SYSTEM INTERCONNECTION DEVICE

PROBLEM TO BE SOLVED: To provide a system interconnection device that uses a power system advantageous to a consumer while stabilizing power supply to the consumer.SOLUTION: A system interconnection device 2 having an inverter circuit 22 for converting DC power acquired from renewable energy 1 to AC power synchronous with a first power system 3 and superimposing the AC power onto the first power system 3 for feeding a load 4 includes an input/output circuit 23 connected to a second power system 5, and configured to convert power acquired from the second power system 5 for combination with the DC power for feeding the inverter circuit 22 and to convert at least part of the DC power to AC power synchronous with the second power system 5 and superimpose the AC power onto the second power system 5.