Rafael Goldbeck

The current increase of electric vehicles in Germany requires an adequately developed charging infrastructure. Large numbers of public and semi-public charging stations are necessary to ensure sufficient coverage. To make the installation worthwhile for the mostly private operators as well as public ones, a sufficient utilization is decisive. An essential factor for the degree of utilization is the placement of a charging station. Therefore, the initial site selection plays a critical role in the planning process. This paper proposes a charging station placement procedure based on real-world data on charging station utilization and places of common interest. In the first step, we correlate utilization rates of existing charging infrastructure with places of common interest such as restaurants, shops, bars and sports facilities. This allows us to estimate the untapped potential of unexploited areas across Germany in a second step. In the last step, we employ the resulting geographical extrapolation to derive two optimized expansion strategies based on the attractiveness of locations for electric vehicle charging.

The three-phase dual-active bridge converter (DAB3) is a promising topology for high-power medium-frequency dc-dc conversion as it features inherent soft-switching capability and galvanic isolation. To enable a highly dynamic control of bidirectional power flow in the DAB3, the instantaneous flux and current control (IFCC) has recently been published. It supplements the state-of-the-art instantaneous current control (ICC) with a flux control feature to eliminate transient dc-bias flux linkage in the transformer core. The IFCC yields excellent results for transformers with negligible winding resistance, eliminating overshoots and oscillations in both transformer current and flux. When applied to less efficient transformer designs, however, residual oscillations in the dc currents are still observed. To guarantee oscillation-free dead-beat behavior for any values of winding resistance, this paper proposes an improved instantaneous flux and current control (IIFCC). The mathematical derivation is consistent with the basic idea of the improved instantaneous current control (IICC), which is shown to be a special case of the suggested generalized solution. To further reduce the computational load of the digital controller, an approximate closed-form solution based on Taylor’s theorem is provided for calculation at run-time with sufficient accuracy. Simulations and an experimental verification on a down-scaled hardware prototype confirm the effectiveness and superior performance of the proposed approach.

In order to reduce development cost and time, frontloading is an established methodology for automotive development programs. With this approach, particular development tasks are shifted to earlier program phases. One prerequisite for this approach is the application of Hardware-in-the-Loop test setups. Hardware-in-the-Loop methodologies have already successfully been applied to conventional as well as electrified powertrains considering various driving scenarios. Regarding driving performance and energy demand, electrified powertrains are highly dependent on the dc-link voltage. However, there is a particular shortage of studies focusing on the verification of variable dc-link voltage controls by Hardware-in-the-Loop setups. This article is intended to be a first step towards closing this gap. Thereto, a Hardware-in-the-Loop setup of a battery electric vehicle is developed. The electric powertrain consists of an interior permanent magnet synchronous machine and an inverter, which are set up as real components at a laboratory test bench. The test bench is connected to a real-time vehicle simulation including a battery model and the dc-dc converter model. The entire Hardware-in-the-Loop setup is successfully validated by vehicle measurements performed on a chassis dynamometer. Thereafter, the battery electric vehicle is tested at this Hardware-in-the-Loop setup for the worldwide harmonized light vehicle test cycle class 3. The tests are performed for electric powertrain configurations with and without dc-dc converter. For the application with dc-dc converter, reductions in energy losses of the traction machine by 5.4% and of the traction inverter by 37.6% are determined. This leads to an efficiency improvement of the entire electric powertrain by 1.5 percentage points, which results in a total energy reduction by 0.28 kWh/100km for the investigated test cycle. This use case demonstrates the efficiency improvements of a variable dc-link voltage and how Hardware-in-the-Loop tests can support the verification of dc-dc converter controls during frontloading phases of automotive development programs.

Low voltage direct current (LVDC) technology is becoming an attractive solution for the integration of renewable energies and the power supply of electronic loads. Since LVDC systems at the customer end are exposed to the daily contact of untrained users, they should be properly configured to guarantee the personal safety even under fault conditions. This paper derives guidelines for the selection of suitable voltage levels and the minimum requirements for protective devices from the perspective of personal safety in LVDC customer-end networks. For this purpose, a comprehensive analysis of the underlying influencing factors is presented, followed by a thorough discussion of the state-of-the-art in LVDC fault protection.

For the successful electrification of global transportation, the reliability of power electronic modules is of major importance. Today, one of the main reasons for module failure is the thermo-mechanically induced fatigue of bond wires as a result of strong load variations. A multitude of studies have been conducted to analyze the operational stress of bond wires based on thermal simulations using simple repetitive load patterns. This paper proposes a compact electro-thermal model for detailed time-efficient simulations of the thermal stress within bond wires. It incorporates the impact of parasitic electromagnetic coupling effects for an accurate loss determination over a wide frequency range. Finally, the bond wire model is embedded into a system simulation of the drive train of an electric vehicle. This allows to determine the realistic temperature distribution along the bond wires over time for specific mission profiles.