Investigations in the Modeling and Control of a Medium-Voltage Hybrid Inverter System That Uses a Low-Voltage/Low-Power Rated Auxiliary Current Source Inverter

Hybrid converters consist of a main inverter processing the bulk of the power with poor waveform performance and a fast and versatile auxiliary inverter to correct the distortion. In this paper, the main converter is a medium-voltage (MV) neutral point-clamped inverter, and the auxiliary inverter is a low-voltage and low-current rated current source inverter (CSI), with series capacitor being used to minimize the CSI voltage stress. The result is a high output current quality, which is obtained with a very low switching stress in the main converter and a very small added installed power (<4%) in the CSI. This paper expands this concept by investigating the hybridization of an MV inverter with an existing LCL filter, investigating the additional challenges related to resonances, and proposing a solution for stable operation. The experimental validation of active ripple cancellation has been provided at 3 kW.