SIMULATION OF REACTIVE POWER CONTROL IN AC TRANSMISSION SYSTEMS USING STATIC VAR COMPENSATOR

Voltage stability is a major concern when planning and operating electrical power systems. As demand for electric power increases, power systems are stressed more and more. Since the construction of new transmission lines is very expensive, and the right of way requirements are not easy to come by, a cost-effective policy is to use the existing lines to their maximum thermal and stability limits, and this requires optimum sharing of power flow in the system. Flexible AC Transmission Systems (FACTS) such as Static Var Compensators (SVC) were introduced to utilize the existing system to a higher degree, while still maintaining system stability. This project investigates the effect of adding a SVC on the voltage profile of a given bus and overall buses in a power system. Placement of the SVC was based on power flow studies to identify the weak buses (buses whose voltage profile are below the specified values for system reliability). The power system was modeled as a 5-bus system with two salient pole synchronous generators with its source of mechanical power from a hydro turbine. Simulations were performed with both the added SVC and without the SVC and the results were compared against each other. This simulation study was performed in MATLAB/SIMULINK, a powerful software for power system modeling, based on a phasor model of the SVC and the results show that inserting a SVC on a typical bus in the system controls the reactive power requirement of the bus and thus maintains the specified voltage at the bus for system reliability. The voltage at the targeted bus increased from 0.85 to 1pu ensuring that the voltage does not go below or above 5% of the nominal value. Use of SVC in a system has shown considerable increase in voltage profile and power flows while decrease in losses by responding to the reactive power need of the system.