Performance comparison of quadratic, nonlinear, and mixed integer nonlinear MPC formulations and solvers on an air source heat pump hydronic floor heating system

There is a gap in literature on comparisons between different MPC optimal control formulations

and solver choices for the same building HVAC system. Mixed Integer Nonlinear (MINL) formu-
lations are rarely considered, despite being the most physically accurate way to represent HVAC

systems. This work compares several MPC formulations, including Quadratic, Nonlinear, and MINL,

applied to a case study building and investigates benefits and challenges of MINL MPCs from prac-
tical perspectives. Ten different MPC formulations were developed and implemented using Pyomo.

Then, a detailed emulator model was developed using open-source Modelica libraries and used
with BOPTEST to assess the performance of each MPC. Results show that convergence and control
switching behaviours of MINL MPCs are sensitive to formulations, initialization approaches, solver
selections, and solver parameters. Thus, they require significant effort for tuning. However, a very
well-tuned MINL MPC performed similarly to successful Nonlinear MPC formulations.