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Abstract Background Micro-grid (MG) can be described as a group of controllable loads and distributed energy resources that can be connected and disconnected from the main grid and utilized in grid-connected or islanded modes considering certain electrical constraints. Methods The objective of this article are as follows: (1) predict the uncertainties through the hybrid method of WT-ANN-ICA and (2) determine the optimal generation strategy of a MG containing wind farms (WFs), photovoltaic (PV), fuel cell (FC), combined heat and power (CHP) units, tidal steam turbine (TST), and also boiler and energy storage devices (ESDs). The uncertainties include wind speed, tidal steam speed, photovoltaic power generation (PVPG), market price, power, and thermal load demand. For modeling uncertainties, an effort has been made to predict uncertainties through the hybrid method of wavelet transform (WT) in order to reduce fluctuations in the historical input data. An improved artificial neural network (ANN) based on the nonlinear structure is applied for better training and learning. Furthermore, the imperialist competitive algorithm (ICA) is applied to find the best weights and biases for minimizing the mean square error of predictions. Result The scenario-based stochastic optimization problem is proposed to determine the optimal points for the energy resources generation and to maximize the expected profit considering demand response (DR) programs and uncertainties. Conclusions In this study, three cases are assessed to confirm the performance of the proposed method. In the first case study programming, MG is isolated from grid. In the second case study, which is grid-connected mode, the WT-ANN-ICA and WT-ANN uncertainty prediction methods are compared. In the third case, which is grid-connected mode, the effect of DR programs on the expected profit of energy resources is assessed.

The modern changes in electric systems present new issues for control strategies. When power converters and distributed energy resources are included in the micro-grid, its model is more complex than the simplified representations used, sometimes losing essential data. This paper proposes a unified fuzzy mathematics-based control method applied to the outer loop of a voltage source converter (VSC) in both grid-connected and islanded modes to avoid using simplified models in complex micro-grids and handle the uncertain and non-stationary behaviour of nonlinear systems. The proposed control method is straightforwardly designed without simplifying the controlled system. This paper explains the design of a fuzzy mathematics-based control method applied to the outer-loop of a VSC, a crucial device for integrating renewable sources and storage devices in a micro-grid. Simulation results validated the novel control strategy, demonstrating its capabilities for real field applications.

Mountain huts are stand-alone micro-grid systems that are not connected to a power grid. However, they impact the environment by generating electricity and through day-to-day operations. The installed generator needs to be flexible to cover fluctuations in the energy demand. Replacing fossil fuels with renewable energy sources presents a challenge when it comes to balancing electricity generation and consumption. This paper presents an integration-and-optimization process for renewable energy sources in a mountain hut’s electricity generation system combined with a lifecycle assessment. A custom computational model was developed, validated with experimental data and integrated into a TRNSYS model. Five different electricity generation topologies were modelled to find the best configuration that matches the dynamics and meets the cumulative electricity demand. A lifecycle assessment methodology was used to evaluate the environmental impacts of all the topologies for one typical operating year. The carbon footprint could be reduced by 34% in the case of the actually implemented system upgrade, and by up to 47% in the case of 100% renewable electricity generation. An investment cost analysis shows that improving the battery charging strategy has a minor effect on the payback time, but it can significantly reduce the environmental impacts.

This paper illustrates a new compilation of Micro-grid by distributed energy sources using three phase three -level Space vector multilevel inverter. In olden days only 3Φ inverter was designed and they were connected to the consumer with higher harmonics without automatic control feeding power to the consumer end. But this system we implemented three phase three level inverter was fed power to the consumer and also reduces the switching losses. I have connected three renewable sources are alike Wind-turbine, P.V - cell and Pico-Hydel generator model to increases the potential of power supply to a relatively small jumble of people, an official of the economic lay of a locality. Furthermore costless new semiconductor technologies in the power switches beside the necessity of current on giant consummation inverters necessitate by Renewable-Energy-Systems (R.E.S) by reduced Total-Harmonic-distortion (T.H.D) in the spectrum of switching waveform have expanded the applications of Multi-level inverters. This system also includes M.P.P.T electronic control to operate maximum point of modules so, it is supplying maximal power to the consumer connected load according to the changes in solar-radiation and diffusive-temperature and intern increase the battery charging current. [ABSTRACT FROM AUTHOR]

A Z-source dynamic voltage restorer ( DVＲ) based on simplified emotion control was designed for power quality degradation caused by microgrid voltage transients． The hardware structure of the Z source dynamic voltage restorer was designed． The principle of expanding the voltage compensation range of Z-source network was analyzed． A DVＲ control system based on simplified emotion control and voltage feedforward was designed． The control speed and compensation precision of DVＲ were improved by using the simplified emotion control model， which has the characteristics of PI control structure and automatic correction of parameters through self-learning． In order to verify the feasibility of the proposed DVＲ scheme， modeling simulation and experimental verification were carried out． The results show that compared with DVＲ based on PI control and fuzzy control， the Z-source dynamic voltage restorer based on simplified emotion control has the characteristics of faster response speed， wider voltage compensation range， higher compensation accuracy and better stability． [ABSTRACT FROM AUTHOR]

Summary: The study and identification of stability condition in an islanded micro‐grid are critical due to the lack of generation resources and load changes. On the other hand, the output power of the renewable units and the load level in a micro‐grid are uncertain and the system does not have a dominant operating point. Therefore, small signal analysis methods results have small validity range and cannot be generalized to the whole system. Therefore, a Lyapunov function (LF) based large signal stability method is proposed in this article to address the problem of small signal methods. Also, a Neuro‐Fuzzy system is proposed to consider uncertainties and network modeling. In this study, the Takagi‐Sugeno (T‐S) fuzzy system is used. Artificial neural network is also applied to provide an optimal tool for identifying system uncertainties, while T‐S rules are used to provide a framework of previous knowledge of the system. The main purpose is to propose an identification and modeling process to study the stability condition and boundaries in an islanded micro‐grid. After the uncertain system is modeled, the system LF is calculated using Linear Matrix Inequality and the system domain of attraction is determined. [ABSTRACT FROM AUTHOR]

Micro-grids are small-scaled power grids, with local clean energy generation and intelligent management units. Micro-grids equipped with PV panels, wind turbines and batteries are known as hybrid power systems. Since these systems are a promising solution to build the future smart city, different designs were proposed and implemented. The present study compares two micro-grid-connected PMSG designs, with PV panels and batteries, based on system performance and power quality. In the first design, the wind turbine is connected to the common DC bus through a rectifier, while in the second configuration, it is connected to the 3-phase AC circuit via a transformer. The comparison is carried-out under different weather and system conditions. According to simulation results, the first design is less affected by voltage harmonics and has a better power quality, while the second design is robust to inverter or transformer failures and supports more loads. [ABSTRACT FROM AUTHOR]

Micro-grids consist of distributed power generation systems (DGs), distributed energy storage devices (DSs), and loads. Micro-grids are small-scale networks at low voltage levels that are use to provide thermal and electrical loads of small locations where there is no access to the main electrical grid. Given the environmental and economic issues for these areas, micro-grids can be a good solution for energy production. In this paper, determining the size and location of optimal electrical energy storage systems is presented. In other side, a new method based on the cost benefit analysis for optimal sizing of an energy storage system in a microgrid (MG) is proposed. The uncertainties associated with renewable energy sources and the occurrence of defects in the grid connection network and the effect of the contribution of load responses in a micro-grid are taken into account. The combined system consists of wind turbines and fuel cells. Basically, wind power is not definitively available. The new proposed method is based on two-stage randomization design (TSRD) for modeling the effect of wind power uncertainty so that the predicted wind energy error is considered as the main random parameter in the model. A standard probability distribution function is used to represent the error variations. Given the continuity of the mentioned function, the probability error function is extracted using the new discrete method and a certain number of scenarios with a certain probability. Finally, the problem has been transformed into an optimization problem, and a gray wolf optimization (GWO) algorithm has been used to solve it. In the proposed developed model based on local and global search, the algorithm tries to reach the final result in the shortest possible time and with the most precision. The results of the simulation show the efficiency of the proposed method in solving the micro-grid problem. • Providing a model for determining the optimum location and size of the micro-grid storage system. • Providing a probability of wind energy uncertainty and photovoltaic system through prediction error modeling. • Considering the possibility of a downstream grid failure as a random phenomenon. • Providing an extended gray wolf optimization algorithm. • Reviewing and analyzing the proposed model in different scenarios. [ABSTRACT FROM AUTHOR]

Currently, many remote communities rely on costly diesel engine (DE) generators as their only energy resource. Therefore, to reduce cost and CO2 emissions, renewable energy such as photovoltaic (PV) power is widely used. However, such integration may have reliability issues due to intermittency and uncertainty of PV power. Hence, energy storage is further implemented to compensate for the variability of PV output. As a result, the critical problem is to find an optimized PV-storage control strategy and capacity considering the techno-economic aspects, cost, and reliability. Previous research has not provided convincing results due to the little attention paid to the practical operational constraints of existing DEs (time delay management, spinning reserve strategies, ramp rate, etc.), and rough hourly usage data in a time-series model. Besides, no applicable systematic evaluation method has been established. This paper develops a new model which fully considers the DE generator's operational characteristics. Furthermore, based on the recorded 1-min load and PV generation data in a real microgrid, a systematic evaluation method is proposed, which searches for the best results for both control strategies and capacities of all components. This method can be utilized for the integration of high renewable (PV) penetration into existing DE powered remote networks. [ABSTRACT FROM AUTHOR]

Copyright of Journal of East China University of Science & Technology is the property of Journal of East China University of Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the efficient salp swarm algorithm (ESSA) is proposed to solve the energy management (EM) with emission problem of renewable micro-grid (MG) including storage devices. Because of the uncertainties in the renewable energy sources (RESs), load demand and market prices, the probabilistic approach based on (2m + 1) point estimate method and ESSA is employed to solve the probabilistic EM problem. The proposed ESSA can be derived by introducing two modifications on the conventional salp swarm algorithm (SSA) to improve the balance between exploration and exploitation, speed up the convergence and avoiding the stuck in local optima of the SSA. The ESSA is employed to solve the deterministic and probabilistic EM with emission problem. Where the multi-objective optimization problem of cost and emission functions is transferred into a single objective function to minimize the total operating cost of the MG. The proposed ESSA is evaluated using a typical grid-connected MG with energy storage devices and compared with other methods. The results verify the superiority of the ESSA to solve the EM problem of the MG over other methods. • The probabilistic approach based on ESSA and point estimate method is proposed. • The proposed method is used to solve the deterministic and probabilistic EM of MG. • The EM problem considers minimization of cost and emission as a single problem. • The proposed method has been evaluated using a typical MG with different scenarios. • Results of all cases show the superiority of the proposed method over other methods. [ABSTRACT FROM AUTHOR]

More than 70% of the population in Ethiopia lack access to electricity and thus rely on conventional sources of energy such as biomass that is associated with negative consequences on health and the environment. Decentralized community-based micro-hydropower plants (MHPs) are being utilized as effective means to transition to modern low-carbon energy systems providing access to electricity to communities in remote areas. However, there exist a knowledge gap regarding energy justice dimensions and gendered impacts related to sustainable energy transitions in the Global South. This research investigates the gendered justice implications of low-carbon energy projects in the case of four community-based micro-hydropower projects in Ethiopia implemented by the German Development Cooperation (GIZ). Although the projects generally achieved positive outcomes for the lives of the villager's socio-economic impacts on income; productive use, health and education affected men and women differently. The particular energy needs, uses and challenges that women face were insufficiently addressed and hence are limiting the opportunities for women to benefit equally from access to electricity. Generally, procedural justice aspects such as access to information, consultation and participation seemed to be insufficient to create a sense of ownership which in turn can jeopardize the long-term sustainability of the hydropower plants. [ABSTRACT FROM AUTHOR]

This paper aims to establish an Arduino and IoT-based Hierarchical Multi-Agent System (HMAS) for management of loads' side with incentive approach in a micro-grid. In this study, the performance of the proposed algorithm in a micro-grid has been verified. The micro-grid contains a battery energy storage system (BESS) and different types of loads known as residential consumer (RC), commercial consumer (CC), and industrial consumer (IC). The user interface on a smartphone directly communicates with the load management system via an integrated Ethernet Shield server which uses Wi-Fi communication protocol. Also, the communication between the Ethernet Shield and the Arduino microcontroller is based on Wi-Fi communication. A simulation model is developed in Java Agent Development Environment (JADE) for dynamic and effective energy administration, which takes an informed decision and chooses the most feasible action to stabilize, sustain, and enhance the micro-grid. Further, the environment variable is sensed through the Arduino microcontroller and sensors, and then given to the MAS agents in the IoT environment. The test results indicated that the system was able to effectively control and regulate the energy in the micro-grid. [ABSTRACT FROM AUTHOR]

Hydrogen has been a promising energy carrier to meet the world's energy needs as well as reduce pollutant emissions. Although many countries have policies and programs to expand hydrogen production, the potential for hydrogen production in different regions of Qatar has not yet been evaluated. Therefore, this paper, for the first time, evaluates the possibility of an average annual cogeneration of 14 kWh of electricity and 85 kg/day of hydrogen by a home-scale solar-wind system connected to the grid in Qatar. NASA's 20-year average of meteorological data, the electricity tariff and gasoline price in 2018, along with annual real interest rate, were used as inputs to HOMER software. The techno-econo-enviro analysis was done over a one-year period hour by hour. From the results, it was found that the lowest prices of hydrogen and electricity generated, with $ 2.092/kg and $ 11.495/kWh, were related to Grid and PV-Wind-Grid scenarios, respectively. Also, results indicated that Ar-Ruways station and PV-Wind-Grid scenario were the most environmentally suitable options that resulted in a CO 2 emission rate of 1434 kg annually. To select just one station among five areas, a fuzzy method was deployed as a prioritization technique. Its results suggested that Doha Intl Airport site is the most suitable one for constructing solar-wind hybrid energy generation system. • The lowest electricity and hydrogen price are 11.495 $/kWh and 2.092 $/kg, respectively. • The best eco-friendly station and scenario are Ar-Ruways and Wind-PV-Grid, respectively. • Deploying FTOPSIS, implied Doha Intl Airport site was the best option. [ABSTRACT FROM AUTHOR]

In order to solve the problem that the static peak-valley price for electric vehicles cannot truly reflect the relationship between electricity supply and demand, as well as the fact that the low utilization rate of renewable energy in the micro-grid, a dynamic time-of-use pricing strategy for electric vehicle charging considering user satisfaction degree is proposed, to achieve the goal of friendly charging for the micro-grid. Firstly, this paper researches the travel patterns of electric vehicles to establish the grid connection scenes and predict the controllable capacity of electric vehicles. Secondly, the charging preferences of different types of users are studied, and a comprehensive satisfaction degree model is set up to obtain different users' charging strategies. Furthermore, the paper raises a pricing strategy on account of the dispatching requirements of the micro-grid, and realizes the effective dispatch of electric vehicle charging load based on price signals. Finally, we gain the dynamic time-of-use charging price, using the strategy proposed above, and the economic benefits brought to the micro-grid and electric vehicle users are analyzed, which validates the rationality and effectiveness of the pricing strategy. [ABSTRACT FROM AUTHOR]

Most of the Indian rural area is electrified now, but the gap between supply and demand is much greater and increasing due to rapid industrial growth and increase in rural as well as urban living standards. That cause the extra burden on power grid. In order to reduce the burden on the national grid, India is moving fast towards distributed generation, and various studies show that renewable-based micro-grid is a preeminent alternative for decentralized energy generation. Most of the Indian population live in rural areas with access to wide varieties of alternative energy sources (wind, solar, hydro, biomass, etc.). Therefore, to reduce the dependency on heavily loaded power grid, a hybrid renewable energy system is required by utilizing the locally available sources, which incorporates more than one source of energy by combining the benefits and strength of one source to complement each other. This paper proposed a PV-Biomass-Grid-based optimal micro-grid system, based on locally available resources in Kashmir region of Jammu and Kashmir, India. In the proposed micro-grid, load is served on the basis of priorities to employ minimum burden on the grid and increase the use of renewable resources. The overall goal of the study is to minimize the cost of energy and maximize the energy output from hybrid renewable energy system. Extra electricity generated beyond the load demand would be supplied to grid. In this way, system energy cost is reduced with improvement in electrical system and reducing the environmental impact. [ABSTRACT FROM AUTHOR]

White layer (WL) formation in metal cutting is generally found to have negative effects on the corrosion and fatigue life of machined components. Nowadays, the mechanism of the WL formation has not been understood very well, especially about the contribution of the thermal and mechanical loadings generated by the cutting process on WL formation. The relationship between subsurface plastic strain caused by mechanical loadings and the formation of WLs is of our concern. To address this issue, WL formation in hard turning of AISI 52100 under dry and cryogenic cooling conditions is investigated by subsurface plastic strain measurement using the micro-grid technique, observed by scanning electron microscope (SEM). Due to the considerable low temperature, WL is mainly generated by the mechanical effect rather than the thermal one, and this hypothesis is supported by physically based finite element method (FEM) simulations. From the investigations, we discover the existing plastic strain threshold, which governs the occurrence of WL in hard turning of AISI 52100 steel under cryogenic cooling conditions. [ABSTRACT FROM AUTHOR]

Nowadays, renewable energy sources such as photovoltaic and active generators are utilized frequently in modern power systems especially micro-grid. By providing electrical energy using micro-grid systems, the reliability and quality of the system can be improved. A micro-grid connected to the network depends on the main grid and consequently assessing the power quality during independent functioning (islanded mode) is important. The aim of the present work is to perform active, reactive power distribution strategies (control) for active generators used in smart grids. The proposed control method is the sliding mode which controls the active as well as reactive power and frequency. Here, based on sliding mode control method, droop control is developed for active generator. This controller is simulated for active generator by MATLAB/SIMULINK and simulation results are given. Based on the obtained simulation results, efficiency of sliding mode in regulating active and reactive power and controlling domain voltage and frequency are shown. [ABSTRACT FROM AUTHOR]

In this work, a mathematical model called optimization by swarm of particles (PSO), was implemented to optimally solve the location and sizing of capacitor banks in a micro-grid of electrical distribution. The proposed method is based on particle swarm optimization (PSO) and the solution will be obtained with dynamic programming, implementing an algorithm that will be developed entirely in MATLAB. The algorithm calculates the optimal solution satisfying the necessary requirements to guarantee the operation of the electrical system. As a case study, a model of a micro-grid which is typically of 5 bars will be used. However, the algorithm was implemented in a general way and it can respond correctly to multi-bar systems. As a final analysis we made a comparison of the system data without compensating and the compensated system data, highlighting an improvement in the voltage profiles, minimization of the losses in the lines, minimization of the total losses of the system, improvement of the power factor, decrement in the maximum voltage deviation and average voltage deviation, complying with a minimum possible cost restriction criterion. [ABSTRACT FROM AUTHOR]

The energy management will play an important role in the future smart grid by managing loads in an intelligent way. Energy management programs, realized via House Energy Management systems (HEMS) for smart cities, provide many benefits; consumers enjoy electricity price savings, and utility operates at reduced peak demand. This paper proposed an adaptive energy management system for islanded mode and grid-connected mode. In this paper, a hybrid system that includes distribution electric grid, photovoltaics, and batteries are employed as energy sources in the residential of the consumer in order to meet the demand. The proposed system permits coordinated operation of distributed energy resources to concede necessary active power and additional service whenever required. This paper uses home energy management system which switches between the distributed energy and the grid power sources. The home energy management system incorporates controllers for maximum power point tracking, battery charge and discharge and inverter for effective control between different sources depending upon load requirement and availability of sources at maximum powerpoint. Also, in this paper, the Maximum Power Point Tracking (MPPT) technique is applied to the photovoltaic station to extract the maximum power from hybrid power system during variation of the environmental conditions. The operation strategy of energy storage systems is proposed to solve the power changes from photovoltaics and houses loads fluctuations locally, instead of reflecting those disturbances to the utility grid. Furthermore, the energy storage systems energy management scheme will help to achieve the peak reduction of the houses daily electrical load demand. The simulation results have verified the effectiveness and feasibility of the introduced strategy and the capability of the proposed controller for a hybrid microgrid operating in different modes. [ABSTRACT FROM AUTHOR]

In solving the problem of multi-objective optimization operation of distributed power supply in micro-grid, aiming at the limitations of traditional NSGA-II algorithm in terms of approximation and computational efficiency, considering the difference of individual similarity in evolution process and the possibility of the algorithm falling into local optimum, this paper proposed an improved NSGA-II algorithm. The new algorithm introduced the information entropy mechanism to improve the operator, and approximated the crossover probability and mutation probability as the decreasing function model and the Cauchy distribution model respectively. The performance test proves that the new algorithm is effective. Taking distributed power supply access to IEEE 30-node power system as an example for simulation experiment, compared with the traditional NSGA-II multi-objective optimization algorithm, the result shows the superiority of the improved algorithm in improving the convergence speed and the optimization indices. [ABSTRACT FROM AUTHOR]

This paper presents a novel efficient maximum power point tracking algorithm for wind energy conversion system. Conventional techniques to obtain maximum power are susceptible to the mechanical disturbances. Conversely, the perturbation algorithm requires high accuracy of turbine power characteristics. Therefore, a variable speed-variable pitch wind turbine in conjunction with permanent magnet synchronous generator and sensor-less maximum power point tracking has been proposed in this paper. A nonlinear optimum relationship between output power and dc voltage has been developed in this research work. On the basis of mathematical relationship, a new perturbing parameter has been introduced for more effective tracking scheme. The proposed system has been verified on simulation interface, and compared with the conventional perturbations. The comparison results show that the proposed technique increases the overall output power of the system by 5-7%. [ABSTRACT FROM AUTHOR]

Micro-grid (MG) operation using voltage control methods (VCMs) has been widely recommended for parallel operation of three phase voltage source inverters, especially during islanded mode to maintain the voltage level in the MG. In contrast, this paper presents a new unified control strategy for MG parallel operation using a current control method (CCM). A hybrid control scheme which combines a universal robust droop controller (URDC) and quasi-proportional resonant (QPR) regulator is introduced. It ensures equal power sharing among parallel operated inverters during all MG's operating modes. Moreover, an improved adaptive estimator for the reference current magnitude is integrated to meet dynamic load variations. Furthermore, the scheme is enhanced with a self-synchronized capability using a simple synchronous reference frame phase locked loop (SRF-PLL). This obviates the necessity of communication links and external synchronous clocks required for synchronization process. In addition, a decentralized control action is locally managed to restore the inverter's frequency upon any reactive load change. Modeling and simulation results using MATLAB/SIMULINK software are presented to show the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The impact of integrating hybrid (wind and solar) renewable energy sources with energy storage devices in Micro-grid (MG) operations under the deregulated electricity market is becoming a burning issue now a days. Due to the intermittent nature of renewable, accurate load forecasting in the day-ahead electricity market is challenging. As a result, it is very difficult for retailers to balance the supply-demand in the real-time electricity market. This paper comprehensively reviews (i) the optimization approaches to determine the best results for different proposed problem-formulation techniques for precise load forecasting and (ii) profit maximizations for retailers and energy users to decrease the electricity bill for end-users and other utilities. The results obtained from the discussed problem formulation techniques have also been analyzed. Finally, based on the review, potential obstacles in this topic have been identified, and future research directions in this context have been pointed out. [ABSTRACT FROM AUTHOR]

In this paper, the possibility of using synchronous generators with magnetoelectric excitation for the autonomous consumers’ supply with the use of renewable energy sources is considered. To eliminate a number of the disadvantages associated with the difficulty of energy-efficient regulation of the generated parameters, such as the generated current and voltage, the use of modified multi-winding synchronous generators with permanent magnets is proposed. It allows solving the problem of controlling this type of generator. In addition, the use of this type of generator helps to increase the amount of energy generated. The authors have proposed several synchronous generators with permanent magnets of various supply network architectures: single-phase, two-phase and traditional three-phase types. This will simplify the design of architecture for several cases of consumer power supply systems. It will also help to eliminate the need to organize a balanced distribution of loads in phases to prevent accidents, damage and/or disabling of consumers themselves. Here, we considered mathematical descriptions of several types of generators that differ in their assembling, in particular, the number of phases (one-, two- and three-phase generators), the number of pairs of permanent magnet poles on the rotor, and the method of switching the generator windings among themselves. Using the developed mathematical descriptions that describe the operation of every single winding of the generator, their mathematical models were developed in the SimInTech mathematical modeling environment. The results of the mathematical modeling of these generators were presented; their interpretation for use with renewable energy sources was made; and the methods of using these generators were described. The developed mathematical descriptions of synchronous generators with permanent magnets can be used for further study of their operation. It can also help for the development of control systems and power systems for micro-grid energy complexes that use renewable energy sources to increase the energy efficiency of micro-grid systems.

This paper discusses the simulation framework developed for an in-campus pilot micro-grid at MCAST, Malta, to enhance its efficiency and reliability. One year of real-time metered data were used to arrive at the load curves, categorize the loads as essential and non-essential ones, and decide the micro-grid domain within MCAST. The potential scenarios were modeled to observe the behavior of the present status of the micro-grid, with an increased photovoltaic (PV) generation capacity, by using an optimum battery storage system with a diesel generator of suitable capacity and finally integrating electric vehicles (EVs) to discuss the potential of vehicle to grid (V2G) operation modes. The existing building management system (BMS) of MCAST was interfaced within the micro-grid to introduce the geographic information system (GIS) and Building Information Modeling (BIM) for developing an intelligent 3D model of the micro-grid. The results of the simulation framework for various potential case scenarios were obtained in a MATLAB/Simulink environment to assess the performance of the micro-grid. Previously formulated key performance indices (KPIs) that describe the financial aspects of micro-grid operation and ecological benefits of the investigated micro-grid were evaluated. A sensitivity analysis of these KPIs shows encouraging results with the potential of cost-competitiveness.

This study focuses on the sizing and optimization of a micro-grid with storage, which is destined to supply the load of an economic activity zone (EAZ) in Sidi Bouzid, Tunisia. To solve this problem, a genetic algorithm is established and programmed into MATLAB. The objective functions are considered by providing three minimums, namely Greenhouse Gas emissions (GHG), Life Cycle Cost (LCC) and Embodied Energy (EE), for three values of loss of power supply probability (LPSP) previously fixed. The sizing and optimization results are found and evaluated using a time series exchange of energy during a year to determine the optimal component size of a photovoltaic/wind/battery system (PV/WT/Bat). The simulation results show that the lowest ratio of LPSP values corresponds to the higher GHG, EE, LCC, photovoltaic panels area (APV), battery storage capacity (Cn), wind turbines area (AWT) and vice versa. This means that demanding higher energy reliability leads to higher energy cost and pollution. A comparative analysis was made, showing the cons and pros of each LPSP value in order to allow the owner of the plant to choose the most suitable PV/WT/Bat configuration.

The problem of electrical power delivery is a common problem, especially in remote areas where electrical networks are difficult to reach. One of the ways that is used to overcome this problem is the use of networks separated from the electrical system through which it is possible to supply electrical energy to remote areas. These networks are called standalone microgrid systems. In this paper, a standalone micro-grid system consisting of a Photovoltaic (PV) and Wind Energy Conversion System (WECS) based Permanent Magnet Synchronous Generator (PMSG) is being designed and controlled. Fuzzy logic-based Maximum Power Point Tracking (MPPT) is being applied to a boost converter to control and extract the maximum power available for the PV system. The control system is designed to deliver the required energy to a specific load, in all scenarios. The excess energy generated by the PV panel is used to charge the batteries when the energy generated by the PV panel exceeds the energy required by the load. When the electricity generated by the PV panels is insufficient to meet the load’s demands, the extra power is extracted from the charged batteries. In addition, the controller protects the battery banks in all conditions, including normal, overcharging, and overdischarging conditions. The controller should handle each case correctly. Under normal operation conditions (20% < State of Charge (SOC) < 80%), the controller functions as expected, regardless of the battery’s state of charge. When the SOC reaches 80%, a specific command is delivered, which shuts off the PV panel and the wind turbine. The PV panel and wind turbine cannot be connected until the SOC falls below a safe margin value of 75% in this controller. When the SOC goes below 20%, other commands are sent out to turn off the inverter and disconnect the loads. The electricity to the inverter is turned off until the batteries are charged again to a suitable value.

As an efficient alternative to fossil fuels, renewable energy sources have attained great attention due to their sustainable, cost-effective, and environmentally friendly characteristic. However, as a deficiency, renewable energy sources have low reliability because of their non-deterministic and stochastic generation pattern. The use of hybrid renewable generation systems along with the storage units can mitigate the reliability problem. Hence, in this paper, a grid connected hybrid micro-grid is presented, which includes wind and photovoltaic resources as the primary power sources and a hydrogen storage system (including fuel cell and electrolyzer) as a backup. A new power management strategy is proposed to perform a proper load sharing among the micro-grid units. Hybrid (distributed/central) control method is applied for the realization of the control objectives such as DC bus voltage regulation, power factor control, synchronous grid connection, and power fluctuation suppression. Distributed controllers have the task of fulfilling local control objectives such as MPPT implementation and storage unit control. On the other hand, the central control unit is mainly responsible for power management in the micro-grid. Performance and effectiveness of the proposed power management strategy for the presented micro-grid are verified using a simulation study.

In view of problem of harmonic pollution caused by nonlinear loads in micro-grid, a control strategy of harmonic suppression of micro-grid based on virtual harmonic impedance was proposed. The principle of droop control is analyzed, and harmonic suppression model of two inverters running in parallel is given. The harmonic current is detected by SOGI model and voltage zero-steady-state error control is achieved by improved PR quasi-proportional resonant controller based on SOGI model. The virtual harmonic impedance control strategy and its implementation are analyzed. The simulation and experimental results verify correctness and reliability of the control strategy.

Palestine has a large number of rural areas which have no electricity services and cannot be connected to local grid in the near future for political and financial obstacles. This paper present the techno-economic impact of electrification of small communities by using micro-grid photovoltaic (PV) systems, and also reduction in CO2 emission in comparison to using diesel generator which causes high rates of environmental pollution will be analyzed. The implemented two micro-grid PV systems for electrification two communities in Palestine will cover the electricity needs of households and street lighting and can replace traditional unsustainable energy sources. Also, micro-grid PV systems have positive impacts on people’s health and on the environment besides economic and social benefits.

In this paper, an innovative transactive energy approach is proposed as viable option for coordinated distribution system planning across a certain horizon. The proposed approach is evaluated across a multi-looped (meshed) test system and is implemented with load growth having prosumers participating in the electrical market in transactive energy system aiming at evaluation on techno-economic basis. Apart from prosumer sensitivity analysis, evaluations have been carried across reducing total production cost of energy, reduction in per unit price, active power losses. Whereas improving voltage profile, cost of scheduling and consumer per kWh purchase and sales in comparison with traditional counterpart. The proposed framework includes optimization algorithm aiming at sources scheduling and IEEE 69 system for validation. The algorithm minimizes cost, maximizes energy efficiency, increases renewable energy mix and reduces consumers cost of energy purchase. Reduction of 51.44 % in cost of energy is achieved, whereas loss reduction of 12.6% is achieved. The comparison of IEEE 69-bus base case with the 10 %, 15% and 20% transactive energy applied with simulations to evaluate performance parameters that will directly benefit both prosumers and utility alike in-terms of low bills and further reduction of stress on the grid amid load growth across multiple years., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Featured Application: Hybrid micro-grids for residential applications with connections to renewable energy sources, electric vehicle recharging stations and the AC energy grid. This paper analyzes trends in renewable-energy-sources (RES), power converters, and control strategies, as well as battery energy storage and the relevant issues in battery charging and monitoring, with reference to a new and improved energy grid. An alternative micro-grid architecture that overcomes the lack of flexibility of the classic energy grid is then described. By mixing DC and AC sources, the hybrid micro-grid proposes an alternative architecture where the use of bi-directional electric vehicle chargers creates a micro-grid that directly interconnects all the partner nodes with bi-directional energy flows. The micro-grid nodes are the main grid, the RES and the energy storage systems, both, on-board the vehicle and inside the micro-grid structure. This model is further sustained by the new products emerging in the market, since new solar inverters are appearing, where a local energy storage for the RES is available. Therefore, the power flow from/towards the RES becomes bi-directional with improved flexibility and efficiency. [ABSTRACT FROM AUTHOR]