Chopperless Fault Ride-Through Control for DC Microgrids

The dc microgrid should remain connected to the ac utility grid to support the grid stability during faults. However, the bidirectional power flow between the utility grid and the dc microgrid will cause either high-voltage or low-voltage faults at the dc bus. It is difficult to control a large number of heterogeneous sources at the dc bus to ride through the fault, as well as exporting reactive power or reactive current to the utility grid. This article proposes a chopperless fault ride-through control strategy for the dc microgrid. The proposed control strategy utilizes the controllability of dc microgrids without using chopper circuit on the dc side to balance the system power. Following goals are achieved by this control strategy: 1) maximizing the output reactive power to the utility grid; 2) reducing the dc bus voltage ripples; 3) realizing the decentralized emergency power control among different distributed generators. The effectiveness of the proposed control method has been validated through related case studies in both simulation and hardware-in-loop (HIL) tests.