As the proportion of wind power grid-connected capacity in the system continues to increase

the randomness of its output increases the fluctuation range of net load and operating cost of the unit

resulting in negative value. In order to quantify the negative value of wind power grid-connection

this paper establishes an optimal dispatching model for wind turbines. Based on the simulation results

the relationship between the operation mode of conventional wind turbines and the system operating cost at different permeabilities is quantitatively analyzed

and the main reasons for the negative value of wind power grid-connection are pointed out. According to the principle of energy storage and electricity balance

the optimal scheduling model of energy storage devices is established

and the optimal capacity of energy storage devices is determined to improve both the negative value of wind power grid connection and the total operating cost of the system. The results show that

the grid-connection value is positive when the wind power penetration rate is 3.41%. When the permeability increases to 5.36%

the grid-connection value turns negative. In this process

the increase in the starting and stopping times of base-load and waist load thermal power units plays a leading role. When the peak clipping rate reaches 0.75

the total operating cost of the system reaches the minimum

and the energy storage capacity corresponding to the peak clipping rate is the optimal capacity to reduce the negative value of wind power grid connection.