Creating reduces-order battery models for PHEV powertrain control
Plug-in hybrid electric vehicles (PHEVs) offer the benefits of both a battery and an internal combustion engine, automatically shifting between gasoline, electricity or a combination of both depending on power requirements and the battery’s state of charge.
The better the control system that governs those shifts, the better the fuel economy and performance. Today, car companies are increasingly using powertrain models for the control system design. Those powertrain models also require a battery model.
However, modelling the complex electrochemical dynamics of lithium-ion batteries involves many highly non-linear equations. That’s a problem because the more equations there are (and the more complicated they are), the more time and computational effort it takes to solve them.
WISE researchers Nasser L. Azad and John McPhee created a simpler battery model — a so-called “reduced-order model” — that could speed up the calculations without sacrificing accuracy.
They started with an accurate but complicated model and looked for components that weren’t contributing significantly to the battery behaviour in response to input signals. When they examined the incoming battery power signal — which is related to how much power the vehicle requires at any given time — they hit pay dirt.
The researchers observed that most incoming signals fell within a specific frequency range. By removing the battery model components that are not significant in that range, they could simplify the equations significantly.
This approach produced a maximum relative error of just 1 percent for the battery state of charge. However, their simplified model was almost 43 percent faster. As a result, their method offers a computationally efficient model for designing real-time PHEV powertrain control systems.
Researchers: Ramin Masoudi, Amir Taghavipour, Nasser L. Azad, John McPhee
Partners: Natural Sciences and Engineering Research Council of Canada, Toyota, Maplesoft
Source: Masoudi, R., Taghavipour, A., L. Azad, N., & McPhee, J. (2024). A robust model order reduction scheme for lithium-ion batteries in control-oriented vehicle models. Journal of The Electrochemical Society, 171, 053501.