Grid-forming converters play a key role in grids with a high share of renewable energies. Clear definitions and verification procedures for grid-forming Electricity grids with a high proportion of renewable generation require grid-forming converters to ensure system stability. In

order to accelerate the deployment of this new technology, technical requirements for grid-forming converters are needed to form

the basis for new grid codes.

This work makes a new proposal to make the voltage source behaviour, the core property of grid-forming converters, verifiable.

For the first time, this proposal avoids analysing the response of the converter in terms of current or power or requiring islanding

capability. Instead, the voltage source characteristics are verified directly via the behaviour of the voltage space vector of the

converter. This makes the process simple, comprehensible and also applicable when the converter system has hardly any energy

reserves to feed out additional active power.

In an exemplary verification procedure, several converters are measured and analysed on a test bench. The procedure proves that

the novel approach can be accurately executed with real measurements.