Research On Multi-scale Power Supply Flexibility Evaluation And Energy Storage Allocation Of Power System With High-penetration Renewable Electricity

In recent years,renewable energy has been vigorously developed in C hina.Renewable energy plays an increasingly prominent role in the power grid.The access o f large-scale renewable energy makes the grid generation cleaner and more environmentally friendly,but it makes a challenge to the flexible operation of the grid.In the power system with high proportion of renewable energy,the uncertainty of new energy output will intensify the system's demand for flexible regulation,and the proportion of conventional power units in the grid has been compressed by the continuous access of renewable energy,which further reduces the flexible supply scale of the system,a nd increase the inadequate flexibility risk of the system.In this context,considering the multi-time scale output characteristics of renewable energy,this paper proposes the flexibility evaluation method based on multi-scale morphological decomposition and the energy storage allocation model based on a bi-level programme.The main work is as follows:(1)Based on a large number of historical data,using probability statistical analysis and time series analysis method,the output characteristics of large-scale renewable energy in 1-minute,15-minute and 1-hour levels are summarized.Besides,the complementary characteristics of peak modulation in daily scale between wind power and photovoltaic power and the complementary characteristics of power changes in monthly scale between wind power and photovoltaic power are analyzed,which provides ideological guidance for subsequent flexibility assessment and energy storage al ocation.(2)Considering the influence of the multi time scale difference of wind power and photovoltaic power fluctuation on the flexibility of power system,this paper proposes an evaluation index and calculation method of power system flexibility which can effectively distinguish the flexibility demand in multi time scale.Through the multi-scale decomposition algorithm based on WMMF filter,the independent multi-scale components are accurately obtained,and the flexibility demand under the specific fluctuation period is obtained;the adjustment capability models of different types of controllable units in the system under different regulation rate intervals are established to form the multi-scale flexibility resource regulation interval.Finally,through comparison of flexible supplies and demands,the flexibility indexes under the corresponding scale are calculated.(3)According to the requirements of flexibility power in different time scales,a multi-scale energy storage system framework is constructed by matching the output characteristics of energy storage units with the flexibility demands of each scale.Then,the flexibility demand under the specific fluctuation period is obtained through the multi-scale decomposition algorithm based on WMMF filter.Considering the economy of energy storage allocation and the flexibility of system operation,a multi-scale energy storage allocation model based on the bi-level programme is established,and the particle swarm optimization algorithm under the adaptive weight is used for optimization.The example shows that the multi-scale energy storage allocation optimization model can achieve the balance of flexibility demand and flexibility supply in each time scale according to the power output of wind power and photovoltaic power system,and improve the power system flexibility.