Research On Robust Control Of DC Microgrid System With Photovoltaic And Energy Storage Based On Battery SOC Stimation

In recent years,people’s demand for energy is growing,and the environmental and ecological problems are becoming more and more serious.Distributed generation based on clean energy has attracted extensive attention.At the same time,with the proposed strategic goal of "Dual Carbon",vigorous development of clean energy has become an effective way to build an energy-saving and environment-friendly society.The emergence of microgrid technology provides technical support for local consumption,rational allocation and safety management of clean energy.As an operation mode of microgrid,DC microgrid has become a research hotspot in recent years because of its simple topology and no consideration of reactive power and phase synchronization.In this dissertation,the photovoltaic array(PV)and storage system as the main power supply unit of the typical DC microgrid system with photovoltaic and energy storage is taken as the research object of study.Firstly,the mathematical model of the PV,battery energy storage system(BESS)and diesel generator which is enabled in standby mode are built.Because sliding mode control(SMC)is robust to system parameter changes and external disturbance,it is widely used in the field of converter control.In order to improve the robustness of DC microgrid system with photovoltaic and energy storage,SMC is applied to SOC estimation algorithm and bidirectional DC/DC converter controller algorithm in the part of BESS.The SOC estimation algorithm based on adaptive super twisting observer(ASTO)and the double closed-loop high-order sliding mode controller based on variable gain fast super twisting(VGFST)are designed respectively.Finally,aiming at the overall operation coordination of DC microgrid system with photovoltaic and energy storage,a power coordinated control strategy based on SOC estimation is designed,which can not only ensure the continuous power supply for the load,but also improve the power supply reliability and operation economy of the system.The specific research contents of this dissertation are as follows:(1)Firstly,the topological structure of the typical DC microgrid system with photovoltaic and energy storage in this dissertation is given,and the mathematical models of PV and diesel generator in the system are analyzed and modeled.Secondly,based on the modeled mathematical model,the corresponding control algorithm is designed for the converter connected between PV and diesel generator.When the system is in different operating conditions,the appropriate control mode can be selected to provide power output for the system.Finally,the simulation model is built in the simulation platform,and the effectiveness and reliability of the control algorithm are verified by setting simulation parameters to simulate the environmental changes in the actual operation.(2)In order to solve the problem that the SOC value of BESS is unmeasurable,a SOC estimation algorithm is designed to obtain its value accurately.Firstly,the commonly used battery equivalent circuit model is introduced,and the double resistance-capacitance parallel RC equivalent circuit model of BESS is modeled.Secondly,the SOC estimation algorithm based on ASTO is designed for BESS.Finally,the simulation model is built in the simulation platform to verify that the designed SOC estimation algorithm can accurately estimate the SOC value and is robust to measurement noise and external interference.(3)Firstly,the condition of power balance of the DC microgrid system with photovoltaic and energy etorage is analyzed.Secondly,based on the characteristics of BESS with two-way energy flow,a double closed-loop high-order sliding mode controller based on VGFST is designed for the connected bi-directional DC/DC converter.The control algorithm can effectively restrain the DC bus voltage fluctuation caused by the intermittence of photovoltaic array and load disturbance.Finally,the effectiveness and robustness of the designed control method are verified by simulation platform.(4)In order to ensure the stable operation of the DC microgrid system with photovoltaic and energy etorage,maximizing the use of photovoltaic resources,ensuring the power balance in the system and ensuring the safe and stable operation of BESS,the power coordinated control strategy of the DC microgrid system with photovoltaic and energy etorage based on SOC is designed.The system can reasonably dispatch each distributed generation according to different operation modes.Finally,the system model is built in the simulation platform to simulate the operation conditions under different conditions in practice.Simulation results verify the effectiveness of the control strategy.