Sensitivity analysis of a wind farm with integrated flywheel energy storage

Integration of quick response energy storage with wind-based generation sites has the potential to enhance the performance of these sites. Flywheel Energy Storage Systems (FESSs) are ideally placed to be utilized in this way due to their long lifetime and high cyclability. The effectiveness of this integration is dependent on a set of variables and constraints. A sensitivity analysis has been conducted to investigate the effect of changing system variables on output metrics using a mathematical simulation model

Performance and Economic Evaluation of Storage Technologies

In the last decade there has been a drastic increase in the penetration of variable generation (VG) such as wind and solar. VG increases the MW variability that must be met in the regulation and reserve markets. If VG penetration levels are allowed to increase without providing additional flexibility in the form of fast response regulation, reserves, and capacity, then the required capabilities will be provided by the existing conventional generation fleet. This do-nothing approach will lead to increased cycling of the existing plants and thus weaken the health of the current grid. The increase VG capacity penetration will also necessitate increased transmission capability in the grid in order to facilitate increased VG energy penetration. All these boils down to endowing the grid with the capability to be flexible by investigating the various options such as transmission expansion, demand control, fast responding generation, VG MW output control, expanding the balancing areas and/or investing in storage technology. In this dissertation, the primary focus is on storage technologies, which is one of the attractive means to meet VG variability due to their fast response. With sufficient energy storage capability, they also promise many other valuable grid services such as peak shaving, load leveling, relieving congestion, increasing VG energy penetration, and deferring generation and transmission expansion plans. The objective and contribution of the dissertation is hinged on developing tools and assessment methodologies to perform economic assessment of storage. The work develops a high-fidelity technology adaptive storage dispatch model for production costing study within a co-optimized energy and ancillary market. This tool is used to investigate the grid benefits and economic viability of different class of storage under various wind penetration scenarios, compare them with other competing solutions, and devise appropriate monetizing schemes for their services. This work also proposes an integrated approach involving production costing and automatic generation control simulation tools to assess short-term storages. Based on the application in IEEE 24 bus system, many conclusions and indicators on storage venture\u27s profitability and risks are drawn

Comparative Sustainability Assessment of Decentralised Power Supply Systems in Remote Areas

Electricity generation for remote area power supply (RAPS) has serious environmental and economic implications that need to be addressed. This thesis aimed to integrate these two pillars of sustainability to achieve improvement in the eco-efficiency performance of RAPS in Western Australia. A comprehensive eco-efficiency analysis framework was developed to integrate environmental life cycle assessment (ELCA), life cycle costing (LCC), eco-efficiency strategies and eco-efficiency portfolio analysis for the selection of eco-efficient RAPS options

Energy-Driven Analysis of Electronically-Interfaced Resources for Improving Power System Dynamic Performance

This dissertation investigates the strengthening of power system dynamics with regard to electromechanical oscillations by using electronically-interfaced resources (EIR). The dissertation addresses (1) the modeling and control design of a flywheel energy storage system and a large-scale solar PV plant. The latest is enabled to participate in oscillation damping control without the need for power curtailment. (2) A new dynamic performance evaluation and coordination of damping controller is also developed to analyze systems with several critically low damping ratios. This is studied by using the system oscillation energy to define the total action and total action sensitivity, which allow the identification of control action that benefit exited modes, rather than fixed targeted modes. Finally, (3) this dissertation proposes a solution for the site selection of EIR-based damping controllers in a planning stage. The effect of wind power variability and correlation between geographically closed wind farms is modeled to analyze the system performance and determine the site selection that maximizes the probability of dynamic performance improvement. Mathematical description as well as simulations in different multi-machine power systems show the advantages of the methods described in this work. The findings of this thesis are expected to advance the state-of-the-art of power system control by effectively and efficiently utilizing the fast power capabilities of EIR in systems with high penetration of renewable energy

Design and Development of a Next Generation Energy Storage Flywheel

Energy storage is crucial for both smart grids and renewable energy sources such as wind or solar, which are intermittent in nature. Compared to electrochemical batteries, flywheel energy storage systems (FESSs) offer many unique benefits such as low environmental impact, high power quality, and larger life cycles. This dissertation presents the design and development of a novel utility-scale FESS that features a shaftless, hubless rotor. The unique shaftless design gives it the potential of a doubled energy density and a compact form factor. Its energy and power capacities are 100 kWh and 100 kW, respectively. The flywheel is made of high-strength steel, which makes it much easier to manufacture, assemble, and recycle. Steels also cost much less than composite materials. In addition, the system incorporates a new combination active magnetic bearing. Its working principle and the levitation control for the flywheel are presented. The development of an integrated, coreless, permanent-magnet (PM) motor/generator for the flywheel is briefly discussed as well. Initial test results show that the magnetic bearing provides stable levitation for the 5443-kg flywheel with small current consumptions. Furthermore, this dissertation formulates and synthesizes a detailed model for designing and simulating a closed-loop control system for the proposed flywheel system at high speed. To this end, the magnetic bearing supporting structure is considered flexible and modeled by finite element modeling. The magnetic bearing is characterized experimentally by static and frequency-dependent coefficients, the latter of which are caused by eddy current effects and presents challenges to the levitation control. Sensor- runout disturbances are measured and included in the model. System nonlinearities in power amplifiers and the controller are considered as well. Even though the flywheel has a large ratio of the primary-to-transversal moment of inertias, Multi-Input-Multi-Output (MIMO) feedback control demonstrates its effectiveness in canceling gyroscopic torques and stabilize the system. Various stages of PD controllers, lead/lag compensators, and notch filters are also implemented to suppress the high-frequency sensor disturbances and structural vibrations

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

On the contribution of wind farms in automatic generation control: Review and new control approach

© 2018 by the authors. Wind farms can contribute to ancillary services to the power system, by advancing and adopting new control techniques in existing, and also in new, wind turbine generator systems. One of the most important aspects of ancillary service related to wind farms is frequency regulation, which is partitioned into inertial response, primary control, and supplementary control or automatic generation control (AGC). The contribution of wind farms for the first two is well addressed in literature; however, the AGC and its associated controls require more attention. In this paper, in the first step, the contribution of wind farms in supplementary/load frequency control of AGC is overviewed. As second step, a fractional order proportional-integral-differential (FOPID) controller is proposed to control the governor speed of wind turbine to contribute to the AGC. The performance of FOPID controller is compared with classic proportional-integral-differential (PID) controller, to demonstrate the efficacy of the proposed control method in the frequency regulation of a two-area power system. Furthermore, the effect of penetration level of wind farms on the load frequency control is analyzed

Mitigating the erosion of transient stability margins in Great Britain through novel wind farm control techniques

The predominant North-to-South active power flow across the border between Scotland and England has historically been limited by system stability considerations. As the penetration of variable-speed wind power plants in Great Britain grows (reducing the generation share of traditional synchronous generation), it is imperative that stability limits, operational flexibility, efficiency and system security are not unduly eroded as a result. The studies reported in this thesis illustrate the impacts on critical fault clearing times and active power transfer limits through this North-South corridor, known as the B6 boundary, in the presence of increasing penetrations of wind power generation on the GB transmission system. By focussing on the transient behaviour of a representative reduced test system following a three-phase short-circuit fault occurring on one of the two double-circuits constituting the B6 boundary, the impacts on the transient stability margins are qualitatively identified. There is a pressing necessity for new wind farms to be able to mitigate, as much as possible, their own negative impacts on system stability margins. The transient stability improvement achieved by tailoring the low voltage ride-through reactive power control response of wind farms is first investigated, and a novel control technique is then presented which can significantly mitigate the erosion of the transient stability performance of power systems, in the presence of in-creasing amounts of wind power, by tailoring the immediate post-fault active power recovery ramp-rates of the wind power plants around the system. The impacts of these control techniques on critical fault clearing times and power transfer limits are investigated. In particular, it has been found that the use of slower active power recovery from wind farms located in exporting regions when a short circuit fault occurs on the export corridor will provide significant benefits for both of these metrics, while a faster active power recovery in importing regions will provide a similar transient stability benefit. However, it is also shown that there are potential detrimental effects for system frequency stability. In addition, important impacts of wind farm settings in respect of low voltage ride through are revealed whereby the LVRT controls can act to erode stability margins if careful consideration of their settings is not taken. Assuming a future power system with high levels of centralised observability and controllability (or decentralised co-operative control systems), it may be possible to continually “dispatch” the reactive power gains and active power recovery ramp rates discussed in this thesis to match the current system setpoint and to seek an optimal transient response to a range of credible contingencies.The predominant North-to-South active power flow across the border between Scotland and England has historically been limited by system stability considerations. As the penetration of variable-speed wind power plants in Great Britain grows (reducing the generation share of traditional synchronous generation), it is imperative that stability limits, operational flexibility, efficiency and system security are not unduly eroded as a result. The studies reported in this thesis illustrate the impacts on critical fault clearing times and active power transfer limits through this North-South corridor, known as the B6 boundary, in the presence of increasing penetrations of wind power generation on the GB transmission system. By focussing on the transient behaviour of a representative reduced test system following a three-phase short-circuit fault occurring on one of the two double-circuits constituting the B6 boundary, the impacts on the transient stability margins are qualitatively identified. There is a pressing necessity for new wind farms to be able to mitigate, as much as possible, their own negative impacts on system stability margins. The transient stability improvement achieved by tailoring the low voltage ride-through reactive power control response of wind farms is first investigated, and a novel control technique is then presented which can significantly mitigate the erosion of the transient stability performance of power systems, in the presence of in-creasing amounts of wind power, by tailoring the immediate post-fault active power recovery ramp-rates of the wind power plants around the system. The impacts of these control techniques on critical fault clearing times and power transfer limits are investigated. In particular, it has been found that the use of slower active power recovery from wind farms located in exporting regions when a short circuit fault occurs on the export corridor will provide significant benefits for both of these metrics, while a faster active power recovery in importing regions will provide a similar transient stability benefit. However, it is also shown that there are potential detrimental effects for system frequency stability. In addition, important impacts of wind farm settings in respect of low voltage ride through are revealed whereby the LVRT controls can act to erode stability margins if careful consideration of their settings is not taken. Assuming a future power system with high levels of centralised observability and controllability (or decentralised co-operative control systems), it may be possible to continually “dispatch” the reactive power gains and active power recovery ramp rates discussed in this thesis to match the current system setpoint and to seek an optimal transient response to a range of credible contingencies