Grid interconnection apparatus

A grid interconnection apparatus 1 includes a voltage conversion section 11 including DC/DC converters 21a to 21d to step up or down output voltages of DC power sources 2a to 2d. The voltage conversion section 11 combines DC power outputs from the DC/DC converters 21a to 21d into combined DC power and output the DC power. A power conversion section 12 converts the DC power output from the voltage conversion section 11 into AC power, and outputs the AC power to a power grid 3. A current detector 13 detects a current input into the power conversion section 12. A voltage detector 10a to 10d detects a voltage input into the power conversion section 12. A controller 14 controls the DC/DC converters 21a to 21d to maximize the power outputs from the DC power sources 2a to 2d based on the detected current and the detected voltage.