Current-Sensing Techniques for Revenue Metering and for Detecting Direct Current Injection from Electric Vehicles: A Review

Contemporary power networks increasingly include distributed generation and storage, which must follow interconnection standards to ensure power quality and grid safety. One such standard is IEEE 1547-2018, “Limitation of DC injection.” Any poorly designed or malfunctioning power converter can inject DC, but high power converters, such as those used for electric vehicle (EV) chargers, are a proportionally larger concern. We propose that electric vehicle supply equipment (EVSE) be responsible for monitoring the DC injection level in AC current to and from EV on-board inverters to be compliant with IEEE 1547-2018 despite any on-board equipment failure. Another function of the EVSE is high-precision AC measurements for revenue metering. Due to mass production of EVSE, it is important to integrate DC injection detection into EVSE system cost-effectively. Therefore, it is advantageous for AC and DC injection to be measured with a single device. Due to inability of the most common revenue metering system to detect DC, a new system with AC and DC measuring capabilities needs to be designed. The important design challenge is the large (two orders of magnitude) differences of measured AC vs. DC quantities on the same line. This article introduces the DC injection problem in relation to EVs and provides a review of commonly used current-sensing techniques to evaluate the most promising candidates for the aforementioned system design.