| The three-phase AC power supply is currently used for high power load, because of the more strict quality code for grid, rapid development of power electronics industry and growing demand for high performance rectifier from customers, diode and thyristor rectifier is gradually replaced by PWM rectifier, which is widely used in many areas. By using advanced control methods, the steady harmonics performance, dynamic performance for power and dc link voltage is improved. The PWM rectifier can decrease switching frequency and switching losses, improve efficiency and decrease system capacity and cost, while meeting the requirement of grid code.This paper focuses on three popular methods for controlling PWM rectifier, which are the classic double PI closed-loop current control, direct power control (DPC) and model predictive control (MPC) methods. The steady and dynamic performance of three methods is researched under same switching frequency, We found that the steady performance of classic double-loop PWM rectifier current PI is fine, but the dynamic performance is not good, the direct power control (DPC) dynamic performance is better than the classic double-loop PI control, but the steady-state power ripple effect is large, the model predictive control (MPC) dynamic performance is the best, but its current THD performance is between DPC and double-loop PI control method. Based on above observation,an improved model predictive control method is proposed in this paper. The proposed method holds the best current THD performance among all methods, and has same fast dynamic performance as MPC method. The validity and good steady and dynamic performance of proposed method is verified by simulation results. The proposed method shows potential to improve other types of traditional MPC control methods also. |
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