Numerical techniques in solution of power-system load-flow problems

Laughton, M.A.; Davies, Mark

doi:10.1049/piee.1964.0259

Cited by 37 publications

(9 citation statements)

References 33 publications

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“…At this time, the power system industry slowly started to use digital computers for power system analysis [75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91]. With the use of digital computers, the power system industry no longer had to worry about the component limitations in the network analyzer and the need for equivalent circuits was diminished.…”

Section: Evolution Of Equivalent Circuits Over Timementioning

confidence: 99%

Development of an Equivalent Circuit of a Large Power System for Real-Time Security Assessment

Wijeweera

Annakkage

Zhang

et al. 2018

IEEE Trans. Power Syst.

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More and more system operators are interested in calculating transfer capability in realtime using real-time power flow models generated from the Energy Management System (EMS). However, compared to off-line study models, EMS models usually cover only a limited portion of the interconnected system. In most situations, it is not practical to extend the EMS model to capture the impact of the external systems and therefore using an equivalent network becomes necessary.The development of equivalent circuits to represent external areas was a topic discussed over the last 50 years. Almost all of these methods require impedance information about the external area to develop the equivalent circuit. Unfortunately utilities do not have the external impedance information in the real-time. Therefore, normal industry practice is to use off-line studies to develop an equivalent circuit and use that circuit in the real-time operation without any validation. This can result in errors in the security assessment. Therefore, power industry need a method to develop or validate an equivalent circuit based on the available real-time information. This thesis work is focussed on meeting that industry need.The work on this thesis presents two new methods that can be used to generate an equivalent circuit based on the boundary conditions. This method involves calculating equivalent impedance between two areas based on the boundary stations voltages, voltage angles and power leaving the boundary stations into external areas.This thesis uses power system simulation between two areas to change the system condition to obtain different boundary bus voltages, voltage angles and power injections to generate necessary data. Regression analysis and least square method is then used to generate the equivalent circuit using these data. It is expected that system changes will provide necessary information in the real-time to generate the equivalent circuit.The proposed methodology is validated with modified three area 300 bus system as well as using Manitoba Hydro's system. Contingency analysis, transfer level calculation and PV curves analysis is used to validate the proposed method. Simulation results show that the proposed method produces adequate accuracy in comparison with detailed off-line system models.The main advantage of the proposed method as compared to other existing methods such as Ward and REI is that the proposed method does not require external impedance information to generate the equivalent circuit. The ability to generate reasonably good equivalent circuit only using available boundary information will help utilities to generate or validate the equivalent circuit based on the current system conditions, which will intern help improve the accuracy of the security assessment.i Acknowledgments I would like to express my appreciation and sincere thanks to Udaya Annakkage, my research advisor, for his guidance, support and advice throughout this research. I was truly enriched by the many discussions we had over the course of thi...

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Section: Evolution Of Equivalent Circuits Over Timementioning

confidence: 99%

Development of an Equivalent Circuit of a Large Power System for Real-Time Security Assessment

Wijeweera

Annakkage

Zhang

et al. 2018

IEEE Trans. Power Syst.

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“…The power this paper is connected by the linear l components, and it is applied to the power sy simple schematic representation of the powe in m is continuously ty, system stability er system engineer ewer and better m problem more study [1][2][3][4] is an applied to a power basis for planning the power systems tance of load-flow f power systems as f existing systems. power flow study he voltage at each in each line.…”

Section: Conventional Power Flowmentioning

confidence: 99%

A novel approach of power flow analysis by power perturbation method

Bose

Bhowmik

Rajan

2011

2011 IEEE Control and System Graduate Research Colloquium

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“…If a line of impedance z is added between the nodes p, q, the new matrix X is given by In the special case of example {b), this reduces to a standard procedure. 5 A combination of this procedure with the use of alpha operations, in which the lines of the network are added one at a time, and alpha operations are carried out on each node in turn at the earliest opportunity (i.e. as soon as the operation no longer requires dividing by zero), provides an efficient algorithm both for the initial calculation of the impedance matrices required, and for their subsequent modification following changes in the network.…”

Section: Calculation Of the Network Matricesmentioning

confidence: 99%

Automatic load scheduling in a multiarea power system

Benthall¹

1968

Proc. Inst. Electr. Eng. UK

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SynopsisIn the paper an algorithm is described for solving the problem of secure economic load scheduling on a large power system. The method is an extension of that of Wells, which solves the problem as a linear program by means of the dual simplex algorithm. A dual form of the decomposition principle of Dantzig and Wolfe is used in order to reduce the size of the problem, so that it can be solved efficiently on a computer system. This is correlated with a corresponding decomposition of the power system into autonomous areas, co-ordinated by the specification of recommended boundary transfers and spinning spare capacity. Further levels of decomposition are incorporated in a similar fashion, allowing three or more levels, say, for the CEGB supply system. Although the entire problem can be solved on a single computer, for application to online control a more complex computing system is anticipated. Hj bo, Go, c 0 , Z, w 0 , Pkj> List of principal symbolsXj = variables ofyth subsystem Zj -intervention parameters ofyth subsystem y -variables of co-ordinating system Qj = connection matrix = constraint limits j = matrices of constraint coefficients = incremental costs = total costs = dual variables = homogeneous solutions to dual subproblem = basic solutions to dual subproblem Pkj> T PJ = variables in associated problem y p j, f kj , f P j = coefficients in associated problem ipj = variable corresponding to the total cost of yth subsystem / -injected power J = power transfers V = nodal voltages C = connection matrix A,B, D, X, Y, Z = network matrices T = transposed matrix IntroductionAs the size of a system grows, the effort required to control it increases very rapidly, and it has long been realised that for large systems a hierarchical control system is desirable. Such systems, which occur universally in complex natural organisms, are designed to exploit the natural structure of the system to be controlled by its division into a number of subsystems, which contain their own controllers but are instructed by a co-ordinating system which exercises overall control. In mathematical terms, the communication between the co-ordinating system and each subsystem is expressed in terms of a few variables, known as 'intervention parameters'. When these are specified by the co-ordinating system, each subsystem operates independently; the function of the co-ordinator is to determine the best values for the intervention parameters by considering suitable performance criteria for the subsystems. Such a structure can be continued, if desired, through several levels of control. The result of this decomposition of the system is to reduce strikingly the complexity of the control mechanisms required.Load scheduling in the CEGB supply system is at present carried out by such a hierarchical system. Each station is instructed in its total output by the Grid control centre, and each control centre operates to satisfy the requirements for interarea transfers specified by national control. The introduction of the 3-tier control has only empha...

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Numerical techniques in solution of power-system load-flow problems

Cited by 37 publications

References 33 publications

Development of an Equivalent Circuit of a Large Power System for Real-Time Security Assessment

Development of an Equivalent Circuit of a Large Power System for Real-Time Security Assessment

A novel approach of power flow analysis by power perturbation method

Automatic load scheduling in a multiarea power system

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