Flexible control of electrical power system to enhance small signal stability

As a result of the increasing amount of energy transmission over a long distance, low frequency interarea oscillations have been becoming an increasingly important concern in the planning and operation of practical power systems. This undesirable phenomenon may cause very serious results, such as the lost of interconnects, load curtailments and even system blackouts.; This thesis presents a novel way to achieve fast damping of interarea oscillations and improve the dynamic stability of interconnected power systems by using Flexible AC Transmission System (FACTS) devices. The performance of FACTS controllers is determined by several factors, including the design of damping controllers, the selection of input signals, and the placement of controllers. This thesis intends to explore the technologies for improving the state of the art in all these three aspects.; Two new damping controller design approaches are proposed in this thesis. The first one is a rule-based fuzzy controller. A unique advantage of the proposed design is that the fuzzy rules are derived from the intuitive physical explanation of Equal Area Criterion Theory. The second method, which is based on Artificial Neural Fuzzy Inference System (ANFIS), presents an attempt to solve the parameter setting difficulties involved in the design of the basic rule-based fuzzy controller.; The selection of input signals is crucial to the controller's performance. Oscillation controllers traditionally only use locally measurable signals. Due to the advances in computer and communication technologies, power engineers now have a practical opportunity to use remotely measured system states in close loop control systems. In this thesis, the author explored the possibility of using remote signals in a fuzzy logic based oscillation controller design. Transient simulation is employed to compare the effectiveness of various input schemes, both local and remote. Simulation results indicate that a performance advantage can be achieved with the usage of remote input signals.; For large complex systems, systematic approaches are needed to identify the best locations to install FACTS devices. The oscillation of machine rotors and the exchange of oscillation energy are two aspects featuring swing oscillation in power systems. Almost all existing controller allocation algorithms are established from the rotor oscillation perspective, which are very suitable for generator-based controllers. However, the principle of using FACTS devices for oscillation damping is based on blocking the exchange of oscillation energy. The Power Oscillation Flow (POF) algorithm [12, 13] is able to reveal the oscillation energy exchange path across a power system. This novel method is adopted and enhanced in this thesis to assist the selection of the suitable places for FACTS damping controllers.; Large modern power systems may possess complex characteristics that do not exist in small systems. For this reason, many methodologies developed in a simple two-area system have difficulties in being applied to large systems. To verify the proposed methods in a large system, the author implements the proposed controller design and allocation approaches in a simplified WSCC system model. The Simulation result shows that the controller achieved very good damping results.