Fabian Kurtz

Software-defined networking for Smart Grid communications: Applications, challenges and advantages

Future power systems are characterized by a high degree of complexity with a large number of intelligent devices, exchanging and processing both huge amounts of data and realtime critical information. Accordingly reliable, real-time capable and secure communication networks are required for enabling autonomous monitoring, management and control to guarantee stable power system operation. In this paper, we present and analyse a flexible and dynamic network control approach based on Software-Defined Networking (SDN) for meeting the specific communication requirements of both distribution and transmission power grid. Therefore a testbed is introduced, enabling the evaluation of multiple failure scenarios such as link disturbance and congestion by analysing corresponding fast recovery and prioritization solutions. The performance and robustness of the developed strategies is shown using highly-critical monitoring and control messages on basis of IEC 61850 and considering the mutual impact with low priority background traffic. Results indicate the advantages of SDN compared to traditional routing and Quality-of-Service mechanisms, providing a more reliable communication network, which is able to handle complex failure scenarios. In particular, SDN enables the integration of diverse network management functions and thus offers the power system new options for dealing with faults even in the case of overall outages. On the basis of these results, we demonstrate challenges and derive future benefits for a SDN-enabled Smart Grid communication network, holding the potential to evolve into a self-healing infrastructure.

Cluster-Based Vehicular Data Collection for Efficient LTE Machine-Type Communication

Machine-Type Communication (MTC) poses an ongoing research topic in the development of cellular communication systems. In this context, the efficient collection of extended Floating Car Data (xFCD) via Long Term Evolution (LTE) is a major challenge. In this paper, we present cluster-based xFCD collection schemes in order to form clusters with a long lifetime. As a result, the proposed clustering algorithms reduce the occurring cellular communication traffic. For the performance evaluation of the presented algorithm, a novel system model is used. By means of the system model, the user mobility can be modeled realistically and a precise quantification of the utilization of the LTE network for xFCD transmission is possible. The results show that the LTE network utilization can be significantly reduced by the proposed clustering algorithms.

Empirical comparison of virtualized and bare-metal switching for SDN-based 5G communication in critical infrastructures

Advancements in the field of Critical Infrastructures (CI), such as the advent of Smart Grids or automated transportation systems, offer new services and functionalities. However these novel Cyber Physical Systems (CPS) necessitate increasingly complex monitoring and control schemes, which are commonly orchestrated by industrial Supervisory Control and Data Acquisition (SCADA) systems. As thousands of distributed field devices are involved in the operation of Critical Infrastructures, the enabling communication technologies need to fulfil exacting performance requirements as well as provide high levels of robustness, Quality of Service, flexibility and scalability. The ongoing evolution of cellular LTE (Long Term Evolution) towards 5G networks promises to meet all these specifications. In this context Software-Defined Networking (SDN) is set to play a crucial part within the mobile networks wired backhaul as well as core infrastructures and is thus included in many proposed 5G architectures. However, basic performance characteristics allowing a comparison of the two prevalent approaches to SDN, fully virtualised and hardware based Bare-Metal switching, are currently not widely available. Therefore this paper proposes a test-platform for the benchmarking of SDN as well as a prototypical architecture. The latter serves to facilitate the evolutionary development of LTE towards 5G for use in Critical Infrastructure communication in general and Smart Grids in particular. A comparative evaluation of switching performance, realized via the described testbed, is presented and an assessment is given. Based on the introduced architecture and testbed, future work will develop new mechanisms for end-to-end slicing as well as application aware scheduling.

Intertwined: Software-defined communication networks for multi-agent system-based Smart Grid control

Facing current and future developments of the energy system, including the integration of large numbers of renewable energy sources and electric vehicles, live monitoring and control becomes essential for stable operation of the power grid. This transition to a Smart Grid requires coupling the power system with a reliable and real-time capable communication infrastructure. In response to this demand, we propose a combined approach for the control of power and communication systems, exploiting the opportunities of Software-Defined Networking (SDN). Due to its real-time capability, a Multi Agent System (MAS) is applied for controlling power flows, handling overloads and guaranteeing voltage stability in a decentralized manner. The MAS is supported by an Information and Communication Technologies (ICT) infrastructure, which follows the paradigms of SDN by applying a programmable controller platform with global network view to orchestrate traffic flows. To meet specific requirements of the MAS, we implement an SDN Northbound Interface, enabling control agents to communicate with the SDN controller directly. Thus, agents can advertise their demands to the controller, which translates them into corresponding forwarding rules and establishes them in the network. By applying fine grained prioritisation and integrating MAS and SDN controller, we showcase reliable and timely transmission of critical command messages, thereby ensuring power grid stability.

Communication architecture for monitoring and control of power distribution grids over heterogeneous ICT networks

In order to provide a comprehensive monitoring and controll infrastructure capable of fulfilling the requirements for security, control-ability and reliability of a modern Smart Grid, several factors for the adaptation of ICT technologies and architectures need to be considered. In this context Smart Grid systems operate on two time scales: first requiring delays in the order of μs for reporting events, e.g. short-circuits or component failures, and second data collection of the operational grid state from a huge number of sources, e.g. smart meters, sensors, etc., on the order of seconds to minutes. In this paper we focus on how network technologies can support this communication requirement of Smart Grid operation. Therefore, the focus is on reliability and control-ability of the network by providing the appropriate quality of service. For this purpose an overall heterogeneous communication architecture is presented, mapping the logical components and interfaces of multi-domain use cases to particular physical components and interfaces, which are implemented in testbeds and simulation models for assessment. Hereby, the major objective of the presented reference architecture is an unique definition of technical interfaces, components and information flows. It furthermore provides a framework for the specification of different technological options, information management and data aggregation. This work results in a novel approach for monitoring and controlling of energy distribution grids over heterogeneous communication networks is presented, which is based on two inter-related inner and outer control-loops for energy grid and communication network control. Furthermore, an application scenario is presented based on the integration of advanced meter reading and customer energy management systems into the overall architecture.

Enhanced Fast Failover for Software-Defined Smart Grid Communication Networks

Future energy systems depend on a corresponding Information and Communication Technology (ICT) overlay, allowing timely transmission of critical grid information in particular in case of failures or other unanticipated events. Therefore, to maintain grid stability, Smart Grid communication networks are required to be highly reliable and real-time capable. Within this paper, we propose and evaluate techniques for improved fault tolerance with regard to link failures within the ICT infrastructure, utilizing the concepts of Software-Defined Networking (SDN). centralized and decentralized approaches for both failure detection and traffic recovery are compared. While decentralized approaches, employing Bidirectional Forwarding Detection and OpenFlows fast failover groups, allow for shorter traffic disruptions by saving the delay of controller-switch communication, they result in sub-optimal configurations and possibly overloaded links. Vice versa, controller-driven approaches, using a custom heartbeat detection mechanism, may offer better alternative configurations due to fast re-calculation of routes, yet incur higher delays. Combining the advantages of both approaches, a hybrid concept is proposed, which enables nearly instant local recovery, succeeded by immediate optimal route updates, issued by the SDN controller. Thus, failover times are reduced to 4.5 ms mean delay, fulfilling IEC 61850 Smart Grid requirements, while providing optimal routes almost continuously and maintaining defined Quality-of-Service (QoS) levels.