DC photovoltaic feed-in system

Abstract

DC photovoltaic feed-in system (1) for feeding DC current generated by photovoltaics into a DC grid (3), - with at least one control cabinet, - with at least one direct current distribution line (4), - with at least one photovoltaic module (6) which is connected to the direct current distribution line (4) via at least one direct current converter (12), - with at least one contactor (11) arranged between the at least one photovoltaic module (6) and the at least one DC-DC converter (12), - with at least one control and regulation unit (32) for insulation monitoring and voltage-dependent current regulation, - wherein the DC distribution line (4) is connected to the DC network (3) via at least one modular electromechanical DC circuit breaker (5), - wherein the at least one contactor (11) and / or the at least one modular electromechanical DC line switch (5) can be switched via the at least one control and regulating unit (32).

Description

[0001] The invention relates to a direct current photovoltaic feed-in system for feeding direct current generated by photovoltaics into a direct current grid.

[0002] Direct current photovoltaic feed-in systems are known on the market. WO 2021 / 204 519 A1 discloses a DC / DC converter device and a control / regulation system for a power grid. EP 3 915 825 B1 discloses a modular charging station for direct current charging of an electric vehicle battery. DE 20 2023 103 356 U1 discloses a low-voltage direct current distribution system.

[0003] The object of the present invention is to improve a direct current photovoltaic feed-in system.

[0004] The object is achieved according to the invention by a direct current photovoltaic feed-in system having the features specified in claim 1.

[0005] According to the invention, it was recognized that a control and regulation unit for insulation monitoring and voltage-dependent current regulation, which can switch at least one contactor and / or at least one modular electromechanical DC circuit breaker, ensures a safe and reliable DC photovoltaic feed-in system. The control and regulation unit can ensure that a building's DC grid is not overloaded by the DC current generated by photovoltaics. At the same time, it can ensure that insufficient DC current production prevents current from flowing back into the photovoltaic modules, which could damage them.

[0006] The control and regulation unit can switch the at least one contactor and / or the at least one modular electromechanical DC circuit breaker, in particular independently, based on predetermined limit values.

[0007] The modular electromechanical DC circuit breaker is preferably modularly scalable. The DC circuit breaker has, in particular, several contactor switches, via which the two inputs of the modular electromechanical DC circuit breaker can be separated.

[0008] The DC circuit breaker comprises a series connection of a first and a second switching element, a fuse, and a braking resistor as a current-limiting device. Instead of the braking resistor, an overvoltage protection device can alternatively be connected in parallel or in series as a current-limiting device.

[0009] Furthermore, the modular electromechanical DC circuit breaker has sensors, which can preferably be used to measure a Hall effect that occurs on a magnetic core that is placed around the lines in the circuit breaker. These sensors serve as a current monitoring unit. The DC circuit breaker preferably has at least one such current monitoring unit. The DC circuit breaker can in particular have at least two, in particular at least three, in particular at least four, in particular at least five current monitoring units.

[0010] Furthermore, the DC line breaker preferably has several parallel switchable lines, wherein at least one of these lines can be switched with the original current, and at least one further line has a braking resistor via which the switchable current can be braked. The circuit breaker in particular has a contactor control via which the internal contactors of the switch arrangement can be switched.

[0011] Such a DC circuit breaker is also called a Modular Residual Current Device (MRCD for short) and has at least one leakage current monitoring unit and at least one power contactor as a switching element with isolating properties.

[0012] An MRCD can be used in the area of “protection against electric shock as fault protection by automatically switching off the power supply in the event of a fault” or as a preventive fire protection measure.

[0013] An MRCD can be flexibly adapted to a system. Furthermore, an MRCD reduces nuisance tripping. An MRCD enables fault current detection using a measuring current transformer, independent of the line voltage and / or line frequency. An MRCD can also be used with high load currents.

[0014] Using an MRCD, information on the insulation level can be determined early on before shutdown. Furthermore, an MRCD can prevent unplanned and costly plant downtimes and ensure greater operational and plant safety.

[0015] Preferably, the DC photovoltaic feed-in system can comprise more than one photovoltaic module. The DC photovoltaic feed-in system can comprise, in particular, at least two photovoltaic modules, in particular at least three photovoltaic modules, in particular at least four photovoltaic modules, in particular at least five photovoltaic modules, in particular at least 10 photovoltaic modules, in particular more than ten photovoltaic modules.

[0016] The DC photovoltaic feed-in system comprises, in particular, at least one switch cabinet. Preferably, all components of the DC photovoltaic feed-in system are arranged in the at least one switch cabinet. Alternatively, the components of the DC photovoltaic feed-in system can be distributed among several interconnected switch cabinets.

[0017] The DC photovoltaic feed-in system further comprises at least one DC distribution line, which is connected to the DC grid via the DC circuit breaker. The DC distribution line is also connected to the photovoltaic modules via the DC-DC converters. The DC-DC converters can convert the DC current generated by the photovoltaic modules into the rated power of the DC grid. The DC distribution line enables the electrical connection of the individual components of the DC photovoltaic feed-in system.

[0018] Using at least one contactor, individual photovoltaic modules can be selectively disconnected from the DC distribution line. This allows power generation to be controlled. Furthermore, damage to individual photovoltaic modules can be prevented in the event of an overload on the DC distribution line. Furthermore, individual photovoltaic modules can be disconnected from the power grid for maintenance.

[0019] The DC photovoltaic feed-in system according to claim 2 enables a modular photovoltaic structure. Each assembly preferably has at least one series connection of at least two photovoltaic modules. Each photovoltaic assembly can preferably have at least two, in particular at least three, in particular at least four, in particular a maximum of five series connections of photovoltaic modules. Each series connection has, in particular, at least two photovoltaic modules. Each series connection can, in particular, have at least five photovoltaic modules, in particular at least ten photovoltaic modules, in particular at least fifteen photovoltaic modules, in particular at least twenty photovoltaic modules, in particular at least twenty-five photovoltaic modules, in particular a maximum of thirty photovoltaic modules.

[0020] By providing multiple series connections per photovoltaic module, it is possible to disconnect only individual series connections from the DC grid. In particular, only individual series connections can be disconnected for maintenance or in the event of defects in individual photovoltaic modules, without shutting down the entire system. This results in high availability of at least some of the photovoltaic modules for power generation.

[0021] A DC photovoltaic feed-in system according to claim 3 allows the generated power to be discharged via an insulation cable when the photovoltaic module is disconnected from the DC grid. This ensures that the photovoltaic module is not damaged by the generated power. Furthermore, the insulation cable enables measurement via an insulation measurement. The measured value can be queried by the control and regulation unit to determine the power generated by the photovoltaic modules connected to the insulation cable.

[0022] A DC photovoltaic feed-in system according to claim 4 allows the photovoltaic module to be connected to the insulation line only when needed. For this purpose, the switching matrix has, in particular, four contacts connected in series. The switching matrix can also have three contacts, in particular two contacts, or in particular only one contact connected in series. Alternatively, the switching matrix can have more than four contacts connected in series.

[0023] A DC photovoltaic feed-in system according to claim 5 ensures that the photovoltaic modules are not damaged by an overvoltage.

[0024] A DC photovoltaic feed-in system according to claim 6 enables the control and regulation unit to be operated using the power generated by the photovoltaic modules. For this purpose, the DC voltage can be converted to 24 V DC, which can correspond to the input voltage of the control and regulation unit. In particular, the DC-DC converter can be configured to provide the appropriate input voltage for a control and regulation unit used.

[0025] A DC photovoltaic feed-in system according to claim 7 guarantees at least short-term operation of the control and regulation unit in the event of a power failure. This ensures that the control and regulation unit can open or close the at least one contactor and / or the at least one circuit breaker even after a power failure, in order to establish a safe state of the DC photovoltaic feed-in system, preventing damage to the DC photovoltaic feed-in system, for example, upon restart of the power flow. Furthermore, the uninterruptible power supply can absorb voltage spikes to prevent damage to the control and regulation unit.

[0026] A direct current photovoltaic feed-in system according to claim 8 represents a preferred embodiment. 650 V direct voltage has proven particularly effective in practice.

[0027] A DC photovoltaic feed-in system according to claim 9 prevents overloading of the individual components due to overcurrent.

[0028] A direct current photovoltaic feed-in system according to claim 10 enables the connection of the direct current grid to an alternating current grid. In particular, the alternating current grid of a building can be connected to the photovoltaic system mounted on the roof and the resulting direct current grid.

[0029] A DC photovoltaic feed-in system according to claim 11 prevents damage to components in case of overload.

[0030] A DC photovoltaic feed-in system according to claim 12 prevents damage to the components of the DC photovoltaic feed-in system in the event of an overload.

[0031] A direct current photovoltaic feed-in system according to claim 13 represents a preferred embodiment. A three-phase alternating current network is formed, for example, by the alternating current network of a building.

[0032] A DC photovoltaic feed-in system according to claim 14 is suitable for use with an AC network of a building.

[0033] A DC photovoltaic feed-in system according to claim 15 ensures that the components of the DC photovoltaic feed-in system are not damaged in the event of an overload.

[0034] An embodiment of the subject matter of the invention is shown in the figure. It shows: Fig. 1 a circuit diagram of a feed-in system according to the invention.

[0035] In Fig.Figure 1 shows a circuit diagram of a direct current photovoltaic feed-in system 1. The circuit arrangement of the direct current photovoltaic feed-in system 1 is arranged in a control cabinet (not shown). The feed-in system 1 is designed to feed direct current from a photovoltaic array 2 into a direct current grid 3. The direct current grid 3 has a nominal voltage of 650 V. For this purpose, the photovoltaic array 2 is connected to a direct current distribution line 4.

[0036] The DC distribution line 4 is connected to the DC network 3 via a modular electromagnetic DC circuit breaker 5.

[0037] The photovoltaic arrangement 2 comprises several photovoltaic assemblies 6 and an insulation line 7. The insulation line 7 has an insulation measurement 16.

[0038] Each photovoltaic assembly 6 comprises three series circuits 8 with several photovoltaic modules 9. In general, each series circuit 8 can have up to thirty photovoltaic modules 9. Each photovoltaic assembly 6 can in turn have up to five series circuits 8.

[0039] The individual series circuits 8 of a photovoltaic module 6 are connected to one another in a parallel circuit, wherein each line of the individual series circuits 8 has a fuse disconnector 10 comprising a DC fuse.

[0040] Each photovoltaic module 6 is connected to the DC distribution line 4 via a line section. Contactors 11, a unidirectional AC converter 12, and AC fuses 13 are arranged in the line section between the photovoltaic module 6 and the DC distribution line 4. The contactors 11 and the AC fuses 13 are provided in each conductor of the line section.

[0041] The photovoltaic module 6 is also connected to the insulation line 7 and to an overvoltage contactor 14 via a line section in the line section between the contactor 11 and the unidirectional AC converter 12. The line section between the photovoltaic module 6 and the insulation line 7 has a switching matrix 15 for the insulation measurement 16.

[0042] The modular electromechanical DC line breaker 5 comprises several components. The structure of the circuit breaker 5 is described in more detail below, with the first-mentioned components being arranged on the DC distribution line 4 side, and the order of component naming corresponding to the order in which the components are arranged. In other words, the structure is described from bottom to top in the illustration.

[0043] The circuit breaker 5 comprises power contactors 17, a magnetic core 18, which encompasses both the positive and negative lines, a sensor 19 arranged on the magnetic core 18, which is preferably designed as a Hall-effect sensor, and another magnetic core 20, which extends only around the positive line, with another sensor 21, which is preferably also designed as a Hall-effect sensor. The sensors 19 and 21 are signal-connected to an evaluation device 22.

[0044] After the measurement by the sensors 19, 21, the circuit breaker 5 has a line section with two parallel line sections. In the first line section, both the plus line and the minus line each have a contactor 23, followed by a fuse 24, followed by another contactor 25. In a second parallel line section, the plus-minus line has a braking resistor 26, which preferably has a braking resistance of 140 Ω. Subsequently, both the plus line and the minus line have a contactor 27, followed by a fuse 28 and another contactor 29. The contactors 23, 25, 27, and 29 can be controlled via a contactor control 30. By selectively switching the contactors 23, 25, 27, 29, the DC distribution line 4 can be coupled to the DC network 3 with or without braking resistor 26.

[0045] The DC network 3 also has an overvoltage protection 31.

[0046] The DC photovoltaic feed-in system 1 further comprises a control and regulation unit 32. The control and regulation unit 32 is connected to the DC distribution line 4 via a line section. The line section between the control and regulation unit 32 and the DC distribution line 4 comprises an uninterruptible power supply 33 providing 24 V DC, a DC converter 34 capable of converting 650 V DC to 24 V DC, and AC fuses 13. The control and regulation unit 32 is signal-connected to the contactors 11, the power contactors 17, the switching matrix 15, the insulation measurement unit 16, the DC converters 12, and the evaluation device 22. Via the signal connection, the control and regulation unit 32 can receive measurement results and send control signals for controlling the contactors 11.

[0047] Individual photovoltaic modules 6 or the entire photovoltaic array 2 can be coupled into or decoupled from the direct current grid 3 via the control and regulation unit 32. The control and regulation unit 32 couples and / or decouples the photovoltaic modules 6 depending on the measurement signals from the insulation measurement device 16 and the evaluation device 22.

[0048] Overall, the control and regulation unit 32 is responsible for the independent control of direct current generation. Control can be carried out, in particular, based on prescribed limit values stored in the control and regulation unit 32.

[0049] The direct current network 3 is connected to an alternating current network 35. The connection between the direct current network 3 and the alternating current network 35 is established via a bidirectional voltage converter 36. DC fuses 37 are arranged between the direct current network and the bidirectional voltage converter 36. AC fuses 38 are arranged between the alternating current network 35 and the bidirectional voltage converter 36.

[0050] The AC network 35 has a nominal voltage of 400 V and is three-phase. The AC network represents the AC network of a building.

[0051] Through the connection between the direct current network 3 and the alternating current network 35, the energy generated can be used in the house itself or fed back into the power grid. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] WO 2021 / 204 519 A1

[0002] EP 3 915 825 B1

[0002] DE 20 2023 103 356 U1

[0002]

Claims

[1] DC photovoltaic feed-in system (1) for feeding DC current generated by photovoltaics into a DC grid (3), - with at least one control cabinet, - with at least one direct current distribution line (4), - with at least one photovoltaic module (6) which is connected to the direct current distribution line (4) via at least one direct current converter (12), - with at least one contactor (11) arranged between the at least one photovoltaic module (6) and the at least one DC-DC converter (12), - with at least one control and regulation unit (32) for insulation monitoring and voltage-dependent current regulation, - wherein the DC distribution line (4) is connected to the DC network (3) via at least one modular electromechanical DC circuit breaker (5), - wherein the at least one contactor (11) and / or the at least one modular electromechanical DC line switch (5) can be switched via the at least one control and regulating unit (32). [2] Feed system (1) according to claim 1, characterized by that the at least one photovoltaic assembly (6) comprises at least one series circuit (8) of at least two photovoltaic modules (9). [3] Feed system (1) according to one of claims 1 or 2, characterized by at least one insulation line (7) which is in electrically conductive connection with the at least one photovoltaic module (6). [4] Feed system (1) according to claim 3, characterized by at least one switching matrix (15) which can be switched by the control and regulation unit (32) and which is arranged between the at least one insulation line (7) and the at least one photovoltaic module (6). [5] Feed system (1) according to one of the preceding claims, characterized byat least one overvoltage protection device (14) which is arranged between the at least one photovoltaic module (6) and the at least one DC-DC converter (12). [6] Feed system (1) according to one of the preceding claims, characterized by that the at least one control and regulating unit (32) is connected to the direct current distribution line (4) via at least one further direct current converter (34). [7] Feed system (1) according to claim 6, characterized by that an uninterruptible power supply (33) is arranged between the at least one control and regulating unit (32) and the at least one further DC-DC converter (34). [8] Feed system (1) according to one of the preceding claims, characterized by that the direct current network (3) has a nominal voltage of 650 V. [9] Feed system (1) according to one of the preceding claims, characterized bythat a DC fuse (13) is arranged between the at least one DC voltage converter (12) and / or the at least one further DC voltage converter (34) and the DC distribution line (4). [10] Feed system (1) according to one of the preceding claims, characterized by that the direct current network (3) is connected to an alternating current network (35) via a bidirectional voltage converter (36). [11] Feed system (1) according to claim 10, characterized by that at least one DC fuse (37) is arranged between the DC network (3) and the bidirectional voltage converter (36). [12] Feed system (1) according to one of claims 10 or 11, characterized by that at least one AC fuse (38) is arranged between the bidirectional voltage converter (36) and the AC network (35). [13] Feed-in system (1) according to one of claims 10 to 12, designed for a three-phase alternating current network (35). [14] Feed system (1) according to one of claims 10 to 13, characterized by that the alternating current network (35) has a nominal voltage of 400 V. [15] Feed system (1) according to one of the preceding claims, characterized by that the direct current network (3) has an overvoltage protection (31).

Images