说明：  This paper deals with the design and implementation of a multilevel voltage source converter based static synchronous compensator (STATCOM) employing an effective modulation control technique simulated in a MATLAB Simulink environment. The main objective of this paper is to maintain the voltage stability by compensating the reactive power in the power system. Hence, a new efficient control strategy is proposed, in order to reduce the voltage fluctuations like sag and swell conditions and also to isolate current and voltage harmonics in the transmission system. The multilevel STATCOM which can be used at the point of common coupling (PC C), for improving power quality is modelled and simulated using proposed control strategy and the performance is compared by applying it to an llOkv line with and without STATCOM. Relative Harmonic analysis is also discussed in this paper based on the total harmonic distortion (THD) calculations.