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Xiaolong Cai,Jianwen Zhang,Gang Shi,Xu Cai,Jianqiao Zhou,Zhuyong Li,Jiacheng Wang,Jiajie Zang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In the future AC-DC hybrid distribution system, solid state transformer (SST) will take place of conventional transformer, as it could reduce the weight and volume of transformer, and achieve voltage and current regulation, power flow control, power quality enhancement. MMC-based SST is a novel SST topology, which could provide the MVDC port. However, the excessive bulky submodule capacitors limits this topology into practical application. This paper proposes a fluctuation power control strategy for MMC-based SST to reduce the submodule capacitor voltage oscillation, which could optimize the capacitance and reduce the volume and cost of capacitor. The feasibility of this proposed method is verified by MATLAB simulation.
강상욱,Jianwen Cai 한국통계학회 2010 Journal of the Korean Statistical Society Vol.39 No.3
In stratified case-cohort designs, samplings of case-cohort samples are conducted via a stratified random sampling based on covariate information available on the entire cohort members. In this paper, we extended the work of Kang and Cai (2009) to a generalized stratified case-cohort study design for failure time data with multiple disease outcomes. Under this study design, we developed weighted estimating procedures for model parameters in marginal multiplicative intensity models and for the cumulative baseline hazard function. The asymptotic properties of the estimators are studied using martingales, modern empirical process theory, and results for finite population sampling.
Modeling and Evaluation of Inertia Emulation Control for DFIG Wind Turbine
Haoshu SHAO,Xu CAI,Jianwen Zhang,Yunfeng Cao,Fangquan RAO,Dapeng ZHENG,Dangsheng ZHOU,Yan WANG 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
With the increasing penetration of renewable energy generators in power grid, many inertia emulation control strategies have been raised to solve the problem of reduced power system inertia. A co-simulation research platform is built based on RTDS and GH Bladed, detailed comparisons are made in terms of inertia response performance, weak grid operation stability, secondary frequency drop and wind tower load analysis. Research results point out that different control schemes are similar in inertia response while virtual synchronous generator control (VSG) and inertial synchronization control (ISynC) can improve weak grid operation stability, VSG strategy is also effective in reducing frequency secondary drop and wind tower fatigue load, the combination of VSG and ISynC can get the best control results.
Jing Lyu,Jinshui Dai,Chen Zhang,Jianwen Zhang,Xu Cai 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper presents a comparative analysis of impedance characteristics of modular multilevel converter (MMC) with direct modulation and compensated modulation. The analytical derivations of the ac-side impedances of the MMC with these two modulation modes are provided, respectively, which are then validated by the measured impedances in the time-domain simulation model. Subsequently, a case study is carried out to show the impact of the two modulation modes on the stability of the MMCbased interconnected system using the impedance-based analysis method. The findings could provide a reference for controller design of MMC-based power electronic systems from a stability perspective.
Trifan Gabriela,Gallo Linda C.,Lamar Melissa,Garcia-Bedoya Olga,Perreira Krista M.,Pirzada Amber,Talavera Gregory A.,Smoller Sylvia W.,Isasi Carmen R.,Cai Jianwen,Daviglus Martha L.,Testai Fernando D. 대한뇌졸중학회 2023 Journal of stroke Vol.25 No.3
Background and Purpose Social determinants of health (SDOH) are non-medical factors that may contribute to the development of diseases, with a higher representation in underserved populations. Our objective is to determine the association of unfavorable SDOH with self-reported stroke/transient ischemic attack (TIA) and vascular risk factors (VRFs) among Hispanic/Latino adults living in the US. Methods We used cross-sectional data from the Hispanic Community Health Study/Study of Latinos. SDOH and VRFs were assessed using questionnaires and validated scales and measurements. We investigated the association between the SDOH (individually and as count: ≤1, 2, 3, 4, or ≥5 SDOH), VRFs and stroke/TIA using regression analyses. Results For individuals with stroke/TIA (n=388), the mean age (58.9 years) differed from those without stroke/TIA (n=11,210; 46.8 years; <i>P</i><0.0001). In bivariate analysis, income <$20,000, education less than high school, no health insurance, perceived discrimination, not currently employed, upper tertile for chronic stress, and lower tertiles for social support and language- and social-based acculturation were associated with stroke/TIA and retained further. A higher number of SDOH was directly associated with all individual VRFs investigated, except for at-risk alcohol, and with number of VRFs (β=0.11, 95% confidence interval [CI]=0.09–0.14). In the fully adjusted model, income, discrimination, social support, chronic stress, and employment status were individually associated with stroke/TIA; the odds of stroke/TIA were 2.3 times higher in individuals with 3 SDOH (95% CI 1.6–3.2) and 2.7 times (95% CI 1.9–3.7) for those with ≥5 versus ≤1 SDOH. Conclusion Among Hispanic/Latino adults, a higher number of SDOH is associated with increased odds for stroke/TIA and VRFs. The association remained significant after adjustment for VRFs, suggesting involvement of non-vascular mechanisms.