POWER STORAGE DEVICE AND METHOD FOR SUPPLYING POWER STORAGE TYPE POWER

PROBLEM TO BE SOLVED: To reduce an occurrence of a loss at a power converter in the case of leveling a load by using a method for supplying a power storage type power. SOLUTION: A power storage device 1 comprises a power storage unit 2 for storing a power, and the power converter 3 for converting an AC power into a DC power or the DC power into the AC power. The device 1 is connected to a power source system 8 via a system interconnection transformer 4. The converter 3 has an AC-DC power converter 3a at the system 8 side and a DC-AC power converter 3b at a power storage unit 2 side. In this case, a DC load 5b for forming a peak load in the daytime is connected between the converter 3a and the converter 3b. An AC load 5a is connected to the system 8 side in parallel with the device 1. The DC power stored in the device 1 from the system 8 at night is supplied to the load 5b by regulating an input voltage to be input to the output of the unit 2 by the converter 3b to an output voltage suitable for the load 5b and supplied to the load 5b without intermediary of the converter 3a of the converter 3 at a peak time in the daytime.