The accuracy of mathematical model of surface-mounted permanent magnet synchronous motor (SPMSM) is critical for high-performance sensorless control. However, the eddy-current and hysteresis effects of the iron core are usually neglected in the existing SPMSM mathematical models, affecting control accuracy of the SPMSM sensorless control. Based on the vector magnetic circuit (VMC) theory, the influence of eddy-current and hysteresis effects on the SPMSM is considered. To simplify the VMC model, a R-L coordinate transformation and its coordinate system were proposed. A mathematical model of the SPMSM considering eddy-current and hysteresis effects is established, where the magnetic impedance angle can characterize the effects of the eddy-current and hysteresis on the phase shifts between the magnetic flux and the magnetomotive force (MMF). Meanwhile, the disturbance mechanism of the eddy-current and hysteresis effects on the sliding-mode observer is revealed. Based on these findings, a novel sliding model observer (SMO) and the sensorless control strategy are proposed. The experimental results show that the proposed method can improve the accuracy of rotor position estimation of SPMSM sensorless control.

For high-temperature superconducting-based electrical machines, the magnetic shielding performance of the Dewar system has become one of the most attractive research topics in electromagnetic compatibility (EMC) practice and applications. The unknown or inaccurate knowledge about the electromagnetic properties of Dewar materials, as well as the limitations of experimental configurations, e.g., background interference, low temperature, and enclosed structures, has made it difficult to evaluate the magnetic shielding performance of the Dewar. Here, we propose a simple method for measuring the shielding performance of the Dewar at low-frequency range (below 1 kHz), and also provide a prediction of the shielding performance at low temperature (273, 76, and 20 K). To minimize the impact of background noise, the closed shielding chamber, e.g., the reverberation chamber (RC) made of galvanized steel plates, is used as a testing facility in which the measurement configuration is performed, taking into account the magnetic field that may affect the superconducting magnets. To verify the measurement method, the COMSOL Multiphysics 6.0 is employed, and comparisons have confirmed that the experimental results follow the numerical simulation with very good repeatability and very small uncertainty (less than 0.9 dB for 40 Hz-1 kHz). By using the temperature-dependent conductivity, the shielding performance has been predicted at low temperature (e.g., 273, 76, and 20 K), being regarded as an alternative estimate of the experimental results that are not easily obtained for the actual Dewar module.

The low-frequency oscillation of large generators poses great harm to the shaft system. In the case of brushless excitation turbogenerators, the oscillation will affect the coaxial exciter. In this article we focus on the impact of the low-frequency oscillation of large-scale generator shaft system on the coaxial exciter parameters. Starting from the influence of oscillation on the conduction law of the armature winding, the expression of the armature current was derived, and the expression of the armature magnetic field was further extracted to predict the harmonic characteristics in terms of excitation current. Simulation verification was implemented on an 8-pair pole 3-phase brushless exciter, and the experimental verification was completed on a 7-pair pole 3-phase brushless exciter. The research indicates that the specific frequency harmonics in the excitation current of the brushless exciter can be utilized to monitor the torsional vibration of the turbogenerator shaft system.

Flux-reversal permanent magnet electrical machine (FRPMEM) has advantages such as high torque density and high power density, and has broad application prospects in offshore wind power generation. However, the current-carrying capacity of the traditional copper armature winding is limited, making it difficult to further increase the motor's electrical load. This paper proposes a Modular Dewar Multiplexing High-Temperature Superconducting Armature Flux-Reversal Permanent Magnet Electrical Machine (MHTSA-FRPMEM), which uses high-temperature superconducting (HTS) armature windings instead of traditional copper armature windings. This paper details the topology and working principle of the MHTSA-FRPMEM, finding that compared to the conventional HTS armature winding permanent magnet synchronous machine (HTSAW-PMSM), the permanent magnet excitation magnetic field of the MHTSA-FRPMEM has less influence on the HTS armature winding. The winding arrangement of the twelve-phase HTS armature winding is analyzed, and an electromagnetic scheme for a 20MW MHTSA-FRPMEM is designed and its key parameters are optimized. Compared with the conventional HTSAW-PMSM with the same rated power, its torque density can be increased by >40%.

The traditional mathematical models of surface-mounted permanent magnet synchronous motor (SPMSM) usually ignore the influences of the eddy current and hysteresis effects due to the fact that there is no appropriate parameter to quantitatively characterize these effects. However, with the increase in operating frequency of the SPMSM and switching frequency of the converter, their influences are becoming increasingly serious and have to be considered. The vector magnetic circuit (VMC) theory contains three basic magnetic circuit parameters, i.e., reluctance, magdutance, and hysteretance, which respectively characterize the magnetization, eddy current effect, and hysteresis effect in the magnetic circuit, and provide a new perspective for motor control to consider the eddy current and hysteresis effects. Therefore, based on the VMC theory, this article establishes the mathematical model of the SPMSM by proposing an R-L coordinate transformation to consider eddy current and hysteresis effects in the iron core, but keeps the d- and q-axis equations decoupled. Consequently, based on the proposed mathematical model, the novel i(d) = 0 vector control of SPMSM is designed. Simulation and experimental results show that compared with the traditional id = 0 vector control, the novel id = 0 vector control has higher current control accuracy, better steady state, and dynamic performances.

In order to solve the problems of mesh node dynamic connection between the stator and rotor and the inability of single reluctance element to characterize the eddy current and hysteresis effects of ferromagnetic materials in the conventional equivalent magnetic network (EMN) model, this article proposes an EMN model with three elements: magnetic flux source, reluctance, and magductance (TEEMN). The "magnetic flux source" is arranged in the air-gap mesh, whose magnitudes can be quickly determined by the analytical method. Changing the magnitudes of the magnetic flux source to imitate "virtual rotation" of the rotor solves the problem of mesh dynamic connection of the EMN model. At the same time, the "magductance L" element is introduced to characterize the influence of eddy current and hysteresis effects on the magnetic flux density. Further, considering the saturation effect of the magnetic circuit, a calculation method of the saturation factor of "effective magnetic impedance" is proposed to further improve the calculation accuracy of the TEEMN model. Taking a dual three-phase vernier permanent magnet (PM) machine as an example, the modeling process and analysis method of the TEEMN model is presented in detail and verified by the finite element analysis results and experimental results.

Large-capacity superconducting (SC) generators have broad application prospects in offshore wind power. Replacing copper armature windings with higher current-carrying capacity SC tapes can further increase the power density of the generator. The phase current in high-capacity SC armature generators can be on the order of kiloamperes. To conduct such high armature current, multiple parallel-stranded SC tapes need to be employed. However, the current-carrying capacity and AC losses of SC armature windings will be affected by both the external magnetic field and their own magnetic field. Because of the effects of the external magnetic field, the current distribution in the parallel SC tapes is uneven, resulting in low tape utilisation. In order to weaken the influence of the external magnetic field on SC tape, the electromagnetic shield is usually utilised, but these shielding components introduce additional losses and reduce reliability. Therefore, this paper proposes a double-pancake coil tape transposition method based on analysis of the coupled magnetic fields between multiple SC tapes. This method can improve the uniformity of current transmission within the SC tapes and the overall current-carrying capacity of the SC coils, thereby further enhancing the power density of the SC generator.

The phase current of mega watt (MW) class superconducting (SC) armature permanent magnet electrical machine (SCPMM) is quite high, usually from several hundred amperes to 1 kA, therefore, the current-carrying capacity of a single SC tape is insufficient to meet the phase current requirements. The main purpose of this article is to investigate a kind of parallel SC coils and analyze the arrangement of multiphase SC armature windings and its loss regularity under external magnetic fields. The main effect factors of parallel SC coils on ac loss are obtained under the conditions of self-field and external periodic magnetic field and a kind of arrangement of the low-loss parallel coils are proposed through coordinating spatial distribution of SC coils and phase shift of transmitting current. This work provides references for the design optimization multiphase SCPMSM.

The conventional sliding mode observer (SMO) employed in the sensorless control for the permanent magnet synchronous machine (PMSM) has the problems of chattering phenomena and phase delay, which results in large errors between the estimated and actual values of the rotor speed and position. Thus, this paper proposes an improved SMO based on fuzzy logic controller (FLC) and dual second-order generalized integrator-frequency-locked loop (DSOGI-FLL) structure. The FLC is used to adjust the parameters of the SMO to improve the adaptive ability of the system and reduce the chattering. At the same time, in order to reduce the adverse effects from low-pass filter (LPF), DSOGI-FLL is used to accurately extract the back electromotive force (back-EMF) and effectively eliminate the high-order harmonic components. Finally, the proposed method is verified by simulation and experiment, and compared with a novel super-twisting algorithm-base SMO with a complex vector generalized integrator (STASMO-CVGI), the results show that the improved SMO has better performance.

This article proposes an active power control strategy for dynamically maximizing power production in waked wind farm (WF) based on an accelerated asynchronous distributed calculation scheme (DCS). By adopting a two-degree-of-freedom (2Dof) active power control strategy based on model predictive control (MPC), the generator speed and pitch angle of wind turbines (WT) can be coordinated to enhance the long-term WF-level cumulative power production and power reserve subject to strong wake effects. The proposed strategy is significantly different from existing model-free control strategies, and can quickly respond to time-varying wind speeds through online feedback of both WT mechanical status and dynamic wake. The proposed strategy can greatly improve the efficiency of solving large-scale optimization problems through two designs: first, using asynchronous DCS to reduce computation time and strengthen robustness to communication failures. Second, the Nesterov acceleration strategy is introduced to significantly reduce the number of iterations and enhance the convergence rate. Additionally, a novel control command issuance strategy is devised to address the issue of wake delay. In a 1000s simulation, the proposed strategy achieves a remarkable improvement of 10.81% and 18.29% in cumulative power production and power reserve of WF, respectively.

With the growing demand for dynamic reactive power support in ultra-high-voltage direct current (UHVDC) systems, synchronous condensers play a vital role in grid stability. This study presents a non-intrusive acoustic method for detecting rotor winding inter-turn short-circuit (ITSC) faults. A coupled electromagnetic – structural – acoustic model of a TTS-300-2 condenser is developed to analyze electromagnetic noise under normal, over-, and under-excitation. Both simulation and experiments reveal that ITSC faults generate distinct d/p-order harmonic components and reduce the second-harmonic amplitude, consistent with theoretical predictions of magnetic asymmetry. The proposed approach enables contactless fault detection and offers a practical solution for online condition monitoring of large synchronous condensers.

Model predictive current control (MPCC) with optimal duty cycle has been widely studied and applied in the field of permanent magnet synchronous motor (PMSM) drive due to its advantages of simplicity, fast dynamic response and good steady state performance. Recent research on two-vector MPCC (TV-MPCC) has shown that the pulse arrangement of placing a nonzero vector on both sides of a zero vector results in smaller current harmonics and lower switching frequency than the traditional pulse arrangement that places a zero vector on both sides of a nonzero vector. However, the state-of-the-art method still fails to obtain the global optimal steady-state performance, because the freedom of vector combinations and vector duration optimization are not fully utilized. This article proposes an improved two-vector model-free predictive current control (TV-MFPCC) method. An adaptive ultralocal model is adopted to achieve strong robustness. The proposed TV-MFPCC takes the combination of two nonzero vectors into account, thereby improving the steady-state performance at high speeds. It further optimizes the time allocation of the voltage vector placed on both sides, obtaining the minimal current total harmonic distortion (THD). Compared with the state-of-the-art TV-MFPCC method that involves placing a nonzero vector on both sides of a zero vector, the proposed TV-MFPCC not only produces slightly lower switching frequency, but also reduces the current THD significantly in the entire speed range, which can be more than 50% at the rated speed. Additionally, the proposed TV-MFPCC achieves a lower current THD than its counterpart using SVM under the same switching frequency and the maximum current THD reduction is up to 36.6%.

ABSTRACT To address the safety concerns regarding the mechanical performance of the rotor, a coupled electromagnetic–structural–fatigue simulation model is established to investigate the impact of transient shock processes under rotor interturn short circuit (RISC) and static air‐gap eccentricity (SAGE) faults on the dynamic response and fatigue damage of the rotor shaft system during forced excitation operation of the synchronous condenser. First, the unbalanced magnetic pull (UMP) acting on the rotor is theoretically derived and its magnitude is obtained through electromagnetic simulation, followed by the calculation of the rotor's vibration response and corresponding experimental validation. Subsequently, a coupled electromagnetic–structural–fatigue simulation model is established to analyse the stress distribution of the rotor and verify its transient load‐bearing capacity. Finally, a fatigue simulation is conducted to evaluate the impact of forced excitation fault operation on the rotor's service life. The results show that the rotor can maintain stable vibration in normal operation, and the amplitude of rotor characteristic frequency vibration increases during fault. Forced excitation operation with faults has a significant effect on the fatigue damage of the rotor shaft system. As the degree of fault increases, the fatigue life of the rotor shaft system decreases sharply.

It is known that high-temperature superconducting (HTS) magnets can operate in higher temperature margin compared with conventional low-temperature superconductors, and the characteristics of AC loss and screening current are very important for the optimal design of HTS magnets. In this article, two methods for evaluating the critical current of HTS magnet at different temperatures are compared. The effects of operating temperature and applied external magnetic field on the AC loss and screening current of the HTS magnet stacked by annular plates are discussed and analyzed. The results show that when the amplitude of the ac magnetic field is lower than that of the fully penetrating magnetic field, the magnetization loss decreases with the decrease of the operating temperature. The hysteresis loop area of the HTS magnet stacked by Rare-Earth-BaCu oxides annular plates increases at higher temperature under the same magnetic field.

Synchronous condensers provide strong short-term overload capacity and instantaneous reactive power support, playing a crucial role in addressing issues such as insufficient reactive reserves, reduced short-circuit capacity, and commutation failures in ultrahigh-voltage direct current (UHVDC) transmission systems. However, rotor interturn short-circuit (ITSC) faults can lead to severe consequences, including increased vibrations, magnetic field distortion, and even forced shutdown. To improve the accuracy and robustness of fault detection, this article proposes a data-driven fault diagnosis method based on multisource data fusion. Excitation current, radial leakage flux, and electromagnetic noise are selected as noninvasive diagnostic signals. To mitigate the impact of noise and nonstationary characteristics in the acquired signals, a correlation variational mode decomposition (CVMD) algorithm is employed to denoise and extract effective signal components prior to feature processing. The decomposed signals are then fed into a convolutional neural network-long short-term memory (CNN-LSTM) model for deep feature learning and classification. Experimental validation using an MJF-30-6 salient pole synchronous motor demonstrates that the proposed method significantly enhances diagnostic performance, achieving a fault identification accuracy of 99.3% and effectively overcoming the limitations of single-signal diagnosis under complex operating conditions.

High-temperature superconducting (HTS) electrical machines can offer high efficiency and power density, but the HTS magnets in these machines commonly suffer performance degradation caused by external alternating magnetic fields. Hence, superconducting shielding layers (SSLs) are used to enhance the critical current and reduce the AC loss of HTS magnets. Therefore, optimizing the design of SSLs is crucial to achieving the optimal performance of HTS magnets. In this paper, focusing on a double-stator HTS machine (DS-HTSM), a layered multi-objective optimization design based on parameter sensitivity analysis is conducted for SSLs, in which both the structural parameters and positions of SSLs are optimized simultaneously. A quantitative performance comparison of HTS magnets between initial and optimal design is conducted by using the finite element analysis (FEA), and the results demonstrate an improvement in the critical current safety margin, a significant reduction in AC loss, and effective space utilization, thus providing valuable insights for the design of high-performance HTS electrical machines.

The fundamental magnetization curve, or BH curve, represents the relationship between magnetic flux density B and magnetic field strength H when H varies periodically, typically determined through experimental measurements. This study presents an innovative method, grounded in vector magnetic circuit theory, to extrapolate BH curves across various frequencies from a known BH curve at a specific reference frequency. Building on the semi-infinite model of the silicon steel sheet, the expressions for reluctance and magductance, along with their relationship to frequency, are derived by applying electromagnetic field theory and vector magnetic circuit theory. Using a known BH curve at a specific frequency as a reference, the relationship between H and B can be calculated based on Kirchhoff’s magnetic circuit law of vector magnetic circuit theory. Finally, the feasibility and validity of this BH curve extrapolation method is confirmed through experimental results.

Offshore wind power generation has broad application prospects. The current single-unit capacity of offshore wind generators exceeds 20 MW. Superconducting (SC) armature permanent magnet (PM) generators have high current-carrying characteristics and can overcome the bottlenecks of the copper armature PM synchronous generator in terms of volume and weight. However, existing SC armature windings usually use an integrated Dewar, which is difficult and costly to design and is not conducive to maintenance. In addition, SC armature windings are mostly three-phase windings, and the fault-tolerant operational capability of SC armature electrical machines is poor. In response to the above problems, this paper proposes a dual three-phase PM vernier SC armature electrical machine (DTVSM), which adopts an SC magnet with a static seal of the cooling medium. Each SC magnet used a modular Dewar and contained two sets of SC coils. The SC magnets are connected externally to form a dual three-phase SC armature winding, which improves the fault-tolerant operational capability of the SC armature PM electrical machine. Compared with the 20 MW copper armature PM synchronous electrical machine, the unit volume torque density of the proposed DTVSM is about 108.22 kN·m m −3 , which represents an improvement of about 60%, indicating significant application potential. This study designs and tests a 10 kW prototype, focusing on the electrical machine topology, working principle, and manufacture of SC magnets and prototype, and the related experimental tests verify the feasibility of the DTVSM technology route.

This paper presents a comprehensive investigation into the effects of key operational parameters under axial eccentricity (AE) on the mechanical behavior of the rotor in permanent magnet synchronous generators (PMSGs). The parameters studied include the degree of AE, load size, and power factor. The rotor's mechanical behaviors analyzed encompass unbalanced magnetic pull (UMP) and vibration responses. The research combines theoretical analysis, finite element analysis (FEA), and experimental validation. The findings indicate that UMP becomes significant under AE conditions, with a dominant frequency at 100 Hz. Moreover, as the degree of AE or the power factor increases, the 100 Hz of UMP and vibration responses also intensify. In contrast, larger load sizes result in reduced UMP and lower vibration amplitudes.