Direct space vector PWM strategy for matrix converters with reduced number of switching transitions

This paper proposes a novel “Direct Space Vector PWM (Direct SVPWM)” strategy based on the direct AC/AC conversion approach for three‐phase to three‐phase matrix converters. This method allows the sinusoidal input and output waveforms as a major premise, and gives top priority to the improvement of output control performance in motor drive applications, such as providing maximum riding comfort in elevators, etc. Output voltage harmonics, switching losses, and common‐mode voltages can be reduced across the entire voltage region. In addition, the switching count can be reduced even further by fully utilizing the output current detection value. Direct space vectors are first defined, and the method of selecting space vectors is described. Next, the PWM duty calculation technique is explained. Finally, the validity of the proposed method is demonstrated by comparison with the conventional virtual indirect method based on experimental and analytical results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(3): 52–63, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20953     

A control method for the matrix converter based on virtual AC/DC/AC conversion using carrier comparison method

This paper proposes a novel control method based on the virtual AC/DC/AC conversion for the matrix converter. The virtual AC/DC/AC conversion method is a very simple strategy to control the input current and the output voltage for the matrix converter. There are two new topics proposed in this paper. First, this paper proposes the minimum switching loss modulation on the virtual rectifier. In our proposed modulation, only two arms switching in the virtual rectifier using DC link current control by the virtual inverter can obtain clean sinusoidal input current. Second, a novel lean controlled carrier modulation on the virtual inverter is proposed. The leans of the triangle carrier are controlled by the duty ratio of the rectifier side pulse. The lean controlled carrier reduces harmonic distortion of the input current by avoiding interference between the rectifier control and the inverter control. These new proposals are confirmed by simulation and experimental results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 65–73, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20144     

An investigation of methods to improve input/output waveforms in matrix converters

The matrix converter is a three‐phase AC‐to‐AC direct converter without any energy storage requirement such as DC link capacitors. However, the matrix converter has some practical problems such as the necessity for bidirectional power devices, necessity for special commutation sequence, and complexity of the control method. Thus, there are no practical systems in which matrix converters are used. In this paper, the control strategy for matrix converters with basic configuration is investigated so as to realize practical matrix converters. First, the necessity of the phase detector for the input voltage and the output current sensor is pointed out from the viewpoint of realization of the basic operation. With these sensors required in the basic configuration, the instantaneous control of the output current is realized. It is also pointed out that three‐phase switching is effective in improving the input current waveforms. Some methods for implementation of three‐phase switching are proposed. The effectiveness of the proposed control methods is confirmed by some experimental results employing a test system. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(4): 55–64, 2005; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20031     

基于补偿函数的SPWM矩阵变换器控制策略

应用矩阵变换器的交直交等效模型,在其交直和直交2个虚拟环节上,分别采用不控整流和SPWM2种简单易实现的调制方式。在三相输入电压对称或非对称的情况下,虚拟整流环节输出的是直流波动电压,为消除此直流波动电压对虚拟逆变环节SPWM调制输出的电压、电流波形的影响,利用开关函数概念推导了对SPWM的调制波进行补偿的补偿函数。其原理是通过向调制波中注入反极性的、幅值随直流波动电压瞬时值变化的正弦波来消除输出电压中的低次谐波。该方法同样适用于输入电压非对称的情况,而且其硬件实现电路简单。应用Matlab/Simulink进行了仿真,仿真结果表明在输入电压对称或非对称的情况下都能获得良好的输出电压波形,验证了所提控制算法的正确性。     

双级矩阵变换器的过调制策略

针对双级矩阵变换器常规调制策略电压传输比低的问题,在不改变双级矩阵变换器拓扑结构的前提下,该文提出了一种可以提高电压传输比的双级矩阵变换器调制策略。该调制策略将双级矩阵变换器分为两级控制：整流级采用常规电流空间矢量合成法;逆变级根据电压传输比的不同要求将电压空间矢量调制区域分为线性调制区和过调制区。根据过调制程度要求的不同,又将过调制区域分为过调制区域Ⅰ和过调制区域Ⅱ,各个区域分别采用不同的调制模式控制逆变级的输出。论文从理论上分析了过调制策略的原理。仿真和实验结果表明, 双级矩阵变换器过调制时输出电压基波可以精确控制,谐波畸变率比较小,输入输出电流波形质量好。     

PDM Control Method for a Matrix Converter Converting Several‐Hundred‐kHz Single‐Phase Input to Commercial Frequency Three‐Phase Output

This paper discusses pulse density modulation (PDM) control methods for a single‐phase to three‐phase matrix converter (MC) in high‐frequency applications. The proposed circuit is used as an interface converter for a wireless power transfer system. This converter can input a frequency of several hundred kilohertz and output a low frequency, that is, 50 Hz or 60 Hz, for a commercial power grid. The proposed circuit implements zero voltage switching (ZVS) operation by using PDM control methods and obtains high efficiency. In this paper, two PDM control strategies are compared: delta–sigma conversion and the PDM pattern generation method based on space vector modulation (SVM), which is proposed here. Also, the experimental results obtained with the proposed system will be presented and discussed. The total harmonic distortions (THDs) of the output voltage with delta–sigma conversion and the PDM pattern generation method based on SVM are found to be 5.96% and 2.15%, respectively. In addition, the maximum efficiencies with delta–sigma conversion and the PDM control based on SVM are 93.4% and 97.3%, respectively. From the results, the validity of the PDM control based on SVM has been confirmed for improvement of the output waveforms and reduction of the switching loss.     

A control method to realize sinusoidal input and output current waveforms for matrix converters based on PWM

A matrix converter (MC) is a three‐phase AC‐to‐AC direct converter without any energy storage requirement. It is expected to be a next‐generation converter by reason of possibilities of small size and high efficiency. At present, there are some problems preventing it from being used practically. One of the problems is the distortion in the input current. The control methods proposed so far have not realized sufficient reduction of the input current harmonics compared with conventional PWM rectifiers. As a solution to these problems, many approaches have been proposed. In the present paper, an improved PWM method that can achieve both sinusoidal input and output currents simultaneously is considered. In this method, the MC is treated as a controlled voltage source viewed from the load side. On the other hand, it is treated as a controlled current source viewed from the line side. The proposed control method is based on the mathematical expression of the function of the PWM operation of MC. To improve the input current waveform, two line‐to‐line voltages of the three‐phase line are used to control the output current. The output duty ratio of the two line‐to‐line voltages is utilized to improve the input current waveform without affecting the controllability of the output current. In addition, the compensation of the variations in the line voltage and the output current are introduced. In this way, the proposed method can realize the sinusoidal input and output currents. The effectiveness of the proposed control method is confirmed by some experimental results employing a laboratory prototype. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 66–76, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20242     

Matrix converter control using direct AC/AC conversion approach to reduce output voltage harmonics

This paper presents a control scheme for matrix converters for reducing the output voltage harmonics. The proposed control scheme is based on the direct AC/AC conversion approach and the carrier‐based PWM control to obtain the constant switching frequency. The proposed scheme can achieve simultaneous control of both the output voltage and the input power factor. A feature of the proposed control scheme is the reduction of both the output voltage harmonics and the number of instances of commutations. The effectiveness of the proposed control algorithm for a matrix converter has been verified by simulations. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(2): 61–72, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20550     

PWM control of three‐phase to three‐phase matrix converters for reducing the number of commutations

This paper presents a control scheme of three‐phase to three‐phase matrix converters for reducing the number of commutations. The number of commutations during a control period in the proposed control scheme can be reduced to three from four in the conventional control scheme. It can be realized by using the output currents in the calculations of the duty factors. As a result, one of the output line voltage waveforms during a control period consists of two voltage levels with the same sign of the reference. The switching loss and the output voltage harmonics can be reduced. The effectiveness of the proposed control algorithm of the matrix converters has been verified by experiments. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(2): 60–69, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20824     

基于双空间矢量调制的矩阵变换器-永磁同步电机矢量控制系统

结合永磁同步电机磁场定向控制的特点,将矩阵变换器用于永磁同步电机的调速系统,实现永磁电机的交交直接控制并且达到近似单位功率因数.首先阐述矩阵变换器双空间矢量调制的原理,输入侧采用电流空间矢量,输出侧采用电压空间矢量构建了矩阵变换器-永磁同步电机矢量控制系统;然后为了降低转矩脉动,加入电流补偿环节,文中给出了补偿环节的设计方法.原理样机试验结果表明,采用双空间矢量调制的矩阵变换器-永磁同步电机系统不仅达到了良好的控制效果与较好的网侧性能,而且电流补偿环节也是确实有效的.     

级联型逆变器的新型简化多电平空间矢量调制方法

传统多电平空间矢量调制(space vector modulation,SVM)方法需要大量的矢量选择等复杂运算,级联数目较高时,算法变得异常复杂而难以实现。该文借鉴载波移相调制的思想,提出一种新颖的基于两电平SVM的简化多电平SVM方法。将各级H桥逆变器施加相同幅值和相位的电压矢量,而将各自的电压矢量更新时间相互错开,进而形成相应的多电平输出电压波形。每个采样周期只需依据两电平SVM算法计算一单元的主、辅电压矢量及其作用时间,计算量与级联数目无关,进而显著简化了算法难度,并增强了可扩展性。三单元情况的仿真和实验结果证明了所提出方法的正确性和可行性。     

一种优化的级联型多电平拓扑及其实现

为减少独立直流电源数量,获得高质量的输出电压特性,提出了一种优化的级联型多电平拓扑结构。新型拓扑只需一个直流电源,采用了三相变压器。研究了新型拓扑的运行机理及输出特性。试验结果表明,提出的三相拓扑仅用9个H桥单元,就可获得13电平的输出相电压。与传统3种基本拓扑结构相比,不仅减少了元器件、直流电源的数量,降低了制造成本,而且改善了输出波形质量。即使在低调制因数下,其输出电压、电流性能也良好,适合在大功率及交流传动场合使用。     

基于逆阻式IGBT的三相/单相矩阵式变换器

针对三相/单相矩阵式变换器系统,提出一种平均电压脉宽调制方法,通过实时检测三相输入相电压,经过简单计算即可对输出进行正弦调制.采用新型开关器件逆阻式IGBT(RB-IGBT)实现了一台3kW的三相/单相矩阵式变换器样机,并针对RB-IGBT独特的漏电流特性,提出一种基于输入电压大小检测、适用于RB-IGBT的两步换流方法.实验结果表明,该样机可以实现正弦的输出波形.从而证明了本文提出的控制策略和换流方法的有效性和可靠性.     

A servo system of AC motor based on voltage modulation fitting for FPGA and consideration of voltage saturation

This paper proposes a space voltage vector modulation (SVM) method for a speed servo system to obtain a quick current response. The proposed SVM method shortens the control lag time of the conventional SVM inverter. In addition, this proposed method is easily implemented in hardware using an FPGA (Field Programmable Gate Array) because the proposed SVM equations are transformed into expressions that hardly need multiplication. By using the proposed SVM method, the servo system realizes quick and stable current control with wide bandwidth. Moreover, by using PI controllers considering the voltage saturation and the torque limiter to the speed servo system, the servo system carries out stable speed control on voltage saturation. Both the proposed SVM method and the PI controllers considering voltage saturation are applied to the speed servo system of a vector controlled induction motor. The effectiveness of both the proposed SVM method and the PI controllers considering voltage saturation is verified by the experimental results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 60–68, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20989     

改进矩阵变换器在非对称输入情况下的空间矢量调制策略

分析了基于空间矢量调制矩阵变换器在输入电压非对称时的输出电压谐波问题,提出了一种有效的改进措施,通过在虚拟整流空间矢量调制矢量中注入负序分量,使得输出电压的谐波含量和不对称性均得到明显改善。通过数值仿真验证了所提方法的正确性。     

Visualization of PWM Strategy for a Direct Matrix Converter During Input and Output Voltage Periods

This paper presents a visualization of the PWM strategy of a matrix converter during input and output voltage periods. General relations for the duty cycles based on the input current references and the output voltage references are derived. Because the input current references and the output voltage references are treated as continuous values in the time domain, the PWM strategy can be extended to the input and output voltage periods from the control period treated as constant values. At a low carrier frequency compared with the actual frequency, the PWM patterns that reduce the number of commutations for switching loss reduction can be visualized. The PWM strategy can be directly evaluated by using the waveforms of the input current and the output voltage. In the transient state with change of the output voltage reference, the output voltage and input current can be visualized. The effectiveness of the visualization of the PWM strategy has been verified by comparison with the experimental waveforms.     

A multilevel-voltage source rectifier with a three-phase diodebridge circuit as a main power circuit

A novel system obtaining very low distorted waveforms of input AC currents of three-phase rectifier circuits are proposed. The proposed rectifier system consists of a three-phase diode bridge circuit as a main power circuit, AC reactors, and an additional circuit which serves as an active filter with low switching frequencies and a forced-commutation circuit for the diodes. This paper describes the operation principle, analysis of the waveforms of input voltage and current, multiple phase-shifted systems, and the experimental results. The proposed system gives excellent input current waveforms and has many advantages over conventional systems     

一种提高矩阵变换器电压增益的空间矢量调制法

与传统的电压源型逆变器相比,矩阵变换器主要的缺点之一是在输入及输出电流为正弦时,输出输入电压传输比限制在0.866。为克服此缺点,在传统的矩阵变换器空间矢量调制方法的基础上,提出了一种提高电压增益的调制策略,进行了详细说明,概念清楚、控制简单,不需要复杂的数学计算。此调制策略没有使用零矢量,较传统方法换流数量减少,输出输入电压传输比提高到0.95以上,但输出电压及输入电流波形出现了一定程度的畸变。通过仿真证实了理论分析,也显示了此调制策略的优缺点。     

矩阵变换器在非对称输入情况下输出电压波形的改善

在非对称输入电压情况下,对基于双空间矢量调制的矩阵变换器的输出电压波形进行了分析。提出了利用时变调制比改善输出电压波形的方法,在牺牲一定增益和增加少量计算时间的前提下,用可获得对称的输出电压。     

Integrated Filters and Their Combined Effects in Matrix Converter

A matrix converter has a topology that inherently exhibits sinusoidal input current waveforms and has small output voltage steps. This paper proposes to integrate the matrix converter with filters, which provide lower electromagnetic interference (EMI), lower common-mode current, lower shaft voltage, and sinusoidal output voltage waveforms. A salient aspect of the proposed integration is its ability to significantly reduce the value of the input EMI filter capacitors and still meet strict EMI regulations. This helps in reducing the ground leakage current, which in the past has been a serious limitation in applying EMI filters with low ground currents for human and cattle safety