Decentralized Control with Submodule Temperature Balancing for Modular Multilevel Converter

Abstract:
Modular multi-level converters (MMCs) are common topology in medium or high voltage applications because to their functionality, hardware implementation, configuration complexity, output power quality, reliability, low output current total harmonic distortion (THD), and high efficiency. Temperature control of semiconductor devices in submodules (SMs) is critical for the safe and reliable performance of MMC since it employs more semiconductor devices than other topologies with hundreds of submodule per arm. To extend the lifetime of MMCs in abnormal operation, this paper proposes a decentralized sub-module temperature balancing control for the MMC using the decentralized self-aligned phase-shifted pulse width modulation method. This temperature balancing approach, which is integrated into the capacitor voltage balancing, is proposed to control the temperature of the SMs in normal operating conditions and also in case of cooling system failure or SMs parameter mismatch. The key approach is that each SM local controller regulates its own voltage and temperature by utilizing information from adjacent SM controllers. Simulation results demonstrate the viability of the proposed control scheme in association with self-aligned phase-shifted carriers.