Hybrid DC transmission technology is used in new energy transmission due to its advantages of large capacity and long distances.Line-commutated converter-voltage source converter-multi-terminal DC(LCC-VSC-MTDC)is one ...Hybrid DC transmission technology is used in new energy transmission due to its advantages of large capacity and long distances.Line-commutated converter-voltage source converter-multi-terminal DC(LCC-VSC-MTDC)is one of the more important development directions in future power grids.But the multi-terminal high voltage direct current system has problems of inconsistent boundary characteristics,inconsistent control,and fault response characteristics,which places higher requirements on the protection scheme.A protection scheme based on the undistorted factor is proposed to ensure the safe operation of the system.First,the inconsistent line mode voltage attenuation characteristics of different fault locations are used to construct the undistorted factor.Subsequently,the undistorted factor is used to identify fault.The advantage of this scheme is that it remains unaffected by boundary elements,control strategies,and distributed capacitance.Finally,the LCC-VSC-MTDC model verifies the correctness and superiority of the proposed protection scheme.展开更多
Preparation of large rylenes often needs the use of solubilizing groups along the rylene backbone,which results in the distortion of the skeleton and thus broadening of the absorption spectrum.In this work,we successf...Preparation of large rylenes often needs the use of solubilizing groups along the rylene backbone,which results in the distortion of the skeleton and thus broadening of the absorption spectrum.In this work,we successfully synthesized 2,5,8,16,19,22-hexakis[2,6-bis(tri-fluoromethyl)phenyl]hexarylene(H)by using an oxidative fusion reaction of perylene trimer in 5%yield.The product is soluble in common organic solvents and could be purified with column chromatography.Single-crystal X-ray diffraction analysis revealed that the hexarylene core is not disturbed by the substituents very much and is almost planar.The longest absorption of H exhibits a sharp peak at 831 nm and an on-set at 875 nm in toluene with a small full-width-at-half-maximum(FWHM)of 660 cm^(-1).The molar extinction coefficient is as large as 131,000 M^(-1)cm^(-1).The substituents could not perturb the electronic properties of the hexarylene because aryl groups are perpendicular to the hexarylene core and the carbon atoms at 2,5,16,19-positions have negligible coeffi-cients on its HOMO and LUMO,estimated by theoretical calculations.As a result,the hexarylene having less absorption at the visible light region was stable enough in solution under the LED room light for more than 1 week.This strategy gives a useful guideline to establish the near-infrared materials that exhibit stability under ambient conditions.展开更多
基金supported by the National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2066210).
文摘Hybrid DC transmission technology is used in new energy transmission due to its advantages of large capacity and long distances.Line-commutated converter-voltage source converter-multi-terminal DC(LCC-VSC-MTDC)is one of the more important development directions in future power grids.But the multi-terminal high voltage direct current system has problems of inconsistent boundary characteristics,inconsistent control,and fault response characteristics,which places higher requirements on the protection scheme.A protection scheme based on the undistorted factor is proposed to ensure the safe operation of the system.First,the inconsistent line mode voltage attenuation characteristics of different fault locations are used to construct the undistorted factor.Subsequently,the undistorted factor is used to identify fault.The advantage of this scheme is that it remains unaffected by boundary elements,control strategies,and distributed capacitance.Finally,the LCC-VSC-MTDC model verifies the correctness and superiority of the proposed protection scheme.
基金supported by Grants-in-Aid for Scientific Research(Nos.JP20H02816(HH),JP20H00379(HY),JP20H05833(HY),JP20H02711(NA),JP22H19067(NA),JP22K05225(KM),JP20K15261(KM))。
文摘Preparation of large rylenes often needs the use of solubilizing groups along the rylene backbone,which results in the distortion of the skeleton and thus broadening of the absorption spectrum.In this work,we successfully synthesized 2,5,8,16,19,22-hexakis[2,6-bis(tri-fluoromethyl)phenyl]hexarylene(H)by using an oxidative fusion reaction of perylene trimer in 5%yield.The product is soluble in common organic solvents and could be purified with column chromatography.Single-crystal X-ray diffraction analysis revealed that the hexarylene core is not disturbed by the substituents very much and is almost planar.The longest absorption of H exhibits a sharp peak at 831 nm and an on-set at 875 nm in toluene with a small full-width-at-half-maximum(FWHM)of 660 cm^(-1).The molar extinction coefficient is as large as 131,000 M^(-1)cm^(-1).The substituents could not perturb the electronic properties of the hexarylene because aryl groups are perpendicular to the hexarylene core and the carbon atoms at 2,5,16,19-positions have negligible coeffi-cients on its HOMO and LUMO,estimated by theoretical calculations.As a result,the hexarylene having less absorption at the visible light region was stable enough in solution under the LED room light for more than 1 week.This strategy gives a useful guideline to establish the near-infrared materials that exhibit stability under ambient conditions.
