Guo Qing Wu

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.

Finite Element Analysis of Thrust Bearing Magnetic Field in 22KW Spindle

There is a magnetic field inside thrust bearing. The magnetic field distribution is one of the key factors which decide the running state and performance. With the finite element of ANSYS software, the magnetic field of thrust bearing has been analyzed. The rule of changes between the magnetic field and the influencing factors has been discovered. The analysis shows that the direction of exciting current should be opposite other than identical. The greater the ratio of gap length between stator and rotor and working gap length is, the less magnetic field leakage is. The flux leakage of thrust bearing attains 37 percent when the ratio of the gap is 4.0. If the design of a complete machine is not proper, the flux leakage may attain 20 percent upwards through other gaps although that of the bearing itself is almost zero. Calculation of bearing capacity indicates that theoretical value is not exact due to its neglect of magnetic saturation and flux leakage, while FEM value comparably matches the real substance with considering the magnetic saturation and flux leakage. The research provides the theoretical basis for optimization of system structure and selection of current direction control.

The Analysis of Monitoring System of Wind Turbine

Monitoring system of wind turbine is the guarantee of normal operation of the wind turbine. It has significance on the study, promotion and application of wind turbines. The research status of wind turbine monitoring system was mainly elaborated. The structure of wind turbine monitoring system was analyzed. The monitoring systems based on VB, VC, configuration software and LabVIEW have been made a comparison. And several further research directions of the wind turbine monitoring system have been proposed.

Vibration Test of Bearing Ball Fatigue Testing Machine Based on VB

Ball bearing life test, once the failure specimen ball fatigue, if not timely shutdown, will lead to a series of chain reactions caused by the fault processing is not seasonable, serious word may also lead to the damage of equipment. Therefore the vibration test is very important to accurately determine the specimen failure, ball. In this paper, the vibration test for bearing fatigue testing machine, the test results to be real-time and accurate judgment sample ball failure.

Simulation Experiment of Roll Bending Machine in Valveless Servo System

Valveless servo system is a new technology which is widely used in recent years. Compared to the traditional hydraulic system, valveless servo system has a lot of advantages such as high efficiency, less pollution and saving energy, which will be the main research direction of the hydraulic control in the future. Roll bending machine is a large industrial machine, but the efficiency of existing hydraulic system of roll bending machine is low and the cost of maintenance management is high. Applying valveless system on roll bending machine can overcome these defects. This paper made a study of the control strategies which were about valveless servo system on roll bending machine. And software MATLAB was used to do simulation experiment on valveless servo system. This paper summarized the steady-state error and dynamic characteristics according to output signals in different input signals.

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.

The Friction and Wear of Silicon Nitride Ceramic with BSA Lubricant

To research the friction and wear of silicon nitride ceramic with bovine serum albumin lubricant, the tribological properties of silicon nitride ceramic against stainless steel were investigated on CETR UMT-2 under lubrication of bovine serum albumin, deionized water, physiological saline and physiological saline mixed with bovine serum albumin. The worn surfaces of silicon nitride ceramic ball and stainless steel pin were examined with a digital microscope (VHX-2000). The friction coefficients of steady state are 0.26, 0.35, 0.69 and 0.8 under bovine serum albumin, physiological saline mixed with bovine serum albumin, physiological saline and deionized water. The lowest friction coefficient of steady state is 0.26 which is under lubrication of bovine serum albumin. The highest friction coefficient is 0.8 under the lubrication of deionized water. The measured worn areas of silicon nitride ceramic balls are 1282.3μm2, 1898.6μm2, 2753.9μm2 and 3645.7μm2 under bovine serum albumin, physiological saline mixed with bovine serum albumin, physiological saline and deionized water. The smallest worn area of silicon nitride ceramic ball is 1282.3μm2 which is measured under the lubrication of bovine serum albumin. The highest worn area of silicon nitride ceramic ball is 3645.7μm2 which was measured under the lubrication of deionized water. The same wear mechanism of silicon nitride ceramic ball had been found under the lubrication of bovine serum albumin, deionized water, physiological saline and physiological saline mixed with bovine serum albumin. The depth of scratches of worn surface of silicon nitride ceramic ball lubricated with BSA is 3μm which are the shallowest.

Tribological Characteristics of Silicon Nitride Ceramic in Three Water-Based Lubricants

The friction coefficient of tribology pair between silicon nitride ceramic and stainless steel was researched with bovine serum albumin, saline and water lubricants. The coefficient of friction of silicon nitride in bovine serum albumin is lower than those in saline and water. Using digital microscope, the worn surfaces of silicon nitride and stainless steel were viewed. The groove depths of worn stainless steel surface were measured. The depth with bovine serum albumin is shallower than those in saline and water. The results showed that ceramic in bovine serum albumin has good tribological characteristic. This research provides the reference for the development of ceramic artificial joint.

Design and Simulation of the Hydraulic Synchronous Control System of the Upper Roller in Bending Machine

This paper sketches the overall structure of the hydraulic system of bending machine, and designs the hydraulic synchronous control system of the upper roller in bending machine. Then making use of AMEsim software to establish hydraulic system simulation model to analyze the pressure, velocity, displacement and other parameters of hydraulic cylinders in two cases when in open loop and closed loop system. After that, use PID algorithm to simulate the upper roller of bending machine in hydraulic closed loop synchronous system, which verifies that it can meet the motion requirements and get a higher synchronous precision.

10 kw Vertical Axis Wind Turbine Spindle Design and Optimization

The spindle of a 10 kw vertical axis wind turbine is designed in this paper, and the relevant geometric parameters is given, and build the geometry of the finite element model. Calculation of the spindle under wind load and dead weight , and analyse the spindle Von Mess stress, deformation nephogram, and give the former six order vibration mode of the spindle. Through the analysis, Then the design parameters of the spindle are optimized. and the optimized structure of spindle has been got. optimized spindle is in lower quality, more satisfy the requirement of wind turbine running under high load at the same time .