• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.153-155
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• 2004

Various problems such as the increase of the power loss and the voltage instability may often occur in the case of low load power factor. The demand of reactive power increases continuously with the growth of active power and the restructuring of electric power companies makes the integrated management of ractive power a troublesome problem, so that the systematic control of load power factor is required. In this paper, the load power factor sensitivity of the generation cost is used for determining the locations of reactive power compensation devices effectively and for enhancing the load power factor appropriately. In addition, the integrated costs are used for determining the value of the load power factor from the point of view of the economic operation. It is shown through the application to a large-scale power system that the system power factor can be enhanced effectively and appropriately using the load power factor sensitivity and integrated costs.

• Journal of Power Electronics
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• 제16권3호
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• pp.1152-1162
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• 2016

The unequal impedances of the interconnecting cables between paralleled inverters in the island mode of microgrids cause inaccurate reactive power sharing when the traditional droop control is used. Many studies in the literature adopt low speed communications between the inverters and the central control unit to overcome this problem. However, the losses of this communication link can be very detrimental to the performance of the controller. This paper proposes an improved reactive power-sharing control method. It employs infrequent measurements of the voltage at the point of common coupling (PCC) to estimate the output impedance between the inverters and the PCC and then readjust the voltage droop controller gains accordingly. The controller then reverts to being a traditional droop controller using the newly calculated gains. This increases the immunity of the controller against any losses in the communication links between the central control unit and the inverters. The capability of the proposed control method has been demonstrated by simulation and experimental results using a laboratory scale microgrid.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.284-286
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• 2003

The low load power factor causes various problems such as the Increase of the power loss and the voltage instability. The demand of reactive power increases continuously with the growth of active power and the restructuring of electric power companies makes the integrated management of ractive power troublesome, from which the systematic control of load power factor is required. In this paper, the load power factor sensitivity of the generation cost and integrated costs are used for determining the locations and capacities of reactive power compensation devices effectively and for enhancing the load power factor appropriately. It is shown through the application to a small-scale power system that the system power factor can be enhanced effectively and appropriately using the load power factor sensitivity and integrated costs.

• 전력전자학회논문지
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• 제21권4호
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• pp.356-363
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• 2016

The design methodology of an adequate input voltage and magnetizing inductance to minimize reactive power is suggested to design a wireless power transfer (WPT) converter for high-power transfer efficiency. To increase the magnetizing inductance, the turn number of the WPT coil is increased, thus causing high parasitic resistance in the WPT coil. Moreover, the high coil resistance produces high conduction loss in the transfer and receive coils. Therefore, the analysis of conduction loss is used in the design of the WPT coil and the operating point of the WPT converter. To verify the proposed design methodology, the mathematical analysis of the conduction loss is presented by experimental results.

• 한국조명전기설비학회지:조명전기설비
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• 제8권1호
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• pp.37-45
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• 1994

본 논문은 전력계통 운용에 관한 합리적인 유효전력 및 무효전력 제어방법을 제시한 논문으로 무효전력 제어에 퍼지 선형계획법을 적용하여 목적함수의 값을 최소화하고 전체 계산시간을 단축시키고 운용의 융통성을 주기 위하여 시도한 논문으로 본 논문의 특징은 다음과 같다. 1) 유효전력 제어는 선로손실을 고려한 전력수급 평형식으로서 B정수를 이용하지 않고 전력 조류 방정식의 쟈코비 행렬의 스파스한 성질을 이용하여 간단히 계산하고 Lagrange함수법을 이용함으로써 계산시간을 단축시키고 기억용량을 대폭 경감시킬 수 있으며 반복계산을 하지 않고 직접 발전기의 최적부하 배분량을 결정할 수 있다. 2) 무효전력 제어시에도 목적함수로서는 총 선로손실을 취하지 않고 발전소의 총 연료비를 취하여 이를 최소화함으로써 보다 합리적인 경제성을 도모하였다. 또 이때 필요한 제어변수에 대한 발전기 출력시 모선전압의 감도행렬의 계산은 조류 방정식의 쟈코비 행렬의 스파스한 성질을 충분히 이용하여 계산시간을 단축시킬 수 있도록 하였다. 3) 특히 무효전력 제어시에는 많은 함수형 부등식 제약조건을 즉 모선전압의 상하한 제약조건을 일정한 값으로 고정하지 않고 어떤 허용 변동폭을 주어 조건을 완화하는 퍼지 선형계획법을 적용하므로써 확정적인 제약을 갖는 일반 선형계획법을 적용할 때보다 유리한 점이 확인되었다.

• KIEE International Transactions on Power Engineering
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• 제4A권2호
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• pp.58-68
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• 2004

This paper presents an optimal routing algorithm (ORA) for maximizing voltage stability as well as for minimizing power loss in radial power systems. In the proposed ORA, a novel voltage stability index (VSI) for real-time assessment is newly introduced based on the conventional critical transmission path framework. In addition, the suggested algorithm can automatically detect the critical transmission paths resulting in voltage collapse when additional real or reactive loads are added. To implement an effective ORA, we have developed an improved branch exchange (IBE) method based on a loss calculation index and tie-branch power flow equations, which are suggested for real-time applications. The proposed algorithm has been tested with IEEE test systems as well as a large-scale power system in Korea to demonstrate its effectiveness and efficiency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.212-214
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• 1997

This paper presents a genetic algorithm based optimal reactive power dispatch (ORPD) in which voltage dependent load model is considered. The objective of this study is to minimize the transmission loss with consideration of voltage and reactive power constraints. The proposed algorithm has been evaluated with the IEEE 30-bus system. Simulation results, compared with each cases, are presented to show the performance of the proposed method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.190-192
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• 1999

This paper presents an algorithm for optimal reactive power dispatch problem based on genetic algorithm. Optimal reactive power dispatch is particularized to the minimization of transmission line losses by suitable selection of generator reactive power outputs and transformer tap settings. To attain for the objective, in this paper, loss re-distribution algorithm(LRDA) is applied to ORPD. The proposed method has been evaluated on the IEEE 30 bus system. Results of the application of the method are compared with a simple genetic algorithm.

• 전기학회논문지
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• 제59권7호
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• pp.1187-1193
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• 2010

This paper provides the methods for enhancing the stability with normal or emergency operating conditions in real power systems and copes with the unbalance of demand of reactive power due to the loss of facility, such as 765kV transmission line. In this paper, we focused on the maximum allowable transmission power(hereafter, MAXTP) in the metropolitan area. In order to increase the MAXTP, the application of reactive power compensators, SVC, and Shunt compensator and reactor, is analyzed as an enhancing method of stability and MAXTP. Particularly, the f-V analysis was performed for the postulated contingency, in order to evaluate the effects on SVC. Conclusively, the stability of power systems could be enhanced and the MAXTP is increased effectively with Dongseoul SVC which has the capacity 200MVAr.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.1103-1106
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• 2002

This paper presents SVC which use PAM method and eliminate harmonics. Inverter is connected directly so that SVC improve output voltage waveform into 24 steps. Inverter output waveform THD is reduced to 6.89%. Leading control of reactive power generated in power system is possible. Snubber is added to reduce switching loss.