Field-programmable gate arrays are replacing commercial central processing units in order to successfully achieve high-fidelity simulation for testing control units for electric motor drives.
MONTREAL — As new generations of EVs and HEVs continue to roll off assembly lines, OEMs are looking to extract every bit of efficiency out of the electric motors in their vehicles, while ensuring safe and reliable performance. A critical part of achieving this objective is having an effective control unit for the motor drive. The control unit optimizes and maintains performance over a range of operating conditions and also compensates for nonlinear effects such as field saturation and high-order harmonics. Furthermore, the controller needs to operate safely in failure modes, for example, when there is a fault in the power electronics that drive the motor.
For the mechanical systems in vehicles, such as IC engines and transmissions, controllers are tested and validated using hardware-in-the-loop (HIL) simulation. HIL simulation connects the controller used in the vehicle with a simulated engine or transmission. This process enables the controller to be tested safely, quickly and cost effectively, as a controller failure will only result in failure of the simulated engine or transmission. However, if the controller were tested in a lab with an actual engine or transmission, the engine or transmission could be damaged, and replacement is both expensive and time-consuming.
Mechanical systems typically have slower dynamics that can be simulated in real time using time steps of around 1ms. However, electric motor drives are typically driven by switching pulses that occur at 10s of kHz, and thus, real-time simulation of electric motor drives requires simulation time steps of the order of 1µs. Achieving these time steps is not possible on commercial CPUs, so high-fidelity simulation of electric motors has to be done on field-programmable gate arrays (FPGAs). FPGAs, however, are very difficult to program because one has to deal with low-level considerations such as fixed-point scaling and timing synchronization during execution.
OPAL-RT has created a suite of tools to make FPGA-based simulation accessible to engineers developing controllers for electric drives. First, a set of real-time motor models, covering a wide range of motors used for automotive applications including PMSMs, SRMs and BLDC motors, has been pre-packaged to run on FPGAs. The users do not need to know how to program an FPGA for simulation; they merely need to parameterize the motor appropriately using an intuitive GUI. The simulated motor inputs and outputs are converted to signals that can then be connected to the controller to complete the test setup. Next, the FPGA motor-test package enables the user to create power electronics faults to validate failure-mode operation of the controller. Third, the motor simulation can be integrated with a full-vehicle simulation running on a CPU for integration with other controllers, such as an ABS controller, that may need to be tested. Finally, OPAL-RT provides a test automation package that allows the development of test scripts to run whole batches of test sequences, thus providing an efficient method of conducting exhaustive controller testing.
FPGA-based simulation testing is a powerful method that ensures the controllers for next generation electric drives meet exacting performance requirements. OPAL-RT is making this technology accessible to every automotive engineer in the field.
About OPAL-RT TECHNOLOGIES:
OPAL-RT is a world leading developer of open, Real-Time Digital Simulators and Hardware-In-the-Loop testing equipment for electrical, electro-mechanical and power electronics systems. Our simulators are used by engineers and researchers at leading manufacturers, utilities, universities and research centers around the world. http://www.opal-rt.com/hybridelectrical-testing