284289 Infinite-Horizon Economic MPC for Building HVAC Systems

Monday, October 29, 2012
Hall B (Convention Center )
David Mendoza-Serrano and Donald J. Chmielewski, Illinois Institute of Technology, Chicago, IL

Energy consumption by HVAC systems is usually heaviest when electricity prices are at their highest. The method of Economic Model Predictive Control (EMPC) can be used in conjunction with Thermal Energy Storage (TES) to time-shift power consumption away from periods of high demand to periods of low energy cost. In addition to enormous computational costs, implementation of such algorithms can result in unexpected and sometimes pathological closed-loop behavior, including inventory creep and bang-bang actuation. This paper will present an infinite-horizon formulation of the EMPC problem. While the design of this controller is achieved by a fairly simple convex optimization problem, it will be shown to alleviate many of the pathological behaviors observed in the finite-horizon case as well as significantly reduce the computational effort required for implementation. The method is illustrated on a simple building example using active TES. Implementation of the IH-EMPC policy resulted in a 99.987% reduction in computational effort, while only sacrificing 3.75% in operational cost. The new policy also eliminated much of the spiky behavior typically observed in EMPC implementations.

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