| With the development of the world industry and economy,the traditional fossil energy has been exhausted day by day.The exploration and research of new energy has become a hot spot in the world.In this context,micro-grid technology emerged as the times require.As a supplement to the traditional large power grid,the micro-grid can alleviate the energy crisis to a certain extent.However,there is instability in the operation of micro-grid due to the intermittent randomness of distributed generation(photovoltaic,wind power,etc.)which is used in micro-grid.This instability not only affects the power quality and power characteristics of the micro-grid,but also limits the grid connection with large power grid.In order to solve the problem of transient impact of micro-grid bus caused by sudden change of load power,this paper takes DC photovoltaic micro-grid as the research object by consulting a large number of domestic and foreign literatures.The simulation model of DC micro-grid system is built on the Matlab/Simulink simulation platform.The structure and control algorithm of hybrid energy storage system of battery and super capacitor are studied in detail.The study contents of this paper are as follows:Firstly,the working principle,theoretical derivation and mathematical model of photovoltaic power generation module,maximum power point tracking module,battery energy storage module and super capacitor energy storage module are introduced in detail.Then building the simulation model of each micro-grid unit by using Matlab/Simulink simulation platform.Secondly,the paper uses the parallel structure of battery and super capacitor as the structure of hybrid energy storage system.Introducing and deducing the structure of the hybrid energy storage system and the working principle of the peripheral bidirectional DC chopper.Then the power balance management strategy of hybrid energy storage system and the charge/discharge control strategy based on double closed loop PI control are formulated.The control structure,control strategy and system transfer function of double closed loop Pi control algorithm are introduced in detail.At last,establishing the priority control of battery and super capacitor in energy storage system in order to solve the problem of transientimpulse of bus which is caused by sudden change of load power in theory.Finally,establishing the simulation model of DC micro-grid integrated system,the simulation model of control algorithm and the simulation model of variable power resistor in Matlab/Simulink simulation environment.Then verifying the validity and correctness of the structure of hybrid storage energy system and double closed loop PI charging and discharging control algorithm which are used in suppressing the DC bus transient impulse caused by the sudden change of load power. |
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