In order to achieve a timely transition towards sustainable energy systems within a large landscape of multi-sectors and multi-technologies, decision-makers and industry practitioners can rely on time- and space-discretized energy system optimization models. However, such models are often burdened by the computational costs arising from the growing problem complexity, which is especially due to the time discretization. The common strategy to lower the computational cost is to uniformly reduce the temporal resolution, sacrificing the quality of the solution. In light of this, we propose the concept and a formulation of fully flexible temporal resolution, wherein each decision variable and constraint can have a separate temporal resolution. After introducing the formulation in detail, we demonstrate its capability by applying it to an EU-wide case study optimizing both capacity investment and operation decisions of the inter-connected energy system across the different countries. We show that the proposed flexible formulation allows us to flexibly remove variables and constraints that are not needed without losing accuracy, and to simplify the time discretization (e.g., in space) while pushing the Pareto front by simultaneously speeding up computation and limiting losses in accuracy. In conclusion, we highlight the promise of adopting fully flexible temporal resolution and encourage future research to explore further temporal resolution configurations beyond our examples.

As energy sectors become increasingly interconnected, selecting appropriate representations of physical characteristics in energy system optimization models has become challenging. This study evaluates the necessity of transmission and generator models by systematically excluding each one and assessing the impact on objective values, solution time, and feasibility of the resulting system design. We apply this analysis to two contrasting case studies optimizing the design and operation of: the IEEE 118-bus test power system and a zero-emission multi-energy system of the Netherlands. Results show that modeling Kirchhoff's Voltage Law (KVL) and alternating-current (AC) transmission losses is essential for accuracy and feasibility. KVL prevents unrealistic network loops; hence improving network utilization. Additionally, we evaluate two linearization methods for the AC transmission losses. Our findings indicate that tangent-based linear approximations often lead to infeasibility with three or fewer segments, whereas a piecewise-linear approach with at least two segments ensures accurate and computationally efficient solutions.

Virtualization in digital substations is a rising trend in the power sector, opening up interesting research avenues. The virtualization of intelligent electronic devices (IEDs) is thought to enable more flexible and agile cybersecurity software updates and patching processes while seamlessly integrating with current physical IEDs. However, no studies have yet considered a general cybersecurity assessment for such novel hybrid systems. To fill this gap, a systematic cybersecurity assessment of a digital substation composed of hybrid (virtual and physical) IEDs is presented in this paper. A testbed was developed to assess the different attack vectors with a focus on targeting virtual machines (resource exhaustion) and injection attacks on IEC 61850-compliant communication streams. A hybrid protection selectivity use case was successfully demonstrated with multiple targeted cyber attacks on the testbed where the non-attacked IED successfully cleared the grid fault. The attacks’ impacts ranged from minor to major effects on the IEDs’ tripping signals (and eventually circuit breaker actions) including forced signal delays, signal latching, and signal drops. The results of this study highlight the importance of providing a proper cybersecurity by design strategy for integrating hybrid substation systems with virtualization technologies.

As power system's operational technology converges with innovative information and communication technologies, the need for extensive resilience testing for scenarios covering the electrical grid, networking bottlenecks, as well as cyber security threats, become a necessity. This paper proposes a comprehensive, multi-disciplinary simulation framework to test virtualized intelligent electronic devices (vIEDs), considering 1) functional requirements, 2) performance and quality of service of the underlying communication network using software-defined networking, and 3) cyber security intrusion detection schemes. This work serves as a reference for researchers interested in the grid modernization of information and communication infrastructure for future power systems. Six different cyber security attack surfaces have been identified within the framework scope. It was observed that migration of vIEDs due to device maintenance or external anomalies is interesting from an operational perspective yet still poses significant security threats. Therefore, both host-based and network-based intrusion detection schemes were analyzed. Also, the setup has been mapped to an offshore wind case study demonstrating its potential and possible scenarios to simulate.