A new modular multilevel converter for HVDC applications

Hassan, Zain (2021) A new modular multilevel converter for HVDC applications. PhD thesis, University of Nottingham.

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In the coming years, due to an increasing shift towards electric mobility and further industrialisation, a rapid growth in the demand for electricity is expected. At the same time, this energy demand must be met in a clean and sustainable manner, to reduce climate change as well as to ensure security of supply. It is predicted that the High Voltage Direct Current (HVDC) transmission technology will play a key role in the future power systems which are expected to feature higher levels of interconnection and more renewable-based generation. HVDC transmission is preferred over AC transmission in applications such as power transmission over long distances and from offshore wind sources, and interconnection of asynchronous systems. The main elements of an HVDC system are the AC/DC converters that take up the majority of the initial set up cost, and therefore, there has been a huge focus lately on improving these converters in terms of functionality, cost and efficiency.

Today, the state-of-the-art converter topology for Voltage Source Converters (VSC) based HVDC transmission is the Modular Multilevel Converter (MMC), which replaced the earlier two- and three-level VSC topologies. Recently, a new breed of VSC converters, known as the `hybrid VSCs' are introduced, that combine the aspects of two- and three-level VSCs with the modular multilevel structure of the MMC.

In this work, a new hybrid VSC, the Switched Mid-Point Converter (SMPC), has been proposed. While maintaining the same efficiency as the MMC, the energy storage requirement of the SMPC is shown to be less than half of that of the MMC. The operating principle and the particular voltage waveshaping of the chainlinks of the submodules is investigated. For effective operation of the SMPC, suitable control strategies are proposed. The converter concept and the developed control schemes are verified both using computer simulations and a lab-scaled experimental prototype.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Clare, Jon
Watson, Alan
Keywords: High Voltage DC, Power Converters, Modular Multilevel Converter, Hybrid VSCs
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK3001 Distribution or transmission of electric power
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 64832
Depositing User: Hassan, Zain
Date Deposited: 02 Oct 2023 08:58
Last Modified: 02 Oct 2023 08:58
URI: https://eprints.nottingham.ac.uk/id/eprint/64832

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