Inductance Estimation of an Electric Vehicle

Electric vehicles are no longer a rarity on Europe’s streets. But battery electric vehicles (BEVs) still have a long way to go to be the dominant vehicle type on the streets. In the last years, not only has the number of passenger cars risen, but also the number of electric trucks and heavy-duty vehicles. In 2023 electric trucks have share of 1.5% in the market. For the truck industry higher charging powers are even more important. Due to European regulations drivers of vehicles with more than 3.5t weight or buses with more than 10 passengers must rest for 45 minutes after 4.5hours of drive. Therefore, higher charging powers were needed, and the Megawatt Charging System (MCS) standard was developed. The voltage level goes up to 1250V and currents of 3000A are defined. This allows the battery of heavy-duty vehicles to be completely charged within the driving breaks. As with the upcoming MCS standard, the charging power increases, also the failure risk rises. Higher charging currents lead to higher amounts of storable energy on the HV (high voltage) level. Through failures during the charging process this energy can cause major damage. Such failures can be short circuits or a load dump during the energy transmission phase. To minimize the risk and increase the electric safety, the inductance must be determined and in a specific range. The estimation of this parameter is not a straightforward process due to the complexity of the charging path. Consequently, an alternative measurement setup must be developed. This paper presents two concepts for estimating the vehicle's inductance and compares their respective advantages and disadvantages. Both are based on the digital twin of the electric vehicle. The first one will focus on all known inductances within the system. The second one will focus on the impedance by linearizing the system.