An Improved Method for Capacitor Voltage Balancing Control and Capacitance Monitoring in Modular Multilevel Converter

The modular multi-level converter (MMC) is widely recognized as one of the most promising structures for high-voltage and high-power applications due to its fully modular design, lack of bulky output filters, and independence from multiple DC sources. However, the large number of flying capacitors within the MMC architecture presents significant challenges to system reliability, particularly in maintaining accurate voltage balance. Traditional methods to ensure voltage balancing require numerous voltage sensors, which increase both the cost and complexity of the system, potentially undermining its reliability. This paper introduces an innovative capacitor voltage balancing method aimed at enhancing the reliability of the MMC. By using a single voltage sensor for both half-bridge submodules (HB-SM), the proposed method simplifies the system architecture while ensuring precise voltage estimation through a simple sensor configuration. Furthermore, the unique placement of the voltage sensor facilitates a capacitance monitoring technique that accurately assesses the health of the capacitors, thereby further enhancing the converter's reliability. The proposed method's efficiency has been confirmed by simulation and experimental investigations in various scenarios.

کلیدواژه ها:

Multilevel Converter (MMC) ، Capacitor Voltages Balance ، Half-bridge submodules(HB-SM) ، capacitance monitoring