| 1. |
- Agredano Torres, Manuel, et al.
(författare)
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Decentralized Dynamic Power Sharing Control for Frequency Regulation Using Hybrid Hydrogen Electrolyzer Systems
- 2024
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Ingår i: IEEE Transactions on Sustainable Energy. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3029 .- 1949-3037. ; 15:3, s. 1847-1858
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen electrolyzers are promising tools for frequency regulation of future power systems with high penetration of renewable energies and low inertia. This is due to both the increasing demand for hydrogen and their flexibility as controllable load. The two main electrolyzer technologies are Alkaline Electrolyzers (AELs) and Proton Exchange Membrane Electrolyzers (PEMELs). However, they have trade-offs: dynamic response speed for AELs, and cost for PEMELs. This paper proposes the combination of both technologies into a Hybrid Hydrogen Electrolyzer System (HHES) to obtain a fast response for frequency regulation with reduced costs. A decentralized dynamic power sharing control strategy is proposed where PEMELs respond to the fast component of the frequency deviation, and AELs respond to the slow component, without the requirement of communication. The proposed decentralized approach facilitates a high reliability and scalability of the system, what is essential for expansion of hydrogen production. The effectiveness of the proposed strategy is validated in simulations and experimental results.
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| 2. |
- Agredano Torres, Manuel, et al.
(författare)
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Dynamic power allocation control for frequency regulation using hybrid electrolyzer systems
- 2023
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Ingår i: 2023 IEEE Applied Power Electronics Conference And Exposition, APEC. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 2991-2998
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Konferensbidrag (refereegranskat)abstract
- The increase in hydrogen production to support the energy transition in different sectors, such as the steel industry, leads to the utilization of large scale electrolyzers. These electrolyzers have the ability to become a fundamental tool for grid stability providing grid services, especially frequency regulation, for power grids with a high share of renewable energy sources. Alkaline electrolyzers (AELs) have low cost and long lifetime, but their slow dynamics make them unsuitable for fast frequency regulation, especially in case of contingencies. Proton Exchange Membrane electrolyzers (PEMELs) have fast dynamic response to provide grid services, but they have higher costs. This paper proposes a dynamic power allocation control strategy for hybrid electrolyzer systems to provide frequency regulation with reduced cost, making use of advantages of AELs and PEMELs. Simulations and experiments are conducted to verify the proposed control strategy.
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| 3. |
- Anggraini, Dita, et al.
(författare)
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Electric Vehicle Charging Considering Grid Limitation in Residential Areas
- 2024
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Ingår i: 2024 IEEE Transportation Electrification Conference and Expo, ITEC 2024. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- The growing adoption of electric vehicles (EVs) has introduced substantial challenges to the grid. Uncontrolled EV charging may lead to grid overloading, voltage instability, increased power losses, accelerated aging of distribution transformers, and risk of outages. Therefore, a strategic approach is required to tackle the adverse impacts of uncontrolled EV charging to the grid. A promising approach is using EV batteries collectively as a flexible load. Residential areas have the most pronounced EV flexibility potential due to the significant length of uninterrupted parking. In this paper, models of EV charging in residential areas are formulated, followed by Monte Carlo simulations. Three charging models are developed: uncontrolled charging, controlled charging without considering grid limitation and controlled charging considering grid limitation. An optimization problem based on quadratic programming is used in the controlled charging. A residential area based on the IEEE European LV test feeder adopting the deregulated Swedish electricity market is taken as a case study for the simulation. The case study findings indicate that incorporating grid limitation into controlled charging strategies can prevent grid overload and significantly reduce charging and battery degradation costs. In this case study, controlled charging can reduce the charging costs to approximately 42% compared to uncontrolled charging. Considering the battery degradation costs, controlled charging costs are 24% lower than uncontrolled charging. It is possible to postpone the costly grid reinforcement by applying strategic EV charging scheduling. The methods and outcomes pave the way for developing, testing, and implementing business models to manage the grid impacts of growing EV charging.
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| 4. |
- Astero, Poria, 1984-, et al.
(författare)
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Improvement of RES hosting capacity using a central energy storage system
- 2017
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Ingår i: 2017 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538619537 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- High penetration of renewable energy sources (RESs) in distribution systems leads to reverse active power and voltage rise in low voltage (LV) grids, which limits the hosting capacity. Energy storage systems (ESSs) have been used to improve the hosting capacity by decreasing the reverse active power in some literature. ESSs can still improve the hosting capacity more by providing reactive power. The reactive power shows a little effect in existing researches, because they have mostly simulate LV grids without modeling transformers. However, the high reactance of the transformer magnifies the effectiveness of the reactive power control even more than the active power in some buses. This paper develops an optimal method for placement, sizing, and active and reactive power control of a central ESS to improve the hosting capacity. The simulation results in highly RES penetrated grids at Germany show the effectiveness of the proposed method.
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| 5. |
- Astero, Poria, 1984-, et al.
(författare)
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Improving Hosting Capacity of Rooftop PVs by Quadratic Control of an LV-Central BSS
- 2017
-
Ingår i: IEEE Transactions on Smart Grid. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3053 .- 1949-3061. ; PP:99, s. 1-1
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Tidskriftsartikel (refereegranskat)abstract
- High integration of rooftop photovoltaic (PV) plants in distribution systems leads to new technical challenges: reverse-active power and voltage rise in low-voltage (LV) and medium-voltage (MV) grids. These challenges limit the maximum amount of power can be produced by PVs in LV and MV grids, called the hosting capacity (HC). Battery storage systems (BSSs) have been used in many studies to decrease the reverse power and improve the HC by controlling the active power. However, the influence of a central BSS on the HC can be greatly improved by using a quadratic power control, simultaneous active and reactive power control, and by selecting of the optimal battery size, the converter size, and the place of the central BSS. The effectiveness of the quadratic power control was not seen in previous works due to the fact that grids with one level of voltage without modeling of MV/LV transformers were simulated. This paper develops a method to select the optimal size of the battery and converter unit as well as the optimal place of an LV-central BSS having an optimal quadratic power control. The simulation results show considerable effects of the optimal selection of an LV-central BSS on the HC improvement.
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| 6. |
- Astero, Poria, 1984-, et al.
(författare)
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Improving PV Dynamic Hosting Capacity Using Adaptive Controller for STATCOMs
- 2019
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Ingår i: IEEE transactions on energy conversion. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8969 .- 1558-0059. ; 34:1, s. 415-425
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Tidskriftsartikel (refereegranskat)abstract
- High penetrations of renewable energy sources (RES) in distribution grids lead to new challenges in voltage regulation. These challenges are not just limited to the steady-state voltage rise, but they are extended to rapid voltage changes due to wind speed variations and moving clouds, casting shadows on photovoltaic panels. According to EN50160 in low-voltage (LV) grids, the steady-state voltage should not exceed 1.1 pu (static characteristic), and rapid voltage changes should be kept less than 0.05 pu (dynamic characteristic). These two characteristics may limit the maximum amount of RES that can be installed in LV grids, called, respectively, the static hosting capacity (SHC) and dynamic hosting capacity (DHC). Although existing research just evaluated SHC in distribution grids, high-penetrated RES grids can be faced with such large voltage changes, which cause a smaller DHC than the SHC. This paper studies both SHC and DHC in distribution grids and proposes an adaptive controller for static synchronous compensators to regulate the steady-state and dynamic voltage while avoiding the unnecessary increase in the reactive power. The simulation results in some German distribution grids show considerable effects of the proposed adaptive controller on improving both SHC and DHC.
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| 7. |
- Astero, Poria, 1984-, et al.
(författare)
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Improving PV Hosting Capacity of Distribution Grids Considering Dynamic Voltage Characteristic
- 2018
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Ingår i: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC). - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- Since the penetration of renewable energy sources is rapidly increasing in distribution grids, the hosting capacity (HC) of distribution systems becomes the main concern. According to EN 50160, in LV grids, the mean value of voltage cannot exceed 1.1 pu (static characteristic) and voltage rapid changes should be kept less than 0.05 pu (dynamic characteristic). Existing researches evaluated the HC of distribution grids just based on the static characteristic. However, wind speed variations and rapid moving cloud, casting shadow on solar panels, can cause rapid voltage changes in LV grids. This paper studies the rapid voltage change by modeling the moving cloud shadow and compares the HC from perspective of both dynamic and static characteristic, which is not done before. Since voltage dynamic characteristic could be more restrictive than the static characteristic, as shown in a German distribution grid, a static synchronous compensator (STATCOM) is proposed and controlled to regulate dynamic voltage profile and to improve the HC.
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| 8. |
- Astero, Poria, 1984-, et al.
(författare)
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Transactive Demand Side Management Programs in Smart Grids with High Penetration of EVs
- 2017
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Due to environmental concerns, economic issues, and emerging new loads, such as electrical vehicles (EVs), the importance of demand side management (DSM) programs has increased in recent years. DSM programs using a dynamic real-time pricing (RTP) method can help to adaptively control the electricity consumption. However, the existing RTP methods, particularly when they consider the EVs and the power system constraints, have many limitations, such as computational complexity and the need for centralized control. Therefore, a new transactive DSM program is proposed in this paper using an imperfect competition model with high EV penetration levels. In particular, a heuristic two-stage iterative method, considering the influence of decisions made independently by customers to minimize their own costs, is developed to find the market equilibrium quickly in a distributed manner. Simulations in the IEEE 37-bus system with 1141 customers and 670 EVs are performed to demonstrate the effectiveness of the proposed method. The results show that the proposed method can better manage the EVs and elastic appliances than the existing methods in terms of power constraints and cost. Also, the proposed method can solve the optimization problem quick enough to run in real-time.
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| 9. |
- Biel, Martin
(författare)
-
Distributed Stochastic Programming with Applications to Large-Scale Hydropower Operations
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stochastic programming is a subfield of mathematical programming concerned with optimization problems subjected to uncertainty. Many engineering problems with random elements can be accurately modeled as a stochastic program. In particular, decision problems associated with hydropower operations motivate the application of stochastic programming. When complex decision-support problems are considered, the corresponding stochastic programming models often grow too large to store and solve on a single computer. This warrants a need for parallel approaches to enable efficient treatment of large-scale stochastic programs in a distributed environment. In this thesis, we develop mathematical and computational tools to efficiently store and solve distributed stochastic programs. First, we present a software framework for stochastic programming implemented in the Julia programming language. A key feature of the framework is the support for distributing stochastic programs in memory. Moreover, the framework includes a large set of structure-exploiting algorithms for solving stochastic programming problems. These algorithms are based on the classical L-shaped, progressive-hedging, and quasi-gradient algorithms and can be run in parallel on distributed stochastic programs. The distributed performance of our software framework is improved by exploring algorithmic innovations and software patterns. We present the architecture of the framework and highlight key implementation details. Finally, we provide illustrative examples of stochastic programming functionality and benchmarks on large-scale problems. Then, we pursue further algorithmic improvements to the distributed L-shaped algorithm. Specifically, we consider the use of dynamic cut aggregation. We develop theoretical results on convergence and complexity and then showcase performance improvements in numerical experiments. We suggest several aggregation schemes that are based on parameterized selection rules. In brief, cut aggregation can bring major performance improvements to L-shaped algorithms in distributed settings. Next, we consider a fast smoothing scheme for large-scale stochastic programming. We derive a smooth approximation of the subproblems in the quasi-gradient algorithm. This allows us to utilize modern acceleration methods for gradient descent. We derive problem-dependent approximation bounds and convergence properties and note a trade-off between accuracy and speed. We then pose a hybrid procedure that is both fast and accurate and show that it is competitive with the L-shaped method on large-scale benchmarks. Finally, we consider applications to hydropower operations. We consider three case studies in the Swedish river Skellefteälven. The day-ahead planning problem involves specifying optimal order volumes in a deregulated electricity market, without knowledge of the next-day market price, and then optimizing the hydropower production. We provide a detailed introduction to the day-ahead model and explain how it can be implemented in our framework. Using a sample-based algorithm that internally relies on our structure-exploiting solvers, we obtain tight confidence intervals around the optimal solution of the day-ahead problem. We then consider a maintenance scheduling problem as a variation of the day-ahead problem. Last, we consider a capacity expansion problem with a long planning horizon.
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| 10. |
- Blom, Evelin, et al.
(författare)
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Accurate model reduction of large hydropower systems with associated adaptive inflow
- 2022
-
Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 200, s. 1059-1067
-
Tidskriftsartikel (refereegranskat)abstract
- Simulation of sizeable hydro-thermal power systems, such as Northern Europe or larger, requires several extensive simplifications and model reductions to decrease simulation time. Such reductions for hydrosystem sare often called Equivalent models. Their purpose is to mimic a more detailed hydropower model whiled ecreasing computation time. Both aspects are vital for accurate and useable simulation results. Here, different Equivalent models for hydropower have been developed together with a new function for adaptive Equivalentinflow based on local inflows to the detailed system. The models were computed via a bilevel optimization problem factoring in the novel adaptive inflow. Based on this, the new function for adaptive inflow was calculated using regression. The Equivalents have then been evaluated in a case study of hydropower systems in Northern Sweden regarding accuracy in hourly and total power generation, revenue estimation, and relative computation time. For all Equivalents, the computation time is decreased by >96%. Further, the Equivalents demonstrate improved performances in hourly and total power production and revenue estimations. The best hourly power difference was 9.2%, and the best revenue estimation was 5.9%. Especially notable is the low total power production difference of <0.5% compared to the more detailed model.
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| 11. |
- Blom, Evelin, et al.
(författare)
-
Comparison of Different Computational Methods and Formulations for Hydropower Equivalents
- 2022
-
Ingår i: 2022 7th IEEE International Energy Conference (EnergyCon).
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Konferensbidrag (refereegranskat)abstract
- Simplified models of hydropower systems are necessary for simulation of large power systems, long-term analysis, and future studies. One common simplification has been to aggregate all hydropower within an area based on historical data. Another option is to use mathematical so-caned hydropower Equivalents. Here, hydropower Equivalents represent an optimized model reduction of a more Detailed model depicting the complete hydropower system within a specific area. These Equivalents are computed based on a bilevel optimization problem formulation. In this paper, the impact different Equivalent model constraints have on the performance is analyzed via a novel investigation of new model formulations. Moreover, recent solution methods and a baseline aggregation of the hydropower from statistics are compared and evaluated for the first time. All bilevel Equivalents show a significantly better performance than the baseline aggregation; the accuracy in hourly power generation relative to the Detailed model is almost twice as high for all bilevel Eqmvalents.
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| 12. |
- Blom, Evelin, et al.
(författare)
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Computation of Multi-Scenario Hydropower Equivalents Using Particle Swarm Optimization
- 2020
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Ingår i: Proceedings - 2020 IEEE International Conference on Environment and Electrical Engineering and 2020 IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2020. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- Simulation of large hydro-thermal power systems requires several extensive simplifications and model reductions. For hydropower systems with several interconnected power stations, these reductions can be particularly challenging and are denoted Equivalent models. The purpose of the Equivalent model is to mimic a more detailed hydropower model, while decreasing computation time, to be used in larger power system models. In this paper different Equivalent models for hydropower systems have been computed with a novel approach using a Particle swarm optimization-algorithm and are evaluated with respect to accuracy in hourly and total power generation as well as computation time. For each of the Equivalent models, computation time is decreased with over 99.99 % and the difference in power production is less than 11% compared to a more detailed model.
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| 13. |
- Blom, Evelin
(författare)
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Hydropower Area Equivalents : Reduced Models for Efficient Simulation of Large-Scale Hydropower Systems
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With over 4000 TWh yearly electricity production worldwide, hydropower plays an important role in many power systems. Unlike many other renewable energy sources, hydropower has a certain degree of controllability and high levels of flexibility over several time scales. This flexibility is estimated to be integral for the transition of the energy systems towards more variable renewable energies and thus reducing greenhouse gas emissions. Given the important role that hydropower currently plays and is expected to play in future power systems, accurate models of hydropower are vital. As hydropower electricity production is a non-convex function of the discharge with for example non-linear head dependencies and forbidden zones of operation, detailed models of real hydropower systems quickly become computationally heavy. Even linear models with high numbers of interconnected stations are often too complex for large-scale power system models. For this reason, reduced or aggregated models of hydropower are commonly used to simulate its operation in different power system models. Due to the temporal and spatial connections in many hydropower systems with large rivers, the aggregation of hydropower can pose significant challenges. This means that aggregation from historical data might not be good enough to accurately simulate the hydropower operation. However, accurate reduced models of hydropower are still needed for long-term current and future studies of energy systems worldwide. In this thesis, the basic assumption is that the simplified reduced hydropower model should mimic the real hydropower operation. Thus, instead of aggregating the existing hydropower stations within a certain geographical area, one computes a new hydropower area Equivalent model with the aim to match the simulated power production of a more Detailed model of the real hydro system in that area. In this work, the area Equivalent models are calculated by computing the model parameter values. Here, this is mainly done based on a bilevel optimization problem formulation. In this thesis, different methods to compute the area Equivalents are proposed together with different model formulations and bilevel problem formulations. These are all compared using case studies of Swedish hydropower systems. Moreover, a Baseline aggregation method is outlined and compared to the developed area Equivalents. The studies presented in this thesis highlight the potential trade-offs in the accuracy of the area Equivalent model. Some problem formulations give a higher accuracy in hourly power production, others in peak power production or total power production over the simulation period. All area Equivalents perform better than the Baseline aggregation. In general, the average error in hourly power production is reduced by 50% using the area Equivalent compared to the Baseline aggregation. Moreover, they all successfully reduce the simulation time compared to the reference Detailed model with over 96%.
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| 14. |
- Blom, Evelin, et al.
(författare)
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Optimal Segmented Efficiency In Hydrosystem Area Equivalents To Capture Real Production Peaks
-
Ingår i: Energy Systems, Springer Verlag. - 1868-3967 .- 1868-3975.
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Tidskriftsartikel (refereegranskat)abstract
- Modeling large energy systems requires different forms of simplifications and aggregations. This is especially true for large hydropower systems. One way to simplify the modeling of hydropower as a part of large scale energy systems is to utilize so-called Equivalent models. The hydropower Equivalent model is a simplified hydropower area model with only one (or a few stations) which aims to mimic the behavior of an Original more detailed model containing all stations in a specific area. However, one drawback has been that the Equivalent model fails to match the highest production peaks of the real Original system. Methods to increase the maximum peaks in the Equivalent model have so far resulted in overall lower performance, where the production during lower peaks instead would be overestimated. Thus, in this paper, a method for computing hydrosystem area Equivalent models that not only have good average performance but also can capture the production peaks of the real hydropower system is developed. The new method allows for optimal partition and efficiency of different segments in the hydropower marginal production function.
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| 15. |
- Blom, Evelin, et al.
(författare)
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Optimal segmented efficiency in hydrosystem area equivalents to capture real production peaks
- 2023
-
Ingår i: Energy Systems, Springer Verlag. - : Springer Nature. - 1868-3967 .- 1868-3975.
-
Tidskriftsartikel (refereegranskat)abstract
- Modeling large energy systems requires different forms of simplifications and aggregations. This is especially true for large hydropower systems. One way to simplify the modeling of hydropower as a part of large scale energy systems is to utilize so-called Equivalent models. The hydropower Equivalent model is a simplified hydropower area model with only one (or a few stations) which aims to mimic the behavior of an Original more detailed model containing all stations in a specific area. However, one drawback has been that the Equivalent model fails to match the highest production peaks of the real Original system. Methods to increase the maximum peaks in the Equivalent model have so far resulted in overall lower performance, where the production during lower peaks instead would be overestimated. Thus, in this paper, a method for computing hydrosystem area Equivalent models that not only have good average performance but also can capture the production peaks of the real hydropower system is developed. The new method allows for optimal partition and efficiency of different segments in the hydropower marginal production function.
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| 16. |
- Blom, Evelin, et al.
(författare)
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Performance of multi-scenario equivalent hydropower models
- 2020
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Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 187
-
Tidskriftsartikel (refereegranskat)abstract
- Simulations and analysis of large hydro-thermal power systems easily become computationally heavy without simplifications of the system at hand. Hydropower, in particular, presents a challenge as complex river systems add a large amount of variables and linked constraints to the analysis. A possible simplification is to use aggregated Equivalent models for different parts of the hydrosystem which give similar results, with respect to e.g. power production, as a more detailed description of the Original system. In this paper, novel linear multi-scenario Equivalent models for hourly simulations of nonlinear hydropower systems are developed and their performance investigated. The new models consider multiple scenarios for inflow, price and start resp. end content in the reservoirs as well as reserves for balancing capacity. The performance analysis is based on case studies over Swedish hydropower systems located in the electricity trading area SE1. The average relative error in power production is 9-15% and the computation time is reduced from 9 hours to between 0.4 and 36 seconds.
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| 17. |
- Blom, Evelin, et al.
(författare)
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Sensitivity Analysis of Hydropower Equivalent Parameters With Fast Identification Using PSO
- 2022
-
Ingår i: 2022 14th IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- Hydropower system Equivalents are fictive model reductions of a more detailed hydropower model of all individual hydropower stations within an area. The system Equivalent only has one or a few stations and can significantly reduce the computational effort compared to the detailed system. The aim is to at the same time maintain accuracy in power production. To achieve this a bilevel problem formulation can be utilized. In this bilevel problem, the optimal system Equivalent parameter values are calculated. However, this computation can be very time-consuming and the problem formulation is very complex. Moreover, which of the parameters are most important for overall Equivalent performance and accuracy is unknown. To get a better understanding of the system Equivalent model parameters and their connection to performance, this paper performs a sensitivity analysis and develops a method to determine the parameter importance. Based on these results methods to reduce the computational time of the bilevel problem can be devised, with an example given here. It is shown that the most important parameter is the maximum discharge limit.
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| 18. |
- Blom, Evelin, et al.
(författare)
-
Single-Level Reduction of the Hydropower Area Equivalent Bilevel Problem for Fast Computation
-
Tidskriftsartikel (refereegranskat)abstract
- For inclusion in large-scale power system models, various aggregations and simplifications in the modeling of relevant actors and assets are needed. This paper focuses on simplified reduced models of hydropower, or area Equivalent models. They use a simplified topology but are not a direct aggregation of the real hydropower system. Instead, the area Equivalent is constructed to mimic the simulated power production of a more detailed hydropower reference model. Here, this goal is fulfilled by formulating a bilevel problem minimizing the difference in simulated power production between the area Equivalent and its reference. Solving this can be computationally heavy. Thus, for fast solution of this bilevel problem, a single-level reduction is done which is then solved using two methods. The first method includes McCormick-envelopes to form a linear single-level problem. Second, is a modified Benders with a relaxed sub-problem to handle the non-convex single-level. These are compared to Particle Swarm Optimization. Moreover, six new upper-level objectives are investigated and compared based on a case study of the hydropower in northern Sweden. The method using McCrmick-envelopes is very fast (2-5 min) but the area Equivalent shows lower average performance. The modified Benders finds a solution in (5-31 min) with good performance.
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| 19. |
- Blom, Evelin, et al.
(författare)
-
Single-level reduction of the hydropower area Equivalent bilevel problem for fast computation
- 2024
-
Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 225
-
Tidskriftsartikel (refereegranskat)abstract
- For inclusion in large-scale power system models, various aggregations and simplifications in the modeling of relevant actors are needed. This paper focuses on reduced models of hydropower, so called area Equivalent models. They use a simplified topology but are not a direct aggregation of the real hydropower system. Instead, the area Equivalent is constructed to mimic the simulated power production of a more detailed hydropower reference model. Here, this goal is fulfilled by formulating a bilevel problem minimizing the difference in simulated power production between the area Equivalent and its reference. Solving this can be computationally heavy. Thus, for a fast solution of this bilevel problem, a single-level reduction is done, which is then solved using two methods. The first method includes McCormick envelopes to form a linear single-level problem. Second is a modified Benders with a relaxed sub-problem to handle the non-convex single-level. These are then also compared to Particle Swarm Optimization. Moreover, six new upper-level objective functions are investigated for a case study of hydropower in northern Sweden. The method using McCormick envelopes is fast (2–5 min), but the area Equivalent shows lower average performance. The modified Benders finds a solution in 5–31 min with good performance.
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| 20. |
- Calvillo Munoz, Christian Francisco, 1987-
(författare)
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Energy Management in Smart Cities
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Models and simulators have been widely used in urban contexts for many decades. The drawback of most current models is that they are normally designed for specific objectives, so the elements considered are limited and they do not take into account the potential synergies between related systems. The necessity of a framework to model complex smart city systems with a comprehensive smart city model has been remarked by many authors.Therefore, this PhD thesis presents: i) a general conceptual framework for the modelling of energy related activities in smart cities, based on determining the spheres of influence and intervention areas within the city, and on identifying agents and potential synergies among systems, and ii) the development of a holistic energy model of a smart city for the assessment of different courses of action, given its geo-location, regulatory and technical constraints, and current energy markets. This involves the creation of an optimization model that permits the optimal planning and operation of energy resources within the city.In addition, several analyses were carried out to explore different hypothesis for the smart city energy model, including:a) an assessment of the importance of including network thermal constraints in the planning and operation of DER systems at a low voltage distribution level,b) an analysis of aggregator’s market modelling approaches and the impact on prices due to DER aggregation levels, andc) an analysis of synergies between different systems in a smart city context.Some of the main findings are:It is sensible to not consider network thermal constraints in the planning of DER systems. Results showed that the benefit decrement of considering network constraints was approximatively equivalent to the cost of reinforcing the network when necessary after planning without considering network constraints.The level of aggregation affects the planning and overall benefits of DER systems. Also, price-maker approaches could be more appropriate for the planning and operation of energy resources for medium to large aggregation sizes, but could be unnecessary for small sizes, with low expected impact on the market price.Synergies between different energy systems exist in an interconnected smart city context. Results showed that the overall benefits of a joint management of systems were greater than those of the independently managed systems.Lastly, the smart city energy model was applied to a case study simulating a real smart city implementation, considering five real districts in the southern area of Madrid, Spain. This analysis allowed to assess the potential benefits of the implementation of a real smart city programme, and showed how the proposed smart city energy model could be used for the planning of pilot projects. To the best of our knowledge, such a smart city energy model and modelling framework had not been developed and applied yet, and no economic results in terms of the potential benefits of such a smart city initiative had been previously reported.
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| 21. |
- Crosara, Alessandro, et al.
(författare)
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Generation Adequacy in the Nordic and Baltic Area : The Potential of Flexible Residential Electric Heating
- 2019
-
Ingår i: Proceedings of 2019 IEEE PES Innovative Smart Grid Technologies Europe, ISGT-Europe 2019. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- Generation adequacy is a concern in today's electricity market where intermittent renewable energy sources are rapidly becoming a greater share of the generation mix. This paper focuses on the North-European power system that is comprised of the system areas of the Nord Pool spot market. Sequential Monte Carlo Simulation is applied to assess the generation adequacy of this multi-area system for several future scenarios defined within the Nordic Flex4RES project. The paper gives insights into the characteristics of these adequacy problems that the system could face in a more sustainable future and quantifies their magnitude. Finally, some solutions based on the demand flexibility of residential electric heating are discussed.
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| 22. |
- Crosara, Alessandro, 1994-, et al.
(författare)
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Generation Adequacy in the Nordic and Baltic Region: Case Studies from 2020 to 2050 : Flex4RES Project Report
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Generation adequacy is a concern in today's electricity market where intermittent renewable energy sources are rapidly becoming a greater share of the generation mix. This study focuses on the Nordic and Baltic power system that is comprised of the system areas of the Nord Pool spot market. Sequential Monte Carlo Simulation is applied to assess the generation adequacy of this multi-area system for several future case studies, based on scenarios defined within the Nordic Flex4RES project. The report gives insights into the characteristics of these adequacy problems that the system could face in a more sustainable future, quantifies their magnitude and presents their characteristics. Finally, a solution based on the demand flexibility of residential electric heating is discussed, as a way to counter capacity deficit problems.
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| 23. |
- Dabar, Omar Assowe, et al.
(författare)
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Wind resource assessment and economic analysis for electricity generation in three locations of the Republic of Djibouti
- 2019
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Ingår i: Energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-5442 .- 1873-6785. ; 185, s. 884-894
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Tidskriftsartikel (refereegranskat)abstract
- In the Republic of Djibouti, due to increasing electricity demands, the government has planned to increase power supply by using renewable resources such as geothermal, solar and wind energy. This work presents the first wind resource assessment in the Republic of Djibouti using measured wind speed data for the period of three years by meteorological stations at eight locations. The results confirmed that three of the eight locations (i.e. GaliMa-aba, Ghoubbet and Bada Wein) have the best resource, with mean annual wind speeds of more than 6.0 m/s. Wind simulations using NCEP-CFSR and ERA5 models reanalysis shows that the seasonal variations are stable between different years and are broadly consistent with the observed wind speed. The feasibility of three wind farms with total capacity of 275 MW at GaliMa-aba, Ghoubbet and Bada Wein is examined. Using the WindPRO program and two commercial wind turbines in according to IEC 61400-1 design criteria, the electricity generation were technically assessed. These wind farms can produce 1073 GWh of electricity per year, approximately equal to Djibouti's expected average annual electrical demand in 2030. The economic evaluation using the present value cost (PVC) method estimate that the generation cost per kWh at these locations varies from 7.03 US.$ cent/kWh to 9.67 US.$ cent/kWh. Elsevier Ltd. All rights reserved.
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| 24. |
- Hamon, Camille, et al.
(författare)
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Review Paper on Wind Power Impact on Operation of Reserves
- 2011
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Ingår i: 2011 8th International Conference on the European Energy Market, EEM 11. - 9781612842844 ; , s. 895-903
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Konferensbidrag (refereegranskat)abstract
- This paper reviews studies concerning new challengesfor European transmission system operators (TSOs) when operating primary, secondary and tertiary reserves in a systemwith large amounts of wind power. The review adopts three perspectives. First, the impact on existing markets is discussed and it is shown that need for additional reserve requirements does not necessarily mean need for new reserve capacity. Secondly, possible designs of improved load-frequency control schemes are presented.The proposed solutions exhibit a trend towards market-based procurement mechanisms and automation of reserve operations. Finally, participation of wind power in load-frequency control is examined. Technical designs are presented for participation inprimary control.
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| 25. |
- Herre, Lars, 1990-, et al.
(författare)
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A Study on the Flexibility of Electricity Consumers for the Swedish Context : Modelling, Quantification and Analysis of Notice Time
- 2016
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Konferensbidrag (refereegranskat)abstract
- Demand Side Management enables flexible electricity consumers to participate in services that contribute to reliable operation of the power system. The specific market, pricing scheme and demand response program decide in which way consumers receive incentives and provide services. The consumers’ response depends on the price and other parameters. Here, the impact of notice time on the flexibility of consumers is investigated. We summarize projects and literature on consumer elasticity and conduct a simulation study. The results show the significance of notice time dependent elasticity of consumers on power balancing in forward markets.
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