Improving LVRT Characteristics in Variable-speed Wind Power Generation by means of Fuzzy Logic

Wind system using a fixed-speed wind power generation SCIG (Squirrel-cage Induction Generator) tends to drain large amount of reactive power from the grid, potentially causing a drop voltage and perhaps voltage stability conundrum. To improve the SCIG's low voltage ride through (LVRT) characteristics, this paper presents a new control strategy for a variable-speed wind power generation DFIG (Doubly-fed Induction Generator) located closely to the SCIG-based wind system by utilizing the control capability of fuzzy logic technique. The proposed control system regulates effectively reactive power output of the DFIG wind turbine by controlling both grid-side and rotor-side converters to compensate the reactive power absorbed by the SCIG-based wind turbine. The effectiveness of the proposed control strategies is proven by simulation results. These illustrates that the LVRT characteristics and stability margin of the SCIG-based wind system is significantly improved when extra reactive power is compensated from the DFIG wind system in the proximity.