Non-isolated DC/DC converters based on Modular Multilevel Converters for application in high power DC transmission grids

Aberdeen HVDC research centre is offering a PhD research project on the topic of high-power DC/DC converters using MMC technology. The candidate should have good background knowledge in power electronics, power systems and control engineering, and should be motivated to perform theoretical research, simulation studies, but also hardware-based development and testing in the laboratory.

The DC/DC converters take the role of transformers in facilitating power exchange between two DC systems of different DC voltages, and therefore they are expected to become a key component in future DC transmission grids. They will also provide the function of DC Circuit breakers, although this is new application which needs much further research.

Modular multilevel converters have become standard topology for high power applications in the last 10 years. However MMC topology has been used mainly for AC/DC conversion.

This project will research the topologies for direct DC/DC conversion using MMC topology. Direct conversion (without intermediate transformers) offers the advantages in terms of component count, losses and converter size.

It is important to understand the trade-offs between performance and costs/size, as well as options for the topology and structure of these converters. The response under DC faults and DC Circuit Breaker function are very important research questions for any high-power converter.

The project will employ theoretical studies and simulations using detailed converter models on PSCAD simulation platform. Further demonstrations and testing may be carried on a hardware M2DC DC/DC converter in the HVDC centre laboratory.

Aberdeen HVDC research centre is offering a PhD research project on the topic of high-power DC/DC converters using MMC technology. The candidate should have good background knowledge in power electronics, power systems and control engineering, and should be motivated to perform theoretical research, simulation studies, but also hardware-based development and testing in the laboratory.

The DC/DC converters take the role of transformers in facilitating power exchange between two DC systems of different DC voltages, and therefore they are expected to become a key component in in future DC transmission grids. They will also provide the function of DC Circuit breakers, although this is new application which needs much further research.

Modular multilevel converters have become standard topology for high power applications in the last 10 years. However MMC conversion has been used only with 50Hz applications.

This project will research the feasibility of developing MMC for higher frequencies with the aim of application in DC/DC converters. The optimal operating frequency will be determined based on an in-depth background research compromising the efficiency, size, cost, and insulation aspects of various components. It is important to understand the physical limitations of a long string of (up to hundreds of) MMC cells when the frequency of fundamental oscillating signal is increased. The constraints also exist in the control circuit since very fast balancing of large number of capacitors is needed in a very short time.

The project will employ theoretical studies and simulations using detailed converter models on PSCAD simulation platform. Further demonstrations and testing will be carried on a hardware 30kW MMC-based DC/DC converter in the HVDC centre laboratory.

Candidates should have (or expect to achieve) a UK honours degree at 2.1 or above (or equivalent) in Electrical and Electronic Engineering.

It is essential that the successful applicant has a background in Electrical and Electronic Engineering and knowledge of Power Electronics and Power Systems.

APPLICATION PROCEDURE:

• Apply for Degree of Doctor of Philosophy in Engineering
• State name of the lead supervisor as the Name of Proposed Supervisor
• State ‘Self-funded’ as Intended Source of Funding
• State the exact project title on the application form

When applying please ensure all required documents are attached:

• All degree certificates and transcripts (Undergraduate AND Postgraduate MSc-officially translated into English where necessary)
• Detailed CV

Informal inquiries can be made to Prof D Jovcic ([Email Address Removed]) with a copy of your curriculum vitae and cover letter. All general enquiries should be directed to the Postgraduate Research School ([Email Address Removed])

The other supervisor on this programme is Dr Peng Li (School of Engineering)