| With the large-scale access of new energy sources such as wind power to power systems,the interaction between various power electronic devices and the power grid has led to increasingly significant new oscillation issues,and the risk of oscillation in new energy power systems is increasing.There are various types of wind turbines and control parameters,making it more difficult to identify the main influencing parameters of oscillation and how to adjust them to improve the stability of grid connected systems.Accurate positioning of the oscillation source after oscillation is more complex.Therefore,this paper conducts the following research on the oscillation stability and oscillation source location of direct-driven and doubly fed wind power grid connected systems:(1)Considering the detailed dynamic process of wind turbines,a sequential impedance modeling method for direct-driven and doubly-fed wind turbines is proposed based on the parameter sensitivity of open-loop transfer functions.Combining open loop transfer functions that reflect the stability of wind power grid connected systems with sensitivity,intuitively analyzes the impact of various parameters,including system parameters,on the oscillation stability of wind power grid connected systems,and proposes parameter optimization measures based on the sensitivity results.Finally,simulations are conducted in a direct drive wind power grid connected system and a doubly fed wind power grid connected system,respectively,to verify the effectiveness of the proposed method.(2)In response to the issue of the "black box" model of the fan being unable to derive a frequency domain impedance model,in order to improve measurement efficiency and verify the correctness of the derived sequence impedance model,a multi platform impedance identification module was established.Based on Simulink,ADPSS digital platform,and RT-LAB semi physical simulation platform,a custom harmonic injection device and impedance identification module were established,effectively improving measurement efficiency.On this basis,an improved impedance identification method is proposed to address the impact of resonant components on the accuracy of impedance identification in wind farm impedance identification with oscillation risk,which can effectively avoid the impact of resonant components on impedance identification.Finally,impedance identification of the doubly fed wind power grid connected system was conducted through offline and online simulations.The results of impedance identification were used for sub synchronous oscillation analysis,verifying the effectiveness of the established multi platform impedance identification method and the improved impedance identification method.(3)To solve the problems of the shortage of vibration source localization methods and complex computation in large hybrid wind farm stations mentioned above,a vibration source localization method for large hybrid wind farm stations based on frequency domain oscillation contribution factors is proposed.Firstly,the equivalent impedance model of a large hybrid wind farm station is established using online impedance measurement method,and the frequency domain oscillation contribution factor is derived;Then,the dominant oscillation mode is obtained based on the impedance method;Then,through the node admittance matrix of the dominant oscillation mode and the large hybrid wind farm station,the contribution factor under the dominant oscillation mode is calculated;Through quantitative analysis of oscillation contribution factors,online positioning of oscillation sources in wind farm stations is achieved;Finally,the effectiveness of frequency domain contribution factors for oscillation localization in large-scale hybrid wind farms is verified through simulation of the interaction between doubly-fed fans and series compensation capacitors and the interaction between direct-driven fans and SVG on the ADPSS/ETSDAC platform. |
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