keeping high utilization of the output voltage

Abstract: Three-phase PWM rectifier systems in principle show a common-mode voltage with switching frequency between the mains neutral point and the center point of the output voltage. Without any counter-measures this leads to a high common-mode noise emission of the system and possibly to disturbances of the control unit of the converter being fed by the rectifier. In this paper a detailed discussion of the formation of the common-mode voltage for the VIENNA Rectifier I is given and a modified circuit topology which significantly reduces the switching frequency component of the common-mode voltage is given. The proposed circuit modification is applicable also to other three-phase PWM rectifier topologies. The filtering concept is analyzed by digital simulation and guidelines for the dimensioning of the filter components are given. The reduction of the common-mode noise is verified by EMI measurements taken from a 10 kW laboratory unit of a VIENNA Rectifier I. Finally, the advantages and drawbacks of the proposed filtering concept are compiled in the form of an overview.

Advanced nonlinear control of three-phase PWM rectifiers

Abstract: A nonlinear control of the three-phase PWM rectifier is proposed in which the input q-axis current and output voltage dynamics are modelled in a single-variable nonlinear system, with the d-axis current dynamics excluded. The nonlinear model is linearised by a feedback linearisation technique, not by small-signal analysis, which makes it easier to design the controllers. Furthermore, with the inner capacitor-current control loop, the direct voltage transient response can be faster. The size reduction of the DC electrolytic capacitor due to the fast voltage control of the proposed scheme is studied. The validity of the scheme has been verified through experiment using a TMS320C31 DSP chip.

Design and implementation of a single phase three-arms rectifier inverter

Abstract: A high performance single phase three-arms PWM rectifier inverter is presented. A switching control approach for the common arm is proposed such that control of the rectifier arm and inverter arm can be designed independently. Variable structure control (VSC) executed with capacitor current control is developed to design the inverter. For the rectifier design, an instantaneous power feedback controller using filter theory is proposed to enhance the DC voltage regulator to reduce DC voltage fluctuation and minimise input current distortion. A 3 kVA system is implemented to confirm the effectiveness of the proposed approaches.

Repetitive controlled three-phase reversible PWM rectifier

Abstract: In this paper, a repetitive current control scheme for three-phase reversible PWM rectifier is proposed. The proposed control scheme is of typical dual-loop structure: inner AC current loop with plug-in repetitive plus feedback deadbeat controller, and outer DC voltage loop with PI controller. The unit power factor and constant DC bus voltage are obtained under load disturbance. Simulation results are illustrated to show the validity of the proposed control scheme.

Modular PM generator/converter topologies, suitable for utility interface of wind/micro turbine and flywheel type electromechanical energy conversion systems

Abstract: In this paper, modular PM generator and converter topologies, suitable for the utility interface of wind turbine, micro turbine and flywheel type electromechanical energy conversion systems are explored. It is shown that winding connections of the standard PM generator in the above applications can be reconnected into several single-phase and three-phase groups, each powering a separate PWM rectifier, resulting in high performance electromechanical energy conversion systems. The proposed approaches are fault tolerant and can continue to function at reduced power levels under faults. An example 3-phase, 10 hp, 4 pole, 60 Hz, 230 V/460 V PM motor/generator winding connection diagram along with the associated converter configurations is fully analyzed for the above listed applications.

New ZCS turn-on and ZVS turn-off unity power factor PWM rectifier with reduced conduction loss and no auxiliary switches

Abstract: A ZCS turn-on and ZVS turn-off unity power factor PWM rectifier, which features soft switching with no auxiliary switches and reduced conduction losses is presented. The ZVS and ZCS switching are achieved by using a simple commutation circuit with no auxiliary switches, and reduced conduction losses are achieved by employing a single converter instead of a typical front-end diode rectifier followed by a boost rectifier. Furthermore, thanks to features such as simple PWM control at constant frequency. Low switch stress and low VAr rating of commutation circuits, it is suitable for high-power applications. The principle of operation is explained and analysed, and the design considerations and experimental results of the new converter are included.

A novel current source PWM drive topology with specific harmonic elimination switching patterns

Abstract: This letter presents a novel current source PWM rectifier/inverter topology which has low input current harmonics and high input displacement factor, for high-power induction motor drive applications. A suitable PWM specific harmonic elimination (PWM-SHE) switching pattern is developed in order to just eliminate the 11th and 13th harmonics, required by the proposed topology. A genetic algorithm and the conjugate gradient descent method are combined to solve the nonlinear transcendental functions for PWM-SHE. This scheme converges quickly.

Method and apparatus for stabilization and minimization of losses of a series connection of dc/dc-converters connected to the output-side partial voltages of a three-level pwm rectifier system

Abstract: A method and an apparatus for active stabilization of the voltage sharing of a series connection of DC/DC converter stages (7, 8), and a method and an apparatus for minimization of the current stress of the input capacitors (5) of DC/DC converters operating at the output of a three level converter. For each DC/DC converter there is one pulse width modulation-stage (57, 58), where at the input side summing elements get control signal defining the power flow to the secondary power circuit from a supervising output voltage controller and/or an output current controller. The symmetry controller creates a positive and negative offset of this control signal in case of an asymmetry of the partial input voltages of the DC/DC-converters. The offset controls the power flow of the DC/DC converters in a way that the DC/DC converter with higher input voltages takes less power from its input capacitor.

A novel current source PWM drive topology with specific harmonic elimination switching

Abstract: This paper presents a novel current source PWM rectifier/inverter topology, having low input current harmonics and high input displacement factor, which is intended for high power motor drive applications. A suitable PWM specific harmonic elimination (PWM-SHE) switching pattern is developed in order to just eliminate 11th and 13th harmonics required by proposed topology. Genetic algorithm and conjugate gradient descend method are combined to solve the nonlinear transcendental functions for PWM-SHE. This scheme has advantages of easy convergence and requires less computing time. The input/output results are provided in this paper.

High efficiency soft-switching 3-phase PWM rectifier

Abstract: A new soft switching 3-phase PWM rectifier with simple circuit configuration and high efficiency has been developed. The proposed circuit is a kind of auxiliary resonant commutated pole (ARCP) converter. The conventional ARCP converter requires 3 auxiliary reactors and 6 auxiliary switches for the soft switching auxiliary circuit and for these switching elements, a gate drive circuit and a control circuit are required, resulting in high part count as a disadvantage. In the main circuit proposed in this paper, the auxiliary soft switching circuit is composed of 2 auxiliary reactors, 2 auxiliary switches and several diodes. In addition, common use of the PWM control circuit for 2 switches will make the control circuit of the auxiliary switches simple. By means of function of the soft switching auxiliary circuit, the main switching element performs zero voltage switching operation and the auxiliary switches performs the zero current switching. In this paper, the circuit configuration and the operational analysis of the proposed circuit are described at first and then experimental results are reported. By using a prototype with 5 kW capacity, a conversion efficiency of maximum 98.8% and a power factor of 99% or higher were obtained.

A regenerative cell with reduced input current harmonics for multilevel inverters

Abstract: This work presents a basic unit for a medium voltage multilevel inverter, capable of regeneration of power from the load to the three-phase source. This basic cell uses a single-phase PWM rectifier to reduce the input current harmonics. The work is focused on the control, modeling and simulation of the regenerative cell, which generates practically sinusoidal currents at the output and at the input and works with near unity power factor. Experimental results obtained in the series parallel connection of two regenerative cells confirm the simulation studies.

Three-phase PWM voltage source rectifier with a reduced number of switches

Abstract: This paper deals with the analysis of three-phase PWM voltage source rectifiers with reduced number of active switches. The main contribution of this paper is to simplify the control system and to minimize the number of active switches used in the standard three-phase-three-pole and three-phase-four-pole topologies of a PWM rectifier. The popular topologies with reduced number of switches are given. A new topology of three-phase-four-pole PWM voltage source rectifier is proposed. The proposed topology uses only four active switches (IGBTs). The new rectifier topology is analyzed and its performance is compared with a standard topology of the PWM rectifier. To improve the performance of the proposed new topology and to minimize the content of even harmonics in the supply current /spl pi//2 symmetry is introduced in its carrier based PWM current controller (used for generation of switching signals). The new rectifier topology is tested for different steady state and transient operating conditions of the load to establish performance and design criteria. Key results are given.

PWM inverter harmonic correction topologies for three-phase diode rectifiers

Abstract: The functional operation of a range of harmonic correction topologies are described that draw sinusoidal AC supply currents using filter inductor sizes typically in the range 0.02 to 0.06 pu. The PWM inverter cell used in each of the various topologies can be operated with current ratings around 0.3 to 0.5 pu as compared with 1 pu for a standard PWM rectifier. The various topologies described have a range of potential advantages, such as: (a) low per-unit current ratings, (b) low dv/dt stresses between the rectifier DC link and the AC supply, (c) control of the rectifier output voltage and rectifier DC-link currents, (d) can be placed on top of a standard diode rectifier configuration, (e) balanced supply currents when the supply voltage is unbalanced, (f) bidirectional power flow, and (g) functionally equivalent structures using either AC or DC diode rectifier inductors. The features of the various topologies are illustrated using both circuit waveforms and performance curves.

Research on Main Circuit Parameters Selection of Single-Phase PWM Rectifier

Abstract: A selection method for AC and DC filter parameters of single phase PWM rectifier is analyzed and given Simulation has been done for unity and non unity power factor with DC voltage higher than AC peak voltage The results have shown the parameter selecting method is effective and the AC current can also be controlled when DC voltage is higher than AC peak voltage

A novel line synchronisation method for PWM rectifiers-theory and application

Abstract: A control method has been described that allows a standard AC motor drive to be used as a PWM rectifier without additional hardware. By using the PWM modulator output voltage to give indirect supply voltage sensing, phase information is available at every sample. When used with a PLL, this gives robust line synchronisation as has been demonstrated. Pre-start tests, required to pre-load various parts of the control system when starting, have been described and proven to give excellent supply synchronisation. Field experience with systems up to 1 MW has shown the method to be very reliable.

Techniques for attaching a low per-unit current harmonic correction PWM inverter cell to the input stage of an industrial drive

Abstract: This paper compares and contrasts the functional operation of a range of harmonic correction circuit topologies using a three-phase PWM bridge that draws low distortion AC supply currents and that can be attached to diode rectifiers in standard industrial drive systems using inductor sizes with a per-unit impedance in the range 0.01 to 0.05 pu. The three-phase PWM bridge used are operated with current ratings around 0.2 to 0.4 pu as compared with 1 pu for a standard PWM rectifier. The harmonic correction topologies considered have a range of potential advantages, such as: (a) low /sup dv///sub dt/ stresses between the rectifier output terminals and the AC supply neutral; (b) controlled rectifier output voltage; (c) can be placed on top of a diode rectifier operating at the standard output voltage; (d) balanced supply currents with an unbalanced ac supply voltage; and (e) bidirectional power flow. The relative advantages and disadvantages of each topology ore described together with appropriate current control techniques. SPICE simulations are used to obtain performance curves and to investigate the operation of novel circuit topologies.

A novel switching regulator with active commutation PWM rectifier

Abstract: This paper presents a new prototype of phase-shifted transformer parasitic components-assisted ZVS-PWM DC-DC converter with choke input type DC smoothing filter which incorporates ZCS active power switches in series with each rectifier diode in high-frequency transformer secondary-side. This efficient DC-DC converter with a wide ZVS operation ranges which is suitable for high-power applications can achieve soft-switching operation under a condition of no circulating current. Its operating principle and unique features are described. The steady-state operating characteristics of the proposed DC-DC converter topology are illustrated and discussed on the basis of the simulation and some experimental results of 2 kW-40 kHz breadboard set up.