DE102011010172A1 - Signal generating inverter and operating method for an inverter - Google Patents

Abstract

An inverter (20) for feeding power provided by a DC power source (10) via a DC link (60) to an AC power grid (30) is disclosed. The inverter (20) has a status unit (25) for detecting a normal state and a special state of the inverter (20), which is coupled to a signal generator (40) for generating a life signal (70) on the direct current connection (60) only in the normal state, the life signal (70) is generated. The life signal (70) can be generated inductively, capacitively or via a triggering of a tactile switch (150). The life signal (70) can be received via an associated switching element, which converts the DC power source (10) or the DC link (60) in the absence of the life signal (70) in a safe state. A corresponding operating method for the inverter (20) is also disclosed.

Description

The invention relates to an inverter, in particular an inverter as part of a power generation plant having the features of claim 1, and a method having the features of claim 13.

Inverters find use, inter alia, in decentralized power generation plants, in particular solar plants, in order to convert the direct current provided therein by a generator into grid-compatible alternating current which is fed into a public power grid or into a stand-alone grid. With the increasing use of such decentralized power generation plants whose generators are installed not only freestanding, but also on private, public or commercial buildings in solar systems, it is increasingly becoming aware that the DC voltage provided by the generators poses a potential danger to people due to electric shock or arcs represents. This danger exists in particular for fire-fighters with extinguishing and rescue work on and in the building by the generator itself as well as by in the building from the generator to the inverter running direct current lines, since at these also after the usual in the case of a fire alternating voltage cut off the power supply of the building as before supplied by the generator DC voltage is applied. The danger is for the same reason also for installers in installation, maintenance and repair work on the DC side of the power plant. Safety devices for reliably transferring the live parts of a power plant to a safe state are therefore desirable.

The font DE 10 2006 060 815 A1 discloses a solar power plant whose generator is composed of a plurality of interconnected PV modules, and which feeds via an inverter into a low-voltage grid. Each module is associated with a switching element, with which the respective module is switched dead in a missing enable signal. The enable signal is a modulated on the DC lines carrier signal, the release is to be carried out by a downstream equipment. By the DE 10 2006 060 815 A1 Thus, initially only a safe generator is created; However, there is no concrete indication in the text as to which means and by what triggering event a downstream resource will cause such a release.

As an alternative to a switching action on the PV modules describes the DE 10 2005 018 173 B4 a photovoltaic system with a generator field, which is connected by means of DC cables with an inverter, in which the generator field can be switched by a switching device on the generator field in a safe operating point. The triggering of a protective device contained in the switching device takes place here by a control signal via a separate control line, being provided as triggering means only solutions such as manual switches or sensors. Also by the DE 10 2005 018 173 B4 Thus, a secure generator is provided for which there is a need for an efficient and reliable generation of a control signal.

Against this background, it is an object of the present invention to provide an inverter capable of generating a signal receivable by associated switching elements having receiving units, such that a correspondingly established generator or the electrical connection between the generator and the inverter is selectively transferred between a safe state and an operating state for feeding power to an AC grid.

The inverter according to the invention as part of a power generation plant for feeding a power, which is provided by a DC power source via a DC link in an AC power network has a status unit for detecting a normal state and a special state, or for distinguishing between these states of the inverter. This status unit is coupled to a signal generator for generating a life signal on the DC link, such that only in the normal state, the life signal is generated. The life signal may then be received, for example, from a suitably established receiver associated with a generator or part of a generator, such as a module, then from a safe state in which there is no or only a safe voltage on the lines of the DC link the power generation plant is present, in the necessary for feeding power into an AC power operating condition to transfer. Accordingly, such a generator will remain in the safe state or transferred into this, if the life signal is not or no longer generated in the case of the special state of the inverter.

In the event of fire, but also during installation, maintenance or repair work, it is a common measure to perform an AC side shutdown of the power supply of a building or the affected parts of the building. The inverter is therefore preferred set up so that the status unit recognizes the special status when the AC network is no longer available.

In one possible embodiment, the signal generator is set up to generate a high-frequency alternating-current signal lying a multiple above a mains frequency as a life signal. This alternating current signal can be inductively coupled into the direct current connection, for example, by means of a coupling coil which is connected to the signal generator. Inverters often have additional DC-DC converters, such as a step-up converter, step-down converter or a galvanically isolating resonant converter, in the construction of which coils are used in front of the converter circuit which converts the direct current into alternating current. In an advantageous embodiment, the coupling coil can therefore be part of a DC converter of the inverter.

An alternative form of coupling of the signal generated by the signal generator life signal in the DC connection can be realized that the signal generator is connected via a coupling capacitor for capacitive coupling of the life signal to the DC connection.

Instead of an inductive or capacitive coupling of the life signal generated by the signal generator in the DC link, the signal generator, the life signal on the DC voltage connection by means of a clockable switch, the drive is connected to the signal generator, generate.

For example, by means of the tactile switch, the signal generator can generate a current signal or voltage signal corresponding to the switch timing on the DC connection. The switch can be arranged for example in one or between the DC lines. It can also be used to generate the signal several switches to generate the signal. In particular, existing switches for generating the signal can also be used in the converter circuits of the inverter, for example in a step-up converter or step-down converter. The task of signal generation can be combined in this case with the task of the switch or switches within the converter circuit.

Inverters typically include a Maximum Power Point Tracking (MPP) unit configured to adjust the power of the DC power source to a maximum value by varying a voltage of the DC power source. Such an MPP tracker may also serve as a signal generator and generate the life signal on the DC link, the life signal of a characteristic magnitude of the voltage generated by the MPP tracker, in particular a frequency of change, a jump level or a rate of variation of the voltage, or a combination corresponds to these sizes.

In a further embodiment of the inverter according to the invention can be generated by the signal generator not only in the normal state, the life signal, but also in the special state, a second signal different from the life signal on the DC link.

It is also possible that the signal generator is deactivated in the special state.

In order to prevent a corruption of the life signal or the signal generated in the special state, for example by interference with an existing on the DC link interference signal, but also to a possibly possible confusion, for example, a present on the DC link interference signal with the life signal or the signal generated in the special state, it can be advantageous to the life signal and / or the signal generated in the special state composed of complex signal forms, such as code sequences, which have a redundancy function.

In a method according to the invention for operating an inverter with a direct current connection for connecting a direct current source and an alternating current connection for connection to an alternating current network, an operating state of the inverter is first determined, at least distinguishing between a normal state and a special state. Only in the case that a normal state of the inverter is detected, the inverter generates a live signal on the DC link. The life signal can be used as described above to implement a backup function for the DC power source.

The determination of the operating state can be advantageously carried out in the form of a monitoring of the AC network to the AC connection, whereby the change in the special state can be brought about by an activation of the inverter or the building in which the inverter is located, of an electrical supply network, which is a standard measure of the fire department in case of fire.

The generation of the life signal can be carried out by operating a DC converter or an MPP tracker of the inverter in a first manner, which differs from a second mode of operation, which use the aforementioned components of the inverter in a special state. The two modes of operation differ by temporal courses of current and / or voltage on the direct current connection, whose differences then make up the life signal.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages of embodiments according to the invention necessarily having to be achieved. Further features can be taken from the drawings. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims.

Of course, it is also possible to provide the inverter as a multi-phase, in particular three-phase inverter, although in the interest of clarity in the following the invention is explained only by the example of a single-phase inverter. An implementation of the inventive concept on multiphase systems is familiar to the expert.

In the following the invention is illustrated by means of figures. Show it:

1 a block diagram of a power generation plant according to the invention,

2 an inverter with inductive coupling of a life signal into a direct current connection,

3 an inverter with capacitive coupling of a life signal into a direct current connection,

4 an inverter in which the inductive coupling is realized via a coupling coil as part of a DC-DC converter, and

5 an inverter in which the life signal is generated by means of a tactile switch.

In the 1 shown power generation plant 1 has a DC source 10 on, for example, a photovoltaic generator, which has a direct current connection 60 with an inverter 20 connected to the power transmission. The power transmitted as DC is supplied by the inverter 20 by means of a converter circuit 50 converted into an alternating current and via an alternating current connection 90 in an AC network 30 fed. According to the invention, the inverter 20 a status unit 25 on, which monitors the operating state of the inverter, and between a normal state and a special state of the inverter 20 can differentiate.

In general, the special state is at least assumed when events are detected by the inverter, the safe state of the DC power source 10 or the DC connection 60 require. This can be, for example, events of an electrical nature, which the inverter detects, for example, via its current and voltage sensors or its programming. Furthermore, safety-relevant events such as the operation of an emergency stop switch, smoke, fire, gas or water alarms or such events as the inverter 20 via its communication devices receives as data signals, a change of the status unit 25 trigger into the special state. In particular, the transition to the special status between inverters which are in a data connection with each other, can be reported further, so that a common shutdown of a plurality of inverters in case of danger is made possible. Also a self-test of the functionality of the inverter 20 can be used to cause a transition between the states of the inverter.

Information about the status is sent to the status unit 25 coupled signal generator 40 transmit that a life signal 70 only then generated and in the DC connection 60 brings in when the inverter 20 is in the normal state. The life signal 70 is via the DC connection 60 to a receiver 80 transmitted, which is adapted to the presence of the life signal 70 on the DC connection 60 determine.

The recipient 80 can be near the DC source 10 are located and depending on the presence of the life signal 70 on the DC connection 60 the DC source 10 check. For example, it is conceivable that the receiver 80 the supply of power from the DC power source 10 in the absence of the life signal 70 on the DC connection 60 interrupts, for example, by connecting the DC link 60 between DC source 10 and inverters 20 disconnects or the DC source 10 shorts. In this way, the DC connection 60 at the instigation of the inverter 20 be transferred to a safe state, if necessary.

In addition, the inverter can 20 the successful transition of the DC source 10 in the safe state via the DC link 60 Detect and signal to the outside or on existing communication channels weiterermelden, for example, by current or voltage on the DC link 60 be determined or by the recipient 80 via another transmission path (wired or wireless) the successful transfer of the DC power source 10 in the safe state to the inverter 20 or reports its own signaling device. On the part of the inverter 20 the successful transition to the safe state can be connected so that only in this case the DC connection 60 can be disconnected, for example by an electromechanical safety lock is released from corresponding connectors.

The transition from a normal state to a special state can hereby be brought about because of a large number of events. For example, the detection of a network loss can lead to a special status caused by the inverter 20 is accepted, whereupon the signal generator 40 the generation of the life signal 70 on the DC connection 60 completed. For this purpose, the in 2 shown inverters 20 a network monitoring 110 for monitoring the AC mains 30 on, here at the AC power outlets 91 . 92 connected, with the network monitoring 110 with the status unit 25 is connected, and a corresponding signal in case of elimination of the AC network 30 transfers. Parallel in this case also typically the AC connection 90 at the connections 91 . 92 by means of a mains disconnector 130 separated.

The inverter continues to show 2 a coupling coil 100 , which is an inductive coupling of the signal generator 40 generated life signal 70 in the DC connection 60 , made by the DC connections 61 . 62 , allows. In the case of inductive coupling includes the life signal 70 preferably a high-frequency AC signal in a frequency range between 10 kHz and 300 kHz.

Alternatively, the coupling of a high-frequency life signal 70 also be done in a capacitive manner, the frequency range is comparable. Here is how in 3 shown between the signal generator 40 and the DC connection 60 a coupling capacitor 140 arranged. Both in the inductive coupling according to 2 as well as in the capacitive coupling according to 3 is the signaler 40 galvanic from the DC connection 60 separated.

In a particularly cost-effective variant, the inductive coupling can also be realized by means of the inductance, which is part of a DC-DC converter 120 , for example a boost converter. A corresponding structure of an inverter 20 is in 4 shown. Alternatively, other known types of DC-DC converters can be used.

Instead of an inductive or capacitive coupling, the generation of the life signal 70 also be accomplished by a tactile switch 150 that with the DC connection 60 connected via the signal transmitter 40 is controlled. It is conceivable that via the control of the tactile switch 150 a voltage or current source clocked with one of the terminals 61 . 62 the DC connection 60 connected, and so the life signal 70 generated in the form of a switch timing corresponding current signal or voltage signal. The tactile switch 150 can specifically for this purpose in the inverter 20 be integrated, or the signaler 40 is so connected to the control of an already existing tactile switch that its timing is changed so that the life signal 70 on the DC connection 60 The switch is also another function within the inverter 20 Fulfills. An example of an existing tactile switch is a switch of a DC-DC converter 120 out 4 dar. Here, the life signal 70 For example, in the choice of an operating frequency of the switch or in the selection of a characteristic clock pattern exist.

Another possibility, without additional components, is the generation of a life signal 70 To accomplish, is the use of a so-called MPP (Maximum Power Point) tracker, whose task is a voltage of the DC power source 10 adjust so that this gives a maximum performance. For this purpose, the MPP tracker varies the voltage of the DC power source at regular intervals 10 and checks whether a higher power can be achieved by varying the voltage. The signal generator 40 can interact with the MPP tracker such that a characteristic size for the operation of the MPP tracker depending on the state caused by the status unit 25 is given, is changed. As possibilities for the changed characteristic size come For example, the time intervals in which the voltage is changed, or the amount of voltage change, or the speed at which the voltage is changed, or combinations of these sizes into consideration. In this case, then there is the life signal 70 in the choice of a value for the corresponding characteristic size.

Both in the case of using the DC-DC converter 120 as well as in the case of using the MPP tracker to generate the life signal 70 thus becomes the inverter 20 used in the normal state in a first mode of operation and in a special state in a second mode of operation, wherein the two modes of operation to mutually distinguishable temporal courses of current and / or voltage on the DC connection 60 to lead.

In general, the signal transmitter 40 in the case of the inverter 20 in the special state, a second signal to the DC link 60 imprint that is different from the life signal 70 different, or the signaler 40 can be disabled in this case and no signal. It is also conceivable that the life signal 70 and / or the second signal are composed of complex signal forms which have a redundancy function, such that an erroneous recognition of the one or the other signal form by the receiver 80 can be minimized or excluded.

The return from the special state to the normal state of the inverter 20 This can be triggered by the fact that the inverter has caused the event 20 has changed from the normal state to the special state, no longer exists. For example, the inverter 20 automatically return to normal when the AC mains 30 after the previous omission resumes, which by the network monitoring 110 can be detected. Often it is also desirable that the inverter 20 does not automatically return to normal.

For example, this is the case when the result that triggered the change to the special state was a safety-relevant event, such as the shutdown of the network by the fire department due to a fire. In this case, it would be desirable that the change from the special state to the normal state only by a manual intervention on the inverter 20 can be made.

If it is desired to maintain the normal state during the time during which the DC source 10 no power over the inverter 20 feed, in the case of a photovoltaic system, for example, at night, the life signal 70 continue to be generated during this time. So that the energy required for this is available, it is advantageous to the inverter 20 even during this time with the AC mains 30 to connect, and not, as is often customary, via the power disconnector 130 disconnect from this. This includes the alternative that the AC connection 90 for feeding power into a connected AC network 30 is separated, but another AC connection to supply a vehicle electrical system of the inverter 20 is maintained. In the latter case, the elimination of the AC network 30 be accomplished via a monitoring circuit of the electrical system. Of course, the use of an energy storage, z. As a rechargeable battery, conceivable to ensure the maintenance of the life signal generation or condition monitoring during the periods in which other energy sources are not available.

The invention is not limited to the described embodiments, which can be modified in many ways and expertly supplemented. In particular, it is possible to carry out the features mentioned in other than the said combinations. Also, other or additional actions can be triggered within the power generation system with the life signal.

LIST OF REFERENCE NUMBERS

1

Power generation plant

10

DC power source

20

inverter

30

AC power

40

signaler

50

converter circuit

60

DC link

61, 62

DC power connector

70

live signal

80

receiver

90

AC connection

91, 92

AC connection

100

coupling coil

110

network monitoring

120

DC converter

130

Mains switch

140

coupling capacitor

150

tactile switch

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 102006060815 A1 [0003, 0003]
• DE 102005018173 B4 [0004, 0004]

Claims (15)

Inverter ( 20 ) for feeding a power from a DC power source ( 10 ) via a direct current connection ( 60 ) into an AC network ( 30 ), characterized in that the inverter ( 20 ) a status unit ( 25 ) for detecting a normal state and a special state of the inverter ( 20 ), which in such a way with a signal generator ( 40 ) for generating a life signal ( 70 ) on the DC connection ( 60 ), that only in the normal state the life signal ( 70 ) is produced. Inverter according to claim 1, characterized in that the inverter is set up such that the status unit ( 25 ) in the absence of the AC mains ( 30 ) recognizes the special status. Inverter according to Claim 1 or 2, characterized in that the signal generator ( 40 ) for generating a high-frequency alternating current signal as a life signal ( 70 ) is set up. Inverter according to claim 3, characterized in that the signal generator ( 40 ) with a coupling coil ( 100 ) for the inductive coupling of the life signal ( 70 ) into the DC connection ( 60 ) connected is. Inverter according to Claim 4, characterized in that the coupling coil ( 100 ) Part of a DC-DC converter ( 120 ) of the inverter ( 20 ). Inverter according to claim 3, characterized in that the signal generator ( 40 ) via a coupling capacitor ( 140 ) for the capacitive coupling of the life signal ( 70 ) with the direct current connection ( 60 ) connected is. Inverter according to one of claims 1 to 3, characterized in that the signal transmitter ( 40 ) with a control of a tactile switch ( 150 ) for generating the life signal ( 70 ) on the DC connection ( 60 ) connected is. Inverter according to Claim 7, characterized in that the signal generator ( 40 ) by means of the tactile switch ( 150 ) a current signal or voltage signal corresponding to the switch timing on the DC connection ( 60 ) generated. Inverter according to claim 1 or 2, wherein the inverter ( 20 ) an MPP tracker as a signal generator ( 40 ) for adjusting the power of the DC power source ( 10 ) by varying a voltage of the DC power source ( 10 ) is set to a maximum value, characterized in that the life signal ( 70 ) corresponds to a characteristic quantity of the variation of the tension, in particular a change frequency, a jump height or a variation rate of the tension. Inverter according to one of the preceding claims, characterized in that the signal generator ( 40 ) in the special state a second, from the life signal ( 70 ) different signal on the DC connection ( 60 ) generated. Inverter according to one of Claims 1 to 9, characterized in that the signal generator ( 40 ) is deactivated in special status. Inverter according to one of the preceding claims, characterized in that the life signal ( 70 ) and / or the second signal are composed of complex signal forms that provide a redundancy function. Method for operating an inverter ( 20 ) with a direct current connection ( 60 ) for connecting a DC power source ( 10 ) and an AC connection ( 90 ) for connection to an AC mains ( 30 ) comprising the steps of: - determining an operating state of the inverter ( 20 ), whereby at least one distinguishes between a normal state and a special state and - generating a vital signal ( 70 ) on the DC connection ( 60 ) only in the case that a normal state of the inverter ( 20 ) is detected. A method according to claim 13, characterized in that the detection of the operating state monitoring the AC network ( 30 ) at the AC connection ( 90 ). Method according to claim 13 or 14, characterized in that the generation of the life signal ( 70 ) a first mode of operation of a DC-DC converter ( 120 ) or an MPP tracker of the inverter ( 20 ), which differs from a second mode of operation, which the inverter ( 20 ) used in special condition.

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