LCL type grid-connected converter no startup inrush current control method based on capacitor branch voltage feedforward
Dual-loop PI control strategy for LCL type grid-connected converter is usually used in wind power generation. Serious inrush current will be caused when grid-connected converter runs on the rectified status at the start time if no effective control strategy is taken, so it is necessary to improve the startup control performance and the grid voltage feedforward method is usually used. However, in wind power generation, the grid voltage of the transformer's high voltage side can't be directly sampled. To deal with it, a method is proposed based on the feedforward of filter capacitor branch's voltage. Firstly, the mathematical model of LCL type grid-connected converter, under the synchronous rotating reference frame, is established. And the cause of inrush current at the rectified start time of grid-connected converter is analyzed in detail. Then, the feedforward of capacitor branch's voltage is introduced into the output of current loop, and the theoretical analysis on its effectiveness of inrush current suppression is made. Finally, the simulation analysis based on the 10kW LCL type grid-connected converter and the experiments based on the 10kW direct drive wind power grid-connected converter prototype are carried out. The results verify that this method can effectively suppress startup inrush current and improve dynamic response of the grid current control.