Approach For Real-time Simulation Research Articles

Smart investment framework for energy resilience: A case study of a campus microgrid research facility

Energy resilience is a vital consideration for ensuring the survivability of modern infrastructure systems. Achieving 100% resilience, however, is often impractical and economically burdensome. In this paper, we propose a smart investment framework that enables decision-makers to determine optimal investments in energy resilience based on available resources and desired levels of resilience. To illustrate the effectiveness of this framework, we present a case study of a campus microgrid research and testing facility. Using a real-time simulation approach conducted with Typhoon Hardware In Loop (HIL), we evaluate the performance of the microgrid system over 24 hours following 4 historically significant hurricanes that have affected Louisiana in the past few years. The microgrid is designed to power local loads during outages, providing an effective solution for enhancing energy resilience. Real solar data collected from our 1.1 Megawatt (MW) solar facility on the University of Louisiana at Lafayette campus is integrated into the simulation, enabling a realistic evaluation of the system’s performance under hurricane-induced disruptions. By employing the proposed smart investment framework, decision-makers can better identify and address resilience challenges. The framework facilitates informed investment decisions by considering available resources and aligning them with the desired level of resilience. This approach avoids over-investment in unnecessary redundancy while ensuring critical systems are adequately protected. Our research contributes to the field by demonstrating the practicality and benefits of a smart investment framework for energy resilience in a real-world scenario. The case study of the campus microgrid research facility provides valuable insights for decision-makers in similar contexts, highlighting the potential of this framework to guide resilient energy infrastructure planning and investment strategies.

Real-Time Testing Optimal Power Flow in Smart-Transformer-Based Meshed Hybrid Microgrids: Design and Validation

The smart transformer (ST) is a multiport and multi-stage converter that allows for the formation of meshed hybrid microgrids (MHMs) by enabling AC-DC ports in medium and low voltage. This type of microgrid has advantages over the performance of conventional hybrid AC-DC microgrids (HMGs); however, the number of degrees of freedom of the ST increases the complexity of the energy management systems (EMSs), which require adequate and accurate modeling of the power flow of the converters and the MG to find the feasible solution of optimal power flow (OPF) problems in the MHM. An ST’s equivalent power flow model is proposed for formulating the MHM OPF problem and developing low-frequency equivalent models integrated with a decoupled hierarchical control architecture under a real-time simulation approach to the ST-based MHM. A simulation model of the MHM in the Simulink® environment of Matlab® 9.12 is developed and implemented under a digital real-time simulation (DRTS) approach on the OPAL-RT® platform. This model allows for determining the accuracy of the developed equivalent models, both low-frequency and power flow, and determining the MHM performance based on optimal day-ahead scheduling. Simulation test results demonstrated the ST equivalent model’s accuracy and the MHM’s accuracy for OPF problems with an optimal day-ahead scheduling horizon based on the model-in-the-loop (MIL) and DRTS approach.

Data-driven approach for the detection of faults in district heating networks

At present, District Heating Networks (DHNs) are required to operate more and more reliably and efficiently in order to further save primary energy and reduce environmental impact. Thus, monitoring and diagnostic approaches are necessary to identify the typical faults that affect this type of systems (e.g., anomalous heat and pressure losses), with the final goal of optimizing DHN operation and management. To this aim, this paper presents a data-driven diagnostic methodology that exploits NARX (nonlinear autoregressive network with exogenous inputs) neural networks to simulate DHN healthy operation and a threshold-based criterion for fault detection and identification. The novel diagnostic methodology is tested for evaluating the health state of the DHN of the campus of the University of Parma (Italy), based on the availability of time series of measurable variables (mass flow rate, pressure, and temperature) for both the power plant and the end-users. Both single and multiple faults of anomalous heat losses and anomalous pressure losses, with different magnitudes and location, were artificially implanted in DHN pipes. The main novel contribution of this paper with respect to state-of-the-art literature relies on the development of a real-time simulation approach aimed to predict DHN future operation and detect abnormal deviations from normal operation. The methodology proves to correctly detect and identify all simulated faults related to heat and pressure losses, by also correctly estimating their magnitude even in the most challenging scenarios.

Efficient bead-on-plate weld model for parameter estimation towards effective wire arc additive manufacturing simulation

AbstractDespite the advances in hardware and software techniques, standard numerical methods fail in providing real-time simulations, especially for complex processes such as additive manufacturing applications. A real-time simulation enables process control through the combination of process monitoring and automated feedback, which increases the flexibility and quality of a process. Typically, before producing a whole additive manufacturing structure, a simplified experiment in the form of a bead-on-plate experiment is performed to get a first insight into the process and to set parameters suitably. In this work, a reduced order model for the transient thermal problem of the bead-on-plate weld simulation is developed, allowing an efficient model calibration and control of the process. The proposed approach applies the proper generalized decomposition (PGD) method, a popular model order reduction technique, to decrease the computational effort of each model evaluation required multiple times in parameter estimation, control, and optimization. The welding torch is modeled by a moving heat source, which leads to difficulties separating space and time, a key ingredient in PGD simulations. A novel approach for separating space and time is applied and extended to 3D problems allowing the derivation of an efficient separated representation of the temperature. The results are verified against a standard finite element model showing excellent agreement. The reduced order model is also leveraged in a Bayesian model parameter estimation setup, speeding up calibrations and ultimately leading to an optimized real-time simulation approach for welding experiment using synthetic as well as real measurement data.

ANN-Aided Data-Driven IGBT Switching Transient Modeling Approach for FPGA-Based Real-Time Simulation of Power Converters

This article develops a novel feedforward neural networks (FFNNs)-based device-level model from a physical insulated-gate bipolar transistor (IGBT) model dataset by the proposed artificial neural network (ANN)-aided data-driven IGBT switching transient modeling approach, so that the physics-based IGBT models can be indirectly integrated into field programmable gate array (FPGA)-based real-time simulation of power converters. The main concept is to fit the turn-on/turn-off transient waveforms generated from a physics-based IGBT model by using multiple FFNNs with the same structure but different coefficients. Each FFNN is trained by a dataset covering the transient voltage/current values corresponding to all possible operating conditions at a given discrete time point during a transient. All FFNN coefficients are stored on FPGA. By applying the corresponding FFNN coefficients at each simulation time step, the switching transient waveforms can then be accurately reproduced. The proposed FFNN-based device-level model is designed into two intellectual property (IP) cores at 200 MHz with a fully pipelined structure, which allows the model to authentically reproduce transient waveforms with a 5-ns resolution. A four-phase floating interleaved boost converter (FIBC) is selected as a case study and simulated on a NI-PXIe FlexRIO FPGA real-time platform. The FPGA-based experimental results are compared with that from the LTspice offline simulator, which enables the validation of the accuracy and effectiveness of the proposed modeling approach for real-time simulation of power converters.

System Level Real-Time Simulation and Hardware-in-the-Loop Testing of MMCs

In this paper we present an approach for real-time simulation and Hardware-in-the-Loop (HIL) testing of Modular Multilevel Converters (MMCs) that rely on switching models while supporting system level analysis. Using the Latency Based Linear Multistep Compound (LB-LMC) approach, we achieved a 50 ns simulation time step for systems composed of several MMC converters and for converters of various complexity. To facilitate system level testing, we introduce the use of a serial communication-based (Aurora) interface for HIL testing of MMC converters and we analyzed the effect that communication latency has on the accuracy of the HIL test. The simulation and HIL results are validated against an MMC laboratory prototype.

An Optimization Based Community Model of Consumers and Prosumers: A Real-Time Simulation and Emulation Approach

The electricity consumption pattern is being increased day by day. Currently, network operators are moving towards renewable energy resources and applying demand response programs. However, the small and medium scale consumers and producers are needed to be aggregated and participate in the electricity markets as a unique resource. This paper proposes an optimization-based community model for aggregating the small scales consumers and producers. The model includes a central controller, which is considered as an aggregator, and several local community managers to keep the network balanced locally. Furthermore. real-time simulation approach and several real devices as hardware-in-the-loop are used to validate the system under practical challenges. The results of the paper reveal a gap between the simulation and experimental results and prove the performance of system in real-time mode using actual devices.

A Benchmark System for Hardware-in-the-Loop Testing of Distributed Energy Resources

In order to overcome challenges associated with the integration of distributed energy resources (DER) into state-of-the-art and future power grids, a common basis for testing using appropriate benchmark systems is required. Real-time hardware-in-the-loop (HIL) simulation has proven to be an advanced and efficient tool for the analysis and validation of electric power systems and DER components. However, a common methodology for HIL testing of DER along with the required set of reference systems has not yet been developed. This task-force paper proposes a benchmark system for HIL testing incorporating DER into the real-time simulation environment. A low-voltage benchmark system with detailed HIL setup is proposed for the testing of DER performance. The modeling of DER for real-time applications is discussed, and the detailed laboratory procedures and setups for both controller HIL (CHIL) and power HIL (PHIL) are provided. Results from CHIL simulation related to the centralized controls and experimental results of PHIL simulation related to local control on the benchmark system substantiate the suitability of the proposed real-time simulation approach.

System-Level, FPGA-Based, Real-Time Simulation of Ship Power Systems

In this paper, we present a scalable approach for real-time simulation of ship power systems with high-frequency power electronics converters (100–200 kHz). The proposed approach is based on the latency-based linear multistep compound method and relies on field-programmable gate array (FPGA) execution. Several examples of increasing dimension and complexity are used to evaluate the scalability—both of in terms of computational delay and of resources usage—of the proposed approach. Real-time execution with a 50 ns time step is achieved for all the examples considered.

Real-Time Error Control for Surgical Simulation.

To present the first a posteriori error-driven adaptive finite element approach for real-time simulation, and to demonstrate the method on a needle insertion problem. We use corotational elasticity and a frictional needle/tissue interaction model. The problem is solved using finite elements within SOFA.1 For simulating soft tissue deformation, the refinement strategy relies upon a hexahedron-based finite element method, combined with a posteriori error estimation driven local -refinement. We control the local and global error level in the mechanical fields (e.g., displacement or stresses) during the simulation. We show the convergence of the algorithm on academic examples, and demonstrate its practical usability on a percutaneous procedure involving needle insertion in a liver. For the latter case, we compare the force-displacement curves obtained from the proposed adaptive algorithm with that obtained from a uniform refinement approach. Error control guarantees that a tolerable error level is not exceeded during the simulations. Local mesh refinement accelerates simulations. Our work provides a first step to discriminate between discretization error and modeling error by providing a robust quantification of discretization error during simulations.

Real-time model for simulating a tracked vehicle on deformable soils

Simulation is one possibility to gain insight into the behaviour of tracked vehicles on deformable soils. A lot of publications are known on this topic, but most of the simulations described there cannot be run in real-time. The ability to run a simulation in real-time is necessary for driving simulators. This article describes an approach for real-time simulation of a tracked vehicle on deformable soils. The components of the real-time model are as follows: a conventional wheeled vehicle simulated in the Multi Body System software TRUCKSim, a geometric description of landscape, a track model and an interaction model between track and deformable soils based on Bekker theory and Janosi–Hanamoto, on one hand, and between track and vehicle wheels, on the other hand. Landscape, track model, soil model and the interaction are implemented in MATLAB/Simulink. The details of the real-time model are described in this article, and a detailed description of the Multi Body System part is omitted. Simulations with the real-time model are compared to measurements and to a detailed Multi Body System–finite element method model of a tracked vehicle. An application of the real-time model in a driving simulator is presented, in which 13 drivers assess the comfort of a passive and an active suspension of a tracked vehicle.

A novel drivetrain modelling approach for real-time simulation

This article opens perspectives for generic modelling and real-time simulation of automotive gear transmissions containing multiple friction elements. Generic mathematical drivetrain modelling is challenging, as friction elements cause a system to vary its order and structure. Furthermore, adaptive time-step methods are not suitable for real-time simulation. Unfortunately, literature lacks flexible fixed time-step approaches for multiple friction elements. The modelling solution proposed in this article is designed for fixed time-step execution and is applicable to all types of gear transmissions. The approach is verified on an exemplary simplified drivetrain. It is demonstrated on a complex hybrid-electric automatic drivetrain topology and validated via transmission test bench measurement. Finally, the approach is applied to a conventional automatic drivetrain and validated via vehicle measurement.

MMC-HVDC Simulation and Testing Based on Real-Time Digital Simulator and Physical Control System

Real-time simulation of modular multilevel converter (MMC)-based HVDC is one of the most important and difficult technologies in the area of utility-scale power electronics research. This paper describes an efficient modeling approach for real-time simulation of MMC-HVDC. Taking advantages of the full parallel architecture of the field-programmable gate array (FPGA), more than 1500 submodules are able to be simulated in a single FPGA. The design details of the physical MMC control system are also presented. The presented MMC-HVDC real-time simulator and physical control system are successfully performed in the Nan-ao Island MMC-HVDC project, which is the world’s first three-terminal MMC-HVDC system for research on operation and fault characteristics. The results validate the accuracy of proposed approach and real-time MMC simulator.

Advanced Simulation of the Power Electronic Converters of VSC FACTS and HVDC in Hybrid Real Time Simulators of Power System

The present paper focuses on simulation of VSC (voltage source converter) based on FACTS (Flexible Alternating Current Transmission System) and HVDC (High Voltage Direct Current) transmission technologies. Particular attention is paid to hybrid real-time simulation approach which provides adequate and comprehensive modeling of electric power systems (EPS), containing FACTS and HVDC. The results of experimental research support the necessary level of adequate simulation of commutation processes and suitability of the presented concept and simulation tools for effective solution of research and development tasks of effective use of HVDC and FACTS devices in EPS.

Systems-on-chip approach for real-time simulation of wheel–rail contact laws

This paper presents the development of a systems-on-chip approach to speed up the simulation of wheel–rail contact laws, which can be used to reduce the requirement for high-performance computers and enable simulation in real time for the use of hardware-in-loop for experimental studies of the latest vehicle dynamic and control technologies. The wheel–rail contact laws are implemented using a field programmable gate array (FPGA) device with a design that substantially outperforms modern general-purpose PC platforms or fixed architecture digital signal processor devices in terms of processing time, configuration flexibility and cost. In order to utilise the FPGA's parallel-processing capability, the operations in the contact laws algorithms are arranged in a parallel manner and multi-contact patches are tackled simultaneously in the design. The interface between the FPGA device and the host PC is achieved by using a high-throughput and low-latency Ethernet link. The development is based on FASTSIM algorithms, although the design can be adapted and expanded for even more computationally demanding tasks.

Development of a real-time bogie test rig model based on railway specialised multibody software

The design of mechatronic systems of rail vehicles requires performing verification and validation in the real-time mode. One useful validation instrument is the application of software-in-the-loop, hardware-in-the-loop or processor-in-the-loop simulation approaches. All of these approaches require development of a real-time model of the physical system. In this paper, the investigation of the usage of the model of the locomotive's bogie test rig created in Gensys multibody software has been performed and the calculation time for each time step has been analysed. The verification of the possibility of the usage of such an approach for real-time simulation has been made by means of a simple data transferring process between Gensys and Simulink through the TCP/IP interface. The limitations and further development issues for the proposed approach have been discussed in this paper.

Real-time Simulation of Dynamic Vehicle Models using a High-performance Reconfigurable Platform

A purely software-based approach for Real-Time Simulation (RTS) may have difficulties in meeting real-time constraints for complex physical model simulations. In this paper, we present a methodology for the design and im-plementationofRTS algorithms,basedontheuseof Field-ProgrammableGateArray(FPGA) technologytoimprove the response time of these models. Our methodology utilizes traditional hardware/software co-design approaches to generate a heterogeneous architecture for an FPGA-based simulator. The hardware design was optimized such that it efficiently utilizes the parallel nature of FPGAs and pipelines the independent operations. Further enhancement is obtained through the use of custom accelerators for common non-linear functions. Since the systems we examined had relatively low response time requirements, our approach greatly simplifies the software components by porting the computationally complexregionsto hardware.We illustratethe partitioningofa hardware-based simulator design across dual FPGAs, initiateRTS usinga system input froma Hardware-in-the-Loop (HIL) framework, and use these simulation results from our FPGA-based platform to perform response analysis. The total simulation time, which includes the time required to receive the system input over a socket (without HIL), software initialization, hardware computation, and transferof simulation results backovera socket, showsa speedup of 2× as compared to a simi-lar setup with no hardware acceleration. The correctness of the simulation output from the hardware has also been validated with the simulated results from the software-only design.

Real-time digital simulation of power electronics systems with Neutral Point Piloted multilevel inverter using FPGA

Most of actual real time simulation platforms have practically about ten microseconds as minimum calculation time step, mainly due to computation limits such as processing speed, architecture adequacy and modeling complexities. Therefore, simulation of fast switching converters’ instantaneous models requires smaller computing time step. The approach presented in this paper proposes an answer to such limited modeling accuracies and computational bandwidth of the currently available digital simulators.As an example, the authors present a low cost, flexible and high performance FPGA-based real-time digital simulator for a complete complex power system with Neutral Point Piloted (NPP) three-level inverter. The proposed real-time simulator can model accurately and efficiently the complete power system, reducing costs, physical space and avoiding any damage to the actual equipment in the case of any dysfunction of the digital controller prototype. The converter model is computed at a small fixed time step as low as 100ns. Such a computation time step allows high precision account of the gating signals and thus avoids averaging methods and event compensations. Moreover, a novel high performance model of the NPP three-level inverter has also been proposed for FPGA implementation. The proposed FPGA-based simulator models the environment of the NPP converter: the dc link, the RLE load and the digital controller and gating signals. FPGA-based real time simulation results are presented and compared with offline results obtained using PLECS software. They validate the efficiency and accuracy of the modeling for the proposed high performance FPGA-based real-time simulation approach. This paper also introduces new potential FPGA-based applications such as low cost real time simulator for power systems by developing a library of flexible and portable models for power converters, electrical machines and drives.

A Phenomenological Approach for Real-Time Simulation of the Two-Way Shape Memory Effect in NiTi Alloys

A phenomenological model to simulate the two-way shape memory effect (TWSME) in nickel-titanium alloys (NiTi) is proposed. The model is based on the Prandtl–Ishlinksii operator and it is able to simulate the hysteretic behavior of the material in the strain-temperature response. Starting from some experimental measurements of well known thermomechanical characteristics of NiTi alloys, the parameters of the phenomenological model are identified by simple and efficient numerical procedures. The model was developed in the commercial software package SIMULINK® and it is able to simulate the effects of applied stresses on the TWSME as well as partial thermal cycles, which generate incomplete martensitic transformations. A systematic comparison between experimental measurements, carried out under different values of applied stress, and numerical predictions are illustrated for both complete and incomplete phase transformations. The results are considered satisfactory both in accuracy and in computational time; therefore, the method is robust and suitable for use in real-time applications.

Assessment of manoeuvring performance of large tankers in restricted waterways: a real-time simulation approach

During the past 30 years there has been a steady growth in the size and number of ships that use the Strait of Istanbul (Bosporus) which is one of the most hazardous, crowded, difficult and potentially dangerous waterways in the world. There have been over 200 accidents over the past decade resulting in loss of life and serious damage to the environment. This paper presents the results of a real-time ship manoeuvring simulation study investigating the manoeuvring performance of large tankers in the Bosporus. The study was conducted with a ship manoeuvring simulator which is capable of subjecting a given hull form to any combination of environmental conditions, i.e. wind, current and wave drift forces. The results indicate that when realistic environmental conditions are taken into account the size of ships which can navigate safely in compliance with the traffic separation lanes is limited.