Current-Controlled Synchronverter: A Grid Fault Tolerant Grid Forming Inverter

A synchronverter (SV) equipped with an output admittance synthesizer is modified to avoid the usual transient instability of grid forming inverters in presence large grid disturbances, keeping the injected currents at safe values. The proposal consists of changing the control objective of the SV: instead of controlling the injected active and reactive powers, the injected active and reactive currents are controlled (as in a grid following inverter). The resulting system [called here current controlled SV, (CCSV)], injects balanced currents, even against asymmetric faults. The CCSV is capable of operating both in island mode and in grid connected mode, and can switch between these modes without prior synchronization. Like the SV, the CCSV does not use a dedicated algorithm for synchronization (such as a phase-locked loop).