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.

Multi-Phase Fault Tolerant PMSM Drive Systems

The drive to develop electric machines with a wide constant power-speed range (CPSR), high torque capabilities, excellent efficiency, superior reliability, and a reduced environmental footprint for EV traction and ship propulsion systems has led to research interest in various Permanent Magnet Synchronous Motors (PMSM). One particular area of interest is multi-phase fault tolerant PMSM drive systems, which are integral to the development of electric traction systems with all-inclusive motors that include sensors, inverter modules, and a cooling system, much like an automobile engine. Furthermore, these designs simplify fault condition maintenance because their independent single-phase structure allows them to be used with replaceable modular inverter units which have one H-bridge for each phase. In order to provide high reliability for the PMSM drive systems, even in a fault condition, simple but effective current control methods are necessary. An interior PMSM configuration with 5 independent phases is presented for electric vehicle (EV) traction and ship propulsion applications along with the proposed design procedure as well as an associated inverter design and current control methods. The proposed design process is verified using finite element analysis (FEA). An existing 5-phase 15-slot 4-pole Interior PMSM was modified to remove the neutral point, thus allowing for independent control of the 5 phases with 5 H-bridge inverters through a fabricated custom-made control board. Bipolar and unipolar switching methods were evaluated and an effective switching method was proposed to drive the motor. Closed loop speed control was implemented using Step VSI control, SPWM control, and hysteresis control methods. Finally, the 5-phase 10-lead PMSM systems were evaluated under the various control methods using simulated and experimental data after fabricating a new inverter interface board with TI floating point DSP, Delfino (F28335). The results suggest that multi-phase fault tolerant PMSM drive systems could play a key role in the future of EV traction and ship propulsion systems. An interior PMSM configuration with 5 independent phases is presented for electric vehicle (EV) traction and ship propulsion applications along with the proposed design procedure as well as an associated inverter design and current control methods. The proposed design process is verified using finite element analysis (FEA). An existing 5-phase 15-slot 4-pole Interior PMSM was modified to remove the neutral point, thus allowing for independent control of the 5 phases with 5 H-bridge inverters though a fabricated custom-made control board. Bipolar and unipolar switching methods were evaluated and an effective switching method was proposed to drive the motor. Closed loop speed control was implemented using Step VSI control, SPWM control, and hysteresis control methods. Finally, the 5-phase 10-lead PMSM systems were evaluated under the various control methods using simulated and experimental data after fabricating a new inverter interface board with TI floating point DSP, Delfino (F28335). The results suggest that multi-phase fault tolerant PMSM drive systems could play a key role in the future of EV traction and ship propulsion systems

Sensorless control of deep-sea ROVs PMSMs excited by matrix converters

The paper reports the development of model-based sensorless control methodologies for driving PMSMs using matrix converters. In particular, experimental results show that observer-based state-estimation techniques normally employed for sensorless control of PMSMs using voltage source inverters (VSIs), can be readily exported to matrix converter counterparts with minimal additional computational overhead. Furthermore, zero speed start-up and speed reversal are experimentally demonstrated. Finally, the observer is designed to be fault tolerant such that upon detection of a broken terminal (phase fault), the PMSM remains operational and could be utilized to provide a limp-home capabilit

Low-cost, high-resolution, fault-robust position and speed estimation for PMSM drives operating in safety-critical systems

In this paper it is shown how to obtain a low-cost, high-resolution and fault-robust position sensing system for permanent magnet synchronous motor drives operating in safety-critical systems, by combining high-frequency signal injection with binary Hall-effect sensors. It is shown that the position error signal obtained via high-frequency signal injection can be merged easily into the quantization-harmonic-decoupling vector tracking observer used to process the Hall-effect sensor signals. The resulting algorithm provides accurate, high-resolution estimates of speed and position throughout the entire speed range; compared to state-of-the-art drives using Hall-effect sensors alone, the low speed performance is greatly improved in healthy conditions and also following position sensor faults. It is envisaged that such a sensing system can be successfully used in applications requiring IEC 61508 SIL 3 or ISO 26262 ASIL D compliance, due to its extremely high mean time to failure and to the very fast recovery of the drive following Hall-effect sensor faults at low speeds. Extensive simulation and experimental results are provided on a 3.7 kW permanent magnet drive

Enhanced Torque Control of a PMSM Supplied by a Four-Leg Voltage Source Inverter Using the Third Harmonic

This paper investigates an electrical drive composed of a four-leg voltage source inverter and a three-phase starconnected surface permanent magnet synchronous machine with concentrated windings. The inverter fourth leg is clamped to the neutral point of the machine. We find the current references leading to smooth torque and maximal torque per ampere operation in the presence of a third harmonic electromotive force component. We further analyze the advantages of the proposed topology in terms of torque increase and dc-link voltage requirements

Control Strategies for Open-End Winding Drives Operating in the Flux-Weakening Region

This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc-link is associated with the machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional over-modulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. The paper describes the aforementioned strategies and then a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame and therefore zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter and a hybrid DSP/FPGA controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.Projet SOFRACI/FU

Modular switched reluctance machines to be used in automotive applications

In the last decades industry, including also that of electrical machines and drives, was pushed near to its limits by the high market demands and fierce competition. As a response to the demanding challenges, improvements were made both in the design and manufacturing of electrical machines and drives. One of the introduced advanced technological solutions was the modular construction. This approach enables on a hand easier and higher productivity manufacturing, and on the other hand fast repairing in exploitation. Switched reluctance machines (SRMs) are very well fitted for modular construction, since the magnetic insulation of the phases is a basic design requirement. The paper is a survey of the main achievements in the field of modular electrical machines, (especially SRMs), setting the focus on the machines designed to be used in automotive applications

Detekcija odspojene faze i na kvarove otporno upravljanje pretvaračem napajanim sinkronim motorom s permanentnim magnetima

In this paper first a current predictive method for single open-phase fault detection in a three phase drive with a permanent magnet synchronous machine is presented. The proposed method is based on a predictive stator current calculation. For each sampling interval the difference between the actual stator current and its predicted value in a previous sampling interval is calculated. To identify the location of a single open-phase fault, an identification method is presented which is based on the analysis of the stator current vector angle. After the single open-phase fault is detected and identified it is desirable for the electrical machine to continue operating with a reduced number of phases. For this purpose, a modified direct torque control algorithm for the fault-tolerant control is implemented. In order to improve the performance of the drive, a pre-firing angle is additionally introduced. All proposed methods have been simulated in Matlab/Simulink and verified on an experimental model.U članku je prvo predstavljena metoda za detekciju kvara odspojene faze u trofaznom elektromotornom pogonu sa sinkronim motorom s permanentim magnetima zasnovana na predikciji struja statora. U svakom koraku uzorkovanja računa se razlika između trenutne mjerene struje statora i prediktirane vrijednosti iz prethodnog koraka. U svrhu određivanja lokacije odspojene faze, predstavljena je metoda identifikacije zasnovana na analizi kuta vektora struje statora. Nakon otkrivene i utvrđene odspojene faze, poželjno je nastaviti rad električnog stroja sa smanjenim brojem faza. U ovu svrhu implementiran je izmijenjeni algoritam izravnog upravljanja momentom za postizanje na kvarove otpornog upravljanja. Da bi se unaprijedilo vladanje sustava elektromotornog pogona, dodatno je uveden kut prethođenja aktivacije impulsa. Sve predložene metode simulirane su u Matlab/Simulink okruženju i provjerene na eksperimentalnom postavu

Analysis of vertical strip wound fault-tolerant permanent magnet synchronous machines

This paper investigates the behavior of a vector- controlled, fault-tolerant, permanent magnet motor drive system adopting a vertically placed strip winding (VSW) which can limit inter-turn short-circuit (SC) fault current to its rated value regardless of the position in the slot containing the shorted turns. The drives’ dynamic behavior is simulated using a per-phase equivalent circuit model with the winding inductances and resistances analytical calculated based on the machine geometry and fault location. A simplified thermal model is also grafted into the system model to effectively simulate the dynamic behavior of the machine during healthy, inter-turn SC fault and post-fault controlled scenarios. The SC fault current limiting capability, the additional losses and thermal behavior of the winding are studied and compared with conventional winding adopting round conductors winding (RCW). The proposed winding design is verified with Finite Element (FE) analysis and then validated experimentally. Results show that the VSW inherently limits the SC current, reduces its dependence on the position of the fault within the slot but results in an increase in AC losses