| Recently,the stability problem caused by a large scale wind farm connected has brought about such problems as broadband oscillation,large-scale wind power off-grid and even large-scale power outage to the power grid in the western region with high proportion of new energy in China,which has attracted the attention of power grid with large-scale wind power grid connection.In order to study the broadband oscillation problem of the grid system connected with wind farm,the corresponding research is carried out from two parts in this paper.The one part is about the specific range of control system and line parameters,which inflect the instability of system.The other part is about the choice of clustering methods for the reasonable simulation model.Based on research of wind power connection stability of Ningxia Mahuangshan wind farm,the influence of each system parameters on stability is analyzed quantitatively.The general impedance model in synchronous frame is given with the parts of wind generator,outlet filter,the transformer,the inner and outer loop and phase-locked loop in both rotor-side controller and grid-side controller as well as the DC part between them.By applying the generalized Nyquist stability criterion in analyzing each system parameters,the results verify that the RSC parameters,DC outer loop parameter in GSC and line inductance have obvious effect on system stability.Based on the impedance modle in multi-output and multi-input system,the generalized Nyquist stability criterion is used to analyze the each parameters’ influence on the stability of wind turbine grid-connected system.The specfic range of parameters of a single DFIG turbine is provied,triggering the unsafe state of system.This can also avoid the wind power connection oscillation cased by the unreasonable setting of control and line parameters.The result shows that the control parameters of rotor side converter,the DC outer loop control parameters of grid side converter and system inductance parameter have obvious influence on the stability.In order to verify wind power grid stability by simulation,the equivalent model of wind farm which has less dimension and memory and faster response is needed.A complete system of selection clustering methods is established,including the selection of the grouping indicator,data standardization,clustering measurement,clustering method and clustering effect evaluation.Through the comparative analysis of various clustering elements,the selsction result is definited.Wind speed,power and current are chosen as indicators,range standardization and BIRCH clustering method is chosen as clustering method,F test is used in the final validation.This general clustering elements selection system is used to build clustering model of Mahuangshan wind farm and verify the parameters in each system in this simulation model.The simulation result shows that the control parameter range calculated in the single wind turbine can also applicable to the stability analysis of grid-connection wind farm. |
