Optimal hybrid power dispatch for distributed energy resources with dynamic constraints

Abstract

Consider a microgrid with a hybrid collection of distributed energy resources (DERs) that include fossil, renewables and energy storage battery systems. Given the dynamic variability of the DERs in terms of power production, this paper presents an optimization approach for the optimal power dispatch in such a hybrid microgrid by taking into account amplitude and rate constraints on each DER. The constrained multi-objective power dispatch problem is solved by formulating a weighted convex optimization with penalty terms imposed to take both power dynamics and allowable energy levels of each DER into account. The paper also analyzes the weighting used in the optimization as a trade-off between the use of renewable energy, energy storage and the cost of fossil fuel to achieve power dispatch demands. The optimization approach is illustrated on the combination of a fossil and a (multi-)battery system where the State of Charge (SoC) levels of the batteries are required to stay close to each other while minimizing frequent power switching (chattering) and battery round-trip losses. Simulations results demonstrate how economic incentives can be used to formulate the optimal hybrid power dispatching between fossil and renewable resources, while battery SoCs can be balanced (converge to the same mean value) by sharing power optimally among different batteries.