A Compensation Component Injection Method Based on a Hybrid Modulation for Minimizing the Neutral-Point Voltage Oscillations in a Five-Level Flying Capacitor Rectifier

Neutral-point (NP) voltage oscillating is an inherent problem for multilevel converters with split dc-link capacitors. In this article, a compensation component injection method based on a hybrid modulation for minimizing the NP voltage oscillations in a five-level flying capacitor rectifier is proposed. In specific, the equivalent modulation waves are first obtained by adopting an existing simplified space-vector modulation method. And a hybrid modulation which gives both the same optimal harmonic performance as phase-disposition pulse width modulation (PWM) and the same superiority of flying capacitor voltage regulation as phase-shifted PWM is adopted. Meanwhile, the solved optimal compensation component in each subsector is injected to make the average NP current equal to zero for minimizing the NP voltage oscillations. Simulations and experiments were conducted to verify the performance of the proposed compensation method based on the hybrid modulation.