Grid Forming Preserving Control Current Limitation Strategies and Impacts on Grid Support

This paper discusses current limitation for HVDC grid forming converters. Section 1 gives a general introduction where different ways of limiting converter current during grid events are discussed. For grid forming converters, directly changing current orders via K-factor to limit current, is not applicable since grid forming properties are then lost. It is stated that a reasonable alternative to limit the current, is instead to limit only the current magnitude to support frequency and voltage. This can be done either by altering the voltage behind impedance or by scaling the current reference vectors if an embedded current controller is employed. Section 3 describes how the voltage behind impedance can be altered in a consistent way to achieve this for different grid events and that this…