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Generation, Transmission and Distribution, IEE Proceedings-

Issue 3 • Date May 2000

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Displaying Results 1 - 9 of 9
  • Universal power quality manager with a new control scheme

    Page(s): 183 - 189
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A new universal power quality manager is proposed. The proposal treats a number of power quality problems simultaneously. The universal manager comprises a combined series and shunt three-phase PWM controlled converters sharing a common DC link. A control scheme based on fuzzy logic is introduced and the general features of the design and operation processes are outlined. The performance of two configurations of the proposed power quality manager are compared in terms of a recently formulated unified power quality index. The validity and integrity of the proposed system is proved through computer simulated experiments View full abstract»

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  • Modelling of small secondary energy storage units in long-term planning

    Page(s): 143 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    Long-term planning involves the use of stochastic simulations to obtain reliability indices (loss of load expectation, unserved energy, etc.) and operation indices (expected ageing of components, expected operating costs). To make the use of probabilistic methods possible, the simulation interval should be large enough, and normally weekly or monthly intervals are used. When the simulation interval is greater than the storage autonomy and filling time of the storage facilities considered in the system, the behaviour of such “small” storage units cannot be properly described using the existing conventional models. To avoid this problem, a model for secondary energy storage units that allows the use of simulation intervals greater than the storage autonomy is presented. The model is validated with a real system using renewable energy sources, a diesel generator and a small electrochemical storage device View full abstract»

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  • Branch and bound algorithm for transmission system expansion planning using a transportation model

    Page(s): 149 - 156
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    A method for optimal transmission network expansion planning is presented. The transmission network is modelled as a transportation network. The problem is solved using hierarchical Benders decomposition in which the problem is decomposed into master and slave subproblems. The master subproblem models the investment decisions and is solved using a branch-and-bound algorithm. The slave subproblem models the network operation and is solved using a specialised linear program. Several alternative implementations of the branch-and-bound algorithm have been tested. Special characteristics of the transmission expansion problem have been taken into consideration in these implementations. The methods have been tested on various test systems available in the literature View full abstract»

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  • MVA constraint handling method for unified power flow controller in loadflow evaluation

    Page(s): 190 - 194
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The unified power flow controller is a promising power electronics device capable of providing complex control for power systems. The device can control the series power flow and also provide reactive power support to one node. Along with its complex operation come various operational constraints, which must be modelled within load flow to allow for system studies and analysis. A method for modelling the unified power flow controller's MVA constraint in the shunt converter is presented. The technique is analogous to the reactive power limit switching applied to generation nodes during the load flow solution. The method enables the maximum shunt compensation to be obtained while satisfying the operational constraints of the device. The method is implemented in the Newton-Raphson load flow method and applied to standard power systems for validation View full abstract»

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  • Thermal generating unit commitment using an extended mean field annealing neural network

    Page(s): 164 - 170
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    An extended mean field annealing neural network approach is used for short-term thermal unit commitment. In power systems, the major goal of the generating unit commitment is to minimise the total fuel cost of the thermal units subject to some practical constraints. This also means that it is desirable to find the optimal generating unit commitment in the power system for the next H hours. The annealing neural network combines good solution quality for simulated annealing with rapid convergence for artificial neural network. The extended mean field annealing neural network is used to find short-term thermal unit commitment. By doing so, it can help in finding the optimum solution rapidly and efficiently. The effectiveness of the proposed approach is demonstrated by thermal unit commitment of the Taiwan power system. It is concluded from the results that the proposed approach is very effective in reaching proper unit commitment View full abstract»

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  • Concise method for evaluating the probability distribution of the marginal cost of power generation

    Page(s): 137 - 142
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    In the developing electricity market, many questions on electricity pricing and the risk modelling of forward contracts require the evaluation of the expected value and probability distribution of the short-run marginal cost of power generation at any given time. A concise forecasting method is provided, which is consistent with the definitions of marginal costs and the techniques of probabilistic production costing. The method embodies clear physical concepts, so that it can be easily understood theoretically and computationally realised. A numerical example has been used to test the proposed method View full abstract»

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  • Harmonic cancellation for HVDC systems using a notch-filter controlled active DC filter

    Page(s): 176 - 181
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    A notch-filter controlled active DC filter is applied to suppress the current harmonics in a high-voltage-direct-current (HVDC) system. The design principle of the notch filter controlled is discussed and the sensitivity and stability of the proposed control scheme are analysed. Simulation results obtained show effective and robust cancellation of unwanted harmonics on the DC transmission line and demonstrate that the controlled outperforms the conventional proportional+integral (P+I) based approach. Simulation also shows that the control scheme is insensitive to the changes of AC system frequency View full abstract»

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  • Network reconfiguration for enhancement of voltage stability in distribution networks

    Page(s): 171 - 175
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    Network reconfiguration is performed by altering the topological structure of distribution feeders. By reconfiguring the network, voltage stability can be maximised for a particular set of loads in distribution systems. A new algorithm is formulated for enhancement of voltage stability by network reconfiguration. Initially, a certain number of switching combinations is generated using the combination of tie and its two neighbouring switches, and the best combination of switches for maximising the voltage stability in the network among them is determined. Then the search is extended by considering the branches next to the open-branches of the best configuration one by one to check whether there is any other switching combination available which gives further improvement in voltage stability. The enhancement of voltage stability can be achieved by the proposed method without any additional cost involved for installation of capacitors, tap-changing transformers and the related switching equipment in the distribution systems. The method has been tested on a 69-bus test system, and the results indicate that it is able to determine the appropriate switching options of the optimal (or near optimal) configuration for voltage stability enhancement with less computation. It has also been shown that power losses are reduced when voltage stability is improved by network reconfiguration View full abstract»

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  • Impact of remotely connected wind turbines on steady state operation of radial distribution networks

    Page(s): 157 - 163
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    Remotely connected wind farms can have a significant impact on voltages, load demand and power losses in radial distribution networks. Quantification of these effects is important in determining the true value of wind energy and requires detailed simulations of integrated network behaviour over an extended period of time. The steady-state behaviour of commercial and residential radial distribution feeders with remotely connected wind turbines has been investigated using a recursive load flow-based simulation algorithm and time series data from a known system. The results of annual simulations reveal that large wind farm capacities can be freely operated in remote locations without violation of voltage limits and with a net reduction in feeder energy consumption. With automatic control of real and reactive power flows from the wind farm, the connected capacity can be significantly expanded before operation becomes infeasible View full abstract»

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