In order to suppress the fast decrease of the transfer efficiency of magnetic resonance coupled wireless power transfer system(MRCWPTS) with distance increase,this paper investigates the impact factors of the system t...In order to suppress the fast decrease of the transfer efficiency of magnetic resonance coupled wireless power transfer system(MRCWPTS) with distance increase,this paper investigates the impact factors of the system transfer efficiency and is,then formulates a new efficiency optimal control method based on frequency control.Based upon this control method two optimal control schemes are designed to achieve transfer efficiency control of the system.Simulations and experiments show that the proposed efficiency optimal control method can effectively stabilize the system transfer efficiency in a certain range so as to successfully solve the subtle issue of transfer efficiency variation with distance.展开更多
The grid connection of a large-scale wind farm could change the load flow/configuration of a power system and introduce dynamic interactions with the synchronous generators(SGs),thus affecting system small-signal angu...The grid connection of a large-scale wind farm could change the load flow/configuration of a power system and introduce dynamic interactions with the synchronous generators(SGs),thus affecting system small-signal angular stability.This paper proposes an approach for the separate examination of the impact of those affecting factors,i.e.,the change of load flow/configuration and dynamic interactions brought about by the grid connection of the wind farm,on power system smallsignal angular stability.Both cases of grid connection of the wind farm,either displacing synchronous generators or being directly added into the power system,are considered.By using the proposed approach,how much the effect of the change of load flow/configuration brought about by the wind farm can be examined,while the degree of impact of the dynamic interaction of the wind farm with the SGs can be investigated separately.Thus,a clearer picture and better understanding of the power system small-signal angular stability as affected by grid connection of the large-scale wind farm can be achieved.An example of the power system with grid connection of a wind farm is presented to demonstrate the proposed approach.展开更多
In recent years,the large-scale integration of re-newable energy sources represented by wind power and the widespread application of power electronic devices in power systems have led to the emergence of multi-frequen...In recent years,the large-scale integration of re-newable energy sources represented by wind power and the widespread application of power electronic devices in power systems have led to the emergence of multi-frequency oscillation problems covering multiple frequency segments,which seriously threaten system stability and restrict the accommodation of renewable energy.The oscillation problems related to renewable energy integration have become one of the most popular topics in the field of wind power integration and power system stability research.It has received extensive attention from both academia and industries with many promising research results achieved to date.This paper first analyzes several typical multi-frequency oscillation events caused by large-scale wind power integration in domestic and foreign projects,then studies the multi-frequency oscillation problems,including wind turbine’s shafting torsional oscillation,sub/super-synchronous oscillation and high frequency resonance.The state of the art is systematically summarized from the aspects of oscillation mechanism,analysis methods and mitigation measures,and the future research directions are explored.展开更多
文摘In order to suppress the fast decrease of the transfer efficiency of magnetic resonance coupled wireless power transfer system(MRCWPTS) with distance increase,this paper investigates the impact factors of the system transfer efficiency and is,then formulates a new efficiency optimal control method based on frequency control.Based upon this control method two optimal control schemes are designed to achieve transfer efficiency control of the system.Simulations and experiments show that the proposed efficiency optimal control method can effectively stabilize the system transfer efficiency in a certain range so as to successfully solve the subtle issue of transfer efficiency variation with distance.
基金supported by the National Basic Research Program of China (973 Program) (2012CB215204)the key project of the SKLAEPS and the international collaborative project jointly funded by the NSFC (51311122) Chinathe EPSRC,UK.
文摘The grid connection of a large-scale wind farm could change the load flow/configuration of a power system and introduce dynamic interactions with the synchronous generators(SGs),thus affecting system small-signal angular stability.This paper proposes an approach for the separate examination of the impact of those affecting factors,i.e.,the change of load flow/configuration and dynamic interactions brought about by the grid connection of the wind farm,on power system smallsignal angular stability.Both cases of grid connection of the wind farm,either displacing synchronous generators or being directly added into the power system,are considered.By using the proposed approach,how much the effect of the change of load flow/configuration brought about by the wind farm can be examined,while the degree of impact of the dynamic interaction of the wind farm with the SGs can be investigated separately.Thus,a clearer picture and better understanding of the power system small-signal angular stability as affected by grid connection of the large-scale wind farm can be achieved.An example of the power system with grid connection of a wind farm is presented to demonstrate the proposed approach.
基金This work was supported by the National Natural Science Foundation of China(No.51577174).
文摘In recent years,the large-scale integration of re-newable energy sources represented by wind power and the widespread application of power electronic devices in power systems have led to the emergence of multi-frequency oscillation problems covering multiple frequency segments,which seriously threaten system stability and restrict the accommodation of renewable energy.The oscillation problems related to renewable energy integration have become one of the most popular topics in the field of wind power integration and power system stability research.It has received extensive attention from both academia and industries with many promising research results achieved to date.This paper first analyzes several typical multi-frequency oscillation events caused by large-scale wind power integration in domestic and foreign projects,then studies the multi-frequency oscillation problems,including wind turbine’s shafting torsional oscillation,sub/super-synchronous oscillation and high frequency resonance.The state of the art is systematically summarized from the aspects of oscillation mechanism,analysis methods and mitigation measures,and the future research directions are explored.
