Research On Smooth Switching Control Strategy Of Optical Storage And Micro-grid

The energy crisis and environmental problems brought by the traditional fossil energy constantly promote the use of clean energy represented by solar energy.As an effective means to integrate the use of distributed new energy,micro-grid(MG)can effectively improve the utilization efficiency of distributed energy(DE)and play an irreplaceable role in the power system.Compared with traditional power grid,the micro-grid system inertia is smaller,and the generation of Photovoltaic(PV)micro-source is susceptible to the influence of external natural conditions,which makes the power supply stability and reliability of optical-storage micro-grid lower.This paper mainly studies the control strategy of parallel/off-grid operation and smooth mode switching of micro-grid system.Firstly,the structure,micro-source characteristics and control strategy of optical storage and micro-grid are studied and analyzed.In view of the disadvantages of traditional perturbation observation algorithm in tracking the maximum power output of photovoltaic power supply,such as low efficiency and large oscillation.A perturbation and observation method based on uncertainty reasoning is proposed to minimize the output power oscillation of photovoltaic array near the maximum power point and improve the tracking stability and tracking speed.In view of the difficulty of maintaining stable voltage and output power in parallel operation of multiple batteries under the traditional control mode,a control strategy combining adaptive droop control and double closed-loop control is adopted.Secondly,modeling and analysis are carried out for the optical storage and microgrid system,and the inverter control models are established for grid-connected and off-grid operation respectively.When the micro-grid operates in grid-connected mode,the system’s electrical energy parameters are controlled by the large grid,and the micro-source inverter is controlled by PQ.When the micro-grid operates in off-grid mode,the energy parameters need to be controlled by the energy storage device,and the main micro-source inverter is controlled by V/f.At the same time,in order to accurately judge the operation mode of optical storage and microgrid system,an island detection method based on even order harmonic injection is proposed.Finally,This paper analyzes the voltage fluctuation,current shock and power mutation in the process of parallel and off-grid switching of micro grid,and proposes a comprehensive control method based on improved pre-synchronization control and state tracking control to realize smooth switching of optical storage micro grid.The MATLAB platform is used for simulation verification,proving that the control method adopted in this paper has good applicability to the operation of optical storage and micro-grid system,and the correctness and rationality of the proposed smooth switching control strategy.