The OpenIPSL was developed to be a familiar alternative to traditional power system analysis tools. There are, however, some particularities to the nature of the library, presented in this Section.

Power flow and Initialization

All models in a Modelica library require initial guess values that should come from a solution of the steady state of the overall model. This initial guess is called power flow. However, there is no power flow solver associated to the library as of the present time. When building a use case, initialization of all variables must be performed with a power flow software. The users are free to choose their power flow software of choice.

Almost all of our models have been developed to provide the same response than a reference power system simulation tool, e.g., PSAT and PSS®E. You can use these tools to create a power flow solution for your network. If you do not have access to these tools or do not want to use them, there are several power flow solvers available on GitHub. Examples on how to generate Modelica records from open source and proprietary power flow solvers, specifically GridCal and PSS®E can be found in this paper and in this GitHub repository.

From these values, a Modelica tool solves the initialization problem for all algebraic and differential - state variables. All models in OpenIPSL are programmed in such way that by introducing a power flow solution (from another tool), the initial guesses are computed as parameters within each model and are provided into the initial equations that are used as an initial guess to solve the overall initialization problem. See this paper for a more detailed explanation.

As we have just mentioned, the full initialization of the components' internal variables and states is achieved by a set of internal initial equations that are to be derived by the developer of the model. In a effort to harmonized the presentation of the power flow parameters, a model should extend pfComponent that will provide all the necessary parameters for data coming from power flow solutions to be used in the initialization of the model. The pfComponent also provide the support for the common SystemBase component that provides a single instance of the system's common parameters, i.e., frequency and base power.

Running Time Domain Simulations

The time domain simulations are prepared to work with Modelica-compliant tools. Users of the OpenIPSL are free to choose their tool of choice. However, note that the development of OpenIPSL has been carried out using OpenModelica, Dymola, Modelon Impact and Wolfram SystemModeler. The library is, also, systematically checked using the two mentioned tools (see Library Testing). Nonetheless, it might be possible to face issues when using other Modelica Tools that we have not fully tested.

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