A New PWM Method of a Three-Level Inverter Considering Minimum Pulse Width and Neutral Voltage Balance Control

Abstract

A new PWM method of the three-level inverter using a digital signal processor, which is useful for large capacity instantaneous current controlled GTO inverters is presented. In case of the three-level inverter, short pulses are always necessary to output medium voltage vectors. The output waveform deteriorates from the ideal PWM waveform by the influence of the minimum pulse width limit of the GTO thyristors. In this PWM method, firstly, the switching sequences of voltage vectors which enable the neutral voltage balance control are selected. And then, from these sequences of voltage vectors, sequences which are not affected by the minimum pulse width limit of GTO are selected. Using these switching sequences, the voltage vector mean value control PWM method based on the space-vector control is proposed. © 1993, The Institute of Electrical Engineers of Japan. All rights reserved.