Strategies for AC and DC Faults Ride-through Operation of Hybrid MMC based HVDC Link without using Fast Communication

Abstract

This paper proposes a set of operational strategies implemented through suitable control characteristics for a point to point (PTP) HVDC link using hybrid modular multilevel converter. The proposed strategies ensure stable operation of the PTP system under various operating conditions, like AC and DC side faults while maintaining average submodule (SM) capacitor voltages to their nominal values. Further, during DC side fault, the converter is capable of making the DC side current zero without sacrificing the reactive power injection capability into the AC grid. During AC side fault, the control characteristics are adjusted to regulate the average SM capacitor voltages, which help quick restoration of power flow after fault clearance. The performance of the proposed strategy is verified under different operating conditions through simulations in PSCAD/EMTDC platform.