Baum, Lukas

To increase the service life or durability of PEM fuel cells, no-load operation at open circuit voltage has to be avoided to reduce destructive electrochemical effects. This paper shows two approaches to realize a regulated base-load with a fuel cell protection unit for application in aircraft multi-powertrain-concepts. Firstly, a clocked MOSFET in the form of a chopper circuit, and secondly, a MOSFET in linear operation as current source. This contribution describes the design concept of both approaches and the validation of prototypes in a laboratory pHiL-environment. Both approaches are proven to be viable solutions, with the current source approach resulting in smoother operation.

Hydrogen fuel cells have become one of the most viable power sources for electric aircraft. Models representing the electrical behavior of the fuel cell stack over the full dynamic operation region are essential for the development of power electronic energy systems powered by fuel cell stacks. This work presents an electrical equivalent circuit model for PEM fuel cell stacks representing the static and dynamic electrical behavior of the fuel cell stack under pulsed loads up to frequencies of 10 kHz. Dynamic phenomena on time scales slower than the considered timescale of power-electronic switching, such as reactant flow, membrane hydration, and temperature effects, are considered stationary. The parameterization method proposed is developed on measured data from a 110 W PEM fuel cell stack and validated with a set of measured data from a 2 kW stack. The time-domain simulated behavior of the parameterized model shows an accurate representation of the measured behavior: the parameterized model reproduces both the static polarization behavior and the behavior under high-frequency pulsed loading with errors of less than 1% with respect to the nominal stack voltage. The model is suitable for dynamic simulation of power electronic systems directly connected to fuel cell stacks and can be parameterized without special electrochemical impedance spectroscopy measurements.

The large-scale deployment of grid-friendly controllable charging infrastructure or electric vehicle supply equipment for e.g. congestion management does pose the necessity for dedicated testing equipment. This work presents the design requirements and test device concepts for such a test device. The proposed test device combines test capabilities for both Mode 3/AC and Mode 4/DC charging infrastructure. The norm-conforming communication protocols are implemented and available for monitoring, while also testing under real load conditions is available while being independent of a mains connection. Further, the test device was validated using extensive testing with different EVSE. The applicability for in-field usage is shown.

The large-scale deployment of charging infrastructure poses challenges to the distribution grid stability. In Hamburg, the project Electrify Buildings for Electric Vehicles (ELBE) implements and tests a demand side management communication protocol that allows the distribution grid operator to reduce the charging power of electric vehicle charging stations if necessary. For this purpose, a test device capable of testing the signal chain as well as a real load reduction is presented for DC charging infrastructure. The standardized high-level communication protocols are described. With the charger’s power electronics located in the DC charging station, the need for a battery emulation arises, which is also discussed. Finally, a novel concept for a mobile and modular test setup for combined testing signal and real load reduction of AC and DC charging infrastructure is presented.

This work presents the development and parameterization of a dynamic equivalent circuit model of proton exchange membrane (PEM) fuel cell stacks. The model represents the static and dynamic behavior of the fuel cell stack under pulsed ohmic loading up to switching frequencies of 10 kHz. The model is developed using established mathematical descriptions of fuel cell processes. The model is then parameterized and validated using measurement data obtained from an 11 cell, 110 W PEM fuel cell stack.