Abstract:
Abstract:Microgrid is a new type of power grid which combines micro power supply, multiple loads and energy storage system. Renewable energy generation is the main form of micro power supply, and it has the characteristics of intermittent and instability, which greatly affects the stability and security of micro grid operation. In order to improve the stability and security of micro grid operation, improve the absorption capacity of micro grid for renewable energy generation, and reduce the adverse impact of renewable energy generation in micro grid on micro grid and external grid, the role of energy storage system is particularly important. In order to optimize the traditional micro grid hybrid energy storage system, the grid distribution and capacity matching method of the hybrid energy storage system were studied, and the adaptive grid hierarchical control strategy was proposed. Taking an industrial park in the north of Hebei Province as an example, there were dozens of industrial enterprises in the park. The park adopted the mode of comprehensive energy system to achieve the maximum self-sufficiency of the park's energy consumption. With the same characteristics, each enterprise has a large area of available roof, which can use photovoltaic power generation to supply the park's energy; the park surrounding mountains can be built with distributed wind power or wind farms. The micro grid system includes external grid, regional grid, wind power, photovoltaic power generation, hybrid energy storage system and industrial load. Based on the basic conditions of the industrial park, the micro grid model including wind power, photovoltaic, grid composite energy storage system and distributed load was established. The micro grid was divided into four grids according to the simulation analysis of the research content, and the configuration of the composite energy storage system was solved by the improved particle swarm optimization (PSO). Before the optimization of composite energy storage, the external power outputs of the four grids were 1 280, 399, 1 284 and 957 kW; The external power demands were 1 480, 1 459, 1 396 and 1 247 kW, respectively. The results showed that the proposed grid format optimization method and adaptive grid hierarchical control strategy could eliminate all the renewable energy generation in the micro grid without external power output, at the same time, reduce the dependence of the external grid to the maximum, and achieve large-scale power self-sufficiency. The external power demands of the four grids were 79, 661, 81 and 253.8 kW, respectively, the total maximum external power demand was 895.8 kW, only 6.40% of the upper limit of transmission power. The power demand of the external power grid occurs in the two time periods of 00:00-05:00 and 18:00-21:00, both of which were the time of low load of the power grid, which had little impact on the external power grid and would not bring heavy pressure to the external power grid. It can be seen that the grid optimization method proposed in this paper can effectively suppress the fluctuation of source side and user behavior in micro grid system, improve the consumption capacity of renewable energy to the grid, and reduce the dependence and influence of renewable energy on the external grid.