Advances in Rotating Electric Machines

It is difficult to imagine a modern society without rotating electric machines. Their use has been increasing not only in the traditional fields of application but also in more contemporary fields, including renewable energy conversion systems, electric aircraft, aerospace, electric vehicles, unmanned propulsion systems, robotics, etc. This has contributed to advances in the materials, design methodologies, modeling tools, and manufacturing processes of current electric machines, which are characterized by high compactness, low weight, high power density, high torque density, and high reliability. On the other hand, the growing use of electric machines and drives in more critical applications has pushed forward the research in the area of condition monitoring and fault tolerance, leading to the development of more reliable diagnostic techniques and more fault-tolerant machines. This book presents and disseminates the most recent advances related to the theory, design, modeling, application, control, and condition monitoring of all types of rotating electric machines

Nonlinear adaptive control for robust wide speed range operation of IPMSM drives

Various applications, including robotics, spindle drives, machine tools, etc. rely on accurate, reliable controllers to deliver the required drive performance. With recent advances in magnetic materials and semiconductor technology, machines such as the permanent magnet synchronous machine (PMSM) family of ac drives have seen a rise in popularity, owing to the high power density, efficiency and relative longevity as compared to conventional ac motors. In particular, interior permanent magnet synchronous machines (IPMSM) are characterized by all the features of the PMSM family, with the additional possibility of improved efficiency due to rotor construction, making them ideal for critical applications with high performance demands. Notably, despite the advantageous aspects of PMSM motors in general, control of this class of ac machines is complex if full performance potential is to be realized. In order to achieve optimal efficiency while permitting wide speed range operation, it is crucial to design controllers that are capable of delivering this high performance. Due to the nonlinearity of magnetic flux distribution during operation, the parameters of the PMSM may vary significantly. Thus, a high performance controller must be capable of optimizing efficiency while maintaining excellent response characteristics from set-point or loading variations. As a result of the nonlinear flux distribution caused by rotor/stator magnetic field interactions, direct control of PMSM in the stator reference frame is not possible as the level of mathematical complexity renders it infeasible. Expression of the PMSM stator variables in the rotating rotor reference frame permits the effective decoupling of machine variables into velocity and torque control components. This is roughly analogous to separately excited direct current (DC) motors, where control of the rotor speed (field magnetization) and shaft torque (armature current) are decoupled as a function of the design. Analysis of the PMSM model in the rotating reference frame shows that the “d” and “q” axis currents are principally responsible for indirect air gap flux control and developed shaft torque, respectively. Traditional linear type control techniques based on proportional-integral-derivative (PID) controllers are able to achieve moderate success in controlling the PMSM family. The performance achieved is however typically within a narrow operational band and without the ability to adapt to parametric variation or optimize efficiency. This restriction makes PID type controllers non-ideal for more demanding applications that require highly accurate control and high efficiency regardless of load, temperature, machine age or operating environment. Therefore, this thesis presents a robust nonlinear control algorithm utilizing an adaptive back-stepping technique with flux control for optimizing developed torque and improved operational range. Further, global asymptotic stability of the proposed controller is assured through Lyapunov’s stability criterion in conjuncture with criterion supported by Barbalat’s lemma. The proposed control algorithm ensures that the machine operates at precise command speeds, coping with system uncertainties and disturbances, while reducing losses and enabling operation over a wide speed range. Simulation of the proposed system is carried out in MATLAB/Simulink, as well as in a cosimulation environment utilizing MATLAB/Simulink and PSIM. The first scenario implements an ideal mathematical system model with the controller in Simulink; whereas the second scenario uses PSIM to host the dynamic system model, with MATLAB/Simulink hosting the controller. This co-simulation permits rapid, accurate system analysis, by employing more accurate software models for switching elements, synchronous machine and any reactive elements not reflected in the basic mathematical model. Simulation results from both methods indicate excellent performance and robust operation, with excellent disturbance rejection. Real-time implementation of the system is realized utilizing the DS1104 digital signal processor (DSP) in conjuncture with an IPMSM commutated by a three-phase two-level insulated gate bipolar transistor (IGBT) inverter, with a direct current (DC) generator as dynamic load. Performance of the proposed controller have been verified through experimental implementation for a range of operating conditions

Efficiency Optimization and Control of Permanent Magnet Synchronous Brushless Motors in Three-Phase Pulse Width Modulated Voltage Source Inverter Drives

In high performance drives where it is desirable to exploit the usefulness of reluctance torque and machine saliency, permanent magnet synchronous brushless motors are machines of choice. However, speed control of these machines especially in the flux weakening region becomes more complex due to the non-linear coupling among the winding currents as well as the nonlinearity present in the torque. While numerous research efforts in the past have considered control and efficiency improvements of induction motors, and synchronous motors with field windings, research efforts in developing an efficiency optimization and control strategy applicable to all salient-type permanent magnet synchronous brushless motors are still in their infancy.;A traditional control technique that has commonly been employed in efficiency improvement efforts is the stator\u27s zero d-axis current (i ds=0) technique. In this method, the rotor flux is aligned with the direct-axis so that the stator\u27s direct-axis current is zero and the torque becomes a linear function of the stator\u27s quadrature-axis current. Although this method achieves decoupling of winding currents and simplicity of control, it does not fully exploit the use of the machine\u27s saliency and reluctance torque, and is also not well-suited for wide-range load operations. The maximum torque per ampere (MTPA) technique is another less complex technique that has been considered which fully exploits the use of machine saliency with motor torque selected along the geometric curve of minimum-amplitude current space vectors for minimum loss operation. The drawback of the MTPA technique is that it does not provide high efficiency performance for synchronous reluctance motors running at low fractional loads.;In this work, the problem of efficiency optimization in the salient-type permanent magnet synchronous brushless motors is investigated. A machine model which includes the effect of core losses is proposed for developing a loss minimization algorithm that dynamically determines the optimal reference currents and voltages required for minimizing the total electrical losses (copper losses and core losses) within the feasible operating regions imposed by the motor and inverter capacities. The loss minimization strategy is implemented within a speed control loop for a synchronous reluctance motor drive and the effectiveness of the proposed scheme is validated by comparing performances with that of the traditional maximum torque per ampere and stator\u27s zero d-axis current vector control methods. It is shown that the proposed scheme offers the advantages of simplicity and superior performance throughout the entire operating range, and also improves motor efficiency to 96% at full load and full-speed operating condition

Comparative Study of Sensorless Control Methods of PMSM Drives

Recently, permanent magnet synchronous motors (PMSMs) are increasingly used in high performance variable speed drives of many industrial applications. This is because the PMSM has many features, like high efficiency, compactness, high torque to inertia ratio, rapid dynamic response, simple modeling and control, and maintenance-free operation. In most applications, the presence of such a position sensor presents several disadvantages, such as reduced reliability, susceptibility to noise, additional cost and weight and increased complexity of the drive system. For these reasons, the development of alternative indirect methods for speed and position control becomes an important research topic. Many advantages of sensorless control such as reduced hardware complexity, low cost, reduced size, cable elimination, increased noise immunity, increased reliability and decreased maintenance. The key problem in sensorless vector control of ac drives is the accurate dynamic estimation of the stator flux vector over a wide speed range using only terminal variables (currents and voltages). The difficulty comprises state estimation at very low speeds where the fundamental excitation is low and the observer performance tends to be poor. The reasons are the observer sensitivity to model parameter variations, unmodeled nonlinearities and disturbances, limited accuracy of acquisition signals, drifts, and dc offsets. Poor speed estimation at low speed is attributed to data acquisition errors, voltage distortion due the PWM inverter and stator resistance drop which degrading the performance of sensorless drive. Moreover, the noises of system and measurements are considered other main problems. This paper presents a comprehensive study of the different methods of speed and position estimations for sensorless PMSM drives. A deep insight of the advantages and disadvantages of each method is investigated. Furthermore, the difficulties faced sensorless PMSM drives at low speeds as well as the reasons are highly demonstrated. Keywords: permanent magnet, synchronous motor, sensorless control, speed estimation, position estimation, parameter adaptation

High-frequency issues using rotating voltage injections intended for position self-sensing

The rotor position is required in many control schemes in electrical drives. Replacing position sensors by machine self-sensing estimators increases reliability and reduces cost. Solutions based on tracking magnetic anisotropies through the monitoring of the incremental inductance variations are efficient at low-speed and standstill operations. This inductance can be estimated by measuring the response to the injection of high-frequency signals. In general however, the selection of the optimal frequency is not addressed thoroughly. In this paper, we propose discrete-time operations based on a rotating voltage injection at frequencies up to one third of the sampling frequency used by the digital controller. The impact on the rotation-drive, the computational requirement, the robustness and the effect of the resistance on the position estimation are analyzed regarding the signal frequency

A Rotor Flux Linkage Estimator and Operating Envelopes of a Variable-Flux IPM Synchronous Machine

Interior permanent magnet synchronous machines (IPMSMs) with rare-earth magnets are widely used by the electric and hybrid electric vehicle industry due to their high efficiency and high torque density. The drawbacks of the IPMSMs like the fluctuating prices of the rare-earth permanent magnets (PMs), the difficulty in flux weakening, and relatively low efficiency in the high-speed region, triggered the need for alternative electrical machines for traction applications. The variable-flux type IPMSMs, also called memory motors, is a promising technology for electrified transportation applications. These machines make use of low-coercivity magnets such as AlNiCo magnets, which makes them rare-earth PM independent. Moreover, owing to the low-coercivity, the AlNiCo magnets can be demagnetized in the high-speed region. This reduces or eliminates the extra current component needed for flux weakening, which results in lower copper/iron losses and improved machine efficiency. Besides, the variable-flux IPMSMs can provide torque densities comparable to rare-earth IPMSMs in high-torque low-speed regions. Since the magnetization state of AlNiCo magnets can be varied online by a short stator current pulse, and the current needed for a particular magnetization state is machine parameter dependent, it is of a vital importance to the drive system to keep track of the magnet flux during transient and steady-state conditions. Moreover, failing in depicting the actual magnetization state of the magnets means a mismatch between the real value of the magnet flux in the machine and the estimated one in the controller, which directly affects the resultant torque and performance. In addition, the current pulse excitation method for magnetization causes non-uniform variable flux distribution in the air-gap. Therefore, an estimation algorithm of the rotor flux linkage of variable-flux IPMSMs via flux harmonics extraction has been proposed. Compared to the existing methods, this method does not need any voltage or current signal injection into the stator winding. The algorithm was experimentally evaluated for different magnetization states and showed a good performance in tracking the rotor flux linkage variations during transient and steady-state conditions The operating envelopes of the variable-flux IPMSM were found to be affected by the nonlinearity of the magnet flux with the machine direct axis current. New analytical solutions for the operating point were reached for maximum power and maximum output voltage control for the variable-flux IPMSM taking into consideration this nonlinearity. The experimental measurement performed also support the analytical results. The irreversible demagnetization of the low-coercivity magnets in the high-speed region results in extending the braking time of the variable-flux IPMSMs. A simple yet effective minimal-time braking algorithm is proposed and experimentally validated

Assessment of the Energy Consumption and Drivability Performance of an IPMSM-Driven Electric Vehicle Using Different Buried Magnet Arrangements

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)This study investigates the influence of the buried magnet arrangement on the efficiency and drivability performance provided by an on-board interior permanent magnet synchronous machine for a four-wheel-drive electric car with two single-speed on-board powertrains. The relevant motor characteristics, including flux-linkage, inductance, electromagnetic torque, iron loss, total loss, and efficiency, are analyzed for a set of six permanent magnet configurations suitable for the specific machine, which is controlled through maximum-torque-per-ampere and maximum-torque-per-voltage strategies. Moreover, the impact of each magnet arrangement is analyzed in connection with the energy consumption along four driving cycles, as well as the longitudinal acceleration and gradeability performance of the considered vehicle. The simulation results identify the most promising rotor solutions, and show that: (i) the appropriate selection of the rotor configuration is especially important for the driving cycles with substantial high-speed sections; (ii) the magnet arrangement has a major impact on the maximum motor torque below the base speed, and thus on the longitudinal acceleration and gradeability performance; and (iii) the configurations that excel in energy efficiency are among the worst in terms of drivability, and vice versa, i.e., at the vehicle level, the rotor arrangement selection is a trade-off between energy efficiency and longitudinal vehicle dynamics.Peer reviewedFinal Published versio

Sensorless SVPWM-FADTC of a new flux-modulated permanent-magnet wheel motor based on a wide-speed sliding mode observer

published_or_final_versio

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

Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine

Optimal performance of the electric machine/drive system is mandatory to improve the energy consumption and reliability. To achieve this goal, mathematical models of the electric machine/drive system are necessary. Hence, this motivated the editors to instigate the Special Issue “Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine”, aiming to collect novel publications that push the state-of-the art towards optimal performance for the electric machine/drive system. Seventeen papers have been published in this Special Issue. The published papers focus on several aspects of the electric machine/drive system with respect to the mathematical modelling. Novel optimization methods, control approaches, and comparative analysis for electric drive system based on various electric machines were discussed in the published papers