Xikai Sun

Optimal Design of Double-Layer Permanent Magnet Dual Mechanical Port Machine for Wind Power Application

Dual mechanical port (DMP) machine, a continuous electrical variable transmission, is a very competitive alternative for vulnerable constant speed-ratio mechanical gearbox. In this paper, an optimal design method of a double-layer permanent magnet (PM) DMP machine for wind power application with random low wind turbine speed input and constant high synchronous speed output is proposed. With the stator efficiency and the cooling effect of the inner rotor as reference, an analytical model is built for the initial design of the machine and the finite element analysis (FEA) is investigated for optimization. Then, FEA results are given and the over-load capability of the machine is evaluated. Finally, a 10 kW DMP prototype machine with the cooling system is designed.

Coupled Electromagnetic-Thermal-Mechanical Analysis for Accurate Prediction of Dual-Mechanical-Port Machine Performance

The performance of an electrical machine depends not only on electromagnetic (EM) parameters but also on the cooling system, the mechanical deformation, and the control system, which are closely coupled with each other. In this paper, a coupled EM-thermal-mechanical analysis for accurate prediction of dual-mechanical-port (DMP) machine performance is proposed. A unified model for the coupled analysis with the same mesh is built, in which the material properties are nonlinear and adjusted on the basis of temperature distribution. Two-dimensional EM finite-element analysis is carried out with the temperature feedback from thermal analysis. The detailed temperature distribution is derived from the losses in the EM analysis. Then, with the force and temperature distributions, mechanical analysis of the surface-mounted permanent-magnet outer rotor with glass fiber is implemented to examine the mechanical deformation and testify the mechanical strength under rated working condition. Finally, with the coupled analysis, a prototype DMP machine is designed, fabricated, and tested in the laboratory. Experimental results are given to verify the accuracy of the proposed analysis.

Application of Electrical Variable Transmission in Wind Power Generation System

In the widely applied non-direct driven wind power generation system, a gearbox is connected between the wind turbine and the high speed doubly-fed induction generator (DFIG) so that the system could be smaller and supply power with constant voltage and constant frequency as the wind turbine speed varies. However, the multi-level mechanical gearbox is rather vulnerable and poses many difficulties to maintain. Electrical variable transmission (EVT), an electrical continuous variable gearbox, is a very competitive alternative for vulnerable constant speed-ratio mechanical gearbox. In this paper, the application of EVT in wind power generation system with its unique power conversion characteristics is presented. EVT machine structures and the main principles of the EVT-based wind power generation system are introduced. Unique power conversion characteristics of the EVT-based system are investigated and compared among the conventional DEIG system and direct-driven permanent magnet generator (PMG) system. A controller without maximum power point tracking (MPPT) control to the outer rotor is implemented in Matlab/Simulink and speed sensorless control of the inner rotor is tested. The operational principle and the operation modes are evaluated by computer simulation and system experiments.

Comparative study of linear double salient permanent magnet motors

In this paper, two novel structures of linear double salient permanent magnet motor (LDSPM) having magnets, armature windings in primary are proposed and compared, including the configurations and static characteristics based on finite element analysis. The results indicate that the proposed topology can avoid the asymmetry of back-EMF waveforms and reduce cogging force and thrust force ripple.

Analysis of flux-switching permanent-magnet machine by nonlinear magnetic network model considering saturation

In this paper, a nonlinear magnetic network model considering saturation is proposed for a three-phase 12-stator-slot/10-rotor-pole flux-switching permanent-magnet motor, which can predict the open-circuit air-gap field distribution, phase PM flux-linkage, phase back-electromotive force (back-EMF) waveform and winding inductances with considerable accuracies. The predicted results are confirmed by both finite element analysis and experimental measurements.

Design and analysis of permanent magnet induction generator for grid-connected direct-driven wind power application

Without power electronics and mechanical gearbox, the permanent magnet induction generator (PMIG), a new grid-connected direct-driven wind generator concept, is considered to be a highly efficient, low maintenance solution for high capacity offshore wind power generation system. In this paper, the characteristics and optimal design method of this generator for wind power application are investigated. The working principle and the dynamic model are deduced. Two kinds of permanent magnet rotors as well as the magnetic characteristics are analyzed and compared by the magnetic circuit. The size equation is analytically derived and the initial calculation of machine dimensions and parameters, namely, the core diameter, stack length, and permanent magnet size, are also discussed. Moreover, finite element analysis (FEA) is carried out for design optimization, in which the machine overload capability and demagnetization protection under grid short circuit fault are investigated. Finally, a design guideline form the PMIG is developed. A 10 kW prototype machine is built in the laboratory and the experimental results are given to verify the design and analysis.

Comparison of flux-regulation capability of a hybrid-excited flux-switching machine with different magnet materials

This paper investigates the flux-regulation capability of a novel hybrid-excited flux-switching (HEFS) machine with alternative magnets materials based on finite element analysis. It is found that in the case of Ferrite the air-gap flux can be modulated to a wide range, while in the case of NdFeB, the regulation capability is limited due to high saturation.

Mechanical design of outer-rotor structure for dual mechanical port machine

Recent years, a new kind of dual mechanical port (DMP) machine is widely researched because of its high prospect in wind power application and hybrid vehicles as a variable gearbox. In this paper, the mechanical design of both double-layer surface mounted and buried permanent magnet (PM) outer-rotor structures is investigated by both theoretical method and finite element analysis (FEA). Optimal design of buried PM outer-rotor structure is made to and multi-block PM buried structure is proposed and researched to get robust outer-rotor structures with both good electromagnetic and mechanical performances in high speed application. At last different kinds of structure are compared and conclusion is made at a rated speed of 4000r/min application.

Optimal design of a double-stator permanent magnet brushless machine with series magnetic circuit

This paper presents the optimal design of an 18-slot 8-pole double-stator permanent magnet brushless (DS-PMBL) machine. The key is to optimize the split ratio, namely the ratio of the inner-stator outside diameter to the outer-stator outside diameter, to achieve the maximum torque density under the same copper loss. Both the finite element analysis and experimental results are given to verify the proposed optimal design.

Thermal analysis of dual mechanical port machine for wind power application with co-simulation method

Dual mechanical port machine (DMP) — a kind of continuous electrical variable transmission, is a very competitive alternative for vulnerable constant speed-ratio mechanical gearbox in high capacity wind power generation system. As the inner rotor is surrounded by the stator and the outer rotor, the DMP machine suffers from PM demagnetization and insulation failure under severe thermal condition. To calculate the heat sources, like copper loss and iron loss more accurately, a transient co-simulation method which integrates the transient electromagnetic analysis into system circuit simulation and takes not only the spatial harmonics of the motor but also PWM and control logics into consideration is employed. The precise knowledge of temperature distribution and the design of cooling system are investigated by finite element method (FEM).