A Passive Variable Switching Frequency PWM for Three‐Phase Three‐Level T‐type Converter With Reduced Harmonic and Low Switching Loss

Abstract

To address the issues of concentrated harmonic energy and high electromagnetic interference (EMI) peaks in T‐type neutral‐point‐clamped converters(T‐NPC) under the traditional constant switching frequency pulse width modulation (CSFSPWM), this paper proposes a passive variable switching frequency pulse width modulation (PVSFPWM) method. The core of this method lies in introducing a periodic injection function with specific symmetry and phase relationships, which realizes the passive adjustment of switching frequency and the natural balancing of midpoint potential without the need for additional control loops. Theoretical analysis and experimental verification show that the proposed method can effectively disperse harmonic energy and reduce switching losses. This research provides a modulation strategy with both superior performance and control simplicity for T‐NPC.