DE102015001010A1 - Energy transmission system and method of its operation - Google Patents

Abstract

The invention relates to an energy transmission system for transmitting electrical energy from an energy storage system (3) comprising a plurality of battery cells (2) to an internal power supply network (1) which can be connected to consumers and which has at least one active power measuring device (13) for determining the voltage via the internal power supply network (1). transmitted active power is coupled. In order to achieve that at different loads, in particular at low loads, each optimal adjustment of the overall efficiency of the energy transmission system (4) is achieved, the invention proposes to start from a power transmission system (4), wherein each battery cell (2) of a Energy storage system (3) via a bidirectional power transmission module (8) comprising an inverter module (10), with the internal power supply network (1) is connectable. In this case, the energy transmission modules (8) comprise at least one switching device (11) which can be controlled by a central unit (12) via which the corresponding energy transmission module (8) can be electrically connected to the internal power supply network (1) or from which the energy transmission module (8) can be electrically disconnected in that, for a load connected to the internal power supply network (1), only so many energy transfer modules (8) are connected to the internal power supply network (1) by the central unit (12) just enough to supply that load with energy.

Description

The invention relates to a power transmission system for transmitting electrical energy from an energy storage system comprising a plurality of battery cells to an internal power supply network which can be connected to consumers. The invention further relates to a method for operating the energy transmission system when discharging the battery cells and to a method for operating the energy transmission system during charging of the battery cells of the energy storage system.

From the publication DE 20 2011 003 799 U1 For example, it is known to determine the active power required by a plurality of consumers by means of an active power measuring device and then to provide it by a power generator from renewable energy sources and / or an energy store. If in this case the available active power is not sufficient for the operation of all consumers, either consumers are switched off from the internal power supply network or other generators or the public alternating current network are switched on with the aid of an electronic central unit. In this case, the DC outputs of the energy storage and the power generator are connected in parallel and the corresponding DC voltage then converted via a common inverter in a line voltage corresponding AC voltage.

A disadvantage of this known device is, inter alia, that at low load of the inverter with respect to the available for the load to be provided active power requires a very high self-consumption of power and therefore a poor efficiency (ratio between the AC power taken from the inverter and the Inverter supplied DC power).

In the unpublished German patent application with the file number 10 2014 012 994.2 An energy transfer system is described which comprises at least two energy transfer modules which are connected to an electronic central processing unit controlling them. In this case, each energy transmission module is assigned to a battery cell, and each energy transmission module converts the DC voltage generated by its associated battery cell into an AC voltage whose voltage value corresponds to the AC voltage of the internal power supply network. The energy transfer modules each comprise a bidirectional DC converter module (DC / DC module) for transmitting the electrical energy of its associated battery cell to a DC link and a downstream of the DC / DC module, bidirectional inverter module (DC / AC module) for feeding electrical energy the DC link in the internal power grid.

The invention has for its object to provide a power transmission system, with which it is possible to achieve optimal adaptation of the overall efficiency at different loads, especially at low loads. The invention is further intended to disclose methods for operating the energy transfer system when discharging the battery cells and to a method for operating the energy transfer system during charging of the battery cells.

This object is achieved according to the invention with regard to the energy transmission system by the features of claim 1, with regard to the method for operating the energy transmission system during discharge of the battery cells by the features of claim 5 and with respect to the method for operating the energy transmission system during charging of the battery cells by the features of claim 6 , Further, particularly advantageous embodiments of the invention disclose the dependent claims.

Essentially, the invention is based on the idea of starting from an energy transmission system, as described by the unpublished German patent application with the file number No .: 10 2014 012 994.2 is described. In addition to the energy transmission system described in this patent application, the individual energy transmission modules are each connected to at least one controllable by the central unit switching device via which the corresponding energy transfer module with both the energy storage system and with the internal power supply network is electrically connected or through which internal power grid can be separated from the energy storage system.

Such a construction of the new energy transmission system makes it possible to easily achieve a transmission of electrical energy from the energy storage system to the internal power supply network with optimum efficiency. For this purpose, the active power transmitted by the internal power supply network for the operation of active consumers is continuously, or at predetermined time intervals, measured by the central unit. Based on the measured active power is then determined by the central unit, the minimum number of energy transfer modules, which is sufficient to provide the measured active power. Subsequently, the central unit generates switching signals, which on the Switching devices of the energy transfer modules act, such that only the energy transfer modules remain connected to the internal power supply network, which are imperative for the operation of the consumer.

With the aid of the energy transmission system according to the invention, however, it is also possible in a simple manner to recharge the battery cells of the energy storage system with optimum efficiency by means of at least one plant also connected to the internal power supply network for generating regenerative energy. For this purpose, the central unit constantly determines, or at predetermined time intervals, both the state of charge of the individual battery cells as well as by means of the plant for generating regenerative energy for charging the battery cells available charging power and then connects by pressing the switching devices only those energy transfer modules with the internal Power supply network whose associated battery cells are to be charged.

If less charging power is provided by the plant for generating regenerative energy for the charging process, as this is required for charging all to be charged battery cells, the central unit connects the internal power supply network only with the energy transfer modules whose associated battery cells have the lowest state of charge.

The switching devices for switching on and off the power transmission modules can be arranged both at the output of the respective DC / AC module and between the respective DC / AC module and the upstream DC / DC module of the corresponding energy transmission module. However, it has proven to be particularly advantageous if the switching devices are inserted high-flow side into the respective DC / DC module (i.e., on the input side into the corresponding energy transmission module). Because this is reliably avoided that are generated in deactivated power transmission module power losses in the subsequent units.

When using known DC / DC modules, which are bidirectional push-pull flow converters with full-bridge control (see, for example, from the Internet at http://de.wikipedia.org/wiki/Gegentaktflusswandler retrievable article, retrieved on 06.07.2014), the switching elements usually used for clocking, high-current side are preferably also used as a switching device for switching on and off of the DC / DC module.

It can also be provided that the switching elements of the corresponding DC / DC module at least one of the energy transfer modules each composed of a plurality of parallel, switchable power transistors (usually field effect transistors), so that depending on the state of these power transistors different energies on the corresponding Energy transfer module can be transferred to the internal power grid.

Further details and advantages of the invention will become apparent from the following, explained with reference to figures embodiment. Show it:

1 the schematic representation of a three energy transmission modules comprehensive, inventive energy transmission system, which connects an energy storage system with an internal power supply network;

2 the schematically illustrated DC / DC converter of a power transmission module with a switching device for switching on and off of the power transmission module;

3 a switching element consisting of three switchable power transistors for transmitting different energies via the energy transfer module to the internal power supply network.

In 1 is with 1 refers to a single-phase internal power grid, which is for example a building network. This internal power supply network 1 is with one of several battery cells 2 existing energy storage system 3 via an inventive energy transfer system 4 connected.

The internal power supply network 1 is also available with a public AC power network 5 as well as with a conventional photovoltaic system 6 via a solar inverter 7 connected.

The energy transfer system 4 includes three energy transfer modules 8th , each with one (or more parallel) battery cell (s) 2 of the energy storage system 3 and the outer conductor L of the internal power supply network 1 are connectable. In this embodiment, each of the three power transmission modules 8th a maximum output power of 400W available, so that on the internal power grid 1 a maximum power of 1.2 kW from the energy storage system 3 is transferable.

Each energy transfer module 8th includes a bidirectional DC-DC converter module 9 (DC / DC module) with a fixed transmission ratio for transmitting the electrical energy of the associated battery cell 2 on a DC link. The DC / DC module acts here 9 in the discharge process of the respective battery cell 2 as an up-converter (the cell voltage of the battery cell 2 , which is for example 3 V, is z. B. transformed to an intermediate circuit voltage of 60 V) and when charging the battery cell 2 as a down-converter.

The DC / DC module 9 of the respective energy transfer module 8th is in each case a bidirectional inverter module 10 Downstream (DC / AC module), so that the electrical energy from the DC link converted into a corresponding AC voltage and into the internal power grid 1 is fed.

According to the invention, it is now provided that the DC / DC modules 9 the energy transfer modules 8th on the input side each a switching device 11 included by a central processing unit 12 depending on the with the internal power grid 1 connected load (not shown) are anssteuerbar.

In 2 a corresponding DC / DC module is shown. This module consists of a known push-pull converter with full-bridge drive. According to the invention, the switching elements S1-S4 (usually controlled by a central unit), which are usually arranged on the input side for clocking the direct current, are also used as switching devices 11 for switching the DC / DC converter on and off, and thus the entire energy transfer module 8th , used. For this purpose, all switching elements S1-S4 are either opened or closed simultaneously.

The central unit 12 is with a bidirectional active power counter 13 connected.

Should now electrical energy from the energy storage system 3 on the internal power grid 1 be transferred, so first the switching devices 11 of all power transmission modules 8th opened and thus disabled the three power transmission modules. The power supply network 1 is therefore (with the photovoltaic system switched off) initially only with energy from the public AC grid 5 provided.

The active power counter 13 gives the difference value between the public AC grid 5 taken power to supply the consumer (eg 700 W) and that of the energy storage system 3 provided power (0 W) to the central unit 12 further.

This then generates a first switching signal for actuating the switching device 11 and thus to activate a first energy transfer module 8th ,

This energy transfer module 8th then provides the internal power supply network with a power of 400 W, so that the active power counter 13 the central unit 12 reports that there is still a difference of 300W to cover with the internal power grid 1 connected load is required.

The central unit 12 then activates a second energy transfer module 8th , which then provides the remaining power of 300W.

The with the internal power grid 1 Connected load is now exclusively from the battery network 15 powered without the third power supply module 8th must be activated and thus connected to this module battery cells 2 each remain in their charged state. The central unit 12 thus determines with the help of the active power counter 13 each the minimum number of energy transfer modules 8th , which are sufficient to provide the required real power for each load.

To further optimize the load-dependent energy supply through the energy storage system 3 It has proven to be advantageous if at least one energy transmission module 8th designed for different load ranges.

This is done using the in 2 shown Gegentaktflusswandlers characterized in that each of the four switching elements S1-S4 consists of several, arranged in parallel, switchable power transistors. In 3 this is shown for the switching element S1, which consists of three parallel-connected power transistors S1 ', S1''andS1'''.

In the case of a DC / DC module which, for example, has to transmit currents which correspond to a power of 500 W, multiple parallel-connected power transistors S1 ', S1' 'and S1' '' often have to be used when using semiconductor switching elements Protective circuits are provided for the respective switching element. On the other hand, if the power to be transmitted is only 200 W, the corresponding effort is lower and the power losses are lower.

Depending on the power of the energy transmission module to be transmitted 8th switch therefore the central processing unit 12 only one power transistor (lowest power to be transmitted) or more power transistors. It is initially assumed that the largest transferable power value (all three power transistors S1 ', S1''andS1''' in 3 are closed) and the actual power to be transmitted is measured at the output of the corresponding DC / DC converter. In accordance with this measured value, the unneeded additional power transistors (eg S1 'and S1'') are then switched off.

In the above-described mode of operation of the energy transmission system according to the invention 4 it was assumed that the photovoltaic system 6 is off. If this system is also in operation, the active power counter compares 13 Of course, not only those from the public AC network 5 provided power with that of the energy storage system 3 via the energy transfer modules 8th provided power, but also with the addition to the energy storage system 3 from the photovoltaic system 6 delivered power and then transmits the corresponding difference values to the central unit 12 ,

To the battery cells 2 of the energy storage system 3 by means of the same with the internal power supply network 1 connected photovoltaic system 6 charging, determines the central unit 12 also constantly, or at predetermined time intervals, both the state of charge of the individual battery cells 2 as well as by means of the photovoltaic system 6 for charging the battery cells 2 available charging power, and then connects by operating the switching devices 11 those energy transfer modules 8th with the internal power supply network 1 , their associated battery cells 2 have to be charged.

If less charging power from the photovoltaic system 6 is provided for charging, as this for charging all to be charged battery cells 2 is required, connects the central unit 12 the internal power supply network 1 only with selected energy transfer modules 8th , These are chosen such that initially the already discharged battery cells 2 to be charged.

Of course, the invention is not limited to the embodiment described above. Thus, the energy transmission system according to the invention comprises 4 in a practical embodiment, not only three, but twenty power transmission modules, each providing a power of 400W, so from the energy storage system 3 about 8 kW are transferable to the internal power grid.

Furthermore, it must be the internal power supply network 1 not necessarily a single-phase network. Rather, a three-phase internal power supply network can be provided, which can be connected to a three-phase public AC network. In this case, a plurality of energy transfer modules can then be connected to each of the three outer conductors of the internal power supply network.

Except the above-described control of the switching devices 11 according to the on the internal power grid 1 located load (consumer), has the central unit 12 further tasks. Among other things, it ensures that, in the case of grid-controlled operation (ie, the public grid operates without interference and is connected to the internal network), it is the energy storage system 3 and the energy transfer modules 8th existing battery network 15 through the public AC network 5 in terms of phase, frequency and amplitude is synchronized, so that the internal power grid 1 parallel energy from the public AC network 5 , the battery network 15 and the photovoltaic system 6 can be fed.

Unless the internal power supply network 1 not with the public AC network 5 is connected (especially so in case of power failure of the public network), the central unit provides 12 sure that the battery network 15 serves as a voltage source, wherein in the case of a three-phase power supply network, the voltages provided on the individual outer conductors of the internal power supply network 1 have a phase shift of 120 °.

Will the internal power grid 1 then again with the public AC network 5 connected because the power failure is resolved causes the central unit 12 a synchronization of the phases of the voltages on the outer conductors of the public AC network 5 and the outer conductors of the battery network 15 connected internal power supply network 1 , and the battery network 15 therefore acts again as a power source.

LIST OF REFERENCE NUMBERS

1

internal power supply network

2

battery cell

3

Energy storage system

4

Power transmission system

5

public AC network

6

Photovoltaic system, plant for the production of regenerative energy

7

Solar inverters

8th

Power transmission module

9

DC converter module, DC / DC module

10

Inverter module, DC / AC module

11

switching device

12

central processing unit

13

Active power measuring devices, active power meters

15

battery power

L

Outer conductor (internal power supply network)

L '

External conductor (public network)

S1-S4

switching elements

S1 ', S1' ', S1' ''

power transistors

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 202011003799 U1 [0002]
• DE 102014012994 [0004, 0007]

Cited non-patent literature

• http://de.wikipedia.org/wiki/Gegentaktflusswandler [0012]

Claims (7)

Energy transfer system for transferring electrical energy from a plurality of battery cells ( 2 ) comprehensive energy storage system ( 3 ) to an internal electricity supply network ( 1 ), which with at least one active power measuring device ( 13 ) for the determination of the internal power grid ( 1 ) is coupled with the features: a) the energy transmission system ( 4 ) comprises at least two energy transfer modules ( 8th ) and one of the energy transfer modules ( 8th ) controlling electronic central unit ( 12 ) with the active power measuring device ( 13 ), b) each energy transfer module ( 8th ) is connected to one or more battery cell (s) ( 2 ) of the energy storage system ( 3 ), wherein in the case of multiple battery cells ( 2 ) all the respective energy transfer module ( 8th ) associated battery cells ( 2 ) are connected in parallel; c) the energy transfer modules ( 8th ) each comprise a bidirectional DC-DC converter module (DC / DC module) ( 9 ) for transmitting the electrical energy of the associated battery cell (s) ( 2 ) to a DC link and a DC / DC module ( 9 ) downstream, bidirectional inverter module (DC / AC module) ( 10 ) for feeding electrical energy from the DC link to the internal power grid ( 1 ), and d) the energy transfer modules ( 8th ) each comprise at least one of the central unit ( 12 ) controllable switching device ( 11 ), depending on the internal power grid ( 1 ) a load transfer from the (n) the respective energy transfer module ( 8th ) associated battery cell (s) on the internal power grid ( 1 ) or interrupt this energy transfer. Energy transmission system according to claim 1, characterized in that the information provided by the central unit ( 12 ) controllable switching device ( 11 ) of the respective energy transfer module ( 8th ) is arranged such that it the DC / DC module ( 9 ) of the corresponding energy transfer module ( 8th ) turns on or off. Power transmission system according to claim 2, characterized in that it is in the DC / DC module ( 9 ) is a bidirectional Gegentaktflusswandler with full bridge drive, whose high current side arranged switching elements (S1-S4) for clocking of the (n) battery cell (s) ( 2 ) provided as a switching device ( 11 ) for switching on and off the DC / DC module ( 9 ) be used. Energy transmission system according to claim 3, characterized in that the switching elements (S1-S4) of the DC / DC module ( 9 ) at least one of the energy transfer modules ( 8th ) each composed of a plurality of parallel, switchable power transistors (S1 ', S1'',S1'''), so that depending on the state of these power transistors (S1 ', S1'',S1''') different energies on the corresponding energy transfer module ( 8th ) are transferable. Method for operating the energy transmission system according to claim 1 in the transmission of electrical energy from the energy storage system ( 3 ) to the internal power grid ( 1 ), with the characteristics: of the central unit ( 12 ) is kept permanently, or at predetermined intervals, by the internal power grid ( 1 ) measured for the operation of active consumers transmitted active power, based on the measured active power determines the central unit ( 12 ) the minimum number of energy transfer modules ( 8th ), which are sufficient to provide the measured active power, and the central unit ( 12 ) subsequently generates switching signals which are transmitted to the switching devices ( 11 ) of the energy transfer modules ( 8th ) such that only the energy transfer modules ( 8th ) with the internal power supply network ( 1 ), which are at least necessary for the operation of the consumer. Method for operating the energy transmission system according to claim 1 during charging of the battery cells ( 2 ) of the energy storage system ( 3 ) by means of at least one also with the internal power grid ( 1 ) connected to regenerative energy production ( 6 ), with the features: the central unit ( 12 ) constantly, or at predetermined intervals, both the state of charge of the individual battery cells ( 2 ) and by means of the regenerative energy plant ( 6 ) for charging the battery cells ( 2 ), and the central unit ( 12 ) then connects by actuation of the switching devices ( 11 ) those energy transfer modules ( 8th ) with the internal power supply network ( 1 ), their associated battery cells ( 2 ) should be charged. A method according to claim 6, characterized in that in the event that less charging power is provided by the plant for generating regenerative energy for the charging process, than that for charging all to be charged battery cells ( 2 ), the central unit ( 12 ) the internal power supply network ( 1 ) first with those battery cells on the associated energy transfer modules ( 8th ), the state of charge is the lowest.

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