We have developed a new method to determine an optimal generator scheduling using probabilistic demand scenarios. The demand scenarios are created statistically as a set of load curves by the past demand data. Covariance matrix is used to reconstruct the distribution of the demand scenarios. Unit commitment calculation is executed for each demand scenario and the operation cost is estimated. Optimal generator scheduling is selected by the expected value of the unit price with including the additional cost to compensate the demand variation. The risk of the scenarios is also estimated to select the optimal generation scenario. The advantage of this method is that the optimum generator scheduling can be calculated in the present load dispatching system since the existing scheduling algorism can be easily adopted with a minimum modification.
The Operator Training Simulator (OTS) system, which is integrated with a real-time transient stability analysis program, has been in operation at the training center of Hokuriku Electric Power Co., since July, 1990. The developed OTS system achieves real-time transient stability analysis with approximately 100 generator and 400 node power systems by parallel processing performed on a computer system with multiprocessor architecture. This paper outlines the developed OTS system and describes the requirements, design concepts, modeling and parallel calculation method of transient stability analysis and the verification result of the developed transient stability analysis program.< >
Various stabilizing equipments have been installed in modern power systems to enhance power system stability and its stabilizing algorithms have become more complicated(3). Most of training simulators, however, simulate a power system by performing power flows and frequency deviation calculations(2). Since these simulators ignore dynamics of individual generators, it is impossible to simulate power swings and out-of-step phenomena which are closely connected with these equipment's actions. To simulate these actions automaticaly in the training simulator, a transient stability calculation program must be incorporated. There are two methods. In one method, a transient stability calculation program is linked to a conventional training simulator using an event sequence file and called every time it is required(4)(5). In the other method, a training simulator involvs a transient stability calculation program itself and simulates the generator dynamics and stabilizing equipment continuously(6). However, to adopt the latter method, a transient stability calculation program that can simulate power swings in real time must be developed. The application of this method to a large power system with more than 100 generators has not been reported so far. This paper presents a transient stability calculation method which can simulate a large power system with more than 100 generators faster than real phenomena, and it's application to a training simulator.
This paper proposes estimation methods of short circuit current using phasor measurement unit (PMU) measurements (phasors). The methods follow the basic notion of representing the source side of a power system by an equivalent circuit with a voltage behind back impedance, and employ a set of voltage and current phasors measured at substations during the normal variation of loads in their estimation. In order to improve the estimation accuracy of the proposed methods, the concept of using the changes between the consecutive phasors is introduced. Furthermore, to make the methods applicable to the real world system, a reference phasor concept to remove the effects of system wide frequency variations and a filtering process to filter out the outlier phasors, are proposed and implemented. The validity and effectiveness of the proposed methods were checked and confirmed using experiments and field tests.
This paper reports an on-line TSC system outline, and power shedding selection data based on actual operating experience. The comparison of on-line TSC with conventional systems and availability of on-line TSC systems are described.
This paper introduces an architecture for computer communications applied to the operation and maintenance of power systems, the distributed real-time computer network architecture (DRNA). The architecture consists of four functional entities, namely, application programs associated with information models, an adaptation function, a transport function, and network- and security-management functions to achieve seamless, real-time, adaptive, and secure information exchange between distributed power system control devices. DRNA uses off-the-shelf and standardized technologies along with dedicated ones. Through careful application of the technology, an experimental setup of a distributed cooperative voltage-control network was constructed in a power system simulator to verify the architectural concept. The implemented technologies include mobile agents, middleware for prioritized and redundant communication schemes, label-switched and Ethernet-based transport networks, and a secure virtual private network. The experiment demonstrated the effectiveness of DRNA.
A novel method and recently developed stabilizing equipment to prevent the loss of synchronism of generators in pumped-storage plants due to spreading are presented. The method includes functions to estimate the swing of each generator by using online generator output sampled 600 times per second after an occurrence of a disturbance (such as a fault, faulty equipment, etc). Generator swing 200-300 milliseconds ahead and loss of synchronism between generators in pumped-storage plants and those in thermal and nuclear plants can be predicted 200-300 ms ahead, and the number of generators that must be shed to maintain stability can be decided.< >
