APPLICATION OF ARTIFICIAL NEURAL NETWORKS FOR EXTERNAL NETWORK EQUIVALENT MODELING

In this paper an artificial neural network (ANN) based methodology is proposed for determining an external network equivalent. The modified Newton-Raphson method with constant interchange of total active power between internal and external system is used for solving the load flow problem. A multilayer perceptron (MLP) with backpropagation training algorithm is applied for external network determination. The proposed methodology was tested with the IEEE 24-bus test network and simulation results show a very good performance of the ANN for external network modeling

Upbringing by observation: some specifics of education according to Montessori pedagogy

Specifična slika djeteta u Montessori pedagogiji utječe na značajke Montessori odgojitelja, njegovu osobnu i stručnu pripremu te njegovu unutarnju pripremu. U ovom se radu analiziraju specifičnosti navedene pedagogije glede djeteta, odgojitelja i pripremljene okoline. Montessori pedagogija računa s periodima ili razdobljima posebne osjetljivosti kod djece i pridaje im veliku razvojnu i odgojnu važnost, a da bi dijete uspješno prošlo svaki od perioda, potrebno je da odrasli slijede i odgovaraju na potrebe djeteta. Na kraju rada istaknut ćemo glavne specifičnosti razvoja i poimanja djeteta prema ovoj pedagogiji.A specific picture of the child in Montessori pedagogy affects the qualities of Montessori educators, their personal and professional preparation and their internal preparation. This paper analyses the specifics of the mentioned pedagogy regarding the child, the educator and the prepared environment. Montessori pedagogy counts on periods or times of special sensitivity in children and attaches great developmental and educational importance to them, so that, should the child successfully pass each of the periods, it is necessary for adults to follow and respond to the needs of the child. At the end of the paper we will highlight the child’s main developmental characteristics and understanding of the child according to this pedagogy

Bus Split Contingency Analysis Implementation in the NetVision DAM EMS

Implementation of the bus coupler outage scenarios, commonly known as bus splitting, in the NetVision DAM energy management system (EMS) contingency analysis is presented in this paper. In order to identify the bus coupler branches in the network model, the existing topology processor was upgraded. The description of the topological algorithm for detection of the bus couplers is given. Based on the topology analysis results, calculation subnodes are created. Calculation model was modified in order to include the bus couplers and the subnodes as the new calculation objects. These modifications are fundamental for the introduction of the bus coupler outages in the contingency analysis. Implications of the bus coupler outages on the load flow mathematical model are discussed. Implemented NetVision DAM solution for the analysis of such outage scenarios is presented

Harmonic Performance Analysis of Static Var Compensator Connected to the Power Transmission Network

The static var compensator (SVC) is a device which is designed to compensate reactive power, increase voltage stability and to reduce voltage fluctuations. Thyristor controlled reactors (TCRs) are composed of reactors in series with bidirectional pair of thyristors. Current through reactors can be continuously controlled by changing the firing angle of thyristor valves, thus the inductive power can be easily controlled. Typical applications of TCRs in AC systems are voltage stabilization and temporary overvoltage reduction, stability improvement, damping of power oscillations and load balancing. In this paper, harmonic performance analysis of SVC equipped with TCRs is presented. SVCs utilizing TCRs generate harmonic currents and therefore it is necessary to determine the effect of harmonics generated by the SVC on the power system and its elements. This includes interaction of the SVC with the system, the SVC performance under balanced and unbalanced operating conditions and finally, evaluation of countermeasures such as installation of harmonic filters. In order to carry out these analysis, it is necessary to determine harmonic characteristics of the network at the point of SVC connection, existing levels of harmonics, and to know appropriate standards regarding acceptable harmonic levels in the power system. Since harmonic distortions in the system are caused by the interaction between SVC and the system, all system contingencies which may affect system’s frequency response should be evaluated. Detailed power system model should be considered to make sure that parallel resonance points of system do not directly coincide with characteristic harmonics from the SVC. Harmonics generated by SVCs are largely dependent on the operating point within the SVC characteristic. A conservative approach is to use the maximum values of harmonics generated within the spectrum irrespective of the operating point. The results of harmonic performance analysis are important for appropriate design of SVC. Harmonic performance analysis related to SVC application which are presented in this paper include the determination of: frequency response of the transmission network impedance required for the specification and design of filters; the effects of SVC generated harmonics on the power system; the overall filter requirements and countermeasures to reduce harmonics to acceptable level