PROBLEM TO BE SOLVED: To provide a high reliability power storage system by adding a function for reducing flickers of a linkage system, in a arrange which will not influence the operation, although the power storage system is normally used for equalizing a load. SOLUTION: In a control system of an A/D converter 10 in the power storage system, a positive phase voltage 14 (e.g., effective value of the fundamental wave for the past 20 ms) is calculated continuously from a voltage at a battery system linkage point 6 by using DFT (Discrete Fourier Transform), a PQ vector control (a control for independently self-regulating active and reactive power of a self-excited converter to an arbitrary PQ instruction value) is implemented, by using the positive phase voltage at the linkage point as a reference, and the flickers are suppressed by filtering the positive phase voltage by using a high-pass filter, multiplying a filtered signal by the gain and adding the multiplied result to a horizontal axis current regulating part of the PQ vector control as a correction quantity.