Research On Mitigating Voltage Flicker For The Grid Connected Technology Of The Wind Power Generation

In recent years, wind power, as a kind of clean and renewable energy, was paid more and more attention to globally. Because of the unstable characteristics of wind speed and the inherent properties of wind turbine system, the wind turbine's output power is not stable. This unstable power which is injected to grid, will influence the power quality, and causes the voltage fluctuation and flicker.In order to solve the voltage flicker problem of doubly-fed induction generator (DFIG), the wind speed model, wind turbine, shafting, DFIG, and full scale converter model were separately established. In order to simulate the real situation of the wind speed, considering the wind shear and tower shadow effect factors in the new wind turbine's model, simulation was undertaken. Static synchronous compensator (STATCOM) can restrain the voltage flicker in distribution network, so it was applied to solve DFIG's voltage flicker. Formerly many of the control methods of STATCOM were focused on the decoupling of system variables and design of PI controller. But STATCOM was a multiple-input multiple-output (MIMO) system. Its variables can't be decoupled completely. So it had bad control performance sometimes. PID control method which can give quick response, but it was difficult to select the best parameters values. The genetic algorithm was used for optimization of parameters. It gived the system the best dynamic response in the shortest time. Finally, this paper gived two methods of mitigating the voltage flicker of DFIG: 1) If the wind speed exceeded the ratings, the section proposed the method of combination control. 2) The section designed the flicker mitigation controller for the voltage flicker caused by the wind shear and tower shadow effect; at the same time, it taked genetic algorithm on off-line tuning of PID parameters.