Energy storage for complementary services in grid-tied PV systems

The continuous increase in penetration of renewable-based power plants together with the intermittent and variable nature of those natural resources have made grid stability issues a major concern, imposing limitations to higher penetration rates. Energy Storage Systems (ESS) have arise as an enabling technology capable of providing PV/ESS configurations with additional capabilities, as such as ancillary or complementary services. This work presents a complete analysis of three difierent complementary services (Maximum Power Ramp Rate limitations, Power Clipping and Peak Shaving). Additionally two different PV/ESS configurations are analysed. For that purpose, three different power converter interfaces between PV and ESS were tested. The results obtained from those tests, showing the performance of the aforementioned complementary services, are presented in this thesis. Moreover, the experimental validation of a PV/ESS, which consists of a full bridge based partial power converter as power interface between PV system and ESS, is also presented in this document. This document also includes two different ESS sizing strategies, each for an specific complementary service. These sizing strategies rely on a prediction of a year of PV power generation obtained from annual measurements of irradiance and temperature. In both cases, the resulting power prediction is contrasted against a desired power profile

Energy storage for complementary services in grid-tied PV systems

The continuous increase in penetration of renewable-based power plants together with the intermittent and variable nature of those natural resources have made grid stability issues a major concern, imposing limitations to higher penetration rates. Energy Storage Systems (ESS) have arise as an enabling technology capable of providing PV/ESS configurations with additional capabilities, as such as ancillary or complementary services. This work presents a complete analysis of three difierent complementary services (Maximum Power Ramp Rate limitations, Power Clipping and Peak Shaving). Additionally two different PV/ESS configurations are analysed. For that purpose, three different power converter interfaces between PV and ESS were tested. The results obtained from those tests, showing the performance of the aforementioned complementary services, are presented in this thesis. Moreover, the experimental validation of a PV/ESS, which consists of a full bridge based partial power converter as power interface between PV system and ESS, is also presented in this document. This document also includes two different ESS sizing strategies, each for an specific complementary service. These sizing strategies rely on a prediction of a year of PV power generation obtained from annual measurements of irradiance and temperature. In both cases, the resulting power prediction is contrasted against a desired power profile

Advanced Signal Processing Techniques Applied to Power Systems Control and Analysis

The work published in this book is related to the application of advanced signal processing in smart grids, including power quality, data management, stability and economic management in presence of renewable energy sources, energy storage systems, and electric vehicles. The distinct architecture of smart grids has prompted investigations into the use of advanced algorithms combined with signal processing methods to provide optimal results. The presented applications are focused on data management with cloud computing, power quality assessment, photovoltaic power plant control, and electrical vehicle charge stations, all supported by modern AI-based optimization methods

Energy storage systems and grid code requirements for large-scale renewables integration in insular grids

This thesis addresses the topic of energy storage systems supporting increased penetration of renewables in insular systems. An overview of energy storage management, forecasting tools and demand side solutions is carried out, comparing the strategic utilization of storage and other competing strategies. Particular emphasis is given to energy storage systems on islands, as a new contribution to earlier studies, addressing their particular requirements, the most appropriate technologies and existing operating projects throughout the world. Several real-world case studies are presented and discussed in detail. Lead-acid battery design parameters are assessed for energy storage applications on insular grids, comparing different battery models. The wind curtailment mitigation effect by means of energy storage resources is also explored. Grid code requirements for large-scale integration of renewables are discussed in an island context, as another new contribution to earlier studies. The current trends on grid code formulation, towards an improved integration of distributed renewable resources in island systems, are addressed. Finally, modeling and control strategies with energy storage systems are addressed. An innovative energy management technique to be used in the day-ahead scheduling of insular systems with Vanadium Redox Flow battery is presented.Esta tese aborda a temática dos sistemas de armazenamento de energia visando o aumento da penetração de energias renováveis em sistemas insulares. Uma visão geral é apresentada acerca da gestão do armazenamento de energia, ferramentas de previsão e soluções do lado da procura de energia, comparando a utilização estratégica do armazenamento e outras estratégias concorrentes. É dada ênfase aos sistemas de armazenamento de energia em ilhas, como uma nova contribuição no estado da arte, abordando as suas necessidades específicas, as tecnologias mais adequadas e os projetos existentes e em funcionamento a nível mundial. Vários casos de estudos reais são apresentados e discutidos em detalhe. Parâmetros de projeto de baterias de chumbo-ácido são avaliados para aplicações de armazenamento de energia em redes insulares, comparando diferentes modelos de baterias. O efeito de redução do potencial de desperdício de energia do vento, recorrendo ao armazenamento de energia, também é perscrutado. As especificidades subjacentes aos códigos de rede para a integração em larga escala de energias renováveis são discutidas em contexto insular, sendo outra nova contribuição no estado da arte. As tendências atuais na elaboração de códigos de rede, no sentido de uma melhor integração da geração distribuída renovável em sistemas insulares, são abordadas. Finalmente, é estudada a modelação e as estratégias de controlo com sistemas de armazenamento de energia. Uma metodologia de gestão de energia inovadora é apresentada para a exploração de curto prazo de sistemas insulares com baterias de fluxo Vanádio Redox

Evolution of microgrids with converter-interfaced generations: Challenges and opportunities

© 2019 Elsevier Ltd Although microgrids facilitate the increased penetration of distributed generations (DGs) and improve the security of power supplies, they have some issues that need to be better understood and addressed before realising the full potential of microgrids. This paper presents a comprehensive list of challenges and opportunities supported by a literature review on the evolution of converter-based microgrids. The discussion in this paper presented with a view to establishing microgrids as distinct from the existing distribution systems. This is accomplished by, firstly, describing the challenges and benefits of using DG units in a distribution network and then those of microgrid ones. Also, the definitions, classifications and characteristics of microgrids are summarised to provide a sound basis for novice researchers to undertake ongoing research on microgrids

Demand Side Management of Electric Vehicles in Smart Grids: A survey on strategies, challenges, modeling, and optimization

The shift of transportation technology from internal combustion engine (ICE) based vehicles to electricvehicles (EVs) in recent times due to their lower emissions, fuel costs, and greater efficiency hasbrought EV technology to the forefront of the electric power distribution systems due to theirability to interact with the grid through vehicle-to-grid (V2G) infrastructure. The greater adoptionof EVs presents an ideal use-case scenario of EVs acting as power dispatch, storage, and ancillaryservice-providing units. This EV aspect can be utilized more in the current smart grid (SG) scenarioby incorporating demand-side management (DSM) through EV integration. The integration of EVswith DSM techniques is hurdled with various issues and challenges addressed throughout thisliterature review. The various research conducted on EV-DSM programs has been surveyed. This reviewarticle focuses on the issues, solutions, and challenges, with suggestions on modeling the charginginfrastructure to suit DSM applications, and optimization aspects of EV-DSM are addressed separatelyto enhance the EV-DSM operation. Gaps in current research and possible research directions have beendiscussed extensively to present a comprehensive insight into the current status of DSM programsemployed with EV integration. This extensive review of EV-DSM will facilitate all the researchersto initiate research for superior and efficient energy management and EV scheduling strategies andmitigate the issues faced by system uncertainty modeling, variations, and constraints

Deep Learning in Energy Modeling: Application in Smart Buildings With Distributed Energy Generation

Buildings are responsible for 33% of final energy consumption, and 40% of direct and indirect CO2 emissions globally. While energy consumption is steadily rising globally, managing building energy utilization by on-site renewable energy generation can help responding to this demand. This paper proposes a deep learning method based on a discrete wavelet transformation and long short-term memory method (DWT-LSTM) and a scheduling framework for the integrated modelling and management of energy demand and supply for buildings. This method analyzes several factors including electricity price, uncertainty in climatic factors, availability of renewable energy sources (wind and solar), energy consumption patterns in buildings, and the non-linear relationships between these parameters on hourly, daily, weekly and monthly intervals. The method enables monitoring and controlling renewable energy generation, the share of energy imports from the grid, employment of saving strategy based on the user priority list, and energy storage management to minimize the reliance on the grid and electricity cost, especially during the peak hours. The results demonstrate that the proposed method can forecast building energy demand and energy supply with a high level of accuracy, showing a 3.63-8.57% error range in hourly data prediction for one month ahead. The combination of the deep learning forecasting, energy storage, and scheduling algorithm enables reducing annual energy import from the grid by 84%, which offers electricity cost savings by 87%. Finally, two smart active buildings configurations are financially analyzed for the next thirty years. Based on the results, the proposed smart building with solar Photo-Voltaic (PV), wind turbine, inverter, and 40.5 kWh energy storage has a financial breakeven point after 9 years with wind turbine and 8 years without it. This implies that implementing wind turbines in the proposed building is not financially beneficial.Peer reviewe

Integration of Flywheel Energy Storage Systems in Low Voltage Distribution Grids

Mit dem Ziel, den Stromsektor zu dekarbonisieren und dem Klimawandel zu begegnen, steigt der Anteil erneuerbarer Energieressourcen in den Energiesystemen rund um den Globus kontinuierlich an. Aufgrund des intermittierenden Charakters dieser Ressourcen kann die Aufrechterhaltung des momentanen Gleichgewichts zwischen Erzeugung und Verbrauch und damit der Netzfrequenz ohne angemessene Maßnahmen jedoch eine Herausforderung darstellen. Da erneuerbare Energiequellen mit Umrichterschnittstellen dem System selbst keine Trägheit verleihen, nimmt gleichzeitig die kumulative Systemträgheit ab, was zu schnelleren Änderungen der Netzfrequenz und Bedenken hinsichtlich der Netzstabilität führt. Ein Schwungrad-Energiespeichersystem (Flywheel Energy Storage System, FESS) kann schnell große Leistungsmengen einspeisen oder aufnehmen, um das Netz nach einer abrupten Änderung der Erzeugung oder des Verbrauchs zu unterstützen. Neben der schnellen Reaktionszeit hat ein FESS den Vorteil einer hohen Leistungsdichte und einer großen Anzahl von Lade- und Entladezyklen ohne Kapazitätsverlust während seiner gesamten Lebensdauer. Diese Eigenschaften machen das FESS zu einem gut geeigneten Kandidaten für die Frequenzstabilisierung des Netzes oder die Glättung kurzfristiger Leistungsschwankungen auf lokaler Ebene. In dieser Dissertation wird die Netzintegration eines Hochgeschwindigkeits-FESS auf der Niederspannungsebene aus mehreren Perspektiven untersucht. Zunächst wird das Problem der Platzierung und Dimensionierung eines FESS in Niederspannungsverteilnetzen für Leistungsglättungsanwendungen behandelt. Um den am besten geeigneten Standort für ein FESS zu finden, wird eine datengetriebene Methode zur Abschätzung der relativen Spannungsempfindlichkeit vorgestellt, die auf dem Konzept der Transinformation basiert. Der Hauptvorteil der vorgeschlagenen Methode besteht darin, dass sie kein Netzmodell erfordert und nur Messwerte an den interessierenden Punkten verwendet. Messergebnisse aus einem realen Netz in Süddeutschland zeigen, dass mit dem vorgeschlagenen Ansatz die Netzanschlusspunkte mit einer höheren Spannungsempfindlichkeit gegenüber Wirkleistungsänderungen, welche am meisten von einem durch FESS ermöglichten, glatteren Leistungsprofil profitieren können, erfolgreich zugeordnet werden können. Darüber hinaus wird eine neue Methode zur Dimensionierung von Energiespeichersystemen unter Verwendung von Messdaten eingeführt. Der vorgeschlagene Ansatz erkennt wiederkehrende Verbrauchsmuster in aufgezeichneten Leistungsprofilen mit Hilfe des "Motif Discovery"-Algorithmus, die dann zur Dimensionierung verschiedener Speichertechnologien, einschließlich eines FESS, verwendet werden. Anhand von gesammelten Messdaten aus mehreren Niederspannungsnetzen in Deutschland wird gezeigt, dass die Speichersysteme mit den aus den detektierten Mustern abgeleiteten Charakteristika während der gesamten Messperiode effektiv für ihre Anwendungen genutzt werden können. Als nächstes wurde ein dynamisches Modell eines Hochgeschwindigkeits-FESS entwickelt und mit experimentellen Ergebnissen in mehreren Szenarien, unter Berücksichtigung der Verluste und des Hilfsenergiebedarfs des Systems, validiert. In den untersuchten Szenarien wurde eine maximale Differenz von nur 0,8 % zwischen dem Ladezustand des Modells und dem realen FESS beobachtet, was die Genauigkeit des entwickelten Modells beschreibt. Nach Festlegung des erforderlichen Aufbaus wurde die Leistungsfähigkeit eines 60 kW Hochgeschwindigkeits-FESS während mehrerer Frequenzabweichungsszenarien mit Hilfe von Power Hardware-in-the-Loop-Tests beurteilt. Die Ergebnisse der PHIL-Tests zeigen, dass das Hochgeschwindigkeits-FESS sehr schnell nach einer plötzlichen Frequenzabweichung reagiert und in knapp 60 ms die erforderliche Leistung erreicht, wobei die neuesten Anforderungen der Anwendungsregeln für die Frequenzunterstützung auf der Niederspannungsebene erfüllt werden. Um schließlich die Vorteile des schnellen Verhaltens des FESS für Energiesysteme mit geringer Trägheit zu demonstrieren, wurde ein neuartiger adaptiver Trägheits-Emulationsregler für das Hochgeschwindigkeits-FESS eingeführt und seine Leistung in einem Microgrid mit geringer Trägheit durch Simulationen und Experimente validiert. Die Simulationsergebnisse zeigen, dass die Verwendung des FESS mit dem vorgeschlagenen Trägheits-Emulationsregler die maximale Änderungsrate der Frequenz um 28 % und die maximale Frequenzabweichung um 44 % während der Inselbildung des untersuchten Microgrid reduzieren kann und mehrere zuvor vorgestellte adaptive Regelungskonzepte übertrifft. Der vorgeschlagene Regler wurde auch auf einem realen 60 kW FESS mit dem Konzept des Rapid Control Prototyping implementiert, und die Leistungsfähigkeit des FESS mit dem neuen Regelungsentwurf wurde mit Hilfe von PHIL-Tests des FESS validiert. Die PHIL-Ergebnisse, die die allererste experimentelle Validierung der Trägheitsemulation mit einem FESS darstellen, bestätigen die Simulationsergebnisse und zeigen die Vorteile des vorgeschlagenen Reglers

Integration of Flywheel Energy Storage Systems in Low Voltage Distribution Grids

A Flywheel Energy Storage System (FESS) can rapidly inject or absorb high amounts of active power in order to support the grid, following abrupt changes in the generation or in the demand, with no concern over its lifetime. The work presented in this book studies the grid integration of a high-speed FESS in low voltage distribution grids from several perspectives, including optimal allocation, sizing, modeling, real-time simulation, and Power Hardware-in-the-Loop testing