Journal of Control, Automation and Electrical Systems https://doi.org/10.1007/s40313-018-00421-2 Allocation of Static Var Compensator in Electric Power Systems Considering Different Load Levels Edmarcio A. Belati 1 · Claudionor F. Nascimento 2 · Haroldo de Faria Jr. 1 · Edson H. Watanabe 3 · Antonio Padilha-Feltrin 1 Received: 1 March 2018 / Revised: 8 June 2018 / Accepted: 24 September 2018 © Brazilian Society for Automatics–SBA 2018 Abstract This paper proposes an approach to determine the optimal location of static var compensators (SVCs) in electric power systems in order to improve voltage profile and minimize active power losses. A multi-scenario framework that includes different load levels with different time periods is considered in this approach. The problem is formulated as a mixed-integer nonlinear programming problem using an optimal power flow (OPF). The SVC value and location are modeled as a variable susceptance inside the bus admittance matrix and as a binary decision variable, respectively. The problem is solved using the branch and bound algorithm associated with the OPF. Studies and simulations were conducted on the IEEE 118-bus test system considering variations in both the objective function and the amount of SVCs to be allocated. Analysis of results demonstrate that the performance of the power system can be effectively enhanced due to the optimal allocation of SVC equipment if considering different load levels with different time periods for the allocation of SVCs, rather than allocate the SVCs separately. Keywords Branch and bound algorithm · Flexible alternating current transmission systems · Optimal power flow · Static var compensator 1 Introduction During the last decade, the increase in electric power demand and the growth of alternative renewable energy sources (e.g., B Claudionor F. Nascimento claudionor@ufscar.br Edmarcio A. Belati edmarcio.belati@ufabc.edu.br Haroldo de Faria Jr. haroldo.faria@ufabc.edu.br Edson H. Watanabe watanabe@coe.ufrj.br Antonio Padilha-Feltrin padilha@dee.fei.unesp.br 1 Universidade Federal do ABC (CECS/UFABC), Avenida dos Estados, 5001, Santo André, SP 09210-580, Brazil 2 Universidade Federal de São Carlos (CCET/UFSCar), Rod. Washington Luís km 235, C.P. 676, São Carlos, SP 13565-905, Brazil 3 Universidade Federal do Rio de Janeiro (COPPE/UFRJ), CT Bloco H-321, C.P. 68504, Rio de Janeiro, RJ 21-941-972, Brazil wind and solar) connected to the grid have been causing changes in power systems due to the necessity of enhanc- ing power transfer capability, and system controllability and stability (Hingorani and Gyugyi 2000). Moreover, the oper- ation of the power system faced technical challenges due to deregulation and restructuring of electricity markets. These changes and challenges demand studies and investments in order to permit a more efficient and secure operation of the power system. In this sense, flexible alternating current trans- mission systems (FACTS) controllers, which are based on power electronic converter systems, can improve the system operation when optimally allocated in the power system. FACTS controllers are able to rapidly control one of the parameters of the power system (e.g., voltage, impedance, or angle; Hingorani and Gyugyi 2000). An effective applica- tion of FACTS controllers uses high-power semiconductor devices to control the reactive power and thus increase ac power transmission capacity at long distances more effi- ciently. Shunt connected FACTS controllers, such as static com- pensator (STATCOM) and static var compensator (SVC), are equipment that can regulate and control the voltage to the 123