Multilevel inverter for cryogenic power systems

Patent metadata

Field	Value
Publication number	US-10205379-B2
Application number	US-201715399309-A
Country	US
Kind code	B2
Filing date	Jan 5, 2017
Priority date	Jan 5, 2017
Publication date	Feb 12, 2019
Grant date	Feb 12, 2019

Abstract

A power system includes a first unit block having first resonant circuitry that receives power from a DC bus, a first controlled rectifier that provides a first portion of power to one or more loads at a first voltage level, and a first transformer coupled between the first resonant circuitry and the first controlled rectifier. A second unit block includes second resonant circuitry that receives power from the DC bus, a second controlled rectifier configured to provide a second portion of power to the one or more loads at a second voltage level, and a second transformer coupled between the resonant circuitry and the controlled rectifier. The first and second unit blocks are coupled in series to output a summation waveform.

First claim

The invention claimed is:

1. A multilevel inverter for a cryogenic power system, comprising:
a first unit block comprising at least a first phase, the first phase comprising:
first resonant circuitry configured to receive power from a DC bus;
a first controlled rectifier configured to provide a first portion of power to one or more loads at a first voltage level; and
a first transformer coupled between the first resonant circuitry and the first controlled rectifier, wherein the first transformer is configured to galvanically isolate power received from the resonant circuitry and the first portion of power delivered by the first controlled rectifier; and

a second unit block comprising at least a second phase coupled in series with the first phase, the second phase comprising:
second resonant circuitry configured to receive power from the DC bus;
a second controlled rectifier configured to provide a second portion of power to the one or more loads at a second voltage level;
a second transformer coupled between the resonant circuitry and the controlled rectifier, wherein the second transformer configured to galvanically isolate power received from the second resonant circuitry from the second portion of power delivered by the second controlled rectifier;

wherein the first phase and the second phase are coupled in series to output a summation waveform, wherein the first phase is configured to provide the first portion of power at a first voltage level and the second phase is configured to provide the second portion of power at the second voltage level; and
wherein the first resonant circuitry and the second resonant circuitry is configured to reduce ripple frequency of the output to be less than or equal to 2N times a switching frequency of the multilevel inverter, where N is a total number of phases.

2. The multilevel inverter for a cryogenic power system of claim 1 , wherein the first resonant circuitry and the second resonant circuitry each comprises an inductor, a capacitor, or both, to shape the output to include a reduced voltage ripple, reduced ripple frequency, or both.

3. The multilevel inverter for a cryogenic power system of claim 1 , wherein the first transformer and the second transformer have floating outputs with respect to the power received to enable series output connection of each of the first phase and the second phase.

4. The multilevel inverter for a cryogenic power system of claim 1 , comprising a third phase, wherein the third phase is coupled in parallel to the first phase, wherein current through each of the first phase and the third phase is divided to deliver additional power to the one or more loads without increasing magnetic fields generated by the current, and wherein the third phase is coupled in parallel to the second phase.

5. The multilevel inverter for a cryogenic power system of claim 1 , wherein circuitry of the first phase is the same as circuitry of the second phase.

6. The multilevel inverter for a cryogenic power system of claim 1 , wherein the first phase and the second phase are configured to form a summation waveform without the use of a passive filter.

7. The multilevel inverter for a cryogenic power system of claim 1 , wherein each of the first unit block and the second unit block are modular to enable connection of the first unit block in series or in parallel with the second unit block.

8. The multilevel inverter for a cryogenic power system of claim 1 , comprising a controller configured to receive a reference signal and to send control signals to switches of each of the first phase and the second phase to control the output of the summation waveform based on the reference signal.

9. The multilevel inverter for a cryogenic power system of claim 1 , wherein the summation waveform comprises a sinusoidal waveform or a triangle waveform.

10. A method of operating a cryogenic power system having an inverter, wherein the method comprises: receiving, at a master controller, a reference signal; receiving, at a first phase, power from a DC bus, wherein the first phase comprises first resonant circuitry, a first controlled rectifier, and a first transformer coupled between the first resonant circuitry and the first controlled rectifier, wherein the first transformer is configured to galvanically isolate power received from the resonant circuitry and power delivered by the first controlled rectifier; receiving, at a second phase, power from the DC bus, wherein the second phase comprises second resonant circuitry, a second controlled rectifier, and a second transformer coupled between the second resonant circuitry and the second controlled rectifier, wherein the second transformer is configured to galvanically isolate power received from the second resonant circuitry and power delivered by the second controlled rectifier; sending one or more control signals from the master controller to a first slave controller of the first phase to cause the first slave controller to control switches of the first phase to output a first portion of power; sending one or more control signals from the master controller to a second slave controller of the second phase to cause the second slave controller to control switches of the second phase to output a second portion of power; and providing power output from the first phase and the second phase to one or more loads based on the reference signal; wherein the one or more control signals from the master controller reduce ripple frequency of the power output to be less than or equal to 2N times a switching frequency of the inverter, where N is a total number of phases.

11. The method of operating a cryogenic power system having an inverter of claim 10 , comprising controlling switches of the first phase to output the first voltage while the reference signal is below a first threshold voltage.

12. The method of operating a cryogenic power system having an inverter of claim 11 , comprising controlling switches of the second phase to output the second voltage while the reference signal is between the first threshold voltage and a second threshold voltage to produce a combined voltage of the first voltage and the second voltage.

13. The method of operating a cryogenic power system having an inverter of claim 10 , comprising dividing current between the first phase and the second phase, wherein the first phase is coupled in parallel with the second phase.

14. A power system, comprising:
an inverter comprising a plurality of phases, each phase of the plurality of phases comprising:
resonant circuitry configured to receive power from a DC bus;
a controlled rectifier configured to provide a portion of power to one or more loads;
a transformer coupled between the resonant circuitry and the controlled rectifier, wherein the transformer is configured to galvanically isolate power received from the resonant circuitry and the portion of power delivered by the controlled rectifier; and
slave controller circuitry configured to control operation of switches of the controlled rectifier, the resonant circuitry, or both; and

a master controller comprising:
a processor configured to:
receive a reference signal; and
send one or more control signals to the slave controller circuitry of each phase to control operation of the switches to cause each of the phases to output power based on the reference signal;
wherein the resonant circuitry is configured to reduce ripple frequency of the power output to be less than or equal to 2N times a switching frequency of the inverter, where N is the number of phases of the plurality of phases.

15. The power system of claim

Assignees

• Gen Electric

Inventors

• Caiafa Antonio

Classifications

• H02M7/4807

  having a high frequency intermediate AC stage · CPC title

• H02M7/49

  Combination of the output voltage waveforms of a plurality of converters · CPC title

• H02M7/48 Primary

  using discharge tubes with control electrode or semiconductor devices with control electrode · CPC title

• H02M3/33592

  having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer · CPC title

• H02M3/285

  Single converters with a plurality of output stages connected in parallel (parallel operation of a plurality of converters in DC distribution networks H02J1/10) · CPC title