Abstract
To accurately simulate electric vehicle DC fast chargers' (DCFCs') harmonic emission, a small time step, i.e., typically smaller than 10 μs, is required owing to switching dynamics. However, in practice, harmonics should be continuously assessed with a long duration, e.g., a day. A trade-off between accuracy and time efficiency thus exists. To address this issue, a multi-time scale modeling framework of fast-charging stations (FCSs) is proposed. In the presented framework, the DCFCs' input impedance and harmonic current emission in the ideal grid condition, that is, zero grid impedance and no background harmonic voltage, are obtained based on a converter switching model with a small timescale simulation. Since a DCFC's input impedance and harmonic current source are functions of the DCFC's load, the input impedance and harmonic emission at different loads are obtained. Thereafter, they are used in the fast-charging charging station modeling, where the DCFCs are simplified as Norton equivalent circuits. In the station level simulation, a large time step, i.e., one minute, is used because the DCFCs' operating power can be assumed as a constant over a minute. With this co-simulation, the FCSs' long-term power quality performance can be assessed time-efficiently, without losing much accuracy.
Highlights
To accurately simulate electric vehicle DC fast chargers’ (DCFCs’) harmonic emission, a small time step, i.e., typically smaller than 10 μs, is required owing to switching dynamics
The DCFCs and battery energy storage system (BESS) are connected to the distribution grid with power converters that comprise power electronics and power filters
Modular design is typical for DCFCs, especially for those with high-power ratings, because of 1 the wide battery voltage range, 2 less stress on the power electronic components, 3 less design pressure on the cooling system, and 4 flexible compatibility with different electric vehicle (EV) with different rated charging powers [2]
Summary
For widespread electric vehicle (EV) adoption, fast-charging stations (FCSs) are being built along highways as crucial infrastructures that can alleviate EV customers’ range anxiety for long-distance trips [1,2]. Based on this simulation model, the DCFC’s input impedance and harmonic current source at certain operating power can be obtained. Lu Wang et al.: Python Supervised Co-simulation for a Day-long Harmonic Evaluation of EV Charging load profile, the FCS’s long-term harmonic performance can be simulated by updating the DCFCs’ input impedance and harmonic current source per minute
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