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Scheduling of Software-Defined Microgrids for Optimal Frequency Regulation

Zhongda Chu, Guoxuan Cui, Fei Teng

TL;DR

The paper tackles frequency stability in software-defined microgrids with high inverter-based resource penetration by jointly optimizing virtual inertia, virtual damping, and non-essential load shedding within a software-defined scheduling framework. It develops SOC-based nadir constraints, linear RoCoF/steady-state constraints, and robust formulations to account for IBR update failures, all integrated into a two-stage stochastic microgrid schedule. Case studies on a modified IEEE 33-bus system demonstrate significant economic benefits from simultaneous inertia/damping provisioning and show the critical impact of non-essential load shedding delays and update robustness on frequency security. The work provides a practical, cyber-resilient approach to coordinating IBRs and demand-side actions for reliable islanding frequency regulation in future power systems.

Abstract

Integrated with a high share of Inverter-Based Resources (IBRs), microgrids face increasing complexity of frequency dynamics, especially after unintentional islanding from the maingrid. These IBRs, on the other hand, provide more control flexibility to shape the frequency dynamics of microgrid and together with advanced communication infrastructure offer new opportunities in the future software-defined microgrids. To enhance the frequency stability of microgrids with high IBR penetration, this paper proposes an optimal scheduling framework for software-defined microgrids to maintain frequency stability by utilizing the non-essential load shedding and dynamical optimization of the virtual inertia and virtual damping from IBRs. Moreover, side effects of these services, namely, the time delay associated with non-essential load shedding and potential IBR control parameter update failure are explicitly modeled to avoid underestimations of frequency deviation and over-optimistic results. The effectiveness and significant economic value of the proposed simultaneous and dynamic virtual inertia and damping provision strategy are demonstrated based on case studies in the modified IEEE 33-bus system.

Scheduling of Software-Defined Microgrids for Optimal Frequency Regulation

TL;DR

The paper tackles frequency stability in software-defined microgrids with high inverter-based resource penetration by jointly optimizing virtual inertia, virtual damping, and non-essential load shedding within a software-defined scheduling framework. It develops SOC-based nadir constraints, linear RoCoF/steady-state constraints, and robust formulations to account for IBR update failures, all integrated into a two-stage stochastic microgrid schedule. Case studies on a modified IEEE 33-bus system demonstrate significant economic benefits from simultaneous inertia/damping provisioning and show the critical impact of non-essential load shedding delays and update robustness on frequency security. The work provides a practical, cyber-resilient approach to coordinating IBRs and demand-side actions for reliable islanding frequency regulation in future power systems.

Abstract

Integrated with a high share of Inverter-Based Resources (IBRs), microgrids face increasing complexity of frequency dynamics, especially after unintentional islanding from the maingrid. These IBRs, on the other hand, provide more control flexibility to shape the frequency dynamics of microgrid and together with advanced communication infrastructure offer new opportunities in the future software-defined microgrids. To enhance the frequency stability of microgrids with high IBR penetration, this paper proposes an optimal scheduling framework for software-defined microgrids to maintain frequency stability by utilizing the non-essential load shedding and dynamical optimization of the virtual inertia and virtual damping from IBRs. Moreover, side effects of these services, namely, the time delay associated with non-essential load shedding and potential IBR control parameter update failure are explicitly modeled to avoid underestimations of frequency deviation and over-optimistic results. The effectiveness and significant economic value of the proposed simultaneous and dynamic virtual inertia and damping provision strategy are demonstrated based on case studies in the modified IEEE 33-bus system.
Paper Structure (23 sections, 1 theorem, 39 equations, 14 figures, 3 tables)

This paper contains 23 sections, 1 theorem, 39 equations, 14 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Microgrid Frequency Dynamics
  3. Frequency Trajectory After Unintentional Islanding Events
  4. Modeling of Virtual Inertia from Wind Turbines (WTs)
  5. Modeling of Virtual Inertia and Damping from Energy Storage Devices
  6. Derivation of Frequency Metrics
  7. Frequency Constraint Formulation
  8. Frequency Nadir Constraint
  9. RoCoF and Steady-State Frequency Constraints
  10. Robust Frequency Constraints Against Parameter Update Failure
  11. Software-Defined Microgrid Scheduling with Optimal Frequency Regulation
  12. Objective Function
  13. Constraints
  14. Constraints of battery storage system
  15. Frequency security constraints subsequent to islanding events
  16. ...and 8 more sections

Key Result

Proposition 1

$\forall\, \mathsf{k}\in\Set{0,1, ..., k}$, $\exists \, \mathsf{z}^{F,*}_{\mathsf{k}} \in \mathsf{Z}^F_{\mathsf{k}}$, such that $\left| \Delta f_{\mathrm{max}}(\mathsf{z}^{F,*}_{\mathsf{k}}) \right | \ge \left| \Delta f_{\mathrm{max}}(\mathsf{z}^{F}) \right |$, $\forall\, \mathsf{z}^{F} \in \mathsf{

Figures (14)

  • Figure 1: Relationship between disturbance and load shedding.
  • Figure 2: Overall framework of the proposed software-defined microgrid scheduling.
  • Figure 3: Single line diagram of modified IEEE 33-bus system.
  • Figure 4: Microgrid frequency and RoCoF evolution after an islanding event.
  • Figure 5: Frequency nadir histogram with 95% confidence interval of one-day scheduling.
  • ...and 9 more figures

Theorems & Definitions (1)

  • Proposition 1