Research On Power System Frequency Adaptive Estimation Algorithm

Frequency is one of the important indexes of power quality and the most important parameter reflecting the operating state of power system.In recent years,adaptive filtering theory has been greatly developed,and has been widely used in system identification,active noise control,echo cancellation,beamforming and power system harmonic parameter estimation.Many scholars have tried to apply the classical adaptive filtering theory to frequency estimation,and achieved good results.Based on the augmented complex least mean square(ACLMS)algorithm,this paper proposes several augmented complex adaptive filtering algorithms for different environments in frequency estimation,which expands the application of adaptive filtering theory in frequency estimation.Firstly,this paper improves the ACLMS algorithm,reduces the steady-state error of the algorithm on the premise of computational complexity and convergence speed,and proposes the augmented complex least mean square/fourth(ACLMS/F)algorithm.The cost function of this algorithm combines the advantages of least mean fourth(LMF)cost function and least mean square(LMS)cost function,which has better steady-state performance than ACLMS algorithm in Gaussian white noise.This paper also analyzes the performance of ACLMS/F algorithm,obtains the stability bound of step size.The MATLAB simulations were used to test the frequency estimation performance of the proposed algorithm in different conditions of the power system.The simulation results show that the algorithm has better steady-state performance than ACLMS and other algorithms.Secondly,aiming at the performance degradation of ACLMS algorithm in impulsive noise environment,an augmented complex least lncosh cost(AClncosh)algorithm is proposed.Based on the frequency estimation model of ACLMS algorithm,the cost function is changed to natural logarithm of hyperbolic cosine function,which improves the anti-impact noise performance of the algorithm.The simulation results show that the performance of AClncosh algorithm is no less than ACLMS algorithm in noiseless and Gaussian white noise environment,furthermore the AClncosh algorithm will not occur performance degradation like ACLMS algorithm under impact noise environment.Distributed adaptive filtering algorithm has been an important research in recent years.Many adaptive filtering algorithms have been extended to distributed networks,and some scholars have applied distributed adaptive filtering algorithm to frequency estimation.On the basis of the proposed AClncosh algorithm,the author extends the algorithm to distributed network,proposes the diffusion augmented complex least lncosh cost(DAClncosh)algorithm.The mean square performance of the DAClncosh algorithm was analyzed,and the stability bound of step size was obtained.In MATLAB simulation,the frequency estimation performance of the algorithm is verified in different conditions of power system.