Systems and methods for dynamic AC line voltage regulation with energy saving tracking

• US 9,304,522 B2
• Filed: 04/19/2013
• Issued: 04/05/2016
• Est. Priority Date: 04/19/2012
• Status: Active Grant

• Current Assignee: Sentient Energy Technology LLC
• Original Assignee: Varentec Incorporated (KOCH Industries Incorporated)
• Inventors: Divan, Deepakraj M, Prasai, Anish
• Primary Examiner(s): Behm, Harry
• Application Number:
  US13/867,006
• Publication Number:
  US 20130278235A1
• Time in Patent Office: 1,082 Days
• Field of Search: 363/148, 363/149, 363/152, 363/153, 363/154, 363/159, 363/351, 363/253, 363/126, 363/370, 323/282
• US Class Current: 1/1
• CPC Class Codes: G05F 1/12 wherein the variable actually regulated by the final control device is ac G05F1/625 takes precedence
• CPC Class Codes: G05F 1/253 the transformers including plural windings in series between source and load G05F1/247 takes precedence
• CPC Class Codes: H02J 3/12 for adjusting voltage in ac networks by changing a characteristic of the network load
• CPC Class Codes: H02J 3/16 by adjustment of reactive power
• CPC Class Codes: H02J 3/18 Arrangements for adjusting, eliminating or compensating reactive power in networks for adjustment of voltage H02J3/16
• CPC Class Codes: H02M 5/12 for conversion of voltage or current amplitude only
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

Systems and methods for dynamic AC line voltage regulation are provided. A simple and cost-effective method for achieving AC line voltage regulation in AC systems including split-phase systems, of which the voltage for each voltage line may be regulated over a specified range, is provided. Buck and boost regulation is achieved for lowering or increasing the line voltage, respectively, with reference to the incoming grid voltage. Systems for dynamic AC line voltage regulation may comprise an AC/AC converter which uses fractionally rated switches and magnetics that handle only a fraction of the load current, resulting in lower costs. The use of an AC snubber further provides safe and robust switching of the main switching devices by eliminating failure prone switching sequences that are dependent on accurate assessment of voltage and/or current polarity for AC or bi-directional switches.

Claims

1. A voltage regulation system, comprising:

a converter comprising

a set of switches, and

a transformer comprising a primary winding and a plurality of secondary windings, wherein each of the primary winding and the plurality of secondary windings couple to a distribution transformer, the primary winding further couples to a neutral line, and each of the plurality of secondary windings further couple to a corresponding AC line, such that the primary winding forms a parallel circuit with each of the plurality of secondary windings;

wherein the primary winding has more turns than any of the plurality of secondary windings; and

a control module regulating a duty cycle of the converter.

2. The voltage regulation system of claim 1, wherein the control module determines a duty cycle according to a desired voltage of an AC line, wherein the converter generates an additive or a subtractive voltage to be injected in series with the voltage of the AC line in response to the duty cycle of the converter.

3. The voltage regulation system of claim 1, wherein the control module comprises a first control loop and a second control loop in parallel to the first control loop.

4. The voltage regulation system of claim 3, wherein the set of switches are regulated according to the first control loop when the voltage and the current of the voltage regulation system are within a predetermined range.

5. The voltage regulation system of claim 3, further comprising a bypass switch coupled across the primary winding of the transformer, wherein the set of switches are disabled and the bypass switch is enabled according to the second control loop when a line current is above a threshold.

6. The voltage regulation system of claim 5, wherein the bypass switch comprises a thyristor pair and a relay.

7. The voltage regulation system of claim 1, further comprising an active snubber comprising a switch, a resistor, a diode, and a capacitor, wherein the voltage across the capacitor is regulated to track the incoming line voltage when the polarity of the incoming line voltage is positive.

8. The voltage regulation system of claim 1, wherein the voltage regulation system is coupled across a distribution transformer comprising a center-tapped secondary winding.

9. The voltage regulation system of claim 8, further comprising an electromagnetic interference (EMI) filter coupled to the distribution transformer.

10. The voltage regulation system of claim 1, further comprising an energy saving tracking module.

11. The voltage regulation system of claim 10, wherein the energy saving tracking module tracks a variation of real and reactive power consumed when the line voltage varies.

12. The voltage regulation system of claim 11, wherein the energy saving tracking module determines a sensitivity metric measuring the percent change in real and reactive power to a small imperceptible change in line voltage.

13. The voltage regulation system of claim 11, wherein the energy saving tracking module determines a voltage point corresponding to a minimum power consumption and regulates the line voltage to the voltage point.

14. The voltage regulation system of claim 1, wherein the primary winding has at least twice as many turns as any of the plurality of secondary windings.

15. The voltage regulation system of claim 1, wherein the primary winding has at least twenty times as many turns as any of the plurality of secondary windings.