WO2006084294A1

WO2006084294A1 - Rectifier system for supply in a 3-phase network and rectifier unit for a 3-phase network

Info

Publication number: WO2006084294A1
Application number: PCT/AT2006/000031
Authority: WO
Inventors: Gerald Bart; Clemens Bittmann; Edwin Gschandtner; Markus Gundendorfer
Original assignee: Fronius International Gmbh
Priority date: 2005-02-10
Filing date: 2006-01-20
Publication date: 2006-08-17
Also published as: DE212006000001U1; WO2006084294A8; AT501422A1; AT501422B1

Abstract

The rectifier system serves for individual supply of a 3-phase network, dependent on solar radiation. With increased solar radiation, more energy or power is supplied to the 3-phase network. It is hence sensible to combine the individual rectifiers (4) or connect the same in parallel as required, whereby a rectifier (4) is defined by a central controller (6) as master according to particular criteria and all further rectifiers serve as slaves. The single-phase rectifiers (4) are also arranged in three groups, i.e. one group per phase preventing imbalance in the phases.

Description

Inverter system for feeding into a 3-phase grid as well as inverter system for a 3-phase grid

The invention relates to an inverter system for feeding into a 3-phase network, in which a plurality of inverters and a control unit j e are connected in parallel as required and an inverter as a master and the other inverters are defined as a slave.

Furthermore, the invention relates to an inverter system for a 3-phase network, consisting of a cabinet or housing in which a plurality of inverters and a control unit are arranged, wherein the wiring for the interconnection of the inverter and the control unit and connection sockets for a power generator, in particular for solar modules, the input side and the output side are integrated in the cabinet for the 3-phase network.

In known inverter systems, such as according to US 6,252,785 Bl and DE 100 61 724 Al, several independent inverters for utilization reasons j e as required connected in parallel, wherein a control unit via switching elements according to inverter on or off, d. H . - that with increasing input power, an additional inverter is activated, whereby the input power is split and now a simultaneous feed of the active inverters in each phase of the 3-phase grid is performed. If, on the other hand, the input power drops, then an inverter connected to the grid is deactivated again. Furthermore, it is known from the prior art that the selection of which inverter to supply or. is turned off, is made by a control unit according to certain criteria, where a criterion may be, for example, the operating hours of the individual inverters or the selection of the inverters by means of a random generator.

Inverter arrangements with switchable inverter modules to meet the needs of varying loads are known from WO 2000/69221 A1 to CA 963 087 A or SU 1 812 606 A1. The disadvantage here is that the inverters are designed as separate units and such a structure is only possible for expensive three-phase inverters, as when using a single-phase inverter, as is desirable and provided in the inventive solution, there is a load unbalance in the phases of a 3-phase network can come, d. H . in that in each phase of the 3-phase network different energy is fed in by the inverters.

The object of the invention is that the most flexible possible structure is created to achieve a very high reliability.

The object of the invention is achieved by dividing the single-phase inverters into three groups, ie one group for each phase, and selecting the master by one or more inverters or a separate, central control unit according to stored criteria, in particular Operating hours of the inverter, is carried out, wherein the other possibly parallel-connected inverters are controlled or regulated as slaves and the master the slaves setpoints, in particular an operating point, specifies. The advantage here is that this always a change of the master, which is always the first active, is made, whereby the load on the components is approximately equal to the inverter is divided, whereby the life is significantly increased. In the inverter systems known from the prior art, the assignments of the master and the slaves are fixed, so that the master always has the highest operating hours, whereby the risk of failure of the inverter is substantially increased. Another advantage is that the flexible assignment of the master and a failure of the currently assigned master does not lead to a standstill of the inverter system, as simply from the remaining inverters a new master is defined. Thus, a very high reliability is achieved by such a structure of an inverter system, since only a failure of the inverter system is caused when all inverters are defective. It is also advantageous that the Selected master setpoints, in particular an operating point to the slaves pretends, as this optimum performance adjustment and optimum efficiency of the inverter system is achieved. The integrated intelligence in the inverter, so the controller can be performed weaker and thus more cost-effective, since the master only need to control a smaller number of slaves. In the central control unit, the most diverse data, such as operating hours, input power, output power, noise, etc., can be detected, evaluated and stored. Thus, it is achieved in an advantageous manner that the user all data on the central control unit are available and he can read or change them from there. Another advantage is that, for example, by a software update of the central control unit an adjustment can be made, since then due to the new software, the control unit from the stored data can set corresponding setpoints for the master or master.

Another advantage is that the inverters, so master and slave, are redundant, equal and similar structure and that the control or regulation for the energy supply to a phase of the 3-phase network of a built-in inverters intelligence, so a control device , is performed, since each inverter performs its own regulation and only the setpoints for the inverter must be specified. Thus, the data transfer between the inverters and / or a central control unit is reduced to a minimum. This also achieves faster regulation and thus faster adaptation of the inverters.

But it is also possible that the inverters, so master and slave, redundant, equal and similar structure and that the control or. Control the inverter for the power supply to a phase of the 3-phase network is controlled by the central control unit. This ensures that a very cost-effective design of the inverter can be used. - A -

It is also advantageous that a wide variety of setpoints for the control are determined by the central control unit and sent to the master or masters. This ensures that the user carries out his settings centrally at one point, namely the central control unit, whereupon the setpoint values are determined by the latter and then automatically forwarded to the master.

However, it is also possible for the inverters, ie master and slave, to transmit measured data, in particular actual values of the input power, output power, etc., to the control unit, which ensures that the central control unit knows the status of each of the inverters and thus It is possible to exert influence by adapting the setpoints to the inverters. Thus, it is advantageously achieved that the inverters always work with the optimum efficiency.

It is advantageous that the number of inverters to be switched in parallel is determined by the control unit, wherein the inverter switching on and off by software, for example via a data bus, or hardware, for example via switching elements, as this is achieved by always one balanced feed is given in the individual phases of the 3-phase network and thus no unbalanced load, which is allowed only within certain tolerances occur.

A significant advantage is achieved by the measure in which the operating hours of each inverter are recorded, evaluated and stored by the central control unit, since this enables the central control unit to draw conclusions about the expected life expectancy of the individual inverters.

It is advantageous if the master is selected according to the hours of operation stored in the central control unit, whereby the inverter with the lowest operating hours is selected by the central control unit, as this increases the service life of the individual inverters, since this is not always achieved in Operation are. By the measures that defective inverters are detected by the control unit and / or disturbances are transmitted from the inverters to the control unit, whereupon these are deactivated by the control unit and at the same time a non-activated, but still functional, and preferably independent from the group inverter is set, is achieved that a standstill of the inverter system is avoided. It can only happen that less energy is fed into the 3-phase grid, but this ensures that the inverter system always works.

Another advantage is that in the event of failure of a master of the control unit, an active or deactivated slave is determined as a new master, as this always optimum control or control of the inverter system is achieved and not as in the prior art in case of failure of the master Inverter system must be switched off.

By the measure that an equal number of inverters is activated by the control unit for a load unbalance of the phases per group, it is achieved that thereby a simple energy distribution of the available energy for the feed is created.

But it is also the measure that is given for a load unbalance of the phase per group at different performance trained inverters from the control unit, an equal output, advantage, since in the inverter system inverters can be used with different output powers and thus an adjustment can be made to the energy generated, for example, in a further expansion of solar modules.

Furthermore, the object of the invention is also achieved in that the inverters are constructed as modules and that in the cabinet or housing slots are arranged in the form of a rack, which are connected or wired to each other so that upon insertion of an inverter automatic contacting takes place. It is advantageous hereby that a simple exchange of the inverters can be made thereby and thus no service technician is necessary. In the event of an inverter failure, the user can simply pull it out of the rack and insert a new inverter, allowing the inverter system to work with its potential performance.

Each inverter can be used in any slot, so the user does not need any special knowledge when exchanging.

Furthermore, it is advantageous if the or. a slot consisting of slide rails and a slot is executed. Thus, it is achieved that systems already known from the prior art are used, whereby the cost of such an inverter system can be reduced.

An advantage is an embodiment in which the central control unit is part of the cabinet or housing or is present as part of an inverter, as a very flexible design of the system is achieved so that existing inverters can be used in this.

An embodiment in which an inverter or control device is arranged in the inverters ensures that each inverter is autonomously regulated by its own intelligence and thus the data transfer to a data bus is reduced.

In an embodiment in which an interface for controlling is arranged in the inverters via the central control unit, it is achieved that the inverter can dispense with its own intelligence and thus can manufacture it more cost-effectively. It is also possible that both inverters with their own intelligence and inverters without their own intelligence can be used together.

An embodiment is also possible in which the inverters are interconnected into three groups, that is to say a group for one phase, and the inverters are formed by hardware technology, for example by fixed cabling, or by software technology, for example via a data bus, to form the groups. are bound. It is thus achieved that cheap single-phase inverters can be used in the inverter installation, wherein in each case an inverter is fed into one phase of the three-phase grid.

In an embodiment in which each group is assigned an inverter as a master and if necessary further necessary inverters are connected in parallel as slaves, it is achieved that the control and regulation tasks are divided among several inverters so that the control device arranged in the inverters dimensioned less powerful can be.

An advantage is also an embodiment in which the slot is designed at the slot corresponding to the slot on the inverter, since each inverter can be used on each slot, and thus the user does not need any special knowledge when exchanging.

The fact that the inverters, ie master and slave, are designed similarly with regard to slots and slots, ensures that each inverter can be used as a master or as a slave. Thus, a very flexible design of the system is achieved, whereby the reliability of the system was substantially increased.

Also advantageous is an embodiment in which the inverters are designed with different output power, since this allows an optimal adaptation of the inverter system to the possible input power to be generated.

Finally, a training of advantage in which each inverter od in the cabinet. Housing is designed to equal rights and thus can be used as a master and slave, as it can be used by the central control j j eder inverter as a master. Thus, in the event of a defect of the master, it is possible that another inverter can be used as master and thus the inverter system does not stand still. The present invention will be further explained by means of an embodiment with reference to the drawings. Show:

Fig. 1 a cabinet according to the invention with a rack of an inverter system according to the invention in a schematic representation in an oblique view;

Fig. 2 the cabinet with rack of an inverter system in a schematic representation in elevation;

Fig. 3 the cabinet with rack of an inverter system in a schematic representation in a sectional side view according to the lines H-II in Figure 2;

4 shows an inventively provided inverter in a schematic representation.

In the Figs. 1 to 4, an inverter system 1 is shown, wherein the inverter system 1 is modular and integrated, for example, in a cabinet with a rack 2, which has similar slots 3 for inverter 4 and a slot 5 for a control unit 6.

The slots 3 and 5 consist of slide rails 7 and. "Slots 8, wherein the slots 8 for automatic contact- on insertion of the inverter 4 and the control unit 6, which has a corresponding slot 9, in particular in Fig. 4 for the inverter can be seen, serve, serve. At the rear end or at the back of the rack 2 is a wiring 10, as shown in FIG. 3 schematically shown between all slots 3 and 5, via the slots 8, executed. This makes it possible to use all inverters 4 of the same type, with respect to slots 3 and slots 8 and 9, at an arbitrary position, except for the central control unit 6. Thus, a defective inverter 4 can be easily replaced. It is also possible that not all slots 3 need to be equipped with inverters 4, but depending on the power of the inverter system 1 a corresponding number set. can be set.

Further, the insertion slots 3 and slots 8 and 9 are formed with respect to the output regardless of the type of the inverters 4, that is, as shown in FIG. H . that inverters 4 can be used with different power, so that an optimal power adjustment can be made. Likewise, the slots 3 with connection sockets 11, which are integrated in the cabinet 1 and the input side for energy producers, such as solar modules, or. on the output side for the 3-phase network, wired.

The inverters 4 preferably have their own intelligence, that is to say their own control device 12, as can be seen in FIG. 4, the inverters 4 being connected to one another and to the control unit 6 via a bus system. The inverters 4 are thus designed on an equal basis, whereby each inverter 4 can be used as master or slave, as will be explained in more detail below. However, it is also possible that inverters 4 are used without their own intelligence or control device 12, but they have an interface in order to be able to be coupled to the bus system. It is thus possible for these inverters 4 to be controlled by the control unit 6.

In the solution according to the invention, the inverter installation 1 is designed such that it is equipped with single-phase inverters 4, which, however, feed energy into a three-phase alternating voltage network. In this case, the inverter system 1 is constructed such that a group is defined per phase, d. H . in that three groups are formed with the inverters 4, each group feeding into one phase of the three-phase alternating voltage network.

The formation of the three groups can be done in terms of hardware or software technology. In a hardware solution, the slots 3 are divided directly into three groups via the wiring 10, d. H . in that, for example, in the case of an inverter installation 1 with 15 slots 3 for the inverters 4, as illustrated, the three groups are represented by j e- because five inverters 4 are formed, for which purpose the outputs of the five inverters 4 are connected in parallel. In such a wiring, a fixed assignment of the inverters 4 for a group is given.

If, however, the inverter system 1 is constructed by a software solution for forming the three groups, all the outputs of the possible inverters 4 to be used, ie the fifteen inverters 4 in the exemplary embodiment shown, are connected in parallel, with switchable switching elements being interposed in the cabling 10 or Inverter 4 are formed accordingly. Preferably, the software technical solution, since in this case the central control unit 6 via a data bus which connects the slots 3 and 5 or the slots 8 and 9 and the control unit 6 on the back of the rack 2, the inverter 4 or. can control the switching elements and thus a flexible group formation is possible. The hardware-technical solution requires a fixed cabling 10 or so-called DIP switch for coding, whereby each inverter 4 is permanently assigned to a group.

Furthermore, the cabinet is constructed such that it has a central cooling system for the inverter 4 and the control unit 6, wherein in the area of the footprint of the cabinet suction openings are arranged and on the opposite upper side of the cabinet, a central exhaust pipe is arranged. In order to achieve an air flow, a corresponding fan is arranged so that an air flow is caused in the cabinet from bottom to top and thus a cooling of the components is achieved.

The inverter system or the inverter system 1 thus serves for an individual supply of generated energy from single-phase inverters 4 in a 3-phase network. Preferably, the inverter system is used for solar modules, so that, depending on the solar radiation, an injection into the 3-phase network takes place, d. H . , the more solar radiation, the more energy resp. Performance is to be fed into the 3-phase network. For this reason, it makes sense to judge 4 as needed or to combine. for which a so-called master is defined as inverter 4 by the central control unit 6 and all further inverters 4 serve as slave. The central control unit 6 can for example be integrated in an inverter 4 or control the inverters 4 as a separate unit, as described above for the construction of the inverter installation 1.

Since in the solution according to the invention all inverters 4 have equal rights and, for example, have their own control device 12, each inverter 4 can be used as a master or a slave, the master being an inverter 4, which is the first power in a phase of the 3 Feeds in phase network.

The decision as to which inverter 4 serves as the master is made by the central control unit 6. This is done in such a way that the inverters 4 count their operating hours and transmit them to the central control unit 6, for which purpose fixedly defined times are provided or a query is started by the control unit 6, whereupon the inverters 4 send their operating hours. Subsequently, the inverter 4, which has sent the least sum of operating hours to the central control unit and is functional, is defined by the control unit 6 as a master. This ensures that the operation or use of the inverter 4 is kept approximately the same, whereby the life of all inverters 4 is extended, d. H. in that the load on the components in the overall system is reduced since different inverters 4 are always used as masters. Preferably, each inverter 4 has an identifier, so that when replacing an inverter 4 of the control unit 6 can recognize that now a new inverter 4 has been used and thus the operating hours for this inverter 4 newly queried and stored.

In addition to the operating hours, other data, such as the input power of the solar modules connected to the inverter system, or the output power, which is in the 3-phase sennetz is received by the central control unit 6, evaluated and stored. Furthermore, the central control unit will receive any malfunctions or error messages of the inverters 4, as a result of which the central control unit can store the status of the inverters 4, whether functional or defective or whether (as frequently) faults or error messages are sent by an inverter 4. However, not every fault message resp. Error message that an inverter 4 is defective and can not be used. It is determined by the control unit 4 due to the fault message, in particular a sent fault code, whether the inverter 4 is used or not.

However, if it is detected, for example, by the central control unit 6 that the master is defective, the control unit 6 automatically defines a functioning, active or deactivated slave as the new master. Each functioning inverter 4, whether active or inactive, can replace a defective inverter 4, preferably independently of the group. Thus, a difference from the known from the prior art inverter systems is given that in the inventive solution in case of failure of the master, the inverter system 1 is still ready for operation or. is operated, whereas in the prior art by the failure of the master, the entire system is stationary. Since a plurality of inverters 4 are arranged in the cabinet, it is thus almost impossible for the inverter system 1 to fail completely. Namely, if an inverter 4 is defective, there are still enough other inverters 4 available that can be used until the arrival of a replacement inverter 4. The defective inverter 4 can then be pulled out of the slot 3 due to the modular structure by the user and replaced by inserting a new inverter 4.

If energy is produced by the energy generators connected to the inverter system, such as solar modules, wind turbines, etc., then an inverter 4 becomes active and supplies the central control unit 6, whereby the operation of the inverter system 1 is recorded. Through the control unit 6, the inverter 4 with the lowest operating hours, ie the master, is then determined, which first feeds the energy produced into one phase of the 3-phase network. At the same time, two further inverters 4 are activated for the further phases, so that a same feed takes place simultaneously in all phases, ie, for the minimum operation of the inverter system 1 for feeding into the grid three inverters 4 are active, wherein the pending input power to the three inverters 4 is divided.

But it is also possible that at first only the master is activated, which feeds into a phase of the 3-phase network. If the input power increases so far that an additional inverter 4 can be activated, then a further inverter 4 is activated by the control unit 6 for the next phase of the 3-phase network. As the input power continues to increase, in turn the next inverter 4 is activated so that it is thus fed into each phase of the 3-phase network. If, therefore, inverters 4 are activated at each phase of the 3-phase network, an inverter 4 will be added for each phase as the input power increases further. in that after the first individual switching on of an inverter 4 per phase, three inverters 4, that is to say an inverter 4 for each phase, are subsequently activated. This can be continued until all inverters 4 of the inverter system 1 are activated.

If the input power continues to increase, one or more slaves per group are connected by the control unit 6, so that always the same number of inverters 4 per group are connected to the three-phase network. This is done by the fact that the control unit 6, as already mentioned, is constantly informed about the input power and output power from the master and thus recognizes due to predetermined adjustable setpoints that in the near future, the active inverter 4 can no longer process the input power. Therefore, the control unit 6, another slave per group with the next lowest operating hours connected, which receives the operating point MPP for independent control of the master, whereby the input power is divided and the Efficiency is increased or optimized. On the other hand, if the input power drops, one or more slaves per group are switched off by the control unit 6 and the still active inverters 4 take over the output power from the deactivated slave. In this case, all inverters 4 are switched off which have the highest operating hours, but since none of them are masters. This avoids that an inverter 4 is unnecessarily active, and thus ensures that the inverter system 1 always works with the best possible efficiency.

The switching on or off of an inverter 4 can be done, for example, by software via a data bus to which each inverter 4 is connected, or in hardware via a fixed wiring or a switch element which is controlled by the control unit 6, as described above has been . By the zu- or. Switching off an inverter 4 per group ensures that the same output power per phase is always fed into the 3-phase grid, which prevents unbalanced phases and does not exceed the permitted tolerance. The Zu- or. Switching off an inverter 4 per group is only necessary if all inverters 4 of an inverter system have the same output power, as is the case in the illustrated embodiment. If inverters 4 with different output power are used, it is not absolutely necessary to switch on or off an inverter 4 per group, but it must merely be ensured that the same power is fed into each phase of the 3-phase network, ie. H . in that, for example, on the first and second phases, in each case, an inverter 4 operates with 9 kW, whereas on the third phase, three inverters 4 are used, each with 3 kW. Then decreases the input power, so that not the full output power can be fed, so the first two inverters 4 are controlled so that they feed only more 6kW, and on the third phase, an inverter 4 is turned off. This in turn ensures that there is no unbalanced load during the feed-in. The control of the output power can be done in different ways. On the one hand, the control is performed by the master, for which purpose the master specifies the setpoint to all further active inverters 4, that is to say to the slaves. On the other hand, the control can also be done via the control unit 6, for which purpose the corresponding input power and output power is sent from the master, whereupon the control unit β sets a target value for the output power which is sent to all inverters 4, that is to master and slaves , The control to the specified value is performed independently by each inverter 4.

It is also possible that not only one master, but one master per group is determined by the central control unit 6. In this case, the operating point is not passed on by a master to the slaves, but the control unit 6 receives the operating points of the master and evaluates them. The evaluated operating point, which is the most effective for the efficiency of the inverter system is then passed from the control unit 6 to the master and subsequently to the slaves. Thus, three masters control three groups, the three masters in turn being controlled by the control unit 6. As described in the first embodiment, the failure redundancy, determination of the master, avoiding the unbalanced load, etc., also apply here.

The manner in which the control of the inverter installation 1 takes place can be determined by the manufacturer or else defined by the user via the control unit 6. Basically, it should be noted that the control unit 6 an input and output device, in particular keys, switches, encoders, LCD display, etc. , over which the user can make an individual adjustment or. the output device can read all the data, such as the actual and nominal input power and / or output power, the operating hours of the individual inverters, the faults that have occurred, etc.

Claims

Claims:

1. Inverter system for feeding into a 3-phase network, in which a plurality of inverters and a control unit are connected in parallel as needed and an inverter is defined as a master and the further inverters as a slave, characterized in that the single-phase inverter formed in three groups, ie for each phase a group is divided, and the selection of the master is carried out by one or more inverters or a separate, central control unit according to stored criteria, in particular after operating hours of the inverters, wherein the other possibly parallel-connected inverters as SIA ves be controlled or regulated and the master the slaves setpoints, in particular an operating point, pretending.

2. Inverter system according to claim 1, characterized in that the inverters, so master and slave, redundant, equal and similar structure and that the control or regulation for the energy supply to a phase of the 3-phase network of an integrated intelligence in the inverters , So a control device is performed.

3. inverter system according to claim 1, characterized in that the inverters, so master and slave, redundant, equal and similar structure and that the control or regulation of the inverter for the power supply in a phase of the 3-phase network controlled by the central control unit becomes .

4. Inverter system according to one of claims 1 to 3, characterized in that from the central control unit, the various setpoints for the control are set and sent to the master or master.

5. Inverter system according to one of claims 1 to 4, characterized in that the inverters, so master and slave, measurement data, in particular actual values of the input power, output power, etc. , to the control unit.

6. Inverter system according to one of claims 1 to 5, characterized in that the number of parallel inverters to be switched is determined by the control unit, wherein the switching on and off of the inverter software, for example via a data bus, or hardware, for example via switching elements, he follows .

7. Inverter system according to one of claims 1 to 6, characterized in that recorded by the central control unit, the operating hours j edes inverter, evaluated and stored.

8. Inverter system according to one of claims 1 to 7, characterized in that the master is selected according to the stored in the central control unit operating hours, being selected by the central control unit that inverter with the lowest operating hours.

9. Inverter system according to one of claims 1 to 8, characterized in that defective inverters detected by the control unit and / or disturbances are transmitted from the inverters to the control unit, whereupon they are deactivated by the control unit and at the same time a non-activated, but j edochoperable and preferably determined by the group of independent inverters.

10. Inverter system according to one of claims 1 to 9, characterized in that in case of failure of a master of the control unit, an active or inactive slave is determined as a new master.

11. Inverter system according to one of claims 1 to 10, characterized in that for a load unbalance of the phases per group an equal number of inverters is activated by the control unit.

12. Inverter system according to one of claims 1 to 10, characterized in that for a unbalance compensation of the phase per group at different performance designed inverters from the control unit a same output performance is given.

13. Inverter system for a 3-phase network, consisting of a cabinet or housing in which a plurality of inverters and a control unit are arranged, wherein the wiring for the interconnection of the inverter and the control unit and connection sockets for a power generator, in particular for solar modules, input side and output side for the 3-phase network are integrated in the cabinet, characterized in that the inverters are constructed as modules and that in the cabinet or housing slots are arranged in the form of a rack, which are connected or wired to each other so that when inserting an inverter an automatic Contact takes place.

14. Inverter system according to claim 13, characterized in that a slot is made of slide rails and a slot.

15. Inverter system according to claim 13 or 14, characterized in that the central control unit, a part in the cabinet or housing or as part of an inverter is executed.

16. An inverter system according to one of claims 13 to 15, characterized in that a control device is arranged in the inverters.

17. Inverter system according to one of claims 13 to 16, characterized in that an interface for controlling via the central control unit is arranged in the inverters.

18. Inverter system according to one of claims 13 to 17, characterized in that the inverters in 3 groups, that is a group for one phase, are interconnected.

19. Inverter system according to one of claims 13 to 18, characterized in that the formation of the groups, the inverter hardware technology, for example by a fixed Wiring, or software technology, for example via a data bus, are connected.

20. Inverter system according to one or more of claims 13 to 19, characterized in that each group is assigned an inverter as a master and ev. Further necessary inverters are connected in parallel as slaves.

21. Inverter system according to one or more of claims 13 to 20, characterized in that the inverters, so master and slave, are carried out similar in terms of slots and slots.

22. The inverter system according to claim 21, characterized in that the inverters are designed with different output power.

23. Inverter installation according to one of claims 13 to 22, characterized in that each inverter in the cabinet od. Housing is designed to equal rights and thus can be used as a master and slave.