• 대한전기학회논문지:전력기술부문A
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• 제53권1호
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• pp.1-6
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• 2004

This paper suggests an extended power flow analysis algorithm based on a modified economic load dispatch concept. Meaningfully, the proposed method makes it possible to perform the power flow analysis without a slack bus. And the 'equal incremental cost' rule which is obtained by economic load dispatch prior to power flow is maintained even during the proposed power flow analysis. In this paper, both 5 - bus and 14 - bus power systems are used to offer the theoretical accuracy and practical applications of this algorithm.

• 디지털산업정보학회논문지
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• 제4권1호
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• pp.9-16
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• 2008

This paper presents a frequency selection algorithm for minimization power consumption of processor in Mobile System. The proposed algorithm has processor designed low power processor using clock gating method. Clock gating method has improved the power dissipation by control main clock through the bus which is embedded clock block applying the method of clock gating. Proposed method has compared power consumption considered the dynamic power for processor, selected frequency has considered energy gain and energy consumption for designed processor. Or reduced power consumption with decreased processor speed using slack time. This technique has improved the life time of the mobile systems by clock gating method, considered energy and using slack time. As an results, the proposed algorithm reduce average power saving up to 4% comparing to not apply processor in mobile system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.797-799
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• 1996

This paper presents a simple method for evaluating of voltage stability using the line flow equation. Line flow equations($P_{ij}$, $Q_{ij}$) are comprised of state variable, $V_i$, ${\delta}_i$, $V_j$ and ${\delta}_j$, and line parameter, r and x. Using the feature of polar coordinate, these equations become one equation with two variables, $V_i$ and $V_j$. Moreover, if bus j is slack bus or generator bus, which is specified voltage magnitude, it becomes One equation with one variable $V_i$, that is, may be formulated with the second-order equation for $V_i^2$. Therefore, solutions are obtained with simple computation. Solutions obtained are used for evaluating of voltage stability through sensitivity analysis. Also, considering of reactive power source, method for evaluating the voltage stability is introduced. The proposed method was validated to 2-bus and IEEE 6-bus system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.201-204
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• 1992

In the conventional load flow technique, it is assumed that the generator at the slack bus is used to supply the transmission losses and the change of power due to the generator outage. The assumption is not true in physical sense. This paper presents a new load flow technique that considers the governor-frequency characteristics and load-frequency characteristics and the technique is consistent with the actual power system phenomenon. This paper proposes an efficient methodology using sensitivity with the new technique for contingency analysis, which is used to calculate the line flows. Computational results of this technique applied to IEEE 14-bus system are presented.

• KIEE International Transactions on Power Engineering
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• 제4A권3호
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• pp.134-140
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• 2004

This paper presents an improved group of energy functions reflecting generator damping effects for multi-machine power systems by using Center of Inertia (COI) formulation as an extension of the previous work. Since rotor angles at the Stable Equilibrium Point (SEP) of post-fault systems are generally calculated in COI, system transient energy can be found without assumption of infinite or slack bus, which is a crucial drawback of the absolute rotor angle frame approach. The developed energy functions have a structure preserving property with which it is very flexible to incorporate various models of power system components, especially various load and generator models. The proposed damping-reflected energy functions are applied to the Potential Energy Boundary Surface (PEBS) method, one of the direct methods. Numerical simulation of WSCC 9-bus shows that conservativeness of the PEBS method can be considerably reduced.

• 대한전기학회논문지
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• 제33권6호
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• pp.232-240
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• 1984

이 논문은 전력계통에서의 상정사고 해석과 상정사고 대책에 관한 감도 행열에 관해 새로운 앨고리즘을 제시 하였다. 이 앨고리즘은 다른 일방적인 상정사고 해석 앨고리즘에 비해 선로사고나 모선사고시 실재상황에서 일어나는 모선전력 변화를 고려하여 개선된 AC 조류 계산법을 사용하여 정확한 조류변화를 얻었고 계산시간을 단축했다. 이 앨고리즘을 워어드헤일 5모선 계통과 IEEE의 24모선 계통에 적용하여 만족할만한 결과를 얻었다.

• 에너지공학
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• 제7권1호
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• pp.65-72
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• 1998

이 논문은 극좌표이 선로조류방정식을 이용하여 전압안정성 여유전력을 평가하는 고속계산법을 제안한다. 여기서, 선로조류방정식은 상태변수 Vi, $\delta$i, Vj와 $\delta$i 그리고, 선로정수 r과 x로 구성되는데 극좌표계의 특징을 이용하면 이것은 두 개의 변수 Vi와 Vj를 가진 하나의 식이 된다. 그리고, j 모선이 조류계산에서 전압크기로 지정되는 발전기 또는 slack 모선이라면, 변수 Vi만을 가진 하나의 식 즉, {{{{ { V}`_{i } ^{2 } }}에 대한 2차 방정식으로 정식화된다. 그러므로, 전력조류다근은 간단한 계산을 통해 구할 수가 있는데 이와 같이 구해진 다근은 감도해석 또는 다근의 근접도를 통해 전압안정도를 평가할 수 가 있었다. 또한, 전압안정도 평가시에 중요한 요소인 전력용 콘덴서와 같은 조상설비를 고려하여 전압안정성 여유전력을 평가하는 방법을 개발하였다. 제안한 방법을 시험계통에 적용하여 유효성을 입증하였다.

• 대한전기학회논문지:전력기술부문A
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• 제50권9호
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• pp.424-430
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• 2001

A multi-level optimal power flow(OPF) algorithm has been evolved from a simple two stage optimal Power flow algorithm for constrained power economic dispatch control. In the proposed algorithm, we consider various constraints such as ower balance, generation capacity, transmission line capacity, transmission losses, security equality, and security inequality constraints. The proposed algorithm consists of four stages. At the first stage, we solve the aggregated problem that is the crude classical economic dispatch problem without considering transmission losses. An initial solution is obtained by the aggregation concept in which the solution satisfies the power balance equations and generation capacity constraints. Then, after load flow analysis, the transmission losses of an initial generation setting are matched by the slack bus generator that produces power with the cheapest cost. At the second stage we consider transmission losses. Formulation of the second stage becomes classical economic dispatch problem involving the transmission losses, which are distributed to all generators. Once a feasible solution is obtained from the second stage, transmission capacity and other violations are checked and corrected locally and quickly at the third stage. The fourth stage fine tunes the solution of the third stage to reach a real minimum. The proposed approach speeds up the two stage optimization method to an average gain of 2.99 for IEEE 30, 57, and 118 bus systems and EPRI Scenario systems A through D testings.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.926-928
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• 1998

A fast optimization algorithm has been evolved from a simple two stage optimal power flow(OPF) algorithm for constrained power economic dispatch. In the proposed algorithm, we consider various constraints such as power balance, generation capacity, transmission line capacity, transmission losses, security equality, and security inequality constraints. The proposed algorithm consists of four stages. At the first stage, we solve the aggregated problem that is the crude classical economic dispatch problem without considering transmission losses. An initial solution is obtained by the aggregation concept in which the solution satisfies the power balance equations and generation capacity constraints. Then, after load flow analysis, the transmission losses of an initial generation setting are matched by the slack bus generator that produces power with the cheapest cost. At the second stage we consider transmission losses. Formulation of the second stage becomes classical economic dispatch problem involving the transmission losses, which are distributed to all generators. Once a feasible solution is obtained from the second stage, transmission capacity and other violations are checked and corrected locally and quickly at the third stage. The fourth stage fine tunes the solution of the third stage to reach a real minimum. The proposed approach speeds up the coupled LP based OPF method to an average gain of 53.13 for IEEE 30, 57, and 118 bus systems and EPRI Scenario systems A through D testings.

• 전기학회논문지
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• 제60권2호
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• pp.257-265
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• 2011

As the competitive market system has been introduced to the electrical power trade, the priority concern would be that the price of electrical power should be reasonable. It is because, when this rule is solid, we can avoid the distortion of competition and assure the greater efficiency in management. LMP(Locational Marginal Price) means marginal price at each bus. This components consist of energy, loss and congestion cost. At this point, the LMP result that is calculated by traditional model is changeable by the location of the slack and can not be used in bilateral Transaction. This paper proposed algorithm is proved its rationality and credibility by comparing the result of the simulation of virtual 6_bus system that is calculated by traditional method, and showed that the LMP components are changed according to the Transaction Strategy. Furthermore, It shows the effect of additional congestion cost on the transmission line that has bottle neck frequently by simulation.