Constraints on HVDC injections in AC networks

摘要

This paper presents a constraint formulation for the dynamic control of HVDC links that are used to support the surrounding AC power grid during power oscillations and electromechanical transients. The admissible HVDC injection references have to respect physical constraints, imposed by the converter and the strength of the connected AC network. The main result is a derivation of the HVDC constraint set based on the AC grid model and the original voltage and current bounds. The set is convex and a closed form expression of the boundary can be computed. As a second result, it is shown how the constraint set can be computed without using a full AC grid model, but only local parameters of the HVDC buses. The result is a generalization of the classical HVDC PQ-chart, which assumes a constant AC bus voltage at the HVDC terminals. It is particularly useful for HVDC control in power grids with intermittent sources and a wide range of operating conditions, where the constant bus voltage assumption does not hold.