Controllability and diagnosis in electric power systems

While modern electric power systems are often operated under stressed conditions, there is an increasing social demand for reliable electricity supplies. The reliable operation of a power system depends on the power system's ability to maintain a normal operating condition following a disturbance. This study focuses on two aspects of power systems: Controllability and diagnosis, both concerned with the power system operation during events involving disturbances.; This study investigates the possibility of controlling the dynamics of a power system using available power system controls. The complete controllability of the power system refers to the ability to control the system from a state to any other state. This study shows that complete controllability holds at least on a subset of the power system state space. This subset, or the complete controllability region, can be identified. The results imply that during the emergency operation of power systems, if the power system states are in the complete controllability region of the state space, power systems can be steered toward the designated states using the available controls.; This study also investigates the methodology for on-line fault diagnosis using the Sequence-of-Events Recorder (SER) information. The proposed method--multiple hypothesis analysis--generates one or more possible scenarios to interpret the SER data. Based on the possibility evaluation, the analysis is able to identify the hypothesis representing the actual scenario. With the detailed information contained in the SER data, the proposed method is able to perform accurate fault and malfunction analysis. For verification of logic-based fault diagnosis systems, this study proposes the contextual representation method to derive a minimal set of test scenarios. This minimal set is sufficient for the verification of the LBS so that exhaustive testing can be avoided.; During an emergency event induced by a disturbance, fault diagnosis is the first step in the operation of the power system. On-line fault diagnosis provides necessary information for decisions on control actions during the operation. This study is among the first to investigate on-line fault diagnosis using the SER information. It is shown by previous studies that catastrophic emergency events such as voltage collapse are related to the interaction of power system dynamics. From a control viewpoint, this study shows the possibility of controlling the power system dynamics through coordinated power system control actions.