Modeling, Analysis and Controlling of A STATCOM for Power System Stability on Basis of Modulation Index

Abstract-The STATCOM (STATic synchronous COMpensator) is increasingly popular in Power System applications. In general, power factor and stability of the utility system can be improved by STATCOM.Specially, STATCOM can stabilize a given node voltage and compensate the power factor of the system and also load by that node. The steady state and dynamic performance of STATCOM are very critical to the performance of the power system. These performances depend on the modulation index of the converter. The concept of SVPWM (Space Vector Pulse Width Modulation) is extended, in principle, for the inverter switching of STATCOM.The SVPWM gives a greater value of modulation factor in the undermodulation as well as the overmodulation range compared to Sine PWM (SPWM). A PI and an H Controller have been designed for closed-loop control of the system. It is found through simulation that, H controller gives better responses than PI controller.