Susumu Yamashiro

Novel Distributed Power Generating System of PV-ECaSS Using Solar Energy Estimation

This paper describes the construction and the performance of a distributed power generating system of photovoltaics (PV) using solar energy estimation. Instead of conventional batteries a new storage device, called energy capacitor system (ECaSS), is used for its various advantages. A procedure is described to estimate the PV output power by calculating solar radiation. To calculate the daily insolation, Hottels equation and Liu-Jordans equation have been used with some modification. The accuracy of the procedure is verified by comparing the calculated solar radiation with the practically measured one. To apply the procedure even in cloudy/rainy weather, the characteristic of the PV output in different weather conditions has been studied using 1-day-ahead weather forecasts. With an aim to set the optimum amount of buy power, a simulation program has been developed. The system is being operated in optimal economic mode in different weather conditions. The financial benefit and load-leveling capacity of the system have been studied and presented here. It was found that the system provides an excellent economic benefit for nonflat price of electricity and load-leveling facility with a good overall efficiency.

On-Line Secure-Economy Preventive Control of Power Systems by Pattern Recognition

A fast transient stability assessment method and a preventive control strategy, considering both security and economy of power systems, are presented. The pattern recognition approach with two dimensional feature space is used to assess transient security. If a power system is said to be in an alert state, then quick and appropriate control actions are required. A transient security constrained economic load dispatch(ELD) which is able to shift generator outputs so that system security can be maintained, is developed. The effectiveness of the proposed method is ascertained through numerical examples for model power systems.

Application of an expert system to decisions on countermeasures against snow accretion on transmission lines

An expert system is discussed which assists in deciding the deicing countermeasures against snow accretion on 187 kV and 66 kV transmission lines. The distinctive features of the system are the application of an expert system to the completely hierarchical design of the whole system, and ranking by messages instead of by certainty factor. The system has been developed as a prototype using micro-Prolog and is under trial use in real power-system operations. An example illustrates the consulting behavior of the system. >

A viable grid-connected PV-ECS system with load leveling function using a day-ahead weather forecast

A small grid-connected distributed power generating system based on PV panel and ECS has been developed. The system can produce power by PV panel, store energy during lower demand of load and supply the stored energy to load during higher demand. It takes a fixed amount of power from grid line and supplies to load by day and charges the ECS at night to perform the load leveling function. A procedure to estimate the output power of PV panel has also been developed by calculating solar radiation. To find out the weather dependent characteristic of the PV panel, its output in different weather conditions have been measured and compared with the estimated output. Using this weather dependant characteristic and a day-ahead weather forecast, we can estimate the output power of the PV panel in any weather condition. A simulation program has also been developed to set the optimum value of the power taken from grid line.

A fast scheduling method for power system operation considering an environmental constraint and system reliability

Abstract A fast scheduling method for power system operation is presented, in which the limits of both system reliability and environmental pollution are satisfied. The limit of system reliability is estimated by the probability of the power supply, and NO x emission from thermal stations is considered as a typical example of environmental pollution in this paper. Both reliability and environmental constraints are assessed probabilistically. For rapid estimation, two types of approximate scheduling technique are introduced: one is based on control of the output power of only two units to satisfy the line capacities; the other is primarily aimed at emission control to satisfy the environmental constraint and may not be optimum in terms of operating cost. To confirm the usefulness of the proposed method, the strict scheduling method using quadratic programming is described and numerical examples of both methods for a model system are also shown.

Evaluation of loads in restoration state by the cost of interruption of electrical service

Abstract A method of determining a load restoration priority is presented, which considers the interruption cost of the electrical service. Two types of solutions for this problem are developed. One of them takes into account the distributions of the interruption cost and the generator output. The other uses their expected values. It is concluded that the solution which uses expected values is sufficient for evaluating the load restoration priority, if the effect of load change is considered in the algorithm.

Optimization of DC Power Flow by Transmission Loss Allocation Method

A transmission loss allocation (TLA) method for generator and load nodes is presented by considering mathematical formulation between node power and line power flow. The formulation is based on X-matrix in DC transmission network. By the TLA method, an optimization strategy of DC power dispatch is proposed compare with AC optimal power flow (OPF) and former DC-OPF method. The proposed TLA method is also one of useful way to assess network use cost for individual transaction participant in the deregulated power market. The effectiveness of the proposed methods is illustrated through numerical examples for IEEE-118 power system.