An online TL （transmission line） impedance TPIS （transmission line parameter identification system） using PMU （phasor measurement unit） was recently developed and implemented at CSG （china southern power grid c...An online TL （transmission line） impedance TPIS （transmission line parameter identification system） using PMU （phasor measurement unit） was recently developed and implemented at CSG （china southern power grid company）, Traditional approaches for TL impedance calculation only approximate the effect of conductor sags and ignore the dependence of impedances on temperature variation. Utilizing PMU measurements may improve the accuracy of TL parameters calculation. The challenge is that the parameters identified are very sensitive to noise and errors in PMU measurements, which are difficult to quantify and can be uncertain under different system operating/loading condition, TPIS provides an innovative yet practical problem formulation for TL sequence parameter estimation based on least-squares with linear constraints. A bootstrapping-based resampling technique is developed and a new metric is proposed to determine the credibility of the estimated sequence impedances. This paper discusses the proposed methodologies, challenges, as well as implementation issues identified during the development of TPIS.展开更多
We investigate the phase coherent transport in a single channel system. The theory that the transmission zeros lead to abrupt phase change and in-phase resonances is confirmed numerically in two tight-binding models. ...We investigate the phase coherent transport in a single channel system. The theory that the transmission zeros lead to abrupt phase change and in-phase resonances is confirmed numerically in two tight-binding models. After calculating the eigenvalues and eigenvectors of the Hamiltonians we also confirmed that the same symmetry of the eigenvectors also leads to the abrupt phase change and in-phase resonances that equal the transmission zero.展开更多
In this paper we describe a full-integrated circuit containing all building blocks of a completed PLL-based synthesizer except for low pass filter（LPF）. The frequency synthesizer is designed for a frequency hopping ...In this paper we describe a full-integrated circuit containing all building blocks of a completed PLL-based synthesizer except for low pass filter（LPF）. The frequency synthesizer is designed for a frequency hopping （FH） transceiver operating up to 1.5 GHz as a local oscillator. The architecture of Voltage Controlled Oscillator （VCO） is optimized to get better performance, and a phase noise of -111.85-dBc/Hz @ 1 MHz and a tuning range of 250 MHz are gained at a centre frequency of 1.35 GHz. A novel Dual-Modulus Prescaler（DMP） is designed to achieve a very low jitter and a lower power. The settling time of PLL is 80 μs while the reference frequency is 400 KHz.This monolithic frequency synthesizer is to integrate all main building blocks of PLL except for the low pass filter, with a maximum VCO output frequency of 1.5 GHz, and is fabricated with a 0.18 μm mixed signal CMOS process. Low power dissipation, low phase noise, large tuning range and fast settling time are gained in this design.展开更多
There are three well known types of wire lines for transmitting electrical energy or information. The first type is ordinary two wires line （below A-Line）. The second type is so-called single-wire line, where ground...There are three well known types of wire lines for transmitting electrical energy or information. The first type is ordinary two wires line （below A-Line）. The second type is so-called single-wire line, where ground plays the role instead of second wire. Polyphase systems belong to the third type, three phase system is the most popular among them. The purpose of this article is another attempt to build a one-wired （without ground） system--the transmission of electrical energy. In this paper an original idea of building such a system is justified, the results of simulations and laboratory modeling are presented. It is shown that the proposed method can reduce the cost of electric transmission lines, the losses in them and significantly reduce interferences.展开更多
文摘An online TL （transmission line） impedance TPIS （transmission line parameter identification system） using PMU （phasor measurement unit） was recently developed and implemented at CSG （china southern power grid company）, Traditional approaches for TL impedance calculation only approximate the effect of conductor sags and ignore the dependence of impedances on temperature variation. Utilizing PMU measurements may improve the accuracy of TL parameters calculation. The challenge is that the parameters identified are very sensitive to noise and errors in PMU measurements, which are difficult to quantify and can be uncertain under different system operating/loading condition, TPIS provides an innovative yet practical problem formulation for TL sequence parameter estimation based on least-squares with linear constraints. A bootstrapping-based resampling technique is developed and a new metric is proposed to determine the credibility of the estimated sequence impedances. This paper discusses the proposed methodologies, challenges, as well as implementation issues identified during the development of TPIS.
文摘We investigate the phase coherent transport in a single channel system. The theory that the transmission zeros lead to abrupt phase change and in-phase resonances is confirmed numerically in two tight-binding models. After calculating the eigenvalues and eigenvectors of the Hamiltonians we also confirmed that the same symmetry of the eigenvectors also leads to the abrupt phase change and in-phase resonances that equal the transmission zero.
文摘In this paper we describe a full-integrated circuit containing all building blocks of a completed PLL-based synthesizer except for low pass filter（LPF）. The frequency synthesizer is designed for a frequency hopping （FH） transceiver operating up to 1.5 GHz as a local oscillator. The architecture of Voltage Controlled Oscillator （VCO） is optimized to get better performance, and a phase noise of -111.85-dBc/Hz @ 1 MHz and a tuning range of 250 MHz are gained at a centre frequency of 1.35 GHz. A novel Dual-Modulus Prescaler（DMP） is designed to achieve a very low jitter and a lower power. The settling time of PLL is 80 μs while the reference frequency is 400 KHz.This monolithic frequency synthesizer is to integrate all main building blocks of PLL except for the low pass filter, with a maximum VCO output frequency of 1.5 GHz, and is fabricated with a 0.18 μm mixed signal CMOS process. Low power dissipation, low phase noise, large tuning range and fast settling time are gained in this design.
文摘There are three well known types of wire lines for transmitting electrical energy or information. The first type is ordinary two wires line （below A-Line）. The second type is so-called single-wire line, where ground plays the role instead of second wire. Polyphase systems belong to the third type, three phase system is the most popular among them. The purpose of this article is another attempt to build a one-wired （without ground） system--the transmission of electrical energy. In this paper an original idea of building such a system is justified, the results of simulations and laboratory modeling are presented. It is shown that the proposed method can reduce the cost of electric transmission lines, the losses in them and significantly reduce interferences.
