Enhancement Fault Ride-Through of DFIG with Applications of ISM Control for Balance and Unbalance Voltage Sag

With the high penetration of the grid-connected wind power sources, the FRT capability is significantly required for the DFIG wind turbine to mitigate the system instability. For the FRT problem, because the DFIG is very vulnerable to the grid faults, it may not be able to ride through. These faults may result in a large voltage dip at the connection point of the DFIG. Subsequently, the voltage dip will cause the over current in the stator and rotor windings which may be damaged. In this paper, applications of integral sliding mode control (ISMC) will be investigated for the fault ride -through (FRT) enhancement of the doubly-fed induction generator wind power system. In ISMC will be studied for rotor-side converter (RSC) and stator-side converter (SSC) and series grid side converter (SGSC) control. In ISMC approach, supplementary control generated by the complete models is achieved for FRT enhancement. Since the proposed methods are based on the general non-linear system theory, the FRT capability can indeed improve even under severe fault conditions. Performance comparisons among several existing FRT enhanced control will also be examined to show the effectiveness of these PI control schemes.