Power storage system and method of controlling the same
A power storage system supplies electric power to a load, and includes: a secondary battery; a capacitor connected in parallel to the secondary battery; and a controller performing control to prioritize charging and discharging of the capacitor over charging and discharging of the secondary battery.
1. A power storage system comprising:
a power converter whose load-side terminals are connected to a load;
a secondary battery connected to power-supply-side terminals of the power converter;
a capacitor connected to the power-supply-side terminals of the power converter via a DC/DC converter in parallel to the secondary battery; and
a controller controlling the DC/DC converter to prioritize charging and discharging of the capacitor over charging and discharging of the secondary battery,
wherein the controller includes:
a first control unit that generates a target current value of the capacitor based on a deviation of a current of the secondary battery from a predetermined target current value of the secondary battery, the predetermined target current value being zero or close to zero; and
a second control unit that generates a conduction ratio of the DC/DC converter based on a deviation of a current of the capacitor from the target current value of the capacitor, and outputs the conduction ratio to the DC/DC converter.
2. The power storage system according to claim 1 , wherein
the predetermined target current value of the secondary battery is a current value less than or equal to a one-hour current rate of the secondary battery.
3. The power storage system according to claim 1 , wherein
the predetermined target current value of the secondary battery is zero.
4. The power storage system according to claim 1 , wherein
the first control unit is configured to generate the target current value of the capacitor based on a current for keeping SOC of the secondary battery to a predetermined value and the deviation of the current of the secondary battery from the predetermined target current value of the secondary battery.
5. A method of controlling a power storage system, the power storage system including: a power converter whose load-side terminals are connected to a load; a secondary battery connected to power-supply-side terminals of the power converter; a capacitor connected to the power-supply-side terminals of the power converter via a DC/DC converter in parallel to the secondary battery; and a controller,
the method comprising:
generating, by the controller, a target current value of the capacitor based on a deviation of a current of the secondary battery from a predetermined target current value of the secondary battery, the predetermined target current value being zero or close to zero;
generating, by the controller, a conduction ratio of the DC/DC converter based on a deviation of a current of the capacitor from the target current value of the capacitor, and outputting, by the controller, the conduction ratio to the DC/DC converter; and
controlling the DC/DC converter by the controller to prioritize charging and discharging of the capacitor over charging and discharging of the secondary battery.