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Data-driven Coordinated AC/DC Control Strategy for Frequency Safety

Qianni Cao, Chen Shen

TL;DR

The paper tackles emergency frequency control in modern hybrid AC-DC grids with high renewable penetration by proposing CEFC, a data-driven framework that coordinates emergency DC power support with load shedding. It introduces a Koopman-operator-based, globally linear frequency model learned from data, enabling real-time prediction and optimization of both DC regulation and one-shot shedding via a moving-horizon and LQR-based control scheme. A robustness analysis establishes conditions under which modeling errors do not compromise shedding decisions, and a CEPRI-FS case study demonstrates improved prediction accuracy, reduced control cost, and reliable frequency safety under non-envisioned disturbances. The work advances practical EFC by combining fast DC power adjustability with carefully timed, minimal-load shedding, suitable for deployment in grids with strong converter penetration.

Abstract

With high penetrations of renewable energy and power electronics converters, less predictable operating conditions and strong uncertainties in under-frequency events pose challenges for emergency frequency control (EFC). On the other hand, the fast adjustability of converter-based sources presents opportunities to reduce economic losses from traditional load shedding for EFC. By integrating DC power emergency support, a data-driven coordinated AC/DC control strategy for frequency safety - Coordinated Emergency Frequency Control (CEFC) - has been designed. CEFC coordinates both the initiation and control amount of emergency DC power support (EDCPS) and traditional load shedding. Based on real-time power system response data, CEFC ensures system frequency safety at a minimum control cost under non-envisioned operating conditions and large power deficits. A sufficient condition where data-driven modeling errors do not affect the precision of the control strategy for power system frequency is rigorously provided. Simulation results demonstrate CEFC's adaptability, prediction accuracy, and control effectiveness.

Data-driven Coordinated AC/DC Control Strategy for Frequency Safety

TL;DR

The paper tackles emergency frequency control in modern hybrid AC-DC grids with high renewable penetration by proposing CEFC, a data-driven framework that coordinates emergency DC power support with load shedding. It introduces a Koopman-operator-based, globally linear frequency model learned from data, enabling real-time prediction and optimization of both DC regulation and one-shot shedding via a moving-horizon and LQR-based control scheme. A robustness analysis establishes conditions under which modeling errors do not compromise shedding decisions, and a CEPRI-FS case study demonstrates improved prediction accuracy, reduced control cost, and reliable frequency safety under non-envisioned disturbances. The work advances practical EFC by combining fast DC power adjustability with carefully timed, minimal-load shedding, suitable for deployment in grids with strong converter penetration.

Abstract

With high penetrations of renewable energy and power electronics converters, less predictable operating conditions and strong uncertainties in under-frequency events pose challenges for emergency frequency control (EFC). On the other hand, the fast adjustability of converter-based sources presents opportunities to reduce economic losses from traditional load shedding for EFC. By integrating DC power emergency support, a data-driven coordinated AC/DC control strategy for frequency safety - Coordinated Emergency Frequency Control (CEFC) - has been designed. CEFC coordinates both the initiation and control amount of emergency DC power support (EDCPS) and traditional load shedding. Based on real-time power system response data, CEFC ensures system frequency safety at a minimum control cost under non-envisioned operating conditions and large power deficits. A sufficient condition where data-driven modeling errors do not affect the precision of the control strategy for power system frequency is rigorously provided. Simulation results demonstrate CEFC's adaptability, prediction accuracy, and control effectiveness.
Paper Structure (17 sections, 22 equations, 4 figures, 1 table)

This paper contains 17 sections, 22 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. Motivation
  3. Literature Review
  4. Contribution
  5. Emergency Frequency Controller Design
  6. System frequency modelling
  7. Koopman-Operator-Based EFC Optimal Coordination Methods
  8. Activation of EFC
  9. Initiation for load shedding
  10. Load shedding strategy
  11. Optimal DC power reference regulation
  12. Robustness Analysis and Error Estimation
  13. Case Study
  14. Test System Description
  15. Prediction Accuracy
  16. ...and 2 more sections

Figures (4)

  • Figure 1: Comparison between true frequency trajectory(red) and predicted frequency trajectory during future 60s with proposed CEFC(blue).
  • Figure 2: Control effectiveness of CEFC
  • Figure 3: Comparison between CEFC and SOTAs on a scenario in the test set.
  • Figure 4: Comparison between the proposed closed-loop EDCPS and time-invariant EDCPS.