A Review on Grid-Connected Converter Control for Short-Circuit Power Provision Under Grid Unbalanced Faults

As an increasing amount of converter-based generation on power electronics is connected to power systems, transmission system operators are revising the grid-connection requirements to streamline the connectivity of the devices to maintain security of supply. Converter-based generation can behave significantly different from the traditional alternators under grid faults. In order to evaluate the potential impact of the future converter-based power systems on protective relays, it is necessary to consider diverse current control strategies of voltage-source converters (VSCs) under unbalanced faults as the performance of converters primarily depends on their control objectives. In this paper, current control strategies of VSCs under unbalanced faults for short-circuit power provision are reviewed in two groups, namely, power-characteristic-oriented and voltage-support-oriented control strategy, respectively. As the fault current provided by converters should be restricted within secure operation limits considering semiconductor capabilities, converter current limit issue is also discussed.