Unlocking the Potential of Flexible Energy Resources to Help Balance the Power Grid

Flexible energy resources can help balance the power grid by providing different types of ancillary services. However, the balancing potential of most types of resources is restricted by physical constraints such as the size of their energy buffer, limits on power-ramp rates, or control delays. Using the example of Secondary Frequency Regulation, this paper shows how the flexibility of various resources can be exploited more efficiently by considering multiple resources with complementary physical properties and controlling them in a coordinated way. To this end, optimal adjustable control policies are computed based on robust optimization. Our problem formulation takes into account power ramp-rate constraints explicitly, and accurately models the different timescales and lead times of the energy and reserve markets. Simulations demonstrate that aggregations of select resources can offer significantly more regulation capacity than the resources could provide individually.Comment: arXiv admin note: text overlap with arXiv:1804.0389

Provision of secondary frequency regulation by coordinated dispatch of industrial loads and thermal power plants

Demand responsive industrial loads with high thermal inertia have potential to provide ancillary service for frequency regulation in the power market. To capture the benefit, this study proposes a new hierarchical framework to coordinate the demand responsive industrial loads with thermal power plants in an industrial park for secondary frequency control. In the proposed framework, demand responsive loads and generating resources are coordinated for optimal dispatch in two-time scales: (1) the regulation reserve of the industrial park is optimally scheduled in a day-ahead manner. The stochastic regulation signal is replaced by the specific extremely trajectories. Furthermore, the extremely trajectories are achieved by the day-ahead predicted regulation mileage. The resulting benefit is to transform the stochastic reserve scheduling problem into a deterministic optimization; (2) a model predictive control strategy is proposed to dispatch the industry park in real time with an objective to maximize the revenue. The proposed technology is tested using a real-world industrial electrolysis power system based upon Pennsylvania, Jersey, and Maryland (PJM) power market. Various scenarios are simulated to study the performance of the proposed approach to enable industry parks to provide ancillary service into the power market. The simulation results indicate that an industrial park with a capacity of 500 MW can provide up to 40 MW ancillary service for participation in the secondary frequency regulation. The proposed strategy is demonstrated to be capable of maintaining the economic and secure operation of the industrial park while satisfying performance requirements from the real world regulation market

Fleksibilnost elektroenergetskih sustava

Modern power systems rely on power generation from renewable sources, predominantly from wind and solar. However, the intermittency and variability of these sources require additional power system flexibility. Due to retirement of conventional thermal generation, the need for flexibility is increased, while the flexible resources are reduced. Thus, new flexibility resources are sought. This paper examines real-world examples of the increased flexibility requirements, identifies the new sources of flexibility in the form of batteries and demand response, presents relevant mathematical models, and provides guidelines on future research needs in this area.Moderni elektroenergetski sustavi oslanjaju se na proizvodnju električne energije iz obnovljivih izvora energije, prvenstveno vjetra i Sunca. Međutim, nepravilnost i promjenjivost njihove proizvodnje električne energije uzrokuje povećane zahtjeve za fleksibilnošću sustava. Nadalje, uslijed prestanka rada konvencionalnih termalnih elektrana, koje su i same bile izvor fleksibilnosti, nedostatak iste sve je više izražen. Stoga su potrebni novi izvori fleksibilnosti. Članak izučava stvarne primjere povećanih zahtijeva za fleksibilnošću, identificira nove izvore fleksibilnosti (baterije i odaziv potrošnje), te predstavlja relevantne matematičke modele i daje preporuke za buduća istraživanja u ovom području

Opening of Ancillary Service Markets to Distributed Energy Resources: A Review

Electric power systems are moving toward more decentralized models, where energy generation is performed by small and distributed power plants, often from renewables. With the gradual phase out from fossil fuels, however, Distribution Energy Resources (DERs) are expected to take over in the provision of all regulation services required to operate the grid. To this purpose, the opening of national Ancillary Service Markets (ASMs) to DERs is considered an essential passage. In order to allow this transition to happen, current opportunities and barriers to market participation of DERs must be clearly identified. In this work, a comprehensive review is provided of the state-of-the-art of research on DER integration into ASMs. The topic at hand is analyzed from different perspectives. First, the current situation and main trends regarding the reformation processes of national ASMs are analyzed to get a clear picture of the evolutions expected and adjustment required in the future, according to the scientific community. Then, the focus is moved to the strategies to be adopted by aggregators for the effective control and coordination of DERs, exploring the challenges posed by the uncertainties affecting the problem. Coordination schemes between transmission and distribution system operators, and the implications on the grid infrastructure operation and planning, are also investigated. Finally, the review deepens the control capabilities required for DER technologies to perform the needed control actions

Operational concepts for grid services using electric vehicles

The European electricity grid is subject to increasing stresses due to increasing share of volatile renewable energy technologies. These technologies, coupled with higher volatility in demand, pose challenges to the stability and security of the European grid, erstwhile dominated by large and relatively reliable conventional generation. As the contribution of wind and photovoltaic generation increases in the energy mix, it demands an assessment of the corresponding risk to frequency stability and possible preventive measures. Uncontrolled charging of the increasing number of electric vehicles in Germany also demands a thorough investigation of methods for their integration in the electricity grid to not only improve grid frequency stability but also to provide secondary benefits to electric vehicle users. This work analyzes the load frequency control systems for their suitability for integration of electric vehicles and the impact of increase in volatile renewable energy on frequency stability for the case of Germany, showing a significant increase in reserve requirements. Evaluation of alternative approaches to load frequency control on the basis of infrastructure requirements shows that introduction of an aggregator of distributed energy resources can significantly reduce the overall infrastructure requirements for grid operators. The operational concepts herein proposed are evaluated using several case studies for optimizing the use of electric vehicles for grid flexibility services by taking into account the usage requirements of the vehicle owner and supply requirements of grid services.Das europäische Stromnetz ist aufgrund des steigenden Anteils volatiler erneuerbare Energiequellen einer zunehmenden Belastung ausgesetzt. Diese Technologien, in Ver-bindung mit einer höheren Volatilität der Nachfrage, stellen eine Herausforderung für die Stabilität und Sicherheit des europäischen Netzes dar, das früher von einer zentrali-sierteren Erzeugung in großen und relativ zuverlässigen konventionellen Kraftwerken geprägt war. Mit zunehmendem Beitrag der Wind- und Photovoltaikerzeugung am Energiemix ist eine Bewertung des Risikos für die Frequenzstabilität und mögliche Prä-ventivmaßnahmen erforderlich. Die ungesteuerte Aufladung der zunehmenden Anzahl von Elektrofahrzeugen in Deutschland erfordert auch eine gründliche Untersuchung der Methoden für ihre Integration in das Stromnetz, um nicht nur die Stabilität der Strom-netzfrequenz zu verbessern, sondern auch einen sekundären Nutzen für die Elektrofahr-zeug-Nutzer zu erzielen. Diese Arbeit analysiert die Lastfrequenzregelungssysteme auf ihre Eignung zur Integration von Elektrofahrzeugen ins Stromnetz sowie die Auswir-kungen der Erhöhung des Anteils von volatilen erneuerbaren Energien auf die Frequenz-stabilität in Deutschland, und zeigt einen deutlichen Anstieg der Anforderungen an Re-servekapazität. Die Bewertung alternativer Ansätze zur Lastfrequenzsteuerung auf der Grundlage von Infrastrukturanforderungen zeigt, dass die Einführung eines verteilten Energieressourcen Aggregators den gesamten Infrastrukturbedarf der Netzbetreiber deutlich reduzieren kann. Die hierin vorgeschlagenen Betriebskonzepte werden anhand mehrerer Fallstudien zur Optimierung des Einsatzes von Elektrofahrzeugen für Flexibili-tätsdienstleistungen im Stromnetz unter Berücksichtigung der Anforderungen der Fahr-zeughalter und des Versorgungsbedarfs von Netzdiensten bewertetThis thesis deals with the challenges to frequency stability in the European electricity grid posed by the increasing share of renewable energy resources and electric vehicles. It evaluates European load frequency control systems for their suitability for integration of electric vehicles and the impact of increase in photovoltaic and wind power on frequency stability for the case of Germany, demonstrating a consequent significant increase in frequency control reserve requirements. Evaluation of alternative approaches to load frequency control shows that introduction of an aggregator of distributed energy resources can also significantly reduce the overall infrastructure requirements for grid operators. The operational concepts herein proposed are evaluated using several case studies for optimizing the use of electric vehicles for grid flexibility services by taking into account the user behavior of vehicle owners and supply requirements of these grid services

Towards flexibility trading at TSO-DSO-customer levels : a review

The serious problem of climate change has led the energy sector to modify its generation resources from fuel-based power plants to environmentally friendly renewable resources. However, these green resources are highly intermittent due to weather dependency and they produce increased risks of stability issues in power systems. The deployment of different flexible resources can help the system to become more resilient and secure against uncertainties caused by renewables. Flexible resources can be located at different levels in power systems like, for example, at the transmission-level (TSO), distribution-level (DSO) and customer-level. Each of these levels may have different structures of flexibility trading as well. This paper conducts a comprehensive review from the recent research related to flexible resources at various system levels in smart grids and assesses the trading structures of these resources. Finally, it analyzes the application of a newly emerged ICT technology, blockchain, in the context of flexibility trading.fi=vertaisarvioitu|en=peerReviewed

Towards Flexibility Trading at TSO-DSO-Customer Levels: A Review

The serious problem of climate change has led the energy sector to modify its generation resources from fuel-based power plants to environmentally friendly renewable resources. However, these green resources are highly intermittent due to weather dependency and they produce increased risks of stability issues in power systems. The deployment of different flexible resources can help the system to become more resilient and secure against uncertainties caused by renewables. Flexible resources can be located at different levels in power systems like, for example, at the transmission-level (TSO), distribution-level (DSO) and customer-level. Each of these levels may have different structures of flexibility trading as well. This paper conducts a comprehensive review from the recent research related to flexible resources at various system levels in smart grids and assesses the trading structures of these resources. Finally, it analyzes the application of a newly emerged ICT technology, blockchain, in the context of flexibility trading

A Framework for Flexible Loads Aggregation

L'abstract è presente nell'allegato / the abstract is in the attachmen

Short-term Self-Scheduling of Virtual Energy Hub Plant within Thermal Energy Market

Multicarrier energy systems create new challenges as well as opportunities in future energy systems. One of these challenges is the interaction among multiple energy systems and energy hubs in different energy markets. By the advent of the local thermal energy market in many countries, energy hubs' scheduling becomes more prominent. In this article, a new approach to energy hubs' scheduling is offered, called virtual energy hub (VEH). The proposed concept of the energy hub, which is named as the VEH in this article, is referred to as an architecture based on the energy hub concept beside the proposed self-scheduling approach. The VEH is operated based on the different energy carriers and facilities as well as maximizes its revenue by participating in the various local energy markets. The proposed VEH optimizes its revenue from participating in the electrical and thermal energy markets and by examining both local markets. Participation of a player in the energy markets by using the integrated point of view can be reached to a higher benefit and optimal operation of the facilities in comparison with independent energy systems. In a competitive energy market, a VEH optimizes its self-scheduling problem in order to maximize its benefit considering uncertainties related to renewable resources. To handle the problem under uncertainty, a nonprobabilistic information gap method is implemented in this study. The proposed model enables the VEH to pursue two different strategies concerning uncertainties, namely risk-averse strategy and risk-seeker strategy. For effective participation of the renewable-based VEH plant in the local energy market, a compressed air energy storage unit is used as a solution for the volatility of the wind power generation. Finally, the proposed model is applied to a test case, and the numerical results validate the proposed approach