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

The increasing deployment of offshore wind farms necessitates robust and stable High-Voltage Direct Current (HVDC) networks. Achieving optimal stability, especially in damping oscillations on the DC side, remains a significant challenge. This study
focuses on mitigating post-fault converter de-blocking oscillations, a critical issue exacerbated by complex interactions between AC and DC systems, converter dynamics, and system faults.These behavior are governed by nonlinear system dynamics, making traditional control methods less effective in ensuring stability. A comprehensive analysis of DC side oscillations
and their interaction with converter dynamics is developed to understand the key factors influencing system stability.
The research investigates a DC voltage regulation damping approach, identified as the most effective solution in the literature. Comprehensive parametric sensitivity analysis evaluates system behavior under diverse operational conditions. Addressing current
damping method limitations during converter de-blocking, this work proposes an innovative control approach integrating Fuzzy Logic Control (FLC) and Proportional-Integral (PI) controllers. This approach enhances DC voltage regulation and incorporates
a modified Circulating Current Suppression Control (CCSC) in the inner loop. The proposed control strategy leverages FLC’s ability to adapt in real-time to nonlinear dynamics, based on fuzzy set theory, and is designed to mitigate nonlinear oscillations
more effectively than conventional linear control methods. The coordinated FLC-PI controller dynamically adjusts to
nonlinear system dynamics in real-time, providing a robust framework for improved post-fault recovery. It aims to achieve faster recovery times and reduced overshoot compared to conventional methods. The proposed controller’s efficacy is validated through
comparative analysis with existing approaches. Electromagnetic Transient (EMT) simulations using the Real-Time Digital Simulator (RTDS) platform demonstrate the controller’s performance under realistic operating conditions.