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     

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     

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     

A Complete Harmonic Elimination Approach to DC Link Voltage Balancing for a Cascaded Multilevel Rectifier

This paper presents a complete method that is used to balance dc link voltages in a cascaded H-Bridge (CHB) multilevel rectifier. Recently, such converters have been the subject of extensive research due to their suitability for high-power applications. One requirement in using a multilevel active rectifier at high levels of power is to limit the switching losses by reducing the switching frequency to a minimum. Another requirement for these converters is to ensure that individual dc link capacitor voltages for each cell of the converter are always balanced to ensure controllability and to limit stress on the converter cells. This paper presents a complete method in solving both of these problems using a selective-harmonic-elimination pulsewidth-modulation scheme. The scheme utilizes a simple controller to track each cell dc link capacitor voltage magnitude and accordingly biases the power flowing into each cell to ensure that the voltages across each cell capacitor converge. This is the case even when the loads attached to the individual cells are not balanced. The theory is supported by both simulated results from Saber and by experimental results from a seven-level CHB single-phase multilevel rectifier.     

Characteristics of load resonant converters operated in ahigh-power factor mode

The performance of the parallel resonant power converter and the combination series/parallel resonant power converter (LCC converter) when operated above resonance in a high power factor mode are determined and compared for single phase applications. When the DC voltage applied to the input of these converters is obtained from a single phase rectifier with a small DC link capacitor, a relatively high power factor inherently results, even with no active control of the input line current. This behavior is due to the pulsating nature of the DC link and the inherent capability of the converters to boost voltage during the valleys of the input AC wave. With no active control of the input line current, the power factor depends on the ratio of operating frequency to tank resonant frequency. With active control of the input line current, near-unity power factor and low-input harmonic currents can be obtained     

A Novel High-Power-Density Three-Level LCC Resonant Converter With Constant-Power-Factor-Control for Charging Applications

This paper proposes a variable-frequency zero-voltage-switching (ZVS) three-level LCC resonant converter that is able to utilize the parasitic components of the high turns-ratio transformer. By applying a three-level structure to the primary side, the voltage stress of the primary switches is half of the input voltage. Low-voltage MOSFETs with better performance can be used in this converter, and zero-current-switching (ZCS) is achieved for rectifier diodes. By applying a magnetic integration technique, only one magnetic component is required in this converter. The power factor concept of resonant converters is proposed and analyzed, and a novel constant power-factor control scheme is proposed. Based on this control strategy, the circulating energy of resonant converters is considerably reduced. High efficiency can be obtained for high-voltage high-power charging applications. The operation principle of the converter is analyzed and verified on a 700-kHz, 3.7-kW prototype, with which a power density of 72 ${hbox {W/inch}}^{3}$ is achieved.      

Unity power factor ZVS AC-to-DC converters with an active filter

Unity power factor zero-voltage-switched (ZVS) AC-to-DC power converters with an active filter are proposed. The line voltage is supplied to AC-to-DC power converters through a rectifier circuit with an input filter, to reduce high-frequency ripple components. The line current is almost synchronized to the line voltage, due to the low impedance of the input filter. Forward ZVS multiresonant power converters (ZVS-MRCs) are utilized for high-frequency operation and lossless switching. An active filter is introduced to minimize the twice line-frequency ripple component of the output voltage without large-size passive filters. Experimental results show that the proposed scheme gives good steady-state performances of the AC-to-DC power converters     

Improved light-load efficiency for synchronous rectifier voltageregulator module

DC/DC converter with high efficiency over a wide load range is necessary for many low voltage applications, such as battery supplied systems and micro-processor power supplies-voltage regulator module (VRM). In order to improve the efficiency of low voltage converters, synchronous rectifier technology is widely used. The disadvantage of this technology is low efficiency at light load. This paper proposes a new technology, which utilizes the duty cycle signal, to improve light load efficiency with simple implementation. Since current sensors are not required, high density and high efficiency can be achieved that makes the whole circuit suitable for integration. In the paper, two application examples are given. Experimental results verified that the proposed control schemes significantly improve the efficiency of synchronous rectifier buck converters at light load     

A novel control scheme for the multilevel rectifier/inverter

A novel three-level pulsewidth modulation (PWM) rectifier/inverter is proposed: this single-phase three-level rectifier with power factor correction and current harmonic reduction is proposed to improve power quality. A three-phase three-level neutral point clamped (NPC) inverter is adopted to reduce the harmonic content of the inverter output voltages and currents. In the adopted rectifier, a switching mode rectifier with two AC power switches is adopted to draw a sinusoidal line current in phase with mains voltage. The switching functions of the power switches are based on a look-up table. To achieve a balanced DC-link capacitor voltage, a capacitor voltage compensator is employed. In the NPC inverter, the three-level PWM techniques based on the sine-triangle PWM and space vector modulation are used to reduce the voltage harmonics and to drive an induction motor. The advantages of the adopted th-ree-level rectifier/inverter are (1) the blocking voltage of power devices (T1, T2, S_a1-S_c4) is clamped to half of the DC-link voltage, (2) low conduction loss with low conduction resistance due to low voltage stress, (3) low electromagnetic interference, and (4) low voltage harmonics in the inverter output. Based on the proposed control strategy, the rectifier can draw a high power factor line current and achieve two balance capacitor voltages. The current harmonics generated from the adopted rectifier can meet the international requirements. Finally, the proposed control algorithm is illustrated through experimental results based on the laboratory prototype.     

单周期控制三相电压型PWM整流器

文章对基于单周期控制的三相PWM高功率因数整流器进行了研究,推导了单周期控制三相电压型PWM整流器的控制规律。它不需要乘法器更不需要对输入电压进行检测,其控制逻辑简单并且以恒定频率工作,可以在每个开关周期控制输入电流跟踪正弦参考量,从而实现低电流谐波畸变和高功率因数。基于Multisim2001软件平台,建立了基于单周期控制的三相电压型PWM整流器的仿真模型,完成了6kW三相PWM整流器的设计和实验研究,仿真和试验结果都验证了理论分析的正确性。     

A Novel Driving Scheme for Synchronous Rectifiers in LLC Resonant Converters

This paper proposes a novel synchronous rectifier (SR) driving scheme for resonant converters. It is very suitable for high-frequency, high-efficiency, and high-power-density dc–dc resonant converters with SRs. In this paper, an LLC resonant converter with the proposed synchronous rectification is designed and analyzed. With the proposed driving scheme, the SR body diode conduction is reduced to almost zero. The driving scheme eliminates the reverse-recovery problem of SRs. Both current and voltage stresses are greatly decreased, and the conduction loss and switching loss of SRs are also reduced considerably. The experimental results show that the proposed LLC resonant converter with SRs can achieve low stress, high efficiency, and high power density.      

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.     

Soft switching resonant converter with duty-cycle control in DC micro-grid system

Resonant converter has been widely used for the benefits of low switching losses and high circuit efficiency. However, the wide frequency variation is the main drawback of resonant converter. This paper studies a new modular resonant converter with duty-cycle control to overcome this problem and realise the advantages of low switching losses, no reverse recovery current loss, balance input split voltages and constant frequency operation for medium voltage direct currentgrid or system network. Series full-bridge (FB) converters are used in the studied circuit in order to reduce the voltage stresses and power rating on power semiconductors. Flying capacitor is used between two FB converters to balance input split voltages. Two circuit modules are paralleled on the secondary side to lessen the current rating of rectifier diodes and the size of magnetic components. The resonant tank is operated at inductive load circuit to help power switches to be turned on at zero voltage with wide load range. The pulse-width modulation scheme is used to regulate output voltage. Experimental verifications are provided to show the performance of the proposed circuit.     

A Family of Interleaved DC–DC Converters DeducedFrom a Basic Cell With Winding-Cross-CoupledInductors (WCCIs) for High Step-Upor Step-Down Conversions

A basic cell with winding-cross-coupled inductors (WCCIs) and interleaved structure is proposed in this paper. A family of dc–dc converters is deduced from the proposed basic cell, which is suitable for high step-up or step-down conversions. The passive-lossless clamp scheme is derived from the active clamp scheme to recycle the leakage energy and to suppress the voltage spikes caused by the leakage inductance. The advantages of the derived interleaved boost converter with WCCIs and passive-lossless clamp circuits are analyzed as an example. The voltage gain is extended and the switch voltage stress is reduced to minimize the conduction losses. The rectifier reverse-recovery problem is alleviated by the leakage inductance. Furthermore, a series of dc–dc converters with WCCIs and passive-lossless clamp circuits are summarized for high efficiency, high power and high step-up or step-down applications. A clear picture is made in this paper on the general law and structure of the WCCIs for dc–dc conversion in high step-up or step-down applications. At last, the simulated and experimental results of a 1 kW 40 V-to-380 V prototype with WCCIs and passive-lossless clamp circuits verify the significant improvements in performance.      

基于空间矢量调制三相电压型PWM整流系统的仿真

正弦脉冲宽度调制(SPWM)技术应用于传统的电压型PWM整流中,SPWM的控制波形可由相间解耦得到。然而,这个过程复杂且直流电压利用率很低。本文提出了一种在同步参考坐标下的三相电压模型的控制策略,空间矢量脉冲宽度调制(SVPWM)。整流器具有高质量的直流侧电压和功率因数。文章提供了MATLAB/SIMULINK的仿真模型。结果证实了模型的正确性及其控制方法。仿真结果表明,与传统的SPWM方法相比,这种方法能明显提高系统的动态性能。     

Novel zero-voltage and zero-current-switching (ZVZCS) full-bridge PWM converter using coupled output inductor

A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge pulse-width-modulated (PWM) converter is proposed to improve the previously proposed ZVZCS full-bridge PWM converters. By employing a simple auxiliary circuit with neither lossy components nor active switches, soft-switching of the primary switches is achieved. The proposed converter has many advantages such as simple auxiliary circuit, high efficiency, low voltage stress of the rectifier diode and self-adjustment of the circulating current, which make the proposed converter attractive for the high voltage and high power applications. The principles of operation and design considerations are presented and verified on the 4 kW experimental converter operating at 80 kHz.     

A High-Quality Rectifier Based on Sheppard–Taylor Converter Operating in Discontinuous Capacitor Voltage Mode

This paper presents a single-phase soft-switched high power factor (PF) Sheppard-Taylor rectifier suitable for applications requiring low-voltage and high-current output. The proposed rectifier is designed to operate at discontinuous capacitor voltage mode. The Sheppard-Taylor converter in this mode of operation provides zero-voltage turnoff switching, as well as natural input PF correction over a wide range of input voltage, which makes the converter suitable for universal input applications. Due to its simplified control circuitry and reduced switch current stress, this converter presents better efficiency and higher reliability. In addition, the presented converter features continuous input-output currents, which result in low electromagnetic interference emission. Principle of operation, theoretical analysis, and experimental results from a laboratory prototype rated at 45 W/10 Vdc output voltage are presented. The measured efficiency and total harmonic distortion of the input line current were 85% and 3.2%, respectively. The input current harmonics meet the EN61000-3-2 Class D requirements.     

Control techniques for a high power factor multilevel rectifier based on double boost converter

In this paper three novel control schemes for the single-phase ac/dc converter with two-level or three-level pulse width modulation are proposed to improve the power quality. A diode rectifier with two power switches is adopted as a power factor correction circuit to achieve high power factor and low harmonic distortion. The proposed control schemes are based on look-up tables with a hysteresis current controller instead of the conventional complex control algorithm. The proposed control scheme can (1) draw a sinusoidal line current, (2) achieve a unity power factor and (3) improve voltage unbalance problem on the dc bus capacitors. The software simulations and experimental results are shown to verify the proposed control algorithms. It is shown that the measured harmonic currents and input power factor satisfy the international standard requirements such as International Electrotechnical Commission 1000-3-2.     

Soft-switched DC/DC converter with PWM control

In this paper, a new power converter with two variations is proposed. A novel asymmetrical pulse-width-modulation (PWM) control scheme is used to control the power converter under constant switching frequency operation. The modes of operation for both variations are discussed. The DC characteristics, which can be used in the design of the power converters, are also presented. Two 50 W power converters were built to verify the characteristics of the converters. Due to the zero-voltage-switching (ZVS) operation of the switches and low device voltage and current stresses, these power converters have high full- and partial-load efficiencies. They are, therefore, potential candidates for high-efficiency high-density power supply applications     

Analysis and Implementation of a Hybrid High-Power-Factor Three-Phase Unidirectional Rectifier

This paper describes the conception and analysis of a unidirectional hybrid three-phase rectifier suitable for medium- and high-power applications. The rectifier is composed of a single-switch diode bridge boost-type rectifier in parallel with a pulsewidth modulation (PWM) three-phase unidirectional boost rectifier. The objective is to obtain a structure capable of providing sinusoidal input currents with low harmonic distortion and dc output voltage regulation. The diode rectifier operates at low frequency and has a higher output power rating. Therefore, the PWM unidirectional rectifier is designed to operate with a small power rating and at a high switching frequency. The total harmonic distortion of the proposed structure varies between 0% and 32%, depending only on the amount of power processed by the PWM three-phase unidirectional rectifier. The rectifier topology conception, principle of operation, control scheme, and simulation and experimental results of a 20-kW laboratory prototype are also presented in this paper.