Negative Sequence Impedance Based Inverter On-board Open Phase Detection

Inadvertent occurrence of open phase conditions is a concern for DER integration, due to the unregulated voltage on the opened phase. This situation can lead to overvoltage or ferroresonance, resulting in equipment damage and even posing risks to public safety. Although IEEE standard 1547-2018 mandates DER to detect and trip for open phase condition at its reference point of applicability (RPA), it may be challenging for DER to detect an open phase condition upstream on the feeder, especially with local loads. This paper presents a feeder open phase condition detection method that only utilizes the inverter’s onboard resources, without any additional sensor or relay. The method utilizes inverter perturbations to evaluate the network negative sequence impedance, identifying the open phase conditions. Simulation verifications are demonstrated under various circuit conditions, including different transformer configurations, loading conditions, etc., indicating the effectiveness of the proposed method.