Library Categories: Technical Reports

Stability Assessment and Mitigation of Converter Interactions (Phase I)

A key research outcome of ‘’Stability Assessment and Mitigation of Converter Interactions (Phase I)’’ project with the University of Strathclyde

The article discuss the details about the innovative analytical methods for small-signal impedance model of modular multilevel converters (MMCs) using harmonic state-space (HSS) method and is studied the stability assessment of single and multiple converters that University of Strathclyde has developed. In this impedance model, the multi-infeed interaction factor (MIIF) measure is adopted to analyse the most significant interactions for multi-infeed converter systems. The effect of different control modes on converter impedance and system stability are considered. The analytical studies and time-domain simulation results are provided to validate the proposed concept and gained further confidence of the obtained impedance models using both methods. This work provides solid foundation for further studies to identify states where risk of instability may exist in a multi-infeed converter system, so as to help and inform operating away from those network or avoid certain converter operating states.

This paper has been accepted in the prestigious IEEE Journal.

Pre-Print version:

To access this paper:


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Evolution of Protection Testing in Low-Strength and Converter-rich areas within the GB Grid

Protection schemes form part of the most fundamental components of any power system. They ensure that when faults occur on networks, the effect of the fault is seen only briefly by the wider system and its connections, isolating the faulted infrastructure or generator from the network, hence allowing the healthy elements to continue to operate. By doing so, risks to personnel and risks of damage to the infrastructure of the AC power system are reduced. This article explains how declining system strength presents challenges to confidence over future protection relay operation – and highlights how the HVDC Centre is helping to address these challenges. Click here to read the full briefing note or Download  file below.

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De-risking Integrated Offshore Networks in GB

The Offshore Wind Industry Council (OWIC) transmission group sought guidance from the National HVDC Centre on options for de-risking integrated offshore transmission approaches in GB. The HVDC Centre in consultation with industry led publication of a report, which identifies that:

  • Integrated offshore transmission is technically feasible for projects at design stage;
  • Solutions can be built in stages to meet offshore wind growth and benefit the onshore grid; and
  • Bipole HVDC with return cable option appear to offer greater flexibility and less export cables.

Click here for the full report published on 25 June 2020.


Download File (PDF, 1.50 MB)

Grid-access Technologies for GB Offshore Wind Industry

The National HVDC Centre leads publication of technology report for the Future Transmission Group of the Offshore Wind Industry Council (OWIC). Click here to read the full report published in January 2020.

Executive Summary

The UK Government has set an ambitious target to reduce all greenhouse gas emissions to net zero by 2050. This would require large-scale integration of up to 75GW offshore wind capacity into the GB electricity system, up from 8GW in 2018, according to the Committee on Climate Change. The coordinated development of future offshore electricity transmission infrastructure is essential to achieve the levels of deployment required 

With government’s commitment to a strategic target (of 40GW of offshore wind by 2030), the Offshore Wind Industry Council (OWIC) wanted to investigate how the future offshore electricity transmission system should develop to realise the full potential of GB’s offshore wind resource.  

In response to this, the OWIC formed a Future Offshore Transmission group comprising a Technical Solutions work stream led by The National HVDC Centre in collaboration with three offshore windfarm developers (EDPR, Scottish Power Renewables and Vattenfall) and the Offshore Renewable Energy (ORE) Catapult. The technical solution work stream led a review into Grid-access Technologies for the GB Offshore Wind Industry. 

This report, by the Technical Solutions work stream identifies the following issues to be analysed: 

  1. Integrated electricity transmission planning – coordinated planning can facilitate economic and efficient development of future offshore and onshore transmission networks, based on High Voltage -Alternating Current (HVAC) or Direct Current (HVDC) technologies; 
  2. Key enabling infrastructures  – shared transmission assets such as coastal HVAC grid hubs; offshore HVDC hubs; and demonstration and innovation hubswould be required to realise the full potential of GB’s offshore wind resource; and 
  3. Design authority and system operator – there is a need to plan appropriate enabling infrastructures and funding of the future offshore transmission systems. 

The full report publish in January 2020 is available at:

Download File (PDF, 1.12 MB)