Research On Control Method Of Single-phase Photovoltaic Grid Inverter

Solar energy has gradually become the focus in the field of new energy application with its advantage in its reserves and being greener. PV grid power generation technology is one of the effective ways to solve the current energy and environmental problems, being the hot topic in energy application research. For the research of PV grid inverter control methods, the thesis content is as following:To a better controlling of grid inverter, combining grid system running states, divided the running of grid system into four modes: maximum power output mode, frequency-active mode, voltage-reactive mode, active-reactive mode. Based on the structure of two levels of single phase full bridge inverter, detailed analysis of the various patterns’ application features, respectively corresponding control methods are presented. The disturbance observation was used to solve the problem of the maximum power output on the former. The active-reactive power decoupling control method makes the inverter’s independent controlling of active power, reactive power, realizes the inverter output active and reactive power of the constant output function. The simulation demonstrated the validity of the inverter operation mode control method.The thesis analyses the four operating mode of inverters and the running state of grid, transition conditions and switching methods between modes are given. For the problem that PV grid system transient impact the grid in the process of switching between operation modes, combining the principle of droop, modes’ parameters and characteristics, introduces the corresponding amount before mode switching as feed forward, change the droop coefficient, implement the smooth transformation, basically eliminates the transient impact produced by the system, improves the corresponding speed of the system. The simulation verified the effectiveness of the controlling model switching.According to the actual single-phase PV grid inverter experimental platform, software programming is finished for the inverter operation mode and the mode switch controlling method in this thesis, implementing the mode switch and control method above.