New Static Var Compensator Control Strategy And Coordination With On-Load Tap Changer

The Reactive Power/Voltage control of the power system is an efficient method, which could guarantee the secure and economical operation of the power system. At the same time, it is an important way to reduce the network loss, to save the energy and to improve the operation level of the power system. The static var compensator (SVC) has fast dynamic characteristics so that it is widely used in the power system. On-load tap changer (OLTC) is also utilized as a main method to control the voltage. How to support effective system voltage following disturbances and keep reactive power reserve in SVC during steady-state operation to provide reactive power requirements during system dynamics have been the main concerns.This paper describes the presents of the reactive power and the voltage control, and points out: The performance of the static var compensator is affected by the reactive signal detection link and the voltage regulation link. Methods are proposed to deal with the situation, which are as follows:(1) The presentation of the instantaneous reactive power theory provides a new way for the detection of the SVC signals. The application of instantaneous reactive power theory in the detection of the SVC signals in the three-phase system improves the accuracy of the signals, the real time stability, and the ability, and ensures the precise of the SVC.(2) This paper presents a new SVC control strategy with two stages of regulation slopes and two voltage regulation controls, which are fixed-voltage reference control and variable (floating) voltage reference control. The aim of this control is to limit the reactive power output from the SVC to the desired value during the steady-state voltage range and compensate the reactive power requirement from the upstream networks via the coordination with the on-load tap changer (OLTC). However, when the voltage deviates the steady-state voltage range, the SVC will react to support the system voltage using the SVC reactive power reserve. When a disturbance results in a new operating point, with a steady-state reactive-power output, the variable voltage reference control effectively changes the SVC output slowly and returns it within the steady-state margin to keep the voltage stable and improve the power quality.(3) Considering the power system with on-load tap changer transformers and shunt capacitors, this paper puts forward a mathematical model whose purpose is to regulate the voltage and reduce the movements of the OLTC of the system. Then we analyze the dynamic performance of control system and give the parameter of device cling to the device model and build a simulation model by employing MATLAB/Simulink. The simulation and analyzing of the results validate that the control method can support effective system voltage following disturbances and keep reactive power reserve in SVC during steady-state operation to provide reactive power requirements during system dynamics.