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Generation, Transmission and Distribution, IEE Proceedings-

Issue 3 • Date May 2003

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Displaying Results 1 - 17 of 17
  • Systematic method for the design of a full-scale fuzzy PID controller for SVC to control power system stability

    Page(s): 297 - 304
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (546 KB)  

    A systematic method was introduced to design a full-scale fuzzy PID controller for power system stability control. The proposed controller uses the incremental form of a conventional PID controller as its underlying structure. To show the effectiveness of this method a form of full-scale fuzzy PID controller is designed. The rule-generated function is used to generate the rule base. The parameters of a conventional PID controller, which can be achieved by several well-known methods in control theory such as Ziegler-Nichols, Cohen-Cool and the genetic algorithm, make it possible to simplify the design process, as is desirable from an industrial point of view. One advantage of the new full-scale fuzzy PID controller is that it has the same structure and simplicity of its conventional counterparts but with more effectiveness and robustness. In order to illustrate the effectiveness of this controller a SVC-based stabiliser is designed using the proposed fuzzy PID controller. View full abstract»

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  • Direct solution method for initialising doubly-fed induction wind turbines in power system dynamic models

    Page(s): 334 - 342
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (550 KB)  

    The modelling of a doubly-fed induction generator (DFIG) wind turbine in large power system dynamic simulation software is discussed, and the steady state equivalent circuit and reduced order dynamic DFIG models are described. A direct solution method for obtaining injected rotor voltages, which satisfy the dynamic model control objectives, is derived from the approximate steady state model. An initialisation procedure is given for the reduced order dynamic DFIG machine model. Simulation results are presented from initialised dynamic DFIG wind turbine models. PQ and PV bus representations of the DFIG for load flow studies are compared and simulated with typical turbine and network data for wind farm installations. View full abstract»

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  • Modelling of the interline power flow controller and the generalised unified power flow controller in Newton power flow

    Page(s): 268 - 274
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The latest generation FACTS controller named the convertible static compensator (CSC) was recently installed at the New York Power Authority (NYPA) Marcy substation as part of a project that will increase power transfer capability and maximise the use of the existing transmission network. Within the general framework of the CSC, two innovative FACTS controllers, the interline power flow controller (IPFC) combining at least two converters and the generalised unified power flow controller (GUPFC) combining at least three converters, can be configured. Mathematical models of the IPFC and GUPFC and their implementation in Newton power flow are reported. Numerical results based on the IEEE 30-bus 118-bus and 300-bus systems are presented to demonstrate the performance of the Newton power flow algorithm with incorporation of the IPFC and GUPFC. View full abstract»

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  • Enhancement of power system damping using VSC-based series connected FACTS controllers

    Page(s): 353 - 359
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (473 KB)  

    An equivalent model is proposed to analyse the capabilities of voltage source converter (VSC)-based series connected flexible AC transmission system (FACTS) controllers of various types to damp power system oscillations. A universal control strategy using a fuzzy logic method is developed for controlling these VSC-based series connected FACTS controllers. Only the magnitude of the injected voltage needs to be controlled, along with its phase angle which is always set to be constant at π/2 with respect to different reference voltage vectors for the different controllers. Local measurable signal-voltage phase angle difference between two local buses-is selected as an input base. Two inputs, namely the speed rate and acceleration, derived from the phase angle difference, are required for the fuzzy controller, which is robust and easy to tune, to damp power system oscillations. Case studies for a single machine infinite bus (SMIB) and two-machine test systems are conducted at the switch level using the well-established PSCAD/EMTDC software package. View full abstract»

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  • Accelerated trip scheme for second-zone distance protection

    Page(s): 325 - 333
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    The theoretical aspects, design and testing of a new accelerated trip scheme for second-zone distance protection of HV/EHV transmission lines is described. The scheme is simple and provides relatively high-speed (60-70 ms) operation of the second-zone distance protection without requiring a communication channel. The scheme has been extensively tested using EMTDC simulations under various power system operating conditions. Simulation results show that the selectivity and speed of the proposed scheme are satisfactory for practical use in HV/EHV transmission line distance relays. View full abstract»

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  • Reactive power optimisation with voltage stability consideration in power market systems

    Page(s): 305 - 310
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (485 KB)  

    A method is presented which incorporates the voltage collapse problem, to optimise reactive power support in power market systems. Voltages and reactive power support are inextricably linked and the role of reactive power support is to maintain a proper voltage profile. In an open electricity market reactive power support is an ancillary service for real power transportation. The cost and price analysis of such support needs to be established for the market to function properly. Cost analysis and voltage stability analysis are integrated using an optimal power flow formulation, which is solved using the sequential quadratic programming method. The proposed methodology is tested on the IEEE 14-bus system. View full abstract»

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  • Distribution network reconfiguration for load balancing with a coloured Petri net algorithm

    Page(s): 317 - 324
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (534 KB)  

    A rule-based expert system with a coloured Petri net (CPN) algorithm is developed for load balancing of distribution systems. CPN models of the distribution components such as four-way line switches are proposed to derive the proper switching operations. In this way, the loads on transformers and feeders will become more balanced. Heuristic rules based on the standard load transfer operation procedures of the Taipower distribution system are included in the best first search of the CPN to obtain the desired switching operations for load balancing. For the overload contingency during the summer peak season, load shedding is also considered in the CPN models, to provide service to as many key customers and loads as possible. The priority indices of each feeder and service zone are determined in advance according to the key customers within the service territory. A Taipower distribution system with 68 feeders is selected for computer simulation to demonstrate the effectiveness of the proposed methodology. It is found that load balancing of the distribution system can be obtained very efficiently and the risk of overloads can be reduced by applying the proposed CPN model to determine the optimal switching operation. View full abstract»

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  • High-pulse conversion techniques for HVDC transmission systems

    Page(s): 283 - 290
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (446 KB)  

    A high-pulse conversion technique for high voltage and high power applications such as HVDC transmission system is proposed. The proposed technique, based on the DC current reinjection, further decreases the number of components in the auxiliary circuit to achieve the same pulse number. An optimised control strategy over the whole range of phase delay angle is provided along with sophisticated input current and output voltage analysis. With the pulse multiplication strategy the proposed schemes demonstrate 24-pulse, 36-pulse and 48-pulse characteristics both in the input current and in the output voltage. Experimental results from a 3 kVA laboratory prototype verify the proposed concept. View full abstract»

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  • Short-term load forecasting with a hybrid clustering algorithm

    Page(s): 257 - 262
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    Load forecasting is an important part of the operational procedure for a power system and a considerable amount of research effort has been expended on the development of accurate prediction methodologies. The electrical load series leads the field for the construction and application of state-of-the-art forecasting models, especially those based on artificial intelligence. The hybrid models, which are developed using a clustering algorithm to group data with similar characteristics and a function approximation to capture the underlying characteristics of each cluster of data, form a special class. For the majority of clustering algorithms, clusters are formed using some distance measure, thus identifying each cluster as a group of data allocated closely together. The clustering scheme that is developed generates clusters that are described by the same linear model. A demonstration of the proposed methodology is performed for the one-step ahead forecasting of load data from the Californian and the New York state power systems. The analysis of the forecasting results showed that the proposed algorithm was able to reduce the forecasting error by 7.5% and 9%, respectively, for the two data sets, compared to a neural network developed using the traditional load forecasting methodology. View full abstract»

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  • Application study of a STATCOM with energy storage

    Page(s): 373 - 384
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    With advances in energy storage technology the application of STATCOMs with energy storage for utility applications, such as active- and reactive-power compensation of loads, network-voltage control and mitigation of power system disturbances, is increasingly feasible. As it is more expensive to produce active power than reactive power, it is important to consider methods which can be adopted to minimise the use of the energy store. An application study of a STATCOM with energy storage giving special emphasis to control strategies which minimise the use of the stored energy is reported. Calculation techniques to determine the current rating of the IGBTs, diodes and connecting transformer as well as the losses associated with the switches when the compensator is operated under space-vector modulation are demonstrated. Application studies of the compensator with energy storage for load compensation, steady-state voltage control, mitigation of voltage sags and elimination of power oscillations are described. The analytical studies of each of these applications are supplemented by simulation results carried out in PSCAD/EMTDC and by experimental results obtained from a laboratory prototype. View full abstract»

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  • Boundary element approach for the analysis and design of grounding systems in presence of nonhomogeneousness

    Page(s): 360 - 366
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    A numerical model, based on boundary element technique, is presented for the analysis of complex grounding systems. The model is applied to the analysis of different grounding systems, evaluating its accuracy and reliability. In particular, the presence of extended or localised nonhomogeneousness is considered, comparing the results with other approaches proposed in the literature. The merits and the drawbacks of the proposed approach are highlighted. View full abstract»

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  • Relaxed approach for the parallel solution of security-constrained dispatch with post-contingency rescheduling

    Page(s): 291 - 296
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (458 KB)  

    Some approaches for the solution of the security-constrained dispatch with post-contingency corrective rescheduling problem in a multiprocessing environment are presented. These approaches can be interpreted as relaxed versions of the classical Benders decomposition. The idea is to improve the computational efficiency when the problem is solved by using parallel processing. Results from one of these approaches implemented into an asynchronous algorithm are reported here. Some strategies for improving performance are discussed and test results with two real-life Brazilian systems are reported. View full abstract»

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  • Comparison of fixed speed and doubly-fed induction wind turbines during power system disturbances

    Page(s): 343 - 352
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (653 KB)  

    The dynamic modelling of large (MW) capacity fixed and variable speed induction generator wind turbines is discussed. A reduced order dynamic machine model is derived suitable for modelling both fixed speed and doubly-fed asynchronous generator wind turbines. Control schemes for variable speed turbines, using doubly-fed induction generators (DFIG), are described and simulated. Speed control characteristics and converter protection of the DFIG are implemented in the model. The operation of the models during power system disturbances such as network voltage sags and three-phase faults, as well as the possibility of network voltage instability, are investigated. Simulation results are presented using typical turbine and network data for wind farm installations. View full abstract»

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  • Improvement of power system transient stability by coordinated operation of fast valving and braking resistor

    Page(s): 311 - 316
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (422 KB)  

    Fast valving and braking resistors, individually, are an effective means of improving the stability of a power system under large and sudden disturbances. The fast valving schemes, like other methods, are not always suitable for all power systems for enhancing the transient stability. Minor variations in the switching parameters of the fast valving scheme drastically affect the stability of the system. Moreover, there are some other associated problems such as risk of safety valve operation owing to increased boiler pressure, the problem of second swing instability etc. Similarly the dynamic braking resistor has its own limitations such as excessive heat loss and the resultant temperature rise of the resistor. Therefore, coordinated fast valving and braking resistor control is proposed. The coordinated control scheme is very effective in reducing the mismatch between the mechanical input power and electrical power output of the generator, thereby reducing the generator accelerating power during the fault period. This dual control from load side and generation side substantially improves the transient stability performance of the system. Various schemes of fast valving control and coordinated control operation were tested on a single machine infinite bus system and the results are compared. View full abstract»

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  • Useful multi-objective hybrid evolutionary approach to optimal power flow

    Page(s): 275 - 282
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (505 KB)  

    Optimal power flow (OPF) in electric power systems is a static, nonlinear, multi-objective optimisation problem of determining the optimal settings of control variables for minimising the cost of generation, emissions, transmission losses and voltage and power flow deviations. OPF is an important problem in power systems operation not only due to operational security considerations but also because even a small saving per hour translates to a large annual saving. The solution of the OPF problem, with a simultaneous and adequate consideration of all its facets within reasonable computing time, is still to be achieved. A multi-objective hybrid evolutionary strategy (MOHES) is presented for the solution of the comprehensive model for OPF. The hybridisation of GA with SA effects a beneficial synergism of both. MOHES concentrates on the 'better' areas of the search space. The greater modelling power of the method enables representation of nonlinear and discontinuous functions and discrete variables easily without involving approximations, and its enhanced search capabilities lead to better solutions. A complete set of noninferior solutions representing the trade-off between various objectives is provided in a single run. MOHES has been designed to use the small perturbation analysis to avoid computing a complete load flow in every fitness evaluation. This results in considerable savings in computational expense. Test results provided on standard systems reported in the literature clearly indicate its efficacy. View full abstract»

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  • Method for voltage-sag-source detection by investigating slope of the system trajectory

    Page(s): 367 - 372
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (421 KB)  

    A method of determining the voltage-sag-source direction is proposed. The slope of a line fitting two parameters during the disturbance is employed for the detection. A least-squares method is used to perform the line fitting. The voltage-sag-source direction is determined by examining the sign of the slope. The method is verified to be promising by theoretical analysis, simulations and actual field measurements. Simplicity, ease of implementation and robustness are the advantages of the method. View full abstract»

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  • Load profile assignment of low voltage customers for power retail market applications

    Page(s): 263 - 267
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    To facilitate retail choice in a competitive power market, the knowledge of hourly load shape by customer class is necessary. Requiring a meter as a prerequisite for lower voltage customers to choose a power supplier is not considered practical at the present time. A technique which uses load research and customers' monthly energy usage data for a preliminary screening of customer load profiles is presented. Two data mining techniques, namely, the fuzzy c-means (FCM) method and an artificial neural network (ANN) based pattern recognition technique, are utilised in this work. The proposed method can be used by the Energy Service Provider (ESP) to assign customers to specific load profiles with certainty factors. Customers with less certainty in the assignment will need meter installation or further investigation in order to determine which classes they belong to. Test data are from actual measurement and the customer information system (CIS) of Taiwan Power Company (TPC). Promising results on assigning existing under 220 V customers to their proper load profiles are illustrated. View full abstract»

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