Based on the analysis of the principles of frequency-phase scanning 3-D （three-dimensional） radar and the scattering mechanism of 3-D radar, the target and clutter IF （intermediate frequency） signals model of freq...Based on the analysis of the principles of frequency-phase scanning 3-D （three-dimensional） radar and the scattering mechanism of 3-D radar, the target and clutter IF （intermediate frequency） signals model of frequencyphase scanning 3-D radar is presented. The IF signals model of different channels of 3-D radar is presented in one simple formula in which complex waveform effects are considered. The simulation results obtained during tests are also provided in the end.展开更多
Transient issues arising from voltage drops in distribution networks with high penetration of renewable energy,as well as post-fault reclosing challenges,are often addressed separately through low-voltage ride-through...Transient issues arising from voltage drops in distribution networks with high penetration of renewable energy,as well as post-fault reclosing challenges,are often addressed separately through low-voltage ride-through(LVRT)and quasi-simultaneous control,without a comprehensive stability analysis covering the entire fault stage.This paper reveals the temporal correlation between LVRT control and quasi-simultaneous control and proposes an integrated optimal control strategy.The strategy enhances the transient stability of droop-controlled inverters following voltage drops,ensures reliable load supply during off-grid operation,and achieves seamless grid reconnection without current surges during reclosing.During the LVRT phase,the inverter power reference is dynamically adjusted based on power angle characteristics and reactive power-current relationships to stabilize the power angle and limit output current.In the reclosing transition phase,a combined frequency and phase angle regulation mechanism is employed to minimize discrepancies in voltage frequency and phase angle,accounting for transient op-erating condition changes.The effectiveness and practi-cality of the proposed strategy are validated through simulations and experimental results.展开更多
Constellation mapping has provided a great convenience to measure the performance of digital signal modulation in Euclid space. However, traditional in-phase and quadrature(IQ) plane is difficult to express the freque...Constellation mapping has provided a great convenience to measure the performance of digital signal modulation in Euclid space. However, traditional in-phase and quadrature(IQ) plane is difficult to express the frequency modulation scheme such as minimum shift keying(MSK) and the time domain modulation such as cyclic code shift keying(CCSK). How to represent the digital signal modulation visually through constellation mapping is an attractive problem. To address this issue, in this paper, the combined frequency and phase modulation are utilized to define a new kind of constellation mapping, where the phase and frequency are quantized to the same elements. The uniform geometric construction for combined phase and frequency modulation is redefined in the 3D cylindrical coordinate system based on frequency(f), in-phase component(I) and quadrature component(Q). In the new coordinates, the quadrature frequency-phase shift keying(QFPSK) is produced by the QPSK with dimensional rotation matrix and denoted by the reduced dual quaternion. Furthermore, the spatial extension from QFPSK to chirp cyclic shift keying(Chirp CSK) is analyzed with bandwidth efficiency and energy efficiency. At last, the QFPSK is combined with the 2D OFDM, yielding the image OFDM system.Experimental results verify the effectiveness of QFPSK in the proposed system with the time-varying wireless channel and frequency selective fading channel respectively.展开更多
文摘Based on the analysis of the principles of frequency-phase scanning 3-D （three-dimensional） radar and the scattering mechanism of 3-D radar, the target and clutter IF （intermediate frequency） signals model of frequencyphase scanning 3-D radar is presented. The IF signals model of different channels of 3-D radar is presented in one simple formula in which complex waveform effects are considered. The simulation results obtained during tests are also provided in the end.
基金supported by the Research and Application of Active Support and Operation Control Technology for High Penetration Distributed PV Grid Integration(No.5211DS230003).
文摘Transient issues arising from voltage drops in distribution networks with high penetration of renewable energy,as well as post-fault reclosing challenges,are often addressed separately through low-voltage ride-through(LVRT)and quasi-simultaneous control,without a comprehensive stability analysis covering the entire fault stage.This paper reveals the temporal correlation between LVRT control and quasi-simultaneous control and proposes an integrated optimal control strategy.The strategy enhances the transient stability of droop-controlled inverters following voltage drops,ensures reliable load supply during off-grid operation,and achieves seamless grid reconnection without current surges during reclosing.During the LVRT phase,the inverter power reference is dynamically adjusted based on power angle characteristics and reactive power-current relationships to stabilize the power angle and limit output current.In the reclosing transition phase,a combined frequency and phase angle regulation mechanism is employed to minimize discrepancies in voltage frequency and phase angle,accounting for transient op-erating condition changes.The effectiveness and practi-cality of the proposed strategy are validated through simulations and experimental results.
基金supported in part by National Natural Science Foundation of China(Grant Nos.61501051,61421001)Ph.D.Programs Foundation of Ministry of Education of China(Grant No.20121101130001)
文摘Constellation mapping has provided a great convenience to measure the performance of digital signal modulation in Euclid space. However, traditional in-phase and quadrature(IQ) plane is difficult to express the frequency modulation scheme such as minimum shift keying(MSK) and the time domain modulation such as cyclic code shift keying(CCSK). How to represent the digital signal modulation visually through constellation mapping is an attractive problem. To address this issue, in this paper, the combined frequency and phase modulation are utilized to define a new kind of constellation mapping, where the phase and frequency are quantized to the same elements. The uniform geometric construction for combined phase and frequency modulation is redefined in the 3D cylindrical coordinate system based on frequency(f), in-phase component(I) and quadrature component(Q). In the new coordinates, the quadrature frequency-phase shift keying(QFPSK) is produced by the QPSK with dimensional rotation matrix and denoted by the reduced dual quaternion. Furthermore, the spatial extension from QFPSK to chirp cyclic shift keying(Chirp CSK) is analyzed with bandwidth efficiency and energy efficiency. At last, the QFPSK is combined with the 2D OFDM, yielding the image OFDM system.Experimental results verify the effectiveness of QFPSK in the proposed system with the time-varying wireless channel and frequency selective fading channel respectively.
