Workshop on Black-start from Grid-forming Converters: Transformers Inrush Current Mitigation

Abdulrahman Alassi, Ph.D., Power Systems Team Lead – Iberdrola Innovation Middle East, Doha-Qatar

Black-start from Grid-forming Converters: Transformers Inrush Current Mitigation

Abstract: “Black-start is a network restoration process that has been classically attributed to synchronous generators. The rising grid penetration of renewable-energy resources through power converters requires a shift to this classical paradigm. Though, unlike synchronous generators, power converters have very limited overcurrent capabilities to withstand the inrush currents resulting from transformer or cable energizations. This requires adapting the energization process to accommodate the converter limits through compatible inrush current mitigation techniques. This tutorial thus aims to provide hands-on insights on network restoration through a grid-forming converter, focusing on transformer inrush current mitigation strategies such as controlled-switching and soft energization. This process is influenced by several factors such as network parameters, converter control and the energized network. These factors are addressed in the tutorial”.

Duration: 3 hours

Session Needs: Participants are encouraged to have laptops equipped with PSCAD or MATLAB/Simulink for the hands-on session (optional).

Agenda:

Part 1: Theoretical Background (45 minutes).

• Power transformers saturation and inrush current causes.
• Transformer modelling.
• Transformer Core Flux: correlation between theory and practice.
  • Hard energization.
  • Point-on-wave (PoW) switching.
  • Soft Energization.
• Converter Control: Perceived Impact.

———————————- Break (15 minutes) ———————————-

Part 2: Hands-On Session (2 hours).

• Implementing a GFC-fed three-phase transformer model in PSCAD.
• Demonstrating the inrush current phenomenon.
• Validation of GFC compatible inrush current mitigation techniques.
• Impact of network and transformer and network parameters on inrush mitigation.
• Summary and takeaway messages.