A control method for a photovoltaic system and a photovoltaic system

Abstract

The embodiment of the present invention discloses a control method and a photovoltaic system. The photovoltaic system includes a main control module, a plurality of photovoltaic components and a plurality of parallel sub-control modules; the control method of the photovoltaic system is executed by the main control module, and the control method of the photovoltaic system includes: obtaining the total power currently required by the load, the power currently provided by each sub-control module, the target output voltage and the real-time output voltage; when the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, at least part of the sub-control modules are current-controlled with the preset target current-sharing value; when the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets the second preset condition, the sub-control module is subjected to maximum power point tracking control. The technical solution of the embodiment of the present invention is conducive to increasing the comprehensive service life of the photovoltaic system and reducing maintenance costs.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of photovoltaic power generation, and in particular to a control method of a photovoltaic system and a photovoltaic system. Background Art

[0002] As traditional energy resources are increasingly scarce, the use of solar energy has received more and more attention and importance from humans. As a clean energy source, solar energy is greatly affected by the environment, weather, and climate, so the output power of the photovoltaic array is nonlinear. Each photovoltaic array has only one maximum power value at a certain moment, which is the maximum point of the photovoltaic array output power curve. This point is called the maximum power point (MPP). Existing photovoltaic systems generally use controllers to control the photovoltaic array to operate at the maximum power point. When the output power of the photovoltaic array is greater than the current demand of the load, the controller operates in constant voltage mode. When the output power of the photovoltaic array is less than or equal to the current demand of the load, the controller operates in maximum power point tracking (MPPT) control mode.

[0003] At present, a single controller can no longer meet the working requirements of the photovoltaic system, and multiple controllers working in parallel is an ideal solution. The working mode switching method of a single controller is no longer applicable to the working scheme of a multi-machine parallel controller. The cost of a multi-machine parallel controller is high and it is prone to failure. Once a failure occurs, the system will become a single-machine operation mode, causing a series of problems such as high bus voltage noise, slow control response speed and uncontrollable total bus current, which will reduce the service life of the multi-machine parallel controller. Summary of the invention

[0004] The embodiments of the present invention provide a control method and a photovoltaic system, which realize the state switching between current balancing control and maximum power point tracking control for multiple parallel sub-control modules. When the sub-control modules are subjected to current balancing control, it is beneficial to increase the comprehensive service life of the photovoltaic system and reduce the maintenance cost. When the sub-control modules are subjected to maximum power point tracking control, it helps to ensure that the output power of the sub-control modules can be maintained at the maximum power point.

[0005] According to one aspect of the present invention, a control method for a photovoltaic system is provided, wherein the photovoltaic system comprises a main control module, a plurality of photovoltaic modules and a plurality of sub-control modules connected in parallel; the sub-control modules are arranged in a one-to-one correspondence with the photovoltaic modules, the sub-control modules are connected to the corresponding photovoltaic modules, and the output power of the photovoltaic modules is output to the load after being controlled by the sub-control modules; the main control module is connected to each sub-control module in communication, and the control method for the photovoltaic system is executed by the main control module, and the control method for the photovoltaic system comprises:

[0006] Obtain the total power currently required by the load, the power currently available from each sub-control module, the target output voltage, and the real-time output voltage;

[0007] When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, current sharing control is performed on at least part of the sub-control modules with a preset target current sharing value;

[0008] When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets the second preset condition, the sub-control module is subjected to maximum power point tracking control.

[0009] According to another aspect of the present invention, there is provided a photovoltaic system, comprising: a main control module, a plurality of photovoltaic modules and a plurality of parallel-connected sub-control modules;

[0010] The sub-control modules are set in one-to-one correspondence with the photovoltaic modules. The sub-control modules are connected to the corresponding photovoltaic modules. The output power of the photovoltaic modules is controlled by the sub-control modules and then output to the load. The main control module is connected to each sub-control module in communication. The main control module is used to:

[0011] Obtain the total power currently required by the load, the power currently available from each sub-control module, the target output voltage, and the real-time output voltage;

[0012] When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, current sharing control is performed on at least part of the sub-control modules with a preset target current sharing value;

[0013] When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets the second preset condition, the sub-control module is subjected to maximum power point tracking control.

[0014] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising:

[0015] at least one processor; and

[0016] a memory communicatively connected to the at least one processor; wherein,

[0017] The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the photovoltaic system control method described in any embodiment of the present invention.

[0018] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the photovoltaic system control method described in any embodiment of the present invention when executed.

[0019] The control method and photovoltaic system of the photovoltaic system provided by the embodiment of the present invention are provided with a photovoltaic system including a main control module, a plurality of photovoltaic components and a plurality of parallel sub-control modules. The control method of the photovoltaic system is executed by the main control module. When the numerical relationship between the power currently available to each sub-control module and the total power currently required by the load meets the first preset condition, the control method of the photovoltaic system performs current sharing control on at least part of the sub-control modules with a preset target current sharing value, so as to explore the output current capacity of the sub-control module when the current energy surplus degree of the photovoltaic system meets the demand, which is helpful to maximize the utilization of the power generation power of the photovoltaic system, and help to avoid the failure of multiple parallel sub-control modules and change to a single-machine operation mode, and reduce the power bus noise of the photovoltaic system, so as to realize real-time control of the total output current of the photovoltaic system, so that the service life of each sub-control module is similar, which is beneficial to increase the comprehensive service life of the photovoltaic system and reduce the maintenance cost. When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets the second preset condition, the main control module performs maximum power point tracking control on the sub-control module, so that when the current real-time output voltage of the sub-control module cannot meet the requirement of the target output voltage, the current sharing control state is exited to ensure that the output power of the sub-control module can be maintained at the maximum power point. In addition, this solution switches the control state of the sub-control module according to the first preset condition and the second preset condition, which also helps to improve the dynamic response speed of the photovoltaic system, so that the control state speed of the sub-control module is faster.

[0020] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 It is a structural schematic diagram of a photovoltaic system provided in Embodiment 1 of the present invention.

[0023] Figure 2It is a flow chart of a control method of a photovoltaic system provided in the first embodiment of the present invention.

[0024] Figure 3 It is a flow chart of a control method of a photovoltaic system provided in the second embodiment of the present invention.

[0025] Figure 4 It is a flow chart of a control method of a photovoltaic system provided in the third embodiment of the present invention.

[0026] Figure 5 This is a data distribution diagram of a first output current and a second output current provided in Embodiment 3 of the present invention.

[0027] Figure 6 It is a flow chart of a control method of a photovoltaic system provided in Embodiment 4 of the present invention.

[0028] Figure 7 It is a structural schematic diagram of a photovoltaic system provided in Embodiment 5 of the present invention.

[0029] Figure 8 It is a schematic diagram of the structure of an electronic device provided in Embodiment 6 of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. 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.

[0032] Embodiment 1

[0033] Embodiment 1 of the present invention provides a control method for a photovoltaic system. This embodiment can be applied to the situation of controlling a photovoltaic system. The control method for the photovoltaic system can be executed by a main control module in the photovoltaic system. The main control module can be implemented in the form of hardware and / or software. The main control module can be configured in an electronic device. Figure 1 Schematic diagram of a photovoltaic system provided by the first embodiment of the present invention. Figure 1 The photovoltaic system includes a main control module 110, a plurality of photovoltaic modules 130 and a plurality of sub-control modules 120 connected in parallel. The sub-control modules 120 are arranged in a one-to-one correspondence with the photovoltaic modules 130. The sub-control modules 120 are connected to the corresponding photovoltaic modules 130. The output power of the photovoltaic modules 130 is controlled by the sub-control modules 120 and then output to the load. The main control module 110 is connected to each sub-control module 120 for communication, and the control method of the photovoltaic system is executed by the main control module 110.

[0034] Figure 2 Schematic diagram of a control method for a photovoltaic system provided in the first embodiment of the present invention. Figure 2 , the method specifically comprises the following steps:

[0035] S210 , obtaining the total power currently required by the load, the power currently provided by each sub-control module, the target output voltage, and the real-time output voltage.

[0036] The following will be combined Figure 1 The specific structure of the photovoltaic system shown in the figure is used to specifically describe the control method of the photovoltaic system. Among them, the main control module 110 is used to control each sub-control module 120. The main control module 110 can be connected to each sub-control module 120 through a communication network 140. The main control module 110 can be a host. The sub-control module 120 can control the output power of the photovoltaic component 130. For example, the sub-control module 120 includes a maximum power point tracking controller (hereinafter referred to as an MPPT controller). Each sub-control module 120 can be connected in parallel through an output power bus 150, and connected to a load (not shown in the figure) through the output power bus 150. The photovoltaic component 130 includes a photovoltaic panel. The output power of the photovoltaic component 130 includes an output voltage and an output current. The sub-control module 120 can control the output voltage and output current of the photovoltaic component and output them to the load.

[0037] Specifically, the main control module 110 can obtain the total power currently required by each load, the power currently available from each sub-control module 120 , the target output voltage of each sub-control module 120 , and the real-time output voltage of each sub-control module 120 through the communication network 140 .

[0038] S220: When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets a first preset condition, current sharing control is performed on at least part of the sub-control modules using a preset target current sharing value.

[0039] Among them, current sharing control refers to a technology that balances the output currents of each power module by changing the voltage source characteristics of each parallel power module, or changing the amplitude of the voltage source of each parallel power module. The first preset condition can be the numerical relationship between the difference between the power currently available to each sub-control module and the total power currently required by the load and the preset excess power. The difference between the power currently available to each sub-control module and the total power currently required by the load represents the actual excess power of the photovoltaic system. The numerical relationship between the actual excess power of the photovoltaic system and the preset excess power can reflect the excess degree of energy currently generated by the photovoltaic system. For example, when the difference between the power currently available to each sub-control module and the total power currently required by the load is greater than the preset excess power, it indicates that the numerical relationship between the power currently available to each sub-control module and the total power currently required by the load meets the first preset condition. When the difference between the power currently available to each sub-control module and the total power currently required by the load is less than or equal to the preset excess power, it indicates that the numerical relationship between the power currently available to each sub-control module and the total power currently required by the load does not meet the first preset condition.

[0040] Specifically, the sub-control module 120 can operate in the initial control state when it is turned on. When the main control module 110 detects that the numerical relationship between the power currently available to each sub-control module 120 and the total power currently required by the load meets the first preset condition, it indicates that the current energy surplus of the photovoltaic system meets the demand, and the preset target current sharing value can be sent to at least some of the sub-control modules 120, and the output current of at least some of the sub-control modules 120 can be controlled by the preset target current sharing value, so that at least some of the sub-control modules 120 work in the current sharing control state, thereby realizing the mining of the output current capacity of the sub-control module 120.

[0041] Optionally, the first preset condition includes: the difference between the power currently provided by each sub-control module and the total power currently required by the load is greater than the product of the total power currently required by the load and the preset excess power ratio of the photovoltaic system.

[0042] Specifically, the preset excess power ratio can be the percentage of the excess power of the photovoltaic system to the total power currently required by the load, and the size of the preset excess power ratio can be set according to demand. The power currently available for each sub-control module 120 can be recorded as Qs, the total power currently required by the load can be recorded as Qn, and the preset excess power ratio can be recorded as a%, then the first preset condition can be expressed as (Qs-Qn)>(Qn*a%).

[0043] Exemplarily, the power Qs that can currently be provided by each sub-control module 120 is 120W, the preset excess power ratio a% is pre-set to 50%, the total power Qn currently required by the load is 100W, and after calculation, it is obtained that (120W-100W)<(100W*50%), and it is determined that the first preset condition (Qs-Qn)>(Qn*a%) is not satisfied. At this time, the sub-control module 120 does not enter the current sharing state; when the power Qs that can currently be provided by each sub-control module 120 is 180W, the preset excess power ratio a% is pre-set to 50%, and the total power Qn currently required by the load is 100W, after calculation, it is obtained that (180W-100W)>(100W*50%), and it is determined that the first preset condition (Qs-Qn)>(Qn*a%) is satisfied. At this time, the sub-control module 120 enters the current sharing state.

[0044] S230: When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, perform maximum power point tracking control on the sub-control module.

[0045] Among them, the maximum power point tracking control refers to a control method that enables the output power of the sub-control module 120 to be maintained at the maximum power point. The second preset condition is used to determine whether the real-time output voltage can meet the requirements of the target output voltage. When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets the second preset condition, it can be determined that the current real-time output voltage of the sub-control module 120 cannot meet the requirements of the target output voltage.

[0046] When the main control module 110 detects that the numerical relationship between the real-time output voltage of the sub-control module 120 and the current target output voltage meets the second preset condition, the sub-control module 120 can be controlled to switch from the current control state to the maximum power point tracking control state so that the output power of the sub-control module 120 can be maintained at the maximum power point.

[0047] Optionally, the second preset condition includes: the real-time output voltage of the sub-control module is less than the difference between the current target output voltage and the first preset error value.

[0048] Among them, the first preset error value can be understood as the voltage sampling error of the sub-control module 120. The first preset error value can be specifically set to the voltage sampling error △V of the sub-control module 120, or set to the voltage sampling error △V of the sub-control module 120 multiplied by the set margin, for example, △V*(1+b)*100%, (1+b) represents the set margin. Exemplarily, the real-time output voltage of the sub-control module 120 is recorded as Vr, and the current target output voltage of the sub-control module 120 is recorded as Vt. When the first preset error value is equal to △V, the second preset condition can be expressed as Vr<(Vt-△V), and when the first preset error value is equal to △V*(1+b)*100%, the second preset condition can be expressed as Vr<(Vt-△V*(1+b)*100%).

[0049] Exemplarily, when the real-time output voltage of the sub-control module 120 is 50V, the target output voltage is 80V, the voltage sampling error of the sub-control module 120 is 2V, and the margin is set to (1+b)=1.05, it is calculated that 50V<(80V-2V*1.05), and it is determined that the second preset condition Vr<(Vt-△V*(1+b)*100%) is met, and the sub-control module 120 recovers from the current sharing control state to the MPPT control state; when the real-time output voltage of the sub-control module 120 is 80V, the target output voltage is 50V, and the voltage sampling error of the sub-control module 120 is 2V, it is calculated that 80V>(50V-2V*1.05), and it is determined that the second preset condition Vr<(Vt-△V*(1+b)*100%) is not met, then the sub-control module 120 continues to operate in the current sharing control state.

[0050] The technical solution of the embodiment of the present invention is to set a photovoltaic system including a main control module, multiple photovoltaic modules and multiple parallel sub-control modules. When the numerical relationship between the power currently available to each sub-control module and the total power currently required by the load meets the first preset condition, the main control module performs current sharing control on at least part of the sub-control modules with a preset target current sharing value, so as to tap the output current capacity of the sub-control module when the current energy surplus of the photovoltaic system meets the demand, which is helpful to maximize the use of the power generation power of the photovoltaic system, and to avoid multiple parallel sub-control modules from failing and becoming a single-machine operation mode, and reduce the power bus noise of the photovoltaic system, so as to achieve real-time control of the total output current of the photovoltaic system, so that the service life of each sub-control module is similar, which is conducive to increasing the comprehensive service life of the photovoltaic system and reducing maintenance costs. When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets the second preset condition, the main control module performs maximum power point tracking control on the sub-control module, so as to exit the current sharing control state when the current real-time output voltage of the sub-control module cannot meet the requirements of the target output voltage, and ensure that the output power of the sub-control module can be maintained at the maximum power point. In addition, the present solution switches the control state of the sub-control module according to the first preset condition and the second preset condition, which also helps to improve the dynamic response speed of the photovoltaic system, so that the control state speed of the sub-control module is faster.

[0051] Embodiment 2

[0052] Figure 3 1 is a flow chart of a control method for a photovoltaic system provided by Embodiment 2 of the present invention. This embodiment further refines the above embodiment on the basis of the above embodiment. This embodiment can be combined with various optional solutions in one or more of the above embodiments. Figure 3 As shown, the method may include the following steps:

[0053] S310, obtaining the total power currently required by the load, the power currently provided by each sub-control module, the target output voltage and the real-time output voltage.

[0054] S320, obtaining the first output current and the second output current of each sub-control module, the first output current being the output current when the target output voltage of each sub-control module is an initial voltage value, and the second output current being the output current when the target output voltage of each sub-control module is a preset voltage value, and the preset voltage value is greater than the initial voltage value.

[0055] In this embodiment, still combined with Figure 1The specific structure of the photovoltaic system shown in the figure specifically describes the control method of the photovoltaic system. Specifically, the initial voltage value can be the target output voltage of each sub-control module when it is currently working, and the preset voltage value is greater than the initial voltage value. By obtaining the output current when the target output voltage of each sub-control module 120 is the preset voltage value, the output current potential of each sub-control module 120 can be determined. The first output current and the second output current of each sub-control module 120 are obtained through the main control module 110, which can be used as a reference to set the preset target current sharing current value.

[0056] Exemplarily, the total number of sub-control modules 120 in the photovoltaic system is recorded as n, the initial voltage value is recorded as V, and the preset voltage value is recorded as Vun, then Vun>V. The first output current IVi (1≤i≤n) is the output current when the target output voltage of each sub-control module 120 is V, and the first output current IVi of the 1st to nth sub-control modules 120 can be expressed as: IV1, IV2, IV3, ..., IVn. The second output current Iui (1≤i≤n) is the output current when the target output voltage of each sub-control module 120 is Vun, and the second output current Iui of the 1st to nth sub-control modules 120 can be expressed as: Iu1, Iu2, Iu3, ..., Iun.

[0057] S330. When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, and the minimum value of the second output current of each sub-control module is greater than the third output current, according to the relationship between the second output current and the third output current of each sub-control module, a corresponding preset target current sharing value is set to perform current sharing control on at least some of the sub-control modules.

[0058] The third output current is an average value of the first output currents of the sub-control modules, and at least some of the sub-control modules correspond to different preset target current sharing values.

[0059] Specifically, the third output current is the average value of the first output currents IV1, IV2, IV3, ..., IVn of each sub-control module 120, and the third output current can be recorded as Im. The minimum value of the second output currents Iu1, Iu2, Iu3, ..., Iun of each sub-control module 120 can be recorded as Idmin. The numerical relationship between the power Qs currently available for each sub-control module 120 and the total power Qn currently required by the load satisfies the first preset condition, and the minimum value Idmin of the second output current Iui of each sub-control module 120 is greater than the third output current Im, which can be expressed as (Qs-Qn)>(Qn*a%) and Idmin>Im. When the main control module 110 detects that (Qs-Qn)>(Qn*a%) and Idmin>Im, the second output current Iui and the third output current Im of each sub-control module 120 when the target output voltage is Vun can be compared one by one, and according to the difference between the second output current Iui and the third output current Im of each sub-control module 120, that is, the fluctuation degree of the second output current Iui around the third output current Im, the corresponding preset target current sharing value is set to perform current sharing control on at least part of the sub-control modules 120.

[0060] S340: When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, perform maximum power point tracking control on the sub-control module.

[0061] The technical solution of the embodiment of the present invention is to set a corresponding preset target current sharing value to perform current sharing control on at least part of the sub-control modules according to the relationship between the second output current and the third output current of each sub-control module when the numerical relationship between the power currently available to each sub-control module and the total power currently required by the load meets the first preset condition through the main control module, and when the minimum value of the second output current of each sub-control module is greater than the third output current. The corresponding preset target current sharing value is set according to the output current potential of each sub-control module to perform current sharing control, which is helpful to maximize the use of the power generation power of the photovoltaic system, and help avoid multiple parallel sub-control modules from failing and becoming a single-machine operation mode, and reduce the power bus noise of the photovoltaic system, so as to realize real-time control of the total output current of the photovoltaic system, which is beneficial to increase the comprehensive service life of the photovoltaic system and reduce maintenance costs.

[0062] Embodiment 3

[0063] Figure 4 1 is a flow chart of a control method for a photovoltaic system provided by Embodiment 3 of the present invention. This embodiment further refines the above embodiment on the basis of the above embodiment. This embodiment can be combined with various optional solutions in one or more of the above embodiments. Figure 4As shown, the method comprises the following steps:

[0064] S410, obtaining the total power currently required by the load, the power currently provided by each sub-control module, the target output voltage, and the real-time output voltage.

[0065] S420 , controlling each sub-control module with the initial voltage value as the target output voltage, and obtaining the output current of each sub-control module as the first output current.

[0066] In this embodiment, still combined with Figure 1 The specific structure of the photovoltaic system shown in the figure specifically describes the control method of the photovoltaic system. For example, each sub-control module 120 can be operated in the maximum power point tracking control state when it is turned on, and the potential of the photovoltaic system output power is explored by using this solution. The initial voltage value V can be the target output voltage of each sub-control module 120 when it is currently running. Before exploring the potential of the photovoltaic system output power, the first output current IV1, IV2, IV3, ..., IVn when the target output voltage of each sub-control module 120 is V is first obtained.

[0067] S430, adjusting the target output voltage from the initial voltage value to the preset voltage value, controlling each sub-control module, and obtaining the output current of each sub-control module as the second output current.

[0068] After step S420 is completed, the target output voltage of each sub-control module 120 is raised from the initial voltage value V to the preset voltage value Vun to tap the potential of the photovoltaic system's output electrical energy (hereinafter referred to as the potential tapping state). The preset voltage value Vun is the target output voltage in the potential tapping state, and the main control module 110 controls each sub-control module 120 accordingly to obtain the second output current Iu1, Iu2, Iu3, ..., Iun when the target output voltage of each sub-control module 120 is Vun.

[0069] S440, adjusting the target output voltage from the preset voltage value back to the initial voltage value.

[0070] After the main control module 110 obtains the first output currents IV1, IV2, IV3, ..., IVn of the n sub-control modules 120 when the target output voltage is V, and the second output currents Iu1, Iu2, Iu3, ..., Iun of the n sub-control modules 120 when the target output voltage is Vun, the target output voltage of each sub-control module 120 is adjusted from the preset voltage value Vun back to the initial voltage value V, so that the photovoltaic system exits the potential exploitation state and continues to work normally.

[0071] Optionally, after step S440, the main control module 110 determines whether the first output currents IV1, IV2, IV3, ..., IVn of the n sub-control modules 120 when the target output voltage is V, and the second output currents Iu1, Iu2, Iu3, ..., Iun of the n sub-control modules 120 when the target output voltage is Vun have all been acquired; if all the above current values ​​have been acquired, continue to step S450; if not all the above current values ​​have been acquired, repeat steps S420 to S440 until all the above current values ​​have been acquired.

[0072] Figure 5 1 is a schematic diagram of data distribution of a first output current and a second output current provided in Embodiment 3 of the present invention, wherein the horizontal axis represents the value of the current in ampere A, and the vertical axis represents the serial number of the sub-control module 120 . Figure 5 It schematically shows the magnitudes of the first output current IVi and the second output current Iui of each sub-control module 120 obtained when the number of sub-control modules 120 in the photovoltaic system is i=12. The magnitude of the second output current Iui reflects the output current potential of the sub-control module 120.

[0073] S450. When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, and the minimum value of the second output current of each sub-control module is greater than the third output current, according to the relationship between the second output current and the third output current of each sub-control module, a corresponding preset target current sharing value is set to perform current sharing control on at least some of the sub-control modules.

[0074] Optionally, according to the relationship between the second output current and the third output current of each sub-control module, setting a corresponding preset target current sharing value to perform current sharing control on at least part of the sub-control modules may specifically include: when the absolute value of the difference between the third output current and the second output current of the sub-control module is less than or equal to a first preset parameter, performing current sharing control on the sub-control module with the first preset target current sharing value.

[0075] The first preset target current sharing value is the sum of the third output current and the second preset error value.

[0076] Specifically, the value of the first preset parameter can be set according to the demand, for example, the first preset parameter can be 1A. The absolute value of the difference between the third output current Im and the second output current of the i-th sub-control module 120, which is recorded as Iui (1≤i≤n), can be recorded as IΔ=|Im-Iui|. When the main control module 110 detects that (Qs-Qn)>(Qn*a%) and Idmin>Im, the second output current Iui of each sub-control module 120 can be compared with the third output current Im one by one. When IΔ=|Im-Iui|≤1A, it means that the second output current Iui of the sub-control module 120 has a small degree of fluctuation near the third output current Im, and the output current of the sub-control module 120 has a large potential to reach the third output current Im. The first preset target current sharing value can be set to the sum of the third output current Im and the second preset error value. The second preset error value can be IΔ / n, and the first preset target current sharing value is expressed as: Im+IΔ / n. The purpose of setting the first preset target current sharing value is Im+IΔ / n to further reduce the interference caused by the error and output as much current as possible. That is to say, when (Qs-Qn)>(Qn*a%) and Idmin>Im, the first preset target current sharing value Im+IΔ / n>Im, for each sub-control module 120 that satisfies IΔ=|Im-Iui|≤1A, the first preset target current sharing value Im+IΔ / n can be used to control the current sharing of the above sub-control module 120, so that the output current of the above sub-control module 120 is the first preset target current sharing value Im+IΔ / n.

[0077] Further, according to the relationship between the second output current and the third output current of each sub-control module, setting the corresponding preset target current sharing value to perform current sharing control on at least part of the sub-control modules may also include:

[0078] When the absolute value of the difference between the third output current and the second output current of the sub-control module is greater than the first preset parameter, and the relationship between the second output current and the third output current of each sub-control module meets the third preset condition, the sub-control module is controlled to share the current with the third output current;

[0079] When the absolute value of the difference between the third output current and the second output current of the sub-control module is greater than the first preset parameter, and the relationship between the second output current and the third output current of each sub-control module does not meet the third preset condition, the sub-control modules are current-balanced controlled with the rated current limiting value.

[0080] Among them, the third preset condition is: the sum of the first current is less than the sum of the second current; and the second output current of the sub-control module is less than the difference between the third output current and the first preset parameter, or the second output current of the sub-control module is greater than the third output current; the sum of the first current is the sum of the second output currents of each sub-control module that is less than the third output current, and the sum of the second current is the sum of the second output currents of each sub-control module that is greater than the third output current.

[0081] Exemplarily, the first current sum is: the sum of the second output currents Iu1, Iu2, Iu3, ..., Iun of each sub-control module 120 that are less than the third output current Im, and the first current sum can be recorded as ILsum. The second current sum is: the sum of the second output currents Iu1, Iu2, Iu3, ..., Iun of each sub-control module 120 that are greater than the third output current Im, and the second current sum can be recorded as IHsum. Accordingly, the third preset condition can be expressed as: ILsum<IHsum.

[0082] The following still takes the first preset parameter of 1A as an example for explanation. When the absolute value of the difference between the third output current and the second output current of the sub-control module 120 is greater than the first preset parameter, that is, IΔ=|Im-Iui|>1A, it means that the second output current Iui of the sub-control module 120 fluctuates greatly around the third output current Im, and the output current of the sub-control module 120 has a small potential to reach the third output current Im. Therefore, for each sub-control module 120 that satisfies IΔ=|Im-Iui|>1A: when ILsum<IHsum, for the sub-control module 120 with the second output current Iui<(Im-1A), the third output current Im can be set to the current sharing value, and the sub-control module 120 can be controlled for current sharing. For the sub-control module 120 with the second output current Iui>Im, the third output current Im can also be set to the current sharing value, and the sub-control module 120 can be controlled for current sharing, so as to set the corresponding current sharing value according to the output current capability of the sub-control module 120 to perform current sharing control.

[0083] In addition, the relationship between the second output current and the third output current of the sub-control module 120 does not meet the third preset condition, which can be understood as: ILsum≥IHsum; or, ILsum<IHsum and Iui≥(Im-1A); or, ILsum<IHsum and Iui≤Im. For each sub-control module 120 that satisfies IΔ=|Im-Iui|>1A: When the relationship between the second output current and the third output current of the sub-control module 120 does not meet the third preset condition, the rated current limit value of the above sub-control module 120 can be set to the current sharing value, and the above sub-control module 120 can be subjected to current sharing control to avoid damaging the load.

[0084] The following describes the complete process of setting the current sharing values of each sub-control module 120 in combination with the solutions of steps S410 to S450. Specifically, first, each sub-control module 120 is controlled with the initial voltage value V as the target output voltage, and the first output currents IVi of each sub-control module 120 are recorded as IV1, IV2, IV3... IVn respectively; the target output voltage of each sub-control module 120 is increased to the preset voltage value Vun, and the second output currents Iui of each sub-control module 120 are recorded as Iu1, Iu2, Iu3,..., Iun respectively; after the main control module 110 obtains all the first output currents IV1, IV2, IV3,..., IVn and the second output currents Iu1, Iu2, Iu3,..., Iun of the n sub-control modules 120, the target output voltage of each sub-control module 120 is adjusted back from the preset voltage value Vun to the initial voltage value V, so that the photovoltaic system exits the potential excavation state and continues to work normally; calculate the average value of the first output currents IV1, IV2, IV3,..., IVn of each sub-control module 120 to obtain the third output current Im. Each second output current Iui of each sub-control module 120 can be compared with the third output current Im one by one. When IΔ = |Im - Iui| ≤ 1A, it means that the fluctuation degree of the second output current Iui of this sub-control module 120 near the third output current Im is small, and the potential for the output current of this sub-control module 120 to reach the third output current Im is large. The first preset target current sharing value can be set as the sum of the third output current Im and the second preset error value, that is, the first preset target current sharing value is set as Im + IΔ / n; when (I△ = |Im - Iui|) > 1A, sum the current part higher than the third output current Im to obtain the second current sum IHsum, and sum the current part lower than the third output current Im to obtain the first current sum ILsum. When ILsum < IHsum, for the sub-control module 120 with the second output current Iui < (Im - 1A), the third output current Im can be set as the current sharing value to perform current sharing control on the sub-control module 120. For the sub-control module 120 with the second output current Iui > Im, the third output current Im can also be set as the current sharing value to perform current sharing control on the above sub-control module 120, so as to set the corresponding current sharing value according to the output current capacity of the sub-control module 120 to perform current sharing control on it; in addition, when IΔ = |Im - Iui| > 1A, and ILsum ≥ IHsum is satisfied, or ILsum < IHsum and Iui ≥ (Im - 1A) is satisfied, or ILsum < IHsum and Iui ≤ Im is satisfied, the rated current limiting value of the sub-control module 120 can be set as the current sharing value to perform current sharing control on the above sub-control module 120 to avoid damaging the load.

[0085] S460: When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, perform maximum power point tracking control on the sub-control module.

[0086] The technical solution of the embodiment of the present invention sets the corresponding current sharing value according to the output current potential of each sub-control module to perform current sharing control, which not only helps to maximize the use of the power generation power of the photovoltaic system, but also helps to avoid failure of multiple parallel sub-control modules and change to a single-machine operation mode, and reduces the power bus noise of the photovoltaic system, and realizes real-time control of the total output current of the photovoltaic system, which is beneficial to increase the comprehensive service life of the photovoltaic system and reduce maintenance costs.

[0087] Embodiment 4

[0088] Figure 6 is a flow chart of a control method for a photovoltaic system provided according to a fourth embodiment of the present invention, with reference to Figure 6 , the method comprises the following steps:

[0089] S610: Obtain the total power currently required by the load, the power currently provided by each sub-control module, the target output voltage, and the real-time output voltage.

[0090] S620. When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, and the minimum value of the second output current of each sub-control module is greater than the third output current, according to the relationship between the second output current and the third output current of each sub-control module, a corresponding preset target current sharing value is set to perform current sharing control on at least some of the sub-control modules.

[0091] S630. When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, and the minimum value of the second output current of each sub-control module is less than or equal to the third output current, the sub-control modules whose output currents meet the preset current range are subjected to current equalization control.

[0092] In this embodiment, still combined with Figure 1The specific structure of the photovoltaic system shown in the figure is used to specifically describe the control method of the photovoltaic system. For example, based on the above embodiments, when the main control module 110 detects that (Qs-Qn)>(Qn*a%) and Idmin>Im, the corresponding preset target current sharing value can be set according to the relationship between the second output current Iui and the third output current Im of each sub-control module 120 to perform current sharing control on at least part of the sub-control modules 120. When the main control module 110 detects that (Qs-Qn)>(Qn*a%) and Idmin≤Im, the sub-control module 120 whose output current meets the preset current range can be subjected to current sharing control. Among them, the size of the preset current range can be pre-set according to needs, and the output current of each sub-control module 120 that meets the preset current range can be understood as an output current with similar values. In this way, when the main control module 110 detects that (Qs-Qn)>(Qn*a%) and Idmin≤Im, the sub-control modules 120 with similar output currents can be divided into a group and subjected to current equalization control to alleviate the situation where the output power of some sub-control modules 120 is insufficient due to power mismatch of the photovoltaic components 130 or shading.

[0093] S640: When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, perform maximum power point tracking control on the sub-control module.

[0094] When the main control module 110 detects that the numerical relationship between the real-time output voltage of a certain sub-control module 120 and the current target output voltage meets the second preset condition, that is, when a certain sub-control module 120 meets Vr<(Vt-△V), or meets Vr<(Vt-△V*(1+b)*100%), the sub-control module 120 can be controlled to switch from the current current sharing control state to the maximum power point tracking control state, so that the output power of the sub-control module 120 can be maintained at the maximum power point. The technical solution of the embodiment of the present invention determines the corresponding current sharing control strategy for the case where the numerical relationship between the power currently available to each sub-control module and the total power currently required by the load meets the first preset condition, and the minimum value of the second output current of each sub-control module is less than or equal to the third output current, that is, (Qs-Qn)>(Qn*a%) and Idmin≤Im, and the sub-control modules with similar output currents are grouped together and current sharing control is performed on them, which helps to alleviate the situation where the output power of some sub-control modules is insufficient due to power mismatch of photovoltaic modules or shading.

[0095] Embodiment 5

[0096] The embodiment of the present invention also provides a photovoltaic system. Figure 1The photovoltaic system includes: a main control module 110, a plurality of photovoltaic modules 130 and a plurality of parallel sub-control modules 120. The sub-control modules 120 are arranged in a one-to-one correspondence with the photovoltaic modules 130, and the sub-control modules 120 are connected to the corresponding photovoltaic modules 130. The output power of the photovoltaic modules 130 is controlled by the sub-control modules 120 and then output to the load; the main control module 110 is connected to each sub-control module 120 for communication, and the main control module 110 is used to:

[0097] Obtain the total power currently required by the load, the power currently available from each sub-control module, the target output voltage, and the real-time output voltage;

[0098] When the numerical relationship between the power currently provided by each sub-control module and the total power currently required by the load meets the first preset condition, current sharing control is performed on at least part of the sub-control modules with a preset target current sharing value;

[0099] When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets the second preset condition, the sub-control module is subjected to maximum power point tracking control.

[0100] The main control module in the photovoltaic system provided in the embodiment of the present invention can execute the control method of the photovoltaic system provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method, which will not be repeated.

[0101] Figure 7 Schematic diagram of a photovoltaic system provided by Embodiment 5 of the present invention. Figure 7 Optionally, the sub-control module 120 includes a maximum power point tracking controller, ie, an MPPT controller, and any sub-control module 120 that meets preset working conditions is multiplexed as the main control module 110.

[0102] The sub-control module 120 that meets the preset working conditions may be any sub-control module 120 that works normally.

[0103] Specifically, when a sub-control module 120 of the main control module 110 fails, a sub-control module 120 that meets a preset working condition may be automatically selected from the remaining sub-control modules 120 as the main control module 110 .

[0104] Continue to see Figure 7, the sub-control module 120 specifically includes a control unit 121 and a DC-DC converter 122. The control unit 121 in each sub-control module 120 is connected to the DC-DC converter 122, and the sub-control module 120 is connected to the main control module 110 through the communication network 140, and is connected to the photovoltaic module 130 and the output power bus 150 through the DC-DC converter 122. The control unit 121 is provided with an MPPT control loop and a current sharing control loop. The control unit 121 can sample the parameters of the photovoltaic module 130, and obtain the output voltage and output current of the photovoltaic module 130, so as to control the DC-DC converter 122 according to the parameters, output voltage and output current of the photovoltaic module 130. For example, according to the technical solutions of the above-mentioned embodiments, the maximum power point tracking MPPT control method is used to control the DC-DC converter 122, or the DC-DC converter 122 is driven and controlled according to the set current sharing value. The DC-DC converter 122 may be a DC-DC controller. The DC-DC converter 122 can convert the output voltage of the photovoltaic assembly 130 under the control of the control unit 121, so that the output power of the photovoltaic assembly 130 is processed by the DC-DC converter 122 and then output to the load. The output voltage and output current of the sub-control module 120 in the above embodiments may be the output voltage and output current of the DC-DC converter 122.

[0105] Embodiment 6

[0106] Figure 8 1 is a schematic diagram of the structure of an electronic device provided in Embodiment 6 of the present invention. The electronic device 10 is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices (such as helmets, glasses, watches, etc.) and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0107] like Figure 8As shown, the electronic device 10 includes at least one processor 11, and a memory connected to the at least one processor 11, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., wherein the memory stores a computer program that can be executed by at least one processor, and the processor 11 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or the computer program loaded from the storage unit 18 to the random access memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the electronic device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0108] A number of components in the electronic device 10 are connected to the I / O interface 15, including: an input unit 16, such as a keyboard, a mouse, etc.; an output unit 17, such as various types of displays, speakers, etc.; a storage unit 18, such as a disk, an optical disk, etc.; and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0109] The processor 11 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 executes the various methods and processes described above, such as a control method for a photovoltaic system.

[0110] In some embodiments, the control method of the photovoltaic system may be implemented as a computer program, which is tangibly contained in a computer-readable storage medium, such as a storage unit 18. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 10 via the ROM 12 and / or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the control method of the photovoltaic system described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to execute the control method of the photovoltaic system in any other appropriate manner (e.g., by means of firmware).

[0111] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0112] Computer programs for implementing the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the computer program is executed by the processor, the functions / operations specified in the flow chart and / or block diagram are implemented. The computer program may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0113] In the context of the present invention, a computer-readable storage medium may be a tangible medium that may contain or store a computer program for use by or in combination with an instruction execution system, device or equipment. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0114] To provide interaction with a user, the systems and techniques described herein may be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and a pointing device (e.g., a mouse or trackball) through which the user can provide input to the electronic device. Other types of devices may also be used to provide interaction with the user; for example, the feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form (including acoustic input, voice input, or tactile input).

[0115] The systems and techniques described herein may be implemented in a computing system that includes backend components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes frontend components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such backend components, middleware components, or frontend components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0116] A computing system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The client and server relationship is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services.

[0117] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0118] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for a photovoltaic system, characterized in that: The photovoltaic system includes a main control module, a plurality of photovoltaic modules and a plurality of sub-control modules connected in parallel; the sub-control modules are arranged in a one-to-one correspondence with the photovoltaic modules, the sub-control modules are connected to the corresponding photovoltaic modules, and the output power of the photovoltaic modules is output to the load after being controlled by the sub-control modules; the main control module is connected to each of the sub-control modules in communication, and the control method of the photovoltaic system is executed by the main control module, and the control method of the photovoltaic system includes: Obtaining the total power currently required by the load, the power currently available from each of the sub-control modules, the target output voltage, and the real-time output voltage; When the numerical relationship between the power currently provided by each of the sub-control modules and the total power currently required by the load meets the first preset condition, current sharing control is performed on at least part of the sub-control modules with a preset target current sharing value; When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, performing maximum power point tracking control on the sub-control module; The first preset condition includes: the difference between the power currently provided by each of the sub-control modules and the total power currently required by the load is greater than the product of the total power currently required by the load and the preset excess power ratio of the photovoltaic system; The second preset condition includes: the real-time output voltage of the sub-control module is less than the difference between the current target output voltage and a first preset error value.

2. The control method of the photovoltaic system according to claim 1, characterized in that: When the numerical relationship between the power currently provided by each of the sub-control modules and the total power currently required by the load meets the first preset condition, current sharing control is performed on at least part of the sub-control modules with a preset target current sharing value, including: Acquire a first output current and a second output current of each of the sub-control modules, wherein the first output current is an output current when a target output voltage of each of the sub-control modules is an initial voltage value, and the second output current is an output current when a target output voltage of each of the sub-control modules is a preset voltage value, and the preset voltage value is greater than the initial voltage value; When the numerical relationship between the power currently provided by each of the sub-control modules and the total power currently required by the load meets the first preset condition, and the minimum value of the second output currents of each of the sub-control modules is greater than the third output current, according to the relationship between the second output current and the third output current of each of the sub-control modules, a corresponding preset target current sharing value is set to perform current sharing control on at least part of the sub-control modules; The third output current is an average value of the first output currents of the sub-control modules, and the preset target current sharing values ​​corresponding to at least some of the sub-control modules are different.

3. The control method of the photovoltaic system according to claim 2, characterized in that: The obtaining of the first output current and the second output current of each of the sub-control modules includes: Controlling each of the sub-control modules with an initial voltage value as a target output voltage, and acquiring an output current of each of the sub-control modules as a first output current; The target output voltage is adjusted from the initial voltage value to a preset voltage value, each of the sub-control modules is controlled, and an output current of each of the sub-control modules is obtained as a second output current; The target output voltage is adjusted from the preset voltage value back to the initial voltage value.

4. The control method of the photovoltaic system according to claim 2, characterized in that: The setting of a corresponding preset target current sharing value to perform current sharing control on at least part of the sub-control modules according to the relationship between the second output current and the third output current of each of the sub-control modules includes: When the absolute value of the difference between the third output current and the second output current of the sub-control module is less than or equal to a first preset parameter, the sub-control module is subjected to current sharing control with a first preset target current sharing value, wherein the first preset target current sharing value is the sum of the third output current and a second preset error value.

5. The control method of the photovoltaic system according to claim 4, characterized in that: According to the relationship between the second output current and the third output current of each of the sub-control modules, setting a corresponding preset target current sharing value to perform current sharing control on at least part of the sub-control modules also includes: When the absolute value of the difference between the third output current and the second output current of the sub-control module is greater than the first preset parameter, and the relationship between the second output current and the third output current of each sub-control module meets a third preset condition, the sub-control module is subjected to current balancing control with the third output current; When the absolute value of the difference between the third output current and the second output current of the sub-control module is greater than the first preset parameter, and the relationship between the second output current and the third output current of each sub-control module does not meet the third preset condition, the sub-control modules are current-balanced controlled at the rated current limiting value; The third preset condition is: the sum of the first currents is less than the sum of the second currents; and the second output current of the sub-control module is less than the difference between the third output current and the first preset parameter, or the second output current of the sub-control module is greater than the third output current; The first current sum is the sum of the second output currents of the sub-control modules that are smaller than the third output current, and the second current sum is the sum of the second output currents of the sub-control modules that are larger than the third output current.

6. The control method of a photovoltaic system according to any one of claims 2 to 5, characterized in that: The photovoltaic system control method further includes: When the numerical relationship between the power that can currently be provided by each of the sub-control modules and the total power currently required by the load meets the first preset condition, and the minimum value of the second output current of each of the sub-control modules is less than or equal to the third output current, the sub-control modules whose output currents meet the preset current range are subjected to current equalization control.

7. A photovoltaic system, characterized in that: include: A main control module, a plurality of photovoltaic modules and a plurality of parallel-connected sub-control modules; The sub-control modules are arranged in one-to-one correspondence with the photovoltaic modules. The sub-control modules are connected to the corresponding photovoltaic modules. The output power of the photovoltaic modules is controlled by the sub-control modules and then output to the load. The main control module is connected to each of the sub-control modules in communication. The main control module is used to: Obtaining the total power currently required by the load, the power currently available from each of the sub-control modules, the target output voltage, and the real-time output voltage; When the numerical relationship between the power currently provided by each of the sub-control modules and the total power currently required by the load meets the first preset condition, current sharing control is performed on at least part of the sub-control modules with a preset target current sharing value; When the numerical relationship between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, performing maximum power point tracking control on the sub-control module; The first preset condition includes: the difference between the power currently provided by each of the sub-control modules and the total power currently required by the load is greater than the product of the total power currently required by the load and the preset excess power ratio of the photovoltaic system; The second preset condition includes: the real-time output voltage of the sub-control module is less than the difference between the current target output voltage and a first preset error value.

8. The photovoltaic system according to claim 7, characterized in that: The sub-control modules include a maximum power point tracking controller, and any of the sub-control modules that meet preset working conditions is multiplexed as the main control module.

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