Incorporation of active power ancillary services into VSC-HVDC connected energy sources

Abstract

This paper investigates the interaction between frequency containment services (FCS) and power oscillation damping (POD) ancillary services installed in a Voltage Source Converter High Voltage DC (VSC-HVDC) line. In VSC-HVDC systems, ancillary services can be installed to maintain appropriate levels of power system stability. Both FCS and POD controllers are typically installed in the active power control loop separately. The modulation signals generated by these two ancillary services both affect the active power injected by the converter. When operating a VSC with FCS and POD ancillary services the resultant combination of the modulation signals in the active power loop may result in reduced performance. The results in this study show that performance of controllers reduces when both ancillary services are activated, particularly in low-inertia systems. Modifications to the control structures of both controllers that improve their performance under various disturbances are proposed.