Photovoltaic optimization system and photovoltaic power generation system

Abstract

The invention provides a photovoltaic optimization system and a photovoltaic power generation system. The optimization system comprises at least two group strings which are connected in parallel and an inverter which is connected in parallel with the group strings; the output end of at least one photovoltaic module in each group string is connected with a photovoltaic optimizer, each photovoltaic optimizer corresponds to one photovoltaic compensator in the other group strings, each photovoltaic compensator is connected with the photovoltaic module in the corresponding group string in series, and the photovoltaic optimizer is configured to enable the corresponding photovoltaic module in the corresponding group string to be mismatched when the correspondingly connected photovoltaic module is mismatched. According to the invention, voltage-reducing and current-increasing processing is carried out on the corresponding photovoltaic modules, so that the photovoltaic modules in the corresponding strings all output the maximum power point current, and the power output by the corresponding photovoltaic modules is distributed to the strings, so that the power supply voltages of the strings are the same, the problems of series mismatch and parallel mismatch are solved at the same time, and the reliability of the system is improved. And the method has the advantages of simple topology realization, small number of required optimizers and low cost.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a photovoltaic optimization system and a photovoltaic power generation system. Background Art

[0002] At present, string inverters are widely used in photovoltaic power generation systems because of their flexible and convenient installation and can be installed in smaller areas such as roofs and yards.

[0003] However, the mismatch problem in the photovoltaic system is usually caused by local factors, such as component shading, damage, etc. In this case, the string inverter will have both series mismatch and parallel mismatch problems. To solve this problem, photovoltaic optimizers are generally installed in photovoltaic power generation systems. For BUCK-type photovoltaic optimizers, each photovoltaic module in the photovoltaic power generation system needs to be installed with an optimizer; for BUCK-BOOST-type photovoltaic optimizers, each photovoltaic module in the string where the mismatched module is located in the photovoltaic power generation system needs to be installed with an optimizer. These two solutions require a large number of optimizers and are costly.

[0004] Therefore, how to reduce the number of optimizers required for photovoltaic power generation systems while achieving simple topology and low cost has become a technical problem that the industry urgently needs to solve. Summary of the invention

[0005] The present invention provides a photovoltaic optimization system and a photovoltaic power generation system, which solve the technical problem of how to reduce the number of optimizers required for the photovoltaic power generation system while achieving simple topology and low cost.

[0006] According to a first aspect of the present invention, an embodiment of the present invention provides a photovoltaic optimization system applied to a photovoltaic system, wherein the photovoltaic system comprises at least N strings connected in parallel with each other and inverters connected in parallel with the strings, each string comprises M photovoltaic modules connected in series, M and N are both integers, and M≥1, N≥2; the photovoltaic optimization system comprises at least N optimization modules, and the optimization modules comprise a photovoltaic optimizer and N-1 photovoltaic compensators; wherein:

[0007] There is at least one photovoltaic module in each string whose output end is connected to the photovoltaic optimizer, and each photovoltaic optimizer has a corresponding photovoltaic compensator in the remaining N-1 strings, and each photovoltaic compensator is connected in series with the M photovoltaic modules in the corresponding string;

[0008] The photovoltaic optimizer is configured to:

[0009] When a series mismatch occurs in the corresponding connected photovoltaic components, the power supply of the corresponding photovoltaic components is reduced in voltage and increased in current so that the current output by the photovoltaic optimizer is the same as the maximum power point current of the non-mismatched photovoltaic components in the same string; and

[0010] When a parallel mismatch occurs, the power output by the correspondingly connected photovoltaic modules is distributed to adjust the voltage output by the photovoltaic optimizer and the voltage output by the corresponding photovoltaic compensators so that the supply voltages of the strings are the same.

[0011] Optionally, the photovoltaic optimizer is a BUCK type photovoltaic optimizer, and the photovoltaic optimizer and the corresponding photovoltaic compensator distribute the power output by the photovoltaic assembly through inductive coupling; wherein:

[0012] The photovoltaic optimizer includes a first switch tube, a first diode, a primary winding and a first capacitor; the photovoltaic compensator includes a secondary winding, a second diode and a second capacitor;

[0013] The first end of the first switch tube is coupled to the first power supply output end of the corresponding photovoltaic component, and the second end of the first switch tube is coupled to the first end of the primary winding, the second end of the primary winding is coupled to the first end of the first capacitor, the second end of the first capacitor is coupled to the first end of the primary winding through the first diode, and the second end of the first capacitor is also coupled to the second power supply output end of the corresponding photovoltaic component;

[0014] The first end of the secondary winding is coupled to the first end of the second capacitor through the second diode, and the second end of the secondary winding is coupled to the second end of the second capacitor.

[0015] Optionally, the optimization module further includes an MPPT control module, a driving module and N sampling units;

[0016] A sampling unit, coupled to an output end of the photovoltaic optimizer or the photovoltaic compensator, and used to obtain a voltage and a current output by the photovoltaic optimizer or the photovoltaic compensator;

[0017] The MPPT control module is used to obtain the output power of the photovoltaic assembly based on the voltage and current output by the photovoltaic optimizer and the voltage and current output by each photovoltaic compensator, and output a first signal based on the output power of the photovoltaic assembly and the MPPT algorithm, wherein the first signal includes duty cycle adjustment information of the first switch tube;

[0018] The input end of the driving module receives the first signal, and the second end thereof is coupled to the control end of the first switch tube, and is used to control the on and off of the first switch tube based on the first signal to achieve maximum power point tracking of the corresponding photovoltaic component.

[0019] Optionally, the voltage output by the photovoltaic optimizer is the same as the voltage output by each corresponding photovoltaic compensator.

[0020] Optionally, the voltage output by the photovoltaic optimizer is different from the voltage output by each corresponding photovoltaic compensator;

[0021] Then the photovoltaic optimization system also includes a communication module and a power distribution module;

[0022] The communication module is coupled to each sampling unit, and is used to obtain the voltage and current output by each photovoltaic optimizer and its corresponding photovoltaic compensator, and output a second signal;

[0023] The power distribution module is used to control the power output by each photovoltaic optimizer and its corresponding photovoltaic compensator based on the second signal, so that the power supply voltage of each string is the same.

[0024] Optionally, the photovoltaic optimizer includes a cascaded first-stage BUCK circuit and a second-stage BUCK circuit, wherein the first switch tube, the first diode, the primary winding and the first capacitor constitute the first-stage BUCK circuit, and the output end of the second-stage BUCK circuit is connected in series in a corresponding string;

[0025] The photovoltaic compensator further includes a third BUCK circuit, the second capacitor is cascaded with the third BUCK circuit, and the output end of the third BUCK circuit is connected in series in the corresponding string.

[0026] Optionally, the first signal further includes duty cycle adjustment information of the switch tube in the second-stage BUCK circuit and duty cycle adjustment information of the switch tube in the third BUCK circuit;

[0027] The power distribution module is further configured to: control the duty cycle of the switch tube in the second-stage BUCK circuit and the duty cycle of the switch tube in the third BUCK circuit based on the first signal;

[0028] The method of outputting a first signal based on the output power of the photovoltaic module and the MPPT algorithm includes:

[0029] Obtaining an effective duty cycle range and a current duty cycle of the first switch tube;

[0030] If the current duty cycle is within the valid duty cycle range, perform the following steps:

[0031] Increasing or decreasing the duty cycle of the first switch tube based on the second signal and the MPPT algorithm until the maximum power point tracking of the corresponding photovoltaic assembly is achieved;

[0032] If the adjusted duty cycle of the first switch tube is not within the effective duty cycle range, the following steps are performed:

[0033] Increase or decrease the duty cycle of the switch tube in the second-stage BUCK circuit and the duty cycle of the switch tube in the third BUCK circuit until the maximum power point tracking of the corresponding photovoltaic module is achieved.

[0034] Optionally, based on the second signal, the method of controlling the power output by each photovoltaic optimizer and its corresponding photovoltaic compensator so that the power supply voltages of each string are the same includes:

[0035] Based on the second signal, the output voltage of the photovoltaic optimizer and the photovoltaic compensator in each string is obtained;

[0036] Based on the first total output voltage of the photovoltaic optimizer and the photovoltaic compensator in each string, the duty cycle of the switch tube in the second-stage BUCK circuit of each photovoltaic optimizer and the duty cycle of the switch tube in the third BUCK circuit of each photovoltaic compensator are adjusted, wherein:

[0037] If the first total output voltages between different strings are not equal, the duty cycle of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a larger first total output voltage and the duty cycle of the switch tube in the third BUCK circuit of the photovoltaic compensator are reduced, and the duty cycle of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a smaller first total output voltage and the duty cycle of the switch tube in the third BUCK circuit of the photovoltaic compensator are increased until the first total output voltages of all strings are equal.

[0038] Optionally, the photovoltaic optimizer and the corresponding photovoltaic compensator form a forward topology, a flyback topology or an LLC topology.

[0039] Optionally, the photovoltaic optimization system further includes a power grid, and the inverter is connected to the power grid after being connected in parallel with the string group, so as to convert direct current into alternating current.

[0040] According to a second aspect of the present invention, an embodiment of the present invention provides a photovoltaic power generation system, comprising a photovoltaic optimization system as described in any one of the first aspects of the present invention.

[0041] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0042] In the photovoltaic optimization system and photovoltaic power generation system of the technical solution of the present invention, the optimization system includes at least two mutually parallel strings and inverters connected in parallel with the strings, each string includes M photovoltaic modules connected in series; at least one photovoltaic module in each string has an output end connected to a photovoltaic optimizer, each photovoltaic optimizer has a corresponding photovoltaic compensator in the remaining strings, each photovoltaic compensator is connected in series with the photovoltaic module in the corresponding string, and the photovoltaic optimizer is configured to reduce the voltage and increase the current of the corresponding photovoltaic module when a mismatch occurs in the corresponding connected photovoltaic module, so that the M photovoltaic modules in the corresponding string all output the maximum power point current, thereby solving the problem of series mismatch; and the power output by the corresponding photovoltaic module is distributed to each string, so that the power supply voltage of each string is the same, thereby solving the problem of parallel mismatch, while achieving a simple topology, reducing the number of optimizers required and reducing costs.

[0043] Furthermore, the photovoltaic optimizer of the present invention may be a BUCK-type photovoltaic optimizer, and the corresponding photovoltaic compensator is coupled to the corresponding compensation output terminal of the photovoltaic optimizer through inductive coupling. The circuit topology is simple, which further reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a structural schematic diagram of a photovoltaic optimization system corresponding to a BUCK-type photovoltaic optimizer in the prior art;

[0046] Figure 2 It is a structural schematic diagram of a photovoltaic optimization system corresponding to a BUCK-BOOST photovoltaic optimizer in the prior art;

[0047] Figure 3 is a schematic structural diagram of a photovoltaic optimization system in a first embodiment of the present invention;

[0048] Figure 4 is a schematic structural diagram of a photovoltaic optimizer and a photovoltaic compensator in a first embodiment of the present invention;

[0049] Figure 5 is a schematic structural diagram of a photovoltaic optimizer and a photovoltaic compensator in a second embodiment of the present invention;

[0050] Figure 6 is a schematic structural diagram of a photovoltaic optimization system in a second embodiment of the present invention;

[0051] Figure 7 is a schematic structural diagram of a photovoltaic optimizer and a photovoltaic compensator in a third embodiment of the present invention;

[0052] Figure 8 is a schematic structural diagram of a photovoltaic optimization system in a third embodiment of the present invention;

[0053] Fig. 9 is a schematic structural diagram of a photovoltaic optimizer and a photovoltaic compensator in a fourth embodiment of the present invention;

[0054] Fig.10 is a schematic structural diagram of a photovoltaic optimizer and a photovoltaic compensator in a fifth embodiment of the present invention;

[0055] Description of reference numerals:

[0056] 11- Photovoltaic modules;

[0057] 12- Photovoltaic optimizer;

[0058] 121-primary winding;

[0059] 122-RCD module;

[0060] 13- Photovoltaic compensator;

[0061] 131-secondary winding;

[0062] 14-MPPT control module;

[0063] 15- driver module;

[0064] 16-sampling unit;

[0065] 17- Communication module;

[0066] 18-power distribution module;

[0067] 21-Inverter;

[0068] 22-Power grid. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0071] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0072] As described in the background art, it is difficult to reduce the number of optimizers required for a photovoltaic power generation system while achieving a simple topology and low cost in the prior art.

[0073] Please refer to Figure 1 , Figure 1 The figure shows a photovoltaic optimization system corresponding to a BUCK-type photovoltaic optimizer in the prior art, wherein each photovoltaic module 11 is correspondingly equipped with a photovoltaic optimizer 12;

[0074] In this case, the photovoltaic optimization system is configured to: when there is a mismatch in the photovoltaic component 11, control the photovoltaic optimizer 12 to optimize the mismatched photovoltaic component 11 (such as Figure 1 The photovoltaic modules 11 that are blocked by clouds are subjected to voltage reduction and current increase processing, so that the output current of the optimizer 12 corresponding to the mismatched photovoltaic modules is consistent with the output current of the optimizer 12 corresponding to other photovoltaic modules without mismatch, that is, the currents in the string are equal, and the voltage of other photovoltaic modules 11 is reduced, so that the voltage of the normal string is equal to the voltage of the mismatched string. This solves the problems of series mismatch and parallel mismatch.

[0075] Please refer to Figure 2 , Figure 2 The photovoltaic optimization system corresponding to the BUCK-BOOST photovoltaic optimizer in the prior art is shown. It can be seen that each photovoltaic component 11 in the string where the mismatched component is located is correspondingly installed with a photovoltaic optimizer 12.

[0076] In this case, the photovoltaic optimization system is configured as follows: when there is a mismatch in the photovoltaic component 11, the photovoltaic optimizer 12 is controlled to reduce the voltage and increase the current of the mismatched photovoltaic component 11, and to increase the voltage and reduce the current of other photovoltaic components 11 in the string, so that the output current of the optimizer of the photovoltaic component without mismatch in the string is consistent with the output current of the optimizer of the mismatched photovoltaic component, and the voltage of the string corresponding to the mismatched photovoltaic component 11 is equal to the voltage of the remaining strings, so as to solve the problems of series mismatch and parallel mismatch.

[0077] It can be seen that these two solutions require a large number of photovoltaic optimizers 12 and are costly.

[0078] In order to solve the above problems, an embodiment of the present invention provides a photovoltaic optimization system, which includes at least two mutually parallel strings and an inverter 21 connected in parallel with the strings, each string including M photovoltaic modules connected in series; at least one photovoltaic module in each string has an output end connected to a photovoltaic optimizer, each photovoltaic optimizer has a corresponding photovoltaic compensator in the remaining strings, each photovoltaic compensator is connected in series with the photovoltaic module in the corresponding string, and the photovoltaic optimizer is configured to reduce the voltage and increase the current of the corresponding photovoltaic module when a mismatch occurs in the corresponding connected photovoltaic module, so that the M photovoltaic modules in the corresponding string all output the maximum power point current, thereby solving the problem of series mismatch; and the power output by the corresponding photovoltaic module is distributed to each string, so that the power supply voltage of each string is the same, thereby solving the problem of parallel mismatch, while achieving a simple topology, reducing the number of required optimizers and reducing costs.

[0079] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0080] Please refer to Figure 3 , Figure 3 The photovoltaic optimization system of an embodiment of the present invention is shown, which is applied to a photovoltaic system, wherein the photovoltaic system comprises: at least N strings connected in parallel with each other and an inverter 21 connected in parallel with the strings, each string comprising M photovoltaic modules 11 connected in series, M and N being integers, and M≥1, N≥2;

[0081] The photovoltaic optimization system includes at least N optimization modules, and the optimization modules include a photovoltaic optimizer 12 and N-1 photovoltaic compensators 13; wherein:

[0082] In each string, at least one photovoltaic module 11 has its output end connected to a photovoltaic optimizer 12, and each photovoltaic optimizer 12 has a corresponding photovoltaic compensator 13 in the remaining N-1 strings, and each photovoltaic compensator 13 is connected in series with the M photovoltaic modules 11 in the corresponding string;

[0083] The photovoltaic optimizer 12 is configured as follows:

[0084] When a mismatch occurs in the corresponding connected photovoltaic assembly 11, the power supply of the corresponding photovoltaic assembly 11 is reduced in voltage and increased in current, so that the current output by the photovoltaic optimizer 12 is the same as the maximum power point current of the non-mismatched photovoltaic assembly in the same string; and

[0085] When parallel mismatch occurs, the power output by the correspondingly connected photovoltaic modules 11 is distributed to adjust the voltage output by the photovoltaic optimizer 12 and the voltage output by the corresponding photovoltaic compensators 13 so that the supply voltages of the strings are the same.

[0086] It can be seen that the photovoltaic optimizer 12 of the present invention is used to solve the series mismatch. The photovoltaic optimizer 12 reduces the voltage and increases the current of part of the power of the mismatched photovoltaic module 11 to match the current of the corresponding string, thereby eliminating the problem of series mismatch, recovering the power generation loss caused by the series mismatch, and realizing the maximum power point tracking of each module;

[0087] The photovoltaic compensator 13 of the present invention is used to solve the parallel mismatch. By adjusting the voltage ratio between the output of the photovoltaic optimizer 12 and the output of the photovoltaic compensator 13, it is equivalent to adjusting the power ratio between the photovoltaic optimizer 12 and the corresponding photovoltaic compensator 13. By adjusting the voltage ratio, the voltage of the mismatched string is equal to the voltage of the normal string, thereby eliminating the problem of parallel mismatch and recovering the loss caused by the parallel mismatch.

[0088] It should be understood that in the embodiment of the present invention, the output end of the mismatched photovoltaic module 11 must be connected to the photovoltaic optimizer 12. The mismatched photovoltaic module 11 can be understood as a photovoltaic module 11 with problems such as shading and module damage. In practical applications, it can be known whether the photovoltaic module 11 will have a mismatch problem based on the placement position of the photovoltaic module 11 in the environment. The specific method for determining whether the photovoltaic module 11 will have a mismatch problem is a prior art and will not be described in detail here.

[0089] In practical applications, please continue to refer to Figure 3 The photovoltaic optimization system also includes a power grid 22. The inverter 21 is connected to the power grid 22 in parallel with the string group to convert direct current into alternating current.

[0090] The adjustment method of the present invention is now described in conjunction with specific embodiments:

[0091] For a specific implementation, please refer to Figure 3 ,exist Figure 3In the example shown, three strings (string 1, string 2 and string 3) are connected in parallel. The output end of the first photovoltaic component 11 of each string is connected to a photovoltaic optimizer 12. Each photovoltaic optimizer 12 corresponds to a photovoltaic compensator 13 in the remaining two strings.

[0092] For the convenience of further explanation, the first photovoltaic module 11 of the string 1 is set as a mismatched photovoltaic module, and its maximum power point current is the second current value Imp2. The remaining photovoltaic modules 11 are set as normal photovoltaic modules, and their maximum power point currents are the first current value Imp1, where Imp2 <Imp1。

[0093] In this case, the photovoltaic optimizer 12 of the first photovoltaic module 11 of the string 1 is used to reduce the voltage and increase the current of the power supply (power) of the first photovoltaic module 11, which is equivalent to increasing the current of the mismatched photovoltaic module to match the string current, specifically, so that the current output by the photovoltaic optimizer is the same as the maximum power point current of the non-mismatched photovoltaic module in the same string;

[0094] Correspondingly, the output currents of the two photovoltaic compensators 13 corresponding to the photovoltaic optimizer 12 are also the first current value Imp1, which matches the currents of the strings 2 and 3.

[0095] Thus, the present invention solves the problem of series mismatch.

[0096] Now, the output voltage of the photovoltaic optimizer 12 of the first photovoltaic module 11 of the string 1 is set to the first main voltage Vm1, the output voltage of the photovoltaic compensator 13 of the corresponding string 2 is set to the first compensation voltage Vs1, and the output voltage of the photovoltaic compensator 13 of the corresponding string 3 is set to the second compensation voltage Vs2;

[0097] The output voltage of the photovoltaic optimizer 12 of the first photovoltaic module 11 of the string 2 is set to the second main voltage Vm2, the output voltage of the photovoltaic compensator 13 of the corresponding string 1 is set to the third compensation voltage Vs3, and the output voltage of the photovoltaic compensator 13 of the corresponding string 3 is set to the fourth compensation voltage Vs4;

[0098] The output voltage of the photovoltaic optimizer 12 of the first photovoltaic component 11 of string 3 is set to the third main voltage Vm3, the output voltage of the corresponding photovoltaic compensator 13 of string 1 is set to the fifth compensation voltage Vs5, and the output voltage of the corresponding photovoltaic compensator 13 of string 2 is set to the sixth compensation voltage Vs6.

[0099] As long as each photovoltaic optimizer 12 and each photovoltaic compensator 13 satisfies the following formula, the supply voltage of each string can be guaranteed to be the same, thus solving the problem of parallel mismatch:

[0100] Vm1+Vs3+Vs5=Vm2+Vs1+Vs6=Vs2=Vm3+Vs2+Vs4.

[0101] It can be seen that the embodiments of the present invention solve the problems of series coupling and parallel coupling at the same time.

[0102] Since the present invention only needs to step down the voltage of the corresponding photovoltaic component 11 during implementation, in one embodiment, the photovoltaic optimizer 12 in the embodiment of the present invention is a BUCK-type photovoltaic optimizer, which has the advantages of simple topology, simple control, and high efficiency, further reducing the cost.

[0103] In the embodiments of the present invention, please refer to Figure 4 , the photovoltaic optimizer 12 and the corresponding photovoltaic compensator 13 distribute the power output by the photovoltaic assembly through inductive coupling; wherein:

[0104] The photovoltaic optimizer 12 includes a first switch tube Q1, a first diode D1, a primary winding 121 and a first capacitor C1; the photovoltaic compensator 13 includes a secondary winding 131, a second capacitor C2 and a second diode D2;

[0105] The first end of the first switch tube Q1 is coupled to the first power supply output end of the corresponding photovoltaic assembly 11, and the second end thereof is coupled to the first end of the primary winding 121, the second end of the primary winding 121 is coupled to the first end of the first capacitor C1, the second end of the first capacitor C1 is coupled to the first end of the primary winding 121 through the first diode D1, and the second end of the first capacitor C1 is also coupled to the corresponding second power supply output end;

[0106] The first end of the secondary winding 131 is coupled to the first end of the second capacitor C2 through the second diode D2 , and the second end of the secondary winding 131 is coupled to the second end of the second capacitor C2 .

[0107] The first capacitor C1 and the second capacitor C2 are directly connected in series in a corresponding string.

[0108] It should be understood that in Figure 4 In the example, only two secondary windings 131 are shown. In actual applications, the number of secondary windings 131 corresponds to the number of photovoltaic compensators 13.

[0109] In the embodiment of the present invention, both the mismatched photovoltaic module and the non-mismatched photovoltaic module need to operate at the maximum power point.

[0110] To achieve this goal, in a preferred implementation, please refer to Figure 5, the optimization module also includes an MPPT control module 14, a driving module 15 and N sampling units 16;

[0111] A sampling unit 16, coupled to an output end of the photovoltaic optimizer 12 or the photovoltaic compensator 13, for acquiring a voltage and a current output by the photovoltaic optimizer 12 or the photovoltaic compensator 13;

[0112] The MPPT control module 14 is used to obtain the output power of the photovoltaic assembly 11 based on the voltage and current output by the photovoltaic optimizer 12 and the voltage and current output by each photovoltaic compensator 13, and output a first signal based on the output power of the photovoltaic assembly and the MPPT algorithm, wherein the first signal includes the duty cycle adjustment information of the first switch tube;

[0113] The input end of the driving module 15 receives the first signal, and the second end thereof is coupled to the control end of the first switch tube Q1 for controlling the on and off of the first switch tube Q1 based on the first signal to achieve maximum power point tracking of the corresponding photovoltaic component 11 .

[0114] Among them, the MPPT algorithm of the present invention can be a perturbation observation method, the principle of which is to measure the power of the current photovoltaic component, and then add a small voltage component disturbance to the original output voltage. The output power will change. The direction of the power change can be known by measuring the changed power and comparing the power before and after the change. If the power increases, continue to use the original disturbance, and if it decreases, change the direction of the original disturbance.

[0115] In actual implementation, the present invention adjusts the duty cycle of the first switch tube Q1 to implement the perturbation observation method. Its working principle is: the input and output relationship of the BUCK type converter can be adjusted by adjusting the duty cycle of the pulse width modulation signal, thereby realizing the impedance matching function. Therefore, the size of the duty cycle essentially determines the size of the output power of the photovoltaic cell.

[0116] Of course, the so-called MPPT algorithms used in the photovoltaic energy industry are diverse, and this application does not limit the specific MPPT algorithm.

[0117] The method of solving both series coupling and parallel coupling in the embodiment of the present invention is now described:

[0118] In one implementation, the voltage output by the photovoltaic optimizer 12 is the same as the voltage output by each corresponding photovoltaic compensator 13 .

[0119] In actual implementation, as an example, a method of setting the voltage output by the photovoltaic optimizer 12 to be the same as the voltage output by the corresponding photovoltaic compensators 13 is to set the turns ratio of the primary winding to the secondary winding to be 1:1.

[0120] exist Figure 3 In the example, if the voltage output by the photovoltaic optimizer 12 is the same as the voltage output by the corresponding photovoltaic compensators 13, that is, Vm1=Vs1=Vs2, Vm2=Vs3=Vs4, Vm3=Vs3=Vs6, it can be obtained:

[0121] Vm1+Vs3+Vs5=Vm2+Vs1+Vs6=Vs2=Vm3+Vs2+Vs4.

[0122] It should be understood that in this manner, the number of photovoltaic optimizers 12 on each group of strings should be the same.

[0123] In another embodiment, the voltage output by the photovoltaic optimizer is different from the voltage output by each corresponding photovoltaic compensator.

[0124] It should be understood that, in this manner, the present invention does not limit the number of photovoltaic optimizers 12 on the same group of strings.

[0125] Specifically, please refer to Figure 6 ,exist Figure 6 In the example, two strings (string 1 and string 2) connected in parallel are shown, wherein the output end of the first photovoltaic component 11 of the first string and the output end of the second photovoltaic component 11 are both connected to a photovoltaic optimizer 12, the output end of the first photovoltaic component 11 of the second string is connected to a photovoltaic optimizer 12, and each photovoltaic optimizer 12 corresponds to a photovoltaic compensator 13 in the remaining strings;

[0126] For the convenience of further explanation, the first photovoltaic component 11 and the second photovoltaic component 11 of the string 1 are both set as mismatched photovoltaic components.

[0127] It should be understood that the present invention does not limit the placement position of each photovoltaic compensator 13 in the string. As long as they are connected in series in the corresponding string, they are all within the protection scope of the present invention.

[0128] Now the output voltage of the photovoltaic optimizer 12 of the first photovoltaic module 11 of the string 1 is set to the fourth main voltage Vm4, and the output voltage of the photovoltaic compensator 13 of the corresponding string 2 is set to the seventh compensation voltage Vs7;

[0129] The output voltage of the photovoltaic optimizer 12 of the second photovoltaic module 11 of the string 1 is set to the fifth main voltage Vm5, and the output voltage of the photovoltaic compensator 13 of the corresponding string 2 is set to the eighth compensation voltage Vs8;

[0130] The output voltage of the photovoltaic optimizer 12 of the first photovoltaic assembly 11 of the string 2 is set to the sixth main voltage Vm6, and the output voltage of the photovoltaic compensator 13 of the corresponding string 1 is set to the ninth main voltage Vs9.

[0131] In this case, in order to release the parallel coupling, the voltage output by the photovoltaic optimizer 12 and the voltage output by the corresponding photovoltaic compensators 13 need to satisfy the following relationship:

[0132] Vm4+Vm5+Vs9=Vm6+Vs4+Vs8+Vmp;

[0133] Wherein, Vmp is the maximum power point voltage output by a normal photovoltaic module.

[0134] In this case, the present invention needs to dynamically adjust the voltage output by the photovoltaic optimizer 12 and the voltage output by the corresponding photovoltaic compensators 13 until the above relationship is satisfied.

[0135] In a specific implementation, please refer to Figure 7 , the photovoltaic optimization system also includes a communication module 17 and a power distribution module 18;

[0136] The communication module 17 is coupled to each sampling unit 16, and is used to obtain the voltage and current output by each photovoltaic optimizer 12 and its corresponding photovoltaic compensator 13, and output a second signal;

[0137] The power distribution module 18 is used to control the power output by each photovoltaic optimizer 12 and its corresponding photovoltaic compensator 13 based on the second signal, so that the power supply voltage of each string is the same.

[0138] Among them, in actual implementation, each photovoltaic optimizer can also correspond to a communication module, and the communication module can also perform two-way communication with the communication modules corresponding to other photovoltaic optimizers 12, and transmit the voltage and current parameters sampled by the photovoltaic optimizer 12 and the corresponding photovoltaic compensators 13 to other photovoltaic optimizers 12, and obtain the voltage and current parameters sampled by other photovoltaic optimizers 12 and the corresponding photovoltaic compensators 13 through communication.

[0139] For example, the communication method may be a wireless communication method, such as 2.4G RF, Bluetooth, wifi, etc., or a wired communication method, such as RS-485, RS-232 or PLC, etc. The present invention is not limited thereto.

[0140] Now Figure 7 The power output by each photovoltaic optimizer 12 and its corresponding photovoltaic compensator 13 is controlled.

[0141] In one implementation, please continue to refer to Figure 7 The photovoltaic optimizer 12 includes a cascaded first-stage BUCK circuit 123 and a second-stage BUCK circuit 124, wherein the first switch tube Q1, the first diode D1, the primary winding 121 and the first capacitor C1 constitute the first-stage BUCK circuit, and the output end of the second-stage BUCK circuit is connected in series in the corresponding string;

[0142] The photovoltaic compensator 13 further includes a third BUCK circuit 132 , the second capacitor C2 is cascaded with the third BUCK circuit, and the output end of the third BUCK circuit 132 is connected in series in the corresponding string.

[0143] The first-stage BUCK circuit 123 can be understood as being used to track the maximum power point of the photovoltaic assembly 11 , and the second-stage BUCK circuit 124 and the third BUCK circuit 132 can be understood as being used to distribute the power at the maximum power point.

[0144] Furthermore, the power allocation module can also be understood as performing power allocation control on the photovoltaic optimizer 12 and the photovoltaic compensator 13 according to a power allocation control algorithm.

[0145] In a preferred embodiment, the power distribution module is also used to assist in achieving maximum power point tracking of the photovoltaic assembly 11 .

[0146] In this case, the first signal also includes duty cycle adjustment information of the switch tube in the second-stage BUCK circuit and duty cycle adjustment information of the switch tube in the third BUCK circuit;

[0147] The power distribution module is further configured to: control the duty cycle of the switch tube in the second-stage BUCK circuit and the duty cycle of the switch tube in the third BUCK circuit based on the first signal;

[0148] The method of outputting a first signal based on the output power of the photovoltaic module and the MPPT algorithm includes:

[0149] Obtaining an effective duty cycle range and a current duty cycle of the first switch tube;

[0150] If the current duty cycle is within the valid duty cycle range, perform the following steps:

[0151] Increasing or decreasing the duty cycle of the first switch tube based on the second signal and the MPPT algorithm until the maximum power point tracking of the corresponding photovoltaic assembly is achieved;

[0152] If the adjusted duty cycle of the first switch tube is not within the effective duty cycle range, the following steps are performed:

[0153] Increase or decrease the duty cycle of the switch tube in the second-stage BUCK circuit and the duty cycle of the switch tube in the third BUCK circuit until the maximum power point tracking of the corresponding photovoltaic module is achieved.

[0154] The effective duty cycle range may be understood as an effective duty cycle range that ensures the efficiency of the first-stage BUCK circuit 123 .

[0155] In actual adjustment, when obtaining the effective duty cycle range and the current duty cycle of the first switch tube, it also includes:

[0156] Get the duty cycle adjustment step size.

[0157] Furthermore, when increasing or decreasing the duty cycle of the first switch tube, the switch tube in the second-stage BUCK circuit, or the switch tube in the third BUCK circuit, it can be understood that the new duty cycle is equal to the original duty cycle increased or decreased by a duty cycle adjustment step.

[0158] In a specific implementation manner, the power distribution module controls the power output by each photovoltaic optimizer and its corresponding photovoltaic compensator based on the second signal so that the power supply voltage of each string is the same, including:

[0159] Based on the second signal, the output voltage of the photovoltaic optimizer and the photovoltaic compensator in each string is obtained;

[0160] Based on the first total output voltage of the photovoltaic optimizer and the photovoltaic compensator in each string, the duty cycle of the switch tube in the second-stage BUCK circuit of each photovoltaic optimizer and the duty cycle of the switch tube in the third BUCK circuit of each photovoltaic compensator are adjusted, wherein:

[0161] If the first total output voltages between different strings are not equal, the duty cycle of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a larger first total output voltage and the duty cycle of the switch tube in the third BUCK circuit of the photovoltaic compensator are reduced, and the duty cycle of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a smaller first total output voltage and the duty cycle of the switch tube in the third BUCK circuit of the photovoltaic compensator are increased until the first total output voltages of all strings are equal.

[0162] Please refer to Figure 8 The algorithm is further explained in Figure 8 In the example, only two strings (string 1 and string 2) connected in parallel are shown, and the communication module 17 and the power distribution module 18 are not shown, wherein:

[0163] The output end of the first photovoltaic module 11 of the first string is connected to a photovoltaic optimizer 12, the output end of the first photovoltaic module 11 of the second string is connected to a photovoltaic optimizer 12, and each photovoltaic optimizer 12 corresponds to a photovoltaic compensator 13 in the remaining strings;

[0164] For the convenience of further explanation, the first photovoltaic component 11 of the string 1 is set as a mismatched photovoltaic component 11 .

[0165] Now, the output voltage of the photovoltaic optimizer 12 of the first photovoltaic assembly 11 of the string 1 is set to the seventh main voltage Vm7, and the duty cycle of the corresponding first switch tube Q1 is duty_m1. The output voltage of the photovoltaic compensator 13 of the corresponding string 2 is set to the tenth compensation voltage Vs10, and the duty cycle of the corresponding switch tube Qs is duty_s1. The first total output voltage is (Vm7+Vs11)*Imp1;

[0166] The output voltage of the photovoltaic optimizer 12 of the first photovoltaic component 11 of string 2 is set to the eighth main voltage Vm8, and the corresponding duty cycle of the first switch tube Q1 is duty_m2. The output voltage of the corresponding photovoltaic compensator 13 of string 1 is set to the eleventh main voltage Vs11, and the corresponding duty cycle of the switch tube Qs is duty_s2. The first total output voltage is (Vm8+Vs11)*Imp1.

[0167] In this case, as long as Vm7+Vs11=Vm8+Vs11 is ensured, the parallel mismatch problem can be solved.

[0168] If the first total output voltage between string 1 and string 2 is not equal, such as Vm7+Vs11>Vm2+Vs1, the control action is: reduce the duty cycle (duty_m1-△duty) of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a larger first total output voltage, and the duty cycle (duty_s2-△duty) of the switch tube in the third BUCK circuit in the photovoltaic compensator, and increase the duty cycle (duty_m2+△duty) of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a smaller first total output voltage, and the duty cycle (duty_s1+△duty) of the switch tube in the third BUCK circuit in the photovoltaic compensator, until the first total output voltage of all strings is equal.

[0169] Among them, △duty is the adjustment step size.

[0170] It should be understood that under this control, the voltage output by the photovoltaic optimizer is different from the voltage output by the corresponding photovoltaic compensators. For example, if the maximum power point current is 10A, the power output by the first photovoltaic component 11 of the string 1 is 100W, and the power output by the first photovoltaic component 11 of the string 2 is 400W, then the seventh main body voltage Vm7 = 7V, the tenth compensation voltage Vs10 = 3V, the eighth main body voltage Vm8 = 22V, and the eleventh main body voltage Vs11 = 18V can be allocated. Of course, this allocation method is only an example, and the present invention does not limit the specific proportional relationship of the allocation. As long as the output voltages of each string are equal, they are all within the protection scope of the present invention.

[0171] Of course, the present invention is not limited to the specific topology of the photovoltaic optimizer 12, and it can also be other topologies with two outputs or multiple outputs, such as forward, flyback, LLC, etc. Technicians in this field can select a suitable circuit topology as needed.

[0172] In a specific implementation, please refer to Fig. 9 , Fig. 9 A dual-tube forward 2-way output topology is shown. It should be understood that: Fig. 9 Only the circuits related to transformer coupling are shown, where:

[0173] The photovoltaic optimizer 12 includes a primary winding 121, a second switch tube Q2, a third switch tube Q3, a third diode D3 and a fourth diode D4; the photovoltaic compensator 13 includes a secondary winding 131, a first inductor Lo, a fifth diode Df, a sixth diode Dr, an output capacitor Co and an output resistor Ro;

[0174] The first end of the second switch tube Q2 is coupled to the first power supply output end of the corresponding photovoltaic assembly 11, and the second end thereof is coupled to the first end of the primary winding 121. The second end of the primary winding 121 is coupled to the first end of the third switch tube Q3. The first end of the third switch tube Q3 is also coupled to the first end of the second switch tube Q2 through the third diode D3. The second end of the third switch tube Q3 is coupled to the first end of the primary winding 121 through the fourth diode D4. The second end of the third switch tube Q3 is also coupled to the second power supply output end of the corresponding photovoltaic assembly 11.

[0175] The first end of the secondary winding 131 is coupled to the first end of the output capacitor Co through the fifth diode Df and the first inductor Lo in sequence, the second end of the secondary winding 131 is coupled to the second end of the output capacitor Co, the second end of the secondary winding 131 is also coupled to the first end of the first inductor Lo through the sixth diode Dr, and the output resistor Ro is connected in parallel with the output capacitor Co.

[0176] In another specific implementation, please refer to Fig.10 , Fig.10 A flyback 2-way output topology is shown. It should be understood that Fig.10 Only the circuits related to transformer coupling are shown, where:

[0177] The photovoltaic optimizer 12 includes a primary winding 121, a fourth switch tube Q4, an RCD module 122, and a second inductor Lr; the photovoltaic compensator 13 includes a secondary winding 131, a seventh diode D7, an output capacitor Co, and an output resistor Ro;

[0178] The first power supply output terminal of the photovoltaic component 11 is coupled to the first end of the primary winding 121 through the second inductor Lr, the second end of the primary winding 121 is coupled to the corresponding second power supply output terminal of the photovoltaic component 11 through the fourth switch tube Q4, and the second end of the primary winding 121 is also coupled to the first power supply output terminal of the photovoltaic component 11 through the RCD module 122;

[0179] The first end of the secondary winding 131 is coupled to the first end of the output capacitor Co through the seventh diode D7 , the second end of the output capacitor Co is coupled to the second end of the secondary winding 131 , and the output resistor Ro is connected in parallel with the output capacitor Co.

[0180] In actual work, the primary winding 121 and the secondary winding 131 can both be arranged at the photovoltaic optimizer, and the photovoltaic compensator part connected in series with the M photovoltaic components in the corresponding string can only include the output capacitor Co. The present invention is not limited to this, and can also include the output capacitor Co as well as an inductor, a diode, etc., and technicians in this field can select a suitable circuit topology as needed.

[0181] In addition, the present invention also provides a photovoltaic power generation system, including any photovoltaic optimization system as described above, such as a photovoltaic grid-connected system, a photovoltaic grid-connected energy storage system, and the like.

[0182] In summary, the present invention sets a photovoltaic optimization system including at least two mutually parallel strings and an inverter connected in parallel with the strings, each string includes M photovoltaic modules connected in series; the output end of at least one photovoltaic module in each string is connected to a photovoltaic optimizer, each photovoltaic optimizer has a corresponding photovoltaic compensator in the remaining strings, each photovoltaic compensator is connected in series with the photovoltaic module in the corresponding string, and the photovoltaic optimizer is configured to reduce the voltage and increase the current of the corresponding photovoltaic module when a mismatch occurs in the corresponding connected photovoltaic module, so that the M photovoltaic modules in the corresponding string all output the maximum power point current, thereby solving the problem of series mismatch; and the power output by the corresponding photovoltaic module is distributed to each string, so that the power supply voltage of each string is the same, thereby solving the problem of parallel mismatch, while achieving a simple topology, reducing the number of required optimizers and reducing costs.

[0183] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A photovoltaic optimization system, applied to a photovoltaic system, wherein the photovoltaic system comprises at least N mutually parallel strings and inverters connected in parallel with the strings, each string comprises M photovoltaic modules connected in series, M and N are both integers, and M≥1, N≥2; characterized in that: The photovoltaic optimization system includes at least N optimization modules, and the optimization modules include a photovoltaic optimizer and N-1 photovoltaic compensators; in: There is at least one photovoltaic module in each string whose output end is connected to the photovoltaic optimizer, and each photovoltaic optimizer has a corresponding photovoltaic compensator in the remaining N-1 strings, and each photovoltaic compensator is connected in series with the M photovoltaic modules in the corresponding string; The photovoltaic optimizer is configured to: When a series mismatch occurs in the corresponding connected photovoltaic components, the power supply of the corresponding photovoltaic components is reduced in voltage and increased in current so that the current output by the photovoltaic optimizer is the same as the maximum power point current of the non-mismatched photovoltaic components in the same string; and When a parallel mismatch occurs, the power output by the correspondingly connected photovoltaic modules is distributed to adjust the voltage output by the photovoltaic optimizer and the voltage output by the corresponding photovoltaic compensators so that the supply voltages of the strings are the same.

2. The photovoltaic optimization system according to claim 1, characterized in that: The photovoltaic optimizer is a BUCK type photovoltaic optimizer, and the photovoltaic optimizer and the corresponding photovoltaic compensator distribute the power output by the photovoltaic assembly through inductive coupling; wherein: The photovoltaic optimizer includes a first switch tube, a first diode, a primary winding and a first capacitor; the photovoltaic compensator includes a secondary winding, a second diode and a second capacitor; The first end of the first switch tube is coupled to the first power supply output end of the corresponding photovoltaic component, and the second end of the first switch tube is coupled to the first end of the primary winding, the second end of the primary winding is coupled to the first end of the first capacitor, the second end of the first capacitor is coupled to the first end of the primary winding through the first diode, and the second end of the first capacitor is also coupled to the second power supply output end of the corresponding photovoltaic component; The first end of the secondary winding is coupled to the first end of the second capacitor through the second diode, and the second end of the secondary winding is coupled to the second end of the second capacitor.

3. The photovoltaic optimization system according to claim 2, characterized in that: The optimization module also includes an MPPT control module, a driving module and N sampling units; A sampling unit, coupled to an output end of the photovoltaic optimizer or the photovoltaic compensator, and used to obtain a voltage and a current output by the photovoltaic optimizer or the photovoltaic compensator; The MPPT control module is used to obtain the output power of the photovoltaic assembly based on the voltage and current output by the photovoltaic optimizer and the voltage and current output by each photovoltaic compensator, and output a first signal based on the output power of the photovoltaic assembly and the MPPT algorithm, wherein the first signal includes duty cycle adjustment information of the first switch tube; The input end of the driving module receives the first signal, and the second end thereof is coupled to the control end of the first switch tube, and is used to control the on and off of the first switch tube based on the first signal to achieve maximum power point tracking of the corresponding photovoltaic component.

4. The photovoltaic optimization system according to claim 3, characterized in that: The voltage output by the photovoltaic optimizer is the same as the voltage output by each corresponding photovoltaic compensator.

5. The photovoltaic optimization system according to claim 3, characterized in that: The voltage output by the photovoltaic optimizer is different from the voltage output by the corresponding photovoltaic compensators; Then the photovoltaic optimization system also includes a communication module and a power distribution module; The communication module is coupled to each sampling unit, and is used to obtain the voltage and current output by each photovoltaic optimizer and its corresponding photovoltaic compensator, and output a second signal; The power distribution module is used to control the power output by each photovoltaic optimizer and its corresponding photovoltaic compensator based on the second signal, so that the power supply voltage of each string is the same.

6. The photovoltaic optimization system according to claim 5, characterized in that: The photovoltaic optimizer comprises a cascaded first-stage BUCK circuit and a second-stage BUCK circuit, wherein the first switch tube, the first diode, the primary winding and the first capacitor constitute the first-stage BUCK circuit, and the output end of the second-stage BUCK circuit is connected in series in the corresponding string; The photovoltaic compensator further includes a third BUCK circuit, the second capacitor is cascaded with the third BUCK circuit, and the output end of the third BUCK circuit is connected in series in the corresponding string.

7. The photovoltaic optimization system according to claim 6, characterized in that: The first signal also includes duty cycle adjustment information of the switch tube in the second-stage BUCK circuit and duty cycle adjustment information of the switch tube in the third BUCK circuit; The power distribution module is further configured to: control the duty cycle of the switch tube in the second-stage BUCK circuit and the duty cycle of the switch tube in the third BUCK circuit based on the first signal; The method of outputting a first signal based on the output power of the photovoltaic module and the MPPT algorithm includes: Obtaining an effective duty cycle range and a current duty cycle of the first switch tube; If the current duty cycle is within the valid duty cycle range, perform the following steps: Increasing or decreasing the duty cycle of the first switch tube based on the second signal and the MPPT algorithm until the maximum power point tracking of the corresponding photovoltaic assembly is achieved; If the adjusted duty cycle of the first switch tube is not within the effective duty cycle range, the following steps are performed: Increase or decrease the duty cycle of the switch tube in the second-stage BUCK circuit and the duty cycle of the switch tube in the third BUCK circuit until the maximum power point tracking of the corresponding photovoltaic module is achieved.

8. The photovoltaic optimization system according to claim 7, characterized in that: Based on the second signal, the method of controlling the power output by each photovoltaic optimizer and its corresponding photovoltaic compensator so that the power supply voltages of each string are the same includes: Based on the second signal, the output voltage of the photovoltaic optimizer and the photovoltaic compensator in each string is obtained; Based on the first total output voltage of the photovoltaic optimizer and the photovoltaic compensator in each string, the duty cycle of the switch tube in the second-stage BUCK circuit of each photovoltaic optimizer and the duty cycle of the switch tube in the third BUCK circuit of each photovoltaic compensator are adjusted, wherein: If the first total output voltages between different strings are not equal, the duty cycle of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a larger first total output voltage and the duty cycle of the switch tube in the third BUCK circuit of the photovoltaic compensator are reduced, and the duty cycle of the switch tube in the second-stage BUCK circuit of the photovoltaic optimizer in the string with a smaller first total output voltage and the duty cycle of the switch tube in the third BUCK circuit of the photovoltaic compensator are increased until the first total output voltages of all strings are equal.

9. The photovoltaic optimization system according to claim 2, characterized in that: The photovoltaic optimizer and the corresponding photovoltaic compensator form a forward topology, a flyback topology or an LLC topology.

10. The photovoltaic optimization system according to claim 1, characterized in that: The photovoltaic optimization system also includes a power grid, and the inverter is connected to the power grid after being connected in parallel with the string group, so as to convert direct current into alternating current.

11. A photovoltaic power generation system, characterized in that: It comprises the photovoltaic optimization system as described in any one of claims 1 to 10.

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