Hardware-in-the-loop testing for electric vehicle drive applications - Embedded.com

Hardware-in-the-loop testing for electric vehicle drive applications

In recent years, hardware-in-the-loop (HIL) testing has shown significant promise to serve as a comprehensive rapid prototyping and automated testing platform for advanced power systems. HIL testing is a technique that replaces a physical model, such as an electric vehicle drive train, with a mathematical representation that fully describes the important dynamics of the physical model.

A device under-test, such as an embedded controller or electronic control unit (ECU), interfaces directly with a low-latencyrealtime computing platform that computes the response of the physical system. A test bench simulation provides the ability to inject test cycles and faults into the real-timesimulation, which enables the device-under-test controller to be tested with a wide range of normal and fault operating conditions.

Hardware-in-the-loop enables the testingof closed-loop device-under-test controllers under realistic operating conditions without the need to interface with a high-power system.

HIL tools enable: (1) accelerated testingand validation; (2) reduced testing time needed in the lab; (3) simulation of all operating points and scenarios that are difficult or impossible to recreate with a real system; (4)fault injection capability;( 5) real-time access to all signals that are difficult to measure in a real system.

Existing hardware-in-the-loop tools have been used to test and prototype systems with slower dynamics, including power grid dynamics and power system dynamics. However, current state-of-the-art HIL tools have been insufficient for prototyping power electronics converters, which are becoming ubiquitous in energy conversion andpower processing devices.

A power electronics HIL environment can provide a rapid prototyping platform for the design and testing of power electronics hardware, software,and firmware. Power electronics converters, unlike power systems, are characterized by high-frequency switching devices, including controlled switches (e.g. IGBTs,MOSFETs, thyristors, SCRs) and self commutating switches (e.g. diodes) that operate on the order of 10 kHz.

Furthermore, these switching devices introduce differential andcommon mode voltages and currents at frequencies on the order of 1 MHz and above. Indeed, a realtime simulation of a power electronics converter with a carrier frequencyon the order of 20 kHz requires a sampling timeless than 5 microsecond to capture the important system dynamics.

However, the non-linear switching dynamics has poseda challenge for low-latency, real-time simulation of power electronics converters. Existing simulators for power electronics are limited by a sampling time between 10 to 50 microseconds forrealtime execution, or do not have the ability to be executed in real-time.

This paper describes the design, implementation, and validation of a hardware-in-the-loop (HIL) test platform for electric vehicle drive applications. We implement a HIL platform by interfacing a variable speed drive controller with a real-time simulation of an electric vehicle drive.

A real-time test bench simulation enables drive cycle testing and fault injection capability for the HIL platform. We demonstrate theprototyping capability of the HIL platform with the EPA Urban Dynamometer Driving Schedule (UDDS) on an electric vehicle drive system. Real-time comparisons with a real,small-scale electric vehicle drive validate the fidelity of the real-time simulation under various operating and fault conditions.

Test case simulations demonstrate the fidelity andprototyping capability of the hardware-in-the-loop platform when used for electric vehicle drive testing applications. Additionally, real-time simulation and test resultsdemonstrate the ability of the HIL platform to accurately encapsulate electric vehicle dynamics with time constants that span more than five orders of magnitude.

To read this external content in full, download the complete paper from the author archives on line. 

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