Grid Connection Power Conversion Device and Output Current Control Method Thereof

A grid connection power conversion device for connecting a distributed power supply to a three-phase commercial power system, the grid connection power conversion device comprising:

• an inverter for converting DC power based on power input from the distributed power supply to three-phase AC power;
• a line voltage detection circuitry configured to detect a maximum value of each of three line voltages of three-phase AC voltage of the commercial power system;
• an instantaneous voltage drop detection circuitry configured to detect an instantaneous voltage drop in the commercial power system;
• and
• an output current control circuitry configured to control an output current value from the inverter,
• wherein when the instantaneous voltage drop detection circuitry detects an instantaneous voltage drop in the commercial power system, and when a minimum value among the maximum values of the three line voltages detected by the line voltage detection circuitry is equal to or higher than a preset line voltage lower limit value, the output current control circuitry reduces the output current value from the inverter to an output current value corresponding to the minimum value among the maximum values of the three line voltages, and
• wherein when the instantaneous voltage drop detection circuitry detects an instantaneous voltage drop in the commercial power system, and when a minimum value among the maximum values of the three line voltages detected by the line voltage detection circuitry is lower than the line voltage lower limit value, the output current control circuitry reduces the output current value from the inverter to an output current value corresponding to the line voltage lower limit value.

A grid connection power conversion device for connecting a distributed power supply to a three-phase commercial power system, the grid connection power conversion device comprising:

• an inverter for converting DC power based on power input from the distributed power supply to three-phase AC power;
• a phase voltage detection circuitry configured to detect a maximum value of each of three phase voltages of three-phase AC voltage of the commercial power system;
• an instantaneous voltage drop detection circuitry configured to detect an instantaneous voltage drop in the commercial power system;
• and
• an output current control circuitry configured to control an output current value from the inverter,
• wherein when the instantaneous voltage drop detection circuitry detects an instantaneous voltage drop in the commercial power system, and when a minimum value among the maximum values of the three phase voltages detected by the phase voltage detection circuitry is equal to or higher than a preset phase voltage lower limit value, the output current control circuitry reduces the output current value from the inverter to an output current value corresponding to the minimum value among the maximum values of the three phase voltages, and
• wherein when the instantaneous voltage drop detection circuitry detects an instantaneous voltage drop in the commercial power system, and when a minimum value among the maximum values of the three phase voltages detected by the phase voltage detection circuitry is lower than the phase voltage lower limit value, the output current control circuitry reduces the output current value from the inverter to an output current value corresponding to the phase voltage lower limit value.

An output current control method of a grid connection power conversion device comprising an inverter for converting DC power based on power input from a distributed power supply to three-phase AC power, the output current control method comprising the steps of:

• detecting a maximum three-phase instantaneous voltage value of a commercial power system;
• detecting maximum values of three line voltages of the commercial power system;
• detecting an instantaneous voltage drop in the commercial power system;
• and
• reducing an output current value from the inverter to an output current value corresponding to a minimum value among the four maximum voltage values, which are the maximum three-phase instantaneous voltage value and the maximum values of the three line voltages, when the instantaneous voltage drop has been detected.