Photovoltaic inverter and method of assembling the same

Abstract

The application discloses a photovoltaic inverter and an assembling method thereof. The photovoltaic inverter comprises a box body, a main circuit board and an alternating current output module. The alternating current output module comprises a shell, which is installed in the box body; an EMC circuit board, which is arranged in the shell and is provided with a filter; an alternating current input terminal, which is arranged in the shell, one end of the alternating current input terminal is connected to the EMC circuit board, and the alternating current input terminal is further provided with an external input end penetrating out of the shell, the external input end is connected to the main circuit board; and an alternating current output terminal, one end of the alternating current output terminal is located in the shell and is connected to the EMC circuit board, the alternating current output terminal is further provided with an external output end penetrating out of the shell and the box body, and the external output end is configured to be connected to a power grid or a load; wherein the filter is connected between one end of the alternating current input terminal and one end of the alternating current output terminal. The photovoltaic inverter adopts compact design, reduces assembly difficulty of a production line, reduces parasitic parameters, improves filtering efficiency, stabilizes filtering consistency and disperses heat sources.

Description

Technical Field

[0001] This invention relates to a photovoltaic inverter and its assembly method. Background Technology

[0002] A photovoltaic (PV) inverter mainly consists of a DC input terminal, a boost circuit, an inverter circuit, an AC output terminal, a control circuit, a chassis, and heat sinks. Energy storage inverters add battery terminals, off-grid terminals, and generator terminals, and are characterized by bidirectional energy management and independent power supply capabilities. The core of a PV inverter is its ability to convert the variable DC voltage generated by photovoltaic (PV) solar panels into AC power at the mains frequency, which can be fed back to the commercial power transmission system or supplied to the off-grid grid. PV inverter circuit boards must be equipped with EMC filter circuits to suppress high-frequency noise and meet electromagnetic compatibility standards. Existing PV inverters with EMC filter circuits have the following problems: (1) Parasitic inductance problem: The PCB layout needs to take into account all components, resulting in longer traces for the filter circuit and back-and-forth traces under the filter inductor, which greatly increases the parasitic inductance between discrete components (≥50nH). In addition, the distance between the AC input terminal and the PCB terminal wire is ≥80mm, and the parasitic inductance of the wire is ≥50nH.

[0003] (2) Problem of reduced filtering performance: The wires between the AC output terminal and the filtering circuit are easily crosstalked by the internal noise space of the machine, forming a secondary radiating antenna, which reduces the original filtering circuit's intended effect.

[0004] (3) Space utilization issue: An EMC filter circuit is added to the PCB inside the machine, which occupies 20% of the PCB size.

[0005] (4) Assembly Difficulty: Traditional inverters connect the AC input terminals and PCB terminals via long connecting wires. Due to parasitic inductance and secondary interference, the EMC performance is weak, requiring improved EMC performance to meet standard requirements. This typically necessitates additional filtering measures. Currently, the photovoltaic industry's solution is to add a ferrite core and multiple turns to the AC input connection wire, usually more than three turns, to address radiation exceeding standards. However, this introduces several problems: First, because the ferrite core is fixed to the AC input wire, it cannot be pre-processed and must be wound during assembly, increasing assembly difficulty and extending assembly time. Second, due to differences in production line personnel and assembly difficulty, the distance between the ferrite core and the AC input terminal varies, deviating from the expected target and causing EMC consistency deviations. Third, the ferrite cores have inconsistent shapes, resulting in aesthetic discrepancies.

[0006] (5) Heat dissipation problem: The filter circuit is laid out on the PCB and adjacent to the relay, so the heat source is relatively concentrated. It is necessary to add aluminum or copper strips to the projection position of the relay on the PCB for auxiliary heat dissipation. At the same time, the internal fan needs to take into account the airflow of the relay and the common mode inductor. This increases the difficulty of mechanical engineering and indirectly affects the heat dissipation of IGBT and power inductor.

[0007] The information disclosed in the background section is only intended to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0008] This invention provides a photovoltaic inverter with a compact design, integrating the EMC filter circuit with AC terminals. This reduces assembly difficulty on production lines, improves assembly efficiency, reduces parasitic parameters, enhances filtering efficiency, stabilizes filtering consistency, reduces structural design complexity, disperses heat sources, and lowers overall cost. This invention also provides an assembly method for the photovoltaic inverter, further reducing assembly difficulty and improving assembly efficiency on production lines.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A photovoltaic inverter includes a housing and a main circuit board disposed within the housing. The photovoltaic inverter further includes an AC output module, the AC output module comprising: A housing, which is installed inside the box; An EMC circuit board is disposed within the housing, and a filter is disposed on the EMC circuit board; An AC input terminal is disposed inside the housing. One end of the AC input terminal is connected to the EMC circuit board. The AC input terminal also has an external input terminal extending outside the housing, and the external input terminal is connected to the main circuit board. An AC output terminal, one end of which is located inside the housing and connected to the EMC circuit board, the AC output terminal also having an external output terminal extending through the housing and the enclosure, the external output terminal being configured to connect to the power grid or a load; The filter is connected between one end of the AC input terminal and one end of the AC output terminal.

[0010] According to a preferred aspect, the housing encloses a cavity, and the EMC circuit board and the filter are enclosed within the cavity.

[0011] According to a more preferred aspect, the AC output module further includes a sealing material infused within the housing.

[0012] According to a further preferred aspect, the sealing material comprises a thermally conductive adhesive, and the sealing material is infused between the EMC circuit board and / or the filter and the housing.

[0013] According to a preferred aspect, the AC output module includes a common-mode inductor, a Cx capacitor, and a Cy capacitor, which are disposed on the EMC circuit board to form a single-stage or multi-stage filter.

[0014] According to a more preferred aspect, the AC output module further includes a resistor, and the Cy capacitor and the resistor constitute a high-pass filter or a low-pass filter.

[0015] According to a preferred aspect, the AC input terminal includes a live copper busbar and a neutral copper busbar, the live copper busbar and the neutral copper busbar being soldered onto the EMC circuit board; The AC output terminal includes a live copper busbar, a neutral copper busbar, and a ground copper busbar. The live copper busbar and the neutral copper busbar are soldered to the EMC circuit board, and the ground copper busbar is in contact with the housing. The housing includes a metal shielding layer.

[0016] According to a more preferred aspect, the AC input terminal and the filter are directly connected or connected through the line layer of the EMC circuit board, and the AC output terminal and the filter are directly connected or connected through the line layer of the EMC circuit board.

[0017] According to a preferred aspect, the housing is fixed to the bottom plate or side plate of the housing, the main circuit board is disposed above the bottom plate, and in a top view, the external input terminal is aligned with or has a gap with one side edge of the main circuit board, the external input terminal is connected to the main circuit board through a connecting piece, and the width of the gap is less than one-third of the length of the connecting piece.

[0018] The present invention also adopts the following technical solution: An assembly method for the photovoltaic inverter includes the following steps: The EMC circuit board is placed in the housing, one end of the AC input terminal is soldered to the EMC circuit board, and the other end of the AC input terminal is located outside the housing as an external input terminal; one end of the AC output terminal is soldered to the EMC circuit board; wherein, the filter of the EMC circuit board is connected between the AC input terminal and the AC output terminal; The housing is sealed by filling it with sealing material. The housing is placed inside the photovoltaic inverter's enclosure, with the other end of the AC output terminal extending outside the enclosure to form an external output terminal for connecting to the power grid or load. Connect the external input terminal to the main circuit board inside the enclosure.

[0019] According to a preferred aspect, the external input terminal is connected to the main circuit board inside the housing via a bent connecting piece.

[0020] The above-mentioned solution adopted in this invention has the following advantages: The photovoltaic inverter of this invention effectively utilizes space, reducing space occupation by more than 5%, and is lightweight and compact. The AC output terminals and filter circuits have no wire connections, reducing parasitic inductance by 50%. It effectively avoids secondary interference from wires, solves the drawbacks of winding magnetic rings around the input lines of the AC output terminals, improves heat source distribution, facilitates production line assembly, is easy to maintain, and has aesthetically pleasing ports. The assembly method of the photovoltaic inverter of this invention reduces the difficulty of production line assembly and improves assembly efficiency. Attached Figure Description

[0021] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a photovoltaic inverter according to an embodiment of the present invention; Figure 2 This is a perspective view of an AC output module according to an embodiment of the present invention; Figure 3 This is an internal structural diagram of an AC output module according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a filter circuit according to an embodiment of the present invention; Figure 5 This is a schematic diagram of an AC output terminal according to an embodiment of the present invention; Figure 6 This is a circuit diagram of an EMC filtering module according to an embodiment of the present invention.

[0023] in, 1. Housing; 2. Main circuit board; 3. AC output module; 4. Upper shell; 5. Lower shell; 6. AC output terminal; 61. Terminal block; 62. External output terminal; 7. AC input terminal; 71. External input terminal; 8. EMC circuit board; 9. Common mode inductor; 10. Cx capacitor; 11. Cy capacitor; 12. Sealing material; 13. Connecting piece. Detailed Implementation

[0024] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is for the purpose of aiding understanding the present invention, but does not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Reference Figures 1 to 5 As shown, the photovoltaic inverter of this embodiment includes a housing 1, a main circuit board 2, and an AC output module 3. The housing 1 can be a metal housing with one open end. The main circuit board 2 is disposed inside the housing 1, and the open end of the housing 1 can be closed by a top cover. The main circuit board 2 is equipped with an inverter bridge (including multiple IGBTs) for converting DC to AC power. Multiple relays can also be installed on the main circuit board 2 for on / off grid switching, etc. The DC input terminal of the main circuit board 2 can be connected to a photovoltaic panel. Unlike traditional inverter circuit boards, the main circuit board 2 of this embodiment does not have an EMC filter module for the AC output terminal.

[0026] The AC output module 3 includes: a housing, an EMC circuit board 8, AC input terminals 7, and AC output terminals 6. The AC output module 3 integrates AC output and filtering functions.

[0027] The housing may include an upper shell 4 and a lower shell 5 that are flush with each other. The housing is installed inside the enclosure 1, for example, fixed to the bottom plate and / or side plate of the enclosure 1. The housing includes an external metal shielding layer and a plastic structure located inside the metal shielding layer. The metal shielding layer meets certain shielding effectiveness requirements, and the plastic material needs to be flame retardant.

[0028] The EMC circuit board 8 is housed within the casing, and a filter is mounted on the EMC circuit board 8. Specifically, such as... Figure 6 As shown, the AC output module 3 includes a common-mode inductor 9, a Cx capacitor 10, and a Cy capacitor 11. These three capacitors are mounted on the EMC circuit board 8 and housed within the casing to form a single-stage or multi-stage filter, thus creating a filtering module. The common-mode inductor 9 can be an inductor wound with amorphous / manganese-zinc / nickel-zinc materials, and has a toroidal or racetrack-shaped magnetic core. The Cy capacitor 11 can be a capacitor array consisting of multiple capacitors, connected between the phase line and ground, and between the neutral line and ground, in the EMC filter circuit. The Cx capacitor 10 can also be a capacitor array consisting of multiple capacitors, connected between the phase line and neutral line of the EMC filter circuit, or connected in a star configuration between the Cx capacitors 10. This star connection balances the parasitic parameters between the phases, improving the suppression capability of high-frequency differential-mode noise.

[0029] The AC output module 3 also includes a resistor, which is mounted on the EMC circuit board 8. The Cy capacitor 11 and the resistor form a high-pass filter or a low-pass filter. If the resistor is placed before the Cy capacitor 11, a low-pass filter is formed. The higher the signal frequency, the smaller the capacitive reactance, and consequently, the smaller the voltage drop across the capacitor. Therefore, higher frequencies are less likely to be transmitted to the downstream end. If the Cy capacitor 11 is placed before the resistor, a high-pass filter is formed. The higher the signal frequency, the smaller the voltage drop across the capacitor, and consequently, the larger the voltage drop across the resistor. Therefore, higher frequencies are more likely to be transmitted to the downstream end.

[0030] The AC input terminal 7 is located inside the housing. One end of the AC input terminal 7 is connected to the EMC circuit board 8. The AC input terminal 7 also has an external input terminal 71 that extends outside the housing and is connected to the main circuit board 2.

[0031] One end of the AC output terminal 6 is located inside the housing and connected to the EMC circuit board 8. The AC output terminal 6 also has an external output terminal 62 extending outside the housing and enclosure 1. The external output terminal 62 is configured to connect to the power grid or a load. The external output terminal 62 can be a standard threaded terminal or a plug-in interface for connecting to the power grid cable.

[0032] A single or multi-stage filter, consisting of a common-mode inductor 9, capacitor Cx 10, capacitor Cy 11, or resistors, is connected between one end of the AC input terminal 7 and one end of the AC output terminal 6. One end of the AC input terminal 7 and one end of the AC output terminal 6 are directly soldered to both sides of the EMC circuit board 8, employing a wire-free direct connection structure to reduce wire connections. A metal shielding layer completely covers the area where the single or multi-stage filter is located, and the grounding terminal can be integrated into the design. This integrated structure blocks the common-mode current discharge path, reduces parasitic inductance of the wires, simplifies the port design, and constructs a differential-mode resonance suppression network within a housing independent of the inverter enclosure 1 and the main circuit board 2, avoiding secondary interference and facilitating installation.

[0033] The housing forms a cavity, within which the EMC circuit board 8 and the filter are enclosed. The AC output module 3 also includes a sealing material 12 filled into the housing. The sealing material 12 includes thermally conductive adhesive. The sealing material 12 is filled between the EMC circuit board 8 and / or the filter and the housing, which can transfer heat from the heat-generating components of the filter to the housing.

[0034] The AC input terminal 7 includes a live wire copper busbar and a neutral wire copper busbar, which are soldered to the EMC circuit board 8. The AC output terminal 6 includes a live wire copper busbar, a neutral wire copper busbar, and a grounding copper busbar. The live wire copper busbar and the neutral wire copper busbar are soldered to the EMC circuit board 8. The grounding copper busbar is in contact with the housing and conducts electricity. The housing ultimately contacts the metal enclosure 1, forming a grounding path.

[0035] The AC input terminal 7 is directly connected to the filter or connected through the wiring layer of the EMC circuit board 8, and the AC output terminal 6 is directly connected to the filter or connected through the wiring layer of the EMC circuit board 8, which effectively reduces the use of wires.

[0036] Furthermore, the external input terminal 71 is connected to the main circuit board 2 via a connecting piece (such as a copper sheet), the width of which is less than one-third of the length of the connecting piece. The main circuit board 2 is positioned above the base plate. From a top-down view, the external input terminal 71 and one side edge of the main circuit board 2 are aligned or have a very small gap, thereby minimizing the length of the connecting piece. In this embodiment, the AC output module 3 and the main circuit board 2 are on two different planes. In particular, the EMC circuit board 8 of the AC output module 3 is lower than the main circuit board 2. The connecting piece is designed with a bent shape, with one end (lower end) connected to the copper busbar of the external input terminal 71, and the other end (upper end) extending upward (through the aforementioned gap) to connect to the AC output port of the main circuit board 2.

[0037] Specifically, the housing includes an upper shell 4 and a lower shell 5, with the EMC circuit board 8 fixed inside the lower shell 5 by screws. The upper shell 4 or the lower shell 5 is fixed to the bottom plate or side plate of the enclosure 1 by multiple screws. The external output terminal 62 is fixed to a terminal block 61, which is a component of the housing and is fixed to the upper shell 4 and / or the lower shell 5 by multiple screws, and the terminal block 61 is locked to the side plate of the enclosure 1 by multiple screws.

[0038] The external output terminal 62 is also equipped with a sign to prevent misconnection.

[0039] An assembly method for a photovoltaic inverter according to an embodiment includes the following steps: An EMC circuit board 8 with a filter installed is provided, wherein the EMC circuit board 8 is provided with a common mode inductor 9, a Cx capacitor 10, a Cy capacitor 11, and a resistor can also be provided; The EMC circuit board 8 is placed in the housing. One end of the AC input terminal 7 is soldered to the EMC circuit board 8, and the other end of the AC input terminal 7 is located outside the housing as an external input terminal 71. One end of the AC output terminal 6 is soldered to the EMC circuit board 8. The filter of the EMC circuit board 8 is connected between the AC input terminal 7 and the AC output terminal 6. The housing is sealed by filling it with sealing material 12. Place the housing inside the photovoltaic inverter housing 1, so that the other end of the AC output terminal 6 extends outside the housing 1 to form an external output terminal 62 for connecting to the power grid or load. Connect the external input terminal 71 to the main circuit board 2 inside the housing 1.

[0040] The external input terminal 71 is connected to the main circuit board 2 inside the housing 1 by a bent connecting piece.

[0041] In this embodiment, the filter circuit prioritizes EMC performance, featuring a compact layout and short traces, thus controlling parasitic inductance (<20nH). The external input terminal 71 of the AC output module with integrated filtering function is directly connected to the main circuit board, and the external output terminal 62 is directly connected to the plug of the external cable, resulting in a direct-connection structure without wires and controlling parasitic inductance of the wires (<20nH).

[0042] The housing uses a metal shielding layer, which can effectively shield the possibility of electromagnetic interference inside the machine, ensuring the EMC performance of the filter circuit in the AC output module. For the output terminal of the AC output module, i.e., the output terminal of AC output 6, noise from inside the inverter cannot bypass the filter circuit in the AC output module to cause secondary interference to the AC output terminal wires, thus ensuring that the AC output terminal is a clean EMC output.

[0043] The AC output module can be placed between the AC output terminal 6 and the main circuit board wiring terminal, making full use of the space between the AC input terminal 7 and the AC wiring terminal of the main circuit board (the distance between the two is 60mm), thereby saving 20% ​​of the space of the main circuit board and reducing the inverter volume by 5%.

[0044] The photovoltaic inverter in this embodiment is simple to assemble, has high EMC stability, avoids the risk of poor EMC consistency in mass production and shipment, and also reduces the possibility of secondary maintenance by R&D personnel.

[0045] The photovoltaic inverter in this embodiment also improves heat source distribution, reduces auxiliary heat dissipation costs, simplifies structural design, and ensures effective channels for IGBTs and power inductors.

[0046] As indicated in this specification and claims, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, and these steps and elements do not constitute an exclusive list; the 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.

[0047] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to the other feature, or indirectly fixed or connected to the other feature. Furthermore, the descriptions of "up," "down," "left," and "right" used in this invention are only relative to the relative positional relationships of the various components of the invention in the accompanying drawings.

[0048] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are preferred embodiments. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and they should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made according to the principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A photovoltaic inverter, comprising a housing and a main circuit board disposed within the housing, characterized in that, The photovoltaic inverter also includes an AC output module, which includes: A housing, which is installed inside the box; An EMC circuit board is disposed within the housing, and a filter is disposed on the EMC circuit board; An AC input terminal is disposed inside the housing. One end of the AC input terminal is connected to the EMC circuit board. The AC input terminal also has an external input terminal extending outside the housing, and the external input terminal is connected to the main circuit board. An AC output terminal, one end of which is located inside the housing and connected to the EMC circuit board, the AC output terminal also having an external output terminal extending through the housing and the enclosure, the external output terminal being configured to connect to the power grid or a load; The filter is connected between one end of the AC input terminal and one end of the AC output terminal.

2. The photovoltaic inverter according to claim 1, characterized in that, The housing encloses a cavity, and the EMC circuit board and the filter are enclosed within the cavity.

3. The photovoltaic inverter according to claim 2, characterized in that, The AC output module also includes a sealing material filled inside the housing.

4. The photovoltaic inverter according to claim 3, characterized in that, The sealing material includes thermally conductive adhesive, and the sealing material is injected between the EMC circuit board and / or the filter and the housing.

5. The photovoltaic inverter according to claim 1, characterized in that, The AC output module includes a common-mode inductor, a Cx capacitor, and a Cy capacitor, which are disposed on the EMC circuit board to form a single-stage or multi-stage filter.

6. The photovoltaic inverter according to claim 5, characterized in that, The AC output module also includes a resistor, and the Cy capacitor and the resistor constitute a high-pass filter or a low-pass filter.

7. The photovoltaic inverter according to claim 1, characterized in that, The AC input terminal includes a live wire copper busbar and a neutral wire copper busbar, which are soldered onto the EMC circuit board. The AC output terminal includes a live copper busbar, a neutral copper busbar, and a ground copper busbar. The live copper busbar and the neutral copper busbar are soldered to the EMC circuit board, and the ground copper busbar is in contact with the housing. The housing includes a metal shielding layer.

8. The photovoltaic inverter according to claim 7, characterized in that, The AC input terminal and the filter are directly connected or connected through the circuit layer of the EMC circuit board, and the AC output terminal and the filter are directly connected or connected through the circuit layer of the EMC circuit board.

9. The photovoltaic inverter according to claim 1, characterized in that, The housing is fixed to the bottom plate or side plate of the housing, and the main circuit board is disposed above the bottom plate. In a top view, the external input terminal is aligned with one side edge of the main circuit board or has a gap. The external input terminal is connected to the main circuit board through a connecting piece, and the width of the gap is less than one-third of the length of the connecting piece.

10. A method for assembling a photovoltaic inverter according to claim 1, comprising the following steps: The EMC circuit board is placed inside the housing. One end of the AC input terminal is soldered to the EMC circuit board, while the other end of the AC input terminal is located outside the housing as an external input terminal. One end of the AC output terminal is soldered to the EMC circuit board. The filter on the EMC circuit board is connected between the AC input terminal and the AC output terminal; The housing is sealed by filling it with sealing material. The housing is placed inside the photovoltaic inverter's enclosure, with the other end of the AC output terminal extending outside the enclosure to form an external output terminal for connecting to the power grid or load. Connect the external input terminal to the main circuit board inside the enclosure.

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