Research On Harmonic Stability Of DFIG For Wind Power Generation

Doubly-fed wind generator (DFIG) is the most common used, but also the most sensitive generator to grid faults. The wind farm are usually located at the remote location where is always far away from the center of the load area, and it belongs to the weak grid region which is prone to grid faults. Due to the extensive use of grid power electronics and non-linear loads, making the grid often contains a lot of harmonic voltage, the stable operation of the wind power systems poses a serious threat to the grid.DFIG and the grid formed a dynamic interconnection system, there may be less than the dynamic interaction of some of the images in the common connection point of the interconnected system. In recent years, most studies for the dynamic interaction has been widespread concern of scholars at home and abroad, and some achievements had been made. Based on the strategy of PIR harmonic suppression, this article make some analysis for the interoperability issues related to the grid and DFIG The analysis have been verified by simulation and experiment. The concrete research content is as follows:1) Building the DFIG mathematic model under the distorted grid conditions, and analyzes the problem of gird current distortion and voltage pulsation caused by grid voltage harmonics. Based on PIR control strategy, establishing the power mathematical model to reduce the current harmonic components and power pulsation with different control targets. Studying the effect of control strategy on harmonic grid adaptation with different control targets. Concluding and verified the conclusion by simulation and experiment.2) At first, mathematic model in fundamental domain of DFIG and grid was established. On the basis, the DFIG equivalent circuit was derived. series-parallel resonant mathematic was discussed. Meanwhile, the relationships of harmonic amplification factor and the system parameters was analyzed. At last the harmonic transient change process of DFIG in the conditions of grid harmonic sudden changes was analysis. The conclusion has been verified by MATLAB.3) By studying the factors of harmonic control on double-fed induction generator, harmonic current impact factor and harmonic voltage impact factor is proposed to characterize the impact degree of harmonic current and harmonic voltage respectively. The stability of the grid impedance of the doubly-fed generator is analyzed in the research. According to the DFIG harmonic current suppression effect with different DFIG parameters, the harmonics adaptation of control strategy impact on DFIG was analysis.