用于变频电机绝缘测试的PWM电压发生器

在变频电机绝缘测试中,重复脉冲方波电压不能完全模拟变频器输出的PWM电压反映变频电机绝缘失效机理,并且同一实验中使用不同电源影响实验数据的一致性。该文章设计了一台直接输出式PWM电压发生器,既可以输出模拟变频器实际的SPWM电压和SVPWM电压用于绝缘测试,又可以输出重复脉冲方波电压开展对比实验。首先,设计了基于FPGA的脉冲信号发生器,产生基波频率、开关频率可调的SPWM、SVPWM触发脉冲以及频率、占空比可调的重复方波脉冲;然后,设计了基于固态推挽开关的斩波器,在脉冲信号的触发下输出对应的双极性高压脉冲;最后,使用该脉冲电压发生器开展了SPWM电压下变频电机绝缘局部放电实验,验证了系统的可靠性和实用性。     

载波水平移相高压变频器实验研究

介绍了功率单元级联型高压变频器的拓扑结构和载波水平移相控制的工作原理,提出了利用现场可编程门阵列(FPGA)与DSP相结合实现多路SPWM脉冲的方法。该方法利用FPGA实时产生的多路脉冲对功率单元级联型高压变频器进行控制,并用示波器和互感器等对输出电压和电流波形进行了测试。实验验证了FPGA与主控制器相结合实时产生多路脉冲的可行性,以及基于载波水平移相功率单元级联型高压变频器具有优良的电压、电流等输出特性。     

基于TMS320F2812的载波移相PWM发生器的设计

适用于单元级联型多电平电路的载波移相PWM调制方法,其实现的关键在于如何实时产生多路移相PWM控制信号。研制了基于TMS320F2812的PWM脉冲发生器,通过事件管理器硬件实现与CPU软件实现相结合,在DSP的各个GPIO复用管脚输出多路移相PWM波形。基于该脉冲发生器,完成了单相级联七电平逆变器的载波移相实验。实验结果表明,该脉冲发生器简化了多电平硬件电路的设计,算法程序简洁,实时性强,易于扩展。     

单元级联型变频器SPWM控制算法研究及实现

简单介绍了级联型多电平变频器的拓扑结构及其级联输出.详细研究并分析了单元串联多电平变频器的多载波式控制算法.应用Madab软件对11电平的单元级联型系统进行了建模和算法仿真.仿真结果表明,采用载波移相方法,级联式多电平变频器具有优越的控制性能,输出电压波形非常接近正弦波,电压变化率小,输出电压和电流的谐波含量小、共模电压小等.采用基于DSP和FPGA产生30路SPWM控制信号,试验输出电压波形进一步证明了仿真结果的正确性.     

基于FPGA的级联型逆变器的脉冲发生器的实现

设计并实现了基于FPGA的PWM脉冲发生器,该脉冲发生器接收由DSP根据载波移相空间矢量PWM算法计算出的占空比数据,并和多路移相载波进行实时比较,从而产生多路PWM脉冲,该脉冲发生器可以独立于DSP运行.在脉冲发生器的设计中还嵌入了串口接收器模块,接收并解析功率单元的状态及故障信息,返回给DSP读取,大大减轻了DSP处理功率单元信息的任务.最后的实验结果表明基于FPGA的脉冲发生器的设计方案不仅简化了电路的设计,提高了系统的可靠性,而且解决了各个功率单元脉冲触发同步性的问题.     

基于FPGA的级联逆变器直接PWM发生器

为实现中高压变频装置在风机、水泵等应用场合的调速控制,研制了基于现场可编程门阵列(FPGA)实现的多电平直接脉宽调制(PWM)脉冲发生器.该脉冲发生器通过总线与主控制器实现数据交换,接收参考电压采样数据,返回功率单元的状态信息,以模块化方式设计实现PWM脉冲输出.介绍了该脉冲发生器的基本原理、软硬件构成和实现,给出了试验的线电压波形和频谱分析结果.试验结果表明,脉冲发生器脉宽精度高,运行可靠,输出线电压的总谐波畸变率小于3%.     

基于FPGA的级联型逆变器的脉冲发生器的实现

设计并实现了基于FPGA的PWM脉冲发生器,该脉冲发生器接收由DSP根据载波移相空间矢量PWM算法计算出的占空比数据,并和多路移相载波进行实时比较,从而产生多路PWM脉冲,该脉冲发生器可以独立于DSP运行。在脉冲发生器的设计中还嵌入了串口接收器模块,接收并解析功率单元的状态及故障信息,返回给DSP读取,大大减轻了DSP处理功率单元信息的任务。最后的实验结果表明基于FPGA的脉冲发生器的设计方案不仅简化了电路的设计,提高了系统的可靠性,而且解决了各个功率单元脉冲触发同步性的问题。     

适合于多电平变流器的新型驱动方法实现及应用

多电平变流器的开关器件数目远大于常规的桥式PWM变流器,而常用的微控制芯片难以提供足够的PWM触发脉冲。适用于多电平变流器的多路PWM发生器可以通过现场可编程门阵列(FPGA)实现,为此研制了基于DSP和FPCA实现的24路PWM脉冲产生器。在单相级联H桥五电平变流器上进行了实验验证。实验结果表明:所得到的实验波形与自然采样法所得仿真波形的谐波特性很相近。     

基于现场可编程门阵列的多路PWM波形发生器

研制了基于现场可编程门阵列(FPGA)实现的多路PWM脉冲发生器。该脉冲发生器通过接口单元接收DSP写入的PWM脉冲宽度数据，然后产生PWM波形，其工作不受DSP影响。同时介绍了脉冲发生器的基本原理、硬件构成和实现方法。该PWM发生器既简化了电路的设计，提高了系统的可靠性，又可保证逆变器功率元件触发的同步。     

一种新颖的矩阵变换器PWM脉冲产生方法

在分析了矩阵变换器双电压合成原理的基础上,针对该控制原理需要产生不规则的PWM脉冲,提出了一种新颖的脉冲间接产生方法。传统的现场可编程大规模门阵列器件(FPGA)根据计算的占空比数据进行三角波调制,在FPGA内部比较产生需要的不规则PWM脉冲,而未使用微处理器本身集成的PWM脉冲发生器,软件编程复杂且整机系统可靠性不高。提出的脉冲间接产生方法利用微处理的PWM脉冲发生器产生6路标准PWM脉冲,将6路标准PWM脉冲按照不同逻辑运算合成得到矩阵变换器所需要的18路脉冲,该方法不仅降低了编程复杂性,而且与系统没有数据交换,提高了系统可靠性。设计了以dSPACE为主控单元的实验平台,通过实验方法验证了所提脉冲间接产生方法的有效性与正确性。     

基于CO-SFO-PWM级联型多电平逆变器的研究

选取级联型多电平拓扑作为中高压变流器的拓扑结构,对多电平逆变电路及其PWM技术进行了研究,并对级联型9电平逆变器的工作原理进行了分析.采用新型CO-SFO-PWM技术进行级联型9电平逆变器实验,实验结果表明该新型PWM技术不仅在低调制度下可明显改善输出波形,而且在高调制度下同样可获得较低的THD的输出波形,并且提高了直...     

基于FPGA的多电平多载波PWM脉冲发生原理及实现方式

多单元串联型多电平逆变器越来越广泛地应用于高压大功率工业应用场合,其拓扑结构的特殊性决定需要多路驱动脉冲。因此,多路驱动脉冲的发生便成为拓扑所研究的关键性技术之一。针对H桥串联型多电平逆变器,详细地叙述了多载波脉冲的发生原理,基于FPGA,给出了一种通用型多载波脉冲发生器的具体实现方式。最后,基于DSP与FPGA,搭建了一套多电平逆变器数字化实验系统。实验结果表明所构造的多载波PWM脉冲发生器具有很好的扩展性与通用性。     

基于OMAPL138 FPGA的多路PWM发生器设计及应用

为了满足一种新能源发电领域的电力电子变换装置上逆变器触发的要求,研制了利用OMAPL138和FPGA实现的多路PWM脉冲发生器。该脉冲发生器利用接口单元接收OMAPL138写入的PWM脉冲占空比和设置参数等数据,利用FPGA产生PWM波形,达到其工作不受OMAPL138影响的效果。同时介绍了脉冲发生器的硬件架构、基本原理和实现方法,并通过仿真和实验得到验证。该PWM发生器既简化了电路的设计,提高了系统的可靠性,又可保证逆变器功率元件触发的同步。     

A rule-based fuzzy logic controller for a PWM inverter in a standalone wind energy conversion scheme

The paper presents a rule-based fuzzy logic controller to control the output power of a pulse width modulated (PWM) inverter used in a stand-alone wind energy conversion scheme (SAWECS). The self-excited induction generator used in SAWECS has the inherent problem of fluctuations in the magnitude and frequency of its terminal voltage with changes in wind velocity and load. To overcome this drawback the variable magnitude, variable frequency voltage at the generator terminals is rectified and the DC power is transferred to the load through a PWM inverter. The objective is to track and extract maximum power from the wind energy system and transfer this power to the local isolated load, This is achieved by using the fuzzy logic controller which regulates the modulation index of the PWM inverter based on the input signals: the power error; and its rate of change. These input signals are fuzzified, that is defined by a set of linguistic labels characterized by their membership functions predefined for each class. Using a set of 49 rules which relate the fuzzified input signals to the fuzzy controller output, fuzzy set theory and associated fuzzy logic operations, the fuzzy controller's output is obtained. The fuzzy set describing the controller's output (in terms of linguistic labels) is defuzzified to obtain the actual analog (numerical) output signal which is then used to control the PWM inverter and ensure complete utilization of the available wind energy. The proposed rule-based fuzzy logic controller is simulated and the results are experimentally verified on a scaled down laboratory prototype of the SAWECS     

五开关H桥逆变器改进PWM控制方法的研究

针对传统级联五电平逆变器所需开关器件较多的问题,介绍了一种由1个辅助开关电路与H桥电路相结合的五开关H桥逆变器拓扑。根据该拓扑工作原理的特点,对其脉宽调制PWM策略进行了研究,提出了一种基于载波移相脉宽调制的改进型PWM控制方法。该方法依据两单元H桥级联,通过单极倍频CPSPWM方法得到五电平相电压的波形,并把该五电平电压波形作为五开关H桥逆变器的输出目标波形,再结合逆变器的4种工作模式来逆向推导出PWM脉冲信号。最后通过仿真和实验研究证明了该拓扑结构和控制方法的可行性与有效性。     

PWM-VSI inverter-assisted stand-alone dual stator winding induction generator

This paper presents a novel usage of a dual stator winding three-phase induction machine as a stand-alone generator with both controlled output load voltage magnitude and frequency. This generator, with both three-phase power and control windings housed in the stator structure, has the load connected to the power winding and a three-phase pulsewidth modulation (PWM) voltage-source inverter sourcing the control winding. The input to the PWM inverter is either a battery source or a charged DC capacitor. The operational characteristics of these generator schemes with either of the two inverter sources are investigated and shown to have desirable performance. How the load voltage magnitude depends on the various control and design parameters such as rotor speed, compensating capacitance, and load impedance is determined using a detailed mathematical model of the system.     

Design considerations for an inverter output filter to mitigate theeffects of long motor leads in ASD applications

Design considerations for an inverter output filter to mitigate the effects of long motor leads in adjustable-speed drive (ASD) applications are presented. It is shown by analysis that, for a given length of cable, reducing the dv/dt of the pulsewidth modulated (PWM) inverter output voltage applied to the cable below a critical value will eliminate overvoltages due to voltage reflections. Design issues for a low-pass filter at the inverter output terminals to reduce the dv/dt of the inverter output pulse are examined in detail. The filter operation is verified for the entire variable frequency range of the inverter. The performance of the filter is evaluated through simulations and experimentally on a 460 V commercially available AC motor drive (PWM insulated gate bipolar transistor (IGBT)). The proposed inverter output filter is then compared with a motor terminal shunt filter also designed to reduce overvoltages and ringing at the motor terminals     

A modified cascade transformer-based multilevel inverter and its efficient switching function

A modified multilevel PWM inverter is proposed to increase the number of output voltage levels and to improve the system characteristic of a prior 11-level shaped PWM inverter scheme. In appearance, it consists of three full-bridge modules and a cascade transformer; therefore, the configuration of the proposed multilevel PWM inverter is equal to that of the prior one. Only the turn-ratio of one transformer and its corresponding switching function are different from each other. Based on the difference, the proposed multilevel PWM inverter has two promising advantages. First, output voltage levels increase almost two-fold. Consequently, it can generate more sinusoidal output voltage waves. Second, due to a suitable switching pattern, it lightens power imposed on the transformer, which is used for compensating output voltages with chopped pulses between step levels. Operational principle of the proposed 19-level shaped PWM inverter is analysed with comparisons of the prior 11-level shaped PWM inverter. The validity of the proposed inverter system is verified by computer-aided simulations and experimental results based on a 1 kW prototype.     

Current regulated PWM-CSI induction motor drive system without aspeed sensor

This paper deals with a current source inverter-induction motor drive system without a speed sensor, and the speed estimation with only sense of the motor voltage is investigated. The input DC link current which is kept constant by a pulsewidth modulated (PWM) converter with sinusoidal input current is supplied to the PWM inverter. The inverter output current with sinusoidal wave is directly regulated by employing the modulation index control of the PWM strategy. The motor is driven by a slip frequency/current regulation control. The motor speed is estimated by using the measured voltage and current, or using the measured voltage and the estimated current. The filter capacitor which is installed in the inverter circuit is taken into consideration for the current estimation. A digital signal processor is employed for calculation. As the PWM pulse of the inverter is calculated by an online real-time system, the quick regulation of the sinusoidal output current is achieved. The experiments show that the high performance steady state behavior and the acceleration/deceleration characteristics with smooth drives and low noise of the motor is obtained