Progress beyond the state of the art

Definition of representative on-site operating conditions for EVCSs and characterisation of local grid disturbances and local grid impedance (objective 1):
Currently, the most common method of EV modelling is to consider the EV loads as constant power elements without considering the voltage dependency of EV charging systems during the charging process. Several research projects on smart grids are now looking into realistic models representing the realistic behaviour of an EV load to understand the impact of EV charging load, but such models are not yet available nor are the measurement data to support such modelling.

The project will investigate typical EV voltage and impedance patterns as a function of time and state of charge during the charging process, based on on-site traceable measurements at EVCS sites. In some cases, the project will employ an EV load emulator (dummy load) that can simulate these voltage and impedance patterns. The patterns will cover a representative set of the most used EVs, energy transfer modes, and battery capacities.

Development of traceable methods and measurement standards for the characterisation of EVCSs under representative operating conditions for both AC and DC charging (objective 2):
Currently, the characterisation of EVCSs is limited to energy metering based on domestic AC supply meter regulation. Specific aspects of DC metering and aspects of high-power transfer at big charging stations are insufficiently characterised to ensure the reliability of the energy metering and are not fully adequate for estimating the efficiency of the charging stations with sufficient accuracy.

The project will develop the metrological infrastructure for laboratory characterisation of EVCSs including test setups, test methods, test conditions, and reference standards required for traceable characterisation of the energy transfer and energy loss. In some testing scenarios, EV simulators and dummy loads will be used instead of the whole EV. Since facilities for high-power DC charging are still scarce, these will receive extra attention.

Development of metrological infrastructure for on-site verification of EVCS energy metering (objective 3):
OIML TC 12/p 3 has recently produced a guiding document, OIML G 22 “Electric vehicle supply equipment”, but practical technical experience in testing and approving is still lacking in some respects, especially for DC charging applications. Furthermore, its practical implementation is a challenge because some tests require expensive hardware and are very time-consuming. This is not suitable for the fast-growing EVCS market. The project will provide practical technical input to OIML TC 12/p 3 for improvements of the current guide and its successor document on methods for verification of DC and AC EVCSs.

The project will establish the basis for an integrated metrology infrastructure for EVCS metering verification. For this, the project will propose validated simplified test setups and validated simplified test procedures for fulfilling a minimum set of test requirements to verify the EVCS metering accuracy in field conditions.