Quantifying costs and benefits of flexibility for DSOs

Abstract

The energy transition is expected to increase the peak loading of the grid, requiring Distribution System Operators (DSOs) like Stedin to invest an increasing amount of capital and labour in the reinforcement of their network. Flexible resources can be used to decrease the peak loading of the grid through better matching consumption and generation. DSOs can defer or avoid reinforcement by using flexible power to realize sufficient capacity at the lowest possible cost. This thesis provides the means for quantifying the ability of flexible power to act as an alternative to investment in grid reinforcement.
The problems expected to arise as a function of the energy transition are identified by literature research. It was found that of the identified problems, ’Power quality: Voltage dips and swells’- and ’Capacity: Thermal capacity'-problems are likely to be solvable through the application of flexible resources. To assess the intensity of the problems in Stedin's service area and research possible means of categorization, a projection of the energy transition scenarios of Netbeheer Nederland on parts of Stedin's grid is used. These simulations show problems arising mainly from cumulative integration of typical energy transition technologies, like PV, HP and EV. The voltage and capacity problems are shown to be highly related to active power flows, where the influence of reactive power flows is comparatively low.
Through a proposed revision of the 'Reinforce unless'-framework, the means are provided to determine the feasibility of solving encountered problems and bottlenecks through flexible resources. The revised framework quantifies the flexible resources’ ability for mitigating bottlenecks by combining the Jacobian matrix of power flow analysis with the technical abilities of the flexible resources. The application of flexible resources as an alternative to investment reduces the certainty of supply through the possibility of insufficient flexible capacity to mitigate the bottleneck. The resulting risk can be quantified through the 'not delivered'-energy.
Several potential barriers and discussions arise through describing the potential flexible resources in the distribution grid. The main discussion is based on the lack of insight and controllability in the distribution grid, reducing the overall applicability, and the trade-off between applying flexibility or facilitating flexibility. This trade-off requires DSOs to determine where to facilitate and where to use flexibility.
The financial feasibility of applying flexibility as an alternative to investment is discussed on both the procurement as the comparative feasibility towards reinforcement. Based on the review of services currently contracted by the Transmission System Operator (TSO) and literature research, a most likely approach to contract sufficient flexible resources at reasonable costs is described. The resulting method counteracts gaming, guarantees sufficient flexible power for mitigating bottlenecks at reasonable prices, and allows for market operation to provide the lowest possible costs.
This thesis reviews the operational problems that DSOs can expect and the role flexible resources can play to solve them. The framework of 'Reinforce unless' is adapted to fit this wider range of bottlenecks and to include specific methods to assess and substantiate the sufficiency of flexible power to solve the bottleneck.