In recent years, many studies have been made on allocating Na-S batteries in distribution substations to make good use of power facilities and improve the load factor. Besides, it has also been a ...hope to utilize Na-S batteries for controls such as AFC (automatic frequency control) or VQC (voltage reactive-power control), because Na-S batteries can respond faster than existing generator units and can control active and reactive power outputs independently by the function of AC-DC converter systems. In this paper, the authors propose a method for determining the optimal allocation and PQ output ratio of Na-S batteries in order to improve voltage stability. The proposed method combines a sensitivity method with an optimal power flow calculation method to determine the allocation and PQ output ratio efficiently and optimally. Simulations are carried out for a 73-bus distribution system to illustrate and verify the proposed method.
“Tracing Power Flow of Electricity” is the concept that has become a focus of attention recently, as the deregulation or the liberalization of electric power markets proceeds. In this paper, we focus ...on line flows and static capacitors in particular, and we study how to deal with the problem. Although a number of methods, such as “Tracing Method by Power Flow Proportion”, have already been published, reactive power contribution has not been studied much thus far. However, applying 'Tracing Power Flow of Electricity' to ancillary service, for example compensation of reactive power, is very important. Simulations are run using a sample system and the tracing results are shown.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, we consider NAS (natrium sulfur = sodium sulfur) battery systems to be utilized for voltage stability control, and propose a method for determining installation planning and operation ...control schemes of NAS battery systems in order to improve voltage stability. In the stage of installation planning, optimal allocations and capacities of NAS battery systems are determined by solving optimal power flow calculations, which maximize a voltage stability index of an entire power system. In the stage of operation control, optimal PQ (active and reactive) output ratios of NAS battery systems are determined to examine the operation control patterns for various load conditions. Simulations are carried out for verifying the validity of the proposed method using the east 10 machine and west 10 machine system models. IEE of Japan, and successful results are obtained.
Since the revised Electric Utility Law was enforced in March 2000 in Japan, many IPPs (Independent Power Producers) and PPSs (Power Producers and Suppliers) have entered into the Japanese power ...industry. Therefore, the concept called "Power Flow Tracing of Electricity" that determines which generators are supplying particular loads has been focused upon and many tracing methods have been studied recently. It is supposed that the importance of the ancillary service has increased more than ever and it has become important to apply the tracing methods to the ancillary service, if the deregulation progresses and the market expand in the near future. In this paper, we propose a new tracing method for reactive power when we treat generators, static capacitors and line-charging capacitors as reactive power sources. Furthermore, we propose a reactive power supplying service where the proposed tracing method is used at the time of the charge calculation. The purpose of this service is to keep the voltage stability that is one of the functions of ancillary service. Also, the validity of the proposed method is verified using an IEEJ WEST 10 machine-27 bus system.
In this paper, we propose a designing method of a load frequency control that is able to consider the change of operating points in the power system using /spl mu/-synthesis. We consider the change ...of the operating points as parameter variations in the inertia constant, the damping coefficient, and the synchronizing coefficient. As an example, we have designed a case for a three-area system, and run simulations for the system to compare the proposed method with a traditional method (PID type controller). As the results of the simulation, the validity of the proposed method has been confirmed.
The deregulation of the electric power industry has progressed in the world. It contributes to reducing electric rates, but there is possibility that the power system might become deteriorated. Under ...the circumstances, ancillary services that maintain system reliability and security become more important. There are various services in ancillary services, for example long-tern power reserves, power/frequency control, voltage/reactive power control and so on. In these services, it becomes a subject of discussion on how to procure and receive the services and how to pay money for the cost of the supply of ancillary services. In this paper, we focus our attention on reactive power supply of ancillary services. Then, we propose a calculation method for the rates based on an improved nodal pricing, and consider rates of reactive power supply service from generators.
Power systems have become larger and more complicated because of the increase of the electric power demand, and the analysis of a power system needs heavier computation. On the other hand, the social ...dependence on electric power is increasing, so the influence of outages in power systems is becoming more crucial. Therefore online preventive control is more important than ever. In this paper, the authors propose a generation rescheduling method for transient stability preventive control. First they sort all contingencies in the decreasing order of their severity. This process is done by sorting all contingencies in the increasing order of their critical clearing times (CCTs) computed using the dynamic extended equal-area criterion. Second they select several contingencies among them as objects of consideration, and compute generation rescheduling amounts using rotor angles of some machines at the appropriate time and the linearity relationship between CCTs and outputs of critical machines. To investigate the validity of the proposed method, simulations carried out using the 9-machine 20-bus system.
As the electric power demand increases, power systems become larger and more complex. To keep the reliability, preventive control is desired in power system operations. It is necessary to shift a ...system to a stable side beforehand using the preventive control, so that the system may be stable even for some disturbances. In this paper, we use RIDGE theory to judge the transient stability for the preventive control. The authors use the characteristics of RIDGE theory to judge transient stability, and the proposed method can judge the transient stability fast. Simulations are carried out using 3 machine 9 bus and 10 machine 47 bus systems to confirm the validity of the proposed method.
As the electric power demand increases, power systems have become larger and more complex. The dependence on the electric power in society tends to increase such as information products prevail. On ...the other hand, studies on applications of Global Positioning System (GPS) to power systems monitoring are being conducted. In this paper, at first we propose a GPS placement method with a viewpoint of effectively monitoring the power system stability. This method uses the first order eigenvalue sensitivities for phase angles from relationship between eigenvalues and phase angles. Next, we propose a method for determining more appropriate generation dispatch rescheduling to improve the power system stability when the power system stability deceases. At that time we use first and second order eigenvalue sensitivities. The proposed method is demonstrated using a sample 4 machine 10 bus system and we examine effectiveness of the second order eigenvalue sensitivities compared with the first order ones.
