Search

Abstract: This paper presents an overview of results and future challenges related to temperature control and cost optimization in building energy systems. Control and economic optimization issues are discussed and illustrated through simulation examples. The paper concludes with results from model predictive control solutions and identification of important directions for future work. [Copyright &y& Elsevier]

Abstract: This work describes the application of an offset-free model predictive controller (OF-MPC) to a vapor compression cycle (VCC). To this end, first a linear model is identified from data generated from a first-principle model of a VCC, interfaced with a building model implemented in EnergyPlus. Next, a model predictive controller is designed that includes an augmented model (including disturbance states) and an associated Luenberger observer to estimate the disturbance (plant-model mismatch) at steady state and eliminate it. Tuning guidelines are presented that enable partial ‘decoupling’ of the Luenberger design and choice of MPC parameters, leading to offset elimination and superior tracking performance while reducing the energy demand on the VCC, relative to traditional control approaches. The superior closed-loop performance of the OF-MPC strategy is demonstrated for a VCC model in isolation, subject to realistic disturbances and subject to measurement noise. [Copyright &y& Elsevier]

Abstract: Many systems used in buildings for heating, ventilating, and air-conditioning waste energy because of the way they are operated or controlled. This paper explores the application of model predictive control (MPC) to air-conditioning units and demonstrates that the closed-loop performance and energy efficiency can be improved over conventional approaches. This work focuses on the problem of controlling the vapor compression cycle (VCC) in an air-conditioning system, containing refrigerant which is used to provide cooling. The VCC considered in this work has two manipulated variables that affect operation: compressor speed and the position of an electronic expansion valve. The system is subject to constraints, such as the range of permissible superheat, and also needs to regulate temperature variables to set points. An MPC strategy is developed for this type of system based on linear models identified from data obtained from a first-principles model of the VCC. The MPC strategy incorporates economic measures in the objective function as well as control objectives. Tests are carried out on a simulated VCC system that is linked to a simulation of a realistic building that is developed in the U.S. Department of Energy Computer Simulation Program, EnergyPlus. The MPC demonstrated significantly better tracking control relative to conventional approaches (a reduction of 70% in terms of the integral of squared error for step changes in the temperature set-point), while reducing the VCC energy requirements by 16%. The paper describes the control approach in detail and presents results from the tests. [Copyright &y& Elsevier]