PhD position – “Analysis of the DC fault-ride-through capability of high voltage AC-DC transmission systems towards their optimal design”

Posted 1 month ago

SuperGrid Institute brings together 180 employees of 28 different nationalities who work together within a dynamic environment in the city of Lyon. As an independent research and innovation centre, we are dedicated to developing technologies for the future power transmission system, the “SuperGrid”, including HVDC & MVDC technologies.

As a multi-disciplinary research centre with advanced simulation capabilities & multiple test platforms, including numerous associated laboratories, SuperGrid Institute uses its comprehensive expertise to provide a wide range of services and solutions to support our customers in developing power systems, equipment, and components. We specialize in system architecture and work on ensuring network security and stability while allowing for the integration of intermittent renewable energy sources. Find out more by visiting our website: www.supergrid-institute.com

General Context

Integration of large amount of renewable energy sources (RES) (e.g., offshore wind, PV) and energy market integration are two of the main drivers for the future development of the pan-European power grid. This will require a reinforcement of the transmission grid to make it able to transport large amount of power over long distances from generation areas to load areas. Extended High-Voltage Direct Current (HVDC) grids, in Point-to-point (PtP) or Multi-Terminal (MTDC) configuration, covering large distances, are considered to be the preferable solution for the reinforcement of the grid. Those systems will be evolving from simple point to point and radial structures to complex meshed ones. To achieve their development, it is necessary to enhance their operating procedures with major challenges in control and protection. Developing such HVDC systems together with the massive integration of RES, will result in a power system with more and more Power Electronics Interfaced Devices (PEIDs), where AC/DC converters (e.g., VSCs or Modular Multi-level Converters (MMC)) are a key component and have a significant impact on the integrated AC/DC transmission system behavior. Such AC/DC power systems with high integration of RES will be possible only if it can be demonstrated that they are economically viable and that their resilience and reliability can be assured under any realistic condition (normal operation and disturbed situation).

Position Context

The Horizon Europe HVDC-Wise project proposes solutions to foster the development of large HVDC grid infrastructures, able to bring benefits in terms of resilience and reliability to the existing electrical system and capable of integrating the forthcoming large amount of renewable energy.  To this end, The HVDC-Wise project aims to: 1) Propose a set of technological solutions in terms of HVDC architecture and operational algorithms (control and protection) to harness the full potential of HVDC to increase the resilience of the AC/DC system. 2) Provide the necessary tools and methodologies to analyze the reliability and resilience levels of AC/DC systems integrating the proposed HVDC solutions, allowing their design. 3) Validate the proposed solutions on realistic use cases using the developed tools.

The PhD topic described in the following sections focuses on objectives 1 and 3.

 

PhD topic description

 

Scientific context:

The optimal development of future HVDC networks cannot be achieved without clarifying their interactions with AC networks, while considering medium- and long-term perspectives, such as the integration of renewable energies and the development of an HVDC backbone in Europe.

When a DC fault occurs in an HVDC network, AC systems that interface with that HVDC network may experience a temporary power disturbance generated by the loss of active and reactive power supplied by the HVDC network. The magnitude of this disturbance depends on the design of the HVDC network and especially on the design of its protection system.

A given AC system, interfaced with a HVDC grid, may have a capability to tolerate a temporary power disturbance of a given magnitude during DC fault-ride through. This capability depends on the reserves of this particular AC system (e.g., inertial reserves). Nevertheless, current security criteria for AC transmission systems, mainly consider Permanent Loss of Infeed, and do not consider a Temporary Loss of Infeed of higher magnitudes. This approach might be too conservative and lead to a sub-optimal design of AC-DC system.

Therefore, it is proposed to focus this PhD research project on the analysis of the impact of a temporary loss of DC power infeed (respectively active and reactive power) on the AC transmission systems that are connected to the HVDC grid. Ultimately, the research question to be answered is the following one: what shall be the optimal AC-DC system design to be tolerant to DC fault contingencies, taking into account the trend to develop a back-bone HVDC grid to achieve wide-spread AC-DC transmission networks?

Scientific work:

The work will entail deep analysis of the AC-side impacts of DC faults, when various DC protection strategies are used. The risk on system operation will be qualified and discussed with TSO partners from HVDC-WISE project. A combination of analytical approaches (simplified models) and numerical models (benchmark grid models) will be defined.

The work will also entail a review of design features (available technological devices, DC grid configuration, control and protection algorithms, etc.) that could enable DC-fault ride through of AC-DC systems. The main design options (consistent combination of features) for the AC-DC system will be proposed. Particular attention will be done on the design option of HVDC grids connected to AC systems with a high integration of renewable energy sources and power electronics devices. In order to go beyond the state of the art, the candidate may propose new design options (e.g. new protection sequences taking advantages of new technological devices, or new coordinated control algorithms to increase the DC-fault ride through of the entire system, etc.). The investigations will be done using benchmark AC-DC grid model(s) that will be modelled in EMT simulation software environments. In further stages of the project, possibly, cost-benefit analysis for different design features will be used to support the selection of most relevant options. This part of the work will be carried out in close interaction with the HVDC-WISE project activities and partners.

In a final stage of the project, a validation step will be carried out based on simulation experiments (HIL real-time simulation or off-line) to test the proposed/selected design features and to confirm the main findings.

The outcomes of the performed investigations during this PhD will help the transmission industry to formalize grid code draft recommendations on AC-criteria regarding Acceptable Temporary Loss of DC-Infeed.

References

[1] European Commission Set Plan:  Implementation plan on High voltage direct current (HVDC) & direct current (DC) technologies https://setis.ec.europa.eu/implementing-actions/set-plan-documents_en#implementation-plans

[2] PROMOTioN project Deliverable 4.2,

https://www.promotion-offshore.net/results/deliverables/

[3] Gonzalez‐Torres, J.C., Costan, V., Damm, G., Benchaib, A., Bertinato, A., Poullain, S., Luscan, B. and Lamnabhi‐Lagarrigue, F., 2018. HVDC protection criteria for transient stability of AC systems with embedded HVDC links. The Journal of Engineering, 2018(15), pp.956-960.

Candidate Profile

Engineering degree and/or Master’s degree in Electrical Engineering or in Control Engineering (or equivalent).

  • Technical skills:
    • Good skills in Modelling, analysis, and control of AC/DC power systems
    • Good skills in control theory and mathematics
    • Good skills in grid-connected converter control
    • Notions on Multi-terminal HVDC system control and protection
  • Other skills
    • Sens of deduction
    • Ability to work within a research team
    • Very good command of English language is a must (oral and written)
    • Ability to structure activities and planning in a pragmatic and efficient manner
    • Excellent synthesis skills.
    • Good communication and organizational skills

The application must be sent at the following address : juan-carlos.gonzalez@supergrid-institute.com and has to include the job title, candidate name, CV and the most recent marks.

SuperGrid Institute is an equal opportunities employer. We respect and value the diversity of our employees, their backgrounds and their professional experience. We believe in equality and take affirmative action to ensure that discrimination has no place in our recruitment process nor our company.

Job Features

Contract TypeCDD
Duration36 months
Start DateFrom October 2022

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