Das Prinzip eines Schwungmasseenergiespeichers (kurz SMS), d. h. kinetische Energie in rotierenden Massen zu speichern, ist bekannt. In den letzten Jahren haben SMS durch ihre Eigenschaft, große Leistungen bei hohen Zyklenzahlen aufzunehmen/abzugeben, an Attraktivität gewonnen. Durch Neu- und Weiterentwicklungen auf den Gebieten der Leistungselektronik, bei der Herstellung hochfester Werkstoffe wie kohlenstofffaserverstärkte Kunststoffe (kurz CFK, von: carbonfaserverstärkter Kunststoff) für Rotor und Schwungmasse und in der Lagertechnik sind energieeffiziente und sichere SMS bis zu 150 kWh machbar. Mit einem Leistungsband von 0,5-50 MW eignet sich die SMS-Technologie zur Stabilisierung von Verbundnetzen. Dieser Beitrag gibt einen generischen Einblick in die ingenieurwissenschaftlichen Arbeiten an einer Hochgeschwindigkeitsschwungmasse. Dazu wird die strategische Herangehensweise vorgestellt. Die Herausforderungen bei der Gestaltung der hybriden Metall-CFK-Strukturen des Laufzeugs werden vertieft. / The principle of a flywheel storage system (FSS for short), i.e., to store kinetic energy in rotating masses, is well described. In recent years, FSS have become more attractive due to their ability to receive/deliver large power at high cycle rates. Due to new and further developments in the fields of power electronics, in the production of high-strength materials such as carbon fiber reinforced plastics (short CFRP) for rotor and flywheel and in bearing technology, energy-efficient and safe FSS up to 150 kWh are possible. With a power range of 0.5-50 MW, FSS technology is suitable for stabilizing interconnected power grids. This paper gives a generic insight with respect to the engineering work on a high-speed flywheel. The strategic approach is presented. The design challenges regarding the hybrid metal-CFRP structures of the rotating assembly are deepened.

<p>Quality of the castings is affected by several factors which the designer should take into consideration during the product development process. Although residual stress is one of those, it is often not considered in practical computations. Hence residual stresses are one of the forgotten areas in designing of machine parts. This master thesis is focused on the investigation of residual stresses in a high pressure die casted component, with the aim of extending its service life, by taking results from the study as a feedback.</p><p>The investigation of residual stresses was done on a variety of specimens, cast aluminum flywheel, provided by Husqvarna AB. This flywheel is a component in a product of the same company.In evaluating the residual stresses in the part, two tools-simulation and physical measurement were used. Moreover, comparison with these two methods is also done at an area of interest on the flywheel. The simulation was carried out by using MAGMAhpdc-a module for high pressure die casting process, from the commercial software package MAGMAsoft; while for the physical measurements, the hole drilling method was used, a method believed to be less accurate at low stresses areas.</p><p>The findings obtained from this study show that the results from both procedures are close, with small deviations observed, which reveals the reliability of the hole drilling method even when the stress levels are low. It is also found that the compressive residual stresses dominate in the component-a preferred phenomenon with regards to residual stress.</p>

The goal of this dissertation is to evaluate the effectiveness of model predictive control (MPC) for a magnetically suspended flywheel energy storage uninterruptible power supply (FlyUPS). The reason this research topic was selected was to determine if an advanced control technique such as MPC could perform better than a classical control approach such as decentralised Proportional-plus-Differential (PD) control. Based on a literature study of the FlyUPS system and the MPC strategies available, two MPC strategies were used to design two possible MPC controllers were designed for the FlyUPS, namely a classical MPC algorithm that incorporates optimisation techniques and the MPC algorithm used in the MATLAB® MPC toolbox™. In order to take the restrictions of the system into consideration, the model used to derive the controllers was reduced to an order of ten according to the Hankel singular value decomposition of the model. Simulation results indicated that the first controller based on a classical MPC algorithm and optimisation techniques was not verified as a viable control strategy to be implemented on the physical FlyUPS system due to difficulties obtaining the desired response. The second controller derived using the MATLAB® MPC toolbox™ was verified to be a viable control strategy for the FlyUPS by delivering good performance in simulation. The verified MPC controller was then implemented on the FlyUPS. This implementation was then analysed in order to validate that the controller operates as expected through a comparison of the simulation and implementation results. Further analysis was then done by comparing the performance of MPC with decentralised PD control in order to determine the advantages and limitations of using MPC on the FlyUPS. The advantages indicated by the evaluation include the simplicity of the design of the controller that follows directly from the specifications of the system and the dynamics of the system, and the good performance of the controller within the parameters of the controller design. The limitations identified during this evaluation include the high computational load that requires a relatively long execution time, and the inability of the MPC controller to adapt to unmodelled system dynamics. Based on this evaluation MPC can be seen as a viable control strategy for the FlyUPS, however more research is needed to optimise the MPC approach to yield significant advantages over other control techniques such as decentralised PD control. / Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013

Le sujet s'inscrit dans la stratégie d'augmentation de la pénétration des énergies renouvelables dans les réseaux électriques, en particulier ceux qui sont faiblement interconnectés, tels que les réseaux électriques insulaires. Une limite de pénétration des énergies intermittentes de 30% en puissance instantanée dans ces réseaux a été fixée par la loi française. Pour permettre de dépasser cette limite, une solution est de coupler les sources de production décentralisée et intermittente avec du stockage.Dans cette thèse, nous nous sommes intéressés au volant d’inertie, système de stockage permettant de convertir l’énergie électrique sous forme cinétique et vice versa. Celui-ci a en effet un nombre de cycles charge/décharge important en comparaison avec une batterie électrochimique et peut être utilisé pour lisser la production photovoltaïque. La fluctuation de l’énergie photovoltaïque est en effet faiblement prédictible au cours du temps et elle ne peut pas être contrôlée, notamment sa chute de production. La production photovoltaïque peut chuter jusqu’à 80 % de la puissance maximale en 30 secondes, et déstabiliser ainsi le réseau électrique. Le réseau électrique insulaire, tel que celui de la Corse, n’est pas interconnecté au réseau électrique continental. Les réseaux non – interconnectés sont plus fragiles et moins stables. Ainsi, le développement massif des centrales photovoltaïques peut faire fluctuer la fréquence et la tension du réseau. Le volant d’inertie a l’avantage de posséder un faible temps de réponse (quelques centaines de millisecondes). Cependant, il a une capacité énergétique moindre. Nous allons donc exploiter les avantages du volant d’inertie en le gérant en temps réel avec un calculateur approprié. Un volant d’inertie d’une puissance de 15 kVA et d’une capacité énergétique de 112 Wh a été caractérisé et testé à l’INES Chambéry en utilisant un simulateur réseau temps réel (RTLab®), un calculateur temps réel dSPACE® et une centrale PV. Le système de stockage est composé d’une machine électrique asynchrone et d’un volant d’inertie cylindrique en acier. Le logiciel Matlab/Simulink® est utilisé pour implémenter les lois de commande nécessaires à son pilotage. Dans cette thèse, le banc de test est présenté ainsi que les résultats sur les services système (lissage de puissance, régulation de la fréquence et de la tension). Trois méthodes de lissage de puissance sont présentées et évaluées (lissage avec une fonction de transfert, lissage avec limiteur de pente et lissage n’utilisant pas aucune fonction de lissage). La troisième méthode n’utilisant ni une fonction de transfert, ni une fonction limitant la pente des variations, nécessite moins de paramètres et s’avère plus optimale et plus robuste. Un volant d’inertie avec une autre technologie de machine électrique (la machine à réluctance variable) a été également caractérisé. C’est une Alimentation Sans Interruption (ASI), sur laquelle des paramètres tels que l’autodécharge et les rendements du système (en charge, en décharge et au repos) ont pu être mesurés. / The subject is part of the strategy to increase the penetration of renewable energy in power systems, particularly those that are poorly interconnected, such as island grids. A limit of penetration of intermittent energy by 30% in instantaneous power in these electrical grids was set by a French law. To help overcome this limitation, a solution is to couple the sources of decentralized and intermittent generation with energy storage systems. In this thesis, we are interested in flywheel energy storage systems (FESS) that converts electrical energy in kinetic energy form and vice versa. FESS have a number of cycles charge / discharge large compared with electrochemical batteries and can be used to smooth the photovoltaic power generation. The fluctuation of photovoltaic instantaneous power is indeed weakly predictable over time and it cannot be controlled, including its production fall. PV production can decrease up to 80% of its maximum power in 30 seconds, and so destabilize the grid. The island grids, such as that of Corsica, are not interconnected to the mainland power grid. The non - interconnected grids are more fragile and less stable. Thus, the massive development of photovoltaic power plants can cause fluctuations in the frequency and voltage. The flywheel has the advantage of having a low response time (a few hundred milliseconds). However, it has a lower energy capacity. The benefits of FESS are used by managing it in real time with an appropriate computer. A flywheel with a power of 15 kVA and an energy capacity of 112 Wh was characterized and tested at INES Chambery using a real time grid simulator (RTLab®), a real-time computer (dSPACE®) and a PV power plant. The storage system is composed by an asynchronous electrical machine and a cylindrical steel flywheel. The Matlab Simulink / software is used to implement the control laws necessary for its control. In this thesis, the test bench is presented and the results of ancillary services (power smoothing, frequency and voltage regulation). Three power smoothing methods are discussed and evaluated (smoothing with a transfer function, with a slope limiter function and a method not using any smoothing function). The third method uses neither a transfer function, nor a function that limits the slope variations, requires fewer parameters, and is more optimal and more robust. A flywheel with another electrical machine technology (the switched reluctance machine) has also been characterized. This is an Uninterruptible Power Supply (UPS) on which parameters such as self-discharge and efficiencies (charging mode, discharging mode and standby mode) were measured.

For many decades there has been a need in many industries to measure speed and position of ferrous gears. This is commonly done by converting passing gear teeth from trigger wheels to electrical impulses to calculate speed and angular position. By using Hall effect sensors or Giant Magnetoresistance sensors (GMR), a zero speed detection of gear teeth is possible while at the same time be cheap to produce and durable for harsh environments. A specially designed trigger-wheel (cogwheel created for measurements) with gear teeth in a specific pattern, exact position can be detected by using a dual sensor, even when no earlier information is available. The new design of trigger-wheel also makes this new method more accurate and universal compared to previous solutions. This thesis demonstrates and argues for the advantages of using a dual sensor for speed and angular position detection on gear wheels. Were one sensor do quantitative measurements for pattern detection in the teeth arrangements and the other sensor do qualitative measurements for position detection.

This study develops a method to simulate a full-scale inertia friction weld with a sub-scale specimen and modifies a direct drive friction stir welder to perform the welding process. A torque meter is fabricated for the FSW machine to measure weld torque. Machine controls are modified to enable a force control during the IFW process. An equation is created to measure weld upset due to deflection of the FSW machine. Data obtained from a full-scale inertia friction weld are altered to account for the geometrical differences between the sub-scale and full-scale specimens. The IFW are simulated with the sub-scale specimen while controlling spindle RPM and matching weld power or weld RPM. The force used to perform friction welding is scaled to different values accounting for specimen size to determine the effects on output parameters including: HAZ, upset, RPM, torque, power and energy of the weld. Increasing force has positive effects to upset, torque, power and energy of the welds, while reducing the size of the HAZ.

Quality of the castings is affected by several factors which the designer should take into consideration during the product development process. Although residual stress is one of those, it is often not considered in practical computations. Hence residual stresses are one of the forgotten areas in designing of machine parts. This master thesis is focused on the investigation of residual stresses in a high pressure die casted component, with the aim of extending its service life, by taking results from the study as a feedback. The investigation of residual stresses was done on a variety of specimens, cast aluminum flywheel, provided by Husqvarna AB. This flywheel is a component in a product of the same company.In evaluating the residual stresses in the part, two tools-simulation and physical measurement were used. Moreover, comparison with these two methods is also done at an area of interest on the flywheel. The simulation was carried out by using MAGMAhpdc-a module for high pressure die casting process, from the commercial software package MAGMAsoft; while for the physical measurements, the hole drilling method was used, a method believed to be less accurate at low stresses areas. The findings obtained from this study show that the results from both procedures are close, with small deviations observed, which reveals the reliability of the hole drilling method even when the stress levels are low. It is also found that the compressive residual stresses dominate in the component-a preferred phenomenon with regards to residual stress.

This thesis is a part of a larger project that focuses on the development of a highspeed, high energy flywheel using both high-tech composites and levitating magneticbearings alongside a custom made, permanent magnetized generator built into theflywheel itself. The goal of the project is then to integrate this flywheel into anelectrical vehicle.The main focus of this thesis is the composite material. The composite is to be usedas a shell around the flywheel rotor. This composite shell fills two purposes. The firstis to act as the main energy carrying material, storing above 75% of the total energy inthe flywheel. The second purpose it to strengthen the machine, holding it together.This so that higher speeds than normally possible can be achieved, with the goal beingset to 30 000rpm.In order to be able to design the composite shell correctly a method of calculating theload stresses had to be developed. This was done by the creation of a Matlabprogram, named Spin2Win, capable of calculating the stresses inside a compositemetal hybrid flywheel. Using said Matlab code, combined with modelling andsimulations from SolidWorks, a fully-fledged flywheel was designed complete withdrawings and material specifications.The composite analysis surprisingly shows that the best combination of compositematerials is a mixture of both high strength carbon fibres alongside softer glass fibrescoupled with the weight of the central core. This allowed for control of the radialstresses which was shown to otherwise be the limiting factor when designing rotatingcomposite materials.One of the most interesting, and perhaps even unique, parts of the design is that theelectrical machine has been integrated into the flywheel’s composite shell. Having thetwo entities working together in order to control the radial stresses in thecomposite, by utilizing the weight of the permanent magnets.

Control Designs for Low-Loss Active Magnetic Bearings: Theory and Implementation Brian C. D. Wilson 327 Pages Directed by Dr. Panagiotis Tsiotras and Dr. Bonnie Heck-Ferri Active Magnetic Bearings (AMB) have been proposed for use in Electromechanical Flywheel Batteries. In these devices, kinetic energy is stored in a magnetically levitated flywheel which spins in a vacuum. The AMB eliminates all mechanical losses, however, electrical loss, hich is proportional to the square of the magnetic flux, is still significant. For fficient operation, the flux bias, which is typically introduced into the electromagnets to improve the AMB stiffness, must be reduced, preferably to zero. This zero-bias (ZB) mode of operation cripples the classical control techniques which are customarily used and nonlinear control is required. As a compromise between AMB stiffness and efficiency, a new flux bias scheme is proposed called the generalized complementary flux condition(gcfc). A flux-bias dependent trade-off exists between AMB stiffness, power consumption, and power loss. This work theoretically develops and experimentally verifies new low-loss AMB control designs which employ the gcfc condition. Particular attention is paid to the removal of the singularity present in the standard nonlinear control techniques when operating in ZB. Experimental verification is conduced on a 6-DOF AMB reaction wheel. Practical aspects of the gcfc implementation such as flux measurement and flux-bias implementation with voltage mode amplifiers using IR compensation are investigated. Comparisons are made between the gcfc bias technique and the standard constant-flux-sum (cfs) bias method. Under typical operating circumstances, theoretical analysis and experimental data show that the new gcfc bias scheme is more efficient in producing the control flux required for rotor stabilization than the ordinary cfs bias strategy.

This bachelor thesis investigates what kind of battery system that is suitable for an electric driveline equipped with a mechanical fly wheel, focusing on a battery with high specific energy capacity. Basic battery theory such as the principle of an electrochemical cell, limitations and C-rate is explained as well as the different major battery systems that are available. Primary and secondary cells are discussed, including the major secondary chemistries such as lead acid, nickel cadmium (NiCd), nickel metal hydride (NiMH) and lithium ion (Li-ion). The different types of Li-ion chemistries are investigated, explained and compared against each other as well as other battery technologies. The need for more complex protection circuitry for Li-ion batteries is included in the comparison. Request for quotations are made to battery system manufacturers and evaluated. The result of the research is that the Li-ion NMC energy cell is the best alternative, even if the cost per cell is the most expensive compared to other major technologies. Due to the budget, the LiFeMnPO4 chemistry is used in the realisation of the final system, which is scaled down with consideration to the power requirement.