Sammendrag
The large-scale introduction of offshore renewable generation will indeed require a multi-terminal
HVDC transmission system—based on voltage source (power) converters—in order to efficiently
transfer the offshore power to shore over long distances. The conventional power converter control
solutions associated to this technology (typically based on standard current control methods) have
been designed to satisfactory operate near a single nominal operating point. This makes them
inherently unsuitable for guaranteeing uninterrupted operation (stability) of the system in the
event of an unexpected large signal-disturbance. Moreover, the offshore HVDC grid architecture
complexity is expected to increase as more lines and renewable energy sources are connected to
the grid. It then seems desirable to find control alternatives able to operate the system with large-signal stability guarantees, preserved regardless of any topological change or system disturbance
size—and therefore avoiding any costly operational interruption of the system.
This manuscript presents the Energy Balance Based Adaptive (EBBA) outer-loop rooted in the Immersion & Invariance methodology, which replaces the traditional outer-loops while preserving the
large-signal stability certificate on 2-Level VSCs. This novel controller places particular emphasis
on the estimation of the system parameters, crucial for the converter load-flow computation. Additionally, for the development of this Master’s Thesis port-Hamiltonian representation, Lyapunov
theory and Passivity Based Control strategy are used.