Author

# Adam Semlyen

Other affiliations: Instituto Politécnico Nacional, Universidad Michoacana de San Nicolás de Hidalgo

Bio: Adam Semlyen is an academic researcher from University of Toronto. The author has contributed to research in topics: Nonlinear system & Frequency domain. The author has an hindex of 39, co-authored 91 publications receiving 8973 citations. Previous affiliations of Adam Semlyen include Instituto Politécnico Nacional & Universidad Michoacana de San Nicolás de Hidalgo.

Topics: Nonlinear system, Frequency domain, Harmonic, Time domain, Harmonics

##### Papers published on a yearly basis

##### Papers

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TL;DR: The paper describes a general methodology for the fitting of measured or calculated frequency domain responses with rational function approximations by replacing a set of starting poles with an improved set of poles via a scaling procedure.

Abstract: The paper describes a general methodology for the fitting of measured or calculated frequency domain responses with rational function approximations. This is achieved by replacing a set of starting poles with an improved set of poles via a scaling procedure. A previous paper (Gustavsen et al., 1997) described the application of the method to smooth functions using real starting poles. This paper extends the method to functions with a high number of resonance peaks by allowing complex starting poles. Fundamental properties of the method are discussed and details of its practical implementation are described. The method is demonstrated to be very suitable for fitting network equivalents and transformer responses. The computer code is in the public domain, available from the first author.

2,592 citations

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TL;DR: In this article, a power flow method is described for solving weakly meshed distribution and transmission networks, using a multiport compensation technique and basic formations of Kirchoff's laws.

Abstract: A power flow method is described for solving weakly meshed distribution and transmission networks, using a multiport compensation technique and basic formations of Kirchoff's laws. This method has excellent convergence characteristics and is robust. A computer program implementing this scheme was developed and successfully applied to several practical distribution and transmission networks with radial and weakly meshed structures. The method can be applied to the solution of both the three-phase (unbalanced) and single-phase (balanced) representation of the network, however, only the single-phase representation is treated in detail. >

1,046 citations

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TL;DR: In this paper, a linear power system component can be included in a transient simulation as a terminal equivalent by approximating its admittance matrix Y by rational functions in the frequency domain.

Abstract: A linear power system component can be included in a transient simulation as a terminal equivalent by approximating its admittance matrix Y by rational functions in the frequency domain. Physical behavior of the resulting model entails that it should absorb active power for any set of applied voltages, at any frequency. This requires the real part of Y to be positive definite (PD). We calculate a correction to the rational approximation of Y which enforces the PD-criterion to be satisfied. The correction is minimal with respect to the fitting error. The method is based on linearization and constrained minimization by quadratic programming. Examples show that models not satisfying the PD-criterion can lead to an unstable simulation, even though the rational approximation has stable poles only. Enforcement of the PD-criterion is demonstrated to give a stable result.

388 citations

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TL;DR: The paper presents a new approach to the calculation of transients on transmission lines with frequency-dependent parameters to obtain significant computer-time savings by avoiding convolutions by approximating all line and ground distortions and also time variable characteristic admittances by exponential functions.

Abstract: The paper presents a new approach to the calculation of transients on transmission lines with frequency-dependent parameters. Its purpose is to obtain significant computer-time savings by avoiding convolutions. This is achieved by approximating all line and ground distortions and also time variable characteristic admittances by exponential functions, i.e. solutions of linear differential equations. The method produces a simple Norton-type line equivalent which permits its incorporation into an existing system representation like the B.P.A. program for the calculation of transients. The program has been tested on systems of different degrees of complexity and proved to be superior, in terms of speed and accuracy, to other advanced methods.

382 citations

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TL;DR: In this paper, an efficient method for calculating the load flow solution of weakly meshed transmission and distribution systems is presented, which uses active and reactive powers as flow variables rather than complex currents, thus simplifying the treatment of P, V buses and reducing the related computational effort.

Abstract: An efficient method for calculating the load flow solution of weakly meshed transmission and distribution systems is presented. Its essential advantages over a previous approach are the following: (1) It uses active and reactive powers as flow variables rather than complex currents, thus simplifying the treatment of P, V buses and reducing the related computational effort to half; (2) It uses an efficient tree-labeling technique which also contributes to the computational efficiency of the procedure; (3) It uses an improved solution strategy, thereby reducing the burden of mismatch calculations which is an important component of the solution process. Results of tests with 30, 243, 1380, and 4130 bus systems are given to illustrate the performance of the proposed method. >

373 citations

##### Cited by

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[...]

TL;DR: The paper describes a general methodology for the fitting of measured or calculated frequency domain responses with rational function approximations by replacing a set of starting poles with an improved set of poles via a scaling procedure.

Abstract: The paper describes a general methodology for the fitting of measured or calculated frequency domain responses with rational function approximations. This is achieved by replacing a set of starting poles with an improved set of poles via a scaling procedure. A previous paper (Gustavsen et al., 1997) described the application of the method to smooth functions using real starting poles. This paper extends the method to functions with a high number of resonance peaks by allowing complex starting poles. Fundamental properties of the method are discussed and details of its practical implementation are described. The method is demonstrated to be very suitable for fitting network equivalents and transformer responses. The computer code is in the public domain, available from the first author.

2,592 citations

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[...]

TL;DR: This paper presents a detailed overview of the basic concepts of PSO and its variants, and provides a comprehensive survey on the power system applications that have benefited from the powerful nature ofPSO as an optimization technique.

Abstract: Many areas in power systems require solving one or more nonlinear optimization problems. While analytical methods might suffer from slow convergence and the curse of dimensionality, heuristics-based swarm intelligence can be an efficient alternative. Particle swarm optimization (PSO), part of the swarm intelligence family, is known to effectively solve large-scale nonlinear optimization problems. This paper presents a detailed overview of the basic concepts of PSO and its variants. Also, it provides a comprehensive survey on the power system applications that have benefited from the powerful nature of PSO as an optimization technique. For each application, technical details that are required for applying PSO, such as its type, particle formulation (solution representation), and the most efficient fitness functions are also discussed.

1,942 citations

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TL;DR: In this paper, the authors outline a methodology for the computation of the response of a multiconductor transmission line terminated by linear networks, where the lines are embedded in a multilayered lossy dielectric media and have arbitrary cross sections, but uniform along the length.

Abstract: The objective of this paper is to outline a methodology for the computation of the response of a multiconductor transmission line terminated by linear networks. The lines are embedded in a multilayered lossy dielectric media and have arbitrary cross sections, but uniform along the length. To check the accuracy of the theoretical results, extensive experimental verification has been carried out.

1,210 citations

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TL;DR: In this paper, a nonlinear programming problem for capacitors placed on a radial distribution system is formulated and a solution algorithm is developed to find the optimal size of capacitors so that the power losses will be minimized for a given load profile while considering the cost of the capacitors.

Abstract: A capacitor sizing problem for capacitors placed on a radial distribution system is formulated as a nonlinear programming problem, and a solution algorithm is developed. The object is to find the optimal size of the capacitors so that the power losses will be minimized for a given load profile while considering the cost of the capacitors. The formulation also incorporates the AC power flow model for the system and the voltage constraints. The solution algorithm developed for the capacitor sizing problem is based on a Phase I-Phase II feasible directions approach. Novel power flow equations and a solution method, called DistFlow, for radial distribution systems are introduced. The method is computationally efficient and numerically robust, especially for distribution systems with large r/x ratio branches. DistFlow is used repeatedly as a subroutine in the optimization algorithm for the capacitor sizing problem. The test results for the algorithm indicate that the method is computationally efficient and has good convergence characteristics. >

1,208 citations

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TL;DR: In this paper, an evolutionary-based approach to solve the optimal power flow (OPF) problem is presented. And the proposed approach has been examined and tested on the standard IEEE 30bus test system with different objectives that reflect fuel cost minimization, voltage profile improvement, and voltage stability enhancement.

Abstract: This paper presents an efficient and reliable evolutionary-based approach to solve the optimal power flow (OPF) problem. The proposed approach employs particle swarm optimization (PSO) algorithm for optimal settings of OPF problem control variables. Incorporation of PSO as a derivative-free optimization technique in solving OPF problem significantly relieves the assumptions imposed on the optimized objective functions. The proposed approach has been examined and tested on the standard IEEE 30-bus test system with different objectives that reflect fuel cost minimization, voltage profile improvement, and voltage stability enhancement. The proposed approach results have been compared to those that reported in the literature recently. The results are promising and show the effectiveness and robustness of the proposed approach.

1,141 citations