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The use of wind power has grown strongly in recent years and is expected to continue to increase in the coming decades. Solar power is also expected to increase significantly. In a power system, a continuous balance is maintained between total production and demand. This balancing is currently mainly managed with conventional power plants, but with larger amounts of wind and solar power, other sources will also be needed. Interesting possibilities include continuous control of wind and solar power, battery storage, electric vehicles, hydrogen production, and other demand resources with flexibility potential. The aim of this article is to describe and compare the different challenges and future possibilities in six systems concerning how to keep a continuous balance in the future with significantly larger amounts of variable renewable power production. A realistic understanding of how these systems plan to handle continuous balancing is central to effectively develop a carbon-dioxide-free electricity system of the future. The systems included in the overview are the Nordic synchronous area, the island of Ireland, the Iberian Peninsula, Texas (ERCOT), the central European system, and Great Britain. [ABSTRACT FROM AUTHOR]

From its commissioning in 2006 to the present, the Spanish Control Centre for Renewable Energies (CECRE) has been a worldwide pioneer and reference centre in the integration of renewable energies in the electrical system. In the last 15 years, CECRE has allowed a high penetration of renewable energies in Spanish electrical system by means of the supervision and control of renewable facilities, while ensuring the power supply security. This paper defines the bases of renewable energy operation in CECRE and introduces forecasting systems for renewable energies. Furthermore, this paper describes the participation of renewable energies in balancing services and congestion management. Finally, new challenges for Spanish transmission system operator (TSO) are presented for the integration of renewable energies along with the energy transition and decarbonization.

The use of wind power has grown strongly in recent years and is expected to continue to increase in the coming decades. Solar power is also expected to increase significantly. In a power system, a continuous balance is maintained between total production and demand. This balancing is currently mainly managed with conventional power plants, but with larger amounts of wind and solar power, other sources will also be needed. Interesting possibilities include continuous control of wind and solar power, battery storage, electric vehicles, hydrogen production, and other demand resources with flexibility potential. The aim of this article is to describe and compare the different challenges and future possibilities in six systems concerning how to keep a continuous balance in the future with significantly larger amounts of variable renewable power production. A realistic understanding of how these systems plan to handle continuous balancing is central to effectively develop a carbon-dioxide-free electricity system of the future. The systems included in the overview are the Nordic synchronous area, the island of Ireland, the Iberian Peninsula, Texas (ERCOT), the central European system, and Great Britain.

To be able to efficiently maintain a continuous balance between supply and demand in power systems with high shares of variable renewable energy (VRE) sources, a variety of studies related to the topic are needed. A fundamental input parameter for such studies is an assessment of the power system's physical needs for balancing power, in form of power imbalances. This article presents a new model for simulating physical power imbalances with a 1-minute time resolution based on multi-area economic dispatch simulations. Compared to existing models with the same purpose, the new model includes the combination of simulating power imbalances with 1-minute time resolution, simulating forecast uncertainty, simulating the continuous behaviour of all power system components and simulating the transmission for netting of power imbalances between balancing areas. By applying the model to a case study of the Nordic synchronous power system in year 2045, the impact of including these features in the model is highlighted. Case study results also show that the size and pattern of power imbalances much depends on the characteristics of a balancing area, in terms of electricity demand, available generation technologies and interconnections to other balancing areas. • Power imbalance simulation model based on multi-area economic dispatch. • Power imbalances are simulated with a 1-minute resolution. • Forecast uncertainty and transmission for imbalance netting is captured. • Wind and solar power are large power imbalance drivers. [ABSTRACT FROM AUTHOR]

In this study, a new market model is proposed to enable the smooth integration of distributed energy resources (DERs) in day‐ahead (DA) and balancing (BL) markets. The DA market is a joint energy and reserve market. DERs participate in the local market operated by the distribution market operator (DMO) which is coordinated with the wholesale market. During local market clearing, the DMO considers the technical constraints of the distribution grid to keep the operation of the distribution grid within limits. Moreover, the DMO, through preliminary scheduling, estimates preliminary prices for energy, reserve and balancing services. These can be seen as offer prices by which the DMO will bid into the TMO DA and BL market. The uncertainty of renewable‐based DERs is considered through the use of stochastic programming. The proposed market model is compared with a centralised market model. Results show that adding the distribution network constraints to the proposed market model is capable of alleviating overloading and appropriately accounting this effect in terms of increasing the operational cost. Moreover, it has been shown that the scalability of the proposed market model is higher compared to the currently applied centralised market models. [ABSTRACT FROM AUTHOR]

The electricity sector aims to achieve a balanced progress in all three dimensions of the energy trilemma: affordability, decarbonisation and security of supply. Separate strategies for decarbonisation and security of supply have been pursued; each with close attention to minimising costs, thus consistent with the affordability aspect of the trilemma. However, while it is evident that the pathway for decarbonisation increases pressure on security of supply, the pressures that cost-minimising security of supply measures are putting on decarbonisation goes unaddressed. The United Kingdom (UK) is a global leader in the transition towards a decarbonised economy and aims to achieve net-zero emissions by 2050. As a major part of the UK, Great Britain (GB) has achieved greater than 50% of low-carbon electricity generation and the grid’s carbon intensity has dropped by 36% over the period 2015–2019. However, balancing services that provide security of supply uses only 8% of low-carbon generation. Their carbon intensity is double the grid’s average and this gap is widening. This is an effect of a systemic reliance on carbon-intensive fuels. Financial support for capital investment for flexible low-carbon technologies is much needed. The GB context suggests that an integrated strategy covering all three dimensions of the trilemma might achieve an improved balance between them and unlock an affordable, net-zero emissions and secure power system.

In light of the advancing energy transition and an increasing amount of intermittent renewable energy to be integrated, flexibility from distributed energy resources will be key. In this paper, the Italian UVAM (Unità Virtuali Abilitate Miste, i.e., virtually aggregated mixed units) project, one of the biggest pilots in Europe to serve this purpose, is critically reviewed and mapped after two years of operation. The pilot is analyzed on a global level as well as the individual participant level. Based on the extensive analysis of actual market data, different strategies of participating companies to obtain capacity in accordance with the pilot project’s design are identified. Furthermore, the specific bidding strategies of individual participating units on the balancing market are outlined. Alongside this, the overall pilot project’s market integration, in terms of offered and accepted bids, is depicted. The thorough data analysis, therefore, serves as an input and fundamental building block for future electricity market modeling. Comprehending specific data from the coronavirus disease 2019 (COVID-19) pandemic, provides insights for future high renewable-energy scenarios. Based on the analysis findings, valuable deliverables are devised for both policy-makers and decision-makers who aim to leverage the flexibility potential of distributed resources.

Battery energy storage systems (BESSs) are widely used to smooth power fluctuations and maintain the voltage and frequency of the power feeder at a desired level. The National Grid Electricity Transmission (NGET), the primary electricity transmission network operator in the UK, has introduced various frequency response services that are designed to provide a real‐time response to deviations in the grid frequency. In this study, a control algorithm is developed which generates a charge/discharge power output with respect to deviations in the grid frequency and the requisite service specifications. Using historical UK electricity prices, a new balancing service scheduling approach has also been developed to maximise energy arbitrage revenue by layering different types of balancing services throughout the day. Simulation results show that the proposed algorithm delivers both dynamic and non‐dynamic firm frequency response and also an enhanced frequency response to NGET specifications while generating arbitrage revenue as well as service availability payments in the balancing market. A comparative study is also presented to compare the yearly arbitrage revenue obtained from the work presented in this study and a previous reference study. Finally,, experimental results of a grid‐tied 2 MW/1 MWh BESS have been used for verification purposes. [ABSTRACT FROM AUTHOR]

Ancillary services used for active power balancing are called balancing services or operating reserves and their provision is vital for maintaining power system frequency at the nominal value. In a deregulated environment, where generation is unbundled from transmission and distribution operations, independently owned generating companies may elect to provide operating reserves. However, it is not easy to calculate the exact cost of reserve provision and, therefore, bid for it accurately. Although the cost efficiency of reserve provision can be improved by co‐optimising energy and reserve markets, generating companies can still encounter monetary losses caused by the provision of reserve. Currently, these losses are compensated based on ex‐post calculations. Hence, current energy and reserve prices do not adequately factor in the ex‐post compensation caused by reserve provision. This study proposes an energy and reserve co‐optimisation with an explicit consideration of two compensation mechanisms, i.e. lost opportunity and uplift payments. The problem is structured as a bilevel model. The upper level is a mixed‐integer unit commitment problem and the lower level is a continuous economic dispatch problem. The case study shows that the proposed model increases market efficiency. [ABSTRACT FROM AUTHOR]

Ancillary services are intended to ensure the quality, reliability, and security conditions of the electricity supply. Active power‐related ancillary services are considered balancing services, including mandatory services, such as spinning or primary regulation, and optional services, such as secondary and tertiary regulation. These optional balancing services have typically been supplied by conventional power plants, but since their contribution to the production share is decreasing due to high renewable energy penetration, power system operators are currently in need of alternatives. In addition, the recent advances in both the wind power industry and power system observability and controllability, and the necessary changes in balancing markets have made it technically and economically possible for wind power plants to contribute to optional balancing services. Under this framework, our study focuses on the contribution of wind power to balancing markets in the Spanish power system. Specifically, this work analyses the operational capability test for wind energy active power ancillary services provision and the results of the participation of wind energy to tertiary regulation and imbalance management from February 2016 to July 2017. Furthermore, the analysis includes a comparison with other generation technologies and the identification of upward and downward direction margins. These results show the real experience of the contribution of Spanish wind energy to optional active power ancillary services. This article is categorized under: Wind Power > Systems and Infrastructure [ABSTRACT FROM AUTHOR]

The provision of reserve generation is an essential part of maintaining a reliable electricity system and has become an increasingly difficult task with the growing contribution from variable energy sources. Ensuring the cost of balancing supply and demand is minimised is an important aspect, requiring an understanding of how generator costs vary depending on their operation. This paper considers the cost of part loading different generator types, providing a cost breakdown and description of the Levelised Cost of Electricity method of analysing generator costs. This delivers cost-loading level curves for the generator types with the largest contribution to the UK generation portfolio which can be used to perform economic optimisations for generator scheduling. The holding payment for provision of frequency response, an aspect of maintaining balance between generation and demand, is separated by generator type and compared with the calculated part loading costs. To demonstrate the effect on system costs the Winter peak and Summer trough in 2016 and the Future Energy Scenarios in 2020 are considered with maximum and minimum generator numbers connected. Provision of sufficient generation to meet demand and reserves are optimised to reduce costs in each scenario. [ABSTRACT FROM AUTHOR]

The provision of reserve generation is an essential part of maintaining a reliable electricity system and has become an increasingly difficult task with the growing contribution from variable energy sources. Ensuring the cost of balancing supply and demand is minimized is an important aspect which requires an understanding of how generator costs vary depending on their operation. This paper considers the cost of part loading different generator types, providing a cost breakdown and description of the LCOE method of analyzing generator costs. This delivers cost-loading level curves for the generator types with the largest contribution to the UK generation portfolio. The holding payment for provision of frequency response is separated by generator type and compared with the calculated part loading costs. [ABSTRACT FROM AUTHOR]

Renewable energy producers are increasingly displacing conventional generation units – traditional suppliers of balancing services – from the daily electricity dispatch. As a consequence, there is a growing need that renewable generators also contribute to electricity balancing so that system operational security is guaranteed at all times. In Spain, the government recently launched a reform allowing the participation of intermittent renewable producers in balancing markets. Nevertheless, current market designs may not be adapted to this participation. In this context, this paper provides a concise, complete and updated review of balancing arrangements in Spain and identifies market design aspects that may act as barriers to the participation of renewable producers in balancing mechanisms. Empirical data is used to support the discussion. Based on this analysis and existing alternative designs, the authors provide policy recommendations for the adaptation of Spanish balancing arrangements to the participation of renewable producers in electricity balancing. These recommendations can also be useful for European policy makers currently working on the development of the European network codes for electricity balancing. These network codes will be implemented in all European countries in the near future. [ABSTRACT FROM AUTHOR]

Due to the rising share of variable renewable energy, balancing market integration (BMI) has been advocated as a promising solution to achieve flexible resource sharing among different regions and enhance the flexibility of the overall power system. However, BMI can result in welfare transfers among regions, which may correspondingly give rise to resistance to integration. Therefore, an incentive mechanism to facilitate flexible resource sharing under BMI is designed in this paper. We first analyse the sources of the benefits of BMI and compare the influence of different market regulation approaches on the welfare transfer effect via a graphical method. Then, based on the Coase theorem, we design an incentive profit-sharing mechanism that is able to optimize the allocation of flexible resources and eliminate welfare transfers among regions to some extent to reduce possible resistance to integration. Case studies based on the three-region system and a realistic northwest power grid in China show that the balancing cost of multi-region systems can be respectively reduced up to 31% and 25%, and the utilization of flexible units can be increased by over 30% by BMI. Finally, corresponding policy implications for BMI are put forward; the proposed mechanism also provides a useful reference and insight for dealing with welfare transfers in interregional trading. • Balancing market integration results in welfare transfers among regions. • An incentive profit-sharing mechanism based on the Coase theorem is designed. • Balancing market integration benefits from imbalance netting and resource sharing. • Inappropriate market adjustment approaches may lead to efficiency loss. • The contribution rates of each region and transmission lines are considered. [ABSTRACT FROM AUTHOR]

The increasing share of variable renewable energy sources for electricity increases the operating reserve requirements of power systems. This contribution studies the techno‐economic feasibility of procuring reserve capacity as an ancillary service from wind power producers. Research and demonstration have shown that wind power is able to meet the technical requirements of providing these balancing services. This study shows how acceptable availability levels can be achieved when using probabilistic forecast models in combination with day‐ahead procurement. The participation of wind power is analysed with a unit commitment model in order to determine the impact on generation system scheduling, as well as the electricity generation costs. Simulations show how wind power becomes a potential provider of downward reserve capacity when facing high reserve capacity requirements during periods with low demand and high renewable generation. In contrast, its participation in the upward reserve capacity remains limited, explained by the high opportunity cost. [ABSTRACT FROM AUTHOR]

• System flexibility and demand flexibility concepts clarification. This review explains why the known as Explicit Demand Flexibility is the one that offers flexibility to the system. • Congestion management and balancing services in which Explicit Demand Flexibility can bring value, identifying also the barriers found for including it as another market party regarding European products. • Main weaknesses of mathematical models for balancing and congestion management services that include Explicit Demand Flexibility participation. • Analysis of how integrated is Explicit Demand Flexibility in European countries markets and work being performed to develop it. Current power systems are characterized by the increase of renewable generation and distributed energy resources introducing more variability on the generation and enhancing the importance of the management in the consumption side. In this paper, a thorough review about the explicit demand flexibility (EDF) concept is addressed. This review, firstly, brings clarification over the different terms that have been used in the literature and the agents that are involved in the demand flexibility framework. Secondly, analyzes the different balancing services where EDF could participate, identifying the main barriers found for each market. In addition, it contributes to classify how mathematical models include EDF participation in ancillary services and congestion management, finding the main weaknesses and working lines for EDF integration in such models. Finally, a European overview is assessed to see where flexible resources have actual participation and how it is performed. [ABSTRACT FROM AUTHOR]

For restructured electricity industries undergoing energy transition, designing effective and efficient frequency control arrangements is a complex and ongoing task that requires appropriate configuration of controllers, generator technical connection requirements, market arrangements and wider policy settings. In this paper, we provide an overview and assessment of these arrangements in Australia's National Electricity Market - a useful case study given its long-standing frequency control ancillary services markets, yet recent challenges in maintaining secure frequency control. We assess the performance of these evolving arrangements in delivering improved frequency control outcomes, with particular regard to growing renewable penetrations and evident tensions between mandatory requirements and market-based incentives. Based on this assessment, we draw out four key insights on designing frequency control arrangements as power system capabilities and needs change: (1) Understanding control action interactions, (2) Implementing efficient price formation and cost-allocation mechanisms, (3) Monitoring and assessing service provision to better align participant remuneration with service quality, and (4) Considering both regulatory and market mechanisms and their consequences and interactions. In particular, we discuss the trade-offs between effective and efficient outcomes, and provide arguments for more robust and forward-looking frequency control arrangements during energy transition. • Deteriorating frequency control has been observed in the Australian power system. • Market-based mechanisms have been favoured at the expense of effective control. • Both regulatory and market-based mechanisms will be required during transition. • Regulatory mechanisms may prove to be more effective and robust. • Market design can support investment and align remuneration with performance. [ABSTRACT FROM AUTHOR]

Abstract: The expected increase of intermittent electricity production from renewable sources in Northern Europe poses rising challenges to the balancing of the power system. The Nordic hydro based power system, particularly the Norwegian, is in a favourable position to provide the necessary balancing services. In order to provide these services to continental Europe an integration of markets for balancing services (regulating power market) might be advantageous. Contemporaneously the European Union enforces the liberalisation and integration of national European power markets, including the regulating power markets. To investigate the possible outcome of such an integrated market, a regulating power market model is developed, which is based on a common day-ahead market, including Nordic and northern continental Europe. The proposed model considers the procurement of regulating reserves as well as their activation, taking into account available transmission capacity. Different steps of regulating power market integration are studied. The analysis confirms, that there is a socio-economic benefit by integrating regulating power markets. The benefit mainly results from a provision of reserve capacity from the Nordic to the continental European power system, the netting of imbalances and hence the reduced activation of regulating reserves in the continental power system. [Copyright &y& Elsevier]

Abstract: Demand response resources management is one of the most investigated solutions oriented to improve the efficiency in electricity markets. In this paper, the capability of customers to participate in short term markets is analyzed. An available methodology to analyze the daily and monthly energy consumptions of large customers is used to create energy offers and bids. This allows customers to participate in energy markets in order to buy, as first step, the usual electricity consumption and, additionally, to offer demand reductions in the short term electricity markets. Additionally, this paper shows the customer potential to participate in the Spanish electricity markets. [Copyright &y& Elsevier]

• A scalable optimization scheme is designed for prosumers providing ancillary services. • Prosumers are modelled using MILPs, enabling to consider different operating modes. • The distributed algorithm to promptly manage large-scale aggregations. • The numerical results show the effectiveness of the approach for varying aggregations' sizes. This paper addresses the provision of ancillary services in smart energy systems. A large number of prosumers are aggregated by an Energy Service Provider (ESP) in order to provide a manual Frequency Restoration Reserve (mFRR) service, which consists in offering some degree of flexibility and be willing to provide a power variation over a given time interval upon reception of an explicit manual request by the Transmission System Operator (TSO). The main focus of this paper is to define how the ESP can optimally distribute the requested flexibility effort to the prosumers in the pool, promptly providing the agreed mFRR service upon request of the TSO. In particular, a scalable strategy is proposed, able to account for integer decision variables like on/off commands, while reducing the combinatorial complexity of the problem and preserving privacy of local information via distributed computations. Lead and rebound effects are avoided by maintaining the originally scheduled energy exchange profile before and after the time interval where the TSO request must be satisfied. The simulation results show the effectiveness of the proposed approach in terms of scalability and quality of the obtained feasible solution. [ABSTRACT FROM AUTHOR]

The electricity sector aims to achieve a balanced progress in all three dimensions of the energy trilemma: affordability, decarbonisation and security of supply. Separate strategies for decarbonisation and security of supply have been pursued; each with close attention to minimising costs, thus consistent with the affordability aspect of the trilemma. However, while it is evident that the pathway for decarbonisation increases pressure on security of supply, the pressures that cost-minimising security of supply measures are putting on decarbonisation goes unaddressed. The United Kingdom (UK) is a global leader in the transition towards a decarbonised economy and aims to achieve net-zero emissions by 2050. As a major part of the UK, Great Britain (GB) has achieved greater than 50% of low-carbon electricity generation and the grid's carbon intensity has dropped by 36% over the period 2015–2019. However, balancing services that provide security of supply uses only 8% of low-carbon generation. Their carbon intensity is double the grid's average and this gap is widening. This is an effect of a systemic reliance on carbon-intensive fuels. Financial support for capital investment for flexible low-carbon technologies is much needed. The GB context suggests that an integrated strategy covering all three dimensions of the trilemma might achieve an improved balance between them and unlock an affordable, net-zero emissions and secure power system. [ABSTRACT FROM AUTHOR]

• Low reservoir amplitudes in run-of-river hydropower enable extensive grid balancing. • 1 MW of hydropower can facilitate grid integration of up to 11.6 MW of wind or PV. • Potentials for negative balancing services significantly higher than for positive. • Providing balancing services reduces overall energy production. • Nevertheless balancing services can increase the total incomes. The increasing shares of wind energy and photovoltaics in many countries challenge the energy systems in a twofold way. On one hand, there is an increased need for balancing energy in order to compensate abrupt changes in load or power generation. On the other hand, fossil plants being important providers of balancing services are gradually driven out of the system creating a need for renewable substitutes. Due to strict requirements on the upstream water level regime German run-of-river (ROR)-hydropower has until now remained largely unused for providing positive balancing services. However, in this paper we present a novel optimized operation scheme allowing ROR-plants to exactly keep their production schedule and, in addition to that, provide positive and negative balancing services even under these constraints. Our simulations on an exemplary power plant with a very low head show that huge unused balancing power potentials can be expected for ROR-hydropower in Germany enabling a multiplication of fluctuating renewable energy sources. Next to these potentials under current market conditions, this paper elaborates the economic and ecologic aspects of balancing operation. [ABSTRACT FROM AUTHOR]

In light of the advancing energy transition and an increasing amount of intermittent renewable energy to be integrated, flexibility from distributed energy resources will be key. In this paper, the Italian UVAM (Unità Virtuali Abilitate Miste, i.e., virtually aggregated mixed units) project, one of the biggest pilots in Europe to serve this purpose, is critically reviewed and mapped after two years of operation. The pilot is analyzed on a global level as well as the individual participant level. Based on the extensive analysis of actual market data, different strategies of participating companies to obtain capacity in accordance with the pilot project's design are identified. Furthermore, the specific bidding strategies of individual participating units on the balancing market are outlined. Alongside this, the overall pilot project's market integration, in terms of offered and accepted bids, is depicted. The thorough data analysis, therefore, serves as an input and fundamental building block for future electricity market modeling. Comprehending specific data from the coronavirus disease 2019 (COVID-19) pandemic, provides insights for future high renewable-energy scenarios. Based on the analysis findings, valuable deliverables are devised for both policy-makers and decision-makers who aim to leverage the flexibility potential of distributed resources. [ABSTRACT FROM AUTHOR]

To correct grid imbalances and avoid grid failures, the transmission system operator (TSO) deploys balancing reserves and settles these imbalances by penalizing the market actors that caused them. In several countries, it is forbidden to influence the grid imbalances in order to let the TSO retain full control of grid regulation. In this paper, we argue that this approach is not optimal as market actors that trade imbalances under the supervision of the TSO can help balancing the grid more efficiently. For instance, some systems such as solar farms cannot participate in the standard balancing market but do have economic incentives to help regulate the grid by trading with imbalances. Based on this argument, we propose a new market framework where any market actor is allowed to trade with imbalances. We show that, using the new market mechanism, the TSO can keep full control of the grid balance while decreasing the balancing cost. This is of primary importance as: 1) novel approaches to reduce grid imbalances are needed as, while renewable sources are generally not used for grid balancing, the increasing integration of renewable energy sources creates higher imbalances. 2) While long-term storage of energy is key in the energy transition, it needs to become an attractive investment to ensure its widespread use; as we show, the proposed market can guarantee that. Based on a real case study, we show that the new market can provide 10–20% of the total balancing energy needed and reduce the balancing costs. • Market framework that allows renewable sources to provide balancing services. • The new market lowers balancing costs and increases integration of renewable sources. • The proposed framework enhances the economic viability of seasonal storage systems. • The new market ensures competitive trading practices. [ABSTRACT FROM AUTHOR]