Chattering-Free Simulation of Hybrid Dynamical Systems with the Function Mock-Up Interface 2.0

In this paper, we introduce a novel parallelization technique for Discrete Event System Specification (DEVS) simulation of continuous and hybrid systems. Here, like in most parallel discrete event simulation methodologies, the models are first split into several sub-models which are then concurrently simulated on different processors. In order to avoid the cost of the global synchronization of all processes, the simulation time of each sub-model is locally synchronized in a real-time fashion with a scaled version of physical time, which implicitly synchronizes all sub-models. The new methodology, coined Scaled Real-Time Synchronization (SRTS), does not ensure a perfect synchronization in its implementation. However, under certain conditions, the synchronization error introduced only provokes bounded numerical errors in the simulation results. SRTS uses the same physical time-scaling parameter throughout the entire simulation. We also developed an adaptive version of the methodology (Adaptive-SRTS) where this parameter automatically evolves during the simulation according to the workload. We implemented the SRTS and Adaptive-SRTS techniques in PowerDEVS, a DEVS simulation tool, under a real-time operating system called the Real-Time Application Interface. We tested their performance by simulating three large-scale models, obtaining in all cases a considerable speedup.

Solid oxide fuel cell (SOFC)/ gas turbine (GT) hybrid systems possess the capacity for unprecedented performances, such as electric efficiencies nearly twice that of conventional heat engines at variable scale power ratings inclusive of distributed generation. Additionally, these hybrids can have excellent operational flexibility with turndowns possibly as great as 85%. There are, however, developmental needs such as turbomachinery characterization and re-design. A leading example is that of greater propensity to have occurrences of stall-surge given the significantly different operating environment in contrast to conventional heat engines. Additionally, dynamic variation in power generation has to be done with significant a priori insight to avoid thermomechanical threats to cell stack and turbomachinery. State-of-the-art approaches involving hardware-in-the-loop simulation and, ultimately, additive manufacturing are being pursued to enable such characterization and re-design considerations given variable and dynamic operability requirements. Compressor performance in hybrid systems has been characterized at the United States National Energy Technology Laboratory (NETL), inclusive of a capability of feed forward hardware-in-the-loop simulation of hybrid systems under dynamic conditions and a capability of replacing turbine and compressor components at a relatively low cost. This paper highlights some of the simulation results, and the net result is an approach that addresses hybrid system developmental needs for accommodating generation transients.

Piece Linear Aggregates formalism (PLA) for specification and simulation of hybrid systems, when continuous components are described in ordinary differential equations (ODEs). PLA is used to create Quantized State System (QSS) model. QSS is integration based method, created for ODE solving. Since QSS method first was introduced for use in Discreet Event Systems (DEVS) formalism, we adapted it for PLA formalism, which is fundamentally consanguineous to DEVS formalism. Pharmacokinetics model is used as example of hybrid system. Pharmacokinetics is a branch of pharmacology which describes administered drug absorption and distribution in human body. In pharmacokinetics drug distribution is described using ODE. In order to use drug injection in pharmacokinetics model, we have to modify standard QSS model and add some specific capabilities. Result: modified QSS method was obtained and used for pharmacokinetic model specification. Simulation of morphine concentration in plasma was performed using real pharmacokinetics data to test Patient-Controlled Analgesia (PCA) method effectiveness. Ill. 2, bibl. 6 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.110.4.293

This talk will present two detailed examples of hybrid systems, covering design, simulation and implementation. The first concerns an Automated Highway System. The second application deals with a collection of autonomous unmanned aircraft. The paper provides a background about hybrid systems.

Interval-based Solving of Hybrid Constraint Systems

A design (at all levels of the abstraction hierarchy from functional specification to final implementation) is generally represented as a set of components, which can be considered as isolated monolithic blocks, which interact with each other and with an environment that is not part of the design. The model of computation defines the behavior and interaction of these blocks. Compactness of description, fidelity to design styles, ability to simulate, synthesize to an appropriate implementation and optimize its behavior are criteria to follow for the choice of an MOC to describe and manipulate a design. For example, some MOCs are suitable for describing complicated data transfer functions and completely unsuitable for complex control, while others are designed with complex control in mind.

Future power system has several challenges. One of them is the major changes to the way of supply and use energy; building a smarter grid lies at the heart of these changes. The ability to accommodate significant volumes of decentralized and highly variable renewable generation requires that the network infrastructure must be upgraded to enable smart operation. The reliable and sophisticated solutions to the foreseen issues of the future networks are creating dynamically intelligent application/solutions to be deployed during the incremental process of building the smarter grid. The smart grid needs more powerful computing platforms (centralized and dispersed) to handle large-scale data analytic tasks and supports complicated real-time applications. The implementation of highly realistic real-time, massive, online, multi-time frame simulations is required. The objective of this chapter is to present a general introduction to the DIgSILENT PowerFactory, the most important aspects of advanced smart grid functionalities, including special aspects of modelling as well as simulation and analysis, e.g. wide area monitoring, visualization, and control; dynamic capability rating, real-time load measurement and management, interfaces and co-simulation for modelling and simulation of hybrid systems. The chapter presents a very well-documented smart grid functionality, and limited cases are explained: Virtual Control Commissioning: connection to SCADA system via OPC protocol, direct connection to Modbus TCP devices, GIS integration with PowerFactory using API. The explained cases allow showing the full potential of PowerFactory connectivity to fulfil the growing requirements of the smart grids planning and operation.

This paper deals with a model builder for Hybrid Dynamic Systems (HDS), where technological components including sensors in an iconic format can be automatically dragged from a database and interconnected to produce the overall HDS, following industrial technological schemes. Once the model has been created, its consistency can be checked, and a block diagram simulation can be performed. The theory behind the software is based on Hybrid Bond Graphs (HBG), whose structural and causal properties will be exploited for the automatic generation of the diagnosis algorithms, which will be implemented online. Compared with developed programs for automated modeling of HDS, the presented methodology is valid for continuous and hybrid systems, and the HBG is used not only for block diagram simulation builders but also for the generation of Fault Detection and Isolation algorithms. The theory is illustrated by an industrial application that consists of the pneumo-electrical control of metro rolling stock.

This paper presents hybrid system, which combines photovoltaic systems, biomass and utility grid for the Matiranga Upazila in Khagracchari district in Bangladesh. The energy production of the photovoltaic system is inconsistent and the biomass can supply a constant but low supply all the time. So, the utility grid can mitigate energy demand during low supply from PV and biomass and set up energy balance. In this article, modelling and simulation of hybrid system are analysed. The hybrid system is simulated in the MATLAB/SIMULINK environment. The simulation results show the stable energy supply that can fulfill the energy demand by controlling the combination of photovoltaic power, biomass power, and utility grid power in the area.

Molecular dynamics simulation of realistic systems

Simulation of Stochastic Hybrid Systems using probabilistic boundary detection and adaptive time stepping

The simulation of cyber-physical systems involves modular heterogeneous systems. When embedding continuous subsystems in a discrete event system, in a classic approach the different subsystems use the same communication points and wait for each other. The approach presented in this paper uses predictions for every single continuous subsystem. That way the continuous subsystems can be used as discrete components in a discrete event system. This concept is implemented with FMUs (Functional Mock-up Units) generated with OpenModelica and the Discrete Event domain of Ptolemy II as a proof of concept. A model is implemented using this environment and compared to another implementation that uses only Ptolemy II. The results show the better scalability and shorter runtime of the presented approach compared to the pure Ptolemy II approach.

The aircraft power distribution system is a combination of electrical, mechanical, magnetics, and control system. Traditional professional software can only simulate one specific domain, in order to study the coupling characteristics of aircraft power distribution system, a multi-domain simulation tool is needed. A FMI (Functional Mock-up Interface) based multi-domain simulation method is proposed in this paper to utilize the advantages of different software and their professional model libraries. As a case study, this paper built the controllers of aircraft power distribution by Simulink, and then exported as the FMU (Functional Mock-up Unit) model to Dymola platform according to the FMI standard for the modeling and simulation of whole systems. Those models which exported according FMI standard can be independent from the original simulator and applied to other platforms corresponded FMI standard, which realize multi-domain modeling and simulation.

In this paper the majority of research refers to the optimal configuration of hybrid system that uses renewable energy and wind energy and solar radiation in association with diesel aggregate and batteries. These independent energy systems (hybrid systems) are becoming popular due to increasing energy costs and decreasing prices of turbines and Photo-Voltaic (PV) panels. But the only drawback is that their outputs depend upon the climatic conditions. The main goal to optimization a hybrid system is necessary to obtain the configuration of the system as well as the control strategy that minimizes the total cost through the useful life of the installation to meet the desired consumption and/or the pollutant emissions. The HOGA (Hybrid Optimizations by Genetic Algorithms) program was used to simulate the system operation and calculate technical economic parameters for each configuration. The system configuration of the hybrid is derived based on the data of wind and solar radiation which are related to the southern Croatian coast, as on a theoretical annual load at an observed location. Also, technical data for components are taken from the manufacturer’s specifications (datasheet). In this paper the advantages and disadvantages of commonly used types of generators (synchronous and asynchronous generators) are presented. Results show that the hybrid systems have considerable reductions in carbon emission and cost of the system.

Scilab is a free open-source software package for scientific computation. It includes hundreds of general purpose and specialized functions for numerical computation, organized in libraries called toolboxes, which cover such areas as simulation, optimization, systems and control, and signal processing. One important Scilab toolbox is Scicos. Scicos provides a block diagram graphical editor for the construction and simulation of dynamical systems. The objective of this book is to provide a tutorial for the use of Scilab/Scicos with a special emphasis on modeling and simulation tools. While it will provide useful information to experienced users it is designed to be accessible to beginning users from a variety of disciplines. Students and academic and industrial scientists and engineers should find it useful. The book is divided into two parts. The first part concerns Scilab and includes a tutorial covering the language features, the data structures and specialized functions for doing graphics, importing, exporting data and interfacing external routines. It also covers in detail Scilab numerical solvers for ordinary differential equations and differential-algebraic equations. Even though the emphasis is placed on modeling and simulation applications, this part provides a global view of Scilab. The second part is dedicated to modeling and simulation of dynamical systems in Scicos. This type of modeling tool is widely used in industrybecause it provides a means for constructing modular and reusable models. This part contains a detailed description of the editor and its usage, which is illustrated through numerous examples. All codes used in the book is made available to the reader. This new edition includes expanded chapters, new exercises and major rewrites for examples to work with the new Maple.