Table of Content

25 October 2018, Volume 46 Issue 10

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Power & Electrical Engineering

The Design of Phase Locked Loop Based on the Improved SOGI

OUYANG Sen MA Wenjie

2018, 46(10):  1-8.  doi:10.3969/j.issn.1000-565X.2018.10.001

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This paper proposes a PLL based on double second-order generalized integral (DSOGI-PLL) of abstracting grid voltage phase quickly and accurately for low accuracy of traditional PLL in the case of the unbalanced grid voltage in grid-connected PV systems. Firstly, the principle of the SOGI, which can effectively extract the grid voltage positive sequence component, to be used as a quadrature signal generator is analyzed. Secondly, to eliminate the influence of DC offset, an improved structure of SOGI is proposed. So a novel PLL applicable to the case of unbalanced grid which can eliminate the influence of DC offset is shown. Finally, the effectiveness of the proposed PLL is varied by simulation and experiment.

Application of Finite Set Model Predictive Control in VIENNA Ｒectifier

DU Guiping DU Fada

2018, 46(10):  9-14.  doi:10.3969/j.issn.1000-565X.2018.10.002

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The application of finite set model predictive control (FCS-MPC) in three-phase three level VIENNA rectifier is introduced in this paper. The finite set model predictive control uses the discrete characteristic of the converter and the limited switch characteristic directly. Modulation is not needed, and it is easy to add the constraint terms. With these characteristics of FCS-MPC, the mathematical model, objective function and the rolling optimization strategy of VIENNA rectifier are established. Midpoint balance constraints is added directly to the objective function. The midpoint potential balance is realized directly. A 1.8KW platform is built to verify the feasibility of this control strategy in VIENNA rectifier. It can achieve unity power factor, output voltage stability and neutral point potential balance, and the system has strong robustness.

Sheath Currents Model and Parameter Calculation Method on High Voltage Cable Sheath Multipoint Grounding

ZHU NingXi YANG Fan LIU Gang

2018, 46(10):  15-23,49.  doi:10.3969/j.issn.1000-565X.2018.10.003

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In order to explore the variation of sheath current on high voltage (HV) cable metal sheath multipoint grounding, a model of sheath current based on complex matrix equation was proposed by using centralized parameter circuit model. Combined with the model and mathematical theory, the calculation methods of leakage current and earth current in multipoint grounding branch were proposed. In order to verify the accuracy of the model, simulations were performed by ATP-EMTP. Comparing the simulation results with the calculated values of different grounding modes, laying ways, numbers and locations of multipoint grounding, the average relative error of the model was less than 3.26%, which could be used to calculate the sheath current accurately. The model was used to analyze the variation of sheath current on sheath multipoint grounding at cross connecting models. The results showed that the sheath current peak appeared around the phase-change point. Based on the change rule, a method according to the sheath current value monitored at the head and the end of the cable line was proposed, to judge fault phase and location

Commutation Failure Suppression Strategy Based on Multi-Angle Prediction in Hybrid Dual-Infeed HVDC System

ZHU Jia ZUO Jian LI Yinhong

2018, 46(10):  24-31.  doi:10.3969/j.issn.1000-565X.2018.10.004

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In order to take full advantage of the ability of voltage source converter high voltage direct current (VSC-HVDC) to support the reactive power of the ac system, and suppress commutation failures of line-commutated converter high voltage direct current (LCC-HVDC), this paper proposes a commutation failure suppression strategy based on multi-angle prediction in hybrid dual-infeed HVDC system. Combining two prediction methods, constant extinction area prediction and zero-sequence detection and αβ transform prediction, we obtain the extinction angle reference γref. Then, the required reactive power that is calculated by the difference between the extinction angle reference γref and the setting value γset is fed back to the VSC control loop to adjust the reactive power that VSC generates after fault occurs,and thus to improve the immune ability to commutation failure of LCC. This method doesn’t depend on the mesurement of real extinction angle, so it’s more easier to implement. The simulation result obtained in PSCAD/EMTDC shows that the proposed strategy can improve the ability of suppressing commutation failures of LCC-HVDC.

A Constant Frequency, Non-isolated, Multi-channel LED Driver Based on Variable Inductor

LIU Junfeng TIAN Hanlei SUN WeiHua ZENG Jun

2018, 46(10):  32-41.  doi:10.3969/j.issn.1000-565X.2018.10.005

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The capactive charge balance scheme is widely adopted to eliminate current imbalance in driving multi-channel LEDs due to the high accuracy of current sharing. In order to get the required LED driving current, variable frequency control directly leads to large reactive circulation and increases the stress of devices, and the EMI circuit is complex. Soft switching can’t be guaranteed by constant frequency operation under load variations. Hence, a multiplex LED dimming circuit based on variable inductance (VI) is proposed in this paper, which completes the constant frequency operation, alleviates the complexity of EMI circuit, and realizes the ZVS to improve the energy conversion efficiency. The proposed circuit with superimposed half-bridge structure will increase the number of outputs and simultaneously share resonant inductor, so that the power density is improved and the LED dimming unit is simplified. This paper describes the working principle of the circuit, and takes 8-channel LEDs to build 18W experimental prototype for verifying the feasibility of the LED driver.

RLS-KF Indoor Temperature Predictive Method for Cooling Building based on Equivalent Thermal Model

YAN Jun-wei SHI Kai ZHOU Xuan

2018, 46(10):  42-49.  doi:10.3969/j.issn.1000-565X.2018.10.006

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For the accuracy of indoor temperature prediction method for large cooling building is not high enough to fulfill the requirement of energy optimal control for HVAC system, an equivalent thermal model of building and a recursive least squares - Kalman filtering method (RLS-KF) for indoor temperature prediction are proposed in this paper. In order to describe the unsteady state thermal characteristics of the building, a three order building thermal model is established by equivalent circuit method, and air-conditioning cooling load, ambient temperature and solar radiation intensity are selected as input variables of the model. The RLS method is used to identify the model parameters online, however, aiming at the low prediction accuracy of single RLS method, a pseudo-measurement value is constructed, and the KF algorithm is applied to the room temperature prediction problem. Taking an office building in Guangdong as an example, the results show that the prediction accuracy and stability of RLS-KF algorithm is much higher than that of a single RLS method, and the performance is better at short-term room temperature prediction.

Electronics, Communication & Automation Technology

A Reliability Optimization Method of Power Amplifier Based on Electric-Thermal Analysis on Multiple Heat Sources

MA Yuanbo LI Bin WU Zhaohui WU Haigang CHEN Zhijian

2018, 46(10):  50-57.  doi:10.3969/j.issn.1000-565X.2018.10.007

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The coming 5G communication system is giving great challenge to power amplifier (PA) since the increasing power density and highly integrated package demand. Based on this situation, this paper proposes a novel optimized design method, which combines the electric and thermal analysis result, to improve the reliability of power amplifier. The first step of this method is to design the circuit and layout of power amplifier. The subsequent step is to build an accurate model for thermal analysis based on the calculated parameters from circuit and layout. At last, utilizing the thermal distribution result of multi-heat sources inside chip optimizes the circuit and layout to reduce the working temperature and parameter error. By associating the electric design together with thermal result, the proposed method successfully overcomes the disadvantage of traditional temperature simulation methods which separate thermal analysis procedure from circuit design. In this paper, both circuit design and chip modeling are based on 4G LTE product parameters to verify the feasibility of proposed method. By analyses the temperature distribution of multiple on-chipheat sources and its influence on PA circuit performance, the experimental results confirm that through several circuit design and thermal simulation iterations of this method, the reliability of power amplifier chip can be optimized on the premise of minimizing area cost.

Design of a High-precision CORDIC Algorithm with Compressed Look-up Table

YAO Yafeng ZOU Lingzhi HOU Qiang ZHONG Liang

2018, 46(10):  58-62,71.  doi:10.3969/j.issn.1000-565X.2018.10.008

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Currently researches on CORDIC(coordinate rotation digital computer) algorithm are mainly about 16-bit output accuracy, yet higher precision outputs are needed in areas like digital encryption and information security. If some regular methods are adopted to implement 32-bit CORDIC algorithm, problems like long output delay and huge hardware consumption will arise. The 32-bit CORDIC algorithm, with a compressed LUT(look-up table),was proposed in this paper. The improved design, with less circuit resources and 3 clock periods output delay, compressed and decomposed the LUT according to the inner iteration pattern,folded the range, re-coded the angle, and merged some iterations. Simulation indicates that the size of compressed LUT using fixed-point format is reduced to 1.78%, and the output delay periods are reduced from 8 to 3. Moreover the average of magnitude of output error is 2.3048×10-10. The improved design has some advantages such as less hardware consumption, higher precision and less output delay, and it is more applicable for modern communication occasions that demand for brilliant time-real performance and less hardware resources.

Anti - control of Chaos for Manipulator with Unknown Parameters and Bounded Disturbances

WU Yuxiang LI Yang GUAN Weipeng

2018, 46(10):  63-71.  doi:10.3969/j.issn.1000-565X.2018.10.009

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Anti-control of chaos consists in injecting a chaotic behavior by means of a control scheme to a system, which in natural form does not present it. In this paper, an RBF neural network control algorithm with adaptive terminal sliding mode is proposed to realize the anti - control of chaos for manipulator with unknown parameters and bounded disturbances. The RBF neural network is used to approximate the unknown nonlinear function of the system and the adaptive terminal sliding mode control is used to achieve robustness of the system to external disturbances. The uniform ultimate boundedness of all the signals in the closed-loop system is proved by the Lyapunov stability theorem. Finally, take a two-link planar robot manipulator as a simulation example to verify the feasibility and effectiveness of the proposed method.

Low-rank Enhancement-Based Compressed Image Sensing Reconstruction Algorithm

YANG Chunling TANG Ruidong

2018, 46(10):  72-80.  doi:10.3969/j.issn.1000-565X.2018.10.010

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Most existing compressed image sensing algorithms with outstanding reconstruction performance are based on nonlocal self-similarity of natural images, for the reason that reconstruction based on similar-block groups is more prone to exploit sparsity than reconstruction merely based on individual blocks. But at low sampling rates, limited by poor quality of initial reconstruction results, accuracy of similar-block grouping is badly affected by massive reconstructed interference information, leading to an unsatisfying reconstruction result. To solve this problem, a low-rank enhancement reconstruction algorithm based on GSR is proposed. Firstly, a hybrid filtering reconstruction method is proposed in initial reconstruction that BM3D filtering is introduced to attain a better initially reconstructed result. Then a low-rank enhancement pretreatment is conducted before similar-block grouping to help grouping operation focus more on the key features. Simulation results indicate that compared with GSR, the proposed algorithm possesses a better reconstruction performance at low sampling rates.

Mechanical Engineering

Microstructure and Property of Capacitor-Discharging Projection Welding Joints of T-Type Galvanized Nuts to Hot-Stamping Steels

ZHOU Zhaoyao LUO Jiehan ZOU Chunhua ZOU Chunya

2018, 46(10):  81-87.  doi:10.3969/j.issn.1000-565X.2018.10.011

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Resistance projection welding of speed nuts to USIBOR1500 hot-stamped steels was analyzed by the capacitor discharging welding process (CDW). In this investigation, mechanical properties, weld physical attributes and metallographical examinations were used to evaluate the suitable CDW conditions. Hardness characteristics, failure mode and fracture morphology were studied. With the increase of welding volts, nugget size and pull-out strength increase before expulsion, and failure mode changes to PF- and PF-IF mode from IF mode. Quasi cleavage fracture surface was observed on fracture of IF mode. Slip separation and quasi cleavage fracture surface were found on fracture of PF and PF-IF mode. Pronounced HAZ softening was observed on ICHAZ and SCHAZ zone due to the appearance of bainite, ferrite and tempered martensite.

Self-Adaptive Constraint Optimization Algorithm Based on Multiple Surrogates and its Application in the Design of Ｒivet Head

QU Jie HU Yansong XU Liang MA Qiang

2018, 46(10):  88-95.  doi:10.3969/j.issn.1000-565X.2018.10.012

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In order to solve the nonlinear constraint engineering optimization problem which requires high computational resource，a self-adaptive constraint optimization algorithm based on multiple surrogates is proposed. First a candidate set including surrogate model will be assigned to the objective function and each constraint function in the optimization problem, then based on the cross-check, the ranking of the corresponding surrogate model in the candidate models will be determined by the fitting performance of the function; The surrogate model is selected to construct approximate model of the original optimization problem according to the result of the ranking, solved by the sequential quadratic programming algorithm. When the number of surrogate models is different in the candidate set, the priority is selected. The surrogate model will be kept or deleted in the candidate set is determined by the evaluation results of the fitting performance of the function, and the new sample in the algorithm is got by solving the approximate model and the combination of the application of the inhomogeneous variation operator and the hybrid operator. Finally application of the proposed constraint optimization algorithm to solve four representative mathematical optimization problems, the results show that the approximate optimization solutions based on the adaptive optimization algorithm are better approximated to the theoretical optimal solution; And used to optimize the design of the rivet head forming surface in the shaft clinching process of the vehicle wheel bearing unit, the optimization result is better.

Relationship between Vortivity Analysis and Aerodynamic Performances of Axial Flow Cooling Fan and Design of Guide Rib Structural

SHU Hengtao QIU Zhicheng SHANGGUAN Wenbin WANG Xinling DUAN Yaolong

2018, 46(10):  96-102,110.  doi:10.3969/j.issn.1000-565X.2018.10.013

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The method of vorticity analysis for axial flow cooling fan optimization is studied. A mathematical physics relationship is established between the circumferential vorticity and aerodynamic performances of fan. And the average circumferential vorticity on the fan blade and the static pressure are positive correlated. Based on a true axial flow fan, the method of vorticity analysis is described in detail. A simulation model of fan pipeline is set up, and an idea of the fan optimization is pointed out by the method of vorticity analysis. The research results show that the negative circumferential vorticity is cut off by the guide rib, which designed on the blade surfaces according to the distribution of the negative vorticity, and the average circumferential vorticity value is improved. The guide rib is designed reasonably using the analysis method, such as the shape, height and thickness of the rib. The aerodynamic performance is improved obviously after adding the guide rib. The test is preceded after the optimization. The test results states that the method of vorticity analysis can be used for the optimization of axial flow cooling fan.

Modeling and Experimental Study of Temperature Field in Rail Milling-grinding

SHU Hengtao QIU Zhicheng SHANGGUAN Wenbin WANG Xinling DUAN Yaolong

2018, 46(10):  103-110.  doi:10.3969/j.issn.1000-565X.2018.10.014

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Plenty of heat is generated in rail milling-grinding operation which will cause continuous heat rise around the work-piece area, excessive heat can affect the milling-grinding quality. Based on linear heat source method, the temperature field model of form milling and form grinding was built respectively and the joint milling-grinding temperature model was deduced via the superposition of temperature field. The temperature changing curves on the work-piece surface were attained by MATLAB simulation. The milling-grinding experiments were conducted on the specially-built platform which includes cutting and measuring system to obtain the temperature changing curves, and the results were compared with simulation ones to demonstrate the validity of the model. The model can predict the milling-grinding temperature and the temperature control is realized by milling-grinding speed ratio and selecting processing parameters to prevent the rail material burns.

CFD Simulation of Drag Torque of Wet Friction Element with Conical Configuration#br#

WANG Yanzhong WU Xiangyu SONG Yuhuan

2018, 46(10):  111-116,140.  doi:10.3969/j.issn.1000-565X.2018.10.015

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In order to study the drag torque of wet friction element with conical configuration under the lubrication condition of full oil-film and evaluate the effects of geometric parameters, lubrication flow, oil film thickness, relative speed on drag torque, CFD models of two wet friction elements with different geometric parameters have been established. The influence of the lubrication flow, oil film thickness, and relative speed on the drag torque was obtained. The simulation model and the traditional model are analyzed to verify the availability of the simulation model.

Microstructures and Mechanical Properties of AlSi10Mg Aluminum Alloy Fabricated by Laser Melting Deposition

Lǚ Fei TIAN Zongjun LIANG Huixin XIE Deqiao SHEN Lida XIAO Meng

2018, 46(10):  117-125.  doi:10.3969/j.issn.1000-565X.2018.10.016

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In order to improve the manufacturing quality of the AlSi10Mg aluminum alloy fabricated by Laser Melting Deposition based on coaxial powder feeding, this paper carried out the single tracks test, block samples forming experiments and tensile property test to investigate the variation trend on the microstructure and property under different process parameters. The experimental results showed that the manufacturing quality of the LMD processed samples was significantly governed by energy density of laser beam and the hatch spacing. tensile property was improved by decreasing the level of porosity and enhancing the effect of solid solution strengthening. After process optimization, the morphology of the single tracks was smooth without spheroidization. The relative density of the block samples was increased to 99.2% without larger pores and cracks. The microstructure of samples had directional rapid solidification characteristics with Al-Si eutectic microstructure contained three microstructures of cellular crystal, columnar dendritic crystal and divergent dendrite crystal. With the increase of cooling rate, the solubility of Si phase in Al matrix was increased to 7.6%. The effect of solid solution strengthening was enhanced. Therefore, AlSi10Mg samples fabricated by laser melting deposition with good performance could be obtained by optimizing the process parameters. The tensile stress of the samples was 292MPa, which was 33% higher than that of the cast samples.

Environmental Science & Technology

Effects of Extraction Ratio of Black Liquor on Residual Pollution Load of Pulp

LI Youming WEI Zhimin CHEN Tiantian SUN Qihui HOU Yi

2018, 46(10):  126-131.  doi:10.3969/j.issn.1000-565X.2018.10.017

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In order to quantitatively characterize the effects of extraction ratio of black liquor on residual pollution load of pulp, Traditional alkaline cooking was used to cook the pinus koraiensis , and the countercurrent extraction process was used to extract the black liquor.The relationship between the extraction rate of black liquor and the residual lignin content, chemical oxygen demand (CODCr) and biochemical oxygen demand (BOD5) in different pulp concentrations were studied.The results showed that lignin degradation products are the main source of pollution of black liquor organic matter, and high concentration of high black liquor extraction rate can effectively reduce the pollution load.When the extraction rate of high black liquor increased from 71.34% to 98.47%, the content of residual lignin, CODCr and BOD5 in the pulp were significantly reduced.The extraction ratio of black liquor has a linear relationship with remained lignin in pulps, and the remained CODCr and BOD5 in pulps has cubic function of one variable and a uni-variable and hyperbolic relationship respectively.The results showed that high concentration of high extraction was an effective method to reduce the pollution load during pulping and bleaching in papermaking process.

Catalytic Ozonation of Eugenol in the Presence of Fe₂O₃ Supported by Activated Carbon#br#

LEI Lirong DANG Zhongxu LI Youming

2018, 46(10):  132-140.  doi:10.3969/j.issn.1000-565X.2018.10.018

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The catalytic ozonation of eugenol simulated wastewater in the presence of activated carbon load different active components were investigated under different operating conditions. The prepared catalysts were characterized by scanning electron microscopy, X-ray diffractometry and specific surface area analyzer.The effects of active components, loading content,catalyst dosage and initial pH on CODcr removal from eugenol simulated wastewater by catalytic ozonation were evaluated. And kinetics model of the CODcr degradation were explored.Characterization of catalyst indicated that the iron,copper,cerium and nickel loaded on activated carbon were mainly in the form of ferric oxide,copper oxide, ceria,nickel oxide,respectively,which have obvious catalytic activity and remarkably improves the removal efficiency of CODcr in the process of ozonation degradation of eugenol simulated wastewater.The order of catalytic activity is Fe / AC> Ce / AC> Cu / AC> Ni / AC.The presence of ferric oxide on activated carbon positively contributed to its catalytic activity in ozonation of eugenol . Initial pH of 11,iron loading content of 3% and catalyst dosage of 0.3g/L achieved highest eugenol removal of 88.90% among all the tried conditions in 60min as compared with AC catalytic oxidation and ozone alone, the eugenol removal were further improved by 21.13% and 29.95%, respectively. The repeated use six times of the catalyst proved that the Fe/AC catalyst had a good reusability and stability.Finally,apparent second-order kinetics model of the CODcr degradation in the eugenol simulated wastewater with ozone alone，AC，Fe/AC，Ce/AC，Cu/AC and Ni/AC oxidation were established,which indicated that activated carbon-loaded active components effectively increase the kinetic rate of the reaction.

Adsorption of Humic Acid in Water by Activating Carbon-Attached Chitosan

ZHAO Zhengang HAN Dexia

2018, 46(10):  141-148.  doi:10.3969/j.issn.1000-565X.2018.10.019

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Preparation of crosslinked chitosan/activated carbon composite adsorbent by water bath, composite adsorbent was characterized by scanning electron microscopy and fourier transform infrared spectroscopy, and tested for humic acid (HA) removal. The experimental results showed that compared with original activated carbon (AC), the HA adsorption capacity of compound adsorbent increased by 5mg/g. Acidic condition was beneficial to HA removal and cations all exhibited promotion on the uptake of HA. The HA adsorption capacity of compound adsorbent increased with the increase of adsorption time. The adsorption kinetics of HA removal by composite adsorbent agreed well with the pseudo-second-order model (R2 ≥ 0.99), and the adsorption isotherms were well fitted by the Langmuir model. The thermodynamic analysis suggested that HA removal by composite adsorbent was a spontaneous and endothermic process. The compound adsorbent can be recycled because of its good desorption and regeneration. It is positive meaning to give full play to value of AC and chitosan, and improve the quality and safety of drinking water.