bluuebunny/crossref_metadata_2025 huggingface dataset:
Unsupervised feature selection based on spectral regression from manifold learning for facial expression recognition
Authors: Wang Li , Wang Ke , Li Ruifeng
Published: August 2015

In this study, an unsupervised feature selection method is proposed for facial feature recognition (FER) in the absence of class labels. The contribution is the descriptive feature components selector spectral regression representative coefficient scores based on graph manifold learning from high‐dimensional feature space. The spectral regression analysis and L1‐regularised least square are then used to compute the importance of features in the original space, so that less representative features with lower coefficient scores will be removed without prior distribution assumption. To verify the performance of the authors’ method, some classifiers are used to classify facial expressions on three benchmark facial expression databases. The recognition results indicate the availability and effectiveness of the proposed method for FER.
Advanced weight graph transformation matching algorithm
Authors: Wang Song , Guo Xin , Mu Xiaomin , Huo Yahong , Qi Lin
Published: August 2015

An efficient and accurate point matching algorithm named advanced weight graph transformation matching (AWGTM) is proposed in this study. Instead of relying only on the elimination of dubious matches, the method iteratively reserve correspondences which have a small angular distance between two nearest‐neighbour graphs. The proposed algorithm is compared against weight graph transformation matching (WGTM) and graph transformation matching (GTM). Experimental results demonstrate the superior performance in eliminating outliers and reserving inliers of AWGTM algorithm under various conditions for images, such as duplication of patterns and non‐rigid deformation of objects. An execution time comparison is also presented, where AWGTM shows the best results for high outlier rates.
Condition‐based exciter model complexity reduction for improved transient stability simulation
Authors: Kim Soobae , Overbye Thomas J.
Published: August 2015

A reduced model approach to decrease computational complexity in power system transient stability simulation is presented. This study investigates conditions that make fast modes active or inactive using practical power system examples. Modes in the original system where fast dynamics do not appear can be neglected, allowing simulation steps to be increased without numerical stability issues. During a transient simulation, the proposed method switches dynamically between the original exciter model and the reduced one, depending on the switching criterion presented. A high level of accuracy is achieved and computational efficiency is increased. Case studies with the Western Electricity Coordinating Council system are provided to validate the performance of the proposed method.
Statistical approach for transient stability constrained optimal power flow
Authors: Zerigui Amel , Dessaint Louis‐A. , Hannat Ridha , Ah King Robert T.F. , Kamwa Innocent
Published: August 2015

The transient stability constrained optimal power flow (TSC‐OPF) is a big challenge in the field of power systems because of its high complexity and extensive computation effort involved in its solution. This study presents a new approach to compute the transient stability constraint formulated by the critical clearing time (CCT) in TSC‐OPF. CCT has been determined by dual‐kriging, a space interpolation method which has primarily been used in natural resources evaluation. Given the huge dimensionality of the problem, Pareto analysis is firstly used to reduce the number of input variables in an initial database to those which are significant to compute CCT. With the reduced variables, a new database has been constructed using a design of experiment to obtain a reduced number of observed points. As a result of this approach, the sets of dynamic and transient stability constraints to be considered in the optimisation process are reduced to one single stability constraint with only a few variables. Ultimately, the size of the resulting optimisation problem is almost similar to that of a conventional optimal power flow. The effectiveness of the proposed method is tested on the New England 10‐machine 39‐bus system and the larger 50‐machine 145‐bus power system.
Hilbert–Huang transform‐based transient busbar protection algorithm
Authors: Guo Zhenwei , Yao Jiangang , Tan Zhewen
Published: August 2015

A new algorithm for busbar protection is proposed based on the Hilbert–Huang transform in this study. The algorithm decomposes currents of all lines connecting to the busbar into intrinsic‐mode functions and calculates the instantaneous amplitude of the first intrinsic mode function (IMF). Then, the instantaneous amplitude is normalised to eliminate the impact of fault initial angle and transition resistance. When a fault occurs on the busbar, the initial travelling waves on head ends of the lines all have great instantaneous amplitudes; when a fault occurs on any line, the travelling wave on the faulted line is of great instantaneous amplitude, whereas the initial travelling waves on healthy lines are of small instantaneous amplitudes. Thus, through analysing the detected instantaneous amplitudes of travelling waves, a new busbar protection scheme can be constructed, which achieves a high reliability relative to other fault‐travel‐wave‐based algorithms. According to simulation results on a 500 kV substation modelled in ATP‐Draw, the graphical preprocessor to ATP‐EMTP windows version, the proposed algorithm is effective in determining various types of faults.
Islanding detection method based on a Thevenin‐like model
Authors: Di Fazio Anna Rita , Fusco Giuseppe , Russo Mario
Published: August 2015

Reliable detection of islanded operation is essential in distribution systems with large penetration of the distributed generation. Commonly‐used protections present performance limitations in terms of sensitivity and stability. To overcome such limitations, this study proposes to enrich classical protections by adding a passive islanding detector based on a new method. It adopts a linear representation of the low voltage distribution system, referred to as Thevenin‐like model. On the basis of the voltage and current measures at the detector installation point, two model parameters are estimated and are used to distinguish islanded from grid‐connected operation. The proposed detector presents high sensitivity and reliability, does not require expert tuning, can be installed in different points of the distribution system and is economically viable. Numerical analysis and simulations, evidence the effectiveness of the proposed method.
Two‐level decision‐making model for a distribution company in day‐ahead market
Authors: Khazaei Hossein , Vahidi Behrooz , Hosseinian Seyed Hossein , Rastegar Hasan
Published: August 2015

This study presents a two‐level decision‐making (TLDM) model for a distribution company (Disco) in the day‐ahead market (DAM), where Disco has two additional resources, interruptible load (IL) and distribution generation (DG). At the upper level of the model, the competition among Discos for purchasing power from DAM is modelled using a matrix game with the assumption that the cost information of generators and Discos is common knowledge. In the lower level, each Disco's strategy on its ILs and DGs are derived through an optimisation problem. The TLDM model significantly reduces the size of the matrix game and thus lowers the computational barrier. Owing to implementation difficulties of mixed strategies, a reinforcement learning algorithm is used to derive Discos’ strategies from the matrix game. This algorithm always provides pure strategies for Discos, even if the matrix game has no pure Nash equilibrium. An 8‐bus system is used to illustrate the efficiency of the proposed model and solution method. The results are compared with those obtained using a bi‐level optimisation method reported in the literature.
Optimal design of linear subsynchronous damping controllers for stabilising torsional interactions under all possible operating conditions
Authors: Liu Huakun , Xie Xiaorong , Wang Liang , Han Yingduo
Published: August 2015

Torsional damping controllers, such as supplementary excitation damping controllers (SEDCs), are widely used to stabilise subsynchronous resonance (SSR) induced by torsional interactions (TIs) between turbo‐generators and series‐compensated power systems. However, because of the changeable operating situations of a power system, it is a great challenge to design them to guarantee torsional stability under all possible operating conditions. This study proposes a global optimal control‐design procedure for tuning SEDCs to accommodate the variation of system conditions. Considering TI is a small‐signal stability issue, the non‐linear power system is converted into a family of linear parameter varying models and the parameter‐tuning task for multiple SEDCs is formulated into a multi‐model constrained non‐linear optimisation problem. A global optimisation procedure based on genetic algorithm and simulated annealing is designed to efficiently solve this problem and obtain a set of robust or several sets of gain‐scheduling SEDCs. The proposed method is applied to a multi‐machine series‐compensated power system. The results of both eigenvalue analysis and time‐domain simulation have fully demonstrated the effectiveness of the optimised SEDCs in stabilising SSR under all possible operating conditions.
Frequency stabilisation of a hybrid two‐area power system by a novel quasi‐oppositional harmony search algorithm
Authors: Mahto Tarkeshwar , Mukherjee Vivekananda
Published: August 2015

Modelling, simulation and performance analysis of a two‐area thermal‐hybrid distributed generation (HDG) power system having different sources of power generation has been carried out in this study. The thermal power plant is consisting of re‐heat type thermal system, whereas the HDG system includes the combination of wind turbine generator and diesel generator. In the studied model, superconducting magnetic energy storage (SMES) device is considered in both the areas. Additionally, a flexible ac transmission system (FACTS) device such as static synchronous series compensator (SSSC) is also considered in the tie‐line. The different tunable parameters of the proportional‐integral‐derivative (PID) controllers, SMES and SSSC are optimised using a novel quasi‐oppositional harmony search (QOHS) algorithm. Optimisation performance of the novel QOHS algorithm is established while comparing its performance with binary coded genetic algorithm. From the simulation work it is observed that with the inclusion of SMES in both the areas, the system performances toward the achievement of minimal frequency and tie‐line power oscillations are promising under different types of input loading perturbations. It is further revealed from the simulation results that the installation of an expensive FACTS device such as SSSC does not yield any significant improvement to the system performance.
Loss allocation in distribution network with distributed generations
Authors: Jagtap Kushal Manoharrao , Khatod Dheeraj Kumar
Published: August 2015

This study presents a new method for allocation of network losses to distributed generations (DGs) and consumers connected to radial distribution networks in context of liberalised electricity market. The study intends to deal with three aspects, namely, issue of non‐linear relation between power flow and losses, change in network losses because of voltage variation and contribution of DG to the network loss. The proposed method is a branch‐oriented approach based on tracing the real and reactive power of DGs and loads. It establishes a direct relationship between sending and receiving node voltages and apparent power available at the receiving node of a branch. It allocates the losses without any assumptions and approximations by employing backward sweep network reduction technique. The proposed method is simple and effective; and requires only the power flow solution to allocate the losses to DGs and loads. Pro rata method, which is based on the power rating of generators and consumers, is revisited and modified according to branch oriented approach. To show the effectiveness of the proposed method, it has been tested on two test networks, that is, 28‐ and 33‐node test networks. The obtained results are presented, discussed and compared with other published methods.
Stochastic locational marginal price calculation in distribution systems using game theory and point estimate method
Authors: Azad‐Farsani Ehsan , Askarian‐Abyaneh Hossein , Abedi Mehrdad , Hosseinian Seyed Hossein
Published: August 2015

This study presents a new stochastic method to estimate the locational marginal price (LMP) in the distribution networks containing distributed generation (DG). In the proposed method, LMP at each bus is calculated according to the contribution of the DG to the reduced amount of loss and emission. An iterative algorithm which is based on the game theory is proposed to allocate the loss and emission reduction among DG units. Also, a stochastic framework based on the point estimate method is considered to capture uncertainty in the market price and load demand. The proposed policy will provide a robust state estimation tool for distribution companies in the next step of operation. The state estimation tool provides the decision maker with the ability to exert its control over private DG units when loss and emission are minimised. The performance of the proposed algorithm is tested on a realistic distribution network in the deterministic and stochastic frameworks. The obtained results are encouraging.
Identification of dominant low‐frequency modes in ring‐down oscillations using multiple Prony models
Authors: Wadduwage Darshana Prasad , Annakkage Udaya D. , Narendra Krish
Published: August 2015

This study presents a simple approach to modify the Prony algorithm to extract dominant low‐frequency modes present in ring‐down oscillations in power systems. The proposed approach is based on the observation that true modes present in the ring‐down oscillations appear consistently, irrespective of the order of the Prony model. It is shown that the consistently appearing modes can be extracted using a sorting method. The improved Prony algorithm which has the feature of extracting only the true modes present in the input signal is utilised to propose an oscillation monitoring algorithm in this study. The suitability of the proposed oscillation monitoring algorithm for real‐time monitoring of low‐frequency inter‐area oscillations is demonstrated using synthetic signals and simulated signals of different test systems.
State feedback‐based capacitor voltage equalisation scheme in distribution static compensator for load compensation
Authors: Gawande S.P. , Ramteke Manoj R.
Published: August 2015

In this study, shunt compensation using conventional split capacitor‐based distribution static compensator is presented. A new state feedback‐based switching control is proposed to avoid capacitor voltage divergence and to achieve load compensation, simultaneously. Compared with conventional control used for dc‐link voltage regulation, the proposed control reduces the requirement of proportional–integral controllers. The proposed control also nullifies high‐frequency components from the source and neutral current with minimum total harmonic distortion, provides precise dc‐link voltage regulation, thus, minimising the dc power loss. The reference generation for control variables along with the switching control is discussed. To demonstrate the superiority of aforementioned scheme, three‐phase four‐wire distribution system with shunt compensator under steady state as well as transient condition, is considered. To show the simplicity and effectiveness of the proposed control, simulation studies are performed along with the frequency‐response analysis using MATLAB environment. Finally, the detailed simulations using PSCAD/EMTDC and experimental results are provided to validate the efficacy of the proposed control.
Application of brain emotional learning‐based intelligent controller to power flow control with thyristor‐controlled series capacitance
Authors: Hosseinzadeh Soreshjani Mohsen , Arab Markadeh Gholamreza , Daryabeigi Ehsan , Abjadi Navid Reza , Kargar Abbas
Published: August 2015

Thyristor‐controlled series capacitance (TCSC), as a member of flexible AC transmission systems family, controls the interrelated parameters that govern the transmission systems. In this study, an intelligent controller, known as brain emotional learning‐based intelligent controller is used to active power control of a transmission line equipped with TCSC and compared with conventional proportional–integral–derivative and fuzzy logic controllers. Simulation results of two different power systems under different conditions show the effectiveness of the proposed intelligent technique in power flow control.
Voltage stability in unbalanced power systems: a new complementarity constraints‐based approach
Authors: Carpinelli Guido , Caramia Pierluigi , Russo Angela , Varilone Pietro
Published: August 2015

Voltage stability (VS) has become a fundamental issue in the new, liberalised markets due to the fact that the new power systems are approaching more and more the stability limits. Then, several approaches were proposed in the relevant literature to find the critical conditions and recently the problem was faced also with reference to unbalanced three‐phase power systems. The unbalances, in fact, can be responsible of more critical stability conditions than in balanced power systems. Continuation power flow and optimal power flows were applied to analyse such conditions. This study deals with VS analysis in unbalanced power systems and proposes a new optimisation model to determine the critical point based on the use of complementarity constraints. In particular, the maximum stability margin is calculated by a single‐stage or a multistage procedure that accounts for the relationship between the actual operating point and the maximum loading point. In addition, the multistage maximum stability margin problem is formulated also in a probabilistic framework to account for the uncertainties affecting the input data (e.g. load powers). An application is presented on a test system highlighting the feasibility and the goodness of the proposed technique.
Identification of voltage stability critical injection region in bulk power systems based on the relative gain of voltage coupling
Authors: Jiang Tao , Bai Linquan , Jia Hongjie , Yuan Haoyu , Li Fangxing
Published: August 2015

This study proposes a novel adaptive identification method for the voltage stability critical injection region (VSCIR) in bulk power systems. From the viewpoint of a multi‐input multi‐output system, a power system can be partitioned into load and generator coupled subsystems, and the concept of voltage coupling relative gain (RG) is introduced to determine the VSCIRs. A two‐stage partitioning method of VSCIR is presented. In the first stage, the voltage stability weak buses are determined through loading margin and are identified as critical buses in the system. For each critical bus, the load and generator buses that have strong voltage coupling are identified through the cross‐RG and clustered into a VSCIR centred by the corresponding critical bus as pilot buses. In the second stage, practical VSCIRs are obtained through (i) merging VSCIRs that have strong coupled pilot buses, and (ii) allocating the buses that are shared by multiple regions to the most coupled VSCIRs. Further, this study proposes a voltage control strategy for improving the voltage stability of the system based on the practical VSCIRs. The proposed method is tested on the New England 39‐bus system, as well as the bulk 2383‐bus Polish power grid.
Modelling of energy storage dispatch for generation system adequacy studies
Authors: Gafurov Tokhir , Usaola Julio , Prodanovic Milan
Published: August 2015

Energy storage systems (ESS) are expected to play an important role in future electricity networks and more modelling efforts are required to include them in generation system adequacy (GSA) studies based on sequential Monte Carlo simulations. This paper proposes a new, generic approach to ESS dispatch modelling that takes into account both technological and control aspects required for the simulation‐based GSA evaluations. The model features the application of detrended residual load that includes renewable production and distinguishes between different operating timescales. Moreover, by using the correction of ESS dispatch based on the classical proportional integral controller technique the model achieves a realistic representation of storage level variations. In this paper all the necessary model equations and parameter identification procedures are provided along with their underlying assumptions. The effectiveness of the new dispatch model is demonstrated by using a GSA study for a generation system comprising thermal power plants and hydroelectric ESS with annual and daily operating cycles.
Algorithms and field experiences for estimating transmission line parameters based on fault record data
Authors: Wang Yang , Xu Wilsun
Published: August 2015

The impedance parameters of overhead transmission lines are fundamental input data for various power system studies. The data are traditionally calculated based on the structure information of a line. This study proposes a method for estimating the parameters using fault records captured by digital relays. The fault records are the unsynchronised voltage and current waveforms recorded at both ends of a line. One of the main contributions of this work is the use of the wave propagation speed equation to simplify the problem and to improve the estimation accuracy. As a result, both the positive and zero sequence parameters can be estimated using simple algorithms in a decoupled solution process. Simulation results show that the proposed approach has good accuracy. Finally, the method was applied to estimate the impedance data of several actual transmission lines based on the fault record data provided by a utility company.
Value based pricing of distribution generations active power in distribution networks
Authors: Miri Larimi Seyyed Majid , Haghifam Mahmoud Reza , Zangiabadi Mansoureh , Taylor Philip
Published: August 2015

With widespread installation of distribution generations (DG) mainly in distribution networks, a fairly incentive scheme is required to better meet the investment and innovation challenge and to drive the innovation needed to deliver a sustainable energy network with value for money to existing and future consumers. This study proposes a new method to determine DG energy price based on its impact on active loss reduction. This method calculates the actual value of each DG in the active loss reduction and according to this value, determines DG energy price, which is named value based pricing. The proposed approach is applied to a market model with two different agents, namely considered as the distribution company (DisCo) and the owner of DG. In this model, the DisCo is considered as the sole owner and operator of a distribution network and can purchase energy from the wholesale electricity market and/or from DG units owned by independent producers. To illustrate the advantages of the proposed method compared with the local marginal pricing(, both methods are implemented in 33‐bus distribution network.
Interval radial power flow using extended DistFlow formulation and Krawczyk iteration method with sparse approximate inverse preconditioner
Authors: Ding Tao , Li Fangxing , Li Xue , Sun Hongbin , Bo Rui
Published: August 2015

Confronted with uncertainties, especially from large amounts of renewable energy sources, power flow studies need further analysis to cover the range of voltage magnitude and transferred power. To address this issue, this work proposes a novel interval power flow for the radial network by the use of an extended, simplified DistFlow formulation, which can be transformed into a set of interval linear equations. Furthermore, the Krawczyk iteration method, including an approximate inverse preconditioner using Frobenius norm minimisation, is employed to solve this problem. The approximate inverse preconditioner guarantees the convergence of the iterative method and has the potential for parallel implementation. In addition, to avoid generating a dense approximate inverse matrix in the preconditioning step, a dropping strategy is introduced to perform a sparse representation, which can significantly reduce the memory requirement and ease the matrix operation burden. The proposed methods are demonstrated on 33‐bus, 69‐bus, 123‐bus, and several large systems. A comparison with interval LU decomposition, interval Gauss elimination method, and Monte Carlo simulation verifies its effectiveness.
Holonic structure: a state‐of‐the‐art control architecture based on multi‐agent systems for optimal reactive power dispatch in smart grids
Authors: Ansari Javad , Gholami Amin , Kazemi Ahad
Published: August 2015

This study presents a hierarchical distributed structure based on the Holonic concept for reactive power control in smart grids. Holons, as the main parts of the proposed framework, are able to negotiate together, change their boundaries, and alter the role of their members. These abilities improve the flexibility and performance of the novel structure in order to adapt itself to different situations. The proposed methodology is successfully scrutinised through different case studies based on a transmission test system connected to seven distribution networks. The new method is compared with two structures using a set of evaluation indices. The simulation results have revealed that improving the computational efficiency, minimising the active power losses and voltage deviations, optimal utilisation of reactive power sources, less data traffic loads, and increasing the fault tolerance are some key features of the proposed approach.
Dynamic equivalent of microgrid considering flexible components
Authors: Hua Jiacheng , Ai Qian , Yao Yuan
Published: August 2015

Microgrid (MG) contains large scales of flexible components, so the traditional distribution network equivalent method is not applicable in MG equivalent research. In this study, a novel MG model structure considering the influence of control strategy on the external characteristics of MG is presented, in order to make measurement‐based modelling approach more suitable for equivalent research of MG. The proposed model is a non‐mechanism model which can restore the dynamic characteristics of MG better, and the parameters identification of the model is solved by improved immune algorithm. Finally, through the fault validation way the effectiveness of the model is demonstrated.
Optimal sizing of energy storage systems: a combination of hourly and intra‐hour time perspectives
Authors: Kargarian Amin , Hug Gabriela
Published: August 2015

Storage technology is a key enabler for the integration of renewable energy resources into power systems because it provides the required flexibility to balance, the net load variability and forms a buffer for uncertainties. A solution for sizing of energy storage devices in electric power systems is presented. The considered planning problem is divided into two time perspectives: hourly and intra‐hour intervals. For the intra‐hour time horizon, the algorithm determines the optimal size of the energy storage devices to provide the adequate ramping capability for the system. This ramping capability guarantees the system ability to follow the load in the intra‐hour intervals, as well as to alleviate short‐term wind generation and load fluctuations. In the hourly time scale, the optimal size of the storage is determined with respect to having a sufficient generation capacity to support the loads. A 6‐bus test power system is studied to show the effectiveness of the proposed algorithm.
A novel index for identification of weak nodes for reactive compensation to improve voltage stability
Authors: Moger Tukaram , Dhadbanjan Thukaram
Published: August 2015

In this study, a new reactive power loss index (RPLI) is proposed for identification of weak buses in the system. This index is further used for determining the optimal locations for placement of reactive compensation devices in the power system for additional voltage support. The new index is computed from the reactive power support and loss allocation algorithm using Y‐bus method for the system under intact condition and as well as critical/severe network contingencies cases. Fuzzy logic approach is used to select the important and critical/severe line contingencies from the contingency list. The inherent characteristics of the reactive power in system operation is properly addressed while determining the reactive power loss allocation to load buses. The proposed index is tested on sample 10‐bus equivalent system and 72‐bus practical equivalent system of Indian southern region power grid. The validation of the weak buses identification from the proposed index with that from other existing methods in the literature is carried out to demonstrate the effectiveness of the proposed index. Simulation results show that the identification of weak buses in the system from the new RPLI is completely non‐iterative, thus requires minimal computational efforts as compared with other existing methods in the literature.
Artificial intelligence based thermographic approach for high voltage substations risk assessment
Authors: Žarković Mileta , Stojković Zlatan
Published: August 2015

This study deals with the condition monitoring of high voltage equipment (HVE) and risk assessment in transmission power systems. Artificial intelligence is applied to use the currently available information to calculate operational risk, and take appropriate operational measures to deal with the upcoming system states. The study presents a method based on the thermographic approach for determining urgency of intervention of HVE. Age of the HVE, voltage level, overheating temperature of the hot spot, temperature of the previous overheating, dissolved gas analysis, frequency response analysis, temperature of oil insulation, the number and time of operations and gas leaking have been used as the reference inputs for the designed fuzzy controller. The results of such methods have been combined with economic factors and applied in risk maps. The method of minimal paths and method of minimal cross‐section are modified to use fuzzy numbers. These methods are used to analyse the performance of high voltage substations. System performance index is calculated to make a proper decision about reconfiguration and maintenance planning. The results might serve as a good orientation in the HVE condition monitoring and they are implemented in the asset management of transmission power systems using risk map.
Application of a hybrid energy storage system in the fast charging station of electric vehicles
Authors: Deng Jiaxi , Shi Jing , Liu Yang , Tang Yuejin
Published: August 2015

Fast charging is a practical way for electric vehicles (EVs) to extend the driving range under current circumstance. The impact of high‐power charging load on power grid should be considered. This study proposes an application of a hybrid energy storage system (HESS) in the fast charging station (FCS). Superconducting magnetic energy storage (SMES) and battery energy storage (BES) are included in HESS. Based on the quick response of SMES and the high energy density of BES, power magnitude and power change rate of FCS can be limited by compensation of HESS. A controller is designed to generate real‐time power demand to HESS. As a part of the control strategy, the energy regulation control of SMES is highlighted. The regulation control is necessary for SMES to deal with energy imbalance in continuous operation; meanwhile it is beneficial for battery life. Finally, feasibility of this control strategy is verified by simulation.
Optimal active power control of a wind farm equipped with energy storage system based on distributed model predictive control
Authors: Zhao Haoran , Wu Qiuwei , Guo Qinglai , Sun Hongbin , Xue Yusheng
Published: August 2015

This study presents the distributed model predictive control (D‐MPC) of a wind farm equipped with fast and short‐term energy storage system (ESS) for optimal active power control using the fast gradient method via dual decomposition. The primary objective of the D‐MPC control of the wind farm is power reference tracking from system operators. Besides, by optimal distribution of the power references to individual wind turbines (WTs) and the ESS unit, the WT mechanical loads are alleviated. With the fast gradient method, the convergence rate of the D‐MPC is significantly improved which leads to a reduction of the iteration number. Accordingly, the communication burden is reduced. Case studies demonstrate that the additional ESS unit can lead to a larger WT load reduction, compared with the conventional wind farm control without ESS. Moreover, the efficiency of the developed D‐MPC algorithm is independent from the wind farm size and is suitable for the real‐time control of the wind farm with ESS.
Performance analysis of distance relay in presence of unified interphase power controller and voltage‐source converters‐based interphase power controller
Authors: Alizadeh Morteza , Khodabakhshi‐Javinani Naser , Gharehpetian G.B. , Askarian‐Abyaneh Hossein
Published: August 2015

In recent years new FACTS devices based on voltage‐source converters (VSCs) have been investigated. Unified interphase power controller (UIPC) is one of these novel FACTS controllers and the other one is VSC‐based interphase power controller (VSC‐based IPC).The purpose of this study is to investigate and compare the performance of distance relays on transmission lines in the presence of VSC‐based IPC and UIPC, while working in power flow control mode. Simulation results show that the distance relay sees the higher apparent impedance in the presence of proposed FACTS devices. Detailed simulations for different faults types and locations are evaluated. Moreover, the impact of the FACTS device location on the apparent impedance seen by the relay is discussed.
Voltage and power control for minimising converter and distribution losses in autonomous microgrids
Authors: Farasat Mehdi , Arabali Amirsaman
Published: August 2015

Voltage source converters (VSCs) are widely used in microgrids to interface the renewable resources with the electrical network. In autonomous microgrids with the dc distribution network, the optimal dc voltage reference for the one VSC that operates in the voltage regulator mode and the optimal reference power settings of the remaining VSCs working in the power dispatcher mode have to be pre‐determined. Emulating the utility grid, these settings and control modes are commonly selected such that the dc voltage is maintained within desired margins, typically ±10% around the rated value. In this study, the objective function is minimisation of the converter and distribution line losses. All the operational modes and limits of VSCs have been taken into account. Genetic algorithm has been utilised in solving the optimisation problem. Owing to limited available power from renewables, reducing the converter and distribution system losses will enhance the survivability of the microgrid and ease the cooling requirements, resulting in a more compact system. A model of a 20‐bus microgrid with the dc distribution network is employed to verify the effectiveness of the presented optimisation algorithm.
Optimal design of battery energy storage system for a wind–diesel off‐grid power system in a remote Canadian community
Authors: Guo Li , Yu Zhouzi , Wang Chengshan , Li Fangxing , Schiettekatte Jean , Deslauriers Jean‐Claude , Bai Lingquan
Published: August 2015

This study focuses on the design issue of battery energy storage system (BESS) for a wind–diesel off‐grid power system located in the Whapmagoostui community in Quebec, Canada. The local range of wind speed is from 0 to 24.8417 m/s, and the total yearly load demand in 2013 was 11,176 MWh. An optimal planning model is proposed in this study with the objectives of maximising the economic, environmental benefits, and reliability of the system. The battery energy capacity and the rated capacity of converter are selected as the optimal variables. In order to consider the impacts of renewable energy randomness, the uncertainty of component failures, and the power flow constraints on planning results, quasi‐steady state simulation is adopted to calculate the indices for each design scheme of BESS. The proposed optimal planning model of BESS is implemented and verified in the Whapmagoostui community. Also, a detailed analysis of several scenarios is presented. A base scenario with three diesel generators and four wind turbines is investigated, and its optimal BESS integration reduces fuel consumption by 4% and improves the average annual profit by 19%. The optimal designing of BESS enhances the economic, environmental benefits, and reliability of the wind–diesel system with high fuel prices in the Whapmagoostui community.
Improving underground power distribution capacity using artificial backfill materials
Authors: Gouda Ossama E. , El Dein Adel Zein
Published: August 2015

A system of underground distribution cables is usually used to carry electrical energy inside the populated areas. Under loading and faulty conditions backfill soils lose their moisture content around underground distribution cables. This phenomenon forms dry area around the underground cables and leads to the increase of thermal resistance of backfill soil and sequentially decreases in the cable rating. One aim of this study is to determine the most appropriate of the artificial soil that can be used to fill the blanks around the underground distribution cables to minimise the effect of dry zones that cause thermal failure to the cable insulation. The results of the experimental works conducted in this study showed that some soils lose moisture faster than the other; hence in these types of the soil the dry area will be formed around the underground cable faster than the others.
Comparative performance analysis of fruit fly optimisation algorithm for multi‐area multi‐source automatic generation control under deregulated environment
Authors: Mohanty Banaja , Hota Prakash Kumar
Published: August 2015

A new swarm optimisation algorithm, that is, fruit fly optimisation algorithm is proposed to tuned several classical controllers for multi‐area multi‐source interconnected power system under deregulated environment. In deregulated environment, for multi‐source combination of reheat thermal, hydro and nuclear generating units in each control area with appropriate generation rate constraint and AC/DC link. The performance of several controller such as integral (I), proportional‐integral, proportional‐integral‐derivative, integral‐double derivative (IDD) and proportional‐integral‐double derivative (PIDD) are compared under different power system scenario and it is found that PIDD controller performs better than other controllers. Then sensitivity analysis is performed with system parameter variation from their nominal values. Sensitivity analysis reveals that optimum gains of PIDD controller need not be reset for wide variation in system parameters.
Indices for measurement of harmonic distortion in power systems according to IEC 61000‐4‐7 standard
Authors: Dalali Milad , Jalilian Alireza
Published: August 2015

Among harmonic distortion indices presented in International Electrotechnical Commission (IET) standard 61000‐4‐7, only group total harmonic distortion (THDG) can be used for interharmonic pollution analysis. However, existence of interharmonic components around of fundamental frequency may deteriorate accuracy of this index. To solve this problem, two virtual groups according to IEC standard are defined in this study. Then, two new distortion indices are proposed by using virtual groups in equation of THDG index. The new distortion indices are named as: group and subgroup total harmonic distortion and improved THDG. On the basis of various simulation tests and usage of different waveform decomposition methods, it is shown that proposed indices can better show the amount of waveform distortion caused by interharmonics in respect to IEC indices.
Power system reliability evaluation using a state space classification technique and particle swarm optimisation search method
Authors: Benidris Mohammed , Elsaiah Salem , Mitra Joydeep
Published: August 2015

It is well‐known that the reliability evaluation of composite power systems is computationally demanding. This work introduces a state space classification (SSC) technique that classifies a system's state space into failure, success, and unclassified subspaces without performing power flow analysis. The SSC technique was developed based on calculating the maximum capacity flow of the transmission lines and the available generation. An algorithm, which is developed based on a directed binary particle swarm optimisation, was developed to search for failure states in the unclassified subspaces. The key element in controlling the particle swarm optimisation (PSO) search method to search for failure states in the unclassified subspaces is the selection of the weighting factors of the velocity update rule. The work presented in this study proposes an intelligent PSO based search method to adjust these weighting factors in a dynamic fashion. The effectiveness of the proposed method was demonstrated on three test systems, the Institute of Electrical and Electronics Engineers reliability test system (IEEE RTS), the modified IEEE RTS and the Saskatchewan Power Corporation in Canada. The results have shown that the reliability indices obtained using the proposed method correspond closely with those obtained using Monte Carlo simulation with less computation burden.
Probabilistic undervoltage load shedding using point estimate method
Authors: Kaffashan Iman , Amraee Turaj
Published: August 2015

Undervoltage load shedding (UVLS) is executed as a last resort to avoid voltage instability in critical situations. In this study, a robust UVLS scheme based on the point estimate method (PEM) is developed taking load uncertainties into consideration. The utilised PEM converts the continuous probability distribution functions (PDFs) of load uncertainty to discrete statistical moments. The extracted moments could represent the behaviours of original continuous PDFs. The proposed stochastic UVLS strategy is expressed as a non‐linear programming problem, which is optimised using sequential quadratic programming technique. The fulfilment of the suggested scheme is compared with Monte Carlo simulation technique for two IEEE 14‐bus and IEEE 118‐bus test grids.
Signal coordination scheme based on traffic emission
Authors: Ji Yanjie , Hu Bo , Hill Graeme , Guo Weihong , Blythe Phil , Gao Liangpeng
Published: August 2015

This study presents a new optimal signal coordination scheme with an emphasis on emission reduction as a result of minimised passenger delay. By analysing the limitation of the algebraic method, a new algorithm using arrival–departure curves was proposed. A microscopic emission simulation platform based on VISSIM (a microscopic multi‐modal traffic flow simulation model) and comprehensive modal emission model (CMEM) was established to estimate traffic emission reduction. A multi‐objective genetic algorithm was used to find Pareto solutions that simultaneously reduce both passenger delay and vehicle emissions. Using the real‐world traffic data collected in Changzhou city, an example of the signal coordination scheme was developed and its impact on emissions was simulated in the VISSIM‐CMEM platform. The simulation results show that the proposed scheme achieved an average emission reduction of 28.8% on public transport vehicles and 18.7% on all vehicles over existing signal schemes.
Systematic procedure to avoid unintended polarity mismatch in the cascade connection of multiport devices with symmetric feeding lines
Authors: Belenguer Angel , Lucas Borja Alejandro , Diaz Caballero Elena , Esteban Hector , Boria Vicente E.
Published: August 2015

The traditional cascading of generalised scattering matrices (GSMs) assumes that the modal sets at the connected ports of a cascaded network are strictly equal. This implies a careful selection of the modal polarities, or the reference systems, of every port. Usually, the connection scheme of every device is known a priori. Then, the individual GSMs are pre‐processed, or auxiliary devices, which correct possible modal mismatches at the ports, are included in appropriate positions among the cascade, so that the traditional cascading‐by‐pairs approach can be directly applied. This scheme clearly complicates the reutilisation of previously calculated GSMs, and mixes the cascading with the solution of the individual building blocks. In this study, a systematic procedure is proposed to define the polarity of the modes at the ports of a device fed with transmission lines or waveguides showing a single or double symmetry. The modified expressions to calculate the scattering parameters of the cascade of two multiport devices, incorporating the regular modal corrections to apply when this criterion is used to define the modal polarity at the ports, is also presented in this study. This strategy is more convenient from the point of view of programming, less error‐prone and easier to implement.
Common‐mode suppression for balanced bandpass filters in multilayer liquid crystal polymer technology
Authors: Fernández‐Prieto Armando , Qian Shilong , Hong Jiasheng , Martel Jesus , Medina Francisco , Mesa Francisco , Naqui Jordi , Martín Ferran
Published: August 2015

A new multilayer differential transmission line for common‐mode suppression fabricated using an organic liquid crystal polymer multilayer substrate is proposed and analysed. The structure consists of a pair of parallel strip lines printed on the top layer of the substrate that are capacitively coupled to conductor patches periodically etched in an intermediate interface. These patches are symmetrically connected to a solid ground plane by means of short‐circuited high‐impedance microstrip line sections and metalised via holes. The differential signal supported by the coupled strips is not significantly affected by the presence of the middle layer layout, whereas the common‐mode signal propagation is strongly suppressed within a certain frequency band. When this structure is cascaded with a simple differential bandpass filter exhibiting poor common mode rejection, a good common mode response is achieved within the unperturbed differential passband. The measurements confirm a significant enhancement of common‐mode rejection thanks to the use of the proposed differential lines.