Photovoltaic inverter and photovoltaic system

Abstract

The utility model discloses a photovoltaic inverter and a photovoltaic system. The photovoltaic inverter comprises an MPPT circuit, a first switch and a third switch are connected to the positive electrode of the MPPT circuit, and a second switch and a fourth switch are connected to the negative electrode of the MPPT circuit. A first positive terminal, a second positive terminal and a third positive terminal which are sequentially connected with the first to third paths of photovoltaic strings are connected to the first switch, and a fourth positive terminal, a fifth positive terminal and a sixth positive terminal which are sequentially connected with the fourth to sixth paths of photovoltaic strings are connected to the third switch; a first negative terminal, a second negative terminal and a fourth negative terminal which are sequentially connected with the first photovoltaic string, the second photovoltaic string and the fourth photovoltaic string are connected to the second switch, and a third negative terminal, a fifth negative terminal and a sixth negative terminal which are sequentially connected with the third photovoltaic string, the fifth photovoltaic string and the sixth photovoltaic string are connected to the fourth switch. According to the utility model, under the condition that the maximum current of the tripping switches is not changed, the MPPT input current is improved, and the number of the tripping switches is reduced.

Description

Technical Field

[0001] The utility model belongs to the field of photovoltaic inverters, and in particular relates to a photovoltaic inverter and a photovoltaic system. Background Art

[0002] To improve the DC ratio of photovoltaic power generation systems (the ratio of the power of the photovoltaic unit to the input power of the photovoltaic inverter), each MPPT circuit typically connects two or more photovoltaic units. If one photovoltaic unit short-circuits, the short-circuit current is the sum of the output currents of the other connected photovoltaic units. When there is only one connected photovoltaic unit, the short-circuit current is small, and the photovoltaic unit and the circuit can withstand this short-circuit current. However, when there are two or more connected photovoltaic units, the short-circuit current is large, exceeding the photovoltaic unit's tolerance. To protect the photovoltaic units and the circuit, fuses can be connected in series with the positive or negative output terminals of the photovoltaic units. This protects the photovoltaic units and the circuit from overcurrent. However, because fuses typically have a high breaking current and take a long time to blow, they often fail to effectively protect the photovoltaic units and the circuit. Furthermore, fuse failure rates are relatively high, resulting in low reliability.

[0003] To address the above problem, an improved solution is to use a remote tripping switch to interrupt the fault current and achieve protection. Figure 1 The figure shows a connection method, where S1-S3 represent the different pole switches of a trip switch corresponding to an MPPT circuit. Once a PV short circuit or reverse connection is detected, the control system issues a trip command, controlling the corresponding pole switch to open. After the pole switch opens, no more than two PV lines are short-circuited together. In this case, the short-circuit current does not exceed the output current of any single PV line, requiring no special treatment and preventing damage to the PV string. This solution effectively prevents damage to the PV string from abnormally high currents. However, to ensure that no more than two PV lines are short-circuited together, the current in each stage of the trip switch is not balanced; this results in an excessive number of trip switches, limiting further improvements in system power density.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the application and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Utility Model Content

[0005] The utility model provides a photovoltaic inverter and a photovoltaic system, which effectively increase the MPPT input current without changing the maximum current of the trip switch, reduce the number of trip switches, and improve the current utilization rate of the trip switches.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A photovoltaic inverter includes an MPPT circuit and a wiring module for connecting multiple photovoltaic strings to the MPPT circuit, the wiring module including a switch unit, the switch unit including a first switch, a second switch, a third switch, and a fourth switch, one end of the first switch and one end of the third switch being connected to the positive electrode of the MPPT circuit, and one end of the second switch and one end of the fourth switch being connected to the negative electrode of the MPPT circuit;

[0008] The wiring module has a first positive terminal for connecting to the positive electrode of the first photovoltaic string, a second positive terminal for connecting to the positive electrode of the second photovoltaic string, a third positive terminal for connecting to the positive electrode of the third photovoltaic string, a fourth positive terminal for connecting to the positive electrode of the fourth photovoltaic string, a fifth positive terminal for connecting to the positive electrode of the fifth photovoltaic string, and a sixth positive terminal for connecting to the positive electrode of the sixth photovoltaic string, the first positive terminal, the second positive terminal, and the third positive terminal are connected to the other end of the first switch, and the fourth positive terminal, the fifth positive terminal, and the sixth positive terminal are connected to the other end of the third switch;

[0009] The wiring module also has a first negative terminal for connecting the negative pole of the first photovoltaic string, a second negative terminal for connecting the negative pole of the second photovoltaic string, a third negative terminal for connecting the negative pole of the third photovoltaic string, a fourth negative terminal for connecting the negative pole of the fourth photovoltaic string, a fifth negative terminal for connecting the negative pole of the fifth photovoltaic string, and a sixth negative terminal for connecting the negative pole of the sixth photovoltaic string. The first negative terminal, the second negative terminal, and the fourth negative terminal are connected to the other end of the second switch, and the third negative terminal, the fifth negative terminal, and the sixth negative terminal are connected to the other end of the fourth switch.

[0010] In some preferred embodiments, the switch unit is a 4-pole trip switch, and the first switch, the second switch, the third switch, and the fourth switch are pole switches of the 4-pole trip switch respectively.

[0011] In some more preferred embodiments, the positions of the four pole switches of the 4-pole trip switch are arranged in the order of the first switch, the second switch, the third switch to the fourth switch.

[0012] Furthermore, the first switch, the second switch, the third switch and the fourth switch are sequentially arranged on the housing of the four-pole trip switch.

[0013] In some other more preferred embodiments, the positions of the four pole switches of the 4-pole trip switch are arranged in the order of the second switch, the first switch, the third switch, to the fourth switch.

[0014] Furthermore, the second switch, the first switch, the third switch and the fourth switch are sequentially arranged on the housing of the four-pole trip switch.

[0015] In some preferred embodiments, the MPPT circuit includes a first MPPT circuit and a second MPPT circuit, the first switch and the second switch are correspondingly connected to the positive and negative poles of the first MPPT circuit, and the third switch and the fourth switch are correspondingly connected to the positive and negative poles of the second MPPT circuit.

[0016] In some optional embodiments, the MPPT circuit includes a single MPPT circuit, and the first switch, the second switch, the third switch, and the fourth switch are connected to the single MPPT circuit.

[0017] Another technical solution adopted by the utility model is as follows:

[0018] A photovoltaic system includes multiple photovoltaic strings. The photovoltaic system also includes the photovoltaic inverter. The photovoltaic inverter is connected to the six photovoltaic strings via its wiring module.

[0019] In a preferred embodiment, the switch unit is a remote trip switch, the trip switch is electrically connected to a controller, and all switches of the trip switch are remotely controlled to be opened or closed by the controller.

[0020] The above solution adopted by the present invention has the following advantages:

[0021] This photovoltaic inverter achieves more balanced current per pole in the switches used in the wiring modules connecting photovoltaic strings. This effectively increases the MPPT input current without changing the maximum switch current. For the same MPPT and photovoltaic string capacity, the number of switches used in the wiring modules is reduced, improving current utilization and reducing costs. For the same MPPT capacity, photovoltaic string capacity, and switch selection, heating of the wiring module switches is reduced, resulting in more balanced switch current distribution.

[0022] In the preferred solution, the problem of high voltage between adjacent switches of the wiring module after the photovoltaic string is reversely connected is further solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 The present invention is a wiring diagram of a photovoltaic inverter and a photovoltaic string in the prior art.

[0025] Figure 2 This is a wiring diagram of a photovoltaic inverter and a photovoltaic string according to Example 1 of the present utility model.

[0026] Figure 3 Schematic diagram of the switch voltage distribution of the photovoltaic inverter after the third photovoltaic string is reversely connected according to Example 1 of the present utility model.

[0027] Figure 4 This is a wiring diagram of a photovoltaic inverter and a photovoltaic string according to Example 2 of the present utility model.

[0028] Figure 5 Schematic diagram of the switch voltage distribution of the photovoltaic inverter after the third photovoltaic string is reversely connected according to Example 2 of the present utility model.

[0029] Figure 6 This is a wiring diagram of a photovoltaic inverter and a photovoltaic string according to Example 3 of the present utility model.

[0030] in,

[0031] 1. MPPT circuit; 11. First MPPT circuit; 12. Second MPPT circuit;

[0032] 2. Wiring module; 211. First positive terminal; 212. Second positive terminal; 213. Third positive terminal; 214. Fourth positive terminal; 215. Fifth positive terminal; 216. Sixth positive terminal; 221. First negative terminal; 222. Second negative terminal; 223. Third negative terminal; 224. Fourth negative terminal; 225. Fifth negative terminal; 226. Sixth negative terminal. DETAILED DESCRIPTION

[0033] The following describes in detail preferred embodiments of the present invention in conjunction with the accompanying drawings to make the advantages and features of the present invention more easily understood by those skilled in the art. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0034] The photovoltaic inverter of the following embodiment is mainly optimized and improved in the connection between the multi-channel photovoltaic string input and the remote trip switch.

[0035] Example 1

[0036] Figure 2 The figure shows the connection method between the photovoltaic inverter and multiple photovoltaic strings of this embodiment. The photovoltaic inverter includes an MPPT (maximum power point tracking) circuit 1 and a wiring module 2 for connecting the multiple photovoltaic strings to the MPPT circuit 1. In this embodiment, the multiple photovoltaic strings are specifically: a first photovoltaic string PV1, a second photovoltaic string PV2, a third photovoltaic string PV3, a fourth photovoltaic string PV4, a fifth photovoltaic string PV5, and a sixth photovoltaic string PV6. The photovoltaic inverter is connected to the six photovoltaic strings PV1 to PV6 through its wiring module 2.

[0037] The wiring module 2 includes a switch unit, which includes a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4. One end of the first switch S1 and one end of the third switch S3 are connected to the positive electrode of the MPPT circuit 1, and one end of the second switch S2 and one end of the fourth switch S4 are connected to the negative electrode of the MPPT circuit 1. In this embodiment, the MPPT circuit 1 includes a first MPPT circuit 11 and a second MPPT circuit 12. One end of the first switch S1 is connected to the positive electrode of the first MPPT circuit 11, and one end of the second switch S2 is connected to the negative electrode of the first MPPT circuit 11; one end of the third switch S3 is connected to the positive electrode of the second MPPT circuit 12, and one end of the fourth switch S4 is connected to the negative electrode of the second MPPT circuit 12.

[0038] The switch unit is a four-pole trip switch, with the first switch S1, second switch S2, third switch S3, and fourth switch S4 serving as pole switches for the four-pole trip switch. Furthermore, the four pole switches of the four-pole trip switch are arranged sequentially in the order of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4. That is, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are sequentially arranged on the housing of the four-pole trip switch. In some embodiments, four switch slots are arranged in parallel on the housing, with the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 being sequentially arranged in these four switch slots. Thus, in terms of spatial position, the first switch S1 and the second switch S2 are adjacent, the second switch S2 and the third switch S3 are adjacent, and the third switch S3 and the fourth switch S4 are adjacent.

[0039] The wiring module 2 has a first positive terminal 211 for connecting to the positive pole of the first photovoltaic string PV1, a second positive terminal 212 for connecting to the positive pole of the second photovoltaic string PV2, a third positive terminal 213 for connecting to the positive pole of the third photovoltaic string PV3, a fourth positive terminal 214 for connecting to the positive pole of the fourth photovoltaic string PV4, a fifth positive terminal 215 for connecting to the positive pole of the fifth photovoltaic string PV5, and a sixth positive terminal 216 for connecting to the positive pole of the sixth photovoltaic string PV6. The first positive terminal 211, the second positive terminal 212, and the third positive terminal 213 are connected to the other end of the first switch S1, and the fourth positive terminal 214, the fifth positive terminal 215, and the sixth positive terminal 216 are connected to the other end of the third switch S3.

[0040] The wiring module 2 further has a first negative terminal 221 for connecting to the negative pole of the first photovoltaic string PV1, a second negative terminal 222 for connecting to the negative pole of the second photovoltaic string PV2, a third negative terminal 223 for connecting to the negative pole of the third photovoltaic string PV3, a fourth negative terminal 224 for connecting to the negative pole of the fourth photovoltaic string PV4, a fifth negative terminal 225 for connecting to the negative pole of the fifth photovoltaic string PV5, and a sixth negative terminal 226 for connecting to the negative pole of the sixth photovoltaic string PV6. The first negative terminal 221, the second negative terminal 222, and the fourth negative terminal 224 are connected to the other end of the second switch S2, and the third negative terminal 223, the fifth negative terminal 225, and the sixth negative terminal 226 are connected to the other end of the fourth switch S4.

[0041] Specifically, the first photovoltaic string PV1 is connected to the first positive terminal 211 and the first negative terminal 221, and is connected to the positive and negative poles of the first MPPT circuit 11 via the first switch S1 and the second switch S2, respectively. The second photovoltaic string PV2 is connected to the second positive terminal 212 and the second negative terminal 222, and is connected to the positive and negative poles of the first MPPT circuit 11 via the first switch S1 and the second switch S2, respectively. The positive pole of the third photovoltaic string PV3 is connected to the third positive terminal 213, and is connected to the positive pole of the first MPPT circuit 11 via the first switch S1; the negative pole of the third photovoltaic string PV3 is connected to the third negative terminal 223, and is connected to the negative pole of the second MPPT circuit 12 via the fourth switch S4. The positive pole of the fourth photovoltaic string PV4 is connected to the fourth positive terminal 214, and is connected to the positive pole of the second MPPT circuit 12 via the third switch S3; the negative pole of the fourth photovoltaic string PV4 is connected to the fourth negative terminal 224, and is connected to the negative pole of the first MPPT circuit 11 via the second switch S2. The fifth photovoltaic string PV5 is connected to the fifth positive terminal 215 and the fifth negative terminal 225, and is connected to the positive electrode and the negative electrode of the second MPPT circuit 12 through the third switch S3 and the fourth switch S4, respectively. The sixth photovoltaic string PV6 is connected to the sixth positive terminal 216 and the sixth negative terminal 226, and is connected to the positive electrode and the negative electrode of the second MPPT circuit 12 through the third switch S3 and the fourth switch S4, respectively.

[0042] The tripping protection method of the photovoltaic inverter includes:

[0043] If a short circuit or reverse connection fault is detected in the first photovoltaic string PV1 or the second photovoltaic string PV2, the first switch S1 and the second switch S2 are disconnected; specifically, the controller controls all switches of the remote trip switch to be disconnected.

[0044] If a short circuit or reverse connection fault is detected in the fifth photovoltaic string PV5 or the sixth photovoltaic string PV6, the third switch S3 and the fourth switch S4 are disconnected; specifically, the controller controls all switches of the remote trip switch to be disconnected.

[0045] If a short circuit or reverse connection fault is detected in the third photovoltaic string PV3 or the fourth photovoltaic string PV4, the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 are all disconnected; specifically, the controller controls all switches of the remote trip switch to be disconnected.

[0046] Combine Figure 3 To describe the principle of the photovoltaic inverter of this embodiment. In this embodiment, 6 photovoltaic strings are connected to 2 MPPT circuits 1 through a 4-level trip switch. The operating current of each photovoltaic string is In, so the total current processed by each MPPT circuit 1 is 3*In. Figure 1The circuit shown is different. The current flowing through each switch is three times the PV current. This effectively improves the current utilization of the switches, makes the current more evenly distributed, and reduces the number of trip switches used in each MPPT circuit 1. The positive poles of PV strings PV1, PV2, and PV3 are connected to the first switch S1, the negative poles of PV strings PV1, PV2, and PV4 are connected to the second switch S2, the positive poles of PV strings PV4, PV5, and PV6 are connected to the third switch S3, and the negative poles of PV strings PV3, PV5, and PV6 are connected to the fourth switch S4. Thus, the current flowing through switches S1, S2, S3, and S4 is three times the PV current (3*In).

[0047] If any of the PV strings PV1 to PV6 experiences a short circuit or reverse connection fault, the system detects the fault and promptly trips the trip switch. If the short-circuited or reversed string is one of PV1, PV2, PV5, or PV6, a loop current will still form with one of the other strings. However, because there are only two PV strings, only one PV short-circuit current will be generated, eliminating the risk of damage. If the short-circuited or reversed string is PV3 or PV4, the short-circuit path is severed, and no current will flow through any of the PV strings, ensuring safety.

[0048] Figure 3 The following diagram illustrates the reverse connection of PV string PV3, showing the relative potentials on the left side of each switch. Assuming the voltage generated by each PV string is V, the cathodes of PV strings PV1 and PV2 are at 0V (0V), meaning the potential on the left side of second switch S2 is 0V. The anodes of PV strings PV1 and PV2 are at 1 times the photovoltaic voltage (1V), meaning the potential on the left side of first switch S1 is 1V. The anode of PV string PV3, superimposed on the anodes of PV strings PV1 and PV2, is 2V, meaning the potential on the left side of fourth switch S4 is 2V. The anodes of PV strings PV5 and PV6, superimposed on the anode of PV string PV3, is 3V, meaning the potential on the left side of third switch S3 is 3V. Second switch S2 and third switch S3 are adjacent, and therefore face a relatively demanding 3V withstand voltage.

[0049] Example 2

[0050] Figure 4 The figure shows the connection method between the photovoltaic inverter and multiple photovoltaic strings of this embodiment. Figure 2The illustrated embodiment differs in that the connection order of the trip switches is changed, namely, the relative positions of the first through fourth switches S1, S4 are altered. Otherwise, the switch unit is essentially the same as in Example 1. Specifically, the switch unit is still a four-pole trip switch, with the first, second, third, and fourth switches S1, S2, S3, and S4 being the pole switches of the four-pole trip switch. The four pole switches of the four-pole trip switch are arranged in the order of the second switch S2, the first switch S1, the third switch S3, and the fourth switch S4. That is, the second switch S2, the first switch S1, the third switch S3, and the fourth switch S4 are arranged in sequence on the housing of the four-pole trip switch. In some embodiments, four switch slots are arranged in parallel on the housing, with the second switch S2, the first switch S1, the third switch S3, and the fourth switch S4 being arranged in sequence. Consequently, in terms of spatial position, the second switch S2 is adjacent to the first switch S1, the first switch S1 is adjacent to the third switch S3, and the third switch S3 is adjacent to the fourth switch S4.

[0051] The first positive terminal 211, the second positive terminal 212, and the third positive terminal 213 are connected to the other end of the first switch S1, and the fourth positive terminal 214, the fifth positive terminal 215, and the sixth positive terminal 216 are connected to the other end of the third switch S3. The first negative terminal 221, the second negative terminal 222, and the fourth negative terminal 224 are connected to the other end of the second switch S2, and the third negative terminal 223, the fifth negative terminal 225, and the sixth negative terminal 226 are connected to the other end of the fourth switch S4. Specifically, the first photovoltaic string PV1 is connected to the first positive terminal 211 and the first negative terminal 221, and are connected to the positive and negative poles of the first MPPT circuit 11 through the first switch S1 and the second switch S2, respectively. The second photovoltaic string PV2 is connected to the second positive terminal 212 and the second negative terminal 222, and are connected to the positive and negative poles of the first MPPT circuit 11 through the first switch S1 and the second switch S2, respectively. The positive electrode of the third photovoltaic string PV3 is connected to the third positive terminal 213, which is connected to the positive electrode of the first MPPT circuit 11 via the first switch S1. The negative electrode of the third photovoltaic string PV3 is connected to the third negative terminal 223, which is connected to the negative electrode of the second MPPT circuit 12 via the fourth switch S4. The positive electrode of the fourth photovoltaic string PV4 is connected to the fourth positive terminal 214, which is connected to the positive electrode of the second MPPT circuit 12 via the third switch S3. The negative electrode of the fourth photovoltaic string PV4 is connected to the fourth negative terminal 224, which is connected to the negative electrode of the first MPPT circuit 11 via the second switch S2. The fifth photovoltaic string PV5 is connected to the fifth positive terminal 215 and the fifth negative terminal 225, which are connected to the positive electrode and negative electrode of the second MPPT circuit 12 via the third switch S3 and the fourth switch S4, respectively. The sixth photovoltaic string PV6 is connected to the sixth positive terminal 216 and the sixth negative terminal 226, which are connected to the positive electrode and negative electrode of the second MPPT circuit 12 via the third switch S3 and the fourth switch S4, respectively.

[0052] like Figure 4 As shown, the positive poles of the photovoltaic strings PV1, PV2, and PV3 are connected to the first switch S1, the negative poles of the photovoltaic strings PV1, PV2, and PV4 are connected to the second switch S2, the positive poles of the photovoltaic strings PV4, PV5, and PV6 are connected to the third switch S3, and the negative poles of the photovoltaic strings PV3, PV5, and PV6 are connected to the fourth switch S4. This wiring method of Example 2 can reduce the withstand voltage of adjacent switches (especially the adjacent first switch S1 and third switch S3) after the third photovoltaic string PV3 or the fourth photovoltaic string PV4 is short-circuited or reversed. The specific principle is as follows: Figure 5 shown.

[0053] Reference Figure 5, which exemplifies the voltage distribution diagram of the trip switch when the third photovoltaic string PV3 is connected in reverse. Assuming the voltage generated by each photovoltaic string is V, with the cathodes of photovoltaic strings PV1 and PV2 at 0V (0*V), that is, the potential on the left side of second switch S2 is 0V; then the positive electrodes of photovoltaic strings PV1 and PV2 are at 1 times the photovoltaic voltage (1*V), that is, the potential on the left side of first switch S1 is 1*V; the positive electrode of photovoltaic string PV3 superimposes 2*V of the photovoltaic voltage on the positive electrodes of photovoltaic strings PV1 and PV2, that is, the potential on the left side of fourth switch S4 is 2*V; the positive electrodes of photovoltaic strings PV5 and PV6 superimpose 3*V of the photovoltaic voltage on the positive electrode of photovoltaic string PV3, that is, the potential on the left side of third switch S3 is 3*V. As can be seen from the figure, the withstand voltage between adjacent switches (especially the first switch S1 and the third switch S3) does not exceed 2 times the photovoltaic voltage, solving the problem of high withstand voltage between adjacent switches.

[0054] Example 3

[0055] Reference Figure 6 The photovoltaic inverter of this embodiment differs from that of Example 1 in the number of MPPT circuits 1. In this embodiment, the MPPT circuit 1 includes a single MPPT circuit 1, to which the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are connected. That is, six photovoltaic strings are connected in parallel through a single four-stage trip switch and connected to one MPPT circuit 1.

[0056] Specifically, a first photovoltaic string PV1 is connected to a first positive terminal 211 and a first negative terminal 221, and is connected to the positive and negative poles of the MPPT circuit 1 via a first switch S1 and a second switch S2, respectively. A second photovoltaic string PV2 is connected to a second positive terminal 212 and a second negative terminal 222, and is connected to the positive and negative poles of the MPPT circuit 1 via a first switch S1 and a second switch S2, respectively. A third photovoltaic string PV3 is connected to a third positive terminal 213 and a third negative terminal 223, and is connected to the positive and negative poles of the MPPT circuit 1 via a first switch S1 and a fourth switch S4, respectively. A fourth photovoltaic string PV4 is connected to a fourth positive terminal 214 and a fourth negative terminal 224, and is connected to the positive and negative poles of the MPPT circuit 1 via a third switch S3 and a second switch S2, respectively. A fifth photovoltaic string PV5 is connected to a fifth positive terminal 215 and a fifth negative terminal 225, and is connected to the positive and negative poles of the MPPT circuit 1 via a third switch S3 and a fourth switch S4, respectively. The sixth photovoltaic string PV6 is connected to the sixth positive terminal 216 and the sixth negative terminal 226, and is connected to the positive and negative terminals of the MPPT circuit 1 through the third switch S3 and the fourth switch S4, respectively. The operating current of each photovoltaic string is In, and the current handled by each switch is 3*In. Therefore, the total current handled by each MPPT circuit is 6*In.

[0057] In the above embodiment, a novel wiring method reduces the number of trip switches and lowers costs for the same MPPT and PV capacity. It also addresses current imbalance, helping to increase the DC-side PV current capacity. With the same switch selection, it can also increase the capacity of the PV string and MPPT. Furthermore, it can address the issue of high voltage between adjacent switches after reverse connection of PV strings. With the same MPPT capacity, PV capacity, and switch selection, it can also reduce trip switch heating and achieve more balanced switch current distribution.

[0058] As used in this specification and claims, the terms "comprises" and "include" merely indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list; a method or apparatus may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the associated listed items.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. If a definition used herein conflicts or is inconsistent with a definition in other published documents, the definition used herein shall prevail.

[0060] As used in this specification and claims, the terms "comprises" and "include" merely indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list; a method or apparatus may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the associated listed items.

[0061] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0062] Those skilled in the art will appreciate that all or part of the steps in the method for implementing the above-mentioned embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0063] In addition, the functional units in the embodiments may be integrated into a single processing module, each unit may exist physically separately, or two or more units may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or software functional modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they may also be stored in a computer-readable storage medium.

[0064] The above embodiment is intended only to illustrate the technical concept and features of the present invention and is a preferred embodiment. Its purpose is to enable those familiar with the art to understand the content of the present invention and implement it accordingly. It is not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A photovoltaic inverter comprising an MPPT circuit and a wiring module for connecting multiple photovoltaic strings to the MPPT circuit, characterized in that: The wiring module includes a switch unit, the switch unit includes a first switch, a second switch, a third switch and a fourth switch, one end of the first switch and one end of the third switch are connected to the positive electrode of the MPPT circuit, and one end of the second switch and one end of the fourth switch are connected to the negative electrode of the MPPT circuit; The wiring module has a first positive terminal for connecting to the positive electrode of the first photovoltaic string, a second positive terminal for connecting to the positive electrode of the second photovoltaic string, a third positive terminal for connecting to the positive electrode of the third photovoltaic string, a fourth positive terminal for connecting to the positive electrode of the fourth photovoltaic string, a fifth positive terminal for connecting to the positive electrode of the fifth photovoltaic string, and a sixth positive terminal for connecting to the positive electrode of the sixth photovoltaic string, the first positive terminal, the second positive terminal, and the third positive terminal are connected to the other end of the first switch, and the fourth positive terminal, the fifth positive terminal, and the sixth positive terminal are connected to the other end of the third switch; The wiring module also has a first negative terminal for connecting the negative pole of the first photovoltaic string, a second negative terminal for connecting the negative pole of the second photovoltaic string, a third negative terminal for connecting the negative pole of the third photovoltaic string, a fourth negative terminal for connecting the negative pole of the fourth photovoltaic string, a fifth negative terminal for connecting the negative pole of the fifth photovoltaic string, and a sixth negative terminal for connecting the negative pole of the sixth photovoltaic string. The first negative terminal, the second negative terminal, and the fourth negative terminal are connected to the other end of the second switch, and the third negative terminal, the fifth negative terminal, and the sixth negative terminal are connected to the other end of the fourth switch.

2. The photovoltaic inverter according to claim 1, characterized in that: The switch unit is a 4-pole trip switch, and the first switch, the second switch, the third switch and the fourth switch are pole switches of the 4-pole trip switch respectively.

3. The photovoltaic inverter according to claim 2, characterized in that: The positions of the four pole switches of the 4-pole trip switch are arranged in the order of the first switch, the second switch, the third switch to the fourth switch.

4. The photovoltaic inverter according to claim 3, characterized in that: The first switch, the second switch, the third switch and the fourth switch are sequentially arranged on the housing of the four-pole trip switch.

5. The photovoltaic inverter according to claim 2, characterized in that: The positions of the four pole switches of the 4-pole trip switch are arranged in the order of the second switch, the first switch, the third switch, to the fourth switch.

6. The photovoltaic inverter according to claim 5, characterized in that: The second switch, the first switch, the third switch and the fourth switch are sequentially arranged on the housing of the four-pole trip switch.

7. The photovoltaic inverter according to any one of claims 1 to 6, characterized in that: The MPPT circuit includes a first MPPT circuit and a second MPPT circuit, the first switch and the second switch are correspondingly connected to the positive and negative poles of the first MPPT circuit, and the third switch and the fourth switch are correspondingly connected to the positive and negative poles of the second MPPT circuit.

8. The photovoltaic inverter according to any one of claims 1 to 6, characterized in that: The MPPT circuit includes a single MPPT circuit, and the first switch, the second switch, the third switch, and the fourth switch are connected to the single MPPT circuit.

9. A photovoltaic system comprising multiple photovoltaic strings, characterized in that: The photovoltaic system further comprises the photovoltaic inverter according to any one of claims 1 to 8, wherein the photovoltaic inverter is connected to the six photovoltaic strings via a wiring module thereof.

Images