Control strategy for grid-connection converter under the distorted grid condition
With the development of wind industry, more power electronic converter devices are incorporated into the grid, which leads to the increase of harmonic content in the grid. So the harmonic suppression of grid current in double-fed induction generator (DFIG) converter has been a hot topic recently. The mathematical model of DFIG converter, in view of the 5- and 7+ order components of grid voltage harmonics, is proposed and analyzed in detail. Based on the analytical model, more studies are conducted on the current harmonic and power ripple problems under distorted grid. The harmonic suppression of the system with the current regulators based on proportional-integral and resonant (PIR) is compared with proportional-integral (PI). Based on the above analysis, two different control strategies were proposed to reduce the grid current harmonic components and power ripple. Simulation results verify the correctness of the control strategy.