Complex Vector Modeling and Series Decoupling Current Control Strategy of High-Power L/LCL Type Grid-Connected Converter Under Low Switching Frequency

Wang, Yingjie,Jiao, Lanyi,Yang, Bo,Wang, Wenchao,Liu, Haiyuan The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

With power level of grid-connected converters rising, the switching frequency of the switching devices is commonly greatly reduced to improve its power capacity. However, this results in serious couplings of the dq current components, which leads to degradation of the static and dynamic performances of grid-connected converters and fluctuations of the reactive power in dynamic processes. In this paper, complex vector models under low switching frequency are established for an L/LCL grid-connected converter, and the relationship between the switching frequency and the coupling degree is analyzed. In addition, a series decoupling current control strategy is put forward. It is shown that the proposed control strategy can eliminate the couplings, improve the performances and have good robustness to parameter variations through static and dynamic characteristics analyses and a sensitivity analysis. Experimental and simulation results also verify the correctness of the theoretical analyses and the superiority of the proposed control strategy.

Twin-screw extrusion synthesis of low-cost cobalt ferrite ceramic pigments using natural mixed-dimensional palygorskite clay

Yingjie Zhu,Shue Li,Bin Mu,Hao Yang,Lei Wu,Qin Wang,Aiqin Wang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.122 No.-

Due to the disadvantages of traditional solid-phase and liquid-phase methods for preparation of mixedmetal oxide ceramic pigments, it is indispensable to develop a green, clean, low-cost and continuouspreparation technology. In this study, the low-cost and high-performance cobalt ferrite ceramic pigmentswere facilely prepared based on natural mixed-dimensional palygorskite clay by a continuousmechanochemical method using twin-screw extrusion. The incorporation of the mixed-dimensionalpalygorskite clay effectively improved the agglomeration of pigment nanoparticles and decreased theproduction cost. The hybrid pigments presented the optimal color properties (L* = 17.16, a* = 1.07, b* =3.58 and C* = 3.74) when the cobalt ferrite content, calcination temperature and time were 60 wt%,1100 C and 90 min, respectively. Furthermore, the as-prepared hybrid pigments exhibited excellentchemical and thermal stability and biocompatibility, the mass tone and hiding power of the hybrid pigmentswere superior to the commercial cobalt black pigments, thus the obtained hybrid pigments couldbe served as an eco-friendly underglaze pigment for coloring of ceramic embryo body with good colorsaturation. Beyond all doubt, this study will provide a promising strategy for continuous cleaner preparationof low-cost cobalt ferrite ceramic pigments.

CFD simulation of flow and heat transfer characteristics in a 5×5 fuel rod bundles with spacer grids of advanced PWR

Wang Yingjie,Wang Mingjun,Ju Haoran,Zhao Minfu,Zhang Dalin,Tian Wenxi,Liu Tiancai,Qiu Suizheng,Su G.H. 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.7

High fidelity nuclear reactor fuel assembly simulation using CFD method is an effective way for the structure design and optimization. The validated models and user practice guidelines play critical roles in achieving reliable results in CFD simulations. In this paper, the international benchmark MATiS-H is studied carefully and the best user practice guideline is achieved for the rod bundles simulation. Then a 5 5 rod bundles model in the advanced pressurized water reactor (PWR) is established and the detailed three-dimensional thermal-hydraulic characteristics are investigated. The influence of spacer grids and mixing vanes on the flow and hear transfer in rod bundles is revealed. As the coolant flows through the spacer grids and mixing vanes in the rod bundles, the drastic lateral flow would be induced and the pressure drop increases significantly. In addition, the heat transfer is enhanced remarkably due to the strong mixing effects. The calculation results could provide meaningful guidelines for the design of advanced PWR fuel assembly

Complex Vector Modeling and Series Decoupling Current Control Strategy of High-Power L/LCL Type Grid-Connected Converter Under Low Switching Frequency

Yingjie Wang,Lanyi Jiao,Bo Yang,Wenchao Wang,Haiyuan Liu 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

With power level of grid-connected converters rising, the switching frequency of the switching devices is commonly greatly reduced to improve its power capacity. However, this results in serious couplings of the dq current components, which leads to degradation of the static and dynamic performances of grid-connected converters and fluctuations of the reactive power in dynamic processes. In this paper, complex vector models under low switching frequency are established for an L/LCL grid-connected converter, and the relationship between the switching frequency and the coupling degree is analyzed. In addition, a series decoupling current control strategy is put forward. It is shown that the proposed control strategy can eliminate the couplings, improve the performances and have good robustness to parameter variations through static and dynamic characteristics analyses and a sensitivity analysis. Experimental and simulation results also verify the correctness of the theoretical analyses and the superiority of the proposed control strategy.

Blood lipids and all-cause mortality among old people: the Chinese Longitudinal Healthy Longevity Survey 2008-2018

Wang Rongxi,Yu Xiaoyue,Wang Zhiqiang,Liu Yujie,Chen Hui,Liu Shangbin,XU CHENG,Chen Yingjie,Xia Danni,Ge Xin,Chang Ruijie,Xu Gang,Xiang Mi,Wang Ying,Shen Tian,Hu Fan,Cai Yong 한국역학회 2022 Epidemiology and Health Vol.44 No.-

OBJECTIVES: Proper blood lipid levels are essential for survival in older adults, but inconsistent relationships have been reported between blood lipids and all-cause mortality in the elderly. METHODS: This retrospective longitudinal study analyzed data from 1,067 Chinese older adults enrolled in the Chinese Longitudinal Healthy Longevity Survey collected in 2008 and followed up until death or December 31, 2018. The outcome was allcause mortality. Multivariate Cox regression analyses were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with stratification by age (60-80, 80-100, or ≥ 100 years) for further analysis. The survival probability according to lipid profile quartiles was calculated using Kaplan-Meier curves and the log-rank test. RESULTS: The participants’ mean age was 84.84 years, and 57.0% were female. In total, 578 individuals died, and 277 were lost to follow-up. The mean total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels were higher among those who died than among those who survived. Participants in the second HDL-C quartile and the highest LDL-C and triglyceride (TG) quartiles had 28% higher, 23% lower, and 49% lower risks of all-cause mortality, respectively. After further adjustment, the associations remained except for HDL-C, and additional associations were observed between all-cause mortality and the third TC and LDL-C quartiles and the second TG quartile (HR, 1.44; 95% CI, 1.01 to 2.06; HR, 0.68; 95% CI, 0.49 to 0.94; HR, 0.79; 95% CI, 0.62 to 0.99, respectively). CONCLUSIONS: Older adults should maintain an LDL-C level of 1.91-2.47 mmol/L and a TG level of no less than 1.66 mmol/L.

Evaluating and Mitigating Malicious Data Aggregates in Named Data Networking

( Kai Wang ),( Wei Bao ),( Yingjie Wang ),( Xiangrong Tong ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.9

Named Data Networking (NDN) has emerged and become one of the most promising architectures for future Internet. However, like traditional IP-based networking paradigm, NDN may not evade some typical network threats such as malicious data aggregates (MDA), which may lead to bandwidth exhaustion, traffic congestion and router overload. This paper firstly analyzes the damage effect of MDA using realistic simulations in large-scale network topology, showing that it is not just theoretical, and then designs a fine-grained MDA mitigation mechanism (MDAM) based on the cooperation between routers via alert messages. Simulations results show that MDAM can significantly reduce the Pending Interest Table overload in involved routers, and bring in normal data-returning rate and data-retrieval delay.

A study on the wake structure of the double vortex tubes in a ventilated supercavity

Wei Wang,Cong Wang,Yingjie Wei,Wuchao Song 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.4

To study the wake structure of the double vortex tubes in a ventilated supercavity, the computational fluid dynamics (CFD) method based on the finite volume method and the volume of fluids (VOF) multiphase flow model were used to solve the Reynolds-averaged Navier-Stokes (RANS) equations for performing numerical simulation analysis on the wake structure of a supercavitating vehicle. By analyzing the reasons for the upward drift in the tail section of the supercavity and the formation of the double vortex tubes, the effects of gravity and the attack angle of the vehicle on the formation of gas leakage in the double vortex tubes of the supercavity were explained. The pressure and vorticity inside the vortex tubes were thereby analyzed as well. The results showed that, in addition to the gravitational condition, the wetted area of the vehicle with an attack angle also caused the supercavitating tail to form gas leakage in the form of double vortex tubes. Moreover, the wetted area played a dominant role compared to the role of gravity. The supercavity closure to the inside tail section was a high-pressure area, and this area separated downstream into two parts, resulting in the generation of the double vortex tubes. The vorticity and pressure in the vicinity of the vortex tubes attenuated downstream in the direction of the vortex tubes. When the tail section of the cavity leaked gas via three vortex tubes, the values of the vorticity inside the upper part of the vortex tubes became very small, and the air flow inside the upper part of the vortex tubes increased with the attack angle of the vehicle.

On the fuzzy-adaptive command filtered backstepping control of an underactuated autonomous underwater vehicle in the three-dimensional space

JinQiang Wang,Cong Wang,Yingjie Wei,ChengJu Zhang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

This paper studies the three-dimensional path following control problem for an underactuated autonomous underwater vehicle in the presence of parameter uncertainties and external disturbances. Firstly, an appropriate model for the error dynamics was established to solve the path following problem in a moving Serret-Frenet frame. Secondly, an adaptive robust control scheme is proposed through fuzzy logic theory, command filtered backstepping method and an adaptation mechanism. Finally, a suitable Lyapunov candidate function is utilized to verify the stability of the overall control system and demonstrate uniform ultimate boundedness of path following errors. Following novelties are highlighted in this study: (i) The fuzzy method is adopted to solve the problems of model uncertainties, which makes the controller more practical; (ii) to calculate the virtual control derivative, a second-order filter is designed. This reduces the computational effort of the standard backstepping technique. Moreover, the effect of high frequency measurement noise is considerably attenuated via an appropriate filter to attain a more robust control system. (iii) To attain a desired approximation accuracy between the virtual control and the filtered signals, a compensation loop containing the filtered error is established. (iv) An anti-windup design is proposed to solve the problem of integral saturation in control input signals. Finally, comparative simulations are performed to ensure that the presented control scheme has excellent following accuracy and good robustness under multiple uncertainties and external disturbances.

Enhanced Global Asymptotic Stabilization Criteria for Delayed Fractional Complex-valued Neural Networks with Parameter Uncertainty

Xiaohong Wang,Zhen Wang,Yingjie Fan,Jianwei Xia,Hao Shen 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.4

This paper addresses the global asymptotic stabilization of delayed fractional complex-valued neural networks(FCVNNs) subject to bounded parameter uncertainty. The problem is proposed for two reasons: 1) The availablemethods for uncertain dynamical systems may be too conservative; 2) The existing algebraic conditions willlead to huge computational burden for large-scale FCVNNs. To surmount these difficulties, the delayed FCVNNswith interval parameters are transformed into a tractable form at first. Then, a simple and practical controller–linearstate feedback controller is designed to achieve the global asymptotic stabilization. By constructing different Lyapunovfunctions and utilizing the fractional-order comparison principle and interval matrix method, two sufficientglobal asymptotic stabilization criteria expressed in LMI forms, are established. The obtained results in this paperimprove and extend some previous published results on FCVNNs. Finally, two numerical examples are provided toillustrate the correctness of the theoretical results.

Measurement of Intra-Fraction Displacement of the Mediastinal Metastatic Lymph Nodes Using Four-Dimensional CT in Non-Small Cell Lung Cancer

Suzhen Wang,Jianbin Li,Yingjie Zhang,Wei Wang,Fengxiang Li,Tingyong Fan,Min Xu,Qian Shao 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.4

Objective: To measure the intra-fraction displacements of the mediastinal metastatic lymph nodes by using four-dimensional CT (4D-CT) in non-small cell lung cancer (NSCLC). Materials and Methods: Twenty-four patients with NSCLC, who were to be treated by using three dimensional conformal radiation therapy (3D-CRT), underwent a 4D-CT simulation during free breathing. The mediastinal metastatic lymph nodes were delineated on the CT images of 10 phases of the breath cycle. The lymph nodes were grouped as the upper, middle and lower mediastinal groups depending on the mediastinal regions. The displacements of the center of the lymph node in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were measured. Results: The mean displacements of the center of the mediastinal lymph node in the LR, AP, and SI directions were 2.24 mm, 1.87 mm, and 3.28 mm, respectively. There were statistically significant differences between the displacements in the SI and LR, and the SI and AP directions (p < 0.05). For the middle and lower mediastinal lymph nodes, the displacement difference between the AP and SI was statistically significant (p = 0.005; p = 0.015), while there was no significant difference between the LR and AP directions (p < 0.05). Conclusion: The metastatic mediastinal lymph node movements are different in the LR, AP, and SI directions in patients with NSCLC, particularly for the middle and lower mediastinal lymph nodes. The spatial non-uniform margins should be considered for the metastatic mediastinal lymph nodes in involved-field radiotherapy. Objective: To measure the intra-fraction displacements of the mediastinal metastatic lymph nodes by using four-dimensional CT (4D-CT) in non-small cell lung cancer (NSCLC). Materials and Methods: Twenty-four patients with NSCLC, who were to be treated by using three dimensional conformal radiation therapy (3D-CRT), underwent a 4D-CT simulation during free breathing. The mediastinal metastatic lymph nodes were delineated on the CT images of 10 phases of the breath cycle. The lymph nodes were grouped as the upper, middle and lower mediastinal groups depending on the mediastinal regions. The displacements of the center of the lymph node in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were measured. Results: The mean displacements of the center of the mediastinal lymph node in the LR, AP, and SI directions were 2.24 mm, 1.87 mm, and 3.28 mm, respectively. There were statistically significant differences between the displacements in the SI and LR, and the SI and AP directions (p < 0.05). For the middle and lower mediastinal lymph nodes, the displacement difference between the AP and SI was statistically significant (p = 0.005; p = 0.015), while there was no significant difference between the LR and AP directions (p < 0.05). Conclusion: The metastatic mediastinal lymph node movements are different in the LR, AP, and SI directions in patients with NSCLC, particularly for the middle and lower mediastinal lymph nodes. The spatial non-uniform margins should be considered for the metastatic mediastinal lymph nodes in involved-field radiotherapy.