As an effective approach to achieve the“dual-carbon”goal,the grid-connected capacity of renewable energy increases constantly.Photovoltaics are the most widely used renewable energy sources and have been applied on ...As an effective approach to achieve the“dual-carbon”goal,the grid-connected capacity of renewable energy increases constantly.Photovoltaics are the most widely used renewable energy sources and have been applied on various occasions.However,the inherent randomness,intermittency,and weak support of grid-connected equipment not only cause changes in the original flow characteristics of the grid but also result in complex fault characteristics.Traditional overcurrent and differential protection methods cannot respond accurately due to the effects of unknown renewable energy sources.Therefore,a longitudinal protection method based on virtual measurement of current restraint is proposed in this paper.The positive sequence current data and the network parameters are used to calculate the virtual measurement current which compensates for the output current of photovoltaic(PV).The waveform difference between the virtual measured current and the terminal current for internal and external faults is used to construct the protection method.An improved edit distance algorithm is proposed to measure the similarity between virtual measurement current and terminal measurement current.Finally,the feasibility of the protection method is verified through PSCAD simulation.展开更多
Miniaturized mobile electronic devices have aroused great attention due to their convenience to daily life. However, they still face a problem that power supply from the conventional cell needs to be regularly charged...Miniaturized mobile electronic devices have aroused great attention due to their convenience to daily life. However, they still face a problem that power supply from the conventional cell needs to be regularly charged or replaced. Portable electricity supply collecting energy from environment is highly desired. Herein, a highly flexible and stretchable Miura folding based triboelectric nanogenerator (MF-TENG) is prepared by using flexible polyethylene terephthalate (PET) as a folding substrate with a double working side design, specifically one side as the main TENG (M-TENG) and other side as the excitation TENG (E-TENG). The E-TENG supplements charge to M-TENG by a half-wave rectifier circuit. This design increases the TENG working area and reduces its volume. The output performance of the TENG based on Miura folding with charge excitation called MF-CE-TENG is greatly boosted. The optimal output charge and maximum peak power of MF-CE-TENG achieves 1.54 µC and 5.17 mW at 1 Hz, respectively, which is 4.61 and 10.55 times as much as that of MF-TENG without charge excitation. To demonstrate its applications, the MF-CE-TENG is used to light up 456 LEDs brightly and charge a 100 µF capacitor to 6.07 V in 5 min. A calculator and a temperature-humidity sensor work normally powered by MF-CE-TENG with an energy management module. This work provides a new strategy to enhance the output energy of Miura folding TENG by applying a charge excitation mode for the first time, which might be an effective approach to be used in other TENGs.展开更多
Triboelectric nanogenerator (TENG) is a promising strategy for harvesting low frequency mechanical energy. However, the bottlenecks of limited electric output by air/dielectric breakdown and poor durability by materia...Triboelectric nanogenerator (TENG) is a promising strategy for harvesting low frequency mechanical energy. However, the bottlenecks of limited electric output by air/dielectric breakdown and poor durability by material abrasion seriously restrict its further improvement. Herein, we propose a liquid lubrication promoted sliding mode TENG to address both issues. Liquid lubrication greatly reduces interface material abrasion, and its high breakdown strength and charge transmission effect further enhance device charge density. Besides, the potential decentralization design by the voltage balance bar effectively suppresses the dielectric breakdown. In this way, the average power density up to 87.26 W·m^(-2)·Hz^(-1), energy conversion efficiency of 48%, and retention output of 90% after 500,000 operation cycles are achieved, which is the highest average power density and durability currently. Finally, a cell phone is charged to turn on by a palm-sized TENG device at 2 Hz within 25 s. This work has a significance for the commercialization of TENG-based self-powered systems.展开更多
基金funded by State Grid Anhui Electric Power Co.,Ltd.Science and Technology Project(52120021N00L)the National Key Research and Development Program of China(2022YFB2400015).
文摘As an effective approach to achieve the“dual-carbon”goal,the grid-connected capacity of renewable energy increases constantly.Photovoltaics are the most widely used renewable energy sources and have been applied on various occasions.However,the inherent randomness,intermittency,and weak support of grid-connected equipment not only cause changes in the original flow characteristics of the grid but also result in complex fault characteristics.Traditional overcurrent and differential protection methods cannot respond accurately due to the effects of unknown renewable energy sources.Therefore,a longitudinal protection method based on virtual measurement of current restraint is proposed in this paper.The positive sequence current data and the network parameters are used to calculate the virtual measurement current which compensates for the output current of photovoltaic(PV).The waveform difference between the virtual measured current and the terminal current for internal and external faults is used to construct the protection method.An improved edit distance algorithm is proposed to measure the similarity between virtual measurement current and terminal measurement current.Finally,the feasibility of the protection method is verified through PSCAD simulation.
基金This work was supported by the National Natural Science Foundation of China(No.52073037)the Fundamental Research Funds for the Central Universities(No.2019CDXZWL001)Chongqing graduate tutor team construction project(No.ydstd1832).
文摘Miniaturized mobile electronic devices have aroused great attention due to their convenience to daily life. However, they still face a problem that power supply from the conventional cell needs to be regularly charged or replaced. Portable electricity supply collecting energy from environment is highly desired. Herein, a highly flexible and stretchable Miura folding based triboelectric nanogenerator (MF-TENG) is prepared by using flexible polyethylene terephthalate (PET) as a folding substrate with a double working side design, specifically one side as the main TENG (M-TENG) and other side as the excitation TENG (E-TENG). The E-TENG supplements charge to M-TENG by a half-wave rectifier circuit. This design increases the TENG working area and reduces its volume. The output performance of the TENG based on Miura folding with charge excitation called MF-CE-TENG is greatly boosted. The optimal output charge and maximum peak power of MF-CE-TENG achieves 1.54 µC and 5.17 mW at 1 Hz, respectively, which is 4.61 and 10.55 times as much as that of MF-TENG without charge excitation. To demonstrate its applications, the MF-CE-TENG is used to light up 456 LEDs brightly and charge a 100 µF capacitor to 6.07 V in 5 min. A calculator and a temperature-humidity sensor work normally powered by MF-CE-TENG with an energy management module. This work provides a new strategy to enhance the output energy of Miura folding TENG by applying a charge excitation mode for the first time, which might be an effective approach to be used in other TENGs.
基金This work is financially supported by the National Key Research and Development Program of China(2021YFA1201602)the National Natural Science Foundation of China(U21A20147,62071074,and 52073037)the Fundamental Research Funds for the Central Universities(2021CDJQY-019).
文摘Triboelectric nanogenerator (TENG) is a promising strategy for harvesting low frequency mechanical energy. However, the bottlenecks of limited electric output by air/dielectric breakdown and poor durability by material abrasion seriously restrict its further improvement. Herein, we propose a liquid lubrication promoted sliding mode TENG to address both issues. Liquid lubrication greatly reduces interface material abrasion, and its high breakdown strength and charge transmission effect further enhance device charge density. Besides, the potential decentralization design by the voltage balance bar effectively suppresses the dielectric breakdown. In this way, the average power density up to 87.26 W·m^(-2)·Hz^(-1), energy conversion efficiency of 48%, and retention output of 90% after 500,000 operation cycles are achieved, which is the highest average power density and durability currently. Finally, a cell phone is charged to turn on by a palm-sized TENG device at 2 Hz within 25 s. This work has a significance for the commercialization of TENG-based self-powered systems.
