String type inverter and power generation system
By designing the MPPT unit in the string inverter with the positive and negative currents in opposite directions to cancel each other out, the operating bias current of the RSD coupling core is reduced, the integration problem of the RSD transmitter in high-power inverters is solved, low-cost RSD function is realized, and the integrity of PLC signal coupling is maintained.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-08
- Publication Date
- 2026-04-10
AI Technical Summary
For high-power string photovoltaic inverters, the high DC bias current leads to an increase in the core size of the fast shutdown device, which increases the cost and difficulty of integrating the RSD transmitter inside the inverter.
By designing different MPPT units in a string inverter with opposite current directions for the positive and negative lines to cancel each other out, the operating bias current of the RSD coupled magnetic core is reduced. The transmission of the fast turn-off signal is achieved using a PLC carrier signal generator and the coupled magnetic core, avoiding the need to increase the size or number of magnetic cores.
The core saturation current requirement has been reduced, the cost of integrating the RSD transmitter into the inverter has been reduced, the integration problem of the RSD transmitter in high-power inverters has been solved, and the differential mode signal coupling function of the PLC has not been affected.
Smart Images
Figure CN224111131U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to a kind of group string inverter and power generation system, especially a kind of group string inverter of built-in rapid shutdown (RSD) transmitter. BACKGROUND
[0002] For group string photovoltaic inverter, multiple photovoltaic groups in photovoltaic array are connected to the direct current input end of specified group string photovoltaic inverter, and direct current to alternating current conversion is completed at the group string photovoltaic inverter. In some schemes, a rapid shutdown (RSD) is configured and an RSD transmitter is built-in in the photovoltaic inverter. When it is detected that the direct current input to the photovoltaic inverter by the photovoltaic group exceeds the setting, a shutdown signal is sent through the RSD transmitter to quickly cut off the connection between the photovoltaic group and the photovoltaic inverter, and the photovoltaic group cannot inject power to the photovoltaic inverter. However, for high-power group string photovoltaic inverters (more than 50KW), the direct current bias current flowing through the rapid shutdown is high, and the high direct current bias current leads to an increase in the size of the magnetic core of the rapid shutdown, which is not conducive to the integration of the RSD transmitter inside the inverter, and also brings high cost.
[0003] The above information disclosed in the BACKGROUND section is only used to enhance the understanding of the background of the present application, and therefore it can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY
[0004] Therefore, the utility model provides a kind of group string inverter and power generation system, and it is beneficial to realize the transmitter of built-in rapid shutdown with lower cost on the direct current side of inverter.
[0005] The utility model adopts the following technical solutions:
[0006] A kind of group string inverter, including N road MPPT unit, N is greater than or equal to 3 positive integer, each MPPT unit includes DC / DC module, positive direct current access terminal connected with the DC / DC module by positive power line and negative direct current access terminal connected with the DC / DC module by negative power line;
[0007] The group string inverter further includes RSD transmitter, the RSD transmitter includes coupling magnetic core capable of accessing rapid shutdown signal, wherein the positive power line of n road MPPT unit passes through the coupling magnetic core, the negative power line of N-n road MPPT unit passes through the coupling magnetic core, and n is a positive integer less than N.
[0008] In a preferred embodiment, the RSD transmitter is disposed within a housing of the string inverter, and the RSD transmitter further comprises a fast-off signal generator connected to the coupling core to send a fast-off signal to the coupling core.
[0009] In a more preferred embodiment, the fast-off signal transmitter is a PLC carrier signal generator for sending a PLC carrier signal as the fast-off signal.
[0010] In a further preferred embodiment, the coupling core comprises a PLC signal coupling inductor, and the PLC carrier signal generator is connected to the PLC signal coupling inductor through a PLC signal line to send a PLC carrier signal to the PLC signal coupling inductor.
[0011] In a preferred embodiment, N is a positive integer between 3 and 10.
[0012] In a more preferred embodiment, N is an even number, n=N / 2; or, N is an odd number, n=(N+1) / 2.
[0013] In a preferred embodiment, each negative power line of the n MPPT units is located outside the coupling core, and each positive power line of the N-n MPPT units is located outside the coupling core.
[0014] In a preferred embodiment, the string inverter further comprises a DC / AC module, and each output terminal of the MPPT units is connected to the DC / AC module.
[0015] The utility model discloses still adopt following technical scheme:
[0016] A power generation system comprises N DC power generation units, and further comprises N RSD receiving boxes and a string inverter as described above.
[0017] In a preferred embodiment, the RSD receiving box is connected to the positive power line or the negative power line passing through the coupling core to receive the coupled-out SunSpec signal through the positive power line or the negative power line.
[0018] In an embodiment, the DC power generation unit comprises a photovoltaic panel or a battery. In a more preferred embodiment, the DC power generation unit comprises a photovoltaic panel, and the string inverter is a string photovoltaic power generation system.
[0019] The utility model adopts the above scheme and has the following advantages:
[0020] The string type inverter and power generation system of the utility model, through the positive line and the negative line current direction of different MPPT unit opposite offset, reduce the working bias current of RSD coupling magnetic core, do not need to increase the size or quantity of RSD coupling magnetic core can solve the problem that under high input current of high power, it is difficult to integrate RSD transmitter function in inverter DC side, at the same time, any DC power generation unit connected with MPPT unit and inverter still constitute RSD system, do not affect PLC differential mode signal coupling. BRIEF DESCRIPTION OF DRAWINGS
[0021] In order to more clearly illustrate the technical scheme of the utility model, the following will be needed to use the drawings in the embodiment description, obviously, the drawings in the following description only some embodiments of the utility model, for those skilled in the art, under the premise of not paying creative labor, other drawings can also be obtained according to these drawings.
[0022] Figure 1 It is the topology diagram of the power generation system of the comparative example.
[0023] Figure 2 It is the topology diagram of the power generation system according to the embodiment of the utility model.
[0024] Among them: 100-inverter;200-photovoltaic string;300-RSD receiving box;
[0025] 110-first MPPT unit;111-first DC / DC module;112-first positive power line;113-first negative power line;
[0026] 120-second MPPT unit;121-second DC / DC module;122-second positive power line;123-second negative power line;
[0027] 130-third MPPT unit;131-third DC / DC module;132-third positive power line;133-third negative power line;
[0028] 140-DC / AC module;
[0029] 150-RSD transmitter;151-coupling magnetic core;152-PLC carrier signal generator;153-PLC signal line. DETAILED DESCRIPTION
[0030] The preferred embodiments of the utility model are described in detail below in combination with the drawings, so that the advantages and characteristics of the utility model can be more easily understood by those skilled in the art.It needs to be explained here that the description of these embodiments is used to help understanding the utility model, but does not constitute the limitation of the utility model.
[0031] Comparative Example
[0032] Figure 1 A power generation system of the comparative example is shown, which includes a string inverter 100, multiple photovoltaic strings 200 and an RSD system. The RSD system is composed of one RSD transmitter 150 and multiple RSD receiving boxes 300. Each photovoltaic string 200 is connected to the DC side of the string inverter 100 through one RSD receiving box 300.
[0033] As shown in Figure 1 , the inverter 100 includes 3 MPPT units (including a first MPPT unit 110, a second MPPT unit 120, a third MPPT unit 130, or more). Each MPPT unit includes a DC / DC module, a positive DC access terminal and a negative DC access terminal for accessing the DC output of the photovoltaic string 200. The positive DC access terminal is connected to the DC / DC module through a positive power line, and the negative DC access terminal is connected to the DC / DC module through a negative power line. The string inverter 100 includes an RSD transmitter 150. The RSD transmitter 150 includes a coupling magnetic core 151 capable of accessing a fast-off signal, wherein the positive power line of each MPPT unit passes through the coupling magnetic core 151, and the negative power line is located outside the coupling magnetic core 151. The string inverter 100 further includes a DC / AC module 140, and the output of each MPPT unit is connected to the DC / AC module 140. The DC / AC module 140, each DC / DC module, and the RSD transmitter 150 described above are integrated in the box of the string inverter 100.
[0034] As shown in detail Figure 1 , the first positive power line 112 of the first DC / DC module 111 of the first MPPT unit 110 is directly connected to the first positive DC access terminal PV1+, without passing through the coupling magnetic core 151, and the first negative power line 113 is connected to the first negative DC access terminal PV1- after passing through the coupling magnetic core 151. Similarly, the second positive power line 122 of the second DC / DC module 121 of the second MPPT unit 120 is directly connected to the second positive DC access terminal PV2+, without passing through the coupling magnetic core 151, and the second negative power line 123 is connected to the second negative DC access terminal PV2- after passing through the coupling magnetic core 151. The third positive power line 132 of the third DC / DC module 131 of the third MPPT unit 130 is directly connected to the third positive DC access terminal PV3+, without passing through the coupling magnetic core 151, and the third negative power line 133 is connected to the third negative DC access terminal PV3- after passing through the coupling magnetic core 151.
[0035] The RSD transmitter 150 further comprises a PLC carrier signal generator 152 connected with the coupling core 151 to send a PLC carrier signal as a fast turn-off signal to the coupling core 151. The coupling core 151 comprises a PLC signal coupling inductor, and the PLC carrier signal generator 152 and the PLC signal coupling inductor are connected through a PLC signal line 153 to send the PLC carrier signal to the PLC signal coupling inductor. The fast turn-off principle is that the DC input power line passes through the magnetic core of the RSD transmitter to realize differential mode signal coupling, and Sunspec signals are sent to the component-side RSD receiving box in a PLC communication mode.
[0036] In the comparative example, the three PV power lines pass through the coupling core together, and this architecture is only suitable for low-power scenarios. In a high-power scenario, there will be more than 3 PV string inputs, and using this scheme will generate a high DC bias current, causing the coupling core to saturate and fail, and the system will not be able to transmit the PLC carrier signal. Taking a 50KW string inverter as an example, the typical input current is 5*40A=200A (5 PV inputs, 40Amppt current). If the RSD function is integrated in the 50KW string inverter, the 5 input PV power lines need to pass through the magnetic core of the RSD transmitter, and the magnetic core of the RSD transmitter needs to withstand a 200A DC bias current. In order to avoid the saturation failure of the coupling core, a magnetic core with stronger anti-saturation capability needs to be selected, or additional cores are connected in parallel. Either way will result in an increase in system cost and integration difficulty. High DC bias current leads to an increase in the size of the magnetic core, which is not conducive to the integration of the RSD transmitter in the inverter, and also brings higher cost.
[0037] Embodiment
[0038] Figure 2 A power generation system of the embodiment is shown, which comprises a string inverter 100, multiple DC power generation units, and an RSD system. The DC power generation units are PV strings 200, and can also be batteries, etc. The RSD system is composed of an RSD transmitter 150 and multiple RSD receiving boxes 300. Each PV string 200 is connected to the DC side of the string inverter 100 through an RSD receiving box 300. The RSD transmitter 150 is integrated on the DC side of the string inverter 100.
[0039] As Figure 2As shown, one string inverter 100 of the present embodiment includes N MPPT units (including a first MPPT unit 110, a second MPPT unit 120, a third MPPT unit 130, or more), where N is a positive integer greater than or equal to 3. N can further be a positive integer between 3 and 10. Each MPPT unit includes a DC / DC module, a positive DC access terminal and a negative DC access terminal for accessing DC power output by the photovoltaic string 200. The positive DC access terminal is connected to the DC / DC module via a positive power line, and the negative DC access terminal is connected to the DC / DC module via a negative power line.
[0040] The string inverter 100 includes an RSD transmitter 150. The RSD transmitter 150 includes a coupled magnetic core 151 capable of accessing a fast-off signal, where the positive power lines of some of the MPPT units pass through the coupled magnetic core 151, and the negative power lines of the remaining MPPT units pass through the coupled magnetic core 151. In other words, the positive power lines of n MPPT units pass through the coupled magnetic core 151, and the negative power lines of N-n MPPT units pass through the coupled magnetic core 151, where n is a positive integer less than N. It should be noted that the negative power lines of the n MPPT units are located outside the coupled magnetic core 151, and the positive power lines of the N-n MPPT units are located outside the coupled magnetic core 151. If N is even, then n = N / 2; if N is odd, then n = (N+1) / 2.
[0041] In particular embodiments, the string inverter 100 includes a DC / DC module 140, a positive DC access terminal 141 and a negative DC access terminal 142 for accessing DC power output by the photovoltaic string 200. The positive DC access terminal 141 is connected to the DC / DC module 140 via a positive power line, and the negative DC access terminal 142 is connected to the DC / DC module 140 via a negative power line. Figure 2In the shown example, N=3, i.e. three MPPT units are included, accessing three PV strings 200. The first positive power line 112 of the first DC / DC module 111 of the first MPPT unit 110 is directly connected to the first positive DC access terminal PV1+, without passing through the coupling core 151, and the first negative power line 113 is connected to the first negative DC access terminal PV1- after passing through the coupling core 151; the first positive DC access terminal PV1+ and the first negative DC access terminal PV1- are further connected to a RSD receiving box 300 by DC power lines, the RSD receiving box 300 is connected to one of the PV strings 200, and the RSD receiving box 300 controls the PV string 200 to generate power to the first DC / DC module 111. The second positive power line 122 of the second DC / DC module 121 of the second MPPT unit 120 is connected to the second positive DC access terminal PV2+ after passing through the coupling core 151, and the second negative power line 123 is directly connected to the second negative DC access terminal PV2- without passing through the coupling core 151; the second positive DC access terminal PV2+ and the second negative DC access terminal PV2- are further connected to a second RSD receiving box 300 by DC power lines, the second RSD receiving box 300 is connected to a second one of the PV strings 200, and the second RSD receiving box 300 controls the second PV string 200 to generate power to the second DC / DC module 121. Similarly to the first MPPT unit 110, the third positive power line 132 of the third DC / DC module 131 of the third MPPT unit 130 is directly connected to the third positive DC access terminal PV3+ without passing through the coupling core 151, and the third negative power line 133 is connected to the third negative DC access terminal PV3- after passing through the coupling core 151; the third positive DC access terminal PV3+ and the third negative DC access terminal PV3- are further connected to a third RSD receiving box 300 by DC power lines, the third RSD receiving box 300 is connected to a third one of the PV strings 200, and the third RSD receiving box 300 controls the third PV string 200 to generate power to the third DC / DC module 131.
[0042] Although Figure 2 Although three MPPT units are shown, it should be understood that in applications, four, five or more MPPT units can be provided according to requirements, but all need to meet the requirement that the positive power lines of part of the MPPT units pass through the coupling core 151, and the negative power lines of the remaining part of the MPPT units pass through the coupling core 151.
[0043] The RSD transmitter 150 is arranged in the box of the string inverter 100. The string inverter 100 further comprises a DC / AC module 140, and the output of each MPPT unit is connected to the DC / AC module 140. The DC / AC module 140, each DC / DC module, and the RSD transmitter 150 described above are integrated in the box of the string inverter 100. The DC / DC module can be a boost circuit, for example, a direct current boost circuit. The DC / AC module 140 is an energy conversion unit, for example, converting the direct current transmitted by the DC / DC module into alternating current, feeding the power grid or supplying the load.
[0044] The RSD transmitter 150 further comprises a fast shutdown signal generator, and the fast shutdown signal generator and the coupling magnetic core 151 are connected to send a fast shutdown signal to the coupling magnetic core 151. Further, the fast shutdown signal transmitter is a PLC carrier signal generator 152 for sending a PLC carrier signal as a fast shutdown signal. The coupling magnetic core 151 comprises a PLC signal coupling inductor, and the PLC carrier signal generator 152 and the PLC signal coupling inductor are connected through a PLC signal line 153 to send a PLC carrier signal to the PLC coupling inductor.
[0045] In this embodiment, the PLC carrier signal generator 152 can generate a PLC carrier signal conforming to the SunSpec fast shutdown protocol standard. The direct current power line passes through the coupling magnetic core 151 to couple out the SunSpec signal, and the SunSpec signal is transmitted to the RSD receiving box 300 using the direct current power line. The RSD receiving box 300 comprises a fast shutdown receiver, which controls the direct current power generation unit to generate power to the inverter 100. If the RSD receiving box 300 receives the SunSpec signal, the direct current power generation unit can provide direct current input to the inverter 100 through the RSD receiving box 300; if the RSD receiving box 300 cannot receive the SunSpec signal, the RSD receiving box 300 is shut down, and the direct current power generation unit cannot inject power to the inverter 100.
[0046] Figure 2 In this embodiment, the 2-way PV- and 1-way PV+ power lines pass through the coupling magnetic core 151 together. Compared with the comparative example shown in Figure 1 Compared with the comparative example shown in the comparative example, in the improved topology system, any PV can still perform PLC signal differential mode coupling, and the maximum direct current bias current of the coupling magnetic core 151 is reduced, and the minimum can be reduced to 2-way PV current, and the maximum can be reduced to 2-way PV current. This embodiment does not affect the function of the RSD system, but can reduce the saturation current of the magnetic core, which is beneficial to the low-cost integration of the RSD function of the inverter 100, and solves the problem of saturation of the magnetic element of the fast shutdown transmitter (RSD transmitter) integrated in the high-power (more than 50KW) string inverter.
[0047] In the embodiment, the working bias current of the RSD coupling magnetic core 151 is reduced by the opposite directions of the positive line and the negative line between different MPPT units; any DC power generation unit and the inverter 100 still constitute an RSD system, and the PLC differential mode signal coupling is not affected; without increasing the size or the number of the RSD coupling magnetic core 151, the difficulty of integrating the RSD transmitter 150 function under the high input current of the high-power (more than 50KW) inverter can be solved. The saturation bias current requirement of the inverter 100 integrated with the RSD transmitter can be reduced, and the minimum reduction can be matched with the parameter selection according to half of the input current of the inverter 100. The system cost is low, and the installation requirement of the inverter 100 integrated with the RSD transmitter 150 is reduced.
[0048] As shown in the specification and claims, the terms "comprise" and "include" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements. The term "and / or" used herein includes any combination of one or more related listed items.
[0049] It can be further understood that "multiple" in the present disclosure means two or more, and other quantifiers are similar.
[0050] It should be noted that, unless otherwise specified, when a certain feature is referred to as "connected" to another feature, it can be directly connected to the other feature or indirectly connected to the other feature.
[0051] The above embodiments are only for illustrating the technical concept and characteristics of the present application, and are a preferred embodiment, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent transformation or modification made according to the principle of the present application should be covered within the protection scope of the present application.
Claims
1. A string inverter comprising N MPPT units, N being a positive integer greater than or equal to 3, each MPPT unit comprising a DC / DC module, a positive DC access terminal connected to the DC / DC module through a positive power line, and a negative DC access terminal connected to the DC / DC module through a negative power line. characterized in that The string inverter further comprises an RSD transmitter comprising a coupled magnetic core capable of accessing a fast-off signal, wherein the positive power lines of n MPPT units pass through the coupled magnetic core, and the negative power lines of N-n MPPT units pass through the coupled magnetic core, n being a positive integer less than N.
2. The string inverter of claim 1, wherein The RSD transmitter is disposed in a box of the string inverter, and the RSD transmitter further comprises a fast-off signal generator connected to the coupled magnetic core to send a fast-off signal to the coupled magnetic core.
3. The string inverter of claim 2, wherein, The fast-off signal transmitter is a PLC carrier signal generator for sending a PLC carrier signal as the fast-off signal.
4. The string inverter of claim 3, wherein, The coupled magnetic core comprises a PLC signal coupling inductor, and the PLC carrier signal generator is connected to the PLC signal coupling inductor through a PLC signal line to send a PLC carrier signal to the PLC signal coupling inductor.
5. The string inverter of claim 1, wherein, N is a positive integer between 3 and 10.
6. The string inverter of claim 5, wherein, N is an even number, and n = N / 2; or, N is an odd number, and n = (N+1) / 2.
7. The string inverter of claim 1, wherein The negative power lines of the n MPPT units are located outside the coupled magnetic core, and the positive power lines of the N-n MPPT units are located outside the coupled magnetic core.
8. The string inverter of claim 1, wherein, The string inverter further comprises a DC / AC module, and the output terminals of each MPPT unit are connected to the DC / AC module.
9. A power generation system comprising N number of DC power generation units, characterized in that, The power generation system further comprises N RSD receiving boxes and the string inverter of any one of claims 1 to 8, and each DC power generation unit is connected to the positive DC access terminal and the negative DC access terminal of one MPPT unit of the string inverter through one RSD receiving box.
10. The power generation system of claim 9, wherein, The RSD receiving box is connected to the positive power line or the negative power line passing through the coupled magnetic core to receive a coupled SunSpec signal through the positive power line or the negative power line, and the DC power generation unit comprises a photovoltaic panel or a battery.