Power Capability Domain Analysis for M2DC-Based AC/DC/DC Multi-Port Converter

This paper addresses the power capability domain calculation for the specific M2DC-based AC/DC/DC multi-port converter. Such a power capability domain will represent all the possible power flow scenarios (comprehensive of active and reactive power components) the converter can withstand without exceeding the physical limitations (due to the established ratings of installed components, e.g., semiconductors current and voltage). Concerning conventional two-port modular multilevel converters, the <tex-math notation="LaTeX">$P-Q$</tex-math> power capability curve is one of the most common tools employed to track the safe operating region of the converter. However, the increased number of ports and the topology changes on multi-port converters lead to evaluating and representing the power capability domain in a non-conventional way. This article evaluates the power capability of the specific M2DC-based AC/DC/DC asymmetrical monopole converter. Moreover, internal converter asymmetries are considered in the study to express analytical voltages and current behaviour as a function of terminals powers. Then, the power capability domain is calculated and represented for a use-case scenario in which the multi-port converter interconnects High Voltage DC and Medium Voltage DC networks to the AC transmission network. The study also includes power capability domain modifications under port contingencies scenarios, such as fault and port disconnection.