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Modern power systems are at risks of voltage instability problems due to highly stressed operating conditions caused by increased load demand. This paper proposes a hybrid Differential Evolution (DE)/Particle Swarm Optimization (PSO) algorithm based optimal reactive power flow control task incorporating only one type of FACTS device. DE is efficient in exploration through the search space of the problem but not so good in exploitation while PSO is highly efficient in exploitation of the solutions. The hybrid algorithm combines the features of both DE and PSO and is capable of finding the global best solution without easily trapping in to the local minima. Optimal settings of control variables of generator voltages, transformer tap settings and location and parameter setting of TCSC is considered for optimal solution for reactive power flow control and the resultant reactive power reserves. The effectiveness of the proposed work is tested on IEEE-30 Bus test system.