Method for the operational control of an inverter

Patent metadata

Field	Value
Publication number	US-9450512-B2
Application number	US-201213645983-A
Country	US
Kind code	B2
Filing date	Oct 5, 2012
Priority date	Apr 7, 2010
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

A method for the operational control of an inverter designed for DC/AC voltage conversion that has at least one direct-voltage input and that can be connected to a power supply grid via at least one alternating-voltage output, the inverter being involved in a power flow interaction with the grid in such a manner that, during operation of the inverter, a leakage current I A can occur, wherein the leakage current I A is controlled in the operational control.

First claim

The invention claimed is:

1. A method for the operational control of a transformerless three-phase inverter designed for DC/AC voltage conversion that has at least one direct-voltage input configured to couple to an energy generation component and a link and that can be connected to a power supply grid via at least one alternating-voltage output, wherein the direct-voltage input of the inverter does not have a galvanic connection to or with a neutral connection N and/or earth ground potential of the power supply grid when coupled thereto, the inverter being involved in a power flow interaction with the grid, comprising:
operating the inverter by driving a power component assembly of the inverter that has power semiconductors according to a pulse width modulation scheme using a control device;
controlling a leakage current I A during inverter operation by changing a target value setting for a link voltage U ZwK TGT of a link of the inverter, wherein the link voltage is increased upon the leakage current approaching a particular value and the link voltage is a DC voltage.

2. The method as claimed in claim 1 , wherein a pulse width modulation signal of the inverter is generated by modified sine-delta modulation.

3. The method as claimed in claim 2 , wherein a pulse width modulation signal of the inverter generated by sine-delta modulation is generated with time-variant offset.

4. The method as claimed in claim 1 , wherein the leakage current I A is controlled in an operational state of the inverter in which at least one condition is met.

5. The method as claimed in claim 4 , wherein the at least one condition comprises a link voltage U ZwK at an input of an inverter bridge of the inverter is less than twice a peak voltage Û of a line voltage signal.

6. The method as claimed in claim 4 , wherein the at least one condition is met when a link voltage U ZwK at the input of the inverter bridge of the inverter has a voltage value that is greater than a predetermined first voltage limit (U 2 ) and that is less than a predetermined second voltage limit (U 2 ).

7. The method as claimed in claim 4 , wherein the at least one condition is met when the leakage current I A has a current value that is greater than a predetermined first current limit, the leakage current I A then being controlled to a current value that is less than or equal to a second predetermined current limit.

8. The method as claimed in claim 7 , wherein the predetermined first current limit equals zero and the predetermined second current limit is a current value above which the inverter is transferred into a safe state by a residual-current-operated protective device associated therewith.

9. The method as claimed in claim 1 , wherein the leakage current I A is controlled by changing a target value setting, wherein in a determination of the change of the target value setting for a link voltage, a predetermined characteristic is evaluated.

10. The method as claimed in claim 1 , wherein the inverter comprises a DC/DC converter at an input thereof.

11. The method as claimed in claim 1 , further comprising performing a maximum power point tracking for maximizing a power delivered by a PV generator as the energy generator component.

12. The method of claim 1 , wherein controlling the leakage current further comprises reducing the link voltage upon the leakage current being below the particular value.

13. The method of claim 1 , further comprising disconnecting the at least one alternating-voltage output of the transformerless three-phase inverter from the power supply grid upon the leakage current rising above the particular value.

14. A method for the operational control of a transformerless three-phase inverter designed for DC/AC voltage conversion that has at least one direct-voltage input configured to couple to an energy generation component and a link and that can be connected to a power supply grid via at least one alternating-voltage output, wherein the direct-voltage input of the inverter does not have a galvanic connection to or with a neutral connection N and/or earth ground potential of the power supply grid when coupled thereto, the inverter being involved in a power flow interaction with the grid, comprising:
operating the inverter by driving a power component assembly of the inverter that has power semiconductors according to a pulse width modulation scheme using a control device;
controlling a leakage current I A during inverter operation by changing a target value setting for a link voltage U ZwK TGT of a link of the inverter; and
obtaining a measure of the leakage current using a circuit point connecting a first inverter output, a second inverter output, a third inverter output and an inverter input.

Assignees

• Sma Solar Technology Ag

Inventors

• Bremicker Sven
• De Brabandere Karel
• Mueller Tobias

Classifications

• H02M7/487

  Neutral point clamped inverters · CPC title

• H02J3/381

  Dispersed generators · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02M2001/123

  Electricity · mapped topic

• H02M2001/0025

  Electricity · mapped topic