Saturation-bandwidth tradeoffs in grid frequency regulation for wind generation with energy storage

Selection of linear feedback to operate with plants having actuator saturation limits has long been important in control design research, with one approach represented in the work of Saberi and his co-workers. The work here seeks to tailor this "saturation-accommodating" design method to problems motivated by integrating into the grid renewable energy sources, such as wind turbines, and energy storage technologies, such as batteries, ultra-capacitors, or flywheels. We examine the problem of grid frequency control, in which large numbers of actuators (generators or storage devices) offer distributed control action by varying power output. We tailor Saberi's method to enhance controller utilization and regulation performance when actuators fall into two classes: (i) low bandwidth, "slow" actuators with broad saturation limits (e.g., power control available by varying blade pitch in wind generators); and (ii) high bandwidth, "faster" actuators with narrow saturation limits (e.g., power control available from battery or ultra-capacitor energy storage).