• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.308-317
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• 2012

Reactive processing, such as reactive hot pressing (RHP) and reactive spark plasma sintering (R-SPS), is effective densification method to prepare $ZrB_2$-based ultra high temperature ceramics (UHTCs). The present paper reviewed some typical reactive processing of $ZrB_2$-based UHTCs. All the reactions from the starting materials in the reactive processing are thermodynamically favorable, which generate enough energy and driving force for the densification of the final products under a relatively low temperature. Besides, compared with non-reactive processing, anisotropic $ZrB_2$ grains, such as $ZrB_2$ platelets, can only be obtained in the reactive processing, resulting in an improvement of the mechanical properties.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1351-1354
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• 2002

Wind farm which are composed with wind turbine generators can be a good alternatives to solve environmental problem and solutions to cope with energy crisis for using wind energy. Until now, these wind turbine generators have been being studied on the viewpoint of only active power control for reducing the burden of main grid. In this control scheme, we might demand a reactive power compensator in order to make reparation for the reactive power produced from wind turbine generator itself. Therefore, if the reactive power as well as active power of wind turbine generator were controlled according to the demand of reactive power, the installation of a additional reactive power compensator could be reduced. This paper presents the control method of a active and reactive power for wind turbine generators by means of SVPWM(Space Vector Pulse Width Modulation) inverting method and describes a operational coordination of wind turbine generators. The proposed power control algorithm can simply produce the output power of wind turbine generator needed in wind farm, which can reduce the power of main grid more and exclude a supplementary reactive power compensator. We assumed that wind farm are composed with two kinds of wind turbine generators, AC/DC/AC and induction generator types.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.85-88
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• 2000

This paper proposes a methodology to compute the servicing price of reactive power management and voltage control in competitive electrical power market. Compound method is proposed and its result is proved by a sample test. The method can be useful in providing additional insight into power system operation and can be used to determine tariffs of reactive power management service.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.533-535
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• 2001

This paper proposes a methodology to compute the servicing price of reactive power in electrical power market of competitive environment. The result of proposed method is proved by a 6-bus sample test system. In this paper we propose the real-time pricing method assigning to variable charges, the downstream power flow tracing assigning to fixed charges. The reactive power will be active by the proposed method through competitive electrical power market.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.33 no.10
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• pp.410-422
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• 1984

This paper presents a new practical method for optimal active and reactive power control for the economic operation in electrical power system, and the programs are developed for digital computer solution. The major features and techniques of this paper are as follows: 1) The method is presented for finding the equivalent active power balance equation applying the sparse Jacobian matrix of power flow equation instead of using B constant as active power balance equation considering transmission loss, and thus for determining directly optimal active power allocation berween generator unitw satisfying the equality and inequality constraints. 2) The method is proposed for solving directly the optimum economim dispatch problem without using gradient method and penalty function for both active and reactive power control. As a result, the computing time are reduced and convergence characteristic is remarkably improved. 3) Unlike most of conventional methods which adopt the transmission loss as a objective function for reactive power control, the total fuel cost of themal power plant is adopted as objective function for both active and reactive power control. consequently, more reasonable and economic profit can be achieved.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.4
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• pp.208-216
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• 2005

Recently, the study of islanding phenomenon, maintains its operation even when the utility grid is removed has lead to the trend of utility interactive inverters in photovoltaic generation systems. In this paper, a novel Anti-islanding method is presented. the proposed method can keep the real average power component constant by MPPT control and cause the load current frequency with only change of reactive power component under the islanding condition. its periodical change of Reactive power component can decrease the NDZ(Non-Detective zone) so that the detection of various loads will be possible. the insufficient effect if additional reactive power component to the grid is proved theoretically and the islanding detection is also confirmed from a experimental result with a inverter for 3kW photovoltaic generation system applied the proposed Anti-islanding method.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.202-206
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• 1989

A new algorithm is suggested to solve the optimal reactive power control(optimal VAR control) problem. An efficient computer program based on the latest achievements in the sparse matrix/vector techniques has been developed for this purpose. The model minimizes the real power losses in the system. The constraints include the reactive power limits of the generators, limits on the bus voltages and the operating limits of control variables- the transformer tap positions, generator terminal voltages and switchable reactive power sources. The method developed herein employs linearized sensitivity relationships of power systems to establish both the objective function for minimizing the system losses and the system performance sensitivities relating dependent and control variables. The algorithm consists of two modules, i.e. the Q-V module for reactive power-voltage control, Load flow module for computational error adjustments. In particular, the acceleration factor technique is introduced to enhance the convergence property in Q-module, The combined use of the afore-mentioned two modules ensures more effective and efficient solutions for optimal reactive power dispatch problems. Results of the application of the method to the sample system and other worst-case system demonstrated that the algorithm suggested herein is compared favourably with conventional ones in terms of computation accuracy and convergence characteristics.

• KIEE International Transactions on Power Engineering
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• v.11A no.4
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• pp.39-44
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• 2001

As electric power systems have been moving from vertically integrated utilities to a deregulated environment, the charging of reactive power management is a new challenging them for market operators. This paper proposes a new methodology to compute the costs of providing reactive power management service in a competitive electrical power market. The proposed formulation, which is basically different from those shown in the literature, consists of two parts. One is to recover investment capital costs of reactive power supporting equipment based on a reactive power flow tracing algorithm. The other is to recover operational costs based on variable spot prices using the optimal power flow algorithm. The charging shapes resulted from the proposed approach exhibit a quite good meaning viewed from a practical sense. It turns out that reactive power charged are mostly due to recovery of capital costs and slightly due to recovery of operational costs. The methods can be useful in providing additional insight into power system operation and can be used to determined tariffs of a reactive power management service.

• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.337-345
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• 2009

Deregulation in power industry has made the reactive power ancillary service management a critical task to power system operators from both technical and economic perspectives. Reactive power management in power systems is a complex combinatorial optimization problem involving nonlinear functions with multiple local minima and nonlinear constraints. This paper proposes a practical market-based reactive power ancillary service management scheme to tackle the challenge. In this paper a new model for voltage security and reactive power management is presented. The proposed model minimizes reactive support cost as an economic aspect and insures the voltage security as a technical constraint. For modeling validation study, two optimization algorithm, a genetic algorithm (GA) and particle swarm optimization (PSO) method are used to solve the problem of optimum allocation of reactive power in power systems under open market environment and the results are compared. As a case study, the IEEE-30 bus power system is used. Results show that the algorithm is well competent for optimal allocation of reactive power under practical constraints and price based conditions.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.3
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• pp.182-186
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• 2004

In this paper, the cost for capacitive reactive flower is evaluated considering the deregulation environment. For the cost assessment of reactive power, the duration curve of reactive power demand is introduced and investigated. Also, a guideline is suggested to estimate the Q-cost by using the inverse of the Q-demand duration curve. In order to obtain optimal real reactive power allocation, a new algorithm is proposed by using the piecewise linearization of the inverse of the Q-demand duration curve and the Linear Programming technique. The proposed method is tested with sample systems using MATLAB. The test results show that the algorithm yields reasonable reactive power allocation and Provides fair cost evaluation for reactive power.