A Half-Bridge Submodule Modular Multilevel Converter-Based Series HVDC Tap

Abstract

Rural electrification remains a significant challenge due to the limitations of conventional grid expansion, the prohibitive cost of installing extensive infrastructure, and the technical barriers associated with delivering reliable power to remote locations. This study proposes an innovative half-bridge submodule-based modular multilevel converter (MMC) series tap for line-commutated converter (LCC)-based High Voltage Direct Current (HVDC) transmission systems to supply reliable and sustainable power to rural regions. The proposed MMC series tap is configured to deliver a 25 MW at 11 kV three-phase AC load while incorporating a battery-based energy storage system (BESS) to achieve uninterrupted DC–AC power conversion under different demand conditions. Power balance is efficiently obtained during load variations via a closed-loop control developed to coordinate the power exchange between the BESS and the MMC, thereby regulating the MMC DC-link voltage. The proposed approach is validated using MATLAB/Simulink, and the results verify the feasibility and robustness of the system at different loading conditions.