VAR COMPENSATION

VAR compensation is defined as the management of reactive power to improve the performance of ac power systems; maximizing stability by increasing flow of active power. Few Problems forced while reactive power compensation which are:

1. Load compensation
2. Voltage support

LOAD COMPENSATION OBJECTIVES: are to increase the value of the system power factor to balance the real power drawn from the ac supply, compensate voltage regulation and to eliminate current harmonic components produced by large and fluctuating non-linear industries loads.

VOLTAGE SUPPORT OBJECTIVES: It’s generally required to reduce voltage fluctuations at a given terminal of a transmission line.
VAR compensation helps to maintain a substantially flat voltage profile at all levels of power transmission improves HVDC conversion terminal performance increases transmission efficiency ,controls steady state and temporary over-voltage and can avoid disastrous blackout.

Series and shunt VAR compensation are used to modify the natural electrical characteristic of ac power system. Series compensation modifies the transmission or distribution system parameters while shunt compensation changes the equivalent impedance of the load.

Earlier, rotating synchronous condensers and fixed or mechanically switched capacitors or inductors have been used for reactive power compensation. Now a days static VAR compensators employing thyristor switched capacitors and thyristor controlled reactor to provide or absorb the required reactive power have been developed. Use of self-commutated PWM convertors with appropriate control scheme permits the implementation of static compensators capable of generating or absorbing reactive current components with faster time response.