CONTROL OF S V C FOR IMPROVEMENT OF SYSTEM STABILITY

Abstract

The growing requirement of transmitting bulk power to expanding load centers, with existing transmission system is being realized. The power transfer capability of the system is limited by among others by its dynamic state stability. The inherent ability of static VAR system (SVS) to provide rapid, continuously controllable reactive power compensation in response to changing system conditions, has been shown to result with other advantages to increase power transfer capability under steady state. An SVS connected at the mid point of a long transmission line and actuated by a control signal derived from terminal voltage improves the power transfer capability of the network. Any method of design of SVS controller for this purpose must consider the appropriate model of SVS and the systems. In this work a generator of 11l@. MV i supplying power to an infinite bus over a 600 km long line rated at 400 kv has been considered. The SVS is connected at the midpoint of the transmission line and is used to keep this voltage constant and helps in dynamic stability. The SVS considered is of the type FC-TCR. The modelling of each component has been done including transients in transmission line.This results in an high order for the overall system (29th order without auxiliary controller). After the modelling of each subsystem the overall system matrix has been prepared and its eigen values are found to test the stability,14hen generator is supplying 500MW,the SVS is able to stabilize the system but at 8O MW only SVS is not able to stabilize the system. For stabilizing the system auxiliary controller such. as Bus Frequency and Reactive Power have been considered to stabilize the system. '