Implementation of a three-level rectifier for power factorcorrection

In this paper, a new single-phase switching mode rectifier (SMR) for three-level pulse width modulation (PWM) is proposed to achieve high input power factor, low current harmonics, low total harmonic distortion (THD) and simple control scheme. The mains circuit of the proposed SMR consists of six power switches, one boost inductor, and two DC capacitors. The control algorithm is based on a look-up table. There are five control signals in the input of the look-up table. These control signals are used to control the power flow of the adopted rectifier, compensate the capacitor voltages for the balance problem, draw a sinusoidal line current with nearly unity power factor, and generate a three-level PWM pattern on the AC side of adopted rectifier. The advantages of using three-level PWM scheme compared with two-level PWM scheme are using low voltage stress of power switches, decreasing input current harmonics, and reducing the conduction losses. The performances of the proposed multilevel SMR are measured and shown in this paper. The high power factor and low harmonic currents at the input of the rectifier are verified by software simulations and experimental results from a laboratory prototype     

Programmable PFC based hybrid multipulse power rectifier for ultra clean power application

A novel hybrid three-phase rectifier is proposed. It is capable to achieve high input power factor (PF) and low total harmonic input currents distortion (THD/sub I/). The proposed hybrid high power rectifier is composed by a standard three-phase six-pulse diode rectifier (Graetz bridge) with a parallel connection of single-phase Sepic rectifiers in each three-phase rectifier leg. Such topology results in a structure capable of programming the input current waveform and providing conditions for obtaining high input power factor and low harmonic current distortion. In order to validate the proposed hybrid rectifier, this work describes its principles, with detailed operation, simulation, experimental results, and discussions on power rating of the required Sepic converters as related to the desired total harmonic current distortion. It is demonstrated that only a fraction of the output power is processed through the Sepic converters, making the proposed solution economically viable for very high power installations, with fast investment payback. Moreover, retrofitting to existing installations is also feasible since the parallel path can be easily controlled by integration with the existing dc-link. A prototype has been implemented in the laboratory and it was fully demonstrated to both operate with excellent performance and be feasibly implemented in higher power applications.     

Single-phase integrated power quality compensator based oncapacitor-clamped configuration

A control scheme of an integrated power quality compensator, which employs an active rectifier to work simultaneously as an active power filter (APF) to decrease current harmonics, is proposed. The employed rectifier is based on a capacitor-clamped configuration to produce multilevel pulsewidth modulation waveforms which result in low voltage stress and low conduction loss on the power switches. The proposed active rectifier is controlled to track the supply current to be a sinusoidal wave with low current harmonics. The advantages of the proposed control scheme are high power factor, low current harmonics, no complicated calculations for current harmonics elimination, and no dedicated APF needed for harmonic elimination. The experimental results are used to verify the validity and effectiveness of the proposed control scheme     

Digitally controlled high power switch-mode rectifier

High power switch-mode rectifiers offer advantages over conventionally used line-commutated thyristor rectifiers in terms of size and cost. This paper describes operation of the high power switch-mode rectifier based on an original control strategy which is digitally implemented. The rectifier is operated in a constant output current mode. The control strategy provides a fast transient response to disturbances and achieves equal current sharing between the buck converter modules which are paralleled within the switch-mode rectifier. Equal current sharing is maintained in steady-state as well as in transient operation. The paper demonstrates that the transient response to load disturbances achievable with the proposed control strategy is superior to the response obtained with the conventional control strategy in terms of the output current overshoot and the settling time. The control algorithm is digitally implemented on a DSP/FPGA based digital control platform and its performance is verified on a 2 kW scaled-down experimental setup of the switch-mode rectifier.     

A unity power factor PWM rectifier with DC ripple compensation

This paper presents a new topology for a pulsewidth modulation (PWM) rectifier which achieves unity power factor on the AC supply side and ripple reduction on the DC output side. The main circuit of this rectifier consists of a conventional PWM rectifier and a pair of additional switches. The switches and PWM rectifier are controlled such that the ripple current on the DC line is reduced, and unity power factor is achieved on the AC line. As a result, this circuit does not require a large DC capacitor or a passive LC resonant circuit. Furthermore, control of the additional switches and PWM rectifier requires only a simple control circuit. The effectiveness of this circuit was confirmed by experiments and analysis. The rectifier is useful for uninterruptible power systems (UPSs) and DC power supplies, especially for cases in which batteries are connected to the DC line     

Single-phase high power factor pre-regulator with three-level modulation scheme

A control scheme for the single-phase three-level pulse-width modulation active rectifier is proposed. A hysteresis current control scheme is used to draw the sinusoidal line current in phase with the mains voltage. The line current command is derived from a voltage controller and a phase-locked loop circuit. The blocking voltage of each power device is clamped to half of the DC-link voltage in the proposed active rectifier. In order to generate the three-level voltage pattern on the DC side of the active rectifier, the region detector of the line voltage, capacitor voltage compensator and hysteresis current comparator are employed in the adopted control algorithm to achieve high input power factor and low current distortion. To investigate the proposed control algorithm, the adopted rectifier is simulated and experimental tests from a laboratory prototype undertaken.     

三相整流桥直流侧和交流侧并联型有源电力滤波器比较研究

三相直流侧和交流侧有源电力滤波器均可用于三相不可控整流桥的谐波治理。从谐波补偿效果、有源滤波器的补偿容量、开关应力三个方面对二者进行了分析和对比。分析结果表明,由于直流侧有源电力滤波器并联在整流桥的直流侧,在换相处的负载电流变化率比交流侧小得多,因此直流侧有源电力滤波器的补偿性能优于交流侧有源电力滤波器。同时由于直流侧有源电力滤波器工作在电压电流两个象限,因此其补偿容量和开关应力远小于交流侧有源电力滤波器。     

A multilevel buck converter based rectifier with sinusoidal inputs and unity power factor for medium voltage (4160-7200 V) applications

A novel rectifier topology for high power (0.5 to 10 MVA) current source based AC motor drives is proposed. This rectifier is composed of a multi-winding transformer, a multi-level diode rectifier and a modified multi-level buck converter. The rectifier produces near unity input power factor and sinusoidal input current under any operating conditions. In addition, the proposed rectifier features reliable operation and low manufacturing cost. In this paper, the operating principle of the proposed rectifier is introduced. A number of design issues are investigated, which include PWM switching patterns, input power factor and line current harmonic distortion. Some design considerations such as the effect of the line inductance discrepancy on system performance are addressed. Experiments on a 5 kVA/208V four-level prototype are carried out for verification.     

A new control scheme for single-phase PWM multilevel rectifier withpower-factor correction

A new control scheme for a single-phase bridge rectifier with three-level pulsewidth modulation is proposed to achieve high power factor and low current distortion. The main circuit consists of a diode-bridge rectifier, a boost inductor, two AC power switches, and two capacitors. According to the proposed control scheme based on a voltage comparator and hysteresis current control technique, the output capacitor voltages are balanced and the line current will follow the supply current command. The supply current command is derived from a DC-link voltage regulator and an output power estimator. The major advantage of using a three-level rectifier is that the blocking voltage of each AC power device is clamping to half of the DC-link voltage and the generated harmonics of the three-level rectifier are less than those of the conventional two-level rectifier. There are five voltage levels (0, ±V_DC/2, ±V_DC) on the AC side of the diode rectifier. The high power factor and low harmonic currents at the input of the rectifier are verified by software simulations and experimental tests     

基于智能整流技术的电网电流谐波补偿方法研究

目前用于电网电流谐波补偿的电器设备,主要以PWM整流器为主。基于PWM整流器的电源产品只能被动地减小自身向电网输出的谐波电流,而对电网中业已存在的电流谐波污染束手无策。为了解决电网中电流谐波污染以及相关联的电压波形失真问题,采用基于SRM(智能整流模块)技术对电网电流谐波进行补偿。仿真结果表明,基于SRM的电力电子装置在从电网吸取电流并在向负载供电的同时,还能对电网电压的波形进行补偿,使电网电压波形接近正弦波形。     

Integrated active rectifier and power quality compensator withreduced current measurement

This paper describes a three-phase integrated active rectifier and shunt power quality compensator (IPQC). The measurement of only three currents is required, and the control algorithm can be implemented using a low-cost controller. The IPQC improves the harmonic content of the supply current, displacement power factor, supply current balance, and can serve as a four-quadrant active rectifier for motor drives and other DC-link loads. The operation of the IPQC is experimentally verified using a conventional three-phase insulated gate bipolar transistor voltage-source inverter. A low-cost fixed-point DSP-based controller with fixed-band hysteresis current regulation is used for the implementation of the control algorithms     

A modified boost rectifier for elimination of circulating current in power factor correction applications

This paper develops a modified AC/DC boost rectifier for power factor correction applications. The developed rectifier topology uses fewer devices compared to semi-bridgeless type boost rectifiers, and the overall efficiency is increased due to the elimination of the circulating current provided by the inductors. Moreover, it achieves a higher power factor and better total harmonic distortion (THD) in high load conditions. The performance of the developed topology was evaluated and verified by means of simulation and hardware experimental results.     

Reversible unity power factor step-up/step-down AC-DC convertercontrolled by sliding mode

A reversible step-up/step-down AC-DC converter is presented in this paper. It is a fifth-order system, capable of managing power transfer from a DC source to an AC one, with any ratio between the DC and the AC voltage levels, and producing a sinusoidal output current, using only one power processing stage. By reversing the energy flow this circuit becomes a high power factor rectifier. This reversion can be obtained simply by inverting the reference AC current. The system is analyzed as the connection of two independent lower order subsystems, controlled by sliding mode with decentralised switching scheme. Experimental results from a 100 W prototype operating in both senses, as inverter and as rectifier, are shown to confirm the mathematical analyses and simulations     

A single-phase capacitor clamped converter operated simultaneously as a PWM rectifier and an active power filter

A control scheme is proposed that employs an active rectifier to work simultaneously as an active power filter to decrease current harmonics. The adopted capacitor clamped rectifier is controlled to draw a sine wave line current with low current harmonics. A voltage controller, three capacitor voltage compensators and one current controller are used in the proposed control algorithm to achieve a constant DC bus voltage, balanced capacitor voltages and line current tracking. The validity of the proposed system is proved by the results of computer simulations and experimental tests.     

Modeling and analysis of a digitally controlled high power switch-mode rectifier

A recently proposed high power switch-mode rectifier topology offers advantages over the conventional line-commutated thyristor rectifiers in terms of size and cost. This paper presents modeling and analysis of the high power switch-mode rectifier configuration, operated under a newly developed digital control strategy. The developed strategy provides a fast transient response to disturbances and achieves equal current sharing between the buck converter modules which are paralleled within the switch-mode rectifier. A continuous-time state-space model of the switch-mode rectifier and analyses of both the steady-state and the transient operation modes of the digitally controlled rectifier are presented. The continuous-time model is used as a basis for time-domain simulations of the rectifier's behavior in the MATLAB/Simulink environment. The validity of the presented model is demonstrated based on comparison between the simulation results and the corresponding experimental results. The experimental results are obtained from a 2-kW scaled-down laboratory setup of the rectifier. The stability of the digitally controlled rectifier system is also examined based on an overall small-signal sampled-data model of the rectifier system including the controls.     

A clean four-quadrant sinusoidal power rectifier using multistage converters for subway applications

A special 27-level four-quadrant rectifier for subway applications is analyzed. The arrangement uses only three H-bridges per phase, common dc bus, and independent input transformers for each H-bridge. The transformers allow galvanic isolation and power escalation to obtain high-quality voltage waveforms, with total harmonic distortion of less than 1%. Some advantages of this 27-level rectifier are: 1) only one of the three H-bridges, called the main converter, manages more than 80% of the total active power in each phase and 2) it switches at fundamental frequency, reducing the switching losses at a minimum value. The rectifier analyzed in this paper is a current-controlled voltage-source type, with a conventional feedback control loop. Some simulations in a rectifier substation, including power reversal at full load are displayed (750 Vdc, 1200 A). The rectifier shows the ability to produce clean ac and dc waveforms without any ripple, and fast reversal of power. Some experimental results with a small prototype, showing voltage and current waveforms, are finally displayed.     

Low-harmonic GTO converter for fundamental power factorcompensation

A low-harmonic GTO (gate turn-off) thyristor AC-to-DC converter with line current lead-lag phase shift control ability is proposed and analyzed. The converter can be used either as a low-harmonic GTO-controlled rectifier or a fundamental input power factor compensator in a power supply system. The effect of PWM (pulse width modulation) current phase number on the harmonic contents and converter output voltage control range is investigated. Lower order input current harmonics are eliminated over a wide range, using a specially designed PWM current pattern. The effect of the PWM current pulse number on the power factor compensation characteristic is investigated     

A novel active power filter for reactive power compensation and harmonic suppression

A new single-phase active power filter for reactive power compensation and harmonic suppression is proposed. Besides the general performance of other active power filters, it also has the feature that it can maintain the mains current as a sine-wave and correct the displacement power factor close to unity even when the mains voltage is distorted. A prototype of this active power filter is developed and tested under rectifier load to verify its performance. The test results show that the proposed scheme can compensate the reactive power and suppress harmonics of the nonlinear load effectively.     

Conduction power loss in MOSFET synchronous rectifier withparallel-connected Schottky barrier diode

The conduction power loss in an MOSFET synchronous rectifier with a parallel-connected Schottky barrier diode (SBD) was investigated. It was found that the parasitic inductance between the MOSFET and SBD has a large effect on the conduction power loss. This parasitic inductance creates a current that is shared by the two devices for a certain period and increases the conduction power loss. If conventional devices are used for under 1 MHz switching, the advantage of the low on-resistance MOSFET will almost be lost. To reduce the conduction loss for 10 MHz switching, the parasitic inductance must be a subnanohenley     

A new single-phase ZCS-PWM boost rectifier with high power factor and low conduction losses

This paper proposes a new single-phase high-power-factor rectifier, which features regulation by conventional pulsewidth modulation (PWM), soft commutation, and instantaneous average line current control. A new zero-current switching PWM (ZCS-PWM) auxiliary circuit is configured in the presented ZCS-PWM rectifier to perform ZCS in the active switches and zero-voltage switching (ZVS) in the passive switches. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZCS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved because of the following reasons: 1) the circulating current for the soft switching flows only through the auxiliary circuit; 2) a minimum number of switching devices are involved in the circulating current path; and 3) the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Seven transition states for describing the behavior of the ZCS-PWM rectifier in one switching period are described. The PWM-switch model is used to predict the system performance. A prototype rated at 1 kW, operating at 60 kHz, with an input alternating current voltage of 220 V/sub rms/ and an output voltage of 400 V/sub dc/, has been implemented in laboratory. An efficiency of 98.3% and a power factor over 0.99 have been measured. Analysis, design, and the control circuitry are also presented in this paper.