基于脉冲阶梯调制的级联型逆变器研究

脉冲阶梯调制(PSM)是将脉宽调制(PWM)与阶梯调制(SM)相结合,起初应用在高压直流电源系统中。将脉冲阶梯调制技术应用到逆变器领域,提出了基于脉冲阶梯调制的级联型逆变器。介绍了级联逆变器的基本拓扑,分析了PSM级联型逆变器的工作原理,研究了PSM的调制算法。该级联型逆变器具有电路结构简单、控制方法简便、开关损耗小、效率高等优点,适合高压大功率场合。建立了6模块的PSM级联型高压逆变器(可获得有效值为4 kV的输出电压)的Matlab仿真模型进行分析,给出仿真结果。仿真结果表明,PSM级联型高压逆变器的输出波形特性好,谐波含量和THD均很小。     

五电平NPC/H型逆变器SVPWM调制方法研究

文章针对五电平中点箝位H桥级联(NPC/H)型逆变器的SVPWM调制方法进行了研究,给出了五电平SVPWM调制策略,仿真表明该调制策略是有效的。     

H桥级联型多电平逆变器调制策略对比分析

针对H桥级联型多电平逆变器,对比分析了传统的多电平PWM调制策略,指出其存在的输出电压谐波性能问题。提出一种改进的调制策略,不仅抑制了直流母线电压波动引起的低次谐波含量,而且有效地降低了高、次谐波含量。最后通过对比实验,验证了所提出方法的正确性与有效性。     

混合型级联多电平变换器调制策略研究

多电平变换器的调制策略与其主电路拓扑密切相关。文章首先讨论了几种多电平变换器的拓扑特点,推荐了一种混合型多电平变换器,分析了它的几种调制策略和频谱特性,并进行了电路仿真,比较了它们之间的优劣,给出了连续调制方式下的频谱表达式,仿真验证了结果的正确性,最后总结了几点有用的结论。     

基于Simulink的三相两电平逆变器的空间矢量调制的研究与仿真

提出了三相两电平逆变器的空间矢量调制方法，详细讨论了两电平逆变器的工作原理及空问矢量调制的基本原理，并给出一个具体的仿真实例，通过仿真，可以得出实际运行中的电压、电流的波形，而且在文中给出了实例的电路原理图，使得对于空问矢量调制的原理得以更加清楚的认识。     

一种非对称三电平逆变器SVPWM调制方法

提出一种新型的非对称三电平逆变器,并采用空间矢量脉冲宽度调制策略作为调制方法。前级通过双Buck变换器为后级提供四路电平,后级逆变电路包括四路三相桥臂,在不同的开关组合下工作于非对称的三电平状态。非对称三电平结构降低了大电流时开关管所承受的电压应力,降低了后级逆变电路的开关损耗。分析电路的工作原理、调制方法,在Matlab/Simulink环境下建模仿真,仿真结果验证了该电路的有效性及其调制策略的可行性。     

三电平逆变器SVPWM控制算法及其仿真研究

空间矢量调制（SVPWM）在多电平逆变器的控制中应用广泛,但是随着电平数增加控制算法渐趋复杂化。文中提出的三电平SVPWM控制方法,将三电平电压矢量区变换为由两电平空间矢量区构成,从而通过使用两电平SVPWM调制方法简化了控制算法。该方法理论上可应用于更高电平逆变器的控制中。仿真验证了方法的可行性。     

基于神经网络的多电平逆变电路故障诊断

因含有大量的开关器件,多电平逆变器难以用基于模型的方法进行故障诊断。针对这一问题,提出了一种基于神经网络的故障识别和分类方法。采用载波相移脉冲宽度调制（PWM）策略搭建级联五电平逆变电路,对逆变器的输出电压信号进行快速傅里叶变换,获取其频谱并以此作为特征信息。利用反向传播算法（BP）神经网络对输出电压模式进行分类。Matlab仿真结果表明,本文设计的 BP神经网络有效地实现了对逆变器的故障诊断。     

单相电压源变换器减少开关次数调制算法的研究

作为基本的电力电子变换器,单相全桥结构两电平电压源变换器包括单相电压源逆变器、单相并网逆变器、单相电压源整流器和单相有源电力滤波器,具有广泛的应用场合。鉴于单相电压源变换器具有多解性,可以寻找一种减少开关次数的调制算法,以便降低开关损耗。本文根据三相电压源全桥结构两电平电压源变换器的最小开关次数调制算法,设计了一种适合单相全桥结构两电平电压源变换器的最少开关次数的调制算法,在理论分析的基础上,采用MATLAB/SIMULINK进行了仿真验证。     

非对称H桥五电平逆变器及其通用调制策略

非对称H桥五电平逆变器所用功率开关较少,具有较高的性价比。对该类拓扑的结构进行分析,提出一种通用的调制策略,对三种五电平非对称H桥均适用。最后通过电容箝位型五电平非对称H桥实验平台,验证了所提调制方法的正确性与有效性。     

An integrated technique for eliminating harmonics of multilevel inverter with unequal DC sources

For improving the alteration performance of multilevel inverter, selective harmonics elimination methods play a significant role. In this document, an incorporated method is suggested for removing the harmonics of multilevel inverter with uneven DC sources. The suggested incorporated method is the mixture of fuzzy logic intelligent system and particle swarm optimisation (PSO) algorithm. For generating the training information set in terms of switching angle, Fuzzy is one of the synthetic intelligent methods which apply harmonic voltage and harmonic distortion. PSO is one of the swarm intelligence-based optimisation algorithms which is employed for choosing optimal switching angle from the training data set. The suggested hybrid method is executed in MATLAB/Simulink platform. At dissimilar unequal input voltage levels, the performance of the suggested method is checked by cascade H-bridge multilevel inverter. The production of the suggested method is compared with the theoretical effects.     

多电平变频器无速度传感器直接转矩控制的研究

在级联多电平直接转矩控制中,通过引入错时采样空间矢量调制法,采用PI调节与错时采样空间矢量调制,摒弃开关向量表与滞环比较器,可以克服传统直接转矩控制开关向量表复杂、波形质量差、转矩脉动大、开关频率不定等缺点。无速度传感器技术的使用可提高可靠性与降低成本。与其他多电平空间矢量算法相比,其功率单元使用均衡,执行效率高,易于实现,可保证无速度传感器直接转矩控制的实时性。通过仿真对这一方法进行了证明。     

Advanced Control and Analysis of Cascaded Multilevel Converters Based on P-Q Compensation

This paper introduces new controls for the cascaded multilevel power converter. This converter is also sometimes referred to as a ldquohybrid converterrdquo since it splits high-voltage/low-frequency and low-voltage/pulsewidth-modulation (PWM)-frequency power production between ldquobulkrdquo and ldquoconditioningrdquo converters respectively. Cascaded multilevel converters achieve higher power quality with a given switch count when compared to traditional multilevel converters. This is a particularly favorable option for high power and high performance applications such as naval ship propulsion. This paper first presents a new control method for the topology using three-level bulk and conditioning inverters connected in series through a three-phase load. This control avoids PWM frequency switching in the bulk inverter. The conditioning inverter uses a capacitor source and its control is based on compensating the real and reactive (P-Q) power difference between the bulk inverter and the load. The new control explicitly commands power into the conditioning inverter so that its capacitor voltage remains constant. A unique space vector analysis of hybrid converter modulation is introduced to quantitatively determine operating limitations. The conclusion is then generalized for all types of controls of the hybrid multilevel converters (involving three-level converter cells). The proposed control methods and analytical conclusions are verified by simulation and laboratory measurements.     

Hybrid Cascaded H-Bridge Multilevel-Inverter Induction-Motor-Drive Direct Torque Control for Automotive Applications

This paper presents a hybrid cascaded H-bridge multilevel motor drive direct torque control (DTC) scheme for electric vehicles (EVs) or hybrid EVs. The control method is based on DTC operating principles. The stator voltage vector reference is computed from the stator flux and torque errors imposed by the flux and torque controllers. This voltage reference is then generated using a hybrid cascaded H-bridge multilevel inverter, where each phase of the inverter can be implemented using a dc source, which would be available from fuel cells, batteries, or ultracapacitors. This inverter provides nearly sinusoidal voltages with very low distortion, even without filtering, using fewer switching devices. In addition, the multilevel inverter can generate a high and fixed switching frequency output voltage with fewer switching losses, since only the small power cells of the inverter operate at a high switching rate. Therefore, a high performance and also efficient torque and flux controllers are obtained, enabling a DTC solution for multilevel-inverter-powered motor drives.      

级联型多电平逆变器中多载波PWM控制方法的改进

级联型多电平逆变器由于其模块化结构、便于生产高度、更换容易等特点，受到电力电子工程技术人员的广泛关注。本文通过对于级联型多电平逆变器几种典型的控制方法的分析比较，提出了一种改进多载波PWM控制方法。该方法通过改变载波的幅值，使级联逆变器的各个逆变单元开关规律相同，并使所有的开关器件的损耗一致，有利于逆变单元的统一设计和可靠运行。     

Charge balance control schemes for cascade multilevel converter in hybrid electric vehicles

This paper presents transformerless multilevel converters as an application for high-power hybrid electric vehicle (HEV) motor drives. Multilevel converters: (1) can generate near-sinusoidal voltages with only fundamental frequency switching; (2) have almost no electromagnetic interference or common-mode voltage; and (3) make an HEV more accessible/safer and open wiring possible for most of an HEV's power system. The cascade inverter is a natural fit for large automotive hybrid electric drives because it uses several levels of DC voltage sources, which would be available from batteries, ultracapacitors, or fuel cells. Simulation and experimental results show how to operate this converter in order to maintain equal charge/discharge rates from the DC sources (batteries, capacitors, or fuel cells) in an HEV.     

A multilevel inverter system for an induction motor with open-end windings

In this paper, a multilevel inverter system for an open-end winding induction motor drive is described. Multilevel inversion is achieved by feeding an open-end winding induction motor with two two-level inverters in cascade (equivalent to a three-level inverter) from one end and a single two-level inverter from the other end of the motor. The combined inverter system with open-end winding induction motor produces voltage space-vector locations identical to a six-level inverter. A total of 512 space-vector combinations are available in the proposed scheme, distributed over 91 space-vector locations. The proposed inverter drive scheme is capable of producing a multilevel pulsewidth-modulation (PWM) waveform for the phase voltage ranging from a two-level waveform to a six-level waveform depending on the modulation range. A space-vector PWM scheme for the proposed drive is implemented using a 1.5-kW induction motor with open-end winding structure.     

Distributed Control of Hybrid Motor Drives

The hybrid inverter fed motor drive with two cascaded multilevel inverters is an attractive option for high performance high power applications such as naval ship propulsion systems due to a number of unique features. There is a natural split between a higher-voltage lower-frequency “bulk” inverter and a lower-voltage higher-frequency “conditioning” inverter in the cascaded system which matches the availability of semiconductor devices. Furthermore, the bulk inverter may be a commercial-off-the-shelf (COTS) motor drive meaning that only the conditioning inverter needs to be custom made. However, a drive involving a COTS bulk inverter would require a distributed conditioning inverter control which works completely independent of the bulk inverter control. In this paper, a set of distributed control methods are developed for the hybrid inverter drive with cascaded bulk and conditioning inverters, requiring only single dc source. Moreover, a solution to the practical problem of instant synchronization between the two inverters is presented. Laboratory measurements on a 3.7-kW induction motor drive validate the proposed control. Various practical considerations (such as low$m$-index performance and capacitor precharging options) are discussed and their solutions provided.     

Multilevel inverters: a survey of topologies, controls, and applications

Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.     

New basic unit and cascaded multilevel inverters with reduced power electronic devices

ABSTRACT

In this paper, a new cascade multilevel inverter based on series connection of several basic units is proposed. The basic topology consists of 5 dc voltage sources and 12 switches. The required mathematical analysis consisting of voltage on switches, power losses and the values of dc voltage sources is provided. To verify the advantages of proposed topology, the suggested structure is compared with other multilevel inverter topologies in terms of used dc voltage sources, switches, voltage on switches and the number of on-state switches. The proposed structure uses the least numbers of dc voltage sources and switches compared to other multilevel inverters for the same number of levels. Also, voltage rating on the switches in the proposed topology is less than other topologies. These characteristics cause the weight, size and cost of proposed topology to be reduced. The proposed inverter is implemented using experimental setup. The experimental results verify the performance of proposed structure.