基于Walsh函数的多电平逆变器多波段SHEPWM控制技术

Study on Walsh Function Based Multi-Band SHEPWM Control Technology for Multi-Level Inverter

基于Walsh函数变换的特定谐波消除脉宽调制(selected harmonics elimination pulse width modulation,SHEPWM)技术存在调制比受限的问题,为此,提出了基于Walsh函数的多电平逆变器多波段SHEPWM控制技术。该方法通过分析傅里叶级数变换下的多电平多波段SHEPWM电压波形,归纳出调制比从0到1之间变化时多电平逆变器多波段统一的SHEPWM非线性方程组,再利用Walsh函数变换对其进行求解,从而同时解决了拓展调制比、在线计算、实时控制的难题。以7电平为例,给出了各个波段下的Walsh函数分段线性方程组及开关角度轨迹,同时还考虑了调制比切换处多组解的情况。算例结果验证了该方法的可行性。

There is a defect of modulation ratio limitation in the Walsh function transformation based selected harmonics elimination pulse width modulation（SHEPWM） technology, for this reason, a Walsh function based multi-band SHEPWM technology for multi-level inverter is proposed. Analyzing the SHEPWM voltage waveform under modulation modes of different bands by Fourier series transform, the unified nonlinear multi-band SHEPWM equations for multi-level inverter with modulation ratio varying from 0 to 1 are generalized, and then the equations are solved by Walsh function transform, thus the difficulties in modulation ratio expansion, online calculation and real-time control are resolved simultaneously. Taking a sept-level inverter for example, the piecewise linear equations of Walsh function under different bands and the trajectory of switching angles are given, meanwhile the condition of multiple sets of solutions at such a point where the modulation ratio is switched over is taken into account. The feasibility of the proposed method is verified by results of simulation based on MATLAB/SIMULINK.