| In recent years,due to the rapid development of social productivity and the increasing demand for electricity,the demand for energy in China’s power generation industry has gradually increased,and traditional energy generation has become increasingly unable to meet the growing demand for electricity.Photovoltaic microgrid is a new type of power system using photovoltaic power generation,which has received wide attention because of its flexible control and the advantage of "plug and play".Photovoltaic power generation is affected by the natural environment and cannot be obtained continuously,so the energy obtained from photovoltaic power generation needs to be stored appropriately for rational use.The hybrid energy storage system,which is a combination of various energy storage units,can combine the advantages of different energy storage units and compensate for each other’s disadvantages.This article takes a photovoltaic microgrid system with hybrid energy storage as the background to study the hybrid energy storage control strategy and its Situation of the energy flow inside the grid under different modes of microgrids.The main work is as follows.Firstly,the structure,composition and characteristics of the Photovoltaic microgrid system with hybrid energy storage are studied.The main contents include: Photovoltaic cell model and maximum power point tracking(MPPT)control method;battery and supercapacitor modeling and operating characteristics analysis in hybrid energy storage;bi-directional DC-DC converter mathematical model of energy storage unit.Secondly,the topology of hybrid energy storage with dual DC-DC active connection is determined to connect to the microgrid,and the control strategy of hybrid energy storage foundation of PV microgrid is introduced.In view of the shortcomings of low-pass filter frequency division with hysteresis,the power division method is improved based on the fast characteristic of super capacitor to improve the fast compensation ability of the system when power fluctuation occurs,and the SOC limit control of energy storage unit is combined to protect the energy storage unit,which is more conducive to maintain the safe and stable operation of the system.Then,a hybrid energy storage control strategy based on Linear Active Disturbance Rejection Control(LADRC)is designed and Linear Active Disturbance Rejection controllers are designed for voltage loop,battery current loop and supercapacitor current loop in hybrid energy storage control,and the controller performance is analyzed.The linear extended state observer(LESO)is improved in the voltage loop controller design part by combining the proportional differentiation idea,and designed battery current loop controller and supercapacitor current loop controller section based on standard linear active disturbance rejection control.A simulation model is built to verify the feasibility and effectiveness of the control strategy by simulating four different operating conditions.The experimental results show that the designed control strategy has better immunity performance than the traditional PI control strategy and is more conducive to maintaining the stable operation of the Photovoltaic microgrid.Finally,a high-power Photovoltaic microgrid system model is established to simulate the real operation scenario and theoretically analyze the on-grid energy flow in the islanding/gridtied mode of the Photovoltaic microgrid.The power dividing method,SOC limit control and LADRC hybrid energy storage control strategy designed in this paper are used to analyze the energy flow in the Photovoltaic microgrid in islanding mode and grid-connected mode respectively,and the simulation results show that the energy flow in the Photovoltaic microgrid remains stable in both modes and the bus voltage fluctuation is small.The simulation results show that the energy flow in the Photovoltaic microgrid remains stable in both modes,and the bus voltage fluctuations are small. |
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