Analysis Of Interharmonic Resonance Of D-PMSG-based Wind Farm And Research On Its Influencing Factors

Abundant and wide-band interharmonics with non-integer fundamental frequency are injected into the power system,as new energy generation is connected to the grid on a large scale.Affected by it,the interharmonic resonance of grid-connected wind farm based on Direct-drive Permanent Magnet Synchronous Generator(D-PMSG)has frequently occurred in recent years,causing the unit to disconnect from the network in a large area and even the torsional vibration of the thermal generator in the system,which lead to serious economic losses.At present,there are two types of interharmonic resonance that have serious impacts,which are the subsynchronous oscillation(SSO)and the high frequency resonance(HFR).The two are all caused by the interaction between the power grid and the converter control system of D-PMSGs inside wind farm,only the resonance frequency band and the main influencing factors are different.Therefore,in order to fully describe the interharmonic resonance of wind power systems based on D-PMSGs,this paper unifies the two under the interharmonic resonance framework,and conducts modeling analysis and research on influencing factors,respectively.Firstly,the state space model of the grid-connected system of D-PMSG-based wind farm is established,the eigenvalue method is used to analyze the system SSO damping and frequency,and the accuracy of the model and analysis method is verified by PSCAD simulation.A method combining least squares polynomial fitting and eigenvalue analysis is proposed.The curve of SSO frequency and damping change with wind speed and the curve of critical wind speed change with operating PMSG number are fitted.The effect of wind speed and the number of PMSGs on the SSO characteristics of the system is quantitatively analyzed.Then,the uncertainty research of SSO random characteristics considering dynamic influencing factors is carried out.Considering the random characteristics of wind speed,the probability distribution model of SSO frequency and damping of grid-connected D-PMSG-based wind farm is established.time-varying characteristics of dynamic influencing factors,the time series simulation methods of wind speed and the number of operating PMSGs under the wind farm model with the same wind speed and the wind farm model with different wind speeds are proposed,respectively.The relevant risk indicators of SSO are determined and the time sequential Monte Carlo simulation is used to conduct the SSO risk evaluation.On this basis,the strategy of SSO risk suppression by adjusting the cut-in wind speed was discussed.Finally,modeling analysis of the high-frequency inter-harmonic resonance of grid-connected D-PMSG-based wind farms and its influencing factors are carried out.The D-PMSG high-frequency admittance model is established,and combined with the wind farm topology,a large-scale wind farm grid-connected system admittance network model is proposed.Modal analysis,participation factor analysis and quantitative analysis of node voltage disturbance response are carried out.The reliability of the method and the accuracy of the results are verified by PSCAD simulation.The influence of some system parameters on HFR is quantitatively discussed.