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Generation, Transmission & Distribution, IET

Issue 6 • Date June 2012

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Displaying Results 1 - 11 of 11
  • Combined control of a distribution static synchronous compensator/flywheel energy storage system for wind energy applications

    Page(s): 483 - 492
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (689 KB)  

    The integration of wind power generation in power systems is steadily increasing around the world. This incorporation can bring problems onto the dynamics of power systems owing to the lack of controllability over the wind and the type of generation used. In this work, a distribution static synchronous compensator (DSTATCOM) coupled with a flywheel energy storage system (FESS) is used to mitigate problems introduced by wind generation in the electrical systems. A dynamic model of the DSTATCOM/FESS device is briefly presented and a technique to control the active power exchanged between the device and the power system is proposed. The control technique has two control modes. One control mode mitigates the power fluctuations of wind generators, and it is based on fuzzy logic and a special filter. The other control mode contributes to recover the frequency when significant faults arise in the system. Simulation tests on the behaviour of the device are analysed when it works in combination with wind generation in the electrical system. Results show a satisfactory performance of the proposed control techniques along with a high effectiveness to smooth the active power fluctuations of wind generation and to contribute to the recovery of the frequency. View full abstract»

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  • Modified shuffled frog leaping algorithm for optimal switch placement in distribution automation system using a multi-objective fuzzy approach

    Page(s): 493 - 502
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (687 KB)  

    One of the main issues in distribution sector is to achieve simultaneously high system reliability and low capital costs. Distribution automation systems (DASs) involve automatic and remote-controlled switches. The switches play a significant role in system reliability improvement. This paper proposes the modified shuffled frog leaping algorithm (SFLA) to derive the optimal placement of manual and automatic switches in DASs. A fuzzy approach is used to handle the multi objective considerations, and a fuzzy membership function is defined for each term in the objective function. The first objective is reliability improvement by minimising the customer interruption cost (CIC), and the second objective is to minimise switches purchasing and maintenance cost (SPMC). In this paper, a new method is developed to evaluate CIC and SPMC indices in a distribution network. In the proposed method, customer types, customers load patterns, monthly, daily and hourly customers loading rates are considered. In addition, network branches' failure rate, restoration time and repair time are taken into account. The performance of the proposed approach is assessed and illustrated by studying on the IEEE 123-node feeder standard test system. The simulation results verify the capability of the proposed method. View full abstract»

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  • Distribution system planning considering reliable feeder routing

    Page(s): 503 - 514
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (593 KB)  

    The work presents an investigation on the role of reliability consideration in distribution system configuration and planning cost of radial distribution system. A direct search technique is applied for optimum planning which ensures only minimisation of planning cost. Furthermore, the concept of principle of optimality theorem makes the direct method more computationally efficient, reducing total numbers of radial paths. Reliability indices are computed to evaluate the reliability of systems with different feeder configurations. The proposed approach is also tested for optimal feeder routing with variation in number of substations, which provides the information on trade-off between optimality and reliability of the system configuration. Thus, the proposed approach is found to be highly effective in optimal feeder routing considering complex feeder configuration with multiple substations. View full abstract»

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  • Improved particle swarm optimisation for multi-objective optimal power flow considering the cost, loss, emission and voltage stability index

    Page(s): 515 - 527
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (621 KB)  

    The study presents an improved particle swarm optimisation (IPSO) method for the multi-objective optimal power flow (OPF) problem. The proposed multi-objective OPF considers the cost, loss, voltage stability and emission impacts as the objective functions. A fuzzy decision-based mechanism is used to select the best compromise solution of Pareto set obtained by the proposed algorithm. Furthermore, to improve the quality of the solution, particularly to avoid being trapped in local optima, this study presents an IPSO that profits from chaos queues and self-adaptive concepts to adjust the particle swarm optimisation (PSO) parameters. Also, a new mutation is applied to increase the search ability of the proposed algorithm. The 30-bus IEEE test system is presented to illustrate the application of the proposed problem. The obtained results are compared with those in the literatures and the superiority of the proposed approach over other methods is demonstrated. View full abstract»

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  • Modelling input parameter interactions in the possibilistic harmonic load flow

    Page(s): 528 - 538
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (509 KB)  

    In a previous study by the authors, a possibilistic harmonic load flow (PHLF) approach was presented. The PHLF was capable of modelling, through possibility distributions, uncertainties regarding magnitude and composition in both linear (LL) and non-linear loads (NLL) connected at the linear (LL) and non-linear loads(PS). However, in that approach, possibility non-interaction between parameters for modelling LL and NLL was assumed. Such assumption is quite conservative and conduces to uncertainty overestimation. In fact, there are well-defined physical relationships among model parameters that constrain the variability of these. This study presents an improved approach which overcomes the aforementioned drawback by including both linear and non-linear equality constraints into the non-linear programming problem used to compute the PHLF. These linear and non-linear equality constraints are specifically used to model the balance of active and reactive power, respectively, at each bus of the PS. The equality constrains inclusion is supported from a possibility theory point of view by means of the `information fusion concept`. Influence of the possibility interaction consideration is evaluated in the IEEE 14-bus PS for harmonic analysis. Then, the complete PHLF is tested in a real 88-bus PS, and comparisons with Monte Carlo simulation results are performed and discussed. View full abstract»

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  • Damping of subsynchronous oscillations in power system using static synchronous series compensator

    Page(s): 539 - 544
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (445 KB)  

    In this study, a static synchronous series compensator (SSSC) is used to damp the subsynchronous oscillation in a power system compensated by the series capacitor. In order to achieve an effective damping, a supplementary subsynchronous damping controller (SSDC) is added to the SSSC. The only input signal for the SSDC is the rotor speed deviation to generate the modulation index for controlling the injected voltage of the voltage-sourced converter (VSC). Also, the chaotic optimisation algorithm is employed to tune the parameter of SSDC. The design objective is to suppress the subsynchronous resonance (SSR) caused by the series capacitor. By using the SSDC, the SSSC connected at the transmission line is able to damp the SSR. The first system of IEEE second benchmark model is used to evaluate the effective of SSDC on the torsional oscillations. The several simulations are used to demonstrate the ability of SSDC in damping the SSR. View full abstract»

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  • State estimation via mathematical programming: a comparison of different estimation algorithms

    Page(s): 545 - 553
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Although the weighted least of squares technique is an efficient and well-established power system state-estimation procedure, a number of alternative estimation approaches have been proposed in the technical literature. This study presents and compares the most-common estimators formulating them as mathematical programming problems. The numerical accuracy and computational efficiency of the different estimators are analysed using an illustrative case study. View full abstract»

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  • Design and hardware implementation of a modular transient directional protection scheme using current signals

    Page(s): 554 - 562
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (884 KB)  

    This study presents the concept, implementation and test results of a fault direction identification method that applies to identify faulty segments in transmission systems. This method relies on the wavelet analysis of the transient currents. Exchange of fault direction information among intelligent electronics devices located at different locations of network permits identification and isolation of the faulty network segment. A prototype of the fault direction identification unit was implemented using a floating point digital signal processor platform. The performance of the prototype was tested with current signals generated using a real-time waveform playback instrument. The transient waveforms were obtained from an extra high-voltage transmission system simulated in electromagnetic transient-type simulation program. Investigations were carried out under different scenarios such as current transformer saturations, measurement noise etc. View full abstract»

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  • Optimal reactive power dispatch using a gravitational search algorithm

    Page(s): 563 - 576
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (581 KB)  

    This study presents a gravitational search algorithm (GSA) for reactive power dispatch (RPD) problem. RPD is an optimisation problem that decreases grid congestion with one or more objective of minimising the active power loss for a fixed economic power schedule. The proposed algorithm is used to find the settings of control variables such as generator terminal voltages, transformer tap settings and reactive power output of the compensating devices, in order to active power losses minimisation in the transmission system. In this study, GSA is examined and tested on the standard IEEE 30-bus, 57-bus and 118-bus test systems with different test cases such as minimisation of active power losses, improvement of voltage profile and enhancement of voltage stability. To show the proposed algorithm of effectiveness and the obtained results are compared with those reported in the literature. Simulation results demonstrate the superiority and accuracy of the proposed algorithm, and considering the quality of the solution obtained, the proposed algorithm seems to be effective and robust to solve the RPD problem. View full abstract»

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  • Single-phase inverter-based neutral-current suppressor for attenuating neutral current of three-phase four-wire distribution power system

    Page(s): 577 - 583
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (798 KB)  

    In this study, a neutral-current suppressor is proposed. The proposed neutral-current suppressor comprises a zero-sequence transformer, a single-phase power converter and a rectifier. The proposed zero-sequence transformer is implemented by only two single-phase transformers, which are connected to three-phase lines of the three-phase four-wire distribution power system to supply a zero-sequence current path. The single-phase power converter is connected between the zero-sequence transformer and neutral line. A rectifier with small power rating is connected to the DC bus of single-phase power converter for overcoming the power loss of single-phase power converter to sustain a constant DC voltage. The performance of neutral-current suppression for the zero-sequence transformer is advanced by controlling the single-phase power converter so as to make the neutral load current flow through the proposed neutral-current suppressor. Moreover, the proposed neutral-current suppressor can also avoid the neutral current caused by the unbalanced voltage of three-phase four-wire distribution power systems. Hence, the proposed neutral-current suppressor is an effective solution to the neutral-current problem of three-phase four-wire distribution power systems. Both computer simulation and experimental results verify that the proposed neutral-current suppressor can achieve the expected performance. View full abstract»

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  • Integrated emergency frequency control method for interconnected AC/DC power systems using centre of inertia signals

    Page(s): 584 - 592
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (433 KB)  

    An integrated design method for emergency frequency control of interconnected AC/DC power systems with centre of inertia (COI) signals is proposed in this study. It aims to provide emergency power support from reserve-rich area(s) to the disturbed control area(s) through the paralleled AC and DC tie-lines under extreme conditions, when the normal automatic generation control (AGC) is suspended. With the assumption of area COI frequency and the employment of wide-area measurement system (WAMS), the centralised control strategy drives the area COI frequencies to track the overall system COI frequency by virtue of coordination control of emergency generation and high voltage direct current (HVDC) power such that the long-term frequency stability can be promisingly improved. The adaptive backstepping sliding-mode approach holds desired robustness to time-varying generator parameter, modelling error and area load disturbances. Simulations have been conducted on a 3-area-interconnected AC/DC system in computer and the results demonstrate the feasibility and effectiveness of the proposed design method. View full abstract»

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IET Generation, Transmission & Distribution is intended as a forum for the publication and discussion of current practice and future developments in electric power generation, transmission and distribution.

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