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Fast Supplementary Voltage Control Strategy to Mitigate Catastrophic Trip-off Risk of Wind Turbines
Yin Lifu,Liu Yongcheng,Wang Zhuxiu,Xu Ang,Li Zhengtian,Lin Xiangning,Feng Zhongnan,Zhuo Yixin 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.6
There exists such a risk that Magnetic Control Reactor (MCR) type Static Var Compensator (SVC), which is widely used in wind farms, still outputs excessive reactive power after fault removal in the wind farm due to the slow regulating speed of MCR, leading to catastrophic trip-off problem of wind turbine. For the purpose of overcoming the shortage of MCR-type SVC on regulating speed and eff ectively controlling the transient over-voltage level of wind farm due to fault removal, an novel fast supplementary voltage control strategy for MCR-type SVC based on decision tree algorithm is proposed. The over-voltage level and trip-off risk of each wind turbine after fault removal is predicted by the proposed dynamic voltage security decision tree system. According to the predictions, appropriate capacitor banks are shed to lower the risk of wind turbine trip-off due to overvoltage, resulting from reactive power over-compensation. It can be proven with case studies that the proposed strategy is capable of reducing the risk of over-voltage in wind farms, accompanied by the excellent computational effi ciency.
Effects of temperature on the local fracture toughness behavior of Chinese SA508-III welded joint
Li Xiangqing,Ding Zhenyu,Liu Chang,Bao Shiyi,Qian Hao,Xie Yongcheng,Gao Zengliang 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.8
The structural integrity of welded joints in the reactor pressure vessel (RPV) is directly related to the safety of nuclear power plants. The RPV is made from SA508-III steel in a pressurized water reactor. In this study, we investigated the effects of temperature on the tensile and fracture toughness properties of Chinese SA508-III welded joint in different sampling areas in order to provide reference data for structural integrity assessments of RPVs. The specimens used in tensile and fracture toughness tests were fabricated from the base metal (BM), weld metal (WM), and the heat-affected zone (HAZ) in the welded joint. The representative testing temperatures included the ambient temperature (20 C), upper shelf temperature (100 C), and service temperature (320 C). The results showed that temperature greatly affected the fracture toughness (JIC) values for the SA508-III welded joint. The JIC values for BM and HAZ both decreased remarkably from 20 C to 320 C. The fracture morphologies showed that the BM and HAZ in the welded joint exhibited fully ductile fracture at 20 C, whereas partial cleavage fracture was mixed in ductile fracture mode at 100 C and 320 C. The WM exhibited the ductile and cleavage fracture mixed mode at various temperatures, and the JIC values showed slight changes
Han Zhiyu,Wu Zhenkuo,Huang Yongcheng,Shi Yongsheng,Liu Wei 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.6
A study on the design and combustion performance of a new spark-ignition compressed natural gas (CNG) engine for light-duty automotive applications was carried out. The effects of natural gas fuel characteristics on engine design were analyzed in guiding the design of the engine. One-dimensional simulations with added natural gas laminar flame speed data were conducted in upfront to optimize the engine performance with the evaluation of the effects of compression ratio (CR), intake variable valve timing (VVT), and spark timing, etc. The results were validated through engine dyno experiments. It showed the CNG engine’s torque and BSFC could be increased by from 5.2 to 6.6 %, and from 4.6 to 5.7 % , respectively, with increasing the CR from 10.5 to 12. At full engine loads, the intake VVT angles needed re-adjustments for improving the torque output, while the original gasoline-engine adapted VVT resulted in the optimal BSFC under other operation conditions. In additional, the transient emission characteristics of a passenger car powered by the CNG engine were also presented. The CO2 emission of the vehicle under NEDC is 117.32 g/km, which meets China’s 2020 CO2 limit. When equipped with a three-way catalyst, the vehicle can meet the China 6b emission standard.
Yanqiu Wei,Baozhi Yang,Yunlong Li,Yongcheng Duan,Deyu Tian,Baoxiang He,Chuangfu Chen,Wenjun Liu,Limin Yang 대한수의학회 2020 Journal of Veterinary Science Vol.21 No.4
A fluorescent microsphere-based immunochromatographic strip test (FICT) was developed for the rapid, sensitive, and quantitative detection of porcine reproductive and respiratory syndrome virus (PRRSV) antibodies at the pen-side. The assay was based on the formation of a sandwich immune-complex (anti-pig IgG-PRRSV antibodies-NSP7/N), which was validated by a comparison with IDEXX-ELISA using 3325 clinical specimens. The diagnostic specificity, sensitivity, and accuracy of FICT were 97.28, 93.41, and 94.95%, respectively. FICT showed a good correlation with the virus neutralization assay. Overall, a promising pen-side diagnostic tool was developed for the rapid and quantitative detection of PRRSV antibodies within 15 min.