• Energy Research

The increasing proportion of renewable energy introduces both long-term and short-term uncertainty to power systems, which restricts the implementation of energy management systems (EMSs) with high dependency on accurate prediction techniques. A hierarchical online EMS (HEMS) is proposed in this paper to economically operate the Hybrid hydrogen–electricity Storage System (HSS) in a residential microgrid (RMG). The HEMS dispatches an electrolyzer-fuel cell-based hydrogen energy storage (ES) unit for seasonal energy shifting and an on-site battery stack for daily energy allocation against the uncertainty from the renewable energy source (RES) and demand side. The online decision-making of the proposed HEMS is realized through two parallel fuzzy logic (FL)-based controllers which are decoupled by different operating frequencies. An original local energy estimation model (LEEM) is specifically designed for the decision process of FL controllers to comprehensively evaluate the system status and quantify the electricity price expectation for the HEMS. The proposed HEMS is independent of RES prediction or load forecasting, and gives the optimal operation for HSS in separated resolutions: the hydrogen ES unit is dispatched hourly and the battery is operated every minute. The performance of the proposed method is verified by numerical experiments fed by real-world datasets. The superiority of the HEMS in expense-saving manner is validated through comparison with PSO-based day-ahead optimization methods, fuzzy logic EMS, and rule-based online EMS.

A task for new power generation technologies, interfaced to the electrical grid by power electronic converters, is to stiffen the rate of change of frequency (RoCoF) at the initial few milliseconds (ms) after any variation of active power balance. This task is defined in this article as fast active power regulation (FAPR), a generic definition of the FAPR is also proposed in this study. Converters equipped with FAPR controls should be tested in laboratory conditions before employment in the actual power system. This paper presents a power hardware-in-the-loop (PHIL) based method for FAPR compliance testing of the wind turbine converter controls. The presented PHIL setup is a generic test setup for the testing of all kinds of control strategies of the grid-connected power electronic converters. Firstly, a generic PHIL testing methodology is presented. Later on, a combined droop- anFd derivative-based FAPR control has been implemented and tested on the proposed PHIL setup for FAPR compliance criteria of the wind turbine converters. The compliance criteria for the FAPR of the wind turbine converter controls have been framed based on the literature survey. Improvement in the RoCoF and and maximum underfrequency deviation (NADIR) has been observed if the wind turbine converter controls abide by the FAPR compliance criteria.

Novel concepts enabling a resilient future power system and their subsequent experimental evaluation are experiencing a steadily growing challenge: large scale complexity and questionable scalability. The requirements on a research infrastructure (RI) to cope with the trends of such a dynamic system therefore grow in size, diversity and costs, making the feasibility of rigorous advancements questionable by a single RI. Analysis of large scale system complexity has been made possible by the real-time coupling of geographically separated RIs undertaking geographically distributed simulations (GDS), the concept of which brings the equipment, models and expertise of independent RIs, in combination, to optimally address the challenge. This paper presents the outputs of IEEE PES Task Force on Interfacing Techniques for Simulation Tools towards standardization of GDS as a concept. First, the taxonomy for setups utilized for GDS is established followed by a comprehensive overview of the advancements in real-time couplings reported in literature. The overview encompasses fundamental technological design considerations for GDS. The paper further presents four application oriented case studies (real-world implementations) where GDS setups have been utilized, demonstrating their practicality and potential in enabling the analysis of future complex power systems.

Residential load profiles (RLPs) play an increasingly important role in the optimal operation and planning of distribution systems, particularly with the rising integration of low-carbon energy resources such as PV systems, electric vehicles, small-scale batteries, etc. Despite the prevalence of various data-driven models for generating consumption profiles, there is a lack of clear conclusions about their relative strengths and weaknesses. This study undertakes a comprehensive comparison of frequently used data-driven models in recent research, including Generative Adversarial Networks (GANs), Variational Autoencoders (VAE), Wasserstein GANs (WGAN), WGANs with Gradient Penalty (WGANGP), Gaussian Mixture Models (GMMs), and Gaussian Mixture Copulas (GMC). The presented comparison explores the effectiveness of the above-mentioned models on transformer- and consumer-level consumption profiles, as well as for different time resolutions (15-min, 30-min, and 60-min). The objective of this research is to elucidate the respective advantages and drawbacks of these models, thereby providing valuable insights for subsequent research in this field.

This article discusses the application of battery energy storage systems (BESSs) as power redistributors in three-phase distribution grids as an add-on functionality to typical BESS applications, such as congestion management and energy arbitrage. Combining those ancillary services into a single power unit is not yet performed in practice but may constitute an emerging business opportunity to increase the BESS revenues. The unbalanced operation of the BESS voltage source converter (VSC) leads to the circulation of low-frequency current harmonics in the dc-link through the capacitors and the battery cells. Therefore, it is particularly interesting whether relatively large 50- and 100-Hz currents can safely circulate within these components. Analytical modeling and design guidelines for the dc-link of a three-leg four-wire two-level VSC operating under unbalanced loads are detailed. Furthermore, a low-power VSC prototype is used to demonstrate the working principle of the BESS, providing power unbalance redistribution and symmetric power exchange. Additionally, the ICR18650-26F Lithium-ion cells are cycled to reach end-of-life with different current profiles and C-ratings. The analysis shows that charging with a 100 Hz ripple superimposed to the dc current leads to a 10% increment in degradation. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. DC systems, Energy conversion & Storage Intelligent Electrical Power Grids

Coming to an end in April 2020, the ERIGrid project organised its Virtual Final Conference dedicated to presenting the outcomes of the 5 years of work towards the integrated research infrastructure for smart grid systems. The project consortium presented the ERIGrid holistic testing approach for validating cyber-physical energy systems and other outstanding achievements on April 1, 2020. ERIGrid’s free access to Europe’s leading laboratories (Transnational Access) has also been covered, i.e., successful users presented their energy efficient solutions that they tested at the labs of ERIGrid partners. The following presentations have been provided: Session “ERIGrid Achievements“ Welcome and ERIGrid Overview System-level Testing Approach Laboratory Coupling Approach Laboratory and Hardware-in-the-Loop based Assessment Methods Simulation-based Assessment Methods Education and Training Methods and Tools Outlook ERIGrid 2.0 Session “Facilitating Effective Laboratory Testing by Lab Users” Overview of Achievements of the ERIGrid Transnational Access Programme Application of OLTC Transformer and Distributed Generation for Voltage Control on Low Voltage Distribution Networks Datalogging, Power Converters and Machine Learning: How ERIGRID has kick started my research on planned perennity in microgrids Hardware-in-the-Loop Modelling, Simulation and Closed-Loop Testing of a distribution integrated PV Plant VILLAS4ERIGrid: Geographically Distributed Real-time Simulation and PHIL between TU Delft, DTU Risø, Lyngby and RWTH Aachen Extensive Impacts of SunHILL Impact of Time variant Grid Impedance on Power Line Communication System