Showing papers on "PWM rectifier published in 1999"

Status of the techniques of three-phase rectifier systems with low effects on the mains

Abstract: Based on a comprehensive study of the literature, concepts of three-phase rectifier systems with low effects on the mains are classified. Such systems are unidirectional and bidirectional self-commutated power converters with impressed output voltage or output current and line-commutated rectification in connection with passive and active filtering. Selected circuit concepts are analyzed concerning the operational behavior and the obtainable quality of the mains current. Furthermore, an evaluation of the rectifier concepts concerning utilization of the power semiconductors, rated power of the inductive and capacitive components and of the realization effort in general is given. Finally, problems of the practical application of high switching frequency PWM rectifier systems and topics of further research are discussed.

DC ripple current reduction on a single-phase PWM voltage source rectifier

Abstract: A novel topology of single-phase pulsewidth modulation (PWM) voltage-source rectifier capable of achieving not only a sinusoidal input current, but also a zero-ripple output current, is presented. The rectifier consists of a conventional single-phase PWM voltage-source rectifier, a pair of additional switches and an inductor. Hence, the proposed rectifier requires neither a large DC capacitor nor a passive L-C resonant circuit. The input current control is achieved by the conventional PWM current control technique. However, DC ripple current reduction control is difficult because one of the switching legs in the DC ripple current reduction circuit is shared with the PWM rectifier circuit. Two control methods, referred to here as the DC C inductor method and the AC inductor method, are proposed for DC ripple reduction, and the characteristics of these control methods are discussed. These control methods are implemented using a microprocessor, and the effectiveness of the circuit is confirmed experimentally. This rectifier has useful applications in uninterruptible power systems and DC power supplies, especially for cases in which the batteries are connected in parallel to the DC line.

VIENNA rectifier II-a novel single-stage high-frequency isolated three-phase PWM rectifier system

Abstract: Based on an analysis of basic realization possibilities, the structure of the power circuit of a new single-stage three-phase boost-type pulsewidth modulated (PWM) rectifier system (VIENNA Rectifier II) is developed. This system has continuous sinusoidal time behavior of the input currents and high-frequency isolation of the output voltage, which is controlled in a highly dynamic manner. As compared to a conventional two-stage realization, this system has substantially lower complexity and allows the realization of several isolated output circuits with minimum effort. The basic function of the new PWM rectifier system is described based on the conduction states occurring within a pulse period. Furthermore, a straightforward space- vector-oriented method for the system control is proposed which guarantees a symmetric magnetization of the transformer. Also, it makes possible a sinusoidal control of the mains phase currents in phase with the associated phase voltages. By digital simulation, the theoretical considerations are verified and the stresses on the power semiconductors of the new converter system are determined. Finally, results of an experimental analysis of a 2.5-kW laboratory prototype of the system are given, and the direct startup and the short-circuit protection of the converter are discussed. Also, the advantages and disadvantages of the new converter system are compiled in the form of an overview.

Minimum-loss strategy for three-phase PWM rectifier

Abstract: In this paper, the conduction and switching losses of a voltage-fed three-phase pulsewidth modulation (PWM) rectifier are analyzed for various PWM schemes. On the basis of this result, a novel PWM strategy which minimizes the loss of a three-phase PWM rectifier is developed. This minimization result is derived from the following two factors: (1) less switching frequency ratio; and (2) the absence of switching in the vicinity of peak input current. As a result, it is anticipated that the switching loss of the rectifier is reduced by 46%, compared with continuous space-vector PWM rectifiers, and 20% compared with conventional discontinuous space-vector PWM rectifiers. Moreover, the proposed PWM scheme can produce the highest available output voltage because it is based on the concept of the voltage space vector. The effectiveness of the proposed PWM strategy is verified by experiments.

A fuzzy-controlled active front-end rectifier with current harmonic filtering characteristics and minimum sensing variables

Abstract: A control strategy which allows conventional voltage-source current-controlled (VSCC) pulsewidth modulation (PWM) rectifiers to work simultaneously as active power filters is presented. The proposed control strategy also allows compensating the system power factor and compensating unbalanced loads. The measurement and/or calculation of the harmonics and reactive power are not required, making the proposed control scheme very simple. The active front-end rectifier acts directly on the mains line currents, forcing them to be sinusoidal and in phase with the mains voltage supply. To improve the dynamic of the system, the amplitude of the current is controlled by a fuzzy system, which adjusts the DC-link voltage of the PWM rectifier. The strategy is based on connecting all the polluting loads between the PWM rectifier and their input current sensors. The main advantages of this approach are the following: (1) there is no need to install a specially dedicated active power filter; (2) it also works simultaneously as a power factor compensator; and (3) no special and complicated calculations are required for harmonic elimination. The viability of the proposed active front-end rectifier is proved by simulation and with experimental results obtained from a 2 kVA PWM prototype.

Performance improvement of half controlled three phase PWM boost rectifier

Abstract: The potential of the half-controlled three-phase pulse-width modulated (PWM) boost rectifier is investigated based on theoretical analysis, simulations and experiments. The main advantages of this rectifier are: (1) a simpler and economical system compared to a full controlled PWM rectifier (reduced controlled switch count, single power supply for gate drives, and shoot-through free leg structure); and (2) better performance compared to a diode rectifier (actively controllable DC link voltage and lower input current total harmonic distortion (THD)). In particular, it is shown in this paper that the input current THD of this rectifier can be reduced by intentionally introducing a lagging power factor current command. Several issues for further performance improvement are pointed out for future work.

Comparison of not synchronized sawtooth carrier and synchronized triangular carrier phase current control for the VIENNA rectifier I

Abstract: Integrated control circuits being available for the input current control of single-phase power factor correctors are frequently applied also for realizing a simple current control for each phase of a three-phase PWM rectifier system. There, the input currents are controlled independently although the three phases are mutually coupled, i.e., the sum of the phase currents is forced to zero for missing connections between the mains star point and the output voltage center point. However, ignoring of the coupling of the three phases results in increased amplitudes of harmonics with switching frequency and/or in a significantly higher ripple of the rectifier input current. This is shown in this paper by a detailed analysis of different current control concepts for a three-phase three-switch three-level boost-type PWM rectifier (VIENNA Rectifier I) with unity power factor. The theoretical considerations are verified by digital simulations and an experimental analysis of a laboratory prototype and are valid in general for three-phase boost-type voltage DC link PWM rectifier systems.

Single-phase three-level PWM rectifier

Abstract: This paper presents a new PWM control scheme for a single-phase three-level PWM rectifier to improve the power quality. A diode bridge with two power switches is adopted as a PFC circuit to achieve a high power factor and low harmonic distortion. The control scheme is based on a look-up table with hysteresis current controller (HCC). Based on the proposed control scheme, the line current is driven to follow the sinusoidal current command which is in phase with the supply voltage. The software simulation and experimental results are shown to verify the proposed control scheme. It is shown that the measured line current harmonics and power factor satisfy the IEC 1000-3-2 requirements.

A new switching loss reduced discontinuous PWM scheme for a unidirectional three-phase/switch/level boost-type PWM (VIENNA) rectifier

Abstract: In this paper the applicability of discontinuous modulation for a three-phase/switch/level PWM rectifier system is investigated. As an analysis of the voltage formation of the system shows, the clamping in intervals (in each case, of one bridge leg to one bus of the DC output circuit) being characteristic for discontinuous modulation can occur in regions lying symmetrically around the maxims of the related phase currents. This results in a maximum reduction of the switching power loss. The increase of the effective pulse frequency (as compared to continuous modulation for equal switching losses) made possible thereby is calculated analytically. Furthermore, by digital simulation the RMS value of the mains current harmonics resulting for discontinuous modulation and increased pulse frequency is determined in dependency on the modulation depth. Also, it is compared to the harmonic characteristic for harmonic optimal continuous modulation. The load on the power semiconductors and on the output capacitors (characterized by the RMS value and the amplitude of the low-frequency harmonics of the capacitor current) is included into the comparison of the modulation methods. Finally, the time shape of the phase modulation functions (to be provided for the control of the voltage formation of the system based on a subharmonic oscillation method) for discontinuous modulation is calculated and the control of the potential of the output voltage center point is discussed.

An evaluation of the DC-link capacitor heating in adjustable speed drive systems with different utility interface options

Abstract: In this paper, an evaluation of DC-link capacitor heating in adjustable speed drive systems with different utility interface options is presented. The evaluation is based on the level of ripple currents DC-link capacitors can endure that lead to self-heating and reduction of capacitors' operating life. Three popular utility interface options for ASD systems are considered for evaluation. First, a standard six-pulse diode rectifier with and without DC-link inductor is examined. Second, an active PWM rectifier, which draws nearly sinusoidal current from the utility, is studied. Third, an auto-connected 12-pulse rectifier system for utility interface is analyzed. A new term capacitor heating factor (CHF) based on the dependence of ESR on frequency is introduced and is computed for various utility interface options and the results are compared. A mathematical procedure is outlined to analytically compute the capacitor ripple current and hence heating. Simulation and experimental results are presented to verify analytical calculation. Finally, a relative comparison of capacitor heating as a function of utility interface options is presented.

Near unity input displacement factor for current source PWM drives

Abstract: A simple control scheme for near unity input displacement factor (IDF) operation of the three phase current source type PWM rectifier is proposed. The rectifier is operated by a conventional selective harmonic elimination pattern with 420 Hz switching frequency, which is feasible for GTO switches used in high power applications. The article includes a description of the proposed control scheme, IDF compensation limitations based on power circuit components, and simulation results for steady state and transient conditions. We also investigate the IDF values for PWM CSRs with various control strategies supplying CSI based AC drives with different types of industrial loads. Based on the results presented, a power factor correction scheme may not be necessary for a CSR-CSI AC drive supplying a particular type of load. Experimental results on a 10 kVA GTO PWM rectifier are included to confirm the feasibility of the proposed scheme for high power applications.

PWM rectifier using indirect voltage sensing

Abstract: A voltage source PWM converter can be used as the input stage to a four-quadrant variable-speed drive to give bidirectional power flow, and sinusoidal input currents with near unity power factor. The paper describes a method for line synchronisation and control of a PWM rectifier which uses indirect supply voltage sensing and gives fast update of line voltage phase angle while rejecting distortion such as voltage notches. Indirect line voltage sensing allows the use of a standard AC motor drive as a PWM rectifier without additional hardware or line voltage connections. Details of the method used for synchronisation at start-up are given and experimental results demonstrating robust steady-state and dynamic performance are presented.

A novel control of three-phase PWM rectifier using single current sensor

Abstract: This paper proposes a control method for a three-phase PWM rectifier 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. The states of the rectifier switch are modified so that all phase currents can be reconstructed in a switching period although active vectors are applied only for a short time. Therefore, a novel current control using an adjustment scheme of the modulation signal for a three-phase PWM rectifier is discussed, and verified with the experimental results.

Single-phase three-level PWM rectifier with power-factor correction

Abstract: A novel control strategy for single-phase unidirectional switching-mode rectifier (SMR) that draws a sinusoidal line current in phase with the supply voltage is proposed and discussed in this paper In the adopted circuit topology, two AC power switches are placed between the AC side of the SMR and the center-tapped terminal of the DC-link capacitors The control schemes are based on the hysteresis current control (HCC) technique and the simple look-up table The control schemes, stored in a programmable array logic (PAL), are implemented such that the line current is driven to follow the current command There are three voltage levels (u DC , u DC /2, 0) on the AC side of the rectifier in each half cycle The blocking voltage of each AC power switch is clamping to half of the DC-link voltage Software simulations and experimental circuits are implemented and measured to verify the proposed control strategy

Characteristics of New Current Controlled PWM Rectifier-Voltage Source Inverter without DC Link Components for Induction Motor Drive

Abstract: The voltage-source inverters are normally equipped with an electrolytic capacitor in their DC link. The electrolytic capacitor has several disadvantage such as increasing size, limitting converter life and reliability. Therefore, several approaches for removing the DC link capacitor have been studied. This paper proposes a new strategy of the voltage source inverter without DC link components. To restrain the current resonance caused by LC filter of AC source side, rectifier of this inverter is controlled by current closed loop with di/dt feedback (di/dt; differenciation of AC source current). To improve AC source current waveform, feedback gain of di/dt and LC parameters are investigated by calculation for a 0.75kW induction motor driven by this inverter. Both the calculated and measured waveforms of AC source currents maintain nearly sinusoidal waveforms with a unity power factor.

Regulation and design issues of a PWM three-phase rectifier

Abstract: A PWM rectifier can serve as front end of a variable frequency converter to reduce harmonic content injection into an electric utility, or simply stand alone to provide VAr compensation. This paper demonstrates that a traditional induction machine field oriented control principle on a synchronous frame can be well adapted for the regulation of the rectifier. The difference in formulating the current PI regulator loops is pointed out. Practical operation limits and relationship among line voltage, line inductor and DC bus voltage are fully investigated along with experimental verifications. Other design considerations are summarized into conclusion. Although design and regulation principles are illustrated with a three-level neutral point converter, they are applicable to other conventional topologies as well.

Simplified control circuit of three phase PWM rectifier

Abstract: A new simplified control circuit for high performance three phase boost type PWM rectifier is presented. Based on the conception of vector control the AC vector processor (AD2S100) which serves for the AC motor vector control, is applied to high frequency rectification. Consequently, the control circuits are very much simplified. The transfer function of the system is deduced. The paper also presents a way to treat the nonlinear feature of the system. Simulation and experiment verified the proposed scheme.

A space vector modulation based hysteresis current controller for the PWM rectifier with voltage link

Abstract: A space vector modulation (SVM) based hysteresis current controller (HCC) for the PWM rectifier is proposed. This technique utilizes all advantages of the HCC and SVM technique. The controller determines a set of state space vectors from a region detector and applies a space vector selected according to the HCC. A set of state space vectors including the zero vector to reduce the number of switchings is determined from the output signals of three comparators. A simple hardware implementation is proposed and experimental results of the SVM-based HCC are also shown.

A new configuration of drive system for high speed gearless elevator

Abstract: In this paper, a new type of gearless traction machine drive system with a permanent-magnet (PM) motor for high speed elevators is presented. This application of a PM motor to the elevator traction machine enables several improvements including higher efficiency, greater ride comfort, and miniaturization and so on. A voltage-fed 3-phase PWM rectifier is also adopted so that DC bus voltage regulation, bi-directional power flow and controllable power factor with reduced input current harmonics are possible. To guarantee reliability of the whole system, the RC terminator at the motor side is designed for decreasing d/spl nu//dt ratio at motor terminal and then preventing insulation failure of the motor. Some experimental results of 240 m/min operation are given to verify the effectiveness of the proposed scheme.

Power source higher harmonic restraining equipment

Abstract: PROBLEM TO BE SOLVED: To miniaturize equipment and reduce carrier frequencies. SOLUTION: A phase is divided into sections every 60 degrees by a power source phase section determining part 32. When a phase voltage is positive, one of transistors 224a, 225a, 226a in transistors of a transistor module 22 for 3-phase pulse width modulation(PWM) rectifier circuit in a power source phase, wherein the absolute value of phase voltage in each section becomes maximum is fixed, and controlled in the state of on during the section. When a phase voltage is negative, one of transistors 224b, 225b, 226b is fixed and controlled, in the state of on during the section. As to the two left phase, the control amount due to the difference component between the command value of an input current to the transistor module 22 for the 3-phase PWM rectifier circuit, and the detected value is compared with a triangular wave carrier frequency waveform, and the transistor of each phase is on/off controlled by a PWM control part 34.

Study of power quality compensators in power system

Abstract: This paper discusses the different structures of power quality compensator (PQC), and mainly illustrates the influences on its voltampere (VA) rating and compensatory performance, which is exhibited under the condition that the AC input of main circuit's DC supply is extracted from the system or the load side. Meantime, the impacts on PQC are also analyzed when a three-phase rectifier or PWM rectifier is adopted as the DC supply. The simulation results verify the correctness of the theoretical analysis.

Implementation of nondeterministic PWM for inverter drives

Abstract: A single-phase power factor pre-regulator to improve the power quality in the input side of the AC/DC/AC converter and a random PWM to reduce the emitted acoustic noise and the mechanical vibration for induction motor drive is presented in this paper. The hysteresis current control (HCC) technique for a voltage source PWM rectifier is adopted. A control scheme is presented that ensures that the line current is driven to follow the reference current which is derived from the DC bus voltage regulator and the output power estimator. A random pulse position technique for a three-phase PWM inverter system for an induction motor control to reduce the annoying tonal noise and resonant vibration from AC machine drive is described. By randomly varying the instantaneous pulse position from one cycle to the next, the frequency distribution of harmonics is spread in a wide frequency range. The major advantage for using such a strategy is nonrepetitive output spectral characteristics, which results in reduction of torque pulsations in motor drive systems. Experimental results show the nearly unity power factor at the PWM rectifier and the absence of acoustic noise concentrated at the specific tones which is usually present with conventional sinusoidal modulation.

Characteristics of New Current Controlled PWM Rectifier-Voltage Source Inverter without DC Link Components for Induction Motor Drive

Abstract: The voltage-source inverters are normally equipped with an electrolytic capacitor in their DC link. The electrolytic capacitor has several disadvantage such as increasing size, limitting converter life and reliability. Therefore, several approaches for removing the DC link capacitor have been studied. This paper proposes a new strategy of the voltage source inverter without DC link components. To restrain the current resonance caused by LC filter of AC source side, rectifier of this inverter is controlled by current closed loop with di/dt feedback (di/dt; differenciation of AC source current). To improve AC source current waveform, feedback gain of di/dt and LC parameters are investigated by calculation for a 0.75kW induction motor driven by this inverter. Both the calculated and measured waveforms of AC source currents maintain nearly sinusoidal waveforms with a unity power factor.

A current-driven PWM rectifier for DC power systems

Abstract: A novel PWM AC-DC converter is proposed, based on a 'current source inverter' topology, for use as a bulk supply source for DC power reticulation systems. The switching control is based on a modified space vector modulation technique, using twelve nonzero space vectors rather than the usual six. Control of DC side voltage is accomplished in discrete time at the converter switching frequency, using a minimum-time approach for high performance. The discrete-time controller provides voltage commands to the converter, which determines a PWM switching sequence for the next sample period. Performance of the converter is demonstrated in simulations.