IT-gestützte Sektorenkopplung: Digital gesteuerte Brennstoffzellen- und Elektrolysetechnologie für stationäre und mobile Anwendungen

The present work expands on the idea of the electric field modifier (EFM) as a control electrode in the membrane of a fuel cell (FC). Through electrochemical impedance spectroscopy (EIS) measurements it is shown experimentally that an EFM-electrode made of a gold mesh can be integrated into a fuel cell, without disrupting its function. Using the measured impedance spectra and a distribution of relaxation times (DRT)-approach a suitable equivalent circuit (EQC)-model is derived for the measured cell with the integrated EFM. Further measurements show that the EFM can mainly be regarded as a double layer (dl)-capacitor inside of the membrane. This capacitor, in conjunction with a specially designed H∞ -controller are used in a simulation to stabilise the cell voltage, while a square wave current is drawn from the cell, to represent a direct connection of the FC with an inverter. The system is shown to have excellent disturbance rejection.

Utilizing multi-energy renewable microgrids is a promising prospect for decentralized electric power generation. To form a multi-energy microgrid and integrate different renewable energy sources, grid-forming inverters are the core elements. Therefore, their performance has to be tested and validated to increase the quality and reliability of the power supply. The present paper investigates the suitability of a specifically designed and implemented grid-forming inverter as the central component in such microgrid systems. Quality of black-start, frequency and voltage regulation, fast transient response, energy efficiency, low harmonic distortion, proper power factor control, synchronization and phase alignment for integration of renewable energy sources and energy storage devices such as photovoltaics and lithium-ion battery bank, respectively, fault-ride through capability, and resilience to fluctuations imposed by loads are the main features that have been tested and validated for a laboratory-scale grid-forming inverter. The study focuses on the parameters essential for ensuring the reliable and efficient operation of the inverter in dynamic and diverse energy environments, especially its adaptability to varying load profiles and its resilience towards intermittent energy inputs. The findings from this performance evaluation contribute insights for engineers, researchers, and industry professionals involved in the design, deployment, and optimization of multi-energy microgrids.

Grid-forming inverters are the essential components in the effort to integrate renewable energy resources into stand-alone power systems and microgrids. Performance of these inverters directly depends on their control parameters embodied in the controller. Even the most conscientiously designed controller will exhibit suboptimal performance upon implementation due to the presence of parasitic elements in the existing hardware. Hence, the controller has to be tuned and optimized. In the present article, the process of implementation, laboratory verification, and tuning of a matching-controlled grid-forming inverter is presented. In order to assess the efficiency of the grid-forming controller, its operation has been tested and analyzed in blackstart, steady state, and transient operation. For this purpose, a systematic sensitivity analysis has been conducted and the control parameters have been tuned in laboratory tests. The laboratory results verify proper operation of a 7 kW grid-forming inverter in all three test scenarios. After applying the proposed method on the tested grid-forming inverter in steady state operation, total harmonic distortion (THD) of the output voltage is less than 0.5% for its practical loading range (maximum THD is less than 1% in no-load condition). The system is able to blackstart and supply the loads. Finally, the studied grid-forming inverter is stable in the presence of severe step load changes and disturbances, i.e., voltage overshoot is managed well and compensated for with a low settling time using this approach.

A promising method to tackle spatial and temporal challenges of an increasing share of renewables is the coupling of different energy sectors. Especially gas and electricity systems profit from possible bidirectional energy flows in order to support the sensitive electric grid through gas-to-power technologies such as fuel cells and the possibility to store surplus electrical energy using power-to-gas technologies such as electrolyzers. The grid connection is usually realized using power electronics leading to dynamic and transient interactions between gas sector, conversion technology, power electronics and electric sector. Thus, a good understanding of the operation of the conversion technologies under these new circumstances is necessary. In this paper a model of a multi-energy microgrid consisting of a fuel cell system, a battery, a photovoltaic system each connected through power electronics to an AC load is presented. The model is investigated in island mode with volatile solar irradiation and load. The aim is to investigate the fuel cell system aptitude as a grid-forming unit and the benefits of using a battery as grid-supporting unit to enhance grid resilience. The simulation results show that the transient behaviour of the fuel cell system during a load step on fuel cell and grid side could be enhanced by using the fuel cell system‘s DC bus voltage as a reference, in addition to the AC side’s active power, for the battery inverter control.