Showing papers by "Yongjian Li published in 2010"

Equivalent Circuits for Single-Sided Linear Induction Motors

Abstract: Single-sided linear induction motors (SLIMs) have lately been applied in transportation system traction drives, particularly in the intermediate speed range. This is because they have merits, such as the ability to exert thrust on the secondary without mechanical contact, high acceleration or deceleration, less wheel wear, small turning circle radius, and flexible road line. The theory of operation for these machines can be directly derived from rotary induction motors (RIMs). However, while the cut-open primary magnetic circuit has many inherent characteristics of the RIM equivalent circuits, several issues involving the transversal edge and longitudinal end effects and the half-filled slots at the primary ends need to be investigated. In this paper, a T-model equivalent circuit is proposed which is based on the 1-D magnetic equations of the air gap, where half-filled slots are considered by an equivalent pole number. Among the main five parameters, namely, the primary resistance, primary leakage inductance, mutual inductance, secondary resistance, and secondary inductance, the mutual inductance and the secondary resistance are influenced by the edge and end effects greatly, which can be revised by four relative coefficients, i.e., Kr, Kx, Cr, and Cx. Moreover, two-axis equivalent circuits (dq or αβ) according to the T-model equivalent circuit are obtained using the power conversion rule, which are analogous with those of the RIM in a two-axis coordinate system. The linear induction motor dynamic performance, particularly the mutual inductance and the secondary resistance, can be analyzed by the four coefficients. Experimental verification indicates that both the T-model and the new two-axis circuits are reasonable for describing the steady and dynamic performance of the SLIM. These two models can provide good guidance for the electromagnetic design and control scheme implementation for SLIM applications.

Measurement of Soft Magnetic Composite Material Using an Improved 3-D Tester With Flexible Excitation Coils and Novel Sensing Coils

Abstract: In this paper, accurate measurement of three dimensional (3-D) magnetic properties of soft magnetic composite (SMC) material is carried out by using an improved 3-D tester with adjustable excitation coils and novel sensing coils attached upon the surface of the SMC specimen. Comparing with the conventional 3-D tester operating at 50 Hz, the improved 3-D tester enables measurements over wide frequency range from 2 Hz to 1000 Hz. The relationships between the B vector and H vector are measured under both alternating and rotating flux conditions, and the core loss features are analyzed. These experimental results are crucial for designing new SMC electrical machines, which are expected to operate at 200 Hz or above.

Initial Rotor Position and Magnetic Polarity Identification of PM Synchronous Machine Based on Nonlinear Machine Model and Finite Element Analysis

Abstract: In this paper, a DC voltage pulse injection based method is proposed to detect the initial position and rotor polarity of permanent magnet synchronous motor (PMSM). The rotor angle vibration is expressed analytically as a function of the injected pulse. The nonlinear numerical simulation model of PMSM is employed, in which the saturation saliency is incorporated as well as the structural saliency. The proposed scheme is simulated and verified by using the nonlinear model and a 2-D finite element method (FEM) algorithm, respectively. The initial position detection is tested at different starting positions and the results show that the proposed scheme can be used to identify the PMSM initial rotor position.

Magnetic flux penetration in polycrystalline SmFeO0.75F0.2As

Abstract: The recently discovered Fe–As superconducting materials which show high potential ability to carry current due to their low anisotropy have attracted a great number of attentions to understand their superconductivity mechanism and explore their applications. This paper presents a method to synthesis SmFeO0.75F0.20As polycrystalline by hot press in detail. The magnetization at different temperatures and applied fields obtained by a superconducting quantum interference device are also discussed. In addition, the local magnetization process is presented by magneto-optical imaging technique at the conditions of zero-field-cooling and field-cooling. It is found that the collective magnetization process of the newly discovered Fe–As superconductors is very similar to that of high-Tc cuprates. For instance, the Fe–As superconductors and high-Tc cuprates have the same magnetization features due to strong pining and intergrain weak link. The global supercurrent is significantly lower than local grain supercurrent ...

Flux-switching permanent magnet machine drive system for plug-in hybrid electrical vehicle

Abstract: Plug-in hybrid electric vehicle (PHEV) depends mostly on the electric drive system where the internal combustion engine just acts as the auxiliary unit, which has strict constraints for the drive machine. According to the Toyota Prius configuration, one novel PHEV drive system in this paper has been brought forward which primarily includes one drive machine operating as both motor and generator, energy storage unit combining supercapacitor and battery. In the novel PHEV, the ideal tendency is to use the drive machine over the entire torque/speed range, including starting/acceleration, high speed cruising, regenerative braking, etc. The flux-switching permanent magnet machine (FSPMM) for the drive system has been studied in details. Firstly, the structure and operation principle are analyzed theoretically. In order to achieve higher torque/power density and lower torque ripple, FSPMM with 6/7 (stator/rotor) poles and 12/14 poles according to plenty of investigations are optimized based on our setting objective function decided by actual projects. Moreover, it analyzes several typical performance curves, such as cogging/rating torque, flux linkage, back-EMF, and self-/mutual-inductances. Finally the flux-weakening ability and efficiency are estimated by experience. The results indicate that FSPMM is one ideal candidate for our PHEV drive system for its strong thermal dissipation ability, good mechanical robustness, strong flux-weakening ability, etc.

Research of Three-Dimensional Magnetic Reluctivity Tensor Based on Measurement of Magnetic Properties

Abstract: In this paper, a method of studying the three-dimensional (3-D) reluctivity tensor by measuring 3-D vector magnetic properties of the soft magnetic composite (SMC) material is presented. The magnetic flux density B and magnetic field strength H loci under alternating and rotating magnetizations are measured by using an improved 3-D tester. The magnetic reluctivity tensor can be expressed by a second-order three-dimensional full rank matrix by means of the experimental results. Taking the off-diagonal elements into account can benefit to accurate numerical analysis of magnetic field in 3-D flux electrical machines.

Magnetic properties measurement of soft magnetic composite materials over wide range of excitation frequency

Abstract: Accurate measurements of magnetic properties of soft magnetic composite (SMC) material are performed on an improved 3D tester by means of novel precision B-H sensing coils attached to the surface of the specimen. By controlling the adjustable excitation topologies, magnetic properties over wide excitation frequency range from 2 Hz to 1000 Hz are acquired and analyzed. In this paper, the relationship between the magnetic flux density vector B and magnetic field strength vector H has been systematically measured under alternating and 3D conditions, and the core loss features have been analyzed. Compared with the conventional magnetic properties only at 50 Hz, wide-range-frequency magnetic properties contribute to extending application area of the new SMC electrical machines.

Torque ripples and estimation performance of high frequency signal injection based sensorless PMSM drive strategies

Abstract: The developed nonlinear permanent magnet synchronous machine (PMSM) model established a virtual model to simulate and assess the sensorless drive schemes for PMSMs avoiding the experimental trial and error method. In this paper, three sensorless PMSM drive schemes are investigated and compared, which are all based on the high frequency signal injection. The nonlinear PMSM machine model is employed to accurately simulate the machine performance and to analytically assess the efficiency of the sensorless algorithm. Both the structural and saturation saliencies are incorporated in this comprehensive model. The comparison of the machine torque ripples induced by excitation signals are carried out. The magnitude of injected signal and recordable rotor position information are considered together as the efficiency of the estimation algorithm. Additionally, the implementation and signal process computing costs are considered for all the schemes. Finally, a comprehensive comparison of all the methods is developed.

A novel control strategy for Doubly Fed Induction Generator and Permanent Magnet Synchronous Generator during voltage dips

Abstract: This paper proposes a novel control strategy for Doubly Fed Induction Generator (DFIG) based wind power system and Permanent Magnet Synchronous Generator (PMSG) based wind power system during grid voltage dips. Based on a comparative study, the rotor over-current of DFIG and DC-link over-voltage of PMSG are identified as two main issues during grid voltage dips. A novel control strategy is proposed to enhance the wind farm Fault Ride Through (FRT) capability to some degree without additional devices, taking both grid code requirements and wind turbine requirements into account. A wind farm model consisting of DFIGs and PMSGs is built up. The effectiveness of the solution is demonstrated after simulation using MATLAB/SIMULINK.

Rotational magnetic properties of SMC materials in 3-D flux electrical machines

Abstract: Soft magnetic composite (SMC) materials are widely applied in three-dimensional (3-D) magnetic flux electrical machines Conventional methods for analyzing the magnetic properties of SMC materials based on alternating excitation are not comprehensive due to the rotational magnetic properties in the rotating electrical machines In order to completely understand and model the magnetization process and optimize design of the 3-D flux electrical machines, rotational magnetic properties of SMC materials should be measured and analyzed By using an improved 3-D magnetic property tester, this paper presents the measurement of rotational magnetic properties, such as magnetic flux density vector B, magnetic field strength vector H and core loss Moreover, 3-D tester model and magnetic field distribution are analyzed by means of finite element method

Analysis of the 3-D magnetic reluctivity tensor based on magnetic properties measurement of SMC materials

Abstract: In order to comprehensively understand magnetic field distribution in soft magnetic composite (SMC) materials which apply to three-dimensional (3-D) flux electrical machine design, 3-D reluctivity tensor should be taken into account. A 3-D magnetic properties testing system fitting for cubic SMC sample has been constructed and calibrated by means of finite element method (FEM). According to the experimental data from 3-D magnetic property tester, this paper presents the modeling of 3-D magnetic reluctivity tensor, which can be written to a 3×3 full rank matrix. Laboratory results and FEM analysis are presented to testify the rationality of design and optimize the performance of electromagnetic devices.

Magneto-optical visualization of vortices penetration into Ba(Fe1.8Co0.2)As2

Abstract: Vortices penetration into oxygen-free superconducting compounds FeAs-122 system is of interest in understanding superconductivity. This work studies the vortices motion in Ba(Fe1.8Co0.2)As2 single crystal by means of magneto-optical imaging technique in zero field cooled and field cooled conditions. The captured magneto-optical images and corresponding flux profiles show that, at zero field cooled condition, vortices penetrate into the crystal from the edges as external magnetic field increases. A vortices-free region is observed at the center of sample as applied field is less than full penetration field. In field cooled condition, the introduced vortices leave the sample at the edges as field decreases and polarization of the vortices at the edges are opposite as decreasing field approaches to zero. The pinning strength decreases with increasing temperature. The observed vortex behavior is very similar to that in high Tc superconducting materials with strong pinning strength.

A Finite Element Formulation for Tetrahedral Elements Based on Reluctivity Tensor

Abstract: In some cases, the magnetic material's reluctivity becomes a full three-dimensional tensor. In some applications the use of a scalar or a vector reluctivity is accurate enough. However, the consideration of the off-diagonal terms in a reluctivity tensor is necessary in many other calculations. In this paper, a finite element formulation is developed from Maxwell's equations and 4-node tetrahedral element shape function. The uniqueness of the formulation is that the off-diagonal terms of reluctivity tensor are fully considered. A finite element analysis program based on this formulation is compiled, which uses Femap to create a model and to display the magnetic flux distribution. Several simulations of a current-carrying air-core square coil between two iron plates are performed and compared. It shows that off-diagonal terms of reluctivity tensor have influence on distribution of magnetic flux.

Modelling of surface mounted PM machines incorporating saturation saliency and frequency variation

Abstract: In this paper a comprehensive magnetic model is developed for a surface mounted permanent magnet synchronous machine (SPMSM) considering both the structural and the saturation saliencies to enable the numerical simulation of new rotor position detection algorithms. With an identifiable parameter matrix, a numerical nonlinear inductance model is proposed, in which the rotor position and the stator current are taken as two independent variables. Additionally, the stator current frequency is taken as another factor of the inductances and the inductances for different frequencies are investigated. After experimentally identifying out all the parameters, a nonlinear mathematic model of SPMSM is built up based on the new magnetic inductance function. Finite element method (FEM) based calculation and simulation results are used to verify the proposed nonlinear magnetic model.

Modeling and analysis of 3-D tensor magnetic reluctivity properties of soft magnetic composite material

Abstract: In rotating electric machines, magnetic material shows complex three-dimensional (3-D) properties due to rotational domains. In order to comprehensively analyze magnetic field distribution in the rotating flux machines, a 3-D magnetic properties testing system fit for cubic specimen has been constructed and modeled by means of finite element method (FEM). Taking the magnetic reluctivity tensor into account, this paper presents the modeling of 3-D tester core and analyzes the 3-D properties of a kind of SMC material. Experimental results are also presented to testify the rationality of design.

Analytical nonlinear model for permanent magnet synchronous machine incorporating saturation saliencies

Abstract: This paper investigates the nonlinear model of the permanent magnet synchronous machines (PMSMs) In order to incorporate the structural and saturation saliencies, two parameters are defined to indicate the saturation ratios An analytical model is derived and the inductance matrix is expressed in both stationary and rotating reference frames, respectively An incremental inductance measure system is established, on which a real PMSM is tested and numerically simulated The nonlinear inductance matrix is deduced and expressed by a nonlinear function, regressed from the experimental collected data Based on the magnetic parameters observed from the prototype, the estimated inductance curves are compared with the experimentally measured curves Finite Element Method (FEM) is also applied to verify the developed mathematic model Finally, simulations and experiments are carried out to verify the proposed model The results show that the proposed method can be applied to analytically express the machine nonlinearity