A microcomputer-based power factor controller

The paper reports a laboratory model of a microcomputer-based power factor controller (PFC) for compensating the reactive power of rapidly varying loads by switching capacitors sized in a binary ratio, with the help of zero voltage static switches. Four types of control strategies were tried, viz., (1) unity step control method, (2) binary search method, (3) successive approximation method, and (4) look-up table method. Features like (a) independent control of current 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 detection logic and their display, are all incorporated in the software programming. A comparative assessment of their performances using different control strategies has been reported. A number of experiments have been performed on this controller, viz., (i) experiments to verify the 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