Amount Of Renewable Energy Sources Research Articles

BESS Deployment Strategy in Jeju Carbon-Free Islands for Reducing Renewable Energy Curtailment

Renewable energy curtailment often occurs to accommodate large amounts of renewable energy sources in power systems while maintaining system stability and reliability. Widely known methods, such as new transmission line construction, the introduction of demand-side resources, and the reduction of conventional generator output, can minimize the occurrence of curtailment; however, there are difficulties in introducing them because of social and economic problems. For these problems, the Jeju power system adopted a battery energy storage system (BESS) resource to mitigate the curtailment and secure frequency stability with the high penetration of renewable energy. The small-size Jeju island power system is operated with reliability must-run (RMR) units and high-voltage direct current (HVDC) lines connected to the mainland. Since the number of RMR units contributes to frequency stability by providing inertia, reducing the number of operating units for curtailment mitigation is difficult. Therefore, in this paper, based on the current “Carbon-Free island” policy and operation plan of the Jeju power system, we proposed a BESS for reducing the number of RMR units, observe the effect of reducing curtailment using the BESS, and suggest a practical operation plan to reduce the number of RMR units under conditions that secure frequency stability.

Quantifying the Flexibility of Electric Vehicles in Germany and California—A Case Study

The adoption of electric vehicles is incentivized by governments around the world to decarbonize the mobility sector. Simultaneously, the continuously increasing amount of renewable energy sources and electric devices such as heat pumps and electric vehicles leads to congested grids. To meet this challenge, several forms of flexibility markets are currently being researched. So far, no analysis has calculated the actual flexibility potential of electric vehicles with different operating strategies, electricity tariffs and charging power levels while taking into account realistic user behavior. Therefore, this paper presents a detailed case study of the flexibility potential of electric vehicles for fixed and dynamic prices, for three charging power levels in consideration of Californian and German user behavior. The model developed uses vehicle and mobility data that is publicly available from field trials in the USA and Germany, cost-optimizes the charging process of the vehicles, and then calculates the flexibility of each electric vehicle for every 15 min. The results show that positive flexibility is mostly available during either the evening or early morning hours. Negative flexibility follows the periodic vehicle availability at home if the user chooses to charge the vehicle as late as possible. Increased charging power levels lead to increased amounts of flexibility. Future research will focus on the integration of stochastic forecasts for vehicle availability and electricity tariffs.

Unlocking energy flexibility of municipal wastewater aeration using predictive control to exploit price differences in power markets

To accommodate the increasing amount of renewable energy sources in electricity grids it is crucial to utilize the flexibility of all electricity consumers. Municipal wastewater treatment plants consume approximately 1 % of the electricity consumption of a country’s total electricity consumption, to reduce nutrient concentrations from the incoming wastewater before discharging the water back into the environment. In this paper, a novel economic optimal control strategy is proposed for unlocking the available energy flexibility in wastewater treatment. The strategy suggests that the power consumption in wastewater treatment can be flexible since the water is treated in large tanks with long retention times where specialized aeration equipment is repeatedly switched on and off. By controlling these switching times with respect to nutrient concentrations, electricity consumption can be predicted and shifted in time and hence provide short-term demand side flexibility. The proposed principle is used to reduce the operating costs of a wastewater treatment plant by enabling the flexibility to distribute the aeration load to periods with less expensive power prices. The performance of the proposed method is demonstrated for the operation of a single wastewater treatment plant and the strategy is backtested on Nord Pool market data from 2019. This shows modest savings of 1.15% if only the day-ahead market is considered. However, if the regulating and special regulating power prices are included in the optimization the realized savings are in the magnitude of 7.23% and 27.32%, respectively. Thus this study is considered as a step towards exploiting flexibility for the benefit of reducing the combined taxation and aeration cost of wastewarer treatment.

Comparison of Control Strategies to Realize Synthetic Inertia in Converters

The increasing amount of renewable energy sources in the electrical energy system leads to an increasing number of converter-based generators connected to the electrical power grid. Other than conventional power plants that are often connected to the grid via synchronous generators, converter-based generators do not provide mechanical inertia intrinsically. Therefore, ensuring frequency stability in the electrical power grid might become even more difficult in the future. With the concept of synthetic inertia, the converter-based generators partially imitate the behavior of conventional generators. By implementing such a concept in converters, they are capable of contributing to frequency stability as well. This paper compares two strategies to realize synthetic inertia by modeling converter-based generators in MATLAB/SIMULINK and simulating their behavior in a small Microgrid. The results prove that any kind of realization of synthetic inertia helps to improve frequency stability. Each of the two investigated strategies may have their scope of application in a future electrical energy system.

Nonlinear Model Predictive Control of a Variable-Speed Pumped-Storage Power Plant

Optimal operation and control of (variable-speed) pumped-storage power plants (PSPPs) is essential to meet the growing demands on the dynamics for the stabilization of power distribution grids with an increasing amount of renewable energy sources. Existing work on the control of PSPPs is typically based on rather simplified system models, in particular of the (long) pipeline system. In this article, a nonlinear model predictive control (NMPC) strategy is proposed, which enables fast closed-loop dynamics while keeping all system constraints, including the pressure constraints along the pipeline system. The control strategy is based on a physics-based model, which enables easy parameterization and application to other plant sizes or topologies. To ensure real-time capability of the model predictive control (MPC) strategy, a number of measures are outlined in this article. Finally, the feasibility of the proposed control strategy is demonstrated by detailed simulation studies. An accurate tracking for fast changing desired grid powers as well as a high robustness with respect to parameter uncertainties is demonstrated.

Consumer viewpoint on a new kind of energy market

Energy markets are currently evolving due to the rapid digitalization, increasing amount of renewable energy sources, and rapid technology development. Market actors are being forced to adapt their business models to these changes or find new business opportunities. In our earlier work, new change scenarios were identified that reflect the future business potential of Finnish companies in energy domain particularly with respect to demand flexibility, new actor roles, new consumer services and novel activities in a new kind of energy market. The purpose of this paper is to examine the energy consumer viewpoint on these new scenarios. As consumers are becoming more central actors in the energy markets via demand flexibility and new type of services, it is critical to design the solutions in a user-centric way. A consumer survey was conducted to identify consumers’ opinions and attitudes and determine their willingness to participate in the new energy market scenarios. The survey reached a large number of consumers representing a considerable portion of the Finnish population. According to the results, a half of consumers consider the forecasted scenarios as positive changes, but a lot of communication must still be done in order to win the majority support of consumers.

Report on a Plus-Energy District with Low-Temperature DHC Network, Novel Agrothermal Heat Source, and Applied Demand Response

District heating and cooling networks can pose the possibility of including a variety of renewable energy sources as well as waste heat into a district’s heat supply concept. Unfortunately, low demand densities as they increasingly occur through higher building energy standards and in rural areas render conventional heating and cooling networks inefficient. At the same time, power-to-heat is becoming more and more important to make use of a larger amount of renewable energy sources on the electrical side by providing more flexibility by means of demand response and demand-side management. Within this work, a rural Plus-Energy settlement is presented addressing those topics by a low-temperature district heating and cooling network connected to a novel agrothermal collector supplying 23 residential buildings with decentralized heat pumps and PV systems. The collector, the network, and six of the buildings are equipped with comprehensive monitoring equipment. Within those buildings, forecast and optimization algorithms are implemented to adapt their heat pump operation to enable an increase of self-consumption, to include flexible electricity tariffs, and also to participate in power markets. Thereby, for the low-temperature district heating and cooling network, it has been shown that the concept can operate in the future at competitive heat costs. On the building level, up to 50% of cost savings could be achieved under ideal conditions with the optimization of the self-consumption of PV electricity. However, to ensure optimal results, the individual system components have to be dimensioned for this task.

European projects on district energy-renovations and Italian best practices

Buildings are the major source of greenhouse gas releases: lowering their energy consumption and emissions is particularly challenging for the existing building stock. This topic was examined at an individual building level in the International Energy Agency’s EBC Annex 56. However, the increasing request of nearly zero energy buildings highlight another important topic: the need of an increase in energy production for satisfying the required amount of renewable energy sources. This task could be solved at the district level for the existing buildings, even if it is a complex issue. This work presents a general introduction on the topic of Urban and Regional Integrated Energy Planning, with a focus on the regional and supraregional process to create and manage energy plans. After the first introductory part, the method is explained through a description of its main phases and the tools used. The subsequent section presents a general overview on the European projects that deal with the problem of district regeneration; the ones that are more related to the topic of this work are considered in a deeper way through tangible applications in Italian cities. The study of already done examples will help in the definition of benefits and drawbacks, with the aim to defining newer and better energy planning procedures.

Probabilistic Power Flow Analysis for Hybrid HVAC and LCC-VSC HVDC System

Some innovative works have been done to probabilistic power flow (PPF) analysis for hybrid HVAC and LCC-VSC HVDC system in this paper. Firstly, a unified method considering precise model of converters is proposed to solve a general deterministic power flow (DPF) calculation including hybrid LCC (Line Current Converter) and VSC (Voltage Source Converter), the pure VSC-MTDC (Voltage Source Converter-Multiple Terminal Direct Current) and pure LCC system. Meanwhile, with a large amount of renewable energy sources integrated to the main grid through DC grids, it will impose a stochastic impact on the secure operation of such hybrid AC/DC grids. Therefore, it becomes necessary to model the probabilistic uncertainties and analyze their effects on the operation of hybrid AC/DC systems under different control modes. Nevertheless, most power flow analysis methods for hybrid AC/DC system are still deterministic in nature. Therefore, a probabilistic method based on the combination of Nataf transformation and Latin hypercube sampling (LHS) is developed and proposed to solve this complex PPF problem in an efficient manner, which considers correlated various probabilistic uncertainties, e.g. wind speeds, solar radiations and loads following different types of probability distribution. Finally, the effectiveness of the unified DPF method is validated in a modified IEEE 14-bus system, while the proposed PPF is verified in a modified IEEE 118-bus system and the effects of uncertainties on the diverse operation modes of hybrid AC/DC grids are discussed as well.

Integrated model for renewable energy planning in Turkey

ABSTRACTAll economic sectors are associated with energy use; therefore, government organizations aim to supply sustainable energy for human needs and economic growth. In particular, increased environmental concerns of the public in Turkey have impacted policymaking for renewable energy (RE) management in Turkey. The primary objective for RE sources of the Turkish Ministry of Energy is to ensure that 30% of the share of electricity production is from RE resources in 2023. In this paper, the integrated multi-objective, multi-period linear programming model is presented to determine effective allocation of RE supply for seven different geographical regions in Turkey for the period of 2017 to 2024. The integrated model consists of two different stages. The first stage involves qualitative evaluations of RE sources for seven geographical regions. Analytical Hierarchy Process (AHP) is applied to determine criteria priorities and overall ratings of geographical regions across determined criteria for RE sources are computed. The second stage of the integrated model consists of a multi-objective, multi-period linear programming model. The proposed multi-objective linear programming model is coded in MPL (Mathematical Programming Language) and solved using the GUROBI 5.1.0 solver. The output of the integrated model presents the total supply amount of RE sources for geographical regions in planning period. The ε-constraints method is applied to compute the total supply amount of RE from geographical regions for the period of 2017 to 2024. In this study, a systematic decision-making model is generated to allocate renewable energy sources to the geographical regions. The presented model integrates qualitative evaluations and quantitative parameters of different geographical regions to determine the optimal supply amount of RE. The obtained results are consistent with the potential quantities of RE alternatives in geographical regions, regional specifications, and social requirements.

Voltage source converter in a microgrid

Microgird with higher amount of renewable energy sources interconnected with power electronic devices has many challenges, such as loss of inertia, low short circuit ratio, difficulty in power sharing, problem of storage in an islanded condition, which needs to be handled properly. Among other ones, the power sharing is one of the major problems in a microgrid that leads to the voltage and frequency limits violation and increased losses. This paper demonstrates that the voltage source converter (VSC) can extend its role of interfacing renewable sources to a new role of performing a high dynamic response as a generating unit of the microgrid. A Laplace model of the power converter is presented, which allows to analyze the converter behaviour in supporting the grid. The application of the converter to a weak microgrid is also presented to validate the proper behaviour of the power plant as a generation unit of the microgrid. The approach in controlling the converter operation is based on vector control implemented in a rotating reference frame handling the control variables in the dq domain. The VSC along with its controller is used in this paper to contribute the active and reactive power to stabilize the frequency and the voltage of the grid within the permissible limit.

Topological Considerations on the Use of Batteries to Enhance the Reliability of HV-Grids

Abstract The large amount of renewable energy sources (RESs) recently integrated within the electric power systems across the world poses new challenges for their operation. Among several viable solutions, energy storage systems are the most promising to increase reliability and flexibility. This paper proposes a novel topological and probabilistic approach to find the optimal capacity and siting of energy storage devices, in order to increase the system reliability and the hosting capacity of renewables. Wind and solar productions, generators availability, and real-time demand are modeled with proper distribution functions, and the yearly expected energy not supplied is estimated using a sequential Monte Carlo technique. Four siting policies are applied and compared to place the optimal storage capacity on eight grids with different topological characteristics. Power flows are linearized and the optimization of resources is formulated as a linear programming problem. The results show that large-scale batteries operated by the Transmission System Operator can significantly improve system reliability and exploitation of RESs. The presence of energy-hubs and small-world properties strongly increase the transmission effectiveness of weakly- and well-meshed grids. A siting policy based on the Power Transfer Distribution Factors matrix of the grid turns out to be particularly successful.

Application of Synchrophasor Measurements for Improving Situational Awareness of the Power System

Abstract The paper focuses on the application of synchrophasor measurements that present unprecedented benefits compared to SCADA systems in order to facilitate the successful transformation of the Nordic-Baltic-and-European electric power system to operate with large amounts of renewable energy sources and improve situational awareness of the power system. The article describes new functionalities of visualisation tools to estimate a grid inertia level in real time with monitoring results between Nordic and Baltic power systems.

Impact of replacing thermal power plants by renewable energy on the power system

The Egyptian Electricity Holding Company (EEHC) has paid great attention to renewable energy sources; wind power (WP) and photovoltaic (PV). The EEHC Strategy aims at increasing the proportion of power totally generated from renewable energy sources (RES) to 20% by 2022. With increasing such amount of RES in the Egyptian electricity system, some of the on-line thermal power plants will be shut down and replaced by WP and PV. Thus the thermal reserve will be reduced making the available online thermal power plants fewer to share the regulation burden. The power system inertia will be reduced, the frequency deviation will be greater after system disturbance and more oscillation will occur. Therefore, this paper studies the impacts of increasing the renewable energy sources on the frequency control of the Egyptian power system by investigating different scenarios of increasing the RES to 20% after occurring sudden variations in generation. Also the impact of RES on environmental improvement is presented by calculating the expected annual CO2 emission reductions (ER), certified emission reduction (CER) and the amount of fuel saving. The model was created by using DIgSILENT power factory software.

A blockchain-based smart grid: towards sustainable local energy markets

The increasing amount of renewable energy sources in the energy system calls for new market approaches to price and distribute the volatile and decentralized generation. Local energy markets, on which consumers and prosumers can trade locally produced renewable generation directly within their community, balance generation and consumption locally in a decentralized approach. We present a comprehensive concept, market design and simulation of a local energy market between 100 residential households. Our approach is based on a distributed information and communication technology, i.e. a private blockchain, which underlines the decentralized nature of local energy markets. Thus, we provide energy prosumers and consumers with a decentralized market platform for trading local energy generation without the need of a central intermediary. Furthermore, we present a preliminary economic evaluation of the market mechanism and a research agenda for the technological evaluation of blockchain technology as the local energy market’s main information and communication technology.

Multi‐agent transactive energy management system considering high levels of renewable energy source and electric vehicles

The future smart grids (SGs) consist of considerable amount of renewable energy sources (RESs), electrical vehicles (EVs), and energy storage systems (ESSs). The uncertainties associated with EVs and uncontrollable nature of RESs have magnified voltage stability challenges and the importance of an effective energy management system (EMS) in SGs as a practical solution. This study presents a multi-agent transactive energy management system (TEMS) to control demand and supply in the presence of high levels of RESs and EVs, and maximises profit of each participant in addition to satisfying voltage regulation constraints. For this purpose, a real-time pricing is considered based on Cournot oligopoly competition model for demand and merit order effect for production to compensate RESs’ fluctuations in real time by an indirect control method. Simulations are conducted in the modified IEEE 37-bus test system with 1141 customers, 670 EVs, two solar plants, four wind turbines, and one ESS. The results show that the proposed multi-agent TEMS can indirectly control EVs, elastic loads, and ESSs to balance the RESs oscillation, minimise customers cost, and regulate voltage in a real-time manner.

Improvement of frequency stability by using battery to compensate rate shortage of LFC reserve

AbstractBy introducing large amount of renewable energy sources and electricity deregulation, procuring sufficient reserve power for Load Frequency Control (LFC) becomes difficult for system operator. In this paper, at first, impact of ramp rate shortage on frequency stability is shown by simulation study. Next, a novel battery utilization method is proposed to compensate the rate shortage. In the method, a battery is driven by the component of LFC signal which cannot be responded by existing LFC units. Through comparison study with conventional battery control method, it is clarified that the proposed method can efficiently improve LFC performance under the large amount of renewable energy sources interconnection.

Interval radial power flow using extended DistFlow formulation and Krawczyk iteration method with sparse approximate inverse preconditioner

Confronted with uncertainties, especially from large amounts of renewable energy sources, power flow studies need further analysis to cover the range of voltage magnitude and transferred power. To address this issue, this work proposes a novel interval power flow for the radial network by the use of an extended, simplified DistFlow formulation, which can be transformed into a set of interval linear equations. Furthermore, the Krawczyk iteration method, including an approximate inverse preconditioner using Frobenius norm minimisation, is employed to solve this problem. The approximate inverse preconditioner guarantees the convergence of the iterative method and has the potential for parallel implementation. In addition, to avoid generating a dense approximate inverse matrix in the preconditioning step, a dropping strategy is introduced to perform a sparse representation, which can significantly reduce the memory requirement and ease the matrix operation burden. The proposed methods are demonstrated on 33-bus, 69-bus, 123-bus, and several large systems. A comparison with interval LU decomposition, interval Gauss elimination method, and Monte Carlo simulation verifies its effectiveness.

Home demand side management integrated with electric vehicles and renewable energy sources

The microgrid systems will be vital for establishing future smart grid, so important focus will be on their intermittency and availability of energy storage systems. Since in the near future, the number of electric vehicles (EV) will grow considerably, they represent appreciable opportunity as dispatchable energy sources, if battery can be considered as potential energy storage system and connected to grid while parked. Accordingly, foster integration of renewable energy sources and EVs integrated with proper home demand side management can contribute to microgrid stability and decrease grid dependence. The model of a small solar powered buildings is based on the role of active smart grid users referred as energy citizens, whose home demand side management is possible to reduce or postpone demand, due to categorization of home appliances and controlled charging of EVs. The daily load curve will trace daily energy production, cooperating with energy storage system. We develop a mixed-integer program to reach maximum amount of renewable energy sources, scheduling optimal power and operation time for EVs and appliances. Simulation results for different scenarios with different engagement of home demand side management have been presented to demonstrate and verify the effectiveness of the proposed technique.

Advanced Hybrid Transient Stability and EMT Simulation for VSC-HVDC Systems

This paper deals with advanced hybrid transient stability and electromagnetic-transient (EMT) simulation of combined ac/dc power systems containing large amounts of renewable energy sources interfaced through voltage-source converter-high-voltage direct current (VSC-HVDC). The concerning transient stability studies require the dynamic phenomena of interest to be included with adequate detail and reasonable simulation speed. Hybrid simulation offers this functionality, and this contribution focuses on its application to (multiterminal) VSC-HVDC systems. Existing numerical interfacing methods have been evaluated and improved for averaged VSC modeling. These innovations include: 1) ac system equivalent impedance refactorization after faults; 2) amended interaction protocols for improved Thévenin equivalent source updating inside the EMT-type simulation; and 3) a special new interaction protocol for improved phasor determination during faults. The improvements introduced in this contribution lead to more accurate ac/VSC-HVDC transient stability assessment compared to conventional interfacing techniques.