CN116126084A - Control method of photovoltaic system and photovoltaic system - Google Patents

Abstract

The embodiment of the invention discloses a control method of a photovoltaic system and the photovoltaic system. The photovoltaic system comprises a main control module, a plurality of photovoltaic modules and a plurality of sub-control modules which are connected in parallel; the control method of the photovoltaic system is executed by the main control module, and comprises the following steps: acquiring the total power required by the load at present, the power available at present by each sub-control module, the target output voltage and the real-time output voltage; when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition, carrying out current sharing control on at least part of the sub-control modules by using a preset target current sharing value; and when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, carrying out maximum power point tracking control on the sub-control module. The technical scheme of the embodiment of the invention is beneficial to prolonging the comprehensive service life of the photovoltaic system and reducing the maintenance cost.

Description

Control method of photovoltaic system and photovoltaic system

Technical Field

The embodiment of the invention relates to the technical field of photovoltaic power generation, in particular to a control method of a photovoltaic system and the photovoltaic system.

Background

With the increasing decrease of traditional energy resources, the use of solar energy is increasingly receiving attention and importance. Solar energy is used as clean energy, and is greatly affected by environment, weather and climate, so that the output power of the photovoltaic array is nonlinear. Each photovoltaic array has only one maximum power value at a time, which is the maximum point of the photovoltaic array output power curve, which is called the maximum power point (Maximum Power Point, MPP). The existing photovoltaic system generally adopts a controller to control the photovoltaic array to work at a maximum power point, when the output power of the photovoltaic array is larger than the current demand of a load, the controller works in a constant voltage mode, and when the output power of the photovoltaic array is smaller than or equal to the current demand of the load, the controller works in a maximum power point tracking (Maximum Power Point Tracking, MPPT) control mode.

Currently, it is difficult for a single controller to meet the operational requirements of a photovoltaic system, and multiple sets of controllers operating in parallel are ideal solutions. The working mode switching method of the single controller is not suitable for the working scheme of the multi-machine parallel controller any more, the multi-machine parallel controller is high in manufacturing cost and easy to fail, once the multi-machine parallel controller fails, the system changes into a single-machine operation mode, and therefore a series of problems of large bus voltage noise, low control response speed, uncontrollable bus total current and the like are caused, and the service life of the multi-machine parallel controller is shortened.

Disclosure of Invention

The embodiment of the invention provides a control method of a photovoltaic system and the photovoltaic system, which realize the state switching of current sharing control and maximum power point tracking control on a plurality of sub-control modules connected in parallel, are beneficial to prolonging the comprehensive service life of the photovoltaic system when the sub-control modules are subjected to current sharing control, reduce the maintenance cost, and are beneficial to ensuring that the output power of the sub-control modules can be maintained at the maximum power point when the sub-control modules are subjected to the maximum power point tracking control.

According to an aspect of the invention, there is provided a control method of a photovoltaic system, 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 one-to-one correspondence with the photovoltaic modules, and are connected with the corresponding photovoltaic modules, and the output power supply of the photovoltaic modules is controlled by the sub-control modules and then is output to the load; the main control module is in communication connection with each sub-control module, the control method of the photovoltaic system is executed by the main control module, and the control method of the photovoltaic system comprises the following steps:

acquiring the total power required by the load at present, the power available at present by each sub-control module, the target output voltage and the real-time output voltage;

When the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition, carrying out current sharing control on at least part of the sub-control modules by using a preset target current sharing value;

and when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, carrying out maximum power point tracking control on the sub-control module.

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

the sub-control modules are arranged in one-to-one correspondence with the photovoltaic modules, and are connected with the corresponding photovoltaic modules, and the output power supply of the photovoltaic modules is controlled by the sub-control modules and then is output to the load; the main control module is in communication connection with each sub-control module and is used for:

acquiring the total power required by the load at present, the power available at present by each sub-control module, the target output voltage and the real-time output voltage;

when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition, carrying out current sharing control on at least part of the sub-control modules by using a preset target current sharing value;

And when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, carrying out maximum power point tracking control on the sub-control module.

According to another aspect of the present invention, there is provided an electronic apparatus including:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein, the liquid crystal display device comprises a liquid crystal display device,

the memory stores a computer program executable by the at least one processor to enable the at least one processor to perform the method of controlling a photovoltaic system according to any one of the embodiments of the present invention.

According to another aspect of the present invention, there is provided a computer readable storage medium storing computer instructions for causing a processor to execute a control method of a photovoltaic system according to any embodiment of the present invention.

According to the control method of the photovoltaic system and the photovoltaic system, the photovoltaic system comprises the main control module, the plurality of photovoltaic modules and the plurality of sub-control modules connected in parallel, the control method of the photovoltaic system is executed by the main control module, when the numerical relation between the power which can be provided by each sub-control module currently and the total power required by the load currently meets the first preset condition through the main control module, at least part of the sub-control modules are subjected to current sharing control according to the preset target current sharing value, when the current energy surplus degree of the photovoltaic system meets the requirement, the capacity of outputting current of the sub-control modules is mined, the maximum utilization of the power generation power of the photovoltaic system is facilitated, the occurrence of faults of the plurality of sub-control modules connected in parallel is avoided, the noise of a power bus of the photovoltaic system is reduced, the real-time control of the total output current of the photovoltaic system is realized, the service life of each sub-control module is similar, the comprehensive service life of the photovoltaic system is prolonged, and the maintenance cost is reduced. And when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a 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 requirement 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 control state of the sub-control module is switched according to the first preset condition and the second preset condition, so that the dynamic response speed of the photovoltaic system is improved, and the control state speed of the sub-control module is higher.

It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a photovoltaic system according to a first embodiment of the present invention.

Fig. 2 is a flow chart of a control method of a photovoltaic system according to an embodiment of the present invention.

Fig. 3 is a schematic flow chart of a control method of a photovoltaic system according to a second embodiment of the present invention.

Fig. 4 is a schematic flow chart of a control method of a photovoltaic system according to a third embodiment of the present invention.

Fig. 5 is a schematic diagram of data distribution of a first output current and a second output current according to a third embodiment of the present invention.

Fig. 6 is a flow chart of a control method of a photovoltaic system according to a fourth embodiment of the present invention.

Fig. 7 is a schematic structural diagram of a photovoltaic system according to a fifth embodiment of the present invention.

Fig. 8 is a schematic structural diagram of an electronic device according to a sixth embodiment of the present invention.

Detailed Description

In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Example 1

The first embodiment of the present invention provides a control method of a photovoltaic system, where the control method of the photovoltaic system may be performed by a main control module in the photovoltaic system, the main control module may be implemented in hardware and/or software, and the main control module may be configured in an electronic device. Fig. 1 is a schematic structural diagram of a photovoltaic system according to a first embodiment of the present invention. Referring to fig. 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 one-to-one correspondence with the photovoltaic modules 130, the sub-control modules 120 are connected with the corresponding photovoltaic modules 130, and the output power of the photovoltaic modules 130 is controlled by the sub-control modules 120 and then is output to the load. The main control module 110 is communicatively connected to each of the sub-control modules 120, and a control method of the photovoltaic system is performed by the main control module 110.

Fig. 2 is a flow chart of a control method of a photovoltaic system according to an embodiment of the present invention. Referring to fig. 2, the method specifically includes the steps of:

s210, acquiring the total power required by the load currently, the power currently available by each sub-control module, the target output voltage and the real-time output voltage.

The control method of the photovoltaic system will be specifically described with reference to the specific structure of the photovoltaic system shown in fig. 1. The main control module 110 is configured to control each sub-control module 120, where the main control module 110 may be in communication connection with each sub-control module 120 through the communication network 140, and the main control module 110 may be a host. The sub-control module 120 may control the output power of the photovoltaic module 130, for example, the sub-control module 120 includes a maximum power point tracking controller (hereinafter, abbreviated as MPPT controller), and each sub-control module 120 may be connected in parallel through an output power bus 150 and connected to a load (not shown in the drawing) through the output power bus 150. The photovoltaic module 130 includes a photovoltaic panel, the output power of the photovoltaic module 130 includes an output voltage and an output current, and the sub-control module 120 may control the output voltage and the output current of the photovoltaic module and output the output voltage and the output current to the load.

Specifically, the main control module 110 may obtain, through the communication network 140, the total power currently demanded by each load, the power currently available to 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.

S220, when the numerical relation between the power currently available to 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 according to a preset target current sharing value.

The current sharing control refers to a technology of balancing the output current of each power supply module by changing the voltage source characteristics of each parallel power supply module or changing the amplitude of the voltage source of each parallel power supply module. The first preset condition may be a numerical relation between a difference value between a total power currently available to each sub-control module and a total power currently required by the load and a preset surplus power, and the difference value between the total power currently available to each sub-control module and the total power currently required by the load represents an actual surplus power of the photovoltaic system, and the numerical relation between the actual surplus power of the photovoltaic system and the preset surplus power may reflect a surplus degree of energy currently generated by the photovoltaic system. For example, when the difference between the currently available power of each sub-control module and the total power currently required by the load is greater than a preset excess power, it indicates that the numerical relationship between the currently available power of each sub-control module and the total power currently required by the load satisfies a first preset condition, and when the difference between the currently available power of 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 currently available power of each sub-control module and the total power currently required by the load does not satisfy the first preset condition.

Specifically, the sub-control module 120 may operate in an initial control state when powered on. When the main control module 110 detects that the numerical relation between the power currently available by 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 degree of the photovoltaic system meets the requirement, the current sharing control can be performed on the output current of at least part of the sub-control modules 120 by issuing a preset target average current value to at least part of the sub-control modules 120 and using the preset target average current value, so that at least part of the sub-control modules 120 work in the current sharing control state, and the capability of the sub-control modules 120 for outputting the current is mined.

Optionally, the first preset condition includes: the difference between the power currently available to each sub-control module and the total power currently demanded by the load is greater than the product of the total power currently demanded by the load and the preset excess power duty cycle of the photovoltaic system.

Specifically, the preset excess power ratio may be a percentage of the total power of the photovoltaic system that is currently required by the load, and the preset excess power ratio may be set according to the requirement. The power currently available to each sub-control module 120 may be denoted as Qs, the total power currently demanded by the load may be denoted as Qn, the preset excess power ratio may be denoted as a%, and the first preset condition may be denoted as (Qs-Qn) > (qn×a%).

For example, the currently available power Qs of each sub-control module 120 is 120W, the preset excess power ratio a% is preset to be 50%, the total power Qn currently required by the load is 100W, and the calculated total power Qn is (120W-100W) < (100 w×50%), it is determined that the first preset condition (Qs-Qn) > (qn×a%) is not satisfied, and at this time, the sub-control module 120 does not enter the current sharing state; when the currently available power Qs of each sub-control module 120 is 180W, the preset excess power ratio a% is preset to be 50%, the total power Qn of the current demand of the load is 100W, and (180W-100W) > (100 w×50%), it is determined that the first preset condition (Qs-Qn) > (qn×a%) is satisfied, and at this time, the sub-control module 120 enters the current sharing state.

S230, performing maximum power point tracking control on the sub-control module when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition.

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 for determining whether the real-time output voltage can meet the requirement 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 may be determined that the current real-time output voltage of the sub-control module 120 cannot meet the requirement of the target output voltage.

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.

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

The first preset error value may be understood as a voltage sampling error of the sub-control module 120, and may specifically be set as a voltage sampling error Δv of the sub-control module 120, or be set as the voltage sampling error Δv of the sub-control module 120 multiplied by a setting margin, for example, Δv (1+b) ×100%, (1+b) represents the setting margin. For example, the real-time output voltage of the sub-control module 120 is denoted as Vr, the current target output voltage of the sub-control module 120 is denoted as Vt, the second preset condition may be denoted as Vr < (Vt- Δv) when the first preset error value is equal to Δv (1+b) ×100%, and the second preset condition may be denoted as Vr < (Vt- Δv (1+b) ×100%).

For example, 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 set margin (1+b) =1.05, it is calculated that 50V < (80V-2 v×1.05), it is determined that the second preset condition Vr < (Vt- Δv (1+b) ×100%) is satisfied, and the sub-control module 120 is restored 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, the voltage sampling error of the sub-control module 120 is 2V, 80V > (50V-2V 1.05) is calculated, and it is determined that the second preset condition Vr < (Vt- Δv (1+b)) is not satisfied, the sub-control module 120 continues to operate in the current sharing control state.

According to the technical scheme, the photovoltaic system comprises the main control module, the plurality of photovoltaic modules and the plurality of sub-control modules connected in parallel, when the numerical relation between the power currently available by each sub-control module and the total power currently required by a load meets a first preset condition, at least part of the sub-control modules are subjected to current sharing control according to the preset target current sharing value, so that when the current energy surplus degree of the photovoltaic system meets the requirement, the capacity of outputting current of the sub-control modules is mined, the maximum utilization of the power generation power of the photovoltaic system is facilitated, the failure of the plurality of sub-control modules connected in parallel is avoided to be changed into a single-machine operation mode, the noise of a power bus of the photovoltaic system is reduced, the real-time control of the total output current of the photovoltaic system is realized, the service lives of the sub-control modules are similar, the comprehensive service life of the photovoltaic system is prolonged, and the maintenance cost is reduced. And when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a 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 requirement 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 control state of the sub-control module is switched according to the first preset condition and the second preset condition, so that the dynamic response speed of the photovoltaic system is improved, and the control state speed of the sub-control module is higher.

Example two

Fig. 3 is a schematic flow chart of a control method of a photovoltaic system according to a second embodiment of the present invention, where the foregoing embodiment is further refined based on the foregoing embodiment. This embodiment may be combined with each of the alternatives of one or more of the embodiments described above. As shown in fig. 3, the method may include the steps of:

s310, acquiring the total power required by the load currently, the power currently available by each sub-control module, the target output voltage and the real-time output voltage.

S320, obtaining a first output current and a second output current of each sub-control module, wherein the first output current is an output current when the target output voltage of each sub-control module is an initial voltage value, and the second output current is an output current when the target output voltage of each sub-control module is a preset voltage value, and the preset voltage value is larger than the initial voltage value.

In this embodiment, a specific description will be given of a control method of the photovoltaic system, still with reference to the specific structure of the photovoltaic system shown in fig. 1. Specifically, the initial voltage value may be a target output voltage of each sub-control module when the sub-control module currently works, the preset voltage value is greater than the initial voltage value, and the potential of each sub-control module 120 to output current may be determined by obtaining an output current when the target output voltage of each sub-control module 120 is the preset voltage value. The first output current and the second output current of each sub-control module 120 are obtained through the main control module 110, and can be used for setting a preset target average current value in a reference manner.

Illustratively, the total number of sub-control modules 120 in the photovoltaic system is denoted as n, the initial voltage value is denoted as V, the preset voltage value is denoted as Vun, vun > V. The first output current IVi (i.ltoreq.n.1) is an output current when the target output voltage of each sub-control module 120 is V, and the first output currents IVi of the 1 st to n-th sub-control modules 120 may be expressed as: IV1, IV2, IV3, … …, IVn. The second output current Iui (i.ltoreq.n.1) is an output current when the target output voltage of each sub-control module 120 is Vun, and the second output currents Iui of the 1 st to n-th sub-control modules 120 can be expressed as: iu1, iu2, iu3, … …, iun.

S330, when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition and the minimum value in the second output current of each sub-control module is larger than the third output current, setting a corresponding preset target average current value according to the relation between the second output current and the third output current of each sub-control module, and performing 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 at least part of preset target average current values corresponding to the sub-control modules are different.

Specifically, the third output current is an average value of the first output currents IV1, IV2, IV3, … …, IVn of the respective sub-control modules 120, and may be denoted as Im. The minimum value of the second output currents Iu1, iu2, iu3, … …, iun of each sub-control module 120 may be referred to as Idmin. The numerical relationship between the power Qs currently available to each sub-control module 120 and the total power Qn currently demanded by the load satisfies a first preset condition, and the minimum value Idmin in the second output current Iui of each sub-control module 120 is greater than the third output current Im, which may be expressed as (Qs-Qn) > (qn×a%) and Idmin > Im. When the main control module 110 detects (Qs-Qn) > (qn×a%) and Idmin > Im, the second output current Iui of each sub-control module 120 when the target output voltage is Vun can be compared with the third output current Im 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 near the third output current Im, a corresponding preset target average current value is set to perform current sharing control on at least part of the sub-control modules 120.

And S340, carrying out maximum power point tracking control on the sub-control module when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition.

According to the technical scheme, when the numerical relation 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 in the second output current of each sub-control module is larger than the third output current, the corresponding preset target average current value is set to perform current sharing control on at least part of the sub-control modules according to the relation between the second output current and the third output current of each sub-control module, the corresponding average current value can be set according to the potential of the output current of each sub-control module to perform current sharing control, the maximization of the power generation power of the photovoltaic system is facilitated, the failure of a plurality of sub-control modules connected in parallel is avoided to be changed into a single-machine operation mode, the power bus noise of the photovoltaic system is reduced, the real-time control of the total output current of the photovoltaic system is realized, the comprehensive service life of the photovoltaic system is prolonged, and the maintenance cost is reduced.

Example III

Fig. 4 is a schematic flow chart of a control method of a photovoltaic system according to a third embodiment of the present invention, where the foregoing embodiment is further refined on the basis of the foregoing embodiment, and the present embodiment may be combined with each of the alternatives in one or more embodiments. As shown in fig. 4, the method comprises the steps of:

S410, acquiring the total power required by the load currently, the power currently available by each sub-control module, the target output voltage and the real-time output voltage.

S420, controlling each sub-control module by taking the initial voltage value as a target output voltage, and obtaining the output current of each sub-control module as a first output current.

In this embodiment, a specific description will be given of a control method of the photovoltaic system, still with reference to the specific structure of the photovoltaic system shown in fig. 1. Illustratively, each sub-control module 120 may operate in a maximum power point tracking control state when powered on, while employing the present scheme to mine the potential of the photovoltaic system to output electrical energy. The initial voltage value V may be a target output voltage of each sub-control module 120 when currently operating, and before the potential of the photovoltaic system for outputting electric energy is mined, first output currents IV1, IV2, IV3, … …, IVn when the target output voltage of each sub-control module 120 is V are obtained.

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

After step S420 is completed, the target output voltage of each sub-control module 120 is raised from the initial voltage value V to a preset voltage value Vun, so as to mine the potential of the photovoltaic system for outputting electric energy (hereinafter referred to as the mining potential state), the preset voltage value Vun is the target output voltage in the mining potential state, and the main control module 110 controls each sub-control module 120 accordingly, so as to obtain the second output currents Iu1, iu2, iu3, … …, iun when the target output voltage of each sub-control module 120 is Vun.

S440, adjusting the target output voltage from the preset voltage value to the initial voltage value.

After the main control module 110 obtains all of the first output currents IV1, IV2, IV3, … …, IVn when the target output voltages of the n sub-control modules 120 are V and the second output currents Iu1, iu2, iu3, … …, iun when the target output voltages of the n sub-control modules 120 are Vun, the target output voltages of the respective sub-control modules 120 are adjusted back to the initial voltage value V by the preset voltage value Vun, so that the photovoltaic system exits the excavation potential state and continues to operate normally.

Optionally, after step S440, the main control module 110 determines whether all of the first output currents IV1, IV2, IV3, … …, and IVn of the n sub-control modules 120 when the target output voltage is V and the second output currents Iu1, iu2, iu3, … …, and Iun of the n sub-control modules 120 when the target output voltage is Vun are obtained, if the current values are obtained, step S450 is continuously performed, and if the current values are not obtained, steps S420 to S440 are repeatedly performed until the current values are obtained.

Fig. 5 is a schematic diagram of data distribution of a first output current and a second output current according to a third embodiment of the present invention. Wherein the abscissa represents the value of the current in amperes a and the ordinate represents the serial number of the sub-control module 120. Fig. 5 schematically illustrates the magnitudes of the first output current IVi and the second output current Iui of each sub-control module 120 obtained when the number i=12 of sub-control modules 120 in the photovoltaic system, and the magnitude of the second output current Iui represents the potential of the sub-control module 120 to output current.

S450, when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition and the minimum value in the second output current of each sub-control module is larger than the third output current, setting a corresponding preset target average current value according to the relation between the second output current and the third output current of each sub-control module, and carrying out current sharing control on at least part of the sub-control modules.

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 average current value to perform current sharing control on at least part of the sub-control modules specifically may include: and when the absolute value of the difference between the third output current and the second output current of the sub-control module is smaller than or equal to the first preset parameter, the sub-control module is subjected to current sharing control by using the first preset target current sharing value.

The first preset target average current value is the sum of the third output current and the second preset error value.

Specifically, the value of the first preset parameter may be set according to the requirement, for example, the first preset parameter may be 1A. The absolute value of the difference between the third output current Im and the second output current of the ith sub-control module 120, which is denoted as Iui (1.ltoreq.i.ltoreq.n), may be denoted as iΔ= |im-Iui |. When the main control module 110 detects (Qs-Qn) > (qn×a%) and Idmin > Im, the second output current Iui of each sub-control module 120 may be compared with the third output current Im one by one, when iΔ= |im-Iui |+.1a, it indicates that the fluctuation degree of the second output current Iui of the sub-control module 120 around the third output current Im is small, the potential of the output current of the sub-control module 120 reaching the third output current Im is large, the first preset target average current value may be set to be the sum of the third output current Im and the second preset error value, the second preset error value may be iΔ/n, and the first preset target average current value may be expressed as: im+IΔ/n. The purpose of setting the first preset target average current value to be im+iΔ/n is to reduce the interference caused by the error again, that is, to reduce the output current of the sub-control modules 120 as much as possible, that is, when (Qs-Qn) > (qn×a%) and Idmin > Im, the first preset target average current value im+iΔ/n > Im is used for each sub-control module 120 satisfying iΔ= |im-Iui |is less than or equal to 1A, and current sharing control can be performed on the sub-control modules 120 through the first preset target average current value im+iΔ/n, so that the output currents of the sub-control modules 120 are all the first preset target average current value im+iΔ/n.

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

when the absolute value of the difference between the third output current and the second output current of the sub-control module is larger than the first preset parameter and the relation 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 sharing control by the third output current;

and when the absolute value of the difference between the third output current and the second output current of the sub-control module is larger than the first preset parameter and the relation between the second output current and the third output current of each sub-control module does not meet the third preset condition, current sharing control is carried out on the sub-control module by using the rated current limiting value.

The third preset condition is as follows: the first current sum is smaller than the second current sum; the second output current of the sub-control module is smaller than the difference between the third output current and the first preset parameter, or the second output current of the sub-control module is larger than the third output current; the first current sum is the sum of the second output currents of the sub-control modules which 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 which are larger than the third output current.

Illustratively, the first current sum is: the sum of the second output currents Iu1, iu2, iu3, … …, iun of each sub-control module 120, which is smaller than the third output current Im, may be referred to as ILsum. The second current sum is: the sum of the second output currents Iu1, iu2, iu3, … …, iun of each sub-control module 120, which is greater than the third output current Im, may be referred to as IHsum. Accordingly, the third preset condition may be expressed as: ILsum < IHsum.

The following description will take the first preset parameter 1A as an example. 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, i.e. iΔ= |im-Iui | > 1A, it indicates that the second output current Iui of the sub-control module 120 fluctuates to a greater extent near the third output current Im, and the output current of the sub-control module 120 has a smaller potential to reach the third output current Im. Thus, for each sub-control module 120 that satisfies iΔ= |im-Iui | > 1A: when ILsum is smaller than IHsum, for the sub-control module 120 with the second output current Iui < (Im-1A), the third output current Im may be set as a current equalizing value, the sub-control module 120 may perform current equalizing control, for the sub-control module 120 with the second output current Iui > Im, the third output current Im may also be set as a current equalizing value, and the sub-control module 120 may perform current equalizing control, so as to set a corresponding current equalizing value according to the capability of the sub-control module 120 to output current, and perform current equalizing control.

In addition, the relationship between the second output current and the third output current of the sub-control module 120 does not satisfy the third preset condition, which can be understood as: ILsum is more than or equal to IHsum; or ILsum < IHsum and Iui is more than or equal to (Im-1A); alternatively, ILsum < IHsum and Iui.ltoreq.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 limiting value of the sub-control module 120 may be set to be a current equalizing value, and current equalizing control is performed on the sub-control module 120 to avoid damaging the load.

The following describes a complete process of setting the average current value of each sub-control module 120 in conjunction with the schemes of step S410 to step S450. Specifically, the initial voltage value V is first used as a target output voltage to control each sub-control module 120, 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 raised to a 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 to the initial voltage value V by the preset voltage value Vun, so that the photovoltaic system exits from the excavation potential state and continues to work normally; calculating the average value of the second output currents Iu1, iu2, iu3, … … and Iun of each sub-control module 120 to obtain a third output current Im, comparing the second output current Iui of each sub-control module 120 with the third output current Im one by one, when iΔ= |im-Iui |is less than or equal to 1A, indicating that the fluctuation degree of the second output current Iui of the sub-control module 120 near the third output current Im is smaller, and setting the first preset target average current value as the sum of the third output current Im and the second preset error value, that is, setting the first preset target average current value as im+iΔ/n, where the output current of the sub-control module 120 has larger potential to reach the third output current Im; when (I delta= |im-Iui |) is greater than 1A, summing the current part higher than the third output current Im to obtain a second current sum IHsum, and summing the current lower than the third output current Im to obtain a first current sum ILsum, when ILsum < IHsum, setting the third output current Im as a uniform current value for the sub-control module 120, performing current sharing control for the sub-control module 120, setting the third output current Im as a uniform current value for the sub-control module 120, and setting the third output current Im as a uniform current value for the sub-control module 120, performing current sharing control for the sub-control module 120, and performing current sharing control for the sub-control module 120 according to the current output capacity of the sub-control module 120; in addition, when iΔ= |im-Iui | >1A and ILsum is greater than or equal to IHsum, or ILsum < IHsum and Iui (Im-1A) is greater than or equal to, or ILsum < IHsum and Iui is less than or equal to Im, the rated current limit value of the sub-control module 120 may be set to a current average value, and current sharing control may be performed on the sub-control module 120 to avoid damaging the load.

S460, carrying out maximum power point tracking control on the sub-control module when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition.

According to the technical scheme, corresponding current sharing values are set according to the potential of output currents of each sub-control module to conduct current sharing control, so that the maximum use of the generated power of the photovoltaic system is facilitated, the situation that a plurality of sub-control modules connected in parallel are failed to be changed into a single-machine operation mode is avoided, the noise of a power bus of the photovoltaic system is reduced, the real-time control of the total output current of the photovoltaic system is achieved, the comprehensive service life of the photovoltaic system is prolonged, and the maintenance cost is reduced.

Example IV

Fig. 6 is a flowchart of a control method of a photovoltaic system according to a fourth embodiment of the present invention, and referring to fig. 6, the method includes the following steps:

and S610, acquiring the total power required by the load currently, the power currently available by each sub-control module, the target output voltage and the real-time output voltage.

S620, when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition and the minimum value in the second output current of each sub-control module is larger than the third output current, setting a corresponding preset target average current value according to the relation between the second output current and the third output current of each sub-control module, and performing current sharing control on at least part of the sub-control modules.

And S630, carrying out current sharing control on the sub-control modules with the output currents meeting a preset current range when the numerical relation between the current available power of each sub-control module and the total power of the current demand of the load meets a first preset condition and the minimum value of the second output currents of each sub-control module is smaller than or equal to the third output current.

In this embodiment, a specific description will be given of a control method of the photovoltaic system, still with reference to the specific structure of the photovoltaic system shown in fig. 1. Illustratively, when the main control module 110 detects (Qs-Qn) > (qn×a%) and Idmin > Im, the corresponding preset target average current value may be set to perform current sharing control on at least some of the sub-control modules 120 according to the relationship between the second output current Iui and the third output current Im of each sub-control module 120. When the main control module 110 detects (Qs-Qn) > (qn×a%) and Idmin is less than or equal to Im, the sub-control module 120 whose output current satisfies the preset current range may perform current sharing control. The magnitude of the preset current range can be preset according to the requirement, and the output current of each sub-control module 120 meeting the preset current range can be understood as an output current with similar values, so when the main control module 110 detects (Qs-Qn) > (qn×a%) and Idmin is less than or equal to Im, the sub-control modules 120 with similar output currents can be divided into a group to perform current sharing control, so as to alleviate the situation that the output power of some sub-control modules 120 is insufficient due to the mismatching of the power of the photovoltaic module 130 or due to shielding.

And S640, performing maximum power point tracking control on the sub-control module when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition.

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 a second preset condition, that is, that a certain sub-control module 120 meets Vr < (Vt- Δv), or meets Vr < (Vt- Δv (1+b) ×100%), the sub-control module 120 can be controlled to switch from the 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. According to the technical scheme provided by the embodiment of the invention, the numerical relation between the power which can be provided by each sub-control module and the total power which is required by the load at present meets the first preset condition, and the minimum value in the second output current of each sub-control module is smaller than or equal to the third output current, namely (Qs-Qn) > (Qn is a%) and Idmin is smaller than or equal to Im, so that the corresponding current sharing control strategy is determined, the sub-control modules with similar output currents are divided into a group, current sharing control is carried out on the sub-control modules, and the situation that the output power of some sub-control modules is insufficient due to mismatching of the power of the photovoltaic module or due to shielding is facilitated.

Example five

The embodiment of the invention also provides a photovoltaic system. Referring to fig. 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 one-to-one correspondence with the photovoltaic modules 130, the sub-control modules 120 are connected with the corresponding photovoltaic modules 130, and the output power of the photovoltaic modules 130 is controlled by the sub-control modules 120 and then is output to a load; the main control module 110 is communicatively connected to each of the sub-control modules 120, and the main control module 110 is configured to:

acquiring the total power required by the load at present, the power available at present by each sub-control module, the target output voltage and the real-time output voltage;

when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition, carrying out current sharing control on at least part of the sub-control modules by using a preset target current sharing value;

and when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, carrying out maximum power point tracking control on the sub-control module.

The main control module in the photovoltaic system provided by the embodiment of the invention can execute the control method of the photovoltaic system provided by any embodiment of the invention, has corresponding functional modules and beneficial effects of the execution method, and is not repeated.

Fig. 7 is a schematic structural diagram of a photovoltaic system according to a fifth embodiment of the present invention. Referring to fig. 7, optionally, the sub-control modules 120 include a maximum power point tracking controller, that is, an MPPT controller, and any sub-control module 120 satisfying a preset operation condition is multiplexed as the main control module 110.

The sub-control module 120 satisfying the preset operating condition may be any sub-control module 110 that operates normally.

Specifically, when the sub-control module 120 serving as the main control module 110 fails, one sub-control module 110 satisfying a preset working condition may be automatically selected from the remaining sub-control modules 120 as the main control module 110.

With continued reference to fig. 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, the sub-control modules 120 are connected to the main control module 110 through the communication network 140, and the photovoltaic module 130 and the output power bus 150 are connected through the dc-dc converter 122. The control unit 121 is provided with an MPPT control loop and a current sharing control loop, where the control unit 121 may sample parameters of the photovoltaic module 130 and obtain an output voltage and an output current of the photovoltaic module 130, so as to control the dc-dc converter 122 according to the parameters, the output voltage and the output current of the photovoltaic module 130, for example, according to the technical solutions of the foregoing embodiments, a maximum power point tracking MPPT control method is used to control the dc-dc converter 122, or according to a set current sharing value, drive and control the dc-dc converter 122. The DC-DC converter 122 may be a DC-DC controller, and the DC-DC converter 122 may convert the output voltage of the photovoltaic module 130 under the control of the control unit 121, so that the output power of the photovoltaic module 130 is output to the load after being processed by the DC-DC converter 122. 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.

Example six

Fig. 8 is a schematic structural diagram of an electronic device according to a sixth embodiment of the present invention. The electronic device 10 is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. Electronic equipment may also represent various forms of mobile devices, such as personal digital processing, cellular telephones, smartphones, wearable devices (e.g., helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions, are meant to be exemplary only, and are not meant to limit implementations of the inventions described and/or claimed herein.

As shown in fig. 8, the electronic device 10 includes at least one processor 11, and a memory, such as a Read Only Memory (ROM) 12, a Random Access Memory (RAM) 13, etc., communicatively connected to the at least one processor 11, in which the memory stores a computer program executable by the at least one processor, and the processor 11 may 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 into the Random Access Memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the electronic device 10 may also be stored. The processor 11, the ROM 12 and the RAM 13 are connected to each other via a bus 14. An input/output (I/O) interface 15 is also connected to bus 14.

Various 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, and the like; a storage unit 18 such as a magnetic disk, an optical disk, or the like; and a communication unit 19 such as a network card, modem, wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information/data with other devices via a computer network, such as the internet, and/or various telecommunication networks.

The processor 11 may be a variety of general and/or special purpose processing components having processing and computing capabilities. Some examples of processor 11 include, but are not limited to, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), various specialized Artificial Intelligence (AI) computing chips, various processors running machine learning model algorithms, digital Signal Processors (DSPs), and any suitable processor, controller, microcontroller, etc. The processor 11 performs the various methods and processes described above, such as the control method of the photovoltaic system.

In some embodiments, the control method of the photovoltaic system may be implemented as a computer program tangibly embodied on a computer-readable storage medium, such as the storage unit 18. In some embodiments, part or all of the computer program may be loaded and/or installed onto 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 perform the control method of the photovoltaic system by any other suitable means (e.g. by means of firmware).

Various implementations of the systems and techniques described here above may be implemented in digital electronic circuitry, integrated circuit systems, field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), application Specific Standard Products (ASSPs), systems On Chip (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include: implemented in one or more computer programs, the one or more computer programs may be executed and/or interpreted on a programmable system including at least one programmable processor, which may be a special purpose or general-purpose programmable processor, that may receive data and instructions from, and transmit data and instructions to, a storage system, at least one input device, and at least one output device.

A computer program for carrying out 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, special purpose computer, or other programmable data processing apparatus, such that the computer programs, when executed by the processor, cause the functions/acts specified in the flowchart and/or block diagram block or blocks to be implemented. The computer program may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present invention, a computer-readable storage medium may be a tangible medium that can contain, or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer readable storage medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Alternatively, the computer readable storage medium may be a machine readable signal medium. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, 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 disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

To provide for interaction with a user, the systems and techniques described here can 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 a user; and a keyboard and a pointing device (e.g., a mouse or a trackball) through which a user can provide input to the electronic device. Other kinds of devices may also be used to provide for interaction with a user; for example, 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, speech input, or tactile input.

The systems and techniques described here can be implemented in a computing system that includes a background component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front-end component (e.g., a user computer having a graphical user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such background, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: local Area Networks (LANs), wide Area Networks (WANs), blockchain networks, and the internet.

The computing system may include clients and servers. The client and server are typically remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server can be a cloud server, also called a cloud computing server or a cloud host, and is a host product in a cloud computing service system, so that the defects of high management difficulty and weak service expansibility in the traditional physical hosts and VPS service are overcome.

It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps described in the present invention may be performed in parallel, sequentially, or in a different order, so long as the desired results of the technical solution of the present invention are achieved, and the present invention is not limited herein.

The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.

Claims (10)

1. The control method of the photovoltaic system is characterized in that the photovoltaic system comprises a main control module, a plurality of photovoltaic modules and a plurality of sub-control modules which are connected in parallel; the sub-control modules are arranged in one-to-one correspondence with the photovoltaic modules, the sub-control modules are connected with the corresponding photovoltaic modules, and the output power supply of the photovoltaic modules is controlled by the sub-control modules and then is output to a load; the main control module is in communication connection with each sub-control module, the control method of the photovoltaic system is executed by the main control module, and the control method of the photovoltaic system comprises the following steps:

Acquiring the total power required by a load at present, the power currently available by each sub-control module, target output voltage and real-time output voltage;

when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition, carrying out current sharing control on at least part of the sub-control modules by using a preset target current sharing value;

and when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, carrying out maximum power point tracking control on the sub-control module.

2. The method for controlling a photovoltaic system according to claim 1, wherein the first preset condition includes: the difference between the power currently available 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.

3. The method for controlling a photovoltaic system according to claim 1, wherein the second preset condition includes: the real-time output voltage of the sub-control module is smaller than the difference between the current target output voltage and a first preset error value.

4. The method according to claim 1, wherein when the numerical relationship between the power currently available to each of the sub-control modules and the total power currently required by the load satisfies a first preset condition, performing current sharing control on at least part of the sub-control modules at a preset target current sharing value, includes:

obtaining a first output current and a second output current of each sub-control module, wherein the first output current is an output current when the target output voltage of each sub-control module is an initial voltage value, and the second output current is an output current when the target output voltage of each sub-control module is a preset voltage value, and the preset voltage value is larger than the initial voltage value;

when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition and the minimum value in the second output current of each sub-control module is larger than a third output current, setting a corresponding preset target average current value to perform current sharing control on at least part of the sub-control modules according to the relation between the second output current and the third output current of each sub-control module;

The third output current is an average value of the first output currents of the sub-control modules, and at least part of preset target average current values corresponding to the sub-control modules are different.

5. The method according to claim 4, wherein the obtaining the first output current and the second output current of each of the sub-control modules includes:

controlling each sub-control module by taking the initial voltage value as a target output voltage, and obtaining the output current of each sub-control module as a first output current;

adjusting the target output voltage from the initial voltage value to a preset voltage value, controlling each sub-control module, and obtaining the output current of each sub-control module as a second output current;

and regulating the target output voltage from the preset voltage value to the initial voltage value.

6. The method according to claim 4, wherein the setting a corresponding preset target average current value according to a relation between the second output current and the third output current of each sub-control module performs current sharing control on at least part of the sub-control modules, including:

And when the absolute value of the difference between the third output current and the second output current of the sub-control module is smaller than or equal to a first preset parameter, the sub-control module is subjected to current sharing control by a first preset target current sharing value, wherein the first preset target current sharing value is the sum of the third output current and the second preset error value.

7. The method according to claim 6, wherein the setting the corresponding preset target average current value according to the relationship between the second output current and the third output current of each sub-control module performs current sharing control on at least part of the sub-control modules, further comprises:

when the absolute value of the difference between the third output current and the second output current of the sub-control module is larger than the first preset parameter, and the relation between the second output current and the third output current of each sub-control module meets a third preset condition, carrying out current sharing control on the sub-control module by using 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 larger than the first preset parameter, and the relation between the second output current and the third output current of each sub-control module does not meet a third preset condition, carrying out current sharing control on the sub-control modules at a rated limiting value;

Wherein, the third preset condition is: the first current sum is smaller than the second current sum; and the second output current of the sub-control module is smaller than the difference between the third output current and the first preset parameter, or the second output current of the sub-control module is larger than the third output current;

the first current sum is the sum of the second output currents of the sub-control modules which 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 which are larger than the third output current.

8. The control method of a photovoltaic system according to any one of claims 1 to 7, characterized in that the control method of a photovoltaic system further comprises:

and when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition and the minimum value in the second output current of each sub-control module is smaller than or equal to a third output current, carrying out current sharing control on the sub-control modules of which the output currents meet a preset current range.

9. A photovoltaic system, comprising: the photovoltaic system comprises a main control module, a plurality of photovoltaic modules and a plurality of sub-control modules which are connected in parallel;

The sub-control modules are arranged in one-to-one correspondence with the photovoltaic modules, the sub-control modules are connected with the corresponding photovoltaic modules, and the output power supply of the photovoltaic modules is controlled by the sub-control modules and then is output to a load; the main control module is in communication connection with each sub-control module, and the main control module is used for:

acquiring the total power required by a load at present, the power currently available by each sub-control module, target output voltage and real-time output voltage;

when the numerical relation between the power currently available to each sub-control module and the total power currently required by the load meets a first preset condition, carrying out current sharing control on at least part of the sub-control modules by using a preset target current sharing value;

and when the numerical relation between the real-time output voltage of the sub-control module and the current target output voltage meets a second preset condition, carrying out maximum power point tracking control on the sub-control module.

10. The photovoltaic system of claim 9, wherein the sub-control modules include a maximum power point tracking controller, any of the sub-control modules meeting a preset operating condition being multiplexed as the main control module.

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