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Title: Quantized State Systems (QSS) Solver with Functional Mock-Up Units (FMU) Support


Quantized State Systems (QSS) Solver with Functional Mock-Up Units (FMU) Support

Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
Report Number(s):
QSS Solver with FMU Support; 005413MLTPL00
SWR 17-44
DOE Contract Number:
Resource Type:
Software Revision:
Software Package Number:
Software CPU:
Open Source:
Source Code Available:
Related Software:
EnergyPlus (NREL SWR 17-23) and SOEP (NREL SWR 17-46)
Country of Publication:
United States

Citation Formats

. Quantized State Systems (QSS) Solver with Functional Mock-Up Units (FMU) Support. Computer software. Vers. 00. USDOE Office of Energy Efficiency and Renewable Energy (EERE). 7 Aug. 2017. Web.
. (2017, August 7). Quantized State Systems (QSS) Solver with Functional Mock-Up Units (FMU) Support (Version 00) [Computer software].
. Quantized State Systems (QSS) Solver with Functional Mock-Up Units (FMU) Support. Computer software. Version 00. August 7, 2017.
title = {Quantized State Systems (QSS) Solver with Functional Mock-Up Units (FMU) Support, Version 00},
author = {},
abstractNote = {Quantized State Systems (QSS) Solver with Functional Mock-Up Units (FMU) Support},
url = {},
doi = {},
year = 2017,
month = 8,
note =

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  • A Functional Mock-up Interface (FMI) defines a standardized interface to be used in computer simulations to develop complex cyber-physical systems. FMI implementation by a software modeling tool enables the creation of a simulation model that can be interconnected, or the creation of a software library called a Functional Mock-up Unit (FMU). This report describes an FMU wrapper implementation that imports FMUs into a C++ environment and uses an Euler solver that executes FMUs in parallel using Open Multi-Processing (OpenMP). The purpose of this report is to elucidate the runtime performance of the solver when a multi-component system is imported asmore » a single FMU (for the whole system) or as multiple FMUs (for different groups of components as sub-systems). This performance comparison is conducted using two test cases: (1) a simple, multi-tank problem; and (2) a more realistic use case based on the Modelica Buildings Library. In both test cases, the performance gains are promising when each FMU consists of a large number of states and state events that are wrapped in a single FMU. Load balancing is demonstrated to be a critical factor in speeding up parallel execution of multiple FMUs.« less
  • This paper describes software tools developed at the Lawrence Berkeley National Laboratory (LBNL) that can be coupled through the Functional Mock-up Interface standard in support of the design and operation of building energy and control systems. These tools have been developed to address the gaps and limitations encountered in legacy simulation tools. These tools were originally designed for the analysis of individual domains of buildings, and have been difficult to integrate with other tools for runtime data exchange. The coupling has been realized by use of the Functional Mock-up Interface for co-simulation, which standardizes an application programming interface for simulatormore » interoperability that has been adopted in a variety of industrial domains. As a variety of coupling scenarios are possible, this paper provides users with guidance on what coupling may be best suited for their application. Furthermore, the paper illustrates how tools can be integrated into a building management system to support the operation of buildings. These tools may be a design model that is used for real-time performance monitoring, a fault detection and diagnostics algorithm, or a control sequence, each of which may be exported as a Functional Mock-up Unit and made available in a building management system as an input/output block. We anticipate that this capability can contribute to bridging the observed performance gap between design and operational energy use of buildings.« less
  • This paper discusses design decisions for exporting Modelica thermofluid flow components as Functional Mockup Units. The purpose is to provide guidelines that will allow building energy simulation programs and HVAC equipment manufacturers to effectively use FMUs for modeling of HVAC components and systems. We provide an analysis for direct input-output dependencies of such components and discuss how these dependencies can lead to algebraic loops that are formed when connecting thermofluid flow components. Based on this analysis, we provide recommendations that increase the computing efficiency of such components and systems that are formed by connecting multiple components. We explain what codemore » optimizations are lost when providing thermofluid flow components as FMUs rather than Modelica code. We present an implementation of a package for FMU export of such components, explain the rationale for selecting the connector variables of the FMUs and finally provide computing benchmarks for different design choices. It turns out that selecting temperature rather than specific enthalpy as input and output signals does not lead to a measurable increase in computing time, but selecting nine small FMUs rather than a large FMU increases computing time by 70%.« less
  • This fact sheet provides an overview of the software development, modeling, and analysis for wind turbine performance, loads, and stabiluty analysis.

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