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抢先看 | CES TEMS 2022年第4期目次及摘要
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Deputy Editor-in-Chief: Professor Lijian Wu
Guest Editors:
Kai Wang, Dawei Li, Cungang Hu, Junquan Chen, Xiao Liu, Shi Jin, Wei Wang, Feng Niu, Hui Yang, Xiaoqin Zheng, Jien Ma
Authors:
F. Xu, T. R. He, Z. Q. Zhu, H. Bin, D. Wu, L. M. Gong, and J. T. Chen
Abstract—Split ratio, i.e. the ratio of stator inner diameter to outer diameter, has a closed relationship with electromagnetic performance of permanent magnet (PM) motors. In this paper, the toroidal windings with short end-winding axial length are employed in the 6-slot/2-pole (6s/2p) PM motor for high speed applications. The split ratio is optimized together with the ratio of inner slot to outer slot area, i.e. slot ratio, considering stator total loss (stator iron loss and copper loss). In addition, the influence of maximum stator iron flux density and tooth-tip on the optimal split ratio, slot ratio, and average torque is investigated. The analytical predictions show that when the slot ratio is 0.5, the maximum torque can be achieved, and the optimal split ratio increases with the decrease of slot ratio, as confirmed by the finite element (FE) analyses. Finally, some of predicted results are verified by the measured results of 6s/2p prototype motor with 0.5 slot ratio.
Authors:
Ran Xu, and Wenming Tong
Abstract— To solve the problem of large torque ripple of interior permanent magnet synchronous motor (IPMSM), the rotor surface notch design method was used for V-type IPMSM. In order to accurately obtain the optimal parameter values to improve the torque performance of the motor, this paper takes the output torque capacity and torque ripple as the optimization objectives, and proposes a multi-objective layered optimization method based on the parameter hierarchical design combined with Taguchi method and response surface method (RSM). The conclusion can be drawn by comparing the electromagnetic performance of the motor before and after optimization, the proposed IPMSM based on the rotor surface notch design can not only improve the output torque, but also play an obvious inhibition effect on the torque ripple.
Optimal Designs of Wound Field Switched Flux Machines with Different DC Windings Configurations
Authors:
Wenting Wang, Yuankui Wang, Enlin Ma, and Lijian Wu
Abstract—Wound field switched flux (WFSF) machines exhibits characteristics of the simple robust rotor, flexible flux-adjustable capability, and no risk of demagnetization. However, they suffer from a poor torque density compared with permanent magnet machines due to the saturation. Therefore, in this paper, two WFSF machines with single- and double-layer DC windings, respectively, are optimized for the maximum torque. The end-winding (EW) lengths differ in these two machines, which can affect the optimal design. Design parameters including the DC to armature winding copper loss ratio, slot area ratio and split ratio are optimized when two machines have the same copper loss and overall sizes. In addition, the influence of the flux density ratio, total copper loss, air-gap length and aspect ratio on the optimal split ratio is investigated using the finite element method and results are explained through the analytical model accounting for the saturation. It is discovered that the EWs have no effect on the optimal copper loss ratio, which is unity. In terms of the slot area ratio, the machine with single-layer DC windings prefers smaller DC slot areas than armature slot areas. In the WFSF machine with longer EWs, the optimal split ratio becomes smaller. Moreover, compared with other parameters, the flux density ratio can significantly affect the optimal split ratio.
Authors:
Hui Wen, Yufei Wang, Yuting Zheng, Wen Zeng, Xiao Qu, and Jiongjiong Cai
Abstract—Electrically-excited flux-switching machines are advantageous in simple and reliable structure, good speed control performance, low cost, etc., so they have arouse wide concerns from new energy field. However, they have much lower torque density/thrust density compared with the same type PM machines. To overcome this challenge, electromagnetic-thermal coupled analysis is carried out with respect to water-cooled electrically-excited flux-switching linear machines (EEFSLM).
The simulation results indicate that the conventional fixed copper loss method (FCLM) is no longer suitable for high thrust density design, since it is unable to consider the strong coupling between the electromagnetic and thermal performance. Hence, a multi-step electromagnetic-thermal joint optimisation method is proposed, which first ensures the consistency between the electromagnetic and thermal modelling and then considers the effect of different field/armature coil sizes. By using the proposed joint optimisation method, it is found that the combination of relatively large size of field coil and relatively low field copper loss is favourable for achieving high thrust force for the current EEFSLM design. Moreover, the thrust force is raised by 13-15% compared with using the FCLM. The electromagnetic and thermal performance of the EEFSLM is validated by the prototype test.
Authors:
Qingguo Sun, Xiaolei Zhu, and Feng Niu
Abstract—To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer, a piecewise square root switching function with continuously varying characteristics is designed, and its stability is analyzed by using Lyapunov stability criterion. Secondly, according to the relationship among bus current, switching state and phase current, a single bus resistance sampling current reconstruction scheme without current sensors is adopted, which effectively reduces the cost of motor system. Finally, the feasibility and effectiveness of the proposed scheme are verified by simulation.
An Enhanced Sensorless Control Scheme for PMSM Drives Considering Self-inductance Asymmetry
Authors:
Lijian Wu, Zekai Lyu, Zekai Chen, Jiaming Liu, and Ying Lu
Abstract—Inductance asymmetry, which is brought by inherent asymmetric parameters, manufacture tolerance, winding fault, cables with unequal lengths, etc., of permanent-magnet synchronous machines (PMSMs) can cause current harmonics and inaccurate position estimation. This paper proposes an enhanced fundamental model based sensorless control strategy for PMSMs with asymmetric inductances. The proportional-integral-resonant current regulator is introduced to reduce the second-order harmonics of currents, but there are still negative sequence components in the estimated back-electromotive forces (EMFs), which can cause the position estimated error. Differing from conventional methods in which negative sequences are filtered out before the phase-locked loop (PLL) module, the proposed method directly applies the estimated back-EMF with negative sequences as the reference input of PLL. An improved PLL with a bi-quad filter is proposed to attenuate the arising second harmonic position error and heighten the steady-state accuracy. Then, this position error is used for asymmetric inductance identification and its result is utilized to update the observer model. Furthermore, the dynamic performance is improved by the output limitation on the bi-quad filter as well as the implementation of a fast-locking technique in the PLL. The effectiveness of the proposed scheme is verified by experimental results.
Two-vector Dimensionless Model Predictive Control of PMSM Drives Based on Fuzzy Decision Making
Authors:
Nabil Farah, Gang Lei, and Jianguo Zhu, and Youguang Guo
Abstract— Model predictive controls (MPCs) with the merits of non-linear multi-variable control can achieve better performance than other commonly used control methods for permanent magnet synchronous motor (PMSM) drives. However, the conventional MPCs have various issues, including unsatisfactory steady-state performance, variable switching frequency, and difficult selection of appropriate weighting factors. This paper proposes two different improved MPC methods to deal with these issues. One method is the two-vector dimensionless model predictive torque control (MPTC). Two cost functions (torque and flux) and fuzzy decision-making are used to eliminate the weighting factor and select the first optimum vector. The torque cost function selects a second vector whose duty cycle is determined based on the torque error. The other method is the two-vector dimensionless model predictive current control (MPCC). The first vector is selected the same as in the conventional MPC method. Two separate current cost functions and fuzzy decision-making are used to select the second vector whose duty cycle is determined based on the current error. Both proposed methods utilize the space vector PWM modulator to regulate the switching frequency. Numerical simulation results show that the proposed methods have better steady-state and transient performances than the conventional MPCs and other existing improved MPCs.
Authors:
Shuai Liang, Shi Jin, and Long Shi
Abstract—The brushless doubly-fed wind power system based on conventional power control strategies lacks ‘inertia’ and the ability to support grid, which leads to the decline of grid stability. Therefore, a control strategy of brushless doubly-fed reluctance generator (BDFRG) based on virtual synchronous generator (VSG) control is proposed to solve the problem in this paper. The output characteristics of BDFRG based on VSG are similar to a synchronous generator (SG), which can support the grid frequency and increase the system ‘inertia’. According to the mathematical model of BDFRG, the inner loop voltage source control of BDFRG is derived. In addition, the specific structure and parameter selection principle of outer loop VSG control are expounded. The voltage source control inner loop of BDFRG is combined with the VSG control outer loop to establish the overall architecture of BDFRG-VSG control strategy. Finally, the effectiveness and feasibility of the proposed strategy are verified in the simulation.
Authors:
Ying Fang, Jinghua Ji, and Wenxiang Zhao
Abstract—The paper develops accurate analytical subdomain models for predicting the magnetic and armature reaction fields in fault-tolerant flux-switching permanent-magnet machines. The entire region is divided into five subdomains, followed by rotor slots, air-gap, stator slots, PM, and external air-gap imported to account for flux leakage. The coil turns and the remanence of magnets are adjusted by keeping the magnetic and electrical loading on the motor constant. The distance between the centers of two adjacent stator slots varies due to the introduction of fault-tolerant teeth. According to the variable separation method, the general solution expression of each region can be determined by solving the partial differential systems of equations. The magnetic field distributions of subdomains are obtained by applying the continuity conditions between adjacent regions. Some analytical field expressions are represented as new forms under armature reaction field condition compared to those under no-load condition. Based on the developed analytical models, the flux density distribution and the electromagnetic performance can be calculated under no-load or armature reaction field condition separately. The finite element analysis is carried out to verify the validity of the proposed analytical model.
Authors:
Zhe Liang, Deliang Liang, Peng Kou, and Shaofeng Jia
Abstract—The paper presents an accurate analytical subdomain model for predicting the electromagnetic performance in the symmetrical dual three-phase surface-mounted permanent magnet synchronous machine (PMSM) under open-phase faulty conditions. The model derivations are extended from previous accurate subdomain models accounting for slotting effects. Compared with most conventional subdomain models for traditional three-phase machines with nonoverlapping winding arrangement, the subdomain model proposed in this paper applied for the 24-slot/4-pole dual three-phase machine with symmetrical overlapping winding arrangement. In order to investigate the postfault electromagnetic performance, the reconfigured phase currents and then current density distribution in stator slots under different open-circuit conditions are discussed. According to the developed model and postfault current density distribution, the steady-state electromagnetic performance, such as the electromagnetic torque and unbalanced magnetic force, under open-circuit faulty conditions are obtained. For validation purposes, finite element analysis (FEA) is employed to validate the analytical results. The result indicate that the postfault electromagnet performance can be accurately predicted by the proposed subdomain model, which is in good agreement with FEA results.
Three-dimensional Analytical Modeling of Axial Flux Permanent Magnets Maglev Motor
Authors:
Wei Qin, Gang Lv, and Yuhua Ma
Abstract—The three-dimensional(3D) analytical model of the magnetic field in an Axial Flux Permanent Magnets Maglev Motor(AFPMMM) is proposed and investigated the influence of the structural parameters on electromagnetic characteristics. Firstly, the topology and working principle of the AFPMMM is introduced, and the model is transferred into a mathematical model in 3D cartesian coordinate. Then, the volume integral method and equivalent current sheets model is applied to find the 3D magnetic field distribution function of Halbach rotor. A unified form expression can be obtained by two dimensional discrete fourier transform (2-D DFT) is applied on the 3D magnetic field distribution function. Thirdly, the conductive and nonconductive regions of AFPMMM will be formulated by the second order vector potential (SOVP) to built the 3D analytic model. The expression of the lift force, torque and power losses was derived. Besides, the relationship between electromagnetic characteristics and structural parameters of the AFPMMM were analyzed based on 3D analytic model and validated using the 3D finite element analysis(FEA). Finally, the experiments based on a small scale prototype are carried out to verify the analytical results.
Authors:
Zhidong Yuan, Shaofeng Jia, Deliang Liang, Xiuli Wang, and Yong Yang
Abstract—Offshore wind energy is an important part of clean energy, and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals. The combination of the fractional frequency transmission system (FFTS) and the direct-drive wind turbine generator will be beneficial to the development of the offshore wind power industry. The use of fractional frequency in FFTS is beneficial to the transmission of electrical energy, but it will also lead to an increase in the volume and weight of the generator, which is unfavorable for wind power generation. Improving the torque density of the generator can effectively reduce the volume of the generators. The vernier permanent magnet machine (VPM) operates on the magnetic flux modulation principle and has the merits of high torque density. In the field of electric machines, the vernier machine based on the principle of magnetic flux modulation has been proved its feasibility to reduce the volume and weight. However, in the field of low-speed direct-drive machines for high-power fractional frequency power generation, there are still few related researches. Therefore, this paper studies the application of magnetic flux modulation in fractional frequency and high-power direct-drive wind turbine generators, mainly analyzes the influence of different pole ratios and different pole pairs on the generator, and draws some conclusions to provide reference for the design of wind turbine generators.
Optimal Pole Ratio of Spoke-type Permanent Magnet Vernier Machines for Direct-drive Applications
Authors:
Yu Zhao, Dawei Li, Xiang Ren, Ronghai Qu, Jianbo Sun, and Ping Yu
Abstract—Due to magnetic gearing effects, spoke-type permanent magnet vernier machines (ST-PMVMs) have the merit of high torque density, where an extra torque amplification coefficient, i.e., pole ratio (the pole-pair ratio of PMs to armature windings) is introduced. However, different from surface-mounted PMVM, the variation of torque against pole ratio in ST-PMVMs is non-linear, which is increased at first and then decreased. This article is devoted to identify the optimal pole ratio of ST-PMVMs by equivalent magnetic circuit model. It is found that except the Prth air-gap magnetomotive force (MMF) harmonic having the same pole-pair of PM, the Path air-gap MMF harmonic having the same pole-pair of armature winding is also induced due to the modulation of doubly salient air-gap structure. The Prth MMF harmonic produces positive torque, while Path MMF harmonic produces negative torque. With the increase of pole ratio, the proportion of Path MMF harmonic as well as negative torque is increased, which reduces the advantages of high pole ratio coefficient. Further, the influence of dimension parameters on the performance of ST-PMVMs under different pole ratio are investigated. Results show that ST-PMVMs with pole ratio 2.6 have high torque density, low cogging torque and high power factor simultaneously. Finally, a prototype is manufactured to validate the analysis.
Authors:
Zongwang Li, Yuxuan Du, Jinghua Ji, Tao Tao, and Wenxiang Zhao
Abstract—Dual three-phase permanent-magnet synchronous machines (DTP-PMSM) connected with a single neutral point provide a loop for zero-sequence current (ZSC). This paper proposes a novel space vector pulse width modulation (SVPWM) strategy to suppress the ZSC. Five vectors are selected as basic voltage vectors in one switching period. The fundamental and harmonic planes and the zero-sequence plane are taken into consideration to synthesis the reference voltage vector. To suppress the ZSC, a non-zero zero-sequence voltage (ZSV) is generated to compensate the third harmonic back-EMF. Rather than triangular carrier modulation, the sawtooth carrier modulation strategy is used to generate asymmetric PWM signals. The modulation range is investigated to explore the variation of modulation range caused by considering the zero-sequence plane. With the proposed method, the ZSC can be considerably reduced. The simulated and experimental results are presented to validate the effectiveness of the proposed modulation strategy.
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🔗 【专题征稿】 Drive Motor Systems for Electric Vehicles
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