Volume 67, Issue 11 - Special Issue: Modeling and control of multimodal and hybrid energy systems Modellierung und Regelung multimodaler und hybrider Energiesysteme / Martin Wolter, Veit Hagenmeyer

Information and communication technology (ICT) and the technology of coupling points including power-to-gas (PtG), power-to-heat (PtH) and combined heat and power (CHP) reshape future energy systems fundamentally. To study the resulting multimodal smart energy system, a proposed method is to separate the behavior of the component layer from the control layer. The component layer includes pipelines, power-lines, generators, loads, coupling points and generally all components through which energy flows. In the work at hand, a model is presented to analyze the operational behavior of the component layer. The modeling problem is formulated as state and phase transition functions, which present the external commands and internal dynamics of system. Phase transition functions are approximated by ordinary differential equations, which are solved with integral methods. State transition functions are nonlinear algebraic functions, which are solved numerically and iteratively with a modified Newton–Raphson method. In a proof-of-concept case study, a scenario shows the expected multi-sector effects based on evaluated models.

This paper describes a multiple-input, multiple-output distributed control concept for the operation of a distribution network. The concept aims to coordinate a set of distributed generators within the distribution grid to regulate the active and reactive power flow exchange with the transmission network and adjacent distribution grids. The control concept further aims to control the distribution network voltage profile such that voltages continuously remain within a predefined secure operation range. The implementation of such a concept can substitute for the decreasing flexibility in the transmission network which results from the decommissioning of conventional power plants in the future. As proof-of-concept, an implementation is tested through time-domain simulation.

Zusammenfassung Die Implementierung von VSC-basierten eingebetteten HGÜ-Systemen unterstützt das bestehende AC-System durch Wirkleistungsübertragung und Blindleistungsbereitstellung. Aus Sicht der ÜNB ermöglichen die eingebetteten HGÜ-Systeme eine Unterstützung des bestehenden Wechselstromübertragungssystems hinsichtlich der Betriebssicherheit. Diese Koordination wird durch Optimal Power Flow Berechnungen realisiert. In dieser Arbeit wird ein multikriterielles Konzept für eine optimale Planung der HGÜ-Wirkleistungsarbeitspunkte im Hinblick auf die Systemsicherheit erarbeitet. Bestehende Optimierer für OPF-Probleme umfassen deterministische und metaheuristische Ansätze. Darüber hinaus werden mehrere Optimierer beider Klassen in einem Testsystem bewertet, um ihre allgemeine Eignung für das daraus resultierende Optimierungsproblem zu beurteilen.

Zusammenfassung Dieser Beitrag beschäftigt sich mit verteilten, beschränkten Gradientenverfahren zur Optimierung eines Energie-Management-Problems. Zwei verschiedene Lösungsstrategien werden betrachtet. Zum einen wird ein Entkopplungsansatz analysiert, bei dem über einen Lagrange-Multiplikatoransatz die Beschränkungen in die Zielfunktion aufgenommen werden. Durch ein Gegenbeispiel wird gezeigt, dass dieses Verfahren nicht in jedem Fall auf das globale Optimum des Energie-Management-Problems konvergieren kann. Die zweite Strategie berücksichtigt Nebenbedingungen über einen Straffunktionsansatz und löst das Problem durch die Push-Sum-Konsensus-Dynamik. In der anschließenden Analyse dieses Verfahrens durch Simulation wird auf die Problematik der optimalen Parameterwahl sowie auf das Konvergenzverhalten bei unterschiedlicher Knoten- und Kantenanzahl des Graphen eingegangen.

This paper proposes a standardized simulation environment to evaluate current and to design future multi-level grid control strategies in terms of a safe and reliable operation in future converter-dominated grids. For this, the first step is to develop a taxonomy for the uniform description of multi-level grid control strategies, to define relevant design options and to derive the relevant evaluation and comparison criteria. Furthermore, aspects of new ICT-methods (e. g., machine learning decoders for aggregated flexibility description) are presented, which can help to tap the decentral flexibility potentials in future grid control strategies. Lastly, the major converter-related aspects are investigated. In particular, the stability of converter clusters in large-scale energy systems is analysed and new monitoring possibilities utilizing converter systems will be introduced.

To optimally design integrated energy systems a widely used approach is the Energy Hub. The conversion, storage and transfer of different energy vectors is represented by a coupling matrix. Yet, the coupling matrix restricts the configuration of the Energy Hub and the constraints, that can be included. This paper proposes a MILP based optimization framework, which allows a high variability and adaptability and is based on energy flows. The functionality of the developed framework is tested on four use cases depicting different system sizes and Energy Hub configurations. It is shown that the framework is able to simplify the design process of an Energy Hub.

Simulating energy systems integration scenarios enables a comprehensive consideration of interdependencies between multimodal energy grids. It is an important part of the planning for the redesign of the current energy system infrastructure, which is essential for the foreseen drastic reduction of carbon emissions. In contrast to the complex implementation of monolithic simulation architectures, emerging distributed co-simulation technologies enable the combination of several existing single-domain simulations into one large energy systems integration simulation. Accompanying disadvantages of coupling simulators have to be minimized by an appropriate co-simulation architecture. Hence, in the present paper, a new simulation architecture for energy systems integration co-simulation is introduced, which enables an easy and fast handling of the therefore required simulation setup. The performance of the new distributed co-simulation architecture for energy systems integration is shown by a campus grid scenario with a focus on the effects of power to gas and the reversal process onto the electricity grid. The implemented control strategy enables a successful co-simulation of electrolysis coupled with photovoltaics, a hydrogen storage with a combined heat and power plant and a variable power consumption.