A space vector based PWM switching scheme for the reduction of common-mode voltages for a dual inverter fed open-end winding induction motor drive

Abstract

It has been demonstrated that two two-level inverters connected at each end of an open end winding induction motor are capable of achieving the functionality of a three-level inverter. In this paper, a space vector based PWM switching scheme for the dual inverter fed open end winding induction motor drive is proposed. The common-mode voltages associated with such a drive are significantly reduced with the proposed PWM strategy., compared to the work reported earlier. In this work, the redundancy of the space vector combinations at a particular location is exploited, to reduce the common-mode voltages at lower indices of modulation. In the work reported earlier, the common mode voltages were enhanced with the decrement of modulation index. On the contrary, the common-mode voltages are reduced with the decrement of the modulation index with the PWM strategy presented in this paper. This PWM scheme for open-end winding induction motor drives may be suitable for applications, which call for frequent starting and run at low speeds. This scheme employs only the instantaneous reference phase voltages for the implementation. The time consuming task of sector identification is avoided with the proposed switching scheme. Another advantage with this scheme is that it does not require any look-up tables for its implementation. The scheme ensures a smooth switching all through, ensuring equal switching duty for both the inverters