Modelling load balance type static var compensator control system response

Abstract

As power system interconnection becomes more prevalent, there has been an increase in use of thyristor controlled shunt connected compensation devices for dynamic power system compensation and power transmission capacity increase. A Static Var Compensator (SVC) functions as a variable reactance capable of operating in both the inductive and capacitive region as required on a cycle by cycle basis to provide compensation at the point of connection to the power system. Voltage regulation is the operational objective of most SVCs. Therefore, transient response of SVC control systems impacts overall power system performance and inappropriate settings may lead to voltage instability. SVCs are also commonly used to convert single phase load into balanced three phase load, thereby reducing negative phase sequence voltages and currents within the power transmission system. As most load balancing SVCs are consistently operated to their capacity, removal from service to apply and test control system setting changes impacts system regulation and stability. Therefore, model development of a load balancing type SVC control system to predict response to setting changes may provide an alternative to lengthy outages of SVC plant. This paper examines the theoretical basis of thyristor controlled shunt compensation, establishing conditions for voltage support and unbalanced load compensation. Load balancing type SVC control system model development and validation is documented.