Control Design for Energy Storage Dispatch in Existing Critical Facility Microgrids Connected to Weak Utility Systems

This work presents a modeling and control design approach for energy storage integration to enhance power quality and resilient operation in existing critical facility microgrids (CFM) during utility transients. It consists of three steps, fast detection of undesired transients under upstream faults or oscillations, prompt islanding at point of common coupling (PCC), and coordinated control to avoid a blackout. Firstly, a state space model is developed for an aggregate equivalent model for the CFM, the PCC, and the utility system. A linearized state model is identified for different operating conditions identifying unstable dynamic behaviors for required operating conditions. A battery dispatch control is designed to compensate for post-islanding oscillation and frequency drop so as to avoid tripping for local generation and subsequent blackout in CFM. Stability of the novel control design approach is validated through eigenvalue analysis and a linearized model for the post-islanding response. The performance of the control has been tested using an Electromagnetic Transient modeling platform, PSCAD, with a detailed model validated with field collected data.