Modeling and stability analysis of current controllers for multi-paralleled grid-connected converters with LCL-filter

This paper presents the modeling and the stability analysis of a current controller for multi-paralleled grid-connected converters with LCL-filter. A detailed discrete-time state-space model for multi-paralleled grid-connected converters is developed. The impedance-based stability criterion is also presented for multiple converters. A discrete-time current controller is designed for a single converter with uncertain equivalent impedance. Then, the same controller is also applied to a second converter and the stability of the whole system is analyzed. It is shown that it is possible to infer about the stability of the controllers from both detailed state-space model or impedance-based stability criterion. Simulation and hardware-in-the-loop results are shown when a single and two converters are connected in parallel to validate the proposal.