Harmonic Current Compensation Control and Hardware-in-the-Loop Study of a Medium-Voltage Flexible Interconnection Device

Distribution networks face low supply reliability and limited fault-recovery capability. Flexible interconnection devices enable looped operation of AC feeders and facilitate optimal power-flow control, which helps address these operational challenges. This paper proposes a novel medium-voltage flexible interconnection device with a star-connected topology, together with a compact power-module structure and its main-circuit topology. Because distribution networks often contain high background harmonics, a control scheme is developed for the device, comprising a phase-locked loop, hierarchical capacitor-voltage control, and an inner current-control loop. A harmonic-current compensation control strategy is further designed to suppress current harmonics. A hardware-in-the-loop (HIL) testing platform is built to validate the proposed strategy. The results show that the proposed topology enables flexible interconnection of distribution networks, and the proposed control strategy operates stably under high background harmonics while effectively compensating current harmonics.