中文说明：这是个新型的单相三电平逆变器，用一个三电平桥臂和一个普通桥臂组成，SPWM控制。在matlab2008上运行
English Description：
This is a new single-phase three-level inverter, which is composed of a three-level bridge arm and a common bridge arm, and is controlled by SPWM. Running on MATLAB 2008