Conference Agenda

This paper proposes a conformal mapping and magnetic circuit hybrid model for predicting the magnetic field of Halbach array permanent-magnet (PM) motors considering iron saturation. The equivalent PM current replacing Halbach array is introduced to show the analytical air-gap field solution produced by Halbach PM array. In the hybrid analytical model, the slotted air-gap field is calculated using the conformal mapping model while the nonlinear iron field is represented by the magnetic circuit model. The interaction between the air-gap and iron region is based on the air flux source and equivalent saturation current. They are essential to iteratively solve the hybrid analytical model. The finite-element analysis of an 8-pole/9-slot PM motors with Halbach array PM is carried out to verify the effectiveness of the hybrid analytical model.

An integrated analytical model of permanent magnet synchronous motor (PMSM) system by direct coupling circuit equations and analytical field calculation equations is proposed in this paper. The proposed model establishes the analytical relationship of the phase current, motor supply voltage and structure parameters directly through winding flux linkage. Therefore, the integrated analytical model can take into account the influence of both the control circuit and structure parameters on electromagnetic performance, with the advantages of high accuracy, high efficiency and clear relationships of physical quantities, which can be applied to synthetical design and optimization of the PMSM.

In this work, a novel general pattern of assisted flux barriers in an asymmetric V-shape interior permanent magnet (AVIPM) machine is presented. The AVIPM machine has a symmetric permanent magnet (PM) structure and an asymmetric rotor core structure to realize magnetic-field-shifting (MFS) effect. The general pattern can represent four possible types of assisted flux barriers at different positions on the rotor core and the final structure can be automatically determined by using optimization method. The advantage of the proposed optimization pattern is that the optimal design of assisted flux barriers in V-shape interior permanent magnet (VIPM) machines with high torque and low torque ripple can be generated within a short computing time. The proposed optimization method is applied to improve the structure of a conventional 8-pole 48-slot VIPM machine, which is commonly used for driving electric vehicles (EVs). A genetic algorithm (GA) method is used for the optimization of both a VIPM machine and an AVIPM machine. The output torque and torque ripple are computed by using a finite element analysis (FEA) method. Moreover, to perform an accurate separation of PM torque and reluctance torque, a frozen permeability (FP) method is applied. The results exhibit that the output torque of the AVIPM machine is increased by 6.5% comparing to a conventional VIPM machine with the same PM volume. In addition, the mass of the rotor core decreases by 11% due to the existence of assisted flux barriers, which enhances the torque/mass density of the whole machine.

This paper presents an optimal design of a novel asymmetric hybrid-pole permanent magnet (AHPM) machine, in which the rotor combines consequent-pole and V-shape interior permanent magnet (VIPM) rotors. It utilizes the magnetic-field-shifting (MFS) effect to improve the torque performance, including output torque and torque ripple. The high permanent magnet (PM) torque and high reluctance torque are both effectively and simultaneously used. In addition, a general pattern of AHPM is proposed to represent all possible structures offered in the design to obtain an optimal structure within a short computing time. The asymmetric flux barrier configuration, asymmetric PM configuration, and both can be simply obtained by changing design parameters in the general pattern. And a Tabu search method is adopted to determine the final AHPM structure. The optimization algorithm is coupled to the finite analysis method (FEM) directly to achieve a fully automatic process. Moreover, to accurately evaluate the contribution of PM torque and reluctance torque to the synthetic torque, a frozen permeability (FP) method is applied. To verified the effectiveness of the MFS effect, a comparison is conducted between the conventional hybrid-pole permanent magnet (HPM) machine and the proposed AHPM with the same stator, rotor diameter and PM volumes. The simulation result shows the APHM can reach higher output torque and lower torque ripple.

The charging efficiency and electromagnetic radiation of wireless charging system of electric vehicle limit its popularization. This paper studies the design method of non-fixed frequency metamaterial in kHz frequency band, and analyzes its influence on the coupling characteristics of electric vehicle wireless charging. The resonance characteristics of metamaterial array under the influence of harmonics are explored. Furthermore, the regulation of the efficiency and loss of wireless charging system by non-fixed frequency metamaterials is analyzed. The experimental model of metamaterial is made, and the simulation device of wireless charging system will be built to verify the feasibility and efficiency of wireless charging technology based on non-fixed frequency metamaterial. It provides a theoretical basis for the efficiency improvement and technology promotion of wireless charging technology, and provides a safe and convenient charging method for the growing number of electric vehicles.

To study a low frequency electromagnetic device coupled with an electrical circuit, an approach based on the co-simulation principle can be developed. Then, each part of the system is solved by a decidated software. To reduce the computational time of a co-simulation, a Model Order Reduction (MOR) method such as the Proper Generalized Decomposition (PGD) method can be used. In this communication, the PGD approach is investigated in the context of the co-simulation of a low frequency electromagnetic problem coupled with electrical equations. A three-phase transformer coupled with electrical circuits is studied.

Multi-degree-of-freedom (multi-DOF) spherical actuators have been developed for the fields of robotics and industrial machinery. We have proposed an outer rotor type three-DOF spherical actuator that can realize a high torque density. Each coil input current is calculated using a torque generating equation based on the torque constant matrix. Permanent magnet type actuators have a problem that a PID control limit is exceeded when a cogging torque which is different from design is generated, which is a problem due to manufacturing fluctuation factors. Therefore, we applied a deep neural network that is expected to realize a strong non-linearity control of spherical actuators, and introduced a feedforward current compensator by reinforcement learning, and applied it to uncertainty problems such as manufacturing fluctuations of cogging torque.

The paper introduces an electromagnetic model of induction machines based on a circuit representation with state-dependent parameters precalculated in an automatable set of magnetostatic calculations. In contrast to usual circuit approaches, the proposed technique considers both saturation and the impacts of slotting and distributed winding. The quality of its results is comparable to those achieved by full time-stepping field calculations, while simulation time is substantially lower. The paper discusses the details of the model and is completed by demonstrations of its accuracy in numerical examples.

Co-simulation studies of electric power systems and electric machines have been always a challenge. In order to reduce the simulation time to a reasonable value, less-accurate lumped parameters Electric-Machines models are commonly used in electric power system modeling software packages to avoid the heavy computational burden of more accurate modeling methods especially Finite Element Method (FEM). In this paper, a dynamic phasor finite element modeling technique is proposed to model a wind-turbine driven Doubly Fed Induction Generator (DFIG) while connected to the public grid. The proposed technique combines the Dynamic Phasor Modeling technique for power system simulations with FEM to accurately model the DFIG while connected to the grid. Use of dynamic phasors enables a large simulation time-step resulting in significant reduction in the simulation time compared to traditional time-domain modeling. The mathematical foundation of the proposed modeling method is presented including core saturation of the generator. The comparison of simulation results of a C++ code of both time-domain and DPM methods proves the validity of the proposed technique in modeling the system accurately with substantially reduced simulation time.

In this paper, a mesh-based magnetic equivalent circuit model is proposed to consider the parasitic airgap in the segment stator. The magnetomotive force of permanent magnet is calculated by the analytical mode. The electromagnetic field of a prototype is analyzed based on the developed method and the results are verified by 2D finite element method (FEM). It shows that the magnetic performance are reduced when we use the segment stator, and the model predicts the air-gap magnetic field accurately. The cogging torque, phase flux linkage, electromagnetic torque and back electromotive force (EMF) are calculated based on the analysis, and experiments are carried out accordingly. Experimental results show that the EMF waveform calculated by the analytical model matches the measured waveform. The proposed method in the paper needs less CPU time, but maintain high accuracy.

Two-degree-of-freedom (DOF) mechanisms are used in various fields such as robots and drones. The mechanisms have a large size due to the combination structure of several motors and mechanical elements. Two-DOF actuators are expected to solve this problem. However, the conventional actuators have a complicated structure and large driving circuits. Then we proposed a basic idea of a novel two-DOF voice coil actuator (VCA) that can be driven by three-phase. This paper describes the torque characteristics, modeling, and dynamic analysis. The torque is calculated by a three-dimensional finite element method. The dynamic behavior is evaluated under feedback control in the dynamic simulation. The simulation results show that the actuator can be driven and controlled by the proposed principle.

When the transformer is energized under no-load condition, the residual flux density (Br) will accelerate the saturation of the core, and generated magnetizing inrush current will cause many harms to the power grid. In order to determine the Br of the transformer core with a closed magnetic circuit structure, this paper proposes a method for measuring the Br of the transformer based on the phase difference between the test voltage and the transient current. First, the relationship between the phase difference and Br is established using the method of field-circuit combination. Secondly, the finite element method is used to model and analyze the core to be tested, determine the appropriate test circuit parameters, and obtain an empirical formula for calculating the Br based on the simulation results. Finally, an experimental measurement platform was built, and the measurement results verified the feasibility and accuracy of the proposed method.

The authors had developed a finite element method avoiding the remeshing step in any iterative processes, as optimization and movement modeling based on a level-set approach. Nevertheless, the efficiency of this method (called projection method) is compensated by a poor quality in discontinuities accounting (materials boundaries for example). This paper proposes a hybrid model, in which static parts of the system are modeled by standard FEM and moving parts by projection. Furthermore, multiphysic phenomena can be easily taken into account by the way of projection functions: an example of current flow resolution coupled to a magnetic resolution in DC machine is then presented. The projection of a position dependent conductivity at the interface of commutator allows the implementation of a transient-state current flow resolution. Preliminary results are promising and useful comparisons are provided.

This paper presents a method to take into account the frequency-dependent behavior of the elements of lumped parameter models of electrical machine windings. First, frequency-dependent inductances, resistances and capacitances are determined thanks to time harmonic finite element (FE) computations in the frequency range of interest. Then, equivalent electrical networks are deduced using the vector-fitting (VF) algorithm, which allows for their inclusion in transient circuit solvers. The resulting time-domain voltage distributions can therefore be extracted and the whereabouts of partial discharges (PD) predicted using Paschen's law. This will enable the usage of this method as a diagnostic tool before or during the design phase of the winding of electrical machines.

Embedding artificial intelligence into current communication systems will substantially assist the development of ecosystems beyond 5G. In this study, a new neural network (NN) approach applied to antenna array adaptive beamforming is presented. A Recurrent NN (RNN) based on the Gated Recurrent Unit (GRU) architecture is used as a beamformer in order to receive the angles of arrival (AoA) of incoming signals and produce the complex weights for the feeding of the elements of the antenna array. These weights are subsequently compared with the respective weights derived by a null steering beamforming (NSB) algorithm to measure the accuracy of the RNN. The proposed RNN utilizes four hidden GRU layers and one extra layer for linear transformation. The RNN training is performed by using a large data set derived from a realistic antenna array using NSB as the beamforming technique. The RNN performance is tested using the root mean square error (RMSE) metric, whereas its beamforming performance is evaluated by estimating the mean deviation of the main lobe and null directions from their respective desired directions. A comparison between various NN structures and an overall study of the proposed RNN-based beamformer are also presented.

The DC-Biased vernier reluctance machines (DCB-VRMs) do not involve permanent magnet excitation, which has the advantage of low cost and no demagnetization risk, so it can be used for long-stroke linear applications. In this paper, the vernier reluctance linear machines with different winding pole pairs and secondary poles are compared. First, the combinations of different winding pole pairs and secondary slots of 12-slot vernier reluctance linear machines are analyzed, and four bilateral linear machine models are established. Then, the thrust ripple of four combinations are optimized by reduce the detent force and the cogging force. Finally, the loss and efficiency are compared with different DC excitation ratio. The results show that DC-Biased vernier reluctance linear machines (DCB-VRLMs) have low thrust ripple, which proved that the theory of DCB-VRMs is completely applicable in the field of linear machines.

This paper presents the novel computation method of carrier harmonics losses for synchronous reluctance motors (SynRMs). Carrier harmonics occur from switching of the inverter and it result carrier harmonic losses. Therefore, analysis using current from inverter as input source is necessary for precise core loss calculation. To compute core loss accurately, finite-element method (FEM) has been employed in many cases. However, it requires long time owing to non-linear property and post-processing despite of its high accuracy. Moreover, inverter-fed analysis takes longer time compared to sine current analysis, because of its convergence property and number of steps. Therefore, method considering the carrier harmonic loss with reduced time is necessary. In this paper, we propose a fast computation method to obtain carrier harmonic losses for all operating area. Proposed method is verified by comparing with the result of FEM.

The magnetic-force-deformation model due to magnetostriction (MS) strain and Maxwell stress model caused by joints are developed based on the major sources of vibration and acoustic noise in power transformer core in this paper. On the basis of the forces created by the two sources, structure finite element method (SFEM) is used to calculate the core vibration, and then calculate the acoustic noise. Meanwhile, a three-dimensional (3-D) structure model of power transformer is constructed, the natural frequencies and vibration modes of each order modal of the main system components are obtained according to the modal analysis, and sufficient experimental testing is used to verify all the steps of the study in detail. In the end, a novel ontological structure design with the core and windings position interchange is put forward. The testing results of the prototype show that it is an effective means to reduce vibration and acoustic noise of power transformer.

In this paper, we propose a general analysis method for cogging torque and torque ripple of rotating machines to understand their generation mechanisms. In the method, the torque of any kinds of rotating machine is expressed by some of phasors, which are expressed by time and space harmonic components of air-gap flux density. The proposed method is applied to both a permanent magnet synchronous motor and induction motor. The mechanism of torque ripple reduction of these motors due to shape optimizations are clarified by the proposed method.