ENERGY STORAGE SYSTEM AND METHOD FOR DIRECT COUPLING ENERGY STORAGE AND POWER SOURCE

• US 20190319473A1
• Filed: 04/23/2018
• Published: 10/17/2019
• Est. Priority Date: 04/16/2018
• Status: Active Grant

• Current Assignee: Dynapower Company LLC (Sensata Technologies Holding Plc)
• Original Assignee: Dynapower Company LLC (Sensata Technologies Holding Plc)
• Inventors: SOMANI, Apurva, XIA, Xiaorong, CASTELINO, Gysler
• Granted Patent: US 10,581,266 B2
• Time in Patent Office: Days
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/40 Synchronising a generator for connection to a network or to another generator
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

An energy storage system for direct DC coupling includes a power source electrically connected to a first node, a power converter coupled to the first node, an energy storage unit coupled to the first node through direct DC coupling, and a control system. The power converter controls the output voltage of the power source under the control of the control system. The energy storage unit draws energy from the power source or the bus when charging and supplies energy to the bus when discharging. A main switch is coupled between the first node and the energy storage unit. The control system is configure to control the power converter to adjust the output voltage to the energy storage unit voltage, control the main switch to electrically connect the energy storage unit to the first node, and control the main switch to electrically disconnect the energy storage unit from the first node.

Claims

1. An energy storage system for direct DC coupling, the energy storage system comprising:

a power source electrically connected to a first node;

a power converter coupled to the first node, the power converter controlling the output voltage of the power source, the power converter having a first port coupled to the first node and a second port coupled to a bus;

an energy storage unit coupled to the first node through direct DC coupling, wherein the energy storage unit draws energy from the power source or the bus when charging and supplies energy to the bus when discharging;

a main switch for electrically connecting and electrically disconnecting the energy storage unit from the first node, the main switch being coupled between the first node and the energy storage unit;

a control system for controlling the electrical connection and electrical disconnection of the energy storage unit from the first node, the control system being configured to;

control the power converter to adjust the magnitude of the output voltage at the first node to a magnitude of an energy storage unit voltage;

control the main switch to electrically connect the energy storage unit to the first node; and

control the main switch to electrically disconnect the energy storage unit from the first node.

2. The energy storage system of claim 1, further comprising a break path coupled to the first node and for diverting power away from the first node when the break bath is electrically connected to the first node.

3. The energy storage system of claim 2, wherein the control system being configured to control the power converter to adjust the magnitude of the output voltage to a magnitude of the energy storage unit voltage and control the main switch to electrically connect the energy storage unit to the first node includes the control system being configured to:

electrically connect the break path to the first node;

control the power converter to adjust the magnitude of the output voltage at the first node to the magnitude of the energy storage unit voltage;

once the magnitude of the output voltage at the first node is adjusted to the magnitude of the energy storage unit voltage, electrically connect the energy storage unit to the first node and electrically disconnect the break path from the first node.

4. The energy storage system of claim 2, wherein the control system being configured to electrically disconnect the energy storage unit from the first node includes the control system being configured to:

when the energy storage unit is discharging;

control the power converter to reduce a discharge power of the energy storage unit;

control the main switch to open to electrically disconnect the energy storage unit from the first node; and

control the power converter to operate in maximum power point tracking (MPPT) mode;

when the energy storage unit is charging;

control the power converter to reduce a charge power of the energy storage unit;

control the main switch to open to electrically disconnect the energy storage unit from the first node; and

control the power converter to operate in maximum power point tracking (MPPT) mode.

5. The energy storage system of claim 4, wherein the control system being configured to electrically disconnect the energy storage unit from the first node further includes the control system being configured to:

when the energy storage unit is charging;

electrically connect the break path to the first node prior to opening the main switch; and

electrically disconnect the break path after opening the main switch.

6. The energy storage system of claim 2, wherein the break path is formed between the first node and across the energy source.

7. The energy storage system of claim 6, wherein the break path comprises a break switch and a break resistor connected in series between the first node and across the energy source.

8. The energy storage system of claim 7, wherein the control system being configured to control the power converter to adjust the magnitude of the output voltage to a magnitude of the energy storage unit voltage and control the main switch to electrically connect the energy storage unit to the first node includes the control system being configured to:

control the break switch to electrically connect the break path to the first node;

control the power converter to adjust the magnitude of the output voltage at the first node to the magnitude of the energy storage unit voltage; and

once the magnitude of the output voltage at the first node is adjusted to the magnitude of the energy storage unit voltage, control the main switch to electrically connect the energy storage unit to the first node and open the break switch to electrically disconnect the break path from the first node.

9. The energy storage system of claim 2, wherein the break path is formed between the first node and a second node, the second node being an electrical connection point between the main switch and the energy storage unit.

10. The energy storage system of claim 9, wherein the break path comprises a break resistor and a break switch connected in series between the first node and the second node.

11. The energy storage system of claim 10, wherein the control system being configured to control the power converter to adjust the magnitude of the output voltage to a magnitude of the energy storage unit voltage and control the main switch to electrically connect the energy storage unit to the first node includes the control system being configured to:

control the break switch to electrically connect the break path to the first node; and

control the main switch to electrically connect the energy storage unit to the first node and open the break switch to electrically disconnect the break path from the first node.

12. The energy storage system of claim 1, wherein the main switch comprises a first main switch and a second main switch connected in series between the first node and the energy storage unit, wherein:

the first main switch is a power electronics switch that when turned off prevents power from flowing from the first node to the energy storage unit and when turned on allows power to flow; and

the second main switch is a power electronics switch that when turned off prevents power from flowing from the energy storage unit to the first node and when turned on allows power to flow.

13. The energy storage system of claim 7, wherein the main switch comprises a first main switch and a second main switch connected in series between the first node and the energy storage unit, wherein:

the first main switch is a power electronics switch that when turned off prevents power from flowing from the first node to the energy storage unit and when turned on allows power to flow; and

the second main switch is a power electronics switch that when turned off prevents power from flowing from the energy storage unit to the first node and when turned on allows power to flow,

wherein the control system being configured to control the power converter to adjust the magnitude of the output voltage to a magnitude of the energy storage unit voltage and control the main switch to electrically connect the energy storage unit to the first node includes the control system being configured to;

control the break switch to electrically connect the break path to the first node;

control the power converter to adjust the magnitude of the output voltage at the first node to the magnitude of the energy storage unit voltage;

control the first main switch to turn on such that power can flow into the energy storage unit but not from the energy storage unit;

control the break switch to electrically disconnect the break path from the first node; and

control the second main switch to turn on such that power can flow bi-directionally.

14. The energy storage system of claim 10, wherein the main switch comprises a first main switch and a second main switch connected in series between the first node and the second node, wherein:

the first main switch is a power electronics switch that when turned off prevents power from flowing from the first node to the energy storage unit and when turned on allows power to flow; and

the second main switch is a power electronics switch that when turned off prevents power from flowing from the energy storage unit to the first node and when turned on allows power to flow,

wherein the control system being configured to control the power converter to adjust the magnitude of the output voltage to a magnitude of the energy storage unit voltage and control the main switch to electrically connect the energy storage unit to the first node includes the control system being configured to;

control the break switch to electrically connect the break path to the first node;

control the first main switch and the second main switch to turn on such that power can flow bi-directionally;

control the break switch to electrically disconnect the break path from the first node.

15. The energy storage system of claim 7, wherein the main switch comprises a first main switch and a second main switch connected in series between the first node and the energy storage unit, wherein:

the first main switch is a power electronics switch that when turned off prevents power from flowing from the first node to the energy storage unit and when turned on allows power to flow in both directions; and

the second main switch is a power electronics switch that when turned off prevents power from flowing from the energy storage unit to the first node and when turned on allows power to flow in both directions,

wherein the control system being configured to electrically disconnect the energy storage unit from the first node includes the control system being configured to;

when the energy storage unit is discharging;

control the power converter to reduce the discharge power from the energy storage unit;

control the first main switch to open;

control the second main switch to open such that the energy storage unit is electrically disconnected from the first node;

when the energy storage unit is charging;

control the power converter to reduce a charge power of the energy storage unit,

control the second main switch to open such that power cannot flow from the energy storage unit to the first node;

control the break switch to electrically connect the break path to the first node;

control the first main switch to open such that the energy storage unit is electrically disconnected from the first node and control the break switch to electrically disconnect the break path from the first node; and

control the power converter to operate in MPPT mode.

16. The energy storage system of claim 10, wherein the main switch comprises a first main switch and a second main switch connected in series between the first node and the energy storage unit, wherein:

the first main switch is a power electronics switch that when turned off prevents power from flowing from the first node to the energy storage unit and when turned on allows power to flow; and

the second main switch is a power electronics switch that when turned off prevents power from flowing from the energy storage unit to the first node and when turned on allows power to flow,

wherein the control system being configured to electrically disconnect the energy storage unit from the first node includes the control system being configured to;

when the energy storage unit discharging;

control the power converter so as to reduce the discharge power from the energy storage unit;

control the first main switch to open; and

control the second main switch to open such that the energy storage unit is electrically disconnected from the first node;

when the energy storage unit is charging;

control the power converter to reduce a charge power of the energy storage unit;

control the second main switch to open such that power cannot flow from the energy storage unit to the first node;

control the first main switch to open such that the energy storage unit is electrically disconnected from the first node; and

control the power converter to operate in MPPT mode.

17. The energy storage system of any one of claims 1, wherein the energy storage unit is a battery.

18. The energy storage system of any one of claims 1, wherein the power source is a photovoltaic (PV) array.

19. A method of electrically connecting an energy storage unit to a power source in an energy storage system comprising the energy storage unit direct DC coupled to the power source at a first node through a main switch and a power converter electrically connected to the first node and capable of adjusting a magnitude of a voltage at the first node, the method comprising:

attempting to adjust the magnitude of the voltage at the first node to a magnitude of an energy storage unit voltage; and

closing the main switch to electrically connect the energy storage unit to the first node.

20. The method of claim 19, wherein attempting to adjust the magnitude of the voltage at the first node to a magnitude of an energy storage unit voltage and closing the main switch to electrically connect the energy storage unit to the first node comprises:

determining whether adjusting the magnitude of the voltage at the first node to the magnitude of the energy storage unit voltage will cause power to exceed the power converter'"'"'s limits; and

when adjusting the magnitude of the voltage at the first node to the magnitude of the energy storage unit voltage will not cause power to exceed the power converter'"'"'s limits;

closing the main switch to electrically connect the energy storage unit to the first node once the magnitude of the voltage at the first node matches the magnitude of the energy storage unit voltage.

21. The method of claim 20, wherein attempting to adjust the magnitude of the voltage at the first node to a magnitude of an energy storage unit voltage and closing the main switch to electrically connect the energy storage unit to the first node further comprises:

when adjusting the magnitude of the voltage at the first node to the magnitude of the energy storage unit voltage will cause power to exceed the power converter'"'"'s limits;

electrically connecting a break path to the first node for diverting power away from the first node;

adjusting the magnitude of the voltage at the first node to match the magnitude of the energy storage unit voltage; and

once the magnitude of the voltage at the first node is adjusted to match the magnitude of the energy storage unit voltage, electrically connecting the energy storage unit to the first node and electrically disconnecting the break path from the first node.

22. The method of claim 20, wherein attempting to adjust the magnitude of the voltage at the first node to a magnitude of an energy storage unit voltage and closing the main switch to electrically connect the energy storage unit to the first node further comprises:

electrically connecting a pre-charge break path comprising a pre-charge switch and a pre-charge resistor connected in series between the first node and a second node, the second node being an electrical connection point between the main switch and the energy storage unit;

closing the main switch to directly electrically connect the energy storage unit to the first node; and

opening the break switch to electrically disconnect the pre-charge break path.

23. The method of claim 20, wherein the main switch comprises a first main switch and a second main switch, and attempting to adjust the magnitude of the voltage at the first node to a magnitude of an energy storage unit voltage and closing the main switch to electrically connect the energy storage unit to the first node further comprises:

when adjusting the magnitude of the voltage at the first node to the magnitude of the energy storage unit voltage will cause power to exceed the power converter'"'"'s limits;

electrically connecting a break path to the first node for diverting power away from the first node;

adjusting the magnitude of the voltage at the first node to the magnitude of the energy storage unit voltage;

turning on the first main switch such that power can flow into the energy storage unit but not from the energy storage unit;

electrically disconnecting the break path from the first node; and

turning on the second main switch such that power can flow bi-directionally.

24. A method of electrically disconnecting an energy storage unit from a power source in an energy storage system comprising the energy storage unit direct DC coupled to the power source at a first node through a main switch and a power converter electrically connected to the first node and capable of adjusting a magnitude of a voltage at the first node, the method comprising:

when the energy storage unit is discharging;

controlling the power converter to reduce a discharge power of the energy storage unit;

opening the main switch to electrically disconnect the energy storage unit from the first node; and

controlling the power converter to operate in maximum power point tracking (MPPT) mode;

when the energy storage unit is charging;

controlling the power converter to reduce a charge power of the energy storage unit;

opening the main switch to electrically disconnect the energy storage unit from the first node; and

controlling the power converter to operate in maximum power point tracking (MPPT) mode.

25. The method of claim 24, further comprising:

when the energy storage unit is charging;

electrically connecting a break path to the first node prior to opening the main switch to divert power away from the first node; and

electrically disconnecting the break path after opening the main switch.

26. The method of claim 25, wherein the main switch comprises a first main switch and a second main switch, and opening the main switch to electrically disconnect the energy storage unit from the first node comprises:

prior to electrically connecting the break path, opening the second main switch such that power cannot flow from the energy storage unit to the first node; and

after closing the break switch, opening the second main switch to electrically disconnect the energy storage unit from the first node.

27. A power converter for coupling with a power source and at a first node and for controlling electrical connection and disconnection of an energy storage unit that is direct DC coupled to the first node, the power converter comprising:

a power inverter for converting DC to AC, the power converter having a DC input port coupled to the first node and an AC output port coupled to a bus;

a control system for controlling the electrical connection and electrical disconnection of the energy storage unit from the first node, the control system being configured to;

control the power inverter to adjust the magnitude of the output voltage at the first node to a magnitude of the energy storage unit voltage;

control the electrical connection and the electrical disconnection of the energy storage unit with the first node.

28. The power converter of claim 27, wherein the control system being configured to control the power inverter to adjust the magnitude of the output voltage to a magnitude of the energy storage unit voltage and control the electrical connection of the energy storage unit to the first node includes the control system being configured to:

electrically connect a break path to the first node for diverting power away from the first node;

control the power inverter to adjust the magnitude of the output voltage at the first node to the magnitude of the energy storage unit voltage;

once the magnitude of the output voltage at the first node is adjusted to the magnitude of the energy storage unit voltage, electrically connect the energy storage unit to the first node and electrically disconnect the break path from the first node.

29. The power converter of claim 27, wherein the control system being configured to electrically disconnect the energy storage unit from the first node includes the control system being configured to:

when the energy storage unit is discharging;

control the power inverter to reduce a discharge power of the energy storage unit;

electrically disconnect the energy storage unit from the first node; and

control the power inverter to operate in maximum power point tracking (MPPT) mode;

when the energy storage unit is charging;

control the power inverter to reduce a charge power of the energy storage unit;

electrically disconnect the energy storage unit from the first node; and

control the power inverter to operate in maximum power point tracking (MPPT) mode.

30. The power converter of claim 29, wherein the control system being configured to electrically disconnect the energy storage unit from the first node further includes the control system being configured to:

when the energy storage unit is charging;

electrically connect a break path to the first node prior to electrically disconnecting the energy storage unit to divert power away from the first node;

electrically disconnect the energy storage unit; and

electrically disconnect the break path.