A voltage control apparatus, when a voltage drop of an output voltage of an inverter is equal to or larger than a threshold, calculates first virtual impedance using various variables, calculates, such that an output current of the inverter does not exceed a rated value, second virtual impedance to be temporarily added to the first virtual impedance, calculates a virtual active voltage and a virtual reactive voltage by multiplying each of an active current and a reactive current calculated by the output current, by virtual impedance obtained by adding up the first virtual impedance and the second virtual impedance, and performs voltage control based on the virtual active voltage and the virtual reactive voltage such that each of the active current and the reactive current can approach each of an active current command value and a reactive current command value required of a power grid.

A frequency detector detects a system frequency from an AC voltage on an AC power line to which a power conditioner performing system interconnection of a distributed power supply is connected. A power converter is configured to inject lead reactive power or delay reactive power into the AC power line. A controller controls reactive power output from the power converter to output the lead reactive power in response to an increase in the system frequency while outputting the delay reactive power in response to a decrease in the system frequency.

A frequency detector detects a system frequency from an AC voltage on an AC power line to which a power conditioner performing system interconnection of a distributed power supply is connected. A power converter is configured to inject lead reactive power or delay reactive power into the AC power line. A controller controls reactive power output from the power converter to output the lead reactive power in response to an increase in the system frequency while outputting the delay reactive power in response to a decrease in the system frequency.

A voltage control apparatus, when a voltage drop of an output voltage of an inverter is equal to or larger than a threshold, calculates first virtual impedance using various variables, calculates, such that an output current of the inverter does not exceed a rated value, second virtual impedance to be temporarily added to the first virtual impedance, calculates a virtual active voltage and a virtual reactive voltage by multiplying each of an active current and a reactive current calculated by the output current, by virtual impedance obtained by adding up the first virtual impedance and the second virtual impedance, and performs voltage control based on the virtual active voltage and the virtual reactive voltage such that each of the active current and the reactive current can approach each of an active current command value and a reactive current command value required of a power grid.