Provision Of Frequency Containment Reserve Research Articles

Enhanced Frequency Containment Reserve provision from battery hybridized hydropower plants: Theory and experimental validation

This paper presents a solution to address wear and tear of Run-of-River (RoR) Hydropower Plants (HPPs) providing enhanced Frequency Containment Reserve (FCR). In this respect, the study proposes the integration of a Battery Energy Storage System (BESS) with RoR HPPs controlled by a double-layer Model Predictive Control (MPC). The upper layer MPC acts as a state of energy manager for the BESS, employing a forecast of the required regulating energy for the next hour. The lower-layer MPC optimally allocates the power set-point between the turbine and the BESS. Reduced-scale experiments are performed on a one-of-a-kind testing platform to validate the proposed MPC-based control considering a comparison with different control strategies and different BESS sizes. The results demonstrate superior performance of the proposed framework, compared to simpler techniques like dead-band control or to the standalone RoR scenario, leading to improved FCR provision, reduced servomechanism stress, and extended hydropower asset lifespan.

An Optimal Wind Farm Operation Strategy for the Provision of Frequency Containment Reserve Incorporating Active Wake Control

This study proposes a novel operation strategy for wind farms' optimal Frequency Containment Reserve (FCR) provision that simultaneously distributes FCR and optimally controls wake formation. The power reserve allocation is dynamically decided at the wind farm supervisory control level, considering the intermittent wind power and direction, grid frequency stochasticity, and the aerodynamic complexity of the wake. A two-stage stochastic programming approach supports decision-making for an optimal contribution to day-ahead energy/FCR markets considering sub-hourly wind power and grid frequency uncertainty. Moreover, a novel method is used to reduce the computational complexity by employing a data-driven surrogate model of wake formation in the optimizer. This surrogate model consists of a neural network trained on the Gauss-Curl-Hybrid wake model in FLORIS. This deep learning approach allows fast estimation of the wake control parameters, i.e., the optimal yaw angles and axial induction factors. Then, a coevolutionary-based multi-objective particle swarm optimization searches for the optimal deloading of the WTs and maximizes the total power production and kinetic energy while minimizing wake. The performance of the proposed algorithm is evaluated on the C-Power wind farm layout in the North Sea. Simulation results demonstrate its effectiveness in improving the wind farm's overall performance for different operational conditions.

The role of hydrogen electrolysers in frequency related ancillary services: A case study in the Iberian Peninsula up to 2040

This paper investigates the contribution of hydrogen electrolysers (HEs) for frequency related Ancillary Services (AS), namely Frequency Containment Reserve (FCR), Synthetic Inertia (SI) and Fast Frequency Response (FFR) in future operation scenarios in the Iberian Peninsula (IP) considering low system inertia. The proposed framework for analysis consists of a dynamic model developed in MATLAB/Simulink. Simulations show that an instantaneous inverter based resource (IBR) trip induced by a grid fault may lead to the occurrence of values of Rate of Change of Frequency (RoCoF) close to undesirable thresholds if the FCR is provided solely by the conventional generators. The obtained results illustrate that HEs can outperform conventional generators on the provision of FCR. Furthermore, the FCR is unable to unlock the full potential of fast responding HEs. This suggests the advantage of providing additional AS such as SI or FFR in critical periods. Simulations also show that the benefit of additional AS can be limited in specific conditions, especially depending on the evolution of HEs’ ramping capabilities, but are still a relevant complement to other solutions designed to deal with low inertia in power systems such as synchronous compensators.

Operating strategy optimization considering battery aging for a sector coupling system providing frequency containment reserve

Battery storage systems are increasingly used in the frequency containment reserve (FCR) application. Coupling the battery with a power-to-heat module can further increase the system’s profitability. Different studies optimized the hybrid system’s operation by considering country-specific regulations. However, lithium-ion battery aging has not yet been included. This work analyses the impact of system dimension and operation on net present value, considering battery aging. The operation strategy consists of adjusting the target SoE and using the deadband degree of freedom, which allows to suspend provision of FCR for minor frequency deviations. Battery lifetime is simulated using a semi-empirical aging model describing graphite anode aging mechanisms. The highest NPV is obtained with a battery dimension of 0.5 Wh/W, 90% target SoE, and normal deadband utilization. For the considered NMC battery cells, deadband utilization contributes to battery lifetime extension when operating at high SoE. Without this cell chemistry-specific lifetime gain, a lower target SoE of 60% and a larger system size of 0.6 is economically more advantageous. In a sensitivity analysis, battery aging was detected as the most crucial parameter influencing system profitability at high FCR prices. The results highlight the importance of including reliable battery aging simulations in future FCR operation optimizations.

Environmental and economic analysis of sector-coupling battery energy storage systems used for frequency containment reserve

Battery energy storage systems (BESSs) are advocated as crucial elements for ensuring grid stability in times of increasing infeed of intermittent renewable energy sources (RES) and are therefore paving the way for more sustainable energy systems. Providing frequency containment reserve (FCR) is an attractive business model for capital intensive stationary BESSs, but the current German FCR regulative framework restricts the BESS usage for other applications as capacity shares have to be reserved (FCR energy capacity requirement). Hence, stationary BESSs operating at the FCR market are not fully utilised from an economic and environmental perspective. Linking BESSs with other sectors as potential sinks such as power-to-heat modules or electrolysers, enables unlimited energy infeed and is discussed as potential means to diminish this constraint. Whilst, a couple of studies investigated the economic advantages of such sector-coupling BESSs, their environmental consequences were hardly analysed so far. Based on the life cycle thinking approach, the environmental and economic impacts of FCR provision in Germany by standalone and sector-coupling BESSs (i.e. with power-to-heat unit or electrolyser) were studied in this work. The sector-coupling BESSs were considered regarding different FCR energy capacity requirements (E/P ratios). It was shown that the CAPEX for the sector-coupling unit were primarily critical for the economic performance of BESSs favouring power-to-heat over electrolysers and standalone BESSs. The results of the environmental life cycle assessment indicated to potential benefits due to the reduced battery capacities depending on the varied FCR energy capacity requirement. The environmental implications of the operational stage showed that electrolysers can increase the environmental impacts by up to 10 % due to higher conversion losses compared to power-to-heat units. Finally, it was concluded that future energy system and market designs should foster the implementation of sustainable sector-coupling solutions considering technology-specific economic and environmental characteristics.

An adaptive operational strategy for enhanced provision of frequency containment reserve by Wind Turbines: Data-driven based power reserve adjustment

Due to the growing penetration of renewables, Wind Turbines (WT) are becoming increasingly crucial for grid balancing services, such as Frequency Containment Reserve (FCR). This study proposes an adaptive operational strategy that optimally accommodates the power reserve and controls the active power based on grid frequency uncertainties and stochastic wind variations. The proposed approach includes an end-to-end solution, considering fixed and percentage reserve methods, from estimating an appropriate reserve margin to the real-time computation of generator torque and pitch control setpoints in response to grid frequency variations. A real-time look-up table is incorporated to actively adjust the reserve and adapt the deloading rotor speed-power curve based on a short-term estimation of the grid frequency using a deep-learning technique. Applying the proposed strategy improves WTs’ FCR contribution by at least 3.3 times reserve in MW. Moreover, adaptive fuzzy-PI pitch-torque controllers are suggested to enhance the WT dynamic response and ensure smooth provision of FCR. Simulation results of a 5 MW-NREL offshore model show the improvement of the fuzzy-PI in power reference tracking, rotor speed regulation, and average studied mechanical load parameters in the range of 2.14–11.69%, 11.1%, and 8.81%, respectively, for an average of 250 kW reserve, confirming an overall improvement.

Impact Assessment of Dynamic Loading Induced by the Provision of Frequency Containment Reserve on the Main Bearing Lifetime of a Wind Turbine

The components of an operational wind turbine are continuously impacted by both static and dynamic loads. Regular inspections and maintenance are required to keep these components healthy. The main bearing of a wind turbine is one such component that experiences heavy loading forces during operation. These forces depend on various parameters such as wind speed, operating regime and control actions. When a wind turbine provides frequency containment reserve (FCR) to support the grid frequency, the forces acting upon the main bearing are also expected to exhibit more dynamic variations. These forces have a direct impact on the lifetime of the main bearing. With an increasing trend of wind turbines participating in the frequency ancillary services market, an analysis of these dynamic forces becomes necessary. To this end, this paper assesses the effect of FCR-based control on the main bearing lifetime of the wind turbine. Firstly, a control algorithm is implemented such that the output power of the wind turbine is regulated as a function of grid frequency and the amount of FCR. Simulations are performed for a range of FCR to study the changing behaviour of dynamical forces acting on the main bearing with respect to the amount of FCR provided. Then, based on the outputs from these simulations and using 2 years of LiDAR wind data, the lifetime of the main bearing of the wind turbine is calculated and compared for each of the cases. Finally, based on the results obtained from this study, the impact of FCR provision on the main bearing lifetime is quantified and recommendations are made, that could be taken into account in the operation strategy of a wind farm.

Analytical Modeling and Control of Grid-Scale Alkaline Electrolyzer Plant for Frequency Support in Wind-Dominated Electricity-Hydrogen Systems

Integration of the hydrogen sector into power systems via electrolyzers could greatly facilitate energy sustainability by producing green hydrogen, moreover, assist in reinforcing frequency stability based on optimal control of electrolyzers. In order to improve the frequency performance of the wind-dominated electricity-hydrogen systems (WEHS), this paper investigates how to analytically evaluate and implement the dynamic frequency regulation (DFR) supported by a grid-scale alkaline electrolyzer (AEL) plant. The DFR's potential of the AEL plant is released by an emulated power-frequency characteristic, and its contributions to improving system frequency response are also analytically evaluated from the aspects of transient, steady-state, and stability indicators. Furthermore, the DFR dependency on the frequency containment reserve provision and pre-contingency operating points of AELs are analytically clarified. A DFR-driven controller to coordinate multiple modules in the AEL plant is also designed in detail. In addition, the economic analysis is presented to evaluate the profitability of AELs providing frequency support. Cases of a simple WEHS and a modified IEEE 9-bus system integrated with grid-scale AEL plants during frequency contingencies are studied to validate the proposed DFR method, which can improve the system frequency response with smoother transients and lower steady-state deviation.

Environmental assessment of prosumer digitalization: The case of virtual pooling of PV battery storage systems

The emergence of decentralized renewable energies together with digitalization enable new possibilities for the provision of system services that are needed for the energy transition. In Germany and worldwide, prosumers with a PV battery storage system are on the rise. With the aid of digital information and communication technologies (ICT), energy service providers can pool individual battery storage units to form a virtual battery energy storage system (VBES). The VBES is supposed to provide flexibility services and, thereby, support the transition towards an energy system with high shares of intermittent renewables. Although the concept is environmentally motivated, a holistic environmental assessment is missing so far. Therefore, we carry out a life-cycle analysis that considers environmental benefits, as well as burdens of VBES. For this, we compare a PV battery storage unit in a German single-family household with and without participation in a VBES for the year 2018. We assess three levels of environmental effects: direct effects due to digitalization (data transfer, ICT resources for VBES operation), indirect effects from external optimization on the household-level (changes in battery life and power supply), and enablement effects on the system level (provision of Frequency Containment Reserve, redispatch, and preventing renewables curtailment). We find that digitalization has a comparably low direct impact but it can enable relatively high environmental benefits for climate protection, and in other impact categories. Conditions for our findings are that battery life and the household's degree of self-sufficiency with PV electricity are not significantly affected by the external control of the VBES operator. We conclude that current and future battery owners should be encouraged to allow external access for system services. Furthermore, the necessary ICT roll out should be implemented in the short- to mid-term.

Industrial peak shaving with battery storage using a probabilistic forecasting approach: Economic evaluation of risk attitude

Industrial peak shaving is a regularly discussed application of battery storage. We introduce the notion of risk attitude in the context of joint industrial peak shaving and frequency containment reserve provision with battery storage. To this end, we combine a probabilistic quantile forecast with a rolling-horizon battery control mechanism. Probabilistic forecasts incorporate prediction uncertainty by generating a distribution of future load. An industrial consumer has an incentive to plan conservatively when reserving battery capacities for peak shaving, as a single missed peak can drive up annual electricity costs steeply in the presence of peak-load charges. However, this limits the potential use of battery storage capacity for other financially attractive applications. We find that extremely risk averse planning behavior can lead to a decrease of up to 10% in economic performance of a battery investment. This loss might be tolerated in exchange for the significantly reduced risk of missing a critical peak. Moreover, moderately risk averse planning behavior does not lead to financial losses in most cases and can even improves economic performance by up to 3% in certain of the evaluated cases.

Modelling of Battery Energy Storage System Providing FCR in Baltic Power System after Synchronization with the Continental Synchronous Area

This paper presents the case study of provisions of frequency containment reserve (FCR) with a battery electric storage system (BESS). The aim of the case study is the evaluation of the technical possibility to provide FCR in Latvian power systems after all Baltic power systems will synchronize with the Continental Europe Synchronous Area (CESA). To simulate the dynamics of BESS capacity and its state of charge (SOC), authors have developed an algorithm and mathematical model (it can be realized in different calculation programs). The case study calculations verified the model. The algorithm is conditionally divided into two parts—FCR provision and SOC recovery–which in turn is divided into three possible models of BESS state of charge recovery options: (1) overfulfillment—exceeding the specified FCR amount, (2) deadband utilization, and (3) BESS charging or discharging through scheduled transactions in intraday power market. The modelling was performed using historic frequency data of Latvian and French power systems. The case study of BESS with charging capacity of 12 MW and stored energy volume of 7 MWh for provision of determined FCR for Latvian power system was considered. The obtained results from the simulation were used in the separate model to evaluate economic feasibility of BESS for FCR.

Balancing group deviation & balancing energy costs due to the provision of frequency containment reserve with a battery storage system in Germany

The energy transition in the electrical energy supply sector is leading to a steadily increasing share of fluctuating renewable energy sources in the power grid. Thus, control reserves such as frequency containment reserve are gaining in importance and need further investigation. In Germany, the power grid is divided into balancing groups, in which supply and demand must be balanced out. The provision of frequency containment reserve, creates an imbalance in the respective balancing group depending on the grid condition. However, this energetic imbalance and the resulting costs for the balancing group manager are further to be quantified. This work provides a simulation model that examines the energetic imbalances resulting from the provision of frequency containment reserve. We validate the simulation results with field-data from the operation of a 6 MW battery storage system and derive the resulting cost for the energy imbalances. In addition, flexibility options for batteries given by the regulatory framework in form of the degrees of freedom are evaluated. The results show, that the degrees of freedom enable a battery storage operator to additionally charge up to 8.68MWh/MW frequency containment reserve per month or dis-charge up to 9MWh/MW frequency containment reserve per month on average. The additional profits from the German imbalance settlement price vary on average between 302€ and 1,068€ per MW frequency containment reserve per month. In Conclusion, the field-data confirm the simulation data in terms of energy deviations in the balancing group due to the provision of FCR. Over the period of one month, the deviation usually leads to a cost-related advantage for the balancing group manager. The provision of frequency containment reserve as a grid service can therefore be seen as a positive gain for a balancing group.© 2017 Elsevier Inc. All rights reserved.

Flexible operation strategy for formic acid synthesis providing frequency containment reserve in smart grids

The demand-side contribution to grid frequency regulation is becoming increasingly important due to the growing penetration of renewable energy in the power system. Among energy-intensive industrial loads, chemical plants have a high potential to offer grid balancing services due to their existing control infrastructure and storage capabilities. However, applying fast ramp rates and providing time-critical grid services is not straightforward due to strict constraints and the nonlinear dynamics of chemical systems. Therefore, adaptive operating approaches are required to increase the process’s flexibility and facilitate the fast demand response operation. This work proposes a flexible operating strategy for the cooperative operation of a Polymer Electrolyte Membrane (PEM) electrolyser and multi-stage compression systems in a chemical process to provide Frequency Containment Reserve (FCR). This strategy aims to realise the desired power regulation dynamics on the grid side while maintaining the reactor’s optimal operating conditions, i.e., temperature, pressure and flow rate ratio. A techno-economic analysis is performed to obtain optimal operating points. The techno-economic analysis shows that operating the process at a baseload of 73% while offering the remaining capacity as a power reserve can create additional revenue and improve the economic profit by around 10%. The proposed approach is validated by dynamic simulations of a Carbon Capture and Utilisation (CCU) process for formic acid production. The results show that the proposed strategy can enhance the process’s operational flexibility and enable FCR provision with a limited impact on reactor efficiency (<1%).

Improving frequency containment reserve provision in run-of-river hydropower plants

The paper presents a model-based control strategy for optimal asset management of hydroelectric units in run-of-river hydropower plants. The proposed control strategy aims to operate the unit at the best efficiency while improving water flow management and minimise components wear during frequency containment reserve provision. This approach is designed for a double regulated turbine (Kaplan) with adjustable guide vanes angle and runner blades angle and can be extended to other turbines adopted in run-of-river hydropower plants. The optimal discharge set-point is computed for maximising the frequency containment reserve provision while controlling the head of the river. The best efficiency is achieved by solving a suitably defined convex optimisation problem leveraging a regressive model of the hydraulic characteristics of the turbine and dynamics of the guide vanes and blades servomotors. The discharge set-point combines three terms: the dispatch plan set-point, the regulating discharge, proportional to the grid frequency deviation, and an offset term computed to control the average flow through the machine. Furthermore, a method to forecast the energy required in the following hour for the provision of grid frequency regulation is exploited to enhance the unit’s frequency containment reserve action. The control strategy is validated by simulating a month of operation for the full-scale run-of-river hydropower plant located in Vogelgrun (France) and by comparing the results with operational statistics. Results show the effectiveness of the proposed control strategy able to increase the provision of frequency containment reserve while decreasing the number of movements of the machine components and maximise the efficiency.

Analysis of taxation and framework conditions for hybrid power plants consisting of battery storage and power-to-heat providing frequency containment reserve in selected European countries

Flexible energy plants are one of the key requirements for future energy systems with high levels of fluctuating renewable energy. In the course of the transition to sustainable energy systems, regulatory frameworks and tax systems should promote carbon-reduced flexible power plants in a timely manner.This paper considers hybrid systems consisting of battery energy storage systems (BESS) and Power-to-Heat (PtH) modules which can contribute to a more flexible energy system by providing Frequency Containment Reserve (FCR). Contrary to many papers, this contribution explicitly focuses on taxes for FCR providing power plants, which are incurred annually or based on energy consumption. Additionally, regulatory frameworks are investigated, meaning requirements for FCR provision and conditions for energy trading. The effects of these factors on the economic efficiency of hybrid power plants providing FCR are analysed.The regulatory framework conditions and tax systems from three countries are analysed: Germany, France and Austria. For each of these countries four scenarios are simulated in which the net present values (NPV) are calculated considering the corresponding national tax systems and framework conditions. Additionally, operational strategies using the degrees of freedom (DoF) are examined regarding their influence on the economic performance.The comparison shows a huge influence of taxes on the profitability of the hybrid system. Framework conditions mostly play a minor role in this context. Compared to a benchmark scenario with uniform framework conditions and without taxes, on average the NPV decreases more rapidly considering taxes (−107 k€ in France to −710 k€ in Austria) than considering country specific framework conditions (−122 k€ in France to −308 k€ in Austria). Since framework conditions mostly determine the size of the battery capacity, they primarily affect the investment costs. Additionally, the longer the time slices and the earlier the gate closure is, the more often the hybrid systems violate requirements for FCR provision.

Balancing Group Distortion &amp; Balancing Energy Costs Due to the Provision of Frequency Containment Reserve in Germany

Balancing Group Distortion &amp; Balancing Energy Costs Due to the Provision of Frequency Containment Reserve in Germany

Optimised capacity and operating strategy for providing frequency containment reserve with batteries and power-to-heat

Batteries provide growing amounts of Frequency Containment Reserve (FCR) in the German electricity market. We examine the ideal battery capacity as well as the state of charge (SoC) setpoint for provision of FCR following a profit maximisation approach. While a lot of research neglects taxes, their huge influence on the results is considered. In addition to stand-alone battery systems, we also consider hybrid systems, combining a battery storage with a Power-to-Heat (PtH) module. The hybrid system has two variants: in one variant energy is sold when the battery is fully charged, while in the other one the PtH module is used. Based on historical frequency and market data for one year, the performance of the different system variants is evaluated via a simulation. 2048 different combinations of battery capacity and SoC setpoint are examined. The performance of each configuration is evaluated with the net present value (NPV) method, allowing an economic comparison. The results show a financial advantage for the hybrid systems which sell energy when the battery is fully charged. The system configuration with the best NPV is a hybrid system with a battery capacity of 480 kWh and an SoC setpoint of 98%. The best battery capacity of all considered variants has a lower capacity to power ratio than the usual ratio of 1 MWh to 1 MW, assumed in most other studies. Non-optimal battery capacities have a stronger negative effect on the economic efficiency of the systems than non-optimal SoC setpoints. The results emphasise that the battery capacity is a critical investment decision.

Novel optimization algorithm for the power and energy management and component sizing applied to hybrid storage-based photovoltaic household-prosumers for the provision of complementarity services

Combining complementarity services such as frequency containment reserve (FCR) and photovoltaic self-consumption (PV SFC) can increase revenues for household-prosumers supported by battery/supercapacitor-based hybrid energy storage systems (HESSs). Nonetheless, to calculate the best financial profitability, optimization algorithms should be applied to power and energy management as well as component sizing. For this purpose, this research developed a four-dimensional optimization algorithm based on the teaching-learning-based optimization (TLBO) method. The optimization of management strategies was based on wavelet transform. An objective function was expressed in economic terms, including the investment, cycling, energy exchange and FCR provision, among other costs. Furthermore, a battery durability model was introduced. This algorithm was illustrated by a case study in Spain. The algorithm not only determined the optimal management, but also the best overall component sizing. A HESS was found to be a cost-effective way of enhancing PV SFC and providing FCR by increasing the profitability of the asset. Planning both complementarity services led to maximum revenues. The results showed that the optimal supercapacitor hybridization was 3.98–10.50%, depending on the planned services. This increased the profitability of battery-only configurations by more than 5.37–10.37%. Battery aging played a crucial role because of replacement cost.

Optimal sizing and management strategy for PV household-prosumers with self-consumption/sufficiency enhancement and provision of frequency containment reserve

This study provides a methodology to assess the techno-economic performance of photovoltaic household-prosumers that jointly provide self-consumption/sufficiency enhancement (SCSE) and frequency containment reserve (FCR). It thus addresses the following issues: (i) battery aging; (ii) supercapacitors joined to batteries building hybrid storage systems; (iii) management strategies of SCSE and charge level in energy storage systems; (iv) an integrated system with a 1-ms simulation step and high-resolution inputs. The methodology was applied to one Spanish household-prosumer. The study compared three charge-level management strategies by using different technical and economic performance indicators and concluded that the deadband recovery was the best. Moreover, the best techno-economic indicators were achieved by broadening the storage capacity band of unrestricted operation for SCSE (30–90%). Regarding the prosumer sizing, the optimal converter-battery configuration was determined so as to minimize the total energy supply cost. Long-term performance confirmed that when FCR provision was added to the SCSE, profitability increased up to 14.01%, with a relatively low impact on battery aging. A sensitivity analysis guaranteed a cost reduction of 3.68% for the prosumer energy and of 16% for the storage system life cycle at the optimal hybrid storage sizing. This sizing involved a 1% supercapacitor hybridization and a time constant of 150 s for power splitting.

Grid-Scale BESS for Ancillary Services Provision: SoC Restoration Strategies

The future power system, characterized by lower inertia, reduced programmability and more distributed architecture, will depend on prompt and reliable control systems. Quick ancillary services provided by battery energy storage systems (BESS) could be a resource in order to deliver fast and precise response to frequency events. Degrees of freedom in the design of innovative products traded on ancillary services markets give the asset manager room for developing state-of-charge (SoC) restoration mechanisms. These are necessary to effectively exploit BESS as key resources for electricity balancing. This study compares the main SoC restoration strategies. It aims to define which ones are suitable for guaranteeing the reliability of the provision and the return on the investment. A robust regulatory framework analysis describes the degrees of freedom guaranteed by the main experiences around Europe. In this paper, a BESS model with variable efficiency is used to compare the provision of Frequency Containment Reserve (FCR) with different SoC restoration strategies exploiting one or more degrees of freedom. Here, we show that the degrees of freedom are key to the reliability of provision. Among most diffused mechanisms, dead-band strategies secure the desired consistency, but require large energy flows for SoC management. Thus, BESS life and economics decrease. The strategies based on minimum available energy guarantee assured reliability while being fair with BESS life and operation costs.