Ancillary services and operation of multi-terminal HVDC grids

This paper addresses the problem of ancillary services in ac systems interconnected by a multi-terminal HVdc system. It presents opportunities for new control schemes and discusses operation strategies for three types of HVdc grid operators, namely a coordination center, an independent operator, and the transmission system operator in charge of one of the areas interconnected by the multi-terminal HVdc grid. In these contexts, the paper envisions the challenges of using the HVdc infrastructure to provide frequency, voltage, and rotor angle stability-related ancillary services. It also analyzes the technical and economic impacts of the operation strategies on the ac areas’ dynamics.