Electromechanics of an Ocean Current Turbine

The development of a numeric simulation for predicting the performance of an Ocean Current Energy Conversion System is presented in this thesis along with a control system development using a PID controller for the achievement of specified rotational velocity set-points. In the beginning, this numeric model is implemented in MATLAB/Simulink® and it is used to predict the performance of a three phase squirrel single-cage type induction motor/generator in two different cases. The first case is a small 3 meter rotor diameter, 20 kW ocean current turbine with fixed pitch blades, and the second case a 20 meter, 720 kW ocean current turbine with variable pitch blades. Furthermore, the second case is also used for the development of a Voltage Source Variable Frequency Drive for the induction motor/generator. Comparison among the Variable Frequency Drive and a simplified model is applied. Finally, the simulation is also used to estimate the average electric power generation from the 720 kW Ocean Current Energy Conversion System which consists of an induction generator and an ocean current turbine connected with a shaft which modeled as a mechanical vibration system

Electromechanics of an Ocean Current Turbine

The development of a numeric simulation for predicting the performance of an Ocean Current Energy Conversion System is presented in this thesis along with a control system development using a PID controller for the achievement of specified rotational velocity set-points. In the beginning, this numeric model is implemented in MATLAB/Simulink® and it is used to predict the performance of a three phase squirrel single-cage type induction motor/generator in two different cases. The first case is a small 3 meter rotor diameter, 20 kW ocean current turbine with fixed pitch blades, and the second case a 20 meter, 720 kW ocean current turbine with variable pitch blades. Furthermore, the second case is also used for the development of a Voltage Source Variable Frequency Drive for the induction motor/generator. Comparison among the Variable Frequency Drive and a simplified model is applied. Finally, the simulation is also used to estimate the average electric power generation from the 720 kW Ocean Current Energy Conversion System which consists of an induction generator and an ocean current turbine connected with a shaft which modeled as a mechanical vibration system

Analysis, design optimisation and experimental performance of synchronous reluctance and permanent magnet assisted synchronous reluctance machines

The research studies, in detail, the synchronous reluctance machine (SynRM) and permanent magnet assisted synchronous reluctance machine (PMSynRM) to improve the machine performances. In this study, the SynRM analytical models are revisited, and functional characteristics are mathematically developed to improve the machine performance. The performance parameters such as torque density, power factor, and efficiency are investigated along with torque ripples. SynRM is known for its high torque density in a compact size. Its improvement is analytically studied further by optimising rotor properties. The power factor of these machines is rather low compared with its equivalent AC machines. Although the machine’s power factor can be improved using control techniques, it is still not high enough. The machine has gone through significant development over the years since J.K Kostko published the first paper on reluctance machines back in 1923. The researchers have tested various types of anisotropies, such as axially laminated and transversally laminated. The machine torque and power factor depend on its saliency ratio. Although the axially laminated structure offers high saliency ratio due to the naturally distributed flux barrier structure, it has mechanical constraints. The axial rotor segments are fixed together by specially designed bolts that are conductive material in nature. This mechanical arrangement increases quadrature axis inductance, consequently reduces the saliency ratio of the machine. On the other hand, the transversally laminated structure is more mechanically feasible and offers comparatively high performance. One of the primary focus of this study is to improve the power factor. It has been comprehensively investigated. The SynRM machine is also known for high torque ripples. The non-linear structure and its reluctance path along the air-gap make the machine highly susceptible to torque pulsation. The cross induction due to the D and Q axis along the air-gap increases the machine’s ripples. Besides, poor stator winding (both sinusoidal and step excitation) also increases the machine torque ripples. The existing ripple reduction practices are revisited in this study to further understand the torque ripples of this machine. The rotor of SynRM is redesigned and optimised to reduce the ripples effect. The causes of ripples are also analytically studied in detail, and mathematical models are developed and presented for understanding the phenomena. Two different ways of analysing the ripple effects are considered, and the pros and cons of both methods are discussed. The SynRM is simulated using an advanced finite element analysis (FEM) software to verify the analytical models as well as optimise the machine performance. Firstly, primitive rotor structures are developed so that they can be automatically varied during parameterisation and optimisation. Four flux barrier shapes are analysed to determine the optimum shape for high performance by investigating flux’s natural path. From the results, a multi-barrier arrangement is studied with an advanced algorithm for three and four-layer designs, and an optimum rotor is proposed based on the simulations. Using a single-objective and multi-objective optimisation techniques, the SynRM is optimised from the simulated design. An advanced topology is developed for automated optimisation that can offer flexibility in varying optimisation variables as part of this research. The optimised design’s performance is analysed in detail and compared with analytical models. The torque ripples are discussed in detail, and an advanced torque ripple minimisation topology is developed. Then the design is optimised for two types of barrier shapes. A number of designs are prototyped for experimental verification. Finally, the current trend in rare-earth magnets is investigated with its cost per volume ratio. The rare-earth neodymium magnets are focused on this study for improved performance with optimum volume. The analytical model of PM assisted design is studied in detail, and its performance parameters are compared with SynRM. A PMSynRM with a linear-barrier is simulated for a detailed analysis of the machine that discusses different PM volumes and the impact on machine performance due to the volume of PM and location. The performance parameters, discussed in the analytical model, are compared with the simulation results. The improvement in power factor and torque density is investigated using various designs. The optimisation is performed in two ways. The first one is adding PMs to the optimised SynRM. Single-objective and multi-objective optimisation are performed using an advanced optimisation algorithm. Secondly, the topology of SynRM is modified for PMSynRM in such a way the entire machine can be automated during optimisation by adding the PM’s variables to the existing one. The performances of the two optimised designs have been compared. PMSynRM prototypes are developed to verify the simulation results. The eight SynRM designs are prototyped to report the practical results. Six of them are to verify various performance parameters of SynRM and two of them to test the ripples effect. Moreover, two PMSynRM prototypes are fabricated to verify the simulation results. The saliency of each SynRM is measured and compared with simulated results. Then, each design is tested experimentally in all possible scenarios and compared. Extensive testing is performed on all prototypes under various operating conditions and reported

Sensorless position control of induction machines using high frequency signal injection

The aim of this research project was to develop a position controlled induction machine vector drive operating without a speed or position sensor but having a dynamic performance comparable to that of a sensored position vector drive. The methodology relies on the detection of a rotor saliency in the machine by persistent high-frequency voltage injection. The rotor position is then estimated from the resulting stator current harmonics that are modulated by the spatial rotor saliency. This can be a built-in rotor saliency (a designed asymmetry) or the natural saliency due to rotor slotting. This project investigates the demodulation of the extracted high-frequency current spectrum and different topologies for the estimation of rotor position. The tracking of rotor position through rotor saliencies helps to overcome the limitations of model-based approaches that are restricted to speeds above 30rpm on a 4-pole machine and are sensitive to parameter mismatches. The project addresses the difficult problem of separating the modulation effects due to the rotor saliency from distorting modulations due to the saturation saliency and inverter effects. In previous research it had been found that the saturation saliency causes a deterioration of the position estimate that can result in a loss of position and eventually causes the drive to fail. The application of filters to remove the interfering saturation harmonics is not possible. In this research a new approach was developed that compensates online for the saturation effect using pre-commissioned information about the machine. This harmonic compensation scheme was utilized for a 30kW, 4-pole induction machine with asymmetric rotor and enabled the operation from zero to full load and from standstill up to about ±150rpm (±5Hz). The steady-state performance and accuracy of the resulting sensorless drive has been found to operate similarly to a sensored drive fitted with a medium resolution encoder of 600ppr. The project involved studies of the inverter switching deadtime and its distorting effect on the position estimation. A second compensation strategy was therefore developed that is better suited if a large interfering modulation due to the inverter deadtime is present in the machine. The new compensation method was implemented for a second 30kW machine that utilizes the rotor slotting saliency. Good tracking results were obtained with a mean error of less than ±0.5° mechanical under steady-state. The derivation of the position signal for higher speeds introduces an additional speed-dependent error of about 4° mechanical at 170rpm. Sensorless position control was realized for operation from zero to full load for the fully fluxed machine. The performance allowed low and zero speed operation including position transients reaching a speed of 50rpm. The high-frequency modulation introduced by the fundamental currents during transient operation was examined and identified as the main factor limiting the dynamics of the sensorless drive. Two rigs were used for the research. The first rig is build around a network of Transputers, the second rig uses state-of-the-art TMS320C40 and TMS320F240 digital signal processors for the control and was designed and constructed as part of the research

Dimensionnements et comparaisons de convertisseurs électromécaniques à bas coût et à grande disponibilité pour véhicules électriques

Today, the concerns of the energy crisis and the reduction of gas emissions stimulate the research in several electric vehicle domains. As the cost of rare earth magnetic materials has increased significantly in recent years, electrical motors without permanent magnets draw more attention, such as induction motors, wound-synchronous motors, switched reluctance motors, and synchronous reluctant motors. In this thesis, induction and synchronous reluctant machines are chosen to be studied for the electric vehicle traction application since they are low costly and fed up with similar power electronics and control strategies.Nonlinear analytical models of induction and synchronous reluctant machines are established and validated. Besides, economical and mechanical models are developed as well. Based on established analytical models, the geometry and the control parameters of these studied machines are calculated to define the total energy losses during the driving cycle. A bi-objective optimization is carried out to minimize total energy losses and motor costs. At last, the optimized machines are compared from their electric, energetic and economic performances, with the help of the Pareto Fronts obtained.Aujourd'hui, l'électrification des véhicules constitue une des solutions mises en œuvre par les constructeurs automobiles dans la lutte contre les émissions de gaz polluants et pour la réduction des consommations. Comme le prix des aimants terres rares a fortement augmenté ces dernières années, les moteurs électriques sans aimants permanents sont attractifs, comme les moteurs asynchrones, synchrones à rotor bobiné, à réluctance variable (double saillance ou synchrone). Dans cette thèse, les machines asynchrones et synchrones à réluctance variable sont étudiées et comparées pour des véhicules électriques. Ces deux machines ont un coût faible et possèdent des structures de puissance et de contrôles similaires.Des modèles analytiques non linéaires de machines asynchrones et synchrones à réluctance variable sont établis et validés. En outre, leurs modèles économiques et mécaniques sont également mis en œuvre. Sur la base des modèles analytiques établis, la géométrie et les paramètres de commande des machines étudiées sont dimensionnés afin de réduire les pertes énergétiques durant des cycles de conduite. Une optimisation bi-objective est proposée afin de minimiser en même temps les pertes énergétiques et le coût du moteur. Enfin, les machines optimisées sont comparées, à l’aide de Fronts de Pareto, pour évaluer leurs performances électriques, énergétiques et économiques

Proceedings of the 8th International Conference EEMODS'2013 Energy Efficiency in Motor Driven Systems

This book contains the papers presented at the eighth international conference on Energy Efficiency in Motor Driven Systems EEMODS 2013 EEMODS 2013 was organised in Rio de Janeiro, Brasil from 28 to 30 October 2013. This major international conference, which was previously been staged in Lisbon (1996), London (1999), Treviso (2002), Heidelberg (2005), Beijing (2007), Nantes (2009) and Washington DC (2011) has been very successful in attracting an international and distinguished audience, representing a wide variety of stakeholders in policy implementation and development, manufacturing and promotion of energy-efficient motor systems, including key policy makers, equipment manufacturers, academia and end-users. Potential readers who may benefit from this book include researchers, engineers, policymakers, energy agencies, electric utilities, and all those who can influence the design, selection, application, and operation of electrical motor driven systems.JRC.F.7-Renewables and Energy Efficienc

Efferent Modulation of Spontaneous Activity in Developing Sensory Systems

Patterned spontaneous activity plays an instructive role in developing sensory systems. Before hearing onset, inner support cells release ATP and induce spontaneous firing of neighboring inner hair cells. This periphery-initiated spontaneous activity propagates throughout the auditory hierarchy via the afferent pathway, coordinating neural activity in distinct tonotopic zones in the central auditory system. Similarly, spontaneous retinal waves initiated in the retina by starburst amacrine cells (stage II) or bipolar cells (stage III) were observed throughout the visual system via the retinotopic visual afferent circuits. Deciphering the underlying mechanisms of patterned spontaneous activity is critical to elucidate its instructive role in priming the developing nervous system prior to sensory experience. On the other hand, anatomical and functional evidence suggests that centrifugal efferent systems may contribute to neural dynamics before sensory inputs. In the first half of this study, we profiled spatiotemporal and correlational features of auditory spontaneous activity over the entire pre-hearing period. We discovered that the olivocochlear efferent system controlled the coupling strength of bilateral auditory spontaneous activity and demonstrated the profound impact of such modulation on the development of auditory functions. In the second half of this work, we introduced a novel experimental technique that enabled access to in situ retinal calcium dynamics in awake animals. We demonstrated in situ recordings of spontaneous retinal waves from distinct neuronal populations in the retina. Moreover, our result indicated that retinal activity was directly modulated by locomotion. Our approach is well suited to study retinopetal projections in vivo and whether they contributed to locomotion-related modulation on retinal dynamics. Together, these findings provide new perspectives on the functional roles of efferent modulations in shaping spontaneous activity and promoting the development of auditory and visual systems