Microgrid has a prominent position in the smart grid and distribution network.It is composed of various distributed power sources,control equipment,energy storage devices and loads.It can be used for power generation and power distribution.The microgrid can be operated not only in the network but also in isolation;when the network is running,the frequency and voltage are controlled by the large grid;when the island is operated,the frequency and voltage must be controlled by itself,and the deviation of each index must not exceed the specified range.Although the traditional droop control can realize decoupling control,in this control mode,the voltage and frequency deviate from the rated value,the power cannot be reasonably distributed,and the running cost is also high.In order to solve the above deficiencies,this paper proposes a distributed optimal control method,the whole control is composed of the underlying control and the optimized secondary control.The bottom layer control realizes the frequency and voltage stability of the microgrid under the island operation mode,and the secondary optimization control is to realize the economic operation of the micro grid.The main research contents of this paper are as follows:(1)Starting from the control method of the microgrid and the mathematical model of the grid-connected inverter,the four control methods of distributed power supply are analyzed: PQ control,V/f control,Droop control and VSG control,and the principle and the advantages and disadvantages of the droop control are analyzed.(2)In order to make up for the deficiencies of droop control,a distributed optimal droop control strategy for island microgrid based onmulti-agent consistency is proposed.The distributed optimization droop control is used to adjust the power and frequency,and the incremental cost consistency algorithm is used to achieve optimal economic operation.On the basis of calculating the optimized power value by consistency algorithm,each optimized power value is sent to each local controller,and then the operation cost of the system is optimized and the frequency is restored to the rating value.(3)In order to study the parallel control of multiple microgrids,this paper proposes a hierarchical distributed optimization coordinated control strategy based on micro-increasing rate.Construct a two-layer coordinated control architecture with micro-network level and component level,obtain global information consistency through multi-agent consistency,and design a quadratic optimization controller based on micro-increment rate consistency on component-level agents.To achieve accurate distribution of tie line power,and eliminate voltage and frequency deviations,so that each microgrid is economically interconnected.Finally,the effectiveness of the control strategy and the plug-and-play characteristics of the distributed power supply are verified on the simulation platform. |