Frequency Responsive Charge Sustaining Control of Electricity Storage Systems for Ancillary Services on an Electrical Power Grid
First Claim
1. A method of responding to changes in the operating frequency of an electricity grid by means of energy storage devices that are energetically coupled with the electricity grid, the method comprising:
- determining whether the operating frequency of the electricity grid is within a predetermined range of a nominal operating frequency;
if the operating frequency is determined to be outside said range, regulating the grid frequency by transferring energy between the energy storage device and the electricity grid;
if the operating frequency is within said range, determining whether a state of charge (SOC) of the energy storage device is within predetermined limits; and
transferring energy between the energy storage device and the electricity grid to bring the SOC within said predetermined limits when the operating frequency is within said range and the SOC of the energy storage device is outside said predetermined limits.
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Accused Products
Abstract
Systems, apparatus, and methods are provided for maintaining the state of charge of energy storage devices such as batteries, flywheel, capacitors, or other technologies that are energetically coupled with the electricity grid to support ancillary services. To reliably respond to requests to regulate the grid, the charge on the energy storage device is sustained or restored to a specified range in a manner that optimizes the readiness of the energy storage device to supply ancillary services in light of the condition of the grid. A state of charge (SOC) of the energy storage device and the grid frequency may be monitored. When a request from the operator to regulate the grid frequency is not being serviced, the charge of the energy storage device may be increased or decreased so that the charge may be sustained within the specific range. Once the SOC falls outside of the first range, charge may be added to or removed from the energy storage device when the grid frequency has appropriate values, e.g. if the grid frequency is respectively above a first setpoint or below a second setpoint.
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Citations
24 Claims
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1. A method of responding to changes in the operating frequency of an electricity grid by means of energy storage devices that are energetically coupled with the electricity grid, the method comprising:
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determining whether the operating frequency of the electricity grid is within a predetermined range of a nominal operating frequency; if the operating frequency is determined to be outside said range, regulating the grid frequency by transferring energy between the energy storage device and the electricity grid; if the operating frequency is within said range, determining whether a state of charge (SOC) of the energy storage device is within predetermined limits; and transferring energy between the energy storage device and the electricity grid to bring the SOC within said predetermined limits when the operating frequency is within said range and the SOC of the energy storage device is outside said predetermined limits. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of responding to changes in the operating frequency of an electricity grid by means of energy storage devices that are energetically coupled with the electricity grid, the method comprising:
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determining whether a parameter of the operating frequency of the electricity grid is within a predetermined range; if the operating frequency parameter is determined to be outside said range, adjusting the grid frequency by transferring energy between the energy storage devices and the electricity grid; if the operating frequency is within said range, determining whether a state of charge (SOC) of the energy storage devices is within predetermined limits and whether the operating frequency is within a predetermined band around a nominal operating frequency; and transferring energy between the energy storage device and the electricity grid to bring the SOC within said predetermined limits when the operating frequency is within said predetermined band and the SOC of the energy storage device is outside said predetermined limits. - View Dependent Claims (11, 12, 13, 14)
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15. A system for responding to changes in the operating frequency of an electricity distribution grid, comprising:
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a least one energy storage device; a converter that, in response to a command to add energy to or absorb energy from the grid, selectively couples said storage cell to the grid to transfer energy between the energy storage device and the grid; and a state-of-change (SOC) maintenance system that determines whether the operating frequency of the electricity grid is within a predetermined range of a nominal operating frequency, determines whether the SOC of the energy storage device is within predetermined limits, and controls said converter transfer energy between the energy storage device and the electricity grid to bring the SOC within said predetermined limits when the operating frequency is within said range and the SOC of the energy storage device is outside said predetermined limits. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification