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Improved Fractional-order Damping Method for Voltage-controlled DFIG System Under Weak Grid

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Journal of Modern Power Systems and Clean Energy 2022年第6期10卷 1531-1541页

作者： zhen xie Xiang Gao Shuying Yang Xing Zhang School of Electrical Engineering and Automation Hefei University of TechnologyHefeiChina

When a doubly-fed induction generator(DFIG)is connected to a weak grid,the coupling between the grid and the DFIG itself will increase,which will cause stability *** is difficult to maintain the tracking accuracy and robustness of the phase-locked loop(PLL)in the weak grid,and the risk of instability of the current-controlled DFIG(CC-DFIG)system will *** this paper,a new type of voltage-controlled DFIG(VC-DFIG)mode is adopted,which is a grid-forming structure that can independently support the voltage and frequency with a certain adaptability in the weak grid.A small-signal impedance model of the VC-DFIG system is also *** impedance of DFIG inevitably generates coupling with the grid impedance in the weak grid,especially in parallel compensation grids,and results in *** the basis of the VC-DFIG,impedance stability analysis is performed to study the influences of the control structure and short-circuit ***,a feedforward damping method is proposed to modify the impedance of the VC-DFIG system at resonance *** proposed fractional order damping is utilized,which can enhance the robustness and rapidity of resonance suppression under parameter ***,the experimental results are presented to validate the effectiveness of the proposed control strategy.

关键词： Weak grid voltage-controlled doubly-fed induction generator(DFIG) resonance feedforward damping fractional-order damping

Immobilization of heavy metals in sludge using phosphoric acid and monobasic calcium phosphate

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第3期14卷 177-186页

作者： Ping TANG Yong-chao ZHOU zhen-miao xie College of Environment and Material Engineering Hangzhou Dianzi University College of Civil Engineering and Architecture Zhejiang University

The purpose of this research is to investigate the potential of pre-treatment with phosphoric acid(PA) and monobasic calcium phosphate(MCP) for the stabilization of heavy metals in sludge and its bottom *** tannery sludge samples were collected in Wenzhou,China and heavily contaminated with heavy metals,such as Pb,Cr and so *** samples were pre-treated with PA or *** XRD and TCLP tests were adopted as the evaluating methods to characterize the Pb,Cr,Cu,Zn and Cd immobilization in the pre-treated sludge and its bottom *** results showed that this treatment effectively immobilized Pb and Cd in the sludge,lightly stabilized the metal Cu,and adversely,enhanced the leachability of *** incineration at 900℃,Pb and Cr in the bottom ash of pre-treated sludge were significantly stabilized due to the formation of their highly thermostable phosphates and pyromorphite-like minerals during the incineration ***,an increase of Cu and Zn solubility was observed which might be attributable to the acidification of sludge due to the addition of PA or MCP.

关键词： Tannery sludge Bottom ash Heavy metals Phosphate Stabilization

Sequence Impedance Model and Resonance Damping of Voltage Source based DFIG 32

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Sequence Impedance Model and Resonance Damping of Voltage So...

Coordinated Primary Frequency Regulation and Inertia Response Based on DFIG using Over Speed and Torque Reserve 36

第32届中国控制与决策会议

作者： CHEN Junhe xie zhen National and Local Joint Engineering Laboratory for Renewable Energy Access to Grid Technology Hefei University of technology

ISBN: (纸本)9781728158549

When a voltage-source based doubly fed induction generator（DFIG） wind power system is connected to a parallel-compensated weak grid, due to the impedance interaction between the two systems, the problem of medium-high frequency resonance is prone to occur. In order to solve the problem of medium and high frequency resonance and improve the stability of the operation of the voltage-source based DFIG wind power system when connected to the parallel compensation weak grid, this paper proposes an active damping resonance suppression control strategy. First, the harmonic impedance linearization method was used to establish the sequence impedance model of the voltage-source based DFIG. Then, based on the impedance model, the stator current is fed forward into the current inner loop of the generator-side converter in real time, and the combined damping of virtual positive resistance and positive capacitance is used to reshape the DFIG wind power system impedance to achieve medium-high frequencies. Purpose of resonance suppression. Experimental results verify the effectiveness of the proposed DFIG system damping control strategy.

关键词： Voltage-source based DFIG Active damping resonance Medium-high frequency resonance

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Coordinated Primary Frequency Regulation and Inertia Respons...

Experiments on self-excited oscillation in a thin-walled collapsible tube

第36届中国控制会议

作者： FENG Yantao xie zhen School of Electrical Engineering ＆ Automation Hefei Univ.Tech

ISBN: (纸本)9781538629185

large scale integration of wind farm combined to the grid is a tendency for the development of the new energy,which causingthe issue of low system *** analyzingthe mode of operation and the Maximum Power Point Tracking strategy（MPPT）of double fed induction generator（DFIG）,reviewing advantage and disadvantage of scholars’ works on inertia control in thepast few years,this paper proposed a new strategy to mode the DFIG,that is over speed and torque *** wind farm changes its electromagnetic power depending on the frequency of the gird,as a result,the reduced the drop of frequency and increase the inertia of the *** the other hand,the farm coordinates primary frequency regulation and avoids the second frequency *** paper builds a system with Simulink to validate the strategy,and the results confirmed its effectivenes s.

关键词： double fed induction generator virtual inertia over speed torque reserve

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Acta Mechanica Sinica 2015年第6期31卷 817-826页

作者： Hai-Jun Wu Lai-Bing Jia xie-zhen Yin Department of Modern Mechanics University of Science and Technology of China Department of Naval Architecture and Marine Engineering University of Strathclyde

Self-excited oscillation in a collapsible tube is an important phenomenon in physiology. An experimental approach on self-excited oscillation in a thin-walled collapsi- ble tube is developed by using a high transmittance and low Young＇s modulus silicone rubber tube. The elastic tube is manufactured by the method of centrifugal casting in our laboratory. An optical method for recording the evolution of the cross-sectional areas at a certain position along the longitudinal direction of the tube is developed based on the technology of refractive index matching. With the transparent tube, the tube law is measured under the static no-flow condition. The cross section at the middle position of the tube transfers from a quasi-circular configuration to an ellipse, and then to a dumbell-shape as the chamber pressure is increased. During the self-excited oscillation, two periodic self-excited oscillating states and one transitional oscillating state are identified. They all belong to the LU mode. These different oscillating states are related to the initial cross-sectional shape of the tube caused by the difference of the downstream transmural pressure.

关键词： Collapsible tube Refractive index matching ·Cross-sectional area measurement· Self-excited oscillatingstates LU mode

NUMERICAL ANALYSIS OF THE UNSTEADY FORCE IN INSECT FORWARD FLIGHT

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Journal of Hydrodynamics 2006年第2期18卷 143-147页

作者： ZHA Xiong-quan LU Xi-yun YIN xie-zhen Department of Mechanics and Mechanical Engineering University of Science and Technology of China Hefei 230026 China

The objective of this study is to get into physical insights to the unsteady force and the relevant mechanisms in forward flight of insects. Unsteady force in the forward flight was studied, based on a virtual model problem of a foil with oscillating translation and rotation in a uniform flow, by solving the two-dimensional incompressible Navier-Stokes equations with a finite element method. The effects of typical parameters, including the advance ratio, the inclined angle of stroke plane, the stroke amplitude, and the amplitude of pitching angle of attack, on the forces and the flow structures were analyzed.

关键词： unsteady flow vortex dynamics thrust and lift,flapping motion biomechanics

Viscoelastic Characteristics of Fins, Muscle and Skin in Crucian Carp (Carassius Auratus) Described by the Fractional Zener Model

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Chinese Physics Letters 2011年第8期28卷 340-343页

作者： CHEN Ming JIA Lai-Bing YIN xie-zhen Department of Modern Mechanics University of Science and Technology of ChinaHefei 230027

Fish are supposed to be able to adapt to various underwater *** mechanical properties of the body of a fish is of essential importance in order to explore the source of high efficiency during fish *** investigate the viscoelastic properties of the fins,muscle and skin of Crucian carp(carassius auratus).A fractional Zener model is used to fit the relaxation force and the results show that the model can describe the relaxation process *** a Fourier transform,we discuss the response functions of the fins,muscle and skin of Crucian carp under the external excitation of a harmonic *** of these results with the cruising frequency of Crucian carp shows that the dissipation due to internal viscoelasticity during cruising is small.

关键词： fish relaxation Skin

Control strategy of wide-speed-range doubly fed induction generator based on stator-winding short circuited in low speed mode 36

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Control strategy of wide-speed-range doubly fed induction ge...

Numerical simulation study on the effect of temperature on the restricted diffusion in porous media

第36届中国控制会议

作者： Li Mengjie WANG Lingxiang xie zhen School of Electrical Engineering & Automation Hefei University of Technology

ISBN: (纸本)9781538629185

When the doubly-fed induction generator(DFIG) is acting as a generator,for its limit of the power electronic converter rating,making the DFIG can only work at the speed of the range of the synchronous speed plus or minus 30%.So,when wind speed is low,the DFIG cannot work as a *** paper adopts a combinatorial topology which is wide-speed-range DFIG(WDFIG).If the wind speed is low,the stator-winding of DFIG is short circuited,and the stator flux of DFIG is controlled by rotor side converter(RSC) also generating to grid through rotor side *** the wind speed is high,the stator-winding of DFIG which is short circuited become connecting to the power grid directly,and its architecture is same as the traditional *** this paper,DFIG simplified mathematical model is first displayed and the method of stator-flux-oriented vector control(SFOVC) is adopted,then this paper displayed the simplified mathematical model of the two topology in d-q synchronous rotating reference frame,on that basis,deducing the control ***,in order to guarantee the uninterruptible operating of the system,and avoid the lash such as flux,current,voltage and so on when the structure of the stator-winding of DFIG change from short circuited mode to grid connected *** paper gives theoretical analysis for the suitable switching moment,that ensure the variation range of flux,current,voltage during the switch moment are within *** last,the simulation results proved that the proposed control architecture could ensure the DFIG work as a generator no matter wind speed is low or high.

关键词： Doubly-fed induction generator Rotor side converter Stator-flux-oriented Stator-winding short circuited Switched control architecture

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Magnetic Resonance Letters 2023年第2期3卷 118-126,I0003页

作者： zhen xie Lizhi Xiao Sihui Luo Guangzhi Liao College of Artificial Intelligence China University of PetroleumBejing102249China State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing02249China College of Carbon Neutral Energy China University of PetroleumBeijing102249China

It is of great significance to study how temperature affects the restricted diffusion in pores for an accurate evaluation of reservoir physical properties by using nuclear magnetic resonance(NMR)diffusion-transverse relaxation(D-T2)spectrum under reservoir temperature *** this paper,we simulate the restricted diffusion and twodimensional(2D)NMR D-T2 spectra of water molecules at different temperatures using random-walk *** one-dimensional(1D)restricted diffusion simulation results show that the diffusion coefficient in the pore at room temperature decays with the diffusion time and eventually reaches a *** the condition of long-time diffusion,the ratio of restricted diffusion coefficient to bulk diffusion coefficient at different temperatures tends to be the same *** the increase in temperature,the simulated D-T2 spectra also gradually move *** simulated D-T2 spectra at all temperatures are consistent with the Pade interpolation *** addition,the results calculated by Pade interpolation equation demonstrate that the degree of temperature influence on the D-T2 spectrum of rock is quantitatively related to the pore radius,porosity and cementation index.

关键词： D-T_(2)spectra Temperature Restricted diffusion Numerical simulation