A Predictive Operation Controller for an Electro-Thermal Microgrid Utilizing Variable Flow Temperatures

TL;DR

The paper addresses flexible operation of electro-thermal microgrids by exploiting the thermal network's storage through variable flow temperatures. It develops a discrete-time, multi-layer ETMG model that couples a thermal district heating network with an electrical grid via heat pumps, and formulates a convex Model Predictive Control framework to optimize operation under constraints. The key contributions include a discrete-time thermal-hydraulic storage model, an integrated ETMG model with MPC, and a case study showing reduced main-grid power demand and operating costs when exploiting thermal storage. The results highlight the potential of sector coupling and dynamic temperature control to enhance RES-based operation and overall system efficiency in future energy systems.

Abstract

We propose an optimal operation control strategy for an electro-thermal microgrid. Compared to existing work, our approach increases flexibility by operating the thermal network with variable flow temperatures and in that way explicitly exploits its inherent storage capacities. To this end, the microgrid is represented by a multi-layer network composed of an electrical and a thermal layer. We show that the system behavior can be represented by a discrete-time state model derived from DC power flow approximations and 1d incompressible Euler equations. Both layers are interconnected via heat pumps. By combining this model with desired operating objectives and constraints, we obtain a constrained convex optimization problem. This is used to derive a model predictive control scheme for the optimal operation of electro-thermal microgrids. The performance of the proposed operation control algorithm is demonstrated in a numerical case study.

Figures (2)

• Figure 1: Schematic of a minimal realization of an ETMG.
• Figure 2: Assumed load case, optimized control inputs $u_{\mathrm{e}}(k)$, stored electrical energy $x_{\mathrm{e}}(k)$ and supply temperature $T_{\mathrm{e,}1}(k)$ for both scenarios. Admissible operating boundaries are indicated by dash-dotted lines.