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Frequency Control and Power Sharing in Combined Heat and Power Networks

Xin Qin, Ioannis Lestas

TL;DR

The paper tackles leveraging electrified district heating via heat pumps to provide primary frequency control while preserving stability in combined heat and power networks. It introduces an average-temperature control signal $\bar{T}$ to achieve optimal power sharing among electric and heating sources without requiring disturbance knowledge, and proposes two regulation schemes for heat pumps that guarantee stability in general network topologies. It proves stability under both Mode 1 (frequency-dependent load) and Mode 2 (converter-linked load) and extends the framework to general input-strictly passive dynamics, with simulations showing improved sharing and reduced frequency deviations, particularly under Mode 2. The work offers a scalable pathway for high-penetration electrified heating to participate in grid ancillary services, balancing system reliability, cost, and inertia-aware operation.

Abstract

We consider the problem of using district heating systems as ancillary services for primary frequency control in power networks. We propose a novel power sharing scheme for heating systems based on the average temperature, which enables an optimal power allocation among the diverse heat sources without having a prior knowledge of the disturbances. We then discuss two approaches for heating systems to contribute to frequency regulation in power networks. We show that both approaches ensure stability in the combined heat and power network and facilitate optimal power allocation among the different energy sources.

Frequency Control and Power Sharing in Combined Heat and Power Networks

TL;DR

The paper tackles leveraging electrified district heating via heat pumps to provide primary frequency control while preserving stability in combined heat and power networks. It introduces an average-temperature control signal to achieve optimal power sharing among electric and heating sources without requiring disturbance knowledge, and proposes two regulation schemes for heat pumps that guarantee stability in general network topologies. It proves stability under both Mode 1 (frequency-dependent load) and Mode 2 (converter-linked load) and extends the framework to general input-strictly passive dynamics, with simulations showing improved sharing and reduced frequency deviations, particularly under Mode 2. The work offers a scalable pathway for high-penetration electrified heating to participate in grid ancillary services, balancing system reliability, cost, and inertia-aware operation.

Abstract

We consider the problem of using district heating systems as ancillary services for primary frequency control in power networks. We propose a novel power sharing scheme for heating systems based on the average temperature, which enables an optimal power allocation among the diverse heat sources without having a prior knowledge of the disturbances. We then discuss two approaches for heating systems to contribute to frequency regulation in power networks. We show that both approaches ensure stability in the combined heat and power network and facilitate optimal power allocation among the different energy sources.

Paper Structure

This paper contains 17 sections, 4 theorems, 21 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Preliminaries
  3. Model Formulation
  4. Electric power system
  5. Heating system
  6. Generation control
  7. Heat pump
  8. Stability of Combined Heat and Power Network
  9. Power Sharing in the Combined Heat and Power Network
  10. Mode 1
  11. Mode 2
  12. General passive dynamics
  13. Problem Statement
  14. Stability under General Passive Dynamics
  15. Power Sharing under General Passive Dynamics
  16. ...and 2 more sections

Key Result

Theorem 5

Consider the combined heat and power network described by eq.edynamics-eq.pumpmodel, eq.pumpm1 or eq.edynamics-eq.pumpmodel, eq.pumpm2. Consider an equilibrium point of this system that satisfies Assumption assum.equ. Then, there exists an open neighbourhood of this equilibrium point such that all s

Figures (3)

  • Figure 1: Typology of the combined heat and power system.
  • Figure 2: (a) Frequency at bus 2 and bus 3, and (b) maximum frequency deviation in the transient response, where M2 denotes Mode 2 and M1 denotes Mode 1.
  • Figure 3: Power adjustments of (a) generators and (b) heat sources. The cost coefficients of the generators at buses 1 and 2 are 2 and 1, respectively, and the cost coefficients of the heat sources at edges 5 and 9 are 0.5 and 1.

Theorems & Definitions (7)

  • Remark 1
  • Remark 2
  • Remark 3
  • Theorem 5: Stability
  • Proposition 6: Optimality under Mode 1
  • Theorem 7: Optimality under Mode 2
  • Corollary 9