Research On Using Hybrid Energy Storage To Stabilize Power Fluctuation Of Photovoltaic Micro-grid

The random and uncertain characteristics of distributed energy will bring voltage flicker,voltage fluctuations and other adverse effects to the local load and the large power grid.The addition of energy storage system can stabilize the power fluctuation in the new energy generation and satisfy the load and the demand for the power quality of the large power grid.In this paper,the photovoltaic microgrid system with mixed energy storage unit will be the object of study.The output power of the PV array will directly affect the efficiency of the photovoltaic power generation system,It is necessary to track the maximum output power point of the PV panel becomes.In this paper,several commonly used MPTT algorithms of PV are compared,the variable step perturbation observation method is used and verified on the simulation platform.A single energy storage device is difficult to meet the needs of micro-grid.In this paper,batteries and super capacitors are used to form a hybrid energy storage unit through comparing the advantages and disadvantages of a variety of energy storage methods.The equivalent model of the batteries and the super capacitors and the structure of the DC / DC bidirectional converters are analyzed.Based on the traditional low-pass filter method,a power shunt algorithm based on fuzzy control is proposed,which takes into account the charge state of the energy storage element fully when allocating the power borne by each energy storage unit.The simulation results show that this algorithm can optimize the charge and discharge cures of each energy storage element.The working mode of micro-grid is divided into grid and island.In this paper,the control strategies of three-phase inverter in grid-connected mode and isolated island mode are studied.PQ control strategy is used to the grid-connected mode and VF control strategy is used to the isolated island mode.The simulation results show that the two control strategies can meet the demand of power quality for the large power grid and load.Finally,the power balance between the energy units in the photovoltaic micro-grid system is listed in this paper.The simulation model of PV micro-grid system is built on Matlab/Simulink,and establishing a system experimental platform.The simulation and experimental results show that the whole micro-grid system can be stably and harmoniously,which proves that the hybrid energy storage system plays a very good role to stabilize the power fluctuation in the PV micro-grid.