Enhanced Inverter Current Control Method for Variable Frequency Drive System with Small Film DC-Link Capacitor

The power factor (PF) and grid current distortion are two major issues for the promotion of variable frequency drive system with small film capacitors. This paper proposes an inverter current control method to shape the inverter current following grid current, and hence high PF can be obtained. Considering the cutoff effect of diode rectifier, the main components of the inverter current are analyzed. The inverter current loop with proportional integration multi-resonant (PI-MR) controller is proposed to regulate ac component with multi times of base frequency. Both the system loop stability and tracking performance are ensured with the proper parameters design. In addition, an error compensation method with the prediction of inverter current variation is developed to enhance the inverter current control, which improves the grid current performance with the sampled grid and dc-link voltage. Experimental results verify the validity of the proposed method and the PF is up to 0.987.