The resistive ground fault of PWM voltage inverter in the EV charging station

Marta Zurek-Mortka; Jerzy R Szymanski

doi:10.1038/s41598-021-00715-7

The resistive ground fault of PWM voltage inverter in the EV charging station

Sci Rep. 2021 Oct 27;11(1):21236. doi: 10.1038/s41598-021-00715-7.

Authors

Marta Zurek-Mortka^#¹, Jerzy R Szymanski^#²

Affiliations

¹ Department of Control Systems, Lukasiewicz Research Network-Institute for Sustainable Technologies, 26-600, Radom, Poland. marta.zurek-mortka@itee.lukasiewicz.gov.pl.
² Faculty of Transport, Electrical Engineering and Computer Science, Kazimierz Pulaski University of Technology and Humanities, 26-600, Radom, Poland.

^# Contributed equally.

Abstract

During the direct touch of the inverter output voltage or with the ungrounded shield of the cable connecting the inverter to the motor or other type of load, the nonsinusoidal ground currents with a basic harmonic frequency between 1.5 and 16 kHz, flow via a human's body. Here was proved that Residual Current Device (RCD) ([Formula: see text] = 30 mA) does not switch off the power supply when a ground current with a value of about some hundred milliamps occurs. Because RCDs do not disconnect the power supply, the touch on the inverter's voltage is dangerous to health and life. For the authors, the RCD usage in the Voltage Frequency Converters (VFCs) is not a good engineer practice when high-frequency common-mode distortion currents flow through it. The paper presents tests of RCD operation in the event of a resistance ground fault (via human body) during EV battery charging where the PWM voltage inverter is connected to the external rectifier to provide DC charging battery voltage. Finally, the authors propose a method of eliminating common-mode (CM) current from short protection system by using a separate circuit in which the parasitic leakage current omits an RCD.