Cluster Supervisory Control of large Offshore Wind Power Plants

Offshore wind power plants (OWPPs) are emerging as a promising technology among renewable energy generation over conventional power plants. Nowadays, WPPs are being grouped together resulting in the formation of a ‘cluster’. A wind power plant cluster is thus a logical (and of course electrical) aggregation of independent physical offshore WPPs geographically existing in close proximity which are connected to the same grid node.

The aim of such a ‘cluster’ formation is to increase its grid integration capabilities, admit more wind energy into the grid, allow the wind energy to better fulfil the Transmission System Operator (TSO) requirements and allow TSOs to govern wind energy as a conventional source of power. The individual WPPs could be owned by same or separate owners and they could be AC connected or connected through a Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) link to the shore. For such an integration, VSC-HVDC transmission system qualifies as a technically preferred solution as the distance of OWPPs from the shore is becoming ever larger.

However, there are no cluster supervisory controllers existing in practice in the offshore wind power plants today. The lack of regulatory, operational and technical framework for a cluster controller that will operate on several assets with different legal owners prohibits its existence today.

Project description:

There are different control hierarchies within an OWPP cluster, starting with converter control, WT level control, WPP level control and then the higher level cluster control communicating with the individual WPP controllers. Based on this understanding, the suitable control architectures that could be used to control very large offshore WPP clusters will be investigated besides the different possible control strategies for offshore grid voltage.
The OWPP cluster control should be able to adjust and allocate the active and reactive power reference set points to the OWPPs so as to maintain the power balance during normal, fault and post fault conditions. The role and performance of cluster control under normal, fault and post fault conditions will be investigated in addition to the fault ride through capability of the WPP cluster.

The Ph.d. project will include the following activities:

  • Investigate the different control hierarchies in a WPP and develop the model for OWPP with complete control architecture.
  • Develop a model for OWPP cluster with a VSC HVDC transmission system and investigate the control strategies for offshore grid voltage.
  • Implement the active and reactive power control during steady state and evaluate the performance using time domain simulations.
  • Extend the study to investigate the AC interconnection of OWPPs with multiple offshore VSC stations and develop the control for this configuration.
  • Analyse the dynamic cluster control performance during and post faults (inspired by on-going projects) conditions using time domain simulations.
  • Examine the contribution of cluster controller in Low Voltage Ride Through (LVRT)/Fault Ride Through (FRT) capability of HVDC connected OWPP cluster.
  • Perform the small signal modeling or mathematical modeling of the system for theoretical verification.

Expected outcome:

  • Models for OWPP cluster configurations with different control levels for time domain simulations
  • Controller for active and reactive power management within OWPP cluster during normal, fault and post fault conditions
  • Control strategies for AC interconnected OWPPs with multiple offshore VSC stations
  • A small signal model of the system for theoretical verification
  • Case study for faults inspired by on-going projects

Contact

Anup Kavimandan
PhD student
DTU Wind Energy