Pitch control battery backup methods and system

The device for controlling a wind turbine (100) pitch control system (406) method. A method comprises: The backup battery is provide the charging (408), wherein the backup battery is constructed with when the reciprocating said AC power input to the DC ring (410) and energy, wherein the direct current ring comprising a direct current ring capacitor (416). A method further - comprising to storing on the direct current ring capacity of the energy on the feathering control system; the reciprocating the AC power input absorbing the process according or two end of the work, and work in the feathering control system and backup of the stabilizing drop of direct current ring capacitor two sides for charging held on the electric charging the direct current ring energy.