Patent Publication Number: US-2022224136-A1

Title: Electric vehicle portable charger arc fault circuit interrupter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 63/135,200 filed Jan. 8, 2021, which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The present invention relates generally to electrical vehicle supply equipment (EVSE) and in particular to portable EVSE having arc fault detection. 
     An electric vehicle charging station, also called EV charging station, electric recharging point, charging point, charge point, electronic charging station (ECS), and electric vehicle supply equipment (EVSE), is a machine that supplies electric energy for the recharging of plug-in electric vehicles—including electric cars, neighborhood electric vehicles and plug-in hybrids. In some instances, the EVSE plugs includes a first cable connected to the power grid via a standard household wall outlet-socket and a second cable connected to the electric vehicle to supply charging power to the electric vehicle. Typically, the power supplied by the EVSE is alternating current (AC), wherein the vehicle includes an AC-to-DC converter for converting the AC power to DC power utilized to charge the battery. 
     In many applications, the EVSE is portable and is installed in a garage for use in charging the electric vehicle. Due to the nature of the use—for example, within a garage environment—damage may occur to one or more of the cables. It would be beneficial if the EVSE equipment could detect damage to the one or more cables and prevent the occurrence of faults. 
     SUMMARY 
     According to one aspect, a portable electric vehicle supply equipment (EVSE) includes a first line and a second line, a current sensor, a microcontroller, and at least one protective relay. The current sensor is connected to monitor at least one of the first line or the second line and a current module is connected to sample the monitored current. The microcontroller is configured to detect arc faults in the first line and/or the second line based on the sampled current and to selectively open the protective relay in response to a detected arc fault. 
    
    
     
       DETAILED DESCRIPTION 
       The present disclosure is directed to electric vehicle supply equipment (EVSE), and in particular to portable EVSE having arc fault circuit interruption (AFCI) protection. Portable EVSE typically includes a grid cord cable that connects to a wall socket/outlet, a coupler cable that interfaces with the electric vehicle (EV), and an EVSE module connected between the respective cables. Arc faults can occur in response to the cables—either the coupler cable or the grid cord cable—becoming damaged or ruptured. In some embodiments, the EVSE module includes a controller configured to monitor the charging of the EV. In some embodiments, monitoring includes monitoring the current on one or both of the conductors and analyzing the monitored current to detect arc faults. In some embodiments, arc fault detection requires high-frequency monitoring of the delivered current. In response to a detected arc fault, the controller opens one or more protective relays located in the EVSE module to prevent the flow of current. In addition, the controller may generate an alert or warning indicating that an arc fault has been detected. 
         FIG. 1  is a diagram of an electric vehicle supply equipment (EVSE)  100  configured to provide charging power from a wall outlet/socket  102  to an electric vehicle (EV)  104 . The EVSE  100  includes a socket  106 , a grid cord cable  108 , an EVSE module  110 , a coupler cable  112 , and an EV port  114  configured to mate with an EV socket  116 . In some embodiments, EVSE  100  is portable, and may be utilized to charge EV  104  from a typical wall outlet/socket  102 . For example, EVSE  100  may be sold with EV  100  (or purchased separately) and utilized by the user to charge the EV  100  at home—typically within a garage. This type of environment may result in damage to one or both of the grid cord cable  108  and/or coupler cable  112 . In particular, both the grid cord cable  108  and/or coupler cable  112  include inner conductors surrounded by an outer, insulative jacket. Damage to the outer jacket—for example as a result of the cords being run over—may result in exposure of the inner conductors that results in series and/or parallel arc faults. In some applications, the wall outlet/socket  102  may be equipped with arc fault detection (e.g., arc fault circuit interrupter (AFCI)), but in many applications this is not the case. In some embodiments, EVSE module  110  includes an arc fault circuit interrupter (AFCI) protective device and protective relays selectively opened in response to a detected arc fault. In addition, in some embodiments the EVSE module  110  may include other protective devices, such as residual current devices (RCD) to protect from leakage currents. 
         FIG. 2  is a simplified block diagram of EVSE module  110 . In this embodiment, the EVSE includes a protective earth (PE) conductor, a first line (L 1 ) conductor, and a second line (L 2 /N) conductor. In some embodiments, the EVSE module  110  includes a residual current device (RCD) sensor  200 , a current sensor  202 , a RCD module  204 , a current module  206 , a microcontroller  208  that includes AC load current frequency monitoring  210 , and first and second protective relays  212   a ,  212  connected on the first line L 1  and second line L 2 /N, respectively. 
     
    
    
     In some embodiments, RCD sensor  200  is a current transformer that monitors for imbalances between the first line L 1  and the second line L 2 /N. During normal operation, the current flowing on the first line L 1  is approximately equal to the current flowing (in the opposite direction) on the second line L 2 /N. The output of the RCD sensor  200  is approximately zero because the difference between the currents on the respective lines is approximately zero. An undesirable residual or leakage current causes an imbalance in the respective line currents that results in generation of a voltage representative of the current differential. RCD module  204  monitors the voltage provided by the RCD sensor  200  and generates a trip in response to the voltage exceeding a threshold level. The trip or response is provided to the microcontroller module  208 , which in turn generates control signals to open or trip the protective relays  212   a ,  212   b , preventing additional current from flowing through the first line L 1  and second line L 2 /N. 
     In addition, current sensor  202  monitors current through one or both of the lines. In the embodiment shown in  FIG. 1 , current sensor  202  monitors current through the second line L 2 /N, but in other embodiments additional current sensors may be utilized to monitor the current in the first line L 1 , the second line L 2 /N, or both the first line L 1  and the second line L 2 /N. Current module  206  samples the monitored current and converts the monitored currents to a digital value that is provided to the microcontroller  208 . The monitored current may be utilized for both overcurrent detection as well as for arc fault detection. Overcurrent detection requires comparison of the monitored current to a threshold value (in some embodiments over a period of time). The comparison may be done by the current module  206  or by the microcontroller  208 . In response to an overcurrent condition, the microcontroller  208  opens one or both of the protective relays  212   a ,  212   b . In addition, to provide arc fault circuit interruption (AFCI) functionality, the current module  206  samples the monitored current at a given frequency. In some embodiments, arc faults are characterized by a high-frequency signature which requires sampling the monitored current at the required frequency (e.g., 100 kHz). In some embodiments, current module  206  samples the monitored current for a period of time (e.g., several milliseconds). The monitored AC current is provided to microcontroller  208  for storage and analysis. 
     In some embodiments, microcontroller  208  includes an AC load current frequency monitor that analyzes monitored current to detect series and/or parallel arc faults. In some embodiments, analysis of the monitored current includes comparing the monitored current to signature signals representing a series and/or parallel arc fault. In other embodiments, other types of arc fault analysis may be utilized to detect series and/or parallel arc faults. In response to a detected arc fault condition, the microcontroller  208  generates control signals to open the first and second relays  212   a ,  212   b  to prevent the flow of current to the electric vehicle. In some embodiments, in addition to generating a control signal to open the protective relays  212   a ,  212   b , the microcontroller  208  generates an output (e.g., visual, audio, etc.) alerting an operator to the type of fault detected (e.g., arc fault versus RCD). For example, in response to a detected fault condition the microcontroller  208  instructs output  214  to generate an audio and/or visual output indicating the detected fault condition. In some embodiments a visual output may include a light indicating either by location or color the presence and/or type of fault detected. Similarly, an audio output may include an audible warning indicating the presence and/or type of fault detected. 
     A benefit of this approach is that the portable EVSE provides arc fault circuit interrupt (AFCI) capability regardless of the type of wall socket/plug to which the EVSE is connected. In addition, because EVSEs are typically required to include RCD sensing and overcurrent sensing, the overhead for implementing arc fault detection and interruption is very low. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.