Fengxiang Wang

Modeling and simulation of variable speed constant frequency wind power generation system with doubly fed brushless machine

The variable speed constant frequency (VSCF) wind power generating system with doubly fed brushless generator (DFBG) has the advantage of high reliability and high efficiency. This paper introduces the structure of DFBG and the composition of VSCF wind power generating system with DFBG. The coupling inductance parameters of DFBG are also given and analyzed. Based on MATLAB/SIMULINK technology, the simulation model of DFBG was built, and the control performances of VSCF wind power generation system with DFBG are simulated. The results show that the DFBG can realize VSCF operation and the DFBG simulation module built in this paper can be used for simulation study on the DFBG and associated control systems.

A new control strategy by combining direct torque control with vector control for doubly fed machine

A new control strategy by combining vector control with direct torque control is proposed in this paper. The new method has the advantages of both vector control and direct torque control, such as fast response and easy implementation without field orientation. The detailed operation principle, implementation method and simulation result of the proposed control strategy are discussed.

A Multi-Pole Low Speed Doubly Fed Brushless Generator for Direct Driven VSCF Wind Power System

Doubly fed induction machines are widely used in large variable speed constant frequency (VSCF) wind power generation system due to low cost. However, the brushes and slip ring of the conventional doubly fed machine not only need regular maintenance but also reduce the reliability of the wind power system. There is currently a great deal of interest in directly driven generator without gears. The reliability and efficiency of the wind power generation system will be increased in a direct driven brushless wind generator. This paper introduces a multi-pole low speed doubly fed brushless generator (DFBG) for direct driven VSCF wind power system which not only keeps the low cost feature of the doubly fed wind generator but also increases the operation reliability due to the gearless and brushless structure. The design, simulation and control strategy of the DFBG are discussed in detail.

Operation principle and control method of a linear motor made by magnetically controlled shape memory alloy

Magnetically controlled shape memory (MSM) materials are a new way to produce motion and force. The material changes shape in a magnetic field. Shape changes are even 10 percent and response time is less than a millisecond. Usual applications of the material are actuators that produce linear motion. In this paper the magnetic controlled properties of MSM material, the operation principle, design and control method of an inchworm type linear MSM motor are introduced. The tested results of a prototype machine are also presented.

Comparison of High Speed PM Generator with PM Doubly Fed Reluctance Generator for Distributed Power Generation System

The high speed permanent magnet (PM) machine has been widely used in compressor, energy storage flywheel, and distributed power generation since it has high speed, small size, high efficiency and power density. The PM doubly fed reluctance machine is a combination structure of a reluctance rotor with stator having three-phase winding and PM, which has similar feature with reluctance. Taking the high speed generator distributed generation system as an example in this paper, the comparative study on the above two kinds of machine shows that the PM machine has better electromagnetic property and the PM doubly fed reluctance machine has better mechanical behavior.

Actuation principle and property of magnetically controlled shape memory alloy actuators

This paper introduces the operation principle of magnetically controlled shape memory alloy (MSMA) actuators based on the shape variation of the NiMnGa alloys under external magnetic field. The experimental results show that the relationship between strain of MSMA and magnetic field is a nonlinear characteristic with saturate nature. Under the condition of constant temperature and magnetic field, the strain of the MSMA reduces linearly with respect to the pre-pressure increment. The magnetic control property of MSMA is sensitive to the temperature variation, and can be held only in the martensite phase. The tested dynamic magnetically conductive characteristics of MSMA show that the magnetic permeability of the MSMA is not constant, and reduces with respect to the increment of magnetic field. The relative saturate magnetic permeability of MSMA is about 1.5. Therefore, the MSMA is almost a non-magnetically conductive material.

Study on cogging torque reduction methods of PM stepping motor

Cogging torque is the main factor that causes a PM stepping motor to be shaken, noisy and even influences its safe operation. After introducing the structure of PM stepping motor, this paper analyzes the effect of the power supply mode on the electromagnetic torque, and the measures to reduce cogging torque of PM stepping motor. The calculation and comparison of several different design techniques for reducing the cogging torque are discussed based on finite element analysis.

Characteristic Simulation of Adjusting Speed System With Doubly-Fed Brushless Machine

After introducing simply the structure and operation theory of doubly-fed brushless machine (DFBM), the coupling parameters between main winding and auxiliary winding are analyzed. The mathematics model of the DFBM is derived and constant power angle control strategy in the real coordinate is also put forward in this paper. Based on SIMULINK technology, the common simulation module of DFBM has been built. The correctness and credibility of mathematics model and common simulation module have been proved by the consistency of the simulation and experimental results

A Novel Mathematic Model of Doubly Fed Brushless Machine

Due to the different pole numbers of power winding and control winding, the rotating speeds of magnetic fields generated by the two winding currents of the doubly fed brushless machine (DFBM) are different. Different rotating reference frames are usually needed to analyze the performance of the DFBM. In order to simplify the complicacy of the mathematic model and to implement easily vector control, a new model of DFBM based on the slip frequency rotating equivalent control winding is proposed in this paper. By taking the equivalence that the rotating magnetic field generated by the stationary stator control winding can be produced by an equivalent rotating winding with the slip frequency rotating speed like the rotor winding of a wound rotor induction machine. The new model of DFBM can be used for performance analysis and vector control in the same way as that of the conventional wound rotor induction machine.

The Effect of Design Parameters on Coupling Capability of Brushless Doubly Fed Wind Power Generator

Recent work has illustrated benefits of the brushless doubly fed generator (BDFG) in wind power generation applications. Coupling capability between the stator main and auxiliary windings is the most significant factor which affects the power density and operation performance of the BDFG. In this paper, the calculation method for the winding inductance parameters are put forward based on winding function. The effect of different design parameters, such as pole numbers, pole- arc factor and winding pitch and so on, on coupling capability is investigated by inductances and their waveforms obtained from above method. It is found the design parameters should be selected appropriately in order to get the optimum coupling inductances and operation characteristics of the BDFG.