An Improved Sensorless Method to Submodule Voltage Balancing in Grid-Connected Modular Multilevel Converters

This article proposes an improved sensorless capacitor voltage balancing (CVB) method for modular multilevel converters (MMCs) for high-voltage direct current applications. The suggested method prioritizes achieving precise, straightforward, and computationally efficient control of MMCs, eliminating the necessity for external sensors. Simultaneously, it guarantees effective management of capacitor voltage balance within the converter arms. Combining the proposed sensorless control technique and CVB methods improves converter performance, reduces complexity, and increases overall system reliability. To validate the effectiveness of the proposed strategy, full simulations are performed. The simulation setup includes the MMC structure, the control algorithm, and the sensorless CVB method. The simulation results demonstrate the accurate regulation of energy flow while maintaining balanced capacitor voltages between the arms of the MMC. In addition, experimental verification is carried out using a scaled-down laboratory prototype of the MMC system. The experimental results validate the practical feasibility and reliability of the proposed control strategy.