Modeling and Passivity Properties of Multi-Producer District Heating Systems

TL;DR

This paper develops a detailed nonlinear model of multi-producer district heating systems, analyzing their passivity properties to enhance understanding of their stability and control.

Contribution

It introduces a comprehensive nonlinear ODE model for multi-producer district heating systems and analyzes their hydraulic and thermal passivity properties.

Findings

Hydraulic subsystem exhibits shifted passivity due to flow monotonicity.

Thermal subsystem's passivity analyzed using a thermodynamic storage function.

Model captures temperature dynamics explicitly in a meshed network topology.

Abstract

We propose a comprehensive nonlinear ODE-based thermo-hydraulic model of a district heating system featuring several heat producers, consumers and storage devices which are interconnected through a distribution network of meshed topology whose temperature dynamics are explicitly considered. Moreover, we analyze the conditions under which the hydraulic and thermal subsystems of the model exhibit shifted passivity properties. For the hydraulic subsystem, our claims on passivity draw on the monotonicity of the vector field associated to the DH system's flow dynamics, which mainly codifies viscous friction effects on the system's pressures. For the temperature dynamics, we propose a storage function based on the ectropy function of a thermodynamic system, recently used in the passivity analysis of heat exchanger networks.