Virtual Generator-Storage Pairing for Robust Multistage Decisions in Power Systems

In this article, we present a robust optimization-based framework for day-ahead reliability assessment (RA) and real-time dispatch to ensure power system reliability under multistage renewable uncertainty. Our framework jointly considers fossil-fuel generators and energy storage in the system. To obtain near-optimal performance in grid reliability, we develop robust multistage decisions based on the concept of "safe-dispatch sets" in the literature. Although such safe-dispatch sets directly answer the RA and real-time dispatch problem, their computation often incurs high computational complexity. To develop low-complexity algorithms, we adopt a divide-and-conquer paradigm. First, we derive the conditions to describe the safe-dispatch sets for a pair of energy storage and generator. The results from this simple building block provide us with useful insights on how the grid reliability is related to the parameters, e.g., the generators' ramp speeds and the storage capacity. To tackle the general multibus scenario, the uncertainty is split among virtual generator-storage pairs (VGSPs), where we can utilize the results from the one-bus building block. Numerical studies on a standard IEEE 30-bus test case illustrate that our proposed solution requires much lower storage capacity to ensure system reliability compared to state-of-the-art approaches, without renewable curtailment.