Frequency droop control is widely used in permanent magnet synchronous generators(PMSGs)based wind turbines(WTs)for grid frequency support.However,under frequency deviations,significant DC-link voltage fluctuations ma...Frequency droop control is widely used in permanent magnet synchronous generators(PMSGs)based wind turbines(WTs)for grid frequency support.However,under frequency deviations,significant DC-link voltage fluctuations may occur during the transient process due to sudden changes in real power of such WTs.To address this issue,a current feedforward control strategy is proposed for PMSG-based WTs to reduce DC-link voltage fluctuations when the WTs are providing frequency support under grid frequency deviations.Meanwhile,the desired frequency support capability of the PMSG-based WTs can be ensured.Simulation results verify the rationality of the analysis and the effectiveness of the proposed control method.展开更多
对实验室直驱风力机发电机组模拟系统进行系统分析和建模,通过建模和分析给出风力发电机组模拟系统的建立方法及参数折算方法。使用该方法分析10 k W模拟系统模拟1 MW风电机组的情况,并进行相应仿真研究。通过该方法建立一套17 k W风力...对实验室直驱风力机发电机组模拟系统进行系统分析和建模,通过建模和分析给出风力发电机组模拟系统的建立方法及参数折算方法。使用该方法分析10 k W模拟系统模拟1 MW风电机组的情况,并进行相应仿真研究。通过该方法建立一套17 k W风力发电机组的实验室模拟系统,并进行工况突变实验与电压跌落实验。展开更多
Based on the perspective of international vertical specialization,this paper creates a set of new approach to estimating the domestic technological sophistication(DTS)of export goods.Deducting the values of imported i...Based on the perspective of international vertical specialization,this paper creates a set of new approach to estimating the domestic technological sophistication(DTS)of export goods.Deducting the values of imported intermediate inputs contained in export goods,this paper conducts an estimation and analysis of the DTS of China's industrial finished goods for export between 2002 and 2007 at the national,industrial and regional levels.Results of our study indicate that:(1) the DTS of China's export goods demonstrates an overall tendency of steady increase and its evolving pattern demonstrates distinctive differences across sectors;(2) the DTS is on the increase for natural resources sectors,low-technology sectors,medium-technology sectors and certain high-technology sectors including transportation equipment manufacturing,general and dedicated equipment manufacturing,and electrical machinery and apparatus manufacturing while the DTS is on the significant decrease for electronic and communication equipment manufacturing and instruments,meters and other metering devices manufacturing;and(3) provinces with relatively high average values of DTS of export goods are primarily located in China's eastern region while provinces with significant DTS growth rates are mainly located in China's central and western regions and the gaps of DTS of export goods among China's eastern,central and western regions have a tendency of convergence.展开更多
基金This work is jointly supported by the National Key R&D Programme of China(No.2017YFB0902000)the National Natural Science Foundation of China(No.U1766206)the Science and Technology Programme of the State Grid Corporation(No.52110418000P).
文摘Frequency droop control is widely used in permanent magnet synchronous generators(PMSGs)based wind turbines(WTs)for grid frequency support.However,under frequency deviations,significant DC-link voltage fluctuations may occur during the transient process due to sudden changes in real power of such WTs.To address this issue,a current feedforward control strategy is proposed for PMSG-based WTs to reduce DC-link voltage fluctuations when the WTs are providing frequency support under grid frequency deviations.Meanwhile,the desired frequency support capability of the PMSG-based WTs can be ensured.Simulation results verify the rationality of the analysis and the effectiveness of the proposed control method.
文摘Based on the perspective of international vertical specialization,this paper creates a set of new approach to estimating the domestic technological sophistication(DTS)of export goods.Deducting the values of imported intermediate inputs contained in export goods,this paper conducts an estimation and analysis of the DTS of China's industrial finished goods for export between 2002 and 2007 at the national,industrial and regional levels.Results of our study indicate that:(1) the DTS of China's export goods demonstrates an overall tendency of steady increase and its evolving pattern demonstrates distinctive differences across sectors;(2) the DTS is on the increase for natural resources sectors,low-technology sectors,medium-technology sectors and certain high-technology sectors including transportation equipment manufacturing,general and dedicated equipment manufacturing,and electrical machinery and apparatus manufacturing while the DTS is on the significant decrease for electronic and communication equipment manufacturing and instruments,meters and other metering devices manufacturing;and(3) provinces with relatively high average values of DTS of export goods are primarily located in China's eastern region while provinces with significant DTS growth rates are mainly located in China's central and western regions and the gaps of DTS of export goods among China's eastern,central and western regions have a tendency of convergence.
