| With the cross-regional interconnection of power network,the growth of power network structure and the large-scale application of power system stabilizer(PSS)in our country,power network low frequency oscillation phenomenon caused by negative damping mechanism has been well suppressed.However,when the motor,governor,excitation system and load produce continuous periodic disturbance in power system,it may cause forced oscillation,which seriously threatens the safe and stable operation of power grid.Due to the characteristics of forced oscillation,such as strong randomness,fast onset,long duration and rapid attenuation after losing the source of oscillation,it is of great significance to locate the source of oscillation quickly and accurately to eliminate forced oscillation.Wide area measurement system(WAMS)is deployed in a large scale in power grid,which provides the basis for on-line locating forced oscillation sources.Combined with the above background,this paper studies a new method of forced oscillation source location in power system driven by data.The main research contents are as follows:(1)A dissipation energy flow(DEF)location method based on wide-area measurement data is introduced.Based on the analysis of the forced oscillation energy composition and conversion relationship,the practical dissipation energy flow model of the branch connected to the generator node is constructed,and the relationship between the positive and negative dissipation energy and the oscillation source is clarified.The time-domain dissipation energy of each generator can be calculated only with wide-area measurement data,and then the oscillation source can be located by analyzing the positive and negative energy of each generator and its variation trend.Finally,the method is analyzed and verified by using WECC179 node test system,and the results effectively verify the accuracy and effectiveness of the method.(2)A dissipation energy spectrum(DES)based method for locating forced oscillation sources in power systems is proposed.Firstly,the short-time Fourier transform(STFT)is applied to the wide-area measurement information of power system.On this basis,the "time-frequency domain" dissipated energy conversion relationship based on short-time Fourier transform is derived.The dissipation energy spectrum is defined and the equivalence between the dissipation energy flow in time domain and the dissipation energy spectrum in frequency domain is demonstrated.The forced oscillation frequency is determined according to the characteristics of the peak/valley variation of the dissipation energy spectrum.Then the forced oscillation source is located according to the dissipation energy spectrum at the forced oscillation frequency.Finally,the proposed method is analyzed and verified by using the simulation data of WECC179 node test system and the measured data of ISO New England power grid.The results effectively verify the correctness and practicability of the proposed method.(3)A wavelet dissipation energy spectrum(WDES)based method for locating forced oscillation sources in power system in frequency domain is proposed.Firstly,the continuous wavelet transform(CWT)is applied to the wide-area measurement information of power system.On this basis,the wavelet dissipation energy spectrum based on continuous wavelet transform is constructed.The equivalence between wavelet dissipation energy spectrum in frequency domain and dissipation energy flow in time domain is proved.Furthermore,the forced oscillation frequency of the system is determined according to the jump characteristics of the wavelet dissipation energy spectrum.Then,according to the wavelet dissipation energy spectrum of each generator at the forced oscillation frequency,the exact location of the forced oscillation source is realized.Finally,the proposed method is analyzed and verified by using the simulation data of WECC179 node test system and the measured data of ISO New England power grid.The results effectively verify the correctness and practicability of the proposed method. |
