摘要
为寻找适应复杂信道环境的双向工频通信解调方法,结合系统电压相位分析了工频调制信号的时域特征,进而采用时频分析方法研究工频调制信号的幅度衰减和时延情况;通过仿真分析并结合电网现场测试发现,以本地电压过零为基准进行的传统解调方式存在缺陷,除了电网干扰外,信号收发端电压相位差会导致解调时域出现偏差从而降低通信性能,而电压相位差与线路阻抗、负载、变压器连接方式等多种因素有关,无法事先确定。基于此,提出了改进工频通信性能的解调新方法,发送端增加基于伪随机序列编码的同步信息,接收端根据同步信息中工频调制信号的能量分布情况确定调制信号的实际时域,这样工频通信的解调就能够自适应收发端电压相位差从而提高通信性能,新方法的有效性通过现场规模化试验得到了证明。
To find the demodulation method for bi-directional power frequency communication that is suitable to complex channel environment, combining with system voltage phase the time-domain feature of two-way power frequency automatic communication system （TWACS） signals are analyzed, and then the amplitude attenuation and time-delay of power frequency modulation signals are researched by time-frequency analysis. By means of simulation analysis and combining with field measurement in power network, it is found that there are defects in the traditional demodulation mode that takes the local power grid voltage zero-crossing as the benchmark, that is, except interfereces in power network, the voltages phase difference at the terminals of sender and receiver will lead to deviation in demodulation time domain, therefore the communication performance is degraded, however the voltage phase difference is related to multi factors such as impedance of transmission line, load, connection mode of power transformer and so on, and these factors are imposible to be predetermined. For this reason, a new modulation method to improve the performacne of power frequency communcation is proposed： the preamble information based on the pseudo-random sequence encoding is added into the sender＇s terminal, and at the receiver terminal the actual time-domain of modulation signals is determined according to the energy distribution of power frequency modulation signal in preamble information. This way, the demodulation of TWACS signals can be adaptive to voltage phase difference between the terminals of sender and receiver, and then the communication performance is improved. The effectiveness of the proposed method is proved by field scale tests.
出处
《电网技术》
EI
CSCD
北大核心
2011年第4期187-193,共7页
Power System Technology
关键词
双向工频通信系统
配电网
传输模型
时频分析
电压相位差
two way power frequency automaticcommunication system （TWACS）
distribution network
transmission model
time-frequency analysis
voltage phasedifference
