Inverter DC link volts “tooth” modulation scheme

• US 6,654,261 B2
• Filed: 10/29/2001
• Issued: 11/25/2003
• Est. Priority Date: 10/27/2000
• Status: Expired due to Fees

• Current Assignee: The Switch Controls and Converters, Inc.
• Original Assignee: Youtility Incorporated
• Inventors: Bond, Karl, Griessel, Richard E, Welches, Richard Shaun, Beckedahl, Peter
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US10/052,802
• Publication Number:
  US 20030012038A1
• Time in Patent Office: 757 Days
• Field of Search: 363/41, 363/42, 363/17, 363/98, 363/131, 363/132, 363/135, 363/160
• US Class Current: 363/41
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage

Abstract

The invention in the simplest form is a power conditioning and inverting system for improved and efficient power generation. In particular, the present invention is a modulated dc link scheme that dramatically reduces the switching frequency ripple across the PWM output filter inductor and provides cost, size, and weight reductions, as well as efficiency enhancements. In a preferred embodiment of the present invention, the DC-DC converter control takes a feedback signal proportional to the inverter output voltage. This feedback is “summed” into the primary DC-DC volts command thereby causing the dc bus/link voltage to vary at a multiple of the output fundamental frequency causing the DC link to become a signal at a fundamental frequency voltage with a dc offset. The tooth modulator DC supply tracks the AC output voltage, reducing the difference between the applied DC volts and the AC output volts, thereby reducing inductor core losses.

Claims

1. A dc links tooth modulator for producing an AC output, comprising:

a converter producing a converter output signal, wherein said converter has an input end and an output end, wherein said input end is connected to a power source;

a control feedback circuit delivering a composite voltage error signal to a pulse width modulator controller;

an output inverter connected to said output end of said converter and communicating to said pulse width modulator controller for pulse width modulating said converter output signal and producing an inverter output signal at a fundamental frequency with a dc links signal at a multiple of said fundamental frequency, wherein said dc links signal tracks an envelope of said inverter output and is offset from said inverter output by a dc term.

2. The dc links tooth modulator according to claim 1, further comprising an offset generator producing said dc term.

3. The dc links tooth modulator according to claim 1, further comprising an EMI/RF filter section connecting to said inverter output signal.

4. The dc links tooth modulator according to claim 1, wherein said inverter is a DC-AC inverter.

5. The dc links tooth modulator according to claim 1, wherein under a no-load condition said output signal remains at a low fixed level until a load is re-established.

6. The dc links tooth modulator according to claim 1, wherein said output inverter is selected from the group consisting of thyristor type inverters and IGBT based output inverters.

7. A dc links tooth modulation topology for a poly-phase AC output, comprising:

a converter producing a converter output signal, wherein said converter has an input end and an output end, wherein said input end is connected to a power source, and wherein a voltage sensor measures a voltage feedback signal;

an inverter connected to said output end of said converter with a pulse width modulator controller for pulse width modulating said converter output signal and producing an inverter output;

a control feedback circuit delivering a composite voltage error signal to said pulse width modulator controller, wherein said composite voltage error signal comprises a first feedback signal proportional to said inverter output with said voltage feedback signal, and wherein said inverter output is an AC signal at a fundamental frequency with a dc links signal at a multiple of said fundamental frequency offset by a dc term.

8. The dc links tooth modulation topology according to claim 7, wherein a plurality of said dc links tooth modulation topology are connected in parallel to produce said poly-phase AC output from said power source.

9. The dc links tooth modulation topology according to claim 7, further comprising a switch, wherein said switch connects to a reference generator to produce said inverter output signal.

10. The dc links tooth modulation topology according to claim 7, further comprising an offset generator, wherein said offset generator produces said dc term.

11. The dc links tooth modulation topology according to claim 7, wherein said feedback signal proportional to said inverter output is produced by the process of taking an absolute value of said inverter output signal to produce a positive output signal;

inverting said positive output signal to produce an inverted output signal;

summing said inverted output signal with a dc level to produce a tooth modulated signal.

12. The dc links tooth modulation topology according to claim 7, further comprising an imbalance limiter summed to said voltage feedback signal.

13. A power conditioning system, comprising:

a power source;

a dc-dc converter producing a dc output signal, wherein said dc-dc converter has an input end and an output end, wherein said input end is connected to said power source;

an output inverter connected to said output end of said dc-dc converter for pulse width modulating said dc output signal and producing an inverter output voltage at a fundamental frequency;

a control loop feedback signal connecting to said output inverter, wherein said control loop feedback signal is proportional to said inverter output voltage, and wherein a dc link voltage is a multiple of said fundamental frequency.

14. The power conditioning system according to claim 13, wherein said dc-dc converter comprises a dc capacitor connected parallel to said power source, a plurality of power switches connected parallel to said dc capacitor, a high frequency step up transformer connected to said plurality on a first side;

a rectifier section connected to a second side of said transformer, and a filter section connected to said rectifier section.

15. The power conditioning system according to claim 13, further comprising an offset generator producing said dc term.

16. The power conditioning system according to claim 13, further comprising an EMI/RF filter section connecting to said inverter output signal.

17. The power conditioning system according to claim 13, wherein said inverter is a DC-AC inverter.