Pitch control battery backup methods and system

An apparatus for controlling pitch of a blade of a wind turbine, said apparatus comprising:

• a pitch control system;
• a DC link having a DC link capacitor and configured to provide power to said pitch control system;
• a source of AC input power to provide power to said DC link;
• and
• a backup battery configured to supply no energy to the DC link when full AC input power is available,
• said apparatus configured to:
• use energy stored in said DC link capacitor to operate said pitch control system during a loss or dip of AC input power;
• and
• maintain charge on said DC link capacitor using said backup battery as voltage across said DC link capacitor drops during operation of said pitch control system, said source of AC input power remains coupled to said DC link when said backup battery maintains charge on said DC link capacitor.

A wind turbine comprising:

• at least one blade and a generator coupled to said at least one blade and configured to generate AC power;
• a pitch control system configured to control a pitch of said at least one blade about an axis;
• a DC link having a DC link capacitor and configured to provide power to said pitch control system;
• a source of AC input power to provide power to said DC link, said source of AC power not necessarily comprising said generator;
• and
• a backup battery configured to supply no energy to said DC link when full AC input power is available, said wind turbine configured to:
• use energy stored in said DC link capacitor to operate said pitch control system during a loss or dip of AC input power;
• and
• maintain charge on said DC link capacitor using said backup battery as voltage across said DC link capacitor drops during operation of said pitch control system, said source of AC input power remains coupled to said DC link when said backup battery maintains charge on said DC link capacitor.