Influence of Electric Vehicle Charging on the Grid Access Impedance from 20 kHz to 500 kHz

This paper aims to analyze the potential effect of the Electric Vehicle charging process (EVCP) on the mean and sub-cycle grid access impedance from 20 kHz to 500 kHz. The characterization is carried out in a controlled Low Voltage (LV) grid and covers the still uncharacterized frequency band assigned to Narrowband Power Line Communications (NB-PLC) up to 500 kHz. The results show that the measured impedances, regardless of whether an EV is charging in the network or not, are considerably lower than the reference impedances defined in CISPR 16-1-2 and IEC 61000-4-7 standards. Moreover, the influence on the grid impedance of the distance between the measurement point and the Point of Connection (POC) where the EV Charging Stations (EVCSs) are installed has been evaluated, concluding, first, that the highest impedance variations do not necessarily occur at the electrical point where the EV is connected and, second, that the influence of a certain EVCP depends not only on the EVCP itself, but also on the impedance in the default situation (when no EV is connected). Finally, a time-dependent behavior within the fundamental period of the mains (20 ms) has been observed at specific frequencies both in the absence of EVs and when each EV is charging. Maximum differences within the cycle of 3.3 Ω and 0.9 rad in the modulus and phase, respectively, have been reported.