Capacitor-based UPS
The present invention generally relates to the field of uninterruptable power supplies (UPSs) and more specifically, to UPSs using supercapacitors (also may be referred to as ultracapacitors) and/or other capacitor and/or battery elements. In an embodiment, a UPS of the present invention can individually regulate the charging of its capacitive elements to avoid overcharging and/or achieve a more efficient charge state.
1. An uninterruptable power supply (UPS) comprising:
at least one energy storage module having a plurality of capacitive elements connected in series;
input circuitry for providing electrical power from an input to the at least one energy storage module;
output circuit for providing electrical power from the at least one energy storage module to an output; and
capacity-measuring circuitry in communication with the at least one capacitive element to:
measure a first and a second voltage across the plurality of capacitive elements, the measurement of the second voltage occurring at a time Δt after the measurement of the first voltage,
measure a current through the plurality of capacitive elements over the time Δt;
calculate a capacitance of the plurality of capacitive elements based on the measured first and second voltages and the measured current;
derive an amount of remaining energy in the at least one energy storage module from the calculated capacitance; and
output an estimated amount of real-time hold time remaining in the at least one energy storage module based on an amount of electrical power being provided on the output circuit from the at least one energy storage module and the derived amount of remaining energy in the at least on energy storage module.
2. The UPS of claim 1 , wherein said at least one said capacitive element comprises an ultra-capacitor.
3. The UPS of claim 1 , wherein said at least one storage module is hot-swappable.
4. The UPS of claim 1 further comprising charge-balancing circuitry, wherein said charge-balancing circuitry at least partially retards charging of said at least one said capacitive element when a voltage across said at least one said capacitive element is determine to be greater than a voltage across at least one other said capacitive element by at least some first threshold amount, and wherein said charge-balancing circuitry resumes normal charging of said at least one said capacitive element when said voltage across said at least one said capacitive element is determined to be less than said voltage across said at least one other said capacitive element by at least some second threshold amount.
5. The UPS of claim 4 , wherein said charge-balancing circuit comprises a bleed resistor and a switch, said bleed resistor being connected in parallel with said at least one said capacitive element when said switch is activated.
6. The UPS of claim 5 , wherein said charge-balancing circuit further comprises an inductor connected in series between said at least one said capacitive element and said bleed resistor.
7. The UPS of claim 5 , wherein said switch comprises a MOSFET.
8. The UPS of claim 5 further comprising a microcontroller, said microcontroller at least partially controlling a maximum charge voltage across said at least one said capacitive element by at least one of activating and deactivating said switch.
9. The UPS of claim 8 further comprising communication circuitry providing a data communication link to an external managing device, wherein said microcontroller at least partially controls said maximum charge voltage across said at least one said capacitive element in response to an input received from said communication circuitry.