Research On Photovoltaic Grid-connected Control Strategy Based On Hybrid Energy Storage

With the shortage of fossil fuels,people pay more attention to renewable energy power generation.Among the various renewable energy sources,solar energy is widely used.However,photovoltaic power generation is affected by external factors such as solar intensity and temperature,its output power has greatly flunctuate,so there are still some problems when it is connected to the grid on a large scale.In response to this problem,the introduction of hybrid energy storage equipment in the photovoltaic power generation system to suppress the fluctuation of the output power of the photovoltaic system and improves the power quality of photovoltaic grid-connected.In order to improve the efficiency of the photovoltaic power generation system,it is necessary to track the maximum power point(MPPT)during the operation of the system.Therefore,the traditional disturbance observation method is improved to improve the speed and accuracy of tracking the maximum power point,and a simulation model is built.The operating characteristics of the battery and the supercapacitor are compared and analyzed through simulation,and the hybrid energy storage system composed of the battery and the super capacitor is selected to smooth the power fluctuation.The cost of energy storage equipment is relatively high.To reduce the costs,when building a solar storage power generation system,the capacity of the energy storage equipment needs to be reasonably configured,and the capacity of the energy storage equipment should be optimized under the premise of satisfying the stable operation of the system.The particle swarm optimization algorithm with adaptive inertia weight is used to optimize the configuration of energy storage capacity,and compared with the particle swarm optimization algorithm with linearly decreasing inertia weight,it is verified through simulation analysis and the optimal capacity configuration of hybrid energy storage equipment is obtained.The batteries and the supercapacitors are connected to the DC bus througe a bidirectional DC/DC converter to smooth the photovoltaic output power.In order to solve the power distribution problem in the hybrid energy storage systems,the traditional low-pass filtering algorithm distributes power according to the working characteristics of batteries and supercapacitors.The unreasonable selection of the filter time constant reduces the life of the energy storage equipment,and can not make full use of the capacity of the energy storage equipment.In order to solve this problem,a power distribution strategy based on the state of charge of supercapacitors is proposed to redistribute the low-frequency power passing through the low-pass filter to ensure that the supercapacitors work in the safe range of the state of charge while making full use of their capacity.In the mean time,the number of charging and discharging of the battery is reduced,and the service life is prolonged.Finally,the results of the whole system is verified by Matlab/Simulink simulation experiment.