Capacitor Voltage Monitoring in Modular Multilevel Converter

A Modular Multilevel Converter (MMC) is an attractive solution for power conversion without transformers. As MMC consists of cascade connections and floating dc capacitors, it requires continuous voltage monitoring. An adaptive observer design has been presented to estimate the capacitor voltages from the measurement of arm currents. This work introduces a capacitance value of the cell capacitors as a parameter uncertainty for making the system performance robust with unknown constant parameters. Stability and convergence of the proposed observer are analytically proved using Lyapunov theory. Simulation results confirm the validity of the proposed approach.