Voltage balancing control for reduced flying capacitor converters using hybrid phase-shifted carrier phase-disposition PWM

This paper proposes a new approach of modular cell converter with reduced flying capacitors (RFCC) using hybrid phase-shifted carrier phase-disposition PWM (PSC-PD-PWM). The proposed topological design is achieved by clamping a series of modular cell onto a low operational frequency cell. By doing so, the transformerless RFCC significantly reduces the component counts, cost and size. The voltage balancing of the flying capacitors are importantly concerned which may affect both reliability and stability of the system. Thus, a closed-loop flying capacitor voltage balancing control is proposed as well. The hardware prototype is also developed to prove the feasibility of the proposed RFCC and the voltage balancing control based on the seven-level (7L) pole voltage waveforms under various dynamic operating conditions.