Voltage and Reactive Power Control in a Power System

Control of reactive power and voltage is necessary in order to improve the performance of ac power systems. This is known as var compensation - defined as the management of reactive power to improve the performance of ac power systems. Traditional static var compensators (SVCs) employ reactors and capacitors. These standard reactive power elements are controlled to produce or absorb rapid and variable reactive power. Reactive power compensation can be implemented with var generators connected in parallel or in series. In this paper the principle of series reactive power compensation is the focus. There are many SVC configurations. The configuration known as thyristor-controlled series compensator (TCSC) is described, modelled and analyzed. Model equations are derived and used to demonstrate the applicability of this SVC in power system var compensation. Power electronic switching devices like the thyristor etc. are used to control the flow of reactive power. The control variable is the delay angle, of the switches. The paper shows how the application of this SVC raised the power factor of a system to unity, regulate bus voltage and consequently reduced power loss, and increased active power transfer capability of transmission or distribution line.