Junction box for photovoltaic modules and photovoltaic power generation system

Abstract

The present application provides a junction box for photovoltaic components and a photovoltaic power generation system, the junction box includes an inverter circuit, having a plurality of first switch tubes; a transformer, having a first port, a second port and a third port, the first port being connected to the inverter circuit; a rectifier circuit, having a plurality of second switch tubes and a first output terminal, the rectifier circuit being connected to the second port; a power optimization module, configured to generate a control signal for controlling the opening and closing of the plurality of first switch tubes and the plurality of second switch tubes according to the difference between the power information of the first output terminal and the reference power information, wherein the reference power information is a preset percentage of the output power information of the photovoltaic component. The junction box of the present application can not only separate the high-quality power and the low-quality power in the output power of the photovoltaic component, but also can use the separated low-quality power to power electrical appliances with low power quality requirements, thereby improving the utilization rate of the output power of the photovoltaic component.

Description

Technical Field

[0001] The present application mainly relates to the field of photovoltaic technology, and in particular to a junction box for a photovoltaic module and a photovoltaic power generation system. Background Art

[0002] Due to the influence of factors such as changes in light intensity and temperature, the output power of photovoltaic modules fluctuates, which will cause power mismatch, large voltage fluctuations, and harmonic pollution when photovoltaic modules are connected to the grid. Therefore, it is necessary to optimize the output power of photovoltaic modules. The technology for optimizing output power includes: setting a multi-stage filter circuit in the circuit to filter out unnecessary high-order harmonics to improve the smoothness of the DC voltage; using the maximum power point tracking (MPPT) technology to make the output power of the photovoltaic components smoother. Among them, the filter circuit is currently a commonly used output power optimization method. Its basic principle is to optimize the output power of photovoltaic modules by using the characteristics of inductance and capacitance having special impedance to alternating current. The filter circuit allows the current of a specific frequency in the circuit to pass or prevents the current of a specific frequency from passing, thereby reducing the AC component in the circuit and retaining the DC component to reduce the fluctuation of the output power. However, the filter circuit essentially transfers the AC component in the circuit to the inductor or capacitor, and the inductor and capacitor will consume this part of the AC component. Therefore, the AC component in the circuit is not utilized. In addition, the above-mentioned technical solution for optimizing output power also has the disadvantage of poor optimization effect. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a junction box for a photovoltaic module and a photovoltaic power generation system, which can separate the high-quality power and the low-quality power in the output power of the photovoltaic module, and the separated low-quality power can be used to power electrical appliances with lower requirements on power quality, thereby improving the utilization rate of the output power of the photovoltaic module.

[0004] To solve the above technical problems, the present application provides a junction box for a photovoltaic module, comprising: an inverter circuit having multiple first switching tubes; a transformer having a first port, a second port and a third port, the first port being connected to the inverter circuit; a rectifier circuit having multiple second switching tubes and a first output end, the rectifier circuit being connected to the second port; and a power optimization module, configured to generate a control signal for controlling the opening and closing of the multiple first switching tubes and the multiple second switching tubes according to the difference between the power information of the first output end and the reference power information, wherein the reference power information accounts for a preset percentage of the output power information of the photovoltaic module.

[0005] In an embodiment of the present application, the current output by the third port is alternating current.

[0006] In one embodiment of the present application, the power optimization module is configured to generate a control signal for controlling the opening and closing of the multiple first switching tubes and the multiple second switching tubes based on the difference between the power of the first output end and the reference power, wherein the reference power accounts for a preset percentage of the output power of the photovoltaic component.

[0007] In an embodiment of the present application, the preset percentage is 50% to 90%.

[0008] In an embodiment of the present application, the control signal includes a hysteresis time length of the plurality of second switch tubes relative to the corresponding first switch tubes.

[0009] In one embodiment of the present application, the power optimization module includes a proportional-integral controller and a control signal generator, and the proportional-integral controller is connected to the control signal generator, wherein the proportional-integral control is configured to generate the lag time according to the difference and send the lag time to the control signal generator, and the control signal generator generates the controller signal according to the lag time.

[0010] In an embodiment of the present application, the control signal is a pulse width modulation signal (PWM).

[0011] In one embodiment of the present application, a three-phase inverter circuit is further included, wherein the three-phase inverter circuit has a second output end, and the three-phase inverter circuit is connected to the first output end to convert the direct current output by the rectifier circuit into three-phase alternating current.

[0012] In one embodiment of the present application, the first switch tubes located on the same bridge arm are not turned on at the same time, and the second switch tubes located on the same bridge arm are not turned on at the same time.

[0013] The present application also proposes a photovoltaic power generation system, comprising: a plurality of photovoltaic modules; and a plurality of junction boxes as described above, each of the photovoltaic modules being connected to a corresponding junction box.

[0014] Compared with the technical solution of using inductance and capacitance to separate the high-quality power and low-quality power in the output power of photovoltaic modules, the junction box of the present application can not only separate the high-quality power and low-quality power in the output power of photovoltaic modules, but also use the separated low-quality power to power electrical appliances with lower requirements on power quality, thereby improving the utilization rate of the output power of photovoltaic modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0016] Figure 1 This is a schematic structural diagram of a junction box for a photovoltaic module according to an embodiment of the present application;

[0017] Figure 2 is a schematic diagram of the connection between the junction box and the photovoltaic module in one embodiment of the present application;

[0018] Figure 3 This is a schematic diagram of the working principle of a junction box in one embodiment of the present application;

[0019] Figure 4 It is a structural schematic diagram of an inverter circuit, a transformer and a rectifier circuit in one embodiment of the present application;

[0020] Figure 5 and Figure 6 It is a schematic diagram of the working principle of the power optimization module in two embodiments of the present application;

[0021] Figure 7 It is a schematic diagram of a pulse width modulation signal for controlling a first switch tube and a second switch tube in an embodiment of the present application.

[0022] Reference numerals

[0023] Photovoltaic module 10 first port 121

[0024] Battery cell 11 Second port 122

[0025] Heating device 20 third port 123

[0026] Wire 30 Rectification circuit 130

[0027] Junction box 100 First output terminal 131

[0028] Positive terminal box 101 Three-phase inverter circuit 140

[0029] Intermediate junction box 102 Second output terminal 141

[0030] and negative terminal box 103 power optimization module 150

[0031] Diode 104 Proportional-integral controller 151

[0032] Inverter circuit 110 Control signal generator 152

[0033] Transformer 120 DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0035] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0036] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0037] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0038] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0039] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0040] Next, the junction box of the present application is described through embodiments.

[0041] Figure 1 Schematic diagram of the structure of a junction box for a photovoltaic module according to an embodiment. Figure 1 As shown, the junction box 100 has input terminals PV+ and PV-, three-phase AC output terminals A~, B~ and C~, DC output terminals V+ and V-, and two-phase AC output terminal V~. Among them, the input terminals PV+ and PV- can be used to connect with the photovoltaic assembly 10 to receive the electric energy output by the photovoltaic assembly 10; the three-phase AC output terminals A~, B~ and C~ can be used to connect with electrical appliances or be incorporated into the power grid; the DC output terminals V+ and V- can be used to connect with electrical appliances; the two-phase AC output terminal V~ can be used to connect with the heating device 20 to supply power to the heating device. In some embodiments, the junction box 100 may not have the three-phase AC output terminals A~, B~ and C~.

[0042] Figure 2 Schematic diagram of the connection between the junction box and the photovoltaic module in one embodiment. Figure 2In the embodiment, the junction box is a three-part junction box, which includes a positive junction box 101, an intermediate junction box 102, and a negative junction box 103. The input terminals PV+ and PV- are located in the negative junction box 103, the input terminal PV+ is connected to the positive output terminal of the photovoltaic module 10 through the positive junction box 101, and the input terminal PV- is connected to the negative output terminal of the photovoltaic module 10. Figure 4 The circuit in the embodiment can be integrated in the negative terminal box 103, or in the positive terminal box 101 or the intermediate terminal box 102. It can be understood that the terminal box of the present application can also be an integrated terminal box, for example, Figure 2 The positive electrode terminal box 101, the middle terminal box 102 and the negative electrode terminal box 103 are integrated together.

[0043] The photovoltaic module 10 includes a plurality of cells 11, and the cells 11 in the same row form a cell string. A diode 104 is provided in the positive terminal box 101, the middle terminal box 102, and the negative terminal box 103. When a hot spot appears in the photovoltaic module 10, the diode 104 will be turned on to prevent the photovoltaic module 10 from being burned.

[0044] Figure 2 There are two photovoltaic modules 10, each photovoltaic module 10 has a corresponding positive terminal box 101, an intermediate terminal box 102 and a negative terminal box 103. The two photovoltaic modules 10 can be connected in series through a wire 30 to form a photovoltaic array. Specifically, the wire 30 is connected to the positive terminal box 101, the middle terminal box 102 and the negative terminal box 103. Figure 2 The DC output terminal V+ of the photovoltaic assembly 10 in the upper middle part and the DC output terminal V- of the photovoltaic assembly 10 in the lower part. It should be understood that the number of photovoltaic assemblies 10 in the photovoltaic array is not limited to 2 and can be set according to needs.

[0045] Figure 3 Schematic diagram of the working principle of the junction box in one embodiment. Figure 1 and Figure 3 As shown, the output power of the photovoltaic module 10 fluctuates (or the output voltage and / or current of the photovoltaic module 10 fluctuates). If the above-mentioned fluctuating output power is transmitted to electrical appliances with high requirements for power quality, these appliances will be damaged. The junction box 100 can separate the output power of the photovoltaic module 10 into high-quality power with no fluctuation (or low fluctuation) and low-quality power with high fluctuation. The high-quality power can be used to power electrical appliances with high requirements for power quality (such as mobile phones, computers and washing machines) or connected to the power grid through an inverter, and the low-quality power can be used to power electrical appliances with low requirements for power quality (such as heating equipment). In this way, on the one hand, the demand of electrical appliances for high-quality electricity is met; on the other hand, the low-quality power in the output power of the photovoltaic module 10 is fully utilized to avoid the waste of output power.

[0046] refer to Figure 4 As shown, the junction box 100 includes an inverter circuit 110, a transformer 120 and a rectifier circuit 130. The inverter circuit 110, the transformer 120 and the rectifier circuit 130 can separate the output power of the photovoltaic module into high-quality power and low-quality power.

[0047] Specifically, the inverter circuit 110 has four first switch tubes: Q1_1, Q1_2, Q1_3 and Q1_4. Among them, the first switch tube Q1_1 and the first switch tube Q1_3 are located in the same bridge arm, and both are turned on and off at the same time; the first switch tube Q1_2 and the first switch tube Q1_4 are located in the same bridge arm, and both are turned on and off at the same time. The inverter circuit 110 converts the direct current input from the input terminals PV+ and PV- of the photovoltaic module into alternating current by switching on and off the first switch tubes located in different bridge arms.

[0048] Figure 7 The schematic diagram shows the pulse width modulation signal (PWM) for controlling the first switch tubes Q1_1, Q1_2, Q1_3, and Q1_4. Figure 7 As shown, the first switches on the same bridge arm in the inverter circuit 110 are not turned on at the same time to prevent a short circuit in the inverter circuit 110. To ensure that the first switches on the same bridge arm are not turned on at the same time, a switch dead zone is set between two adjacent PWM signals for controlling the first switches to turn on.

[0049] Specific, combined Figure 4 and Figure 7 As shown, the first switch tubes Q1_1 and Q1_4 are turned on at the same time, and when the first switch tubes Q1_1 and Q1_4 are turned on, the first switch tubes Q1_2 and Q1_3 are in the off state. The first switch tubes Q1_2 and Q1_3 are turned on at the same time, and when the first switch tubes Q1_2 and Q1_3 are turned on, the first switch tubes Q1_1 and Q1_4 are in the off state. The switch dead zone is set between the PWM signal for controlling the first switch tubes Q1_1 and Q1_4 to be turned on and the PWM signal for controlling the first switch tubes Q1_2 and Q1_3 to be turned on. The switch dead zone can ensure that the two first switch tubes located on the same bridge arm are not turned on at the same time, thereby preventing the inverter circuit 110 from being short-circuited. In one embodiment, the duration of the first switch tubes Q1_1 and Q1_4 being turned on, and the duration of the first switch tubes Q1_2 and Q1_3 being turned on each account for 48.5% of the period T, and the duration of the switch dead zone accounts for 3% of the period T. The duration of the switch dead zone is not limited to 3% of the period T and can be increased or decreased.

[0050] Back to Figure 4As shown, the transformer 120 has a first port 121, a second port 122 and a third port 123. The first port 121 is connected to the inverter circuit 110, the second port 122 is connected to the rectifier circuit 130, and the third port 123 is a two-phase AC output terminal V. The transformer 120 can output the electric energy input by the inverter circuit 110 from the second port 122 and the third port 123.

[0051] The rectifier circuit 130 can convert the AC power outputted from the second port 122 into DC power, and can further output the DC power. Specifically, the rectifier circuit 130 has a first output terminal 131 and four second switch tubes Q2_1, Q2_2, Q2_3 and Q2_4, wherein the first output terminal 131 corresponds to Figure 1 The rectifier circuit 130 can convert the AC power into the DC power by controlling the on and off of the second switch tubes Q2_1 , Q2_2 , Q2_3 and Q2_4 , and can output the DC power from the first output terminal 131 .

[0052] The inverter circuit 110 and the rectifier circuit 130 transmit electric energy through the transformer 120, and the transformer 120 has an electrical isolation effect on the inverter circuit 110 and the rectifier circuit 130. Compared with the non-isolated power transmission method, the use of the transformer 120 to transmit electric energy has the advantages of strong anti-interference ability and easy to achieve voltage step-up and step-down. In addition, the transformer 120 has two output ports (the second port 122 and the third port 123), so it has the advantage of multi-channel output.

[0053] In the rectifier circuit 130, the second switch tubes Q2_1 and Q2_3 are located in the same bridge arm, the second switch tubes Q2_2 and Q2_4 are located in the same bridge arm, and the second switch tubes on the same bridge arm are not turned on at the same time to prevent the rectifier circuit 130 from short-circuiting. Figure 4 and Figure 7 As shown, the PWM signal is used to control the four second switch tubes Q2_1, Q2_2, Q2_3 and Q2_4 to be turned on and off in a certain cycle and sequence. Similar to the PWM signal for controlling the first switch tubes Q1_1, Q1_2, Q1_3 and Q1_4, the cycle for controlling the second switch tubes Q2_1, Q2_2, Q2_3 and Q2_4 is also T, and the PWM signal also has a switch dead zone. The duration of the second switch tubes Q2_1 and Q2_4 being turned on, and the duration of the second switch tubes Q2_2 and Q2_3 being turned on each account for 48.5% of the cycle T, and the duration of the switch dead zone accounts for 3% of the cycle T.

[0054] refer to Figure 4As shown, in one embodiment, the junction box further includes a three-phase inverter circuit 140. The three-phase inverter circuit 140 is connected to the first output terminal 131, and can convert the direct current outputted from the first output terminal 131 into three-phase alternating current, and can also output the three-phase alternating current from the second output terminal 141. The three-phase inverter circuit 140 can be connected to the power grid through the second output terminal 141 to transmit the three-phase alternating current to the power grid.

[0055] like Figure 4 As shown, the three-phase inverter circuit 140 has six third switch tubes Q3_1, Q3_2, Q3_3, Q3_4, Q3_5 and Q3_6, wherein Q3_1 and Q3_4 are located in the same bridge arm, Q3_3 and Q3_6 are located in the same bridge arm, and Q3_2 and Q3_5 are located in the same bridge arm. Turning off Q3_1, Q3_3 and Q3_5 or turning off Q3_4, Q3_6 and Q3_2 can stop the three-phase inverter circuit 140 from converting direct current into three-phase alternating current.

[0056] The junction box of the present application also includes a power optimization module. Figure 4 As shown, the power optimization module can generate a control signal for controlling the first switch tube and the second switch tube to be turned on and off according to the difference between the power information of the first output terminal 131 and the reference power information. The reference power information accounts for a preset percentage of the output power information of the photovoltaic component. The power information can be voltage, correspondingly, the reference power information is the reference voltage, and the output power information is the output voltage; the power information can also be power, correspondingly, the reference power information is the reference power, and the output power information is the output power.

[0057] Next, two examples using power and voltage as electrical energy information are used for further explanation.

[0058] Example 1: The electric energy information is voltage.

[0059] refer to Figure 4 and Figure 5As shown, the rectifier circuit 130 converts the AC power output from the second port 122 into DC power. The power optimization module 150 generates a PWM signal for controlling the on and off of the first switch tube (Q1_1, Q1_2, Q1_3, Q1_4) and the second switch tube (Q2_1, Q2_2, Q2_3, Q2_4) according to the difference ΔV between the voltage V1 of the first output terminal 131 and the reference voltage Vref. The reference voltage Vref is a preset percentage of the output voltage Vout of the photovoltaic module, for example, Vref = 90% Vout. The voltage V1 can be collected in real time by a voltage sensor connected to the first output terminal 131, and the voltage sensor can send the voltage V1 to the power optimization module. Similarly, the output voltage Vout can be collected in real time by a voltage sensor connected to the input terminals PV+ and PV-, and the voltage sensor can send the output voltage Vout to the power optimization module.

[0060] refer to Figure 7 As shown, the PWM signal includes a hysteresis time length D of the second switch tubes Q2_1, Q2_2, Q2_3 and Q2_4 relative to the corresponding first switch tube. Specifically, the second switch tubes Q2_1 and Q2_4 correspond to the first switch tubes Q1_1 and Q1_4, and the second switch tubes Q2_2 and Q2_3 correspond to the first switch tubes Q1_2 and Q1_3. The interval between the moment when the second switch tubes Q2_1 and Q2_4 are turned on and the moment when the first switch tubes Q1_1 and Q1_4 are turned on is a time length D, and the second switch tubes Q2_1 and Q2_4 are turned on after the first switch tubes Q1_1 and Q1_4. Similarly, the interval between the moment when the second switch tubes Q2_2 and Q2_3 are turned on and the moment when the first switch tubes Q1_2 and Q1_3 are turned on is a time length D, and the second switch tubes Q2_2 and Q2_3 are turned on after the first switch tubes Q1_2 and Q1_3.

[0061] The power optimization module 150 optimizes the output power of the photovoltaic module by controlling the hysteresis time D, so as to separate high-quality power (ie, non-fluctuating power or low-fluctuating power) from the output power of the photovoltaic module. Figure 5 As shown, the power optimization module 150 includes a proportional integral controller 151 (Proportional Integral Controller, PI) and a control signal generator 152. The proportional integral controller 151 is connected to the control signal generator 152, and the two can communicate through the connection. The proportional integral control can generate a lag time D according to the difference ΔV, and send the lag time D to the control signal generator 152. The control signal generator 152 can generate a PWM signal for controlling the on and off of the first switch tube and the second switch tube according to the lag time D, and send the PWM signal to the first switch tube and the second switch tube. Combined Figure 4As shown, the voltage V1 at the first output terminal can be stabilized at the reference voltage Vref through the above PWM signal, thereby avoiding or reducing the fluctuation of the voltage V1. In this way, the high-quality power is separated from the output power of the photovoltaic module, wherein the high-quality power is output from the first output terminal 131, and the remaining low-quality power in the output power of the photovoltaic module is output from the third port 123 of the transformer.

[0062] The junction box of the present application allows the user to adjust the power outputted from the first output terminal 131 and the power outputted from the third port 123 according to the needs. Specifically, the power distributed to the second port 122 and the power distributed to the third port 123 by the transformer 120 can be adjusted by controlling the preset percentage. For example, increasing the preset percentage can increase the power distributed to the second port 122, and correspondingly, the power distributed to the third port 123 can be reduced, thereby increasing the power outputted from the first output terminal 131 and reducing the power outputted from the third port 123.

[0063] Example 2: The electric energy information is power.

[0064] refer to Figure 4 and Figure 6 The schematic diagram of the working principle of the power optimization module 150 shown. The power optimization module 150 can generate a PWM signal for controlling the opening and closing of the first switch tube and the second switch tube according to the difference ΔP between the power P1 of the first output terminal 131 and the reference power Pref. The reference power Pref accounts for a preset percentage of the output power Pout of the photovoltaic component. The voltage and current at the first output terminal 131 can be collected in real time by a voltage sensor and a current sensor connected to the first output terminal 131, and the power optimization module 150 can calculate the power P1 based on the collected voltage and current. Similarly, the voltage and current output by the photovoltaic component can be collected in real time by a voltage sensor and a current sensor connected to the input terminals PV+ and PV-, and the power optimization module 150 can calculate the output power Pout based on the collected voltage and current.

[0065] refer to Figure 3 and Figure 6 As shown, the proportional integral control can generate a hysteresis time length D according to the difference ΔP, and send the hysteresis time length D to the control signal generator 152. The control signal generator 152 can generate a PWM signal for controlling the first switch tube and the second switch tube to turn on and off according to the hysteresis time length D, and can also send the PWM signal to the first switch tube and the second switch tube. The power P1 at the first output terminal can be stabilized at the reference voltage Pref by the above PWM signal, so as to realize the separation of the output power of the photovoltaic module, wherein the high-quality power is output from the first output terminal 131, and the low-quality power is output from the third port 123 of the transformer.

[0066] Preferably, the electric energy information of the present application is power. Because, in Example 1, there is such a situation: the voltage V1 of the first output terminal is stable at the reference voltage Vref, but the current of the first output terminal fluctuates, which causes the power of the first output terminal to fluctuate. Therefore, selecting power as the electric energy information can take into account both the voltage and current of the first output terminal.

[0067] In the process of using inductors and capacitors to separate high-quality power and low-quality power in the output power of photovoltaic modules, low-quality power is consumed by inductors and capacitors, which results in low-quality power being wasted. The junction box of the present application can not only separate high-quality power and low-quality power in the output power of photovoltaic modules, but also use the separated low-quality power to power electrical appliances with low requirements for power quality, thus improving the utilization rate of the output power of photovoltaic modules.

[0068] The present application also proposes a photovoltaic power generation system, which includes: a plurality of photovoltaic modules and a plurality of junction boxes as described above, each photovoltaic module is connected to a corresponding junction box. For the description of the connection between the photovoltaic module and the junction box, please refer to the above related Figure 2 The junction box in the photovoltaic power generation system can separate the high-quality power and low-quality power in the output power of the photovoltaic module, and the separated low-quality power can be used to power electrical appliances with low requirements for power quality, thus improving the utilization rate of the output power of the photovoltaic module.

[0069] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0070] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0071] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more application embodiments, in the above description of the embodiments of this application, multiple features are sometimes merged into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0072] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0073] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A junction box for a photovoltaic module, characterized in that: include: An inverter circuit (110) having a plurality of first switch tubes; A transformer (120) having a first port (121), a second port (122) and a third port (123), wherein the first port is connected to the inverter circuit; A rectifier circuit (130) having a plurality of second switch tubes and a first output end (131), wherein the rectifier circuit (130) is connected to the second port (122); as well as A power optimization module (150) is configured to generate a control signal for controlling the opening and closing of the plurality of first switch tubes and the plurality of second switch tubes according to a difference between the power information of the first output terminal (131) and the reference power information, wherein the power optimization module (150) separates the output power of the photovoltaic component into high-quality power and low-quality power, the high-quality power being output from the first port (121) and the low-quality power being output from the third port (123), wherein the reference power information accounts for a preset percentage of the output power information of the photovoltaic component.

2. The junction box according to claim 1, characterized in that: The current output by the third port (123) is alternating current.

3. The junction box according to claim 1, characterized in that: The power optimization module is configured to generate a control signal for controlling the opening and closing of the plurality of first switch tubes and the plurality of second switch tubes according to a difference between the power of the first output terminal (131) and a reference power, wherein the reference power accounts for a preset percentage of the output power of the photovoltaic component.

4. The junction box according to claim 3, characterized in that: The preset percentage is 50% to 90%.

5. The junction box according to claim 1, characterized in that: The control signal includes a hysteresis time length of the plurality of second switch tubes relative to the corresponding first switch tubes.

6. The junction box according to claim 5, characterized in that: The power optimization module comprises a proportional-integral controller (151) and a control signal generator (152), wherein the proportional-integral controller (151) is connected to the control signal generator (152), wherein the proportional-integral controller (151) is configured to generate the lag time according to the difference and send the lag time to the control signal generator (152), and the control signal generator (152) generates the controller signal according to the lag time.

7. The junction box according to claim 6, characterized in that: The control signal is a pulse width modulation signal (PWM).

8. The junction box according to claim 1, characterized in that: It also includes a three-phase inverter circuit (140), the three-phase inverter circuit (140) having a second output end (141), and the three-phase inverter circuit (140) is connected to the first output end (131) to convert the direct current output by the rectifier circuit (130) into three-phase alternating current.

9. The junction box according to claim 1, characterized in that: The first switch tubes located on the same bridge arm are not turned on at the same time, and the second switch tubes located on the same bridge arm are not turned on at the same time.

10. A photovoltaic power generation system, characterized in that: include: Certain photovoltaic modules; and A number of junction boxes according to any one of claims 1 to 9, wherein each photovoltaic component is connected to a corresponding junction box.

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