Current Balancing Control of High Power Parallel-Connected AFE with Small Current Ripples

Xinbo Cai,Zhenbin Zhang,Liang Cai,Ralph Kennel 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Parallel connected Active Front End (AFE) voltage converters are widely employed in high-power grid interfaces for renewable energy applications. With parallel connected two level power converters, the power rating of the system can be easily increased with higher stability and less control efforts than multilevel power converter based solutions. However, due to unmatched modules, unbalanced currents inevitably happen to different modules of the same phase, which seriously impacts the efficiency and performances of the converter. This paper presents an improved current balancing control methods for a high power (600 kVA) parallel connected AFE for wind energy applications. The proposed current balancing method is integrated within a well-known Voltage Oriented Control Scheme with few implementation efforts. The simulation results show that with the proposed strategy the current ripples of each parallelconnected converter leg decrease evidently and the THDs are therefore decreased. Moreover, the effectiveness of the proposed method is also confirmed by experimental results with a grid-code compatible testing set-up.

Theoretical research and experimental study for a new measurement method of standing wave levitation force

Xinbo Li,Hai Jiang,Xiaoyang Jiao,Kai Zhang,Guojun Liu,Jian-Fang Liu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5

Based on the lever principle, a novel measurement method for the standing wave levitation force is investigated and the measurementdevice is developed. The relative levitation force was simulated by MATLAB software, from which the relative levitation force distributionand the curves of relative levitation force in vertical and horizontal directions were obtained. To verify the rationale of the measurementmethod, a series of experiments were carried out with the designed measurement device system. The levitation force distributionand the curves of levitation force in vertical and horizontal directions were also obtained from the experiment. Comparing the experimentalresults with the simulation, the levitation force distribution situation from the experimental results and the simulation is identical.

Dexamethasone enhances glucose uptake by SGLT1 and GLUT1 and boosts ATP generation through the PPP-TCA cycle in bovine neutrophils

Xinbo Wang,Mingyu Tang,Yuming Zhang,Yansong Li,Jingdong Mao,Qinghua Deng,Shusen Li,Zhenwei Jia,Liyin Du 대한수의학회 2022 Journal of Veterinary Science Vol.23 No.5

Background: Clinical dexamethasone (DEX) treatment or stress in bovines results in extensive physiological changes with prominent hyperglycemia and neutrophils dysfunction. Objectives: To elucidate the effects of DEX treatment in vivo on cellular energy status and the underlying mechanism in circulating neutrophils. Methods: We selected eight-month-old male bovines and injected DEX for 3 consecutive days (1 time/d). The levels of glucose, total protein (TP), total cholesterol (TC), and the proinflammatory cytokines interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α in blood were examined, and we then detected glycogen and adenosine triphosphate (ATP) content, phosphofructosekinase-1 (PFK1) and glucose-6-phosphate dehydrogenase (G6PDH) activity, glucose transporter (GLUT)1, GLUT4, sodium/glucose cotransporter (SGLT)1 and citrate synthase (CS) protein expression and autophagy levels in circulating neutrophils. Results: DEX injection markedly increased blood glucose, TP and TC levels, the Ca2+/P5+ ratio and the neutrophil/lymphocyte ratio and significantly decreased blood IL-1β, IL-6 and TNF-α levels. Particularly in neutrophils, DEX injection inhibited p65-NFκB activation and elevated glycogen and ATP contents and SGLT1, GLUT1 and GR expression while inhibiting PFK1 activity, enhancing G6PDH activity and CS expression and lowering cell autophagy levels. Conclusions: DEX induced neutrophils glucose uptake by enhancing SGLT1 and GLUT1 expression and the transformation of energy metabolism from glycolysis to pentose phosphate pathway (PPP)-tricarboxylic acid (TCA) cycle. This finding gives us a new perspective on deeper understanding of clinical anti-inflammatory effects of DEX on bovine.

FPGA HiL Simulation of Back-to-Back Converter PMSG Wind Turbine Systems

Zhenbin Zhang,Fengxiang Wang,Metehan Acikgoz,Xinbo Cai,Ralph Kennel 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

This work presents a back-to-back power converter Permanent-magnet Synchronous Generator (PMSG) wind turbine real-time simulation system based on FPGA Hardware-in-the-Loop (HiL) concept. The proposed system can be used for Electric Control Units (ECUs) evaluation in a real-time manner. The refreshing rate effect of a HiL emulator is discussed and analyzed with real-time simulation proof. Within this work, perunit system model of a 2MW Back-to-Back converter direct-drive PMSG wind turbine system is developed both in continuous and discrete formats. The effectiveness of the discrete per-unit system model is firstly verified through off-line simulation in Matlab/Simulink environment. Then by using a so-called Single-Cycle-Timed- Loop (SCTL) technique, the per-unit discrete system model is implemented on an FPGA based platform as the emulator, achieving a very high refreshing-rate (up to 250 kHz, i.e., 4μs). The emulator refreshing rate effect is evaluated in a real-time operating manner by implementing an ECU (using FOC/VOC control scheme) in a second FPGA chassis. At the end of this paper the results are analyzed and theoretically interpreted.

Effect of teeth bending and mushrooming damages on leakage performance of a labyrinth seal

Xin Yan,Xinbo Dai,Kang Zhang,Jun Li,Kun He 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.10

To achieve higher aerodynamic performance, turbine usually works at tight clearance, which results in inevitable rub between the rotor and stator parts of labyrinth seal due to vibrations, misalignment, mechanical force, thermal stress, etc. In the rubbing events, contact between labyrinth fin and rotor part will commonly induce the teeth bending and mushrooming damages, which significantly affect the discharge performance of a labyrinth seal. To account for the influence of teeth bending and mushrooming on leakage performance of a straight-through labyrinth seal, the leakage rates and flow fields in the worn labyrinth seal are measured and also compared with the original design cases. With numerical methods, the discharge behaviors of the labyrinth seal with different degrees of bending and mushroom damages are analyzed. It shows that the predicted leakage performance and flow fields in the labyrinth seals match well with the experimental tests. For the bending cases, the leakage rates and flow patterns in labyrinth seals are dependent on the effective clearance and bending angle. The leakage ratio of forward bending case is smaller than that of backward bending case with the same geometrical dimensions. However, for the mushroomed labyrinth seals, the leakage rates and flow patterns are much dependent on the effective clearance but slightly dependent on the mushroom radius.

Behavior of Steel Plate Shear Wall Connected to Frame Beams Only

Lanhui Guo,Qin Rong,Xinbo Ma,Sumei Zhang 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.4

This paper presents the study of steel plate shear walls which are connected to frame beams only. As the shear walls are not connected to frame columns, the premature failure overall buckling or local buckling of frame columns can be prevented. In fact, most of both structural design engineers and architects prefer this kind of steel plate shear walls because the dimension of their opening space is relatively flexible by using several steel plates with small span-to-height ratio placed parallel to each other. In this paper, two steel plate shear walls were fabricated and tested. The influence of stiffeners on the hysteretic behavior of this kind of member was studied. The experimental results showed that this kind of specimen had good ductility and energy dissipation capacity. The energy dissipation capacity of specimen with stiffeners was larger than that of the specimens without stiffeners. Meanwhile, the finite element method was applied to analyze the behavior of steel plate shear walls, whose results were validated by comparing with the corresponding experimental results. Analytical results showed that the free edges deformed with evident out-of-plane deformation and should be constrained by stiffeners to meet the design requirements. The energy dissipation capacity is much better for steel plate shear walls with lower height-to-thickness ratio and larger span-toheight ratio. At last, the skeleton curve of steel plate shear wall was proposed for calculating the elastic rigidity and loadcarrying capacity.

Multi-objective optimization modification of a tooth surface with minimum of flash temperature and vibration acceleration RMS

Xigui Wang,Yongmei Wang,Yixiang Liu,Xinbo Zhang,Dayu Zheng 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7

The minimum of tooth surface flash temperature and vibration acceleration RMS design is proposed and analyzed. The tooth contact analysis (TCA) and the load tooth contact analysis (LTCA) method and multi-objective optimization are also detailed. Satisfying design variables in multiple physical quantities leads to the minimum of multi-objective optimization. Considering the tooth surface loading conditions are uniform or not, the optimal modification of the tooth surface for improving gear comprehensive characteristics under various load bearing conditions is improved. The tooth surface flash temperature and vibration acceleration root mean square (RMS) values in different transmission modes of marine ship power rear gears drive system are derived. This research considers the multi-objective optimization modifications of tooth surface, and its main purpose is to propose an approach to help design tooth corrections to simultaneously optimize several objective physical quantities.