A Real-Time Performance Assessment Scheme for Half-Bridge Submodules of Modular Multilevel Converters

This paper proposes a real-time testing scheme for individual modules of Modular Multi-level Converters (MMCs), which are used in VSC-HVDC systems and high-voltage electric motor drives. In MMCs for voltage-source HVDCs, multiple submodules (SMs) are connected in series to form one arm. For MMCs comprising hundreds of identical submodules connected in series, testing the entire system is highly time-consuming and costly, while the proposed method enables real-time testing of each submodule, thereby significantly reducing overall system development cost and time. This study presents a method for configuring one SM from the series-connected SMs with an external circuit, allowing it to be tested under actual MMC operating conditions. The proposed method is comprehensively validated via Hardware-in-the-Loop Simulation (HILS), incorporating operability assessments and a real-time implementation of the circuit model to verify its practical applicability.