Protection systems for HVDC-VSC converters

The purpose of the protection system is to quickly take the HVDC link out of service in the event of a fault, such as when a short circuit on the AC grid is cleared too late or when the HVDC station begins to operate in an unusual manner that could cause damage or interfere with the operation of the rest of the grid. The protection system then sends a blocking command to the valves and then an opening command to the AC circuit breakers at the interfaces with the AC grid in order to isolate the HVDC link from the rest of the AC grid.

In the event of temporary external faults in the AC grid, the HVDC-VSC can stop or limit power transmission until the fault has been eliminated. However, during the voltage dip, the converter must remain stable and the protection system must not send a trip command as long as the voltage remains within the voltage dip template defined...