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The inclusion of renewable energy sources in a distribution system to form a dispersed or decentralized generation network has gained tremendous progress in recent years. The architecture of the distribution system has the potential to serve as a microgrid during an islanding operation connected directly to the load center while excited fully by renewable technologies. This paper deals with planning and designing of a medium voltage power distribution system in a rural area of Pakistan affluent with abundant reserves of renewable sources of electricity. Two types of distribution system architectures, namely radial and ring systems, are simulated using a power flow algorithm with three types of renewable generation technologies: solar, wind, and biogas. The theoretical study involves realistic parameters such as total houses, estimated load, distance of the load from proposed generation site, solar irradiance, wind speed, and biogas reserves. As a result, transformer losses, line losses, power factor, and voltage profile across the load are evaluated for both system types and compared. It is concluded that the ring system maintains better voltage profile, higher power factor, and less transformer and line losses as compared to the radial system. All the relevant construction details together with the electrical and operational parameters of the power system need to be processed accurately in a computer program. Such a program has been modeled as part of this research with embedded methods and conditions outlined in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a new method for restoration of distribution networks after a fault occurrence. This problem is solved from the viewpoint of the distribution system operator with the main goal of minimizing the operating cost during the fault clearance period. The effects of distributed generation (DG) units and direct load control (DLC) programs are considered in designing the proposed restoration procedure. Moreover, the uncertainties associated with the predicted loads of different nodes and the availability of DG are modeled here. Robust optimization is used to model the uncertainties of restoration problems and manage their associated risks. Finally, a robust reconfiguration plan is obtained solving a bilevel problem using a genetic algorithm (GA). The upper-level problem is concerned with evaluating the optimum configuration by GA and the lower-level problem obtains the optimum schedules of DG and DLC with an AC optimal power flow. A 32-bus test system is used to demonstrate the applicability of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, heuristic optimization techniques, such as integrated particle swarm optimization (IPSO), teaching-learning-based optimization (TLBO), and Jaya optimization, were applied effectively for the first time to optimize the radial distribution network (RDN) by simultaneously considering reconfiguration of the network and allocation and sizing of the distributed generations (DG). The objectives were to maximize the voltage stability and to minimize the power loss of the network without violating the system constraints. In standard PSO technique, the movement of current particle depends upon global best position and its own best position up to current step. However, if the particle lies too close to any of these positions, the guiding role highly decreases and even vanishes. To resolve this problem and to find the global best solution, IPSO was utilized to optimize the network reconfiguration and DG allocation and sizing problem in the RDN. Also, the optimization techniques, such as TLBO and Jaya optimization, which do not require any tuning of parameters, unlike other heuristic optimization techniques, were implemented successfully in this paper. Seven test cases were generated from different combinations of network reconfiguration and DG allocation and sizing. Moreover, for comparison, the optimization techniques, such as particle swarm optimization (PSO), adaptive cuckoo search algorithm (ACSA), harmony search algorithm (HSA), and fireworks algorithm (FWA), were also applied to IEEE 33- and 69-bus distribution test networks. The comparison results prove overall superiority of Jaya optimization when applied on the two IEEE bus systems with seven test cases undertaken. [ABSTRACT FROM AUTHOR]

Global environmental problems associated with traditional energy generation have led to a rapid increase in the use of renewable energy sources (RES) in power systems. The integration of renewable energy technologies is commercially available nowadays, and the most common of such RES technology is photovoltaic (PV). This paper proposes an application of hybrid teaching-learning and artificial bee colony (TLABC) technique for determining the optimal allocation of PV based distributed generation (DG) and battery energy storage (BES) units in the distribution system (DS) with the aim of minimizing the total power losses. Besides, some potential nodes identified by the power loss sensitivity factor (PLSF). Thereupon TLABC is applied to determine the location of the DG and its size from the candidate nodes. The beta probability distribution function (PDF) is employed to characterize the randomness of solar radiation. High penetration of RES can lead to a high level of risk in DS stability. To maintain system stability, BES is considered to smooth out the fluctuations and improve supply continuity. The benefits of using BES is mainly dependent on operational strategies related to PV and storage in DS. The performance of the developed approach is tested on the 69 node and 118 node DSs and compared with the differential evolution (DE) algorithm, genetic algorithm (GA), for a fair comparison. Besides, the developed approach compared with other methods in literature which are solved the same problem. The results show how practical is the developed approach compared with other techniques. [ABSTRACT FROM AUTHOR]

This paper proposes a rapid analytical method to determine the locations and sizes of multiple distributed generations (DGs) inside a distribution network. DGs' locations are chosen with the aim of enhancing voltage stability and their sizes are picked so as to minimize system power losses. To evaluate the effect of the DG's nature on the system's performance, the proposed DG allocation method is tested for all DG types and the impact of the combination of different types of DGs is equally investigated, which offers a guide to designing an optimal hybrid network. [ABSTRACT FROM AUTHOR]

High penetration of photovoltaic and wind turbine-based distributed generators (DGs) can help reduce carbon emissions which is an important goal for the whole world. DG can be used to improve the voltage stability, present generation reserve/emergency, and consequently, the system power quality can be improved. However, it is very important to select the right size and location of a DG so that the power system can increase the gained benefits of such an installation to the maximum. In this paper, a hybrid optimization technique is proposed to determine the optimal allocation of DG in the standard IEEE 33-bus radial distribution system in order to improve the voltage stability and minimize the total power loss. The proposed hyprid technique is based on the gray wolf optimizer algorithm with loss sensitivity factor. The performance of the system is analyzed without DG installation, then it is compared with the performance of the system when DGs are installed with the predefined optimal sizes and locations. The study is performed by MATLAB M-Files and NEPLAN software. [ABSTRACT FROM AUTHOR]

Integration of distributed generation is continually and gradually affecting the stability of interconnected power systems. In this paper, the impacts of distributed synchronous generators on oscillatory stability are studied. In various parameter sub-spaces of interest, feasibility regions can be calculated to determine the conditions to sustain the stable operation of an interconnected power system. Through computations of the feasibility boundaries corresponding to Hopf bifurcations of electromechanical oscillatory modes, we determine the operating limits for a stable operation of the system under small and continual disturbances such as predictable changes in loading conditions of generators. Thus, with the case studies given in the paper, under different operating conditions, we investigate the effects of distributed synchronous generators on the oscillatory small-signal stability. It has been shown that penetrations of these generators can cause local or inter-area oscillatory instabilities depending on the system's topology, operating point and control parameters. [ABSTRACT FROM AUTHOR]

Grid-connected inverters are now increasingly used in distributed microgrid and smart-grid applications. The advantages of a quasi-Z-source inverter (QZSI), like single-stage operation, lower component rating, continuous input current, and common DC rail, led to an investigation of this converter for grid-connected applications. This paper presents a grid-connected QZSI with both AC and DC side controls. A new battery-charging configuration is also suggested across the capacitor through which the DC side control loop is regulated. Fast dynamic response and reduced harmonics are demonstrated through simulation and experimental results. [ABSTRACT FROM AUTHOR]

This study aims to perform fast fault diagnosis and intelligent protection in an active distribution network (ADN) with high renewable energy penetration. Several time-domain simulations are carried out in EMTP-RV to extract time-synchronized current and voltage data. The Stockwell transform (ST) was used in MATLAB/SIMULINK to preprocess these input datasets to train the adaptive fault diagnosis deep convolutional neural network (AFDDCNN) for fault location identification, fault type identification, and fault phase-detection for different penetration levels. Based on the AFDDCNN output, the intelligent protection scheme (IDOCPS) generates the signal for isolating a faulty section of the ADN. An intelligent fault diagnosis scheme that combines ST and deep learning methods aids the artificial intelligence-based protection scheme in isolating the faulty section. This study uses the PyTorch framework to build both the AFDDCNN and IDOCPS. The proposed protection technique classifies and isolates faults and coordinates protection with minimum operating time in the IEEE 13-bus ADN. It consistently gives high accuracy for fault diagnosis and minimum operating time for the IDOCPS even when the network's topology is modified to the IEEE 34-bus ADN. The experimental results indicate that the proposed model is more accurate and provides faster fault diagnosis and isolation than state-of-the-art methods. [ABSTRACT FROM AUTHOR]

The restructuring of the electrical market, improvement in the technologies of energy production, and energy crisis have paved the way for increasing applications of distributed generation (DG) resources in recent years. Installing DG units in a distribution network may result in positive impacts, such as voltage profile improvement and loss reduction, and negative impacts, such as an increase in the short-circuit level. These impacts depend on the type, capacity, and place of these resources. Therefore, finding the optimal place and capacity of DG resources is of crucial importance. Accordingly, this paper is aimed at finding the optimal place and capacity of DG resources, in order to improve the technical parameters of the network, including the power losses, voltage profile, and short-circuit level. The proposed formulation of this paper significantly increases the convergence and the speed of the finding the answers. Furthermore, to select the optimal weighting coefficients, an algorithm is proposed. The weighting coefficients are decided on according to the requirements of each network and deciding on them optimally prevents the arbitrarily selection of these resources. The genetic algorithm is used to minimize the objective function and to find the best answers during the investigation. Finally, the proposed algorithm is tested on the Zanjan Province distribution network in Iran and the simulation results are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper discusses some issues related with the growing importance of wind power and in modern power systems and some challenges raised by the emergence of distributed generation, and how computational intelligence and other modern techniques have been able to provide valuable results in solving the new problems. It presents some solutions obtained with a number of computational intelligence techniques and their application to real cases. [ABSTRACT FROM AUTHOR]

This paper focuses on the designing procedure of a regulatory framework in distribution networks with the main goal being to facilitate the integration of distributed generation (DG) units. The proposed framework is based on the concept of the reward penalty scheme (RPS) and creates effective financial incentives for distribution companies (DISCOs) in improving the quality of their services by applying DG units. To achieve this goal, reliability indices and annual energy losses of a distribution network are considered as two significant measures used in designing the structure of several RPSs. Employing these schemes, the regulators can quantify the quality of services provided by DISCOs. In order to examine the abilities of the proposed method, a case study on a test distribution system connected to bus 6 of the RBTS is performed. The obtained results show that a well-designed regulatory scheme can motivate DISCOs to adopt higher penetration of DG in such a way that their technical criteria can be improved. [ABSTRACT FROM AUTHOR]

This paper presents a new method for locating a fault in distribution systems using the similarity of fault impedance. A four-step approach is proposed to locate the fault in the networks. First, pre- and during-fault voltages from smart feeders along the primary feeders are measured. Second, three-phase impedance to calculate fault current corresponding to voltage deviation from each smart meter is achieved. Third, a relation between fault current and fault impedance for each type of fault is extracted. Finally, based on the similarity of the estimated fault impedance for each bus, an error index is calculated. Moreover, an auxiliary process is utilized to analyze the estimated fault impedance. The proposed method uses both smart meters and phasor measurement units to obtain voltage sag. Distributed generation and loads are modeled as constant impedances and then they are considered in the three-phase impedance matrix. The suggested approach is evaluated in the IEEE 34-bus test distribution network, which is simulated in the PSCAD/EMTDC environment. The obtained numerical results confirm the acceptable accuracy of the proposed methodology for all types of faults with various fault resistances. [ABSTRACT FROM AUTHOR]

Distributed generation (DG) is widely used to minimize total power losses in distribution networks. However, one of the problems of DG in a grid system is reverse current ow (RCF), which is when the DG output becomes greater than the connected load. Therefore, this paper proposes a multiobjective artificial bee colony (MOABC) algorithm to determine the optimal network reconfiguration for reducing total RCF in DG. The proposed algorithm is tested on 33-bus radial distribution systems in two different scenarios, i.e. base case and with 50% load. The proposed technique can reduce reverse current by up to 93%; however, the total power loss in the system will increase by 7%. Therefore, a suitable weight value is needed in MOABC for balancing the effect of RCF and the power loss value. [ABSTRACT FROM AUTHOR]

This paper presents a load shedding scheme (LSS) based on system frequency and voltage stability (VS). In the proposed scheme, the amount of power imbalance is determined using a rate of change of frequency, and the load shedding priority is carried out based on a VS index. The load with the highest tendency for voltage collapse (based on the index value) is given first priority to be shed. Thus, by shedding the most sensitive load, the distribution system can be saved from power collapse and then the system can return to its nominal state after load shedding. The proposed LSS is validated through simulation using PSCAD/EMTDC software on a Malaysian distribution network that consists of two mini-hydro generators. The simulation results show that the proposed scheme manages to shed the optimal amount of load when compared to conventional and adaptive frequency LSS. Moreover, apart from frequency stability, the proposed scheme also shows a significant improvement in the voltage profile of the islanded system. [ABSTRACT FROM AUTHOR]

One of the effective mitigation solutions of the problems due to the penetration of distributed generation (DG) into the distribution network is a fault current limiter (FCL). Main attention is given to designs for resistive and inductive FCLs and others should meet the same requirements. At first in this paper network analysis is used to determine a suitable type of limiting impedance of a FCL in a distribution network in the presence of DG and then a comparative study of resistive, inductive, and complex FCLs is conducted to show the effect of size and type of FCL on the amplitude and phase of DG and network fault current. To illustrate the impact of FCLs on relay coordination restoration, an optimization algorithm is used to determine the minimum size of FCL and subsequently the role of FCL impedance type on the coordination time interval of the main and backup relays in a sample IEEE typical distributed network is investigated. Simulations are carried out by programming in MATLAB and the obtained results are reported and discussed. [ABSTRACT FROM AUTHOR]

Droop controlled power sharing with an assumption that the value of line impedance is unavailable has been proven to have limitations; the power sharing is problematic in systems with significantly resistive lines. Furthermore, when the droop is applied in the islanding mode of operation of a microgrid, the system is likely to become unstable. In this paper, the droop control is replaced by an analytical solution. The proposed approach of power sharing is powerangle control of distributed generators (DGs), such as voltage source converters, a type of DG with extrapolation of power injected to the connected bus. It is demonstrated that the power injection to the bus could be tracked within the DG's capacity autonomously. Simulation and experimental results demonstrate the validity of the approach and it is shown that the proposed approach is suitable for DGs with either inductive or resistive line impedance. Moreover, this method can be operated in complex networks, such as meshed networks. [ABSTRACT FROM AUTHOR]

Power management in a grid-integrated power system consisting of distributed renewable energy sources is necessitated by ever-increasing energy consumption, the high cost of production, the limited resource of fossil fuel, and the worsening global environment. Wind and solar power generation are two of the most promising renewable power generation technologies. The growth of wind and photovoltaic (PV) power generation systems has exceeded the most optimistic levels of expectations. Fuel cells (FCs) also have great potential to be green power sources of the future because of the many merits they have, such as high efficiency and zero or low emission of pollutant gases. In this paper the modeling, control, and analysis of grid-connected PV power, a proton exchange membrane fuel cell (PEMFC), and a wind energy system (WES) connected through a common DC bus linked to an AC grid is discussed. In coordination with the PEMFC, the hybrid system's output power becomes controllable so that full utilization of PV and wind power takes place based on its availability, and the DC bus voltage is maintained constant even at varying load conditions for the desired power sharing between the distributed generation (DG) sources, load, and the AC grid. The hybrid system is controlled through a combination of two proposed control modes, namely the DG control mode and grid control mode. The coordination of the power controller, voltage source converter controller, and load controller is such that the transition between the two control modes is done as smoothly as possible. Thus, the total DG power will be a combination of PV power, WES power, and power produced by the PEMFC. Any additional power if required up to the maximum loading will be supplied by grid. If the load exceeds its maximum value, then the load controller will carry out load shedding. The composite system is available for safe operation in on-grid as well as off-grid mode satisfying voltage and power balance constraints. Different modes of operation have been demonstrated to verify and validate the desired power management among the DG sources, load, and the grid. MATLAB/Simulink software was used for simulating the composite model. [ABSTRACT FROM AUTHOR]

The usage of distributed generation resources, particularly distributed generation with renewable sources, has increased to generate electrical power close to consumers. One of the factors that can reduce penetration of distributed generation resources is the limitation of power quality, such as harmonic distortions. Distributed generation sources, in addition to producing power, due to using of power electronic converters and changing the power ow, increase harmonic currents. On the other hand, local compensation of reactive power by parallel capacitor banks is one of the effective methods to reduce power system losses and harmonic distortions. Since the capacitor impedance varies at different frequencies and resonance can be produced at harmonic frequencies, providing an efficient method to optimize capacitor banks' placement in the presence of nonlinear loads and distributed generation is important. In this paper, first the adverse effects of distributed generation on power system harmonic distortions and therefore on power quality are illustrated by experiments. The problem of the optimal capacitor placement in the presence of nonlinear loads and distributed generation (wind power) is then expressed as a fuzzy multiobjective model. In the proposed model, annual profit maximization resulting from loss reduction, bus voltage deviation minimization, and reduction of power system harmonics are considered as optimization objectives. The presented model is solved with a PSO algorithm and a special version of the backward-forward sweep considering the system harmonics. Efficiency of the proposed model is demonstrated by running experiments on an 18-bus IEEE distributed network. [ABSTRACT FROM AUTHOR]

As distributed generation resources penetrate into distribution systems, protection and service continuity are becoming major issues. A new approach for protection coordination and higher reliability of a distribution system with distributed generation is explored in this paper. The concept of central coordination relay (CCR) is developed for this purpose. After a brief introduction of the design and operating procedures of CCR, the utilization of the proposed relay on two feeders of a substation in the Kocaeli region of Turkey is simulated using DIgSILENT PowerFactory. The study results show that CCR can provide better protection coordination and improved reliability indices for distributed generation systems. [ABSTRACT FROM AUTHOR]

Unlike the traditional way of efficiency assessment of renewable energy sources integration, the smart grid concept is introducing new goals and objectives regarding increased use of renewable electricity sources, grid security, energy conservation, energy efficiency, and deregulated energy market. Possible benefits brought by renewable sources integration are evaluated by the degree of the approach to the ideal smart grid. In this paper, fuzzy analytical hierarchy process methodology for the integration efficiency has been proposed, taking into account the presence of multiple criteria of both qualitative and quantitative nature, different performance indicators, and the uncertain environment of the smart grid. The methodology has been illustrated on the choice of the size and location of a distributed generator in the radial distribution feeder. [ABSTRACT FROM AUTHOR]

In this paper, a new method based on artificial neural network (ANN) and discrete wavelet transform (DWT) is proposed for electrical islanding detection. Transient signals produced during an event are used in the proposed method. ANN is trained to classify the transient events as islanding and nonislanding. The required features for classifying are extracted through DWT of voltage and current transient signals. The proposed method is then simulated on a medium voltage distribution system of CIGRE with 2 kinds of DGs. Results show that this method can detect electrical islands more rapidly and accurately. [ABSTRACT FROM AUTHOR]

The development of distributed generations (DGs) is essential to help solve energy crises and improve the reliability of electricity supplies. However, the involvement of a DG in a grid along with an increase of the nonlinear load will reduce the power quality. To solve this problem, we want the converter used in the DG to work flexibly, intelligently, and more accurately. To contribute to the improvement of quality of the DG, this paper proposes a multifunction converter (MFC) model. With the proposed model, the photovoltaic generator, which can be operated at harmonic suppression, and the power injection are more flexible than in the conventional controller used in DG. The controller of the MFC, which is designed based on the Lyapunov function, always ensures the stability of the system. Simulations and experimental results are presented to validate the correctness and effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

Growing concerns over environmental impacts, improvement of the overall network conditions, and rebate programs offered by governments have led to an increase in the number of distributed generation (DG) units in commercial and domestic electric power production. However, a large number of DG units in a distribution system may sometimes contribute to high levels of harmonic distortion, even though the emission levels of the individual DG units comply with the harmonic standards. It is known that the nonoptimal size and nonoptimal placement of DG units may lead to high power losses, bad voltage profiles, and harmonic propagations. Therefore, this paper introduces a sensitivity analysis to determine the optimal location of DG units, as well as evolutionary programming and harmonic distribution load flow for determining the optimal size of DG units in radial distribution systems. A multiobjective function is created to minimize the total losses and average total harmonic distortion voltage (THDv) of the distribution system. The proposed methodology is tested with a 69-bus radial distribution system. The proposed optimal placement and sizing of the DG units is found to be robust and provides higher efficiency for the improvement of the voltage profile and the minimization of the losses and THDv. [ABSTRACT FROM AUTHOR]