Integration of fast charger stations - A technical investigation on grid connected high powerconverters and their filter solutions with focus on harmonicemissions and size reduction by utilising interleaved operation

Abstract

In this paper, measurements are performed on an operating 300 kW bus charger station. A description of how the charger is constructed is given and the measurement results are presented. The efficiency of the charger was, at a 240 kW load level found to be around 95 %. The harmonic content is also presented for both current and voltage, and it was found to be within allowed levels specified in enforcing Swedish regulations, both in individual harmonic amplitudes and total harmonic distortion (THD). A simulation model has been constructed in plecs®/Similunk® and the model was tweaked for the harmonic results to match those of the measurements. Simulations of a 50 kW converter, switched at 25 kHz, has been performed in normal operation and interleaved operation for comparison of their emissions and the need of filtering. Simulations have shown that interleaved operation can fulfil valid standards and regulations of harmonics and opens for reduced filter size. The authors urges that a holistic view of the charger station is important to be able to reduce its total size. Further simulations with different real grid parameters have given support for that the grid location has a small or no impact on converter operation or risk of filter resonance.