Showing papers by "Chen-Ching Liu published in 1993"

Generation capability dispatch for bulk power system restoration: a knowledge-based approach

Abstract: Results of the development of a knowledge-based system (KBS) for power system restoration are presented. An extensive list of critical constraints and parameters is identified. Based on these constraints and parameters, a goal-driven strategy for system restoration is developed. Part of the strategy is a procedure to determine the generator starting times, which helps maximize the megawatt hour load served over a restoration period. The KBS is implemented in the Knowledge Engineering System (KES) software. Simulations of the KBS are performed with data from the Philadelphia Electric System. >

Voltage security assessment using generalized operational planning knowledge

Abstract: An expert system called SEEKS (security evaluation knowledge-based system) has been developed to apply operational planning knowledge to the static security assessment problem. SEEKS performs the contingency selection and remedial action tasks usually conducted offline by an operational planner. Rule-based techniques are used to select contingencies expected to cause steady state bus voltage violations. The selection identifies the most severe outage in each local area such that power flows need only be run for these worst-case outages. Both single and double branch outages are considered. Double outages are defined as scenarios where two branches share one bus, thereby providing coverage for events where a single branch outage evolves into a double branch outage due to protection, relay, or breaker failure. This system has been tested using the IEEE 30-bus system and a Los Angeles Department of Water and Power 182-bus system. >

IOPADS (intelligent operational planning aid for distribution systems)

Abstract: A knowledge-based system (KBS) which provides an integrated operational planning environment for distribution systems is presented. Four functions are incorporated: remedial control; protective device coordination; loss reduction; and service restoration. A real-time KBS development environment is used, which provides a high level user interface and acceptable processing speed. A systematic method is used to optimize the object-oriented data structure. The KBS has been tested with data from an electric utility. >

An integrated model- and rule-based approach to design of automatic switching for subtransmission lines

Abstract: Automatic switching is the protective scheme installed on subtransmission lines to maintain service to distribution substations along each line after faults. At present, control engineers design the automatic switching for the new/modified subtransmission lines using a manual, time-consuming process. Not only is this process laborious, but many solutions are possible. The designer needs to select the one which yields maximum service restoration subject to constraints based on priority of loads and probable fault locations. This paper presents a new knowledge-based approach to design of automatic switching. This methodology uses model-based reasoning to incorporate information of the substation loads, segment lengths, fault probabilities, and protective devices as well as the relative priorities of the substations. This model is used in conjunction with design constraints, analytical criteria, and heuristic rules to guide the designer through the process of identifying the placement of automatic switches, the functions to be used, and the time setting(s) for each. Further, this approach can explain the detailed reasoning process and provide evaluation information in a causal/temporal network format. >

A negotiation methodology and its application to cogeneration planning

Abstract: Power system planning has become a complex process in utilities today. This paper presents a methodology for integrated planning with multiple objectives. The methodology uses a graphical representation (goal-decision network) to capture the planning knowledge. The planning process is viewed as a negotiation process that applies three negotiation operators to search for beneficial decisions in a GDN. Also, the negotiation framework is applied to the problem of planning for cogeneration interconnection. The simulation results are presented to illustrate the cogeneration planning process. >

Bounding the computation time of forward-chaining rule-based systems

Abstract: For real-time applications of expert systems, success depends on the computational efficiency of the implementation. In this study, we propose an analytical method for evaluating the processing time of forward-chaining rule-based systems. An upper bound based on this system model is developed. If the upper bound stays within the time available for planning the operational or control task, the expert system would be able to complete the rule-processing in time. To compute the upper bound, the worst case working memory element sets are obtained for each functional step of the matching procedure. The worst case time for rule selection in the conflict resolution step is also derived. The maximal number of firings for each rule is considered in order to arrive at a bound for total processing time. Numerical examples are presented which point out the importance of rule and data structures in the efficient implementation of rule-based systems.