High efficiency sensorless fault tolerant control of permanent magnet assisted synchronous reluctance motor

In the last decades, the development trends of high efficiency and compact electric drives on the motor side focused on Permanent Magnet Synchronous Machines (PMSMs) equipped with magnets based on the rare-earth elements. The permanent magnet components, however, dramatically impact the overall bill of materials of motor construction. This aspect has become even more critical due to the price instability of the rare-earth elements. This is why the Permanent Magnet Assisted Synchronous Reluctance Motor (PMaSynRM) concept was brought to the spotlight as it gives comparable torque density and similar efficiencies as PMSM although at a lower price accredited for the use of magnets built with ferrite composites. Despite these advantages, PMaSynRM drive design is much more challenging because of nonlinear inductances resulting from deep cross saturation effects. It is also true for multi-phase PMSM motors that have gained a lot of attention as they proportionally split power by the increased number of phases. Furthermore, they offer fault-tolerant operation while one or more phases are down due to machine, inverter, or sensor fault. The number of phases further increases the overall complexity for modeling and control design. It is clear then that a combination of multi-phase with PMaSynRM concept brings potential benefits but confronts standard modeling methods and drive development techniques. This Thesis consists of detailed modeling, control design, and implementation of a five-phase PMaSynRM drive for normal healthy and open phase fault-tolerant applications. Special emphasis is put on motor modeling that comprises saturation and space harmonics together with axial asymmetry introduced by rotor skewing. Control strategies focused on high efficiency are developed and the position estimation based on the observer technique is derived. The proposed models are validated through Finite Element Analysis (FEA) and experimental campaign. The results show the effectiveness of the elaborated algorithms and methods that are viable for further industrialization in PMaSynRM drives with fault-tolerant capabilities.En últimas décadas, las tendencias de desarrollo de accionamientos eléctricos compactos y de alta eficiencia en el lado del motor se centraron en las maquinas síncronas de imanes permanentes (PMSM) equipadas con imanes basados en elementos de tierras raras. Sin embargo, los componentes de imán permanente impactan dramáticamente en el coste de construcción del motor. Este aspecto se ha vuelto aún más crítico debido a la inestabilidad de precios de los elementos de tierras raras. Esta es la razón por la que el concepto de motor de reluctancia síncrona asistido por imán permanente (PMaSynRM) se ha tomado en consideración, ya que ofrece una densidad de par comparable y eficiencias similares a las de PMSM, aunque a un precio más bajo acreditado para el uso de imanes construidos con compuestos de ferritas. A pesar de drive PMaSynRM resulta muy complejo debido a las inductancias no lineales que resultan de los efectos de saturación cruzada profunda. Esto también es cierto para los motores PMSM polifásicos que han ganado mucha atención en los últimos años, en los que se divide proporcionalmente la potencia por el mayor número de fases. Además, ofrecen operación tolerante a fallas mientras una o más fases están inactivas debido a fallas en la máquina, el inversor o el sensor. Sin embargo, el número de fases aumenta aún más la complejidad general del diseño de modelado y control. Está claro entonces que una combinación de multifase con el concepto PMaSynRM tiene beneficios potenciales, pero dificulta los métodos de modelado estándar y las técnicas de desarrollo del sistema de accionamiento. Esta tesis consiste en el modelado detallado, el diseño de control y la implementación de un drive PMaSynRM de cinco fases para aplicaciones normales en buen estado y tolerantes a fallas de fase abierta. Se pone especial énfasis en el modelado del motor que comprende la saturación y los armónicos espaciales junto con la asimetría axial introducida por la inclinación del rotor. Se desarrollan estrategias de control enfocadas a la alta eficiencia y se deriva la estimación de posición basada en la técnica del observador. Los modelos propuestos se validan mediante Análisis de Elementos Finitos (FEA) y resultados experimentales. Los resultados muestran la efectividad de los algoritmos y métodos elaborados, que resultan viables para la industrialización de unidades PMaSynRM con capacidades tolerantes a fallas.Postprint (published version

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

Efficiency and time-optimal control of fuel cell - compressor - electrical drive systems

The proton exchange membrane fuel cell (PEMFC) based power generation sys- tem is regarded as one of the perspective energy supply solutions for a wide variety of applications including distributed power plants and transport. The main compo- nent of the FC system is the FC stack, where the process of electrochemical energy conversion takes place. Additionally, such systems usually contain an auxiliary compression subsystem which supplies the reactant gases to the FC stack as well as maintains certain operation conditions: pressure, temperature, humidity, etc. The proper operation of the compression system signi¯cantly improves the performance characteristics of the total system. On the other hand, it consumes a portion of the electrical energy produced, thus reducing the net e±ciency of the total system. This thesis focuses on an innovative way to improve both the energy e±ciency and the response characteristics of a power generation system with a PEMFC. The approach principally consists of the control of the air compressor powered by the electrical drive. This method could be considered as an alternative to a redesign of the complete system (changing the power level, using an extra energy bu®er, etc). The modern high-speed centrifugal compressor has been regarded as one of the best candidates for the FC system. It has appropriate characteristics with respect to e±ciency, reliability, compact design, etc. However, the presence of a stability margin or so-called "surge line" limits its operation area. With the aim to overcome this constraint, a novel active surge suppression approach has been proposed for application in the system. This control method relies on the high-performance speed control of the electrical drive and accurate measurement and estimation of the thermodynamic quantities, such as air pressure and mass °ow. The choice of an induction motor drive has been justi¯ed by its commonly known advantages: low cost, simple construction, high reliability, etc. These features be- come especially important in high-speed applications. For the detailed investigation and performance prediction of the prime mover, a global electromagnetic design pro- cedure with thermal analysis of a high-speed induction motor has been performed. The obtained analytical results have been veri¯ed numerically by a high-precision Finite Elements Method. A good agreement between the analytical and FEM simu- lation results has been achieved. The mentioned active surge control in combination with the high-performance ¯eld-oriented control of the induction motor has been im- plemented and tested. The test bench comprises the centrifugal compressor with the PVC piping system, the high-speed induction motor drive, the real-time data acquisition and the control system. The experimental results proved the e®ective- ness of the active surge suppression by means of the drive torque actuation: the operation point of the compressor can be moved beyond the surge line while the process remains stable. Using the combined mathematical models of the FC stack, the centrifugal com- pressor and the ¯eld-oriented controlled induction motor drive, the static and dy- namic behavior of the total system have been simulated, allowing to clarify the interaction between the electrochemical processes in the FC stack, the thermody- namic processes in the compression system and the electromechanical performance of the drive. Various system operating regimes have been proposed and analyzed. When the FC electrical load changes frequently and fast, the constant-speed operating regime can be used. In case of a slow variation of the FC electrical load, the variable- speed operating regime is advisable, providing a high energy e±ciency at low FC load. In intermediate cases, the load-following-mass °ow operating regime with the application of the active surge control of the compressor becomes preferable. This operating regime eliminates the relatively long mechanical transient process, keep- ing the energy consumption of the balance of plant (BoP) approximately linearly proportional to the main load. The operating regime with applied linear quadratic Gaussian (LQG) time-optimal control has been proposed as an alternative to the load-following-mass °ow operating regime and the variable-speed operating regime. The transition between two steady-state operating points, where the system e±- ciency is maximum, follows the time-optimal trajectory, keeping the transient re- sponse time small. Finally, recommendations for further research have been formulated concerning the dynamic response and energy-e±ciency of a fuel cell system. Mainly, the recom- mendations concern further improvements of presented control strategies and their more comprehensive experimental veri¯cation using a complete FC system. First of all, the use of a direct induction motor drive for the compressor stabiliza- tion would signi¯cantly improve the e®ectiveness of the surge control. It would allow to control the surge of higher frequency, or to stabilize the compressor operation at larger distance from the surge line. Second, a combination of the electrical drive torque control with a valve position control would result probably in a more e®ective surge control, together with fast transients of the system operating point. Third, the application of the electrical drive for the compressor active surge control in a FC system would require new control algorithms for energy-e±ciency improvement of the induction motor, not compromising its high-performance capa- bilities

Recent Advances in Robust Control

Robust control has been a topic of active research in the last three decades culminating in H_2/H_\infty and \mu design methods followed by research on parametric robustness, initially motivated by Kharitonov's theorem, the extension to non-linear time delay systems, and other more recent methods. The two volumes of Recent Advances in Robust Control give a selective overview of recent theoretical developments and present selected application examples. The volumes comprise 39 contributions covering various theoretical aspects as well as different application areas. The first volume covers selected problems in the theory of robust control and its application to robotic and electromechanical systems. The second volume is dedicated to special topics in robust control and problem specific solutions. Recent Advances in Robust Control will be a valuable reference for those interested in the recent theoretical advances and for researchers working in the broad field of robotics and mechatronics

Automated Netlist Generation for 3D Electrothermal and Electromagnetic Field Problems

We present a method for the automatic generation of netlists describing general three-dimensional electrothermal and electromagnetic field problems. Using a pair of structured orthogonal grids as spatial discretisation, a one-to-one correspondence between grid objects and circuit elements is obtained by employing the finite integration technique. The resulting circuit can then be solved with any standard available circuit simulator, alleviating the need for the implementation of a custom time integrator. Additionally, the approach straightforwardly allows for field-circuit coupling simulations by appropriately stamping the circuit description of lumped devices. As the computational domain in wave propagation problems must be finite, stamps representing absorbing boundary conditions are developed as well. Representative numerical examples are used to validate the approach. The results obtained by circuit simulation on the generated netlists are compared with appropriate reference solutions.Comment: This is a pre-print of an article published in the Journal of Computational Electronics. The final authenticated version is available online at: https://dx.doi.org/10.1007/s10825-019-01368-6. All numerical results can be reproduced by the Matlab code openly available at https://github.com/tc88/ANTHE

Embedded Sensors and Controls to Improve Component Performance and Reliability Conceptual Design Report

The objective of this project is to demonstrate improved reliability and increased performance made possible by deeply embedding instrumentation and controls (I&C) in nuclear power plant (NPP) components and systems. The project is employing a highly instrumented canned rotor, magnetic bearing, fluoride salt pump as its I&C technology demonstration platform. I&C is intimately part of the basic millisecond-by-millisecond functioning of the system; treating I&C as an integral part of the system design is innovative and will allow significant improvement in capabilities and performance. As systems become more complex and greater performance is required, traditional I&C design techniques become inadequate and more advanced I&C needs to be applied. New I&C techniques enable optimal and reliable performance and tolerance of noise and uncertainties in the system rather than merely monitoring quasistable performance. Traditionally, I&C has been incorporated in NPP components after the design is nearly complete; adequate performance was obtained through over-design. By incorporating I&C at the beginning of the design phase, the control system can provide superior performance and reliability and enable designs that are otherwise impossible. This report describes the progress and status of the project and provides a conceptual design overview for the platform to demonstrate the performance and reliability improvements enabled by advanced embedded I&C

Reduced-order modeling of power electronics components and systems

This dissertation addresses the seemingly inevitable compromise between modeling fidelity and simulation speed in power electronics. Higher-order effects are considered at the component and system levels. Order-reduction techniques are applied to provide insight into accurate, computationally efficient component-level (via reduced-order physics-based model) and system-level simulations (via multiresolution simulation). Proposed high-order models, verified with hardware measurements, are, in turn, used to verify the accuracy of final reduced-order models for both small- and large-signal excitations. At the component level, dynamic high-fidelity magnetic equivalent circuits are introduced for laminated and solid magnetic cores. Automated linear and nonlinear order-reduction techniques are introduced for linear magnetic systems, saturated systems, systems with relative motion, and multiple-winding systems, to extract the desired essential system dynamics. Finite-element models of magnetic components incorporating relative motion are set forth and then reduced. At the system level, a framework for multiresolution simulation of switching converters is developed. Multiresolution simulation provides an alternative method to analyze power converters by providing an appropriate amount of detail based on the time scale and phenomenon being considered. A detailed full-order converter model is built based upon high-order component models and accurate switching transitions. Efficient order-reduction techniques are used to extract several lower-order models for the desired resolution of the simulation. This simulation framework is extended to higher-order converters, converters with nonlinear elements, and closed-loop systems. The resulting rapid-to-integrate component models and flexible simulation frameworks could form the computational core of future virtual prototyping design and analysis environments for energy processing units