Virtual Synchronous Machine fault ride through capability with Reactive Power Synchronization

This paper presents the fault ride through capabilities of a proposed Virtual Synchronous Machine (VSM) control strategy for a Voltage Source Converter (VSC). In a grid which is evolving towards so-called smart grid, it is necessary to prove that power electronic converters have a good performance facing critical grid events. They must fulfill all grid operator requirements to guarantee supply reliability. The VSC is tested in a test bench with a synchronous generator (SG) to simulate the behaviour of the converter in the power grid, and without the SG to study its performance under islanded conditions. VSC reactive power synchronization is used to improve the performance of the converter, including its grid forming and grid supporting capabilities. The proposed implementation has proven to be stable under fault conditions and able to recover pre-fault conditions once the fault is cleared. Under unbalanced faults, the VSM is able to naturally inject negative sequence current in response to the negative sequence voltage appeared during the fault.