Real-Time Co-Optimization

Abstract

As renewable energy penetration increases and system inertia levels drop, primary frequency response is becoming a critical concern. To address this problem the Electric Reliability Council of Texas (ERCOT) is introducing a Fast Frequency Responsive (FFR) reserve product to the electricity market that helps to arrest frequency decline in the event of a large generator outage. This reserve type is required to be capable of nearly instant deployment of allocated reserve, which differs from traditional Primary Frequency Responsive (PFR) reserve that exhibits ramping limitations on power output. This paper derives a real-time co-optimization problem from first principles that ensures the reserve allocation is sufficient to arrest frequency decline before reaching some critical frequency threshold. The reserve constraints that are introduced capture the coupling between PFR reserve, FFR reserve, and system inertia, which is assumed constant in the context of the real-time market. Numerical results illustrate this coupling via a realistically large representation of the Texas power system.