| Abstract |
To accurately simulate the harmonic emission of EV DC fast chargers (DCFCs) and the harmonicvoltage of the power grid to which the chargers are connected, a small time-step, i.e., typically smallerthan 10µs, is required. However, for harmonic assessment, a long timescale, typically a day, isrequired. A conflict between accuracy and time efficiency exists. To address this issue, a multitimescalemodeling framework of fast charging stations (FCSs) is proposed in this paper. In thepresented framework, the DCFCs' input impedance and harmonic current emission in the ideal gridcondition, i.e., the grid impedance is zero and there are no background harmonic voltages, is obtainedfirstly through a converter switch model with a small timescale. Since the DCFC's input impedanceand harmonic current source change in the charging course, the input impedance and harmonicemission at different input power should be obtained. Then, the DCFCs' input impedance andharmonic emission will be used in the fast-charging station modeling, where the DCFCs are simplifiedas their Norton equivalent circuits. In the station level modeling, a bigger time step, i.e., 1 minute, isused, since the DCFCs' operating power can be assumed as a constant in one minute. With thisframework, the FCSs' long-term power quality performance can be assessed efficiently withoutneglecting the DCFCs' small timescale dynamics. |
