Research On Grid-connectecd Inverter Of Small Vertical Axis Fan

In areas with low wind speed,the grid-connected generation of low-power vertical axis fans can expand the available wind resources and reduce system costs.Small vertical axis wind power grid-connected system is mainly composed of vertical axis wind turbine,disk permanent magnet generator,grid-connected inverter,control system and low voltage grid.The small vertical axis wind turbine grid-connected inverter system studied in this paper is to study a kind of inverter suitable for small vertical axis wind power grid-connected.On this basis,the system model,control strategy analysis and related simulation verification are given.In order to solve the problems of high switching loss and low efficiency of traditional inverters,LLC resonant converter is used in boost link.The original side of LLC converter MOSFET is used to turn on ZVS,and the output diode ZCS is turned off.There is no reverse recovery problem and the switching loss is small.Firstly,the mathematical model of LLC converter is established,and the model of complex LLC resonant converter is simplified from the seventh order to the second order.Then the load feedback linearization control strategy is applied to improve the dynamic performance of LLC resonant converter effectively.By using load feedback,the non-linear characteristics of the system are eliminated and the output characteristics can be adjusted as expected.Finally,the LLC converter circuit and control system are built by using the simulation experiment of MATLAB/Simulink.In view of the power quality problems of common grid-connected points,because the output voltage of the inverter bridge of grid-connected inverters contains abundant switching harmonics,in order to suppress the grid-connected current harmonics caused by the switching harmonics,it is necessary to add a filter between the inverter bridge and the grid.In this paper,the single-phase grid inverter with LLCL filter is taken as the research object.Firstly,the mathematical model of LLCL filter is established,and the frequency characteristics of L,LCL and LLCL filter systems are compared and analyzed.Then,according to the requirements of new energy grid-connected standard,the parameters of inverters are designed,and further analysis and research are carried out.LLCL filter can filter the current harmonics at the switching frequency to a greater extent and reduce the inductance of the filter,but the resonance phenomenon is still a key problem in the system.Therefore,the active damping method based on proportional resonance controller is used to solve the resonance phenomenon.In order to ensure the stable operation of the system,the stability of the system is analyzed.Finally,the simulation model of LLCL grid-connected inverters is built in Matlab/Simulink,and the control algorithm of single-phase grid-connected inverters is simulated and verified.