Abstract: 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.

Abstract: Each of a plurality of unit converters includes: a main circuit; a control circuit that controls the plurality of switching elements according to a control signal received from the controller; a power supply that lowers a voltage of a first capacitor to generate a power supply voltage and supplies the power supply voltage to the control circuit; and a current-limiting resistance circuit having a variable resistance value and disposed between the main circuit and the power supply. The power supply includes a second capacitor, an overcharge suppression circuit, a power supply circuit, and a controller. The controller includes: an overcharge suppression control circuit that controls the overcharge suppression circuit in accordance with a magnitude of a voltage of the second capacitor; and a resistance switching circuit that changes a resistance value of the current-limiting resistance circuit in accordance with a magnitude of a voltage of the first capacitor.

Abstract: Each of a plurality of unit converters includes: a main circuit; a control circuit that controls the plurality of switching elements according to a control signal received from the controller; a power supply that lowers a voltage of a first capacitor to generate a power supply voltage and supplies the power supply voltage to the control circuit; and a current-limiting resistance circuit having a variable resistance value and disposed between the main circuit and the power supply. The power supply includes a second capacitor, an overcharge suppression circuit, a power supply circuit, and a controller. The controller includes: an overcharge suppression control circuit that controls the overcharge suppression circuit in accordance with a magnitude of a voltage of the second capacitor; and a resistance switching circuit that changes a resistance value of the current-limiting resistance circuit in accordance with a magnitude of a voltage of the first capacitor.