Control solutions for multiphase permanent magnet synchronous machine drives applied to electric vehicles

207 p.En esta tesis se estudia la utilización de un accionamiento eléctrico basado en una máquina simétrica dual trifásica aplicada al sistema de propulsión de un vehículo eléctrico. Dicho accionamiento está basado en una máquina síncrona de imanes permanentes interiores. Además, dispone de un bus CC con una configuración en cascada. Por otra parte, se incorpora un convertidor CC/CC entre el módulo de baterías y el inversor de seis fases para proveer el vehículo con capacidades de carga rápida, y evitando al mismo tiempo la utilización de semiconductores de potencia con altas tensiones nominales. En este escenario, el algoritmo de control debe hacer frente a las no linealidades de la máquina, proporcionando un comando de consigna preciso para todo el rango de par y velocidad del convertidor. Por lo tanto, deben tenerse en cuenta los efectos de acoplamiento cruzado entre los devanados, y la tensión de los condensadores de enlace en cascada debe controlarse y equilibrarse activamente. En vista de ello, los autores proponen un novedoso enfoque de control que proporciona todas estas funcionalidades. La propuesta se ha validado experimentalmente en un prototipo a escala real de accionamiento eléctrico de 70 kW, probado en un laboratorio y en un vehículo eléctrico en condiciones reales de conducción.Tecnali

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

Control of dual three-phase IPMSM drive with cascaded DC-link capacitors for third generation EV

In this work, a dual three-phase Interior Permanent Magnet Synchronous Machine (IPMSM) drive connected to a high voltage DC/DC converter (800 V) at its input is considered for electric vehicle (EV) applications. The drive is constituted by two cascaded three-phase inverters, enabling fast charging capabilities. In this particular configuration, balancing the input voltages of the two inverters is mandatory during operation. A novel control approach that not only provides such voltage balancing but also considers the cross-coupling effects of the dual-three phase IPMSM is proposed, guaranteeing an adequate torque regulation through the whole operation range of the drive. Simulation results, generated by means of a high fidelity platform, are provided to validate the proposed approach. Additionally, preliminary experimental results are also included.This research has received funding from the European Union’s Horizon 2020 research and innovation programme under project FITGEN grant agreement No 824335. This work has been supported in part by the Government of the Basque Country within the fund for research groups of the Basque University system IT978-16 and the research program ELKARTEK (project ENSOL2-KK-2020/00077), and also by the Ministerio de Ciencia e Innovacion of Spain within the ´ project PID2020-115126RB-I00 and FEDER funds

Review of flux-weakening algorithms to extend the speed range in electric vehicle applications with permanent magnet synchronous machines

This article reviews Flux-Weakening (FW) algorithms for Permanent Magnet Synchronous Machines (PMSMs), focusing on the automotive sector, especially in electric and hybrid electric vehicles. In the past few years, the spread of Electric Vehicles (EVs) has improved the technology of electric machines and their control to achieve more compact and competitive solutions. PMSMs are the most widespread electric machines used in EVs thanks to their high-power density and potential operation at constant power range during high speed. Such high speed implies a high electromotive force. An FW technique is mandatory to reduce the electromagnetic flux generated by the electric machine due to the voltage limits of the traction inverter and the energy source. This article classifies and analyses the state-of-the-art FW control strategies by comparing their main advantages and drawbacks. The Vector Current Control (VCC) method that regulates the modulus of the applied voltage is the most common one in the literature thanks to i) its robustness to parameter modification and model unsureness, ii) low computational complexity, and iii) high dynamic response and control stability.Peer ReviewedPostprint (published version

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

NOVEL MODELING, TESTING AND CONTROL APPROACHES TOWARDS ENERGY EFFICIENCY IMPROVEMENT IN PERMANENT MAGNET SYNCHRONOUS MOTOR AND DRIVE SYSTEMS

This thesis investigates energy efficiency improvement in permanent magnet synchronous motor (PMSM) and drive system to achieve high–performance drive for practical industrial and primarily, traction applications. In achieving improved energy efficiency from a system level, this thesis proposes: (1) Accurate modeling and testing of loss components in PMSM considering inverter harmonics; (2) Easy–to–implement, accurate parameter determination techniques to understand variations in motor parameters due to saturation, cross–saturation and temperature; and (3) Control methodologies to improve system level efficiency considering improved loss models and parameter variations. An improved loss model to incorporate the influence of motor–drive interaction on the motor losses is developed by taking time and space harmonics into account. An improved winding function theory incorporating armature reaction fields due to fundamental and harmonic stator magnetic fields is proposed to calculate the additional harmonic losses in the PMSM. Once all contributing losses in the motor are modelled accurately, an investigation into control variables that affect the losses in the motor and inverter is performed. Three major control variables such as DC link voltage, switching frequency and current angle are chosen and the individual losses in the motor and inverter as well as the system losses are studied under varying control variables and wide operating conditions. Since the proposed loss as well as efficiency modeling involves machine operation dependent parameters, the effects of parameter variation on PMSM due to saturation and temperature variation are investigated. A recursive least square (RLS) based multi–parameter estimation is proposed to identify all the varying parameters of the PMSM to improve the accuracy and validity of the proposed model. The impact of losses on these parameters as well as the correct output torque considering the losses are studied. Based on the proposed loss models, parameter variations and the investigation into control variables, an off–line loss minimization procedure is developed to take into account the effects of parameter variations. The search–based procedure generates optimal current angles at varying operating conditions by considering maximization of system efficiency as the objective. In order to further simplify the consideration of parameter variations in real–time conditions, an on–line loss minimization procedure using DC power measurement and loss models solved on–line using terminal measurements in a PMSM drive is proposed. A gradient descent search–based algorithm is used to calculate the optimal current angle corresponding to maximum system efficiency from the input DC power measurement and output power based on the loss models. During the thesis investigations, the proposed models and control techniques are extensively evaluated on a laboratory PMSM drive system under different speeds, load conditions, and temperatures

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

Flux-Weakening Control for Permanent-Magnet Synchronous Motors Based on Z-Source Inverters

Permanent magnet synchronous machines (PMSMs) have high efficiency, high power density, high torque-to-inertia ratio, and fast dynamic response. These features make this kind of machines very attractive for electric vehicle (EV) applications. However, because of their nature, i.e., constant magnet flux provided by magnets, these machines have a narrow constant power speed range (CPSR). This limitation is a strong drawback for application of PMSMs in electric vehicles, where high speed is the top requirement. Two different approaches can extend the maximum speed under constant power: (1) Increasing a drive\u27s output voltage, and (2) implementing flux-weakening (FW) control methods. However, a conventional drive\u27s output voltage is limited by its dc bus. Furthermore, FW control methods are constrained by the maximum output voltage of a drive. In this work, a new approach is demonstrated to obtain a wider CPSR range by implementing a Z-source inverter as a motor-drive. Such a Z-source inverter can provide highly boosted voltage and is immune to dead time and shoot through issues. In addition, in this thesis, a constant power FW control algorithm is developed and simulated for this new approach

Adaptive Torque Estimation for an IPMSM with Cross-Coupling and Parameter Variations

This paper presents a new adaptive torque estimation algorithm for an interior permanent magnet synchronous motor (IPMSM) with parameter variations and cross-coupling between d- and q-axis dynamics. All cross-coupled, time-varying, or uncertain terms that are not part of the nominal flux equations are included in two equivalent mutual inductances, which are described using the equivalent d- and q-axis back electromotive forces (EMFs). The proposed algorithm estimates the equivalent d- and q-axis back EMFs in a recursive and stability-guaranteed manner, in order to compute the equivalent mutual inductances between the d- and q-axes. Then, it provides a more accurate and adaptive torque equation by adding the correction terms obtained from the computed equivalent mutual inductances. Simulations and experiments demonstrate that torque estimation errors are remarkably reduced by capturing and compensating for the inherent cross-coupling effects and parameter variations adaptively, using the proposed algorithm.111Ysciescopu