三相电压源逆变器 三种方波调制算法的仿真分析(下)

根据桥臂中点目标电压波形的不同,三相电压源逆变器具有多种调制方式,如方波调制、梯形波调制、SPWM调制和SVPWM调制等。本文从学习的角度,采用仿真方法分析了三相电压源逆变器采用方波调制时120°、150°和180°导电方式的工作原理,并进行了简单的比较分析。     

空间矢量调制原理分析及数字化实现

详细分析了空间矢量调制的原理,得出了相关的算法和结论:分析了空间矢量调制数字化实现的编程方法,采用dsPIC30F单片机,针对开环控制方式,实现了三相电压源型逆变器空间矢量调制波形的输出,并给出了实验结果。     

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。     

正弦波逆变器SPWM调制教学研究

正弦波逆变器SPWM调制是电力电子技术教学中的重点和难点内容。通常,这部分的教学内容对于同学们如何厘清各种调制方式的优缺点以及如何得出结论,进而如何将SPWM调制信号(弱电)转化为正弦波逆变器输出电压(强电)并进行分析存在一定困难。鉴于此,本文在原有教学内容基础上进行了扩展分析,首先从SPWM调制的实际工程来源介绍了三种调制方式,对载波比为奇数以及3的倍数时波形具有良好的对称性进行了数学推导,并以此分析了三种调制方式的优缺点。接着,给出了基于桥式结构的正弦波逆变器基本变换单元,分析了其将SPWM调制信号转化为输出电压的桥梁作用,并延伸出了单相和三相桥式逆变器,给出了逆变器电压利用率计算方法,最后对其采用的倍频单极性难点问题进行了扩展分析。     

基于TMS320LF2407的空间电压矢量PWM的研究

电压空间矢量脉宽调制是一种先进的调制方法。在分析空间矢量调制(SVPWM)基本原理和输出电压特性的基础上,详细介绍了TMS320LF2407芯片产生SVPWM的硬件结构。结合电机控制专用高速数字信号处理器TMS320LF2407运算速度快、精度高、可以实时完成SVPWM控制算法的特点。给出了一种基于DSP的数字化三相感应电动机控制的软件实现方法,这种方法在三相电压源逆变器中能产生更少的谐波并减少了损耗。     

三相电压源整流器最小开关损耗调制算法的研究(上)

三相全桥PWM电压源整流器(VSR)是一种优质的升压型四象限AC·DC变换器,能够输出稳定的直流电压和获得可调的输入电流位移因数。在许多应用领域中.对三相电压源整流器的整体效率要求日益提高。考虑到三相电压源整流器的开关损耗与调制算法密切相关.为此需要改进已有的调制算法.本文在理论上推导了电压源整流器多解性原理基础上.分析了传统SPWM和SVPWM算法的本质联系.提出了一种在三相电压源整流器目标函数中注入零序分量的最小开关损耗SPWM和SVPWM调制算法.并推导了功率器件的功耗计算公式。在利用MATLAB/SIMULINK对采用最小开关损耗SPWM和SVPWM调制算法的整流器进行仿真分析之后,采用DSP F28335实现了最小开关损耗PWM调制算法的电压源整流器实验平台.验证了有关结论。相比传统的SPWM和SVPWM调制算法.最小开关损耗PWM算法能够将整流电路提升效率2~3%     

三相电压源整流器最小开关损耗调制算法的研究(下)

三相全桥PWM电压源整流器(VSR)是一种优质的升压型四象限AC-DC变换器,能够输出稳定的直流电压,获得可调的输入电流位移因数。在许多应用领域中,对三相电压源整流器的整体效率要求日益提高。考虑到三相电压源整流器的开关损耗与调制算法密切相关,为此需要改进已有的调制算法。本文在理论上推导了电压源整流器多解性原理基础上,分析了传统SPWM和SVPWM算法的本质联系,提出了一种在三相电压源整流器目标函数中注入零序分量的最小开关损耗SPWM和SVPWM调制算法,并推导了功率器件的功耗计算公式。在利用MATLAB/SIMULINK对采用最小开关损耗SPWM和SVPWM调制算法的整流器进行仿真分析之后,采用DSP TMS320F28335实现了最小开关损耗PWM调制算法的电压源整流器实验平台,验证了有关结论、相比传统的SPWM和SVPWM调制算法,最小开关损耗PWM算法能够将整流电路提升效率2~3%。     

基于升降压斩波电路的三相DC/AC逆变器研究

为了解决常用的逆变器所带来的问题,我们提出一种新型的带升降压功能的三相DC/AC变换器拓扑,并介绍了其工作原理。借助于PSIM仿真软件,对单相和三相电路进行了仿真研究,提出了由单相组成三相电压输出的构成方法。在列出仿真参数的前提下,给出了负载电压,负载电流以及调制给定电压和逆变器输出电压的仿真结果。仿真结果表明三相DC/AC逆变器可以实现50 kHz高频功率变换下宽输入电压范围工频逆变输出,证明了理论分析的正确性。     

三相Z源逆变器延时控制的定性分析研究

传统的三相电压型逆变器的输出总是小于输入,想要得到一个大的输出的话就必须要外接一个升压电路,这会造成成本的增加。Z源逆变器的提出能够有效的解决这个问题,z源逆变器作为一个可以自由控制升、降压范围的单级式的逆变模型,具有简单的拓扑结构、高效的利用率和系统的可靠性等特点,目前正被广泛的应用到各种新能源系统中。本文通过对Z源逆变器电路工作原理进行分析,在正弦脉冲宽度调制技术（SPWM控制）的基础上提出了延时控制方式,在保持所有上桥臂导通时间不变的情况下,对三个下桥臂的导通时间做一个延时滞后处理,利用延时产生的微小的时间差,获得直通零矢量,从而实现对输出电压调节的目的。最后利用matlab仿真验证了Z源逆变器的加入能提高输出电压的大小,并且能够很好的控制谐波畸变率。     

Z源逆变器中SVPWM技术实现的研究

在传统SVPWM调制方法里,通过在零矢量中插入直通状态（逆变器同一桥臂同时开通）,使其应用在Z源逆变器（ZSI）中。Z源逆变器在实现交流输出的同时,实现了对直流侧电压任意倍数的升压。文章具体阐述了基于ZSI的SVPWM调制方法,并给出开关信号调制图,说明了直通调制比D、升压因子B与参考电压幅度间的约束关系。仿真结果证实了该调制方法的正确性和有效性。     

Elimination of common-mode voltage in three-phase sinusoidal powerconverters

This paper presents an active solution to a common-mode voltage created by typical three-phase inverters. It is shown that the addition of a fourth leg to the bridge of a three-phase inverter eliminates the common-mode voltage to ground created by the modulation of the inverter. An appropriate four-phase LC filter is inserted between the inverter and the load in order to create sinusoidal output line-to-line voltage. A simple modification of the modulation strategy is implemented for the four-phase inverter to achieve a three-phase wye-output neutral-to-ground voltage which is equal to zero at all times for an ideal inverter. The modulation strategy thereby completely eliminates the common-mode potential produced by traditional modulation techniques with traditional three-phase inverter topologies     

Common-Mode Ripple Current Estimator for Parallel Three-Phase Inverters

For the three-phase parallel voltage source inverter systems with common dc link, several control methods were developed to suppress the common-mode circulating current. The common-mode ripple current is the main disturbance source of the common-mode circulating current control system that forms part of the parallel discontinuous pulsewidth modulation (PWM) inverter system. In this paper, a real-time analysis method for the common-mode ripple voltage of the three-phase discontinuous PWM inverter is proposed, whereby the amplitude of the common-mode ripple current can be estimated correctly, the hysteresis width of the circulating current controller can be adjusted to be as small as possible, and consequently, the rms circulating current is minimized as well. The simulation and experimental results are presented to confirm the theoretical analysis method of the common-mode ripple current and the performance of the proposed common-mode ripple current estimator.      

Three-phase power quality compensator under the unbalanced sources and nonlinear loads

A three-phase voltage-source inverter for a power quality compensator under the unbalanced mains and nonlinear loads is proposed to provide balanced three-phase source current and improve input power factor. The proposed converter is based on the conventional three-phase voltage-source inverter with three additional ac power switches to achieve three-level pulsewidth modulation. The voltage stress of three ac power switches is clamped to half the dc-link voltage. The balanced reference mains currents are estimated using the dc-bus voltage and load currents. A proportional-integral voltage controller is used in the outer loop to compensate the switching losses of the voltage-source inverter. To perform the integrated power quality compensation, a hysteresis current control scheme is adopted to track the balanced line current command in phase with mains voltage. Three voltage levels are generated on the ac terminal of the proposed inverter. Computer simulation and experimental results are provided to verify the effectiveness of the proposed control scheme.     

High-speed electro-thermal modelling of a three-phase insulated gate bipolar transistor inverter power module

In this article, a high-speed electro-thermal (ET) modelling strategy to predict the junction temperature of insulated gate bipolar transistor (IGBT) devices of a three-phase inverter power module is presented. The temperature-dependent power loss characteristics of IGBT and diode devices are measured and stored in lookup tables, which replace the conventional complicated physics-based compact models. An inverter is modelled as a voltage controlled voltage source, which allows the inverter-based power train simulation to be carried out in the continuous time domain with a large simulation time-step (1 ms). Using the simulated sinusoidal voltage and current components of the inverter output, the given pulse width modulation mode, the conduction time (duty ratio) and the current of the devices are extracted. Based on the lookup tables, on-times and conduction currents of devices, the average power loss over each simulation time-step is calculated, which is then fed into the inverter thermal model to predict the devices' temperatures. The advantage of the proposed model is that an accurate ET simulation of inverter for long real-time (many minutes) operation can be carried out within an acceptable computational time using a standard modern personal computer. Both simulation and experimental validation have been carried out, and an excellent agreement has been achieved between the simulation and experimental data.     

基于DSP的SVPWM与载波PWM的统一性研究

 针对脉宽调制(PWM)逆变器,在研究逆变电源电压矢量的基础上,将空间矢量脉宽调制(SVPWM)技术应用于三相和单相PWM逆变电源,分别给出了三相和单相SVPWM的数字信号处理(DSP)算法,给出了一种开关模式优化的单相SVPWM算法,导出了三相和单相SVPWM基于载波调制的调制波形式以及零序信号形式,指出载波零序信号在本质上对应着逆变器零电压矢量作用时间分配与分布,论证了SVPWM与载波PWM的统一,实验结果验证了SVPWM算法的有效性.     

The nearest three virtual space vector PWM - a modulation for the comprehensive neutral-point balancing in the three-level NPC inverter

This letter presents a new modulation approach for the complete control of the neutral-point voltage in the three-level three-phase neutral-point-clamped voltage source inverter. The new modulation approach, based on the virtual space vector concept, guarantees the balancing of the neutral-point voltage for any load (linear or nonlinear) over the full range of converter output voltage and for all load power factors, the only requirement being that the addition of the output three-phase currents equals zero. The implementation of the proposed modulation is simple according to the phase duty-ratio expressions presented. These expressions are only dependent on the modulation index and reference vector angle. The performance of this modulation approach and its benefits over other previously proposed solutions are verified experimentally.     

Application of a three-level NPC inverter as a three-phase four-wire power quality compensator by generalized 3DSVM

A two-level four-leg inverter has been developed for the three-phase four-wire power quality compensators. When it is applied to medium and large capacity compensators, the voltage stress across each switch is so high that the corresponding dv/dt causes large electromagnetic interference. The multilevel voltage source inverter topologies are good substitutes, since they can reduce voltage stress and improves output harmonic contents. The existing three-level neutral point clamped (NPC) inverter in three-phase three-wire systems can be used in three-phase four-wire systems also, because the split dc capacitors provide a neutral connection. This paper presents a comparison study between the three-level four-leg NPC inverter and the three-level NPC inverter. A fast and generalized applicable three-dimensional space vector modulation (3DSVM) is proposed for controlling a three-level NPC inverter in a three-phase four-wire system. The zero-sequence component of each vector is considered in order to implement the neutral current compensation. Both simulation and experimental results are given to show the effectiveness of the proposed 3DSVM control strategy. Comparisons between the 3DSVM and the 3-D hysteresis control strategy are also achieved.     

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.