Generalized voltage droop control with inertia mimicry capability - step towards automation of multi-terminal HVDC grids

Abstract

The level of inertia in modern power systems is reducing drastically due to the increasing penetration of renewables to the power grid. In the near future the grid will face high penetration of renewable resources because of countries policies. However, renewables provides no inertia. On the other hand, voltage source converter (VSC) based multi terminal HVDC system is a promising solution for connection of offshore wind farms to transmit huge amount of harvested energy to ac grids. This paper proposes a complete VSC-HVDC control structure which enables candidate converter station to mimic the inertia of a synchronous machine considering generalized voltage droop strategy. The emulated inertia comes from the capacitor of the dc link. The proposed strategy enables a VSC station with a fixed dc link capacitor to mimic inertia constant in a considerable range, by configuring a range of dc-link dc voltage variation. Sudden load changes in weak ac grid will be compensated by the emulated inertia that is provided by the candidate grid side VSC station.