Development of an Energy Management Strategy for a Series Hybrid Tractor
Pylkkänen, Eemeli (2025)
2025
Energiamurroksen DI-ohjelma - Master’s Programme in Energy Transition
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
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Hyväksymispäivämäärä
2025-02-07
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202502072076
https://urn.fi/URN:NBN:fi:tuni-202502072076
Tiivistelmä
To effectively combat global climate change, it is essential to drastically reduce fossil fuel usage. In agricultural equipment, one effective solution is the introduction of hybrid powertrains, such as diesel-electric hybrids, which enable new degrees of freedom for drivetrain control. This added flexibility can be used to optimize overall system efficiency, leading to significant fuel economy improvements and reduced greenhouse gas emissions. However, to fully realize this fuel consumption reduction potential, a sophisticated energy management strategy must be implemented.
The purpose of this thesis was to research and develop a real-time energy management strategy for a series hybrid tractor, where power can be delivered not only electrically from the DC-link but also directly in mechanical form from the mechanical coupling of the engine and the generator. The objective was to reduce the overall fuel consumption compared to simple rule-based strategies. Additionally, the developed strategy’s fuel economy results were compared to globally optimal solution, calculated with an iterative dynamic programming algorithm. The performance results were investigated using different working cycles designed to reflect the most common tasks a tractor performs.
The developed energy management strategy was designed to take into account the combined efficiencies of the engine, the generator, and the battery. As a result, at each time instant the strategy managed to find an engine operation point that maximized the instantaneous total system efficiency. Also, the decision on whether the engine should be on or off was influenced by the maximum instantaneous total system efficiency. The main advantages of the approach were the ability to operate the system efficiently in varying operational conditions, and the modularity of the solution, meaning that it can be modified to work with various hybrid configurations. The main downside was that the engine operation point might change rapidly under certain load conditions.
The simulation results concluded that the fuel economy of the developed energy management strategy was effectively the same as the optimal solution throughout the investigated cycles. Additionally, the developed strategy improved the weighted average fuel economy by 1.3% compared to a rule-based power follower strategy and by 21% compared to a conventional, non-hybrid tractor. The improvements were the most significant in cycles with low average power demand and in those requiring moderate power from the mechanical powertrain.
The purpose of this thesis was to research and develop a real-time energy management strategy for a series hybrid tractor, where power can be delivered not only electrically from the DC-link but also directly in mechanical form from the mechanical coupling of the engine and the generator. The objective was to reduce the overall fuel consumption compared to simple rule-based strategies. Additionally, the developed strategy’s fuel economy results were compared to globally optimal solution, calculated with an iterative dynamic programming algorithm. The performance results were investigated using different working cycles designed to reflect the most common tasks a tractor performs.
The developed energy management strategy was designed to take into account the combined efficiencies of the engine, the generator, and the battery. As a result, at each time instant the strategy managed to find an engine operation point that maximized the instantaneous total system efficiency. Also, the decision on whether the engine should be on or off was influenced by the maximum instantaneous total system efficiency. The main advantages of the approach were the ability to operate the system efficiently in varying operational conditions, and the modularity of the solution, meaning that it can be modified to work with various hybrid configurations. The main downside was that the engine operation point might change rapidly under certain load conditions.
The simulation results concluded that the fuel economy of the developed energy management strategy was effectively the same as the optimal solution throughout the investigated cycles. Additionally, the developed strategy improved the weighted average fuel economy by 1.3% compared to a rule-based power follower strategy and by 21% compared to a conventional, non-hybrid tractor. The improvements were the most significant in cycles with low average power demand and in those requiring moderate power from the mechanical powertrain.