Improved Feedforward to Enhance Harmonic Suppression for Grid-Connected Inverter

Boyang Liu,Hua Lin,Jianjie Xiao 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

In most cases, for grid-connected inverters, the grid is not ideal at the point of common coupling. When proportional feedforward is used to suppress grid voltage harmonics, the existence of grid impedance will deteriorate the stability of grid-connected LCL-filtered inverter. To enhance stability, the multi-resonant feed-forward strategy was proposed in some papers. However, because of the phase lag caused by digital delay, the suppression ability of this method to grid harmonics is not good enough. Therefore, this paper proposes a compensation strategy for phase lag of feedforward channel at resonant frequencies, which makes different resonant frequencies correspond to different dq rotation coordinates, and respectively changes initial phase of every dq rotation coordinate properly to compensate phase lag. Then the ability to suppress grid harmonics is obviously enhanced. Finally, experimental results verify the effectiveness of proposed control strategy.

Construction of fat1 Gene Expression Vector and Its Catalysis Efficiency in Bovine Fetal Fibroblast Cells

Liu, Boyang,Yang, Runjun,Li, Junya,Zhang, Lupei,Liu, Jing,Lu, Chunyan,Lian, Chuanjiang,Li, Zezhong,Zhang, Yong-Hong,Zhang, Liying,Zhao, Zhihui Asian Australasian Association of Animal Productio 2012 Animal Bioscience Vol.25 No.5

The FAT-1 protein is an n-3 fatty acid desaturase, which can recognize a range of 18- and 20-carbon n-6 substrates and transform n-6 polyunsaturated fatty acids (PUFAs) into n-3 PUFAs while n-3 PUFAs have beneficial effect on human health. Fat1 gene is the coding sequence from Caenorhabditis elegans which might play an important role on lipometabolism. To reveal the function of fat1 gene in bovine fetal fibroblast cells and gain the best cell nuclear donor for transgenic bovines, the codon of fat1 sequence was optimized based on the codon usage frequency preference of bovine muscle protein, and directionally cloned into the eukaryotic expression vector pEF-GFP. After identifying by restrictive enzyme digests with AatII/XbaI and sequencing, the fusion plasmid pEF-GFP-fat1 was identified successfully. The pEF-GFP-fat1 vector was transfected into bovine fetal fibroblast cells mediated by Lipofectamine2000$^{TM}$. The positive bovine fetal fibroblast cells were selected by G418 and detected by RT-PCR. The results showed that a 1,234 bp transcription was amplified by reverse transcription PCR and the positive transgenic fat1 cell line was successfully established. Then the expression level of fat1 gene in positive cells was detected using quantitative PCR, and the catalysis efficiency was detected by gas chromatography. The results demonstrated that the catalysis efficiency of fat1 was significantly high, which can improve the total PUFAs rich in EPA, DHA and DPA. Construction and expression of pEF-GFP-fat1 vector should be helpful for further understanding the mechanism of regulation of fat1 in vitro. It could also be the first step in the production of fat1 transgenic cattle.

Adaptive Differential Evolution-based Receding Horizon Control Design for Multi-UAV Formation Reconfiguration

Boyang Zhang,Xiuxia Sun,Shuguang Liu,Xiongfeng Deng 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.12

The complicated and constrained reconfiguration optimisation for unmanned aerial vehicles (UAVs) is a challenge, particularly when multi-mission requirements are taken into account. In this study, we evaluate the use of the adaptive differential evolution-based centralised receding horizon control approach to achieve the formation reconfiguration along a given formation group trajectory for multiple unmanned aerial vehicles in a three-dimensional (3D) environment. A rolling optimisation approach which combines the receding horizon control method with the adaptive differential evolution algorithm is proposed, where the receding horizon control method divides the global control problem into a series of local optimisations and each local optimisation problem is solved by an adaptive differential evolution algorithm. Furthermore, a novel quadratic reconfiguration cost function with the topology information of UAVs is presented, and the asymptotic convergence of the rolling optimisation is analysed. Finally, simulation examples are provided to illustrate the validity of the proposed control structure.

Formation Control of Multiple UAVs Incorporating Extended State Observer-Based Model Predictive Approach

Boyang Zhang,Xiuxia Sun,Shuguang Liu,Xiongfeng Deng 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.4

This paper studies the extended state observer-based state space predictive control approach to deal with the multiple unmanned aerial vehicle formation flight with unknown disturbances. The distributed control problem for a class of multiple unmanned aerial vehicle systems with reference trajectory tracking and disturbance rejection is formulated. Firstly, a local distributed controller is designed by using the state space predictive control approach based on an error model to achieve stable tracking. Then, a feedforward compensation controller is introduced by using the extended state observer to estimate and compensate disturbances and improve the ability of anti-interference. Besides, the bounded stability of the designed extended state observer is analyzed as well. Finally, the simulation examples are provided to illustrate the validity of the proposed control structure.

Adaptive Differential Evolution-Based Distributed Model Predictive Control for Multi-UAV Formation Flight

Boyang Zhang,Xiuxia Sun,Shuguang Liu,Xiongfeng Deng 한국항공우주학회 2020 International Journal of Aeronautical and Space Sc Vol.21 No.2

The complicated formation flight for multi-unmanned aerial vehicles is a challenge, especially when multi-mission requirements are taken into account. This paper studies the adaptive differential evolution-based distributed model predictive control approach to deal with the multi-unmanned aerial vehicle flight achieving obstacle/collision avoidance and formation keeping simultaneously in the complex environment. Specifically, the distributed model predictive controller is designed to achieve stable flight for each unmanned aerial vehicle as well as taking the state and input saturation into account, where the local optimization problem is solved by the adaptive differential evolution algorithm. Besides, the adaptive adjustment to the prediction horizon for the model predictive controller is introduced, while the asymptotic convergence of the rolling optimization is analyzed as well. Finally, simulation examples are provided to illustrate the validity of the proposed control structure.

Efficient Public Verification on the Integrity of Multi-Owner Data in the Cloud

Boyang Wang,Hui Li,Xuefeng Liu,Fenghua Li,Xiaoqing Li 한국통신학회 2014 Journal of communications and networks Vol.16 No.6

Cloud computing enables users to easily store their dataand simply share data with others. Due to the security threats inan untrusted cloud, users are recommended to compute verificationmetadata, such as signatures, on their data to protect the integrity. Many mechanisms have been proposed to allow a publicverifier to efficiently audit cloud data integrity without receivingthe entire data from the cloud. However, to the best of our knowledge,none of them has considered about the efficiency of publicverification on multi-owner data, where each block in data issigned by multiple owners. In this paper, we propose a novel publicverification mechanism to audit the integrity of multi-ownerdata in an untrusted cloud by taking the advantage of multisignatures. With our mechanism, the verification time and storageoverhead of signatures on multi-owner data in the cloud are independentwith the number of owners. In addition, we demonstratethe security of our scheme with rigorous proofs. Compared to thestraightforward extension of previousmechanisms, ourmechanismshows a better performance in experiments.

Synthesis of γ-valerolactone from ethyl levulinate hydrogenation and ethyl 4-hydroxypentanoate lactonization over supported Cu-Ni bimetallic, bifunctional catalysts

Yafei Li,Xiaocheng Lan,Boyang Liu,Tiefeng Wang 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.107 No.-

A stable and highly efficient supported Cu-Ni catalysts for the conversion of ethyl levulinate (EL) toc-valerolactone (GVL) was developed. The catalysts were characterized by XRD, TEM, TPD, TPR, andXPS. The support effect of metal oxides (Al2O3, SiO2, ZrO2, and TiO2) revealed that Cu-Ni supported onAl2O3 showed the highest activity for EL hydrogenation to ethyl 4-hydroxypentanoate (EHP) and thesubsequent intramolecular esterification of EHP to GVL. EHP intramolecular esterification to GVL in theethanol solution was a reversible reaction with an equilibrium constant of 24 at 453 K. A simplified reactionkinetic network was established. The solvent had a significant influence on the reaction equilibriumand the catalyst stability. Cu-Ni/Al2O3 in n-hexane solvent gave a higher GVL yield than that in ethanolsolvent, and showed better recyclability than that in toluene solvent. With optimizing the conditions, Cu-Ni/Al2O3 gave 99.9% conversion and 98% selectivity to GVL with a space–time yield of 1.13 gGVL gcat-1 h1 inn-hexane solvent with good recyclability.

Direct observation of the hysteretic Fermi level modulation in monolayer MoS2 field effect transistors

Yuhang Wang,Dongyong Li,Xubo Lai,Boyang Liu,Yibao Chen,Fengping Wang,Rongming Wang,Liuwan Zhang 한국물리학회 2020 Current Applied Physics Vol.20 No.2

The hysteresis in the transfer curve of MoS2 has significant impact on the device performance. However, the hysteresis mechanism is still not clear. Here, we investigate the hysteresis of the monolayer MoS2 by probing the local Fermi level variations as a function of the back gate voltage in different atmosphere using the Kelvin probe microscopy. While the Fermi level of the MoS2 in air is much lower than that in vacuum, both the MoS2 devices in vacuum and air show large Fermi level hysteresis. The Fermi level hysteresis direction is clock-wise, identical to that observed in the transfer curves. Both the hysteresis in Fermi level and transfer curve can be explained consistently by taking into account the charge trapping. Our findings confirm that carrier density modulation in MoS2 plays a vital role in the hysteresis, and provide insight into the hysteresis mechanism for the optimization of the device performance.

Research on Zero Voltage Switching Non-inductive Current Circulation Control of Bidirectional DC/DC Converter for Hybrid Energy Source System of Electric Vehicle

Sun Yanzhou,Xiaogang Wu,Zhengxin Liu,Yu Boyang 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.2

The hybrid energy source system (HESS) with batteries and super-capacitor can eff ectively prolong the cycle life of batteries in electric vehicles (EVs). In order to further highlight the advantages of HESS in improving EVs effi ciency, The DC/DC converter in HESS should have the advantages of high effi ciency and fast response speed. Therefore, a soft-switching nonisolated buck-boost bidirectional DC/DC converter is applied to the HESS system of EVs in this paper. The converter has the advantages of being a simple circuit, a reduced number of components and can realize ZVS of all switches without an auxiliary circuit. In addition, a non-inductive current circulation control method is adopted in order to further improve the effi ciency of the converter. The controller of the converter is designed based on small signal modeling, and an experimental prototype has been developed. The experimental results show that, compared to the inductive current circulation method, the non-inductive current circulation control method can eff ectively reduce the loss of the inductor, and the maximum effi ciency of the converter is 92.8% in step-down mode and 93.2% in step-up mode.

Segmented Douglas-Peucker Algorithm Based on the Node Importance

( Xiaofei Wang ),( Wei Yang ),( Yan Liu ),( Rui Sun ),( Jun Hu ),( Longcheng Yang ),( Boyang Hou ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.4

Vector data compression algorithm can meet requirements of different levels and scales by reducing the data amount of vector graphics, so as to reduce the transmission, processing time and storage overhead of data. In view of the fact that large threshold leading to comparatively large error in Douglas-Peucker vector data compression algorithm, which has difficulty in maintaining the uncertainty of shape features and threshold selection, a segmented Douglas-Peucker algorithm based on node importance is proposed. Firstly, the algorithm uses the vertical chord ratio as the main feature to detect and extract the critical points with large contribution to the shape of the curve, so as to ensure its basic shape. Then, combined with the radial distance constraint, it selects the maximum point as the critical point, and introduces the threshold related to the scale to merge and adjust the critical points, so as to realize local feature extraction between two critical points to meet the requirements in accuracy. Finally, through a large number of different vector data sets, the improved algorithm is analyzed and evaluated from qualitative and quantitative aspects. Experimental results indicate that the improved vector data compression algorithm is better than Douglas-Peucker algorithm in shape retention, compression error, results simplification and time efficiency.