Research on a Multi-Objective Control Strategy for Current-source PWM Rectifiers under Unbalanced and Harmonic Grid Voltage Conditions

Geng, Yi-Wen,Liu, Hai-Wei,Deng, Ren-Xiong,Tian, Fang-Fang,Bai, Hao-Feng,Wang, Kai The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

Unbalanced and distorted grid voltages cause the grid side current of a current source PWM rectifier to be heavily distorted. They can also cause the DC-link current to fluctuate with a huge amplitude. In order to enhance the performance of a current-source PWM rectifier under unbalanced and harmonic grid voltage conditions, a mathematical model of a current-source PWM rectifier is established and a flexible multi-objective control strategy is proposed to control the DC-link current and grid-current. The fundamental positive/negative sequence, $5^{th}$ and $7^{th}$ order harmonic components of the grid voltage are first separated with the proposed control strategy. The grid current reference are optimized based on three objectives: 1) sinusoidal and symmetrical grid current, 2) sinusoidal grid current and elimination of the DC-current $2^{nd}$ order fluctuations, and 3) elimination of the DC-current $2^{nd}$ and $6^{th}$ order fluctuations. To avoid separation of the grid current components, a multi-frequency proportional-resonant controller is applied to control the fundamental positive/negative sequence, $5^{th}$ and $7^{th}$ order harmonic current. Finally, experimental results verify the effectiveness of proposed control strategy.

CONSUMER ATTITUDE TOWARDS BEAUTY IN CHINA --- EVIDENCE FROM COSMETICS INDUSTRY IN CHINA

Cui Geng,Yang Fang 글로벌지식마케팅경영학회 2016 Global Marketing Conference Vol.2016 No.7

By adopting regression and time series analysis, this article tries to quantify people’s enthusiasm towards beauty based on sales performance of cosmetics product in previous years in China. The basic assumption in this paper is that people’s attitude towards beauty is positively associated with their purchase behavior of cosmetics product.

Research on a Multi-Objective Control Strategy for Current-source PWM Rectifiers under Unbalanced and Harmonic Grid Voltage Conditions

Yi-Wen Geng,Hai-Wei Liu,Ren-Xiong Deng,Fang-Fang Tian,Hao-Feng Bai,Kai Wang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

Unbalanced and distorted grid voltages cause the grid side current of a current source PWM rectifier to be heavily distorted. They can also cause the DC-link current to fluctuate with a huge amplitude. In order to enhance the performance of a current-source PWM rectifier under unbalanced and harmonic grid voltage conditions, a mathematical model of a current-source PWM rectifier is established and a flexible multi-objective control strategy is proposed to control the DC-link current and grid-current. The fundamental positive/negative sequence, 5th and 7th order harmonic components of the grid voltage are first separated with the proposed control strategy. The grid current reference are optimized based on three objectives: 1) sinusoidal and symmetrical grid current, 2) sinusoidal grid current and elimination of the DC-current 2nd order fluctuations, and 3) elimination of the DC-current 2nd and 6th order fluctuations. To avoid separation of the grid current components, a multi-frequency proportional-resonant controller is applied to control the fundamental positive/negative sequence, 5th and 7th order harmonic current. Finally, experimental results verify the effectiveness of proposed control strategy.

The Effects of Physicochemical Factors and Cell Density on Nitrite Transformation in a Lipid-Rich Chlorella

( Fang Liang ),( Kui Du ),( Xiaobin Wen ),( Liming Luo ),( Yahong Geng ),( Yeguang Li ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.12

To understand the effects of physicochemical factors on nitrite transformation by microalgae, a lipid-rich Chlorella with high nitrite tolerance was cultured with 8 mmol/l sodium nitrite as sole nitrogen source under different conditions. The results showed that nitrite transformation was mainly dependent on the metabolic activities of algal cells rather than oxidation of nitrite by dissolved oxygen. Light intensity, temperature, pH, NaHCO3 concentrations, and initial cell densities had significant effects on the rate of nitrite transformation. Single-factor experiments revealed that the optimum conditions for nitrite transformation were light intensity: 300 μmol/㎡/s; temperature: 30℃; pH: 7-8; NaHCO3 concentration: 2.0 g/l; and initial cell density: 0.15 g/l; and the highest nitrite transformation rate of 1.36 mmol/l/d was achieved. There was a positive correlation between nitrite transformation rate and the growth of Chlorella. The relationship between nitrite transformation rate (mg/l/d) and biomass productivity (g/l/d) could be described by the regression equation y = 61.3x (R(2) = 0.9665), meaning that 61.3 mg N element was assimilated by 1.0 g dry biomass on average, which indicated that the nitrite transformation is a process of consuming nitrite as nitrogen source by Chlorella. The results demonstrated that the Chlorella suspension was able to assimilate nitrite efficiently, which implied the feasibility of using flue gas for mass production of Chlorella without preliminary removal of NOX.

Growth Rate and Biomass Productivity of Chlorella as Affected by Culture Depth and Cell Density in an Open Circular Photobioreactor

( Fang Liang ),( Xiao Bin Wen ),( Yahong Geng ),( Zheng Rong Ouyang ),( Li Ming Luo ),( Ye Guang Li ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.4

The effects of culture depth (2-10 cm) and cell density on the growth rate and biomass productivity of Chlorella sp. XQ-200419 were investigated through the use of a selfdesigned open circular pond photobioreactor-imitation system. With increases in culture depths from 2 to 10 cm, the growth rate decreased significantly from 1.08 /d to 0.39 /d. However, the biomass productivity only increased slightly from 8.41 to 11.22 g/m2/d. The biomass productivity (11.08 g/m2/d) achieved in 4 cm culture with an initial OD540 of 0.95 was similar to that achieved in 10 cm culture with an initial OD540 of 0.5. In addition, the duration of maximal areal productivity at a 4 cm depth was prolonged from 1 to 4 days, a finding that was also similar to that of the culture at a 10 cm depth. In both cases, the initial areal biomass densities were identical. Based on these results and previous studies, it can be concluded that the influence of culture depth and cell density on areal biomass productivity is actually due to different areal biomass densities. Under suitable conditions, there are a range of optimal biomass densities, and areal biomass productivity reaches its maximum when the biomass density is within these optimal ranges. Otherwise, biomass productivity will decrease. Therefore, a key factor for high biomass productivity is to maintain an optimal biomass density.

Research on floating slab track isolator based on mixed media theory

Zheng Fang,Chuanzhi Geng 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10

To improve the control effect of the floating slab track system under lowfrequency vibration, a vibration isolator scheme based on a liquid and gas mixture is proposed. Taking the elastic element of the air cushion as the research object, the fluid-structure coupling theory is used to analyze its deformation law under high load conditions, and the nonlinear stiffness calculation method of the liquid and gas mixture isolator is given and verified. Using the theory of mixed media, the parameters and structure of the liquid-gas mixture isolator are designed and trial-manufactured. The wheel load drop is used to analyze and compare the lowfrequency vibration reduction effects of different elastic supports. The vibration reduction effect of the liquid and gas mixture isolator relative to the steel spring isolator and rubber isolator is 4.75 dB and 10.12 dB, respectively, showing a good comprehensive vibration control effect.

A Unify Unbalance Compensation Strategy for Islanded Microgrid with Unbalanced Condition

Hongtao Shi,Fang Zhuo,Zhiqing Geng,Dong zhang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Due to the unbalance condition, the voltage of microgrid would be deteriorated. In this paper, a unify unbalance compensation strategy is proposed to suppress the unbalanced voltage and the voltage variation for islanded microgrid with unbalanced condition. Comparing to the traditional compensation strategy, where only negative sequence components of voltage are suppressed, in the proposed scheme, the voltage and frequency variations resulted from the unbalanced condition are also eliminated. A simulation model of microgrid is developed in PSIM and the simulation and experimental results verify the effectiveness of the proposed method.

Experimental Investigation of the Effects of Aperture Ratio, Chamber Pressure and Soil Conditioning on the Clogging Behavior of EPB Shields

Gongyun Xu,Yong Fang,Yubo Wang,Liupan Dou,Ruyong Deng,Fangchuang Geng 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10

Earth pressure balance (EPB) shield excavation in cohesive strata frequently encounters cutterhead clogging, consuming time and economic costs. Engineering practice shows that cutterhead aperture ratio, soil chamber pressure and soil conditioning have important influences on the clogging behavior of EPB shields. In order to study these factors, a series of laboratory tests were conducted using a setup that can closely simulate the shield tunnelling process. The indicators analyzed were excavation speed, torque, specific energy and soil distribution on the cutterhead. The results indicate that cutterhead aperture and cutter arrangement are important factors in clogging potential. Clogging creates a significant reduction in excavation speed. Torque is not a sensitive parameter reflecting clogging because of the effect of the consolidated soil on the cutters. The presence of soil chamber pressure makes it difficult to remove the clogging through the shearing action of the excavation surface. The injection of a sufficient amount of foam can reduce the risk of shield clogging, but it may lead to an increase of soil adhesion on the cutterhead. The amount of soil that adheres to the cutterhead cannot be used as a classification criterion for clogging potential. Based on experimental phenomena and established studies, a mechanical model called ‘beam-bridge’ was proposed to study the behavior of the soil through the cutterhead opening and damage form of clogging. The results will help to the excavation control of EPB shields.

RAMS evaluation for a steel-truss arch high-speed railway bridge based on SHM system

Zhao, Han-Wei,Ding, You-Liang,Geng, Fang-Fang,Li, Ai-Qun Techno-Press 2018 Structural monitoring and maintenance Vol.5 No.1

The evaluation theory of reliability, availability, maintainability and safety (RAMS) as a mature theory of state evaluation in the railway engineering, can be well used to the evaluation, management, and maintenance of complicated structure like the long-span bridge structures on the high-speed railway. Taking a typical steel-truss arch bridge on the Beijing-Shanghai high-speed railway, the Nanjing Dashengguan Yangtze River Bridge, this paper developed a new method of state evaluation for the existing steel-truss arch high-speed railway bridge. The evaluation framework of serving state for the bridge structure is presented based on the RAMS theory. According to the failure-risk, safety/availability, maintenance of bridge members, the state evaluation method of each monitoring item is presented. The weights of the performance items and the monitoring items in all evaluation levels are obtained using the analytic hierarchy process. Finally, the comprehensive serving state of bridge structure is hierarchical evaluated.

Life history responses of the cabbage beetle Colaphellus bowringi to temperature change

Jian‐Jun Tang,Hai-Min HE,Ting GENG,Shu FU,Fang-Sen XUE 한국곤충학회 2016 Entomological Research Vol.46 No.6

Temperature is considered one of the most important mediators of phenotypic plasticity in ectotherms. Here, we investigated life history traits of the cabbage beetle, Colaphellus bowringi Baly (Coleoptera: Chrysomelidae), at a wide range of temperatures (16, 19, 22, 24, 26 and 28°C). The larval and pupal times were significantly decreased with increasing rearing temperature and growth rate was positively correlated with temperature. However, the relationship between body size and rearing temperature in C. bowringi did not follow the temperature–size rule; both males and females reached the highest body weight at 19°C. Females were significantly larger than males at all temperatures. Male pupae lost significantly more weight at metamorphosis compared to females. However, diapausing males gained significantly higher weight after feeding compared to diapausing females at higher temperatures of 22, 24, 26 and 28°C. Body weight tended to decrease with increasing rearing temperature, whereas sexual size dimorphism (SSD) tended to increase with increasing rearing temperature; thus, Rensch's rule is upheld. The degree to which SSD changed with temperature varied with different development stages. SSD was lowest in pupae, highest in newly emerged adults and intermediate in diapausing adults.