Control and power management
of DRU HVDC based offshore WPP

Assessment of existing solutions, proposition of enhanced grid forming control and
umbilical cable free black start strategy

Description

An extensive review and assessment of existing grid forming solutions are done, implementing some of them in EMT models. This review is completed by an in depth analysis and understanding of the physical behavior of the OWF in both islanding (DRU not conducting) and connected operation modes. An enhanced grid forming solution is proposed, concatenating some principles proposed in existing solutions. It consists in the modification of the WTG grid side converter control to achieve active power control by managing AC collector magnitude and to regulate the AC collector frequency through a distributed reactive power Q/f droop control (all WTGs participating to frequency regulation). This solution does not need any measurement of the voltage phase at the WTG grid side converter output through a phase lock loop (PLL). A new black start strategy is proposed and implemented. This strategy relies on using local energy storage systems (ESS) at some WTG locations and as much as possible wind energy for full energization of the OWF. A discrete event system (DES) based supervisor is implemented to manage the different sequences of the OWF black start. This supervisor is able to deal with normal and fault operations during the black start sequences.

TRL SCALE

TRL_3_9_SuperGrid_Institute

Advantages

  • Cost reduction by removing the umbilical MVAC cable
  • An extensive review and assessment of existing grid forming solutions
  • A enhanced and robust (no need for voltage phase measurement with PLL) grid forming solution
  • A black start solution using as much as possible wind energy

Applications

  • DRU HVDC based offshore WPP
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