Apparatus and method for controlling delta-connected cascaded multilevel converter

Patent metadata

Field	Value
Publication number	US-12113456-B2
Application number	US-202017753860-A
Country	US
Kind code	B2
Filing date	Feb 28, 2020
Priority date	Feb 28, 2020
Publication date	Oct 8, 2024
Grant date	Oct 8, 2024

Abstract

Embodiments of present disclosure relate to an apparatus and a method for controlling a delta-connected cascaded multilevel converter. The apparatus (100) for controlling a delta-connected cascaded multilevel converter (110) comprises: a converter controller (102) configured to: receive current signals indicating phase currents flowing through respective phase arms of the converter (110); determine a harmonic current signal indicating a circulating current of the converter (110) from the current signals; and generate, based on the determined harmonic current signal and a reference current signal, a harmonic voltage signal to cause an amplitude of the circulating current flowing through the phase arms of the converter (110) to be a predetermined amplitude.

First claim

What is claimed is:

1. An apparatus for controlling a delta-connected cascaded multilevel converter, comprising:
a converter controller configured to:
receive current signals indicating phase currents flowing through respective phase arms of the converter;
determine a harmonic current signal indicating a circulating current of the converter from the current signals;
generate, based on the determined harmonic current signal and a reference current signal, a harmonic voltage signal to cause an amplitude of the circulating current flowing through the phase arms of the converter to be a predetermined amplitude;
receive a phase voltage reference signal associated with a load electrically coupled to the converter; and
generate, by combining the harmonic voltage signal with the phase voltage reference signal, a control signal for controlling the converter to cause a peak amplitude of the phase currents to be a first amplitude,
wherein the first amplitude is associated with a second amplitude of the circulating current in the phase currents.

2. The apparatus of claim 1 , wherein the converter controller is configured to:
determine the harmonic current signal indicating a third order harmonic circulating current of the converter from the current signals; and
generate the harmonic voltage signal to cause the amplitude of the third order harmonic circulating current to be 0.167 times of the amplitude of the rated current of the converter.

3. The apparatus of claim 1 , wherein the converter controller is configured to generate the harmonic voltage signal based on a comparison of the harmonic current signal and the reference current signal.

4. The apparatus of claim 3 , wherein the converter controller is configured to:
determine a first DC component of the harmonic current signal from the current signals;
compare the first DC component with a first reference DC component of the reference current signal to generate a first DC difference;
determine a second DC component of the harmonic current signal from the current signals;
compare the second DC component with a second reference DC component of the reference current signal to generate a second DC difference; and
generate the harmonic voltage signal based on the first DC difference and the second DC difference.

5. The apparatus of claim 4 , wherein the first reference DC component of the reference current is set to be 0.167 times of an amplitude of a rated current of the converter, and the second reference DC component of the reference current is set to be zero.

6. The apparatus of claim 3 , wherein the converter controller is configured to:
determine a first AC component of the harmonic current signal from the current signals;
compare the first AC component with a first reference AC component of the reference current signal to generate a first AC difference;
determine a second AC component of the harmonic current signal from the current signals;
compare the second AC component with a second reference AC component of the reference current signal to generate a second AC difference; and
generate the harmonic voltage signal based on the first AC difference and the second AC difference.

7. The apparatus of claim 1 , further comprising:
a cell controller configured to control, based on a cell control signal generated from the control signal, one of a plurality of converter cells in the phase arm to cause the amplitude of the circulating current to be the predetermined amplitude.

8. The apparatus of claim 7 , wherein the cell controller is further configured to:
receive a DC voltage value indicating a DC voltage across a capacitor in the one of the plurality of converter cells;
compare the DC voltage value with a nominal value to generate a compensation factor; and
control the one of the plurality of converter cells based on the generated compensation factor and the cell control signal.

9. The apparatus of claim 8 , wherein the cell controller is configured to generate the compensation factor by dividing the DC voltage value by the nominal value.

10. The apparatus of claim 9 , wherein the cell controller is configured to:
determine a compensated control signal by dividing a level of the cell control signal by the compensation factor; and
control the one of the plurality of converter cells based on the compensated control signal.

11. A system for controlling a delta-connected cascaded multilevel converter, comprising:
the apparatus of claim 1 ;
a first controller configured to generate a phase voltage reference signal based on a load electrically coupled to the converter; and
a second controller configured to generate a plurality of cell control signals for the plurality of converter cells based on the harmonic voltage signal.

12. A method for controlling a delta-connected cascaded multilevel converter, comprising:
receiving current signals indicating phase currents flowing through respective phase arms of the converter;
determining a harmonic current signal indicating a circulating current of the converter from the current signals;
generating, based on the determined harmonic current signal and a reference current signal, a harmonic voltage signal to cause an amplitude of the circulating current flowing through the phase arms of the converter to be a predetermined amplitude;
receiving a phase voltage reference signal associated with a load electrically coupled to the converter; and
generating, by combining the harmonic voltage signal with the phase voltage reference signal, a control signal for controlling the converter to cause a peak amplitude of the phase currents to be a first amplitude,
wherein the first amplitude is associated with a second amplitude of the circulating current in the phase currents.

13. The method of claim 12 , wherein determining the harmonic current signal indicating the circulating current comprises determining the harmonic current signal indicating a third order harmonic circulating current, and
wherein generating the harmonic voltage signal to cause the amplitude of the circulating current to be the predetermined amplitude comprises generating the harmonic voltage signal to cause the amplitude of the third order harmonic circulating current to be 0.167 times of the amplitude of the rated current of the converter.

14. The method of claim 12 , wherein generating the harmonic voltage signal comprises generating the harmonic voltage signal based on a comparison of the harmonic current signal and the reference current signal.

15. The method of claim 14 , wherein generating the harmonic voltage signal based on the comparison comprises:
determining a first DC component of the harmonic current signal from the current signals;
comparing the first DC component with a first reference DC component of the reference current signal to generate a first DC difference;
determining a second DC component of the harmonic current signal from the current signals;
comparing the second DC component with a second reference DC component of the reference current signal to generate a second DC difference; and
generating the harmonic voltage signal based on the first DC difference and the second DC difference.

16. The method of claim 15 , wherein comparing the first DC component with the first reference DC component comprises comparing the first DC component with an amplitude of 0.167 times of a rated current of the converter, and
wherein comparing the second DC component with the second reference DC component comprises comparing the second DC component with zero.

17. The method of

Assignees

• Abb Schweiz Ag

Inventors

• Huang Xing
• Xie Hailian
• Pei Guangming
• Wei Hua
• Li Min

Classifications

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title

• H02M1/15

  using active elements · CPC title

• H02M5/458

  using semiconductor devices only · CPC title

• H02M1/12

  Arrangements for reducing harmonics from AC input or output · CPC title

• H02J3/01

  Arrangements for reducing harmonics or ripples · CPC title