CN117879481A - Junction box for photovoltaic module and photovoltaic power generation system - Google Patents

Abstract

The application provides a junction box for a photovoltaic module and a photovoltaic power generation system, wherein the junction box comprises an inverter circuit, a first switching tube and a second switching tube, wherein the inverter circuit is provided with a plurality of first switching tubes; the transformer is provided with a first port, a second port and a third port, and the first port is connected with the inverter circuit; the rectification circuit is provided with a plurality of second switching tubes and a first output end, and is connected with the second port; the power optimization module is configured to generate control signals for controlling the on and off of the first switching tubes and the second switching tubes according to the difference value between the electric energy information of the first output end and the reference electric energy information, wherein the reference electric energy information is output electric energy information of a photovoltaic module with a preset percentage. The junction box can separate high-quality power and low-quality power in output power of the photovoltaic module, and the separated low-quality power can be used for supplying power to electric appliances with low requirements on electric energy quality, so that the utilization rate of the output power of the photovoltaic module is improved.

Description

Junction box for photovoltaic module and photovoltaic power generation system

Technical Field

The application mainly relates to the technical field of photovoltaics, in particular to a junction box for a photovoltaic module and a photovoltaic power generation system.

Background

Due to the influence of factors such as illumination intensity change, temperature change and the like, the output power of the photovoltaic module fluctuates, and the problems of power mismatch, large voltage fluctuation, harmonic pollution and the like can be caused when the photovoltaic module is connected in a grid. Therefore, there is a need to optimize the output power of the photovoltaic module. Techniques for optimizing output power include: a multistage filter circuit is arranged in the circuit to filter unnecessary higher harmonics so as to improve the smoothness of the direct-current voltage; and the output power of the group photovoltaic element is smoother by adopting a maximum power point tracking (Maximum Power Point Tracking, MPPT) technology. The filter circuit is a commonly used output power optimization method at present, and the basic principle is to optimize the output power of the photovoltaic module by utilizing the characteristic that the inductor and the capacitor have special impedance to alternating current. The filter circuit allows or prevents the passage of current of a specific frequency in the circuit, thereby reducing the alternating current component in the circuit and retaining the direct current component to reduce the fluctuation of the output power. The filter circuit essentially transfers the ac component of the circuit to an inductor or capacitor, which consumes the ac component. Therefore, the ac component in the circuit is not utilized. In addition, the above technical solution for optimizing output power has the disadvantage of poor optimizing effect.

Disclosure of Invention

The technical problem to be solved by the application is to provide a junction box and a photovoltaic power generation system for a photovoltaic module, the junction box and the photovoltaic power generation system can separate high-quality power and low-quality power in output power of the photovoltaic module, and the separated low-quality power can be used for supplying power to an electric appliance with lower requirements on electric energy quality, so that the utilization rate of the output power of the photovoltaic module is improved.

For solving above-mentioned technical problem, this application provides a terminal box for photovoltaic module, include: an inverter circuit having a plurality of first switching transistors; the transformer is provided with a first port, a second port and a third port, and the first port is connected with the inverter circuit; the rectification circuit is provided with a plurality of second switching tubes and a first output end, and the rectification circuit is connected with the second port; and the power optimization module is configured to generate control signals for controlling the on and off of the plurality of first switching tubes and the plurality of second switching tubes according to the difference value between the electric energy information of the first output end and the reference electric energy information, wherein the reference electric energy information accounts for a preset percentage of the output electric energy information of the photovoltaic module.

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

In an embodiment of the present application, the power optimization module is configured to generate control signals for controlling the on and off of the plurality of first switching tubes and the plurality of second switching tubes according to a difference between the power of the first output end and a reference power, where the reference power is a preset percentage of the output power of the photovoltaic module.

In an embodiment of the present application, the preset percentage is 50% -90%.

In an embodiment of the present application, the control signal includes a delay time of the plurality of second switching tubes relative to the corresponding first switching tubes.

In an embodiment of the present application, the power optimization module includes a proportional-integral controller and a control signal generator, where the proportional-integral controller is connected to the control signal generator, and the proportional-integral controller is configured to generate the lag duration according to the difference value, and send the lag duration to the control signal generator, and the control signal generator generates the controller signal according to the lag duration.

In one embodiment of the present application, the control signal is a pulse width modulated signal (PWM).

In an embodiment of the present application, the power inverter further includes a three-phase inverter circuit, the three-phase inverter circuit has a second output end, and the three-phase inverter circuit is connected to the first output end, so as to convert the direct current output by the rectifying circuit into a three-phase alternating current.

In an embodiment of the present application, the first switching tubes located on the same bridge arm are not turned on at the same time, and the second switching tubes located on the same bridge arm are not turned on at the same time.

The 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.

Compared with the technical scheme of separating high-quality power and low-quality power in the output power of the photovoltaic module by using the inductor and the capacitor, the junction box 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 for supplying power to an electric appliance with lower requirements on electric energy quality, so that the utilization rate of the output power of the photovoltaic module is improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the accompanying drawings:

fig. 1 is a schematic structural view of a junction box for a photovoltaic module according to an embodiment of the present application;

FIG. 2 is a schematic illustration of the connection between a junction box and a photovoltaic module in an embodiment of the present application;

FIG. 3 is a schematic diagram of the working principle of the junction box according to an embodiment of the present application;

FIG. 4 is a schematic diagram of an inverter circuit, a transformer and a rectifier circuit according to an embodiment of the present disclosure;

fig. 5 and 6 are schematic diagrams illustrating the working principle of the power optimization module in two embodiments of the present application;

fig. 7 is a schematic diagram of a pwm signal for controlling a first switching tube and a second switching tube according to an embodiment of the present application.

Reference numerals

First port 121 of photovoltaic module 10

Second port 122 of battery piece 11

Third port 123 of heating apparatus 20

Rectifying circuit 130 for lead 30

First output 131 of junction box 100

Three-phase inverter circuit 140 of positive terminal box 101

Second output 141 of intermediate junction box 102

And negative terminal box 103 power optimization module 150

Diode 104 proportional-integral controller 151

Inverter circuit 110 controls signal generator 152

Transformer 120

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are used in the description of the embodiments will be briefly described below. It is apparent that the drawings in the following description are only some examples or embodiments of the present application, and it is obvious to those skilled in the art that the present application may be applied to other similar situations according to the drawings without inventive effort. Unless otherwise apparent from the context of the language or otherwise specified, like reference numerals in the figures refer to like structures or operations.

As used in this application and in the claims, the terms "a," "an," "the," and/or "the" are not specific to the singular, but may include the plural, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that the steps and elements are explicitly identified, and they do not constitute an exclusive list, as other steps or elements may be included in a method or apparatus.

The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present application unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

In the description of the present application, it should be understood that, where azimuth terms such as "front, rear, upper, lower, left, right", "transverse, vertical, horizontal", and "top, bottom", etc., indicate azimuth or positional relationships generally based on those shown in the drawings, only for convenience of description and simplification of the description, these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present application; the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In addition, the terms "first", "second", etc. are used to define the components, and are merely for convenience of distinguishing the corresponding components, and unless otherwise stated, the terms have no special meaning, and thus should not be construed as limiting the scope of the present application. Furthermore, although terms used in the present application are selected from publicly known and commonly used terms, some terms mentioned in the specification of the present application may be selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein. Furthermore, it is required that the present application be understood, not simply by the actual terms used but by the meaning of each term lying within.

The terminal block of the present application will be described by way of examples.

Fig. 1 is a schematic structural view of a junction box for a photovoltaic module according to an embodiment. Referring to fig. 1, the junction box 100 has input terminals pv+ and PV-, three-phase ac output terminals a to B to C, dc output terminals v+ and V-, and two-phase ac output terminals V to C. Wherein the input ends PV+ and PV-are operable to connect with the photovoltaic module 10 to receive electrical energy output by the photovoltaic module 10; the three-phase alternating current output ends A to B to C can be used for being connected with electric appliances or combined into a power grid; the direct current output ends V+ and V-can be used for being connected with an electric appliance; the two-phase ac output V-may be used in connection with a heating device 20 to supply power to the heating device. In some embodiments, junction box 100 may not have three-phase ac outputs a-B-C.

Fig. 2 is a schematic diagram of a connection between a junction box and a photovoltaic module in an embodiment. In fig. 2, the junction box is a three-split junction box including a positive junction box 101, a middle junction box 102, and a negative junction box 103. The input terminals pv+ and PV-are located in the negative terminal block 103, the input terminal pv+ is connected to the positive output terminal of the photovoltaic module 100 through the positive terminal block 101, and the input terminal PV-is connected to the negative output terminal of the photovoltaic module 100. The circuit in fig. 4 may be integrated in the negative terminal block 103, or in the positive terminal block 101 or the intermediate terminal block 102. It is understood that the junction box of the present application may also be an integral junction box, for example, the positive electrode junction box 101, the intermediate junction box 102, and the negative electrode junction box 103 in fig. 2 are integrated together.

The photovoltaic module 10 includes a plurality of battery cells 11, and the battery cells 11 located in the same row form a string of battery cell substrings. Diodes 104 are provided in each of the electrode terminal block 101, the intermediate terminal block 102, and the negative terminal block 103. When the photovoltaic module 10 is hot spot, the diode 104 is turned on, thereby preventing the photovoltaic module 10 from being burned out.

In fig. 2, there are two photovoltaic modules 10, and each photovoltaic module 10 has a positive electrode terminal box 101, an intermediate terminal box 102, and a negative electrode terminal box 103 corresponding thereto. The two photovoltaic modules 10 can be connected in series through the electric conduction 30 so as to form a photovoltaic array. Specifically, the dc output terminal v+ of the upper photovoltaic module 10 and the dc output terminal V-of the lower photovoltaic module 10 in fig. 2 are connected by the lead 30. It should be understood that the number of photovoltaic modules 10 in the photovoltaic array is not limited to 2 and may be set as desired.

Fig. 3 is a schematic diagram of the working principle of the junction box in an embodiment. Referring to fig. 1 and 3, there is a fluctuation in the output power of the photovoltaic module 100 (or, there is a fluctuation in the output voltage and/or current of the photovoltaic module 100). If the fluctuating output power is delivered to electrical appliances with high requirements on the quality of the electrical energy, the electrical appliances can be damaged. The junction box 100 can separate the output power of the photovoltaic module 10 into a high-quality power without ripple (or low ripple) and a low-quality power with high ripple. High quality power may power appliances (e.g., cell phones, computers, and washing machines) that require higher power quality or may be incorporated into the power grid via an inverter, and low quality power may power appliances (e.g., heating devices) that require lower power quality. Thus, on one hand, the requirement of the electric appliance on high-quality electric energy is met; on the other hand, the low-quality power in the output power of the photovoltaic module 10 is fully utilized, and the waste of the output power is avoided.

Referring to fig. 4, the junction box 100 includes an inverter circuit 110, a transformer 120, and a rectifying circuit 130. The inverter circuit 110, the transformer 120, and the rectifying circuit 130 may separate the output power of the photovoltaic module into high-quality power and low-quality power.

Specifically, the inverter circuit 110 has 4 first switching transistors: q1_1, q1_2, q1_3, and q1_4. The first switching tube Q1_1 and the first switching tube Q1_3 are positioned on the same bridge arm, and are simultaneously turned on and turned off; the first switching tube Q1_2 and the first switching tube Q1_4 are positioned on the same bridge arm, and are simultaneously turned on and turned off. The inverter circuit 110 converts direct current input from the input end pv+, PV-into alternating current by switching on and off the first switching tubes located in different bridge arms.

Fig. 7 shows a schematic diagram of a pulse width modulated signal (Pulse width modulation, PWM) controlling the first switching transistors q1_1, q1_2, q1_3, q1_4. Referring to fig. 7, the first switching transistors on the same leg of the inverter circuit 110 are not turned on at the same time to prevent the inverter circuit 110 from being shorted. In order to ensure that the first switching tubes on the same bridge arm are not turned on at the same time, a switching dead zone is arranged between two adjacent PWM signals for controlling the first switching tubes to be turned on.

Specifically, as shown in fig. 4 and 7, the first switching transistors q1_1 and q1_4 are simultaneously turned on, and when the first switching transistors q1_1 and q1_4 are turned on, the first switching transistors q1_2 and q1_3 are in an off state. The first switching transistors q1_2 and q1_3 are simultaneously turned on, and when the first switching transistors q1_2 and q1_3 are turned on, the first switching transistors q1_1 and q1_4 are in an off state. The switching dead zone is set between the PWM signal for controlling the first switching transistors q1_1 and q1_4 to be turned on and the PWM signal for controlling the first switching transistors q1_2 and q1_3 to be turned on. The dead zone of the switch can ensure that two first switching tubes positioned on the same bridge arm are not simultaneously turned on, thereby preventing the inverter circuit 110 from being shorted. In one embodiment, the duration of the first switching tubes q1_1 and q1_4 being turned on and the duration of the first switching tubes q1_2 and q1_3 being turned on each account for 48.5% of the period T, and the duration of the switching dead zone accounts for 3% of the period T. The duration of the switching dead zone is not limited to 3% of the period T and may be increased or decreased.

Returning to fig. 4, 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 may output the power input from the inverter circuit 110 from the second port 122 and the third port 123.

The rectifying circuit 130 may convert the ac power output from the second port 122 into dc power, and may further output the dc power. Specifically, the rectifying circuit 130 has a first output 131 and 4 second switching transistors q2_1, q2_2, q2_3, and q2_4, wherein the first output 131 corresponds to the dc outputs v+ and V-in fig. 1. The rectifying circuit 130 may convert the alternating current into the direct current by controlling the on and off of the second switching transistors q2_1, q2_2, q2_3, and q2_4, and may output the direct current from the first output terminal 131.

The inverter circuit 110 and the rectifying circuit 130 perform electric energy transmission through the transformer 120, and the transformer 120 has an electric isolation effect on the inverter circuit 110 and the rectifying circuit 130. Compared with a non-isolated power transmission mode, the transformer 120 is used for transmitting power, has the advantage of strong anti-interference capability, and is easy to realize voltage boosting and reducing. In addition, the transformer 110 has two output ports (the second port 122 and the third port 123), and thus has the advantage of multiplexing output.

In the rectifying circuit 130, the second switching transistors q2_1 and q2_3 are located in the same bridge arm, and the second switching transistors q2_2 and q2_4 are located in the same bridge arm, so that the second switching transistors on the same bridge arm are not turned on at the same time to prevent the rectifying circuit 130 from being shorted. As shown in fig. 4 and 7, 4 second switching transistors q2_1, q2_2, q2_3, and q2_4 are controlled to be turned on and off in a certain period and sequence by PWM signals. Similar to the PWM signals controlling the first switching transistors q1_1, q1_2, q1_3, and q1_4, the periods controlling the second switching transistors q2_1, q2_2, q2_3, and q2_4 are also T, the PWM signals also have switching dead zones, the periods during which the second switching transistors q2_1 and q2_4 are turned on, and the periods during which the second switching transistors q2_2 and q2_3 are turned on each account for 48.5% of the period T, and the periods of the switching dead zones account for 3% of the period T.

Referring to fig. 4, 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 dc power output from the first output terminal 131 into three-phase ac power, and can output the three-phase ac power from the second output terminal 141. The three-phase inverter circuit 140 may be connected to the power grid through the second output 141 to deliver three-phase ac power to the power grid.

As shown in fig. 4, the three-phase inverter circuit 140 has 6 third switching transistors q3_1, q3_2, q3_3, q3_4, q3_5, and q3_6, wherein q3_1 and q3_4 are located in the same leg, q3_3 and q3_6 are located in the same leg, and q3_2 and q3_5 are located in the same leg. Turning off q3_1, q3_3, and q3_5 or turning off q3_4, q3_6, and q3_2 may cause the three-phase inverter circuit 140 to stop converting the direct current into the three-phase alternating current.

The junction box of the present application also includes a power optimization module. Referring to fig. 4, the power optimization module may generate a control signal for controlling the first switching transistor and the second switching transistor to be turned on and off according to a difference between the power information of the first output terminal 131 and the reference power information. The reference electrical energy information is a preset percentage of the output electrical energy information of the photovoltaic module. The electric energy information can be voltage, and correspondingly, the reference electric energy information is reference voltage, and the output electric energy information is output voltage; the power information may be power, and the reference power information is reference power, and the output power information is output power.

Further description will be made below by way of two examples of information about power and voltage, respectively, as electric energy.

Example one: the electrical energy information is a voltage.

Referring to fig. 4 and 5, the rectifying circuit 130 converts the alternating current output from the second port 122 into direct current. The power optimization module 150 generates PWM signals for controlling the on/off of the first switching tube (q1_1, q1_2, q1_3, q1_4) and the second switching tube (q2_1, q2_2, q2_3, q2_4) according to a difference Δv between the voltage V1 of the first output terminal 131 and a reference voltage Vref, where 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 may be collected in real time by a voltage sensor connected to the first output 131, and the voltage sensor may send the voltage V1 to the power optimization module. Similarly, the output voltage Vout may be collected in real time by voltage sensors connected to the input terminals pv+ and PV-, which may send the output voltage Vout to the power optimization module.

Referring to fig. 7, the PWM signal includes a delay period D of the second switching tubes q2_1, q2_2, q2_3, and q2_4 with respect to the corresponding first switching tube. In the development, the second switching tubes q2_1 and q2_4 correspond to the first switching tubes q1_1 and q1_4, and the second switching tubes q2_2 and q2_3 correspond to the first switching tubes q1_2 and q1_3. The interval D between the time when the second switching tubes q2_1 and q2_4 are turned on and the time when the first switching tubes q1_1 and q1_4 are turned on, and the second switching tubes q2_1 and q2_4 are turned on later than the first switching tubes q1_1 and q1_4. Similarly, the second switching transistors q2_2 and q2_3 are turned on with a time interval D between the time when the first switching transistors q1_2 and q1_3 are turned on, and the second switching transistors q2_2 and q2_3 are turned on later than the first switching transistors q1_2 and q1_3.

The power optimization module 150 optimizes the output power of the photovoltaic module by controlling the hysteresis duration D to separate high quality power (i.e., no or low ripple power) from the output power of the photovoltaic module. Specifically, referring to fig. 5, 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 with each other through the connection. The proportional-integral control may generate a delay period D according to the difference Δv and send the delay period D to the control signal generator 152, and the control signal generator 152 may generate PWM signals for controlling on-off of the first switching tube and the second switching tube according to the delay period D and send the PWM signals to the first switching tube and the second switching tube. As shown in fig. 4, the voltage V1 at the first output terminal can be stabilized at the reference voltage Vref by the PWM signal, so as to avoid or reduce the fluctuation of the voltage V1. In this way, a separation of high quality power from the output power of the photovoltaic module is achieved, wherein the high quality power is output from the first output 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.

The junction box of the present application allows a user to adjust the power output by the first output 131 and the power output by the third port 123 as desired. Specifically, the power allocated to the second port 122 and the power allocated to the third port 123 by the transformer 120 may be adjusted by controlling the preset percentage, for example, increasing the preset percentage may increase the power allocated to the second port 122, and correspondingly, the power allocated to the third port 123 may be decreased, thereby increasing the power output from the first output terminal 131 and decreasing the power output from the third port 123.

Example two: the electrical energy information is power.

Reference is made to the schematic operation of the power optimization module 150 shown in fig. 4 and 6. The power optimization module 150 may generate PWM signals for controlling the first switching transistor and the second switching transistor to be turned on and off according to a difference Δp between the power P1 of the first output terminal 131 and the reference power Pref. The reference power Pref occupies a preset percentage of the output power Pout of the photovoltaic module. The voltage and current at the first output terminal 131 may be collected in real time through a voltage sensor and a current sensor connected to the first output terminal 131, and the power optimizing module 150 may calculate the power P1 according to the collected voltage and current. Similarly, the voltage and current output by the photovoltaic module may 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 may calculate the output power Pout according to the collected voltage and current.

Referring to fig. 3 and 6, the proportional-integral control may generate a delay period D according to the difference Δp and transmit the delay period D to the control signal generator 152, and the control signal generator 152 may generate PWM signals for controlling the first and second switching transistors to be turned on and off according to the delay period D and may also transmit the PWM signals to the first and second switching transistors. The power P1 at the first output end can be stabilized at the reference voltage Pref by the PWM signal, so as to separate the output power of the photovoltaic module, wherein the high-quality power is output from the first output end 131, and the low-quality power is output from the third port 123 of the transformer.

Preferably, the electrical energy information of the present application is power. Because, in example one there is such a case: the voltage V1 at the first output terminal stabilizes at the reference voltage Vref, but the current at the first output terminal fluctuates, which causes the power at the first output terminal to fluctuate. Therefore, selecting power as the electrical energy information may compromise both the voltage and the current at the first output.

In separating high-quality power and low-quality power in output power of a photovoltaic module using inductance and capacitance, the low-quality power is consumed by the inductance and capacitance, which results in the low-quality power being wasted. The junction box can separate high-quality power and low-quality power in output power of the photovoltaic module, and the separated low-quality power can be used for supplying power to electric appliances with low requirements on electric energy quality, so that the utilization rate of the output power of the photovoltaic module is improved.

The application also proposes a photovoltaic power generation system, this photovoltaic power generation system includes: a number of photovoltaic modules and a number of junction boxes as described hereinbefore, each photovoltaic module being connected to a corresponding junction box. For a description of the connection between the photovoltaic module and the junction box, reference is made to the description of fig. 2, which is not repeated here. The junction box in the photovoltaic power generation system can separate high-quality power and low-quality power in output power of the photovoltaic module, and the separated low-quality power can be used for supplying power to an electric appliance with low power quality requirements, so that the utilization rate of the output power of the photovoltaic module is improved.

While the basic concepts have been described above, it will be apparent to those skilled in the art that the foregoing application disclosure is by way of example only and is not intended to be limiting. Although not explicitly described herein, various modifications, improvements, and adaptations of the present application may occur to one skilled in the art. Such modifications, improvements, and modifications are intended to be suggested within this application, and are therefore within the spirit and scope of the exemplary embodiments of this application.

Meanwhile, the present application uses specific words to describe embodiments of the present application. Reference to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic is associated with at least one embodiment of the present application. Thus, it should be emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various positions in this specification are not necessarily referring to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of the present application may be combined as suitable.

Likewise, it should be noted that in order to simplify the presentation disclosed herein and thereby aid in understanding one or more application embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not intended to imply that more features than are presented in the claims are required for the subject application. Indeed, less than all of the features of a single embodiment disclosed above.

In some embodiments, numbers describing the components, number of attributes are used, it being understood that such numbers being used in the description of embodiments are modified in some examples by the modifier "about," approximately, "or" substantially. Unless otherwise indicated, "about," "approximately," or "substantially" indicate that the number allows for a 20% variation. Accordingly, in some embodiments, numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and employ a method for preserving the general number of digits. Although the numerical ranges and parameters set forth herein are approximations that may be employed in some embodiments to confirm the breadth of the range, in particular embodiments, the setting of such numerical values is as precise as possible.

While the present application has been described with reference to the present specific embodiments, those of ordinary skill in the art will recognize that the above embodiments are for illustrative purposes only, and that various equivalent changes or substitutions can be made without departing from the spirit of the present application, and therefore, all changes and modifications to the embodiments described above are intended to be within the scope of the claims of the present application.

Claims (10)

1. A junction box for a photovoltaic module, comprising:

an inverter circuit (110) having a plurality of first switching transistors;

a transformer (120) having a first port (121), a second port (122), and a third port (123), the first port being connected to the inverter circuit;

-a rectifying circuit (130) having a plurality of second switching tubes and a first output (131), the rectifying circuit (130) being connected to the second port (122); and

and the power optimization module (150) is configured to generate control signals for controlling the on and off of the first switching tubes and the second switching tubes according to the difference value between the electric energy information of the first output end (131) and reference electric energy information, wherein the reference electric energy information accounts for a preset percentage of the output electric energy information of the photovoltaic module.

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

3. The junction box according to claim 1, wherein the power optimization module is configured to generate control signals for controlling the switching on and off of the plurality of first switching tubes and the plurality of second switching tubes according to a difference between the power of the first output terminal (131) and a reference power, wherein the reference power is a preset percentage of the output power of the photovoltaic module.

4. A junction box according to claim 3, characterized in that the preset percentage is 50-90%.

5. The junction box of claim 1 wherein the control signal includes a lag time period of the plurality of second switching tubes relative to the corresponding first switching tubes.

6. The junction box according to claim 5, wherein the power optimization module comprises a proportional-integral controller (151) and a control signal generator (152), the proportional-integral controller (151) being connected to the control signal generator (152), wherein the proportional-integral controller (151) is configured to generate the lag time duration from the difference value and to send the lag time duration to the control signal generator (152), the control signal generator (152) generating the controller signal from the lag time duration.

7. The junction box of claim 6 wherein the control signal is a pulse width modulated signal (PWM).

8. The junction box according to claim 1, further comprising a three-phase inverter circuit (140), the three-phase inverter circuit (140) having a second output (141), the three-phase inverter circuit (140) being connected to the first output (131) to convert the direct current output by the rectifying circuit (130) into a three-phase alternating current.

9. The junction box of claim 1 wherein a first switching tube located on the same leg is not turned on at the same time and a second switching tube located on the same leg is not turned on at the same time.

10. A photovoltaic power generation system, comprising:

a plurality of photovoltaic modules; and

a plurality of junction boxes according to any one of claims 1 to 9, each of said photovoltaic modules being connected to a corresponding junction box.