A quantum-classical hybrid framework for optimal energy storage systems planning

The extensive deployment of power-electronics introduce spatial-temporal variability that can degrade voltage quality and operational reliability. Energy storage systems (ESS) can mitigate these effects through fast active and reactive power support, but their value is contingent on coordinated siting and sizing. Integrated formulations that minimize voltage deviations, reduce substation power-flow variability, and account for installation costs typically yield in large-scale mixed-integer optimization problems that are computationally burdensome for classical solvers and may yet not lead to the most optimum solution. To address these challenges, this paper proposes a two-stage hybrid quantum-classical planning framework that separates binary siting from continuous sizing and operation. In Stage I, the siting problem is reformulated as a Quadratic Unconstrained Binary Optimization model and solved via a hybrid quantum workflow. Acting as a "quantum sieve," stochastic sampling generates a diverse set of candidate site combinations that classical single-point methods can overlook. In Stage II, selected site sets are evaluated using a classical convex solver (SOCP) to compute optimal ESS capacities and operating setpoints subject to network constraints, ensuring physical feasibility. Experiments on IonQ Forte hardware show grid-standard accuracy with industry-standard classical solvers. Although current hardware latencies limit performance in the NISQ era, the paper outlines scaling pathways and discusses key practical hurdles, including state-preparation overlap and higher-order cost couplings.