Method to minimize the low-frequency neutral-point voltage oscillations with time-offset injection for neutral-point-clamped inverters

Abstract

This paper proposes a method to reduce the lowfrequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a timeoffset to the three phase turn-on times. The proper time-offset is simply calculated considering the phase currents and dwell time of small and medium voltage vectors. The proposed method does not affect the outputs and there is no increase in the switching frequency. Further, it does not require additional hardware or complex calculations. Simulation and experimental results verify the validity and feasibility of the proposed strategy.I. 978-1-4799-0336-8/13/$31.00 ©2013 IEEE

A simplified hybrid carrier‐based PWM technique for three‐level NPC inverters considering neutral‐point voltage balance

“…, is the most widely studied and used in all types of industrial applications in the range of 2.3–4.16 kV, with some applications up to 6 kV . A vast amount of literature is mainly dedicated to the modulation strategies and the balancing control of the neutral‐point voltage. Seo et al .…”

“…1, is the most widely studied and used in all types of industrial applications in the range of 2.3-4.16 kV, with some applications up to 6 kV [11]. A vast amount of literature [2,4,6,7,[12][13][14][15][16][17][18][19][20][21][22][23] is mainly dedicated to the modulation strategies and the balancing control of the neutral-point voltage. Seo et al [12] proposed a simplified three-level space vector pulse width modulation (SVPWM) method.…”

“…The DC imbalance can cause distortion of the output currents, but it can be easily solved by the balancing algorithm. Compared to the DC imbalance problem, the AC imbalance problem is discussed in many papers [2,6,13,15,16,[18][19][20]23]. The frequency of the neutral-point voltage oscillation is 3 times the fundamental frequency, and its amplitude strongly depends on the output current, the power factor, and the value of the capacitor [2,17,24].…”