中文说明：
利用Matlab中的simulink工具箱仿真。单相桥式PWM逆变电路，采用单极性触发方式，负载 ，电源 ，建立模型，制作PWM触发模块，画出基波幅值与占空比关系图。
English Description：
Use Simulink toolbox in MATLAB to simulate. Single phase bridge PWM inverter circuit adopts unipolar trigger mode, load and power supply, establishes a model, makes PWM trigger module, and draws the relationship between fundamental wave amplitude and duty cycle