Safe battery energy management systems, battery management system nodes, and methods
A system and method for hierarchical arc fault monitoring in an energy storage system, where the energy storage system includes a plurality of stacks that are electrically coupled together. Each stack includes a plurality of battery management system nodes that are electrically coupled together. The method includes (1) obtaining respective electrical measurement values for each stack; (2) determining, for each stack, that the stack is free of arc faults, using the respective electrical measurement values for the stack; (3) obtaining electrical measurement values for the energy storage system; and (4) determining that the energy storage system is free of arc faults outside of the plurality of stacks, using (a) the electrical measurement values for the energy storage system and (b) a subset of the respective electrical measurement values for each stack.
1. A method for addressing an arc fault in an energy storage system including a stack of a plurality of battery management system nodes that are electrically coupled together, the method comprising:
determining that an arc fault has occurred in the stack, the arc fault being a flow of electrical current between electrical conductors of the stack that are at different electrical potentials, the arc fault being due to ionization of gas between the electrical conductors of the stack that are at different electrical potentials;
in response to determining that the arc fault has occurred in the stack, electrically isolating a respective battery of each battery management system node at least partially by opening a respective isolation switch electrically coupled to the battery; and
causing the stack to operate in a floating mode by causing a respective node output shorting switch electrically coupled across an output port of each battery management system node to operate in its off state, in response to determining that the arc fault has occurred in the stack.
2. The method of claim 1 , wherein the gas between the electrical conductors of the stack that are at different electrical potentials comprises air.
3. A method for addressing an arc fault in an energy storage system including a stack of a plurality of battery management system nodes that are electrically coupled together, the method comprising:
determining that an arc fault has occurred in the stack, the arc fault being a flow of electrical current between electrical conductors of the stack that are at different electrical potentials, the arc fault being due to ionization of gas between the electrical conductors of the stack that are at different electrical potentials; and
in response to determining that the arc fault has occurred in the stack, electrically isolating a respective battery of each battery management system node at least partially by opening a respective isolation switch electrically coupled to the battery;
wherein the arc fault in the stack is a series arc fault in the stack, and the method further comprises:
obtaining electrical measurement values for the stack, and
determining that the series arc fault has occurred in the stack in response to a mismatch between a sum of voltages across each battery management system node of the stack and a measured voltage across the stack.
4. The method of claim 3 , further comprising:
sending a measurement command to each battery management system node; and
at each battery management system node, in response to the measurement command, obtaining a respective subset of the electrical measurement values for the stack, each subset of the electrical measurement values for the stack corresponding to a time prescribed by the measurement command.
5. The method of claim 4 , further comprising propagating electrical measurement values for a first node of the plurality of battery management system nodes through at least one other node of the plurality of battery management system nodes.
6. The method of claim 3 , further comprising removing power conversion switching noise and associated harmonics from the electrical measurement values for the stack, before determining that the series arc fault has occurred in the stack.
7. The method of claim 3 , wherein the gas between the electrical conductors of the stack that are at different electrical potentials comprises air.
8. A method for addressing an arc fault in an energy storage system including a stack of a plurality of battery management system nodes that are electrically coupled together, the method comprising:
determining that an arc fault has occurred in the stack, the arc fault being a flow of electrical current between electrical conductors of the stack that are at different electrical potentials, the arc fault being due to ionization of gas between the electrical conductors of the stack that are at different electrical potentials; and
in response to determining that the arc fault has occurred in the stack, electrically isolating a respective battery of each battery management system node at least partially by opening a respective isolation switch electrically coupled to the battery;
wherein the arc fault in the stack is a parallel arc fault in the stack, and the method further comprises:
obtaining electrical measurement values for the stack, and
determining that the parallel electrical arc fault has occurred in the stack in response to a mismatch between respective currents flowing through two battery management system nodes of the stack.
9. The method of claim 8 , further comprising:
sending a measurement command to each battery management system node; and
at each battery management system node, in response to the measurement command, obtaining a respective subset of the electrical measurement values for the stack, each subset of the electrical measurement values for the stack corresponding to a time prescribed by the measurement command.
10. The method of claim 9 , further comprising propagating electrical measurement values for a first node of the plurality of battery management system nodes through at least one other node of the plurality of battery management system nodes.
11. The method of claim 8 , further comprising removing power conversion switching noise and associated harmonics from the electrical measurement values for the stack, before determining that the parallel arc fault has occurred in the stack.
12. The method of claim 8 , wherein the gas between the electrical conductors of the stack that are at different electrical potentials comprises air.
13. A method for addressing an arc fault in an energy storage system including a stack of a plurality of battery management system nodes that are electrically coupled together, the method comprising:
determining that an arc fault has occurred in the stack, the arc fault being a flow of electrical current between electrical conductors of the stack that are at different electrical potentials, the arc fault being due to ionization of gas between the electrical conductors of the stack that are at different electrical potentials;
in response to determining that the arc fault has occurred in the stack, electrically isolating a respective battery of each battery management system node at least partially by opening a respective isolation switch electrically coupled to the battery; and
performing a controlled discharge of each battery within its respective battery management system node, in response to determining that the arc fault has occurred in the stack.
14. The method of claim 13 , wherein the gas between the electrical conductors of the stack that are at different electrical potentials comprises air.