Peak electrical power conversion system

• US 5,659,465 A
• Filed: 09/23/1994
• Issued: 08/19/1997
• Est. Priority Date: 09/23/1994
• Status: Expired due to Fees

• Current Assignee: Golden Genesis Company
• Original Assignee: Aerovironment
• Inventors: Flack, Albert J., Vail, Michael D.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): BERHANE, ADOLF D
• Application Number:
  US08/311,740
• Time in Patent Office: 1,061 Days
• Field of Search: 363/71, 363/78, 363/79, 363/123, 320/2, 323/906, 323/299, 136/291, 136/293, 307/38, 307/45, 307/66, 307/82
• US Class Current: 363/71
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/388 Islanding, i.e. disconnection of local power supply from the network
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 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
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

An electrical power conversion system that supplies the maximum available output power from a power source such as a solar array to a plurality of loads such as rechargeable batteries. The output power of the solar array peaks at an optimum current that is less than is maximum available output current. The system includes a controller and a plurality of dc-to-dc converters that charge the batteries. The controller monitors the solar array'"'"'s output power and adjusts the battery charging by generating a current control signal that tracks a peak of the solar array'"'"'s available output power and sets a current limit such that the combined current draw of the plurality of dc-to-dc converters is substantially equal to the solar array'"'"'s optimum current at which it provides its maximum available power. The electrical power and control signals are transmitted from the power source and controller to the power converters on three bus bars, including a power bus, a control bus, and a common bus. The current control signal and the voltage control signal are multiplexed onto the single control bus. The controller and the dc-to-dc converters are mounted on planar printed circuit boards having clips arranged in a triangular pattern that allow the dc-to-dc converters to be easily attached to and removed from the buses.

Claims

1. An electrical power conversion system for delivering the maximum available output power to a plurality of electrical power loads from a power source that has an output power that varies with changes in the output current of the power source such that the output power from the power source peaks at an optimum current that is less than the maximum available output current of the power source, comprising:

a voltage sensor that generates an output voltage signal based on the output voltage of the power source;

a current sensor that generates an output current signal based on the output current of the power source;

a controller that calculates the output power of the power source based on the output voltage signal and the output current signal and generates a current control signal associated with the calculated output power; and

a plurality of electrical power converters associated with the plurality of power loads, each power converter receiving the current control signal and drawing current from the power source in accordance with a predetermined current limit set by the current control signal;

wherein the controller tracks a peak in the available output power of the power source and sets the predetermined current limit of the current control signal such that the combined current draw of the plurality of power converters is substantially equal to the optimum current, thereby allowing the power converters, in combination, to consume the maximum available power from the power source.

2. An electrical power conversion system as defined in claim 1, further comprising:

a temperature sensor that generates a temperature signal based on the temperature of the plurality of electrical power loads;

wherein the controller generates a voltage control signal based on the temperature signal; and

wherein the plurality of converters set a load voltage for the converters'"'"' respective power loads based on the voltage control signal.

3. An electrical power conversion system as defined in claim 2, wherein the controller combines the voltage control signal and the current control signal to form a bi-phase pulse control signal, and wherein the load voltage is represented by the amplitude of a first polarity of the bi-phase pulse control signal and the predetermined current limit is represented by the amplitude of a second signal polarity of the bi-phase pulse control signal.

4. An electrical power conversion system as defined in claim 1, wherein the plurality of power converters are dc-to-dc converters.

5. An electrical power conversion system as defined in claim 1, wherein the predetermined limit of the current control signal represents a current threshold and wherein each of the plurality of power converters reduces its current draw from the power source if the current draw of the respective power converter is greater than the current threshold.

6. An electrical power conversion system as defined in claim 1, further comprising:

a power bus that transmits the output power from the power source to the plurality of power converters;

a control bus that transmits the current control signal from the controller to the plurality of power converters; and

a common bus that provides a return for the power bus and the control bus;

wherein the power bus, control bus, and common bus are spaced apart from each other such that they are parallel and coplanar.

7. An electrical power conversion system as defined in claim 6, wherein the controller includes a planar circuit board having first, second, and third clips on one side that are spaced apart in a triangular configuration to be engageable with the power bus, the control bus, and the common bus.

8. An electrical power conversion system as defined in claim 6, wherein each of the plurality of power converters includes a planar circuit board having first, second, and third clips on one side that are spaced apart in a triangular configuration to be engageable with the power bus, the control bus, and the common bus.

9. An electrical power conversion system as defined in claim 1, wherein:

the controller is configured to periodically increment or decrement the current control signal, each time calculating the resulting output power of the power source and determining if the output power increased or decreased from the output power calculated immediately previously;

the controller increments the current control signal if it immediately previously incremented the current control signal and the resulting output power was determined to increase or if it immediately previously decremented the current control signal and the resulting output power was determined to decrease; and

the controller decrements the current control signal if it immediately previously decremented the current control signal and the resulting output power was determined to increase or if it immediately previously incremented the current control signal and the resulting output power was determined to decrease.

10. An electrical power delivery system for delivering electrical power and a control signal from a power source to a plurality of power loads comprising:

a power bus that transmits electrical power from the power source to the plurality of power loads;

a control bus that transmits a control signal from the power source to the plurality of power loads;

a common bus that provides a return for the power bus and the control bus;

wherein the power bus, control bus, and common bus are spaced apart from each other such that they are parallel and coplanar with each other; and

a plurality of planar circuit boards, each circuit board associated with a separate one of the plurality of power loads, and each having first, second, and third clips on one side that are spaced apart in a triangular configuration and engageable with the power bus, the control bus, and the common bus.

16. A method of delivering the maximum available power as defined in claim 10, wherein tracking includes:

periodically incrementing or decrementing the current control signal, each time calculating the resulting output power of the power source and determining if the output power increased or decreased from the output power calculated immediately previously;

the current control signal is incremented if it immediately previously had been incremented and the resulting output power was determined to increase or if it immediately previously had been decremented and the resulting output power was determined to decrease; and

1. The current control signal is decremented if it immediately previously had been decremented and the resulting output power was determined to increase or if it immediately previously had been incremented and the resulting output power was determined to decrease.

11. A method of delivering the maximum available output power to a plurality of electrical power loads from a power source that has an output power that varies with changes in the output current of the power source such that the output power from the power source peaks at an optimum current that is less than the maximum available output current of the power source, comprising:

generating an output voltage signal based on the output voltage of the power source;

generating an output current signal based on the output current of the power source;

providing a plurality of electrical power converters associated with the plurality of power loads, each power converter drawing current from the power source in accordance with a current control signal; and

tracking a peak in the available output power of the power source by calculating the output power of the power source based on the output voltage signal and the output current signal and setting the current control signal such that the combined current draw of the plurality of power converters is substantially equal to the optimum current, thereby allowing the power converters, in combination, to consume the maximum available power from the power source.

12. A method of delivering the maximum available output power as defined in claim 11, further comprising:

generating a temperature signal based on the temperature of the plurality of electrical power loads;

generating a voltage control signal based on the temperature signal; and

causing the plurality of power converters to set a load voltage for the converters'"'"' respective power loads based on the voltage control signal.

13. A method of delivering the maximum available output power as defined in claim 12, further comprising:

combining the voltage control signal and the current control signal to form a bi-phase pulse control signal, wherein the load voltage is represented by the amplitude of a first polarity of the bi-phase pulse control signal and the predetermined current that is represented by the amplitude of a second polarity of the bi-phase pulse control signal.

14. A method of delivering the maximum available output power as defined in claim 11, wherein the plurality of power converters are dc-to-dc converters.

15. A method of delivering the maximum available output power as defined in claim 11, wherein the predetermined limit of the current control signal represents a current threshold and wherein each of the plurality of power converters reduces its current draw from the power source if the current draw of the respective power converter is greater than the current threshold.

17. An electrical power system for delivering electrical energy to a plurality of electrical power loads, comprising:

a solar electrical power source that has an electrical output power that varies with changes in the output current of the power source such that the output power from the power source peaks at an optimum current that is less than the maximum available output current of the power source;

a voltage sensor that generates an output voltage signal based on the output voltage of the power source;

a current sensor that generates an output current signal based on the output current of the power source;

a controller that calculates the output power of the power source based on the output voltage signal and the output current signal and generates a current control signal associated with the calculated output power; and

a plurality of electrical power converters associated with the plurality of power loads, each power converter receiving the current control signal and drawing current from the power source in accordance with a predetermined current limit set by the current control signal;

wherein the controller tracks a peak in the available output power of the power source and sets the predetermined current limit of the current control signal such that the combined current draw of the plurality of power converters is substantially equal to the optimum current, thereby allowing the power converters, in combination, to consume the maximum available power from the power source.

18. A method of delivering electrical energy to a plurality of electrical power loads, comprising:

providing a solar electrical power source that has an electrical output power that varies with changes in the output current of the power source such that the output power from the power source peaks at an optimum current that is less than the maximum available output current of the power source;

generating an output voltage signal based on the output voltage of the power source;

generating an output current signal based on the output current of the power source;

providing a plurality of electrical power converters associated with the plurality of power loads, each power converter drawing current from the power source in accordance with a current control signal; and

tracking a peak in the available output power of the power source by calculating the output power of the power source based on the output voltage signal and the output current signal and setting the current control signal such that the combined current draw of the plurality of power converters is substantially equal to the optimum current, thereby allowing the power converters, in combination, to consume the maximum available power from the power source.