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Technical Lecture

PWM Strategies

T34.1 - A Space Vector PWM Strategy for Charging of Bootstrap Capacitor in Three-Level Neutral-Point-Clamped Inverter

Thursday, March 20, 2025
10:10 AM – 10:30 AM ET
Location: Level Three, A311
This paper presents a space vector PWM method to achieve a high power density three level inverter(3LI) with a bootstrapped gate drive circuit. The proposed method solves an inherent issue of the charging of the bootstrap capacitors during the inverter operation. The effectiveness of the method is demonstrated through experiments carried out on a 5kW motor drive with an input voltage of 350V and switching frequency varying from 8 kHz to14 kHz. Stable and efficient performance is maintained across a wide modulation index range, with a bootstrapped 3LI board approximately half the size of a conventional 3LI. Furthermore, loss comparisons between the bootstrapped 3LI board and a 2LI board with LR load show that the power output can be increased by 1.5 times due to reduced switching losses.