The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according...The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according to certain rules along the time axis. The synthesized command can suppress the arbitrary unwanted vibration harmonic while achieving the desired rigid body motion. The number of the components increases rapidly when the number of harmonic vibration is growing. In this article, the CSVS based on zero-placement technique is used to construct the synthesized command to suppress the multi-harmonics simultaneously in the discrete domain. The nature of zero-placement method is to put enough zeros to cancel system poles at necessary points. The designed synthesized command has equal time intervals between each component and which is much easier to be implemented. Using this method, the number of components increases linearly with the increasing of the number of being suppressed harmonics. For the spacecraft with flexible appendages, CSVS based on zero-placement is used to design the time optimal large angle maneuver control strategy. Simulations have verified the validity and superiority of the proposed approach.展开更多
When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is...When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is much slower. This paper analyses the DC component of fault branch, and has found it is much bigger than that of the normal branches in transient state. All the simulation results obtained from three compensation types, different fault time and different wave cycles show that the DC component of fault branch is much higher than that of those normal branches. These results verify the effectiveness of taking the DC component as the method of fault line selection in the arc suppression coil grounding system.展开更多
Considering the characteristics of two component forces on component synthesis vibration suppression （CSVS） method, two theorems on two component forces suppressing fractional multiple design frequency are given res...Considering the characteristics of two component forces on component synthesis vibration suppression （CSVS） method, two theorems on two component forces suppressing fractional multiple design frequency are given respectively. Meanwhile, the control force, which is composed by two arbitrary component forces with different initial time, can suppress certain frequencies for second-order undamped vibration system. Using the above theorems, control moment of jet attitude maneuver on flexible spacecraft is designed on the basis principle of CSVS method. The simulations validate the correctness and effectiveness of the orooosed method.展开更多
New electric power systems characterized by a high proportion of renewable energy and power electronics equipment face significant challenges due to high-frequency(HF)electromagnetic interference from the high-speed s...New electric power systems characterized by a high proportion of renewable energy and power electronics equipment face significant challenges due to high-frequency(HF)electromagnetic interference from the high-speed switching of power converters.To address this situation,this paper offers an in-depth review of HF interference problems and challenges originating from power electronic devices.First,the root cause of HF electromagnetic interference,i.e.,the resonant response of the parasitic parameters of the system to high-speed switching transients,is analyzed,and various scenarios of HF interference in power systems are highlighted.Next,the types of HF interference are summarized,with a focus on common-mode interference in grounding systems.This paper thoroughly reviews and compares various suppression methods for conducted HF interference.Finally,the challenges involved and suggestions for addressing emerging HF interference problems from the perspective of both power electronics equipment and power systems are discussed.This review aims to offer a structured understanding of HF interference problems and their suppression techniques for researchers and practitioners.展开更多
Ground roll is an interference wave that severely degrades the signal-to-noise ratio of seismic data and affects its subsequent processing and interpretation.In this study,according to differences in morphological cha...Ground roll is an interference wave that severely degrades the signal-to-noise ratio of seismic data and affects its subsequent processing and interpretation.In this study,according to differences in morphological characteristics between ground roll and reflected waves,we use morphological component analysis based on two-dimensional dictionaries to separate ground roll and reflected waves.Because ground roll is characterized by lowfrequency,low-velocity,and dispersion,we select two-dimensional undecimated discrete wavelet transform as a sparse representation dictionary of ground roll.Because of a strong local correlation of the reflected wave,we select two-dimensional local discrete cosine transform as the sparse representation dictionary of reflected waves.A sparse representation model of seismic data is constructed based on a two-dimensional joint dictionary then a block coordinate relaxation algorithm is used to solve the model and decompose seismic record into reflected wave part and ground roll part.The good effects for the synthetic seismic data and application of real seismic data indicate that when using the model,strong-energy ground roll is considerably suppressed and the waveform of the reflected wave is effectively protected.展开更多
To overcome the inter-carrier interference （ICI） of orthogonal frequency division multiplexing （OFDM） systems subject to unknown carrier frequency offset （CFO） and multipath, this paper develops a blind adaptive...To overcome the inter-carrier interference （ICI） of orthogonal frequency division multiplexing （OFDM） systems subject to unknown carrier frequency offset （CFO） and multipath, this paper develops a blind adaptive interference suppression scheme based on independent component analysis （ICA）. Taking into account statistical independence of subcarriers＇ signals of OFDM, the signal recovery mechanism is investigated to achieve the goal of blind equalization. The received OFDM signals can be considered as the mixed observation signals. The effect of CFO and multipath corresponds to the mixing matrix in the problem of blind source separation （BSS） framework. In this paper, the ICA- based OFDM system model is built, and the proposed ICA-based detector is exploited to extract source signals from the observation of a received mixture based on the assumption of statistical independence between the sources. The blind separation technique can increase spectral efficiency and provide robustness performance against erroneous parameter estimation problem. Theoretical analysis and simulation results show that compared with the conventional pilot-based scheme, the improved performance of OFDM systems is obtained by the proposed ICA-based detection technique.展开更多
Mid-and high-frequency resonance(MHFR)is highly likely to occur at the sending end of voltage source con-verter-based ultra-high voltage direct current(VSC-UHVDC)for large-scale renewable energy transmission.It is of ...Mid-and high-frequency resonance(MHFR)is highly likely to occur at the sending end of voltage source con-verter-based ultra-high voltage direct current(VSC-UHVDC)for large-scale renewable energy transmission.It is of great im-portance to investigate the resonance characteristics and the corresponding suppression strategies.Firstly,this paper intro-duces the overall'control scheme of VSC-UHVDC for large-scale renewable energy transmission.Then,the impedance mod-els of VSC under grid-forming control with AC voltage coordi-nated control are established.The mid-and high-frequency im-pedance characteristics of VSC-UHVDC are analyzed.The key factors affecting the impedance characteristics have been re-vealed,including the AC voltage control,the voltage feedfor-ward,the inner current loop,the positive-sequence and nega-tive-sequence independent control(PSNSIC),and the control de-lay.The MHFR characteristics at the sending-end system are analyzed in the whole operation process,including the black start and the normal power transmission operation.An integrat-ed control scheme is proposed to address the MHFR problems.Finally,extensive case studies are conducted on a planned VSC-UHVDC project to verify the theoretical analysis.展开更多
文摘The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according to certain rules along the time axis. The synthesized command can suppress the arbitrary unwanted vibration harmonic while achieving the desired rigid body motion. The number of the components increases rapidly when the number of harmonic vibration is growing. In this article, the CSVS based on zero-placement technique is used to construct the synthesized command to suppress the multi-harmonics simultaneously in the discrete domain. The nature of zero-placement method is to put enough zeros to cancel system poles at necessary points. The designed synthesized command has equal time intervals between each component and which is much easier to be implemented. Using this method, the number of components increases linearly with the increasing of the number of being suppressed harmonics. For the spacecraft with flexible appendages, CSVS based on zero-placement is used to design the time optimal large angle maneuver control strategy. Simulations have verified the validity and superiority of the proposed approach.
文摘When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is much slower. This paper analyses the DC component of fault branch, and has found it is much bigger than that of the normal branches in transient state. All the simulation results obtained from three compensation types, different fault time and different wave cycles show that the DC component of fault branch is much higher than that of those normal branches. These results verify the effectiveness of taking the DC component as the method of fault line selection in the arc suppression coil grounding system.
基金Sponsored by the National Natural Science Foundation of China (Grant No. 61171189)the Aerospace Science and Technology Innovation Foundation of China (Grant No. CASC200902-81)
文摘Considering the characteristics of two component forces on component synthesis vibration suppression （CSVS） method, two theorems on two component forces suppressing fractional multiple design frequency are given respectively. Meanwhile, the control force, which is composed by two arbitrary component forces with different initial time, can suppress certain frequencies for second-order undamped vibration system. Using the above theorems, control moment of jet attitude maneuver on flexible spacecraft is designed on the basis principle of CSVS method. The simulations validate the correctness and effectiveness of the orooosed method.
基金supported by the science and technology project of State Grid Shanghai Municipal Electric Power Company(No.52094023003L).
文摘New electric power systems characterized by a high proportion of renewable energy and power electronics equipment face significant challenges due to high-frequency(HF)electromagnetic interference from the high-speed switching of power converters.To address this situation,this paper offers an in-depth review of HF interference problems and challenges originating from power electronic devices.First,the root cause of HF electromagnetic interference,i.e.,the resonant response of the parasitic parameters of the system to high-speed switching transients,is analyzed,and various scenarios of HF interference in power systems are highlighted.Next,the types of HF interference are summarized,with a focus on common-mode interference in grounding systems.This paper thoroughly reviews and compares various suppression methods for conducted HF interference.Finally,the challenges involved and suggestions for addressing emerging HF interference problems from the perspective of both power electronics equipment and power systems are discussed.This review aims to offer a structured understanding of HF interference problems and their suppression techniques for researchers and practitioners.
基金supported by the National Scientific Equipment Development Project,"Deep Resource Exploration Core Equipment Research and Development"(Grant No.ZDYZ2012-1)06 Subproject,"Metal Mine Earthquake Detection System"and 05 Subject,"System Integration Field Test and Processing Software Development"
文摘Ground roll is an interference wave that severely degrades the signal-to-noise ratio of seismic data and affects its subsequent processing and interpretation.In this study,according to differences in morphological characteristics between ground roll and reflected waves,we use morphological component analysis based on two-dimensional dictionaries to separate ground roll and reflected waves.Because ground roll is characterized by lowfrequency,low-velocity,and dispersion,we select two-dimensional undecimated discrete wavelet transform as a sparse representation dictionary of ground roll.Because of a strong local correlation of the reflected wave,we select two-dimensional local discrete cosine transform as the sparse representation dictionary of reflected waves.A sparse representation model of seismic data is constructed based on a two-dimensional joint dictionary then a block coordinate relaxation algorithm is used to solve the model and decompose seismic record into reflected wave part and ground roll part.The good effects for the synthetic seismic data and application of real seismic data indicate that when using the model,strong-energy ground roll is considerably suppressed and the waveform of the reflected wave is effectively protected.
基金supported by a grant from the national High Technology Research and development Program of China(863 Program)(No.2012AA01A502)National Natural Science Foundation of China(No.61179006)Science and Technology Support Program of Sichuan Province(No.2014GZX0004)
文摘To overcome the inter-carrier interference （ICI） of orthogonal frequency division multiplexing （OFDM） systems subject to unknown carrier frequency offset （CFO） and multipath, this paper develops a blind adaptive interference suppression scheme based on independent component analysis （ICA）. Taking into account statistical independence of subcarriers＇ signals of OFDM, the signal recovery mechanism is investigated to achieve the goal of blind equalization. The received OFDM signals can be considered as the mixed observation signals. The effect of CFO and multipath corresponds to the mixing matrix in the problem of blind source separation （BSS） framework. In this paper, the ICA- based OFDM system model is built, and the proposed ICA-based detector is exploited to extract source signals from the observation of a received mixture based on the assumption of statistical independence between the sources. The blind separation technique can increase spectral efficiency and provide robustness performance against erroneous parameter estimation problem. Theoretical analysis and simulation results show that compared with the conventional pilot-based scheme, the improved performance of OFDM systems is obtained by the proposed ICA-based detection technique.
基金This work was supported by National Key Research and Development Program of China(No.2023YFB2405900)the Technology Project of China Southern PowerGrid(No.ZBKJXM20232198).
文摘Mid-and high-frequency resonance(MHFR)is highly likely to occur at the sending end of voltage source con-verter-based ultra-high voltage direct current(VSC-UHVDC)for large-scale renewable energy transmission.It is of great im-portance to investigate the resonance characteristics and the corresponding suppression strategies.Firstly,this paper intro-duces the overall'control scheme of VSC-UHVDC for large-scale renewable energy transmission.Then,the impedance mod-els of VSC under grid-forming control with AC voltage coordi-nated control are established.The mid-and high-frequency im-pedance characteristics of VSC-UHVDC are analyzed.The key factors affecting the impedance characteristics have been re-vealed,including the AC voltage control,the voltage feedfor-ward,the inner current loop,the positive-sequence and nega-tive-sequence independent control(PSNSIC),and the control de-lay.The MHFR characteristics at the sending-end system are analyzed in the whole operation process,including the black start and the normal power transmission operation.An integrat-ed control scheme is proposed to address the MHFR problems.Finally,extensive case studies are conducted on a planned VSC-UHVDC project to verify the theoretical analysis.
