In this paper, we propose a method to determine the optimum operating point of Voltage Source Converter (VSC) which is connected as Back-To-Back (BTB) for Grid service. Using a swarm intelligence-based optimization technique, we use a method that minimizes multiple objective functions. Also, objective functions are defined to minimize the total line loss and the deviation of the line loading in the network. Using the proposed method, it is possible to secure the economical efficiency by line loss reduction, and also is possible to make the grid more flexible by minimizing the line loading variation. The proposed method is verified through the IEEE-39 test system. Through case studies, it is verified that operation of BTB VSC by using optimal setpoints of active and reactive power output can contribute to total line loss minimization and equalization of line loading in the transmission grid.