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For future multi‐terminal HVDC networks, protection systems based on DC circuit breakers (DCCBs) are envisioned to limit the loss of power transmission towards AC grid(s). Yet, HVDC protection system design is considered a major challenge—especially in a multi‐vendor setup. In particular, protection systems shall enable HVDC converters to ride through DC faults without protective blocking. Several studies have performed sensitivity analyses to determine the DCCB properties and current‐limiting inductor properties that are required to enable converter fault‐ride‐through (FRT), but the HVDC converters themselves have been simplified and kept identical. However, in a multi‐vendor setup, the exact converter design is not known at the time of DC protection planning. Therefore, this paper investigates the impact of different converter properties on the DC‐FRT behaviour, and reveals implications on HVDC protection design. Firstly, analytical approaches are proposed to mathematically derive potential impact factors on the converters' FRT characteristics, also considering different converter control architectures. Secondly, a comprehensive EMT study demonstrates a significant impact of the converter parameters on the FRT behaviour. Analytical approaches and EMT results are compared with regard to limitations and applicability, such that the paper's findings can support the development of functional requirements for multi‐vendor multi‐terminal HVDC networks. [ABSTRACT FROM AUTHOR]

In the field of sector integration, the expansion of district heating (DH) is traditionally discussed with regard to the efficient integration of renewable energy sources (RES) and excess heat. But does DH exclusively benefit from other sectors or does it offer advantages in return? So far, studies have investigated DH only as a closed system or determined intersectoral benefits in a highly aggregated approach. We use and expand an integrated generation and transmission expansion planning model to analyze how the flexibility of DH benefits the energy system and the power transmission grid in particular. First of all, the results confirm former investigations that show DH can be used for efficient RES integration. Total annual system cost can be decreased by expanding DH, due to low investment cost and added flexibility, especially from large-scale heat storage. The high short-term efficiency of heat storage—in combination with electric heating technologies—can be exploited to shift heat demand temporally and, using multiple distributed units, locally to solve electric grid congestion. Although it is unclear whether these results can be replicated in the real world, due to the aggregation and detail of the model, further research in this direction is justified. [ABSTRACT FROM AUTHOR]

• Optimal power and gas flow problem considering power-to-gas. • Quasi-stationary modeling considering DC power flow and gas dynamics. • Scalable approach using successive linear programming. • Use case analyzing dispatch of renewable energy systems. The integrated modeling of power and gas systems gains importance as a result of increasing interdependencies due to bidirectional coupling in renewable energy systems through power-to-gas and gas-fired power plants. The optimal power and gas flow problem (OPGF) aiming to minimize system dispatch costs is mostly applied to small test systems. However, to investigate system-wide effects of sector coupling, large-scale transmission grids must be considered. Due to nonlinearities especially in the pressure loss equation, a nonlinear optimization problem results. This paper aims to demonstrate that successive linear programming, in contrast to other discussed approaches, is suitable for solving large-scale and multi-period OPGF-problems. The presented approach shows high solution quality despite short computing time even for large-scale systems such as the German power and gas transmission grid. [ABSTRACT FROM AUTHOR]

• Coupled steady-state and dynamic reactive power planning. • Assessment and planning of voltage control in intra-hour transitions. • Technology-dependent optimisation of active compensation devices to ensure short-term voltage stability. • Mixed-integer linear optimisation considering various voltage control requirements. Planning of reactive power compensation devices as part of the grid planning process is becoming increasingly important due to decreasing reactive power reserves from conventional power plants. Planning such devices requires the consideration of the reactive power demand both during steady-state operation and disturbances as well as gradual power-flow shifts. To control the voltage in these scenarios, a portfolio comprising location, rated power and technology of reactive power compensation devices must be identified. In this paper, a planning approach with a coupled determination of steady-state and dynamic reactive power demand is applied to a generic transmission system. Different characteristic grid use cases are analysed for the identification of the steady-state reactive power demand. The determination of the dynamic demand involves the analysis of critical power-flow shifts within an hourly generation time series. Shifts leading to insufficient voltage stability reserves and high voltage gradients are considered in the planning approach. Furthermore, critical line-outage and short-circuit scenarios are analysed in connection with an increasing demand for dynamic reactive power compensation. Results emphasise that the coupled determination of steady-state and dynamic reactive power demand identifies suitable portfolios of different compensation devices using synergies for voltage control during steady-state operation, disturbances and power-flow shifts. [ABSTRACT FROM AUTHOR]