Design and implementation of a SVPWM technique using low cost multifunction data acquisition card

Space vector pulse width modulation (SVPWM) technique has become a popular technique for three-phase voltage source inverters in ac drive applications. This paper realizes the SVPWM technique using low cost multifunction data acquisition card (DAC). The switching patterns of this technique are generated using sector dependent digital words to minimize the storage memory and to eliminate the saw tooth carrier generator. The paper introduces a novel digital scheme for measuring the fundamental component of the modulated voltage of the SVPWM algorithm, which is a basic measuring quantity in many control and estimation strategies. The proposed scheme converts the modulated voltage to digital pulses, whose frequency is proportional to the input voltage using a powerful synchronous voltage to frequency converter IC (SVFC). By counting the out pulses over one sampling interval, we obtain an average value of the modulated voltage during this sampling period. The proposed measuring scheme can easily realized with higher noise immunity and without external critical components. To validate the proposed implementations of the SVPWM technique, a 3-phase voltage source inverter is built from commercially available discrete components and used in Volt//Hertz closed loop speed control of a three-phase induction motor (IM). Extensive experimental results are carried out to show the effectiveness and applicability of the proposed schemes.