Electrical energy storage system with cascaded frequency response optimization
A frequency response controller includes a high level controller configured to receive a regulation signal from an incentive provider, determine statistics of the regulation signal, and use the statistics of the regulation signal to generate a frequency response midpoint. The controller further includes a low level controller configured to use the frequency response midpoint to determine optimal battery power setpoints and use the optimal battery power setpoints to control an amount of electric power stored or discharged from a battery during a frequency response period.
1. A frequency response controller comprising:
a high level controller configured to receive a regulation signal from an incentive provider, determine statistics of the regulation signal, and use the statistics of the regulation signal to generate a frequency response midpoint, wherein the frequency response midpoint is a baseline power consumption value relative to which the frequency response controller causes the electric power to be added to an energy grid or removed from the energy grid in response to the regulation signal; and
a low level controller configured to use the frequency response midpoint to determine optimal battery power setpoints and use the optimal battery power setpoints to control an amount of electric power stored or discharged from a battery during a frequency response period.
2. The frequency response controller of claim 1 , wherein the high level controller is configured to determine the frequency response midpoint that maintains the battery at a same state-of-charge at a beginning and an end of the frequency response period while participating in a frequency response program.
3. The frequency response controller of claim 1 , wherein the high level controller is configured to determine an optimal frequency response midpoint that achieves a desired change in a state-of-charge of the battery while participating in a frequency response program.
4. The frequency response controller of claim 1 , wherein:
the high level controller is configured to generate filter parameters based on the frequency response midpoint; and
the low level controller is configured to use the filter parameters to filter the regulation signal and determine the optimal battery power setpoints using the filtered regulation signal.
5. The frequency response controller of claim 1 , wherein the frequency response controller is configured to generate an objective function comprising:
an estimated amount of frequency response revenue that will result from the battery power setpoints; and
an estimated cost of battery degradation that will result from the battery power setpoints.
6. The frequency response controller of claim 5 , wherein the frequency response controller is configured to implement constraints on the objective function, the constraints comprising at least one of:
constraining a state-of-charge of the battery between a minimum state-of-charge and a maximum state-of-charge; and
constraining the midpoint such that a sum of the midpoint and a campus power usage does not exceed a maximum power rating of a power inverter for the battery.
7. The frequency response controller of claim 1 , wherein the frequency response controller is configured to use a battery life model to determine an estimated cost of battery degradation, the battery life model comprising a plurality of variables that depend on the battery power setpoints, the variables comprising at least one of:
a temperature of the battery;
a state-of-charge of the battery;
a depth of discharge of the battery;
a power ratio of the battery; and
an effort ratio of the battery.
8. The frequency response controller of claim 1 , wherein the high level controller is configured to provide a bid price to the incentive provider and receive the regulation signal specifying a regulation award from the incentive provider.
9. The frequency response controller of claim 1 , further comprising a battery power loss estimator configured to estimate an amount of power lost in the battery based on the statistics of the regulation signal.
10. A method for optimizing frequency response, the method comprising:
receiving a regulation signal from an incentive provider;
determining statistics of the regulation signal;
using the statistics of the regulation signal to generate a frequency response midpoint, wherein the frequency response midpoint is a baseline power consumption value relative to which the frequency response controller causes the electric power to be added to an energy grid or removed from the energy grid in response to the regulation signal;
using the frequency response midpoint to determine optimal battery power setpoints; and
using the optimal battery power setpoints to control an amount of electric power stored or discharged from a battery during a frequency response period.
11. The method of claim 10 , wherein generating the frequency response midpoint comprises determining the frequency response midpoint that maintains the battery at a same state-of-charge at a beginning and an end of the frequency response period while participating in a frequency response program.
12. The method of claim 10 , wherein generating the frequency response midpoint comprises determining an optimal frequency response midpoint that achieves a desired change in a state-of-charge of the battery while participating in a frequency response program.
13. The method of claim 10 , further comprising:
generating filter parameters based on the frequency response midpoint;
using the filter parameters to filter the regulation signal; and
determining the optimal battery power setpoints using the filtered regulation signal.
14. The method of claim 10 , further comprising generating an objective function comprising:
an estimated amount of frequency response revenue that will result from the battery power setpoints; and
an estimated cost of battery degradation that will result from the battery power setpoints.
15. The method of claim 14 , further comprising implementing constraints on the objective function, the constraints comprising at least one of:
constraining a state-of-charge of the battery between a minimum state-of-charge and a maximum state-of-charge; and
constraining the midpoint such that a sum of the midpoint and a campus power usage does not exceed a maximum power rating of a power inverter for the battery.
16. The method of claim 10 , further comprising using a battery life model to determine an estimated cost of battery degradation, the battery life model comprising a plurality of variables that depend on the battery power setpoints, the variables comprising at least one of:
a temperature of the battery;
a state-of-charge of the battery;
a depth of discharge of the battery;
a power ratio of the battery; and
an effort ratio of the battery.
17. The method of claim 10 , further comprising:
providing a bid price to the incentive provider; and
receiving the regulation signal specifying a regulation award from the incentive provider.
18. The method of claim 10 , further comprising estimating an amount of power lost in the battery based on the statistics of the regulation signal.
19. A frequency response optimization system comprising:
a battery configured to store and discharge electric power;
a battery power inverter configured to control an amount of the electric power stored or discharged from the battery at each of a plurality of time steps during a frequency response period;
a high level controller configured to generate a frequency response midpoint based on a regulation signal, wherein the frequency response midpoint is a baseline power consumption value relative to which the frequency response controller causes the electric power to be added to an energy grid or removed from the energy grid in response to the regulation signal; and
a low level controller configured to use the frequency response midpoint to determine optimal setpoints for the battery power inverter.
20. The frequency response optimization system of claim 19 , wherein:
the high level controller is configured to generate filter parameters based on the frequency response midpoint; and
the low level controller is configured to use the filter parameters to filter the regulation signal and determine the optimal setpoints for the battery power inverter using the filtered regulation signal.