Capacitor Voltage Balancing Schemes in Flying Capacitor Multilevel Inverters

This paper focuses on the development of capacitor voltage balancing methods in a flying capacitor multilevel inverter (FCMLI). Three such strategies have been described and have been applied to a five-level CMLI. The sinusoidal pulse width modulation technique has been used while making the proposals. The first scheme works on the principle of selection of the most favorable switching state depending on the preferential charging and discharging of capacitors. It uses a two-level comparator for each capacitor state detection. In the second scheme, capacitor voltages are controlled in a three-level comparator to achieve better performance. In the third scheme, a sampling frequency-based approach for controlling the capacitor voltages has been proposed to achieve further improved performance. The performance of proposed strategies is confirmed through both simulation and experimental investigations.