Inverter not only has the function of direct AC conversion, but also has the function of maximizing solar cell performance and system fault protection. To sum up, there are automatic operation and shutdown functions, MPPT, single machine operation prevention function (power grid system), automatic voltage regulation function (power grid system), DC detection (power grid system) and DC grounding detection (power grid system). This paper briefly introduces automatic operation, shutdown function and maximum power tracking control.

1. Automatic operation and shutdown

After sunrise, the intensity of solar radiation gradually increases, and the output of solar cells also increases. When the inverter reaches the required output power, it will automatically run. When put into operation, the inverter will always monitor the output of the solar cell module. If the output power of the solar cell module is greater than the expected output power of the inverter, the inverter will continue to operate until it stops at sunset, even in rainy days. When the output of solar cell module becomes smaller, the output of inverter is close to zero, and the inverter will be in standby state.

2. Maximum power tracking control

The output of solar cell module changes with the intensity of solar radiation and the temperature of solar module itself (chip temperature). In addition, because the characteristic of solar cell module is that the voltage decreases with the increase of current, there is an optimal operating point to obtain the maximum power. The intensity of solar radiation is changing, and obviously the best working point is also changing. Relative to these changes, the working 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 point tracking control. Maximum power point tracking (MPPT) is the most important feature of solar power generation system with inverter.