New Challenges on the Electromagnetic Compatibility of Electric Vehicles

The massive use of electronics in modern electric vehicles poses new challenges to the coexistence of electric power units, analog and digital sensors and vehicle-to-infrastructure (v2i) communication systems. Indeed, power units like traction inverters or DC-DC converters have constantly improved over time in terms of power density and efficiency. However, this has led to increase the electromagnetic interference (EMI) they generate. In addition, the need of high capacity wireless and wired communication channels and the use of radars has increased the number of on board radio frequency and mm wave transmitters, which increase the level of electromagnetic pollution as well. Clearly, this renewed scenario poses new challenges to reduce the emission and increase the immunity to EMI of on board electronic units. In this context, the µEMC group has development some techniques aimed to reduce the electromagnetic emission generated by power modules, thus reducing the size of the EMI filters. For instance, it has been shown that a fine alignment of complementary switching voltages (see Fig. 1(a),(b)) reduces the conducted emission at low frequency (150kHz - 10MHz) significantly, as highlighted by the plot in Fig. 1(c) [1]. The group has also proposed solutions aimed to damp the oscillations resulting from fast switching based on resonant snubbers or active gate drivers [2,3]. For instance, the solution proposed in [3] allows one to damp the voltage oscillations triggered by hard switching at high frequency, as highlighted in Fig. 2. Regarding the immunity to EMI of analog front-end, since A/D converters based on ΣΔ modulation are increasingly used for signal conditioning, a study on the susceptibility of modulators [4] has been performed. Two second-order modulators have been considered, and the performance of Continuous-Time (CT) and Discrete-Time (DT) loops has been compared. Simulations have been carried out in different amplitude and frequency injection conditions showing that the DT modulator can be highly susceptible to RFI, resulting in a large offset voltage, as shown in Fig. 3(a). CT modulators showed to be more resilient to RFI, presenting a smaller offset voltage. However, spectral analysis showed even-order harmonic distortion in the presence of low frequency disturbances, as shown in Fig. 3(b).