Tuning Free DPC for ETO-Based MMC-HVDC System with Unbalance Fault-Ride-Through Capability

This study presents a direct power predictive control strategy for a Modular Multilevel Converter (MMC) based HVDC transmission system using Emitter Turn-Off (ETO) thyristors. The presented predictive control strategy provides unbalanced voltage fault-ride-through capability to the converter without the use of any weighting factors and thus avoiding any tuning. The control scheme is divided into three stages to handle different objectives which are power regulation, mitigation of circulating currents of MMC and submodule capacitor voltage balancing. Power regulation stage does not require any phase locked loop (PLL) thus simplifying the control strategy. The MMC-HVDC transmission system is simulated in MATLAB/Simulink and the results presented here demonstrate a satisfactory response.