A novel method to optimize the active crowbar resistance for low voltage ride through operation of doubly-fed induction generator based on wind energy

Nowadays, wind power has been developed very fast in China and the installed capacity of wind turbine has been increased rapidly. As an important wind driven generator, doubly-fed induction generator (DFIG) has been applied very popularly for its many advantages, such as less converter losses and simpler control methods. When the grid voltage dip occurs, a crowbar beside the rotor-side converter is usually activated. Unfortunately, the selection of the crowbar resistance is a new problem for great influence by non-linear circuit parameters. It must be large enough to limit the fault current in the rotor, meanwhile it can´t induce high voltage ripple in the DC-link circuit. In terms of such requirements, this paper proposes a novel strategy to optimize the resistance of the crowbar. In the objective function, the rotor current and DC-link voltage are used as the criteria and an index is set to reflect the influence of these two variables, then an optimized crowbar resistance which makes the best response of this system is obtained. Simulation executed in MATLAB/SIMULINK is proposed to validate relevant theoretical investigation, which indicates the new algorithm is effective to find the best crowbar resistance for low voltage ride through (LVRT) operation.