1,976 research outputs found
Modeling and stability issues of voltage-source converter dominated power systems: A review
Get PDFWith the substantive increase in the proportion of voltage-source converter (VSC)-based equipment, traditional power systems that primarily constituted of synchronous generators (SGs) gradually evolved into VSC-dominated ones. At the same time, there is an urgent need for modeling and stability assessment of such systems, since low inertia and weak damping features impair the ability of the systems to resist random disturbances. Existing works model the system dynamic processes from various domains (i.e., time, frequency and energy), and analyze/determine the system stability under small or large disturbances. Among them, small-signal stability assessments mainly adopt the time-domain analysis based on the state-space model while frequency-domain methods include the impedance model, phase-amplitude dynamics model, and static synchronous generator model. Large-signal stability assessments mainly exploit the time-domain simulation with detailed models (i.e., continuous/discrete-time mixed model with differential-difference-algebraic equations), and the energy-domain analysis is based on energy function models. This paper presents a comprehensive review of existing modeling and stability analysis methods for VSC-dominated power systems, including their basic principles, key features, application scenarios and development tendencies. Key technical issues related to modeling and stability analysis are also summarized
Fig. 8 in Terpene Shikimate conjugated meroterpenoids from the endophytic fungus Guignardia mangiferae
No full textFig. 8. ΔδH(S-R) value of MTPA esters of 6 in CDCl3.Published as part of Chen, Keliang, Chen, Chunmei, Liu, Xiulan, Sun, Weiguang, Deng, Yanfang, Liu, Junjun, Wang, Jianping, Luo, Zengwei, Zhu, Hucheng & Zhang, Yonghui, 2021, Terpene Shikimate conjugated meroterpenoids from the endophytic fungus Guignardia mangiferae, pp. 1-9 in Phytochemistry (112860) 190 on page 6, DOI: 10.1016/j.phytochem.2021.112860, http://zenodo.org/record/825739
Steady-State Angle Stability Analysis of Parallel Grid-Forming Converters in Current Saturation Mode
Get PDFGrid-forming converters (GFCs) usually operate in parallel to supply power to unknown loads. Nevertheless, unknown loads may lead to overcurrent, causing parallel GFCs to enter the current saturation mode (CSM). The steady-state angle stability of parallel GFCs in CSM is crucial for ensuring reliable operation under unknown loads, yet this issue has not been studied previously. This article presents a novel power model for parallel GFCs in CSM and conducts the first-ever investigation of steady-state angle stability in this context. The analysis results reveal that the steady-state angle stability of the equilibrium points (EPs) under overall inductive load is opposite to that under overall capacitive load. Specifically, it is shown that the EP with even power allocation is unstable, and the parallel GFCs will transition to the EP with circulating currents in the presence of overall capacitive loads. Eventually, all the capacity of GFCs is occupied by the circulating currents, failing to supply voltage to the loads. The proposed model and analysis are validated through experimental results, highlighting the significant risk of power supply failure for parallel GFCs in CSM and providing general guidance for the operation of GFCs in parallel
Fig. 2. Key 1H–1H in Terpene Shikimate conjugated meroterpenoids from the endophytic fungus Guignardia mangiferae
No full textFig. 2. Key 1H–1H COSY and HMBC correlations of compounds 1, 3, 6, and 9.Published as part of Chen, Keliang, Chen, Chunmei, Liu, Xiulan, Sun, Weiguang, Deng, Yanfang, Liu, Junjun, Wang, Jianping, Luo, Zengwei, Zhu, Hucheng & Zhang, Yonghui, 2021, Terpene Shikimate conjugated meroterpenoids from the endophytic fungus Guignardia mangiferae, pp. 1-9 in Phytochemistry (112860) 190 on page 4, DOI: 10.1016/j.phytochem.2021.112860, http://zenodo.org/record/825739
Five undescribed steroids from Talaromyces stipitatus and their cytotoxic activities against hepatoma cell lines
No full textZhang, Mi, Deng, Yanfang, Liu, Fei, Zheng, Meijia, Liang, Yu, Sun, Weiguang, Li, Qin, Li, Xiao-Nian, Qi, Changxing, Liu, Junjun, Chen, Chunmei, Zhu, Hucheng, Zhang, Yonghui (2021): Five undescribed steroids from Talaromyces stipitatus and their cytotoxic activities against hepatoma cell lines. Phytochemistry (112816) 189: 1-10, DOI: 10.1016/j.phytochem.2021.112816, URL: http://dx.doi.org/10.1016/j.phytochem.2021.11281
Fig. 4 in Five undescribed steroids from Talaromyces stipitatus and their cytotoxic activities against hepatoma cell lines
No full textFig. 4. Experimental ECD curve of 5 and calculated ECD curves of 5 and ent-5.Published as part of Zhang, Mi, Deng, Yanfang, Liu, Fei, Zheng, Meijia, Liang, Yu, Sun, Weiguang, Li, Qin, Li, Xiao-Nian, Qi, Changxing, Liu, Junjun, Chen, Chunmei, Zhu, Hucheng & Zhang, Yonghui, 2021, Five undescribed steroids from Talaromyces stipitatus and their cytotoxic activities against hepatoma cell lines, pp. 1-10 in Phytochemistry (112816) 189 on page 4, DOI: 10.1016/j.phytochem.2021.112816, http://zenodo.org/record/825957
Fig. 3 in Five undescribed steroids from Talaromyces stipitatus and their cytotoxic activities against hepatoma cell lines
No full textFig. 3. The NOESY correlations of compounds 1, 2, and 4–6.Published as part of Zhang, Mi, Deng, Yanfang, Liu, Fei, Zheng, Meijia, Liang, Yu, Sun, Weiguang, Li, Qin, Li, Xiao-Nian, Qi, Changxing, Liu, Junjun, Chen, Chunmei, Zhu, Hucheng & Zhang, Yonghui, 2021, Five undescribed steroids from Talaromyces stipitatus and their cytotoxic activities against hepatoma cell lines, pp. 1-10 in Phytochemistry (112816) 189 on page 3, DOI: 10.1016/j.phytochem.2021.112816, http://zenodo.org/record/825957
Fig. 3 in Structurally diverse and bioactive alkaloids from an insect-derived fungus Neosartorya fischeri
No full textFig. 3. Selected NOESY/ROESY correlations of compounds 1–4, 8, 12, and 16.Published as part of Lin, Shuang, He, Yan, Li, Fengli, Yang, Beiye, Liu, Mengting, Zhang, Sitian, Liu, Junjun, Li, Huaqiang, Qi, Changxing, Wang, Jianping, Hu, Zhengxi & Zhang, Yonghui, 2020, Structurally diverse and bioactive alkaloids from an insect-derived fungus Neosartorya fischeri, pp. 1-10 in Phytochemistry (112374) 175 on page 4, DOI: 10.1016/j.phytochem.2020.112374, http://zenodo.org/record/829536
Adaptive sliding mode reliable control for switched systems with actuator degradation
No full textThe problem of sliding mode control is considered for a class of uncertain switched systems subject to actuator faults. It is assumed that there may happen degradation in each actuator channel. Besides, the authors relax the restrictive assumption that each subsystem shares the same input channel, which is different from some existing works. In this work, a weighted sum approach of the different input matrices is introduced to construct a common sliding surface. Moreover, by on-line estimating the loss of effectiveness of the actuators, an adaptive sliding mode controller is designed. This does not only compensate the effects of the actuator degradation effectively, but can also reduce the conservatism compared with some existing approaches which only utilise the bound of the gain variation. It is shown that the reachability of the specified sliding surface can be ensured, and a sufficient condition on the exponential stability of sliding mode dynamics is obtained via the average dwell time method. Finally, a numerical example is given to demonstrate the effectiveness of the proposed method
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