Research On Control Strategy Of Multi Inverter In Hybrid AC/DC Microgrid

As the problem of energy shortage becomes increasingly severe,the development and utilization of new energy has become a social development trend.Therefore,the adoption of distributed energy supply technologies has received increasing attention.The hybrid AC/DC microgrid is a new frontier technology based on distributed generation,which can fully realize the potential of distributed generation.In the hybrid AC/DC microgrid,the inverter is the most important energy conversion device.The control problem of the inverter and the circulation problem of the inverter parallel system affect the efficient and reliable operation of the microgrid system.Firstly,the structure of hybrid AC/DC microgrid is studied.The modeling and simulation of the photovoltaic system and wind power system in the microgrid are carried out.The control strategy of the charge and discharge of the energy storage device is studied,and the simulation verification is carried out.In view of the control operation of the single micro source grid-connected inverter in the microgrid,the structure model of the three-phase grid-connected inverter is set up.The SVPWM control scheme is adopted,and the system simulation analysis is carried out with the photovoltaic grid-inverter as an example.The photovoltaic power system and inverter system are nonlinear when the sun-light environment and other conditions change seriously,which makes the harmonic distortion rate of the grid-connected current in the inverter output increases and affects the power quality.To solve this problem,fuzzy PI control strategy is applied to control photovoltaic grid-connected inverter to improve system response speed and control accuracy.The simulation results show that the control scheme can improve the dynamic performance of the photovoltaic grid-connected network,reduce the harmonic distortion of the grid-connected current,and finally realize the smooth connection of the photovoltaic system.In the microgrid,the distributed generation is connected to the grid through grid-connected inverters.The parallel connection of grid connected inverters is common.Because the software and hardware parameters of parallel inverters are different,the circulation is generated.The circulating current not only increases the power loss of the system,but also seriously deforms the output current and reduces the power quality.In view of the circulation suppression of parallel inverter,the mathematical model of the inverter parallel system is established,and the cause of the circulation of the three-phase inverter parallel system is deeply analyzed.On this basis,the zero vector distribution method is used to suppress the circulation.The zero vector distribution method can restrain the generation of the circulating current by reasonably distributing the time of zero vectors in the inverter.The simulation results show that the control method is effective and feasible for the circulation suppression.