Doubly-fed Induction Generator Wind Farm Aggregated Model Based On Crowbar And Integration Simulation Analysis

With the increasing integration of wind generation in power system, Analysis of its influence on power system is becoming more and more important. The low voltage ride-through is an urgent issue of doubly-fed induction generator (DFIG) wind farm. It’s necessary to establish a proper aggregated wind farm model. Thus, in this paper, a method for wind farm aggregation is proposed considering the features of crowbar. Wind farm integration simulation is carried out. And integration characteristics of the wind farm is discussed in the simulation analysis. Specific works can be summarized as follow:(1) The principle of doubly-fed induction generator, wind turbine and aerodynamics is analyzed. The control scheme of rotor and grid side converter is presented. Using these basics, the rotor side current during grid fault is calculated. Meanwhile the crowbar of the DFIG is introduced and its features are reviewed through simulation.(2) Wind farm double machine aggregated model is proposed. The voltage of DFIG during normal operation and grid fault is calculated through power flow and short circuit analysis; The rotor current during grid fault is calculated using the expression derived from the analysis before. According to the calculated value and the threshold value of crowbar, the number of DFIG which activate the crowbar during grid fault can be confirmed. Then, the wind farm are separated into two groups. Capacity-weighted method is adopted to calculate aggregated parameters of each group. The proposed method can reflect the different operation state and crowbar activation of DFIG inside the wind farm.(3) A WSCC9-bus system with50MW DFIG wind farm integration is studied. The two-machine aggregation model is derived. Through simulation and comparison with single-machine aggregation, the proposed model can represent the wind farm during grid farm with more accurate result of voltage dip and reactive power. Adding load model into the proposed model, the transient voltage stability of wind farm integration is analyzed. Voltage collapse is caused by the asynchronous motor near the wind farm.(4) The schemes for enhancing the low voltage ride-through of wind farm is discussed. Applying STATCOM to the proposed model through simulation, the low voltage ride-through capacity of the wind farm is improved.In this paper, a method for wind farm aggregation model considering crowbar is proposed. The method can reflect crowbar activation feature of wind farm during grid fault. And it is suitable for wind farm integration simulation and low voltage ride-through analysis.