An MMC based HVDC system with optimized AC fault ride-through capability and enhanced circulating current suppression control

Modular multilevel converter (MMC) is a proven technology for HVDC applications due to its salient features such as modularity and excellent power quality. To ensure best possible grid support, recent codes require incorporating fault ride-through (FRT) strategies so that stations remain connected maintain reliable operation under various symmetrical asymmetrical AC faults. In this paper, communication-free enhanced technique without the need of DC chopper has been proposed. The proposed FRT strategy ensures quick post recovery can effectively manage link capacitor voltages within safe limits. Along with strategy, in order avoid high circulating current (CC) inside an MMC, paper optimal control approach based on proportional resonant PI controllers abc reference frame. suggested lowers ripple while reducing magnitude CC. Under both balanced unbalanced ac conditions, dc voltage also reduced use dual synchronous frame or any additional controllers. Simulation results confirm effectiveness CC suppression techniques 580-kV, 850-MW MMC-based system.