Design of an almost continuously controlled three-phase static VAR compensator for power factor correction purposes

By Abdulkareem Mokif Obais* and Jagadeesh Pasupuleti


Accepted 31 October, 2011

In this paper, a three-phase four-wire automatic power factor correction system is designed and tested. This system employs three-phase Wye-connected thyristor switched-capacitor banks to generate a controllable static VAR. Each capacitor bank is constructed of five binary weighted thyristor switched-capacitors. This arrangement leads to a capacitor bank capable of generating stepping reactive power having thirty one equidistant non-zero levels. The controlling circuit of each capacitor bank is designed such that maximum absolute deviation from linear response is 1/62 of its rating. Each capacitor is controlled by a single thyristor shunted by a reverse diode. The system is capable of correcting lagging power factor up to unity or adjusting it according to user desire. Each capacitor is connected to a series reactor for protecting the solid state combination from inrush current occurring at the first instant of compensator plug in to power system network. The proposed system is characterized by negligible no load operating losses, no generation of harmonics, energy saving, and reduction of transmission losses. The system is designed and implemented on PSpice which is a computer program very close in performance to real hardware and broadly adopted by manufacturing companies.
Key words: Capacitor bank, power factor correction, power quality, static VAR.