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Improved Decoupling Control Strategy of MMC-HVDC System Connected to the Weak AC Power Grid
Li Bingkun,Li Hongguang,Wang Gang 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2
In order to make full use of the regulation capabilities and avoid energy loss caused by coupling eff ect, a mathematical model of MMC-HVDC system was deduced. Subsequently, the coupling mechanism between the AC current and stations of the MMC system were analyzed via nonlinear equation. On the basis of mechanism analysis, the eff ects of inter-coupling in MMC-HVDC system connected to weak AC power grid were weakened by adding the dynamic feedforward compensation into the control system. In addition, to ensure the system stability and improve dynamic performance of the proposed controller, the control parameters design method was proposed based on the Hurwitz criterion and the time-domain mathematical calculations. By combining the two parts of the control system, an improved decoupling control strategy applicable to MMC system was proposed. Taking MMC-HVDC system as an example, the simulation based on PSCAD/ EMTDC verifi ed the eff ectiveness of the proposed method.
Li, Lianhui,Xu, Guanying,Wang, Hongguang Korea Information Processing Society 2019 Journal of information processing systems Vol.15 No.3
Supplier evaluation is of great significance in green supply chain management. Influenced by factors such as economic globalization, sustainable development, a holistic index framework is difficult to establish in green supply chain. Furthermore, the initial index values of candidate suppliers are often characterized by uncertainty and incompleteness and the index weight is variable. To solve these problems, an index framework is established after comprehensive consideration of the major factors. Then an adaptive weight D-S theory model is put forward, and a fuzzy-rough-sets-AHP method is proposed to solve the adaptive weight in the index framework. The case study and the comparison with TOPSIS show that the adaptive weight D-S theory model in this paper is feasible and effective.
Tunable exchange bias in La1.5Sr0.5CoMnO6 double perovskite doped with nonmagnetic Ga ions
Zhang Hongguang,Chen Wei,Xie Liang,Zhao HuiHui,Li Qi 한국물리학회 2022 Current Applied Physics Vol.35 No.-
The crystal structure, electronic structure, and magnetic behaviors of nonmagnetic Ga ions doped double perovskite La1.5Sr0.5CoMnO6 single phase crystals have been investigated. Different from the traditional magnetic dilution effect of nonmagnetic doping, Ga doping in La1.5Sr0.5CoMnO6 enhances the ferromagnetic (FM) exchange interaction of Co3+-O-Mn3+. Moreover, both conventional and spontaneous exchange bias (EB) effects can be tuned by modulating the Ga doping content, which is accompanied by the variation of the Co3+/4+ and Mn3+/4+ and the effective magnetic moment. The EB field and magnetization can be improved by nonmagnetic Ga3+ doping with content lower than 0.2. The evolution of conventional and spontaneous EB effects in La1.5Sr0.5Co1-xGaxMnO6 can be understood in terms of the unidirectional interface anisotropic coupling between FM/anti-FM, and/or FM/spin glass, which is affected by antisite disorder, spin glass, and the uncompensated coupling between Co and Mn.
The exchange bias effect and Griffiths phase in La1.5Sr0.5Co1-Ni MnO6: The impact of the divalent Ni
Zhang Hongguang,Wang Sen,Chen Wei,Wang Mingjun,Li Yongtao,Xie Liang 한국물리학회 2023 Current Applied Physics Vol.53 No.-
The effects of Co-site doping of Ni2+ ions on the crystal structure, electronic structure, and magnetic properties of La1.5Sr0.5CoMnO6 are investigated. The doping causes an increase in the anti-site disorder and a change in the content of Co2+/3+ and Mn3+/4+, as well as a change in the spin state of Co ions. Ni doping introduces Ni2+-O2-- Mn4+ ferromagnetic interactions to increase the ferromagnetic transition temperature. Samples display different dominant clusters, and field cooling promotes the presence of ferromagnetic clusters, allowing an increase in the Griffiths phase. Interestingly, Ni doping enables tuning the conventional and spontaneous exchange bias (EB) effects, increasing the EB field for intermediate concentrations. Moreover, the maxima of both EB fields do not occur in the same sample, which leads to a new understanding of the relationship between these two effects. The possible mechanisms related to the uncompensated spin and competition between ferromagnetic and antiferromagnetic clusters are discussed, respectively.
Lianhui Li,Guanying Xu,Hongguang Wang 한국정보처리학회 2019 Journal of information processing systems Vol.15 No.3
Supplier evaluation is of great significance in green supply chain management. Influenced by factors such aseconomic globalization, sustainable development, a holistic index framework is difficult to establish in greensupply chain. Furthermore, the initial index values of candidate suppliers are often characterized by uncertaintyand incompleteness and the index weight is variable. To solve these problems, an index framework is establishedafter comprehensive consideration of the major factors. Then an adaptive weight D-S theory model is putforward, and a fuzzy-rough-sets-AHP method is proposed to solve the adaptive weight in the index framework. The case study and the comparison with TOPSIS show that the adaptive weight D-S theory model in this paperis feasible and effective.
Zhang Xiaobing,Li Hongguang,Cao Wei 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.6
It is discussed that a new method for active power measurement under the conditions of distortion signals. Accurate measurement of the power consumed by the distorted signals has been focused on in recent years due to its practical utilities. In this work, a mathematical description of powers is deducted in the conditions of distorted signals according to a simplified model of the electrical network. Then, a rational measuring method of the electric energy for distorted signals is proposed on the basis of the analysis of the power flow. Also, a measuring method based on multiple wavelets was employed for measuring the active power in the conditions of unsteady distorted signals. Experimental results demonstrate that, by using the simulated typical distorted signals, the proposed measurement method can produce extremely accurate results compared to theoretical results.
Mechanism of Tungsten Recovery from Spent Cemented Carbide by Molten Salt Electrodeposition
Hongxuan Xing,Zhen Li,Enrui Feng,Xiaomin Wang,Hongguang Kang,Yiyong Wang,Hui Jin,Jidong Li The Korean Electrochemical Society 2023 Journal of electrochemical science and technology Vol.14 No.1
The accumulation of spent carbide (YG8), not only pollutes the environment but also causes waste of tungsten, cobalt and other rare metal resources. To better address this issue, we proposed a combined electrochemical separation process of low-temperature aqueous solution and high-temperature molten salt for tungsten and cobalt. H<sub>2</sub>WO<sub>4</sub> was obtained from spent carbide in an aqueous solution, and we calcined it to obtain WO<sub>3</sub>, which was used as a raw material to obtain tungsten by using molten salt electrodeposition. The influence of the current efficiency and the electrochemical behavior of the discharge precipitation of W(VI) were also studied. The calcination results showed that the morphology of WO<sub>3</sub> was regular and there were no other impurities. The maximum current efficiency of 82.91% was achieved in a series of electrodeposition experiments. According to XRD and SEM analysis, the recovered product was high purity tungsten, which belongs to the simple cubic crystal system. In the W(VI) reduction mechanism experiments, the electrochemical process of W(VI) in NaCl-Na<sub>2</sub>WO<sub>4</sub>-WO<sub>3</sub> molten salt was investigated using linear scanning voltammetry (LSV) and chronoamperometry in a three-electrode system. The LSV showed that W(VI) was reduced at the cathode in two steps and the electrode reaction was controlled by diffusion. The fitting results of chronoamperometry showed that the nucleation mechanism of W(VI) was an instantaneous nucleation mode, and the diffusion coefficient was 7.379×10<sup>-10</sup> cm<sup>2</sup>·s<sup>-1</sup>.
Ling Qiu,Rong Xu,Siyang Wang,Shuijun Li,Hongguang Sheng,Jiaxi Wu,Yi Qu 생화학분자생물학회 2015 Experimental and molecular medicine Vol.47 No.-
Pentraxin 3 (PTX3) was identified as a marker of the inflammatory response and overexpressed in various tissues and cells related to cardiovascular disease. Honokiol, an active component isolated from the Chinese medicinal herb Magnolia officinalis, was shown to have a variety of pharmacological activities. In the present study, we aimed to investigate the effects of honokiol on palmitic acid (PA)-induced dysfunction of human umbilical vein endothelial cells (HUVECs) and to elucidate potential regulatory mechanisms in this atherosclerotic cell model. Our results showed that PA significantly accelerated the expression of PTX3 in HUVECs through the IκB kinase (IKK)/IκB/nuclear factor-κB (NF-κB) pathway, reduced cell viability, induced cell apoptosis and triggered the inflammatory response. Knockdown of PTX3 supported cell growth and prevented apoptosis by blocking PA-inducted nitric oxide (NO) overproduction. Honokiol significantly suppressed the overexpression of PTX3 in PA-inducted HUVECs by inhibiting IκB phosphorylation and the expression of two NF-κB subunits (p50 and p65) in the IKK/IκB/NF-κB signaling pathway. Furthermore, honokiol reduced endothelial cell injury and apoptosis by regulating the expression of inducible NO synthase and endothelial NO synthase, as well as the generation of NO. Honokiol showed an antiinflammatory effect in PA-inducted HUVECs by significantly inhibiting the generation of interleukin-6 (IL-6), IL-8 and monocyte chemoattractant protein-1. In summary, honokiol repaired endothelial dysfunction by suppressing PTX3 overexpression in an atherosclerotic cell model. PTX3 may be a potential therapeutic target for atherosclerosis.