Submodule capacitor parameter design of modular multilevel converters to avoid system resonance

Submodules play an important role in modular multilevel converter and its capacitor parameter design is crucial for the safe and stable operation of modular multilevel converters. Based on the constraint relations of electrical variables within the system under the steady state, the relationship among the arm current, transmission energy and working states was deduced in detail. Then the current flowed through the capacitor was obtained based on the arm current. Considering the maximum working voltage limit and to avoid system resonance, the design principle and the calculation method for the capacitance value and the highest working voltage were proposed. Simulation results based on MATLAB/Simulink prove the rationality and feasibility of the proposed design method.