| With the popularization of distributed PV grid-connected technology,the capacity of distributed PV in low-voltage distribution network and its influence on distribution network are increasing.Before the distributed photovoltaic project construction,we must predict photovoltaic power generation capacity and analyze its rationality at first;and then consider the optimization problem when PV and energy storage is combined,so as to establish reasonable economic scheduling model and optimize the economical efficiency of the system;and finally,while ensuring the economical efficiency of the system,the stable running state of the distribution system can still be maintained after the PV gridconnected.This paper takes the distribution network of our campus as an example,makes full use of the existing building roof area,and establishes PV-energy storage power generation grid-connected systems to provide pre-research basis for the construction of a demonstration college campus green energy internet.The specific research content is as follows:First of all,based on the geographical location of our university,the calculation model of solar radiation is set up,and the solar radiation data was got by using Matlab/Simulation software.A distributed photovoltaic generation model for building roofs which is in line with the actual situation of our university is established,and the comprehensive conversion efficiency of PV plants is analyzed,and the generation capacity of PV system in unit time is predicted.The current status of the distribution network in our school is studied,and the current power quality problems in the distribution system are analyzed.Secondly,an economic scheduling model of photovoltaic energy storage combined network based on time sharing price is established.Taking the lowest cost of PV and energy storage as the goal,the objective function is established.Considering the load rate of distribution bus as a penalty factor,the installed capacity of PV and energy storage is optimized to optimize the system configuration.According to the actual situation of the distribution network in our school,a case analysis is carried out,and the optimization results are analyzed to verify the economy of the photovoltaic energy storage system.Finally,the power distribution system scheme is redesigned in view of the current power quality problems existing in the power grid of our school.Studying the influence of the change of node load,PV energy storage system output and PV power storage system power factor on the node voltage of distribution network after the grid connected photovoltaic energy storage system,the simulation results show that the node voltage is not limited after grid connected.It is analyzed that the harmonic current injected into the distribution network at the common connection point is analyzed when the PV inverter is working.After analysis and calculation,it can be seen that the harmonic current content is far less than the allowable value of the distribution system.Matlab/Simulink is used to simulate the power flow of the distribution system after normal operation.The simulation results show that the grid loss is significantly reduced after PV grid-connected,and PV grid-connected can effectively reduce the line load rate of the front branch of the grid connected network.There will be a reverse flow of power flow in some branches after the grid connected to the grid,but it does not exceed the maximum power flow of the line.In a word,PV energy storage system grid-connected effectively improves the operation environment of the distribution system,and advances the stability and economy of the system operation. |
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