Virtualization of large scale distribution networks

How do you build a digital twin, in the form of a dynamic simulation model of a district heating network that contains 46 000 pipes, 9 000 customers and has a range of 20 km, within a reasonable time and cost?

It's pretty obvious that it would take too long to hand-build the model and very vulnerable to make misstakes. This problem was posed the EU project OPTi when it was started. Optimation took up the challenge to try to build a simulator model. The model also needed to meet a number of criterias in order to be useful in the various scenarios that would be investigated. Including control of differential pressures at certain points in the network, temperature distribution in the grid depending on the flow and a number of losses in pipes. Other participants in the project worked with modelling of pilot models of specific customers where indoor climate and outdoor temperature recorded.

As test facility in OPTI was appointed the whole of Luleå Energy's district heating network. On the basis that all pipes and customers throughout the network were stored in a GIS (geographical information System), along with how the pipe and customers are connected to each other it is possible to automatically create a model. A model is by definition a simplification of reality. Therefore, one can also assume that the model can be simplified further as long as it still good enough describes reality. From the GIS, data for the pipe, customers and junction points is transferred to a separate SQL database where the data can be processed with a number of simplification algorithms. For example, pipes in series into one tube and residential areas with the same consumption patterns are converted to one consumer. Pilot models and measurement points were reserved so that they remained unique. When all desired simplifications are made the content in the database are written out as a model in the format that the simulation program can handle.

Optimation uses Dymola based on the open Modelica standard. To complete the simulation program with predefined basic components of pipes, customers and junction points, Optimations library for industrial simulation, Visa2, was used. In addition the production plants and pumping stations have to be modeled separately.

Optimation uses Dymola based on the open Modelica standard. To complete the simulation program with predefined basic components of pipes, customers and junction points, Optimations library for industrial simulation, Visa2, was used. In addition the production plants and pumping stations have to be modeled separately.

To use a dynamic model a communication interface is needed. It is possible to choose between several different interfaces, in OPTi was chosen to work with FMI (Functional mock-up Interface) for communication between models.

In a dynamic model, it is possible to study the phenomenon and interact with the model in a way that is not possible with static models. In OPTi the model has been used to investigate superior control, optimization of the supply temperature curve and optimization of user flexibility (demand response).

The same methodology can be used for any large scale distribution network. OPTi logo

The biggest gain is that a new model can easily be generated within a few hours with the help of a few button presses if you for example want to study how a proposed new pipe would have an impact on the system.

To read more about project OPTi go to www.OPTi2020.eu.

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