Generator with DC boost and split bus bidirectional DC-to-DC converter for uninterruptible power supply system or for enhanced load pickup

• US 7,786,616 B2
• Filed: 02/07/2003
• Issued: 08/31/2010
• Est. Priority Date: 02/07/2003
• Status: Active Grant

• Current Assignee: Cummins Power Generation Limited (Cummins Incorporated)
• Original Assignee: Cummins Power Generation Limited (Cummins Incorporated)
• Inventors: Naden, Mark, Bax, Randall
• Primary Examiner(s): Paladini; Albert W
• Assistant Examiner(s): CAVALLARI, DANIEL J
• Application Number:
  US10/361,027
• Publication Number:
  US 20040155526A1
• Time in Patent Office: 2,762 Days
• Field of Search: 307/65, 307/66, 307/110, 307/46, 307/43, 307/64, 290/40.R, 290/52
• US Class Current: 307/64
• CPC Class Codes: H02J 3/28 Arrangements for balancing of the load in a network by storage of energy
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02J 9/08 requiring starting of a prime-mover

Abstract

A local power generation system generates DC voltage at an inverter input, modulated to generate an AC power signal to a load. The inverter input voltage may be obtained from an engine generator, providing a rectified AC power signal. An energy storage device helps maintain DC voltage at the inverter input when load power draw increases or during engine startup or acceleration, for example, until the engine accommodates increased power demand. The system may also be used in an uninterruptible power supply (UPS), in which the load draws power from a utility-provided AC power source until a fault condition appears. When the fault condition appears, the load switches its power draw from the utility-provided AC power source to the inverter output. The energy storage device is charged through a bidirectional DC-to-DC converter and through an inverter operating in rectifier mode to rectify a utility-provided AC power signal.

Claims

1. A system for providing uninterruptible, continuous and uniform AC electrical power to a load device, the system including:

a generator coupled to a combined energy storage device;

a rechargeable energy storage device coupled to the combined energy storage device;

an AC controller device including an AC controller input adapted to be coupled to a utility-provided AC power source and an AC controller output adapted to be coupled to the load device for providing power from the utility-provided AC power source to the load device and adapted to be coupled to the combined energy storage device for providing power from the utility-provided AC power source to the combined energy storage device for charging the rechargeable energy storage device;

a converter device coupled at a first end to the combined energy storage device, and adapted to be coupled at a second end to the AC controller circuit and the load device, wherein the converter device operates in an inverter mode and converts DC power provided by the combined energy source to AC power to be delivered to the load device when the utility-provided AC power source is not capable of providing adequate power to the load device, and when the utility-provided AC power source is capable of providing adequate power to the load device, the converter device operates in a rectifier mode and converts AC power from the utility-provided AC power source to DC power to be delivered to the combined energy storage device to charge the rechargeable energy storage device, and

wherein when the utility-provided AC power source is not capable of providing adequate AC power to the load device, the combined energy source provides DC power that is converted into uninterruptible, continuous and uniform AC power to the load device, the combined energy storage device receiving the DC power from the rechargeable energy storage device, and power from the generator working in tandem.

2. The system of claim 1, wherein when the utility-provided AC power source is not capable of providing adequate power to the load device and during start-up of the generator, the combined energy storage device receives DC power, to be converted into AC power and delivered to the load device, from the rechargeable energy storage device, and

wherein when the utility-provided AC power source is not capable of providing adequate power to the load device and after start-up of the generator, the combined energy storage device receives DC power, to be converted into AC power and delivered to the load device, from the generator.

3. The system of claim 2, wherein when the utility-provided AC power source is not capable of providing adequate power to the load device and after start-up of the generator, the combined energy storage device further receives DC power, to be converted to AC power and delivered to the load device, from the rechargeable energy storage device when power drawn by the load device increases faster than the generator can generate the necessary AC power required to accommodate the increase in AC power needed by the load device.

4. The system of claim 1, further comprising a bidirectional DC-to-DC converter coupled at a first terminal to the rechargeable energy storage device and at a second terminal to the combined energy storage device,

wherein the bidirectional DC-to-DC converter includes a boost mode to step-up DC voltage provided by the rechargeable energy storage device to the combined energy storage device when the utility-provided AC power source does not provide adequate power to the load device, and

a charge mode to step-down DC voltage provided by the combined energy storage device to charge the rechargeable energy storage device, the combined energy storage device receiving AC power from the utility-provided AC power source when the utility-provided AC power source provides adequate power to the load device.

5. The system of claim 1, further comprising a rectifier coupled between the generator and the inverter input, the rectifier configured to convert AC power provided by the generator to DC power provided to the combined energy storage device.

6. A method for providing uninterruptible, continuous and uniform AC electrical power to a load device, the method comprising:

delivering power through an AC controller device from a utility-provided AC power source to the load device if the utility-provided AC power source is capable of providing adequate power to the load device;

charging a rechargeable energy storage device via a combined energy storage device that receives DC power through the AC controller device from a utility-provided AC power source;

converting DC power providing by the combined energy source to AC power that is to be delivered to the load device when the utility-provided AC power source is not capable of providing adequate power to the load device, via a converter device, coupled at a first end to the combined energy storage device and is adapted to be coupled at a second end to an AC controller circuit and the load device, operating in an inverter mode;

converting AC power from the utility-provided AC power source to DC power that is to be delivered to the combined energy storage device to charge the rechargeable energy storage device when the utility-provided AC power source is capable of providing adequate power to the load device, via the converter device operating in a rectifier mode; and

providing uninterruptible, continuous and uniform AC power to the load device via the combined energy storage device when the utility provided AC power source is not capable of providing adequate power to the load device, the combined energy storage device receiving DC power from the rechargeable energy-storage device, and power from a generator working in tandem.

7. The system of claim 6, wherein when the AC controller device determines that the utility-provided AC power source is not capable of providing adequate power to the load device and during start-up of the generator, the combined energy storage device receives DC power, to be converted into AC power and delivered to the load device, from the rechargeable energy storage device.

8. The system of claim 6, wherein when the AC controller device determines that the utility-provided AC power source is not capable of providing adequate power to the load device and after start-up of the generator, the combined energy storage device receives DC power, to be converted into AC power and delivered to the load device, from the generator.

9. The system of claim 8, wherein when the AC controller device determines that the utility-provided AC power source is not capable of providing adequate power to the load device and after start-up of the generator, the combined energy storage device further receives DC power, to be converted to AC power and delivered to the load device, from the rechargeable energy storage device when power drawn by the load device increases faster than the generator can generate the necessary AC power required to accommodate the increase in AC power needed by the load device.