Fault-Tolerant Control of a Flux-switching Permanent Magnet Synchronous Machine

Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.It has become clear that the most successful design approach involves a multiple phase drive in which each phase may be regarded as a single-module. The operation of any one module must have minimal impact upon the others, so that in the event of that module failing the others can continue to operate unaffected. The modular approach requires that there should be minimal electrical, magnetic and thermal interaction between phases of the drive. Flux-Switching permanent magnet synchronous machines (FS-PMSM) have recently emerged as an attractive machine type virtue of their high torque densities, simple and robust rotor structure and the fact that permanent magnets and coils are both located on the stator. Flux-switching permanent magnet (FS-PMSM) synchronous machines are a relatively new topology of stator PM brushless machine. They exhibit attractive merits including the large torque capability and high torque (power) density, essentially sinusoidal back-EMF waveforms, as well as having a compact and robust structure due to both the location of magnets and armature windings in the stator instead of the rotor as those in the conventional rotor-PM machines. The comparative results between a FS-PMSM and a traditional surface-mounted PM (SPM) motor having the same specifications reveal that FS-PMSM exhibits larger air-gap flux density, higher torque per copper loss, but also a higher torque ripple due to cogging -torque. However, for solely permanent magnets excited machines, it is a traditional contradiction between the requests of high torque capability under the base-speed (constant torque region) and wide speed operation above the base speed (constant power region) especially for hybrid vehicle applications. A novel fault-tolerant FS-PMSM drive topology is presented, which is able to operate during open- and short-circuit winding and converter faults. The scheme is based on a dual winding motor supplied from two separate vector-controlled voltage-sourced inverter drives. The windings are arranged in a way so as to form two independent and isolated sets. Simulation and experimental work will detail the driver’s performance during both healthy- and faulty- scenarios including short-circuit faults and will show the drive robustness to operate in these conditions. The work has been published in ten conference papers, two journal papers and a book chapter, presenting both the topology of the drive and the applied control schemes, as well as analysing the fault-tolerant capabilities of the drive.

Direct Flux Field Oriented Control of IPM Drives with Variable DC-Link in the Field-Weakening Region

This paper presents the direct flux control of an interior permanent-magnet (IPM) motor drive in the field-weakening region. The output torque is regulated by the coordinated control of the stator flux amplitude and the current component in quadrature with the flux, and it is implemented in the stator flux reference frame. The control system guarantees maximum torque production taking into account voltage and current limits, in particular in case of large dc-link variations. The field-oriented control does not necessarily require an accurate magnetic model of the IPM motor, and it is able to exploit the full inverter voltage at different dc-link levels with no additional voltage control loop. The feasibility of the proposed control method is investigated in discrete-time simulation, then tested on a laboratory rig, and finally implemented on board of an electric scooter prototype. The motor under test is an IPM permanent-magnet-assisted synchronous reluctance machine, with high-saliency and limited permanent-magnet flu

High performance disturbance observer based control system design for permanent magnet synchronous AC machine applications

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonAn electrical machine is one of the main workforces in different industries and serves them in various applications. Machine drive control design involves many technical issues for efficient and robust exploitation. Over several decades, Permanent Magnet Synchronous Motor (PMSM) is getting preferred for industrial applications over its counterpart Squirrel Cage Induction Motor (SCIM) drive, because of their higher efficiency, power density, and higher torque to inertia ratio. In the prospective that PMSM drives are considered the drives of the future, there are still technical challenges and issues related to PMSM control. Many studies have been devoted to PMSM control in the past, but there are still some open research areas that bring worldwide researchers’ interests back to PMSM drive control. One of the approaches that may facilitate better performance, higher efficiency, and robust and reliable work of the control system is the disturbance observer-based control (DOBC) with linear and nonlinear output feedback control for PM synchronous machine applications. DOBC is adopted due to its ability to reject external and internal disturbances with improving tracking performance in the variable speed wind energy conversion system (WECS) to maximize power extraction. The high order disturbance observer (HODO) is utilized to estimate the aerodynamic torque-based wind speed without the use of a traditional anemometer, which reduces the overall cost and improves the reliability of the whole system. Also, this method has been designed to improve the angular shaft speed tracking of the PMSM system under load torque disturbance and speed variations. The model-based linear and nonlinear feedback control are used in the proposed control systems. The sliding mode control (SMC) with switching output feedback control law and integral SMC with linear feedback and state-dependent Riccati equation (SDRE) based approaches have been designed for the systems. The SDRE control accounts for the nonlinear multivariable structure of the WECS and is approximated with Taylor series expansion terms. The chattering inherited from SMC is eliminated by the continuous approximation technique. The sliding mode is guaranteed by eliminating the reaching mode in the proposed integral SMC. The model-free cascaded linear feedback control system based on the proportional-integral (PI) controllers use a back-calculation algorithm anti-windup scheme. The proposed speed controllers are synthesized with HODO to compensate for the external disturbance, model uncertainty, noise, and modelling errors. Moreover, servomechanism-based SDRE control, a near-optimal control system is designed to suppress the model uncertainty and noise without the use of disturbance observers. The proposed control systems for PMSM speed regulation have demonstrated a significant improvement in the angular shaft speed-tracking performance at the transients. Their performances have been tested under speed, load torque variations, and model uncertainty. For example, HODO-based SMC with switching output feedback control law (SOFCL) has demonstrated improvement by more than 78% than the PI-PI control system of the PMSM. The performance of the HODOs-based Integral SMC with SDRE nonlinear feedback is improved by 80.5% under external disturbance, model uncertainty, and noise than Integral SMC with linear feedback in the WECS. The HODO-based SDRE control with servomechanism has shown an 80.2% improvement of mean absolute percentage error under disturbances than Integral SMC with linear feedback in the WECS. The PMSM speed tracking performance of the proposed HODO-based discrete-time PI-PI control system with back-calculation algorithm anti-windup scheme is improved by 87.29% and 90.2% in the speed commands and load torque disturbance variations scenarios respectively. The simulations for testing the proposed control system of the PMSM system and WECS have been implemented in Matlab/Simulink environment. The PMSM speed control experimental results have been obtained with Lucas-Nuelle DSP-based rapid control prototyping kit.Center for International Program “Bolashak” of the Ministry of Education and Science Republic of Kazakhsta

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

Constrained field-oriented control of permanent magnet synchronous machine with field-weakening utilizing a reference governor

This paper presents a complete solution for constrained control of a permanent magnet synchronous machine. It utilizes field-oriented control with proportional-integral current controllers tuned to obtain a fast transient response and zero steady-state error. To ensure constraint satisfaction in the steady state, a novel field-weakening algorithm which is robust to flux linkage uncertainty is introduced. Field weakening problem is formulated as an optimization problem which is solved online using projected fast gradient method. To ensure constraint satisfaction during current transients, an additional device called current reference governor is added to the existing control loops. The constraint satisfaction is achieved by altering the reference signal. The reference governor is formulated as a simple optimization problem whose objective is to minimize the difference between the true reference and a modified one. The proposed method is implemented on Texas instruments F28343 200 MHz microcontroller and experimentally verified on a surface mounted permanent magnet synchronous machine

Sensorless Passive Control Algorithms for Medium to High Power Synchronous Motor Drives

This study is focused on the definition of sensorless algorithms for Surface-Mounted Permanent Magnet Synchronous Motors (SM-PMSM) and Electrically Excited Synchronous Motors (EESM). Even if these types of motors are rather different from a constructive point of view, they have some common issues regarding sensorless drives. Indeed, SM-PMSMs, which are usually used for low-medium power applications, have a low rotor anisotropy, therefore it is complicated to use sensorless active methods (which are based on high-frequency voltage injection), due to the low signal to noise ratio. On the other hand, active methods on high-power EESM have the drawback of high torque ripple. For these reasons, both for SM-PMSM and EESM, it is interesting to define and use sensorless passive algorithms (i.e., based on observers and estimators). The drawback of such algorithms is that their performance deteriorates significantly in the low-speed region. The aim of this thesis is to define a robust sensorless passive algorithm that could work in a wide speed region and that could start the motor from standstill even with a high load torque. The initial objective of the work is to find, among the various algorithms proposed in the technical literature, the most promising one. For this purpose, four different algorithms are selected. They are chosen considering the most recent articles presented in the technical literature on high reputable journals. Since many improvements are proposed in the literature for the different algorithms, the most recent ones are candidates for being the ones with higher performance. Even if the experimental tests of the four different algorithms are shown in the literature, it is difficult to evaluate a priori which offers the best performance. As a matter of facts, for each algorithm different tests are carried out (e.g., different speed and torque profiles). In addition to that, motor sizing and features are different. Moreover, the test bench characteristics can significantly affect sensorless performance. As an example, inverter features and non-linearities (e.g., switching frequency, dead times, parasitic capacitance) and current measures (e.g., noise, linearity, bias) play a key role in the estimation of rotor position. The added value of this thesis is to perform a fair comparison of the four algorithms, performing the same tests with the same test bench. Additional tests are performed on the most performing algorithm. Even if this sensorless technique is already proposed in the technical literature, a methodology for observer gain tuning is not shown, which is proposed, instead, in this thesis. Moreover, the algorithm is enhanced by adding a novel management of direct axis current, which ensures the stability during fast transient from medium-high speed to low speed. The algorithm is tested with different test benches in order to verify the control effectiveness in various operating conditions. As a matter of facts, it is tested at first in the University of Genoa PETRA Lab on two different test benches. The first test bench is composed of two coupled motors, in which the braking motor could realize different torque profiles (linear torque, quadratic torque and constant torque), whereas in the second test bench the motor is coupled with an air compressor, which is a demanding load since high and irregular torque is applied at standstill. After the test at the University of Genoa, the algorithm is implemented in Phase Motion Control and Physis drive and tested on a six-meter diameter fan. Regarding the EESMs, for these type of motor is necessary to estimate the stator flux amplitude and angle. Indeed, the stator angle is usually used to perform the Park transformations in the FOC scheme and the stator flux amplitude is used to control the excitation current. In this study, the RFO is adapted for estimating the stator flux of an EESM. Regarding the control for EESM, it is tested on a simulative model for high-power motors provided by NIDEC ASI and tested on a small-scale test bench at the University of Genoa

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

Design and Control of Electrical Motor Drives

Dear Colleagues, I am very happy to have this Special Issue of the journal Energies on the topic of Design and Control of Electrical Motor Drives published. Electrical motor drives are widely used in the industry, automation, transportation, and home appliances. Indeed, rolling mills, machine tools, high-speed trains, subway systems, elevators, electric vehicles, air conditioners, all depend on electrical motor drives.However, the production of effective and practical motors and drives requires flexibility in the regulation of current, torque, flux, acceleration, position, and speed. Without proper modeling, drive, and control, these motor drive systems cannot function effectively.To address these issues, we need to focus on the design, modeling, drive, and control of different types of motors, such as induction motors, permanent magnet synchronous motors, brushless DC motors, DC motors, synchronous reluctance motors, switched reluctance motors, flux-switching motors, linear motors, and step motors.Therefore, relevant research topics in this field of study include modeling electrical motor drives, both in transient and in steady-state, and designing control methods based on novel control strategies (e.g., PI controllers, fuzzy logic controllers, neural network controllers, predictive controllers, adaptive controllers, nonlinear controllers, etc.), with particular attention to transient responses, load disturbances, fault tolerance, and multi-motor drive techniques. This Special Issue include original contributions regarding recent developments and ideas in motor design, motor drive, and motor control. The topics include motor design, field-oriented control, torque control, reliability improvement, advanced controllers for motor drive systems, DSP-based sensorless motor drive systems, high-performance motor drive systems, high-efficiency motor drive systems, and practical applications of motor drive systems. I want to sincerely thank authors, reviewers, and staff members for their time and efforts. Prof. Dr. Tian-Hua Liu Guest Edito