Becker, Daniel

This paper serves as a quick guide for the selection process of contactless electrical sensors involved in unmanned aerial systemsbased gridmonitoring applications. Since the selection criteria for such sensors can be enormous and hence challenging, the major key points were elaborated after a thorough review of relevant work. The review presented in this paper, composedof seven current sensors and three voltage sensors topologies, is critically investigated. In terms of flexibility, complexity, sensitivity, and other performance indices, it is concluded that an “all-optical” dual voltage and current contactless sensor would represent an optimum choice to be employed within remote measuring applications. The mainrecommended feature of the suggested sensor is its ability to freely measure electrical quantities while being “relatively” far from the electrical transmission line, implying no need to be “clamped” all around it. By presenting an informative background for intelligent field sensing applications, this paper also suggests the future work relevant to the studied topic.

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.

Hydrogen fuel cell technology is one of the key focus areas to facilitate the transition from carbon-based fuels to more sustainable solutions in the transportation and mobile power sectors. Transient voltage fluctuations due to load changes and even operation of fuel cells with DC/DC and DC/AC converters are detrimental to the lifetime and this paper proposes a method to deal with these fluctuations. Adding electric field modifier (EFM) electrodes made of gold to the membrane of a fuel cell was proposed elsewhere as a way to influence the short term flux of charge carriers through the membrane. While electrochemical impedance spectroscopy shows a limited capacitance of such electrodes, experiments using square wave excitation of the system in the kHz frequency range show a promising reaction of the cell to this treatment. More in-depth analysis of the used electrode material reveals the need to insulate future EFM electrodes in order to prevent oxidative dissolution. However, this work shows that the principle of using EFM electrodes to manipulate transient oscillations is physically sound.

The dynamic controllability of the fuel cell could be improved by the addition of an electric field modifier (EFM), to selectively boost or attenuate the flux of protons through the membrane and, thereby, influence cell performance. This approach follows the commonly accepted idea of the potential gradient across the membrane being the main driving force behind the proton transport in the membrane. To evaluate the applicability of the idea, a simulation model for a membrane with an integrated EFM is developed to study the effects on the membrane behaviour. First, a modified Poisson-Boltzmann-Model (1D) is developed to characterise the capacitive behaviour of the double layer at the EFM. The approach considers steric restrictions in the membrane pores to estimate the double layer capacitance and the range of the effect at the EFM. Second, the characteristic behaviour of the capacitance is implemented in a secondary current distribution model (2D) as a variable capacitance. In transient simulations, boost of the cell current by up to 82% and attenuation up to a complete reversal of the direction compared to the stationary operation are achieved. Thus, it was possible to show the potential of EFMs to influence the characteristics of fuel cells and electrolysers during transient operation.

Optimized integration of fuel cells into grids or on-board power supplies is necessary to facilitate replacement of conventional energy producers by a reliable and plannable power generation technology. Due to the interdependency between fuel cell current and voltage, integration of fuel cells requires a power conditioning system, which increases integration weight and cost. For this reason, integration of electric field modifier electrodes into the setup of proton exchange membrane fuel cells is a new approach to control the output voltage in order to minimize the subsequent power conditioning system. This approach considers the physics of proton transport through the electrolyte membrane and could offer a lever to control the ohmic resistance. In this paper, a fuel cell model is implemented in MATLAB and extended by electric field modifier electrodes, allowing control of the ohmic resistance through an externally applied voltage. The concept of boosting and attenuating fuel cell voltage is presented along with different setups to enable this behavior. Furthermore, an electrical equivalent circuit for electrically controllable fuel cells is developed and implemented in MATLAB/Simulink. A method to parameterize the developed MATLAB and Simulink models by first experimental results is presented.

With the implementation of a high secure communication infrastructure in Germany above the low voltage grid the integration of a wide spectrum of energy applications is conceivable, but not easily testable. The lack of a fundamental model, depicting the properties of the Smart Meter Gateway (SMGW) as the central communication device leads to integration studies with possible variations in the basic assumptions and their comparability. The aim of this paper is the development of a modeling approach that can accurately capture the SMGw properties and the challenges of the utilities and companies under various conditions. The developed methodology can be applied to several grid-compliant or market-oriented engineering questions and their potential for new business models through, e.g. switch-off flexibility communication, utilizing the SMGw as additional signal and data exchange layer of the future grid.