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HVDC auxiliary emergency power control can improve the transient stability of AC/DC power system. Compared with other control methods, HVDC auxiliary emergency power control has the advantages of quick response, large adjustment capacity and less investment, so it is the primary choice to improve the transient stability. Taking multi-infeed DC (MIDC) transmission system as the research object, based on the definition of the traditional power support factor, considering the influence of the electrical connection of the sending-end power grid on the power support, a new power support factor (NPSF) is defined. Based on the NPSF, multiple DC coordination sharing strategies are implemented when one of the DC faults occurs. Finally, MIDC is built on the PSCAD. Single DC auxiliary power control and multiple DC auxiliary power coordinated control were simulated, respectively. Rationality of the definition of NPSF is verified, and it is concluded that multiple DC joint power control is superior to single DC. [ABSTRACT FROM AUTHOR]

A novel high‐voltage direct‐current (HVDC) line fault location method based on phase frequency change characteristics is proposed. The idea of the method is the travelling waves for the fault happened on different positions have different phase distortion characteristics, when they spread to the measuring terminal. By using the discrete Fourier analysis, the phase frequency characteristics were obtained. The frequency data of 40 to 60 Hz and the corresponding phase angle ratio data are selected, forming a N × 3 matrix, each row of data represents the relationship between the fault location and phase angle ratio, fitting each row of data, respectively, the mathematical relationship between the fault location and phase angle ratio can be obtained, finally realise DC line fault location by seeking average. Finally, a lot of different faults are simulated and analysed on the PSCAD platform to verify the effectiveness and robustness of the proposed method. [ABSTRACT FROM AUTHOR]

The grid connection of wind farms affects the load flow of a power system and may introduce an unexpected threat to the power system small signal stability. This study presents an application of probabilistic eigenvalue sensitivity indices (PSIs) for optimal allocation of wind farm in a power system. For this purpose, firstly, probabilistic sensitivity indices are used to identify the strongly correlated electromechanical eigenvalues of generators and to facilitate the wind farm site selection. Two different cases are studied, wind farm replacing synchronous generators or being directly added to the power system. Afterwards, the influence of the wind farm location on power system small signal stability is examined. For this purpose, an index is proposed to measure the small signal stability of the system and is used for optimal allocation of the wind farm. Two examples, i.e. a 3‐machine 9‐bus and an 8‐machine 24‐bus power system, with a wind farm integrated based on PSIs are presented to demonstrate the proposed approach by employing the eigenvalue analysis and a dynamic time‐domain simulation. Finally, the results are compared with the traditional optimal allocation of a wind farm for power loss reduction. [ABSTRACT FROM AUTHOR]

In order to solve the coordinated optimization problem of distributed generation (DG), on‐load tap changer (OLTC) and capacitor banks, a dynamic reactive power optimization (DRPO) method based on fuzzy time clustering is proposed. In the method, fuzzy time clustering algorithm is used to cluster the static optimal switching sequence of OLTC and capacitor banks. The time decoupling of control variables is realized and it meets the constraints of the maximum switching times. Next, the influencing factors of DG reactive power limit are analysed. Considering the control ability of OLTC, capacitor banks and DG in voltage and reactive power optimization, a coordinated optimization method is proposed. Since the adjustment of OLTC tap position directly affects the voltage and reactive power distribution of the whole line, the switching time and tap position of OLTC are determined based on the static optimization results of each time and fuzzy time clustering algorithm. Then, the switching time of capacitor banks is determined by fuzzy time clustering algorithm. At last, the switching capacity of capacitor banks and DG reactive power are jointly optimized to get the final control scheme. The proposed method demonstrated good performance in the modified IEEE33 node system and two actual power grid examples. [ABSTRACT FROM AUTHOR]

Background: The incidence of diabetic osteoporosis is increasing. This article evaluates the effect of combination treatment with the hypoglycemic drug exendin-4 (Ex-4) and the vitamin D analog eldecalcitol (ED-71) on improving diabetic osteoporosis and explores the relevant mechanism of action. Method: Micro-CT, HE staining, immunohistochemistry, qPCR and ELISA were used to evaluate the impact of Ex-4 and ED-71 on bone formation and macrophage polarization in a mouse model of diabetic osteoporosis in vivo. Immunofluorescence, flow cytometry and qPCR were used to characterize the polarization type of macrophages treated with Ex-4 and ED-71 in vitro. A co-culture system of BMSCs and macrophages was established. Subsequently, crystal violet staining, alkaline phosphatase staining and alizarin red staining were used to evaluate the migration and osteogenesis differentiation of BMSCs. Results: Ex-4 combined with ED-71 significantly reduced blood glucose levels and enhanced bone formation in mice with diabetic osteoporosis. In addition, Ex-4 synergized with ED-71 to induce the polarization of macrophages into M2 through the PI3K/AKT pathway. Macrophages treated with the combination of Ex-4 and ED-71 can significantly induce the osteogenic differentiation of BMSCs. Conclusion: Ex-4 synergized with ED-71 to reduce blood glucose levels significantly. And this combination therapy can synergistically induce osteogenic differentiation of BMSCs by promoting M2 macrophages polarization, thereby improving diabetic osteoporosis. Therefore, the combination of Ex-4 and ED-71 may be a new strategy for the treatment of diabetic osteoporosis. [ABSTRACT FROM AUTHOR]

The well-developed unified power flow controller (UPFC) has demonstrated its capability in providing voltage support and improving power system stability. The objective of this paper is to demonstrate the capability of the UPFC in mitigating oscillations in a wind farm integrated power system by employing eigenvalue analysis and dynamic time-domain simulation approaches. For this purpose, a power oscillation damping controller (PODC) of the UPFC is designed for damping oscillations caused by disturbances in a given interconnected power system, including the change in tie-line power, the changes of wind power outputs, and others. Simulations are carried out for two sample power systems, i.e., a four-machine system and an eight-machine system, for demonstration. Numerous eigenvalue analysis and dynamic time-domain simulation results confirm that the UPFC equipped with the designed PODC can effectively suppress oscillations of power systems under various disturbance scenarios. [ABSTRACT FROM AUTHOR]