Hybrid Powertrain Technologies for Agricultural Tractors: A Review of Performance Control and Powertrain Matching

Agricultural tractors operate at low speeds under heavy loads. Disturbances from multiple load sources and coupled power flows challenge the fuel economy, transient response, and adaptability of conventional diesel powertrains. Hybrid powertrains offer a viable route to improve energy efficiency and dynamic performance; however, their design and control must be tailored to agricultural operating conditions. This review synthesizes recent literature on hybrid tractor powertrains through an operating-condition-oriented framework. It first characterizes the power demands of traction, power take-off (PTO), transport, and hydraulic operations and compares the applicability of series, parallel, and compound hybrid architectures. It then reviews key component technologies, including engines, electric-drive systems, and energy-storage systems, with an emphasis on coordinated design and power-flow allocation. Control strategies, energy-management approaches, and powertrain parameter-matching methods are further assessed in relation to transient load compensation, energy balance, and long-duration operation. Emerging directions, including multisource load prediction, data-driven control, and intelligent energy management, are also discussed. The synthesis indicates that powertrain suitability depends on agricultural task requirements and that component sizing and energy management should be evaluated together under representative operating cycles. It examines trade-offs among operational quality, energy consumption, reliability, and cost, and identifies coordinated design and long-duration field validation as priorities for hybrid tractor development.