AMI终端校时策略的优化与仿真

Optimization and simulation of time synchronization strategy for AMI terminal

为了在集中器、专变终端等嵌入式系统中更高效地完成校时任务,文章基于网络时间协议(Network Time Protocol,NTP)的基本工作原理,结合智能用电信息采集系统(Advanced Metering Infrastructure,AMI)的网络延时特点,给出了AMI的终端NTP基本校时算法。针对NTP时间同步算法在处理网络延时中的不足,提出了几种改进的校时策略,不仅提高了校时的准确性和稳定性,而且大幅度降低了工程计算量,从而可以更好的应用于嵌入式系统。首先使用最大似然估计法得出了多次NTP校时的时间偏差最优估计,然后分别介绍了去边缘值、均值滚动筛选和样本滤波方法来进一步改进校时策略。经实验验证,使用所提出的校时策略进行校时,校时误差最大仅为525ms,完全能把校时精度控制在1s以内,并有较好的校时准确性和稳定性,能充分适配嵌入式系统并满足了AMI终端的校时要求。

In order to better complete the clock synchronization in embedded system （ such as concentrator and specif-ic terminal ） , based on the principle of the Network Time Protocol （ NTP） and the network delay characteristics of Ad-vanced Metering Infrastructure （ AMI） , a basic NTP time synchronization strategy for AMI is proposed .By analyzing the shortcomings of the network delay treatment of NTP strategy , improved time synchronization strategies are derived . The new strategies in this paper not only improve the accuracy and stability in time synchronization , but also reduce the computational complexity , thus they can be more efficiently applied to embedded system .First, maximum likeli-hood estimation method is used to get an optimal estimation for time error from several NTP procedures .Moreover , a large-deviation points cutting method , mean value filtering method and a sample filtering method to optimize clock syn-chronization is introduced .Finally, the paper verifies the synchronization strategy through experiments and proves that the maximum synchronization error is 525 milliseconds , which is less than 1 second .The strategies have a better accu-racy and stability , which are more suitable for embedded system and fully meet time synchronization requirements of AMI.