Numerical Analysis and Simulation Verification of Multi-pattern Switching Angles Distribution for Five-Level Selective Harmonic Elimination PWM

Five-level selective harmonic elimination pulse width modulation (SHEPWM) is an essential technology to improve the output performance with a relatively low switching frequency, especially for various middle voltage high power applications. However, the existing researches are mainly focused on two-and three-level SHEPWM, or concentrated on general formulas and numerical algorithms of multilevel SHEPWM. There are few studies on multiple solutions derived from multi-pattern switching angle distribution for five-level SHEPWM. Actually, these multiple solutions will play an important role in expanding control degree of freedom, which facilitates to achieve some key control for five-level converter. Therefore, this article systematically investigates the multi-pattern characteristics of five-level SHEPWM, and obtain some groups of switching angle distributions. The term "multi-pattern" specifically refers to the times of switching between different levels, which will change the constraint equation and cause some new switching angles. The multi-pattern characteristics can effectively broaden the theoretical frame of five-level SHEPWM. It is of benefit to enhance the regulation and control ability of SHEPWM. Some simulation verifications are carried on in this article to show that each switching angle distribution can eliminate the specified low-order harmonics, and prove the correctness of the multi-pattern switching angle distributions.