Approximate error considered fuzzy proportional–integral control of DFIG with regional pole placement for FRT improvement
A novel fuzzy proportional-integral (PI) control with fault ride-through (FRT) capability is investigated for double fed induction generators (DFIGs), where an approximation error considered Takagi-Sugeno fuzzy observer is employed to approximate the non-linear model of DFIG. Based on the obtained observer, a H
 2
 controller with PI structure is used to achieve specified engineering purposes, such as maximum power point tracking and automatic voltage regulator. A H
 ∞
 controller is proposed to cope with the undetected disturbances in the H
 2
 control, and a robust technique is also proposed to override the effect of approximation error due to the fuzzy approximation. Then, the controller design is formulated as a mixed H
 2
/H
 ∞
 suboptimisation problem with the regional pole placement constrain, which can be solved easily by using linear matrix inequality technology. In order to further improve the FRT capability, a power angle compensator is proposed to reduce terminal voltage drop via limiting DFIG power angle jump during faults. The results of dominant eigenvalue analysis and simulation are presented and discussed, which shows the capabilities of DFIG with the proposed control strategy to improve system damping, fault-tolerant control and FRT, and its contribution on power system transient stability support.