Model Predictive Control-Based Coordinated Frequency Regulation of Wind Power and Energy Storage Systems

Abstract

The growing share of wind power in electricity generation has been pushing out conventional synchronous units, and the overall inertia available to the power system keeps dropping. When inertia gets low, even a moderate mismatch between generation and load can pull frequency outside safe limits before primary regulation catches up. This paper puts forward a model predictive control (MPC) strategy for coordinated primary frequency regulation in a wind-storage system. The method treats wind turbine pitch angle and energy storage power output as two control variables that can be dispatched together. A multiobjective rolling optimization model is set up, and it handles two goals at the same time: keeping the frequency deviation small, and keeping the state of charge (SOC) of the storage unit within its allowed window. The performance of the MPC strategy is checked against a conventional PI regulator and a droop-based scheme through simulation. Results show the MPC approach brings down the maximum frequency deviation and the rate of change of frequency (RoCoF), and it also cuts the time the system needs to restore frequency after a disturbance. On the whole, the proposed method gives the wind farm and the storage facility a better way to work together, and it helps keep the frequency stable in power systems that carry a large amount of wind generation.