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The increasing trend of energy generation and management systems towards decentralized structures such as using renewable energy resources makes it necessary to use digital and smart platforms for exchanging information and even conducting financial transactions in a decentralized manner, known as the peer‐to‐peer model. The decentralized transaction verification of cryptocurrencies makes it possible to use these encrypted currencies and decentralized blockchain networks in energy management systems and carry out financial transactions related to carbon trading. Carbon and other greenhouse gas (GHG) emission trading systems reduce the competitiveness of fossil fuel projects in the market and accelerate investment in low‐carbon energy sources such as wind and photovoltaic power generation units. This market mechanism allows large entities such as countries and companies that emit GHGs into the atmosphere to buy and sell these gases. This paper reviews the blockchain solutions developed for carbon markets. Studies related to the design of smart contracts in the platform of blockchain are investigated. Special cryptocurrencies that are used in the field of green energy transactions and carbon trading are introduced. In addition, the application of artificial intelligence and game theory in energy trading is stated. The study of different blockchain frameworks for carbon trading shows that the use of decentralized platforms in carbon trading can have a significant impact on the trend towards low‐carbon measures and achieving the goals of the Kyoto Treaty, increasing the value of green cryptocurrencies and the volume of transactions. These technologies offer a promising avenue for creating a more decentralized, efficient, and environmentally conscious energy ecosystem. [ABSTRACT FROM AUTHOR]

The reliable performance of the shipboard power system (SPS) is essential for the safe and efficient operation of marine vessels. SPSs are subject to various types of electrical faults that can cause equipment failure, system downtime, and even catastrophic events. One effective way to provide redundancy and fault tolerance in the event of a fault or failure is through the use of zonal configuration. However, the protection of such systems is a challenging task due to their complex topology and the potential for multiple sources of fault. Therefore, it is imperative to protect the SPS with zonal configuration from various types of fault to ensure its continuous operation. This article presents a comprehensive coordinated protection strategy for a hybrid AC/DC SPS with the zonal configuration by using the available protective equipment. The proposed strategy consists of fault current limiting, grounding, fault detection, and faulty section isolation, and provides both primary and backup protections for all SPS equipment, including generator, busbar, line, input and output feeders, loads, propulsion motors, and DC system. Also, it does not require a comprehensive communication infrastructure and training dataset. The selective and reliable performance of the proposed protection strategy is verified through several case studies under various fault scenarios in the ETAP environment. The article provides valuable insights into the selection and implementation of appropriate protection measures for the SPS with ring configuration which are useful for the designers, operators, and maintenance personnel, improving the reliability and safety of these critical and autonomous systems. [ABSTRACT FROM AUTHOR]

The protection of high-voltage direct current (HVDC) grids is a crucial aspect in ensuring the reliable and efficient operation of modern electrical energy transmission systems. The high amplitude and rate of change of fault current as well as the presence of multiple paths for fault current contribution of voltage-sourced converters make the protection of HVDC grids with meshed configuration a challenging task. This paper develops a protection scheme for these grids that has three modules: (i) low-resistance fault detection module based on the amplitude of the voltage across the current limiting reactor (CLR) at the line terminal, (ii) high-resistance fault detection module based on quantifying the severity of the CLR voltage signal change, and (iii) fault classification module. No need for communication links increases the reliability and operating speed of the proposed scheme. Moreover, severity measurement based protection increases the sensitivity of fault detection. The ability to faulty line identification in the meshed configuration verifies the selectivity of the proposed scheme. In addition, its robustness is verified due to low susceptibility to measurement noise, DCCB operation, AC fault, various CLR sizes, and power reversal. Several pole-to-pole and pole-to-ground fault scenarios with various fault resistances at different fault locations are conducted to verify the reliable performance of the proposed HVDC protection scheme. • The paper develops a single-end protection scheme for VSC-HVDC grids. • It is based on processing the voltage across current limiting reactors (CLRs). • It can detect both severe and high-resistance fault conditions. • It is robust to the measurement noise, DCCB operation, AC fault, various CLR sizes, and power reversal. • It does not require a high sampling rate. [ABSTRACT FROM AUTHOR]

The high‐surety power supply systems are gaining great attention to enhance the reliability of uninterruptable power supplies. A high‐resistance fault along a high‐surety power supply feeder results in a low fault current, making the conventional high‐surety power supply protection strategy ineffective. To address this problem, this paper develops a directional fault protection strategy for high‐resistance fault detection and faulty feeder identification. Using the intelligent electronic device, the feeder current is sampled and normalised. Then, the fault‐imposed component of the current signal is calculated. This component is added to the input of the forced Helmholtz oscillator to increase the sensitivity of the proposed protection scheme for the detection of high‐resistance faults. The output of the forced Helmholtz oscillator equation is adopted as the fault detection criterion because it is infinity for reverse faults while it is lower than 1 for forward faults, facilitating the fault detection. The developed strategy is local and can detect and classify both pole‐to‐ground and pole‐to‐pole high‐resistance faults. Also, it is effective for both unidirectional and bidirectional converters. The merits of the proposed protection strategy are demonstrated through several fault scenarios using a ±375 V high‐surety power supply system. [ABSTRACT FROM AUTHOR]

Low voltage DC microgrids have been gaining great attention for the integration of renewable energy source and energy storage units, and electronic loads. DC microgrids are commonly controlled using the hierarchical control strategy (HCS) to provide flexible operation in both grid-connected and islanded modes. The HCS relies on proportional-integral (PI) controllers and employs the droop control strategy. To improve the fault ride-through of HCS based extra low voltage DC microgrids, this paper proposes a simple, accurate, and cost-effective current limiting strategy. The proposed control system based scheme modulates the current reference of the primary control level of HCS during an overcurrent condition using the smooth set point automatic adjustment with correction enabled technique. It properly protects the semiconductor switches of interface voltage-sourced DC-DC converters by accurate limiting their inductor currents. The main advantage of the proposed scheme is that it is implemented in the available PI controller based primary control level of the HCS. Also, it does not require the converter and load data. Several case studies performed in MATLAB/Simulink environment are presented to demonstrate the superior ability of this scheme for limiting fault current in different scenarios compared to conventional current limiters. [ABSTRACT FROM AUTHOR]

A high‐impedance fault (HIF) is mostly associated with the arcing phenomenon, and its main features are low current, randomness, non‐linearity, and asymmetry. The low fault current of an HIF is a major challenge for overcurrent‐based protection system of distribution networks. Power loss, potential fire hazard, and electric shock are consequences of an undetected HIF. This study presents a time‐domain HIF detection algorithm based on monitoring the substation current waveform. Using the Kullback–Leibler divergence similarity measure, the non‐linearity, and asymmetry features of two subsequent half cycles of the current waveform are quantified as the HIF detection criterion. A time duration‐based criterion is also used to distinguish HIFs from the load, capacitor, feeder, and distributed energy resource switchings and the voltage sag and swell events. The proposed scheme satisfactorily works in the presence of non‐linear loads. Also, it does not require the training data set, transformation, and calculation of harmonic/sequence components. Extensive time‐domain simulation case studies using the IEEE 13 and 34 node test feeders demonstrate the merits of the proposed HIF detection algorithm. [ABSTRACT FROM AUTHOR]

One of the main challenges for the conventional protection system of a photovoltaic (PV) array is the occurrence of light fault conditions including a low location mismatch fault, a fault with a high fault path resistance, and a fault under low solar irradiance because the fault current increment is not enough for triggering current-based protective devices. The operation of the maximum power point tracking system and utilizing blocking diodes may also result in a light fault condition. An undetected fault condition causes a potential fire hazard and energy loss. This paper proposes a waveshape based statistical fault detection algorithm for light fault detection. The proposed algorithm quantifies the waveshape tailedness of superimposed PV array power by the kurtosis function. The proposed algorithm is able to discriminate the light fault condition from severe partial shading and is also effective for open-circuit faults. In addition to no need for additional sensors, it does not require a training dataset and prior information about the PV array. The merits of the proposed algorithm are corroborated through several case studies on a simulation model of a test PV array considering the parameter uncertainty and the presence of noise in the signals. [ABSTRACT FROM AUTHOR]

Highlights • Detection of low-current fault conditions for PV systems is presented. • A disturbance within PV array is detected by monitoring super-imposed array power. • A wave-shape based feature distinguishes short-circuit faults from partial shading. • The proposed scheme does not need for prior information about the PV array. • The proposed scheme is effective for both grid-connected and islanded PV systems. Abstract With the high penetration of photovoltaic (PV) systems, fault detection scheme is of great importance for the distribution network operation. The low fault current makes the detection of low-irradiance, low-mismatch, and high-impedance faults a challenging task, especially for PV systems with active maximum power point tracking algorithm and equipped with blocking diodes. Energy loss and potential fire hazard are some consequences of an undetected fault within the PV array. This paper presents a DC-side fault detection scheme for PV systems that consists of two stages. Using the amplitude of the normalized super-imposed component of PV array power, the first stage detects a disturbance while the second stage distinguishes a fault condition from partial shading using a wave-shape based feature. The proposed scheme can properly detect string-to-string, string-to-ground, and open-circuit faults under different fault conditions without the need for the prior information about the PV array and the training data set and is effective for both grid-connected and islanded PV systems. The reliable performance of the proposed fault detection scheme is assessed on the simulation models of two PV arrays. [ABSTRACT FROM AUTHOR]

The ability of riding through the grid disturbances can increase the integration of microgrids into the distribution system. Consequently, a grid-connected microgrid should provide ancillary services such as low voltage ride-through (LVRT) capability and reactive power support to sustain the power system operations during abnormal grid conditions. The objective of this paper is to propose an LVRT scheme that improves the power quality of the entire microgrid. The developed method is implemented as the controller of the interface voltage-sourced converter (VSC) of a distributed energy resource and consists of primary and secondary control levels. The former includes the cascaded voltage and current control loops and the droop controller, while the latter controls the reactive power injection during the balanced/unbalanced voltage sags/swells. The proposed scheme is developed based on the independent control of each phase and does not require calculation of symmetrical components. Moreover, it can be employed in the VSC control systems with various reference frames and is effective for droop-based grid-connected microgrids with both single-phase and three-phase four-wire configurations. The proposed strategy is implemented using the hierarchical control system and preserves the plug and play capability. Several case studies are presented to verify the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

The ability of riding through the grid disturbances can increase the integration of microgrids into the distribution system. Consequently, a grid‐connected microgrid should provide ancillary services such as low voltage ride‐through (LVRT) capability and reactive power support to sustain the power system operations during abnormal grid conditions. The objective of this paper is to propose an LVRT scheme that improves the power quality of the entire microgrid. The developed method is implemented as the controller of the interface voltage‐sourced converter (VSC) of a distributed energy resource and consists of primary and secondary control levels. The former includes the cascaded voltage and current control loops and the droop controller, while the latter controls the reactive power injection during the balanced/unbalanced voltage sags/swells. The proposed scheme is developed based on the independent control of each phase and does not require calculation of symmetrical components. Moreover, it can be employed in the VSC control systems with various reference frames and is effective for droop‐based grid‐connected microgrids with both single‐phase and three‐phase four‐wire configurations. The proposed strategy is implemented using the hierarchical control system and preserves the plug and play capability. Several case studies are presented to verify the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Integrating the self‐healing capability realizes the automated protection of smart distribution systems. This article presents a fault location scheme for low voltage (LV) distribution systems based on the information collected from the smart meters. First, a fault condition is detected and classified by processing the current signal at the secondary side of the distribution transformer by an intelligent electronic device. Then, the faulty feeder and section are determined by calculating the fault‐imposed component of nodal voltages. The reliable performance of the proposed scheme is verified through several case studies using a real semi‐rural distribution system. [ABSTRACT FROM AUTHOR]

In this work, voltage evaluation after power components energization such as transmission line, transformer and shunt reactor is analyzed using artificial neural network (ANN)-based approach. Throughout the initial phase of system restoration, unexpected overvoltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. Such an overvoltage might damage some equipment and delay power system restoration. In the cases of transformer and shunt reactor energization, ANN is trained with the worst case scenario of switching angle and remanent flux which reduce the number of required simulations for training ANN. Moreover, for achieving good generalization capability for developed ANN, equivalent parameters of the network are used as ANN inputs. The simulated results for a partial of 39-bus New England test system show that the proposed technique can estimate the peak values and duration of overvoltages during network switching with good accuracy. [ABSTRACT FROM AUTHOR]

This paper presents an intelligent approach to evaluate switching overvoltages during power equipment energization. Switching action is one of the most important issues in power system restoration schemes. This action may lead to overvoltages that can damage some equipment and delay power system restoration. In this work, transient overvoltages caused by power equipment energization are analyzed and estimated using artificial neural network (ANN)-based approach. Three learning algorithms, delta-bar-delta (DBD), extended delta-bar-delta (EDBD), and directed random search (DRS), were used to train the ANNs. In the cases of transformer and shunt reactor energization, ANNs are trained with the worst case scenario of switching angle and remanent flux which reduce the number of required simulations for training ANN. Also, for achieving good generalization capability for developed ANN, equivalent parameters of the network are used as ANN inputs. The simulated results for a partial of 39-bus New England test system, show that the proposed technique can estimate the peak values and duration of switching overvoltages with good accuracy and EDBD algorithm presents best performance. [ABSTRACT FROM AUTHOR]

Overvoltages caused by switching operation of power system equipments might damage some equipment and delay power system restoration. This paper presents a comparison between transmission line (TL) models for overvoltages study and investigates which TL model is most proper for every case study. Both simulation time and accuracy factors of TL models are considered for selecting best TL model. Various cases of switching of transformer, shunt reactor, capacitor bank, and transmission line are investigated and simulation results for a partial of 39-bus New England test system, show that the proposed TL model evaluation increase accuracy and reduce simulation time (accelerate power system restoration) properly. [ABSTRACT FROM AUTHOR]

This paper proposed an artificial neural network (ANN)-based approach to mitigate harmonic overvoltages during transformer energization. Uncontrolled energization of large power transformers may result in magnetizing inrush current of high amplitude and switching overvoltages. The most effective method for the limitation of the switching overvoltages is controlled switching since the magnitudes of the produced transients are strongly dependent on the closing instants of the switch. We introduce a harmonic index that it's minimum value is corresponding to the best case switching time. Also, in this paper three learning algorithms, delta-bar-delta (DBD), extended delta-bar-delta (EDBD) and directed random search (DRS) were used to train ANNs to estimate the optimum switching instants for real time applications. ANNs training is performed based on equivalent circuit parameters of the network. Thus, trained ANN is applicable to every studied system. To verify the effectiveness of the proposed index and accuracy of the ANN-based approach, two case studies are presented and demonstrated. [ABSTRACT FROM AUTHOR]

The shunt reactors located on both line terminals and substation bus-bars are commonly used on long extra high voltage (EHV) transmission systems for controlling voltage during load variations. In a small power system that appears in an early stage of a black start of a power system, an overvoltage could be caused by core saturation on the energization of a shunt reactor with residual flux. The most effective method for the limitation of the switching overvoltages is controlled switching since the magnitudes of the produced transients are strongly dependent on the closing instants of the switch. A harmonic index has been introduced that it's minimum value is corresponding to the best-case switching time. In addition, in this paper an artificial neural network (ANN) is used to estimate the optimum switching instants for real time applications. ANN is trained with equivalent circuit parameters of the network, so that de-veloped ANN is applicable to every studied system. To verify the effectiveness of the proposed index and accuracy of the ANN-based approach, two case studies are presented and demon-strated. [ABSTRACT FROM AUTHOR]

In this paper an intelligent-based approach is introduced to evaluate harmonic overvoltages during three-phase transformer energization. In a power system that appears in an early stage of a black start of a power system, an overvoltage could be caused by core saturation on the energization of a three-phase transformer with residual flux. Such an overvoltage might damage some equipment and delay power system restoration. A new approach based on worst case determination is proposed to reduce time-domain simulations. Also, an artificial neural network (ANN) has been used to estimate the temporary overvoltages (TOVs) due to three-phase transformer energization. Three learning algorithms, delta-bar-delta (DBD), extended delta-bar-delta (EDBD), and directed random search (DRS), were used to train the ANNs. ANN Training is performed based on equivalent circuit parameters of the network; thus trained ANN is applicable to every studied system. The developed ANN is trained with the worst case of the switching condition and remanent flux, and tested for typical cases. The simulated results for a partial of 39-bus New England test system, show that the proposed technique can estimate the peak values and durations of switching overvoltages with good accuracy and EDBD algorithm presents best performance. [ABSTRACT FROM AUTHOR]

One of the most important issues in power system restoration is overvoltages caused by transformer switching. These overvoltages might damage some equipment and delay power system restoration. This paper presents a radial basis function neural network (RBFNN) to study transformer switching overvoltages. To achieve good generalization capability for developed RBFNN, equivalent parameters of the network are added to RBFNN inputs. The developed RBFNN is trained with the worst-case scenario of switching angle and remanent flux and tested for typical cases. The simulated results for a partial of 39-bus New England test system show that the proposed technique can estimate the peak values and duration of switching overvoltages with good accuracy. [ABSTRACT FROM AUTHOR]

This paper presents an artificial intelligence application to measure switching overvoltages caused by shunt reactor energization by applying analytical rules. In a small power system that appears in an early stage of a black start of a power system, an overvoltage could be caused by core saturation on the energization of a reactor with residual flux. A radial basis function (RBF) neural network has been used to estimate the overvoltages due to reactor energization. Equivalent circuit parameters of network have been used as artificial neural network (ANN) inputs; thus, RBF neural network is applicable to every studied system. The developed ANN is trained with the worst case of the switching angle and remanent flux and tested for typical cases. The simulated results for a partial of 39-bus New England test system show that the proposed technique can measure the peak values and duration of switching overvoltages with good accuracy. [ABSTRACT FROM AUTHOR]

Uncontrolled energization of large power transformers may result in magnetizing inrush current of high amplitude and switching over-voltages. The most effective method for the limitation of the switching over-voltages is controlled switching since the magnitudes of the produced transients are strongly dependent on the closing instants of the switch. We introduce a harmonic index that its minimum value is corresponding to the best-case switching time. Also, this paper presents an Artificial Neural Network (ANN)-based approach to estimate the optimum switching instants for real time applications. In the proposed ANN, second order Levenberg-Marquardt method is used to train the multilayer perceptron. ANN training is performed based on equivalent circuit parameters of the network. Thus, trained ANN is applicable to every studied system. To verify the effectiveness of the proposed index and accuracy of the ANN-based approach, two case studies are presented and demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: In most countries, the main step in the process of power system restoration, following a complete/partial blackout, is energization of primary restorative transmission lines. Artificial neural network (ANN) is employed for performing a nonlinear input–output mapping in this work, in order to estimate the temporary overvoltages (TOVs) due to transmission lines energization. In the proposed methodology, Levenberg–Marquardt second order method is used to train the multilayer perceptron. Proposed ANN is trained with equivalent circuit parameters of the network as input parameters, trained ANN has therefore satisfactory generalization capability. Both single and three-phase line energizations are analyzed. The simulated results for 39-bus New England test system, indicate that the proposed technique can estimate the peak values and duration of switching overvoltages with acceptable accuracy. [Copyright &y& Elsevier]

Despite various advantages of integrating distributed generation (DG) units into distribution networks such as power loss reduction and voltage profile improvement, they may disrupt the performance of the conventional protection system due to bidirectional power flow and change of short‐circuit power. With the development of multi‐agent systems (MASs), intelligent protection schemes have been introduced that operate on the basis of data processing by a central controller. However, the possibility of communication failure and cyber attacks reduce reliability of these protection systems. To address this problem, this paper proposes an intelligent protection scheme that relies on peer‐to‐peer communication between agents in the first layer of the MAS. In the case of communication failure, the agents react to the fault condition by using the available data for similar conditions. The main advantages of the proposed scheme are reduction of number of employed agents by using only relay agents and no need for communicating with higher layers of MAS. Implementation of the proposed scheme in the ETAP simulation model of a 14 bus active distribution network shows that data exchange between relay agents properly modifies the operating time of the relays, resulting in protection coordination between main and backup protections. [ABSTRACT FROM AUTHOR]

Increasing the penetration level of distributed generation (DG) units requires overcoming the technical challenges associated with their integration into the distribution systems, especially protection problems. Change in the current profile of the distribution system due to the presence of DG units disrupts the operation of the conventional fuse saving coordination (FSC) scheme. The first objective of this paper is to provide an overview of the state‐of‐the‐art of FSC schemes in distribution systems with distributed generators that has not been systematically presented yet. In addition to comparing the features of reliability, cost, speed, implementation, calculation burden, and requirements, the impact of presence of distributed generations on the performance of the conventional FSC scheme is investigated in details. The second objective of this paper is to propose an FSC restoration scheme for minimizing the challenges of previous works. Using a quasi‐voltage current term, the proposed scheme modifies the adjustable time coefficient of the recloser in two ways of pro and plus. The former scheme provides an approximate FSC with a simple setting while the latter scheme provides complete coordination at the expense of a more complex setting. No need for voltage measurement makes its implementation practical in available distribution systems. The effective performance of the proposed FSC scheme is verified through extensive simulation studies in the ETAP environment. [ABSTRACT FROM AUTHOR]

The mismatched feeder impedance of the voltage-sourced converter (VSC) units may result in reactive power sharing error in the islanded microgrids. This study presents a reactive power sharing strategy for single-phase inverter-based microgrids that eliminates the circulating currents and reduces the coupling between real and reactive powers. The proposed controller is based on an adaptive complex virtual impedance that aims to equalise the E - Q characteristic output of VSCs. The resistive term regulates the virtual voltage drop using the proposed ΔRv - P droop characteristic, while the inductive one controls the phase angle of VSC current and increases the X/R ratio of the microgrid. The proposed strategy does not require a central controller and knowledge of the microgrid lines and loads data and is applicable for the various microgrid topologies. Furthermore, it employs the unidirectional low bandwidth communication link and is robust against the delay and failure of communication channels. The proposed method is implemented using the conventional droop control scheme and presents the medium plug and play capability. Both simulation and experimental case studies using various microgrid topologies are conducted to demonstrate the merits of the proposed scheme. [ABSTRACT FROM AUTHOR]

The mismatched feeder impedance of the voltage‐sourced converter (VSC) units may result in reactive power sharing error in the islanded microgrids. This study presents a reactive power sharing strategy for single‐phase inverter‐based microgrids that eliminates the circulating currents and reduces the coupling between real and reactive powers. The proposed controller is based on an adaptive complex virtual impedance that aims to equalise the E−Q characteristic output of VSCs. The resistive term regulates the virtual voltage drop using the proposed ΔRv−P droop characteristic, while the inductive one controls the phase angle of VSC current and increases the X/R ratio of the microgrid. The proposed strategy does not require a central controller and knowledge of the microgrid lines and loads data and is applicable for the various microgrid topologies. Furthermore, it employs the unidirectional low bandwidth communication link and is robust against the delay and failure of communication channels. The proposed method is implemented using the conventional droop control scheme and presents the medium plug and play capability. Both simulation and experimental case studies using various microgrid topologies are conducted to demonstrate the merits of the proposed scheme. [ABSTRACT FROM AUTHOR]

The installation of photovoltaic (PV) systems is gaining great attention due to the matured PV technology and the lowered price of PV modules. With an increasing penetration of PV systems, the selectivity of distribution network protection may be affected which results in undesirable de-energisation of loads, damage of network equipment, and reduction of reliability. This study presents a method to preserve the protection coordination considering future PV systems installation with any penetration level and different locations along the distribution feeder. Depending on the accessibility of protection device settings or PV control parameters, the proposed method modifies the existing characteristic curve of overcurrent devices or limits the output current of PV sources, respectively. The proposed strategy does not change the structure of existing distribution network protection system and can also be implemented in the old and non-programmable relays. Meanwhile, it does not need the communication links. The merits of the proposed method are demonstrated through several case studies using the Isfahan distribution network. [ABSTRACT FROM AUTHOR]

The installation of photovoltaic (PV) systems is gaining great attention due to the matured PV technology and the lowered price of PV modules. With an increasing penetration of PV systems, the selectivity of distribution network protection may be affected which results in undesirable de‐energisation of loads, damage of network equipment, and reduction of reliability. This study presents a method to preserve the protection coordination considering future PV systems installation with any penetration level and different locations along the distribution feeder. Depending on the accessibility of protection device settings or PV control parameters, the proposed method modifies the existing characteristic curve of overcurrent devices or limits the output current of PV sources, respectively. The proposed strategy does not change the structure of existing distribution network protection system and can also be implemented in the old and non‐programmable relays. Meanwhile, it does not need the communication links. The merits of the proposed method are demonstrated through several case studies using the Isfahan distribution network. [ABSTRACT FROM AUTHOR]

An important requirement for interconnecting distributed generation is anti-islanding protection. This paper uses the capabilities of two methods, application region (AR) and power imbalance AR, to efficiently adjust frequency-based relays. The proposed method gives a proper simple and nonexpensive solution to the synchronous distributed generation islanding detection problem. It employs the common protection devices: frequency or rate of change of frequency relays. These relays are adjusted in order to satisfy the anti-islanding protection and safe and abnormal frequency variation requirements and also to discriminate between islanding and nonislanding disturbances. The procedure is applied to a real system, which is a portion of the Isfahan Regional Electric Network in Iran, to show the effectiveness of the proposed approach. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, a one-cycle control (OCC)-based approach for wind turbines equipped with doubly fed induction generators (DFIGs) is presented. The OCC is used to control back-to-back converter which includes generator-side converter and grid-side converter. The former is used for regulating generator speed, and the latter is used for controlling reactive power. Also, particle swarm optimization is used to improve the accuracy of parameters of PI controllers. The proposed approach is studied under different conditions, including load change, fault and nonlinear loads. Also, uncertainty of wind speed is considered. Moreover, a comparison between pulse width modulation (PWM)-based and OCC-based controllers is done. The OCC is a non-linear PWM method so its control technique turns a non-linear switch into a linear path. In contrast to the traditional PWM method, OCC control realizes PWM and fast/nonlinear control simultaneously by modulating the slope of the saw-tooth waveform. The simulation results show that accuracy and speed control of DFIG converter by OCC are superior in comparison with conventional control strategies from tracking reference signal and oscillations point of view. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: The high penetration level of photovoltaic (PV) units increases their injected fault current that it may result in fuse‐recloser miscoordination in distribution networks. The conventional coordination techniques are based on shifting the fast operation curve of the recloser below the characteristic curve of the fuse for fuse saving in the case of a temporary fault. However, these techniques save fuse if the slopes of fuse and recloser characteristic curves are same. Also, in the case of the high penetration level of PV systems, the conventional schemes are not effective. To address these problems, this paper proposes two fuse saving strategies that not only modify the difference between the slopes of fuse and recloser characteristic curves but also are effective for various penetration levels of PV units in the distribution network. The proposed protection scheme does not require the communication infrastructure and can be implemented in both conventional and digital reclosers installed in the distribution network. The reliable performance of the proposed fuse saving strategies is assessed on the simulation model of the Isfahan distribution network. [ABSTRACT FROM AUTHOR]

Development of an efficient protection strategy is one of the main barriers in paving the way for the implementation of inverter-based microgrids. The limited fault current of voltage-sourced converter (VSC) units as the sole fault feeding sources in the islanded mode of operation makes the fault detection difficult for conventional overcurrent-based protection system. On the other hand, bidirectional power flow due to the presence of distributed energy resource units and looped configuration of microgrids results in miscoordination of the overcurrent relays. To address these problems, this paper proposes a protection strategy for islanded inverter-interfaced looped microgrids. By monitoring the fault-imposed component of VSC current, the proposed scheme quantifies the severity of fault condition as the fault detection criterion. To preserve the protection coordination among available overcurrent relays, the proposed protection scheme adaptively changes the limiting level of hybrid reference frame limiter of the VSC control system proportional to their distances to the fault point. The proposed protection scheme is local, and there is no need for any change in the commercially available overcurrent protection relays. The reliable performance of the proposed protection strategy is assessed on the simulation model of a looped microgrid network. [ABSTRACT FROM AUTHOR]

Interconnection standards prevent islanding operation of distributed generations (DGs) to keep the safety and avoid the equipment failure. To meet this requirement for synchronous DGs (SDGs), the frequency-based relays are commonly used in the active distribution networks. This paper shows that in some conditions, a voltage relay has better islanding detection performance than a frequency relay regarding the SDG operating point, power factor of loads, and network characteristics. In this paper, a method is proposed for adjusting and evaluating a voltage relay based on application region and power imbalance application region to satisfy the islanding detection and safe and abnormal voltage variation criteria and to eliminate the false operation for the non-islanding disturbances including load shedding, load restoration, and 3-phase short-circuit fault, as far as possible. The relay false operation is studied for a combination of the control mode of SDG excitation system and the load type that leads to the highest possibility of relay false operation for the non-islanding disturbances. A number of dynamic simulation case studies are conducted to investigate the characteristics and capabilities of the proposed SDG anti-islanding protection scheme in both single- and multi-DG systems. [ABSTRACT FROM AUTHOR]

Electricity generation is one of the major concerns of today's world due to increasing dependence on this energy. Continuity in power supply and service to network consumers may be disrupted by various disturbances; thus, the power grid requires a reliable and fast protection system. The protection of distribution networks is conventionally performed by overcurrent protective devices which preserving their coordination is a complex task due to bidirectional power flow resulting from the presence of distributed generation (DG) units. This paper presents an adaptive scheme to restore protection coordination in the distribution networks with a high penetration level of DG units. Using the multi-agent system (MAS) structure, the main protection technique monitors the current of the lateral fuse by an intelligent electronic device (IED) to estimate the operating time of the fuse and sends this data to the upstream recloser IED. Then, the recloser IED determines the recloser operating time to preserve the protection coordination. In the case of failing the main technique, the backup technique protects the distribution feeder by using a definite time piecewise linear curve for the recloser based on the proposed recloser current coefficient. The backup technique is independent of communication links. The reliable performance of the developed scheme is assessed on the ETAP simulation model of the IEEE 33 bus test system. • The protection coordination of multi-agent distribution network is restored locally • In the MASPCR method, fuses are controllable by using IEDs • The proposed scheme is equipped with backup protection • In the CCPCR method, the recloser characteristic is replaced by a fixed-time step one • The non-standard curve can be used without replacing the existing protection equipment [ABSTRACT FROM AUTHOR]