Power factor improvement by pulse width modulated switched single capacitor

Reactive power is recognized as an essential factor in the design and good operation of power system. Real and reactive power on a transmission line in an integrated network is governed by the line impedance, voltage magnitudes, the angle of differences at the line ends, and the role the line plays in maintaining network stability under dynamic contingencies. Reactive power compensation or control is essential part in a power system to minimize power transmission loss, to maximize power transmission capability, and to maintain the system voltage within desired level. In this paper a new method is proposed which improves the power factor automatically of varying lagging loads to unity, using one single large shunt capacitor instead of using a bank of switching capacitors. Basically, this control scheme is a static power factor correction method by continuous voltage or current control of a capacitor. In this work the voltage across the capacitor is being changed by a bi-directional switch to control the magnitude of compensating capacitor current and thereby attaining unity power factor. This system incorporates high-speed insulated gate bipolar transistor switching technology. The gate signal of the switching devices is generated by using a compact and commercially available IC chip SG1524B. The scheme is simple in this sense that it uses only one static bi-directional switch controlled by an electronic control circuit that uses only analog ICs and some discrete digital components.