Decentralized control and placement of multiple unified power flow controllers

The dissertation, consisting of 4 papers, presents the results of research on the nonlinear control of Flexible AC Transmission System (FACTS) devices, the optimal placement of Unified Power Flow Controller (UPFC) in power networks and the decentralized control of UPFCs for damping interarea oscillations of power networks.; The first paper proposes a new control approach for a UPFC for power system oscillation damping. This control is simple to implement, yet is valid over a wide range of operating conditions. It is also effective in the presence of multiple modes of oscillation. The proposed control is implemented in several test systems and is compared against a traditional PI control. The second paper introduces a new nonlinear robust control for STATCOM/BESS that provides significant reduction in Electric Arc Furnace (EAF) induced aperiodic oscillations on the power system. The method is also compared with a traditional PI control and shown to have superior performance. The third paper presents the enhancement of interarea oscillation damping of a power network by multiple UPFCs. Hankel singular values and model balanced realization are utilized to reduce the large-scale power network model. An LMI-based approach is used to design decentralized controllers for UPFCs. Optimal control method is used to compare the dynamic properties of various UPFC placements. The fourth paper presents two different control schemes for decentralized Hinfinity control of multiple UPFCs for a power network. In the first scheme, a decentralized Hinfinity control is designed for the whole power network based on LMI theory. In the second scheme, different H infinity controllers are designed for different local areas of the power network separately.