Dual PWM Converter Load Power Feedforward Direct Power Control

Dual PWM converter has advantages of low harmonic distortion of AC side current, unity power factor, constant DC side voltage and bidirectional power flow. When applied to asynchronous motor speed adjust system, it can improve the converter power access point power energy and achieve energy conservation when the motor works in special conditions. This paper analyzes PWM rectifier direct power control (DPC) strategy and dual PWM converter coordinate control strategy.Dual PWM converter power flow character is analyzed in detail based on dual PWM converter topology. The power mathematical model of PWM rectifier is established and space vector modulation (SVM) is adopted in PWM rectifier DPC. The PI regulator and the space voltage vector modulation (SVPWM) method replace the hysteresis controller and the switching table of the conventional DPC system. Constant switching frequency is good for the inductor and the capacitor design and reduces the switch loss. Decoupling control method is taken to power control loop, the simulation model is established and the expected results are gained.The inverter and the motor are treated as a whole part to get the load power calculate method in the asynchronous speed adjust system. To the coordinate control strategy of dual PWM rectifier, this paper propose coefficient modified load power feedforward control strategy, it can adjust PWM rectifier power flow according to the variation of load power to reduce the DC side voltage and AC side current distortion. The simulation results prove the proposed strategy's feasibility.Part experiment is done to the PWM rectifier DPC SVM system and dual PWM converter system. The results show that the AC side current has low harmonics and the DC side voltage can maintain constant.