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Generation, Transmission and Distribution, IEE Proceedings-

Issue 2 • Date Mar 2001

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Displaying Results 1 - 17 of 17
  • Adaptive approach to load shedding including pumped-storage units during underfrequency conditions

    Publication Year: 2001 , Page(s): 165 - 171
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    An adaptive approach is proposed for load shedding including the consideration of pumped-storage units during underfrequency conditions. Based on the idea of average or uniform frequency behaviour, a load-frequency control model is utilised in the scheme design. At this stage, Taiwan Power Company (Taipower) owns ten pumped-storage units that amount to about 13% of the total rating capacity. These units can be operated in generating mode during peak period, to reduce generation cost, or operated in pumping mode during off-peak period, to consume the surplus power. As the difference between the peak load and off-peak load of Taipower is considerable, pumped-storage units are playing a critical role in Taipower operations. Once disturbances take place in off-peak periods, pumped-storage units can be thus shed with a high priority. As they are useful in both restoring system frequency and decreasing the degree of service interruptions, these pumped-storage units have been included in the proposed load-shedding scheme design and tested through the utility data. From test results and comparisons with the existent utility shedding scheme, they have demonstrated the feasibility and practicality of the method for such applications View full abstract»

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  • Dynamic online energy loss minimisation

    Publication Year: 2001 , Page(s): 172 - 176
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    An efficient method for minimisation of energy loss over intervals of time is presented. The proposed method uses different loading conditions during each given time interval instead of one single snapshot of the network. The given interval is divided into several shorter periods: the first load condition is a current snapshot and subsequent ones are forecast. By increasing the number of periods or load profiles, the dimension of the problem rises substantially. This difficulty is handled by using the generalised Benders decomposition technique. Energy and power loss minimisation are compared by simulated application to the modified IEEE 30-bus system and the New Brunswick power network. As seen in these simulation results, the proposed method not only improves the voltage profile but also decreases the total energy loss over the given time interval View full abstract»

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  • Suppress vibrations on turbine blades by high-temperature super-conductive fault current limiter

    Publication Year: 2001 , Page(s): 97 - 103
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    An application area for HTS FCL is proposed. The feasibility of a HTS FCL bank is verified from the viewpoints of alleviating vibrations on turbine blades due to power system faults. The bank, composed of HTS FCL units in parallel with a thyristor-controlled switch: is installed between the generator and the step-up transformer, via a current transformer. In the event of a fault, a large fault current is induced in the bank and the bank loses superconductivity. The Rnormal-state of the bank is then reflected into the system to restrict the asymmetrical fault current. It is found from simulation analysis that only relatively small Rnormal-state and very short period of insertion time for the HTS FCL bank is adequate to alleviate the blade vibrations, which leads to lower power and thermal requirements for the bank View full abstract»

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  • Electric sector deregulation and restructuring in Latin America: lessons to be learnt and possible ways forward

    Publication Year: 2001 , Page(s): 180 - 184
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    The pioneering restructuring and deregulation process of the electricity industry, which started in Latin America as early as 1982, is assessed. Chile and Argentina, among others, have been at the forefront of innovation in the creation of electricity markets. The experience gained and the principal difficulties encountered in these 18 years are reviewed, highlighting the weaknesses and successes of the deregulation processes. A review is made of the challenges and prospects for development of the electrical sector in the region, where energy integration across countries flourishes and world energy players have started acquiring regional utilities. Regulations and market structures are being evaluated, and countries are introducing changes, the danger being that the remedies being considered may be worse than the disease View full abstract»

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  • Current controller for active power filter based on optimal voltage space vector

    Publication Year: 2001 , Page(s): 111 - 116
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    An hysteresis current controller for an active power filter based on the optimal voltage space vector is proposed. The controller jointly utilises two sets of phase current difference comparators to determine the location region of the reference voltage space vector and the current error space vector. When the system reference voltage space vector is changing rapidly and randomly, which makes its location region very difficult to estimate, the novel controller can quickly detect its location region by a trial-and-error process which is essential to the performance improvement of active power filters. The related concept and formulation are presented. A computer simulation is conducted on a test system and the results show that the controller can quickly determine the optimal voltage space vector, therefore effectively reducing the current tracking error. Since the new controller can reduce VSI switching frequency, it can reduce the switching loss and improve APF efficiency noticeably View full abstract»

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  • Liberalisation of electricity market in Finland as a part of Nordic market

    Publication Year: 2001 , Page(s): 194 - 199
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    The Finnish electricity market is a part of the physically interconnected Nordic market which also includes Denmark, Norway and Sweden. All countries are nowadays deregulated in slightly different ways, and the central co-ordination of power generation is replaced with the market based power exchange NordPool. In Finland, the deregulation was performed step by step, so that first the customers above 500 kW were allowed to change their supplier in November 1995. From January 1997, all customers were free to select their suppliers provided that they had a remotely-read hourly meter. Since November 1, 1998 all small customers (below 3×63 A, about 45 kW) have been able to change their supplier without any extra costs. As a result of competition, most of the larger customers have changed their suppliers or negotiated new contracts with their existing supplier. Of the 2.2 million small customers, only about 3%, have changed supplier, but the electricity prices for all customers have decreased View full abstract»

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  • Determination of interface flow margin using the modified continuation power flow in voltage stability analysis

    Publication Year: 2001 , Page(s): 128 - 132
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    A new concept of interface flow margin in terms of steady-state voltage stability is introduced. The interface flow margin is the active power flow margin of the key transmission lines between one region and others under a fixed load demand condition. In addition, a technique is proposed to trace interface flow-voltage (f-V) curves by applying a continuation method. From the f-V curves, the interface flow margin can be easily obtained, which is useful to determine the secure flow limit of the specified interface. In the case study, an illustrative example with the New England 39-bus system is shown View full abstract»

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  • Economic lessons from the market evolution of present US power markets

    Publication Year: 2001 , Page(s): 185 - 188
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (988 KB)  

    Insufficient information provided by the market to participants can cause volatile price swings. An ideal market is presented here. The importance of information from such a market is discussed from the participants' view and also the information needed by participants in the competitive environment is outlined. A comparison of such a market to existing markets within the USA is outlined. The power markets in the USA are evolving based on state and federal government mandates and based on the committee decisions of all market participants. As economic forces empower changes for the participants, changes will be made View full abstract»

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  • Efficiency issues of modular harmonic power flow

    Publication Year: 2001 , Page(s): 123 - 127
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    A modular harmonic power flow (MHPF) program has been developed for the calculation of the periodic steady state of a three-phase power system. Details of implementation are presented which further improve the efficiency of the program. The savings are achieved mainly in the time-domain computation of the incremental admittance matrix, for time-varying components and also by often reusing the same matrix. Test results are presented to demonstrate the efficiency of the program View full abstract»

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  • Bidding strategy based on artificial intelligence for a competitive electric market

    Publication Year: 2001 , Page(s): 159 - 164
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    A bidding strategy using a fuzzy-c-mean (FCM) algorithm and the artificial neural network (ANN) was developed for competitive electric markets. The nodal price information was assumed to be released into the market. The FCM was used, first, to classify the daily load pattern into peak, medium-peak and off-peak levels and, secondly, to classify the competitive generation companies (gencos) into less-menacing, possible-menacing and menacing gencos. The back-propagation ANN was used for determining the bidding price for a genco. The FCM results aided in lessening the training data and reducing the ANN input nodes. The IEEE 30-busbar system was used for illustrating the applicability of the proposed method View full abstract»

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  • Antidistortion method for wavelet transform filter banks and nonstationary power system waveform harmonic analysis

    Publication Year: 2001 , Page(s): 117 - 122
    Cited by:  Papers (28)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    A method is presented for eliminating the effect of imperfect frequency response of the filters in wavelet transform (WT) filter banks, and a WT-based algorithm for harmonic analysis of nonstationary power system waveforms. The method recovers the signal magnitude, which is distorted due to the imperfect response of filters. The WT-based algorithm is then developed. The algorithm is incorporated with the above antidistortion method to give accurate harmonic magnitudes. The power and practicality of the algorithm are illustrated through its application for the diagnosis of a motor-starting problem, which occurred in the Western Australia power system View full abstract»

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  • MVA power flow and loss analysis for electricity market

    Publication Year: 2001 , Page(s): 153 - 158
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    MVA power-flow and loss analysis is the basis for allocating the fixed costs and power losses under electricity-market deregulation. It is pointed out that the decomposition allocation of active and reactive power losses is not reasonable. The theory of active and reactive loss allocation and branch-power-flow decomposition has been proposed. Various contributory factors have been deduced. These contributory factors include the contribution factors of active and reactive generation power, load-power-to-branch flows, the contribution factors of active and reactive generation power to active and reactive load power, the contribution factors of active and reactive load power to generation power, and the contribution factors of active and reactive load power and active and reactive generation power to line power losses. The detailed calculation results are presented and analysed, demonstrating that the theory presented provides a good charging algorithm for all the market participants View full abstract»

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  • Observability analysis for state estimation using linear programming

    Publication Year: 2001 , Page(s): 142 - 145
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    The linear programming technique is used to analyse the observability of power system state estimation networks. This technique has the capability of identifying the observable islands of the system network. It can also identify the necessary branches or nodes needed for pseudomeasurement placement to recover the overall system observability. The technique manipulates only integer numbers. It uses the network connectivity matrix and the measurement Jacobian matrix as equality constraints. Computational aspects of the proposed technique are presented and results of several examples are reported View full abstract»

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  • Role of magnetic materials in power frequency shielding: numerical analysis and experiments

    Publication Year: 2001 , Page(s): 104 - 110
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Shielding of magnetic fields at power frequencies has been investigated by computation and experiment. Different types of low-cost soft magnetic laminations (low-carbon steel, nonoriented Fe-Si, grain-oriented FeSi) and different shield geometries (plane, U-shaped and box-like) have been considered. The shielding factors of model screens have been measured, together with the magnetic flux density in the sheets employed, under field levels typical of industrial environment (~100 μT). Computations have been carried out by means of a hybrid finite-element/boundary element model, which result in good agreement with measurements. It is shown that grain-oriented laminations provide the highest shielding factor, which is reinforced in the plane shield configuration by the addition of an aluminium plate. It is predicted that the screening performance of the U-shaped and box-like shields can be appreciably impaired by the presence of air gaps at the corner joints View full abstract»

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  • Nonlinear co-ordinated excitation and TCPS controller for multimachine power system transient stability enhancement

    Publication Year: 2001 , Page(s): 133 - 141
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    A robust nonlinear co-ordinated generator excitation and thyristor-controlled phase shifter controller is proposed to enhance the transient stability of a multimachine power system. To eliminate the nonlinearities and interconnections of the multimachine power system, a direct feedback linearisation (DFL) compensator through the excitation loop is designed. Considering the effects of plant parametric uncertainties and remaining nonlinear interconnections, a robust decentralised generator excitation controller is proposed to ensure the stability of the DFL compensated system. Only the bounds of the generator parameters need to be known in the design of the proposed controller. while the transmission network parameters, system operating points or the fault locations do not need to be known. As the proposed controller can ensure the stability of a large-scale power system within the whole operating region for all admissible parameters, the transient stability of the overall system can be enhanced significantly. Digital simulation studies were conducted on a three-machine power system to show that the proposed control scheme can enhance the transient stability of the system significantly, regardless of the network parameters, operating points and fault locations View full abstract»

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  • Knowledge-based genetic algorithm for unit commitment

    Publication Year: 2001 , Page(s): 146 - 152
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    A genetic algorithm (GA) augmented with knowledge-based methods has been developed for solving the unit commitment economic dispatch problem. The GA evolves a population of binary strings which represent commitment schedules. The initial population of schedules is chosen using a method based on elicited scheduling knowledge. A fast rule-based dispatch method is then used to evaluate candidate solutions. The knowledge-based genetic algorithm is applied to a test system of ten thermal units over 24-hour time intervals, including minimum on/off times and ramp rates, and achieves lower cost solutions than Lagrangian relaxation in comparable computational time View full abstract»

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  • Volatility in the California power market: source, methodology and recommendations

    Publication Year: 2001 , Page(s): 189 - 193
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1064 KB)  

    Extreme short-term price volatility in competitive electricity markets creates the need for price risk management for electric utilities. Decent methods in California provide examples of lessons that can be applied to other markets worldwide. Value-at-Risk (VAR), a method for quantifing risk exposure in the financial industry, is introduced as a technique that is applicable to quantifing price risk exposure in power systems. The methodology for applying VAR using changes in prices from corresponding hours on previous days is presented. Prices for electricity for the summer of 2000 are examined against previous periods to understand how the hourly VAR entity is exposed when the power system is obligated to serve a load and does not have a contract for supply. The VAR methodology introduced is then applied to a sample company in California that is serving a 100 MW load. Proposed remedies for the problems observed in the competitive California electric power industry are introduced View full abstract»

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