WO2015059195A1 - Inverter system and pv system - Google Patents

Abstract

The invention relates to an inverter system (7), wherein an inverter unit (2) is separated on the AC side when an arc detection device (6) detects an arc.

Description

 Inverter system and PV system

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 an arc fault protection device, which interrupts a current flow in the event of an arc in a cabling on the DC side or in a photovoltaic generator and thereby extinguishes 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. Semiconductor switches in turn 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 made the content of the description by express reference. 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 having a switching contact which is connected or connected between the terminal pole of the inverter unit and the phase of the alternating voltage network and which has a closed and an open switching state, and an arc detection device for detecting a Arc, which is in operative connection with the switching means in such a way that the switching contact assumes the open switching state in a detected arc and thus separates the inverter unit from the phase or phases, whereby the arc extinguishes.

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 or connected for this case between an associated terminal pole and an associated phase of a rotary power 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 a power consumption on the DC side interrupted. 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 may, for example, be used to supply a localized area not connected to supraregional power grids, for example a mountain lodge or a remote area in a less developed country.

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 profile 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. Incidentally, reference should also be made to the relevant specialist literature in order to avoid repetition.

Under an operative connection can be understood both a direct 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 the case of an immediate connection, a direct control line may be present. In an indirect connection, for example, an output signal of the arc detection device can initially be assigned to a control device. leads, which in turn controls the switching means. This allows additional functions to be implemented.

According to an embodiment, the inverter system comprises a photovoltaic inverter, wherein the inverter unit, the switching means and the arc detection device are integrated in the photovoltaic switch. 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 inventive inverter system, 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. Brief description of the drawings

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

Fig. 1: a first embodiment of a PV system and 2 shows a second embodiment of a PV system.

Detailed description of the embodiments

Fig. 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, which more an inverter unit 2, an arc detection device 6 and a switching means 5 having a switching contact 5a. These components are housed in a housing of the PV inverter 7. In the present case, the PV inverter 7 forms an inverter system according to the invention.

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

The inverter unit 2 is further electrically coupled on the AC side via the switching contact 5a with a phase 4 of an AC voltage network. The switching contact 5a is looped or connected between a connection pole 2a of the inverter unit 2 and the phase 4 of the alternating voltage network. The switching means 5 has an open switching state with open switching contact 5a and a closed switching state when the switching contact 5a is closed. Thus, when the switching state of the switching contact 5a is closed, an electrical connection between the inverter unit 2 or its connection pole 2 a and the phase 4 of the alternating voltage network is achieved, which makes it possible to feed electrical energy into the alternating voltage network. It is also possible to interrupt by switching the switching contact 5a in its open switching state, this feed.

The switching means 5 is in operative connection with the arc detection device 6, so that upon detection of an arc by the arc detection device 6, the switching contact 5a is set 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 are transmitted. Alternatively, for example, a central control device in the form of a microprocessor or digital signal processor may be provided which, for example, controls the operation of the alternating judge unit 2 and the switching state of the switching means 5 controls or regulates. The arc detection device 6 can supply a detection signal to the control device, wherein the control unit controls the switching means 5 in response to the detection signal, in particular in a detected arc 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.

FIG. 2 shows an embodiment of a PV system 1 modified in comparison to that of FIG. 1. In this embodiment, a separate switching device 8 is provided, which includes both the arc detection device 6 as well as the switching means 5 with its switching contact 5a in a housing. Incidentally, reference is made to the description of the embodiment of FIG. 1 in order to avoid repetition.

In the exemplary embodiment shown in FIG. 2, it is possible to supplement a conventional inverter unit 2 with an arc detection functionality, it being possible to produce a safe state in the case of a detected arc.

It is understood that in addition to the single phase 4 further phases, for example two further phases, may be present, which are correspondingly electrically connected to further output terminals of the inverter 2 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 in order to maintain a supply of the inverter 2 with electrical energy.

Claims

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