Control device of power conversion unit and method of controlling power conversion unit

Patent metadata

Field	Value
Publication number	US-9312788-B2
Application number	US-201514602277-A
Country	US
Kind code	B2
Filing date	Jan 22, 2015
Priority date	Feb 18, 2014
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

A control device and control method of power conversion unit applied to a three-phase AC grid. The control device includes detection unit, current detection unit, and signal processing unit. The detection unit detects three-phase voltage signal of the three-phase AC grid and calculates and generates negative sequence reactive current given signal. The current detection unit detects current of the power conversion unit to output feedback current signal. The signal processing unit receives the negative sequence reactive current given signal, positive sequence current given signal, and the feedback current signal to output modulation signal. The power conversion unit is electrically coupled to the signal processing unit and the three-phase AC grid. The power conversion unit absorbs negative sequence reactive currents from the three-phase AC grid according to the modulation signal when the three-phase voltage signal is unbalanced to reduce negative sequence voltage at output terminal of the power conversion unit.

First claim

What is claimed is:

1. A control device of a power conversion unit applied to a three-phase AC grid comprising:
a detection unit configured for detecting a three-phase voltage signal of the three-phase AC grid and calculating and generating a negative sequence reactive current given signal;
a current detection unit configured for detecting a current of the power conversion unit to output a feedback current signal; and
a signal processing unit configured for receiving the negative sequence reactive current given signal, a positive sequence current given signal, and the feedback current signal to output a modulation signal;
wherein the power conversion unit is electrically coupled to the signal processing unit and the three-phase AC grid, the power conversion unit absorbs negative sequence reactive currents from the three-phase AC grid according to the modulation signal when the three-phase voltage signal is unbalanced so as to reduce a negative sequence voltage at an output terminal of the power conversion unit.

2. The control device of the power conversion unit of claim 1 , wherein the positive sequence current given signal comprises a first axial positive sequence active current given signal and a second axial positive sequence reactive current given signal, the negative sequence reactive current given signal comprises a first axial negative sequence reactive current given signal and a second axial negative sequence reactive current given signal.

3. The control device of the power conversion unit of claim 2 , wherein the first axis and the second axis are determined based on a dq coordinate.

4. The control device of the power conversion unit of claim 1 , further comprising a space vector modulation module electrically coupled between the signal processing unit and the power conversion unit, the space vector modulation module being configured for receiving the modulation signal and converting the modulation signal to a three-phase modulation signal and outputting the three-phase modulation signal to the power conversion unit.

5. The control device of the power conversion unit of claim 2 , wherein the current detection unit further comprises a positive and negative sequence separation module to separate the feedback current signal so as to output a positive sequence feedback current signal and a negative sequence feedback current signal.

6. The control device of the power conversion unit of claim 5 , wherein the signal processing unit further comprises a positive sequence signal processing module, a negative sequence signal processing module and an error calculation module, the positive sequence signal processing module receives the positive sequence feedback current signal and the positive sequence current given signal to output a positive sequence modulation signal, the negative sequence signal processing module receives the negative sequence feedback current signal and the negative sequence reactive current given signal to output a negative sequence modulation signal, and the error calculation module receives the positive sequence modulation signal and the negative sequence modulation signal to calculate and output the modulation signal.

7. The control device of the power conversion unit of claim 5 , wherein the positive sequence feedback current signal comprises a first axial positive sequence feedback current signal and a second axial positive sequence feedback current signal, the negative sequence feedback current signal comprises a first axial negative sequence feedback current signal and a second axial negative sequence feedback current signal.

8. The control device of the power conversion unit of claim 7 , wherein the positive sequence signal processing module further comprises a first positive sequence error calculation module, a second positive sequence error calculation module, a first positive sequence proportion adjustment module, a second positive sequence proportion adjustment module, and a positive sequence coordinate transformation module, the first positive sequence error calculation module receives the first axial positive sequence active current given signal and the first axial positive sequence feedback current signal to output a first axial positive sequence error signal, the second positive sequence error calculation module receives the second axial positive sequence reactive current given signal and the second axial positive sequence feedback current signal to output a second axial positive sequence error signal, the first positive sequence proportion adjustment module receives the first axial positive sequence error signal to calculate and output a first axial positive sequence proportion modulation signal, the second positive sequence proportion adjustment module receives the second axial positive sequence error signal to calculate and output a second axial positive sequence proportion modulation signal, the positive sequence coordinate transformation module receives the first axial positive sequence proportion modulation signal and the second axial positive sequence proportion modulation signal to output the positive sequence modulation signal.

9. The control device of the power conversion unit of claim 8 , wherein the positive sequence coordinate transformation module transforms the first axial positive sequence proportion modulation signal and the second axial positive sequence proportion modulation signal from a dq coordinate to an αβ coordinate.

10. The control device of the power conversion unit of claim 7 , wherein the negative sequence signal processing module further comprises a first negative sequence error calculation module, a second negative sequence error calculation module, a first negative sequence proportion adjustment module, a second negative sequence proportion adjustment module, and a negative sequence coordinate transformation module, the first negative sequence error calculation module receives the first axial negative sequence reactive current given signal and the first axial negative sequence feedback current signal to output a first axial negative sequence error signal, the second negative sequence error calculation module receives the second axial negative sequence reactive current given signal and the second axial negative sequence feedback current signal to output a second axial negative sequence error signal, the first negative sequence proportion adjustment module receives the first axial negative sequence error signal to calculate and output a first axial negative sequence proportion modulation signal, the second negative sequence proportion adjustment module receives the second axial negative sequence error signal to calculate and output a second axial negative sequence proportion modulation signal, the negative sequence coordinate transformation module receives the first axial negative sequence proportion modulation signal and the second axial negative sequence proportion modulation signal to output the negative sequence modulation signal.

11. The control device of the power conversion unit of claim 10 , wherein the negative sequence coordinate transformation module transforms the first axial negative sequence proportion modulation signal and the second axial negative sequence proportion modulation signal from a dq coordinate to an αβ coordinate.

12. The control device of the power conversion unit of claim 2 , wherein the signal processing unit further comprises a first error calculation module, a positive sequence signal processing module, a negative sequence signal processing module and a second error calculation module, the first error calculation module receives the feedback current signal, the positive sequence current given signal, an

Assignees

• Delta Electronics Shanghai Co

Inventors

• Xue Hai-Fen
• Cai Li
• Tian Chao
• Zheng Dian-Chen

Classifications

• H02M7/537 Primary

  using semiconductor devices only, e.g. single switched pulse inverters · CPC title

• H02M7/53875 Primary

  with analogue control of three-phase output · CPC title

• H02J3/381

  Dispersed generators · CPC title

• G01R25/005

  Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller, or for passing one of the input signals as output signal · CPC title

• G01R21/127

  by using pulse modulation (G01R21/133 takes precedence) · CPC title