An Enhanced Four‐State Protection Strategy for Inverter‐Interfaced Distributed Generation Unit Under Short‐Circuit Fault Condition

ABSTRACT Inverter‐interfaced distributed generation (IIDG) unit requires special attention to keep reliable operation under short‐circuit fault condition. However, when the fault is clear, overvoltage and overcurrent issues of the IIDG unit may occur and even trigger its shutdown. To tackle these issues, an enhanced four‐state protection strategy for the IIDG unit is proposed. Firstly, the model of the IIDG unit under normal and short‐circuit fault conditions is analyzed. Secondly, based on the analyzed model, an enhanced four‐state protection strategy, which contains normal state, hardware current‐limiting state, software current‐limiting state, and recovery state, is presented, respectively. Moreover, the parameter design of the proposed protection strategy is also given comprehensively. Thanks to the enhanced four‐state protection strategy, overvoltage and overcurrent issues of the IIDG unit under short‐circuit fault condition are addressed. What is more, the proposed protection strategy can not only keep satisfactory dynamic performance under short‐circuit fault condition, but also improve the reliability of the IIDG unit. Finally, simulation and experimental results in a 5‐kVA IIDG unit verify the correctness and feasibility of the proposed protection strategy.