Parameters optimization design for LCL-type STATCOMs under complex power grid

Wang, Xiangyu,Wang, Minglei,Wang, Liguo,Fu, Guangjie,Qiao, Jinxin The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.2

LCL filter parameters and control parameters are interdependent and inter-restricted. They can all affect the stability of a static synchronous compensator (STATCOM) under the effects of a complex power grid such as harmonic grid voltage and grid impedance variation. An advanced parameters optimization method integrated with LCL filter and control strategy is proposed. At first, the ABC-Pareto algorithm (Pareto multi-objective optimization of an artificial bee colony algorithm) is used to reasonably choose the LCL filter parameters. Under the premise of using capacitor current feedback active damping control and grid voltage feedforward control, the mathematical models of the STATCOM are derived. The constraints of control performances on the control parameters are obtained. According to these constraints, it is possible to construct a satisfactory 3D space. The control parameters can be chosen reasonably by finding the optimized space when the power grid is changed. Simulation and experimental results show the effectiveness and superiority of the proposed method.

Investigation of Surface Integrity Up-Milling Magnesium Oxide Particle Reinforced Wood-Based Composite

Jinxin Wang,Rongsheng Jiang,Zhanwen Wu,Zhaolong Zhu,Longzhi Yang,Pingxiang Cao 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.3

Metal oxide reinforced composite, as a new kind of engineering material, was an essential research topic to industry. Magnesium oxide as particle-reinforced phase, were mixed with wood fiber-matrix to enhance the mechanical properties of composite. However, the research on the surface quality of this composite is still desirable for expanding its application. In order to investigate the surface integrity of this kind particle-reinforced wood-based composite, spiral up-milling experiments were performed with different cutting depth and cutting speed. The effect of cutting speed and cutting depth on surface integrity was investigated. According to the calculation results of black pixels proportion of binary image of machined surface, surface defects were greatly affected by cutting depth rather than cutting speed. Defects, such as pile-up and debonding of particles, were usually observed under 0.5 mm cutting depth, meanwhile, extensive damage of flacking and fracture of wood fiber-matrix were usually observed under 1.5 mm cutting depth. In all, the machined surface formation mechanism of this composite can be different by changing cutting depth.

Active control of amplitude and phase of high-power RF systems in EAST ICRF heating experiments

Zhu Guanghui,Liu Lunan,Mao Yuzhou,Zhang Xinjun,Guo Yaoyao,Ai Lin,Jiang Runhao,Qin Chengming,Zhang Wei,Yang Hua,Yuan Shuai,Wang Lei,Ju Songqing,Wang Yongsheng,Sun Xuan,Yang Zhida,Wang Jinxin,Cheng Yan 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2

The EAST ICRF system operating space has been extended in power and phase control with a low-level RF system for the new double-strap antenna. Then the multi-step power and periodic phase scanning experiment were conducted in L-mode plasma, respectively. In the power scanning experiment, the stored energy, radiation power, plasma impedance and the antenna's temperature all have positive responses during the short ramp-ups of PL;ICRF. The core ion temperature increased from 1 keV to 1.5 keV and the core heating area expanded from jZj 5 cmto jZj 10 cm during the injection of ICRF waves. In the phasing scanning experiment, in addition to the same conclusions as the previous relatively phasing scanning experiment, the superposition effect of the fluctuation of stored energy, radiation power and neutron yield caused by phasing change with dual antenna, resulting in the amplitude and phase shift, was also observed. The active control of RF output facilitates the precise control of plasma profiles and greatly benefits future experimental exploration.

Residual Load Sway Reduction Control in Double-pendulum Overhead Cranes Using Motion Trajectory Based on Adams-Matlab Joint Simulation

Jinxin Hu,Huimin Ouyang,Wenwei Huang,Ping Xing,Chunmin Yu,Guangming Zhang,Lei Mei,Xin Deng,Deming Wang 제어로봇시스템학회 2017 제어로봇시스템학회 국제학술대회 논문집 Vol.2017 No.10

When the hook mass is greater than the load mass or the load has a distributed mass property, the load sway of the crane system can be considered as a double-pendulum. At this point, the crane system has two kinds of natural angular frequency which greatly increases the difficulty of the dynamic analysis and the controller design. To this end, the linear dynamics of a 2-D overhead crane with double-pendulum effect is derived based on a disturbance observer and is decoupled for controller design by modal analysis. Second, an S-shaped curve, which is widely used in the control fields, is applied to the linearized decoupling crane model. The trajectory parameters are obtained by solving the algebraic equation. Finally, the validity of the method is verified by simulation results.

Ship Twin-propeller Jet Model used to Predict the Initial Velocity and Velocity Distribution within Diffusing Jet

Jinxin Jiang,Wei-Haur Lam,Yonggang Cui,Tianming Zhang,Chong Sun,Jianhua Guo,Yanbo Ma,Shuguang Wang,Gerard Hamill 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3

The current research proposed the theoretical model for ship twin-propeller jet based on the axial momentum theory and Gaussian normal distribution. The twin-propeller jet model is compared to the more matured single propeller jet model with good agreement. Computational Fluid Dynamics (CFD) method is used to acquire the velocity distribution within the twin-propeller jet for understanding of flow characteristics and validation purposes. Efflux velocity is the maximum velocity within the entire jet with strong influences by the geometrical profiles of the blades. Twin-propeller jet model showed four-peaked profile at the initial plane downstream to the propeller compared to the two-peaked profile from a single-propeller. The four-peaked profile merges to be twopeaked velocity profile and then one-peaked profile due to the fluid mixing. Entrainment occurs between the ambient still water outside and the rotating flow within jet due to the high velocity gradient. The research proposes a twin-propeller jet theory with a serial of equations enabling the predictions of velocity magnitude within the jet.

POD-based analysis of time-resolved tornado-like vortices

Mengen Wang,Shuyang Cao,Jinxin Cao 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.1

In this study, three representative configurations of tornado-like vortices, i.e., single vortex, vortex breakdown and multi-vortex, are numerically simulated using large-eddy simulation (LES). Proper orthogonal decomposition (POD) is firstly employed to decompose flow-field snapshots into a series of orthogonal flow patterns (POD modes) and time-dependent coefficients. Then, a conditional-average analysis is conducted to obtain the four kinds of conditionally-averaged flow fields, which are then compared with instantaneous and ensemble-averaged flow fields. Next, a quadruple POD analysis is performed to decompose the instantaneous flow field into mean, coherent, transition and noise components. Finally, a qualitative analysis is implemented for unsteady vortex motions in horizontal and vertical planes. Results show that the conditional average shows larger-scale coherent structures than the classical ensemble average, while it loses the small-scale turbulent fluctuations present in instantaneous flow. The tornado vortex structure is controlled by the mean component in the single-vortex stage. With increase in swirl ratio, the tornado vortex evolves from single-vortex, to vortex-breakdown to multi-vortex, companied by kinetic energy transference to coherent and transition components. The horizontal and vertical vortex motions are essentially the results of horizontal and vertical velocity perturbations.

Effect of glass cooling rate on the crystallization behavior and structure of Al2O3-SiO2-Na2O-CaF2 oxyfluoride glass-ceramics

Mengxuan Li,Jinxin Zou,Guangping Guo,Jianxiang Liu,Guicheng Wang 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.5

The glass cooling rate during molding process has significant effect on the crystallization behavior and structural uniformityof Al2O3-SiO2-Na2O-CaF2 oxyfluoride glass-ceramics. Abaqus Finite Element Analysis indicated that at room temperaturecooling environment, the cooling rate of 8mm thick glass was notably lower than that of 3 mm thick glass. The interiortemperature of 8 mm thick precursor glass was still above 710 oC even after the sample was cooled for 15 s, which caused theformation of “crystal stones” in precursor glass. The microstructure of oxyfluoride glass and glass-ceramics with differentthickness was analyzed by using DTA, XRD, IR and SEM. Since the 8 mm thick glass was cooled slowly, the initial crystalnucleation generated in the interior of glass, mixed crystal phases were formed in the interior after heat treatment, while singleCaF2 crystal phase formed on the surface. On the contrary, there was only uniform CaF2 crystal phase generating in the 3mm thick precursor glass after heat treatment, as a result of high cooling rate during molding process. Besides, the mechanismand ways to optimize the structure uniformity of glass ceramics were also be discussed.

Numerical investigation of effects of rotating downdraft on tornado-like-vortex characteristics

Cao, Shuyang,Wang, Mengen,Zhu, Jinwei,Cao, Jinxin,Tamura, Tetsuro,Yang, Qingshan Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.26 No.3

Appropriate modeling of a tornado-like vortex is a prerequisite when studying the near-ground wind characteristics of a tornado and tornado-induced wind loads on structures. Both Ward- and ISU-type tornado simulators employ guide vanes to induce angular momentum to converge flow in order to generate tornado-like vortices. But in the Ward-type simulator, the guide vanes are mounted near the ground while in the ISU-type they are located at a high position to allow vertical circulation of flow that creates a rotating downdraft to generate a tornado-like vortex. In this study, numerical simulations were performed to reproduce tornado-like vortices using both Ward-type and ISU-type tornado simulators, from which the effects of rotating downdraft on the vortex characteristics were clarified. Particular attention was devoted to the wander of tornado-like vortices, and their dependences on swirl ratio and fetch length were investigated. The present study showed that the dynamic vortex structure depends significantly on the vortex-generating mechanism, although the time-averaged structure remains similar. This feature should be taken into consideration when tornado-like-vortex simulators are utilized to investigate tornado-induced wind forces on structures.

Trichoderma biodiversity in major ecological systems of China

Kai Dou,Jinxin Gao,Chulong Zhang,Hetong Yang,Xiliang Jiang,Jishun Li,Yaqian Li,Wei Wang,Hongquan Xian,Shigui Li,Yan Liu,Jindong Hu,Jie Chen 한국미생물학회 2019 The journal of microbiology Vol.57 No.8

An investigation of Trichoderma biodiversity involving a large-scale environmental gradient was conducted to understand the Trichoderma distribution in China. A total of 3,999 isolates were isolated from forestry, grassland, wetland and agriculture ecosystems, and 50 species were identified based on morphological characteristics and sequence analysis of genetic markers. Trichoderma harzianum showed the largest proportion of isolates and the most extensive distribution. Hypocrea semiorbis, T. epimyces, T. konilangbra, T. piluliferum, T. pleurotum, T. pubescens, T. strictipilis, T. hunua, T. oblongisporum and an unidentified species, Trichoderma sp. MA 3642, were first reported in China. Most Trichoderma species were distributed in Jilin and Heilongjiang Provinces in northeast China and the fewest were distributed in Qinghai Province. Based on the division of ecological and geographic factors, forestry ecosystems and low-altitude regions have the greatest species biodiversity of Trichoderma.

FDTD simulation of the optical properties for a gold nanoparticle-overnanosheet hybrid structure

Yu Chen,Jie Wang,Tao Xu,Min Liu,Jinxin Liu,Han Huang,Fangping Ouyang 한국물리학회 2020 Current Applied Physics Vol.20 No.3

The optical properties of a two-dimensional gold nanoparticle-over-nanosheet (2D-AuNP/NS) have been studied using Finite-Difference Time-Domain (FDTD) method. 2D-AuNP/NS hybrid structure exhibits three typical localized surface plasmon (LSP) resonances, which occur in nanogaps between NP-NP, NP-NS and coupled upper and lower surface of NS respectively. Thus, the influence of AuNP-size, surface AuNP-coverage, NP-NP-spacing and NS-thickness on the localized electric field was analyzed in details. The LSP resonance between NP-NS has been predicted to be the most important effect on SERS, which is dominant, stable and can maintain the SERS intensity even at a relatively low NP-coverage. If a slight deviation of AuNPs away from their original periodic positions was permitted, a disordered model was then constructed which would more closely approximate the real AuNP/NS hybrid structure and was able to calculate the influence of disorder on LSP resonance. A blue shift (rather than red shift) of the resonance peak was observed and its peak intensity would increase first and decrease then with the increase of NP-NP-spacing. FDTD simulations have finally illustrated that NP-coverage should be controlled ranging from 80.0 % to 87.0% or just equal to 100%, if both AuNP-size and NP-thickness is controlled to 10 nm. The FDTD simulation results are qualitative agreement with the existing experimental data and are very useful in the future materials designs for AuNS-based nanocomposite.