English 
The topological structure of the PWM inverter is shown in Fig. 2a. The inverter input is connected with the output end of the DC voltage regulator, the voltage of the input end is the voltage value UDC after the DC voltage regulator, the output end is merged into the power grid through the filter inductor, for the wind power grid-connected inverter system, the output phase voltage, the phase current and the power grid electromotive force satisfy the vector relation shown in Fig. 2b.
For an infinite public power grid, the grid-connected inverter is used as a current source to transmit electricity to the grid. Therefore, the control output power can be achieved by controlling the output current of the inverter. It is shown from FIG. 2b that in order to generate harmonic pollution from the public power grid, the inverter output current must be reversed with the grid voltage to realize the output of the unit power factor of the inverter. In order to achieve this, the inverter control system is designed as shown in Fig. 3.
