DE102013221446A1 - Inverter system and PV system - Google Patents

Abstract

The invention relates to an inverter system in which an inverter unit is separated on the AC side when an arc is detected by an arc detection device.

Description

Field of application and state of the art

The invention relates to an inverter system having an inverter unit. The inverter unit has a DC side for electrical connection to at least one photovoltaic (PV) generator and / or an electrical energy store and an AC side with at least one connection pole for electrical connection to a phase of an AC voltage network.

Such inverter systems are preferably equipped with a safety device, which is referred to, for example, as a fault arc protection device, which interrupts a current flow in the event of an arc in a wiring on the DC side or in a photovoltaic generator and thereby extinguish the arc. This is usually done in generic inverter systems by separation on the DC side with a DC switch suitable for this purpose or with a semiconductor switch. DC switches that are suitable for such purposes are usually expensive and expensive. In turn, semiconductor switches have the disadvantage that they are lossy.

The invention furthermore relates to a photovoltaic (PV) system which has a PV generator and / or an electrical energy store and a described inverter system. In such a PV system, the same problems as just described occur.

Tasks and solution

It is therefore an object of the invention to provide an inverter system in which an interruption of the current flow is possible without the problems mentioned at the occurrence of an arc. It is a further object of the invention to provide a PV system having such an improved inverter system.

This is inventively achieved by an inverter system according to claim 1 and a PV system according to claim 5. Advantageous embodiments are described for example in the subclaims. The content of the claims is hereby incorporated by express reference to the content of the description.

The invention relates to an inverter system, comprising: an inverter unit, comprising: a DC side for electrically connecting to at least one photovoltaic (PV) generator and / or an electrical energy store, and an AC side having at least one connection pole to electrical connection to a phase of an alternating voltage network, at least one controllable switching means with a switching contact, which is looped between the terminal pole of the inverter unit and the phase of the alternating voltage network and having a closed and an open switching state, and an arc detection device for detecting an arc, with such the switching means is in operative connection, that the switching contact occupies the open switching state in a detected arc and thus separates the inverter unit of the phase or phases, whereby the arc extinguished.

It is understood that the inverter unit may have a plurality of terminal poles, each of which is assigned exactly one controllable switching means. In particular, the inverter unit may have three connection poles, wherein correspondingly three switching means are provided. A respective switching contact of the switching means is looped in this case between an associated terminal pole and an associated phase of a three-phase network.

By means of the inverter system according to the invention can be used more cost-effective and easier-to-use components than in embodiments according to the prior art, which have, for example on the DC side an arc fault protection device with DC side separation. This is due in particular to the fact that components which enable separation or switching on the AC side are significantly cheaper than corresponding components which enable separation or switching on the DC side. The use of lossy semiconductor switches can be dispensed with. According to the feed-in function of the inverter unit is terminated by the separation or the (Ab-) switching on the AC side of the inverter unit and thus interrupted a power consumption on the DC side. This leads to a reliable extinction of the arc.

The inverter unit is typically configured to convert a DC voltage supplied on the DC side to an AC voltage to be output on the AC side. It can also be a transformation of the voltage to a lower or higher voltage.

The AC voltage network can be, for example, a typical public three-phase power grid or else an island power supply. An island power supply, for example, to supply a local limited, not with supraregional Connected to power grid connected area, such as a mountain lodge or a remote area in a poorly developed land.

The switching means may preferably be a circuit breaker or a circuit breaker. Such switching means enable switching under load.

The switching means may be a bistable relay. This has in comparison to monostable relays or other monostable switching means in particular the advantage that neither of the two switching states requires a permanent current flow to its maintenance. The bistable relay can also be designed as a circuit breaker or circuit breaker, so that the advantages described in the preceding paragraph are additionally achieved.

It should be noted that the design of the switching means as a bistable relay, in particular on the AC side of the inverter unit, is an independent idea which can be carried out independently of the other features described. This idea can also be combined with any other features described herein.

The arc detection device can be embodied, for example, by means of a camera, a voltmeter, a temperature sensor or otherwise. Preferably, it is associated with the DC side of the inverter unit. For example, it may be associated with a switch, wiring or other electrical component on the DC side. In order to determine whether an arc exists, the arc detection device can measure and evaluate both a voltage curve and a current profile over time. In particular, the current profile has arcing characteristic, high-frequency components. For arcs in series with the load, a current may be below a tripping limit of circuit breakers. It should also be noted in the relevant literature to avoid repetition.

Under an operative connection can be understood both an immediate and an indirect connection or coupling between the arc detection device and the switching means, which leads to the fact that the switching contact occupies the open switching state in a detected arc. For example, in a direct connection, a direct control line may be present. In the case of an indirect connection, for example, an output signal of the arc detection device can first be supplied to a control device, which in turn controls the switching device. This allows additional functions to be implemented.

According to one embodiment, the inverter system has a photovoltaic inverter, wherein the inverter unit, the switching means and the arc detection device are integrated in the photovoltaic inverter. This achieves a compact arrangement which is protected against unauthorized access to individual parts.

According to an alternative embodiment, the inverter system has a separate from the inverter unit switching device, wherein the switching means and the arc detection device are integrated into the switching device. This allows a separate arrangement of the inverter unit relative to the switching means and the arc detection device. This allows the use of the invention even with conventional inverters.

The invention further relates to a photovoltaic (PV) system, comprising: a photovoltaic (PV) generator and / or an electrical energy storage, and an inverter system according to the invention, wherein the DC side of the inverter unit with the PV generator and / or the energy store is electrically connected.

The PV generator can be, for example, a photovoltaic module or an arrangement of a plurality of photovoltaic modules. The electrical energy store may be, for example, a battery, a rechargeable battery, an accumulator, a fuel cell or another suitable energy store.

The PV system according to the invention makes it possible to realize the advantages described with respect to the inverter system according to the invention for a complete PV system which can be used, for example, for feeding into a public grid and / or establishing a stand-alone power supply.

Short description of the drawing

The invention will be described in detail below with reference to the drawings. Here are shown schematically:

1 a first embodiment of a PV system and

2 : a second embodiment of a PV system.

Detailed description of the embodiments

1 shows a photovoltaic (PV) system 1 according to a first embodiment. The PV system 1 has a PV generator 3 and a photovoltaic (PV) inverter 7 on which an inverter unit 2 , an arc detection device 6 and a switching means 5 with a switching contact 5a having. These components are in a housing of the PV inverter 7 accommodated. In the present case, the PV inverter forms 7 an inverter system according to the invention.

The inverter unit 2 is DC-side with the PV generator 3 electrically coupled, which is in the present case designed as an array of photovoltaic modules. As shown, the arc detection device 6 a wiring between the PV generator 3 and the inverter unit 2 assigned. As shown, the arc detection device 6 for example, electrically between the PV generator 3 and a DC side of the inverter unit 2 be looped. Thus, by means of the arc detection device 6 an arc can be detected on the DC side.

The inverter unit 2 is furthermore on the AC side via the switching contact 5a with a phase 4 an alternating voltage network electrically coupled. The switching contact 5a is between a terminal pole 2a the inverter unit 2 and the phase 4 the AC voltage network looped. The switching means 5 indicates with open switching contact 5a an open switching state and with closed switching contact 5a a closed switching state. Thus, when the switching state of the switching contact is closed 5a an electrical connection between the inverter unit 2 or their connection pole 2a and the phase 4 achieved the AC voltage network, which allows an injection of electrical energy into the AC mains. It is also possible by transition of the switching contact 5a in its open switching state interrupt this feed.

The switching means 5 is in operative connection with the arc detection device 6 such that upon detection of an arc by the arc detection device 6 the switching contact 5a is placed in its open switching state. For this purpose, for example, a control signal from the arc detection device 6 via a control line, not shown, to a control input, not shown, of the switching means 5 be transmitted. Alternatively, for example, a central control device in the form of a microprocessor or digital signal processor may be provided which, for example, the operation of the inverter unit 2 and the switching state of the switching means 5 controls or regulates. The arc detection device 6 may provide a detection signal to the controller, the controller controlling the switching means 5 controlled in response to the detection signal, in particular in a detected arc offset in the open switching state.

Thus, an effective AC-side separation can be achieved, in which case the result is a DC side detected arc is deleted, since the system is then no longer under load. The switching means 5 is presently designed as a circuit breaker and is therefore suitable for switching under load.

2 shows one in comparison to that of 1 modified embodiment of a PV system 1 , In this embodiment, a separate switching device 8th provided, both the arc detection device 6 as well as the switching means 5 with its switching contact 5a contained in a housing. Incidentally, the description of the embodiment of 1 directed to avoid repetition.

At the in 2 In the embodiment shown, it is possible to use a conventional inverter unit 2 to supplement an arc detection functionality, wherein in a detected arc a safe state can be produced.

It is understood that in addition to the single phase 4 further phases, for example two further phases, may be present, corresponding to further output terminals of the inverter 2 are electrically connected via further controllable switching means. When a detected arc at least one of the switching means is opened. Preferably, however, at least one of the switching means remains closed to supply the inverter 2 to maintain with electrical energy.

Claims (5)

Inverter system, comprising: - an inverter unit ( 2 ), comprising: - a DC side for electrically connecting to at least one photovoltaic (PV) generator ( 3 ) and / or an electrical energy store, and - an AC side with at least one connection pole ( 2a ) for electrically connecting to a phase ( 4 ) of an AC voltage network, - at least one controllable switching means ( 5 ) with a switching contact ( 5a ) connected between the terminal pole ( 2a ) of the inverter unit ( 2 ) and the phase ( 4 ) is connected to the AC voltage network and having a closed and an open switching state, and An arc detection device ( 6 ) for detecting an arc, which in such a way with the switching means ( 5 ) is in operative connection that the switching contact ( 5a ) assumes the open switching state in the case of a detected arc. Inverter system according to claim 1, characterized in that the switching means ( 5 ) is a bistable relay. An inverter system according to claim 1 or 2, comprising a photovoltaic (PV) inverter ( 7 ), wherein the inverter unit ( 2 ), the switching means ( 5 ) and the arc detection device ( 6 ) in the PV inverter ( 7 ) are integrated. Inverter system according to claim 1 or 2, comprising one of the inverter unit ( 2 ) separate switching device ( 8th ), wherein the switching means ( 5 ) and the arc detection device ( 6 ) in the switching device ( 8th ) are integrated. PV system ( 1 ), comprising: - a PV generator ( 3 ) and / or an electrical energy store, and - an inverter system according to one of the preceding claims, wherein the DC side of the inverter unit ( 2 ) with the PV generator ( 3 ) and / or the energy store is electrically connected.

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