Five-level H-bridge flying capacitor converter voltage balance dynamics analysis

Flying Capacitor (FC) multilevel Pulse Width Modulated (PWM) converters are an attractive choice due to the natural balancing property of the capacitor voltages. A single-leg flying capacitor converter voltage balance dynamics analytical solution may be obtained using switched systems time domain approach based on stitching of switching intervals piece-wise analytical solutions in combination, for inductance dominated load, with a small parameter technique. In this paper, a symmetric five-level H-bridge flying capacitor converter common mode voltage balance dynamics solution is obtained from its single-leg prototype using “mirror hypothesis” formalism. Simple analytical expressions clearly reveal the dependences on load parameters, carrier frequency, and DC PWM normalized voltage command. For AC modulation, the solution obtained by averaging on a fundamental AC period does not depend on a fundamental frequency. The results of the theoretical analysis are confirmed by extensive switched simulations.