多电平电压源逆变器降低共模电压的脉宽调制策略的研究

多电平逆变器因为存在的开关状态多,因此其调制方法也较为复杂。通过选择适当的开关状态,部分共模电压降低调制方法(PCMVPWM)能将共模电压降低到直流侧电源的1/3,而完全共模电压消除调制方法(FCMVPWM)能够完全消除共模电压。本文主要揭示了这两种调制方法与基于载波的脉宽调制的关系并进行仿真比较。最后,在实验室建立的NPC三电平逆变器的原型机上对算法进行了实验验证,结果表明该调制方法能够有效地降低共模电压。     

A simple method for output voltage control of a three‐phase multilevel inverter considering DC voltage fluctuation

Multilevel inverter circuit generates the stair‐like voltage without using transformer and interphase reactor, and it is the circuit which realizes reduction in the harmonics and enlargement of the capacity. In addition, the application of PWM control improves the waveform, and reduces the switching component to the conventional half, and the filter capacity is reduced. In this paper, improvement on the voltage utilization factor and feedback control of output voltage are applied to multilevel inverter circuit. For the DC power supply with the intense fluctuation, it is necessary to construct inverter circuit which can supply stabilized AC voltage. One‐chip microcomputer with various functions is used for the control equipment of this circuit, and miniaturization and cost reduction of the control equipment are realized. Here, the control principle and experimental results of this equipment are mainly reported. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 40–47, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20906     

多电平逆变器通用电容电压平衡优化算法

针对二极管箝位型多电平逆变器电容电压难以控制的问题,分析了一种简单的多电平逆变器等效模型,用于预测结点电压偏差,提出了一种多电平逆变器电容电压平衡优化SVPWM(space vector pulse width modulation)算法。该算法通过预测不同开关状态下直流侧结点电压偏差,建立目标函数并对其寻优,在每个开关周期选取最优的开关组合达到结点电压平衡。理论分析和试验结果表明,该算法适用于任意电平逆变器电容电压平衡的控制,解决了三电平逆变器电容电压平衡的问题,但在三电平以上的逆变器受调制度限制。针对三电平以上高调制度下电容电压失衡的原因进行了分析,并给出了解决方法。仿真和实验验证了算法的正确性。     

基于不对称级联型多电平逆变器的动态电压恢复器研究

提出了一种基于不对称级联型多电平逆变器(ACMI)的动态电压恢复器(DVR)及其控制策略.该DVR在结构上采用不对称级联型多电平逆变器,易于实现装置的大容量化;控制策略上先采用跌落前电压补偿法,然后平缓过渡到同相位电压补偿法,在这种控制策略下,系统电压发生幅值和相位跳变时,能够保证负载电压平滑无突变,减小了对相位突变敏感负荷的影响,补偿效果接近跌落前电压补偿法,而所需补偿的能量与同相位电压补偿法接近.Matlab仿真试验验证了该系统结构和控制策略的实用性、有效性.     

减小共模电压的通用多电平SVPWM算法及FPGA实现

针对电平数增加造成开关矢量数目增多,导致多电平空间矢量脉宽调制算法实现复杂的问题,提出一种通用的多电平空间矢量脉宽调制快速计算方法.该方法基于参考电压分解,利用相电压合成电压矢量,能快速确定合成电压矢量及计算各矢量的作用时间,具有清晰的物理概念.讨论了为减小输出共模电压的7段/5段式空间矢量脉宽调制开关序列的生成方法及FPGA实现的简化方法.所提出的调制算法具有通用性,适用于任意电平且复杂程度与电平数无关,输出共模电压小,始终限制在单位电平的2/3以下,相电压波形正弦对称,谐波含量少.算法计算量小,无需查找表,FPGA实现容易,占用资源少.     

A novel voltage clamped snubber circuit topology suitable for a multilevel inverter with lowered power loss performance

This paper presents a novel prototype of lowered loss snubber circuit topology suitable for multilevel voltage source‐inverters and rectifiers for high‐power applications. The reduced power loss characteristics and voltage capability performances of the proposed voltage clamped snubber circuit are evaluated relative to conventional RCD snubber circuits designed for four‐level voltage‐source inverters using IGBTs on the basis of experimental results. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 70–78, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20015     

基于独立电压控制的多电平光伏逆变MPPT研究

针对太阳能光伏发电系统中由于光伏阵列局部阴影和不匹配导致输出功率降低的问题,采用二极管钳位多电平逆变器方案,提出等效变换脉宽调制控制策略,通过独立控制每一个光伏阵列的工作电压,允许通过不同的电流,保证每个光伏阵列输出最大功率,使整个系统输出功率最大.采用多电平逆变器,降低设备的额定电压,减少输出电压失真,降低输出电流谐波含量,提高转换效率.MATLAB仿真实验验证了该控制策略的可行性和有效性.     

三电平电压型逆变器空间矢量调制算法的研究

本文提出一种三电平逆变电路空间矢量调制的算法。在每个控制周期中加入固定作用时间的输出矢量111,避免了在参考矢量切换扇区时可能出现的矢量突变问题。由于输出矢量的选择和作用时间的计算都是在静止的α-β坐标系下完成,这种算法避免了常规空间矢量调试算法中复杂的三角函数的运算,只需要简单的算述运算即可实现空间矢量的调制。此外,还提出一种简单易行的中点电位控制方法实现了中点电位稳定。仿真和实验结果证明了所提出算法的有效性。     

一种改进的三电平空间电压矢量调制算法

提出了一种新的三电平空间电压矢量调制算法,该算法通过直接对三相参考电压进行比较从而判断出合成参考矢量所在区域,并基于伏秒平衡原理计算得到各个标准矢量的作用时间.通过与传统算法进行比较可以看出,提出的算法与传统算法控制效果相同,但其不需要进行正余弦计算,能够大量节省计算时间.最后通过实验验证了该算法的有效性.     

基于虚拟作用时间变换的N电平逆变器参考电压矢量合成方法

本文提出了一种非正交变换和线性变换相结合的矢量合成方法:将任意参考电压矢量变换到60°非正交坐标系中,根据其坐标求出由第一扇区的两个基本长矢量合成参考电压矢量的虚拟作用时间,并确定三个最近矢量(Nearest Three Vector,NTV),而这三个邻近矢量的作用时间则可以由虚拟作用时间通过线性变换得到,这样使参考...     

A low-power voltage inverter

Practical aspects of design of converters based on compound bipolar transistors are analyzed. The passage of a small reactive current through a compound bipolar transistor is analyzed using the example of a voltage inverter. A frequency converter with input protection is designed and loaded with an asynchronous motor at the output.     

混合级联型多电平逆变器的研究

提出了一种混合级联型多电平逆变器拓扑结构,给出了逆变器的控制方案。仿真结果表明,逆变器能够以较低的开关频率输出接近于正弦波的电压且只有很低的共模电压。     

Novel multilevel inverter carrier-based PWM method

The advent of the transformerless multilevel inverter topology has brought forth various pulsewidth modulation (PWM) schemes as a means to control the switching of the active devices in each of the multiple voltage levels in the inverter. An analysis of how existing multilevel carrier-based PWM affects switch utilization for the different levels of a diode-clamped inverter is conducted. Two novel carrier-based multilevel PWM schemes are presented which help to optimize or balance the switch utilization in multilevel inverters. A 10 kW prototype six-level diode-clamped inverter has been built and controlled with the novel PWM strategies proposed in this paper to act as a voltage-source inverter for a motor drive     

基于数学推导的级联型多电平容错逆变器输出性能研究

载波相移SPWM技术应用于级联型多电平逆变器,其载波相移角度差π／N和2π／N两种相移方式,对不同级联数目的逆变器输出有不同影响。当三相逆变器中功率单元发生故障被切除后,输出电压不再平衡．而利用中性点偏移技术,可使逆变器输出线电压重新达到平衡,从而具备较好的容错能力：通过对载波相移PWM技术和中性点偏移原理的数学推导,得出采用载波相移角π/N方式与中性点偏移技术,逆变器输出性能有较大提高的结论。最后对级联型九电平逆变器A相中某一功率单元故障后状况进行仿真实验．验证了数学推导的正确性。     

Control of a hybrid asymmetric multilevel inverter for competitive medium-voltage industrial drives

In symmetric multilevel inverters, there is a tradeoff between the output quality and the reliability and efficiency of the converter. New asymmetric and hybrid solutions, using different voltages and devices in various parts of the inverter, promise significant improvements for medium-voltage industrial drives. This paper investigates such a hybrid asymmetric nine-level inverter. It consists of a three-phase three-level integrated gate-commutated thyristor inverter (main inverter), with a two-level insulated-gate bipolar transistor H-bridge (subinverter) in series with each phase. To keep the power part simple and the efficiency high, the subinverters have no feeding from the net and can only supply reactive power. This is a very interesting solution in terms of power quality, efficiency, reliability, and cost. But the nonsupplied intermediate-circuit capacitors form an unstable system. This paper proposes a control method to stabilize their voltages. Power balancing is guaranteed by varying the common-mode voltage, using an online nonlinear model-predictive controller. The controller predicts the system evolution as a function of the control inputs. A cost function of system and control quantities is iteratively minimized in real time, to find the optimal control to apply to the system. Simulations and measurements demonstrate stable behavior in steady state and during transients. Precharging of the nonsupplied capacitors is also an issue to consider. This paper proposes a startup method that charges them in parallel with the supplied ones, without any additional equipment. Measurements show its successful application in the proposed drive system.     

级联多电平逆变器的工作原理分析

以每相两功率单元串联为例,介绍了级联多电平逆变器的拓扑结构和相位移载波SPWM调制策略,阐述了该多单元级联逆变器在SPWM调制方法下的工作原理,从理论上分析了逆变器开关切换、输出电压、电流流向以及共模电压的情况,说明了相位移载波SPWM调制方法应用在级联多电平逆变器上的可行性、可靠性和控制的简易性,为实现调制方法的优化和拓扑结构的改进提供了理论基础。     

基于等价输入干扰的三电平AC－DC逆变器中点电压控制(英文)

One problem with a single source three-level inverter is the drafting of its neutral-point voltage. This may occur during transition or when unbalanced loads are connected to the inverter system. Variation of neutral-point voltage may greatly deteriorate the power quality. In this paper, we employ an equivalent-input-disturbance approach to deal with this problem. By adding an extra neutral leg, the control problem of neutral-point voltage is converted to a disturbance rejection problem. This method suppresses the variation of the neutral-point voltage to a low level and reduces the capacity of DC-link capacitors. Simulation results show the effectiveness of the method.     

基于单元组合的多电平逆变器设计

在研究传统的级联型多电平逆变器的基础上提出了一种多电平逆变器基本构成单元的概念,并从这一概念出发,提出了基于基本构成单元串并、并串思想生成多电平逆变器拓扑的方法.以此方法得到的大量多电平逆变器拓扑,不仅涵盖了已有的基本多电平电路拓扑,而且得到一些新的拓扑结构,从而将多电平变换拓扑统一在基本构成单元的概念之内.为了验证所得到拓扑的正确性,以串一并拓扑为例,进行了仿真和实验验证.这一概念也为多电平逆变器新拓扑的生成提供了思路.     

基于多电平变换逆变电路的拓扑分析

多电平变换逆变电路是一种新的、用于“清洁电力电子装置”的变换电路。本文指出实现多电平变换逆变电路的关键问题之一是电平钳位,并以此为依据将现有的多电平电路拓扑结构进行了分类。文中分析了基于“二极管或电容钳位”和“使用独立直流电源钳位”的两类典型多电平路拓扑结构的优缺点,并在现有的“混合单元多电平逆变电路”单元结构基础上提出了一种新的、使用不同电压比的控制方式。