Method for Correcting Errors of the GPS-clock Based on the High Precision Crystal Oscillator
LI Zewen, ZENG Xiangjun, HUANG Zhiwei, LEI Li, MA HongJiang Changsha University of Science and Technology, Changsha 410076, China Hunan Hydro and Power Design Institute, Changsha 410007, China
Numerous measuring and controlling techniques based on the high precision GPS-clock available in power systems nowadays have a common problem, viz. the stability of the clock signal is very poor, thus these techniques can hardly meet the requirements of power systems, e.g. synchronous control with high reliability, phase difference measurement, and so on. By analyzing the GPS-clock error and combining the characteristics of the GPS-clock with the high precision oscillator, methods for correcting the GPS-clock on-line by comparing with the oscillator are proposed. As the GPS-clock is free from cumulative error and the high precision crystal oscillator is free from random error, the two clocks can be effectively combined. Through dynamically averaging the counting values between the second pulses and estimating the error of the second pulse, methods for correcting the GPS-clock on-line have been developed. The device for the high precision clock with high performance price ratio is designed, which has been successfully applied in traveling wave location.