Role of Photovoltaic Grid Connected Inverter

August 06,2022

A photovoltaic grid-connected inverter is an essential key component in the photovoltaic power generation system. It is mainly used in the special inverter power supply in the field of solar photovoltaic power generation. The grid-connected inverter converts the AC generated by the solar panel into the AC that can be directly divided into the power grid through the power electronic conversion technology.


Photovoltaic Grid Connected Inverter


Let's understand the role of a photovoltaic grid-connected inverter.


The inverter not only has the DC / AC conversion function but also has the function of maximizing the performance of solar cells and system fault protection. It can be summarized as automatic operation and shutdown function, maximum power tracking control function, anti-independent operation function (for grid-connected system), automatic voltage adjustment function (for the grid-connected system), DC detection function (for the grid-connected system), and DC grounding detection function (for the grid-connected system).


  1. Automatic operation and shutdown function


After sunrise in the morning, the solar radiation intensity gradually increases, and the output of the solar cell also increases. When the output power required by the inverter is reached, the inverter automatically starts to operate. After entering into operation, the inverter will monitor 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, the inverter will continue to operate; Until sunset, the inverter can operate even on rainy days. When the output of the solar cell module becomes small and the output of the inverter approaches 0, the inverter will form a standby state.


  1. Maximum power tracking control function


The output of the solar cell module varies with the solar radiation intensity and the temperature of the solar cell module itself (chip temperature). In addition, since the solar cell module has the characteristic that the voltage decreases with the increase of the current, there is an optimal operating point that can obtain the maximum power. The solar radiation intensity is changing, and the best working point is also changing. Relative to these changes, the operating point of the solar cell module is always at the maximum power point, and the system always obtains the maximum power output from the solar cell module. This control is the maximum power tracking control. The biggest feature of the inverter used in the solar power generation system is that it includes the maximum power point tracking (MPPT) function.


  1. Power grid detection and grid connection function


Before grid-connected power generation, the grid-connected inverter needs to take power from the power grid, detect the voltage, frequency, phase sequence, and other parameters of power transmission from the power grid, and then adjust the parameters of its power generation to be synchronized with the electrical parameters of the power grid. After the completion, the grid-connected power generation will be completed.


  1. Zero (low) voltage ride-through function


When the power system accident or disturbance causes the voltage sag at the parallel point of the photovoltaic power station, the photovoltaic power station can ensure continuous operation without disconnection within a certain voltage drop range and time interval.


  1. Detection and control of island effect


During normal power generation, the photovoltaic grid-connected power generation system is connected to the large power grid to transmit active power to the grid. However, when the 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. In case of the islanding effect of the inverter, it will cause a great potential safety hazard to personal safety, power grid operation, and the inverter itself. Therefore, the grid access standard of the inverter stipulates that the photovoltaic grid-connected inverter must have the detection and control function of the islanding effect.


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