Incorporating the overmodulation range in space vector pattern generators using a classification algorithm

Operating voltage-source pulsewidth-modulated (PWM) inverters in the overmodulation region extends their voltage and power ranges. Proper operation in this region is of particular importance in AC motor drives. This paper presents a classification algorithm for the implementation of the space vector modulation (SVM) in the pulse-dropping region. It is demonstrated that the proposed algorithm allows smooth transitions through the entire operating range up to square wave operation. It does not require approximations and guarantees exact positioning of the switching instants. In addition, it is shown that the harmonic distortion can be kept lower than with conventional techniques in most of the overmodulation region. The technique requires less computational time, when compared with the conventional SVM methods. The results of the theoretical and mathematical analysis are verified on a 2-kVA prototype unit using a digital signal processor (DSP)-based controller.