System for distributing locally generated energy to multiple load units

Abstract

A system for distributing locally generated energy from at least one renewable DC source to a plurality of local load units of the system, including, for each load unit: an input terminal configured to connect to a grid, and an output terminal configured to connect to at least one load. Further for each load the system includes an inverter including an inverter input and an inverter output, wherein the inverter input is connected to the at least one renewable DC source and the inverter output is connected to the input terminal and to the output terminal of the respective load unit, and wherein the inverter is configured to convert a direct current at the inverter input into an alternating current at the inverter output. The system also includes a power meter including a power meter input connected to the input terminal of the respective load unit, wherein the power meter is configured to determine a current power consumption from the grid, and wherein the power meter includes a power meter output connected to the inverter of the respective load unit, and wherein the power meter is configured to transmit data relating to the current power consumption from the grid to the inverter. The inverter of the respective load unit is configured to determine an input DC voltage applied to its inverter input and to determine a power to be currently converted from the applied input DC voltage and the current power consumption data transmitted thereto.

Claims

1. A system for distributing locally generated energy from at least one renewable DC source to a plurality of local load units of the system, comprising, for each load unit: an input terminal configured to connect to a grid, an output terminal configured to connect to at least one load, an inverter comprising an inverter input and an inverter output, wherein the inverter input is connected to the at least one renewable DC source and the inverter output is connected to the input terminal and to the output terminal of the respective load unit, and wherein the inverter is configured to convert a direct current at the inverter input into an alternating current at the inverter output, a power meter comprising a power meter input connected to the input terminal of the respective load unit, wherein the power meter is configured to determine a current power consumption from the grid, and wherein the power meter comprises a power meter output connected to the inverter of the respective load unit, and wherein the power meter is configured to transmit data relating to the current power consumption from the grid to the inverter, and wherein the inverter of the respective load unit is configured to determine an input DC voltage applied to its inverter input and to determine a power to be currently converted from the applied input DC voltage and the current power consumption data transmitted thereto.

2. The system as claimed in claim 1, wherein the inverter of the respective load unit is configured to determine from the input DC voltage applied to its inverter input a maximum possible power which can be currently converted according to a predefined first characteristic curve.

3. The system as claimed in claim 2, wherein, if the maximum possible power which can be currently converted is greater than or equal to the current power consumption from the grid, the inverter of the respective load unit is configured to determine the power to be currently converted in such a manner that the current power consumption from the grid reaches a preset limit value.

4. The system as claimed in claim 3, wherein the preset limit value is 0 kW.

5. The system as claimed in claim 2, wherein, if the maximum possible power which can be currently converted is less than the power consumption from the grid, the inverter of the respective load unit is configured to determine the power to be currently converted in such a manner that it corresponds to a level of the maximum possible power which can be currently converted, with the result that the current power consumption from the grid is minimized.

6. The system as claimed in claim 1, wherein the inverter is unidirectional and a galvanically-isolating inverter.

7. The system as claimed in claim 2, wherein the first characteristic curves of the respective load units differ from one another.

8. The system as claimed in claim 2, wherein, for at least one load unit, the power converted by the inverter of the load unit is summed up within a time window and a threshold value is predefined for the summed power of the load unit, wherein the inverter of the load unit reduces its currently converted power to zero upon reaching the threshold value.

9. The system as claimed in claim 2, further comprising a storage unit comprising at least one battery and a bidirectional DC chopper, wherein a first terminal of the bidirectional DC chopper is connected to the DC source and a second terminal of the bidirectional DC chopper is connected to the battery, and wherein the bidirectional DC chopper is configured to determine a maximum possible power which can be currently stored from an input DC voltage applied to its first terminal according to a predefined second characteristic curve.

10. The system as claimed in claim 9, wherein the predefined second characteristic curve differs from the predefined first characteristic curve.

11. The system as claimed in claim 9, wherein the bidirectional DC chopper is configured to determine a currently required discharge power from an input DC voltage applied to its first terminal according to the predefined second characteristic curve.

12. A retrofit kit for an electrical distribution panel, in particular an apartment distribution panel, for use in a system according to claim 1, comprising: an inverter, comprising: an inverter output terminal configured to connect to an alternating voltage input of distribution panel, an inverter input terminal configured to connect to at least one renewable DC source, and a controller configured to determine an input DC voltage applied to the inverter input terminal and configured to determine a power to be currently converted from the input DC voltage and a power consumption data, a communication connection configured to transmit the power consumption data from a meter arranged in the distribution panel to the inverter, and a connection interface configured to connect the distribution panel to the renewable DC source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS:

(1) FIG. 1 shows a schematic illustration of an example configuration of a system according to the disclosure;

(2) FIG. 2 shows an example configuration of a load unit of a system according to the disclosure; and

(3) FIG. 3 shows an example configuration of a storage unit of a system according to the disclosure.

DETAILED DESCRIPTION

(4) FIG. 1 schematically shows an example configuration of a system 1 according to the disclosure. Load units 3, 3′, 3″ are connected to a grid 10 at an grid connection 9. This may be, for example, a low-voltage distribution grid of a public AC voltage grid which is generally provided by a grid operator and often has a multi-phase design. The load units 3, 3′, 3″ may be different apartments in an apartment building, floors or other subunits of a building or business. Furthermore, the load units 3, 3′, 3″ are connected to a DC distribution panel 12, to which a shared DC source 2 is also connected. The DC source 2 may be, for example, a photovoltaic installation on the roof of an apartment building. In this case, a DC/DC converter (not shown) will usually also be arranged between the PV generator and the DC distribution panel 12, said controller controlling the maximum power point (MPP) of the PV generator.

(5) FIG. 2 shows an example configuration of a load unit 3, as may be included in a system 1 according to the disclosure. The load unit 3 is connected at its input 4 to the grid connection 9 and to a DC distribution panel 12, as described above. Furthermore, the load unit 3 also comprises an output 5, to which electrical loads 11, 11′, 11″, 11′″ are connected via an AC distribution panel 16. The loads 11, 11′, 11″, 11′″ may be conventional loads in a household such as light fittings, washing machines, cookers etc. but also production machines, for example in a business. The loads 11, 11′, 11″, 11′″, . . . can be configured to consume single-phase or multi-phase AC power and the AC distribution panel 16 can distribute single-phase loads to a plurality of phases, as is conventional in a household, for example. The current power consumption from the grid 10 is determined in the load unit 3 by means of a power meter 13. For this purpose, a power meter input 14 is connected to the input 4. The power meter 13 may be an electricity meter, as is conventionally present in an apartment in an apartment building, for example. However, this meter must be configured at least to transmit the power consumption data currently measured by it.

(6) The load unit 3 also comprises an inverter 6, the inverter input 7 of which is connected to the DC distribution panel 12 and the inverter output 8 of which is connected to the connection between the input 4 and the output 5 of the load unit 3. The inverter 6 is configured to convert DC power available at its input into grid-compliant AC power and to feed the latter into the connection between the input 4 and the output 5 of the load unit 3 or the AC distribution panel 16.

(7) The power meter 13 transmits its currently measured power consumption data to the inverter 6 via a power meter output 15. This transmission can take place in a wired or wireless manner. The idea on which the system 1 according to the disclosure is based is that of consuming the power provided by the DC source 2 as completely as possible within the system 1. For this purpose, the inverter 6 may be configured in such a manner that it increases the power fed in by it until the power consumption from the grid has fallen to zero watts. All loads 11, 11′, 11″, 11′″ connected to the load unit 3 are either then supplied from the local DC source 2 (or there is no consumption at all).

(8) In order to determine whether the DC source 2 has power reserves, that is to say whether the inverter 6 can further increase the power fed in by it in order to supply the connected loads 11, 11′, 11″, 11′″, . . . with more power, the inverter 6 can measure the DC voltage applied to its input 7, for example. The DC voltage may fall in the case of high loading of the DC source 2. The inverter 6 can conclude, for example from a DC voltage which has fallen below a predefined threshold value, that it cannot increase the power converted by it any further. If the DC voltage continues to fall, it is possible to store the fact that the inverter 6 reduces the power fed in by it. Conversely, a high DC voltage can indicate that it is possible to increase the converted power.

(9) Alternatively, the inverter 6 could determine a signal modulated onto the input DC voltage as an indicator of the power reserves of the DC source 2 at its inverter input 7. This signal can be modulated onto the input DC voltage by a DC/DC converter (not shown) arranged between the PV generator and the DC distribution panel 12, and threshold values for this signal can then be used to determine the power reserves of the DC source 2, as described above. The threshold values or characteristic curves for describing the relationship between the signal or DC voltage level and the power reserves of the DC source 2 can be stored in the controller (not shown) of the inverter 6.

(10) The components of a load unit 3 can be in a conventional electrical distribution panel of an apartment. Since the electricity meter and the connections 4 and 5 are usually already present there, the distribution panel can also be subsequently easily upgraded to form a load unit 3 for use in the system 1 according to the disclosure by additionally installing an inverter 6, routing the DC distribution panel 12 and setting up a communication connection between the electricity meter 13 and the inverter 6.

(11) FIG. 3 shows an example configuration of a storage unit 20 for use in a system 1 according to the disclosure. The storage unit 20 comprises a battery 22 and a bidirectional DC chopper (DC/DC converter) 21. A terminal 23 of the DC/DC converter 21 is connected to the DC distribution panel 12 and, via the latter, the DC/DC converter is connected to the DC source 2. A terminal 24 of the DC/DC converter 21 is connected to the battery 22, wherein the battery 22 may consist of a plurality of battery subunits or a plurality of batteries. The DC/DC converter 21 acts, on the one hand, as a charging controller by taking energy from the DC distribution panel 12 and storing it in the battery 22 and, on the other hand, the DC/DC converter 21 also controls the removal and feeding of energy from the battery 22 into the DC distribution panel 12. In a similar manner to the load unit 3 described above, the DC/DC converter 21 can measure the DC voltage applied to its terminal 23 or a signal modulated onto the input DC voltage as an indicator of the power reserves of the DC source 2. The controller of the DC/DC converter 21 stores a second characteristic curve which establishes a relationship between electrical characteristic variables, for example between the applied DC voltage level and an available DC power or the maximum possible power which can be currently stored. This second characteristic curve may have a different gradient than the first characteristic curve, which results in a different response behavior of load units and storage units with respect to the same measured DC voltage level. This may mean that the loads connected to the load units are first of all supplied with electrical energy and the battery is charged only secondarily.

(12) If, for example, the measured DC voltage level falls below a further, lower threshold, this may indicate a higher local consumption of electrical power in comparison with the local generation. This may be the signal for the storage unit to feed its stored energy into the DC distribution panel 12 again. The previously locally excessive energy can thus be supplied for self consumption again.