Abstract
The order of the detailed model of doubly-fed induction generator (DFIG) wind farms are too high and the simulation is difficult. Most of the existing research has used a single-machine equivalent model and clustering aggregation model for equivalence and few papers have explored the principles and equivalent conditions of the single-machine equivalent model under sub-synchronous resonance (SSR). Due to this reason, this paper equates DFIG wind farms connected with series compensated transmission network to two separate units based on the principle of matrix similarity transformation and the mathematical model and physical model of each unit has been studied. Then, the DFIG wind farm equivalent model’s validity is analyzed in number difference and collecting line difference based on linearization analysis. Finally, the system model is built in EMTDC/PSCAD, the damping analysis method is used to test the equivalent model’s validity and further reveal the mechanism of the system’s unstable operation. The results show that: the equivalent model can effectively reduce the system dimension and accurately reflect the dominant oscillation characteristics of DFIG wind farm under SSR; when SSR occurs, the damping coefficient of DFIG wind farm is negative under the oscillation frequency.
Highlights
Large-scale development and utilization of wind energy is an important part of China’s energy strategy
To avoid the influence of chance on the accuracy of the equivalent model, when actual wind speed data at a certain time t2 is selected as the input wind speed of doubly-fed induction generator (DFIG) wind farm, the input wind speed and grouping results are shown in Tables A4 and A5 in Appendix B
Based on the principle that the similarity matrix has the same eigenvalues, the equivalence of DFIG wind farm connected with the series compensated transmission network has been studied and the equivalence process has a strict theoretical basis
Summary
Large-scale development and utilization of wind energy is an important part of China’s energy strategy. Based on the actual oscillation data in Guyuan, Reference [11] verified the negative resistance effect of DFIG by conducting impedance modeling of DFIG and permanent magnetic synchronous generator (PMSG) It studied that control parameters greatly increased the negative resistance at the oscillation frequency, which was the main reason for the self-excited SSR in low series compensation degrees. Based on the damping analysis method, the sub-synchronous oscillation mechanism of DFIG wind farm connected with the series compensated transmission network is further revealed. The rest this 3 farm of 19 paper is organized as follows.
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