Research On Island Microgrid Control Based On Multi-Agent

In recent years,the distributed new energy industry has gained great development.However,a large number of distributed energy sources will affect the safe and stable operation of the power grid.Micro-grid,as an important manifestation of distributed power generation,provides a good interface for distributed energy.Because micro-grid technology can integrate the advantages of distributed power effectively,which can not only meet the demand for load growth,but also ensure the reliability of power supply.So it has received extensive attention and research.Micro-grid has two operating modes,namely grid-connected mode and island mode.In the grid-connected mode,the micro-grid serves as the controlled unit of the main grid,and the dynamic characteristics of the micro-grid are determined by the main grid.However,the fluctuation and intermittent nature of distributed generation in the island mode may affect the frequency and voltage of the micro-grid at any time.Therefore,primary control and secondary control are required to ensure that the frequency and voltage of the micro-grid are stable at the rated value.And how to realize the economic optimal operation of micro-grids must also be considered.In the traditional micro-grid secondary control and economic cost optimization control,centralized control is often used.This control method has a complicated communication structure,a large communication volume,and greatly reduces the reliability of the system.In order to solve these problems,this paper applies a multi-agent consensus protocol to achieve the frequency and voltage control of the island micro-grid and the optimal control in consideration of economic conditions.The resource interaction between distributed power sources is performed in a distributed cooperative control manner.The paper firstly analyzes and designs the micro-grid layered distributed control structure based on the centralized control structure which is mainly designed with the primary controller,the distributed secondary controller,and the distributed economical operation controller.Compared with centralized control of traditional micro-grid,this structure has more advantages because it has a small amount of communication,a simple communication network structure,and has the characteristics of "plug and play".Therefore,this structure greatly improves the robustness and scalability of the system.Secondly,in distributed secondary coordinated control,for the frequency and voltage deviations of the micro-grid caused by the traditional droop control,the state feedback linearization method is used to build a second-order model of the micro-grid system.A distributed collaborative control strategy based on consensus agreement with virtual leaders is proposed by using information sharing and resource interaction between agents.The frequency and voltage deviations of the micro-grid are adaptively adjusted,while coordinating and controlling the active power output of the distributed power source to stabilize them at the rated value.The Lyapunov second method is used to prove that the system is asymptotically stable under the proposed control strategy,and the effectiveness of the control strategy is verified by simulation analysis.Finally,in order to optimize the operation cost of micro-grid system,a distributed economical optimization control strategy is proposed.An economic model of micro-grid system operation is constructed,and first-order consistency is used to optimize the active power output of the distributed power source under the condition of considering the output quota of distributed power generation to achieve the optimal system operation cost.Since the active power solution obtained under cost optimization is dynamically changed,a second-order consistency protocol with power difference as a consistency variable is proposed for power tracking control of distributed power.The change of power will cause the frequency and voltage deviation of the micro-grid system.The second-order consistency protocol can be used to optimize the frequency and voltage of the micro-grid system.Simulation analysis verifies the effectiveness of the proposed control strategy,and through comparison with the situation without considering economic optimization,it shows that the proposed control strategy can correct the frequency and voltage deviation correction while making the system run more economically and ensure the operation stability of the system.