A New Vector Frequency Modulation Method for Power Conversion Circuits

Abstract

This paper presents an excellent PWM method for power conversion circuits. The proposed method is called a Vector Frequency Modulation (VFM) in this paper. VFM does not belong to any conventional PWM methods. Although an idea of space voltage vector is employed in VFM, any traditional equations to calculate the periods of the voltage vectors are not used. The voltage vectors are classified into two groups, zero vectors and non-zero ones. 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 non-zero vectors in the ratio determined by the command voltage or frequency. The behavior of VFM is performed in software and any modulation-wave oscillators, comparators and up-down counters are not needed.
At first, a reversible chopper is modulated by VFM and a 2kW 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 2.2kW induction motor is driven by the inverter. Experimental results are shown to prove that VFM is actually useful for power conversion circuits.