Design of an online microprocessor based individual phase control of a static VAr compensator

An online individual control scheme of the static VAr compensator (SVC) which is constructed using thyristor controlled reactors (TCR) and switched capacitors (SC) is designed to correct power factor and balance three phase line currents. At each sampling instant, the loading conditions are measured by the active power and reactive power (P-Q) transducers between any two phases at the load bus terminal. The compensation value of each phase of the SVC is calculated by three analog adders and sent to the micro-controller which is synthesized by a M68HC11EVM microprocessor board. Then the micro-controller determines the on/off connection of the capacitors and the firing angle of the thyristors in each phase. Test results show that with the cooperation of the SVC, the power factor can be maintained approximately at unity and the line currents viewed at the load bus are balanced. It is noted that with the benefits of power factor correction and balance improvement, the additional power loss caused by the SVC is negligible