Indikative Kapazitätsanalyse - Automatisierte Berechnung der Aufnahmekapazität von Verteilnetzen für dezentrale Energiequellen und zusätzliche Lasten
Introduction
Distribution System Operators are faced with an increasing number of connection requests for distributed energy resources such as PV systems or wind turbines and loads such as charging points for electric vehicles or heat pumps. Power flow is not only directed from central power plants to the
consumers but can also flow from producers in low voltage grids towards higher voltage levels. In addition, private wallboxes have a higher connection power than that of a regular consumer connection.
DSOs need to know the capacity of their grid to rapidly answer connection requests and to plan the grid expansion accordingly. Planning engineers need an efficient automated process that yields results with minimal manual intervention. By means of the ICA - Indicative Capacity Analysis, DIgSILENT offers a solution to determine the capacity of distribution networks based on the well proven algorithms of PowerFactory. This white paper describes the capabilities and the architecture of tge solution.
1 Analysis of Hosting Capacity
Hosting Capacity is the capability of a grid, without any network expansion, to absorb additional generation or load. The capacity is provided for each node of the network model individually. With this calculation it is possible to retrieve the possible generation power of a PV plant at a certain node without lines being overloaded or voltage limits exceeded. By means of this information a connection request can be approved or rejected directly.
The basis of the solution is the standard function Hosting Capacity Analysis available in the PowerFactory module Distribution Network Tools. This function, which can be used for all voltage levels, provides fast evaluation of a network, combining load flow, protection and harmonic analysis. The ICA solution automates Hosting Capacity Analysis, so as to provide results with minimal intervention from the user, and enable multiple scenarios to be evaluated. Examples might include evaluation of different switch states or seasonal conditions.
Key Facts
- It is possible to select the constraints to be used and to define the values for the limits. Limits can be set globally or individually for each network element.
- For the validity range of the constraints the complete network, a specific network region such as a feeder or a custom set of elements can be used.
- The calculation is possible for both balanced or unbalanced networks. A standard load flow can be used, or the LV load flow, which takes into account the stochastic behaviour of loads.
- The capacity is provided with active and reactive power values. The reactive power depends on the power factor to be considered for the calculation.
- The calculation can be parallelised in order to reduce the execution time.
The results of the calculation are the maximum active and reactive power of additional generation or load is provided for nodes. In addition, the limiting component (node, line, transformer,...) is reported, as well as the violated constraint and other electrical quantities.
2 Solution Architecture
The ICA solution consists of PowerFactory engines running the calculations on servers without a graphical user interface. The number of engines depends on the size of network models and the frequency of the calculations. The calculations can be carried out on a regular basis or whenever the network model changes. The engines are controlled by the Connector Service. This is Windows service offered by DIgSILENT, to schedule and monitor tasks. The service uses the powerful API of PowerFactory to provide access between all elements, functions and external tools.
In this solution PowerFactory provides the calculation functions. The solution, itself can be part of a business process of the utility using the results to deal with connection requests or to regularly verify the capabilities of the grid. Alternatively, the results can be provided directly in a web browser by the Connector Service.
The process within the solution consists of three steps: pre-processing → calculation → postprocessing. All steps allow individual configurations or extensions to meet customer requirements with minimal effort. As part of the post-processing, calculation results are provided for further business processes and integration into other systems. The network models and initial states can be versioned to rerun the automated calculations upon user request, for verification or regulation purposes.
3 Data Provisioning
For the calculation, the network topology and associated scenario data are required. The network model can be provided in different ways:
- Interface to SCADA or GIS using CGMES or PowerFactory’s DGS format
- Models from an existing PowerFactory database
- Import from other power system analysis tools
Additional scenario data can be imported in the pre-processing step.
4 Executive Summary
By means of the Indicative Capacity Analysis, DIgSILENT offers utilities an ingenious and scalable solution to automatically and periodically determine the network capacity for additional load and generation. The solution provides a comprehensive overview of grid capacity and helps utilities to manage their assets.
5 Licence Configuration
For the implementation of the use case described, the licence modules shown in the box are required. If more calculation functions should be considered in the automated network analysis, further modules can be required.