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Modelica Electrical System Simulation and Analysis

Final Report Summary - MODELSSA (Modelica Electrical System Simulation and Analysis)

Executive Summary:
The MODELSSA project has delivered new functionality to the CATIA Systems solutions related to Dymola technology (www.dymola.com) to target the area of electrical systems simulation and analysis using Modelica (www.modelica.org). Focus has been on power electronic circuits and the new features have addressed both modeling and simulation aspects, as well as post-processing.
The diagram layer, the view that shows graphically interconnected components, has been extended to support component filtering. Components from different physical domains can be filtered out (dimmed or removed), either using command line functions or via the graphical user interface, to support easier browsing of complex models.
The feasibility of using 3D Electrical information for automatic creation of a corresponding Modelica model has been analysed. A prototype has been implemented using XML as intermediate format in the transfomation from CATIA to Modelica.
An improved graphical user interface for linear system analysis has been developed based on a new, general, mechanism to support user-configurable menus. Evolutions for improved steady-state initialization based on Modelica homotopy has also been delivered.
Two different approaches to increase simulation speed for power electronic circuits have been developed, support for automatic partitioning and code generation for multicore platforms and support for more efficient handling of events. The two approaches are complementing and can be used either together or in isolation depending on the model structure.
New features have been developed to support more convenient parameter studies, including a more user-friendly interface to model experimentation features and new functionality to support interactive tuning of parameters.
It has been demonstrated how properties and requirements modeling can be achieved using Modelica and Dymola technology. A concept of selections has been implemented to facilitate filtering out requirements in models.
The post-processing features have been improved to support plotting of general expressions constructed from signals from a result file. Furthermore, built-in support for signal operators, including root-mean-square (RMS), AC-coupled RMS, Total harmonic distortion (THD), and FFT (Fast Fourier Transform), has been implemented.
Configurable, automatic documentation is enabled by a dynamic report generator, which enables a HTML page loaded in a browser to call functions in Dymola using JavaScript. It is possible to insert a model diagram, change parameters, simulate a model, show plots, show animations, and more.
Project Context and Objectives:
The MODELSSA project has aimed at improving Modelica (www.modelica.org) and the CATIA Systems solutions related to Dymola (www.dymola.com) technology in the area of electrical system simulation and analysis. The project was coordinated by Dassault Systemes. The project partner, Austrian Institute of Technology, has been responsible for providing domain expertise and for testing the new features.
Eight specific tasks were formulated to be targeted by the project. These were split in three work packages dealing with modeling improvements, simulation improvements, and post-processing/documentation, respectively.
The eight specific tasks were; Model layers in the graphical user interface, Modelica model generation from CATIA Electrical, Convenient DC and small signal analysis, Multi-core simulation support, Interactive parameter studies, Requirement modeling, Improved post-processing and signal analysis, and Configurable automatic documentation of simulations.

Project Results:
Model layers:
A prototype implementing the concept of view has been developed. The view in the Dymola tools dedicated to showing graphically interconnected components is referred to as the Diagram layer. In that view it is possible to drag-and-drop Modelica components and to create connections between components with matching connectors.The prototype uses a command line function for filtering out components in the diagram layer. Filtered out components can be shown either dimmed or completely hidden. Once a filter has been created, it can be toggled on/off using dynamically created menus in the user interface. Filters are provided for all Interfaces classes of the Modelica Standard Library.

Modelica model generation from CATIA Electrical Wiring Routing:
The feasibility of using 3D Electrical information for automatic creation of corresponding Modelica model has been analysed. A prototype has been implemented using “Harness Description List (KBL)” XML format as an intermediate format. XSLT has been used for transformation to Modelica. The KBL structure has many similarities with Modelica capabilities, i.e. there is a natural transformation. It seems that sufficient information is available in the database by using cable type names and an additional database for, for example, capacitance and inductance per meter.

Convenient DC and small signal analysis:
The Dymola tools have been extended to support an extendable graphical user interface, which has been used to provide easier access to functions of the Modelica_LinearSystems2 library. A scheme for improved, homotopy-based, steady-state initialization was also designed and implemented. The new methods introduce two new, Dymola-specific, annotations and also includes extensions to the residue-operator. The approach has been tested on an operational amplifier model and was shown to perform well.

Multi-core simulation for power electronic circuits:
The Dymola tools have been extended to support new techniques that enable faster simulation of power electronic circuit models. Two different, but complementing, approaches have been developed.
The first approach is to extend the symbolic machinery of the Dymola technology in order to support automatic model partitioning with the purpose of generating efficient simulation code for multicore platforms. Some models were demonstrated to simulate up to three times faster on an Intel quadcore laptop. The achievable speedup depends very much on the model structure and the amount of calculations that take place in each model partition. The overhead introduced by the parallelization (for startup and synchronization) can have a negative impact on the total performance, something that was also shown in the evaluation. Future work will focus on better diagnostics to inform the user when parallelization is effective.
The second approach targeted event handling and focused on approaches to reduce the number of calculations in the continuous-time solver after an event. By examining the variables/expressions changed during the event, it is possible for the solver to either completely ignore the event or, if handling the event, avoid having to recompute the ODE-Jacobian. The new techniques were shown to achieve substantial speedup for electronic circuit test models provided both by the project partners.

Convenient parameter studies:
A number of improvements related to parameter studies have been implemented. Prototypes have been developed to facilitate more convenient parameter studies using built-in menu options rather than having to open Modelica libraries and execute functions. Support for interactive parameter studies has also been implemented making it possible to change model parameters while running simulations. Various options to perform the parameter updates are available and the optimized parameters can then be written back and saved in the model. Finally, new functionality was added to keep result files, either by manually pinning them or automatically if any signal has been selected for plotting.

Signal observers for requirements as needed for power electronic circuits:
It has been demonstrated how properties and requirements modeling can be achieved using Modelica and Dymola technology. The Dymola concept of selections has been shown to be well suited to filter out requirements in models. Approaches developed in previous and ongoing projects have been adapted to examples from the electrical systems domain.

Configurable post-processing features as needed for power electronic circuits:
The Dymola tools have been improved in the area of post-processing with special focus on the electrical system domain. Support has been implemented to construct and plot general expressions from signals from a result file. Built-in support for signal operators is available (minimum and maximum value, arithmetic mean, rectified mean, root-mean-square (RMS), AC-coupled RMS, First harmonic, Total harmonic distortion (THD), FFT (Fast Fourier Transform), and slew rate). Furthermore, a number of general improvements to the Dymola V6 plot functionality have been implemented.

Configurable automatic documentation of simulation runs:
A dynamic report generator has been designed and developed. It is based on Dymola tools running as a server. It enables a HTML page loaded in a browser to call Modelica functions using JavaScript. It is possible to insert a model diagram, change parameters, simulate a model, show plots, show animations, etc. It can be used as a “notebook” since it’s possible to re-execute function calls, for example to make a simulation with changed parameters and observe the changed plots. The resulting report can then be stored and sent to readers not needing Dymola to view it. The presented features can in the future be extended with many more features, such as graphical editing of models thanks to the power of HTML5 in combination with JavaScript and JSON.

Potential Impact:
The project has successfully targeted all the eight tasks formulated in the original Topic and, consequently, the Dymola technology has been substantially improved for the purpose of electrical system simulation and analysis.
Since many of the improvements developed in the project are directly applicable also outside of the electrical domain, Modelica and Dymola technology will become even more attractive for industrial, large-scale, model-based development.

List of Websites:
No public website.

Contact:
Dan HENRIKSSON
R&D CATIA Systems/Dymola Development Senior Manager
Office: +46 46 286 2521
dan.henriksson@3ds.com