This page contains a list of all conference and journal papers published by the consortium in the course of the HONOR project.
List of Publications
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DOI: 10.1109/SEST50973.2021.9543104
Abstract: To meet new challenges in the transmission and distribution grid, it becomes necessary to implement a flexibility markets mechanism. This paper proposes a framework based on optimal power flow for coordination of flexibility exchange between transmission and distribution grid. The acquiring flexibility assets can be applied effectively in response to possible grid challenges in different electricity grid levels. The proposed power flow approach is formulated as a hybrid AC/DC optimal power flow (AC/DC-OPF) model. This model consists of two different power flow methods. For the distribution grid, a second-order cone AC optimal power flow (SOC-ACOPF) method is formulated. For the transmission grid, a DC optimal power flow (DCOPF) method is applied. This approach also incorporates scenario-based and multi-period modeling, optimizing flexibility usage for a predefined period. The optimization is based on power demand, grid constraints, cost minimization, and operational criteria for distributed energy resources. The results presented in this paper are valuable for creating and implementing an adequate flexibility exchange mechanism between TSO and DSO.
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DOI: 10.48550/arXiv.2111.03300
Abstract: The ongoing integration of renewable generation and distributed energy resources introduces new challenges to distribution grid operation. Due to the increasing volatility and uncertainty, distribution system operators are seeking concepts to enable more active management and control. Flexibility markets offer a platform for economically efficient trading of electricity flexibility between distribution system operators and other participants. The integration of cyber, physical and market domains of multiple participants makes flexibility markets a system of cyber-physical systems. While cross-domain integration sets the foundation for efficient deployment of flexibility, it introduces new physical and cyber vulnerabilities to participants. This work provides a systematic overview of threat scenarios for the cyber-physical systems of flexibility markets. Results reveal several remaining security challenges across all domains, that require more attention. Based on the threat scenarios and a novel generic monitoring requirements model, monitoring concepts for secure participation of distribution system operators in flexibility markets are proposed. By highlighting approaches to tackle identified challenges, this work provides new directions for further investigations, and takes important steps towards secure implementation of flexibility markets.
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Abstract: This paper describes a new methodology to estimate and exploit active and reactive power flexibility in an active distribution network (ADN). The application is designed under consideration of a modular parallel optimization architecture for minimizing computation time. The proposed model is meant to exploit the flexibility of the controllable assets from the distribution network at the grid connection point (GCP), which is connected with a higher voltage network, in a preventive (N-1) secure and costoptimized way. The methodology is validated using a test bench network model with various technical constraints associated with the respective generation units. The results show the assessment of flexibility and capacity to control active and reactive power (PQ) in realtime operation.
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The continuous and intensive integration of renewable energy sources (RES) and the subsequent decommissioning of conventional plants result in technical challenges in planning and operation of electrical networks such as higher uncertainty and absence of reliable ancillary services. One solution to overcome the current challenges is the effective and smart usage of RES connected to a distribution grid. The control characteristics of RES could enable the use of RES as sources of flexible active and reactive power to provide flexibility to a higher voltage network at their interface point. The flexibility of an active distribution network (ADN) is determined at the grid connection point (GCP) which is defined as the interconnection point between two networks (e.g. HV/MV or MV/LV networks). The determined flexibility at the GCP can support in maintaining stability in the power system in terms of managing the network operation and ancillary services, e.g., congestion management, voltage control, frequency services, etc. Based upon the available flexibility at a given time and the respective power flow situation, the calculated flexibility can decrease or increase active and reactive power to suit the needs. For example, congestion in a transmission line can be solved by utilizing the flexibility that an underlying distribution network offers by absorbing active power. Additionally, determination and utilization of flexibility enables effective and efficient grid utilization with the available resources without the need of expanding the grid; thus, diminishing capital investments. Awareness and information of mutual flexibility at multiple GCPs can be supported in use cases, such as congestion management in a meshed distribution network, where multiple GCPs are connected to a common transmission line. Accordingly, this paper proposes a method for the determination of flexibility at multiple GCPs with mutual dependency into consideration. The potential usage of the method from the point of view of grid operator is discussed. The discussion describes a use case and expected visualization that support grid operations contingency constrained security. The demonstration results including the hardware-in-the-loop control system environment will be evaluated.
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DOI: 10.1016/j.apenergy.2022.118647
Abstract: The continuous electrification of the mobility and heating sectors adds much-needed flexibility to the power system. However, flexibility utilization also introduces new challenges to distribution system operators (DSOs), who need mechanisms to supervise flexibility activations and monitor their effect on distribution network operation. Flexibility activations can be broadly categorized to those originating from electricity markets and those initiated by the DSO to avoid constraint violations. Coinciding electricity market driven flexibility activations may cause voltage quality or temporary overloading issues, and the failure of flexibility activations initiated by the DSO might leave critical grid states unresolved. This work proposes a novel data processing pipeline for automated real-time identification of fast-ramped flexibility activation events. Its practical value is twofold: (i) potentially critical flexibility activations originating from electricity markets can be detected by the DSO at an early stage, and (ii) successful activation of DSO-requested flexibility can be verified by the operator. In both cases the increased awareness would allow the DSO to take counteractions to avoid potentially critical grid situations. The proposed pipeline combines techniques from unsupervised detection and open-set classification. For both building blocks feasibility is systematically evaluated and proofed on real load and flexibility activation data.
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DOI: 10.48550/arXiv.2110.04174
The ongoing electrification introduces new challenges to distribution system operators (DSOs). Controllable resources may simultaneously react to price signals, potentially leading to network violations. DSOs require reliable and accurate low-voltage state estimation (LVSE) to improve awareness and mitigate such events. However, the influence of flexibility activations on LVSE has not been addressed yet. It remains unclear if flexibility-induced uncertainty can be reliably quantified to enable robust DSO decision-making. In this work, uncertainty quantification in LVSE is systematically investigated for multiple scenarios of input availability and flexibility utilization, using real data. For that purpose, a Bayesian neural network (BNN) is compared to quantile regression. Results show that frequent flexibility activations can significantly deteriorate LVSE performance, unless secondary substation measurements are available. Moreover, it is demonstrated that the BNN captures flexibility-induced voltage drops by dynamically extending the prediction interval during activation periods, and that it improves interpretability regarding the cause of uncertainty.
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DOI: 10.1109/ISGT50606.2022.9817470
Abstract: The demand for increasing flexibility use in power systems is stressed by the changing grid utilization. Making use of largely untapped flexibility potential is possible through novel flexibility markets. Different approaches for these markets are being developed and vary considering their handling of transaction schemes and relation of participating entities. This paper delivers the conceptual development of a holistic system architecture for the realization of an interregional flexibility market, which targets a market based congestion management in the transmission and distribution system through trading between system operators and flexibility providers. The framework combines a market mechanism with the required supplements like appropriate control algorithms for emergency situations, cyber-physical system monitoring and cyber-security assessment. The resulting methods are being implemented and verified in a remote-power-hardware-in-the-loop setup coupling a real world low voltage grid with a geographically distant real time simulation using state of the art control system applications with an integration of the aforementioned architecture components.