METHOD FOR CONTROLLING STRING INVERTER, CONTROLLER, INVERTER, AND INVERTER SYSTEM

This application provides a control method and a controller for a string inverter, an inverter, and an inverter system. The method includes: in an IV curve scanning process, controlling an output power of an inverter circuit to be a specified power reference value, and controlling an output voltage of each non-IV curve scanning DC-DC circuit to be a specified voltage reference value, where the specified power reference value is less than or equal to a sum of input powers of all non-IV curve scanning DC-DC circuits before IV curve scanning, and the specified voltage reference value is greater than or equal to a preset percentage of a maximum value in open-circuit voltages, before the IV curve scanning, of photovoltaic strings connected to all IV curve scanning DC-DC circuits. The inverter circuit is controlled to maintain a constant output power and a constant bus voltage, with no power fluctuation, and each non-IV curve scanning DC-DC circuit continues to output a power. In this way, photovoltaic energy is effectively utilized, and a huge energy yield loss is avoided.