Research On The Forced Oscillation Location In The Wind Farm Integrated Power Grid

Forced oscillation(FO)is one of the severe threats to the safety and stability of the power system.Locating the disturbance sources is an important part in solving FO problems.Meanwhile,wind power is one of the most promising new energy types,which has very different operating environments and control methods from traditional energy types.Therefore,the impact of the wind farms on the FO disturbance sources in the system remains to be studied.The thesis reveals the differences between wind farms and traditional generators in the FO source location area.Then,the forced oscillation disturbance source location methods that are suitable for wind farm integrated systems are proposed.The thesis provides novel ideas to solve FO location problem under the trend of increasing wind power penetration.The main contributions of the thesis are as follows:(1)A disturbance source location method for FOs caused by wind speed fluctuation is proposed.The characteristics of wind speed fluctuations of wind farms are analyzed,which leads to the study of the propagation and response of power fluctuations caused by wind farms in the power grid.After that,a method to locating the forced oscillation disturbance source caused by wind speed fluctuation is proposed,which uses the bispectrum analysis to identify the oscillation frequency and uses the wavelet transform to identify the phase of oscillation signals.(2)A method for the location of disturbance sources inside the doubly fed induction generator wind turbines(DFIG-WT)is proposed.By combining the energy function of the power grid to the model of DFIG-WT,the energy structure inside the DFIG-WT is derived.Further,the characteristics of forced oscillation energy inside the DFIG-WT are studied.The mapping between the physical components of DFIG-WT and the internal energy function is constructed,which leads to the proposing of an accurate location method that can pinpoint the disturbance to the specific components inside the DFIG-WT.(3)A method to measure the participation of DFIG-WT in FOs events is proposed.The transient energy is constructed by the Hamiltonian function,which reveals the relationship between the DFIG-WT and the disturbance source,the connection from disturbance source to the system,as well as the system states.The participation factor of the DFIG-WT in FOs is defined to propose a method for evaluating the participation of the DFIG-WT in FO events.