| The traditional permanent magnet synchronous motor drive system connects an aluminum electrolytic capacitor between the rectifier circuit and the inverter circuit.The function of aluminum electrolytic capacitor is to decouple the power of the grid side and the motor side to ensure the stability of the DC-link voltage.The life of electrolytic capacitor itself becomes a factor that affects the reliability and use time of the motor drive system.Replacing aluminum electrolytic capacitor with a small film capacitor can greatly improve the life of the system,but at the same time,the small film capacitor brings large fluctuations in the DC-link voltage and poor performance when the motor is in steady state and dynamic working conditions.In order to solve the problem,this article will study the electrolytic capacitor-less motor drive system.The main work of this paper is as follows:First,this paper analyzes the power characteristics of the electrolytic capacitorless drive system and derive the system’s DC-link voltage mathematical model.Analyzes the impact of DC-link voltage fluctuations on the conduction angle of the rectifier diode and the impact of DC-link voltage fluctuations on the performance of the motor.Secondly,on the basis of the traditional boost power decoupling circuit,the strategy that an IP controller combing with the DC-link voltage instantaneous control is proposed.By adopting IP controller,the problem of speed overshoot and q-axis current spike caused by motor speed mutation is solved.By adopting the instantaneous DC-link voltage control strategy,the problem of large DC-link voltage fluctuations and poor motor performance under the dynamic working conditions of the electrolytic capacitor-less drive system is better solved.Thirdly,a new topology structure of electrolytic capacitor-less power decoupling circuit is studied.Compared with the traditional PFC circuit,this circuit further reduces the fluctuation of the DC-link voltage and reduces the voltage stress of the power device.The structure of the circuit is introduced and the four working states of the circuit are analyzed.The key component parameters in the circuit are deduced.Aiming at the power decoupling circuit,a control strategy for suppressing DC-link voltage pulsation is proposed.This control strategy can effectively reduce the DC-link voltage pulsation and further improve the operating performance of the motor.Finally,the theory is simulated and analyzed by Matlab/Simulink simulation platform.The simulation and experimental results verify the control strategy proposed in this paper and the new type of electrolytic capacitor-less drive system can effectively suppress the DC-link voltage fluctuation and improve the dynamic performance of the motor. |
