The inverter not only has the function of direct AC conversion but also has the function of maximizing solar cell performance and the system fault protection function. They are 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 ground detection function (for the grid-connected system). The automatic operation and shutdown function and the maximum power tracking control function are briefly introduced here.
(1) Automatic operation and shutdown function
After the sun rises in the morning, the solar radiation intensity gradually increases, and the output of the solar cell also increases. After entering operation, the inverter will monitor the output of the solar cell module all the time. As long as the output power of the solar cell module is greater than the output power required for the inverter to work, the inverter will run continuously; until the sunset, the inverter will stop, even if it is cloudy or rainy, the inverter can still run. When the output of the solar cell module becomes smaller and the inverter output is close to 0, the inverter forms a standby state.
(2) Maximum power tracking control function
The output of the solar cell module varies with the intensity of solar radiation 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 as the current increases, there is an optimal operating point to obtain the maximum power. The solar radiation intensity is changing, so obviously the optimal operating point is also changing. In relation to these changes, the system always obtains the maximum power output from the solar cell module by keeping the operating point of the solar cell module at the maximum power point, and this control is called maximum power tracking control. The most important feature of inverters for solar power systems is that they include the function of maximum power point tracking (MPPT).
