| With the increasing depletion of global fossil energy and the proposal of the "dual carbon" strategic goal,renewable energy represented by photovoltaics and wind power has been vigorously developed.The large-scale integration of renewable energy will adversely affect the stable operation of traditional power grids.In order to improve the ability to absorb renewable energy,the microgrid system emerges as a flexible and compact organizational form.On the one hand,when the renewable energy is connected to the microgrid system through the power electronic interface,the inertia of the microgrid system will be reduced,which will lead to the decrease of the anti-disturbance ability of the system,and the frequency will fluctuate easily;on the other hand,due to the output or load power is easy to fluctuate,which will lead to changes in the supply and demand balance of the system,resulting in frequency instability.Therefore,it is necessary to study the frequency control method of the microgrid system.Considering the variety of equipment in the microgrid system,the increasingly complex operation mechanism,the increasingly prominent uncertainty of source and load,and the obvious nonlinear characteristics,this paper proposes a frequency control method for islanded microgrid based on digital twin.The main contents of this paper are as follows:(1)The control architecture and operation mechanism of the frequency control digital twin system of the microgrid are analyzed.First of all,it is clarified that the control architecture of the digital twin system for frequency control of the microgrid should include the physical entity layer,the data perception layer and the smart center layer.The physical entity layer mainly introduces the working principle of the distributed power supply in the microgrid system;The type of data and the way of data perception are analyzed;the intelligence center layer introduces the main functions that this layer needs to complete from three aspects: data preprocessing,data storage and management,and analysis and decision-making.Finally,the operation mechanism of the digital twin system is analyzed,and how data interaction and decision analysis are carried out between layers in the control architecture.(2)Based on the control architecture and operation mechanism of the digital twin system proposed above,the pinning consistency cooperative frequency control strategy driven by the digital twin is specifically analyzed under this framework.Firstly,the basic principle of the pinning consensus algorithm is analyzed,and the convergence of the algorithm is compared and analyzed;secondly,the operation principle of the pinning consistency cooperative frequency control based on the digital twin drive is introduced,and on this basis,the digital twin system and the microgrid are introduced.The setting method of the data interaction interface between systems;finally,the digital twin-driven pinning consistency control algorithm is verified by setting three simulation scenarios: load mutation,load mutation,and distributed generator(DG)input,load mutation,and DG removal.control effect.(3)Aiming at the problems in the control accuracy of the pinning consistency cooperative frequency control algorithm based on the digital twin drive,a Deep Deterministic Policy Gradient(DDPG)digital twin-driven pinning consistency cooperative frequency control strategy is further proposed.Firstly,the basic principle of DDPG algorithm is introduced;secondly,the control architecture of the twin system based on DDPG is built,and the DDPG algorithm is used to update and optimize the pinning control value of the pinning consensus algorithm;finally,the DDPG-type digital number is verified by using the same simulation scenario as above.The twin-driven pinning consistency cooperative frequency control strategy is used,and the results show that the algorithm can obtain better control accuracy and convergence speed. |
