Energy-based control schemes of modular multilevel converters for hvdc applications
- Autores: Enric Sánchez Sánchez
- Directores de la Tesis: Oriol Gomis Bellmunt (dir. tes.), Eduardo Prieto Araujo (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2020
- Idioma: español
- Materias:
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- Resumen
High Voltage Direct Current (HVDC) is a power electronics -based technology that enables the transmission of large amounts of power over long distances, the integration of remote offshore wind power to the main land, and the interconnection of asynchronous AC systems. The Modular Multilevel Converter (MMC) is the state-of-the-art technology for Voltage Source Converter (VSC) based HVDC applications .
As compared to the two-level converter, the MMC presents a more complex control scheme. However, it brings additional flexibility into the system. The present work focuses on the (energy-based) control of the MMC for HVDC applications , aiming to understand the additional degrees of freedom related to the internal energy of the MMC. First, DC voltage regulation in HVDC point-to-point links. Moreover, an experimental validation using a scaled MMC-based point-to-point link is carried out, particularly focusing on a novel experimental design of an HVDC cable emulator. With such a laboratory setup, the simulated system dynamics are contrasted with experiments . Furthermore, a generic controller for the same application is presented, and different optimal tuning techniques are addressed. Thus, the most suitable control gains are obtained automatically based on system constraints. In HVDC applications such as remote offshore wind farm clusters or isolated systems with low or non-existing synchronous generation, the MMC needs to operate as grid-forming. The present work explores the role of the internal energy of the MMC through different control structures . Finally, a multi-terminal HVDC grid where some terminals share the regulation of the DC voltage and others operate in grid-forming mode is considered, addressing the distributed DC voltage droop control design.
