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Dual Grid-Forming Converter

Federico Milano

Abstract

This letter proposes a dual model for grid-forming (GFM) controlled converters. The model is inspired from the observation that the structures of the active and reactive power equations of lossy synchronous machine models are almost symmetrical in terms of armature resistance and transient reactance. The proposed device is able to compensate grid power unbalance without requiring a frequency signal. In fact, the active power control is based on the rate of change of the voltage magnitude. On the other hand, synchronization and frequency control is obtained through the reactive power support. The letter shows that the proposed dual-GFM control is robust and capable of recovering a normal operating condition following large contingencies, such as load outages and three-phase faults.

Dual Grid-Forming Converter

Abstract

This letter proposes a dual model for grid-forming (GFM) controlled converters. The model is inspired from the observation that the structures of the active and reactive power equations of lossy synchronous machine models are almost symmetrical in terms of armature resistance and transient reactance. The proposed device is able to compensate grid power unbalance without requiring a frequency signal. In fact, the active power control is based on the rate of change of the voltage magnitude. On the other hand, synchronization and frequency control is obtained through the reactive power support. The letter shows that the proposed dual-GFM control is robust and capable of recovering a normal operating condition following large contingencies, such as load outages and three-phase faults.
Paper Structure (8 sections, 17 equations, 5 figures)

This paper contains 8 sections, 17 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Rationale and Proposed Dual GFM Control Model
  3. Dual Swing Equations
  4. Dual Primary Controllers
  5. Case Study
  6. WSCC 9-bus System
  7. All-Island Irish Transmission System
  8. Conclusions

Figures (5)

  • Figure 1: Classical transient model of the synchronous machine with inclusion of armature losses.
  • Figure 2: Control scheme of the dual-GFM converter.
  • Figure 3: WSCC 9-bus system -- Behavior of relevant variables of the dual-GFMs connected at buses 1-3 following a $20\%$ loss of load at bus 5.
  • Figure 4: WSCC 9-bus system -- Behavior of relevant variables of the dual-GFMs connected at buses 1-3 following a fault at bus 7 occurring at $t=1$ and cleared after $60$ ms.
  • Figure 5: All-island Irish transmission system -- Behavior of relevant variables of three dual-GFMs following the outage of a large load.