Importance of photovoltaic inverter in photovoltaic power station

As the conversion equipment of photovoltaic power station, the function of photovoltaic inverter plays an important role in the whole power station. Photovoltaic inverter is the core device in the photovoltaic power station system, which converts the DC generated by photovoltaic modules into sine wave current, connects to the load or into the grid. Its main function is to convert the DC generated by solar panels into AC used by household appliances.

Photovoltaic inverter not only has DC / AC conversion function, but also has active operation and shutdown function, MPPT function, islanding effect detection and control function, grid detection and grid connection function, zero (low) voltage ride through function

1. Active operation and shutdown function

After sunrise in the morning, the solar radiation intensity gradually strengthens, and the output of solar cells also increases. When the output power required by the inverter task is reached, the inverter will start to operate actively. After entering operation, the inverter will take care of the output of the solar cell module at all times, as long as the output power of the solar cell module is greater than the output power required by the inverter task, The inverter will continue to operate; Until sunset, the inverter can operate even in rainy days. When the output of the solar cell module becomes smaller and the output of the inverter approaches 0, the inverter will be in standby mode.

2. MPPT function of maximum power tracking

When the sunshine intensity and ambient temperature change, the input power of PV module presents a nonlinear change. The PV module is neither a constant voltage source nor a constant current source, and its power changes with the change of output voltage, which has nothing to do with the load. Its output current is a horizontal line at the beginning with the increase of voltage. When it reaches a certain power, it decreases with the increase of voltage. When it reaches the open circuit voltage, the current drops to zero.

3. Detection and control function of islanding effect

In normal power generation, the photovoltaic grid connected power generation system is connected to the power grid to deliver effective power to the power 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 islanding effect. When the islanding effect of inverter occurs, it will cause great security risks to personal safety, power grid operation and inverter itself. Therefore, the grid access standard of inverter stipulates that photovoltaic grid connected inverter must have islanding effect detection and control function.

4. Power grid detection and grid connection function

Before grid connected power generation, grid connected inverter needs to take power from the power grid, detect the parameters such as voltage, frequency, phase sequence and so on, and then adjust the parameters of its own power generation, synchronize with the grid parameters.

5. Low voltage ride through function

When the power system accident or disturbance causes the voltage sag of photovoltaic power station, within a certain range of voltage sag and time interval, the photovoltaic power station can ensure continuous operation without off grid.