| With the construction and application of large-scale distributed power generation,it is inevitable that the microgrid will switch frequently between the island mode and the grid-connected mode.The on-grid/off-grid technology of distributed power generation needs to comprehensively consider the influence of various factors.However,when the microgrid grid-connected/off-grid operation mode is switched,the transient shock caused will pose new challenges to the stable operation of the system and equipment safety.Therefore,the study of seamless switching of microgrid operation mode has far-reaching significance for the large-scale development of distributed power generation.The paper first studies the operation mode of the optical storage microgrid.The operation mode of the optical storage microgrid is divided into master-slave control mode,peer-to-peer control mode and hierarchical control mode.After analysis,the peer-to-peer control mode is selected as the research object of this paper.After establishing the operation mode of the optical storage microgrid,the modeling research of the photovoltaic power generation system in the optical storage microgrid is carried out.The maximum power point tracking technology in the photovoltaic power generation system selects the conductance increment method for modeling.Then,the hybrid energy storage system in the optical storage microgrid is modeled and studied.The battery chooses the lead-acid battery,and the traditional limit management strategy is used to control the state of charge of the lead-acid battery.Due to its high power density and low energy density,supercapacitors are easy to In the event of overcharge and overdischarge,the limit management strategy adopted is based on the traditional energy storage limit management strategy,and its working area is further refined.The grid-connected inverter connects the DC part and the AC part of the optical storage microgrid.After the DC part of the optical storage microgrid is determined,the main control strategies of the existing grid-connected inverter are analyzed,and the droop control is finally selected as the grid-connected inverter in this paper.control strategy.Finally,the model of the filter in the AC part of the optical storage microgrid is studied.Through analysis and selection of LC filter,it can not only ensure a good filtering effect,but also prevent the occurrence of resonance to a certain extent.According to the regulation effect of power on voltage and frequency according to the droop control characteristic equation,the energy storage is connected to the AC side of the microgrid.When the microgrid is connected/disconnected,the energy storage is used to stabilize the power of the system to achieve the purpose of frequency regulation and voltage regulation.Stabilize system frequency and voltage when switching operating modes.Then,the limitations of the traditional droop control strategy are analyzed,and the traditional droop control strategy of the grid-connected inverter is improved to suppress the transient impact caused by the micro-grid connection/de-grid,so that the micro-grid can end the transient process as soon as possible and return to the steady state.Finally,a reference power controller is designed to solve the problem of the failure of the improved droop control on frequency regulation,so that the microgrid can adapt to various working conditions,and at the same time,when the grid-connected inverter adopts the droop control strategy,the output power can be adjusted in the microgrid grid-connected mode.The problem.The inertia link is added to the reference power controller to solve the instability problem of the system caused by the reference power switching.Finally,the built Matlab/Simulink model is used for simulation.The simulation waveforms show that the built model runs normally,and the hybrid energy storage can effectively suppress the power fluctuations caused by photovoltaic output fluctuations and load abrupt changes.Supercapacitors respond quickly to power fluctuations,and the power fluctuations are ultimately borne by the battery,and supercapacitors are not prone to overcharge and overdischarge.When the microgrid operation mode is switched,the energy storage can play a role in stabilizing the system frequency and voltage.The improved droop control strategy has a significant effect on suppressing transient shocks caused by microgrid operation mode switching.The reference power controller can make the whole process of the microgrid from islanding to grid-connected to islanding stable,and make the output power of the microgrid grid-connected mode adjustable under droop control. |
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