Control device of inverter

A solar power generation system, comprising:

• a solar cell;
• an inverter converting electrical power generated by the solar cell into alternating current power connecting to an electric power system;
• a system voltage sensing part sensing a system voltage of the electric power system;
• a direct current voltage control part controlling a direct current voltage to cause the electrical power output from the solar cell to be a maximum when the direct current voltage is higher than a lower limit, the direct current voltage being applied to the inverter;
• a lower limit determination part reducing the lower limit when the system voltage sensed by the system voltage sensing part is lower than a predetermined voltage;
• and
• a reactive power control part controlling reactive power based on the system voltage sensed by the system voltage sensing part, the reactive power being output from the inverter.

A method for controlling an inverter converting electrical power generated by a solar cell into alternating current power connecting to an electric power system, the method comprising:

• sensing a system voltage of the electric power system;
• controlling a direct current voltage to cause the electrical power output from the solar cell to be a maximum when the direct current voltage is higher than a lower limit, the direct current voltage being applied to the inverter;
• reducing the lower limit when the sensed system voltage is lower than a predetermined voltage;
• and
• controlling reactive power output from the inverter, the controlling being based on the sensed system voltage.