A Comparative Review of Advanced Control Strategies for VSC-HVDC Transmission Systems

This paper presents a comparative review and simulation-based analysis of control strategies for Voltage Source Converter-based High Voltage Direct Current (VSC-HVDC) transmission systems. Conventional approaches such as PID controllers remain widely adopted due to their simplicity and ease of implementation, yet they face inherent limitations when dealing with non-linear dynamics and parameter uncertainties. To address these challenges, advanced strategies such as nonlinear, predictive, and intelligent control have been proposed in the literature. Building on this foundation, the paper provides a comprehensive review of control strategies for HVDC systems and develops a detailed case study comparing a conventional PI controller with a backstepping controller, applied to a two-terminal VSC-HVDC system interconnecting two AC grids through a 100 km cable. Simulation results demonstrate that the backstepping controller significantly outperforms the PI controller, achieving superior DC-link voltage regulation, faster active power tracking, and effective reactive power compensation. Quantitative performance indices confirm the robustness and precision of the nonlinear scheme. The findings highlight the growing importance of advanced and hybrid control methods in ensuring reliable and efficient operation of future HVDC networks.