Based on the comparison of existing power flow controllers(PFC)in meshed HVDC grids,the full-bridge modular multilevel converter based PFC(MMPFC)is proposed.At first,the general branch current calculation method of me...Based on the comparison of existing power flow controllers(PFC)in meshed HVDC grids,the full-bridge modular multilevel converter based PFC(MMPFC)is proposed.At first,the general branch current calculation method of meshed HVDC grids with the PFC is presented,and then,the issue of over-voltage on the thyristor based PFC is described and analyzed.Through the analysis of different operating modes of the full-bridge sub-module,the mechanism of over-voltage ride through of the MMPFC is indicated.The control strategy of the MMPFC,which is used to control branch current and keep capacitor voltage balancing,is elaborated.Finally,the performance on current regulation,bidirectional operation and over-voltage ride through is simulated and verified in a built model with PSCAD/EMTDC.展开更多
Multi-paralleled bidirectional power converters(BPCs)are commonly used to improve the power capacity and reliability in an AC/DC hybrid microgrid.However,circulating current through multi-BPCs has been one of the chal...Multi-paralleled bidirectional power converters(BPCs)are commonly used to improve the power capacity and reliability in an AC/DC hybrid microgrid.However,circulating current through multi-BPCs has been one of the challenges and it can be aggravated in the presence of non-ideal operating conditions,such as unbalanced AC voltages,and the mismatch of hardware parameters.In order to suppress the circulating current,this paper proposes a distributed method based on adaptive virtual impedance,which also employs positive sequence power droop control and voltage deviation compensation control.The traditional positive sequence power droop control is adopted to only regulate the positive components of the BPCs output voltage.The negative sequence power term is fed to an adaptive virtual impedance generator to modify the damping characteristics of the BPCs.Also,an adaptive virtual impedance-based voltage deviation compensation method is proposed to recover the fluctuated output voltage of the BPCs due to droop action and the power fluctuations.The fully distributed regulation of adaptive virtual impedance enables the load power to be shared accurately among BPC modules and thus the circulating current can be effectively suppressed.The proposed control strategy does not require an additional communication system and the precise parameters of hardware equipment and line impedance.Furthermore,the effectiveness of the proposed method is verified by the experimental results.展开更多
ObjectiFe To evaiuate surgicai procedure of corrected transposition of the great arteries(CTGA). Methods Twenty one patients with CTGA were ropaired from September 1990 to December 1996 Eighteen pattents were correcte...ObjectiFe To evaiuate surgicai procedure of corrected transposition of the great arteries(CTGA). Methods Twenty one patients with CTGA were ropaired from September 1990 to December 1996 Eighteen pattents were corrected by biventricular repair. The ventricular septal delect (VSD) was repaired through the right atrium or anatomic left ventricle in 11 patients and through the anatomic right ventricle in 7 patients. There were atrioventricular valvular regurgitation or one side ventricular hypoplasia in 3 patients. Two patients had Fontan operation and one had bidirectional shunt. Results Five patients (45%, 5/11) had complete atrioventricular block (CAVB) in these cases with VSD repaired through the right atrium or left ventricle, and 3 patients died (27%, 3/11). One patient (14%,1/7) had CA VB which the VSD was repaired through the anatomic right ventricle with only one death. Conclusion CAVB could be prevented by VSD rePair through the anatomic right ventricle. CTGA with pulmonary hypertension must be repaired early to prevent pulmonary vascular disease. Fontan or bidirectional shunt were suggested for complex CTGA with valvular regurgitation or ventricular unbalance.展开更多
We investigate bidirectional teleportation that works in a fair and efficient manner. Two explicit protocols are proposed to realize bidirectional teleportation with a controller. One is a symmetric protocol for two-q...We investigate bidirectional teleportation that works in a fair and efficient manner. Two explicit protocols are proposed to realize bidirectional teleportation with a controller. One is a symmetric protocol for two-qubit states. The other is an asymmetric protocol for single-and two-qubit states. We then devise a universal protocol for arbitrary n_(1)-and n_(2)-qubit states via a(2n_(1)+2n_(2)+1)-qubit entangled state, where n_(1)≤n_(2).The receiver only needs to perform the single-qubit recovery operation, which is derived by a general expression. Moreover, a(2n_(1)+1)-bit classical communication cost can be saved within the controller’s broadcast channel by the use of network coding technology.展开更多
基金supported by the National High Technology Research and Development Program of China("863"Program)(Grant No.2012AA050205)
文摘Based on the comparison of existing power flow controllers(PFC)in meshed HVDC grids,the full-bridge modular multilevel converter based PFC(MMPFC)is proposed.At first,the general branch current calculation method of meshed HVDC grids with the PFC is presented,and then,the issue of over-voltage on the thyristor based PFC is described and analyzed.Through the analysis of different operating modes of the full-bridge sub-module,the mechanism of over-voltage ride through of the MMPFC is indicated.The control strategy of the MMPFC,which is used to control branch current and keep capacitor voltage balancing,is elaborated.Finally,the performance on current regulation,bidirectional operation and over-voltage ride through is simulated and verified in a built model with PSCAD/EMTDC.
基金This work was supported in part by the National Natural Science Foundation of China(51807130)the National key research and development program of China(2018YFB0904700)+1 种基金the Major Science and Technology Projects in Shanxi Province(20181102028)the Postgraduate Education Innovation Project of Shanxi Province(2019BY048)。
文摘Multi-paralleled bidirectional power converters(BPCs)are commonly used to improve the power capacity and reliability in an AC/DC hybrid microgrid.However,circulating current through multi-BPCs has been one of the challenges and it can be aggravated in the presence of non-ideal operating conditions,such as unbalanced AC voltages,and the mismatch of hardware parameters.In order to suppress the circulating current,this paper proposes a distributed method based on adaptive virtual impedance,which also employs positive sequence power droop control and voltage deviation compensation control.The traditional positive sequence power droop control is adopted to only regulate the positive components of the BPCs output voltage.The negative sequence power term is fed to an adaptive virtual impedance generator to modify the damping characteristics of the BPCs.Also,an adaptive virtual impedance-based voltage deviation compensation method is proposed to recover the fluctuated output voltage of the BPCs due to droop action and the power fluctuations.The fully distributed regulation of adaptive virtual impedance enables the load power to be shared accurately among BPC modules and thus the circulating current can be effectively suppressed.The proposed control strategy does not require an additional communication system and the precise parameters of hardware equipment and line impedance.Furthermore,the effectiveness of the proposed method is verified by the experimental results.
文摘ObjectiFe To evaiuate surgicai procedure of corrected transposition of the great arteries(CTGA). Methods Twenty one patients with CTGA were ropaired from September 1990 to December 1996 Eighteen pattents were corrected by biventricular repair. The ventricular septal delect (VSD) was repaired through the right atrium or anatomic left ventricle in 11 patients and through the anatomic right ventricle in 7 patients. There were atrioventricular valvular regurgitation or one side ventricular hypoplasia in 3 patients. Two patients had Fontan operation and one had bidirectional shunt. Results Five patients (45%, 5/11) had complete atrioventricular block (CAVB) in these cases with VSD repaired through the right atrium or left ventricle, and 3 patients died (27%, 3/11). One patient (14%,1/7) had CA VB which the VSD was repaired through the anatomic right ventricle with only one death. Conclusion CAVB could be prevented by VSD rePair through the anatomic right ventricle. CTGA with pulmonary hypertension must be repaired early to prevent pulmonary vascular disease. Fontan or bidirectional shunt were suggested for complex CTGA with valvular regurgitation or ventricular unbalance.
基金supported by the National Natural Science Foundation of China(Grant Nos.61201253,61572246)the Open Foundation of State Key Laboratory of Networking and Switching Technology(Beijing University of Posts and Telecommunications)(Grant No.SKLNST-2020-2-02)the Open Foundation of Guangxi Key Laboratory of Trusted Software(Grant No.KX202040)。
文摘We investigate bidirectional teleportation that works in a fair and efficient manner. Two explicit protocols are proposed to realize bidirectional teleportation with a controller. One is a symmetric protocol for two-qubit states. The other is an asymmetric protocol for single-and two-qubit states. We then devise a universal protocol for arbitrary n_(1)-and n_(2)-qubit states via a(2n_(1)+2n_(2)+1)-qubit entangled state, where n_(1)≤n_(2).The receiver only needs to perform the single-qubit recovery operation, which is derived by a general expression. Moreover, a(2n_(1)+1)-bit classical communication cost can be saved within the controller’s broadcast channel by the use of network coding technology.
