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Generation, Transmission and Distribution, IEE Proceedings-

Issue 3 • Date May 2001

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Displaying Results 1 - 10 of 10
  • Evolving wavelet-based networks for short-term load forecasting

    Page(s): 222 - 228
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (764 KB)  

    A new short-term load forecasting (STLF) approach using evolving wavelet-based networks (EWNs) is proposed. The EWNs have a three-layer structure, which contains the wavelet (input-layer), weighting (intermediate-layer), and summing (output-layer) nodes, respectively. The networks are evolved by tuning the parameters of translation and dilation in the wavelet nodes and the weighting factors in the weighting nodes. Taking the advantages of global search abilities of evolutionary computing as well as the multi-resolution and localisation natures of the wavelets, the EWNs thus constructed call identify the inherent nonlinear characteristics of the power system loads. The proposed approach is verified through different types of data for the Taiwan power (Taipower) system and substation loads, as well as corresponding weather variables. Comparisons of forecasting error and constructing time reveal that the performance of the EWNs could be superior to that of the existing artificial neural networks (ANNs) View full abstract»

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  • Synchronisation methods for grid-connected voltage source converters

    Page(s): 229 - 235
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    Four different synchronisation methods for a voltage source converter connected to a three-phase grid are investigated. The methods are adapted for use in a digital controller. The performance of the synchronisation methods is studied by response characteristics of phase-shift steps, frequency steps and low-frequency grid voltage harmonics. The low-pass filtering method can be used only if the frequency of the grid is constant and phase jumps do nor occur. If phase jumps occur, the novel space vector filtering method is recommended. The extended space vector filtering method is adapted to handle frequency variations and is also preferred if fast frequency variations occur. This method even has a higher performance than the extended Kalman filter method, in spite of the large number of calculations that must be performed View full abstract»

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  • The selected problems of energy sector development in new economic conditions

    Page(s): 237 - 242
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    General problems of energy market development in Poland are addressed. The structure of Polish energy sector and conditions of its functioning are presented. The general concept of national and local energy market organisation is also discussed. This is particularly crucial in programming the processes of investments in the energy sector under new economic conditions in Poland View full abstract»

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  • VAr planning using genetic algorithm and linear programming

    Page(s): 257 - 262
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    A combined methodology consisting of successive linear programming (SLP) and a simple genetic algorithm (SGA) solves the reactive planning problem. The problem is divided into operating and planning subproblems; the operating subproblem, which is a nonlinear, ill-conditioned and nonconvex problem, consists of determining the voltage control and the adjustment of reactive sources. The planning subproblem consists of obtaining the optimal reactive source expansion considering operational, economical and physical characteristics of the system. SLP solves the optimal reactive dispatch problem related to real variables, while SGA is used to determine the necessary adjustments of both the binary and discrete variables existing in the modelling problem. Once the set of candidate busbars has been defined, the program implemented gives the location and size of the reactive sources needed, if any, to maintain the operating and security constraints View full abstract»

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  • Analysis of power system transient induced radiation for substation plant condition monitoring

    Page(s): 215 - 221
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    Electromagnetic radiation in the form of atmospheric radio waves (or sferics) originate from power system apparatus when transient currents are present. This phenomenon can occur during switching events in substations where an arc forms part of the current path, causing nonlinearities. An experimental investigation over a two-year period has collected data from sferics induced by power system substation switching transients. The paper introduces analysis techniques to extract information from the received switching transient induced sferics and to allow event identification. Digital signal processing (DSP) is used to investigate the time- and frequency-domain characteristics of the experimentally recorded signals. The possible future application of the developed techniques for condition monitoring of substation switchgear is discussed View full abstract»

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  • Identifying a vanishing eigenvalue in voltage collapse analysis with consideration of limits

    Page(s): 263 - 267
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Modal analysis has been widely employed in voltage stability studies. Literature shows that monitoring the least eigenvalue/singular value as a function of load increase may drive one to incorrect conclusions, since these values present a sharp variation at the bifurcation point. A 'well behaved' eigenvalue may be identified, even when limits on the reactive power generation are considered. For this purpose, the centre manifold theorem is employed. Results provide an interesting insight into modal analysis, since some interesting theoretical points are addressed. Some original results are also discussed View full abstract»

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  • Minimum loading resistance and its effects on performance of an isolated self-excited reluctance generator

    Page(s): 251 - 256
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    An approach based on eigenvalue and eigenvalue sensitivity to determine minimum loading resistance of an isolated self-excited reluctance generator (SERG) is presented. A d-q axis equivalent-circuit model is employed to derive dynamic equations of the SERG studied. Both transient and steady-state characteristics of the SERG subject to minimum loading resistance are investigated. Experimental results obtained from a laboratory 0.37 kW reluctance machine driven by a DC motor are compared with simulated results to validate the feasibility of the proposed method View full abstract»

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  • Transient and voltage stability enhancement via coordinated excitation and UPFC control

    Page(s): 201 - 208
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (888 KB)  

    The paper discusses co-ordinated excitation and UPFC control to improve power system transient stability and voltage stability. In the design of an excitation controller, the power system is linearised using a direct feedback technique. A robust approach is used to deal with the uncertainties caused by parameter variations and the inclusion of UPFC controller. Only local measurements are required for designing the excitation controller. The series branch of the UPFC is designed to damp the power oscillation during transients, while the shunt branch aims at maintaining the bus voltage. The performance of the proposed controller is tested on a single-machine, single-load power system. Simulation results show that the co-ordinated excitation and UPFC control is effective for transient stability enhancement. Both of the series and shunt branch control of UPFC help improve transient stability. The impact of the controller on voltage stability is studied through bifurcation analysis. It is shown that the feasibility region can be greatly increased View full abstract»

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  • Enhanced FFT-based parametric algorithm for simultaneous multiple harmonics analysis

    Page(s): 209 - 214
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    An enhanced FFT-based parametric (E-FFT) algorithm suitable for onilne harmonic analysis of electrical power systems is presented. This E-FFT algorithm exploits its iteration loops in combination with the characteristic of steep-descent gradient search strategy, to limit the sensitiveness of the total harmonic distortion caused by changes in the number of parameters involved in distorted signal models. The E-FFT algorithm performs reasonably well with short data record length. Unlike most gradient-descent search algorithms for a global minimum point, the proposed E-FFT algorithm averts the risk of being trapped at any local minimum point in the search path. The E-FFT algorithm differs from other FFT and Kalman filter based tracking algorithms, in that it is able to provide simultaneous tracking of co-variations between integer and noninteger (sub) harmonics in a small number of iteration steps. Numerical illustrative examples demonstrating the operation of this E-FFT algorithm and its simulated performance results are also presented View full abstract»

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  • Design and operation of grid-connected photovoltaic system with power-factor control and active islanding detection

    Page(s): 243 - 250
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (916 KB)  

    An approach to power-factor control and islanding detection of a grid-connected photovoltaic system is proposed. With the designated control circuit, deviation at the output of the inverter can be observed. Coupled with the algorithm developed, this deviation serves as a useful aid to detect islanding more effectively. The proposed method has been tested through different scenarios, including the loss of grid and operation in parallel. Simulation studies and hardware circuits were both made to validate the effectiveness of the method. With the test results they help consolidate the feasibility and practicality of the approach for the applications considered View full abstract»

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