Control-hardware-in-the-loop simulation studies of modular multilevel converters

Abstract

The modular multilevel converter has been used in the high-voltage direct current (HVDC) transmission system due to its modularity and scalability. Besides, it can be applied for the applications that have high voltage. However, there are some control problems which affect the normal operation of the modular multilevel converter. The control problems include the circulating current and capacitor voltage fluctuation. The PR control method is proposed in this report to decrease the circulating current and voltage balancing methods are used to control the capacitor voltage. In order to verify the methods, RT-LAB and Matlab Simulink are used to build the model and analyze the simulation results. Simulation results of the Matlab Simulink and RT-LAB demonstrated the effectiveness of the PR control method. Besides, the simulation results also verify the validity of the voltage-balancing methods. It has been shown that the voltage control methods not only reduce the capacitance voltage fluctuation range, but also decrease the circulating current.