Optimal placement of unified power flow controller and hybrid power flow controller using optimization technique

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Installing Flexible AC Transmission System (FACTS) devices in the power system is an effective alternative for utilizing transmission lines assets to their full extent. Siting of FACTS controllers at the best location in the network is a big challenge. UPFC is a very costly controller because of its configuration. A drawback of installing UPFC is that, when the transmission line with any compensating devices is planned for upgradation by UPFC installation, it does not allow to retrofit the existing devices like SVC, TCSC or even a switched capacitor. Hybrid Power Flow Controller (HPFC) which can be designed using the existing VAR compensator/ controller has the advantage that it is cost-effective and is a performance equivalent alternative of UPFC. The HPFC configuration used in this paper comprises of two VSC connected in shunt through coupling transformers, on either side of TCSC which is connected in series with the transmission line, and the two VSC share a common DC capacitor link. In this paper, optimal placement of UPFC and HPFC is obtained using Genetic Algorithm (GA) based approach. A power flow model of UPFC and HPFC are developed using constraint equations and objective functions. The results so obtained are compared and it is observed that generation cost at the optimal location of HPFC is less than that of with UPFC and total active power loss is comparable with that of UPFC. The same is compared with the uncompensated network. The technique is validated by multi-machine-9 bus system using MATLAB script file.