A MICROCOMPUTER-BASED POWER-FACTOR CONTROLLER

The paper reports a laboratory model of a microcomputer-based power fa ctor controller (PFC) for compensating the reactive power of rapidly v arying loads by switching capacitors sized in a binary ratio, with the help of zero voltage static switches. Four types of control strategie s were tried, viz., 1) unity step control method (USCM), 2) binary sea rch method (BSM), 3) successive approximation method (SAM), and 4) loo k-up table method (LUTM). Features like a) independent control of curr ent in each phase, b) reactive current sensing and capacitor switching in one cycle, c) zero voltage switching of static switches to prevent the occurrence of transients and harmonics, and d) switch failure det ection logic and their display, are all incorporated in the software p rogramming. A comparative assessment of their performances using diffe rent control strategies has been reported. A number of experiments hav e been performed on this controller, viz., i) experiments to verify th e operating performance of the PFC under the four control strategies, ii) experiments to prove its performance as a power factor controller and also iii) as a static Var compensator.