TEMPERATURE CONTROL APPARATUS FOR ELECTRICITY STORAGE DEVICE

In a power storage system including a secondary battery (1) and a capacitor (2), a bidirectional DC-DC converter is set into mode for charging the secondary battery (1) with electricity when a first state of charge (SOC) of the secondary battery (1) is larger than a minimum value of the first SOC, and a second SOC of the capacitor (2) is smaller than a maximum value of the second SOC, and the bidirectional DC-DC converter is set into mode for discharging electricity from the secondary battery (1) when the first SOC is smaller than a maximum value of the first SOC, and the second SOC is larger than a minimum value of the second SOC. On the basis of an internal resistance of the secondary battery (1), the second SOC, a voltage of a direct current link which are obtained when a load is not connected to the direct current link, and a bidirectional DC-DC converter error in a current on a direct current link side, a conduction ratio (D) of the bidirectional DC-DC converter is calculated to control the bidirectional DC-DC converter, so as to control a temperature by means of a change of the internal resistance.