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。
(Using simulink toolbox of Matlab simulation. Single-phase PWM bridge inverter circuit, the use of unipolar trigger mode, load, power, establishment of model, trigger the production of PWM module, draw the fundamental relationship between the amplitude and duty cycle.)