Noise Reduction Method For Power Line Carrier Communication In Power Grid Cyber Physical System

With the application of big data,artificial intelligence and cloud platform technology to the construction of smart grid,the construction of Cyber-Physical Systems(CPS)in smart grids is accelerating.As a basis for constructing the CPS in smart grid,the electricity information collection system can directly contact the user side,which is the basis of realizing digital and intelligent grid.However,due to the complexity of the physical topology of low-voltage distribution network and the randomness of load access,compared with the dedicated communication channel,the communication conditions of the low-voltage distribution network are more complicated,and the communication process is often affected by various interference noises,which will seriously attenuate the reliability of data transmission during low-voltage power line carrier communication.This paper analyzes the various characteristics of the low-voltage power line carrier communication channel of the electricity information collection system in the CPS of smart grid,and studies the types and characteristics of various noise in the communication channel.A noise model is built and noises are divided into two categories according to their spectral and amplitude characteristics: background noise and impulse noise,whose effects on carrier modulated signals are analyzed in subsequent experiments.In order to improve the anti-interference ability of low-voltage power line carrier communication system,based on the frequency domain and time domain characteristics of the carrier signal mixed with noise,a time-frequency hybrid noise reduction algorithm is proposed.Firstly,use Fourier transform to process the signal mixed with noises,obtain the center frequency point of the carrier modulated signal and reserve the mixed signal in the corresponding bandwidth while the mixed signal under other frequency components is removed,realizing the first noise reduction in the frequency domain.Secondly,as the signal in the center frequency point and corresponding bandwidth still contains noises after processing in the frequency domain,the level amplitude threshold value is judged according to the signal's time domain characteristic,and background noise with low level amplitude is eliminated to realize the second noise reduction in the time domain.Finally,considering that the signal after frequency domain and time domain noise reduction still contains a small amount of impulse noise and the amplitude of the signal level is different,the symbol position check and amplitude compensation operation are introduced to check and compensate processed signal and improve the noise reduction effect.The effectiveness and applicability of the proposed algorithm are verified by experimental simulation.Using the signal-to-noise ratio(SNR)as the evaluation criterion in different scenarios and different modulation modes,the experimental results show that the algorithm has better noise reduction effect compared with the wavelet denoising algorithm.