Method for controlling sodium-sulfur battery

A method for controlling a plurality of sodium-sulfur batteries that, in an interconnected system in which a power generation device that fluctuates in output and an electric power storage-compensation device comprising a plurality of sodium-sulfur batteries connected in parallel are combined to supply power to an electric power system, are each included in the electric power storage-compensation device and compensate for output fluctuations of the power generation device, the method comprising compensating for the output fluctuations of the power generation device, while controlling so that all of the plurality of sodium-sulfur batteries are within a predetermined charged range by:

• detecting when one or more of the plurality of sodium-sulfur batteries reaches one of a charge end or a discharge end within the predetermined charged range, wherein when one sodium-sulfur battery of the plurality of sodium-sulfur batteries reaches the discharge end of the predetermined charged range, a sodium-sulfur battery closest to the charge end of the predetermined charged range among other sodium-sulfur batteries is discharged to charge the sodium-sulfur battery reaching the discharge end of the predetermined charged range;
• and simultaneously discharging, voltage from all of the sodium-sulfur batteries other than the sodium-sulfur battery reaching the discharge end to maintain the power output for the interconnected system at a predetermined target value;
• and
• when one sodium-sulfur battery of the plurality of sodium-sulfur batteries reaches the charge end of the predetermined charged range, the sodium-sulfur battery reaching the charge end of the predetermined charged range is discharged to charge a sodium-sulfur battery closest to the discharge end of the predetermined charged range among other sodium-sulfur batteries.

A method for controlling a plurality of sodium-sulfur batteries in an electric storage compensation device that is interconnected with a power generation device having an output that fluctuates, where an output from the power generation device and the electric storage compensation device are combined to supply a predetermined power to an electric power system, the method comprising:

• measuring an output power of the power generation device having an output that fluctuates;
• compensating for output power fluctuations of the power generation device with power from at least one sodium-sulfur battery of the plurality of sodium-sulfur batteries in the electric storage compensation device to supply the predetermined power to the electric power system when the output power of the power generation device is less than the predetermined power supplied to the electric power system;
• charging one or more of the plurality of sodium-sulfur batteries with power from the power generation device when the output power of the power generation device is greater than the predetermined power supplied to the electric power system;
• monitoring a charge state of each of the plurality of sodium-sulfur batteries in the electric storage compensation device, and
• controlling a charge state of each of the plurality of sodium-sulfur batteries so that all of the plurality of sodium-sulfur batteries are within a predetermined charged range by
• detecting when one or more of the plurality of sodium-sulfur batteries reaches one of a charge end or a discharge end within the predetermined charge range,
• charging one sodium-sulfur battery reaching a discharge end of the predetermined charged range from all sodium-sulfur batteries of the plurality of sodium-sulfur batteries other than the one sodium sulfur battery reaching the discharge end when the one sodium-sulfur battery reaches the discharge end of the predetermined charged range, and simultaneously discharging voltage from all of the sodium-sulfur batteries other than the sodium-sulfur battery reaching the discharge end to maintain the power output for the interconnected system at a p determined target value;
• and
• discharging power from one sodium-sulfur battery reaching a charge end of the predetermined charged range to one or more sodium-sulfur batteries of the plurality of sodium-sulfur batteries when the one sodium-sulfur battery reaches the charge end of the predetermined charged range, wherein values for the discharge end and the charge end are set by setting control target values of a bidirectional converter, wherein the charge end of one of the sodium-sulfur batteries is detected by measuring a voltage increase, and wherein the discharge end of one of the sodium-sulfur batteries is detected by measuring a voltage decrease.