An Overcurrent Suppression Strategy for Distributed Photovoltaic Inverters Under Unbalanced Faults Based on Adaptive Linear Active Disturbance Rejection Control

ABSTRACT After distributed photovoltaic (PV) systems are connected to the distribution network, the overcurrent problem caused by transient faults instantaneously threatens the safety of PV inverters and other equipment. This paper proposes a comprehensive control method that combines active‐loop adaptive linear active disturbance rejection control (A‐LADRC) with fault voltage adaptation and reactive‐loop smooth switching to address the transient overcurrent issue of inverters under unbalanced faults. Firstly, the low‐voltage ride‐through (LVRT) control principle of distributed PV systems and the mechanism of overcurrent generation under unbalanced faults in the distribution network are elaborated, the phenomenon of grid‐connected current exceeding the rated threshold due to fault voltage is analysed. Secondly, a fault voltage‐adaptive linear active disturbance rejection control method is designed, which is mainly used to address the overcurrent problem at the moment of fault occurrence and recovery. Additionally, to address the overcurrent caused by reactive power control during the fault period, a reactive power outer‐loop smooth switching method is introduced. Finally, a hardware‐in‐the‐loop (HIL) experimental platform based on a real‐time simulator and an actual PV inverter controller is built to verify the effectiveness and superiority of the proposed method in suppressing overcurrent.