Enhanced battery storage and recovery energy systems
Systems and methods are herein disclosed for efficiently and cost-effectively balancing the voltages across batteries and/or cells in an energy storage system. A controller monitors the battery voltages and instructs regulator circuits to balance voltages between any batteries or sets of batteries having imbalanced voltages. Regulator circuits implementing a modified Ćuk converter can be utilized. Regulator circuits can have two capacitive circuits, one inductive circuit, and two switches. Two capacitors, an inductor, and two field effect transistors can be used in each regulator circuit.
1. An energy storage system comprising:
a plurality of batteries connected in series;
a first regulator circuit configured to balance voltages across two first battery sets of the plurality of batteries, the first regulator circuit comprising at least one switchable connection and at least one energy storage unit, wherein the at least one switchable connection connects the at least one energy storage unit to the two first battery sets;
a second regulator circuit configured to balance voltages across two second battery sets of the plurality of batteries, wherein each set in the two first battery sets includes one set from the two second battery sets; and
a controller connected to the first regulator circuit and the second regulator circuit and configured to:
monitor voltages across the two first battery sets and voltages across the two second battery sets;
identify voltage imbalances between the two first battery sets and voltage imbalances between the two second battery sets; and
adjust the first regulator circuit and the second regulator circuit to minimize the voltage imbalances between the two first battery sets and the voltage imbalances between the two second battery sets.
2. The energy storage system of claim 1 , wherein the at least one switchable connection comprises one or more transistors.
3. The energy storage system of claim 1 , wherein the at least one energy storage unit comprises one or more inductive circuits.
4. The energy storage system of claim 1 , wherein the at least one energy storage unit comprises one or more capacitive circuits.
5. The energy storage system of claim 1 , wherein the second regulator circuit comprises:
two capacitive circuits each connected in parallel with one of the two second battery sets;
an inductive circuit connected to:
the two capacitive circuits; and
the two second battery sets;
two switches each connected to:
the inductive circuit;
one of the two capacitive circuits;
one of the two second battery sets; and
the controller.
6. The energy storage system of claim 5 , wherein the two switches operate at a fifty percent duty cycle when the voltages across the two second battery sets are equal.
7. The energy storage system of claim 5 , wherein the two switches operate at a duty cycle not equal to fifty percent when the voltages across the two second battery sets are not equal, and wherein the duty cycle is such that the voltages across the two sets of batteries converge.
8. The energy storage system of claim 5 , wherein the two switches are transistors.
9. The energy storage system of claim 1 , wherein the plurality of batteries comprises 2 n number of batteries, where n is a positive integer; and the energy storage system comprises only 2 n /2 number of regulator circuits to balance the 2 n number of batteries between each other.
10. The energy storage system of claim 1 , wherein the first regulator circuit is turned off when the voltages across the first two battery sets are balanced.
11. The energy storage system of claim 1 , wherein the controller is further configured to:
monitor the direction of current through the batteries; and
determine whether the batteries are being charged or discharged.
12. A method comprising:
monitoring voltages across two first battery sets;
monitoring voltage across two second battery sets, wherein each set in the two first battery sets includes one set from the two second battery sets;
determining if a difference between the voltages across the two first battery sets exceeds a voltage imbalance threshold;
instructing a first regulator circuit, associated with the two first battery sets, to balance the voltages across the two first battery sets, by:
storing bypass energy in an energy storage unit; and
distributing the stored bypass energy to at least one of the first set of batteries and the second set of batteries;
determining if a difference between the voltage across the two second battery sets exceeds the voltage imbalance threshold; and
instructing a second regulator circuit, associated with the two second battery sets, to balance the voltages across the two second battery sets.
13. The method of claim 12 , wherein the instructing further comprises adjusting a duty cycle of two switches in the first regulator circuit.
14. An energy storage system comprising:
a plurality of batteries connected in series;
a first regulator circuit coupled to two first sets of batteries in the plurality of batteries and configured to balance voltages of the two first sets, and wherein the first regulator circuit comprises:
an inductive circuit;
a first switch; and
a second switch;
a second regulator circuit coupled to two second sets of batteries in the plurality of batteries and configured to balance voltages of the two second sets, wherein each set in the first sets includes one set from the second sets; and
a controller connected to the first regulator circuit and the second regulator circuit and configured to at least:
adjust the first switch and the second switch to minimize imbalance between the voltages of the two first sets; and
minimize imbalance between the voltages of the two second sets.
15. The energy storage system as recited in claim 14 , wherein the first regulator circuit further comprises:
a first capacitive circuit; and
a second capacitive circuit.
16. The energy storage system as recited in claim 15 , wherein:
the first capacitive circuit is connected in parallel with a first one of the two first sets of batteries;
the second capacitive circuit is connected parallel to a second one of the two first sets of batteries
the first switch is connected to the second switch in series;
the first switch and the second switch are connected parallel to the two first sets of batteries;
the inductor is connected between a connection point between the first capacitive circuit and the second capacitive circuit and a connection point between the first switch and the second switch; and
the controller is connected to control the first switch and the second switch.
17. The energy storage system as recited in claim 15 , wherein:
the first capacitive circuit is in parallel with a first one of the two first sets of batteries; and
the second capacitive circuit is in parallel with a second one of the two first sets of batteries.
18. The energy storage system as recited in claim 15 , wherein the inductive circuit comprises a second terminal connected to:
a second terminal of the first capacitive circuit; and
a first terminal of the second capacitive circuit.
19. The energy storage system as recited in claim 14 , wherein the controller is configured to:
identify a voltage imbalance when a difference between the voltages of the two first sets exceeds a voltage imbalance threshold; and
adjust a duty cycle of the first switch and the second switch to decrease the difference.
20. The energy storage system as recited in claim 14 , wherein the controller is connected to the two first sets of batteries.