Simulation of Grid-Connected Solar Micro-inverter Based on Fuzzy PI Controller

Weiliang Liu,Changliang Liu,Huichao Zhang,Yongjun Lin,Liangyu Ma 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.10

Grid-connected solar micro-inverter is a highly nonlinear and time-varying system, so it is difficult to achieve good control effect using traditional PI controller. In this paper, small signal analysis model of micro-inverter is established, grid-connected current control strategy composed of fuzzy PI controller and grid voltage feed-forward is put forward, and the initial parameters of PI controller is optimized using the genetic algorithm. Simulation results show that the control strategy has the virtues of good robustness, small dynamic deviation, and could reduce the harmonic content of grid-connected current.

Analysis and research on dynamic characteristics of 3D braided composite two-stage reducer case

Weiliang Zhang,Xupeng Wang,Xiaomin Ji,Xinyao Tang,Fengfeng Liu,Shuwei Liu,Mingjun Liu,Xiao-Long Gao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

Based on the analysis of the movement rule of 3D five-way braided yarn, the 3D five-way braided case model is divided into three parts: base, case bottom plate and case wall. According to the characteristics of each part, the braiding and forming principle of a 3D five-way composite case was analyzed. Under the assumption of ignoring the influence of friction, bearing and other factors on the system, the differential equations of motion of the two-stage gear transmission system with case were established. The two-stage gear transmission system was numerically analyzed by Euler method, and the influence of dimensionless meshing frequency, clearance, case mass and damping on the dynamic characteristics of the transmission system was studied. After that, high and low frequency disturbance was applied to the input case. The research shows that the damping ratio of the composite case increases and the low frequency attenuation is accelerated due to the decrease of the case mass, so the composite case has better shock resistance to low frequency interference.

Application of cascaded H-bridge multilevel inverter in the speed regulation of medium- and high-voltage asynchronous motor

Weiliang Wu,Xiping Liu,Jianwei Liang,Zhangqi Liu,Chaozhi Huang 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.3

Medium- and high-voltage motors are characterized by high power and large inertia, and are widely used in industrial frequency conversion. The cascaded H-bridge multilevel (CHB-ML) inverter adopts a modular design concept to realize high-voltage and high-power functions by cascading multiple identical low-voltage conversion units. Moreover, the harmonic content of the output current of the inverter is small. For this purpose, a multilevel inverter consisting of eight H-bridge inverter units cascaded in each phase is introduced to drive medium- and high-voltage asynchronous motors for starting and frequency regulation. The carrier phase-shifted sinusoidal pulse-width modulation technique, DC voltage equalization control of power unit, and speed sensorless vector control strategy based on a voltage–current hybrid chain observer are mainly introduced. The simulation and experimental results of the real-time digital simulation system (RTDS) of the asynchronous motor dragged by the inverter verify that the CHB-ML inverter with the proposed control strategy has good starting and frequency regulation performance. These findings provide a technical guarantee for the field of medium- and high-voltage high-power drives.

Research on the tightening strategy of bolted flange for contact stiffness of joint surface

Weiliang Zuo,Zhifeng Liu,Yongsheng Zhao,Nana Niu,Mingpo Zheng 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.3

During bolted flange assembly, the contact stiffness of some areas of the joint surface may be low due to the elastic interaction. In order to improve the contact stiffness at the lowest position of bolted flange, the correlation model between the initial bolt pre-tightening force and the contact stiffness of bolted flange is established in this paper. According to the stress distribution model of a single bolt, an assumption of uniform local contact stiffness of bolted flange is made. Moreover, the joint surface is divided into the compressive stress region and the elastic interaction region. Based on the fractal contact theory, the relationship model of contact stiffness and contact force of the joint surface is proposed. Considering the elastic interaction coefficient method, the correlation model of the initial bolt pre-tightening force and the contact stiffness of bolted flange is established. This model can be employed to reverse determine the tightening strategy of the bolt group according to working conditions. As a result, this provides a new idea for the digital design of tightening strategy of bolt group for contact stiffness of bolted flange. The tightening strategy of the bolted flange is optimized by using the correlation model of initial bolt pretightening force and the contact stiffness of bolted flange. After optimization, the average contact stiffness of the joint surface increased by 5%, and the minimum contact stiffness increased by 6%.

SRRS Effects on ICF Laser Drive Beam with the Variation of Pump Light Distribution on Space

Ying Liu,Dianyang Lin,Zhiwei Lu,Weiliang Zeng 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.6

Tens to hundreds of output high power lasers from ICF (inertial confinement fusion) device, generally need to propagate through a long air path before they reach the target chamber. During the process, interaction between the high power pulse laser and air molecules emerges. Once the SRRS (stimulated rotational Raman scattering) threshold was reached, the SRRS effect would result in the loss of laser energy, the decrease of laser beam quality, or unable to reach the target. Further the transmitted laser would enter the multipliers as fundamental beam, then the conversion efficiency of triple-harmonic would be affected, even cause the destroy of frequency multiplication crystal. In order to improve the output ability, beam quality and control ability of the ICF high power laser drive, ultimately achieve the fusion ignition success, the SRRS effect must be suppressed. Based on SRRS four-dimensional mathematical model which conforms to current ICF experiment conditions, the longitudinal and horizontal rules of SRRS effect on ICF laser drive beam with the variation of pump light distribution on space was obtained. The research provided a support for the parameters choice of ICF laser drive and the optimization of output beam quality.

A DC Charging Pile for New Energy Electric Vehicles

Wu Weiliang,Liu Xiping,Huang Chaozhi 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.6

New energy electric vehicles will become a rational choice to achieve clean energy alternatives in the transportation field, and the advantages of new energy electric vehicles rely on high energy storage density batteries and efficient and fast charging technology. This paper introduces a DC charging pile for new energy electric vehicles. The DC charging pile can expand the charging power through multiple modular charging units in parallel to improve the charging speed. Each charging unit includes Vienna rectifier, DC transformer, and DC converter. The feasibility of the DC charging pile and the effectiveness of the control strategies of each component of the charging unit are verified by simulation and experimental results. This DC charging pile and its control technology provide some technical guarantee for the application of new energy electric vehicles.

Spatio-temporal expression pattern and fasting response of follistatin gene in teleost Larimichthys crocea

Zhifei Liu,Liangyi Xue,Weiliang Shen,Jun Ying,Zhenhua Zhang 한국유전학회 2014 Genes & Genomics Vol.36 No.2

Follistatin is a multifunctional regulatory proteininvolved in numerous physiological activities. Tobetter understand its functions in Larimichthys crocea (L.crocea), the entire cDNA sequence of follistatin from L. crocea was cloned, the transcript abundance of follistatinwas measured at different development stages and in differentgender. A fasting-refeeding protocol was also performedto correlate follistatin tissue expression withnutritional status in the juvenile stage of L. crocea. Theresults showed that follistatin transcripts were weaklydetected before gastrula stage (9 h post-fertilization; hpf),and at the highest level at myogenesis stage (15 hpf) and 30days after hatching (30 dah). In adult fish, follistatin transcriptswere observed in all the ten tissues examined andmost abundant in eye, gill, muscle, brain and intestine. Moreover, the abundance of follistatin transcripts in mosttissues was influenced by the age and gender. Duringfasting and refeeding period, the regulatory response offollistatin in muscle, liver, gonad, spleen and brain of L. crocea varied greatly. Altogether, these findings supportthe evidence that follistatin plays a profound role in theteleost development and that it is an indispensable factorfor the survival of teleosts when challenged with environmentalstresses like fasting.

New Isoxys arthropod from Cambrian (Series 2, Stage 3) Qingjiang Biota, South China

Jiaxin Ma,Cong Liu,Weiliang Lin,Ao Sun,Yu Wu,Dongjing Fu 대한지질학회 2017 대한지질학회 학술대회 Vol.2017 No.10

Effect of Salts on the Thermal Stability of Physically Crosslinked Gelatin Hydrogels

Jianlong Zhang,Congde Qiao,Xianguang Ma,Weiliang Liu,Qinze Liu 한국고분자학회 2017 폴리머 Vol.41 No.4

The effects of preparation conditions, such as polymer concentration, annealing temperature, annealing time and pH, on the melting behavior of gelatin gels were investigated. An optimum condition of gel preparation for calorimetric test is obtained. In addition, the influence of salt including salt concentration and salt type on the melting behavior of gelatin gels was explored by DSC and rheometer. It was found that the melting temperature first increased and then decreased with an increase in salt concentration. This result indicates that electrostatic interactions are important for the formation and stability of gelatin gels. Moreover, the melting temperature of polymer gels with different salt addition conforms to the following orders: Na<SUP>+</SUP><Ca<SUP>2+</SUP><Cr<SUP>3+</SUP>. The different trend observed in respect of the storage modulus indicated that the triple helices dominated the gelatin gel strength, and the binding mechanism of Ca2+ may be different from that of Cr<SUP>3+</SUP>.

The fuzzy comprehensive evaluation (FCE) and the principal component analysis (PCA) model simulation and its applications in water quality assessment of Nansi Lake Basin, China

Shiguo Xu,Yixiao Cui,Chuanxi Yang,Shujing Wei,Wenping Dong,Lihui Huang,Changqing Liu,Zongming Ren,Weiliang Wang 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.2

The Fuzzy Comprehensive Evaluation (FCE) and the Principal Component Analysis (PCA) were simulated to assess water quality of the Nansi Lake Basin, China. The membership functions were established via the Nor-Half Sinusoidal Distribution Method, and the weight was calculated via the Exceeding Standard Multiple Method. To enhance the efficiency of extracting principal pollutant, the eigenequation was solved through the Jacobi Method, and the principal components were extracted based on eigenvalue, contribution ratio, accumulating contribution ratio, principal component loading and score. Water quality classification based on “National Surface Water Environmental Quality Standards of China (GB3838-2002) was used to assess the water quality. Considering the difference of the temporal and spatial distribution in average, water quality of Level I was 28.9%, 28.1%, 25.1%, 25.6%, respectively in spring, summer, autumn, and winter, which suggested that water quality in spring and summer was better than in autumn and winter. The order of water quality was Zhaoyang Lake (Level I) > Nanyang Lake (Level I) > Dushan Lake (Level III) > Weishan Lake (Level III and IV). There were four extracted principal components that can replace the fourteen pollutant indexes for assessing water quality. According to the annual mean data of the 1<SUP>st</SUP> principal components, the most important pollutions were heavy metals, including As (0.933), Hg (0.931), Cd (0.929), Cr(VI) (0.926), Pb (0.925), and Cu (0.534). It is proved that the combined FCE-PCA model could provide valuable information in the water quality assessment for the Nansi Lake Basin.