Jing Feng Mao

Modeling and Decoupling Control of Grid-Connected Voltage Source Inverter for Wind Energy Applications

This paper investigates the modeling and decoupling control of grid-connected voltage source inverter (GC-VSI) for wind energy conversion system (WECS) applications. Firstly, the typical configuration and operation principle of the direct-driven grid-connected WECS are analyzed. Then, by means of input-output modeling method and instantaneous active power theory, a time domain mathematical model of the GC-VSI is set up. Besides, in order to resolve the GC-VSI active current and reactive current cross-coupling nonlinear control problem, a vector decoupling control method for the GC-VSI firing pulse generation is deduced in the dq synchronous rotating coordinates. The proposed decoupling control method can realize the active power and reactive power of the GC-VSI injected into the grid are regulated independently. Finally, the performance of the proposed GC-VSI system is evaluated by using MATLAB/Simulink simulation.

Sliding Mode Control of Magnetic Bearing System Based on Variable Rate Reaching Law

In order to eliminate the chattering phenomena caused by conventional sliding mode control (SMC) method in magnetic bearing system control, this paper proposes a variable rate reaching law approach based sliding mode controller to achieve higher system stability and robustness. In this control law, system states’ normal numbers are brought in to automatic adjust the gain of the switching control part of SMC. The controller output amplitude of chattering can be progressively damped, and the system will converge to zero asymptotically. The system stability is proved by Laypunov theory, and the prerequisite of control law parameters design is deduced out. Simulation results show that the proposed SMC control method has effectiveness in dynamic suspension position tracking performance and obtaining system robustness.

Self Adaptive Integral-Type Sliding Mode Control for Supporting Structure of a Magnetic Vertical Axis Wind Turbine

Vertical axis wind turbine (VAWT) plays one of the important roles in wind power equipments. When joining the magnetic levitation technology, the VAWTs can effectively reduce the friction torque to improve startup performance and increase the power coefficient. At the same time, the mechanical vibration can be reduced, and its actual functioning time can be extended. In this paper, the structure, working principle and mathematical model were introduced respectively with an intention to present the magnetic supporting structure of a VAWT. Then the self adaptive integral-type sliding mode control (AISMC) was offered and designed. Compared with convention-al PID control, the simulations show that the system under the AISMC control has a better dynamic response and robust characteristic.

Design of an Electromechanical Coordination Vibration Suppression Method for VAWT Main Spindle

Because of its advantageous aerodynamic performance, the vertical-axis wind turbine (VAWT) has gained more and more attention. This paper studies the vibration characteristic of the VAWT main spindle, and presents a mechanical and electromechanical coordination vibration suppression method for the VAWT main spindle. The proposed method can measure main spindle current vibration intensity in real-time. And when the main spindle vibration intensity exceeds preset critical control threshold value, the method can use both the on-line intelligent analysis decision and the mechanical and electromechanical coordinated controller to suppress the main spindle vibration, as well as to make the VAWT maintain mechanical stability. At the same time, the method can ensure the VAWT meets maximum wind energy capture efficiency as far as possible.

Statics Analysis on Workbenches of Three Kinds of Electromaglev Linear Feed Unit

Based on the disciplines theory such as the mechanics and electromagnetics, this paper presents three kinds of electromaglev linear feed unit, with the help of the 3D modeling software Solidworks and large general purpose finite element analysis software ANSYS. The statics analysis on workbenches of the three kinds of electromaglev linear feed unit are made by using of ANSYS, then the results are analyzed and compared. It can be identified as the conclusion that, the structural stiffness on workbenches of the three kinds of magnetic linear feed unit can basically meets the requirement, and all of them can be selected as the needed structural design. But the four-L separately suspended and oriented type electromaglev linear feed unit has the better structure stiffness, and take the weight, cost, load capacity and dynamic characteristics and other factors into account, we preferred to choose the workbench design of the four-L-pillar separately suspended and oriented type electromaglev linear feed unit.

Study on the Multiple Voltage Source Inverter for Grid-Connected Large-Scale Wind Energy Conversion System

This paper proposes a novel grid-connected multiple voltage source inverter (VSI) for large-scale wind energy conversion system (WECS) applications. Firstly, the typical configuration, operation principle and mathematical modeling of the direct-drive grid-connected WECS are analyzed in brief. Then, a suitable topology of the grid-connected multiple VSI composed of two six-pulse inverters, two separate zig-zag transformers and a dc-link capacitor is presented. In order to reduce numbers of commutations and to increase dc-link voltage utilization ratio of the proposed grid-connected multiple VSI, a quasi twelve-pulse phase-shift PAM switching strategy is demonstrated. Finally, a simulation test system is set up by using MATLAB/SIMULINK, and the results of simulation validate the effectiveness of the proposed grid-connected multiple VSI.

Fault-Tolerant Permanent Magnet Synchronous Linear Motor

The principle and characteristics of Fault-tolerant Permanent Magnet Synchronous Linear Motor are introduced. The design or computational method of the polar distance of concentrated winding coil, the armature parameters, the armature winding parameters, the coil diameter, the distance from the adjacent armature windings are given. The magnetic thrust equation is derived, and the core issues are analyzed. It provided theoretical basis for structural optimization of the Fault-tolerant Permanent Magnet Synchronous Linear Motor.

The Analysis of Radial Magnetic Bearing’s Magnetic Field in Active Magnetic Bearing Electric Spindle Unit

Introduced the working principle of active magnetic bearing unit and took the electric spindle with 5.5kW for example, finite element analysis of the magnetic fields of radical magnetic bearing was analyzed through finite element analysis by ANSYS software to find out the variation of magnetic field distribution and affecting factors. Analysis results showed that radical magnetic bearing had small leakage magnetic field, the principal axis’ maximum offset from the ideal center line was 0.0025mm and the principal axis had superior radical running accuracy when the circularity of supporting journal on principal axis was 0.003mm, the unilateral air-gap value was 0.3mm while the principal axis suspended normally and the inside track’ circularity of magnetic pole was 0.007mm. It can meet the working requirements of precision machine tool. The research results provided theoretical basis for structural optimization of the active magnetic bearing unit.

Research on Switched Reluctance Generator for Off-Grid Variable-Speed Wind Energy Applications

This paper presents a theoretical analysis and experimental evaluation of the switched reluctance generator (SRG) for off-grid variable-speed wind energy applications. The detailed model, control parameters and operational characteristics of the SRG as well as variable-speed wind turbine are discussed. In order to drive the wind energy conversion system (WECS) to the point of maximum aerodynamic efficiency, a SRG power output feedback control strategy which optimized angle position-current chopping control cooperating PI regulator is proposed. The control strategy is also demonstrated by means of Matlab/Simulink. Moreover, an experimental test system is set up, which a cage induction machine is used to emulate the variable-speed wind turbine. The experimental results validate the proposed control strategy and confirm the SRG performance.

Research on Electromagnetic Field Analysis of Magnetic Levitation Rail Machine

This paper introduced the working principle of magnetic levitation rail machine and carried out the magnetic analysis. Take the weight of 132N simulation workbench prototype for example, finite element analysis of rail electromagnetic fields is applied through ANSYS software to find out the variation law of magnetic field distribution and affecting factors. Analysis shows that magnetic levitation rail machine has small leakage magnetic field, high load capacity and large anti-external disturbances capacity if the parallelism and the straightness of magnetic levitation rail machine are no more than 0.1mm and 0.2mm respectively when the table is suspended normally. The research results provides theoretical basis for structural optimization of the magnetic levitation rail machine.