Three‐phase thyristor controlled reactor using two sets of delta connected switches with low current harmonics

Abstract

This work presents a three-phase thyristor-controlled reactor (TCR), which makes use of two constituent banks of controlled reactors, with coordinated control of the triggering angle of both the banks. The first reactor bank has a set of `delta' connected back-to-back thyristor switches with a balanced set of reactors in series with each switch, while the second reactor bank also has back-to-back thyristor switches in `delta' connection but with a balanced set of reactors in series with each line. It is demonstrated that this arrangement prevents some major current harmonics in the supply line by proper choice of the maximum kVAr ratio between the two reactor banks. The use of delta connected switches in both banks reduces the current rating of the switches. Hence, without using any phase-shifting isolation transformer or filters, the proposed technique permits control of reactive power over a reasonable range, with a low current total harmonic distortion meeting existing harmonics standards. Simple construction and operation of the proposed TCR make it an attractive and cheaper solution. The modelling, analysis and performance assessment of the new TCR are presented.