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In this paper, the power electronic interface between a DC hybrid power source with a photovoltaic main source and battery storage as the secondary power source is modelled based on the state space averaging method. Subsequently, sliding mode controller is designed for maximum power point tracking of the PV array and load voltage regulation. Asymptotic stability is guaranteed through Lyapunov stability analysis. Afterwards, Three common control methods (LQR, PID, PBC) are provided to compare the results with those of the proposed sliding mode controller responses. Simulation of the hybrid system is accomplished using MATLAB and results of the proposed system are very promising.

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In this paper, we propose a general framework to study the impact of contractual agreement between hybrid system and microgrid on hybrid system profit composed of wind farm, photovoltaic and pump-storage hybrid system considering uncertainties. The proposed method is concerned with optimal scheduling of pump-storage hybrid system, aiming to maximize the hybrid system profit under frequency based pricing for a day ahead electricity market. The pump-storage hydro plant is utilized to minimize unscheduled interchange flow and maximize the system benefit by participating in frequency control based on energy price. Because of uncertainties in power generation of renewable sources, generation scheduling is modeled by a stochastic optimization problem. In order to verify the efficiency of the method, the algorithm is applied for various scenarios with different wind and photovoltaic power cases in a day ahead electricity market. The numerical results demonstrate the effectiveness of the proposed approach.

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In recent years, the utilization of clean renewable energies, especially solar energy, have increased dramatically due to their advantages over fossil fuels. Installation of photovoltaic systems is one of the most common methods of solar energy harvesting. The performance of these systems in converting solar energy to electricity is extensively a function of environmental conditions such as solar radiation, ambient temperature, wind, humidity, and other environmental parameters. Therefore, any changes in these parameters have a great influence on the design and performance evaluation of photovoltaic systems. Many regions with high solar potential for installation of photovoltaic panels are arid and deserted areas, in which the dust activities would significantly affect the performance of photovoltaic panels. This problem is much more serious in the climate of Iran, which is repeatedly faced with dust activities as well as aerosol dispersion. Therefore, the present study conducted a comprehensive review of the related literature in the field of the effect of dust on the performance and efficiency of solar panels. The results of the current study can serve as a thorough reference for researchers, designers, and engineers who deal with photovoltaic systems in regions struggling with dust events such as the Middle East, and in particular, Iran.

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Photovoltaic systems (PVs), despite their many advantages, may have effects such as power quality issues (voltage and harmonics increase), short-circuits level increase, protection issues, and transient stability for network. Some of these effects are due to the high PV penetration, which encounters the network with the over-voltage and harmonics problems. In this paper, the location, size and optimal operation of batteries and the passive filters are proposed separately and simultaneously to provide a practical solution to overcome the over-voltage and harmonic problems. In the economic objective function, the fixed and operation costs of batteries and passive filters are considered and constraints are defined to limit the total harmonic voltage and effective voltage of the network buses below the standard ranges. Taking into account the profit of energy arbitrage and reduction of network losses in the objective function, it is concluded that the use of the filter alone has the lowest cost of 736 $ (but results in an effective voltage increase beyond the permissible limit). Also, simultaneous use of battery and filter resulted in the highest loss reduction of 4.1 kWh, with the total harmonic voltage and effective voltage of the network buses are within the 5% range. Also, cables, overhead lines, and transformer are modeled by frequency-dependent characteristics. The studied network is composed of a real low voltage feeder including two PVs; however, in simulations, the PV penetration is increased to study a more challenging situation. Simulations are carried out by using DIgSILENT and MATLAB software and their interface.

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Nowadays, presence of photovoltaic systems in distribution network is not without challenge and it may not have economic productivity for the system under the lack of optimal management. Energy storage systems are able to cope with this problem. Therefore, in this paper, a new method is proposed for energy management of the distribution networks in order to show that how presence of the energy storage systems leads to profitability and high quality. In this method, the frequent charging/discharging of the energy storage systems is controlled so as to avoid from reduction of their lifetime. Moreover, in the proposed approach the convex power flow constraints are applied for energy management of the photovoltaic based distribution systems in order to guarantee the obtained results’ optimality and convergence. Furthermore, price responsive loads and interruptible ones are modelled in the optimization problem. The proposed approach for energy management is implemented to the 33-bus distribution network and the computed results demonstrate that how considering the energy storage systems in the distribution networks had been effective on improvement of the quality of the economic and technical parameters of the network. The obtained results with considering the importance of energy storage systems lifetime and without it have been compared.

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In this paper, a multi-stage protective scheme is proposed to maintain the fuse and reclosers coordination. The proposed method operates online and proportional to the photovoltaic sources penetration rate. In the first step, a non-standard Current - Time - Voltage curve is used for fuse saving. If the new calculated TDS from the first stage is not implementable to the reclosers, the second stage of the protection scheme will be activated, and the fault current contribution of photovoltaic sources decrease proportional to inverter PCC voltage. It should be noted that the proposed method is a combitionary method that in the first step, the effect of reclosers sensitivity in modifying the reclosers fast characteristics is taken into account in compared to other schemes presented in this regard, and in the second step, there is less limitation on the output power of PV sources under fault conditions than other inverter current control presented equations. It It is noteworthy that in order to implement the proposed protection method, there is no need to telecommunication infrastructure. The ETAP software simulation results validates the proposed scheme effectively.

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In this paper, a distributed method for reactive power management in a distribution system has been presented. The proposed method focuses on the voltage rise where the distribution systems are equipped with a considerable number of photovoltaic units. This paper proposes the alternating direction method of multipliers (ADMMs) approach for solving the optimal voltage control problem in a distributed manner in a distribution system with high penetration of PVs. Also, the proposed method uses a clustering approach to divide the network into partitions based on the coupling degrees among different node. The optimal reactive power control strategy is conducted in each partition and integrated using ADMM. The proposed method is tested on a real distribution test system. The result evidence that the proposed method has used the lower reactive power if compared to the conventional method.

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The deployment of multi-carrier energy systems, which are called energy hubs, is one of the most recent and useful strategies in the field of energy systems. The reliability of energy systems and their operation cost and efficiency could be improved by applying the concepts of energy hubs. The simultaneous management of electrical consumptions and heat demands by the concepts of energy hub would be effective. The energy management of residential energy hubs has received a great deal of attention because the energy consumption of the residential sector is significant in the amount of global energy consumption of the world. There is a knowledge gap in developing a new method simultaneously considering optimal operation and optimal allocation of photovoltaic units in residential energy hubs. This paper tries to fill this knowledge gap. Integrating the optimal planning and optimal scheduling of residential energy hubs could improve the system cost and other features. Considering the capacity of the photovoltaic unit as one of the decision variables in the proposed optimization problem besides other operation and scheduling decision variables is one of the most important contributions of this research. The proposed method is applied to a residential energy hub, including the controllable and uncontrollable appliances, combined heat and power units, plug-in hybrid electric vehicles, heating loads, photovoltaic units, and heat storage systems. The proposed optimization problem is solved by the genetic algorithm in MATLAB. Different case studies are analyzed to assess the impacts of photovoltaic units’ capacity, energy storage systems, and simultaneous optimization of planning and operation decision variables. The test results illustrate the advantages of the simultaneous optimization of operation and capacity of the photovoltaic unit in the proposed method. It is inferred from the comparative test results that by applying the proposed method, it is possible to improve the operation cost and efficiency of energy systems, while the constraints of customer satisfaction are concerned. It is revealed that an around 5% improvement in the daily cost of the studied residential energy hub could be achieved compared to conventional studies. The sensitivity analysis is performed to investigate how energy storage systems besides photovoltaic units influence the residential energy hubs.

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There is an increasing demand for low-cost single-phase DC–AC inverters in many applications such as PV systems. PV system may be used without the transformer to improve efficiency and make the whole system lighter, smaller, and easier to install. Using transformerless topology, the system efficiency may be increased by about 2%, and the related cost may be decreased by about 25%. There are large leakage currents in transformerless topologies, especially in photovoltaic systems, where safety issues and electromagnetic interference problems often occur. To overcome such disadvantages, common-ground topologies can be used, which minimize the leakage current of the transformerless inverter ones. The transformerless semi-quasi-Z-source inverter (SqZS) with a common-ground structure offers many advantages over conventional single-phase inverters. Leakage current elimination, high power density, lower components, and low-cost features make it an attractive option as a micro-inverter in photovoltaic applications. The basic topology of SqZSI is especially suitable for a PV module in the low-voltage application as a low-cost micro-inverter with high-voltage SiC switching devices. However, the unity voltage gain is one of the disadvantages of the SqZS inverter, which is referred to as a drawback; In other words, the conventional structure of SqZS is not able to step up the voltage and the maximum amplitude of AC voltage that can be extracted is equal to the input DC voltage; Therefore, in this paper, a modified structure of single-phase inverter (MSqZS) is proposed to achieve voltage boost capability. The voltage boost is achieved in a single-stage conversion just by adding an additional series DC blocking capacitor to the basic inverter. It also maintains the common-ground feature. Nonlinear sinusoidal modulation (NLSPWM) is modified to allow the SqZS basic structure to achieve high voltage gain. However, the proposed inverter is modified in topology and modulation; its complexity is not increased in comparison to the basic SqZSI. The proposed inverter has the least number of components than the similar step-up common-ground topologies. In this paper, the closed-loop control is proposed to improve the performance of the MSqZS under variable input voltage as well as output load and compensation for the undesired and non-ideal effect of the parasitic elements. In addition, the proposed inverter is also capable to generate reactive power. Also, the design considerations for series capacitor is analysed for proper capacitor selection. The simulation and experimental results under various closed-loop and open-loop scenarios comply with the IEEE Std 1547 and verify the appropriate performance of the proposed inverter.

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Nowadays, the need has increased to manage distributed energy resources due to advances in the renewable energies industry, the distance between energy resources and local loads, growth in the number of electric vehicles, and high power transmission costs. In this regard, important challenges, such as power exchange management between distributed energy resources and electric vehicle batteries, have been raised for optimal use of the power generated from these resources. Since home consumers are supposed to have wind turbines or photovoltaics installed to the supply part of their power consumption, the impact of wind and solar radiation uncertainties on their output power should be considered. Considering these challenges and in an attempt to flatten the difference curve between the generated power of resources and consumption power of local loads, this paper proposes an efficient method based on mean-field theory to control the charge and discharge of electric vehicle batteries. On the other hand, with the increase in the number of electric vehicles and distributed energy resources, the control of charging and discharging of too many batteries requires heavy and time-consuming calculations. This paper proposes an innovative method by introducing some coefficients for online estimation of the charge and discharge of batteries, which leads to a reduction in the volume of calculations. To this end, a compromise has been made between the performance, the volume of calculation reduction, and the necessity of these calculations. Simulation results illustrate the quality and efficiency of the charge and discharge estimation of batteries based on the proposed method.

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This paper presents a model for distribution network optimization considering a high penetration of photovoltaic (PV) sources and electric vehicle charging stations (EVCSs) based on on-load tap changing transformers (OLTC) and step voltage regulator (SVR), shunt capacitor (SC), and shunt reactor (ShR). The purpose is to prevent overvoltage due to power injection by PV sources and voltage drop due to EV charging in distribution networks. The proposed model is solved using a new hybrid algorithm called PSO-GA. Relevant studies show that with the increasing number of PSO replications, particle population variability is easily eliminated and placed in local optimization. The idea of ​​combining GA is based on the PSO introduced in this study. Crossover and mutations of GA are performed on the PSO population, which is useful for improving the overall optimal ability of particles and causing the algorithm to deviate from the local optimal point. Two different IEEE standard test networks are tested under different load scenarios to analyze the proposed model. The results reveal the performance of the proposed model.
 

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Energy management between renewable energy sources and energy storage systems is challenging especially in different operating modes in stand-alone DC microgrid. In this paper, a new energy management system strategy based on law and fuzzy logic is proposed for a stand-alone DC microgrid with hybrid energy storage system (HESS) consisting of battery and supercapacitor (SC). The design of the proposed system is simple and does not require the mathematical model of the system. The main advantages of the proposed strategy are: high DC link voltage reference tracking in the presence of source and load power disturbances, keeping the battery and supercapacitor charge level within the permissible range, preventing battery and supercapacitor from overcharge/discharge and controlling the battery charging/discharging rate. Moreover, the proposed strategy increases battery life span while decreasing its current stress by using high charge/discharge cycles in SC and providing the majority of the output current through it. The proposed technique has been simulated in MATLAB and results show the priority of this method from the abovementioned points of view.