ENERGY STORAGE SYSTEM FOR PHOTOVOLTAIC ENERGY AND METHOD OF STORING PHOTOVOLTAIC ENERGY

• US 20180331543A1
• Filed: 05/14/2018
• Published: 11/15/2018
• Est. Priority Date: 05/15/2017
• Status: Abandoned Application

• Current Assignee: Dynapower Company LLC (Sensata Technologies Holding Plc)
• Original Assignee: Dynapower Company LLC (Sensata Technologies Holding Plc)
• Inventors: PALOMBINI, John C., SOMANI, Apurva
• Application Number:
  US15/978,585
• Publication Number:
  US 20180331543A1
• Time in Patent Office: Days
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 3/381 Dispersed generators
• 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: H02M 3/33584 Bidirectional converters
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02P 80/20 using renewable energy
• CPC Class Codes: Y02P 90/50 Energy storage in industry with an added climate change mitigation effect

Abstract

An energy system for renewable energy applications includes a renewable energy source, a bidirectional inverter connected an AC bus and a DC bus, an energy storage unit connected to the bidirectional DC/DC converter, and a control system comprising one or more controllers coupled to the bidirectional inverter and the bidirectional DC/DC converter. The bidirectional inverter is connected to the renewable energy source and a bidirectional DC/DC converter through the DC bus. The system is configured to capture low power of a photovoltaic (PV) array, energy typically lost to inverter clipping, and through the utilization of ramp rate control.

Claims

1. A power system for capturing low voltage energy from a power source, the power system comprising:

the power source coupled to a DC bus;

a DC/DC power converter coupled to the DC bus and an energy storage device;

a power inverter coupled to the DC bus and an AC bus; and

a control system, the control system comprising one or more controllers configured to;

monitor a voltage produced by the power source;

determine whether the power source is producing a voltage greater than a first predetermined threshold;

determine whether the power source is producing a voltage less than a second threshold when it is determined that the power source is producing a voltage greater than the first predetermined threshold;

when it is determined that the power source is producing a voltage between the first threshold and the second threshold;

control the DC/DC power converter to operate in an MPPT mode and store energy generated by the power source in the energy storage device; and

control the power inverter not to operate in an MPPT mode; and

when it is determined that the power source is producing a voltage greater than or equal to the second threshold;

control the power inverter to operate in an MPPT mode and supply the energy generated by the power source to a power grid through the AC bus; and

control the DC/DC power converter not to operate in an MPPT mode.

2. The power system of claim 1, wherein the first predetermined threshold is equal to expected losses in the DC/DC power converter.

3. The power system of claim 1, wherein the power inverter has a wake up voltage being a voltage magnitude that a voltage at the DC bus must reach for the power inverter to be operational, and the second predetermined threshold is equal to the wake up voltage of the power inverter.

4. The power system of claim 1, wherein the voltage produced by the power source is monitored continuously, and the control system continuously controls the DC/DC power converter and the power inverter to transition between operating in an MPPT mode and not operating in an MPPT mode.

5. The power system of claim 1, wherein in determining whether the power source is producing a voltage less than the second predetermined threshold, the control system is further configured to monitor the voltage at the DC bus.

6. The power system of claim 5, further comprising a sensor sensing the voltage at the DC bus and transmitting the sensed voltage to the power system.

7. A power system for capturing clipped energy from a power source, the power system comprising:

the power source coupled to a DC bus;

a DC/DC power converter coupled to the DC bus and an energy storage device;

a power inverter coupled to the DC bus and an AC bus; and

a control system, the control system comprising one or more controllers configured to;

monitor an output power of the power inverter;

compare the output power of the power inverter to a predetermined threshold;

when the output power of the power inverter is greater than the predetermined threshold, control the DC/DC power converter to store output power of the power source that exceeds the predetermined threshold in the energy storage.

8. The power system of claim 7, wherein the predetermined threshold is a maximum power rating of the power inverter.

9. The power system of claim 7, wherein the output power of the power inverter is monitored continuously, and the control system continuously controls the DC/DC power converter and the power inverter to transition between storing and not storing output power of the power source in the energy storage.

10. A power system for selectively dispatching energy from a power source, the power system comprising:

the power source coupled to a DC bus;

a DC/DC power converter coupled to the DC bus and an energy storage device;

a power inverter coupled to the DC bus and an AC bus; and

a control system, the control system comprising one or more controllers configured to;

monitor parameters external to the power system; and

selectively control the DC/DC power converter to store power generated by the power source in the energy storage in accordance with the monitored parameters.

11. The power system of claim 10, wherein the parameters external to the power system comprise:

a PV energy pricing signal for energy supplied to a power grid through the AC bus; and

a curtailment signal for ceasing or reducing an amount of energy supplied to the power grid.

12. The power system of claim 11, wherein the DC/DC power converter stores power generated by the power source in the energy storage when a price in the PV energy pricing signal is below a predetermined threshold.

13. The power system of claim 12, wherein the DC/DC power converter supplies energy stored in the energy storage to the power grid through the power inverter when a price in the PV energy pricing signal is equal to or greater than the predetermined threshold.

14. The power system of claim 10, wherein the parameters external to the power system are monitored continuously, and the control system continuously controls the DC/DC power converter and the power inverter to transition between storing and not storing output power of the power source in the energy storage.

15. A power system for controlling a ramp rate, the power system comprising:

a power source coupled to a DC bus;

a DC/DC power converter coupled to the DC bus and an energy storage device;

a power inverter coupled to the DC bus and an AC bus; and

a control system, the control system comprising one or more controllers configured to;

monitor an output power of the power inverter and a rate of change of the output power of the power inverter;

compare the rate of change of the output power of the power inverter with a pre-defined ramp rate; and

control the DC/DC converter to charge or discharge the energy storage when the rate of change of the output power of the power inverter differs from the pre-defined ramp rate by more than a predetermined amount.

16. The power system of claim 15, wherein the output power of the power inverter and a rate of change of the output power of the power inverter is monitored continuously, and the control system continuously controls the DC/DC power converter to charge or discharge the energy storage until the rate of change of the output power of the power inverter no longer differs from the pre-defined ramp rate by more than the predetermined amount.

17. The power system of claim 15, wherein the DC/DC power converter supplies power to the energy storage when the rate of change of the output power of the power inverter is greater than the pre-defined ramp rate by more than the predetermined amount.

18. The power system of claim 15, wherein the DC/DC power converter discharges power from the energy storage to a power grid through the power inverter when the rate of change of the output power of the power inverter is less than the pre-defined ramp rate by more than the predetermined amount.