Towards a task allocation algorithm for frequency containment reserves

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.

Frequency containment reserves (FCR) or formerly called primary reserves are a major component for the stability of the continental Europe power grid. Up to now, mainly gas power plants are providing FCR and their ongoing decreasing profitability in Europe has a non-negligible impact on the FCR provision cost. In this paper, the concept of FCR with large deadband is introduced and discussed. We show that frequency dynamics after a large disturbance and frequency distribution can be maintained at a satisfactory level. The introduction of FCR with large deadband could lower their procurement cost without impacting significantly the frequency quality and enable new participants, e.g. Demand-Side Management or renewable curtailment, to enter the reserve markets.

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.

Frequency Containment reserves (FCR), previously called primary reserves, are an important feature insuring safe and reliable operations of the Continental Europe grid. Due to their strong technical requirements, gas and hydro power plants are the almost exclusive provider of FCR. Since gas power plants are becoming less profitable in Europe, a lot of efforts are deployed into FCR diversification. This paper assesses the potential for battery energy storage systems (BESS) to deliver FCR combined with a slow-moving thermal power plant and other emergency solutions such as load shedding and dissipating resistances. A proportional-integral energy management control loop is used whose parameters are tuned by an economic evaluation. We show that economic opportunity already exists today. Some limitations are discussed due to simplifying assumptions. The best solution consists of a 1MW/1.4MWh battery and a 0.09MW power plant per MW of provided FCR reducing by 90% the reservation on power plants. Cost-based dimensioning of Battery Energy Storage and energy management system for Frequency Containment Reserves provision (PDF Download Available). Available from: http://www.researchgate.net/publication/280494357_Cost-based_dimensioning_of_Battery_Energy_Storage_and_energy_management_system_for_Frequency_Containment_Reserves_provision [accessed Sep 28, 2015].

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

With the continuous evolution of the power system towards a more renewable energy based system, a natural and gradual transition will be to provide ancillary services by using renewable production units. Research has shown this to be feasible for wind farms by using efficient prediction and sophisticated control systems. In some parts of the world, strict grid codes are already being implemented that require wind farms to provide ancillary services. Moreover, the primary reserve market in Europe is moving towards shorter procurement periods, providing wind farms an opportunity to more efficiently optimise their resources based on short term forecasts. As a result of these developments, it is expected that more wind farms will provide ancillary services in the near future. The provision of Frequency Containment Reserve (FCR) requires a fast regulation of the turbine power based on the changes of the grid frequency. It is expected that this will have an impact on the wake behind the wind turbine. In wind parks with a high capacity density, such as the offshore wind parks in Belgium, it is important to investigate this impact as it can affect other neighbouring turbines. This paper investigates the dynamic behaviour of the wake generated by a wind turbine providing grid frequency support with FCR.

In this paper, we present a methodology for the optimal sizing of the Battery Energy Storage Systems (BESS) in Data Centers (DC) to provide Frequency Containment Reserve (FCR) or Primary Control Reserve (PCR). In this context, the BESS can offer ancillary services to the grid without disrupting the normal operation of the DC. By taking into consideration the requirements in terms of backup power provision to the DC as well as the FCR, along with the investment and operating costs, the optimal sizing of the BESS is determined. The results obtained from the DC's simulation show the economic benefits of providing FCR to the grid using Li-Ion Lead-Acid BESSs, which in turn helps generate additional revenues for the DC operators and reduce the operating costs without hampering the necessary uptime requirements and the normal operation of the DC.

A novel TSO settlement scheme for the Frequency Containment Reserve Cooperation in Europe’s integrated electricity market

Large increase in wind and photovoltaics will lead to lower and more volatile grid inertia but also to the lack of primary frequency control, i.e. frequency containment reserve (FCR) providers in the Continental Europe Grid. This will therefore impact negatively the frequency dynamics. One potential solution for ensuring the frequency to stay in reasonable bounds is to take the dynamics of potential providers into consideration. From this observation, we develop a novel methodology for having a linear programming problem to select the most suited FCR providers. It is based on the minimization of the overall cost while respecting static and dynamic constraints which are respectively ensuring a sufficient amount of FCR and avoiding too large frequency deviations after a large disturbance. The methodology has been tested on a case with 200 potential FCR providers in function of various grid inertia and load damping factors.

The road towards decarbonization and production of sustainable and cheap electricity relies on the use of renewable energy sources such as solar and wind. However, such converter-based plants do not contribute kinetic energy to the system, and so substitution of traditional plants with renewables causes the system kinetic energy to drop, making the grid more unstable and vulnerable to disturbances which in turn increases the use and dependability on frequency containment reserves. Hence the need for increased power requirement and higher ramp rates from the reserves would result in an exponential increase in cost for availing of such services. A solution to mitigate imbalances in grid system power could be found through the utilization of energy storage systems (ESS). The ESS can provide faster and higher power support while keeping the cost comparatively low at high power requirements. A novel research was conducted on a modified N ordic-32 Test system using PSS®E simulation software where various solar PV plants and wind turbines were placed according to Nordic development plans to simulate the future Nordic grid with different levels of renewable energy penetration (REP) and estimate the amount of frequency containment reserve for disturbance (FCR-D) required for N-1 contingency disturbance and compare the overall cost of FCR-D using traditional sources and ESS using Lithium-ion and Vanadium Redox flow b atteries. The results showed the performance of the ESS for frequency regulation was better compared to conventional hydro turbines, showing smaller initial system frequency dip and flexible power r amp-up r ates as required at different REP levels. The overall cost of FCR-D services was reduced by 40% or more when FCR-D services were provided by a combined contribution from traditional sources and ESS when compared to traditional sources alone.

In the past, the reserves were provided by conventional power plants, but the new European energy package is focused on energy transition, where the main role of supply will be transferred to zero and low emissions' technologies, such as storages, prosumers and local energy communities. In addition, the new European legislation defines types of reserves and their participation, after prequalification, in regulation of frequency and active power through the market of balancing capacities and energy. This paper proposes definition of balancing products for frequency containment reserve, technical prequalification of applicants for balancing service provider and methodology for calculation of activated balancing energy.

EU Network Codes are encouraging power system operators to integrate nonconventional generation units in the evolving Ancillary Services Markets. Article 156 of System Operation Guidelines requests TSOs to perform a cost-benefit analysis for defining a minimum delivery time period for Frequency Containment Reserve (FCR) provided by units with Limited Energy Reservoirs (LER). A research group in Politecnico di Milano followed the process closely cooperating with ARERA, the Italian Regulatory Authority. This paper aims at describing in depth the methodology proposed by TSOs for analyzing system costs related to the introduction of a certain share of LER among FCR providers. Some qualitative and quantitative investigations are then proposed. Critical aspects of the methodology proposed by TSOs are described. The impact on energy storage of the differences among countries’ way of providing FCR is highlighted.

To solve the actual task of finding optimal generation mix and dispatch of thermal and nuclear power units, and hydro units of hydro pumped storages of Ukraine to cover day load power profile according to one of possible wind and solar generation curtailment mode the modification of mathematical MIP model is proposed. There are three modes of wind and solar generation curtailment revised in the article: 1) absolute maximum generation curtailment, 2) single for whole day decreased load factor, and 3) one per one hour decreased load factor. The possibility to allocate an exogenously determined level of frequency containment reserves (secondary reserves) on thermal power units is realized in the MIP model. The calculation’s results analysis shows that among revised wind and solar generation curtailment methods the method 2) is most appropriate in the short term because only administrative measures implementation is required, which could be put into force with appropriate legislation and does not require essential investments or implementation of complicated technical measures. The additional possible positive effect caused by the implementation of method 2) is it makes background for participation wind and solar generation in the ancillary services market and intraday balancing. In the middle term, the gradual implementation of method 3) is the most appropriate decision because a more stable power system balancing mode (minimum import/export amounts) could be provided. Moreover, extra nuclear power units and fewer coal thermal power units could be dispatched that is decreases hazard pollutions and carbon emission. The MIP model is written using MathProg language, a freeware version of AMPL. As a solver, the GNU GLPK program is used. The overall time for one calculation with standard table PC is about 30 seconds. MIP model could be used both for short-term power system optimal dispatch and for long-term national generation mix development studies under the growth rates of renewable installed capacities. Keywords: power system, daily load profile, robust decisions, mixed linear-integer problem, frequency containment reserve

This paper presents the validation of a rule-based control strategy trying to maximize the self-consumption of PV-converted power and providing frequency containment reserve power at the same time with a battery energy storage system placed in a residential household with roof-top PV-plant. The single model of a residential household is integrated in a simulation model of a virtual battery energy storage system for providing 1 MW frequency containment reserve power composed of 65 centrally coordinated battery energy storage systems with a local rule-based control strategy. We decided to set up a simulation model to be able to realize a high time-resolution. For its validation we set up an optimization model to compare simulation and optimization results. In conclusion, the comparison shows differences of optimization and simulation, but no inexplicable differences. Thus, the validation underlines the successful modeling of the virtual battery energy storage system.

This paper reports the recent work carried out to engage a pool of large industrial end-users in frequency control complying with the performance criteria of conventional generation. The pooling approach unites the benefits of continuous loads and staggered loads (discrete active power response). Based on a local measurement of the frequency, the primary control signal is dynamically reconstructed through a centrally managed automation infrastructure integrating the industrial constraints and the requirements of the transmission system operators (TSO). The regulation algorithm, minimizing the total number of up and down activations of the loads, as well as the regulation infrastructure, are presented and detailed. After a discussion of the practical implementation at three distant industrial sites, the response of the experimental installation of the pool is discussed through its performance measurements and assessment. From the industrial point of view, the overall regulation system is in operation, adding value to the power system and the end-users and is reported to be economically viable. The implemented entity has been certified by the French TSO RTE.