Research On Control Method Of Electrolyticcapacitor-less Variable Frequency Drive System

According to the conventional permanent magnet synchronous motor variable frequency drive system,the DC bus electrolytic capacitor has the problems of large volume,short life,high price and low power factor of the system,and adopts the electrolytic capacitor-less variable frequency drive system.Due to the small-capacity film capacitor on the DC bus of the electrolytic capacitor-less variable frequency drive system,the DC bus voltage fluctuates,which directly affects the input power,speed and torque of the motor.In order to further improve the performance of the electrolytic capacitor-less variable frequency drive system.The control method for the electrolytic capacitor-less variable frequency drive system is studied.The power flow of the system is analyzed,and the power closed-loop control strategy with input power as the given value is adopted to improve the input power factor of the system.It can be seen from the simulation experiment that compared with the traditional electrolytic capacitor variable frequency drive system,the input power factor of the electrolytic capacitor-less variable frequency drive system under the power control strategy is significantly improved.Through the analysis of the anti-disturbance capability of the system DC bus voltage,a virtual resistance control algorithm is used to calculate the virtual voltage by using the estimated voltage,and the inverter's output voltage is modified according to the virtual voltage value to actively change the dynamic impedance of the system.The virtual resistance control algorithm is beneficial to the stability of the DC bus voltage fluctuation,and the DC bus voltage anti-disturbance capability is ensured when the motor load changes stepwise.When the permanent magnet synchronous motor runs at high speed and drives the load,the system fluctuates at the boundary of the overmodulation when the voltage fluctuation on the DC bus is large.When the output voltage required by the controller is greater than the inverter output voltage limit.Aiming at this problem,an adaptive weak magnetic control algorithm for overmodulation boundary operation is proposed.On the basis of the theoretical and simulation experiments,the experimental verification is carried out on the experimental platform.The experimental results verify the feasibility and effectiveness of the control method.