Power Control Of Photovoltaic Grid-connected System Based On Fast Regulating Of Energy Storage Under LVRT

With the maturity of photovoltaic power generation technology,the scale of photovoltaic power supply connected to the power system is increasing,and the photovoltaic power supply is more and more important to the operation and support of the system.Therefore,the control and function of the photovoltaic grid-connected system are proposed.The higher requirements,which are marked by the low voltage ride through(LVRT)capability of photovoltaic power plants,have been used as an important indicator of photovoltaic grid connection.When the voltage on the grid side drops,it will cause an imbalance between the absorbed power of the grid-side converter and the output of the photovoltaic power,resulting in a drastic change in the DC side voltage of the grid-connected converter,which jeopardizes the reliability of the grid-connected operation.The research design of DC-side power and grid-side absorption power balance control of grid-connected converters with low voltage ride-through has important theoretical significance and practical reference value.This paper proposes the introduction of active regulation of energy storage systems to achieve energy balance control of photovoltaic grid-connected systems to improve the stability and reliability of system-connected operation during low voltage ride through.Firstly,in order to adapt the photovoltaic power generation system to the grid-connected operation when the grid side voltage drops,this paper studies and designs a PQ control with reactive power compensation function based on the modeling and analysis of the photovoltaic grid-connected inverter system.The strategy can suppress the output current of the grid-connected converter and has a certain ability to support the grid side voltage.In order to improve the low-voltage ride-through capability of photovoltaic grid-connected systems,this paper proposes an energy balance control strategy for grid-connected systems based on supercapacitor and battery hybrid energy storage regulation.In this strategy,the battery uses double closed-loop PI control to maintain the DC side bus voltage.The stability of the supercapacitor uses current single-loop control to meet the rapidity of power regulation.The high-pass filter is used to coordinate the power output of the two,which fully exploits the different advantages of the two energy storage components in energy balance control.The control strategy can meet the requirements of the photovoltaic grid-connected system to quickly adjust the power balance during LVRT,and at the same time allow the photovoltaic array to maintain the maximum power point tracking mode and improve the utilization rate of new energy power generation.The simulation,experiment and analysis of the photovoltaic grid-connected system based on hybrid energy storage control are completed.The results show that the designed hybrid energy storage coordinated control strategy is beneficial to improve the low-voltage ride-through capability of the photovoltaic grid-connected system,which is beneficial to improve the system.The stability and reliability of the network operation.