A novel VSC HVDC active power control strategy to improve AC system stability

Bulk power transfer requirements over long distances within a country or between neighboring countries as, well as a large growth in offshore wind farms, have increased the number of high voltage DC links. Apart from the controllable power flow function of HVDC systems, advanced controllers can be employed to extend their functionality for dynamic and transient stability improvement of AC systems. As an attempt to improve the influence of HVDC technology on AC system transient stability, this paper proposes a supplementary active power controller for the VSC HVDC grid side converter. The presented simulation results prove the effectiveness of the proposed method. Relatively large-sized dump loads have been installed within the power system for protective measures against a surplus of generated power. They are distributed over the network and they normally connect to the circuit when a trip signal is issued. DC choppers in HVDC systems as well as wind turbine converters, dump loads in synchronous generators and in wind turbines comprise these distributed dump resistive loads in the network. The effect of the DC chopper to improve active power controllability for improved transient stability has also been tested and verified through the simulations.