Photovoltaic inverter functions

The main functions of photovoltaic inverters in photovoltaic power plants:
1) Maximum power tracking MPPT function
When the sunlight intensity and ambient temperature change, the input power of the photovoltaic module changes nonlinearly, as shown in the figure. It can be seen from the figure that the photovoltaic module is neither a constant voltage source nor a constant current source. Its power changes with the output voltage. It changes because of the change and has nothing to do with the load. Its output current is a horizontal line at first as the voltage increases. When it reaches a certain power, it decreases as the voltage increases. When it reaches the component’s open circuit voltage, the current drops to zero.

2) Detection and control of island effect
During normal power generation, the photovoltaic grid-connected power generation system is connected to the large power grid and delivers active power to the grid. However, when the power grid loses power, the photovoltaic grid-connected power generation system may continue to work and operate independently from the local load. This phenomenon is called the island effect. When the islanding effect occurs in the inverter, it will cause great safety hazards to personal safety, power grid operation, and the inverter itself. Therefore, the inverter grid access standard stipulates that photovoltaic grid-connected in must have islanding effect detection and control functions. .

3) Grid detection and grid connection functions
Before connecting to the grid to generate electricity, the grid-connected inverter needs to take power from the grid, detect the voltage, frequency, phase sequence and other parameters of the grid power transmission, and then adjust its own power generation parameters to be consistent with the grid electrical parameters. Will be connected to the grid to generate electricity.
4) Zero (low) voltage ride-through function
When an accident or disturbance in the power system causes a voltage sag in the voltage at the grid connection point of the photovoltaic power station, within a certain voltage drop range and time interval, the photovoltaic power station can ensure continuous operation without going off the grid.


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