Introduction  With the proposal of the "carbon peak" and "carbon neutrality" goals, the global push for the transformation of the energy structure is accelerating the construction of new power systems dominated by renewable energy. The intermittency and instability of the new energy sources connected to the grid place higher demands on energy storage technologies. Gravity energy storage, as a novel physical energy storage technology, has broad prospects for development. However, its output power lacks stability, and the power curve urgently needs to be optimized.

  Method  This paper analyzed the operation process of a shaft-based gravity energy storage system and established physical, efficiency, and power models. Based on these three fundamental models, an overall model for multi-objective optimization was developed with the goals of stabilizing power output and minimizing fluctuation rates. Constraints were set by combining the three models with real-world conditions to determine the optimal parameter configuration for the weight during operation.

  Result  Simulation verification of the energy storage system shows that the established overall model effectively optimizes the output power curve at the grid demand power levels of 30 MW, 40 MW, and 50 MW. The optimized fluctuation rates are 3.9%, 4.6% and 8.7%, respectively.

  Conclusion  Based on the proposed optimization model, under the condition of constant medium mass of the weight, the output power fluctuation increases as the grid demand power level rises. When the power level increases by 20 MW, the power fluctuation rate increases by 4.8%. Under the condition of constant grid demand power level, the output power fluctuation rate decreases as the medium mass of the weight increases. When the mass of the weight increases from 80 t to 150 t, the power fluctuation rate at 40 MW decreases by 4.2%. The model demonstrates good feasibility and provides valuable guidance for future vertical gravity energy storage projects.