Search

Maintaining proper operation of adaptive protection schemes is one of the main challenges that must be considered for smart grid deployment. The use of reliable cyber detection and protection systems boosts the preparedness potential of the network as required by National Infrastructure Protection Plans (NIPPS). In an effort to enhance grid cyber-physical resilience, this paper proposes a tool to enable attack detection in protective relays to tackle the problem of compromising their online settings by cyber attackers. Implementing the tool first involves an offline phase in which Monte Carlo simulation is used to generate a training dataset. Using rough set classification, a set of If-Then rules is obtained for each relay and loaded to the relays at the initialization stage. The second phase occurs during online operation, with each updated setting checked by the corresponding relay's built-in tool to determine whether the settings received are genuine or compromised. A test dataset was generated to assess tool performance using the modified IEEE 34-bus test feeder. Several assessment measures have been used for performance evaluation and their results demonstrate the tool's superior ability to classify settings efficiently using physical properties only. [ABSTRACT FROM AUTHOR]

This paper proposes a two-stage energy management scheme (EMS) for AC–DC hybrid smart distribution systems (DSs). The proposed EMS is formulated as a multi-objective optimization problem to minimize the DS operation costs and energy losses. The proposed EMS is achieved in two stages. In the first stage, a network reconfiguration algorithm determines the optimal day-ahead reconfiguration schedule for a hybrid DS. In the second stage, a real-time optimal power flow algorithm determines the real-time operational schedule of the energy resources. This paper also introduces a new linearized power flow model for AC–DC hybrid DSs. This new model facilitates the formulation of the first-stage algorithm as a mixed-integer linear programming problem and the formulation of the second-stage algorithm as a linear programming problem. The proposed two-stage EMS was tested on a case study of a hybrid DS that included different types of loads and distributed generators. The results demonstrate the efficacy of the proposed EMS: the optimal day-ahead reconfiguration schedule was successfully obtained in the first stage, and the proper and optimal real-time operation was achieved in the second stage. [ABSTRACT FROM AUTHOR]

The deployment of smart grids has facilitated the integration of a variety of investor assets into power distribution systems, giving rise to the consequent necessity for positive and active interaction between those investors and local distribution companies (LDCs). This paper proposes a novel incentive-based distribution system expansion planning model that enables an LDC and distributed generation (DG) investors to work in a collaborative way for their mutual benefit. Using the proposed model, the LDC would establish a bus-wise incentive program based on long-term contracts, which would encourage DG investors to integrate their projects at specific system buses that would benefit both parties. The model guarantees that the LDC will incur minimum expansion and operation costs while concurrently ensuring the feasibility of DG investors’ projects. To derive appropriate incentives for each project, the model enforces several economic metrics including internal rate of return, profit investment ratio, and discounted payback period. All investment plans committed to by the LDC and the DG investors for the full extent of the planning period are then coordinated accordingly. Several linearization approaches are applied to convert the proposed model into an MILP model. The intermittent nature of both system demand and wind- and PV-based DG output power is handled probabilistically, and a number of DG technologies are taken into account. Case study results have demonstrated the value of the proposed model. [ABSTRACT FROM AUTHOR]

This article presents a new approach to enhance the capabilities of flywheel energy storage systems to enable increasing the integration of small-scale photovoltaic distributed generation units in distribution systems. The storage capabilities of the flywheel energy storage systems are utilized to suppress the system voltage disturbances caused by the intermittent output power of the photovoltaic distributed generation sources in distribution systems. A dynamic model of the flywheel energy storage systems is presented. The flywheel energy storage systems model is simulated in a practical residential distribution network with small-scale photovoltaic distributed generation sources using PSCAD/EMTDC. The performance of the system is studied before and after installing the flywheel energy storage systems. The simulation results show that utilizing the flywheel energy storage systems technology in distribution systems with installed photovoltaic distributed generation sources can effectively reduce the frequent operation of the system automatic voltage regulators and increase the overall utilized energy of the installed photovoltaic distributed generation sources. [ABSTRACT FROM AUTHOR]

An approach to link maintenance and replacement decisions is presented in this paper. This approach proposes a methodical decision-making system to determine the optimal time to replace equipment. It essentially investigates the cost-effectiveness of replacing the equipment both before and after the lifetime is extended by maintenance. To properly investigate the effect of maintenance, maintenance activities should first be scheduled effectively. Therefore, this approach introduces a maintenance strategy based on reliability-centered maintenance (RCM) concept and genetic algorithm (GA) to optimally schedule maintenance activities. Two replacement studies are conducted: with and without the effect of maintenance. A comparison between replacement studies is discussed in the proposed approach. The proposed approach is applied to one of the most critical pieces of equipment in power systems: power transformer. [ABSTRACT FROM AUTHOR]

This paper focuses on extracting and analyzing different spectral features from transrectal ultrasound (TRUS) images for prostate cancer recognition. First, the information about the images' frequency domain features and spatial domain features are combined using a Gabor filter and then integrated with the expert radiologist's information to identify the highly suspicious regions of interest (ROIs). The next stage of the proposed algorithm is to scan each identified region in order to generate the corresponding 1-D signal that represents each region. For each ROI, possible spectral feature sets are constructed using different new geometrical features extracted from the power spectrum density (PSD) of each region's signal. Next, a classifier-based algorithm for feature selection using particle swarm optimization (PSO) is adopted and used to select the optimal feature subset from the constructed feature sets. A new spectral feature set for the TRUS images using estimation of signal parameters via rotational invariance technique (ESPRIT) is also constructed, and its ability to represent tissue texture is compared to the PSD-based spectral feature sets using the support vector machines (SVMs) classifier. The accuracy obtained ranges from 72.2% to 94.4%, with the best accuracy achieved by the ESPRIT feature set. [ABSTRACT FROM AUTHOR]

This paper introduces a novel method for the mitigation of the voltage sag and voltage flicker by using Kalman filter and its derivatives (adaptive, and extended). The Kalman filter is used as a tool to extract both the instantaneous envelope of the voltage sags, and to extract the Instantaneous Flicker Level (IFL) of the voltage flicker. Also, this paper demonstrates the advantages of using the Kalman filter instead of the existing tools for tracking and extracting voltage disturbances. Digital simulation results are presented to illustrate the mitigation of unbalanced voltage sags, and the compensation of the cyclic and noncyclic voltage flicker by employing the proposed algorithm. [ABSTRACT FROM PUBLISHER]

This paper presents a generalized control algorithm for voltage disturbance extraction and mitigation. The proposed mitigating device is the dynamic voltage restorer (DVR). A DVR is commonly used to mitigate the voltage sags. In this paper the proposed DVR can compensate the voltage unbalance and mitigate voltage harmonics in the time of normal operation as well as performs its basic function during the fault condition. The suggested control algorithm employs an adaptive perceptron to effectively and adaptively track and extract the most common voltage harmonics, voltage unbalance (which include negative and zero sequence voltage drops), and different types of voltage sags, which include balanced and unbalanced voltage sags. Digital simulation results are obtained using PSCADIEMTDC to verify the effectiveness of the proposed control algorithm. Experimental results are demonstrated to prove the practicality of the mitigating device. [ABSTRACT FROM AUTHOR]

There has been a growing interest in image fusion technologies, but how to objectively evaluate the quality of fused images has not been fully understood. Here, we propose a method for objective quality assessment of multiexposure multifocus image fusion based on the evaluation of three key factors of fused image quality: 1) contrast preservation; 2) sharpness; and 3) structure preservation. Subjective experiments are conducted to create an image fusion database, based on which, performance evaluation shows that the proposed fusion quality index correlates well with subjective scores, and gives a significant improvement over the existing fusion quality measures. [ABSTRACT FROM AUTHOR]

This paper develops a new control strategy for voltage source converter (VSC) based multi-terminal high voltage dc (MT-HVDC) grids for enhancing the mutual frequency support between MT-HVDC interconnected asynchronous ac systems. The existing droop control structure of VSCs is augmented with an additional feedback voltage-based loop that generates a voltage shifting term to be added to the original dc voltage reference. The addition of this integrator-based controller nullifies the difference between voltage errors seen at adjacent converter stations. This action helps to overcome inaccuracies in the mutual frequency support caused by the uneven voltages across a dc system. The proposed strategy uses only local variables for the continuous-time control; thus, it does not rely on a high-bandwidth communication network, and its performance is not affected by the change of ac systems’ parameters. Modal analysis is carried out to investigate the stability of the proposed controller. Finally, comprehensive simulation studies are used to verify the proposed strategy’s performance and compare it with recently reported alternative controllers. [ABSTRACT FROM AUTHOR]

The recent deployment of distributed generation has led to a revolution in the use of distribution systems and the emergence of “smart grid” concepts. Smart grids are intended primarily as a means of facilitating the integration of renewable energy sources and of achieving greater system reliability and efficiency. Energy storage systems (ESSs) offer a number of benefits that can help utilities move toward those goals. One of those benefits is the capacity to improve the utilization of network infrastructure by means of proper load management. This paper proposes a methodology for allocating ESSs in distribution systems in order to defer system upgrades, minimize system losses, and take advantage of the arbitrage benefit. The cost and arbitrage benefit of energy storage installation are optimized with respect to system upgrade and energy losses costs. The primary goal of this research is to determine the optimal size and location of storage units to be installed, in addition to their optimal operation, so that total system costs are minimized, while system benefits are maximized. In this paper, a probabilistic load model is adopted instead of utilizing time-series based models, which provide an optimal solution that is valid only for the time-series pattern that is applied. [ABSTRACT FROM PUBLISHER]

Recent deployment of distributed generation has led to a revolution in distribution systems and the emergence of “smart grid” concepts. The smart grid mainly intends to facilitate integration of renewable energy sources and to achieve higher system reliability and efficiency. Different distributed generation types found in modern distribution systems can be classified into two main categories: intermittent- and dispatchable-based distributed generation; the latter has a unique capability of enabling successful islanding operation, thus improving system reliability. This article proposes a methodology for allocating dispatchable distributed generation units in distribution systems to economically improve system reliability. Distributed generation installation and operation costs are to be optimized against the reliability value, expressed as customers’ “willingness to pay” (WTP) to avoid power interruptions. Therefore, the main goal of this research work is to determine the optimal combination between distributed generation units to be installed and loads to be shed during all possible contingencies. A probabilistic load model is adopted to determine the optimal size of allocated distributed generation units. [ABSTRACT FROM AUTHOR]

The increasing interest in smart home technologies has created a need for a comprehensive literature survey. This article reviews the goals of a smart home energy management system, along with related definitions, applications, and information about the manufacturing of its components. The challenges associated with smart home energy management systems and possible solutions are examined, and the energy factors that contribute to a customer's electricity bill are discussed. A number of price schemes and the load models needed for solving related scheduling optimization problems are also presented, including a review of the literature related to energy management system scheduling with respect to its control, automation, and communication. [ABSTRACT FROM PUBLISHER]

This paper presents a novel probabilistic distribution load flow (PDLF) algorithm to study the effect of connecting a wind turbine (WT) to a distribution system. This probabilistic approach is used to capture the stochastic behavior of the generation of WTs. Three different models of WTs are developed to be embedded in the PDLF. Consequently, a probabilistic approach to evaluate the impact of wind penetration into distribution systems is developed. Futhermore, the effect of WT penetration on feeder losses, voltage profile and substation powers is presented. [ABSTRACT FROM PUBLISHER]

Analyzing the impacts of large on-grid photovoltaic (PV) systems on the performance of the electric network is an essential task prior to the installation of these systems. To quantify these impacts, a method based on chronological simulations can be used. The main advantage of this method is its ability to provide information about the impacts of the fluctuation of the power generated from the PV systems. However, this method requires performing extensive analysis and simulations, making it impractical for utility studies, especially if long historical data with subhourly time resolution is used. In this paper, a new method that utilizes the data efficiently while preserving the temporal information of the generated PV power is proposed. The method takes advantage of the clustering techniques to group together segments of the output PV power having similar features. Hence, a representative segment for each group can be chosen and used in the analysis and simulations. This representative segment can provide information about the expected performance of other segments of the group. The validity and usefulness of the proposed method are demonstrated by identifying the suitable size and site of a large PV system. [ABSTRACT FROM PUBLISHER]

In this paper, a new method is proposed for the control of voltage regulators that enables the regulation of multiple feeders having diversified loads using only one regulator. The selection of the tap position of the regulator is chosen based on the solution of an integer linear optimization problem. The main advantage of the method is that it has a closed-form solution for the optimal tap; a merit which is very valuable in real-time operation. The constraints for having the voltage of the regulating points within the range of permissible values were ensured. Also, the necessary condition for feasible solutions was examined. A simulation study was carried out to validate the proposed method. [ABSTRACT FROM PUBLISHER]

The non-detection zone is a concept used to evaluate anti-islanding detection methods. The non-detection zone is defined as the loading condition for which an islanding detection method would fail to operate in a timely manner, and it is represented in terms of the load parameters. This article proposes a new three-dimensional non-detection zone representation for quantifying the effectiveness of frequency drift islanding detection methods. The proposed non-detection zone model is represented in terms of active and reactive power mismatch and load quality factor. Various two-dimensional non-detection zone models proposed in the literature are analyzed to highlight the limitations of each model. The analysis is conducted on three different islanding detection methods, including over-frequency protection/under frequency protection, active frequency drift, and Sandia frequency shift methods. The analytical model of the two dimensional non-detection zone representations is presented, and each model is validated through simulation results. The results show that representing the non-detection zone in a two-dimensional space is not sufficient to accurately determine all non-detectable loading conditions. The proposed three-dimensional non-detection zone representation is capable of modeling all possible loading conditions and provides a better approach for assessing islanding detection methods with resistance-inductance-capacitance loads. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive grid-voltage sensor- less control scheme for inverter-based distributed generation units based on an adaptive grid-interfacing model. An adaptive grid- interfacing model is proposed to estimate, in real time, the inter- facing parameters seen by the inverter and the grid-voltage vector simultaneously. A reliable solution to the present nonlinear estimation problem is presented by combining a grid-voltage estimator with an interfacing parameter estimator in a parallel structure. Both estimators adjust the grid-interfacing model in a manner that minimizes the current error between the grid model and the actual current dynamics, which acts as a reference model. The estimated quantities are utilized within the inner high-bandwidth current control loop and the outer power controller to realize an adaptive grid-voltage sensorless interfacing scheme. Theoretical analysis and simulation results are provided to demonstrate the validity and usefulness of the proposed interfacing scheme. [ABSTRACT FROM AUTHOR]

This article investigates the impacts of proper modeling of the wake effects and wind speed delays, between different wind turbines' rows, on the dynamic performance accuracy of the wind farms models. Three different modeling scenarios were compared to highlight the impacts of wake effects and wind speed time-delay models. In the first scenario, wind wake effect and time delay are ignored. Consequently, all wind turbines are assumed subjected to the same wind speed profile. The second scenario considers the wind wake effect, and it was modeled by reducing the incident wind speed values by 0.5 m/s from one row to the next row facing the wind. The last scenario, the proposed model, used the wind wake effect model developed for wind turbines micrositting applications and considered the effect of the delay time between the wind speed profiles incident on the different wind turbines' rows. [ABSTRACT FROM AUTHOR]

The dynamic voltage restorer (DVR) is an effective solution for power quality problems related to voltage. One of the most common control algorithms that are used for the DVR is the symmetrical components method. This paper introduces a new approach for the estimation of the symmetrical components. A modified delta rule structure is proposed and developed which is capable of dealing with multioutput systems for the parameters estimation. An innovative feedforward control, based on the new delta rule structure, is proposed for the series compensator not only to compensate for the zero and negative sequence components, but also to regulate the positive sequence component at the nominal load voltage. One advantage of the proposed control scheme is its insensitivity to parameter variation, a necessity for the series compensator. Experimental verification of the new delta rule algorithm, by using a DSP, is provided. Numerical simulations of the proposed control strategy are conducted to show the robustness, high accuracy, and fast dynamic performance of this novel control algorithm. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic models for adjustable speed drive (ASD) and distribution-static compensator (DSTATCOM) are presented. An eigen domain approach to the transient response investigation is formulated by means of dqo variable in synchronously rotating reference frame to study the dynamic interactions between ASDs and DSTATCOM. Two inverter topologies of ASD, current source inverter and voltage source inverter, are included in the study as well as two control techniques of the DSTATCOM, namely voltage and current control. The study shows that the voltage control DSTATCOM improves the stability boundaries of the ASD utilizing either current or voltage source inverters, while the current control DSTATCOM has minor influence. In addition, the system dynamics show less sensitivity to the dc link capacitance for the voltage control DSTATCOM. These results are supported by analytical study of the characteristic equation of both the voltage and the current control DSTATCOM. [ABSTRACT FROM AUTHOR]

In this paper, a novel algorithm, based on calculating the energy operator of a sinusoidal waveform to track the voltage flicker, is presented. The mathematical derivation of the proposed algorithm different circuit designs required to realize it are described. The proposed algorithm is fast and robust and requires only a few samples to calculate the energy. The simulation and the experimental results prove that the new algorithm can successfully track the envelope. There are no spikes in the envelope even when the voltage signal is suddenly changed at its peak value. [ABSTRACT FROM AUTHOR]

Distributed measurement architecture, due to its efficiency, is used to monitor the power quality in the electric systems. This paper introduces a novel algorithm to determine the optimum allocations of power quality monitors to reduce the cost of the distributed monitoring system taking into account the data redundancy. The optimization problem is formulated as a covering and packing one which can be manipulated by integer linear programm algorithms. The appropriate constraints are deduced by the electrical circuit topology independent of the load parameters. In addition, the problem is adopted to a general form which can be implemented by any optimization package. The proposed algorithm is applied to five different systems for validation. Then, the results are discussed in terms of the cost and data redundancy. [ABSTRACT FROM AUTHOR]

Background: In this paper a novel method for prostate segmentation in transrectal ultrasound images is presented. Methods: A segmentation procedure consisting of four main stages is proposed. In the first stage, a locally adaptive contrast enhancement method is used to generate a well-contrasted image. In the second stage, this enhanced image is thresholded to extract an area containing the prostate (or large portions of it). Morphological operators are then applied to obtain a point inside of this area. Afterwards, a Kalman estimator is employed to distinguish the boundary from irrelevant parts (usually caused by shadow) and generate a coarsely segmented version of the prostate. In the third stage, dilation and erosion operators are applied to extract outer and inner boundaries from the coarsely estimated version. Consequently, fuzzy membership functions describing regional and gray-level information are employed to selectively enhance the contrast within the prostate region. In the last stage, the prostate boundary is extracted using strong edges obtained from selectively enhanced image and information from the vicinity of the coarse estimation. Results: A total average similarity of 98.76%(∞ 0.68) with gold standards was achieved. Conclusion: The proposed approach represents a robust and accurate approach to prostate segmentation. [ABSTRACT FROM AUTHOR]

Envelope tracking has many important applications in electrical distribution systems for either flicker meters or flicker compensators. This paper presents a novel control technique for flicker mitigation. This technique is based on the instantaneous tracking of the measured voltage envelope. The ADAptive LINEar neuron (ADALINE) algorithm, and the Recursive Least Square (RLS) algorithm are introduced for the flicker envelope tracking. The ADALINE algorithm is characterized by a light computational demand, unlike that of existing techniques; the RLS algorithm outperforms the ADALINE algorithm by its fast con- vergence and robust tracking performance. Both the ADALINE and the RLS algorithms give accurate results even under rapid dynamic changes. The paper investigates the effects of different parameters on the performance of the ADALINE algorithm and that of the RLS algorithm. Extensive simulations of the proposed flicker tracking algorithms are conducted to evaluate their performance for the tracking and mitigation of voltage flicker. The ADALINE and the RLS algorithms are examined by tracking and mitigating the flicker produced by a resistance welder and an arc furnace in a simple distribution system simulated in the PSCAD/EMTDC package. [ABSTRACT FROM AUTHOR]

Distributed Generation (DG) exists in distribution systems and is installed by either the utility or the customers. This paper proposes a novel utilization of the existing DG nonlinear interface not only to control the active power flow, but also to mitigate unbalance and harmonics, and to manage the reactive power of the system. The proposed Flexible Distributed Generation (FDG) is similar in functionality to FACTS, but works at the distribution level. Moreover, a novel ADAptive LINEar neuron (ADALINE) structure is presented. The new structure is applied to multi output (MO) systems for parameter tracking/estimation, and is called MO-ADALINE. It is dedicated to symmetrical components estimation. The control loop combines a Fuzzy Logic Controller (FLC) for voltage regulation, and a processing unit-based ADALINE to deal with unbalance, harmonics and reactive power compensation. One advantage of the proposed control system is its insensitivity to parameter variation, a necessity for distribution system applications. Simulations of the suggested FDG based control algorithm are conducted to evaluate the performance of the novel system. [ABSTRACT FROM AUTHOR]

Symmetrical components as well as harmonic tracking are of great importance in many applications in power systems such as power quality and protection. This paper introduces a novel Adaptive linear combiner (ADALINE) structure for symmetrical components estimation. This structure is capable of dealing with multi-output systems for parameter tracking/estimation rather than the existing ADALINE, which deals only with single output systems. As the new topology deals with Multi-Output systems, it is called MO-ADALINE. Moreover, the paper presents a new processing unit, which can estimate sym- metrical and harmonic components from the measured current signals. The advantages of this proposed unit are its independence of the voltage waveform and its ability to give information about the reactive component of the resolved current Simulation results are given to validate the proposed algorithms. [ABSTRACT FROM AUTHOR]

The DC microgrid (DC MG) concept enables the hosting of DC-type renewable energy resources. However, their intermittent nature means that a high penetration of renewables can jeopardize supply adequacy and voltage provision during islanding. The work presented in this paper was therefore directed at developing a probabilistic graphical approach based on Bayesian networks (BNs) for the reliability analysis of renewables-dominated DC MGs. The proposed BN model incorporates a family of novel reliability indices for quantifying the impact of a high penetration of renewables on MG reliability, including loss of renewable power supply, rise in voltage, and reversal of power flow. The model is supported by a newly formulated fast and accurate linearized power flow algorithm for probability calculations. The accuracy of the BN model has been verified against a Monte-Carlo simulation (MCS). The effective application of the new BN model for reasoning and impact assessment reveals that a high penetration of renewables affects reliability indices differently. Case study results suggest that the proposed BN model shows promise as a valuable tool for the reliability analysis of renewables-dominated MGs that feature islanding capability. [ABSTRACT FROM AUTHOR]

Distributed Generation (DG) is used widely in the modern distribution systems. This paper proposes a novel functionality of the interface between DG and the utility network to mitigate the voltage flicker and to regulate the voltage at the Point of Common Coupling (PCC) in addition to its main function of controlling the power flow. A new control algorithm for the DG interface based on the Hilbert transform (HT) is presented. The HT is employed as an effective technique for tracking the voltage flicker levels in distribution systems. The mathematical simplicity of the proposed technique, compared with the commonly used algorithms in the literature, renders them competitive candidates for the on-line tracking of voltage flicker. The accurate tracking of the HT facilitates its implementation for the control of flicker mitigation devices. Simulation results are provided to verify the tracking capabilities of the HT and to evaluate the performance of the proposed DG interface for multifunction operation. [ABSTRACT FROM PUBLISHER]

An introduction to a special section of the journal, which is devoted to distributed generation and microgrids, is presented.