Accurate estimation of the capacity and state of charge of an energy storage system used in wind farms
First Claim
1. A method for estimating an aged capacity of a battery in an energy storage system (ESS) associated with a plurality of wind turbine generators, the method comprising:
- determining an internal impedance and an electromotive force (EMF) of the battery, wherein the determined internal impedance and the determined EMF are derived from a measured voltage of the battery and a measured current into the battery at two different points in time;
determining an approximate age of the battery based on the internal impedance;
determining a relationship between a maximum capacity corresponding to the battery and a number of charging cycles;
determining the aged capacity of the battery based on the approximate age and the relationship;
determining a state of charge (SOC) of the battery based on the determined EMF of the battery;
after determining the aged capacity, measuring an available energy remaining in the battery based on the SOC and the aged capacity; and
upon determining the available energy remaining in the battery is below a predetermined value, increasing power output of the plurality of wind turbine generators by operating the plurality of wind turbine generators to produce additional power output in order to increase a rate at which the battery is charged.
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Accused Products
Abstract
Embodiments of the invention provide techniques and apparatus for accurately estimating an aged capacity (Eaged) of a battery in an energy storage system (ESS) used on a wind farm. Eaged throughout the life of the battery may be estimated by measuring the internal impedance of the battery and using a relationship between the age of the battery (e.g., a number of charging cycles) and a maximum capacity corresponding to the battery. The state of charge (SOC) may be calculated based on the electromotive force (EMF) of the battery. The actual available energy (Eavailable) of the battery may be calculated based on the Eaged of the battery and the calculated SOC. In this manner, embodiments of the present invention may allow a wind farm to function as a virtual power plant (VPP) and deliver peak load electricity, regardless of intermittent wind velocity.
35 Citations
19 Claims
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1. A method for estimating an aged capacity of a battery in an energy storage system (ESS) associated with a plurality of wind turbine generators, the method comprising:
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determining an internal impedance and an electromotive force (EMF) of the battery, wherein the determined internal impedance and the determined EMF are derived from a measured voltage of the battery and a measured current into the battery at two different points in time; determining an approximate age of the battery based on the internal impedance; determining a relationship between a maximum capacity corresponding to the battery and a number of charging cycles; determining the aged capacity of the battery based on the approximate age and the relationship; determining a state of charge (SOC) of the battery based on the determined EMF of the battery; after determining the aged capacity, measuring an available energy remaining in the battery based on the SOC and the aged capacity; and upon determining the available energy remaining in the battery is below a predetermined value, increasing power output of the plurality of wind turbine generators by operating the plurality of wind turbine generators to produce additional power output in order to increase a rate at which the battery is charged. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for estimating an aged capacity of a battery in an energy storage system (ESS) associated with a plurality of wind turbine generators, the apparatus comprising:
at least one processor configured to; determine an internal impedance and an electromotive force (EMF) of the battery, wherein the determined internal impedance and the determined EMF are derived from a measured voltage of the battery and a measured current into the battery at two different instances in time; determine an approximate age of the battery based on the internal impedance; determine a relationship between a maximum capacity corresponding to the battery and a number of charging cycles; determine the aged capacity of the battery based on the approximate age and the relationship; determine a state of charge (SOC) of the battery based on the determined EMF of the battery; after determining the aged capacity, measuring an available energy remaining in the battery based on the SOC and the aged capacity; and upon determining the available energy remaining in the battery is below a predetermined value, increase power output of the plurality of wind turbine generators by operating the plurality of wind turbine generators to produce additional power output in order to improve a rate at which the battery is charged. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A system comprising:
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one or more of wind turbine generators; at least one battery for storing energy produced by the wind turbine generators; and at least one processor configured to; determine an internal impedance and an electromotive force (EMF) of the battery, wherein the determined internal impedance and the determined EMF are derived from a measured voltage of the battery and a measured current into the battery at two different points in time, determine an approximate age of the battery based on the internal impedance, determine a relationship between a maximum capacity corresponding to the battery and a number of charging cycles, determine an aged capacity of the battery based on the approximate age and the relationship, determine a state of charge (SOC) of the battery based on the determined EMF of the battery, after determining the aged capacity, measuring an available energy remaining in the battery based on the SOC and the aged capacity, and upon determining the available energy remaining in the battery is below a predetermined value, increasing power output of the wind turbine generators by operating the wind turbine generators to produce additional power output in order to improve a rate at which the battery is charged. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification