Six-Level DC-DC Flying Capacitor Converter Voltage Balancing Dynamics Analysis for Different Carrier-Based Modulation Strategies

Abstract

N atural balancing in Flying Capacitor Converters (FCC) is typically analyzed for appropriate lead (or lag) carrier-based Phase Shifted Pulse Width Modulation (PS-PWM) strategy. However, multiple PS PWM strategies are possible by different carrier orders. The paper presents a comprehensive analysis of natural balancing properties of six -level DC-DC FCC considering all PS- PWM strategies possible by carrier order combinatorics. The time domain analysis uses stitching of piece-wise analytical solutions for consecutive switching intervals in conjunction with a small parameter approximation. Simple analytical solutions for natural balancing frequencies and decay factors clearly show dependences on converter parameters, DC voltage reference and switching frequency. Classic lead (lag) PS-PWM proves to be the best among possible PS-PWM strategies from the balancing rate perspective.