Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters

Xi Zhang,Zhongwei Zhang,Bocheng Bao,Han Bao,Zhimin Wu,Kaiwen Yao,Jing Wu 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes itsuitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltageloop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stabilityeffect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensatoris taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by theduty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PIcompensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PIcompensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulationsand experimental results are supplied to verify the theoretical analyses.

Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters

Zhang, Xi,Zhang, Zhongwei,Bao, Bocheng,Bao, Han,Wu, Zhimin,Yao, Kaiwen,Wu, Jing The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes it suitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltage loop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stability effect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensator is taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by the duty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PI compensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PI compensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulations and experimental results are supplied to verify the theoretical analyses.

Dynamic Analysis of Time Series Data Based on State Space Model

Yang Zhizhong,Xi Bao 보안공학연구지원센터 2014 International Journal of u- and e- Service, Scienc Vol.7 No.5

The state space model is effective on analyzing non-stationary time series data, especially in adapting better to the dynamic variation analysis of the time series data and forecasting demand,by replacing fixed parameters with the variable ones.This article elaborates the constructing process of state space model by the measurement equation and state equation. This article also selects M0 money supply, M1 money supply, M2 money supply as the characterize variables of monetary policy, selects the national housing climate Index as characterize variables of real estate development,status regression model with stronger dynamic analysis capabilities as empirical analysis tool, with 2005 to 2012 monthly data of relevant variables as empirical analysis object, carry out the empirical study of relationship between the development of China's real estate industry and the amount of the three currencies. The empirical results show that the amount of three currencies elastic influence for real estate development are positive, M2 money supply impact of greater intensity. Among, M0 money supply influence gradually weakened, M1 and M2 money supply influence gradually increased.

Reduced-order Mapping and Design-oriented Instability for Constant On-time Current-mode Controlled Buck Converters with a PI Compensator

Xi Zhang,Jianping Xu,Jiahui Wu,Bocheng Bao,Guohua Zhou,Kaitun Zhang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.

Antioxidant Flavone Glycosides from the Root of Pteroxygonum giraldii

Bao-Lin Li,Lin-Ling Jiang,Hui-Chun Wang,Zhan-Jun Yang,Xi-Quan Zhang,Hong-Mei Gu,Xian-Hua Tian 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.7

Two new flavone glycosides, giraldiin A and B, together with three known compounds, annulatin, myricetin 3-O-α-L-rhamnopyranoside and gallic acid, were isolated from the ethanol extract of the root of Pteroxygonum giraldii Damm. et Diels. The structures of giraldiin A and B are designated as 3'-(α-L-arabinopyranosyloxy)-4',5,5',7-tetrahydroxy-3-methoxyflavone and 4'-(β-D-glucopyranosyloxy)-5,5',7-trihydroxy-2',3-dimethoxyflavone, respectively,on the basis of detailed spectroscopic analyses. The free radical scavenging activity of giraldiin A was evaluated by decolouring spectrophotometry of pentamethine cyanine dye (Cy5) with Fe2+-H2O2 Fenton radical generating system. The results indicated the hydroxyl free radical scavenging activity of giraldiin A (ED50 = 23.7 nmol/mL) is higher than that of some known antioxidants such as rutin, puerarin, daidzein and 2,6-di-tertbutyl-4-methylphenol.

A Base Promoted Synthesis of N,N-dimethylformamidines

Bao-Lin Li,Si Yi Ding,Yu Fei Ren,Liu Chang Wang,Yu Cai Jia,Xi-Quan Zhang,Hong-Mei Gu 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.5

Relationship between the methylenetetrahydrofolate reductase (MTHFR) rs1801133 SNP and serum homocysteine levels of Zhuang hypertensive patients in the central region of Guangxi

Hu Xi-Jiang,Su Mei-Ru,Cao Bao-Wei,Ou Fa-Bang,Yin Rui-Xing,Luo An-De 대한고혈압학회 2023 Clinical Hypertension Vol.29 No.-

Background The relationship between the methylenetetrahydrofolate reductase (MTHFR) single nucleotide polymorphism (SNP) and serum homocysteine (Hcy) levels or H-type hypertension in different populations is inconsistent. This study aimed to explore the association between the MTHFR rs1801133 SNP and serum Hcy levels of Zhuang hypertensive patients in the central region of Guangxi. Methods A total of 606 Zhuang inpatients with essential hypertension were recruited in our hospital from August 2016 to December 2018. The patients were divided into H-type hypertension (Hcy > 10 μmol/L, n = 528) and non–Htype hypertension (Hcy ≤ 10 μmol/L, n = 78) groups. At the same time, an age- and sex-matched group of 379 subjects with normal physical examination in our hospital were selected as the control group. Blood biochemical measurements and genotyping of the MTHFR rs1801133 SNP were performed. Results The prevalence of H-type hypertension was 87.13%. The levels of serum Hcy in patients with hypertension were higher than those in control group (14.20 ± 5.78 μmol/L vs. 11.97 ± 5.39 μmol/L, P < 0.001), especially in patients with H-type hypertension (15.08 ± 5.65 μmol/L, P < 0.001). The frequencies of TT genotype (22.73%) and T allele (46.21%) in patients with H-type hypertension were significantly higher than those in control group (11.35% and 30.47%, respectively) and non–H-type hypertension group (10.26% and 28.85%, respectively; P < 0.001 for all). Multivariate linear regression analysis showed that serum Hcy levels were significantly correlated with creatinine, lowdensity lipoprotein cholesterol, endogenous creatinine clearance rate, and the MTHFR rs1801133 genotypes in control group, while serum Hcy levels were significantly correlated with creatinine, triglyceride, low-density lipoprotein cholesterol, endogenous creatinine clearance rate, glycosylated hemoglobin, and the MTHFR rs1801133 genotypes in H-type hypertension group (P < 0.05–0.001). Serum Hcy levels in the T allele carriers were higher than those in the T allele noncarriers in both H-type hypertension and control groups. Conclusions There was closely related between the MTHFR rs1801133 SNP and serum Hcy levels in Zhuang patients with H-type hypertension in the central region of Guangxi. The MTHFR SNP may be an important reason for the increase of serum Hcy levels in Zhuang patients with H-type hypertension in this region.

A Base Promoted Synthesis of N,N-dimethylformamidines

Li, Bao Lin,Ding, Si Yi,Ren, Yu Fei,Wang, Liu Chang,Jia, Yu Cai,Zhang, Xi Quan,Gu, Hong Mei Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.5

Experimental study on propagation behavior of three-dimensional cracks influenced by intermediate principal stress

Sun, Xi Z.,Shen, B.,Zhang, Bao L. Techno-Press 2018 Geomechanics & engineering Vol.14 No.2

Many laboratory experiments on crack propagation under uniaxial loading and biaxial loading have been conducted in the past using transparent materials such as resin, polymethyl methacrylate (PMMA), etc. However, propagation behaviors of three-dimensional (3D) cracks in rock or rock-like materials under tri-axial loading are often considerably different. In this study, a series of true tri-axial loading tests on the rock-like material with two semi-ellipse pre-existing cracks were performed in laboratory to investigate the acoustic emission (AE) characteristics and propagation characteristics of 3D crack groups influenced by intermediate principal stress. Compared with previous experiments under uniaxial loading and biaxial loading, the tests under true tri-axial loading showed that shear cracks, anti-wing cracks and secondary cracks were the main failure mechanisms, and the initiation and propagation of tensile cracks were limited. Shear cracks propagated in the direction parallel to pre-existing crack plane. With the increase of intermediate principal stress, the critical stress of crack initiation increased gradually, and secondary shear cracks may no longer coalesce in the rock bridge. Crack aperture decreased with the increase of intermediate principal stress, and the failure is dominated by shear fracturing. There are two stages of fracture development: stable propagation stage and unstable failure stage. The AE events occurred in a zone parallel to pre-existing crack plane, and the AE zone increased gradually with the increase of intermediate principal stress, eventually forming obvious shear rupture planes. This shows that shear cracks initiated and propagated in the pre-existing crack direction, forming a shear rupture plane inside the specimens. The paths of fracturing inside the specimens were observed using the Computerized Tomography (CT) scanning and reconstruction.

Antioxidant Flavone Glycosides from the Root of Pteroxygonum giraldii

Li, Bao-Lin,Yang, Zhan-Jun,Jiang, Lin-Ling,Zhang, Xi-Quan,Gu, Hong-Mei,Wang, Hui-Chun,Tian, Xian-Hua Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.7

Two new flavone glycosides, giraldiin A and B, together with three known compounds, annulatin, myricetin 3-O-$\alpha$- L-rhamnopyranoside and gallic acid, were isolated from the ethanol extract of the root of Pteroxygonum giraldii Damm. et Diels. The structures of giraldiin A and B are designated as 3'-($\alpha$-L-arabinopyranosyloxy)-4',5,5',7- tetrahydroxy-3-methoxyflavone and 4'-($\beta$-D-glucopyranosyloxy)-5,5',7-trihydroxy-2',3-dimethoxyflavone, respectively, on the basis of detailed spectroscopic analyses. The free radical scavenging activity of giraldiin A was evaluated by decolouring spectrophotometry of pentamethine cyanine dye (Cy5) with $Fe^{2+}-H_2O_2$ Fenton radical generating system. The results indicated the hydroxyl free radical scavenging activity of giraldiin A (E$D_{50}$ = 23.7 nmol/mL) is higher than that of some known antioxidants such as rutin, puerarin, daidzein and 2,6-di-tertbutyl-4-methylphenol.