A DC DC buck converter c on trolled by naturally sampled, constant frequency PWM is considered. The existe nce of chaotic solutions and the output performance of the system under differen t circuit parameters are s...A DC DC buck converter c on trolled by naturally sampled, constant frequency PWM is considered. The existe nce of chaotic solutions and the output performance of the system under differen t circuit parameters are studied. The transforming pattern of system behavior fr om steady state to chaotic is discovered by the cascades of period doubling bi furcation and the cascades of periodic orbit in V I phase space. Accordingl y, it is validated that change of values of the circuit parameters may lead DC DC converter to chaotic motion. Performances of the output ripples fro m steady state to chaotic are analyzed in time and frequency domains respective ly. Some important conclusions are helpful for opt imization design of DC DC converter.展开更多
A 16 × 16 micro-strip antenna array with high gain characteristic was proposed for the 5.5 GHz W/MAX application. The T-junctions with a power ratio of 2 ： 1 were used to design the feed network. To correct the ...A 16 × 16 micro-strip antenna array with high gain characteristic was proposed for the 5.5 GHz W/MAX application. The T-junctions with a power ratio of 2 ： 1 were used to design the feed network. To correct the stepped discontinuity of impedance change in common multi-section impedance transformer, exponential line matching trans- formers were adopted in the WiMAX frequency band. The reflection coefficient was lower than - 15 dB from 5.08 GHz to 5.87 GHz. The measured gain of the antenna array achieved 29.8 dBi on E-plane at 5.8 GHz.展开更多
To understand the operation principle of the modular multilevel converter(MMC)deeply,it is necessary to study the harmonic characteristics of the MMC theoretically.Besides,the analytical harmonic formulas of the MMC a...To understand the operation principle of the modular multilevel converter(MMC)deeply,it is necessary to study the harmonic characteristics of the MMC theoretically.Besides,the analytical harmonic formulas of the MMC are useful in designing the main circuit,reducing the losses and improving the waveform quality.Based on the average switching function and the Fourier series harmonic analysis,this paper deduces the analytical expressions for such electrical quantities as the arm voltage,the arm current,the capacitor voltage,the capacitor current and the circulating current of the MMC.Finally,a digital model of a 21-level MMC-HVDC system is realized in PSCAD/EMTDC.The results of the analytical expressions coincide with the simulation results,which verify the effectiveness and feasibility of the proposed analytical expressions.展开更多
文摘A DC DC buck converter c on trolled by naturally sampled, constant frequency PWM is considered. The existe nce of chaotic solutions and the output performance of the system under differen t circuit parameters are studied. The transforming pattern of system behavior fr om steady state to chaotic is discovered by the cascades of period doubling bi furcation and the cascades of periodic orbit in V I phase space. Accordingl y, it is validated that change of values of the circuit parameters may lead DC DC converter to chaotic motion. Performances of the output ripples fro m steady state to chaotic are analyzed in time and frequency domains respective ly. Some important conclusions are helpful for opt imization design of DC DC converter.
基金Supported by the National Natural Science Foundation of China(No.60777014)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20090032110027)
文摘A 16 × 16 micro-strip antenna array with high gain characteristic was proposed for the 5.5 GHz W/MAX application. The T-junctions with a power ratio of 2 ： 1 were used to design the feed network. To correct the stepped discontinuity of impedance change in common multi-section impedance transformer, exponential line matching trans- formers were adopted in the WiMAX frequency band. The reflection coefficient was lower than - 15 dB from 5.08 GHz to 5.87 GHz. The measured gain of the antenna array achieved 29.8 dBi on E-plane at 5.8 GHz.
基金supported by the National High Technology Research and Development Program of China("863" Project)(Grant No.2012AA050205)
文摘To understand the operation principle of the modular multilevel converter(MMC)deeply,it is necessary to study the harmonic characteristics of the MMC theoretically.Besides,the analytical harmonic formulas of the MMC are useful in designing the main circuit,reducing the losses and improving the waveform quality.Based on the average switching function and the Fourier series harmonic analysis,this paper deduces the analytical expressions for such electrical quantities as the arm voltage,the arm current,the capacitor voltage,the capacitor current and the circulating current of the MMC.Finally,a digital model of a 21-level MMC-HVDC system is realized in PSCAD/EMTDC.The results of the analytical expressions coincide with the simulation results,which verify the effectiveness and feasibility of the proposed analytical expressions.
