Smooth reference modulation based protection of fault current limiting DC/DC converters

Abstract

Low voltage DC microgrids have been gaining great attention for the integration of renewable energy source and energy storage units, and electronic loads. DC microgrids are commonly controlled using the hierarchical control strategy (HCS) to provide flexible operation in both grid-connected and islanded modes. The HCS relies on proportional-integral (PI) controllers and employs the droop control strategy. To improve the fault ride-through of HCS based extra low voltage DC microgrids, this paper proposes a simple, accurate, and cost-effective current limiting strategy. The proposed control system based scheme modulates the current reference of the primary control level of HCS during an overcurrent condition using the smooth set point automatic adjustment with correction enabled technique. It properly protects the semiconductor switches of interface voltage-sourced DC-DC converters by accurate limiting their inductor currents. The main advantage of the proposed scheme is that it is implemented in the available PI controller based primary control level of the HCS. Also, it does not require the converter and load data. Several case studies performed in MATLAB/Simulink environment are presented to demonstrate the superior ability of this scheme for limiting fault current in different scenarios compared to conventional current limiters.