Interface circuit, string, and system applied to power line communication

A system applied to power line communication, comprising:

• an inverter;
• at least one optimizer group, each of the at least one optimizer group comprising one or more optimizers and one or more photovoltaic modules, each optimizer is connected to each photovoltaic module in a one-to-one correspondence and is configured to convert a direct current output by each photovoltaic module into an adjustable direct current,
• at least one capacitor;
• a magnetic ring;
• power lines;
• and
• a signal line, wherein the at least one optimizer group is
• serially connected to the at least one capacitor through the power lines, the power lines are connected to either end of the at least one capacitor and pass through the magnetic ring, the signal line passes through the magnetic ring and is connected to the inverter, and the signal line, the power lines, the magnetic ring, and the at least one capacitor are configured to transmit a power line communication (PLC) signal.