Bypass arm based DC fault isolation scheme for MMC-HVDC systems

High voltage direct current transmission based on a modular multilevel converter (MMC-HVDC) is an effective method to solve the grid connection of the new energy. A DC fault is an issue that must be solved for MMC-HVDC. This paper proposes a protection scheme for HVDC converters to quickly suppress DC fault current without increasing the operation loss. By employing a bypass arm in conjunction with a switch-type zero-loss current limiter (SZCL), most of the DC current in the bridge arm flows through the bypass arm so the fault current of the power devices is reduced. There are a number of main advantages of this scheme. The fault isolation time can be greatly shortened, the cost of the system is effectively reduced, the steady-state operation loss of the system does not increase, the operation of the AC-grid can be maintained stably when a DC fault occurs, and the overcurrent impulse to the AC-grid is reduced. The proposed scheme is applicable to two-terminal systems and the DC grid, especially for faults at the converter outlet of the DC grid. Simulation results using PSCAD/EMTDC show the superiority of the proposed scheme when compared with other schemes and a comparison of the costs shows the feasibility of the proposed scheme in practical applications

Green Finance Innovation and Regional Green Development

Through the use of 30 provincial panel datasets covering the years from 2013 to 2017, on the basis of constructing the regional green development indicator system, this paper used the fixed-base range entropy weight method to measure the regional green development level. The difference-in-differences model was used to test the policy effect, the mechanism of the establishment of the green financial reform, and the innovation pilot zone on green development. The results showed that: (1) the establishment of the pilot zone promotes regional green development and shows regional differences; (2) under the guidance of policies, the provinces that set up the pilot zone affect the level of regional green development mainly through the upgrading of industrial structure and technological innovation; further research has found (3) a high level of financial investment in environmental protection and marketization, which will help the pilot zone to further play a positive role in promoting the green development of the region. The results of this article indicated that China should continue to expand the scope of green finance reform and innovation pilot zones and make reasonable arrangements among regions according to local conditions to explore new ways of promoting green development. At the same time, the government should actively play the role of green finance in the pilot zone to promote industrial structure upgrading and technological innovation and guide market players to establish green development concepts to gradually build an environmentally friendly, circular model economy to enhance the overall green development capacity of the region

The Dual Impacts of Green Credit on Economy and Environment: Evidence from China

Green credit is regarded as an important means to promote sustainable growth. Based on the provincial panel dataset of China from 2007 to 2017, this paper investigates the dual impacts of green credit on the economy and environment, and it establishes mediating effect models to analyze the Porter hypothesis. The results show that the green credit policy significantly improves economic performance and reduces pollutant emissions. The above results are robust to employing methods with alternative variables and instrumental variables. Second, the green credit policy contributes to innovation; that is, the green credit increases the innovation scale and improves innovation efficiency. The results of mediating effect models suggest that the Porter effect of green credit can be achieved by improving innovation efficiency. The findings of the current study indicate that the green credit policy helps achieve the win–win situation for economic goals and environmental targets

A Comprehensive Model of the Relationship between Miners’ Work Commitment, Cultural Emotion and Unemployment Risk Perception

The psychological health and work commitment of miners are prerequisites to ensuring their sustainable safety behavior, and it is also significant to the sustainable development of coal mines in China. In this context, we conducted a questionnaire survey among coal miners of state-owned coal enterprises to explore the relationships between cultural emotion, unemployment risk perception, Big Five personality traits, and work commitment. The results reveal that (1) cultural emotion and its three dimensions played a significant positive role in promoting work commitment. (2) Unemployment risk perception, policy unemployment risk perception, and individual differential unemployment risk perception had a negative moderating effect. (3) Moreover, work commitment was associated with differences in personality characteristics except for agreeableness. This research is of important theoretical value and practical significance, as it can guide Chinese coal miners to increase their work commitment and thereby improve safety in production

河北省利用外资的策略研究 = On the strategies of utilizing foreign direct investment in Hebei province

The purpose of this paper are to examine factors affecting inward Foreign Direct Investment (FDI) and recommend strategies for attracting FDI in Hebei Province, China.​Master of Science (Managerial Economics

Short-term Study of Bushen Jiangu Decoction Combined with PVP in the Treatment of Elderly Patients with Osteoporotic Thoracolumbar Vertebral Compression Fracture

To investigate the clinical effects of Bushen Jiangu Decoction combined with percutaneous vertebroplasty (PVP) in the treatment of elderly patients with osteoporotic thoracolumbar vertebral compression fracture (OVCF). Seventy-four elderly patients with OVCF were enrolled in our hospital and randomized by digital table method, 37 cases each. The control group received PVP treatment, and the observation group was treated with Bushen Jiangu Decoction on the basis of PVP treatment. Cobb angle, bone mineral density, Oswestry dysfunction index questionnaire (ODI) score, and visual analogue scale (VAS) were compared before and after treatment. After treatment, the Cobb angle of the observation group was smaller than that of the control group, and the bone density was higher than that of the control group (P<0.05). The ODI score of the observation group was lower than that of the control group after treatment (P<0.05); 1 month and 3 months after treatment, the VAS score of the 6-month observation group was lower than that of the control group (P<0.05). Bushen Jiangu Decoction combined with Western medicine in the treatment of elderly patients with OVCF can restore Cobb angle, increase bone density, reduce postoperative pain and improve thoracic and lumbar spine function

Remotely Sensed Vegetation Green-Up Onset Date on the Tibetan Plateau: Simulations and Future Predictions

Vegetation green-up onset date (VGD) is a key indicator of ecosystem structure and processes. As the largest and highest alpine ecoregion, the Tibetan plateau (TP) has experienced markable climate warming during the past decades and showed substantial changes in VGD. However, the existing process-based phenology models still cannot simulate interannual variations in satellite-derived VGD. In this study, we developed a data-driven VGD model for the TP based on the Long short-term memory neural network (called VGD-LSTM). VGD-LSTM considers the complicated nonlinear relationship between VGD and multiple climatic and environmental drivers, including the time series of temperature (daytime, daily minimum, and daily mean) and precipitation, as well as nonsequential variables (elevation and geolocation). Compared with the benchmark process-based VGD model for the TP (i.e., the hierarchical model), VGD-LSTM greatly improved the simulation of interannual VGD variations. We calculated the correlation coefficients (R) between satellite-derived VGDs and VGD simulations during 2000&#x2013;2018; the percentages of pixels with R values above 0.5 increased from 15&#x0025; for the hierarchical model to 41&#x0025; for VGD-LSTM. The advanced trend in the satellite-derived VGD on the entire TP during 2000&#x2013;2018 (&#x2212;0.37 day&#x002F;year) was captured well by VGD-LSTM (&#x2212;0.33 day&#x002F;year) but was underestimated by the hierarchical model (&#x2212;0.08 day&#x002F;year). According to VGD-LSTM simulations, VGDs on the TP are projected to advance by 8&#x2013;10 days by 2100 relative to 2015&#x2013;2020 under high shared socioeconomic pathway scenarios. This study suggests the potential of artificial intelligence in phenology modeling for which the physiological processes are difficult to be fully represented

Decomposition Analysis of the Factors that Influence Energy Related Air Pollutant Emission Changes in China Using the SDA Method

We decompose factors affecting China’s energy-related air pollutant (NOx, PM2.5, and SO2) emission changes into different effects using structural decomposition analysis (SDA). We find that, from 2005 to 2012, investment increased NOx, PM2.5, and SO2 emissions by 14.04, 7.82 and 15.59 Mt respectively, and consumption increased these emissions by 11.09, 7.98, and 12.09 Mt respectively. Export and import slightly increased the emissions on the whole, but the rate of the increase has slowed down, possibly reflecting the shift in China’s foreign trade structure. Energy intensity largely reduced NOx, PM2.5, and SO2 emissions by 12.49, 14.33 and 23.06 Mt respectively, followed by emission efficiency that reduces these emissions by 4.57, 9.08, and 17.25 Mt respectively. Input-output efficiency slightly reduces the emissions. At sectoral and sub-sectoral levels, consumption is a great driving factor in agriculture and commerce, whereas investment is a great driving factor in transport, construction, and some industrial subsectors such as iron and steel, nonferrous metals, building materials, coking, and power and heating supply. Energy intensity increases emissions in transport, chemical products and manufacturing, but decreases emissions in all other sectors and subsectors. Some policies arising from our study results are discussed