Input filter analysis and resonance suppression control for electrolytic capacitor-less inverter

This paper presents an analysis on electrolytic capacitor-less inverter and proposes a strategy for resonance suppression control for a DC-link voltage and input current in electrolytic capacitor-less inverter. The proposed electrolytic capacitor-less inverter can operate both in the motoring mode and regenerating mode owing to its inherent bidirectional power flow capability of the active front-end rectifier whose switching frequency is equal to the input line frequency. However, in the electrolytic capacitor-less inverter, the DC-link voltage is fluctuating with six times of the frequency of input three phase source due to its small DC link capacitance. Also, an input filter should be employed to remove the high frequency component generated by PWM inverter. By the input filter, the DC-link voltage can be resonant, and a specific resonance suppression control is required when the input line-to-line voltage is low and the demanded power is large. In this paper, a novel resonance suppression strategy is proposed for a stable operation of the electrolytic capacitor-less inverter. The experimental results show the effectiveness of proposed strategy.