Electrical Infrastructure & System Integration

Developing reliable and cost-effective electric power components and system solutions to enable profitable large-scale deployment of offshore wind energy in the North Sea.

Work Package 3 is led by Marte Gammelsæter from SINTEF Energy Research and Magnus Korpås from NTNU. Its focus areas are electric power components and system integration of wind energy (WE).

Anticipated results:

  • Reliable and cost-efficient electric power components for
    energy collection
  • Optimised electrical architectures and operational solutions
    for cost- and energy-efficient grid connection
Marte Gammelsæter

Hypothesis

Large-scale offshore wind power can be collected, transmitted and integrated in existing electrical
power systems in a cost-efficient and reliable manner.

Methodology and research tasks

Infrastructure

AC-based export systems, thermal-electrical cable models, subsea substations, new component design, models for degradation and lifetime assessment.

System integration

Development of a framework for transient analysis and stability assessment of large hybrid AC/DC power systems offshore, advanced ancillary services provision from WFs, models to identify economically robust offshore grid configurations and improved legal and regulatory framework.

User case

132 kV Inter-array Cable Network

User Case 4 – FME NorthWind

Innovations

Main results from 2023

Combined User Case and research task: 132kV collection grids

A research task led by Andrzej Holdyk, SINTEF, and a user case led by Jalal Khodaparast from Mainstream with contributions from Statkraft, have both studied power system challenges in a 132 kV collection grid compared to a traditional 66 kV grid. Their joint work was presented as a poster at the EERA DeepWind conference in January 2024.

As wind farms and individual turbines grow in power output, a transition towards higher inter-array voltage level will be necessary to reduce the total number of cables needed and the losses related to power transfer at lower voltages. Increasing voltage level requires careful considerations and design investigations to guarantee the best solution. Two designs of large wind farms were benchmarked, one with a 66 kV collection grid and one with a 132 kV grid. A variety of power system analyses were conducted to assess the feasibility of the voltage transition within the inter-array network. Mainstream Renewable Power (MRP) focused on load flow analysis, reactive power management, export cable voltage, current profiles, and maximum direct connection lengths, while SINTEF performed resonance analysis and harmonic evaluations. The study provided valuable insights for optimising the 132 kV inter-array cable network and advancing the Technology Readiness Level (TRL) to meet the growing demands of offshore wind energy integration.

Publications (peer-reviewed)

PhDs

Lorrana Faria da Rocha, NTNU: Exploring a novel HVDC Drive to decrease cost of offshore wind energy
Department: Electric Energy
Main supervisor: Associate Professor Pål Keim Olsen
Period: 2021-2024

Arkaitz Rabanal Alcubilla, NTNU: Energy storage for grid services in HVDC connected offshore wind farms
Department: Electric Energy
Main supervisor: Professor Elisabetta Tedechi
Period: 2021-2024

Ingvild Ånestad, UiO: Regulatory aspects for development of offshore grid infrastructures
Department: Scandinavian Institute of Maritime Law
Main supervisor: Professor Catherine Banet
Period: 2023-2027

 

Previous results

Electrical infrastructure

  • Conference paper on electro-thermal cable models published in Journal of Physics: Conference Series
  • Conference paper on power electronics converters and architecture for modular HVDC wind generators published in POWERCON
  • Journal paper on steel armour modelling submitted to IEEE Trans. Power Delivery
  • Conference paper on models for degradation and lifetime assessment submitted to EERA DeepWind 2023
  • Two spin-off projects: KSP SeaConnect and KSP NewLifT

 

System integration

  • Conference paper on models to identify economically robust offshore grid configurations submitted to EERA DeepWind 2023
  • Journal paper on advanced ancillary services provision from wind farms submitted to the IEEE journal
  • Conference paper on market challenges for 100% renewable power systems submitted to the International conference on the European energy market (EEM22)
  • Newspaper op-ed on “30 GW wind power timeseries analysis” (Dagens Næringsliv – article in Norwegian)
  • Memo on Small-Signal State-Space Model MATLAB tool for interconnected AC/MTDC grids completed (in-kind from MODULATOR)

 

Electrical infrastructure

  • PhD candidate working on “Power electronics architecture and control methods for a HVDC generator for offshore wind”.
  • Abstract submitted on electro-thermal cable models, full paper to be submitted in 2022.
  • Memo on models for degradation and lifetime assessment, paper to be submitted in 2022.
  • PhD candidate working on “Novel Modular HVDC Generator for Offshore Wind” (associated with NorthWind but financed through other sources).

System integration

  • PhD candidate working on “Energy storage for grid services in HVDC connected offshore wind farms”.
  • Memo on models to identify economically robust offshore grid configurations, paper to be submitted in 2022.
  • Report on “Design and Operation of Energy Systems with Large Amounts of Variable Generation” (IEA Task 25).
  • Newspaper op-ed on Three prerequisites for Norwegian offshore wind success
    (Dagens Næringsliv – the article is in Norwegian).

 

 
Figure outlining how a virtual synchronous machine can be integrated to a wind turbine to allow it to provide ancillary services to the power system.
A virtual synchronous machine (VSM) is a common implementation scheme to provide grid forming capabilities and synthetic inertia.