Distributed control design to regulate grid frequency and reduce drivetrain stress in wind systems using battery storage

Control designs to facilitate increased utilization of wind powered electric generation face challenges from two directions. From the “system” perspective of the grid, increased wind penetration carries responsibility for greater participation in grid frequency regulation, a function historically provided by traditional synchronous generators. From the “component” perspective of the individual turbine, requirements for long mechanical life and low maintenance translate to a need for control imposing low stress on the drivetrain/gearbox. Recent literature has tended to treat these two separately, while the work here proposes and analyzes a distributed control design that jointly addresses both. To achieve the required flexibility, available actuation is assumed to be augmented by modest amounts of controllable power from battery storage, along with industry-standard power controls at the wind turbines themselves (i.e., the new control design focus is on the batteries, to supplement standard, existing controls on wind turbines). Novel features of the methodology include: (i) adoption of an “exosystem” state model representing wind speed disturbances; (ii) assurance that actuators remain within saturation limits for modeled disturbances (e.g., batteries within their maximum power capability); (iii) use of a modest number of phasor unit measurements at the distributed controllers to enhance observability in relevant modal subspaces.