Resonant Controllers Design for Frequency-Selective Impedance Controlled DC Microgrids

The resonant-type controllers are commonly used in dc microgrids in order to suppress the steady-state ripples of a microgrid's dc bus voltage. As the resonant controllers are prone to cause instability issues and anomalous peaks in closed-loop frequency responses, it is of particular importance to investigate it thoroughly for the frequency-selective impedance controlled (FSIC) dc microgids, where the cascade of the resonant-type controllers is used in control of the interfacing power converters to reduce the bus's impedance at the selected frequencies. In this paper, based on the Nyquist plots analysis results, design of the FSIC resonant controllers is carried out and a step-by-step design procedure is proposed to ensure stability and no impedance peaking nearby the FSIC's frequencies. The proposed design is verified through the experiments.