High-speed Permanent Magnet Synchronous Machine Research Articles

Influence of High-Frequency Operation on the Efficiency of a PMSM Drive with SiC-MOSFET Inverter

This paper investigates the effects of high-frequency switching and a high fundamental frequency on the parameters and efficiency of a high-speed permanent magnet synchronous machine (PMSM) drive. We discuss the design and modeling of the PMSM, taking into account these high-frequency effects. The impact of high frequencies is analyzed across three different inverters (IGBT, Fast IGBT, and SiC-MOSFET) and the motor, and we employ theoretical analysis, computer simulations, and experimental tests for validation. Our goal is to enhance our understanding of how these high-frequency factors affect the performance of the motor drive.

High-speed tooth-coil permanent magnet synchronous machine for motorized spindle application

The slender shape of the driving machine leads to a low rigidity and large axial thermal elongation of the motorized spindle, which deteriorates the machining precision. To solve these problems and pursue a more compact size, this paper investigates the feasibility of using a tooth-coil permanent magnet synchronous machine in a high-speed spindle, replacing the original motor that has the conventional distributed winding. Comprehensive performance and behavior of machines with distributed and tooth-coil windings are comparatively analyzed, in terms of the essential torque ripples, winding inductances, electromagnetic losses, rotor integrity, and heat dissipation of the spindle. Thorough numerical simulation results indicate that the newly designed tooth-coil winding solution shows significant advantages over the original design, regarding high rotor rigidity, low torque ripples, reduced electromagnetic losses, and reduced shaft thermal elongation. Prototypes and test setups for the high-speed tooth-coil machine are built, where preliminary measurements are carried out to validate the analysis results and system design.

Confidence Weighted Learning Entropy for Fault-Tolerant Control of a PMSM With a High-Resolution Hall Encoder

There are several non-idealities that can degrade magnetic Hall-effect sensors performance and impact related applications. Thus, a confidence weighted learning entropy (CWLE) is proposed as a fault-tolerant control strategy for field-oriented control (FOC) of permanent magnet synchronous machines (PMSM). It combines sensorless and sensor-based control, while capitalizing on their major advantages, such as operation from standstill and at lower speeds, fast dynamic response, and fault tolerance to encoder errors. Encoder fault detection is based on learning entropy, that monitors weights increments of two predictive filters of angular displacement. If the two observed systems behave similarly, the variance of the weights increments is similar. A higher variance, on the other hand, reflects unforeseen misbehavior of a particular system, leading to a decrease in its confidence. A voting mechanism based on confidence weighted average then decides which of the two systems should be used for FOC of PMSM. The method has been experimentally verified on a high-speed PMSM, achieving more reliable control performance with fast response to encoder failures.

Analytical Solution of Magnetic Field in High-Speed Permanent Magnet Synchronous Machines With Novel Composite Rotor

Analytical Solution of Magnetic Field in High-Speed Permanent Magnet Synchronous Machines With Novel Composite Rotor

Cooling Structure Design of High-Speed Permanent Magnet Synchronous Machine With Axial Ventilation Self-Cooling Rotor

Cooling Structure Design of High-Speed Permanent Magnet Synchronous Machine With Axial Ventilation Self-Cooling Rotor

Sensorless Control Design of High-Speed Electric Drives in Discrete-Time Domain for Mild-Hybrid Turboprop Aircraft Applications

High-speed Permanent Magnet Synchronous Machine (PMSM) sensorless control design is not without challenges, especially when the ratio of power electronic modulation frequency to electrical fundamental frequency (M-F ratio) is relatively low. The Model Reference Adaptive System (MRAS) is a mature sensorless control method and has been widely used in industrial drives. There, an observer is commonly used to estimate rotor speed and angle using machine voltages and currents. The estimated angle is then further implemented for voltage and current frame transformations. Thus, the MRAS sensorless control is indeed a strong-coupled, multi-variable and nonlinear system. This paper proposes a detailed MRAS sensorless control system design method in discrete-time domain for high speed drives with relatively low M-F ratio with good system stability confidence. A detailed discrete local-linearized small-signal model is developed and state-space evolution matrix of current closed-loop system has been derived. The system stability can be defined and analysed with its maximum eigenvalue and the controller design is to make sure that the maximum eigenvalue is falling within the stable region. This proposed design method has been validated on a dual three-phase PMSM by simulation and experiment results with selected stable design point.

First-Order Model Based Inductance Identification With Least Square Method for High-Speed Sensorless Control of Permanent Magnet Synchronous Machines

In sensorless control of high-speed permanent magnet synchronous machines (PMSMs), online inductance identification techniques can be employed to improve the position estimation precision. The high-order inductance identification model which is affected by the flux error, the dead-time effect equivalent voltage and initial rotor position error adopted in conventional methods often face challenges including robustness and accuracy. To address this issue, this paper uses a first-order discrete-time model in the estimated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">γδ</i> -frame to identify the winding inductance with disturbance injection. The first-order model allows the identification to be independent of flux error, initial rotor position error and inverter nonlinearity, thus the robustness is improved. The proposed method takes the computational delay and discrete-time nature of pulse-width-modulation into account to avoid the model error brought by low ratio of carrier-to-fundamental-frequency. Additionally, the results are estimated by least square method to solve fluctuation problem caused by measurement noise and the possible surge phenomenon. Experiments are carried out on a high-speed surface-mounted PMSM for vacuum cleaner to verify the proposed method.

A Novel Energy Balance Control Method for a Modular Multilevel Converter in a High-Speed PMSM Drive Application

Nowadays, high-speed permanent magnet synchronous machines (HSPMSMs) are widely used in high-speed direct-drive applications. Moreover, modular multilevel converters (MMCs) have attracted a lot of attention. In this paper, the mathematical model of the MMC for the HSPMSM was built on high- and low-speed regions, respectively, and the control of each model is completely decoupled. Moreover, energy balance control schemes based on the common mode current injection of the MMC with HSPMSM drive applications have been proposed for high- and low-speed cases, respectively. Based on this model, the controller is proposed for high- and low-speed cases, respectively. Simulation and experiment results indicate that the proposed energy balance control method for an MMC in the high-speed PMSM drive application exhibits significant performance, which can ensure the energy balance of the MMC and eliminate the circulating current of the MMC directly.

Multiobjective Optimization and Multiphysics Design of a 5 MW High-Speed IPMSM Used in FESS Based on NSGA-II

The flywheel energy storage system (FESS) has high-power density and fast response speed, hence it is widely used as a pulse power supply. For the high-speed permanent magnet synchronous machine (HSPMSM) used in high-power FESS, there are two technical problems that need to be solved, including huge centrifugal forces of the rotor at a high-speed operation region and large phase currents at a low-speed operation region. In this paper, a 5 MW high-speed interior PMSM (HSIPMSM) is designed for FESS. The design goal of this electric machine is to reduce the maximum phase current at the lowest speed as much as possible while ensuring the rotor mechanical strength. Based on the response surface (RS) model and non-dominated sorting genetic algorithm II (NSGA-II), the multiobjective design of the HSIPMSM is accomplished using 29 groups of multiphysical field finite element analysis (FEA) sampling experiments. The computational cost is effectively reduced. In addition, the constant power optimal trajectory and control switching speed of the HSIPMSM are analyzed and discussed, and the reason that the constant power flux weakening region of the designed HSIPMSM is not wide and the maximum torque per ampere (MTPA) mode is adopted at a low-speed operation region is further illustrated.

A General Single-Sensor Damping Framework for LCL-Equipped High-Speed PMSM Drives

This letter proposes a general single-sensor active damping framework for LCL-equipped high-speed permanent magnet synchronous machines. By the proposed method, arbitrary damping assignment and stability for the LCL resonance within the Nyquist frequency are achieved with only the inverter-current feedback or motor-current feedback. Moreover, the simplified analytical expression between the physical parameters and the damping performance enables automatic tuning for different drive systems.

Composite PM Rotor Design and Alternating Flux Density Harmonic Component Analysis of a 200 kW High-Speed PMSM Used in FESS

The flywheel energy storage system (FESS) is a short-time high-power energy storage technology widely used in various fields. To improve speed and reduce air friction loss, the rotor of the high-speed permanent magnet synchronous machine (HSPMSM) used in FESS operates at a magnetic suspension state in vacuum. It is very difficult for the rotor to dissipate heat, which may even lead to PM demagnetization. In this paper, a 200 kW 20000 r/min HSPMSM is designed for FESS of an uninterruptible power supply (UPS), and a composite PM rotor with multilayer sleeves is proposed. Distinct from the previously proposed retaining sleeve design of the HSPMSM rotor, a silicon steel sleeve is added in the composite PM rotor, which can provide a bypass for alternating flux density harmonic components in the rotor and prevent them from entering the alloy sleeve and PM. Moreover, a post-processing method of finite-element analysis (FEA) results is proposed to obtain the alternating harmonic components in the rotor and further analyze the suppression effect of the silicon steel sleeve on them. As the silicon steel sleeve is introduced, the amplitudes of alternating harmonic components are effectively suppressed, which can mitigate the eddy current loss and heat generation of the HSPMSM rotor from the source.

Influence of Rotor Sleeve on Multiphysics Performance for HSPMSM

The multiphysics characteristics of high-speed permanent magnet synchronous machines (HSPMSMs) can be significantly affected by the rotor sleeve. This article aims to comprehensively investigate how the electromagnetic, loss, mechanical, and thermal characteristics are influenced by the rotor sleeve. First, the change of the rotor sleeve is divided into two stages. The mechanical air gap length is fixed in the first stage, while the electromagnetic air gap length is fixed in the second stage. Besides, the influence of sleeve thickness of the alloy sleeve and carbon fiber sleeve on electromagnetic characteristics, loss characteristics, rotor stress, and temperature characteristics are obtained within these two stages. Furthermore, four sleeve design configurations with different thicknesses and materials are investigated, and a comprehensive comparison is performed. Finally, a prototype of an HSPMSM is manufactured, and the theoretical analysis is verified through performance testing of the prototype.

Design and Analysis of a Novel High-Speed Permanent Magnet Machine With Dual Semi-Cage Winding

This article proposes a novel high-speed permanent magnet synchronous machine (HSPMSM) topology. The characteristics of the proposed machine are: 1) The stator winding is divided into two parts and each part is connected by the end ring at one end, which is helpful to solve the existing shortage of overlong end length in traditional HSPMSM. 2) The stator of the machine is designed with closed slot, which can greatly weaken the eddy current loss and the cogging torque of the machine. 3) The machine is driven by two separate three phase converter, which can improve the fault tolerance. In this article, the topology, and the corresponding control system is analyzed firstly. After that the electromagnetic performance, including back electromotive force, cogging torque, torque, etc. are analyzed with finite element analysis (FEA). In addition, the losses, including the stator copper loss, the stator iron loss and the eddy current loss of the permanent magnet and sleeve of the rotor, are calculated by FEA. The mechanical strength and dynamic performance of rotor is also checked. Finally, a prototype was designed and manufactured. The experimental results the validity of the topology.

Surrogate Model-Based Multiobjective Optimization of High-Speed PM Synchronous Machine: Construction and Comparison

This article employs surrogate models for large-scale high-speed (HS) electrical machine optimization to reduce heavy computational burden caused by the finite-element method (FEM) based on nondominated sorting genetic algorithm II. Three artificial neural networks, namely, multilayer perceptron (MLP), support vector regression (SVR), and generalized regression neural network (GRNN), and the classical Kriging model are developed based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -fold crossing validation method. To find out the most suitable surrogate model, a HS permanent magnet synchronous machine (PMSM) applied in electrically assisted turbocharger (EATC) considering its multiphysics characteristics is optimized by different models. A detailed comparison is provided in terms of prediction accuracy and modeling time consumption. The optimal design is verified to guarantee the accuracy of optimization results. The key contributions of this article include an automatic HSPMSM optimization process is proposed, where complete modeling and tuning method as well as a reasonable comprehensive evaluation metric of different surrogate models are conducted. It is found that invalid samples from the initial dataset contain useful information to improve prediction accuracy. Hence, an entire surrogate process should benefit from a pretrained classifier. Also, it reveals that MLP, SVR, and Kriging model can greatly improve the design optimization effectiveness with high accuracy, whereas GRNN is not suitable for this specific optimization scenario.

Optimal Design of High-Speed Electric Machines for Electric Vehicles: A Case Study of 100 kW V-Shaped Interior PMSM

The need of compact machines increased in recent years due to increases in raw materials’ price. Hence, many studies are currently being conducted on high-speed challenges to propose an optimal design methodology. AC losses in windings are often not included in the optimization process and are treated in post-processing by choosing a suitable conductor’s diameter to mitigate skin and proximity effects. This paper presents an optimization and design methodology for high-speed electric machines considering these losses, using models with an interesting trade-off between computation time and accuracy, which is helpful for large-scale optimization, in which more than 9,600,000 machines are evaluated. Optimizations are conducted on 100 kW high-speed one-layer V-shaped interior permanent magnet synchronous machines, widely used in vehicles thanks to their high power density, based on the specifications of the Peugeot e208, for different values of pole pairs and maximum speed. The influence of lamination thickness, fill factor, and maximum current density on the optimal design is also investigated. This paper concludes the utility of increasing speed to achieve high power density and proposes best alternatives regarding automotive constraints. Results show that the number of pole pairs is not always a key parameter in obtaining the lowest volume, especially at high speed.

A proposed method to rotordynamic analysis of a high-speed permanent magnet synchronous machine by retention sleeve

In this paper, the authors present a novel analytical model for rotordynamic analysis of a high-speed permanent magnet synchronous machine (HS-PMSM) with a retention sleeve. The proposed analytical model has a fast response, accurate results, and sample formulation, and is validated with the finite-element method (FEM). The obtained results show the proper accuracy of the proposed analytical solution approach. The significant results are: The analytical formulation model proposed for the rotordynamic analysis of the HS-PMSMs can accurately calculate the displacement and the stress of the solid cylinder of the rotor at any high speeds and temperature rises. Furthermore, the proposed analytical model is concerning the temperature changes in the rotor and ensures requirements in any temperature rising and high rotational speeds.

Transient Performance Improvement of Deadbeat Predictive Current Control of High-Speed Surface-Mounted PMSM Drives by Online Inductance Identification

This article presents an analytical derivation of transient performance deterioration for high-speed surface-mounted permanent magnet synchronous machine (SPMSM) drives under parameter mismatches, with an advanced deadbeat predictive current control (DBPCC), which exhibits fast dynamics and strong robustness with disturbances rejection. All the influential factors, including permanent magnet flux linkage and inductance mismatches, inverter nonlinearity, and speeds are taken into account in the analysis. It is shown that the transient performance with the advanced DBPCC is only dependent on inductance accuracy. Large transient overshoot and cross-coupling in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis currents at high speeds arise due to inductance mismatch. Based on the understanding gained through the analysis, a novel inductance identification method is also proposed in this article, which significantly improves the transient performance of high-speed SPMSM drives. The proposed online inductance identification method does not require signal injection, is nonintrusive, and can be easily implemented. By integrating the proposed method with the advanced DBPCC, the close-to-ideal deadbeat control can be achieved for high-speed SPMSM drives even in the presence of parameter mismatch and inverter nonlinearity. Both the analysis and proposed method have been validated experimentally on a prototype high-speed (30 000 r/min) SPMSM drive under various conditions.

Online Inductance Identification Using PWM Current Ripple for Position Sensorless Drive of High-Speed Surface-Mounted Permanent Magnet Synchronous Machines

Back–electromotive force estimation-based rotor position estimation methods are usually adopted for high-speed surface-mounted permanent magnet synchronous machines (SPMSM) drive to deal with the limitations of position sensors in high-speed applications. Considering inductance mismatch is the main cause of the position estimation error, this article proposes a novel pulsewidth modulation (PWM) current ripple-based online inductance identification method to improve the position estimation accuracy. The proposed method utilizes the inherent PWM current ripple of the voltage source inverter for inductance identification. In addition, the transient circuit equations on the estimated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\gamma \delta$</tex-math></inline-formula> frame are adopted as the identification model, and the recursive least squares method is used to obtain the estimated inductance. Compared with the traditional parameter identification methods, the proposed method does not need to inject additional signals or fix parameters. During the sensorless drive of high-speed SPMSM, the proposed method can accurately identify the inductance while not affecting the normal operation of PMSM at all, which is the main contribution of this article. With the proposed method, the estimated inductance can rapidly converge to the accurate value, and then the position estimation error will be eliminated. Finally, the effectiveness of the proposed method is verified by simulations and experiments.

Analysis of alternating flux density harmonics inside the rotor of a 1 MW high-speed interior permanent magnet synchronous machine used for flywheel energy storage systems

With the popularization of renewable distributed energy generation in the power grid, flywheel energy storage systems (FESS) with fast response and high power density are gradually becoming popular for achieving fast frequency modulation. Generally, the rotor of high-speed permanent magnet synchronous machine (HSPMSM) used for FESS rotates in a vacuum to reduce air friction loss, which concurrently makes it difficult to dissipate heat in the rotor. For reducing rotor iron loss and preventing demagnetization of the PM due to high temperature, effective measures need to be applied. In this study, a 1 MW 10,500 r/min high-speed interior PMSM (HSIPMSM) is proposed for an FESS. As rotor iron loss is caused by alternating flux density harmonics (FDH) inside the rotor, the causes and characteristics of alternating FDHs are analyzed. Then, the finite element analysis (FEA) is combined with two-dimensional fast Fourier transform (2D-FFT) to obtain the alternating frequencies and amplitude variation trends of alternating FDHs in the designed rotor. The analytical results indicate that the amplitudes of alternating FDHs on the PM surface are effectively reduced due to bypass of the rotor core at the outside of the PM to alternating FDHs, which helps to restrain the rotor iron loss from the source. This provides a design idea for mitigating the high temperature of high-power high-speed PM rotors.

Comparison of Heat Transfer Characteristics of the Hollow-Shaft Oil Cooling System for High-Speed Permanent Magnet Synchronous Machines

The rotor cooling poses a significant challenge for high-speed permanent magnet synchronous machines. This article presents a recirculating hollow-shaft oil cooling structure. Through the computational fluid dynamics (CFD) method, its convective heat transfer characteristics are studied in depth. Besides, the recirculating hollow-shaft cooling (RHSC) is compared with the direct-through hollow-shaft cooling (DHSC). Based on the CFD analysis, it is found that the convective heat transfer coefficient (CHTC) of the RHSC is higher than that of the DHSC, which can be as high as 58%. Furthermore, the advantage of the RHSC is most prominent at low rotational speed and small flow rate due to its relatively large oil friction loss at a high rotational speed. Moreover, the explanation for the fluctuation of the CHTC before the critical rotational speed, as well as the law of its variation with rotational speed and flow rate, are revealed in this study. The correctness of the simulation analysis is verified by experiments implemented on a rotor setup. In order to summarize the convective heat transfer law of the RHSC better, a dimensionless empirical equation is fitted finally.