In comparison with several zero-voltage transition (ZVT) inverter topologies, a double-PWM converter is presented using a simple ZVT topology. The rectifier and inverter of this double-PWM share a set of commutation...In comparison with several zero-voltage transition (ZVT) inverter topologies, a double-PWM converter is presented using a simple ZVT topology. The rectifier and inverter of this double-PWM share a set of commutation circuit which can provide soft-switching for the power devices and the diodes. The commutation circuit consists of 1 auxiliary device, 6 resonant inductors, and 12 diodes. Its topology is simpler than the conventional auxiliary resonant converter, leading to low loss and easy control. The control strategy and resonant working modes are analyzed. Experimental results show good performance of the system.展开更多
The zero-voltage quasi-resonant boost switching DC-DC converter has been inves-tigated by using the time averaging equivalent circuit approach of periodically switching linearnetworks.The DC steady state and AC small ...The zero-voltage quasi-resonant boost switching DC-DC converter has been inves-tigated by using the time averaging equivalent circuit approach of periodically switching linearnetworks.The DC steady state and AC small signal characteristics of the converter are also given.展开更多
Traveling Wave Tubes(TWTs) are widely used in the radar and communications system as RF power amplifiers. A highly sophisticated power supply is required by TWT. In order to meet the severe requirements of Traveling W...Traveling Wave Tubes(TWTs) are widely used in the radar and communications system as RF power amplifiers. A highly sophisticated power supply is required by TWT. In order to meet the severe requirements of Traveling Wave Tube Amplifier(TWTA), a novel two-stage topology high voltage converter for TWTA is proposed.The converter is based on Zero-Voltage Switching and Zero-Current Switching(ZVS/ZCS) resonant techniques. The high voltage converter operation principles are investigated and major features of the converter are discussed. The power switching mode of ZVS/ZCS is obtained. The experimental results show that the converter has good soft switching characteristics. Compared to the conventional hard switched Pulse Width Modulation(PWM) techniques, the high efficiency and low ripple of the converter for TWTA are realized. The efficiency of High Voltage Electronic Power Conditioners(HV-EPC) over 93.5% under the condition of 38~46 V input voltage and 260~300 W input power. The switching frequency of first-stage(preregulator) of HV-EPC is 89 k Hz and the switching frequency of second-stage(postregulator) is 44.5 k Hz. The highest output voltage of the HV-EPC is helix voltage which is about –6.8 kV. It is especially suitable for TWTA utilized in space satellite applications due to its high switching frequency and high power density.展开更多
Owing to the advantages of high efficiency,high energy density,electrical isolation,low electromagnetic interference(EMI)and harmonic pollution,magnetic integration,wide output ranges,low voltage stress,and high opera...Owing to the advantages of high efficiency,high energy density,electrical isolation,low electromagnetic interference(EMI)and harmonic pollution,magnetic integration,wide output ranges,low voltage stress,and high operation frequency,the LLC resonant converters are widely used in various sectors of the electronics-based industries.The history and development of the LLC resonant converters are presented,their advantages are analyzed,three of the most popular LLC resonant converter topologies with detailed assessments of their strengths and drawbacks are elaborated.Furthermore,an important piece of research on the industrial applications of the LLC resonant converters is conducted,mainly including electric vehicle(EV)charging,photovoltaic systems,and light emitting diode(LED)lighting drivers and liquid crystal display(LCD)TV power supplies.Finally,the future evolution of the LLC resonant converter technology is discussed.展开更多
Whitney's 2-switching theorem states that any two embeddings of a 2-connected planar graph in S2 can be connected via a sequence of simple operations, named 2-switching. In this paper, we obtain two operations on pla...Whitney's 2-switching theorem states that any two embeddings of a 2-connected planar graph in S2 can be connected via a sequence of simple operations, named 2-switching. In this paper, we obtain two operations on planar graphs from the view point of knot theory, which we will term "twisting" and "2-switching" respectively. With the twisting operation, we give a pure geometrical proof of Whitney's 2-switching theorem. As an application, we obtain some relationships between two knots which correspond to the same signed planar graph. Besides, we also give a necessary and sufficient condition to test whether a pair of reduced alternating diagrams are mutants of each other by their signed planar graphs.展开更多
The fast switching behaviors of wide bandgap devices bring some challenges such as high du/dt and limited short-circuit current withstand capability to the reliable operation of the motor drives.The current-source-inv...The fast switching behaviors of wide bandgap devices bring some challenges such as high du/dt and limited short-circuit current withstand capability to the reliable operation of the motor drives.The current-source-inverter(CSI)provides a promising solution in mitigating those challenges by owning the DC-link choke,the reverse-voltage blocking switches and AC commutation capacitors.To further reduce du/dt on switches of CSI fed motor drives,the technique of partial charging of capacitors have been investigated in this paper.By designing the series-connected and the parallel-connected partial-charging circuit for capacitors in DC-link,the voltage profile of CSI could be improved.Specifically,the zero-voltage-switching(ZVS)is achieved for main power switches,the du/dt is reduced and the overvoltage protection is presented.The working mechanism of the technique of partial charging of capacitor is described and one example is discussed on the dual three-phase motor drive.The experimental verification is presented to show the performance of partial charging technique for improving voltage profile of CSI fed motor drives.展开更多
基金Project supported by the Shanghai Post Doctoral Scientific Research Project (Grant No.05R214122)the Shanghai Leading Academic Discipline Project (Grant No.T0103)
文摘In comparison with several zero-voltage transition (ZVT) inverter topologies, a double-PWM converter is presented using a simple ZVT topology. The rectifier and inverter of this double-PWM share a set of commutation circuit which can provide soft-switching for the power devices and the diodes. The commutation circuit consists of 1 auxiliary device, 6 resonant inductors, and 12 diodes. Its topology is simpler than the conventional auxiliary resonant converter, leading to low loss and easy control. The control strategy and resonant working modes are analyzed. Experimental results show good performance of the system.
文摘The zero-voltage quasi-resonant boost switching DC-DC converter has been inves-tigated by using the time averaging equivalent circuit approach of periodically switching linearnetworks.The DC steady state and AC small signal characteristics of the converter are also given.
文摘Traveling Wave Tubes(TWTs) are widely used in the radar and communications system as RF power amplifiers. A highly sophisticated power supply is required by TWT. In order to meet the severe requirements of Traveling Wave Tube Amplifier(TWTA), a novel two-stage topology high voltage converter for TWTA is proposed.The converter is based on Zero-Voltage Switching and Zero-Current Switching(ZVS/ZCS) resonant techniques. The high voltage converter operation principles are investigated and major features of the converter are discussed. The power switching mode of ZVS/ZCS is obtained. The experimental results show that the converter has good soft switching characteristics. Compared to the conventional hard switched Pulse Width Modulation(PWM) techniques, the high efficiency and low ripple of the converter for TWTA are realized. The efficiency of High Voltage Electronic Power Conditioners(HV-EPC) over 93.5% under the condition of 38~46 V input voltage and 260~300 W input power. The switching frequency of first-stage(preregulator) of HV-EPC is 89 k Hz and the switching frequency of second-stage(postregulator) is 44.5 k Hz. The highest output voltage of the HV-EPC is helix voltage which is about –6.8 kV. It is especially suitable for TWTA utilized in space satellite applications due to its high switching frequency and high power density.
基金Supported by the National Natural Science Foundation of China(51907032)the Natural Science Foundation of Guangdong Province(2018A030313365).
文摘Owing to the advantages of high efficiency,high energy density,electrical isolation,low electromagnetic interference(EMI)and harmonic pollution,magnetic integration,wide output ranges,low voltage stress,and high operation frequency,the LLC resonant converters are widely used in various sectors of the electronics-based industries.The history and development of the LLC resonant converters are presented,their advantages are analyzed,three of the most popular LLC resonant converter topologies with detailed assessments of their strengths and drawbacks are elaborated.Furthermore,an important piece of research on the industrial applications of the LLC resonant converters is conducted,mainly including electric vehicle(EV)charging,photovoltaic systems,and light emitting diode(LED)lighting drivers and liquid crystal display(LCD)TV power supplies.Finally,the future evolution of the LLC resonant converter technology is discussed.
基金Supported by National Natural Science Foundation of China(No.11171025)Science Foundation for the Youth Scholars of Beijing Normal University
文摘Whitney's 2-switching theorem states that any two embeddings of a 2-connected planar graph in S2 can be connected via a sequence of simple operations, named 2-switching. In this paper, we obtain two operations on planar graphs from the view point of knot theory, which we will term "twisting" and "2-switching" respectively. With the twisting operation, we give a pure geometrical proof of Whitney's 2-switching theorem. As an application, we obtain some relationships between two knots which correspond to the same signed planar graph. Besides, we also give a necessary and sufficient condition to test whether a pair of reduced alternating diagrams are mutants of each other by their signed planar graphs.
基金Supported by the Jiangsu Natural Science Foundation of China(BK20180013)in part by Shen Zhen Science and Technology Project(CYJ20180306174439784).
文摘The fast switching behaviors of wide bandgap devices bring some challenges such as high du/dt and limited short-circuit current withstand capability to the reliable operation of the motor drives.The current-source-inverter(CSI)provides a promising solution in mitigating those challenges by owning the DC-link choke,the reverse-voltage blocking switches and AC commutation capacitors.To further reduce du/dt on switches of CSI fed motor drives,the technique of partial charging of capacitors have been investigated in this paper.By designing the series-connected and the parallel-connected partial-charging circuit for capacitors in DC-link,the voltage profile of CSI could be improved.Specifically,the zero-voltage-switching(ZVS)is achieved for main power switches,the du/dt is reduced and the overvoltage protection is presented.The working mechanism of the technique of partial charging of capacitor is described and one example is discussed on the dual three-phase motor drive.The experimental verification is presented to show the performance of partial charging technique for improving voltage profile of CSI fed motor drives.