A New Vector Frequency Modulation Method for Power Conversion Circuits

This paper presents an effective PWM method for power conversion circuits. The proposed method is called Vector Frequency Modulation (VFM) in this paper. VFM is different from conventional PWM methods. Although VFM is based on the concept of the space voltage vector, all necessary calculations of the periods of the voltage vectors can be performed without using traditional equations. The voltage vectors are classified into two groups, zero vectors and nonzero vectors. Instead of the complicated equations, a very simple algorithm is employed in VFM. One vector period is fixed and the zero vectors are distributed among the nonzero vectors in the ratio determined by the command voltage or frequency. The action of VFM is performed in software, and no modulation-wave oscillators, comparators, and up-down counters are needed. First, a reversible chopper is modulated by VFM and a 2-kW DC motor is driven by the chopper. The motor speed is regulated by modern control theory. Next, a three-phase inverter is modulated by VFM and a 2.2-kW induction motor is driven by the inverter. Experimental results are presented to demonstrate that VFM is useful for power conversion circuits. (c) 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 59-68, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.20982