Phase unbalance is widespread in the distribution networks in the UK,continental Europe,US,China,and other countries and regions.This paper first reviews the mass scale of phase unbalance and its causes and consequenc...Phase unbalance is widespread in the distribution networks in the UK,continental Europe,US,China,and other countries and regions.This paper first reviews the mass scale of phase unbalance and its causes and consequences.Three challenges arise from phase rebalancing:the scalability,data scarcity,and adaptability(towards changing unbalance over time).Solutions to address the challenges are:1)using retrofit table,maintenance-free,automatic solutions to overcome the scalability challenge;2)using data analytics to overcome the data-scarcity challenge;and 3)using phase balancers or other online phase rebalancing solutions to overcome the adaptability challenge.This paper categorizes existing phase rebalancing solutions into three classes:1)load/lateral re-phasing;2)using phase balancers;3)controlling energy storage,electric vehicles,distributed generation,and micro-grids for phase rebalancing.Their advantages and limitations are analyzed and ways to overcome their limitations are recommended.Finally,this paper suggests future research topics:1)long-term forecast of phase unbalance;2)the whole-system analysis of the unbalance-induced costs;3)the phase unbalance diagnosis for data-scarce LV networks;4)techno-commercial solutions to exploit the flexibility from large three-phase customers for phase balancing;5)the optimal placement of phase balancers;6)the transition from single-phase customers to three-phase customers.展开更多
Direct quadrature modulation technology is suitable for wide-band radar signal generation. However, this method has rigorous requirements on amplitude and phase balance of the orthogonal input signals. If the requirem...Direct quadrature modulation technology is suitable for wide-band radar signal generation. However, this method has rigorous requirements on amplitude and phase balance of the orthogonal input signals. If the requirements are not satisfied, there would be modulation errors such as image frequency and oscillator leakage that cannot be filtered. The modulation errors will therefore raise the noise floor of the range profile and reduce the dynamic range of the Synthetic Aperture Radar (SAR) image as a whole. In this paper, the wide-band In-phase/Quadrature-phase (I/Q) modulation errors are modeling analyzed, and the influence of wide-band I/Q modulation errors on SAR imaging is discussed. Furthermore, a compensation method of modulation errors is proposed, and the circuit implementation of the radar signal generation and pre-distortion is presented. The experimental results illustrate that the curves of the I/Q amplitude and phase imbalance errors are successfully extracted and the rejection of image frequency improved significantly, thus meets the requirements of the SAR imaging.展开更多
文摘Phase unbalance is widespread in the distribution networks in the UK,continental Europe,US,China,and other countries and regions.This paper first reviews the mass scale of phase unbalance and its causes and consequences.Three challenges arise from phase rebalancing:the scalability,data scarcity,and adaptability(towards changing unbalance over time).Solutions to address the challenges are:1)using retrofit table,maintenance-free,automatic solutions to overcome the scalability challenge;2)using data analytics to overcome the data-scarcity challenge;and 3)using phase balancers or other online phase rebalancing solutions to overcome the adaptability challenge.This paper categorizes existing phase rebalancing solutions into three classes:1)load/lateral re-phasing;2)using phase balancers;3)controlling energy storage,electric vehicles,distributed generation,and micro-grids for phase rebalancing.Their advantages and limitations are analyzed and ways to overcome their limitations are recommended.Finally,this paper suggests future research topics:1)long-term forecast of phase unbalance;2)the whole-system analysis of the unbalance-induced costs;3)the phase unbalance diagnosis for data-scarce LV networks;4)techno-commercial solutions to exploit the flexibility from large three-phase customers for phase balancing;5)the optimal placement of phase balancers;6)the transition from single-phase customers to three-phase customers.
基金Supported by 863 Program (2009AA12Z103)973 Program (2009CB72400)
文摘Direct quadrature modulation technology is suitable for wide-band radar signal generation. However, this method has rigorous requirements on amplitude and phase balance of the orthogonal input signals. If the requirements are not satisfied, there would be modulation errors such as image frequency and oscillator leakage that cannot be filtered. The modulation errors will therefore raise the noise floor of the range profile and reduce the dynamic range of the Synthetic Aperture Radar (SAR) image as a whole. In this paper, the wide-band In-phase/Quadrature-phase (I/Q) modulation errors are modeling analyzed, and the influence of wide-band I/Q modulation errors on SAR imaging is discussed. Furthermore, a compensation method of modulation errors is proposed, and the circuit implementation of the radar signal generation and pre-distortion is presented. The experimental results illustrate that the curves of the I/Q amplitude and phase imbalance errors are successfully extracted and the rejection of image frequency improved significantly, thus meets the requirements of the SAR imaging.
