VOLTAGE REGULATION USING STATIC SYNCHRONOUS COMPENSATOR

Abstract

Reactive current introduces power quality problems like voltage sags, swell and poor load power factor, these problems result in unexpected behaviour of sensitive equipments. Reactive power compensation is an important aspect in control of distribution systems, from early days synchronous condenser and mechanically switched capacitor and inductors have been used for this purpose. Significant advances took place with the advent and use of thyristors in place of mechanical switches ; in typical applications TSC(thyristor switched capacitor) provide leading VArs and TCR(thyristor controlled reactor ) provide lagging Vars. use of thyristors eliminated drawbacks of mechanical switches but large size inductor and capacitor were still a problem. Recently the Voltage Source Inverter (VSI) based Static VAR compensators have been recognized as solution, earlier with thyristor based VSI only unidirectional flow of reactive power was possible but with advent of self-commutating devices (IGBT/MOSFET/GTO) bidirectional power flow is made possible, these compensators are known as Advanced Static VAR Compensator (ASVC) or Static Synchronous Compensator (STATCOM). A STATCOM provides effective compensation to linear /nonlinear loads by injecting appropriate reactive power at PCC. A simulation model of the 6-pulse STATCOM using direct and indirect control scheme and application of STATCOM in SEIG has been implemented in MAT LAB. The control strategy for the STATCOM is reactive power control. P1 controller is used to control the flow of reactive power to and from the DC capacitor. Phase Lock Loop components are used in the control to generate the Cosine and sine.PWM switching control is used to switch on and off the MOSFETs in direct control scheme and hysteresis current control is used in indirect control scheme. From the simulation results, The difference of step drop load current during sag is the amount of reactive current needed to be compensated ;the designed STATCOM compensates reactive power demand caused by inductive load switching.