AC/DC hybrid power system

• US 7,145,265 B2
• Filed: 11/06/2003
• Issued: 12/05/2006
• Est. Priority Date: 11/08/2002
• Status: Expired due to Fees

• Current Assignee: WorldWater & Solar Technologies Inc.
• Original Assignee: WorldWater & Power Corp. (Entech Solar, Inc.)
• Inventors: Rangarajan, Anand, Mc Nulty, Thomas C
• Primary Examiner(s): Deberadinis, Robert L.
• Assistant Examiner(s): Kaplan, Hal I.
• Application Number:
  US10/704,241
• Publication Number:
  US 20040095091A1
• Time in Patent Office: 1,125 Days
• Field of Search: 307/44
• US Class Current: 307/44
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: Y02B 10/70 Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies

Abstract

A hybrid power system has two voltage sources, a variable DC power source, and a second power source, connected through selection components to a common node. The variable DC power source may be a solar power source and the second source may be an AC grid. The selection components, e.g. blocking diodes, SCRs, or relays, allow one or both of the sources to be connected to the node depending on the voltages produced by the sources. A variable speed drive and load may be connected to the node.

Claims

1. A hybrid power system for providing power to a load, comprising:

a solar DC power source;

a rectified AC power source; and

first and second selection components connected respectively to the outputs of the solar DC power source and rectified AC power source and having their outputs connected to a common node;

wherein, the first and second selection components select either or both power sources to apply power to the common node depending on the magnitude of the voltage from each source;

wherein a minimum solar voltage level is chosen such that below that level solar power is not sufficient to drive the load; and

wherein the peak rectified AC voltage is selected and controlled to be equal to or slightly greater than the selected minimum solar voltage;

so that when the solar voltage is equal to or greater than the selected minimum, the load is driven by the solar DC power source, and when the solar voltage is less than the selected minimum, the load is driven by the rectified AC power source.

2. The system if claim 1 wherein the solar DC power source is a photovoltaic panel.

3. The system of claim 1 wherein the rectified AC power source is obtained from an AC power grid.

4. The system of claim 1 wherein the rectified AC power source is a 3-phase AC source having three windings and the second selection component has three elements, one connected to each winding.

5. The system of claim 1 wherein the first and second selection components are blocking diodes.

6. The system of claim 1 wherein the first and second selection components are silicon controlled rectifiers (SCRs).

7. The system of claim 1 wherein the first and second selection components are relays.

8. The system of claim 1 further comprising a variable speed drive having its input connected to the common node.

9. The system of claim 8 further comprising a load connected to the output of the variable speed drive.

10. The system of claim 9 wherein the load is a motor.

11. A hybrid power system for providing power to a load, comprising:

a solar DC power source;

a rectified AC power source; and

first and second blocking diodes connected respectively to the outputs of the solar DC power source and rectified AC power source and having their outputs connected to a common node;

wherein the first and second blocking diodes pass one power source and block the other power source to apply power to the common node depending on the magnitude of the voltage from each source;

wherein a minimum solar voltage level is chosen such that below that level solar power is not sufficient to drive the load; and

wherein the peak rectified AC voltage is selected and controlled to be equal to or slightly greater than the selected minimum solar voltage;

so that when the solar voltage is equal to or greater than the selected minimum, the first and second blocking diodes pass the solar DC power source and block the rectified AC power source and the load is driven by the solar DC power source, and when the solar voltage is less than the selected minimum, the first and second blocking diodes block the solar DC power source and pass the rectified AC power source and the load is driven by the rectified AC power source.

12. The system if claim 11 wherein the solar DC power source is a photovoltaic panel and the rectified AC power source is obtained from an AC power grid.

13. The system of claim 11 wherein the rectified AC power source is a 3-phase AC source having three windings and the second blocking diodes comprise three diodes, one connected to each winding.

14. The system of claim 11 further comprising a variable speed drive having its input connected to the common node.

15. The system of claim 14 further comprising a load connected to the output of the variable speed drive.

16. The system of claim 15 wherein the load is a motor.