Method and inverter for distributing power among a plurality of DC sources connected jointly to a DC voltage input of a DC-to-AC converter

Patent metadata

Field	Value
Publication number	US-10056758-B2
Application number	US-201514812090-A
Country	US
Kind code	B2
Filing date	Jul 29, 2015
Priority date	Jan 30, 2013
Publication date	Aug 21, 2018
Grant date	Aug 21, 2018

Abstract

In order to distribute power over multiple direct current sources which are connected in parallel to an input-side direct voltage intermediate circuit of a DC/AC transformer, at least one of which direct current sources is connected to the direct voltage intermediate circuit via a DC/DC transformer, wherein the DC/DC transformer can be actuated to change the power fed into the direct voltage intermediate circuit by the direct current source, the power levels of the direct current sources are decreased differently in a decreased operating mode of the DC/AC transformer in which the power of the DC/AC transformer is decreased compared to the sum of the maximum power levels available from all the direct current sources, and by actuating at least the one DC/DC transformer via which the at least one direct current source is connected to the direct voltage intermediate circuit, variation in the power levels of at least one other direct current source is compensated dynamically.

First claim

The invention claimed is:

1. A method for distributing power among a plurality of DC sources, which are connected in parallel to an input-side DC link of a DC-to-AC converter, of which DC sources at least one is connected, via a DC-to-DC converter, to the DC link, wherein the DC-to-DC converter is actuable in order to cause a change in the power fed into the DC link by the DC source, comprising:
derating powers of the DC sources differently during a derated operation of the DC-to-AC converter that includes a reduction of power at the DC-to-AC converter from an initial power to a derated power in which the power of the DC-to-AC converter is derated with respect to the sum of the maximum powers available from all DC sources;
dynamically compensating a variation in the power of at least one other DC source during the derated operation of the DC-to-AC converter by actuating at least the at least one DC-to-DC converter via which the at least one DC source is connected to the DC link to maintain a sum of powers of the DC sources constant at the derated power during the derated operation,
wherein the power of the at least one other DC source is varied actively by virtue of a DC-to-DC converter via which the at least one other DC source is connected to the DC link being actuated.

2. The method as claimed in claim 1 , wherein the at least one DC source comprises a photovoltaic generator, which is connected to the DC link of the DC-to-AC converter via the actuable DC-to-DC converter.

3. The method as claimed in claim 2 , wherein a plurality of DC sources each comprise a photovoltaic generator, which is connected to the DC link of the DC-to-AC converter via an actuable DC-to-DC converter.

4. The method as claimed in claim 1 , wherein the at least one other DC source comprises a generator comprising an electric machine.

5. The method as claimed in claim 1 , wherein the variation in the power of the at least one other DC source is compensated for with a response time of no more than 10 ms of the DC-to-DC converter via which the at least one DC source is connected to the DC link.

6. The method as claimed in claim 1 , wherein the power of the DC-to-AC converter is derated in accordance with external presets.

7. The method as claimed in claim 1 , wherein the derated power of the DC-to-AC converter is varied dynamically.

8. A method for distributing power among a plurality of DC sources, which are connected in parallel to an input-side DC link of a DC-to-AC converter, of which DC sources at least one is connected, via a DC-to-DC converter, to the DC link, wherein the DC-to-DC converter is actuable in order to cause a change in the power fed into the DC link by the DC source, comprising:
derating powers of the DC sources differently during a derated operation of the DC-to-AC converter that includes a reduction of power at the DC-to-AC converter from an initial power to a derated power in which the power of the DC-to-AC converter is derated with respect to the sum of the maximum powers available from all DC sources;
dynamically compensating a variation in the power of at least one other DC source during the derated operation of the DC-to-AC converter by actuating at least the at least one DC-to-DC converter via which the at least one DC source is connected to the DC link to maintain a sum of powers of the DC sources constant at the derated power during the derated operation,
wherein the power of the at least one other DC source is varied actively by virtue of the DC-to-AC converter being actuated in order to cause a change in a DC-link voltage of its input-side DC link.

9. The method as claimed in claim 1 , wherein the power of the at least one other DC source is varied actively in order to detect at least a part of a characteristic of the at least one other DC source.

10. The method as claimed in claim 1 , wherein, during the variation of the power of the at least one other DC source, an MPP of the at least one other DC source is passed through.

11. The method as claimed in claim 1 , wherein the power of the at least one other DC source is varied actively in order to identify a voltage extension of the at least one other DC source.

12. The method as claimed in claim 1 , wherein the power of the at least one other DC source is varied actively in order to transfer the at least one other DC source from an operating point close to off load to an operating point close to short circuit of the same power, but a lower operating voltage.

13. The method as claimed in claim 1 , wherein the power of the at least one other DC source is varied actively in order to determine and approach an operating point of all of the DC sources which is optimized from at least one point of view.

14. The method as claimed in claim 13 , wherein the point of view is selected from the following:
minimized power losses of all of the DC-to-DC converters and the DC-to-AC converter,
a minimized loading of all of the DC-to-DC converters and the DC-to-AC converter,
a matching of the power losses of components with an identical design within a plurality of the DC-to-DC converters,
an optimized power regulation capacity of the DC-to-AC converter.

15. An inverter, comprising:
a DC-to-AC converter having an input-side DC link,
a plurality of inputs for a parallel connection of a plurality of DC sources to the DC link,
at least one DC-to-DC converter, which is arranged between one of the inputs and the DC link and is actuable in order to cause a change in the power fed via said DC-to-DC converter into the DC link, and
a control device which actuates the at least one DC-to-DC converter in accordance with a method, comprising:
derating powers of the DC sources differently during a derated operation of the DC-to-AC converter that includes a reduction of power at the DC-to-AC converter from an initial power to a derated power in which the power of the DC-to-AC converter is derated with respect to the sum of the maximum powers available from all DC sources; and
dynamically compensating a variation in the power of at least one other DC source during the derated operation of the DC-to-AC converter by actuating at least the at least one DC-to-DC converter via which the at least one DC source is connected to the DC link to maintain a sum of powers of the DC sources constant at the derated power during the derated operation,
wherein the power of the at least one other DC source is varied actively by virtue of a DC-to-DC converter via which the at least one other DC source is connected to the DC link being actuated.

16. The inverter as claimed in claim 15 , wherein the control device has a primary control device element, which regulates the power of the DC-to-AC converter, and a secondary control device element, which distributes this power among the inputs by actuation of the at least one DC-to-DC converter.

17. The inverter as claimed in claim 15 , further comprising actuable DC-to-DC converters provided between all of the inputs and the DC link.

18. The inverter as claimed in claim 15 , wherein no actuable DC-to-DC converter is provided in at least one of the input.

Assignees

• Sma Solar Technology Ag

Inventors

• Unru Alexander
• Schroeder Thomas

Classifications

• H02J1/102 Primary

  being switching converters (H02J1/108, H02J1/12 take precedence) · CPC title

• H02M7/42

  Conversion of DC power input into AC power output without possibility of reversal · CPC title

• H02M3/04

  by static converters · CPC title

• H02J2101/25

  involving maximum power point tracking control for photovoltaic sources · CPC title

• H02J2101/10

  Dispersed power generation using fossil fuels, e.g. diesel generators · CPC title