Rule-Based Real-Time Control of A Flow Battery for Preventing Minimum Import Violation

Hao Xin, Miroslav Penchev, Yun Xue, and Alfredo A Martinez-Morales


Flow battery, Minimum import violation, Real-time battery control algorithm, Energy management system


Per California (CA) Rule 21, large self-generating facilities such as water agencies not only have non-export agreements with their power utility provider in place, but also have a minimum import requirement under their interconnection agreement. In this study, a minimum import violation is triggered when imported grid power falls for more than 2 seconds below 5% of nominal onsite generator capacity. Herein, we present a rule-based real time control algorithm for using a flow battery to help the Victor Valley Wastewater Reclamation Authority facility prevent minimum import violations, while increasing on-site renewable energy utilization. The battery control algorithm comprises of four stages: 1) charging, 2) discharging, 3) pre-refresh, and 4) refresh. Additionally, the control algorithm manages two flow battery packs in cooperation with each other, based on battery operational constraints. Battery operation is controlled by the energy management system based on import grid power measurements.

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