Hybrid DC circuit breaker with reduced fault isolation time and current limiting capability

Qichao Chen,Bingkun Li,Laicheng Yin,Junyuan Zheng,Zhaoyu Duan,Yiqi Liu 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.1

DC circuit breakers (DCCBs) are key pieces of equipment to ensure the safe and stable operation of DC grids. However, current DCCB schemes generally have problems such as a slow fault clearing speed and a poor current limiting effect. This paper proposes a current-limited hybrid DC circuit breaker (CLHCB) that limits fault current and has fast fault isolation, which reduces the capacity requirements. The current limiting inductor in the fault current limiter (FCL) provides the current limiting capability. In addition, the energy dissipation circuit (EDC) is in parallel to reduce the energy dissipation in metal oxide arresters (MOAs) and to decrease the fault isolation time (FIT), which can reduce the thermal effects of MOAs and improve their reliability. Simulation results verify the working principle and advantages of the proposed CLHCB. When compared to an ABB HCB under the same simulation parameters, the CLHCB enables fault current limiting and faster fault isolation. Finally, experiments have verified the effectiveness of the proposed CLHCB.

Underwater contactless wet‑mateable connector using bowl‑shaped coils

Qichao Zhao,Tianlei Wang,Hui Zhi,Xin Wu,Yurui Zhang,Canjun Yang,Yanhu Chen 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.7

Wet-mateable connectors enabling power and communication for underwater equipment are greatly favored for underwater systems. However, conventional underwater wet-mateable connectors with electrical contact conductors have the features of high cost, limited mate/de-mate times, and high risk of ground faults when being applied underwater, which limits their used. In this paper, a contactless underwater wet-mateable connector with bowl-shaped couplers was proposed, and an equivalent circuit for inductive power transmission was modeled and analyzed. Then the mathematical expression of the magnetic induction intensity of the bowl-shaped coil was derived. The parameters including co , zco , and s0 of the coil were analyzed and optimized to attain better performance and lower cost. A prototype was built and tested. Results showed that it can transmit power up to 1125 W with an efficiency of 85%. In addition, it can achieve a data rate up to 6 MB/s under a water pressure of 20 MPa.

SET8 suppression mediates high glucose-induced vascular endothelial inflammation via the upregulation of PTEN

Shen Xuefang,Chen Xiangyuan,Wang Jing,Liu Jing,Wang Zhiyao,Hua Qing,Wu Qichao,Su Yanguang,He Huanzhong,Hu Yuqin,Meng Zhipeng,Xiong Wanxia,Zhu Minmin 생화학분자생물학회 2020 Experimental and molecular medicine Vol.52 No.-

Hyperglycemia-mediated endothelial inflammation participates in the pathogenesis of cardiovascular complications in subjects with diabetes. Previous studies reported that phosphatase and tensin homolog deleted on chromosome ten (PTEN) and SET8 participate in high glucose-mediated endothelial inflammation. In this study, we hypothesize that SET8 regulates PTEN expression, thus contributing to high glucose-mediated vascular endothelial inflammation. Our data indicated that plasma soluble intercellular adhesion molecule-1 (sICAM-1) and endothelial selectin (e-selectin) were increased in patients with diabetes and diabetic rats. PTEN expression was augmented in the peripheral blood mononuclear cells of patients with diabetes and in the aortic tissues of diabetic rats. Our in vitro study indicated that high glucose increased monocyte/endothelial adhesion, endothelial adhesion molecule expression and p65 phosphorylation in human umbilical vein endothelial cells (HUVECs). Moreover, high glucose led to endothelial inflammation via upregulation of PTEN. Furthermore, high glucose inhibited SET8 expression and histone H4 lysine 20 methylation (H4K20me1), a downstream target of SET8. SET8 overexpression reversed the effects of high-glucose treatment. shSET8-mediated endothelial inflammation was counteracted by siPTEN. Furthermore, SET8 was found to interact with FOXO1. siFOXO1 attenuated high glucose-mediated endothelial inflammation. FOXO1 overexpression-mediated endothelial inflammation was counteracted by siPTEN. H4K20me1 and FOXO1 were enriched in the PTEN promoter region. shSET8 increased PTEN promoter activity and augmented the positive effect of FOXO1 overexpression on PTEN promoter activity. Our in vivo study indicated that SET8 was downregulated and FOXO1 was upregulated in the peripheral blood mononuclear cells of patients with diabetes and the aortic tissues of diabetic rats. In conclusion, SET8 interacted with FOXO1 to modulate PTEN expression in vascular endothelial cells, thus contributing to hyperglycemia-mediated endothelial inflammation.

On DC-Side Impedance Frequency Characteristics Analysis and DC Voltage Ripple Prediction under Unbalanced Conditions for MMC-HVDC System Based on Maximum Modulation Index

Liu, Yiqi,Chen, Qichao,Li, Ningning,Xie, Bing,Wang, Jianze,Ji, Yanchao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

On DC-Side Impedance Frequency Characteristics Analysis and DC Voltage Ripple Prediction under Unbalanced Conditions for MMC-HVDC System Based on Maximum Modulation Index

Yiqi Liu,Qichao Chen,Ningning Li,Bing Xie,Jianze Wang,Yanchao Ji 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

The bearing capacity of monolithic composite beams with laminated slab throughout fire process

Junli Lyu,Shengnan Zhou,Qichao Chen,Yong Wang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.1

To investigate the failure form, bending stiffness, and residual bearing capacity of monolithic composite beams with laminated slab throughout the fire process, fire tests of four monolithic composite beams with laminated slab were performed under constant load and temperature increase. Different factors such as post-pouring layer thickness, lap length of the prefabricated bottom slab, and stud spacing were considered in the fire test. The test results demonstrate that, under the same fire time and external load, the post-pouring layer thickness and stud spacing are important parameters that affect the fire resistance of monolithic composite beams with laminated slab. Similarly, the post-pouring layer thickness and stud spacing are the predominant factors affecting the bending stiffness of monolithic composite beams with laminated slab after fire exposure. The failure forms of monolithic composite beams with laminated slab after the fire are approximately the same as those at room temperature. In both cases, the beams underwent bending failure. However, after exposure to the high-temperature fire, cracks appeared earlier in the monolithic composite beams with laminated slab, and both the residual bearing capacity and bending stiffness were reduced by varying degrees. In this test, the bending bearing capacity and ductility of monolithic composite beams with laminated slab after fire exposure were reduced by 23.3% and 55.4%, respectively, compared with those tested at room temperature. Calculation methods for the residual bearing capacity and bending stiffness of monolithic composite beams with laminated slab in and after the fire are proposed, which demonstrated good accuracy.

MMC‑modified sub‑module structure with double reverse blocking IGBTs

Yiqi Liu,Zhaoyu Duan,Qichao Chen,Bingkun Li,Mingfei Ban,Zhenjie Li 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.3

In high-voltage direct current (HVDC) systems, among the voltage source converters (VSCs), the modular multilevel converter (MMC) is a popular choice for power transmission. Unfortunately, the conventional half-bridge sub-module (SM) cannot deal with DC faults by itself. Thus, improved SM topologies enabling DC fault ride-through are significant. With this in mind, an MMC-modified SM structure is presented with double reverse blocking IGBTs (DRBSM). When all of the IGBTs in an MMC are blocked, the DRBSM can insert two capacitors in series to the fault circuit to rapidly overcome the DC fault. First, the DRBSM topology and working principle are analyzed. Second, the DRBSM control strategy is illustrated. Third, the device withstand voltage, DC fault ride-through, cost, and loss performance of the DRBSM are presented in detail. Finally, according to simulation results, the DRBSM fault ride-through speed is shown to be as fast as the full-bridge SM, and faster than the clamp double SM. In addition, experimental results validate the feasibility of the proposed DRBSM structure.

Spatial analysis of tuberculosis treatment outcomes in Shanghai: implications for tuberculosis control

Zhang Jing,Shen Xin,Yang Chongguang,Chen Yue,Guo Juntao,Wang Decheng,Zhang Jun,Lynn Henry,Hu Yi,Pan Qichao,Zhang Zhijie 한국역학회 2022 Epidemiology and Health Vol.44 No.-

OBJECTIVES: Tuberculosis (TB) treatment outcomes are a key indicator in the assessment of TB control programs. We aimed to identify spatial factors associated with TB treatment outcomes, and to provide additional insights into TB control from a geographical perspective.METHODS: We collected data from the electronic TB surveillance system in Shanghai, China and included pulmonary TB patients registered from January 1, 2009 to December 31, 2016. We examined the associations of physical accessibility to hospitals, an autoregression term, and random hospital effects with treatment outcomes in logistic regression models after adjusting for demographic, clinical, and treatment factors.RESULTS: Of the 53,475 pulmonary TB patients, 49,002 (91.6%) had successful treatment outcomes. The success rate increased from 89.3% in 2009 to 94.4% in 2016. The successful treatment outcome rate varied among hospitals from 78.6% to 97.8%, and there were 12 spatial clusters of poor treatment outcomes during the 8-year study period. The best-fit model incorporated spatial factors. Both the random hospital effects and autoregression terms had significant impacts on TB treatment outcomes, ranking 6th and 10th, respectively, in terms of statistical importance among 14 factors. The number of bus stations around the home was the least important variable in the model.CONCLUSIONS: Spatial autocorrelation and hospital effects were associated with TB treatment outcomes in Shanghai. In highly-integrated cities like Shanghai, physical accessibility was not related to treatment outcomes. Governments need to pay more attention to the mobility of patients and different success rates of treatment among hospitals.