An optimization strategy for voltage regulation of three-phase PWM rectifier based on two-degree-of-freedom PID

The VSR-VSI dual three-phase pulse width modulation (PWM) converters based on the cascade connection of a front-end three-phase voltage source rectifier (VSR) and a back-end three-phase voltage source inverter (VSI) have been widely used in elevator energy feedback systems, but the front-end three-phase VSR using the traditional proportional integral (PI) double closed-loop control structure usually has the problem that the mid-end DC voltage cannot take into account the disturbance immunity and the follow-ability. Given this, an improved DC voltage regulation strategy of the three-phase PWM rectifier based on two-degree-of-freedom proportional integral differential (PID) is proposed. Firstly, the structure and working principle of the three-phase VSR-VSI dual three-phase PWM converters are expounded. Then, the PI double closed-loop control scheme of the front-end three-phase VSR and its parameter design process are given to analyze the reasons why this traditional scheme cannot have good disturbance immunity and follow-ability of the DC voltage regulation system. On this basis, an optimized DC voltage regulation improvement strategy for the front-end three-phase VSR based on two-degree-of-freedom PID and its corresponding parameter design method are given. Finally, the correctness and the superiority of the proposed three-phase PWM-VSR DC voltage regulation strategy are verified by using the simulation and experimental comparison results.