Harmonic emissions of a bidirectional electric vehicle charging station - a research methodology based on tests at a reconstructed smart grid

Bidirectional electric vehicle charging stations (EVSE) offer new business models to users and can provide ancillary services to the electrical grid. During charging operation EMC standards and during discharging grid codes are applicable. In this study the harmonic emissions including the total harmonic distortion (THD) and total distortion demand factor (TDD) together with the grid impedance up to 2 kHz of a 10 kW bidirectional charging station are analyzed. While harmonic emission measurements of EVSE at laboratory conditions gives results for idealized conditions and field tests strongly depend on local grid conditions, the real-life operation of an EVSE at a well-known reconstructed grid gives valuable information about the harmonic behavior and impact to the grid impedance. The results show that the bidirectional EVSE can be a main pollutant of harmonic emissions at low power set-points, harmonic phase angle can change from inductive to capacitive behavior and the first resonance frequency of the grid impedance is moved to lower frequencies.