Decentralized controller analysis and design for multi-evaporator vapor compression systems

The high degree of coupling in multi-evaporator vapor compression systems (ME-VCSs) makes independent control of the cooling capacity for each evaporator difficult. This paper examines the sources of coupling in these systems and the importance of this coupling when making control decisions. Structured singular value (SSV) analysis is used to quantify the degree of coupling in relation to the diagonal dominance of these systems. A 5-evaporator system model is used to demonstrate this analysis and shows that these systems are not diagonally dominant, suggesting poor decentralized control performance when individually controlling both cooling capacity and superheat. However, SSV analysis is used to show that decentralized control is capable of controlling cooling capacity if superheat is not included in the feedback. Both centralized and decentralized model predictive control (MPC) architectures were developed to verify the findings of the SSV analysis.