Impact Of The Interconnection Of Large-sclae DFIG Type Wind Power On The Transient Stability Of Power Systems

Bcause of the decrease of traditional fossil energy reserves and increase of environmental pollution problems, the interconnection technology based on wind power generation has been developed rapidly in the world. With the increase of capacity of the interconnection wind power, the impact of its dynamic characteristics on transient stability of power system has become one of the key technology research. This paper mainly focus on the impact of LVRT ability on transient stability of power system and the optimization of wind farms output under transient stability constraints, the main contributions are as follows:Firstly, the impact of DFIG on transient voltage of power system was analyzed. The mathematical model of double-fed induction generator in synchronous rotating coordinate system were established, and the voltage expression of PCC was deduced accroding to that flux can’t be mutation when DFIG has LVRT ability. Based on the voltage expression, the influence factors on transient voltage of power system were analyzed, such as output of DFIG, grounding resistance and short-circuit point location. Furthermore, the transient voltage of PCC under large disturbance case in single machine infinite system was analyzed with time domain simulation method.Then, the mechanism how DFIG impacts transient stability of SMIB under the situation where synchronous machine is replaced with DFIG was analyzed. The transient characteristics of DFIG under large-disturbance was researched. Based on the output characteristics of DFIG, the differences of dynamic characteristics between DIFG and synchronous machine were discussed. The negative impedance model of DFIG was put forward, and based on the model, the impact of DFIG to the acceleration area and deceleration area were discussed. Simulation based on the actual operation data of a power grid demonstrated the conclusion.Finally, one of the method which optimizes wind farm output was put forward under transient stability constraints, and the objective function and constraint criteria were defined. Based on the transient stability margin sensitivity of wind power output, influnce of different wind farm on power system transient stability was analyzed and the optimization algorithm of wind farms’output was put forward. The output limits of wind farm before and after optimizing were contrastive analyzed based on the practical data of a power grid, and the results proved the effectiveness of the algorithm proposed in this paper.