Analysis of the Transmission Performance of Control Pilot Signal Lines for Charging Communication in Electric Vehiclesa

To avoid degradation of transmission performance associated with the lengths of control pilot (CP), protective earth (PE) and the earth structures of chassis in charging-communication between electric vehicle supply equipment (EVSE) and electric vehicle (EV), the dependence of CP and PE signal lines transmission performance on length and structure were investigated. The transmission coefficient (S21) was calculated for the CP and PE signal paired line and the ISO 15118 recommended structure of signal lines over the bandwidth (1.8 similar to 28 MHz) which is defined in homeplug green PHY (HPGP) and ISO standards. The ISO recommended structure was modeled based on the equivalent circuit for HPGP coupling. The results indicated S21 of the CP and PE signal paired line is less than -2.5 dB over the entire operating bandwidth. Whereas the S21 of the ISO recommended configuration is more than -15 dB at some frequencies within the operating bandwidth when the line length exceeds 1.5 m, at around a quarter wavelength (-26 dB at 27 MHz for 2 m, -27 dB at 21 MHz for 2.5 m in simulation). Consequently, it is strongly recommended the CP and PE signal lines length do not exceed 1.5 m when using the ISO configuration.