A Fault Ride-Through Method for LVDC Networks With Photovoltaic Energy Storage Systems

Fault ride-through (FRT) is key to DC distribution networks for both avoidance of system blocking and improvement of the safety of flexible DC devices in the face of faults. This article proposes an FRT method for low-voltage DC distribution networks with a photovoltaic energy storage system, which achieves rapid fault detection and constraint of fault current contributed by DC solid-state transformers (DCSST), making non-blocking FRT viable. An inductor-based current-limiting module (CLM) is designed to cooperate with capacitors on the output terminal of a DCSST to restrain current and maintain voltage in the wake of faults. The system voltage can recover to a stable level swiftly after the FRT process under temporary faults. Correspondingly, permanent faults can be reliably isolated by DC circuit breakers after a reasonable FRT delay to minimize their impacts. Finally, a DC distribution network with a CLM is modeled in PSCAD/EMTDC and a hardware-in-the-loop test platform to verify and validate the overall effects and performance of this proposed method. Consequently, effectiveness and superiority of this method is justified in the test, where the results highlight its quick, stable and controllable fault current suppression capabilities compared with existing FRT methods under various fault conditions.