Control of Energy Storage System Inverter System in a Microgrid Application
First Claim
1. A system for managing power transfer with a power grid comprising:
- a direct current (DC) link;
an energy storage system (ESS) that stores DC power;
an energy storage controller coupled between the DC link and the ESS that manages power flow between the ESS and the DC link; and
a load controller coupled between the DC link and the power grid, the load controller including a DC-to-AC inverter, the load controller operable to adjust an output frequency of the DC-to-AC inverter using a non-linear power-frequency curve responsive to both a state of a frequency of the power grid and a power transfer state of the load controller.
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Accused Products
Abstract
A system that manages a supplemental energy source connected to a power grid uses a two stage control strategy to manage power transfers in and out of the power grid as well as in and out of an energy storage system, such as a battery bank. One stage uses a non-linear transfer function to control an output frequency of a DC-to-AC inverter to limit undesired effects of power transients that occur on the grid. A second stage uses control strategy for transferring energy between the energy storage system and an internal DC link based on a relationship between a voltage on a DC link connecting the first and second stages and a DC link reference voltage, the voltage on the DC link, and a voltage at the energy storage system. The control strategy includes rapid charging, over-charging protection, and grid transient stabilization.
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Citations
20 Claims
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1. A system for managing power transfer with a power grid comprising:
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a direct current (DC) link; an energy storage system (ESS) that stores DC power; an energy storage controller coupled between the DC link and the ESS that manages power flow between the ESS and the DC link; and a load controller coupled between the DC link and the power grid, the load controller including a DC-to-AC inverter, the load controller operable to adjust an output frequency of the DC-to-AC inverter using a non-linear power-frequency curve responsive to both a state of a frequency of the power grid and a power transfer state of the load controller. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of managing power transfer to a power grid using a bidirectional DC-to-AC inverter coupled between the power grid and an energy storage system (ESS), the method comprising:
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sensing a frequency of power on the power grid; determining a power flow at the bidirectional DC-to-AC inverter; selecting a non-linear power-frequency curve; setting an output frequency of the bidirectional DC-to-AC inverter using the non-linear power-frequency curve and a current power flow through the bidirectional DC-to-AC inverter. - View Dependent Claims (10, 11, 12)
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13. A system for managing power transfer between an energy storage system component and a power grid, the system comprising:
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a direct current (DC) link operatively coupled to the power grid; a DC energy storage system (ESS); a DC-to-DC converter coupled between the DC link and the ESS, the DC-to-DC converter adapted for bi-directional current flow; and a controller coupled to the dc-to-dc converter that operates the DC-to-DC converter to control current magnitude and direction based on a relationship between a voltage on the DC link and a DC link reference voltage, the voltage on the DC link, and a voltage at the ESS to provide a plurality of charging and discharging modes. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification