Method and device for protecting several strings of a photovoltaic generator from reverse currents

Patent metadata

Field	Value
Publication number	US-9806516-B2
Application number	US-201514737712-A
Country	US
Kind code	B2
Filing date	Jun 12, 2015
Priority date	Dec 12, 2012
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

In order to protect reverse currents, several strings of a photovoltaic generator, which are connected in small groups respectively via a DC/DC-converter, parallel to a common DC voltage intermediate circuit, the current which flows over each of the DC/DC-converter is detected and if a reverse current is detected flowing through one of the DC/DC converters, the converter is stopped by controlling the DC/DC-converter.

First claim

The invention claimed is:

1. A method for reverse current protection of a number of strings of a photovoltaic generator being connected to a common DC link in parallel in small groups respectively via a corresponding DC/DC converter, comprising:
detecting a current flowing via each of the DC/DC converters; and
inhibiting a reverse current flowing through one of the DC/DC converters by a control of the DC/DC converter in response to the detection,
wherein the reverse current flowing through one of the DC/DC converters is inhibited by a control of the remaining DC/DC converters not having a reverse current, thereby interrupting the flow of current from the strings connected thereby to the common DC link.

2. The method as claimed in claim 1 , wherein the small groups each comprise two or three strings.

3. The method as claimed in claim 1 , wherein the DC/DC converters are configured as boost converters, and wherein the reverse current flowing through one of the DC/DC converters is inhibited by a continuous opening or closure of the boost converter switches on the remaining DC/DC converters not having a reverse current.

4. The method as claimed in claim 3 , further comprising:
initially opening the boost converter switches of the remaining DC/DC converters not having a reverse current;
confirming whether the reverse current has been inhibited accordingly; and
closing the boost converter switches of the remaining DC/DC converters if the reverse current has not been inhibited by the opening of the boost converter switches of the remaining DC/DC converters.

5. The method as claimed in claim 4 , further comprising:
opening a boost converter switch of the DC/DC converter, in which the reverse current has occurred if the reverse current has been inhibited by the closure of the boost converter switches of the remaining DC/DC converters.

6. The method as claimed in claim 1 , further comprising generating a fault signal in response to a reverse current.

7. A device for reverse current protection of a number of strings of a photovoltaic generator being connected to a common DC link in parallel in small groups respectively via a corresponding DC/DC converter, comprising:
a current sensor configured to detect a current flowing via a respective DC/DC converter; and
a central control system configured to inhibit a flow of a reverse current through one of the DC/DC converters by the control of one of the DC/DC converters,
wherein the central control system is configured to inhibit the reverse current flowing through the one of the DC/DC converters by a control of the remaining DC/DC converters not having the reverse current, thereby interrupting the flow of current from the strings connected thereby to the common DC link.

8. The device as claimed in claim 7 , wherein the small groups are each comprised of two or three strings.

9. The device as claimed in claim 7 , wherein the DC/DC converters are configured as boost converters.

10. The device as claimed in claim 9 , wherein the control system is configured to inhibit the reverse current flowing through the one of the DC/DC converters by a continuous opening or closure of boost converter switches of the remaining DC/DC converters not having the reverse current.

11. The device as claimed in claim 10 , wherein the control system is configured such that when the boost converter switches of the remaining DC/DC converters are initially opened, and it is confirmed whether the reverse current in the one of the DC/DC converters has been inhibited accordingly, the boost converter switches of the remaining DC/DC converters are then closed, if the reverse current has not been inhibited by the opening of the boost converter switches of the remaining DC/DC converters.

12. The device as claimed in claim 9 , wherein the control system is configured to open a boost converter switch on the DC/DC converter in which the reverse current has occurred, if the reverse current has not been inhibited by the closure of the boost converter switches of the remaining DC/DC converters.

13. The device as claimed in claim 7 , wherein the control system is configured to generate a fault signal in response to the occurrence of a reverse current.

14. A method for reverse current protection of a number of strings of a photovoltaic generator being connected to a common DC link in parallel in small groups respectively via a corresponding DC/DC converter, comprising:
detecting a current flowing via each of the DC/DC converters; and

inhibiting a reverse current flowing through one of the DC/DC converters by a control of the DC/DC converter in response to the detection,
wherein the DC/DC converters are configured as boost converters, and wherein the reverse current flowing through one of the DC/DC converters is inhibited by a continuous opening or closure of the boost converter switches on the remaining DC/DC converters not having a reverse current.

15. The method as claimed in claim 14 , further comprising:
initially opening the boost converter switches of the remaining DC/DC converters not having a reverse current;
confirming whether the reverse current has been inhibited accordingly; and

closing the boost converter switches of the remaining DC/DC converters if the reverse current has not been inhibited by the opening of the boost converter switches of the remaining DC/DC converters.

16. The method as claimed in claim 15 , further comprising:
opening a boost converter switch of the DC/DC converter, in which the reverse current has occurred if the reverse current has been inhibited by the closure of the boost converter switches of the remaining DC/DC converters.

Assignees

• Sma Solar Technology Ag

Inventors

• Bremicker Sven
• Haering Adrian
• Walter Matthias
• Wolf Henrik
• Laschinski Joachim

Classifications

• H02J2101/24

  Photovoltaics · CPC title

• H02H11/002 Primary

  in case of inverted polarity or connection; with switching for obtaining correct connection · CPC title

• H02M3/155

  using semiconductor devices only · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title

• H02M3/02

  without intermediate conversion into AC · CPC title