Research On Control Of Photovoltaic Power Generation And Hybrid Energy Storage System

The application of photovoltaic-based renewable energy power generation in microgrids has received more and more attention.However,photovoltaic power generation has the characteristics of intermittent,randomness and small inertia,which causes its output power to fluctuate,thereby reducing the power quality of the power grid and causing the grid to be unstable.Energy storage is an effective method to resolve power fluctuations.Among them,energy storage systems have functions such as smooth power fluctuations,energy storage,and peak clipping and valley filling.Therefore,the application of energy storage systems in photovoltaic power generation systems has become an important research topic.Aiming at the instability of photovoltaic power generation and the poor performance of existing hybrid energy storage control,this thesis proposes a current prediction strategy based on the prediction of supercapacitor and lithium battery models,and then builds predictive control on the simulation platform.Simulation model to verify the proposed theory and control method.First of all,this thesis constructs a hybrid photovoltaic and energy storage system structure.The mathematical models of photovoltaic arrays,super capacitors,lithium batteries,and inverters were built,and the working modes of Boost converters for photovoltaic power generation units and Buck-Boost bidirectional converters for energy storage systems were analyzed.Perturbation observation method(P&O)is used to track the maximum power point of photovoltaic cells.A simulation model of photovoltaic power generation subsystems is established in the Matlab/S imulink simulation environment,the correctness of the mathematical model is verified,and Tracking effect.Secondly,according to the structure of photovoltaic power generation and hybrid energy storage system,the topology of the optical storage inverter system is established,the voltage controller parameters and current controller parameters are designed,and the small signal model of the system is established.The trajectory diagram analyzes the stability of the system and determines the dominant control parameters that affect the stability of the system.From the analysis,it can be seen that the magnitude of the reactive sag coefficient and the active sag coefficient are strongly related to the system stability.Finally,in view of the fluctuation of photovoltaic power generation,two hybrid energy storage control methods are proposed to compensate for the photovoltaic power shortage.One is improved PI control.This method can achieve power compensation.However,during photovoltaic power fluctuations,the battery has large power fluctuations in a short period of time,which is not conducive to the life of the battery.Therefore,a model-based prediction is proposed.Current control strategy,which can reasonably allocate energy between the battery and the super capacitor,avoid the impact on the lithium battery during the disturbance,and control the SOC state of the super capacitor that is often charged and discharged quickly within a safe range.Simulation verifies the correctness and feasibility of the proposed model predictive control strategy.