System and method for providing yaw backup to a wind farm

A wind farm comprising:

• a plurality of wind turbines for generating wind power and transmitting the wind power to a power grid, where the wind turbines are electrically coupled to each other;
• a plurality of yaw motors, each yaw motor for controlling a yaw angle of a respective wind turbine of the plurality of wind turbines
• yaw backup systems coupled to the respective wind turbines in the wind farm for controlling delivery of power to the respective yaw motors to control the respective yaw angles of the respective wind turbines during a grid loss condition, wherein each of the yaw backup systems comprises:
• an energy storage element for storing auxiliary power;
• a yaw controller for executing the steps of:
• receiving wind direction signals over time from a sensor;
• determining a wind direction rate of change based on the wind direction signals;
• selecting a tolerance level from a plurality of predetermined and stored tolerance levels, wherein the selected tolerance level correlates to the determined wind direction rate of change with respect to time, the tolerance level comprising a duty cycle at which power is supplied to the yaw motor for a defined range of wind direction rate changes;
• switching to a different tolerance level when the wind direction rate of change exceeds the defined range for the selected tolerance level;
• computing an auxiliary power level of the energy storage element coupled to the respective wind turbine;
• comparing the computed auxiliary power level with a predefined auxiliary power level of the energy storage element coupled to the respective wind turbine;
• and
• controlling the delivery of power from the energy storage element to a respective yaw motor for maintaining the yaw angle of the respective wind turbine in a predefined angular dead band limit relative to wind direction for reducing a load on the respective wind turbine induced by wind, and
• wherein the yaw controller controls the delivery of power from the energy storage element of the respective wind turbine if the computed auxiliary power level is greater than the predefined auxiliary power level for the respective wind turbine, or from an energy storage element of a different wind turbine coupled to the respective wind turbine if the computed auxiliary power level is less than the predefined auxiliary power level for the respective wind turbine based on the tolerance level to control the yaw angle of the respective wind turbine.