Technical Article

Hardware-in-the-Loop Simulation Tools and Implementation

July 08, 2020 by Anushree Ramanath

In this article, learn about some different hardware-in-the-loop simulation tools, their strengths and weaknesses, and how they apply to power system design.

In the first part of this series, we learned what hardware-in-the-loop (HIL) simulation is and how it offers a platform to accomplish real-time validation of complex systems. It is essentially a technique that facilitates the testing of a system in hand using signals that simulate the actual external stimuli.

Typically, a large complicated system is simulated with a few physical devices in order to enable the high fidelity response of actual equipment while retaining the scale of the simulation as shown in Figure 1. 


Figure 1. An example of a HIL simulation setup. Image courtesy of Speedgoat.
Figure 1. An example of a HIL simulation setup. Image courtesy of Speedgoat


The HIL approach is proven to be extremely effective in reducing process costs and time to market when compared to traditional validation techniques. In part two of this series, learn more about available HIL solutions and its use in the wide arena of applications in the field of power electronics and power systems.


Available HIL Systems

There are several companies that are currently offering competitive HIL simulation capabilities as end-to-end solutions. Some of them (stated in no particular order) are Typhoon, OPAL-RT, dSPACE, Plexim’s RT Box, Speedgoat, and NI. A vast majority of these solutions work with simulation models created using the MATLAB/Simulink software platform, thus making the integration and HIL validation process more convenient, intuitive, and user friendly.

Several industries, universities, and research and development centers have benefitted from HIL solutions. Most of them are scalable and flexible, making HIL a great choice for academic and innovative endeavors.


Typhoon HIL Simulation

Typhoon offers ultra-high-fidelity controller HIL simulation capabilities for several applications in the fields of power electronics, microgrids, drives, distribution networks, and traction applications. It promises to offer easy installation of necessary libraries, quick compilation of simulation models, low precise time step, and resolution. 


Figure 2. Sample HIL equipment offered by Typhoon.
Figure 2. Sample HIL equipment offered by Typhoon.


The offered solution is a seamlessly integrated technology stack from application-specific processors and robust numerical solvers to a schematic editor. 


OPAL-RT HIL Simulator

OPAL-RT offers a state-of-the-art HIL simulator with a rapid control prototyping (RCP) system and real power hardware. It offers offline simulation, real-time simulation, and real hardware test capabilities on a single test bench. It promises open architecture, speed, accuracy, and overall high-performance, along with a wide range of demo models. 


Figure 3. Sample HIL equipment offered by OPAL-RT.
Figure 3. Sample HIL equipment offered by OPAL-RT.


The offered real-time simulators are PC/FPGA-based and are mostly used to design, test, and optimize a wide range of systems in areas like power systems, automotive, power electronics, and aerospace. 



dSPACE offers SCALEXIO systems with advanced hardware and software architectures along with highly dynamic turn-key test benches. Its offerings encompass all the test phases including function testing, ECU testing, and network testing. 


Figure 4. Sample HIL equipment offered by dSPACE.
Figure 4. Sample HIL equipment offered by dSPACE.


SCALEXIO supports validation in fields of electric drive technology and data-driven software development for autonomous vehicles, along with providing a comprehensive toolchain for bus simulation and a wide array of software tools.


Plexim RT Box

Plexim offers a new HIL platform specifically for power electronics called RT Box. It facilitates both rapid control prototyping and real-time HIL testing by means of FPGA embedded CPU cores. 


Figure 5. Sample HIL equipment offered by Plexim.
Figure 5. Sample HIL equipment offered by Plexim.


The key application areas for RT Box include power electronic systems such as simple converters, AC drives, or multi-level inverters, specifically emulating the power stage. It claims a low time resolution along with low input/output latency. 



Speedgoat offers real-time target machines with specialized input/output modules and multi-core CPUs and FPGAs, along with a plethora of communication protocol options. Some of the most common applications include battery pack emulation, automotive components, and power electronics. 


Figure 6. Sample HIL equipment offered by Speedgoat.
Figure 6. Sample HIL equipment offered by Speedgoat.


NI HIL Testing

NI offers combined hardware and software tools to cater to high fidelity electric motor simulations. 


Figure 7. Sample HIL equipment offered by NI.
Figure 7. Sample HIL equipment offered by NI.


Their HIL solution provides a platform that enables safe testing of potentially destructive tests like transient and fault condition scenarios. It promises an open, extendable platform with high simulation fidelity and execution speed. The solution enables three levels of control system testing for electric motors including signal-level, power-level, and mechanical testing. 


Implementation of HIL in Power Electronics and Power Systems

Power electronic devices are used in several appliances necessary to perform day-to-day activities effectively. From chargers to mobile phones, consumer electronics to systems that reap the benefit of renewable energy sources, power electronics is a vital component to ensure the reliability and performance of the comprehensive systems. HIL systems can be used for validation of control algorithms that span several applications like renewable energy integration, motor drives for the automotive sector, modular multilevel converters (MMCs), smart grid applications, and so on.

Traditional power grids facilitate the essential generation, transmission, and distribution of electric power. Larger power systems require detailed fault analysis, the study of transient stability, compliance of sub-systems with grid integration standards, and other electromagnetic phenomena. These requirements can be accomplished using HIL setups. In general, the applications for HIL systems range from power system controls to components of the system like grid-tied converters, protection systems, cybersecurity aspects, microgrids, and wide-area monitoring protection.