Selective Power Routing in MTDC Grids for Inertial and Primary Frequency Support
The possibilities of selectively providing inertial and primary frequency support as an emergency support service to asynchronous AC areas through multiterminal direct current (MTDC) grid with minimal-communication are explored. Under nominal condition, only voltage droop is considered to allow the AC systems operate asynchronously as they are meant to. When an AC system needs support, the corresponding converter transmits basic information via a distress signal through the DC lines or existing communication channels used for common DC voltage-droop control. Following AC-side disturbances, the frequency droop is activated with values that are predetermined based on our proposed design procedure, which ensures primary frequency support through selective converter participation. Model predictive control, which aims to achieve the best possible frequency dynamics with a single-point actuation is also implemented at the converter station connected to the affected area to provide inertial support. Following a converter outage, MTDC power references are modified to ensure minimal impact on the AC-side frequencies. Simulation studies showing the effectiveness of the proposed strategies are presented.