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Generation, Transmission & Distribution, IET

Issue 6 • Date June 2014

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Displaying Results 1 - 18 of 18
  • Hybrid computation of corrective security-constrained optimal power flow problems

    Publication Year: 2014 , Page(s): 995 - 1006
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (982 KB)  

    Corrective security-constrained optimal power flow (CSCOPF) considers the use of corrective control to remove system security violations in the post-contingency state. Its optimality not only depends on the pre-contingency state, but also the post-contingency state as well as the involved corrective control actions. This study first gives a comprehensive review on the relevant OPF models and then proposes a hybrid method to solve the CSCOPF problem. It makes use of the evolutionary algorithms to randomly search the maximum feasible region and state-of-the-art OPF solution technique (interior-point method) to provide deterministic solutions in the found region. The two interact iteratively to progressively approach the final solution. The proposed method is verified on the IEEE 14-bus and 118-bus systems. Comparison studies show that (i) CSCOPF can better balance the security and economy and (ii) the hybrid method is overall superior (in solution quality, robustness and convergence characteristic) over the single evolutionary algorithm. Parallel processing is applied to speed-up the computations. View full abstract»

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  • Optimal scheduling of electric vehicle charging and vehicle-to-grid services at household level including battery degradation and price uncertainty

    Publication Year: 2014 , Page(s): 1007 - 1016
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (451 KB)  

    It is expected that electric vehicles (EVs) will soon represent a large share of the demand for electricity. Several research works have extolled the advantages of these devices as flexible demands, not only to charge their batteries when it is cheaper to do so, but also to provide services in the form of vehicle-to-grid (V2G) power injections to the system. These services, however, could reduce the useful life of the battery and thus introduce a cost that needs to be taken into account when scheduling the charging of these vehicles. This study presents a scheduling algorithm for EVs under a real time pricing scheme with uncertainty. The objective function explicitly takes into account the cost of battery degradation not only when used to provide services to the system but also in terms of the EV utilisation for motion. The results show that the scheduling of the V2G services is sensitive to the electricity prices uncertainty and to the degradation costs derived from the energy arbitrage. Also, the optimal energy state of charge of the batteries is highly dependent on whether the cost of battery degradation is taken into account or not. View full abstract»

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  • Simultaneous Integrated stochastic electrical and thermal energy expansion planning

    Publication Year: 2014 , Page(s): 1017 - 1027
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (479 KB)  

    In this study, a stochastic multi-objective framework is proposed for energy expansion planning (EEP). The proposed multiobjective framework can concurrently optimise the competing objective functions including total real energy losses, voltage deviation and the total cost of the installation equipments. Also, regarding the uncertainties of the new complicated energy systems, in this study, for the first time, system uncertainties including load uncertainty are explicitly considered in the EEP problem by the use of the probabilistic load flow technique based on the point estimate method. Since the objectives are different and incommensurable, it is difficult to solve the problem by the conventional approaches that may optimise a single objective. Hence, the metaheuristic algorithm is applied to this problem. Here, the particle swarm optimisation (PSO) algorithm as a new evolutionary optimisation algorithm is utilised. To improve the total ability of the PSO for global search and exploration, a new modification adaptive process is suggested in such a way that the algorithm will search the total search space globally. To evaluate the feasibility and the effectiveness of the proposed algorithm, three modified standard distribution systems are used as the case studies. View full abstract»

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  • Failure rate modelling of electric distribution overhead lines considering preventive maintenance

    Publication Year: 2014 , Page(s): 1028 - 1038
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (591 KB)  

    The electric distribution overhead lines are large-scale complex repairable systems that consist of numerous components. To obtain an acceptable level of reliability in overhead lines, an asset management strategy seems to be necessary. An asset management-based maintenance framework is introduced for overhead lines. Based on the proposed framework, a relevant failure rate model is developed, which is able to show the effect of preventive maintenance according to expending cost and other affecting factors. The application procedure of the proposed model is also discussed in overhead line maintenance planning. Five-year historical data of nine feeders are used to assess the proposed maintenance schedule in comparison to utility predefined one. View full abstract»

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  • Analytical approach for placement and sizing of distributed generation on distribution systems

    Publication Year: 2014 , Page(s): 1039 - 1049
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (338 KB)  

    An analytical method for placement and sizing of distributed generation on power distribution systems for loss reduction is introduced. The proposed analytical method is developed based on a new formulation for the power flow problem, which is non-iterative, direct, and involves no convergence issues even for systems with high R/X branch ratios. Further, this power flow solution is extremely useful whenever fast and repetitive power flow estimations are required. A priority list based on loss sensitivity factors is developed to determine the optimal locations of the candidate distributed generation units. Sensitivity analysis is performed to estimate the optimal size and power factor of the candidate distributed generation units. Various types of distributed generators (DGs) have been dealt with and viable solutions are proposed to reduce total system loss. The proposed method has been tested on 33-bus and 69-bus distribution systems, which are extensively used as examples in solving the placement and sizing problem of DGs. Exhaustive power flow routines are also performed to verify the sizes obtained by the analytical method. The test results show that the proposed analytical method could lead to optimal or near-optimal solution, while requiring lower computational effort. View full abstract»

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  • Solving unit commitment problem by a binary shuffled frog leaping algorithm

    Publication Year: 2014 , Page(s): 1050 - 1060
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (691 KB)  

    Shuffled frog leaping (SFL) algorithm is one of the heuristic algorithms which is classified in swarm intelligence area. The standard version of the SFL and the improved versions of the algorithm operate in continuous space and is being researched and utilised in different subjects by researches around the world. The results obtained show that the improved versions of the algorithm perform well. But many optimisation problems are set in discrete space and there is no binary version of SFL to deal with these problems. Thus, an SFL algorithm is presented for optimising binary encoded problems called as binary SFL (BSFL). To show the effectiveness of the proposed algorithm, BSFL is tested on unit commitment problem, which is one of the most important problems to be solved in the operation and planning of a power system. The results obtained by the proposed algorithm are compared with the previous approaches reported in the literature. The results show that the proposed algorithm produces optimal solution for the study system. View full abstract»

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  • On Hilbert transform methods for low frequency oscillations detection

    Publication Year: 2014 , Page(s): 1061 - 1074
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1226 KB)  

    This study tackles the issue of electromechanical modes identification through a measurement-based methodology employing a novel signal decomposition theorem based upon the Hilbert transform. The methodology aims to answer in a simpler and more pragmatic manner to the main weaknesses of the Hilbert-Huang transform with respect to the major refinements in the relevant literature. These weak points are discussed with sufficient detailed degree in the study. The main contribution of this study consists in combining a recent signal decomposition theorem for separating an assigned signal into elemental ones, each of them characterised by a single frequency component and a robust preliminary non-linear spectral analyser, named Lp periodogram. This procedure's results are very appropriate for analysing some critical cases of electromechanical oscillations, because of the Lp periodogram robustness against heavy-tailed noise and also its intrinsic ability in estimating closely spaced frequency components. The proposed approach is found to be inherently simple, reliable and consistent in performance as well as characterised by low computational burden. Some numerical applications validate the methodology and assess its own performance on synthetic signals, near real-life signals acquired by IEEE test networks and on a real measured signal from a wide-area monitoring system currently in operation. View full abstract»

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  • Excitation prediction control of multi-machine power systems using balanced reduced model

    Publication Year: 2014 , Page(s): 1075 - 1081
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (335 KB)  

    A multi-machine power system excitation predictive control method using balanced reduced model is presented. First, the theory of empirical Gramians balanced reduction was used to reduce the orders of power system non-linear dynamic model to save the time-solving of open-loop optimisation in model predictive control. Then, it used the minimum deviation of system output(state) and control input as the control objective, using the non-linear reduced system sampling linearisation model as equivalent constraints and the change limits of system output and control input as unequivalent constraints to establish the excitation predictive control model based on reduced model. Next, the interior-point method was used to solve the optimal control problem. Finally, took advantage of a four-machine power system to verify the effectiveness of the predictive control method, and the simulating results show that excitation predictive control method using balanced reduced model for the multi-machine power systems can greatly shorten the optimisation time-calculating, meanwhile maintain the voltages of generator terminals within the set points and have a better control performance than traditional excitation control. View full abstract»

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  • Multi-area optimal power flow with changeable transmission topology

    Publication Year: 2014 , Page(s): 1082 - 1089
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (323 KB)  

    This study presents a framework for coordinating multi-area optimal power flow with adjustable network topology in an electric power system. The modelling is accomplished in a coordinated but not a centralised fashion. Each regional operator dispatches its own generation and switches its own transmission network to reach its optimal benefits. The proposed model uses augmented Lagrangian relaxation to realise decomposition. No other information is exchanged between the regional operators except the Lagrangian multipliers. This study compares the centralised transmission switching model and the proposed decentralised method by using several numerical tests. The results verify the effectiveness of the solution methodology. The decomposition framework proposed in this study can serve as a foundation for implementing parallel computing. View full abstract»

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  • Optimal configuration of underground cables to maximise total ampacity considering current harmonics

    Publication Year: 2014 , Page(s): 1090 - 1097
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (517 KB)  

    This study presents an efficient algorithm to find optimal underground cable configuration with maximum ampacity in a concrete duct bank. The current's harmonics and its effects on the sheath losses are considered in the proposed algorithm. To find the optimal configuration of the cables in the duct bank, two heuristic optimisation methods are applied: the first algorithm is the well-known particle swarm optimisation (PSO), and the second one is the shuffled frog-leaping algorithm (SFLA) which has attracted considerable attraction in recent years. The objective function of these methods which has to be optimised is total ampacity. Calculating the total ampacity for a required configuration by using PSO/SFLA is a convex optimisation problem. The interior point method is utilised to solve this problem. The proposed method has been implemented on four test cases to show the importance of considering the current harmonics in determining the optimal configuration. To evaluate the performance of the PSO and the SFLA, the obtained results are compared in different test cases. View full abstract»

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  • Modification of multi-area economic dispatch with multiple fuel options, considering the fuelling limitations

    Publication Year: 2014 , Page(s): 1098 - 1106
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (375 KB)  

    Nowadays, using the units with multiple fuel options is one of the ways to reduce the generation costs and increase the reliability in modern power plants. In such power plants, the minimum generation cost is achieved via selecting the optimal fuel types. Here, the fuelling conditions and limitations of different fuel types indeed have determinative roles, because they not only can significantly influence the system operation point and optimal generation dispatch, but also they certainly affect the fuel consumption cost and the electricity price, as well. This study aims to develop and solve a novel type of multi-area economic dispatch with multiple fuel options, which also considers the mathematical model of the fuelling constraints. Thus, the system operating conditions are modelled in a more realistic way in which all the models of the power plants as well as their fuelling systems are well regarded. This consequently yields a more accurate generation dispatch that can indeed reduce the generation costs, increase the fuelling reliability and subsequently increase the entire system reliability in the actual power systems in which the fuelling constraints are essential and determinative. View full abstract»

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  • Adaptive zero sequence compensation algorithm for double-circuit transmission line protection

    Publication Year: 2014 , Page(s): 1107 - 1116
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    This study presents an adaptive zero sequence compensation algorithm to improve the conventional ground distance relays performance, in double-circuit transmission lines. The proposed approach corrects the estimated impedance by correcting the degree of zero sequence compensation of ground distance relays. The new scheme is proposed for the standalone distance relays and does not inherently require any communication link. However, it is applicable to all well-known pilot protection schemes. The proposed method utilises zero sequence equivalent circuit in order to estimate the compensation term. Afterwards, the estimated impedance is corrected by using a recursive approach. Finally, the proposed method compensates the fault resistance effect. The simulation and experimental results verify the efficiency, security and dependability of the proposed method. The results indicate that by using the proposed method, the maloperation of the conventional distance relay because of the mutual coupling is mostly resolved. View full abstract»

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  • New algorithm for detecting power transformer faults based on M-robust estimation of sound signals

    Publication Year: 2014 , Page(s): 1117 - 1126
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    M-robust algorithm for detecting power transformer inner faults accompanied by an electrical arc based on sound signal processing is presented. The electrical arc, which exists during the fault, generates specific sound waves. The efficiency of the presented algorithm for processing these types of sound signals is confirmed by performing experimental tests. It has been shown that even in the presence of different types of disturbances (including impulse disturbance), the M-robust methodology gives fast and reliable results which lead to the detection of transformer inner fault with electrical arc. The presented algorithm efficiently and quickly detects the unwanted processes in the transformer which do not result in a current increase (the initial discharge which precedes the electrical arc) and which could not be detected by the standard protection functions. The presented methodology gives an opportunity for further development and online implementation of a simple, low cost and broadly applicable system for the detection of internal faults in transformers, independently of the voltage and power level. View full abstract»

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  • Implementation of four-leg distribution static compensator

    Publication Year: 2014 , Page(s): 1127 - 1139
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2393 KB)  

    An implementation of a four-leg distribution static compensator (DSTATCOM) using an adaptive neural network-based control algorithm for compensation of linear/non-linear loads using voltage source converter is presented here. The proposed control algorithm, which is based on adaptive neural network, is used for extraction of fundamental active and reactive power components of load currents which are major components in the estimation of reference supply currents. This control algorithm is implemented on a developed four-leg DSTATCOM for reactive power compensation, harmonics elimination, load balancing and neutral current mitigation under linear and non-linear loads. The performance of DSTATCOM is observed quite satisfactory under various linear and non-linear loads. View full abstract»

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  • Modelling, analysis and control of stand-alone self-excited induction generator-pulse width modulation rectifier systems feeding constant DC voltage applications

    Publication Year: 2014 , Page(s): 1140 - 1155
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2196 KB)  

    An analogue-based pulse width modulation (PWM) hysteresis current mode controller has been developed for the stand-alone operation of self-excited induction generator (SEIG)-PWM rectifier systems for constant DC voltage applications. The configuration and implementation of the control scheme have been fully described. A method for predetermining the steady-state performance of the system for a given rectifier DC output has been explained with relevant analytical expressions derived for suitably reflecting the DC load resistance on the generator terminals. An `abc-dq' axis model has also been formulated for the study of transient behaviour of the system for step changes in the driving speed and DC load on the system. A prototype system consisting of an SEIG, rectifier and the associated control circuits has been built in the laboratory and its satisfactory working has been demonstrated experimentally, for the different loading patterns and the corresponding predetermined results are also provided. View full abstract»

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  • Time-time-transform application to fault diagnosis of power transformers

    Publication Year: 2014 , Page(s): 1156 - 1167
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1244 KB)  

    Application of time-time (TT)-transform for differential protection of power transformers has been suggested. At first, external and internal disturbances are discriminated. If the disturbance is external, relay scheme restrains more analysis and tripping. Otherwise, the differential current signal is analysed by TT-transform and TT-matrix is computed. Next, a suggested index is computed, accordingly. Discrimination between inrush current and internal fault is performed by the proposed index. To investigate the effectiveness of the method, a typical power system has been modelled in EMTP software. Also, the relay scheme has been developed in MATLAB environment. Then, differential currents extracted from the system modelled in EMTP have been fed to MATLAB for analysis. Also, the performance of the method in noisy environments has been assessed. To make an analogy between the TT-transform-based method and wavelet transform-based methods, a wavelet transform-based scheme has been developed in MATLAB environment and results have been compared to the results of the TT-transform-based method. In addition, an S-transform-based method has been implemented in MATLAB and has been compared with the suggested method. The results show that the method is superior to both wavelet transform and S-transform-based methods. View full abstract»

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  • Wide area measurement/wide area information-based control strategy to fast relieve overloads in a self-healing power grid

    Publication Year: 2014 , Page(s): 1168 - 1176
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (477 KB)  

    Self-healing is one of the characteristics of the smart grid. A self-healing power grid can identify and react to disturbance and restore power systems with little or even no human intervention. A wide area measurement (WAM) and wide area information (WAI)-based control strategy is proposed to fast react to overloads and restore the power grid in the self-healing power grid. The basic principle is to redistribute the power flow of a contingency transmission line to other lines with unified power flow controller (UPFC). To implement the control strategy, the reverse current network and nodal analysis method, instead of the iteration algorithm and optimisation method, is applied to redistribute the power flow. The proposed WAM/WAI-based nodal analysis can relieve overloads quickly and effectively while realising the control objective accurately. Moreover, a grid simplification method is applied to further reduce computation cost. IEEE 39-bus test system-based simulation is applied to verify the proposed control strategy. The results show that the control strategy can relieve overloads effectively in about tens of milliseconds. Thus, it could be an online controller for a self-healing power grid to deal with harmful contingencies. View full abstract»

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  • Classification and regression tree-based adaptive damping control of inter-area oscillations using wide-area signals

    Publication Year: 2014 , Page(s): 1177 - 1186
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1549 KB)  

    An adaptive damping control scheme based on the classification and regression tree (CART) using wide-area signals is proposed. A family of robust multiple-input multiple-output controllers are designed offline and used in real-time after the current operating point is retrieved from phasor measurement unit (PMU) data with CART interpolation. When the power system is operating close to a previously set operating point, only the corresponding controller is active. When the power system is not close to any previously set operating point, a combined controller is formed. A 16-machine 68-bus system is used for simulation test. Thyristor controlled series compensation, static var compensator and energy storage device are used as actuators and the remote PMUs frequencies are employed as added inputs in the example control. Simulation results demonstrate good damping performance of the proposed control method against a wide range of changes in operating state. View full abstract»

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