bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on local compensation technology of large diameter steel pipe with heterogeneous structure and analysis of application
Authors: Zhao Kexin , Yang Yongmin
Published: August 2021

When large-diameter steel pipes have special structures with stiffening rings, grouting holes, etc., the electrostatic spray epoxy powder anti-corrosion process is likely to produce large temperature differences due to the sudden thickness changes during heating, which cannot meet the temperature requirements of powder spraying. This paper designs a set of automatic temperature compensation technology for large-diameter steel pipes with stiffening rings and grouting holes, which aims to solve the problem of uneven heating of stiffening rings and grouting holes in the medium frequency induction heating powder spraying process. Through the method of “intermediate frequency heating + stiffening ring temperature compensation”, the inner and outer parts of the steel pipe are heated evenly and the temperature difference is reduced. The temperature difference between the inner wall of the steel pipe is reduced to 3∼15°C in the area of the stiffening ring, and the temperature is reduced in the area of the grouting hole. The difference is reduced from 70°C to 57°C to 20°C, the temperature difference is controlled within the allowable range of technical requirements, and the temperature compensation effect is good. The process has the advantages of simple device structure, high work efficiency, and small temperature difference in the spraying area, and is suitable for use on similar large-diameter steel pipes or other hydraulic metal structures.
Research on the method of skateboard edge grinding by combination of robot and pneumatic constant force grinding device
Authors: Yao Maoyun , Zheng Changwan , Wang Zihao , Qian Jiangzhong , Xi Qiang , Kuang Shaolong
Published: August 2021

The paper presents a method of robot skateboard edging grinding based on pneumatic constant force device. To solve the problem of modeling and complex algorithm of robot end active compliance control during the grinding process, a hybrid position/force control is proposed by controlling position and force separately. That is, a kind of 2 degrees of freedom pneumatic constant force grinding device is designed to realize the constant force control in the horizontal and vertical directions, while a robot is used only for position control. Then a fuzzy PID control algorithm is proposed for smooth grinding based on the dynamic modeling of the grinding device. Experiments show that the use of fuzzy PID can effectively improve the dynamic adjustment performance of the pneumatic constant force grinding system and reduce the steady-state error. Compared with normal PID, fuzzy PID reduces the step response adjustment time of the grinding system from 400ms to within 200ms. In addition, when the constant force control is disturbed, the response adjustment time is less than 100ms and there is no oscillation, and the standard deviation of the grinding force is within 1N, which has good robustness and fulfills the requirements of edging control.
Rotating machinery weak fault signal detection method based on QPSO and stochastic resonance
Authors: Gao Kangping , Xu Xinxin , Zhang Hui , Shi Ning , Jiang Xin , Shang Xiaofei , Jiao Shengjie
Published: August 2021

Due to the weak early vibration signal of rotating machinery, which is nonlinear and non-stationary, the traditional filtering method has some limitations. To this end, a weak signal detection method combining Quantum Particle Swarm Optimization (QPSO) and Stochastic Resonance (SR) is proposed. First, according to the adiabatic approximation theory, make the original signal meet the SR requirements, and optimize the structural parameters of the SR through QPSO; secondly, the signal-to-noise ratio is used as the objective function to make the input signal and the output signal achieve the best match; finally, simulation and experimental data are used to verify the feasibility of the proposed method. Comparative analysis shows that the proposed method increases the amplitude by 46% compared with the characteristic frequency obtained by the PSO optimized SR model.
Thermal characteristic of double-row cylindrical roller bearing of high-speed train using analytical solution and finite element analysis
Authors: Zhang Kai , Hu Hanping , Liu Xiaojie
Published: August 2021

The complicated thermal characteristics critically affect the reliability of double-row cylindrical roller bearing (DCRB) in the high-speed railway, which will cause the deformation and vibration and severely lead to bearing failure. Thus, research on the heat distribution and steady temperature field is essential for DCRB. In this paper, the Green’s function was established and programed with MATLAB under certain boundary conditions to verify the temperature field of DCRB. It computes fast than the finite element analysis (FEA), According to the simulation of ANSYS, temperature in outer ring is higher than inner ring and it is the maximum in roller, while the rib reduces the temperature in bearing and temperature near rib is larger, which result in asymmetry in raceway. All these results are consistent with the accrual working. This paper provided a heat portion equation between the rollers and the raceway and calculated more accurate and comprehensive than other equation. All results in this paper made sure the more exact temperature field in the DCRB with more convenient calculation and verification.
Analysis and research on failure of B-phase lower bridge arm through wall casing in converter station
Authors: Zhang Shuai , Zheng Wenzhe , Fang Zheng , He Jian , Lin Haofan , Fang Chengwei , Lin Jingtao , Wei Bo , Song Guoquan
Published: August 2021

Based on the actual failure of the bushing, this paper conducts analysis and research. Firstly, it analyzes the protection action, on-site harmonic components, bushing structure and disassembly step by step. Then it conducts the research on the discharge and breakdown characteristics of epoxy insulation. Finally, we results show that there are bubbles or impurities in the outer capacitor layer of the capacitor core inside the casing, and the harmonic content is higher under the operating conditions of the converter station. Meanwhile, we gives some relevant suggestions for the through-wall bushing in the design and manufacturing stage to consider relevant harmonic factors are of certain significance to extend the life of the bushing.
Deep transfer attention network for intelligent fault diagnosis of rolling bearings
Authors: Li Shihao , Jia Feng , Shen Jianjun , Ma Junxing
Published: August 2021

Deep learning based on fault diagnosis methods of rolling bearings has attracted much attention with the rapid development of artificial intelligence. However, these methods trained by bearing datasets from one equipment cannot be well applied to correctly identify the fault information of the bearing datasets from another equipment. The main reason for this problem is that the datasets from the different equipment have different probability distributions. In order to solve the above problem, a deep transfer attention network is proposed for intelligent fault diagnosis of the rolling bearings. The steps of this method are listed as follows. Firstly, the feature extraction network is used to extract the features from different bearing datasets. Secondly, the different transfer attention is given to different areas of the sample data by the attention mechanism and distribution differences among the features is reduced by domain adaptation. Finally, the fault recognition network is trained to identify fault status for different bearings. The proposed method is verified by using fault datasets from different bearings equipment. The results show that the proposed method can achieve the fault identification of different bearings equipment.
Fluid-structure coupling analysis of inlet ball valve on pumped-storage power station under extreme conditions
Authors: Liu Chang , Zhou Jianzhong , Duan Ran , Liu Ye , He Yanxi
Published: August 2021

While pumped storage power stations (PSPSs) provide clean energy, they are also facing many problems of safe operation. Inlet ball valves bear the brunt of the impact and disturbance from upstream pressure pipeline under extreme conditions on PSPSs. Artificially change the wicket gate and ball valve closing laws can improve the extremums of key indicators. However, the internal flow field in ball valves is complex, and the internal flow field interacts with the external structure. The performance impact studied only by the indicators of the ball valve inlet and outlet is far from enough. In this study, three-dimensional flow field simulation of an inlet ball valve on PSPS was carried out, and the Realizable k-ε turbulence model was selected to simulate the pressure and velocity changes of the flow field inside the ball valve under load rejection conditions. Based on the theory of fluid-structure coupling and CFX dynamic grid, the response characteristics of the ball valve mechanical structure after being subjected to transient flow field were studied, the distribution of related performance parameters of the structure was obtained, and the mechanism that causes stress, strain and total deformation was analyzed. This study found that the ball valve structure is significantly affected by the three-dimensional transient flow of water under extreme conditions of load rejection. The safety of the ball valve can be enhanced by setting expansion joints and strengthening the base.
Development and implementation on torsional vibration measurement of rotational machinery’s shaft
Authors: Yang Zixuan , Wang Zhifang , Wang Xuan
Published: August 2021

The measurement and analysis on torsional vibration is an important aspect to research the performance state of rotating machinery’s shaft. This paper introduces the basic procedure of torsional vibration measurement, deduces the manifestation of torsional vibration signal, focuses on the hardware design and software implementation of torsional vibration measurement system, and applies the measurement system to a certain type of ship and steam turbine generator shaft in actual testing. The measurement results verify the practicability and accuracy of the system.
Performance and application of an evaluation method for flow conditioner based on CFD
Authors: Wan Yong , Wu Bo , Lu Jiamin
Published: August 2021

As evaluation of the performance of flow conditioner mostly depends on the specific pipeline system, which cannot be timely feedback to improve the structure design, an evaluation method for flow conditioner based on computational fluid dynamics (CFD) is promoted. First, the evaluation coordinates for flow conditioner is established and the coordinate values of each sampling point are solved. Then, the judgment basis of whether the velocity distribution of pipe cross-section is fully developed is derived, and then come to the evaluation index of flow conditioner rectifier performance. Finally, with CFD simulation technology, the verified experiments of grid format flow conditioner are performed. The results showed that, the proposed evaluation method is qualified to evaluate the grid format flow conditioner’s performance quickly and effectively. Besides, it is helpful to analyze the function of flow conditioner’s performance on Reynolds numbers. What’s more, when 5.84 × 106≤Re≤5.84×108, the required minimum length of straight pipe for irregular downstream field of the grid format conditioner achieving fully developed is only 0.5-0.6 times by those without conditioner. It is of great significance to accelerate the flow conditioner designed and to promote fluid energy monitoring.
Finite element analysis and optimization design of beam structure of forging press
Authors: Ji Xin , Liao Shanmei , Zhang Xiaoyan , Gao Xiaoyong , Ma Ruiyang
Published: August 2021

The structural optimization design of 20Mn forging hydraulic press was studied. Firstly, the structure and stress characteristics of the hydraulic press are analyzed, then according to the center load condition, the static structure of the frame is simulated by finite element method, so as to understand the stress and stress concentration of each part, and achieve the purpose of checking the strength and stiffness of each part. On the basis of the above analysis, the strength of the beam is optimized on the basis of reducing the overall stiffness. The simulation results show that the optimized design scheme can reduce the material consumption and save the cost.
Topology Optimization of an aircraft engine gearbox
Authors: Wattananaphakaseam Nuz , Sittisang Natthasit , Phengsalae Napat , Dipasquale Daniele
Published: August 2021

Topology Optimization (TO) is a mathematical method extensively employed to optimize material layout within the design space, for a given set of boundary conditions with the goal of maximizing the performance of the system. This process takes a three-dimensional design space and whittles material away within it to achieve the most efficient design. Currently, engineers use this mathematical approach at a concept level of a design process, leading to results which are often fine-tuned for manufacturability. In some cases, the optimized geometry can be directly manufactured using additive manufacturing, indeed, TO is a key part of design for additive manufacturing. This work aims to apply TO in order to minimize the mass of an engine gearbox while maintaining an acceptable mechanical performance when compared to the original design. Numerical simulations are carried out by means of CAD and FEM software in order to improve the design of an aircraft gearbox composed of four gears, therefore, irrelevant parts of material are removed in the design space to meet the goal of minimizing the mass of the gearbox. The application of TO allows to obtain a better, lighter, and more efficient design of the gearbox by keeping its mechanical performance unchanged.
Heat transfer enhancement in a rectangular channel with pillars
Authors: Jiao Feng , Li Chengzhe , Dai Songjiang , Hu Meilin , He Yongqing
Published: August 2021

This paper numerically studied the heat transfer performance of water flowing in a rectangular channel with pillar structures. We systematically investigated the influence of the pitch, inclination angle, shape, and pillar arrangement on the flow and heat transfer characteristics. The results show that adopting spacing with S/d=2 can improve heat transfer performance sufficiently for a low Reynolds number case. Meanwhile, the noticeable enhancement can also be observed by making the pillar inclination direction consistent with the flow direction or staggered rhombic-shaped.
Numbering method for the kinematic chain isomorphism recognition of a planar mechanism
Authors: Tian Qing , Wei Xiaohui , Li Cai , Liu Ge , Deng Yumei
Published: August 2021

The kinematic chain isomorphism identification of a planar mechanism is an important part of the innovative design of kinematic chain regeneration. Based on the structural characteristics of the kinematic chain of a planar mechanism, a new method, i.e. the numbering method, is proposed for isomorphism identification. Firstly, the links of a kinematic chain are numbered according to certain rules, and they are normalized. Then, the normalized contracted link adjacency matrix is used to represent the connection of the kinematic chain graph. Based on whether the contracted link adjacency matrix of two kinematic chains is the same, we can judge whether the two links are similar.
Optimization of safety valve block of the pitch mechanism of bucket wheel stacker reclaimer
Authors: Guo Ziqing , Zhu Xuebiao , Wang Maoan
Published: August 2021

The luffing mechanism of the 6# stacker-reclaimer (DQ3000/4200) of an iron-making plant has malfunctions in production. After analyzing the fault reason of the original pitching mechanism. We optimize the hydraulic mechanism for solving these problems, and established a 3D model for the optimization part. The original hydraulic system and the improved hydraulic system model were established under AMEsim. The purpose of this study was to compare the movement speed of the hydraulic cylinder piston under different set pressures of the pressure valve to verify the improved hydraulic system meets production needs.
Support vector machine-based sound pressure extrapolation to overcome the finite aperture used in nearfield acoustic holography
Authors: Zhou Hefeng , Zhao Yun , Gao Dongbao , Tian Zhangfu , Zeng Xinwu , Jiang Weikang
Published: August 2021

Sound pressure extrapolation based on support vector machine (SVM) is proposed in order to reduce the reconstruction error in Fourier-based nearfield acoustic holography (NAH) when the aperture is small compared to the source size. The measured pressure on the aperture is introduced into SVM and then a regression model is obtained to extrapolate the sound pressure outside the aperture. Numerical simulations show that the new method allows a relatively accurate and quick reconstruction in comparison with the results using zero-padding and linear predictive border-padding.
Study on variation of thermodynamic parameters in vehicle-mounted LNG gas cylinder under static state
Authors: Huang Si , Yi Tiankun , Guo Jiawei , Yang Gang , Xia Li
Published: August 2021

To study the variation regularities of the mass, evaporation, temperature, and pressure of LNG in the gas cylinder with time, LNG was used as the working medium, and three specifications of LNG gas cylinders (150L, 330L, and 450L) were selected for heat transfer calculation. For the liquefied medium in the LNG gas cylinders, a saturated homogeneous model was adopted. For the heat transfer calculation of the adiabatic layer of LNG gas cylinders, a multilayer insulation structure model of radiation and heat conduction was adopted. According to the thermodynamic relations in the saturated state, the relations between the temperature and the physical parameters of the liquefied medium were fitted. The calculation method and calculation model were verified by the experimental data of liquid nitrogen for three specifications of LNG cylinders (150L, 330L, and 450L). According to the calculation model, the variation regularities of LNG thermodynamic parameters with time were obtained at a normal temperature. In the initial period of evaporation, the increasing temperature rate of LNG, the evaporating rate of LNG, and the pressure-boost rate of LNG in the gas cylinder are slow, and then these rates increase. The final mass of boil-off gas (BOG) produced by the phase change finally reaches 0.68% of the total mass of the medium in the gas cylinder.
An AMESIM-based simulation of hydraulic system design for ultra-high pressure tablet presses
Authors: Feng Kailin , Deng Bihai , Zha Chuanzhen
Published: August 2021

Aiming at the problems of large bore of hydraulic cylinders of high tonnage quantity tablet press, large size of tablet press and wide area, a method of using ultra-high pressure hydraulic system to streamline the structure of tablet press is proposed, and a laboratory ultra-high pressure tablet press for XRF spectral analysis specimen manufacturing is designed. The AMESIM software was used to simulate the established hydraulic system model, and the theoretical analysis and relevant experience were combined to reasonably set the relevant parameters of the simulation model, and the AMESIM simulation results were obtained to analyze the motion and flow characteristics of each hydraulic circuit system, which verified the rationality of the hydraulic system.
Path planning for UAV based on improved dynamic step RRT algorithm
Authors: Xiong Jing , Duan Xiaokun
Published: August 2021

Path planning is an important problem in the field of unmanned aerial vehicles (UAVs). However, it is inefficient for many rapidly-exploring random tree (RRT) based methods to rapidly find a feasible solution in a complex environment. To solve the path planning problem for the UVA in a complex environment, an improved dynamic step size RRT algorithm combined with a new path length control strategy is proposed. Firstly, the algorithm adopts a biased-goal sampling strategy to guide the growth of the tree, and an expansion direction constraint strategy is adopted to limit the expansion direction of the tree. Secondly, an improved dynamic step size strategy is proposed to speed up the path searching process. Thirdly, a path length constraint strategy is designed, which is used to constrain the path length during the searching process for a solution. Finally, simulation results demonstrate that the proposed method achieves improvement in both computational time and the path quality.
Research status of hydraulic oil evaluation technology
Authors: Lu Changbo , Li Hua , Zhang Bin , Wang Mengyi , Xiong Chunhua
Published: August 2021

Hydraulic oil has an important influence on hydraulic system, and the research on its evaluation technology can provide technical support for the rational use of oil in hydraulic system. The status of hydraulic oil evaluation technology research at home and abroad is reviewed, including the physicochemical properties and comprehensive performance indexes of the oil. Combined with military requirements, it is found that the low-temperature cold start performance of hydraulic oil is more critical, but there is less research in this area. Therefore, this paper builds a cold start performance evaluation bench and test method to provide technical support for military oil use.
Feasibility study of swash plate plunger pump system in drainage gas recovery process
Authors: Xiong Wei , Zhang Shengli , Wang Lina , Zhang Xu , Ma Jixiang , Zeng Kang , Tian Jianchao , Wang Meng , Li Ran , Jing Zhiqiang , Wang Quansheng , Zhu Tong , Wang Liya , Liu Jingzhi , Hao Li , Xu Shuanglong , Duan Ran
Published: August 2021

With the continuous development of Sulige gas field, the formation pressure has gradually dropped, problems that liquid loading and water flooding affects the normal production of gas wells have gradually appeared. Drainage gas recovery delays the decline of gas field production to some extent, but the stable production of gas wells with large water production has become a field problem. Therefore, the pneumatic swash plate plunger pump system that does not need external power equipment but has large displacement and is easy to manage is studied. It has become another weapon to prolong the blowout period of gas wells.
Influence of guide vane angle of circulating hot blast stove sleeve on temperature field and flow field
Authors: Xiao Ru , Zhang Jiangyong , Jiao Shengjie
Published: August 2021

In order to improve the heating efficiency and uniformity of the hot air circulation heater, a three-dimensional model of a hot blast stove of hot in-place recycling hot air circulating heater was established, based on the finite element method and CFD software ANSYS, the influence of the guide vane angle of the circulating hot blast stove sleeve on the temperature field and flow field of hot blast stove and air distribution pipe was studied by numerical simulation. The results show that the guide vane angle of the hot blast stove sleeve affects the temperature distribution at different positions of the air distribution pipe, has less influence on the internal temperature field of the hot blast stove, and has greater influence on the temperature distribution of the air distribution pipe. With the increase of the guide vane angle of the hot blast stove sleeve, the velocity and flow path of the circulating hot air in the hot blast stove sleeve increases, which improves the hot air distribution uniformity of the heating device. When the guide vane angle of hot blast stove sleeve is 45°, the hot air transverse distribution uniformity of heating device is the best.
Thermal design and simulation of monitoring payload on manned spacecraft
Authors: Zhai Ruiqiong , Yang Xiaoning , Jiang Lixiang , Yi Zhong , Liu Yenan , Li Jian , Li Xiyuan , Lin Boying , Wang Junfeng
Published: August 2021

Discharge monitor is a kind of primary payload monitor loaded on the manned spacecraft in the Low Earth Orbit, which is designed for monitoring the secondary discharge problem on the solar array. The issue of integrated electronic device heat dissipation is the key for normal operation supporting. In this study, the integral payload is simulated by finite element method, through structure modeling, based on the theory of heat conduction and heat radiation. In the result, under the measures of adjusting the layout of the electronic devices, coating the circuit board with copper, and black anodization for the case, the payload could definitely meet the needs of the heat dissipation in the extreme conditions, survive safely and functionalize perfectly in the orbit, at least from the angle of thermal design.
Mobility analysis of hybrid-driven ten-bar mechanism
Authors: Wang Limin , Wang Ying
Published: August 2021

For a new mechanism, it should be able to move continuously according to the predetermined motion law. Each bar of the mechanism should meet certain size conditions. In this paper, a new type of three degree of freedom ten-bar mechanism with symmetrical structure is proposed. According to the motion requirement, the condition of crank existence is analyzed. The size of the mechanism is determined. The possible limit position space of this mechanism is analyzed. It lays a theoretical foundation for the application of the mechanism.
Research on anti-pilot contamination in massive MIMO
Authors: Yuan Qin , Li Lihua , Xia Weixia , Zhu Gailin , Zhu Xishun , Wu Jianhua
Published: August 2021

In order for the pre-coding technology to suppress the influence of pilot contamination, a hybrid pre-coding scheme is proposed in this paper by combining a full-digital pre-coding technology and an analog beamforming in the context of current massive MIMO. Simulation results show that the proposed pre-coding scheme effectively suppresses the pilot contamination while reducing the system structure complexity and ensuring the system’s basic performance, which is of important significance in practical communication applications.
Research on a projectile-borne measuring apparatus for electromagnetic launcher
Authors: Cao Ronggang , Hu Xueyi , Dong Erwa , Ma Xiao , Zhou Yu
Published: August 2021

In order to evaluate the electromagnetic launch effectiveness and understand the corrosion damage of the electromagnetic launcher, it is necessary to master the magnetic field data in the bore. At present, there is no related research on the measurement of the bore magnetic field of the electromagnetic launcher. Therefore, a small-scale projectile-borne measuring apparatus based on B-dot probe is developed in this paper. This apparatus uses FPGA as the core. Through the static magnetic field measurement experiment, the data of the induced voltage and the induced magnetic field can be obtained. The projectile-borne magnetic field measuring apparatus designed in this paper can accurately measure the bore magnetic field of the electromagnetic launcher, which lays the foundation for further analysis of the influence of the electromagnetic field in the bore on the launch effect and investigation of the corrosion damage of the electromagnetic launcher.
Research on PD source successive approximation positioning method based on multi sample information
Authors: Zhu Qingdong , Zhu Wenbing , Gao Zhixin , Zhu Mengzhao
Published: August 2021

Ultra High Frequency (UHF) detection technology is widely used in Partial Discharge (PD) detection and positioning of electrical equipment. However, how to achieve accurate and reliable fault localization based on UHF PD is an urgent problem to be solved. In this paper, the multi-samples of PD are calculated by the successive approximation method and the optimization function is established by using the linear spatial relationship between the initial value and the sensors. The particle swarm optimization (PSO) is exploited to search for the minimum value of function, and the optimal result is obtained by cyclic calculation. The optimal PD source position determined by this way has higher accuracy, solving the problem of strong dispersion and large error in PD location by a single sample. The positioning error is reduced from tens of centimetres of the single sample to few centimetres, which is fewer than the results calculated by the average method. In addition, it is found that the positioning precision becomes higher as the number of samples selected for optimize calculation (i.e. m) decreases.
Simulation study on genetic algorithm control of hydrogen fuel cell gas supply system
Authors: Cheng Rong , Chen Jing , Cheng Nanding , Xiao Chun
Published: August 2021

Fuel cell as a new clean energy, its advantages of high efficiency, low emission and low noise have attracted the attention of domestic and foreign governments and scholars. To this end, based on the requirement analysis of the hydrogen fuel cell gas supply system, this paper focuses on the genetic algorithm optimization PID control strategy of the hydrogen fuel cell gas supply system. The simulation model is built on the Matlab/Simulink platform and compared with the conventional PID algorithm in the model. The simulation results show that the comprehensive index of PID control algorithm optimized by genetic algorithm is better than that of conventional PID algorithm, which proves the improvement effect of the proposed control strategy on the dynamic response of the gas supply system.
Research status and development trend of PCS
Authors: Wang Xudong , Zhou Weigui , Wang Weishan , Wang Mengyi , Wang Changfu
Published: August 2021

Due to the shortage of conventional energy and serious environmental pollution, new energy (NE), such as wind energy, solar energy, biomass energy, etc. is getting more and more attention. However, the output power of NE is unstable. Energy storage is the most effective way to solve the problem of NE applications. The power conversion system (PCS) determines the output power quality and dynamic characteristics of the energy storage system. This paper reviews the development and application of PCS, conducts a detailed study of its working principle, topology, and key technologies. The main index system of PCS is established by consulting the relevant standards, and the requirements and detection methods of the main indexes are pointed out. This work provides a scientific basis for the selection of PCS. At the end of the paper, summarizes and prospects on PCS.
Research on measures suppressing high frequency transient overvoltage in offshore wind farms
Authors: Li Sisi , Fang Chun’en , Pan Lin , Duan Jiaojiao , Chen Junping
Published: August 2021

A large number of different types of cables, wind turbines, transformers and vacuum circuit breakers (VCBs) are used in power collecting system of offshore wind farms (OWFs). Due to the phenomenon of traveling wave refraction and reflection in cable collector system, transient overvoltage with high amplitude and high steepness will be generated when reignition phenomenon occurs in frequent operation of vacuum circuit breakers on wind turbines, which will cause serious damage to transformers, the problem of overcurrent is also becoming more and more serious. Therefore, through the electromagnetic transient simulation software of ATP-EMTP, a single-phase model of VCB switching-off transformer in offshore wind farm is built to study the influence of the separation speed of contacts of vacuum circuit breaker, high-frequency arc quenching capability and arching time on overvoltage. Then, the medium voltage cable collector system of OWF is built. Installing ferrite ring near the VCB or on the high-voltage side of transformer can suppress high frequency transient overvoltage. The results show that the high frequency transient overvoltage generated by offshore wind farm can be well suppressed after the installation of overvoltage protection device.
Simulation research on phase selection control algorithm of a four-phase interleaved parallel Boost converter
Authors: Zhang Meng , Chen Jing , Li Zhihua , Xiao Chun
Published: August 2021

In order to increase the rated power of the DC/DC converter, the interleaved parallel connection is widely used. Although the interleaved and parallel Boost converters can increase the operating power of the system, at the same time, it has the advantages of smaller system output current ripple and can reduce the stress of switching devices, but when the system is running in low power mode, due to the use of multi-phase Boost, the increase in loss makes the conversion efficiency of the system lower. A phase selection control algorithm is proposed in this paper, by which the conversion efficiency of multi-phase interleaved parallel Boost converters can be effectively improved. Finally, the feasibility of the phase selection control algorithm designed is verified through simulation in this paper.
Staggered parallel asymmetric boost converter based on coupled inductor
Authors: Zhu Longji , Guo Qiang
Published: August 2021

Aiming at the problems of insufficient voltage gain, excessive voltage stress and current stress of switches in DC boost converters, an interleaved parallel asymmetric boost converter is proposed. The circuit adopts interleaved parallel boost converters, coupled inductors and switched capacitors to form an asymmetric boost converter structure, so that the voltage gain of the converter is more than twice that of the traditional coupled inductor boost converter; and it adopts the passive clamp circuit to eliminate the switch voltage spike at the moment of turn-off, so that the voltage stress and current stress on the switch devices are reduced. The simulation results show that the boost converter obtains high voltage gain and high efficiency, and is suitable for applications with large DC boost ratio.
IEEE 1901.1 Power Line Communication electromagnetic emission study
Authors: Amaro Nuno , Saragoça João , Cartaxo Ricardo , Yang Wei , Yi Ren
Published: August 2021

IEEE 1901.1 Standard for Medium Frequency (less than 12 MHz) Power Line Communications for Smart Grid Applications was officially released in 2018. This standard expands the possible applications of Power Line Carriers communications by using a medium frequency technology, allowing for a higher bandwidth and bit rates compared to the current industrially used solutions. As the standard operates below a frequency of 12 MHz, and constituting a new solution in this area, it is fundamental to evaluate electromagnetic emissions and evaluate possible electromagnetic disturbances. In this paper, we pre-sent a methodology to measure electromagnetic emissions of IEEE1901.1 compatible devices. This methodology is then used to measure real emissions from two different IEEE compliant modules from two different manufacturers, including central coordinator and station devices.
Research on improved time difference estimation algorithm based on fourth-order cumulant in UHF PD location
Authors: Zhu Wenbing , Xu Wei , Zhou Jiabin , Xu Ran , Yi Feng
Published: August 2021

Ultra-high frequency (UHF) detection technology is a fast-developing method for partial discharge (PD) diagnosis of electrical equipment in recent years. Extracting accurate time difference is the priority for PD location in electrical equipment using UHF technology. An improved time difference estimation algorithm based on fourth-order cumulants was first proposed in this article. It mainly included the following two steps, that is using the “correlation-shift-superposition” transformation method to process multiple samples collected from a PD source at first, and then utilizing the statistical characteristics of the fourth-order cumulant to calculate the time difference. In addition, the accuracy and stability of the improved algorithm and the other three common methods were compared. The calculation results show that the improved time difference estimation algorithm based on the fourth-order cumulant can obtain a more accurate and stable time difference than the other three methods. Improved time difference estimation algorithm based on fourth-order cumulant can approximately meet the requirements for reliable location of PD sources.
Multi-view based template matching method for surface defect detection of circuit board
Authors: Zhou Junyu , Liu Yaowen , Zhang Xueliang , Yang Zhiming
Published: August 2021

In order to avoid defects (e.g. dust, scratch, static electricity) caused by manual detection, this research proposes a non-contact defect detection approach for circuit board through use of template matching method. In the proposed approach, images of both circuit board to be detected and circuit board selected as template are obtained respectively from multiple views. Then defect index (DI) of each view is constructed based on corresponding matching results between the image to be detected and the template image. Finally, total defect index is obtained by integrating all DI from multiple views, which can characterize the existence of defects in the circuit board (e.g. lack or wrong installation of components). The proposed approach is experimentally investigated to detect two surface defects on a circuit board. Results show that the two defects can be accurately detected with no false alarm by use the proposed method.
Comparative study of the synchronous control for rigidly coupled electro-motors
Authors: Liu Tong , Chen Cheng , Ye Beifa , Chen Yuxi
Published: August 2021

Multiple electro-motors rigidly coupled by multi-points gear meshing is of a typical driving structure, and the synchronous control between parallel motors is the key issue about system stability and performance. Firstly, the drooping control is introduced to modify traditional speed parallel control (SPC) method; classical torque master-slave control (TMSC) using soft control parameter is also proposed as contrast. Subsequently, the basic principle of vector control with rotor flux orientation is described; the non-linear time-varying gear dynamics at the unbalanced pinion-gear meshing stage are also studied. Based on the mathematic analysis, simulation models under three different control methods are established in Simulink, and are comparatively studied against backlash, contact ratio and motor parameter deviations between multiple chains. Finally, SPC with drooping control (SPCD) and soft TMSC (STMSC) are applied on a test rig. The simulation and experimental results show that, SPC, SPCD and STMSC separately has advantages in speed tracking, system stability and torque synchronization, and should be used according to specific preference.
Implementation and testing of a conformance platform for IEEE 1901.1 Power Line Communication Standard
Authors: Amaro Nuno , Saragoça João , Cartaxo Ricardo , Yang Wei , Yi Ren
Published: August 2021

IEEE 1901.1 Standard for Medium Frequency (less than 12 MHz) Power Line Communications for Smart Grid Applications was officially released on 2018. This standard brings new possibilities for power line communications, as the used frequency range allows for broader band and higher bit rates when compared to other PLC communication standards. In this scope, this paper presents a conformance platform that allows testing compliance of devices implementing the standard. This conformance-testing platform is then used to test the station and concentrator devices from three different manufacturers, using the data link layer tests as one example, highlighting the capabilities of the platform and simultaneously evaluating the current status of development of these devices (with regards to standard compliance). Results of these tests are also included.
The development of the online detection network system of coal mine safety instrument and meter
Authors: Tao Xinya , Tian Muling , Liu Xiqing
Published: August 2021

As the main equipment that directly reflects the concentration of various flammable, explosive, toxic and harmful gases in the working environment of mines, the coal mine gas sensors are widely used in coal mine safety monitoring and supervision systems. However, these sensors cannot accurately display the concentration of the detected gas due to problems such as zero and span drift of the catalytic element. Therefore, regular testing is required according to coal mine safety regulations. In this paper, the network system of coal mine safety instrument testing center is designed, and a network on-line testing system of coal mine safety instrument’s input, inspection, output, certification and finance is established, which integrates the network server, company LAN, upper computer automatic analysis, lower computer real-time processing and takes barcode as the identification. It realizes the network operation of sensor storage, waiting for inspection, verification, sending and achieves the goal of improving efficiency and reducing labor intensity.
Design of flyback power supply of DC equipment in PV power plant
Authors: Wang Guoliang , Shi Junhai , Chen Yuchen , Yan Weiwu
Published: August 2021

In photovoltaic (PV) grid-connected power generation systems, the needs of low-voltage DC power supply for equipment in PV power plant areas are common. This article provides a design of wide-range high-input voltage flyback power supply. Firstly, the needs of the input voltage range are analysed, and the power supply indexes are defined. Then, the design of the power supply and the transformer circuit are given. The prototype trial results are also given at the last. The results show that the designed power supply meets the requirements of equipment in PV power plant.
Recent developments in load model parameter identification via ambient PMU signal
Authors: Guo Siyuan , Jiang Yunchen , Chen Daojun
Published: August 2021

Load modelling has a significant impact on operation mode arrangement, transient stability analysis, small disturbance stability calculation and other aspects in power system. It is an important basis and issue for the decision-making of dispatching operation department. As a novel research field of measurement-based identification method, load model parameter identification via ambient PMU signal has gained some developments. This article reviews the current research status of ambient data-based load parameter identification, outlines its basic principle and typical framework, and expounds three technical routes. By summarizing the characteristics of various methods, the future research direction is prospected.
Three-dimensional visualization of secondary system based on digital twin
Authors: Gan Xing , Xiong Zaibao , Du Shaofei , Wu Zhongcheng , Geng Xiaohong , Gao Yu , Guo Yi’nan
Published: August 2021

The digital twin technology has become mature and has entered the stage of popularization and application, but the research on digital twin technology of substation secondary system has not been carried out systematically. This paper provides the idea of digital twin digital analog integration application of secondary system, which realizes the information interconnection of three-dimensional model, loop relationship model and transmission data model. Through the correspondence between physical model such as optical cable and field reality, the physical loop information and corresponding virtual loop information can be viewed more intuitively. Combined with the multi-dimensional data-driven model technology, the correlation information of the secondary physical loop and the logic loop is dynamically displayed in 3D visualization, to provide technical support for the operation and maintenance.
Least squares support vector machine for state of charge estimation of lithium-ion battery using gray wolf optimizer
Authors: Wang Qiao , Ye Min , Wei Meng , Wu Chenguang , Ma Yuchuan
Published: August 2021

An accurate SOC estimation can ensure the effective and normal operation of the battery. To this end, a method for estimating the SOC of lithium-ion battery based on least squares support vector machine (LSSVM) is proposed, and the gray wolf optimizer (GWO) algorithm is used to further optimize the model parameters to overcome the non-linearity and unevenness of the actual working condition. Influence of interference factors, and then obtain accurate SOC estimation results. The optimized LSSVM is verified by collected data at different temperatures, the results shows the proposed optimization model is greatly improved compared to before optimization, the model accuracy is improved by about 35%.
Active power improvement of three-phase grid-connected inverter under unbalanced grid faults
Authors: Zhang Ye , Tian Muqin , Song Jiancheng
Published: August 2021

Unbalanced grid voltage causes fault-phase over-current, affects the life span of devices and even leads to control system instability. The conventional current limiting strategy reduces the output power of grid-connected inverter. In order to increase the active power injected by the grid-connected inverter into the grid, this paper proposes a new current limiting strategy. On the premise of ensuring that the DC side voltage fluctuation and grid-connected current harmonics meet the grid standards, the fault-phase current and the normal phase current are respectively limited. The simulation results verify the proposed strategy can effectively improves the active power output of the grid-connected inverter.
Design of voltage stability monitoring simulation system for PV grid-connected system
Authors: Li Sheng , Cao Zhiyang , Cui Jian , Yu Jiawei , Bao Wenqi
Published: August 2021

Voltage stability monitoring simulation system for photovoltaic (PV) grid-connected system is designed, taking the classic three-node power system model with a PV power station for example. The voltage instability theory and application researches for the monitoring simulation system are carried, and the frame, communication protocol and software functions of the voltage stability monitoring system are discussed. The monitoring simulation system can realize two-computer communication and joint debugging, which can not only monitor the basic operational aspects, but also be used to view the voltage equilibrium point curves and voltage response curves as the operating point is affected by various disturbances. And the system load margin index calculation, load shedding and other voltage stability remote control methods are provided to maintain or improve voltage stability. The monitoring simulation system provides a reference scheme for the application of voltage stability theory in practical engineering.
Design of Ka-band broadband low-noise amplifier using 100nm gate-length GaN on silicon technology
Authors: Zou Yu , Chen Zhijian , Lai Junkai , Li Bin , Wu Zhaohui , Lin Xiaoling
Published: August 2021

Due to the high breakdown voltage and better linearity of gallium nitride (GaN) high electron mobility transistor (HEMT), GaN based RF front-end is widely researched and studied. In this paper, a Ka-band cascode low-noise amplifier (LNA) designed with 100nm gate-length GaN-on-silicon technology is presented. With novel methods such as the introduction of high-pass filters and standing wave filtering capacitors, the LNA achieves a stable gain of 21-22.8dB and a noise figure (NF) of 0.9-1.3dB from 22GHz to 38GHz. The input and output return loss are better than-10dB in band of concern. This LNA occupies an area of 2.3mm × 0.9mm and consumes 265-mW DC power. Compared with silicon-on-insulator (SOI), indium phosphide (InP) and gallium arsenide (GaAs) LNAs, the proposed GaN LNA exhibits better performance of linearity, as well as competitive gain and NF.