Self-Calibration of Voltage Sensors in Modular Multilevel Converter for Voltage Imbalance Suppression

The complexity of MMC measurement system brings about misalignment of sensors, which affects the equalization of the capacitor voltages, causing the risk of over-voltage of the IGBT devices. In this paper, by changing the position of the sensors to the submodule port, the goal of calibrating the sensors is achieved. A method of obtaining the equivalent voltage of the capacitor from the voltage of this port is firstly given. Then, the impact of the measurement misalignment is analysed according to the principle of capacitor voltage balancing control of MMC, and the detailed method of calibrating the misalignment of the sensors and calculating the error parameter is proposed,. Finally, a simulation model is built to verify the correctness and the feasibility of the analysis and the proposed methods.