Kazimierz Wilkosz

Method for power system topology verification with use of radial basis function networks

The topology verification is an important problem in power system engineering. The paper presents the solution for this problem with use of the method, that is independent of state estimation. The method combines utilization of knowledge about power system and radial basis function networks. It allows to perform the power system topology verification as a series of verification processes for particular nodes of a power network. In the paper the possibility of such decomposition is proved. A principle of the method is described. Next, the computational example of topology verification with use of the characterized method is presented. At the end, the features of the method are analyzed, paying special attention to its efficiency.

A multi-agent system approach to power system topology verification

The paper deals with power system topology verification, being an important problem in real-time power system modeling. In the paper, the approach with use of multi-agent system is proposed. At the beginning, benefits from utilization of the agent technology are presented. Then, a theoretical background for the power system topology verification is described. Next, multi-agent system for topology verification and functions of particular agents are characterized. At the end, features of the presented approach to power system topology verification are summed up.

Identification of harmonic sources in a power system: A new method

The paper presents the new method to identification of harmonic sources in a power system. At the beginning, review of existing methods to localization of harmonic sources is made. Then, the theoretical background of the new method is presented. The used criterion of identification of harmonic sources in a power system is based on examining the assessment of the minimum and maximum ratio of magnitudes of source currents of the equivalent sources representing the customer and the utility sides. The results of analysis of the described method are given. At the end, conclusions are presented, summing up features of the considered method to identification of harmonic sources in a power system. It is underlined that the presented method has better properties than existing ones.

Utilization of the voltage rate to localization of harmonic sources in a power system

The paper proposes the new approach to determine which side, the utility or the customer is dominant harmonic source in a power system. At the beginning, review of existing approaches to localization of harmonic sources is given. Then, the theoretical background of the new approach is presented. The used criterion of localization of harmonic sources in a power system is based on examining the voltage ratio, which is defined in the paper. The results of investigation of sensibility of this ratio to the errors burdening quantities used for its calculation are analyzed. The practical conclusions are given. It is underlined that the presented approach has better properties than existing ones.

Influence of UPFC device on power system state estimation

The paper presents comparative studies of state estimation for a power system with and without the UPFC device. Weighted least squares state estimation is considered. Such parameters of state estimation are taken into account as: the condition number of the gain matrix, parameters characterizing accuracy of estimation results, and number of iterations in a computational process. During investigation, impact of existence UPFC in a power system on the mentioned parameters of the state estimation is analyzed for different coordinate systems, in which state vector is considered, for different levels of stress of a power system and data redundancy. In the paper, the considered parameters of state estimation are determined for the IEEE 14-bus test system. The results of the analyses show, that in general, impact of existence UPFC in a power system on features of the state estimation is negative, and particularly essential in some cases.

Harmonic Sources Localization: Comparison of methods utilizing the voltage rate or the current rate

The paper deals with the problem of the localization of harmonic sources in a power system. The aim of the paper is the comparison of two one-point methods utilizing the specially-defined rates. One method utilizes the so-called current rate, i.e. the rate calculated with use of source currents of equivalent sources representing the utility and customer sides. The second method is based on the so-called voltage rate, i.e. the rate calculated with use of source voltages of the equivalent sources representing the utility and customer sides. In the paper, a comparison of the mentioned methods is made taking into account their theoretical background, principles of localization of harmonic sources, utilization, efficiency and case studies. At the end, the conclusion from the performed analyses are given.

Power system topology verification using artificial neural networks: maximum utilization of measurement data

The paper deals with power system topology verification. The correct model of a power system topology is essential for different power system applications. There are different approaches to power system topology verification. One of these approaches assumes utilization of artificial neural networks (ANNs). This approach is considered in the paper, however in the paper one assumes maximal utilization of measurement data differently than in many other papers devoted to topology verification with use of ANNs. This assumption makes possible to increase a number of relationships and also to increase theoretical knowledge used in the verification process. A consequence is increasing a number of cases in which the correct verification decision can be taken. In the paper, a brief review of existing approaches to power system topology verification is presented. Then, the theoretical background of the new approach is given. After the method based on this approach is described an example of its utilization is presented. At the end, features of presented method are discussed.

A generalized approach to localization of sources of harmonics in a power system

Finding an answer to the question who is responsible for the generation of harmonics in power system is an essential problem especially in the conditions of the energy market. In the paper, the method which unlike other methods is reliable and does not require exact knowledge on parameters of equivalent circuit representing the utility and customer sides, is considered. This method utilizes the specially-defined rate, being generalization of the so-called voltage and current rates. Using the generalized localization rate, the localization of sources generating harmonics in voltage differs from the localization of sources generating harmonics in current by other definition of areas of possible changes of variables from which the mentioned rate depends. In the paper, the relatively-simple way of performance of required calculation is also described. As the result of the presented consideration is standardization and simplification of localization of sources of harmonics in voltage or current in a power system.

The analysis of harmonic generation of SVC and STATCOM by EMTDC/PSCAD simulations

In the paper, the harmonic generation of the conventional SVC and modern STATCOM systems is analysed. At the beginning, short description of the SVC and STATCOM systems is given. Then assumed models of a power system, the SVC and STATCOM systems are described. After scope of the investigations is given, results of harmonic analyses are presented. The SVC and STATCOM systems have been modelled using PSCAD/EMTDC program. During the simulation process, the voltage total harmonic distortion has been calculated. Also one has analysed individually higher harmonics of examined voltage. Different parameters and conditions of operation of simulated systems have been taken into account. At the end of the paper, conclusions from investigations are drawn.

Consideration of different operation modes of UPFC in power system state estimation

Power system state estimation is one of the functions performed in modern control centers. When FACTS devices are in a power system they should be taken into account in state estimation. In the paper, existence of UPFC, i.e. the most universal FACTS device, in a power system is considered. UPFC can operate in different modes. It can operate with full utilization of its possibilities or as SSSC or STATCOM. The aim of the paper is to present results of investigations of features of power system state estimation performed with use of the knowledge about actual operating modes of UPFC. The investigations have been made for the WLS power system state estimation. After the proposed approach to state estimation is outlined the results of the computational investigations are presented. During investigations, such features of the state estimation as conditioning of estimation process, accuracy of results, number of iterations in calculations are analyzed. At the end, conclusion from the carried out investigations are drawn.