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[en] With large-scale application of a large number of renewable energy sources, such as wind turbines, photovoltaics, and various power electronic equipment, the power electric system is becoming gradually more power-electronics-based, whose dynamical behavior becomes much complicated, compared to that of traditional power system. The recent developed theory of amplitude–phase motion equation provides a new framework for the general dynamic analysis of such a system. Based on this theory, we study a simple amplitude–phase motion equation, i.e., a single power-electronics device connected to an infinite-large system, but consider its nonlinear effect. With extensive and intensive theoretical analysis and numerical simulation, we find that basically the system shows some similarity with the classical second-order swing equation for a synchronous generator connected to an infinite bus, such as the two types of bifurcation including the saddle-node bifurcation and homoclinic bifurcation, and the dynamical behavior of stable fixed point, stable limit cycle, and their coexistence. In addition, we find that the Hopf bifurcation is possible, but for negative damping only. All these findings are expected to be helpful for further study of power-electronics-based power system, featured with nonlinearity of high-dimensional dynamic systems involved with not only a large timescale but also large space scale.
[en] As Beijing put forward its “one core, two wings” development plan, the development and construction in the Beijing Tongzhou District have turned into a national strategy. However, as a municipal district, energy and CO2 emission data and other statistics are difficult to obtain in Tongzhou and CO2 emissions accounting for a district at this level is rare. This study applies the accounting method of city carbon emissions to the district level. Firstly, we account for the CO2 emissions in the Tongzhou District from 2008 to 2015 according to data availability. Secondly, by using the logarithmic mean Divisa index decomposition approach, the Tongzhou CO2 emissions are decomposed into six main driving factors, including population, per capita GDP, industrial structure, energy intensity, energy consumption structure, and energy-related CO2 emission factors. The result shows that (1) from 2008 to 2015, the CO2 emissions in the Tongzhou District first increased and then decreased and peaked in 2011. (2) Population and per capita GDP both contributed to the change in CO2 emissions in the Tongzhou District during the study period and resulted in 407,200 tons and 346,200 tons increase, respectively. The industrial structure, energy consumption intensity, and energy structure exerted inhibiting effects, offsetting 29,300 tons, 571,500 tons, and 29,300 tons, respectively, and the energy consumption intensity was the most important factor. (3) On this basis, we discuss the annual effects of the driving factors. The results of this study provide great significance and references for research in order to implement the low-carbon development and the “one core, two wings” strategy in the Tongzhou District.
[en] From the perspective of corporate social responsibility and environmental risk management, green credit will have an important impact on corporate performance. The influence of green credit policy on enterprises can be reflected by the borrowing ability and financing cost of the enterprises, which represent the support strength and price preference of green credit policy. Based on this, this paper considers data on long-term borrowing capacity, short-term borrowing capacity, corporate social responsibility report score, and assets’ return rate of 119 listed enterprises of mining, power, and steel industries in China, from 2010 to 2016, and uses a panel data model to estimates the general relationship between the corporate social responsibility, green credit, and corporate performance. We find that: First, taking the social responsibility can promote the enterprises’ long-term borrowing ability and reduce their financing cost, but it can inhibit their short-term borrowing ability. With a 1% improvement in corporate social responsibility score, the long-term borrowing ability of enterprises in three industries will be increased by 0.0867, 0.2688, and 0.0510%, respectively. Second, the positive undertaking of corporate social responsibility will promote the improvement in enterprise performance. The result of enterprise performance improvement for the sample industry is 0.05, 0.03, and 0.07%. Third, the long-term borrowing ability of enterprise green credit has a small promoting effect on the enterprises’ performance, with the coefficients being 0.1266, 0.0539, and 0.0306, respectively. This paper can be used as a reference to promote both implementation of green credit policy and corporate performance.
[en] The process of the production of multi-crystalline silicon is also that of incessant purification of metallurgical grade silicon, during which high energy consumption and environmental pollutants are inevitable. The paper, which is based on life cycle assessment (LCA), presents calculation and analysis on resource input, energy consumption, emissions into and comprehensive impact on environment generated from the whole process in which 1 kg of solar grade multi-crystalline silicon (SoG-Si) is produced with metallurgical route. The program is based on its research on four representative processes in metallurgical route, namely slag refining, wet purification, directional solidification and electron beam melting. Key factors determining environmental load are sought out through contribution analysis and improvement evaluation. Measures and suggestions on how to improve are proposed. For the first time, the LCA model of comparison of metallurgical route and modified Siemens process to SoG-Si environmental impact is constructed. The environmental impacts of SoG-Si production via metallurgical route is compared with purification via modified Siemens process. Results show that the comprehensive environmental impact of metallurgical route SoG-Si is only 49.57% of modified Siemens process SoG-Si. The metallurgical route enjoys obvious environmental advantage. The improvement should be focused on the reduction of electric power consumption in production processes.