LPG-SAC-TCO: A Large Language Model--Policy-Guided Soft Actor-Critic Framework for Total Cost of Ownership--Optimal Energy Management of Hydrogen Fuel Cell Heavy-Duty Trucks

Hydrogen fuel cell heavy-duty trucks (HFCTs) are regarded as a promising solution for decarbonizing long-haul freight transportation. However, existing energy management strategies primarily focus on short-term energy efficiency and neglect long-term economic impacts, such as component degradation, hydrogen price volatility, and asset depreciation. This study reformulates energy management as a financialized long-term optimization problem and proposes LPG-SAC-TCO, a Large Language Model (LLM)--Policy-Guided Soft Actor-Critic framework for total cost of ownership (TCO)--optimal control. The proposed framework integrates a physics-based powertrain model, a full lifecycle TCO model, and a deep reinforcement learning controller. An LLM is introduced as a high-level policy advisor to extract semantic and financial insights from complex operating conditions, dynamically generating cost-priority signals that guide the downstream Soft Actor-Critic (SAC) controller. Unlike conventional reinforcement learning approaches that minimize fuel consumption alone, the proposed method directly minimizes the incremental TCO, incorporating hydrogen consumption cost, battery aging cost, fuel cell degradation cost, and depreciation loss. Simulation experiments are conducted under real-world driving cycles, stochastic hydrogen price scenarios, and varying payload conditions. Experimental results demonstrate that LPG-SAC-TCO reduces lifecycle total cost of ownership by approximately 19% compared with rule-based energy management and by about 11% relative to energy-oriented SAC controllers, while significantly mitigating battery cycling stress and fuel cell power degradation. Long-horizon simulations further show that the proposed framework extends component lifetime and yields more stable cost trajectories under stochastic hydrogen price fluctuations. These results confirm the effectiveness and robustness of LPG-SAC-TCO as a practical decision-support tool for fleet operators, leasing companies, and large-scale logistics enterprises.