In view of the operating characteristics for voltage sags of AC side of the power electronic transformer(PET),a low-voltage ride through(LVRT)strategy adapted to bidirectional power exchange of PET is proposed for the...In view of the operating characteristics for voltage sags of AC side of the power electronic transformer(PET),a low-voltage ride through(LVRT)strategy adapted to bidirectional power exchange of PET is proposed for the purposes of maintaining the system stability,assisting the system voltage recovery and protecting PET safety.During the asymmetric voltage sag,the negative sequence current of PET is eliminated to ensure the symmetry of the injected current.According to the degree of positive sequence voltage sag,the reactive current injection is provided to assist in voltage recovery.According to the PET active power condition before the voltage sag,the level and direction of which are maintained as far as possible without exceeding the limit,for which the disturbance to the AC and DC grids is reduced.Finally,the effectiveness of the proposed LVRT strategy is verified by simulation model.展开更多
Grid-forming converters(GFMs)are faced with the threat of transient inrush current and synchronization instability issues when subjected to grid faults.Instead of disconnecting from the grid unintentionally,GFMs are r...Grid-forming converters(GFMs)are faced with the threat of transient inrush current and synchronization instability issues when subjected to grid faults.Instead of disconnecting from the grid unintentionally,GFMs are required to have fault ride through(FRT)capability to maintain safe and stable operation in grid-connected mode during grid fault periods.In recent studies,different FRT control strategies with distinguishing features and that are feasible for different operation conditions have been proposed for GFMs.To determine their application scope,an intuitive comparison of the transient performance of different FRT control strategies is presented in this paper.First,three typical FRT control strategies(virtual impedance,current limiters,and mode-switching control)are introduced and transient mathematical models are established.A detailed comparison analysis on transient inrush current and transient synchronization stability is then presented.The results will be useful for guiding the selection and design of FRT control strategies.Finally,simulation results based on PSCAD/EMTDC are considered to verify the correctness of the theoretical analysis.展开更多
A new loop and fold wave-guide ion cyclotron resonance frequency （ICRF） antenna with a power output of 3 MW, which can operate at a frequency in the range of 30 MHz to 110 MHz, was designed. The design of key compon...A new loop and fold wave-guide ion cyclotron resonance frequency （ICRF） antenna with a power output of 3 MW, which can operate at a frequency in the range of 30 MHz to 110 MHz, was designed. The design of key components of the new ICRF antenna and the charac- ters of the new,.]~rototype ICRF antenna are presented. The thermo-mechanical analysis of both the Faraday shield and the current straps was conducted, and the stresses due to heat loads are studied in detail with different cooling-water velocities considered. In addition, the movability of prototype ICRF antenna under vacuum condition by the driving system was tested. An engineer- ing commissioning was successfully performed on the prototype ICRF antenna using the original transmitter. The results are close to the expected.展开更多
基金supported by the Science and Technology Program of State Grid Jiangsu Electric Power Co.Ltd.(granted no.5210EF18001D)granted contract-Key technology research of relay protection for the AC-DC hybrid grid with various distributed energy resources.
文摘In view of the operating characteristics for voltage sags of AC side of the power electronic transformer(PET),a low-voltage ride through(LVRT)strategy adapted to bidirectional power exchange of PET is proposed for the purposes of maintaining the system stability,assisting the system voltage recovery and protecting PET safety.During the asymmetric voltage sag,the negative sequence current of PET is eliminated to ensure the symmetry of the injected current.According to the degree of positive sequence voltage sag,the reactive current injection is provided to assist in voltage recovery.According to the PET active power condition before the voltage sag,the level and direction of which are maintained as far as possible without exceeding the limit,for which the disturbance to the AC and DC grids is reduced.Finally,the effectiveness of the proposed LVRT strategy is verified by simulation model.
基金supported by the National Natural Science Foundation of China(Grant No.52207190)Jiangsu Excellent Postdoctoral Program,China(Grant No.2022ZB80).
文摘Grid-forming converters(GFMs)are faced with the threat of transient inrush current and synchronization instability issues when subjected to grid faults.Instead of disconnecting from the grid unintentionally,GFMs are required to have fault ride through(FRT)capability to maintain safe and stable operation in grid-connected mode during grid fault periods.In recent studies,different FRT control strategies with distinguishing features and that are feasible for different operation conditions have been proposed for GFMs.To determine their application scope,an intuitive comparison of the transient performance of different FRT control strategies is presented in this paper.First,three typical FRT control strategies(virtual impedance,current limiters,and mode-switching control)are introduced and transient mathematical models are established.A detailed comparison analysis on transient inrush current and transient synchronization stability is then presented.The results will be useful for guiding the selection and design of FRT control strategies.Finally,simulation results based on PSCAD/EMTDC are considered to verify the correctness of the theoretical analysis.
文摘A new loop and fold wave-guide ion cyclotron resonance frequency （ICRF） antenna with a power output of 3 MW, which can operate at a frequency in the range of 30 MHz to 110 MHz, was designed. The design of key components of the new ICRF antenna and the charac- ters of the new,.]~rototype ICRF antenna are presented. The thermo-mechanical analysis of both the Faraday shield and the current straps was conducted, and the stresses due to heat loads are studied in detail with different cooling-water velocities considered. In addition, the movability of prototype ICRF antenna under vacuum condition by the driving system was tested. An engineer- ing commissioning was successfully performed on the prototype ICRF antenna using the original transmitter. The results are close to the expected.
