Control Uncertainty Based LQR for Frequency Regulation Using Distributed Energy Resources

This paper proposes a dynamically updating robust Linear Quadratic Regulator (LQR), implemented on a Hybrid Energy Storage System (HESS), for improved frequency regulation of a distributed micro-grid. HESS consists of battery and ultra-capacitor banks. They work in conjunction with Photo-Voltaic Distributed Energy Resource (PVDER), making a dispatchable source that is capable of providing inertial support during changing grid conditions. For this purpose, a penalty factor based on control uncertainty is designed for improving the LQR quality function based on the sensitivity of individual HESS devices to changes in frequency. The dynamically updating penalty factors and gains of LQR optimizes HESS output while providing for the inertial and secondary response. Preliminary tests on the modified 123 bus distribution system show that the proposed architecture provides a significant improvement in frequency response (around 26% above droop based control).