2. Steady-state operation

2.1 PQU diagram

The active and reactive power of a VSC converter can be controlled independently within the limits of its PQ diagram (active power, reactive power, and AC voltage).

These limits depend on the physical dimensions of the converter station components. They can be determined based on three variables:

1. The maximum alternating current at the connection point, mainly affected by:

   • maximum current through the coupling transformer,

   • maximum AC portion of the current through the half-arm inductors,

   • maximum AC portion of the current through the valves;

2. The maximum AC voltage...