A Novel Simple Inductor-Controlled VAR Compensator

A novel configuration of a VAR compensator to provide reactive power on high-voltage transmission systems is being proposed. Instead of the usual thyristor-based VAR compensator, this brief proposes an inductor-controlled circuit the terminal impedance of which can be regulated to be capacitive as well as inductive. It is this dual character of the proposed circuit, along with its capability to smoothly regulate the amount of reactive power it injects or absorbs, that suggest its suitability to operate as a VAR compensator. The significance of the circuit with respect to the suggested application is that it consists only of linear components, consequently avoiding, in contrast to other typical thyristor-based VAR compensators, the formation of harmonics. Suppressing undesired harmonics requires added components and complexity which usually involves filter units, rendering not having to face this issue, attractive. The circuit can be realized with discrete components easily obtainable in big variety of different power and voltage ratings permitting thus its employment on low as well as on high voltage levels. One such application is experimentally demonstrated in this work in which the reactive power of a running single phase universal motor is being compensated.