Quantifying Losses in Power Systems Using Different Types of FACTS Controllers

This thesis discusses the placement of conventional power flow controllers (namely the Fixed series capacitor (FSC), Phase Angle Regulating Transformer (PAR)) and Flexible AC Transmission System (FACTS) devices (namely the Thyristor Controlled Series Capacitor (TCSC), the Static Synchronous Series Compensator (SSSC), the Unified Power Flow Controllers (UPFC) and the Sen Transformer (ST)) in bulk power systems to minimize transmission losses in the entire system. This firstly resolves line overloading and improves the overall voltage profile of the entire system. Secondly the transmission losses are minimized and also help in reducing the generation, which results in additional dollar savings in terms of the fuel costs. The sizes of the FACTS devices used were small in order to keep the initial installation costs low for the utility. The reduced FACTS device ratings are mentioned as a benefit, but not included in the overall loss minimization calculations. Various types of FACTS devices were modeled and placed in the power system, and the economic benefits were discussed and compared for different power flow conditions. The FSC, PAR, and TCSC are the FACTS Devices commonly used in the electric utility industry. In addition to the previous devices, the SSSC and UPFC were also modeled in the popular PSS/E and PSAT software's. The Sen Transformer was modeled using an electromagnetic transient simulation program (PSCAD/EMTDC). A line stability index was used to find the optimum location for placing the FACTS device. This thesis also provides a quantified value for the overall losses with the different FACTS devices, which is not available in the previous research literature. The Sen Transformer is a new type of a FACTS device that was developed by a former Westinghouse engineer, Dr. Kalyan Sen in 2003. It is based on the same operating principle as a UPFC (i.e. provides independent active and reactive power control) but uses the proven transformer technology instead. The benefit of the SEN transformer is that it would cost approximately only 30% of the UPFC cost. This thesis studies the Sen Transformer for loss minimization. Since the Sen technology uses a mature transformer technology, its maintenance costs are going to be less and therefore the utilities would be more comfortable using such a device instead of UPFC. A 12 bus test system proposed by FACTS modeling working group was used for validating and testing the FACTS devices in this thesis. This test system is a composite model of Manitoba Hydro, North Dakota, Minnesota, and Chicago area subsystems. This test platform manifests number of operating problems, which the electric utilities typically face. This system has been used for congestion management, voltage support and stability improvement studies with the FACTS devices. The results show that compensating a short transmission line in this system is more effective in minimizing the overall losses and improving the voltage profile compared to a typical approach of compensating long lines. The results also show that the UPFC and Sen Transformer are the most effective in minimizing the overall losses with the Sen Transformer being the most cost effective solution