Grid-connected Configuration Research Articles

Electric vehicle charging by use of renewable energy technologies: A comprehensive and updated review

The majority of the vehicles in the world consuming fossil fuels that causes emissions of harmful greenhouse gases. In order to mitigate the emissions regarding the transport sector, Electric Vehicles (EVs) have attracted attentions. One of the main concerns in the development of EVs is supply of required power for the charging stations. Renewable energy systems would be clean and attractive options for supply of required power of charging stations. In recent years, several studies have investigated applications of renewable energy systems for charging stations of EV and analyzed different aspects of these technologies. This article reviews the research works on the design, optimization and performance investigation of charging stations coupled with renewable energy systems. Studies on EV charging systems powered by stand-alone or hybrid renewable energy systems are considered in the present article. According to the reviewed works, significant potential of renewable energy systems for supply of charging stations can be concluded. Different factors such as the applied technology and components, meteorological data of the installation site and operating condition influence the performance of these systems. Furthermore, it can be concluded that control design system can influence various aspects of EV charging technologies powered by renewable energy systems such as share of renewables in the grid-connected configurations and performance reliability. Challenges and opportunities associated with the development of these systems are provided in the current works and some recommendations are highlighted for the forthcoming studies and projects.

Optimal energy management system for grid-connected hybrid power plant and battery integrated into multilevel configuration

A novel optimal energy management system (EMS) using a nonlinear constrained multivariable function to optimize the operation of battery energy storages (BESs) used in a hybrid power plant with wind turbine (WT) and photovoltaic (PV) power plants is proposed in this work. The hybrid power plant uses a configuration based on a battery-stored impedance-based cascaded multilevel inverter to integrate renewable energy sources (PV power plants and WT) and BESs into the grid. The new optimal EMS seeks for satisfying the demanded power while dispatching power between BESs to optimize their efficiency. A grid-connected configuration is implemented to assess the efficiency of the suggested supervisory control under changes in renewable energy (changes in wind speed and irradiation), and in a varying active and reactive powers’ request. The BES efficiency obtained from the suggested EMS is set side by side to the BES efficiency got from a conventional EMS and a model predictive control (MPC), both working based on the state-of-charge (SOC) of the BES and balancing power EMS. The results from MATLAB simulation and the experimental results with the real-time OPAL-RT simulator (OP4510, OPAL-RT) and dSPACE MicroLabBox show the effectiveness of the suggested approach and the improvement in long-term BES efficiency.

Leakage Current Analysis of Non-Isolated Photovoltaic Grid-Connected System

Amidst mounting concerns over energy scarcity and the environmental repercussions of fossil fuels, renewable sources, spearheaded by solar energy, have garnered substantial societal attention, thereby propelling advancements in photovoltaics (PVs). In the realm of grid-connected (GC) PV systems, a pressing issue is the leakage current suppression in non-isolated GC PV inverters. As a ubiquitous architecture in PV systems, the non-isolated GC configuration is of paramount importance in practical applications. Yet, intrinsic attributes of PV systems have amplified the leakage current challenge within this setup. This paper endeavors to dissect the leakage currents in non-isolated PV GC systems, delving into the salient factors influencing them. It embarks on an exploration of the origins of leakage currents, subsequently analyzing the repercussions of LC filter parameters—spanning filter capacitance, Y capacitance, and common-mode inductance—on these currents. Drawing insights from extant scholarly discourse on leakage current mitigation, this study offers a synthesized perspective accentuated with augmented strategies, elucidating a comprehensive path forward for leakage current suppression.

Review on microgrids design and monitoring approaches for sustainable green energy networks

Microgrids are power distribution systems that can operate either in a grid-connected configuration or in an islanded manner, depending on the availability of decentralized power resources, such as sustainable or non-sustainable power sources, battery backup systems, and power demands. The extensive adoption of inverter-based systems poses numerous technological challenges, necessitating a centralized management system to assure the system reliability and monitoring of the energy delivery networks. Thus, this research begins by highlighting these significant obstacles and then analyzes the present-day advances in multilevel control architecture for delivering on promised functionality. This article also discusses the development of innovative control technologies, such as introducing collaborative distributed approaches and reducing conventional three-stage patriarchal administration to fewer stages of system integration and functioning.

Lagrange Multiplier-Based Optimization for Hybrid Energy Management System with Renewable Energy Sources and Electric Vehicles

The issues of energy scarcity and environmental harm have become major priorities for both business and human progress. Hence, it is important and useful to focus on renewable energy research and efficient utilization of distributed energy sources (DERs). A microgrid (MG) is a self-managed system that encompasses these energy resources as well as interconnected consumers. It has the flexibility to function in both isolated and grid-connected configurations. This study aims to design an effective method of power management for a MG in the two operating modes. The proposed optimization model seeks to strike a balance between energy usage, protecting the life of batteries, and maximizing economic benefits for users in the MG, with consideration of the real-time electricity price and constraints of the power grid. Furthermore, in order to accurately account for the dynamic nature of not only the stationary battery banks used as the energy storage systems (ESS) but also the built-in batteries of electric vehicles (EVs), the model is presented as a multi-objective, multiparametric and constrained problem. The solution is proposed to be found using the Lagrange multiplier theory, which helps to achieve good performance with less computational burden. Lastly, simulation results from both the isolated and grid-connected modes also demonstrate the effectiveness of the designed method.

Renewable Energy Contribution Based on Microgrid Using Photovoltaic and Wind Turbine Scenario

Indonesia's renewable energy mix offers an alternative to conventional fossil fuels. Indonesia has made a significant commitment to the role of exploiting this new energy in accordance with the Paris Agreement. This paper proposes the design of a microgrid architecture for a solar and wind hybrid power plant with grid-connected configuration and micro-scale power plant modeling in Ciheras Village, Cipatujah District, Tasikmalaya Regency, West Java. This architecture is divided into three scenarios in order to determine the best design qualities. The first scenario involves 50% photovoltaic (PV) and 50% wind turbine (WT), the second 60% PV and 40% WT, and the third 70% PV and 30% WT. The findings of the grid-connected microgrid were compared using supporting software, HOMER Pro. The various scenarios yielded performance analysis and renewable energy contribution. Modeling, calculation, simulation, and analysis demonstrate that the first scenario's potential energy output produces 25,655 kWh/year with an 88.2% Renewable Fraction (RF). The second scenario generates 26,194 kWh of energy per year, with a renewable fraction of 87.8%. The third scenario is the best based on the participation and role of distributed energy (PV-WT), with a higher amount of energy output of 30,691 kWh/year and a higher renewable proportion of 89%.

Techno-economic and environmental design of hybrid energy systems using multi-objective optimization and multi-criteria decision making methods

Reliable, affordable and sustainable supply of energy is of paramount importance. This can be achieved by designing and implementing hybrid renewable energy systems, also known as micro/smart-grids. The main goal of this study is the techno-economic and environmental multi-objective optimization of a decentralized energy system to provide electrical and thermal loads of a large energy consuming complex with daily average electric and thermal loads of 38.7 and 99.4 MWh, respectively. Pareto-optimal mix of several renewable and non-renewable technologies including photovoltaic (PV), wind turbine (WT), two types of combined heat and power technologies, namely micro-gas turbine (MGT) and fuel cell (FC), grid power, electrolyzer, hydrogen tank (Htank), battery and inverter is investigated. For this purpose, different configuration of these units were simulated in HOMER software, and the exact Pareto set was found by developing a MATLAB code. A total of 1945 optimal non-dominated designs including 11 stand-alone and 41 grid-connected configurations were found, in which the dominant configuration was PV/FC/Electrolyzer/Htank/Battery/Inverter/20%Grid. The Pareto sets included systems with a wide variety of characteristics; the range (average) of net present cost (NPC), loss of power supply probability (LPSP) and carbon dioxide emissions (CE) were 26.9–44.0 (36.1) M$, 0–10 (5.7)% and 8800.9–13649.2 (9790.4) tons/yr for off-grid scenario and 17.2–37.5 (27.2) M$, 0–10 (4.3)% and 11215.1–17968.2 (13476.1) tons/yr for on-grid scenario, respectively. The TOPSIS combined with weighting methods was introduced to choose final design among non-dominated solutions set. At last, sensitivity analysis revealed that the most significant variables on the NPC of the selected micro-grids are real interest rate, investment costs, electric and thermal loads and level of irradiation, respectively.

Bifurcation Stability Analysis of the Synchronverter in a Microgrid

Synchronized converters are being studied as a viable alternative to address the transition from synchronous generation to power-electronics-based generation systems. One of the important features that make the synchronous generator an unrivaled alternative for power generation is its stability properties and inherent inertial response. This work presents a stability analysis of a synchronverter-based system conducted through the bifurcation theory to expose its stability regions in a grid-connected configuration with an aggregate load model conformed by a ZIP model and an induction motor model. One and two-parameter bifurcation diagrams on the gain, load, and Thévenin equivalent plane are computed and analyzed. All the results confirm the strong stability properties of the syncronverter. Some relevant findings are that the reduction in a droop gain or time constant results in Hopf bifurcations and inertia reduction, but the increase in the time constant leads to decoupling between the reactive and active power loops. It is also found that the increment of a specific time constant (τf>0.02 s) increases the stability region on the droop gains plane to all positive values. It is also found that a low lagging power factor reduces the feasible operating and stable operating regions. For a lagging power factor above 0.755, subcritical Hopf bifurcation disappears, and also, the feasible operating solution overlaps the stability region. Finally, it is also found how the Thévenin equivalent affects the stability and that the stability boundary is delimited by Hopf bifurcations. The bifurcation diagrams are numerically computed using XPP Auto software.

Performance Characteristics of Electric Vehicle Battery using Charging Station System with Grid-Connected Configuration via Matlab Simulation

Due to the increase in demand for electric vehicles (EV) in recent years, the lack of EV charging stations and different EVs’ battery types are causing inconvenience to the user. The paper presents modeling and simulation of the grid-connected EV charging station system using MATLAB Simulink platform. The model consists of LCL filter, inverter, and battery charger. The inverter is regulated by a dq-frame that synchronizes with a phase-locked loop (PLL) to convert a three-phase alternating current (AC) source to a direct current (DC) source. Futhermore, lead acid (Pb-acid), lithium-ion (Li-ion), nickel-cadmium (Ni-Cd), and nickel metal hydride (Ni-MH) were tested and their performances were evaluated using the simulated EV charging station. All simulations were carried out and tested in the MATLAB Simulink platform. The results showed that Li-ion battery reaches the highest state-of-charge (SOC) value which is 51.66%, Pb-acid is 51.60%. Ni-MH is 51.55%, and Ni-Cd is 51.47% within 60s. The voltage values are 226.0V, 225.2V, 220.8V, and 220.2V for Pb-acid, Ni-MH, Ni-Cd and Li-ion, respectively. The findings revealed that the lithium ion is the most suitable for the use of EV since it had the fastest charging and slowest to reach its maximum threshold value of charging voltage.

Feasibility study for size optimisation of a geothermal/PV/wind/diesel hybrid power plant using the harmony search algorithm

ABSTRACT Using hybrid renewable energy systems is a smart choice for reducing the carbon emitted by power plants. It also helps climate change mitigation and global warming, leading to universal health for humans and the environment. The efficiency of these systems depends on choosing the right combination of renewable sources, their sizes, and proper scheduling of the generating units. This paper suggests an optimisation method for sizing a geothermal/PV/wind/diesel system, both in off-grid and grid-connected configurations. In the grid-connected mode, the possibility of selling surplus energy generated by renewable resources to the network is considered. Investigations reveal that without accurate control of geothermal reservoirs, they may become depleted. In this study, a strategy is suggested for unit commitment; moreover, the harmony search algorithm is used to find the optimal size of the hybrid system in both configurations. The effectiveness of the proposed approach is represented by simulating an HRES for Ferdows/Iran.

Hybrid energy system design using greedy particle swarm and biogeography‐based optimisation

Renewable energy systems (RESs) are affordable, clean and sustainable. However, their output power is intermittent. Therefore, RESs are usually combined with an energy storage system or conventional sources to make the overall operation uninterruptable. Optimal sizing of hybrid energy system components is imperative to be financially and technically feasible. In this study, a multi-objective optimisation based on a hybrid optimisation procedure, which combines the exploitation ability of the biogeography-based optimisation (BBO) with the exploration ability of the particle swarm optimisation (PSO), is used to handle the system design. This algorithm is known as greedy particle swarm and BBO algorithm (GPSBBO). Weighted sum method is added to the GPSBBO to handle the multi-objective nature of the design problem. A case study for a hybrid wind-PV energy system design in the standalone and grid-connected configurations is presented to illustrate the proposed method. Coverage of two sets, hypervolume and diversity performance indices are used to compare results of the proposed method to non-dominated sorting genetic algorithm and the multi-objective PSO. These indices show an improved performance of the suggested method in finding the optimal system design.

A techno-environmental assessment of hybrid photovoltaic-thermal based combined heat and power system on a residential home

This paper provides energy, exergy and environmental analyses for hybrid photovoltaic-thermal based combined heat and power system. Grid-connected configuration was used to increase the system reliability when satisfying the load. A series of battery and hot-water storages were applied for saving the excess of electricity and heat, respectively. Technical evaluations were conducted based on experimental data using real-time measurement devices throughout 31 days and estimated annual energy generation. The results showed that the average of electrical energy, thermal energy, electrical exergy and thermal exergy generations in a day were 0.34 kWh/m2, 0.60 kWh/m2, 0.34 kWh/m2, and 0.01 kWh/m2 per day, respectively with the solar irradiation average of 3.25 kWh/m2 per day. The maximum efficiencies of electrical energy, thermal energy, electrical exergy, and thermal exergy generations were 16.73%, 51.09%, 16.73% and 0.85%, respectively. This research also found the electrical and thermal energy efficiencies of the system were degraded by 1.20% and 1.89% per year, respectively. The system reduced the carbon dioxide emission annually by 855.1 kg per year or approximately 26.75% lower than a conventional separated system.

Optimal Sizing of Battery Energy Storage for Grid-Connected and Isolated Wind-Penetrated Microgrid

Renewable energy (RE) sources, particularly wind and solar are gaining more popularity due to their inherent benefits, consequently, nations have set ambitious goals to enhance the penetration of RE into their energy-mix. However, the RE sources especially wind and photovoltaic sources are intermittent, uncertain, and unpredictable. Therefore, there is a need to optimize their usage when they are available. Moreover, energy storage system like battery energy storage has much potential to support the RE integration with the power grid. This study, therefore, investigates the sizes of battery energy storage required to support a grid-connected microgrid and a stand-alone microgrid for 12 months considering hourly wind power potential. In this study, we have considered three Scenarios of operations and have determined the BESS sizes and recommend the best based on the cost of operation. Scenarios 1 and 2 are grid-connected configuration while Scenario 3 is a standalone microgrid supported with diesel generators. In each Scenario, the optimization problem is formulated based on the optimal operation cost of the microgrids. The powers consumed from the main grid are reported in Scenarios 1 & 2 and the extra cost spent on the maintenance of diesel generators is reported in Scenario 3. The study evaluates and analyzes the operational environmental effects and costs between the three Scenarios. The formulated problems are solved using the nonlinear optimization method. Simulations results proved the effectiveness of the study.

Energetic and economic analysis of a stand alone photovoltaic system with hydrogen storage

The study describes a stand-alone photovoltaic system in which the storage is realized using electrolytic hydrogen, converted into electricity in fuel cells. The aim of the research is the optimization of the sizing of the system elements chain (photovoltaic generator, electrolyzer, tank, fuel cell) with respect to the electric load to fulfil.A positive annual balance between hydrogen production and consumption must be guaranteed; furthermore, energy production surplus that cannot be stored or converted into hydrogen due to batteries or tanks capacity limits must be avoided.The energetic analysis and that of hydrogen production and consumption have been carried out on an hourly basis using the HOMER software.The study shows that, being the load active in the evening and the system disconnected from the grid, excess energy cannot be exploited unless large tanks are used, if high gas pressures are to be avoided. Consequently, the system use in public areas or residential buildings, where visual impact generated by tanks is hardly acceptable and safety rules do not allow high gas pressures, is advisable only in grid-connected configurations. Such problems are by far reduced when a marked self consumption is present.

Grid-connected Control Strategies for a Dual Power Flow Wind Energy Conversion System

A novel dual power flow (DPF) wind energy conversion system (WECS) based on an electrical variable transmission (EVT) machine is proposed recently. The structure of the novel EVT-based WECS, especially the grid-connected configuration, is different from any other existing WECSs. In this paper, the grid-connected control strategies of the DPF- WECS are proposed by controlling the DC-link and the inner rotor side converter, where the DC-link with and without the energy storage system (ESS) is considered separately. The relevant control strategies are presented to enhance the grid fault ride through capability of the DPF-WECS. Moreover, the maximum power point tracking control strategy and the pitch control strategy are also studied to implement the complete functionality of the DPF-WECS. The simulation model of the DPF-WECS is developed based on the EVT mathematical models and proposed control strategies. Finally, the simulation results verify the efficiency of the proposed control strategies for the DPF-WECS.

Optimal sizing of a wind/solar/battery hybrid grid‐connected microgrid system

Higher cost and stochastic nature of intermittent renewable energy (RE) resources complicate their planning, integration and operation of electric power system. Therefore, it is critical to determine the appropriate sizes of RE sources and associated energy storage for efficient, economic and reliable operation of electric power system. In this study, two constraint-based iterative search algorithms are proposed for optimal sizing of the wind turbine (WT), solar photovoltaic (PV) and the battery energy storage system (BESS) in the grid-connected configuration of a microgrid. The first algorithm, named as sources sizing algorithm, determines the optimal sizes of RE sources while the second algorithm, called as battery sizing algorithm, determines the optimal capacity of BESS. These algorithms are mainly based upon two key essentials, i.e. maximum reliability and minimum cost. The proposed methodology aims to avoid over- and under-sizing by searching every possible solution in the given search space. Moreover, it considers the forced outage rates of PV, WT and utilisation factor of BESS which makes it more realistic. Simulation results depict the effectiveness of the proposed approach.

Determination of energy to be supplied by photovoltaic systems for fan-pad systems in cooling process of greenhouses

Intending to increase the reliability of photovoltaic systems in agriculture sector, this work was developed to calculate the energy required by fan-pad systems for the cooling process in greenhouses. This calculation aims to ensure that the cooling process is completely sustainable. Today, there are no scientific tools to determine the electrical energy consumed by air exhaust fans. In order to address this problem, a mathematical model that predicts the greenhouse temperatures and ventilation rates, was calibrated with experimental data. The results correspond to a typical summer day with high solar radiation and showed that mathematical model can enhance the management of the energy for the cooling process. These results are: power of exhaust fans and their operating hours. It was used a methodology for selection of photovoltaic systems in order to design grid-connected configurations systems capable of producing, at least, the whole of the required energy by three greenhouses with different areas. It is concluded that the accuracy of the model is acceptable and with the methodology of selection of photovoltaic systems represent a reliable tool for calculus of electric power [W] and electric energy [kWh] consumed by the fans, which represent the main and initial design parameter of any type of photovoltaic system.

Components design and daily operation optimization of a hybrid system with energy storages

The study and the optimization of single devices, plants and integrated systems among producers and users, must be performed considering the possibility of energy storage and conversion among different forms of energy in order to reach the best overall energetic and environmental performance. Small CHP distributed plants are particularly interested in these challenges, both in stand-alone and grid-connected configurations. In this paper, the optimal design and management strategy of a trigeneration system composed by a PV plant, a diesel CHP engine, a reversible heat pump and a boiler is studied. The possibility of hybrid storage by means of a hot and a cold reservoirs, a pack of batteries, and a pumped hydro energy storage is investigated. By applying a model based on the Particle Swarm Optimization, the devices size and the operation strategy are simultaneously optimized. The most suitable devices' hourly-based operation profile and the best management strategy of the energy storages are predicted. The minimization of the overall costs is the problem's optimization target, while the main constrain is the fulfillment of the users' request of electricity, heat, cooling and drinking water.

PEM fuel cells analysis for grid connected applications

Polymer electrolyte fuel cells (PEFCs) fed by hydrogen were investigated with the aim of highlighting their behaviour during grid connected (GC) operation. Starting from the analysis of the systems working under practical conditions on the utility grid, the study was addressed to the materials degradation during GC applications. Endurance tests on 5 kW pre-commercial PEFC fuel cell systems were carried out at direct current constant load and in GC configuration. An evidence of disturbance on the FC system power output was observed. The study was focused on Low Frequency (LF) 100 Hz noise (current ripple) that can mainly affect the fuel cell performance and lifetime. In order to evaluate the issues that occurred on the active components of a PEMFC, when subjected to a current ripple, electrochemical characterizations were performed on single cells of 5 cm 2 subjected to a dynamic load. Post mortem physico-chemical analyses showed materials degradation on the cathode catalyst associated to the current ripple.

Feasibility analysis of renewable energy supply options for a grid-connected large hotel

This study presents an analysis of the technical and financial viability of grid-only, RES-only and grid/RES hybrid power supply configurations for a large-scale grid-connected hotel (over 100 beds). Assessment criteria comprised net present cost (NPC), renewable fraction (RF) and payback time. The RES software HOMER (National Renewable Energy Laboratory, US) was utilised as the assessment tool with modeling performed with hourly load data input from a hotel located in a subtropical coastal area of Queensland, Australia. The results demonstrate that RES, in principle, has the potential to supply significant power for a large-scale tourist accommodation, in conjunction with the grid-electricity supply. Optimisation modeling demonstrated that, at 2004 prices, the NPC of the grid/RES hybrid configuration is comparable with the grid-only supply and resulted in a RF of 73%, a payback time of 14 years and a reduction in greenhouse gas emissions of 65%. Optimisation modeling also showed that whilst a RES-only configuration can potentially supply 100% of power demand, such a configuration is presently uneconomical given current electricity costs. Results indicate that wind energy conversion systems (WECS), rather than photovoltaics, are the most economically viable RES technology for large-scale grid-connected operations. Specifically, large-scale WECS (over 1000 kW) are more efficient and more economical than multiple small-scale WECS (0.1–100 kW). Hydrogen fuel cells and storage are presently uneconomical in grid-connected configurations. Sensitivity analysis demonstrated that operations that rely on grid-only supply are more economically susceptible to escalations in electricity costs and the imposition of carbon taxes, in comparison to grid/RES hybrids. Indeed, at present electricity prices, which have nearly quadrupled since 2004, the grid/RES hybrid is more economical over a 20-year span than the grid-only system, with a NPC which is 50% lower, and a payback time of 4.5 years. The analysis demonstrates that RES is both technically feasible and economically viable as an addition to grid-connected supply for large-scale tourist operations, and should become more attractive as costs of conventional supplies increase.