多载波水平移相PWM调制策略的谐波分析

The Harmonic Analysis of Multi-carrier Horizontal Phase-shifting Modulation

多电平逆变器由于输出容量大、输出电压谐波含量小等优点,在中高压应用领域得到了广泛的应用,同时,调制策略的优劣严重影响着多电平逆变器的性能。基于双边傅立叶变换,提出了一种多载波水平移相调制策略谐波分析方法,得出了输出电压谐波的解析表达式,从理论上论述了水平移相调制策略谐波消除的根本原因。在此基础上,以优化谐波为目的,针对多单元 H 桥串联型多电平逆变器,推导了一种二重化与载波水平移相相结合的 PWM(Pulse Width Modulation)调制策略谐波表达式,详细分析了其谐波分布特性,概括出采用模块化的多电平拓扑结构谐波消除的一般原则。最后,以 DSP 与 CPLD 为基础,搭建了一套多单元串联型逆变器数字化实验系统。仿真与实验结果对所采用的谐波分析方法及水平移相 PWM 调制策略的特性进行了验证。

As muhi-level inverter has lots of advantages such as large output capacity and low harmonic content of output voltage, it is used widely in medium and high voltage applications. But the performance of multi-level inverter is affected much by the modulation strategies. This paper proposed a harmonic analysis method of multi-carrier horizontal phase-shifting modulation, which is based on. double Fourier transformation. The analytic expression of harmonic of the output voltage was obtained, and the reason why the harmonic can be eliminated by horizontal phase-shifting technique was discussed in theory. In this foundation, in order to optimize the harmonic, an expression of double and horizontal phase-shifting was deduced according to multi-module-cascaded inverter, the distributing characteristic of harmonic was analyzed in details, and the general principle of harmonic eliminating to modularized multi-level topologies was summed up. At last, a digital experiment system of multi-module cascaded inverter was build by DSP and CPLD. The harmonic analysis method and characteristic of horizontal phase-shifting PWM modulation was proved by the simulation and experimental results.