A Comparison of Robust and Probabilistic Reliability for Systems with Renewables and Responsive Demand

The effective integration of significant levels of intermittent renewable resources in power system operations will be enabled by increased participation of demand-side resources. In this work, the use of these demand-side resources for balancing reserves is examined in the context of solutions with varying degrees of robustness. The objective is a simulation-based analysis of the impact of requiring robust versus non-robust solutions, the latter in the form of chance-constrained solutions. We use a stochastic optimal power flow formulation that leverages various classes of reserves, from both generation and responsive demand, to manage considerable uncertainty in renewable generation. Case studies with a 30-bus system illustrate that reserve allocations under the robust formulation, though reliable, may cause undue stress to the system that could render the dispatch implementation infeasible. Conversely, the flexibility introduced in a chance-constrained formulation, even at risk-averse probability levels, produces more realistic allocations of generation and reserves, and can be adjusted to provide full robustness at critical, or highly uncertain, periods in the planning horizon. This flexibility is advantageous to the system and customizable by the operator.