链式多电平变换器特定谐波消除脉宽调制方法研究

Research on SHEPWM technique based on cascade multilevel converter

链式多电平变换器调制方法中,特定谐波消除脉宽调制SHEPWM(SelectedHarmonicElimi-nationPulseWidthModulation)具有输出波形质量高、消除谐波效果好、直流电压利用率高等优点。研究了链式多电平变换器的SHEPWM技术,针对其1/4周期对称的阶梯波形,给出了一种每个H桥开关频率相同的控制方法,同时列出了该方法下的链式多电平变换器的SHEPWM通用非线性超越方程组,重点提出了利用单个H桥的开关角度叠加求取初值的方法。以5电平链式多电平变换器为例,通过Matlab仿真证明了结论的正确性。

Among several modulation methods of cascade multilevel converters,SHEPWM （Selected Harmonic Elimination Pulse Width Modulation） has advantages,such as high quality of. output waveform,excellent effect on harmonic elimination and full use of DC voltage. Based on the analysis of SHEPWM, a control method,in which the switching frequency of each H-bridge is same,is proposed according to the quarter symmetric waveform,and its universal nonlinear exceeding equations are listed. Initial values are obtained by adding all single H-bridge switching angles together. The conclusion is verified by simulating a five-level cascade converter with Matlab.