DSP (XC2267) is the main control chip which does the increment PI algorithms and realizes the voltage and current double closed-loop control. Three-phase thyristor rectifier method based on the phase self-adjusting of FPGA is proposed. A method for sweptfrequency start circuit is designed to implement the transition between the high-power and low-power. The invert system uses the compound control of improved PWM and frequency phase lock to improve the control accuracy and efficiency. Lastly, by using bench, the circuit is tested and the feasibility and effectiveness of the whole system are verified.