Study of Credibility Evaluation of Dynamic Models and their Parameters

Guo, Weimin,Ye, Xiaohui,Zhong, Wuzhi,Su, Yi,Tang, Yaohua,Song, Xinli,Liu, Tao The Korean Institute of Electrical Engineers 2014 The Journal of International Council on Electrical Vol.4 No.1

The time-domain simulation plays an important role in planning, designing and operation of the power system, but mismatches between its results and the actual system response show that the credibility evaluation of dynamic models is critical in all the above aspects of power systems. This paper discusses the technologies of credibility evaluation, including hybrid dynamic simulation with PMU measurements, error analysis and the calculated indices. Moreover, a phase shift method is presented to implement hybrid dynamic simulation in PSD-FDS. Then the paper proposes a credibility evaluation scheme to provide solution for the evaluation. At last, one sample is used to validate the implementation of hybrid dynamic simulation, while the other sample illustrates the effectiveness of the credibility evaluation approach.

Texture characteristics of a warm rolled 0.085 wt%-P interstitial free (IF) steel with and without lubrication

Weimin Guo,Zuocheng Wang,Na Xu,Ning Ding,Junbo Shi 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7

A 0.085 wt% P micro - alloyed and Ti-stabilized high strength IF (interstitial free) steel was warm rolled under two conditions: One with lubrication and the other without. The results show that lubrication has a significant effect on texture evolution during warm rolling and the subsequent annealing process. Without lubrication, severe shear deformation occurs in the surface layer, which results in recrystallization and the formation of a <110>//ND (normal direction) texture, while the central layer undergoes plane strain deformation and forms a weak <111>//ND deformation texture (typical of bcc iron). With good lubrication, both the surface and central layer experience plane strain deformation and a strong <111>//ND texture is normally formed. The warm rolling texture (which contains both recrystallized and deformed grains) has a profound effect on the subsequent annealing texture. The final textures influence the draw - ability of the plates, i.e. the r - value (r-value: The ratio of the true width strain to the true thickness strain in a sheet tensile test) and |Dr|-value (planar anisotropy coefficient). After annealing, the lubricated plates are characterized by a higher r - value (1.27) and a much lower |Dr|-value (0.075) than those rolled without lubrication (i.e. 0.96 for the r - value and 0.465 for the |Dr|-value).

Fracture analysis of a welded front axle tube structure from a mini-truck

Weimin Guo,Ning Ding,Na Xu,Long Liu,Nan Li,Junbo Shi,Chi-Man Lawrence Wu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

The failure (fracture) mechanism of a welded front axle tube structure made of C45E4 steel from a mini truck was analyzed. The fracture occurred on the right side of the right support frame with the fracture surface perpendicular to the tube axis. SEM examination showed that the fracture surface could be divided into three areas: intergranular area, cleavage area and dimple area. Crack initiation site of the failed front axle tube was at the front weld joint fixing the right support frame on the axle tube. The crack propagated in two opposite directions along the circumference of the tube and converged at the dimple area. Intergranular fracture was found to be in heat affected zone (HAZ). With higher magnification, fine dimples, intergranular and trans-granular fracture characteristics were observed in the crack initiation site. By metallurgical examination, Widmanstätten ferrites, which could decrease the toughness and strength of the weld joint, were observed in the columnar grains. The hardness of HAZ coarse grain area (623 VHN) was far higher than HAZ fine grain area (310 VHN) and base metal (225 VHN). As the weld process indicates, neither pre-weld nor post-weld treatment was carried out. A non-uniform temperature distribution around the weld joint could generate large thermal residual tensile stress in HAZ; thus, the material was very unstable. It could fracture for very small or even no external stress. Hydrogen atoms would be released during welding and microstructures with the highest hardness are the most susceptible of hydrogen assisted cracking. It is concluded that the fracture was caused by hydrogen assisted brittleness under the induction of weld residual stress. Post-weld aging treatment (PWAT) is recommended to release the residual stress generated during welding process. In this case, PWAT was carried out on the failed weld joint and Vickers hardness of HAZ coarse grain area, HAZ fine grain area and base metal decreased to 232 VHN, 205 VHN and 125 VHN, respectively. That indicates that the PWAT procedure could effectively soften the material and relieve residual stress.

Distributed Secondary Voltage Control of Islanded Microgrids with Event-Triggered Scheme

Guo, Qian,Cai, Hui,Wang, Ying,Chen, Weimin The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

In this study, the distributed secondary voltage control of islanded microgrids with multi-agent consensus algorithm is investigated. As an alternative to a time-triggered approach, an event-triggered scheme is proposed to reduce the communication load among inverter-based distributed generators (DGs). The proposed aperiodic control scheme reduced unnecessary utilization of limited network bandwidth without degrading control performance. By properly establishing a distributed triggering condition in DG local controller, each inverter is only required to send voltage information when its own event occurs. The compensation of voltage amplitude deviation can be realized, and redundant data exchange related to fixed high sampling rate can be avoided. Therefore, an efficient use of communication infrastructure can be realized, particularly when the system is operating in steady state. The effectiveness of the proposed scheme is verified by simulations on a microgrid test system.

LncRNA CRNDE Promotes the Progression of B-cell Precursor Acute Lymphoblastic Leukemia by Targeting the miR-345-5p/CREB Axis

Weimin Wang,Feifei Wu,Ping Ma,Silin Gan,Xue Li,Li Chen,Ling Sun,Hui Sun,Zhongxing Jiang,Feng Guo 한국분자세포생물학회 2020 Molecules and cells Vol.43 No.8

The imbalance between the proliferation and apoptosis of B-cell precursors is an important contributor to the pathogenesis of B-cell precursor acute lymphoblastic leukemia (BCP-ALL), while its specific regulatory mechanism remains perplexing. This study aimed to expound the underlying mechanism of the proliferation and apoptosis of BCP-ALL cells from the perspective of non-coding RNA. In this study, long non-coding RNA colorectal neoplasia differentially expressed (LncRNA CRNDE) was upregulated in the bone marrow of BCP-ALL patients and BCP-ALL cell lines (NALM-6 and RS4;11). Functionally, LncRNA CRNDE knockdown restrained cell proliferation and boosted cell apoptosis in NALM-6 and RS4;11 cells. The subsequent investigation confirmed that LncRNA CRNDE bound to miR-345-5p and negatively regulated miR-345-5p expression. The overexpression of miR-345-5p suppressed cell proliferation and boosted cell apoptosis in NALM-6 and RS4;11 cells. Further experiments revealed that miR-345-5p downregulated cyclic AMP response element-binding protein (CREB) expression by targeting its mRNA directly. CREB overexpression reversed the effect of miR-345-5p mimic on cell proliferation and apoptosis in NALM-6 and RS4;11 cells. Finally, in vivo experiments showed that LncRNA CRNDE knockdown prolonged the survival of mice xenotransplanted with NALM-6 cells. In conclusion, LncRNA CRNDE upregulated CREB expression by suppressing miR-345-5p, thus promoting cell proliferation and reducing cell apoptosis in BCP-ALL.

Structural configurations and dynamic performances of flexible riser with distributed buoyancy modules based on FEM simulations

Chen Weimin,Guo Shuangxi,Li Yilun,Gai Yuxin,Shen Yijun 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1

Flexible risers are usually used as conveying systems to bring ocean resources from sea bed up to onshore. Under ocean environments, risers need to bear complex loads and it is crucial to comprehensively examine riser's configurations and to analyze structural dynamic performances under excitation of bottom vehicle motions, to guarantee structural safe operation and required service lives. In this study, considering a saddle-shaped riser, the influences of some important design parameters, including installation position of buoyancy modules, buoyancy ratio and motion of mining vehicle, on riser's configuration and response are carefully examined. Through our FEM simulations, the spatial distributions of structural tensions and curvatures along of riser length, under different configurations, are compared. Then, the impacts of mining vehicle motion on riser dynamic response are discussed, and structural tolerance performance is assessed. The results show that modules installation position and buoyancy ratio have significant impacts on riser configurations. And, an appropriate riser configuration is obtained through comprehensive analysis on the modules positions and buoyancy ratios. Under this proposed configuration, the structural tension and curvature could moderately change with buoyancy modules and bottom-end conditions, in other words, the proposed saddle-shaped riser has a good tolerance performance to various load excitations.

Distributed Secondary Voltage Control of Islanded Microgrids with Event-Triggered Scheme

Qian Guo,Hui Cai,Ying Wang,Weimin Chen 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

In this study, the distributed secondary voltage control of islanded microgrids with multi-agent consensus algorithm is investigated. As an alternative to a time-triggered approach, an event-triggered scheme is proposed to reduce the communication load among inverter-based distributed generators (DGs). The proposed aperiodic control scheme reduced unnecessary utilization of limited network bandwidth without degrading control performance. By properly establishing a distributed triggering condition in DG local controller, each inverter is only required to send voltage information when its own event occurs. The compensation of voltage amplitude deviation can be realized, and redundant data exchange related to fixed high sampling rate can be avoided. Therefore, an efficient use of communication infrastructure can be realized, particularly when the system is operating in steady state. The effectiveness of the proposed scheme is verified by simulations on a microgrid test system.

Dynamic responses and robustness performance to moving boundary of double-stepped cable during deep-sea mining

Li Yilun,Guo Shuangxi,Guo Yucheng,Yu Xiaoqi,Chen Weimin,Song Jixiang 대한조선학회 2023 International Journal of Naval Architecture and Oc Vol.15 No.-

As the exploration and exploitation of deep-sea oil and gas, along with promising polymetallic nodule&sulfides mining, have been developing toward ultra-deep waters, some innovative concepts of marine cable configuration suitable for ultra-deepwater are proposed, such as stepped cable, hybrid cable and double-stepped cable. For deep-water cables with complex configurations, the structural responses become more complicated due to their non-uniform structural properties. Because the distributed buoyancy modules along cable length might introduce more significant local bending segments. Moreover, the impacts of moving boundary, caused by the motions of top vessel and bottom mining vehicle, should be considered. Through combing the finite element simulations with the hydrodynamic models, the dynamic response analysis approach of ultra-deepwater cables is established in this study. Then the double-stepped cable responses, including axial tension, displacement along with the change of overall configurations caused by moving top vessel and bottom mining vehicle, are calculated. Moreover, wave propagation behaviors during cable response are comprehensively examined, and the influences of non-uniform structural properties on cable response and wave propagation are analyzed using the wave propagation theory of structure with axially varying properties based on the Bessel function. The results show that the presented double-stepped cable can provide suitable configurations during the dynamic response, which has good compliance performance and can effectively buffer its response caused by moving boundary excitation. Finally, we found that the response spatial-temporal evolutions present some interesting phenomena, such as the axially non-uniform characteristics lead to non-monotonic changes in response amplitude and wavelength, with local peaks occurring in the low-tension region, owing to the distributed buoyancy modules, along with axiallyvarying and discontinuous structural properties. And, there exists significant mixed effect coming from both standing waves and traveling waves.

Analysis and Modeling of AC-AC Switched Capacitor Converters

Cai, Hui,Bao, Liting,Guo, Qian,Wang, Ying,Chen, Weimin The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1

A new modeling method for AC-AC switched capacitor converters (SCCs) is introduced in this study. The proposed analytical method aims to accurately describe the input-output characteristics of AC-AC SCCs and establish a mathematical model for static voltage conversion ratio and equivalent resistance, which are key performance metrics for SCCs. A quantitative analysis of converter regulation capability is addressed on the basis of the modeling method. In this analysis, the effects of the control parameters and individual components on SCCs are illustrated extensively. Component stresses, such as the peak value and transient variation of the voltage/current of the converter, are also presented. The effectiveness of the proposed method is verified by comparing it with the existing modeling method and applying it to an AC-AC SCC with a conversion ratio of three. Two 1 kW prototypes are built in a laboratory, and their experimental results exhibit good agreement with the theoretical analysis.

Analysis and Modeling of AC–AC Switched Capacitor Converters

Hui Cai,Liting Bao,Qian Guo,Ying Wang,Weimin Chen 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1

A new modeling method for AC–AC switched capacitor converters (SCCs) is introduced in this study. The proposed analyticalmethod aims to accurately describe the input–output characteristics of AC–AC SCCs and establish a mathematical model forstatic voltage conversion ratio and equivalent resistance, which are key performance metrics for SCCs. A quantitative analysis ofconverter regulation capability is addressed on the basis of the modeling method. In this analysis, the effects of the controlparameters and individual components on SCCs are illustrated extensively. Component stresses, such as the peak value andtransient variation of the voltage/current of the converter, are also presented. The effectiveness of the proposed method is verifiedby comparing it with the existing modeling method and applying it to an AC–AC SCC with a conversion ratio of three. Two 1kW prototypes are built in a laboratory, and their experimental results exhibit good agreement with the theoretical analysis.