Reliability models for DFIGs considering topology change under different control strategies and components data change under adverse operation environments

The doubly-fed induction generators (DFIGs) are widely applied for wind energy conversion. Their reliability models are important to risk analysis of wind power systems, which has not been fully investigated due to changing topology configuration and sensitive reliability data. In this paper, three reliability models are newly proposed for the DFIGs. Under the doubly-fed mode, the DFIG is logically in series configuration with low reliability. With outage of rotor-side converter, or operation of crowbar against short current, the grid-side converter or the power grid provides var support. The DFIG operates as an induction machine, avoids tripping and yields high reliability. The DFIGs' reliability is also dependent on vulnerability of the mechanical components to the strong wind, vulnerability of the electrical components to the short current, effectiveness of the fault-ride-through capability, and possibility of strong wind and severe fault. Logistic curve is applied to modify unavailabilities of the mechanical and electrical components under the adverse operation conditions. The proposed models help to quantify the lifetime and determine the key component of the DFIGs, thus improves reliability of the wind power systems.