Modular multilevel inverter control for electric vehicle propulsion: A capacitor voltage balancing approach

In Modular Multilevel Inverters (MMIs), capacitor voltage balancing is a crucial issue because uneven submodule capacitor charging and discharging can raise harmonic distortion and lower system reliability. An auto-cyclical sequencing approach for a three-phase, three-level MMI designed for squirrel-cage induction motor (SCIM) traction applications is presented in this work. Without the need for extra voltage sensors, sorting algorithms, or intricate balancing controllers, the suggested method ensures consistent capacitor consumption by alternating the switching duties of upper and lower submodules on a regular basis. Simulation studies performed in MATLAB/Simulink using a 2 kW SCIM load demonstrate that capacitor voltages converge to approximately 249–250 V with less than 1 V deviation, while current THD is reduced to 3.89% for the modulation index of 0.9. The viability of the suggested balancing concept is confirmed by experimental validation utilizing a low-voltage hardware prototype. The results show better output waveform quality and capacitor voltage equalization. For upcoming medium- and high-power EV traction inverter applications, the suggested solution provides a straightforward and computationally effective balancing technique.