Integration Of Renewable Sources Research Articles

A Distributed and Robust Energy Management System for Networked Hybrid AC/DC Microgrids

Hybrid AC/DC microgrids (MGs) provide efficient integration of renewable sources into grids and the interconnection of multiple MGs can improve system reliability, efficiency and economy by energy sharing. In this paper, a distributed and robust energy management system is proposed for networked hybrid AC/DC MGs. For each individual MG, an adjustable robust optimization model is proposed to optimize its individual operational cost considering the uncertainty of the renewable generation and load demand. For the networked-MGs system, the energy sharing information of each MG is coordinated by the DC network to minimize the power transmission loss with network constraints. The overall optimization model is formulated, exactly convexified and solved in a distributed manner by the alternating direction method of multipliers (ADMM), where only limited information is required from each MG entity (i.e., the power injection to the network) and thus information privacy is guaranteed. Simulations of the networked hybrid AC/DC MGs are conducted to demonstrate the effectiveness of the proposed energy management system.

Molecular Modeling of Coprocessing Biomass Fast Pyrolysis Oil in Fluid Catalytic Cracking Unit

Integration of renewable sources into a transportation fuels production system through FCC units in an oil refinery has gained increased attention. For better understanding of the effect of the reaction conditions, blending ratios, and feed properties on product yields and qualities, kinetic modeling of FCC units is necessary. In this Article, a novel framework for molecular-level modeling of coprocessing biomass fast pyrolysis oil (FPO) with vacuum gas oil (VGO) in an oil refinery FCC unit is developed, which includes molecular-level characterization of biomass pyrolysis oil and VGO feed blends, synthesis of large-scale and complex reaction network, molecular-level kinetic modeling, and parameter estimation. The rule “same type of reactions have similar activation energies” is employed to reduce the number of kinetic parameters. The kinetic parameters in the proposed model are estimated using a hybrid solution algorithm combining deterministic and stochastic optimization methods. The computational results demonstrate an overall good agreement between measured and predicted yields using the developed kinetic model for VGO:FPO blending ratio, C/O ratio, and reaction temperature of 95:5, 5, and 530 °C, respectively. PONA composition in each layer of product stream (e.g., gasoline, diesel, gasoil, etc.) as well as oxygen compounds compositions and oxygen content are also successfully predicted. The proposed framework can be easily extended for modeling of other refinery processes and creates potentials for rigorous simulation and optimization of refinery operations to achieve maximization of refinery profit or better product quality control.

Electricity market options for heat pumps in rural district heating networks in Austria

The integration of renewable heat sources in the electricity grid represents a challenge in the energy system due to their stochastic production character. Besides, the rural district heating sector in Austria is confronted with a large number of biomass boilers reaching the end of their lifetime and thus operating unprofitably. In this context, heat pumps have a decisive role in supporting both networks and providing flexibility. However, their implementation is not yet extended in Austria. This paper shows the potential of heat pump utilization in several concrete use cases. Results determine that heat pumps can be active players in the Austrian electricity market. Energy costs can be saved by taking advantage of low prices in the day-ahead market and additional revenues can be earned in the balancing market. Offering negative balancing energy for the automatic frequency restoration reserve (aFRR) presents a potentially interesting business case since it provides a considerable reduction in the heat generation costs. Considering the complexity and uncertainty of the future market development, awareness on the most influencing factors gains great relevance. Results show that fluctuations in the biomass price and call probabilities can affect the heat pump profitability.

Optimal Hierarchical Control of DC Microgrids: modelling and experimental validation

Abstract DC Microgrids are receiving a growing interest thanks to the advantages offered by the integration of renewable sources. This paper presents an optimal hierarchical control for DC microgrids that performs multiple control objectives, like (i) voltage regulation, (ii) minimization of the losses, (iii) power-sharing, (iv) energy storage management and (v) economic savings. The hierarchical control is made up of sequential actions so that, at the higher level, the optimal plan for power generators and for storage systems is generated and then sent to the model predictive control. This controller is the core of this study and it has three main functions such as (i) voltage regulation, (ii) energy storage management and (iii) tracking of the optimal planning, taking into account the different characteristics of the DC components and generating the references for the low-level controller. The proposed control based on optimization has been validated with good results on the real low-voltage DC microgrid in RSE.

Optimal distribution grid expansion planning under consideration of dynamic DG curtailment

This study presents a new time-series-based approach based on a dynamic curtailment for the planning of high-voltage distribution grids. The approach enables the optimal integration of renewable energies source (RES) into the existing grid structure and aims to keep the necessary network reinforcements as low as possible. For this purpose, the developed planning method uses a dynamic curtailment method and determines, based on the curtailment results, which lines need to be reinforced most appropriately. The aim of the presented simulation process is to reduce the curtailed energy of RES to a legally defined value and to keep it as low as possible. This enables the targeted identification of grid reinforcements and expansion measures through the developed method in time-series-based, probabilistic grid planning.

Energy Cost Optimization of Hybrid Renewables Based V2G Microgrid Considering Multi Objective Function by Using Artificial Bee Colony Optimization

The worldwide demand for reduction of CO2 pollution, with more penetration of renewable energy sources and an increased number of electric vehicles (EVs), demonstrates the importance of economic dispatch (ED) with taking into account the reduction of CO2 emission. ED is a classical problem in which EVs impose more penetration as a dynamic load, and its impact as vehicle-to-grid (V2G) is the possible future trend with cost minimization. Based on the integration of EVs and hybrid renewable sources concerning both economic dispatch and pollution minimization, the multi-objective function is converted into a single comprehensive objective by using the judgment matrix methodology. In this paper, the investigation involves the minimization of the cost of all three objectives viz. operation cost, pollution cost, and carbon emissions with ED by incorporating V2G technology. The algorithms which include particle swarm optimization, as well as artificial bee colony, are applied under various operation and control strategies. The proposed models are verified and analyzed with different case studies. In terms of operation economics, the simulation results validate the superior performance of EVs based microgrid (MG) model in the coordinated charging and discharging mode. Further, the comparison of both algorithms shows better results with the ABC algorithm in terms of cost minimization of all objectives. ABC is better in V2G based microgrid with coordinated charging and discharging mode while its performance is significant during a large number of EVs (i.e., 700 EVs). Moreover, the load shedding scenarios are integrated which enables the MG system to operate in dual mode (i.e., seamless transition). In this paper, the main contribution involves penetration of EVs as dynamic load and its V2G impact in a coordinated or uncoordinated way, application of ABC algorithm for this particular load problem with improved results, and inclusion of short-term load shedding scenarios.

Recursive Digital Filter Based Control for Power Quality Improvement of Grid Tied Solar PV System

This article deals with the implementation of a control approach for an active power transfer between solar photovoltaic (PV) array and the grid/ load along-with power quality (PQ) improvement by eliminating harmonics and compensating reactive power required by the load in the distribution network. The PQ problems at the point of intersection, are increasing preeminently with respect to voltage and current harmonics due to integration of renewable sources. The recursive digital filter control implemented here for PV grid interfaced system is efficient in improving PQ indices by operating round the clock and ensuring power transfer between utility grid and connected loads. The prominence of the control algorithm lies in the efficient switching of voltage source converter (VSC), by generating reference grid currents, which are obtained through indirect current control technique. The recursive digital filter is utilized for processing the load currents and extracting the active power component of them. These active power components of load currents are used for generating the reference grid currents in this system. A prototype of the system is developed in the laboratory and its performance is studied for varying loads, changing solar insolation, and voltage swell, voltage sag and voltage distortion conditions.

DE Optimized LFC of Three Area Interconnected Power System with DFIG Wind System under Deregulated Environment

Load frequency control (LFC) of an interconnected three-area power system with HVDC link under deregulated environment in presence of wind system is investigated. Integration of renewable sources in to exiting plants will affect the system frequency and hence design of a suitable controller is needed to maintain frequency within limits. Study of impact of wind penetration in to deregulated environment is a key factor. The secondary PID controller improves the overall system performance during sudden load disturbances and random variations of wind input. The optimal values of PID controllers in all three areas and pitch control in wind system are tuned by using Differential Evaluation (DE) algorithm.

Integration of Cold Ironing and Renewable Sources in the Barcelona Smart Port

Cold ironing, which is the procedure of supplying shoreside electrical power to a ship at berth when its engines are turned off, arises as the eco-friendly way to deliver power to ships while they are berthed in ports, thus avoiding the use of diesel engines onboard, which provokes the emission of large amounts of greenhouse gases into the atmosphere. The aim of this study is twofold. First, a survey of research developments on cold ironing is carried out in order to show the state-of-the-art on the problem of greenhouse gases emitted by ships while docked and how to tackle it. Current regulations and examples of current ports that make use of technologies for cold ironing purposes are also shown. Second, the study proposes the use of a cold ironing system in the port of Barcelona, where the power generation is entirely given by renewable energy systems (wind turbines and photovoltaic panels). The idea is to contribute to the wide spread of cold ironing within smart port microgrids to achieve the goal of zero emissions from berthed ships.

Analysis of the influence of DC optimizers on photovoltaic production

Energy efficiency is a key element in the Smart Cities (SC), in which integration of renewable sources is a reality. Small-scale integration is usually implemented with photovoltaic (PV) and solar thermal energy. The shadows on the PV modules are a reality as they are originated by unavoidable buildings and obstacles existing in the cities. These shadows will cause the decrease in PV efficiency. Therefore, the increase in PV efficiency is essential. This increase in efficiency can be achieved by associating the DC-DC converters (DC-DC optimizers) with PV modules. This work presents and compares simulations and real results of the influence of DC-DC optimizers in the efficiency of PV modules. In addition, the work includes an economic study of the installation of DC optimizers considering three different electricity price scenarios.

Large-Scale Pumped Thermal Electricity Storages—Converting Energy Using Shallow Lined Rock Caverns, Carbon Dioxide and Underground Pumped-Hydro

A fast-paced energy transition needs a higher penetration of renewables, of heating and cooling in the worldwide energy mix. With three novelties 1-of using shallow high-pressure LRC (Lined Rock Cavern) excavated close to storage needs, 2-of using a slow-moving CO2 piston applying steady pressure on the hydro part of UPHES (Underground Pumped Hydro Energy Storage) and 3-of relying on inexpensive thermal stores for long-duration storage, CO2 UPHES coupled with PTES (Pumped Thermal Electricity Storage) could become, at expected Capex cost of only 20 USD/kWh electrical, a game-changer by allowing the complete integration of intermittent renewable sources. Moreover, even though this early conceptual work requires validation by simulation and experimentation, CO2 UPHES as well as UPHES-PTES hybrid storage could also allow a low-cost and low-emission integration of intermittent renewables with future district heating and cooling networks.

An ab initio issues on renewable energy system integration to grid

With the introduction of new technologies such as Renewable Energy Resources (RER), Energy Storage Systems (ESS), Smart Grid technologies, Micro-Grid technologies, Distributed Generation (DG), etc., in the generation, transmission and distribution sectors, slowly but surely the entire power system scenario is changing, and it is up to the power system planners, researchers, regulators, operators and policy-makers to ensure that the power system adapts to the changes as smoothly as possible; which is easier said than done. With change comes the unknown (issues and challenges) and unless a majority of these unknowns are identified, analyzed and addressed properly, the system cannot achieve its maximum potential. The proper management, operation and integration of renewable and alternate sources of energy to existing grid is one of the promising ventures to increase the capacity of grid and at the same time make the grid more eco-friendly. This paper presents a review of the challenges and issues associated with renewable energy integration to grid and some of the existing techniques that are in use to address these issues. In order to make this review paper as detailed as possible, we have tried to identify the many issues and their corresponding solutions as much as possible.

Evaluation of energy losses in low voltage distribution grids with high penetration of distributed generation

The transition of the conventional energy supply scheme, typically characterized by integration of more small-scale renewable sources and reduction of greenhouse gas emissions, is an inevitable trend. At the same time, efficient operation of the existing distribution system, which hosts these decentralized generators, is equally important toward achieving a sustainable energy system. In order to keep track of the upcoming changes regarding system efficiency, an accurate determination of grid losses in the distribution system is the fundamental step. However, to evaluate the energy losses of power distribution grids at large scales is a difficult task. Currently, distribution system operators only have limited options for determining grid losses, especially in the low voltage sector. The growing installation rate and the fluctuating nature of distributed generations pose further difficulties and uncertainties for the loss evaluations. For this reason, a comprehensive and accurate evaluation on grid losses, which takes the grid information, the available metering data and the installed distributed generations into account, is highly relevant. In this work, a novel evaluation framework for energy losses for low voltage distribution grids is presented. Our evaluation framework consists of three building blocks: a fully automatic and parallelized generation of grid models, the determination of grid losses based on annual power flow simulations as well as a data-driven reference grid modeling method. We demonstrate and validate this framework based on a data-set of 5000 real distribution grids (including about 31,000 low voltage feeders), located in the service area of one of the largest German distribution system operators. The key contribution of the proposed framework is the automatic approach for grid modeling and feature evaluation at large scales and the implementation of the advanced, comprehensive reference grid modeling method for evaluating relevant grid features and estimating grid losses. This novel reference grid modeling approach and the complete framework are further validated by comparison with both exhaustive simulation results of grid losses and three state-of-the-art regression schemes. Among the case studies, this proposed evaluation framework shows a very good performance in the evaluation of grid losses. Moreover, this evaluation framework provides useful insights concerning the allocation of energy losses as well as the impact of distributed generations on grid losses. Accordingly, this novel evaluation framework gives distribution system operators a powerful tool considering the evaluation and improvement of system efficiency.

Supplementary frequency control in power systems via decentralised V2G/G2V support

One of the smartest evolution in the electrical power system is the integration of various renewable sources. It is an effective way to cater consumers growing power demands. The intermittency issues in renewable sources may lead to generation and demand imbalance. This imbalance creates various issues like frequency fluctuations, voltage variation, power quality problem and so on. This study proposes a method to reduce the frequency deviation. More the electric vehicles (EVs) in this system, then more the mobile storage devices for vehicle to grid (V2G). The charging/discharging rates of EVs are controlled as per the regulation signal coming from the system operator. The proposed scheme has been simulated using the frequency regulation data acquired from PJM. The proposed algorithm controls the total charging/discharging power based on the regulation signal and this is used to modify the charging/discharging rates of EVs. The result shows a better performance during grid to vehicle (G2V), at time 20:00 the regulation signal is −650 kW and it fully met by EVs. However, during V2G the performance is quite good, at time 08:00 the regulation signal is 800 kW and EVs meet only 180 kW due to less number of EVs for discharging.

Demand response-based dynamic dispatch of microgrid system in hybrid electricity market

Purpose Technological development has not only helped in effective integration of renewable sources but also made it possible for consumers to participate in system operation. Different market players are coming up in the electricity market, microgrid being one of them. Thus, this paper aims to investigate consumers’ role in the dispatch of a microgrid system that has a hybrid market structure under varied system conditions. Design/methodology/approach The mathematical model developed has been solved by the CONOPT solver in the GAMS optimization tool. GAMS-MATLAB interfacing is done to obtain solutions. Findings The problem formulated shows the effect of consumers in dispatch and overall operational cost. Consumers’ participation has been proposed through a quadratic cost function. The system operation under pool and bilateral contracts has been investigated. It shows that proper incentives to the consumers can help in reduction and effective management of the demand, carbon emission and overall system operational cost. Originality/value This paper considers the hybrid market structure to find the load dispatch in a microgrid system. The participation of consumers in the microgrid system has been implemented considering variations in wind power, solar power and load. The power exchange between the grid and microgrid system has been modeled showing the contribution of the consumers in system operation.

Multi‐frequency power system for renewable source integration in smart grid

This study presents a new power system enabled by power-electronic technology for renewable source integration in micro-grid. The micro-grid is decoupled into multiple independent power channels. These power channels are used for any source to any load-independent power transfer over the common power transmission line. This system works on the principle of frequency-selective orthogonal power transfer and superposition theorem. To demonstrate the proposed power system, a laboratory-scale prototype of an interconnected two-source two-load system is developed. The two sources independently transfer power to their respective loads at power transmission frequencies of 500 and 0 Hz (DC is also a valid frequency for power transmission), respectively, over the common power transmission path. Thus, a two-source two-load system is decoupled into two independent power channels. The proposed system is modular and scalable in structure and can be extended for any number of sources and loads. Finally, the effectiveness of the proposed system is verified through simulations and experimental results which demonstrates independent transmission of 100 W power in each of the two power channels of the two source-two load interconnected system.

Assessment of tools for urban energy planning

In recent years, studies and policies have encouraged the diffusion of distributed energy supply technologies and large integration of renewable sources. This increases the need for new professionals in energy planning. Several computational tools for energy planning have been developed as described in the technical literature. However, energy planners of urban/district areas engaged in the transition towards smart systems related to buildings energy services require well-documented tools to evaluate the combination of available energy sources by proper conversion technologies. With this, after a scientific review, we selected 17 tools targeted on an urban/districts scale that can evaluate several energy services, sources and/or technologies, and provided with detailed and easily accessible documentation. These tools were classified based on their defined features: analysis type, operation spatial scale, outputs time scale, energy service, and licence. Among them, 6 user-friendly tools were identified (energyPRO, HOMER, iHOGA, EnergyPLAN, SIREN, WebOpt) that can provide hourly energy calculations and can be considered as viable for widespread use. Specifically, the general information, functionalities, structure, graphic user interface, required input data, and outputs were described. Therefore, the energy planners are guided towards choosing the most suitable tool based on their skills, aims, and data availability for a specific application.

Operation of networked multi-carrier microgrid considering demand response

PurposeMicrogrids are inclined to use renewable energy resources within the availability limits. In conventional studies, energy interchange among microgrids was not considered because of one-directional power flows. Hence, this paper aims to study the optimal day-ahead energy scheduling of a centralized networked multi-carrier microgrid (NMCMG). The energy scheduling faces new challenges by inclusion of responsive loads, integration of renewable sources (wind and solar) and interaction of multi-carrier microgrids (MCMGs).Design/methodology/approachThe optimization model is formulated as a mixed integer nonlinear programing and is solved using GAMS software. Numerical simulations are performed on a system with three MCMGs, including combined heat and power, photovoltaic arrays, wind turbines and energy storages to fulfill the required electrical and thermal load demands. In the proposed system, the MCMGs are in grid-connected mode to exchange power when required.FindingsThe proposed model is capable of minimizing the system costs by using a novel demand side management model and integrating the multiple-energy infrastructure, as well as handling the energy management of the network. Furthermore, the novel demand side management model gives more accurate optimal results. The operational performance and total cost of the NMCMG in simultaneous operation of multiple carriers has been effectively improved.Originality/valueIntroduction and modeling of the multiple energy demands within the MCMG. A novel time- and incentive-based demand side management, characterized by shifting techniques, is applied to reshape the load curve, as well as for preventing the excessive use of energy in peak hours. This paper analyzes the need to study how inclusion of multiple energy infrastructure integration and responsive load can impact the future distribution network costs.

Evaluation of environmental and energy effects of biomass district heating by a wide survey based on operational conditions in Italy

Abstract The research aims to evaluate the technical features and the performance of a large sample of biomass district heating plants (BDHP), mainly located in northern Italy and fuelled by wooden chips. These plants have determined the development of a local energy supply chain based on forest by-products, as an alternative to traditional fossil fuels. Main strength of the research is the representativeness of the sample (65 plants of different size and features) and the reliability of data collected. After a deep desk research, data were collected by a questionnaire and then refined and elaborated by an Excel database. Energy, environment and economy indices and indicators were calculated. Despite the large range of variation of results, the following improvements and drivers can be defined: reduction of heat losses between heat generation and final users; optimization of the matching between heat demand and supply during the day and taking into account the winter or summer operative conditions, and, in a smart district heating framework, integration of other renewable sources, cascade use of heat, cogeneration and district cooling (where needed).

Investigation of the Magnetic Response of a Nanocrystalline High-Frequency Magnetic Link With Multi-Input Excitations

With the technological advancement of magnetic materials and semiconductor devices, the use of high-frequency magnetic link made of high-saturation induction and low specific core loss nanocrystalline alloy has been gaining popularity to replace the common dc link or ac link specially in integrating multiple renewable sources to the grid. The magnetic integration of multiple renewable sources through a common magnetic link has a number of advantages including galvanic isolation compared with the common dc or ac link. However, the magnetic response of the common magnetic link under multi-input excitations highly affects the energy conversion efficiency. To the best of the authors' knowledge, the magnetic response of an advanced magnetic-material-based magnetic link under multi-input excitations has not been well investigated in the literature. In this paper, a systematic investigation is carried out to interconnect multiple sources through a common magnetic link. The magnetic response and the procedure used in the investigation are also presented and discussed in this paper.