Improved Post-Fault Recovery in MMC-HVDC Networks using Enhanced Active Damping

Abstract

High-Voltage Direct Current (HVDC) transmission with Modular Multi-level Converter (MMC) - Bipolar Point-to-Point (BPP) configuration is gaining traction as a solution for integrating renewable energy sources into future power grids. However, one critical challenge associated with MMC-BPP systems is the occurrence and mitigation of oscillations on the DC side. These oscillations can arise due to various factors, including interactions between the AC and DC systems, converter de-blocking after fault events, and the dynamic behavior of connected power sources. The research work presented in this paper addresses a gap by investigating and mitigating oscillations specifically occurring during post-fault converter de-blocking. An enhanced active damping method is proposed that achieves a substantial reduction of these oscillations, ensuring improved system stability during this critical phase. Furthermore, a meticulous parametric sensitivity analysis is conducted on a four-terminal MMC-BPP test system using a real-time simulator to extract valuable insights into the damping method’s effectiveness under various operating conditions.