Generalized symmetrical angle PWM technique for A.C. voltage controller

Abstract

Conventional methods of a.c. voltage controllers, such as on-off control and phase-angle control are known to produce harmonic voltages in the o.e. supply lines. This paper introduces the use of forced commutated techniques in a.c. voltage controllers, namely; symmetrical angle pulse width modulation technique. The symmetrically displaced pulses within the sinusoidal voltage waveform is adopted. The advantages of unity displacement factor and high frequency harmonic currents which are easy to filter, can be gained in the suggested control technique. The resulting harmonic currents from the proposed technique are analyzed and compared on a basis of the phase-angle controlled technique. Simple LC filters can be introduced in the supply input side of the voltage controllers to improve the quality of the supply voltage waveform. The analysis of harmonic currents showed that noticeable reduction is gained with increasing the number of pulses per half cycle. © 2004 IEEE.