Research on an improved sliding mode control method for PWM rectifier
For the traditional three-phase two-level pulse width modulation(PWM)rectifier under PI control,the start-up operation of the rectifier under PI control generates a large impulse current instantly,which is easy to damage the circuit components and affect the dynamic and steady-state performance of the sys-tem.A double closed-loop control strategy for sliding mode variable structure using exponential approximation law is proposed.First,the study has established the discrete mathematical model formula for the AC side of the PWM rectifier,and analyzed the relationship between parameter variables that affect the inrush current during startup.The PWM rectifier is pre-charged to reduce the start-up impulse current,and the current feed-forward compensation is carried out to accelerate the dynamic response of the system.Then,by using a varia-ble boundary layer for improved sliding mode control,the impact of system chattering is mitigated.Through simulation experiments,it was verified that the improved sliding mode control produces a smoother output waveform at startup compared to traditional PI control;the dynamic response time is also reduced when the load changes.The chattering of the output waveform in the improved sliding mode variable structure is sup-pressed,and the fluctuation amplitude of the desired parameter variables on the sliding mode surface during steady-state is reduced,avoiding high-frequency switching of the controller.The dynamic and steady-state per-formance of the system is significantly better.
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维普
