Electrical system for connecting at least one photovoltaic module to an energy supply network

Abstract

The invention relates to an electrical system (1) for connecting at least one photovoltaic module (9) to an energy supply network (7), having: an inverter (2) with a control device (11), a DC voltage side (5) and an AC voltage side (6); and a DC voltage switch (3) for electrically connecting the at least one photovoltaic module (9) to the inverter (2), wherein the DC voltage switch (3) is electrically connected to the DC voltage side (5) of the inverter (2) via an electrical connecting line (4), wherein the inverter (2) is connected to the DC voltage switch (3) via a control connection (10) and the control device (11) is designed to switch the DC voltage switch (3) via the control connection between a closed position, in which electrical energy (E) can be transmitted between the inverter (2) and the at least one photovoltaic module (9), and an open position, in which the inverter (2) is electrically disconnected from the at least one photovoltaic module (9).

Description

[0001] Electrical system for connecting at least one photovoltaic module to a power supply network

[0002] The invention relates to an electrical system for connecting at least one photovoltaic module to a power supply network, comprising:

[0003] an inverter comprising a control device, a DC side and an AC side; and a DC switch for electrically connecting the at least one photovoltaic module to the inverter, wherein the DC switch is electrically connected to the DC side of the inverter via an electrical connecting line, wherein the inverter is connected to the DC switch via a control connection and the control device is configured to switch the DC switch via the control connection between a closed position, in which electrical energy can be transferred between the inverter and the at least one photovoltaic module, and an open position, in which the inverter is electrically disconnected from the at least one photovoltaic module.

[0004] Furthermore, the invention relates to a method for operating such an electrical system for connecting at least one photovoltaic module to a power supply network.

[0005] Inverters are used, among other things, to convert the direct currents and voltages generated by photovoltaic modules into alternating currents and voltages, so that the converted electrical energy can be fed into a power grid. This power grid can be, for example, a local grid operated by a network operator or a building's power grid.

[0006] Since high electrical voltages can occur in photovoltaic systems, appropriate safety precautions must be taken to prevent damage in the event of a fault and to protect people present. In particular, in the event of a fire, a rapid and safe electrical disconnection of the photovoltaic modules from the power grid or from an inverter must be possible. Therefore, DC switches are used between inverters and photovoltaic modules. Before extinguishing fires or entering burning roofs on which photovoltaic modules are located, emergency personnel can manually operate the DC switches to disconnect the existing photovoltaic modules from the power grid, thus preventing further damage and reducing the risk of electrical accidents.DC switches are also used to safely disconnect inverters from the photovoltaic modules before acceptance testing or the planned commissioning of a photovoltaic system.

[0007] Prior art DC circuit breakers are described, for example, in WO 2018 / 085873 Al. The disclosed DC circuit breakers can be manually switched, particularly to disconnect photovoltaic modules from a power supply network in emergency situations.

[0008] In addition, DC circuit breakers that can be operated remotely are known. One such DC circuit breaker is disclosed, for example, in DE 10 2005 018 173 B4. Furthermore, DE 20 2012 000 324 Ul discloses a DC circuit breaker that can be switched by means of a remote switch integrated into an uninterruptible power supply. A motor drive can be provided to open or close the DC circuit breaker. An alarm module can control the remote switch. Furthermore, fire, smoke, and / or water detectors can remotely trigger the DC circuit breaker.

[0009] Manually operated DC circuit breakers have the disadvantage that faults must first be detected by personnel present, and then the breakers must be manually operated. Similarly, with remotely operated DC circuit breakers, faults must first be detected or reported by an independent, usually geographically distant, device before the breaker can be operated. Therefore, both manually operated and remotely operated DC circuit breakers suffer from the disadvantage that not all faults can be reliably detected, and the breaker may only be operated with a delay, as some faults are only detected or reported after a certain time.In particular, electrical fault conditions in connection with the photovoltaic modules or the inverters cannot be detected, or can only be detected with a delay, by the known DC switches from the prior art and the associated tripping systems.

[0010] From EP 2 904 677 Bl, a circuit arrangement is known in which switches within actuating devices can be operated by an inverter to disconnect strings of a photovoltaic system from the inverter. Further circuit arrangements are known from LU 92022 Bl and DE 20 2012 007 257 Ul.

[0011] In light of these considerations, the object of the present invention is to at least partially mitigate or even completely eliminate the disadvantages of the prior art. Preferably, the object of the present invention is to provide an electrical system of the type mentioned above in which technical faults are detected quickly and reliably, and immediate activation of the DC switch is enabled, in order to reduce the risk of damage to photovoltaic systems and buildings, as well as the danger to persons present.

[0012] This problem is solved by an electrical system for connecting at least one photovoltaic module to an energy supply network according to claim 1 and by a method according to claim 11.

[0013] According to the invention, in an electrical system of the type mentioned above, the DC switch has a handle and can be switched between the closed and open positions both manually and, preferably, automatically by the inverter. The DC switch can be moved between a coupling position, in which manual switching of the DC switch between the closed and open positions is possible, and a decoupling position, in which manual switching of the DC switch between the closed and open positions is prevented. The connection of the inverter to the DC switch via the control connection enables direct and immediate actuation of the DC switch after a fault condition has been detected by the inverter.Advantageously, fault conditions in the electrical system, such as overloads, electrical faults within the inverter (especially in the inverter's intermediate circuit), or reverse current situations, can be detected by the inverter, and the DC circuit breaker can then be activated. Furthermore, it is possible to disconnect the inverter from at least one photovoltaic module during a rapid shutdown. In a rapid shutdown, the inverter's operation is stopped immediately, for example, by an external signal. Since any energy storage elements, such as capacitors or inductors, may still be charged and thus pose a hazard, the DC circuit breaker can be switched to the open position to de-energize connected equipment.Due to the potential isolation of the at least one photovoltaic module and the inverter by the DC switch, a discharge circuit, as known from the prior art, can be omitted during a rapid shutdown. The inverter can be, in particular, a three-phase inverter configured to generate three AC voltages that are preferably phase-shifted by 120°. The AC voltages can be generated by controlling and switching electrical switches, for example, IGBTs (Insulated-Gate Bipolar Transistors). The at least one photovoltaic module can be connected to the DC side of the inverter via the DC switch. For this purpose, the inverter has at least two inverter input contacts on the DC side.For outputting AC voltages, the inverter can have at least three inverter output contacts on the AC side. The inverter can also include a boost converter and / or a DC link. A DC link capacitor can be integrated into the DC link for intermediate energy storage. The inverter can be configured as a unidirectional or bidirectional inverter. The DC switch preferably has a detent mechanism and at least one switching module connected to the detent mechanism. Preferably, several switching modules, preferably of the same type and in particular mechanically connected in series, are provided. The detent mechanism can actuate the at least one switching module, i.e., switch it between an on position and an off position.The switching module can have at least one fixed contact, at least one second fixed contact, and at least one movable, in particular rotatable, contact. In the switching module's closed position (the closed position of the DC switch), the movable contact can electrically connect both the first and second fixed contacts to enable the transfer of electrical energy between them. In the switching module's open position (the open position of the DC switch), the movable contact is not in contact with the first and / or second fixed contacts, thus electrically isolating them. The movable contact is preferably rotatably mounted. For example, the movable contact can be mounted on a rotating disk.In one embodiment, the movable contact is elongated and has two opposing ends for contacting the first and second fixed contacts. The ends can have clamping elements for contacting and partially receiving the first and second fixed contacts, each forming a receiving area for the fixed contacts. The first fixed contact can be connected to the inverter via the electrical connecting line. The second fixed contact can be connected to at least one photovoltaic module via another electrical connecting line. The electrical connecting line between the DC switch and the inverter can be formed by at least one connecting cable. The other electrical connecting line can also be formed by a connecting cable. The control connection is preferably formed by a wired electrical connection.Alternatively, the control connection can be established via a radio link. The inverter's control unit can comprise one or more microprocessors and / or microcontrollers. To switch the DC switch, which can also be referred to as a direct current switch, the control unit can transmit control signals to the DC switch via the control connection. If the control connection is wired, the DC switch, and in particular its drive motor, can be supplied with electrical energy from the inverter via the control connection. In another embodiment of the invention, the control connection can coincide with the electrical connection between the inverter and the DC switch.In this design, control signals can be transmitted to the DC switch, for example, in the form of modulated signals.

[0014] It is preferred, however, if the control connection and the electrical connection are independent of each other and, in particular, are formed by separate conductors. Preferably, the control connection is formed by a dedicated control line. The control line can run directly between the inverter and the DC switch. In this way, a reliable connection for controlling the DC switch is ensured. If the control connection is formed by a dedicated control line, the power supply to the DC switch, and in particular to an electric drive motor (to be described in more detail below), can also be provided via this line.

[0015] To hold the DC switch in the closed and / or open position and to prevent unintentional switching operations, it is advantageous if the DC switch is pre-tensioned in the closed and / or open position, preferably by a spring element, in particular a torsion spring. The spring element can, for example, be arranged within the detent mechanism or on the at least one switching module. For example, the spring element can be coupled to the aforementioned rotary disc.

[0016] When maintenance or repair work is carried out on a photovoltaic system, the DC circuit breaker is designed to have a handle and be switchable between the closed and open positions, both manually and preferably automatically by the inverter. The DC circuit breaker can thus be manually switched between the closed and open positions using the handle. For this purpose, the handle can be mechanically coupled to the at least one switching module and / or the detent mechanism, in particular the at least one movable contact. The handle can have a rotatable handle element with which the detent mechanism or the switching module can be switched.

[0017] To prevent manual operation of the DC switch, for example, after it has been switched to the open position by the inverter, the DC switch is designed to be switchable between a coupling position, in which manual switching of the DC switch between the closed and open positions is permitted, and a decoupling position, in which manual switching of the DC switch between the closed and open positions is prevented. For this purpose, the DC switch can have a coupling mechanism with a coupling element via which the handle unit can be coupled to the at least one switching module. In the coupling position, the handle unit can be mechanically coupled to the switching module via the coupling element. In the decoupling position, the handle unit can be mechanically decoupled from the switching module by the coupling element.To enable coupling and decoupling, the coupling element can be designed to be slidable. To transmit a rotational movement of the handle element to the switching module, the coupling element can be rotatably mounted.

[0018] In a particularly preferred embodiment of the invention, the DC switch comprises at least one electric drive motor configured to move the DC switch between the closed and open positions. It is advantageous if the drive motor is connected to the inverter via the control connection and is also supplied with electrical energy by the inverter. The drive motor can be, for example, a DC motor or a brushless DC motor. The drive motor can be coupled to the detent mechanism, for example, via a gearbox. By rotating the drive motor in one direction, the DC switch can be moved from the closed position to the open position. By rotating the drive motor in the other direction, the DC switch can be moved from the open position to the closed position.The drive motor can also be moved into a locking or braking position to prevent unintentional activation. In the locking or braking position, the drive motor is braked and therefore cannot move the DC switch from the closed position to the open position or vice versa. In a particularly preferred embodiment of the invention, the drive motor can also be configured to move the DC switch between the coupling and decoupling positions as described above. The drive motor can move the coupling element accordingly, for example, via a cam guide or by means of a gearbox with two outputs, one output being assigned to the coupling mechanism and the other to the detent mechanism.Alternatively, another drive motor can be provided which can move the DC switch between the coupling position and the decoupling position by shifting the coupling element.

[0019] Since DC switches are only rarely operated, but their function is fundamental to safety, checking their functionality is of great importance. Furthermore, it is advantageous for correct control if the position of the DC switch can also be verified. It is therefore beneficial if the control device is configured to detect the motor current and / or voltage of the electric drive motor and, based on this, to detect the switching position of the DC switch and / or identify a fault in the DC switch. The motor current and / or voltage can be detected, for example, by measuring at the control connection. A fault exists, for example, if a gearbox of the drive motor, a switching module, or the detent mechanism is blocked.A defect also exists if the gearbox is broken and the drive motor encounters less resistance. Such defects can be detected by measuring the motor current and / or voltage and comparing it to a target motor current and / or voltage for a given operating situation, as these values ​​will deviate from the known target values ​​in this case. A defect can be detected if the deviation of a measured motor current from a target motor current and / or the deviation of a measured motor voltage from a target motor voltage exceeds a respective limit. For example, in the case of a mechanical blockage of the gearbox, the shift module, or the detent mechanism, the motor current increases more sharply and / or a higher motor current is required than is the case with an unblocked gearbox or detent mechanism.Conversely, a drive motor that is essentially free-running due to a gearbox defect and experiences only minimal mechanical resistance will draw a lower motor current than a gearbox that is not free-running, i.e., functioning. Furthermore, by analyzing the measured motor current and / or voltage, it is possible to determine the switching position of the DC switch. For example, if the open and closed positions of the DC switch are defined by end positions, further rotation of the drive motor beyond the end position is blocked. Due to the mechanical resistance, this leads to a significant increase in motor current, so the switching position can be deduced from knowing the direction of rotation of the drive motor and measuring the motor current and / or voltage.This makes it possible to determine the switching position of the DC switch without actually switching it. Furthermore, if the spring preload is present in both the open and closed positions, and if the direction of rotation and the target motor current and / or voltage are known, it is also possible to determine the switching position of the DC switch without actually switching it by only partially rotating the switch into its spring preload position and measuring the motor current and / or voltage. After the drive motor is deactivated, the spring preload pushes the DC switch back to its initial position – either open or closed.Without knowledge of the direction of rotation, but with different spring preloads in the open and closed positions, it is possible to determine a switching position based on knowledge of the target motor current and / or the target motor voltage when rotating into the different spring preloads and detecting the motor current and / or motor voltage.

[0020] Alternatively, auxiliary contacts in the DC switch, particularly on the detent mechanism and / or on at least one switching module, can be used to detect the switching position of the DC switch. These auxiliary contacts can be switched depending on the switching position, thereby informing the control unit of the DC switch's current position. In one embodiment, the auxiliary contacts are switched, for example, by a projection or recess on the detent mechanism or the switching module. Specifically, actuation of the switching module or the detent mechanism can activate a projection or recess on an auxiliary contact. Switching an auxiliary contact can, for example, close a circuit, thus indicating the respective switching position.In one design, an auxiliary contact can be switched by the latching mechanism when the DC switch is moved to the closed position. Similarly, the coupling mechanism can switch an auxiliary contact to indicate, for example, that the DC switch is in the coupling position.

[0021] It is advantageous if the control unit includes a fault detection unit for recognizing fault conditions in the inverter, the DC switch, and / or at least one photovoltaic module, and if the control unit is configured to switch the DC switch to the open position when the fault detection unit detects a fault condition. This disconnects the inverter from the at least one photovoltaic module. A fault condition can occur, for example, if a voltage is measured in a DC link of the inverter or at another point in the electrical system that exceeds an upper limit or falls below a lower limit. Another fault condition can occur if reverse currents are detected.Reverse currents can arise, for example, from partial shading or covering of at least one photovoltaic module. Reverse currents can also occur if a photovoltaic module is defective. The fault detection unit can be integrated into the inverter's control unit. Reverse currents can be detected, for example, using a current measuring device. A reverse current occurs when a direct current changes its direction, i.e., flows in the opposite direction. A reverse current occurs, for example, when current in a connecting line no longer flows to the inverter but instead flows towards a photovoltaic system. If the fault condition no longer exists, for example, because no more reverse currents are detected, the DC circuit breaker can be returned to the closed position.

[0022] A particularly compact system is achieved when the inverter has an inverter housing and the DC switch is located at least partially, preferably completely, inside the inverter housing. This provides additional protection for the DC switch. Furthermore, it allows for a short control connection. The inverter housing can be made of plastic. The inverter housing can enclose the inverter's power electronics as well as the control unit. The DC switch can be accessed for manual switching via an opening in the inverter housing.

[0023] To control the DC circuit breaker remotely, it is advantageous if the inverter can be connected to a remote server and the control unit is configured to receive commands from the server to switch the DC circuit breaker. This makes it possible, for example, to activate a photovoltaic system remotely after installation and commissioning. Remote activation can be performed, for instance, by the inverter manufacturer, an installation company, or an energy supplier. Furthermore, emergency services, for example, who have been notified of an incident near the photovoltaic system, can proactively shut down the system, i.e., disconnect at least one photovoltaic module from the inverter. The server can be connected to the control unit via a data connection.The data connection can be established via a wireless or wired connection, for example an Ethernet cable.

[0024] The invention also relates to a method for operating an electrical system described above for connecting at least one photovoltaic module to a power supply network. The DC switch is connected to the inverter via the electrical connection line and the control connection. The DC switch is further connected to the at least one photovoltaic module via another electrical connection line. The DC switch, the inverter, and the at least one photovoltaic module are components of a photovoltaic system. The DC switch has a handle and can be switched between the closed and open positions both manually and, preferably, automatically by the inverter.The method provides that the DC switch is switched between a coupling position, in which manual switching of the DC switch between the closed and open positions is permitted, and a decoupling position, in which manual switching of the DC switch between the closed and open positions is prevented. Furthermore, it is provided that...

[0025] The DC switch is switched from the open position to the closed position by the control device in order to electrically connect at least one photovoltaic module to the power supply network and / or

[0026] The DC switch is switched from the closed position to the open position by the control device in order to electrically disconnect at least one photovoltaic module from the power supply network.

[0027] The advantages, effects and characteristics described above in connection with the system for connecting at least one photovoltaic module to an energy supply network are transferable to the method for its operation.

[0028] In one embodiment of the invention, the inverter is connected to a server, and the DC circuit breaker is switched between the closed and open positions remotely via the server. This is particularly advantageous for commissioning a photovoltaic system after installation and commissioning, or for remotely deactivating it in case of danger. For example, an emergency response organization can have access to the server and deactivate the DC circuit breaker before deployment.

[0029] In one embodiment of the invention, after a fault condition is detected, the DC switch is moved to the open position by the inverter via the control connection. This prevents (further) damage and avoids the risk of electrical accidents, for example, for emergency personnel near the electrical system. If no fault condition is present, the DC switch can be moved back to the closed position.

[0030] The error condition could be one of the following:

[0031] - a fault condition of the inverter, for example a defect in an intermediate circuit;

[0032] - a fault condition of the DC switch, for example a blockage, in particular a blockage of a latching mechanism or a switching module; and / or

[0033] - A fault condition of at least one photovoltaic module, for example, shading. A defect in the intermediate circuit can be detected, for example, by measuring an intermediate circuit voltage that exceeds an upper limit or falls below a lower limit. Another fault condition of the inverter can be that an electrical current within the inverter exceeds a limit. A fault condition of the DC-DC switch can occur, for example, if a drive motor of the DC-DC switch is defective, which can be detected, for example, by measuring a motor current and / or a motor voltage. For example, a gear in the gearbox may have come loose, so that the gearbox runs freely and offers no or reduced mechanical resistance.A fault in the DC switch can also occur if, for example, a gearbox or detent mechanism of the DC switch is blocked, which can also be detected by measuring, for example, an increased motor current and / or motor voltage. A fault in the photovoltaic module can be detected by measuring the DC current and / or DC voltage on the DC side. For example, reverse currents can be detected by measuring a change in the current direction.

[0034] The invention can also be described in general form using the following exemplary embodiments:

[0035] Exemplary embodiment 1: Electrical system for connecting at least one photovoltaic module to a power supply network, comprising:

[0036] an inverter comprising a control device, a DC side and an AC side; and a DC switch for electrically connecting the at least one photovoltaic module to the inverter, wherein the DC switch is electrically connected to the DC side of the inverter via an electrical connecting line,

[0037] wherein the inverter is connected to the DC switch via a control connection and the control device is configured to switch the DC switch via the control connection between a closed position, in which electrical energy can be transferred between the inverter and the at least one photovoltaic module, and an open position, in which the inverter is electrically isolated from the at least one photovoltaic module.

[0038] Exemplary embodiment 2: Electrical system according to exemplary embodiment 1, wherein the control connection and the electrical connecting line are independent of each other and are formed in particular by separate lines.

[0039] Exemplary embodiment 3: Electrical system according to exemplary embodiment 1 or 2, wherein the DC switch is pre-tensioned to the closed position and / or the open position preferably with a spring element, in particular a torsion spring.

[0040] Exemplary embodiment 4: Electrical system according to one of the exemplary embodiments 1 to 3, wherein the DC switch has a handle unit and can be switched between the closed position and the open position both manually and preferably automatically by the inverter.

[0041] Exemplary embodiment 5: Electrical system according to exemplary embodiment 4, wherein the DC switch can be moved between a coupling position, in which manual switching of the DC switch between the closed position and the open position is enabled, and a decoupling position, in which manual switching of the DC switch between the closed position and the open position is prevented.

[0042] Exemplary embodiment 6: Electrical system according to one of the exemplary embodiments 1 to 5, wherein the DC switch has at least one electric drive motor which is configured to move the DC switch between the closed position and the open position.

[0043] Exemplary embodiment 7: Electrical system according to exemplary embodiment 6, wherein the control device is configured to detect a motor current and / or a motor voltage of the electric drive motor and, based on the motor current and / or the motor voltage, to detect a switching position of the DC voltage switch and / or to detect a defect of the DC voltage switch.

[0044] Exemplary embodiment 8: Electrical system according to one of the exemplary embodiments 1 to 7, wherein the control device has a fault detection unit for detecting fault conditions of the inverter, the DC switch and / or the at least one photovoltaic module and the control device is configured to switch the DC switch to the open position when the fault detection unit has detected a fault condition.

[0045] Exemplary embodiment 9: Electrical system according to one of the exemplary embodiments 1 to 8, wherein the inverter has an inverter housing and the DC switch is arranged at least partially, preferably completely, inside the inverter housing.

[0046] Exemplary embodiment 10: Electrical system according to one of the exemplary embodiments 1 to 9, wherein the inverter is connectable to a remote server and the control device is configured to receive commands from the server to switch the DC switch.

[0047] Exemplary embodiment 11: Method for operating an electrical system for connecting at least one photovoltaic module to a power supply network according to one of the exemplary embodiments 1 to 10, wherein the DC switch is connected to the inverter via the electrical connecting line and via the control connection, and wherein the DC switch is connected to the at least one photovoltaic module via a further electrical connecting line, wherein the DC switch is switched from the open position to the closed position by the control device in order to electrically connect the at least one photovoltaic module to the power supply network and / or

[0048] wherein the DC switch is switched from the closed position to the open position by the control device in order to electrically disconnect at least one photovoltaic module from the energy supply network.

[0049] Exemplary embodiment 12: Method according to exemplary embodiment 11, wherein the inverter is connected to a server and the DC switch is switched between the closed position and the open position by means of a remote switching via the server.

[0050] Exemplary embodiment 13: Method according to exemplary embodiment 11 or 12, wherein, after detection of a fault condition, the DC voltage switch is transferred to the open position by the inverter via the control connection.

[0051] Exemplary embodiment 14: Method according to exemplary embodiment 13, wherein the fault condition is one of the following:

[0052] - a fault condition of the inverter, for example a defect in an intermediate circuit;

[0053] - a fault condition of the DC switch, for example a mechanical blockage, in particular a blockage of a detent mechanism or a switching module; and / or

[0054] - Fault condition of the photovoltaic module, for example shading.

[0055] The invention is explained in more detail below with reference to figures, to which it is not, however, limited. These show:

[0056] Fig. 1 shows a block diagram of an electrical system;

[0057] Fig. 2 shows a block diagram of components of a DC switch;

[0058] Fig. 3 shows an exploded view of a DC voltage switch;

[0059] Fig. 4 shows an exploded view of a grid system;

[0060] Fig. 5A shows a DC switch according to a first embodiment in a decoupling position; Fig. 5B shows the DC switch of the first embodiment in the coupling position;

[0061] Fig. 6A shows a DC switch according to a second embodiment in a decoupling position; Fig. 6B shows the DC switch of the second embodiment in the coupling position; and

[0062] Fig. 7 shows an engine characteristic curve.

[0063] Fig. 1 shows an electrical system 1 with an inverter 2 and a DC switch 3, which is connected to a DC output 5 of the inverter 2 via at least one electrical connection 4. The inverter 2 is connected to a local power supply network 7 of a building (not shown) via an AC output 6. In the illustrated embodiment, an electrical energy storage device 8 is also connected to the DC output 5 of the inverter 2. The inverter 2 is preferably designed as a three-phase inverter 2a, which generates three AC voltages U that are out of phase with each other. The AC voltages U can have an RMS value of 230 V relative to a neutral conductor (not shown). At least one photovoltaic module 9 with several interconnected cells 9a is connected via the DC switch 3.The DC switch 3 is connected to at least one photovoltaic module 9 via further connecting lines 52. The at least one photovoltaic module 9 can generate DC voltages and DC currents, which are supplied to the inverter 2.

[0064] In order to electrically disconnect at least one photovoltaic module 9 from the inverter 2 in the event of a fault, the DC switch 3 can be switched between a closed position, in which electrical energy E can be transferred between the inverter 2 and the at least one photovoltaic module 9, and an open position, in which the inverter 2 is electrically disconnected from the at least one photovoltaic module 9. To control the DC switch 3, a control connection 10 in the form of a control line 10a is provided, which runs directly between the inverter, in particular a control device 11, and the DC switch 3. The control line 10a is independent of, i.e., separate from, the electrical connection line 4. The control line 10a and the connection line 4 thus each form independent lines.The control unit 11 of the inverter 2 can switch the DC switch 3 via the control connection line 10a. In addition to the control unit 11, the inverter 2 also has a power electronic assembly 50 for generating the AC voltages U. This power electronic assembly 50 may also include a boost converter and / or a DC link.

[0065] Fig. 2 shows a schematic block diagram of the individual components of the DC switch 3. To switch the DC switch 3, an electric drive motor 12 can be provided, which can be controlled by the control unit 11 via the control connection line 10a. The drive motor 12 can, for example, be designed as a brushless DC motor and actuate a detent mechanism 13 of the DC switch 3. The detent mechanism 13 can be mechanically connected to at least one switching module 14, which can have a first fixed contact 15, a second fixed contact 16, and a movable contact 17, as shown in Fig. 3. Two switching modules 14 are shown in Fig. 2. The movable contact 17 can be arranged in a rotary disk 18 for the purpose of rotation. In the closed position of the DC switch 3, the movable contact 17 contacts the first 15 and the second 16.In the open position of the DC switch 3, the movable contact 17 is rotated such that it does not contact either the first 15 or the second contact 16. The detent mechanism 13 can be connected to several switching modules 14, as shown in Figs. 2 and 3. The switching modules 14 can be connected to each other on the rotary disks 18 such that a rotary movement of one switching module 14 is transmitted to the next switching module 14, and the switching modules 14 switch simultaneously. The detent mechanism 13 can, for example, switch the uppermost switching module 14 associated with it. As shown, among other things, in Fig. 2, the detent mechanism 13 can be driven by the drive motor 12, for example, via a gearbox 20, to switch the DC switch 3 between the open and closed positions. The gearbox 20 can have gears to transmit a rotary movement.The first contacts 15 of the switching modules 14 can be connected to the DC side 5 of the inverter 2. The second contacts 16 can be connected to at least one photovoltaic module 9. To secure the DC switch 3 in the open and closed positions, the movable contacts 17 can be pre-tensioned in the respective positions by means of a spring element 21 of the detent mechanism 13.

[0066] In addition to the drive motor 12, the DC switch 3 can have a handle unit 22 with a handle element 23 and a handle axle 27 to manually switch the DC switch 3 between the open and closed positions. The gearbox 20 can be designed to be non-self-locking.

[0067] Fig. 3 shows an exploded view of a DC switch 3 with a detent mechanism 13 and several switching modules 14, whereby the drive motor 12 and the handle unit 22 are not shown for clarity. It can be seen that a housing 51 of the DC switch 3, within which the switching modules 14 and the detent mechanism 13 can be arranged, is made up of several parts.

[0068] Fig. 4 shows an exploded view of a detent mechanism 13. Detent mechanisms 13 and their function are known from the prior art, so they will not be discussed in detail here. It can be seen that the detent mechanism 13 has a drive shaft 19, the spring element 21 in the form of a torsion spring 21a, and further detent mechanism components 53, which serve to latch the DC switch 3 in the open position and / or in the closed position by means of spring preload. The DC switch 3 can be switched by rotating the detent mechanism 13. In one embodiment, the detent mechanism 13 can be rotated up to a limit angle without switching. After exceeding the limit angle, which may be, for example, 70°, the detent mechanism 13 jumps from a first detent position to a second detent position and remains latched there, preferably due to spring tension. The process is analogous when switching from the second to the first detent position.By switching between the detent positions, the DC switch 3 can be switched between the open and closed positions. The drive shaft 19 can be mechanically coupled to the drive motor 12 and / or to the handle axle 27, optionally via a coupling mechanism 24, which will be described in more detail later.

[0069] To prevent the DC switch 3 from being switched after it has already been switched by the drive motor 12, a coupling mechanism 24 can be provided, which may be connected to the detent mechanism 13. The coupling mechanism 24 can move the DC switch 3 between a coupling position (see Fig. 5B), in which manual switching of the DC switch 3 between the closed and open positions is permitted, and a decoupling position (see Fig. 5A), in which manual switching of the DC switch 3 between the closed and open positions is prevented. The coupling mechanism 24 can have a movable coupling element 25, which mechanically couples the handle unit 22 to the detent mechanism 13 in the coupling position and decouples it from the detent mechanism 13 in the decoupling position.For this purpose, the decoupling element 25 can, for example, be slidably mounted along a rotational axis 26 of the ratchet mechanism 13. In the coupled position (see Fig. 5B), a rotational movement of the handle unit 22 can be transmitted to the ratchet mechanism 13 by means of a positive locking of the handle axis 27 with the coupling element 25. The positive locking is particularly effective in a circumferential direction of the handle axis 27. The cross-sectional area of ​​the handle axis 27 can be polygonal for the positive locking. The coupling element 25 can have a corresponding coupling opening 28 into which the handle axis 27 can be positively received in the coupling position in the direction of rotation about the rotational axis 26. In the coupled position, the handle axis 27 engages in the coupling opening 28. The coupling opening 28 can also have a polygonal cross-sectional area.Preferably, the cross-sectional area of ​​the handle axis 27 corresponds substantially to the cross-sectional area of ​​the coupling opening 28. In the decoupling position, the positive locking between the coupling element 25 and the handle axis 27 can be released by displacing the coupling element 25, so that a rotational movement of the handle unit 22 is not transmitted to the ratchet mechanism 13 (Fig. 5A). In the decoupling position, the handle unit 22 can therefore, for example, rotate freely. The drive shaft 19 can also be positively engaged in a corresponding opening of the coupling element 25, with the positive locking again acting circumferentially around the drive shaft 19. The coupling element 25 is displaceable along the axis of the drive shaft 19. The circumferential positive locking between the drive shaft 19 and the coupling element 25 can be present in both the coupled and decoupling positions in one embodiment.

[0070] The coupling mechanism 24 can be actuated, for example, by an additional drive motor 29, such as a linear motor or a motor-gearbox combination, to generate a translational displacement of the coupling element 25. The additional drive motor 29 can displace the coupling element 25 to move the DC switch 3 between the closed and open positions. The additional drive motor 29 can also be controlled, for example, by the control unit 11. The displacement of the coupling element 25 can occur simultaneously with or before the DC switch 3 is moved between the closed and open positions by the drive motor 12.

[0071] Alternatively, the drive motor 12 can actuate the coupling mechanism 24, as illustrated in Figures 6A and 6B. For this purpose, the gearbox 20 can have two mechanical gearbox outputs 30a and 30b. A first mechanical gearbox output 30a can be assigned to the coupling mechanism 24 and move the coupling element 25 along the axis of rotation 26 as described above to move the DC switch 3 between the coupled and uncoupled positions. A second mechanical gearbox output 30b can be assigned to the detent mechanism 13 to move the DC switch 3 between the open and closed positions. In this way, the handle unit 22 can be uncoupled from the detent mechanism 13, and simultaneously or with a time delay, the DC switch 3 can be moved from the closed position to the open position.This prevents the DC switch 3 from being manually returned to the closed position using the handle 23 after it has been moved to the open position by the inverter 2. The DC switch 3 can then be moved back to the closed position and into the coupling position by actuating the drive motor 12 in the opposite direction.

[0072] As already mentioned, the transition between the closed and open positions, as well as between the coupled and uncoupled positions, can occur simultaneously or with a time delay. It is therefore possible for the gearbox 20 to generate a mechanical time delay between the gearbox outputs 30a and 30b. This allows the coupling mechanism 24 to be moved from the coupled position to the uncoupled position first, using the first output 30a of the gearbox 20. Subsequently, with a time delay, the DC switch 3 can be moved from the closed position to the open position. Due to the decoupling of the handle unit 22 from the detent mechanism 13, manual re-entry, i.e., moving the DC switch 3 to the closed position, is prevented.To close the DC switch 3 again, the second gearbox output 30b of the gearbox 20 can first move the DC switch 3 from the open position to the closed position. Subsequently, the coupling mechanism 24 at the first gearbox output 30a can be actuated to move the DC switch 3 into the coupled position. The mechanical time delay of a motion transmission at the gearbox outputs 30a, 30b can be achieved, for example, by one or more mechanical coupling elements (not shown) within the gearbox 20, each of which has a drive element (not shown). The coupling of the outputs 30a, 30b with the drive motor 12 is effected by means of the drive elements of the respective coupling elements.The drive elements can each be arranged locally offset on the coupling elements such that mechanically induced time delays of the couplings result from the coupling elements and thus of the transmission outputs 30a, 30b with the drive motor 12. The two transmission outputs 30a, 30b can be coupled to a common transmission input 30c for the drive motor 12 via the coupling elements.

[0073] It is therefore possible to decouple the handle unit 22 from the ratchet mechanism 13 and simultaneously or subsequently to move the DC switch 3 from the closed position to the open position, whereby in the decoupling position with handle unit 22 the DC switch 3 cannot be manually moved back to the closed position.

[0074] The control unit 11 can be connected to a server 32 via a data connection 31. This allows the DC switch 3 to be switched remotely between the closed and open positions via the inverter 2.

[0075] The control unit 11 can include a fault detection unit 33 for detecting fault conditions of the inverter 2, the DC switch 3, and / or the at least one photovoltaic module 9. The control unit 11 can therefore be configured to switch the DC switch 3 to the open position when the fault detection unit 33 has detected a fault condition. The fault detection unit 33 can be configured to measure electrical currents and / or electrical voltages in or at the inverter 2. Based on the measured currents and / or voltages, fault conditions of the inverter 2, the DC switch 3, and / or the at least one photovoltaic module 9 can be detected by comparison with target currents and / or target voltages.For example, a fault condition of inverter 2 can be detected if a voltage is measured in a DC link of inverter 2 that exceeds an upper limit or falls below a lower limit. Another fault condition of inverter 2 can be detected if currents within inverter 2 exceed an upper limit.

[0076] A fault condition of at least one photovoltaic module 9 can exist if reverse currents are detected. Reverse currents can arise, for example, from partial shading or covering of at least one photovoltaic module 9. Reverse currents can also be present if a photovoltaic module 9 is defective.

[0077] A fault condition of the DC switch 3 can be detected, in particular, by measuring the motor current I_motor and / or the motor voltage U_motor of the electric drive motor 12 and comparing it with a target motor current and / or a target motor voltage. If, for example, the DC switch 3, especially the gearbox 20 or one of the switching modules 14, is mechanically blocked, this leads to an increased motor current I_motor compared to a target motor current. A comparison of the measured motor current I_motor with the target motor current thus indicates a blockage of the DC switch 3. Conversely, if, for example, a gear of the gearbox 20 has come loose and thereby the mechanical resistance of the gearbox 20 has been reduced, this leads to a reduced motor current I_motor compared to a target motor current, which can also be detected.

[0078] By measuring the motor current I_motor and / or the motor voltage U_motor, the switching state of the DC switch 3 – i.e., the open or closed position – can be determined. If, for example, the open and closed positions of the DC switch 3 coincide with its end positions, further rotation of the drive motor 12 beyond the end position is blocked. Due to the mechanical resistance, this leads to a significant increase in the motor current I_motor, so that the switching state can be deduced from the direction of rotation of the drive motor 12 and the measurement of the motor current I_motor and / or the motor voltage U_motor. This makes it possible to determine the switching state of the DC switch 3 without actually switching the DC switch 3.Furthermore, with spring preload provided by the spring element 21 in the open and closed positions, and knowing the direction of rotation when turning into spring preload, and by measuring the motor current I_motor and / or the motor voltage U_motor and comparing it with corresponding target values, it is also possible to determine the switching position of the DC switch 3 without actually switching the DC switch 3, by only partially turning the DC switch 3 into spring preload. After deactivating the drive motor 12, the DC switch 3 is pushed back into its initial position – i.e., the open or closed position – by the spring preload.

[0079] In Fig. 1, the DC switch 3 is arranged remotely from the inverter 2. However, it is also possible that the DC switch 3 is arranged at least partially inside an inverter housing 34 of the inverter 2 or on the inverter housing 34.

[0080] Fig. 7 shows a current waveform 35 of the motor current I_motor as a function of a rotation angle α of the detent mechanism 13. The abscissa describes the rotation angle α in degrees. The ordinate describes the motor current I_motor in amperes. It can be seen that the motor current I_motor increases with increasing rotation angle α. This is due to the spring element 21 of the detent mechanism 13, which is tensioned with increasing angle. The maximum of the motor current I_motor occurs shortly before the switching operation of the detent mechanism 13 and can be present, for example, at a 70° rotation of the detent mechanism 13. Based on the motor current I_motor and with knowledge of the current waveform 35, it can thus be determined whether the DC switch 3 is functioning, in particular whether it can be rotated or is blocked.If the motor current I_motor rises more gradually, it can be assumed that a defect exists which offers less resistance to the drive motor 12, such as a free-running gearbox 20. A more steeply rising motor current I_motor suggests a blockage, such as a jammed detent mechanism 13. The switching position can be derived from the motor current I_motor corresponding to a given rotation angle α. End positions, which result in a very sharp increase in the motor current I_motor, can also be taken into account. Typically, however, the direction of rotation of the drive motor 12 is known, so that the switch position, for example, open or closed, as well as the corresponding rotation angle α, and / or the functionality of the DC switch 3 can be verified from the motor current I_motor and the direction of rotation.

Claims

28 Claims:

1. Electrical system ( 1 ) for connecting at least one photovoltaic module ( 9 ) to a power supply network (7 ) , comprising: an inverter (2 ) with a control device ( 11 ), a DC voltage side (5) and an AC voltage side ( 6 ); and a DC switch (3) for electrical connection of the at least one photovoltaic module (9) to the inverter (2), wherein the DC switch (3) is electrically connected to the DC side (5) of the inverter (2) via an electrical connecting line (4). wherein the inverter (2 ) is connected to the DC switch (3) via a control connection ( 10) and the control device ( 11 ) is configured to switch the DC switch (3) via the control connection ( 10) between a closed position, in which electrical energy (E) can be transferred between the inverter (2 ) and the at least one photovoltaic module ( 9), and an open position, in which the inverter (2 ) is electrically disconnected from the at least one photovoltaic module ( 9), characterized in that the DC switch (3) has a handle unit (22) and can be switched between the closed position and the open position both manually and preferably automatically by the inverter (2), wherein the DC switch (3) can be moved between a coupling position, in which manual switching of the DC switch (3) between the closed position and the open position is enabled, and a decoupling position, in which manual switching of the DC switch (3) between the closed position and the open position is prevented.

2. Electrical system ( 1 ) according to claim 1, characterized in that the control connection ( 10 ) and the electrical connecting line (4 ) are independent of each other and are in particular formed by separate lines.

3. Electrical system ( 1 ) according to claim 1 or 2, characterized in that the DC switch (3) is pre-tensioned to the closed position and / or the open position preferably with a spring element (21 ) , in particular a torsion spring .

4. Electrical system ( 1 ) according to one of claims 1 to 3, characterized in that the DC switch (3) has at least one electric drive motor ( 12 ) which is configured to move the DC switch (3) between the closed position and the open position.

5. Electrical system ( 1 ) according to claim 4, characterized in that the control device ( 11 ) is configured to detect a motor current ( I_motor) and / or a motor voltage (U_motor) of the electric drive motor ( 12 ) and, based on the motor current ( I_motor) and / or the motor voltage (U_motor), to detect a switching position of the DC voltage switch (3) and / or to detect a defect of the DC voltage switch (3).

6. Electrical system ( 1 ) according to one of claims 1 to 5, characterized in that the control device ( 11 ) has a fault detection unit (33) for detecting fault conditions of the inverter (2 ), the DC switch (3) and / or the at least one photovoltaic module ( 9) and the control device ( 11 ) is configured to switch the DC switch (3) to the open position when the fault detection unit (33) has detected a fault condition.

7. Electrical system ( 1 ) according to one of claims 1 to 6, characterized in that the inverter (2 ) has an inverter housing (34 ) and the DC voltage switch (3) is arranged at least partially, preferably completely, inside the inverter housing (34 ).

8. Electrical system ( 1 ) according to one of claims 1 to 7, characterized in that the inverter (2 ) is connectable to a remote server (32 ) and the control device ( 11 ) is configured to receive commands from the server (32 ) to switch the DC switch (3).

9. Method for operating an electrical system (1) for connecting at least one photovoltaic module (9) to a power supply network (7) according to one of claims 1 to 8, wherein the DC switch (3) is connected to the inverter (2) via the electrical connecting line (4) and via the control connection (10), and wherein the DC switch (3) is connected to the at least one photovoltaic module (9) via a further electrical connecting line (52), and wherein the DC switch (3) has a handle unit (22) and can be switched between the closed position and the open position both manually and preferably automatically by the inverter (2), and wherein the DC switch (3) is transferred between a coupling position, in which manual switching of the DC switch (3) between the closed position and the open position is permitted, and a decoupling position, in which manual switching of the DC switch (3) between the closed position and the open position is prevented, and wherein the DC switch (3) is switched from the open position to the closed position by the control device (11) in order to electrically connect the at least one photovoltaic module (9) to the power supply network (7) and / or wherein the DC switch (3) is switched from the closed position to the open position by the control device (11) in order to electrically disconnect the at least one photovoltaic module (9) from the power supply network (7).

10. Method according to claim 9, characterized in that the inverter (2 ) is connected to a server (32 ) and the DC switch (3) is switched between the closed position and the open position by means of a remote switching via the server (32 ).

11. Method according to claim 9 or 10, characterized in that, after detection of a fault condition, the DC voltage switch (3) is transferred to the open position by the inverter (2) via the control connection (10).

12. Method according to claim 11, characterized in that the fault condition is one of the following: - a fault condition of the inverter ( 2 ) , for example a defect in an intermediate circuit ; - a fault condition of the DC switch ( 3 ), for example a mechanical blockage, in particular a blockage of a detent mechanism ( 13 ) or of a switching module ( 14 ); and / or - Fault condition of the photovoltaic module ( 9 ) , for example shading .

Images