基于GPS的高精度时钟在线校频与授时研究

GPS-based Precision Clock Online Frequency Calibration and Time Service

为提高全球定位系统(global position system,GPS)广域授时的精度与稳定度,根据GPS时钟与晶振时钟的不同特性,建立互补时钟的广义回归模型,并利用广义最小二乘法对晶振频率进行估计,算法修正了已有回归模型中因量测值频率漂移而造成的误差,实现了在晶振频率漂移较大或量测值间隔较长时的精确估计,在此基础上生成可与国际协调时间(coordinated universal time,UTC)同步的授时秒脉冲,通过相位补偿算法,校正生成秒脉冲与UTC秒脉冲的相位差,实现精确授时。实验结果验证该算法在使用SBR-LS接收模块与普通有源晶振条件下,授时稳定度和精确度得到大幅提升,在长时间运行中授时误差不超过±25ns,可为广域测量、故障测距等应用提供精确时标,满足电网监控系统在线广域授时要求。

To improve the wide-area timing accuracy and stability of global position system （GPS） clock, the generalized regression model of complementary clock was established according to the different characteristics of GPS clock and crystal oscillator clock, and the crystal oscillator frequency was estimated in real time using generalized least squares method, which fixed the error of the regression model caused by frequency change of measured value, then accurate frequency estimation was achieved in the large crystal frequency drift and long time interval measurements. On this basis, timing pulse per second （PPS） synchronizing with coordinated universal time （UTC） was generated, which realized the precise online time service by using phase correction algorithm to eliminate the phase difference between timing PPS and UTC PPS. The experiment shows that the timing error of the algorithm is less than 4-25 ns during long time operation using the SBR-LS receiver module and ordinary active crystal, which validates that the timing stability and accuracy are greatly improved. Therefore, the proposed algorithm accomplishes the precise online time service for wide area measurement, locating faults and other applications, and meets the online wide-area timing requirements of power grid monitoring system.