Full Scale Experiment for Vibration Analysis of Ice-Coated Bundled-Conductor Transmission Lines

Guifeng Zhao,Zhongbin Lu,Xu Wang,Yongbo Peng,Shaojun Chang 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.1

Full scale experiment has received increasing attention in recent years for the reliability analysis of power supplies and power systems. In this paper, the vibration behaviours of conductors with and without D-section ice coatings are addressed by virtue of a field test platform consisting of the prototype of a transmission tower-line system. Utilizing fibre Bragg grating sensors, the vibration of conductors under artificial displacement and natural wind excitations are monitored, and their dynamic characteristics are assessed by the spectral analysis and the identification technique of Hilbert-Huang transform. It is revealed that the vibrations of ice-free and ice-coated multi-bundled conductors vary wildly despite under similar artificial displacements and natural wind excitations. The vibration of ice-coated conductors is mainly dominated by their low-order modes, especially in the frequency range of 0.24 − 2.0 Hz; while the vibration of ice-free conductors gains more benefits from their high-order modes. Compared to the ice-free conductors, the conductors with eccentric ice coating are prone to suffer from galloping under specified wind attack angle; although their vibrations are still controlled by the low-order modes, yet the frequency values of the dominant modes have changed from one wind attack angle case to another. This kind of frequency modulation phenomenon indicates that nonlinear vibration characteristics of ice-coated conductors might change under different wind conditions, which brings great challenges to the research of wind-induced vibration characteristics of ice-coated conductors.

Intraguild interference of spiders and ladybirds in a cotton field: Evidence from their active time and aphid control efficiency

Wang Guifeng,Dong Zhaoke,Li Lili,Lu Zengbin,Li Chao,Men Xingyuan 한국곤충학회 2021 Entomological Research Vol.51 No.10

In field crop systems, biocontrol efficiency supported by various predators is not always enhanced with occurring simultaneously but can be reduced by predator interference, i.e., competition between predator individuals over access to their prey. Such interference may be related to the active time of each predator. In this study, predator exclusion experiments were used to selectively exclude either one or both predators and to examine the impact of the two predator groups on the suppression of cotton aphid (Aphis gossypii Glover) populations in a cotton field. Main predator species included Propylaea japonica (Thunberg) and Harmonia axyridis Pallas in the ladybird group, and Lycosa spp. and Erigone spp in the spider group. A greater number of spiders was observed in the morning and evening, while ladybird densities did not vary during the day. Removing all predators led to an increase in aphid numbers compared to the other treatments where predators were present. Removing either spiders or ladybirds had similar impacts on aphid control. It is likely that spiders provide an equal level of aphid mortality as ladybirds. When both spiders and ladybirds were present, aphid abundance did not differ from those treatments where only one predator group was present. The presence of both predators did not lead to more aphid suppression, indicating that interference between these predators may have occurred in the cotton field. Although these two predators partly diverged in their activity rhythms, interference may still have occurred and could be common in cotton fields.

Fault-Tolerant Control for 5L-HNPC Inverter-Fed Induction Motor Drives with Finite Control Set Model Predictive Control Based on Hierarchical Optimization

Chunjie Li,Guifeng Wang,Fei Li,Hongmei Li,Zhenglong Xia,Zhan Liu 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

This paper proposes a fault-tolerant control strategy with finite control set model predictive control (FCS-MPC) based onhierarchical optimization for five-level H-bridge neutral-point-clamped (5L-HNPC) inverter-fed induction motor drives. Faulttolerantoperation is analyzed, and the fault-tolerant control algorithm is improved. Adopting FCS-MPC based on hierarchicaloptimization, where the voltage is used as the controlled objective, called model predictive voltage control (MPVC), the postfaultcontroller is simplified as a two layer control. The first layer is the voltage jump limit, and the second layer is the voltagefollowing control, which adopts the optimal control strategy to ensure the current following performance and uniqueness of theoptimal solution. Finally, simulation and experimental results verify that 5L-HNPC inverter-fed induction motor drives havestrong fault tolerant capability and that the FCS-MPVC based on hierarchical optimization is feasible.

Study of structural-thermal characteristics of electrified conductors under aeolian vibration

Meng Zhang,Jian Zhou,Guifeng Zhao,Jiankun Xu,Chao Sun 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.2

High-voltage transmission lines are featured by electrical and structural properties. Current studies on aeolian vibration of transmission lines focus primarily on structural responses of unenergized conductors. However, moderate aeolian vibration can also enhance the convection heat transfer capability of a transmission line, which improves the steady current-carrying capacity. In this paper, a fluid-structure interaction (FSI) model is established to study the structural thermal characteristics of overhead electrified aluminum conductor steel-reinforced cable (ACSR) conductors. Moreover, the fatigue damage of the energized conductor is analyzed under operational conditions. Results show that there is considerable influence from aeolian vibration on the current-carrying capacity of energized conductors. Compared with the nonelectrical conductors, aeolian vibration can enhance the convective heat transfer effect of energized conductors. Additionally, fatigue life of electrified transmission lines is larger than that of nonelectrical conductors under aeolian vibration. The developed structure-fluid-thermal model can be used to aid design and operation optimization of transmission lines.

Polymorphic Forms of Furosemide Characterized by THz Time Domain Spectroscopy

Ge, Min,Liu, Guifeng,Ma, Shihua,Wang, Wenfeng Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.10

Terahertz time domain spectroscopy (THz-TDS) is applied in transmission to identify the five forms of modifications of furosemide and one commercial product from 0.3 THz to 1.6 THz at room temperature. The different absorption spectra of the different forms are sensitive to crystal structures. Density function theory (DFT) calculation was used to understand the vibrational modes of furosemide in the THz region. X-ray powder diffractometry (XRPD) was applied to confirm the different forms of modifications. The results demonstrate that THz-TDS is a potential analytical technique in investigating polymorphic forms in the pharmaceutical fields.

Fault-Tolerant Control for 5L-HNPC Inverter-Fed Induction Motor Drives with Finite Control Set Model Predictive Control Based on Hierarchical Optimization

Li, Chunjie,Wang, Guifeng,Li, Fei,Li, Hongmei,Xia, Zhenglong,Liu, Zhan The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

This paper proposes a fault-tolerant control strategy with finite control set model predictive control (FCS-MPC) based on hierarchical optimization for five-level H-bridge neutral-point-clamped (5L-HNPC) inverter-fed induction motor drives. Fault-tolerant operation is analyzed, and the fault-tolerant control algorithm is improved. Adopting FCS-MPC based on hierarchical optimization, where the voltage is used as the controlled objective, called model predictive voltage control (MPVC), the postfault controller is simplified as a two layer control. The first layer is the voltage jump limit, and the second layer is the voltage following control, which adopts the optimal control strategy to ensure the current following performance and uniqueness of the optimal solution. Finally, simulation and experimental results verify that 5L-HNPC inverter-fed induction motor drives have strong fault tolerant capability and that the FCS-MPVC based on hierarchical optimization is feasible.

Fault-tolerant analysis of two boost inverters for open-end winding induction motor drives

Li, Chunjie,Wang, Guifeng,Li, Hongmei,Li, Fei,Xia, Zhenglong,Liu, Zhan The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.4

An open-end winding induction motor drive system fed by two boost inverters with fault-tolerant capability is presented to improve the reliability and safety of the drive system. The boost inverters consist of an impedance-source network and a two-level inverter. It can realize the boost/buck function. An analysis of its fault-tolerance is presented in detail. Short circuits and open circuits are commonly considered as the two main types of faults. Therefore, the fault types of the dual boost inverters are analyzed and diagnosed. Then, two different fault-tolerant schemes are presented. The presented fault-tolerant inverters are restructured through the power switch itself. In addition, different SVPWM methods are addressed. A simulation model and an experimental platform are constructed. Simulation and experimental results verify the fault tolerance of the drive system.

Polymorphic Forms of Furosemide Characterized by THz Time Domain Spectroscopy

Min Ge,Shihua Ma,Guifeng Liu,Wenfeng Wang 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.10

Terahertz time domain spectroscopy (THz-TDS) is applied in transmission to identify the five forms of modifications of furosemide and one commercial product from 0.3 THz to 1.6 THz at room temperature. The different absorption spectra of the different forms are sensitive to crystal structures. Density function theory (DFT) calculation was used to understand the vibrational modes of furosemide in the THz region. X-ray powder diffractometry (XRPD) was applied to confirm the different forms of modifications. The results demonstrate that THz-TDS is a potential analytical technique in investigating polymorphic forms in the pharmaceutical fields.

Association of Bisphenol A and Its Substitutes, Bisphenol F and Bisphenol S, with Obesity in United States Children and Adolescents

Buyun Liu,Hans-Joachim Lehmler,Yangbo Sun,Guifeng Xu,Qi Sun,Linda G. Snetselaar,Robert B. Wallace,Wei Bao 대한당뇨병학회 2019 Diabetes and Metabolism Journal Vol.43 No.1

Background: Bisphenol F (BPF) and bisphenol S (BPS) are increasingly used as substitutes for bisphenol A (BPA), an environmental obesogen. However, health effects of BPF and BPS remain unclear. In this study, we evaluated the associations of BPA, BPF, and BPS with obesity in children and adolescents. Methods: We used data from the U.S. National Health and Nutrition Examination Survey 2013 to 2014, a nationally representative study. We included 745 participants aged 6 to 17 years old. General obesity was defined based on the 2000 Centers for Disease Control and Prevention body mass index-for-age growth charts for the United States. Abdominal obesity was defined as waist-toheight ratio ≥0.5. Results: After adjustment for demographic, socioeconomic and lifestyle factors, and urinary creatinine levels, the odds ratio of general obesity comparing the highest with lowest quartile of urinary bisphenol levels was 1.74 (95% confidence interval [CI], 0.92 to 3.31) for BPA, 1.54 (95% CI, 1.02 to 2.32) for BPF, and 1.36 (95% CI, 0.53 to 3.51) for BPS. Moreover, the associations were stronger in boys than in girls for BPA and BPF. Similar results were observed for abdominal obesity. Conclusion: This study for the first time showed that exposure to BPF, a commonly used substitute for BPA, was positively associated with higher risk of obesity in children and adolescents. The association of BPA and BPF with general and abdominal obesity was primarily observed in boys, suggesting a possible sex difference. Further investigations on the underlying mechanisms are needed.

Dynamic response of an overhead transmission tower–line system to high-speed train-induced wind

Meng Zhang,Ying Liu,Hao Liu,Guifeng Zhao 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.4

The current work numerically investigates the transient force and dynamic response of an overhead transmission tower–line structure caused by the passage of a high-speed train (HST). Taking the CRH2C HST and an overhead transmission tower–line structure as the research objects, both an HST–transmission line fluid numerical model and a transmission tower–line structure finite element model are established and validated through comparison with experimental and theoretical data. The transient force and typical dynamic response of the overhead transmission tower–line structure due to HST-induced wind are analyzed. The results show that when the train passes through the overhead transmission tower–line structure, the extreme force on the transmission line is related to the train speed with a significant quadratic function relationship. Once the relative distance from the track is more than 15 m, the train-induced force is small enough to be ignored. The extreme value of the mid-span dynamic response of the transmission line is related to the train speed and span length with a significant linear functional relationship.