Modulating and Carrier-Based Dodecagonal Space Vector Pulse Width Modulation Technique With Fifth and Seventh Order Harmonic Elimination for Split-Phase OEIM

This article proposes a modulating and carrier-based dodecagonal space vector pulse width modulation (DSV-PWM) technique for split-phase open-end induction motor (OEIM). The advantage of the DSV-PWM technique is that the fifth and seventh order (6n±1; n=1,3,5,...) harmonics are eliminated from the phase voltage of the split-phase OEIM. The modulating waveform is generated from the sinusoidal reference signals by adding the triplen, and fifth and seventh order harmonics. This modified reference waveform is compared to the triangular carrier waveform to generate the PWM gating signals for inverter-1 so that the vector addition from two inverters results in a 12-sided polygonal space vector structure for the PWM control. The PWM signals for the two-level inverter-2 connected to the other end of the OEIM are produced by performing a small logical operation using the PWM signals of inverter-1. The dc voltage relation between inverter-1 and inverter-2 is 1:0.366. The timing duration for inverter-1 and inverter-2 is the same to generate the dodecagonal space vector structure (DSVS) and can be easily implemented as in the case of a conventional sine-triangle PWM technique in a three-phase drive. So, mapping the space vectors of the DSVS of conventional split-phase to that of the OEIM drive is simple. This can be achieved using a logical operator like xor. Thus, the computation burden of the digital signal processors to produce the DSV-PWM signals is reduced with the proposed algorithm which is 3.45 times than the conventional space vector-based implementation using sector identification, vector time computation, and storing the switching vectors. A detailed analysis of the modulating waveform and DSV-PWM signal generation with the experimental verification of the proposed drive is presented in this article.