CN115528733A

CN115528733A - Photovoltaic power generation system, inverter and MPPT optimization method of inverter

Info

Publication number: CN115528733A
Application number: CN202211245624.0A
Authority: CN
Inventors: 渠武兵; 张干
Original assignee: Sungrow Shanghai Co Ltd
Current assignee: Sungrow Shanghai Co Ltd
Priority date: 2022-10-12
Filing date: 2022-10-12
Publication date: 2022-12-27

Abstract

The application provides a photovoltaic power generation system, an inverter and an MPPT optimization method of the inverter. When all the optimizers in the preset photovoltaic group string do not work in the through area, the current value of the output voltage of the preset photovoltaic group string is increased by the preset value, whether all the optimizers in the preset photovoltaic group string do not work in the through area is judged again, and the current value of the output voltage of the preset photovoltaic group string is not adjusted until at least one optimizer in the preset photovoltaic group string works in the through area.

Description

Photovoltaic power generation system, inverter and MPPT optimization method of inverter

Technical Field

The invention relates to the technical field of power electronics, in particular to a photovoltaic power generation system, an inverter and an MPPT optimization method of the inverter.

Background

At present, in a distributed photovoltaic power generation system, photovoltaic modules are placed at relatively distributed positions, and even if the photovoltaic modules in the same area are different in respective environments, for example, taking a roof as an example, shadow shielding exists in some positions, or the orientations of different positions of the roof are different, so that the generated power of a photovoltaic string composed of a plurality of photovoltaic modules is reduced; in order to improve the power generation power, an optimizer is additionally arranged in the photovoltaic string, and the method specifically comprises the following steps: the output ends of the photovoltaic modules in the photovoltaic string are connected with the input ends of the optimizers in a one-to-one correspondence mode, the output ends of all the optimizers are connected in series, and two poles of the series branch serve as the output ends of the photovoltaic string.

In a distributed photovoltaic power generation system, each photovoltaic string is connected to each dc side of an inverter in a one-to-one correspondence manner; in the inverter, DCDC conversion modules which are in one-to-one correspondence with each photovoltaic group string are connected, and a controller in the inverter executes an MPPT algorithm on each photovoltaic group string to realize the MPPT of each photovoltaic group string; in addition, the controller also executes MPPT disturbance observation algorithm to each photovoltaic group string, namely: if the output power of a certain path of photovoltaic string is not changed at the front voltage point and the rear voltage point of the output voltage of the photovoltaic string, the output voltage of the path of photovoltaic string is controlled to be disturbed leftwards, and the inverter is prevented from being incapable of working normally due to falling into the open-circuit voltage.

Therefore, under the control of the MPPT algorithm and the MPPT disturbance observation algorithm, at least one optimizer in the pv string finally operates at the critical point between the current limiting region and the MPPT region, so that the output voltage of the pv string is low but the output current is high, thereby affecting the life and reliability of the optimizers in the pv string.

Therefore, how to improve the service life and reliability of the optimizer in the photovoltaic string connected to the inverter is an urgent technical problem to be solved.

Disclosure of Invention

In view of the above, the present invention provides a photovoltaic power generation system, an inverter and an MPPT optimization method thereof, so as to improve the lifetime and reliability of an optimizer in a photovoltaic string connected to the inverter.

In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

the application provides in a first aspect a MPPT optimization method for an inverter, where at least one dc side of the inverter is connected to a photovoltaic string; the MPPT optimization method of the inverter comprises the following steps:

judging whether the total number of the photovoltaic string connected to each direct current side of the inverter is less than 2;

if the total number of the photovoltaic group strings connected to each direct current side of the inverter is less than 2, judging whether a preset topology is adopted by the photovoltaic group strings of a preset path; the preset topology is that the output end of each photovoltaic module in the photovoltaic group string is connected with an optimizer, and the output ends of all the optimizers are connected in series;

if the photovoltaic group strings of the preset path adopt the preset topology, judging whether all the optimizers in the photovoltaic group strings of the preset path do not work in a direct-through area currently;

if all the optimizers in the preset path of photovoltaic group strings do not work in the through area currently, increasing the current value of the output voltage of the preset path of photovoltaic group strings by a preset value, and returning to execute the step of judging whether all the optimizers in the preset path of photovoltaic group strings do not work in the through area currently;

and if at least one optimizer in the preset path of photovoltaic group strings works in the through area currently, not adjusting the current value of the output voltage of the preset path of photovoltaic group strings.

Optionally, if all the dc sides of the inverter are connected with the photovoltaic string, determining whether the total number of the photovoltaic strings connected to each dc side of the inverter is less than 2, including:

judging whether the total number of the photovoltaic group strings is larger than the MPPT number of the inverter or not; the MPPT path number is the maximum path number of the inverter which can enable the photovoltaic string to realize MPPT;

and if the total number of the photovoltaic group strings is less than or equal to the MPPT number, executing a step of judging whether all the optimizers in the preset photovoltaic group strings do not work in a direct-connection area currently.

Optionally, determining whether the total number of the photovoltaic string is greater than the MPPT number of the inverter includes:

acquiring the serial numbers of all the photovoltaic group strings connected with the inverter;

determining a temporary value of the serial number of each photovoltaic group string according to the serial number mode of each photovoltaic group string;

judging whether the temporary values of the serial numbers of the photovoltaic group strings of all the paths are larger than or equal to zero and smaller than the MPPT paths of the inverter;

and if the temporary values of the string numbers of the photovoltaic string in each path are all larger than or equal to zero and are all smaller than the MPPT path number of the inverter, judging that the total path number of the photovoltaic string is smaller than or equal to the MPPT path number of the inverter.

Optionally, before increasing the preset value of the preset path of the photovoltaic string, the method further includes:

judging whether the time interval for increasing the preset value of the photovoltaic string on the preset path last time exceeds a preset period or not;

and if the time interval exceeds the preset period, increasing the preset value of the preset path of the photovoltaic string.

judging whether all the optimizers in a preset path of the photovoltaic string do not work in the through area within a first preset time;

and if all the optimizers in the preset path of the photovoltaic group strings do not work in the through area within the first preset time, increasing the preset value of the preset path of the photovoltaic group strings.

Optionally, before the current value of the output voltage of the preset path of the photovoltaic string is not adjusted, the method further includes:

judging whether all the optimizers working in the through area in the photovoltaic group strings of the preset path work in the through area within second preset time or not;

if all the optimizers working in the through region in the preset path of photovoltaic string work in the through region within the second preset time, the current value of the output voltage of the preset path of photovoltaic string is not adjusted.

Optionally, the preset value is a fixed value or a variable value.

Optionally, if the preset value is a variation value, the preset value is in a proportional relationship with a current value of the output voltage of the preset path of the photovoltaic string.

A second aspect of the present application provides an inverter including: the controller, the inverter circuit and at least one DCDC conversion circuit; wherein:

the first sides of the DCDC conversion circuits are respectively connected with the direct current sides of the inverters in a one-to-one correspondence mode, and at least one direct current side of the inverter is connected with a photovoltaic group string;

the direct current side of the inverter circuit is connected with the second sides of all the DCDC conversion circuits, and the alternating current side of the inverter circuit is connected with the alternating current side of the inverter;

the inverter circuit and all the DCDC conversion circuits are controlled by the controller, the controller is in communication connection with a remote platform through communication equipment, the controller is used for obtaining output current and output voltage of each optimizer in each optimizer, and the controller is further used for executing the MPPT optimization method of the inverter according to any one of the first aspect of the application on at least one photovoltaic string connected with the inverter.

Optionally, the communication device is integrated inside the controller.

Optionally, the remote platform is a cloud.

Optionally, the controller includes: a first controller and a second controller; wherein:

the first controller is in communication connection with each second controller, and the inverter circuit and all the DCDC conversion circuits are controlled by the second controllers;

the first controller is used for acquiring the output current and the output voltage of each optimizer in each optimizer path;

the first controller is in communication connection with the remote platform through the communication equipment;

the first controller and all of the second controllers are configured to jointly execute the MPPT optimization method for the inverter according to any one of the first aspect of the present application.

Optionally, each of the second controllers is integrated in the corresponding inverter circuit.

A third aspect of the present application provides a photovoltaic power generation system, including: a grid-side switching device, at least one photovoltaic string, and an inverter according to any of the second aspects of the present application; wherein:

at least one direct current side of the inverter is connected with the photovoltaic string;

and the alternating current side of the inverter is connected with a power grid or a load through a grid side switching device.

Optionally, the method further includes: at least one energy storage device; wherein:

and two poles of each energy storage device are respectively connected with two poles of the output end of the corresponding photovoltaic string.

According to the technical scheme, the invention provides the MPPT optimization method of the inverter, and at least one direct current side of the inverter is connected with the photovoltaic string. In the MPPT optimization method, when all optimizers in the preset path photovoltaic group string do not operate in the through region, the current value of the output voltage of the preset path photovoltaic group string is increased by the preset value, and it is determined again whether all optimizers in the preset path photovoltaic group string do not operate in the through region at present, until at least one optimizer in the preset path photovoltaic group string operates in the through region, the current value of the output voltage of the preset path photovoltaic group string is not adjusted any more, so under the common control of the MPPT optimization method and the MPPT algorithm, at least one optimizer in the preset path photovoltaic group string operates at the junction between the through region and the MPPT region, and the output ends of all optimizers in the preset path photovoltaic group string are connected in series, that is, the output currents of all optimizers in the preset path photovoltaic group string are the same, and therefore the output currents of all optimizers in the preset path photovoltaic group string are reduced, and further the MPPT optimization method of the inverter provided by the present application improves the life and reliability of the photovoltaic group string connected with the inverter.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 and fig. 2 are schematic flow diagrams of two embodiments of an MPPT optimization method for an inverter according to an embodiment of the present disclosure;

fig. 3 is a flowchart illustrating an embodiment of step S210 according to the present application;

FIG. 4a is a schematic diagram of the IV curve of the optimizer

FIG. 4b is a schematic diagram of the PV curve of the optimizer;

fig. 5 is a flowchart illustrating an embodiment of step S130 according to the present application;

6-8 are schematic flow diagrams of three implementations of an MPPT optimization method for an inverter according to an embodiment of the present disclosure;

fig. 9 and fig. 10 are schematic structural diagrams of two embodiments of an inverter provided in an embodiment of the present application, respectively;

fig. 11 and fig. 12 are schematic structural diagrams of two embodiments of a photovoltaic power generation system provided in an example of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.

In this application, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.

In order to improve the service life and reliability of an optimizer in a photovoltaic string, embodiments of the present application provide an MPPT optimization method for an inverter, where at least one dc side of the inverter is connected with the photovoltaic string.

A specific flow of the MPPT optimization method of the inverter is shown in fig. 1, and specifically includes the following steps:

and S110, judging whether the total number of the photovoltaic group strings connected to each direct current side of the inverter is less than 2.

If the total number of the photovoltaic string connected to each direct current side of the inverter is less than 2, executing step 120; if the total number of the photovoltaic string connected to each dc side of the inverter is not less than 2, the process returns to step S110.

It should be noted that, in practical applications, the number of the pv strings connected to each dc side of the inverter is the same, for example, if the inverter has 5 dc sides, and one of the dc sides is connected to one of the pv strings, each of the other dc sides can only be connected to one of the pv strings.

In a specific example, all dc sides of the inverter are connected with the pv strings, as shown in fig. 2, the embodiment of step S110 specifically includes the following steps:

and S210, judging whether the total number of the photovoltaic group strings is larger than the MPPT number of the inverter or not.

If the total number of the photovoltaic string is less than or equal to the MPPT number of the inverter, executing step S120; and if the total number of the photovoltaic group strings is greater than the MPPT number of the inverter, returning to execute the step S110.

The MPPT path number of the inverter is specifically as follows: the inverter can enable the photovoltaic string to achieve the maximum path number of MPPT; for example, if the inverter includes 5 DCDC conversion circuits, and the inverter can make 5 corresponding photovoltaic strings realize MPPT through the 5 DCDC conversion circuits, the number of MPPTs of the inverter at this time is equal to 5.

In a specific example, as shown in fig. 3, the implementation of step S210 specifically includes the following steps:

and S310, acquiring the serial number of each photovoltaic group string connected with the inverter.

In a specific example, the connection relationship of the dc side of the inverter is set by a manual setting method, that is: the staff sets for according to actual conditions: the number of the direct current sides of the photovoltaic group strings is connected to the inverter, which direct current sides of the inverter are connected with the photovoltaic group strings, and the number of the photovoltaic group strings connected to each direct current side of the inverter; in the setting mode, each path of photovoltaic group string is numbered from 1 manually, wherein the number of each path of photovoltaic group string is the string number of each path of photovoltaic group string; in addition, the serial number of each photovoltaic group string needs to be manually input into the cloud; therefore, in this manner, the string number of each photovoltaic string connected to the inverter needs to be acquired from the cloud.

In another specific example, the connection relationship of the dc side of the inverter is set in an intelligent setting manner, that is: after receiving an intelligent station building instruction issued by a cloud, setting according to a built-in algorithm: the number of the direct current sides of the photovoltaic group strings is connected to the inverter, which direct current sides of the inverter are connected with the photovoltaic group strings, and the number of the photovoltaic group strings connected to each direct current side of the inverter; in this way, each photovoltaic string is automatically numbered from 221, where the number is the string number of each photovoltaic string; in addition, the serial number of each photovoltaic group string can be automatically stored, and even the serial number of each photovoltaic group string can be automatically uploaded to the cloud; therefore, in this way, the string number of each photovoltaic string connected with the inverter can be directly obtained or obtained from the cloud.

It should be noted that, it is a relatively mature technology to intelligently set the connection relationship of the dc side of the inverter, and details are not described here, and reference may be made to the prior art.

And S320, determining a temporary value of the serial number of each photovoltaic group string according to the serial number mode of each photovoltaic group string.

In practical applications, if the connection relation on the dc side of the inverter is set manually, that is, when each path of photovoltaic string is numbered, starting from 1, the temporary value of the string number of each path of photovoltaic string is obtained by subtracting 1 from the string number of each path of photovoltaic string.

If the connection relation of the direct current side of the inverter is set in an intelligent setting mode, namely the photovoltaic group strings of each path are numbered from 221, the temporary value of the serial number of each photovoltaic group string is obtained by entering the serial number of each photovoltaic group string into 221.

And S330, judging whether the temporary values of the serial numbers of the photovoltaic group strings are all larger than or equal to zero and are all smaller than the MPPT (maximum power point tracking) number of the inverter.

If the temporary values of the string numbers of the photovoltaic string in each path are all larger than or equal to zero and are all smaller than the MPPT path number of the inverter, executing step S340; otherwise, step S350 is executed.

And S340, judging that the total number of the photovoltaic string is less than or equal to the MPPT number of the inverter.

And S350, judging that the total number of the photovoltaic group strings is larger than the MPPT number of the inverter.

In practical application, the specific implementation manner of step S340 and step S350 is as follows: assigning a corresponding quantity to 1; therefore, when the corresponding variable is equal to 1, the corresponding operation is performed.

It should be noted that, if the above embodiment is adopted in step S110, before returning to step S110, the corresponding variable needs to be initialized, that is, the corresponding variable is assigned to 0; also, the corresponding quantities need to be initialized when the method is first performed.

The above specific example is only a specific implementation of step S210, and in practical applications, including but not limited thereto, it is not specifically limited herein, and it is within the protection scope of the present application as the case may be.

And S120, judging whether the photovoltaic group strings on the preset path adopt a preset topology or not.

If the preset path photovoltaic group string adopts the preset topology, executing step S130; if the preset path photovoltaic group string does not adopt the preset topology, the step S110 is executed again.

The output end of each photovoltaic module in the photovoltaic group string is connected with one optimizer, and the output ends of all the optimizers are connected in series.

It should be noted that, the implementation of determining whether the preset path photovoltaic string adopts the preset topology is a relatively mature technology in the prior art, and is not described herein again.

S130, judging whether all optimizers in the preset path photovoltaic group string do not work in a through area currently.

If all optimizers in the preset path photovoltaic string do not work in the through area currently, executing the step S140, and after the step S140 is executed, returning to execute the step S130; if at least one optimizer in the preset-path photovoltaic string is currently operating in the through region, step S150 is executed.

The preset path of photovoltaic string is the path of photovoltaic string which is used as an execution object of the MPPT optimization method of the inverter in all the photovoltaic strings connected with the inverter; for example, if the MPPT optimization method of the inverter is performed on the third photovoltaic string, the third photovoltaic string is the preset photovoltaic string.

As can be seen from the output characteristics of the optimizer shown in fig. 4a and 4b, there are three working regions for the optimizer: a current limiting region, an MPPT region and a pass-through region; when the optimizer is in a current limiting region, the output current of the optimizer is kept unchanged, and the output power of the optimizer is increased along with the increase of the output voltage of the optimizer; when the optimizer is in the MPPT area, the output current of the optimizer is reduced along with the increase of the output voltage of the optimizer, but the output power of the optimizer is kept unchanged; when the optimizer is in the pass-through region, its output current decreases as its output voltage increases, and its power also decreases as its output voltage increases.

In a specific example, as shown in fig. 5, a specific implementation of step S130 includes the following steps:

s410, determining the number of optimizers currently working in an MPPT (maximum power point tracking) area or a current limiting area in all optimizers of the photovoltaic string.

In practical application, if the output voltage of the optimizer changes around the current voltage value and the output power of the optimizer remains unchanged, the optimizer currently works in the MPPT region; the determination methods of other areas are similar, and are not described herein again; it should be noted that how to determine whether the optimizer works in the MPPT region or the current limiting region is a relatively mature technology, which is only an example, and other examples may refer to the prior art, and are not described herein again.

And S420, judging whether the number of the optimizers currently working in the MPPT area or the current limiting area is equal to the total number of the optimizers in the photovoltaic string.

If the number of the optimizers currently working in the MPPT region or the current limiting region is equal to the total number of the optimizers included in the photovoltaic string, executing step S230; if the number of the optimizers currently operating in the MPPT region or the current limiting region is not equal to the total number of the optimizers included in the pv string, step S240 is performed.

And S430, judging that all optimizers in the photovoltaic group string do not work in a through area currently.

S440, judging that at least one optimizer in the photovoltaic string works in a direct-through area currently.

In the above-mentioned specific example, a specific implementation of determining whether all the optimizers in the pv string are not currently operating in the pass-through region is only used, and in practical applications, including but not limited to this, this is not specifically limited herein, and it is within the scope of the present application according to specific situations.

And S140, increasing the current value of the output voltage of the photovoltaic group string of the preset path by a preset value.

Therefore, the output end of the preset photovoltaic string is connected with one direct current side of the inverter, so that the output voltage of the preset photovoltaic string is equal to the corresponding direct current side voltage of the inverter, and in practical application, the output voltage of the preset photovoltaic string is adjusted by adjusting the corresponding direct current side voltage of the inverter.

Optionally, the preset value may be a fixed value or a variable value, and is not specifically limited herein and is within the protection scope of the present application.

If the preset value is a variation value, the preset value may be in a proportional relationship with a current value of the output voltage of the photovoltaic string, for example, the preset value is equal to 1% of the output voltage of the photovoltaic string; the above is only an example, and in practical applications, including but not limited to the above embodiments, for example, the preset value is reset after each photovoltaic string is added, and the method is not limited in detail here, and may be determined as the case may be, and is within the protection scope of the present application.

And S150, not adjusting the current value of the output voltage of the photovoltaic group string of the preset path.

In practical applications, the MPPT optimization method for the inverter may be performed in real time or periodically, which is not specifically limited herein and may be determined according to specific situations.

Therefore, under the common control of the MPPT optimization method and the MPPT algorithm, at least one optimizer in the preset photovoltaic string can work at the joint of the through area and the MPPT area, the output ends of all the optimizers in the preset photovoltaic string are connected in series, namely the output currents of all the optimizers in the preset photovoltaic string are the same, so that the output currents of all the optimizers in the preset photovoltaic string are all reduced, and the service life and the reliability of the optimizers in the photovoltaic string connected with the inverter are improved by the MPPT optimization method of the inverter.

It is worth noting that by using the MPPT optimization method for the inverter provided by the application, only software upgrading needs to be performed on the inverter, so that the increased cost required for improving the service life and reliability of the optimizer in the photovoltaic string is relatively low, and the operation is convenient.

Another embodiment of the present application provides another implementation of the MPPT optimization method for an inverter, and a specific flow thereof may refer to fig. 6 (fig. 6 is only shown on the basis of fig. 1), and on the basis of the above implementation, before step S140, the implementation further includes the following steps:

and S510, judging whether the time interval for increasing the preset value of the preset path photovoltaic string from the last time exceeds a preset period or not.

If the time interval from the last increase of the preset value of the preset-path photovoltaic string exceeds the preset period, executing step S140; if the time interval from the last increase of the preset value to the preset-path photovoltaic string does not exceed the preset period, the step S130 is executed.

The preset period is a time interval set according to actual conditions, when the preset period is set to be a large value, the adjusting frequency of the output voltage of the photovoltaic string is low, and when the preset period is set to be a small value, the adjusting frequency of the output voltage of the photovoltaic string is high.

In this embodiment, after the step S510 is added, the frequency of adjusting the output voltage of the photovoltaic string may be controlled by adjusting the preset period, so that frequent adjustment of the output voltage of the photovoltaic string may be avoided.

Another embodiment of the present application provides another implementation of the MPPT optimizing method of the inverter, and a specific flow thereof may refer to fig. 7 (fig. 7 is shown only on the basis of fig. 6), and on the basis of the above implementation, before step S140, the implementation further includes the following steps:

s610, judging whether all optimizers in the preset photovoltaic string do not work in a through area within first preset time.

If all optimizers in the preset path photovoltaic string do not work in the through area within the first preset time, executing step S140; if at least one optimizer in the preset-path photovoltaic string operates in the through region within the first preset time, or at least one optimizer in the preset-path photovoltaic string operates in the through region within a part of the first preset time, the step S130 is executed again.

If the first preset time is set to be larger, that is, the difficulty of triggering step S140 is larger, the output voltage of the photovoltaic string cannot be adjusted in time, and thus the optimizer may be damaged; if the first preset time is set to be shorter, that is, the difficulty of triggering step S140 is smaller, the output voltage of the photovoltaic string is adjusted too frequently, so that the power devices inside the inverter are aged and damaged.

In practical applications, the first preset time is set according to actual conditions, and normally, the first preset time is set to 10s.

In this embodiment, if the steps 510 and S610 are included, the step S610 is executed first, and then the step S510 is executed.

In this embodiment, by reasonably setting the first preset time, not only the service life and reliability of the optimizer can be prevented from being affected, but also the service life and reliability of the internal power device of the inverter can be prevented from being affected.

Another embodiment of the present application provides another implementation of the MPPT optimizing method of the inverter, and a specific flow thereof may refer to fig. 8 (fig. 8 is shown only on the basis of fig. 1), and on the basis of the above implementation, before step S150, the implementation further includes the following steps:

and S710, judging whether all optimizers working in the through area in the preset path photovoltaic group string work in the through area within second preset time.

If all the optimizers working in the through area in the preset path photovoltaic group string work in the through area within the second preset time, executing the step S150; if the at least one optimizer in the preset-path photovoltaic group string that operates in the through region does not operate in the through region within the second preset time, or if the at least one optimizer in the preset-path photovoltaic group string that operates in the through region does not operate in the through region within a part of the second preset time, the step S130 is executed again.

If the second preset time is set to be greater, that is, the difficulty of triggering the step S150 is greater, the MPPT optimization algorithm of the inverter cannot be stopped in time, so that the output voltages of all the optimizers working in the through region in the preset path photovoltaic string are greater, and further the optimizers may be damaged; if the second preset time is set to be shorter, that is, the difficulty of triggering step S150 is smaller, the MPPT optimization algorithm of the inverter may be stopped from being executed by an error, that is, after the MPPT optimization algorithm of the inverter is stopped from being executed, all the optimizers of the preset-path photovoltaic string do not operate in the through region, so that the output currents of all the optimizers of the preset-path photovoltaic string are still very large, and further, the optimizers may be damaged.

In practical applications, the second preset time is set according to practical situations, and normally, the second preset time is set to be 10s.

Optionally, the second preset time may be equal to the first preset time, or may not be equal to the first preset time, which is not specifically limited herein and may be determined according to specific situations.

In this embodiment, by reasonably setting the second preset time, the influence on the service life and reliability of the optimizer can be avoided.

Another embodiment of the present application provides an inverter, a specific structure of which can be seen in fig. 9, and specifically includes: the controller 10, the inverter circuit 20 and at least one DCDC conversion circuit 30 (only two DCDC conversion circuits 30 are shown in fig. 9 as an example); the connection relationship between the devices is specifically as follows:

the first sides of the DCDC conversion circuits 30 are respectively connected to the dc sides of the inverters in a one-to-one correspondence, and at least one dc side of the inverter is connected to the pv string 40 (only one dc side is connected to the pv string 40 in fig. 9 as an example), but at most one pv string 40 may be connected to each dc side of the inverter, and the dc sides of the inverter correspond to the pv strings 40 in a one-to-one correspondence.

The specific structure of the photovoltaic string 40 has been described in detail above, and is not described herein again.

The dc side of the inverter circuit 20 is connected to the second side of all the DCDC conversion circuits 30, and the ac side of the inverter circuit 20 is connected to the ac side of the inverter.

The inverter circuit 20 and all the DCDC conversion circuits 30 are controlled by a controller 10, the controller 10 is in communication connection with a remote platform 60 through a communication device 50, the controller 10 is configured to obtain an output current and an output voltage of each optimizer in each optimizer, and the controller 10 is further configured to perform the MPPT optimization method of the inverter as provided in the above embodiment on at least one photovoltaic string 40 connected to the inverter.

Alternatively, the controller 10 may obtain its respective output current and output voltage from each optimizer in each optimizer, or may obtain the output current and output voltage of each optimizer in each optimizer by sampling by the sensor 70, as shown in fig. 9.

It should be noted that, in general, the controller 10 may perform the MPPT optimization method for the inverter according to the embodiment described above on each of the strings 40 connected to the inverter, so as to avoid the damage of the optimizer in each of the strings 40 connected to the inverter.

Optionally, the communication device 50 may be integrated inside the controller 10, or may be independent of the controller 10, which is not specifically limited herein, as the case may be.

Optionally, the remote platform 60 is a cloud, and in practical applications, including but not limited to this, it is not specifically limited herein, and may be determined according to specific situations.

In a specific example, as shown in fig. 10 (illustrated on the basis of fig. 9), one embodiment of the controller 10 specifically includes: a first controller 11 and a second controller 12; the connection relationship and functions between the controllers are as follows:

the first controller 11 is in communication connection with each second controller 12, and the inverter circuit 20 and all the DCDC conversion circuits 30 are controlled by the second controllers 12; the first controller 11 is configured to obtain an output current and an output voltage of each optimizer in each optimizer path; the first controller 11 is in communication connection with a remote platform 60 through a communication device 50; the first controller 11 and all the second controllers 12 are used together to respectively perform the MPPT optimization method of the inverter as provided in the above embodiment on at least one string 40 of pv strings connected to the inverter.

Specifically, the first controller 11 is configured to perform various determinations in the MPPT optimization method, and the second controller 12 is configured to adjust the output voltage of the preset-path photovoltaic string 40 by adjusting the corresponding DCDC conversion circuit 30 when the first controller 11 determines that all optimizers in the preset-path photovoltaic string 40 are not currently operating in the through region, that is, the current value of the output voltage of the preset-path photovoltaic string 40 is increased by a preset value.

Optionally, each second controller 12 may be integrated in the corresponding inverter circuit 20, or may be independently disposed, which is not specifically limited herein and may be determined according to specific situations.

The above is only one embodiment of the controller 10, and in practical applications, including but not limited thereto, the embodiment is not limited herein, and the embodiment is within the protection scope of the present application.

Another embodiment of the present application provides a photovoltaic power generation system, a specific structure of which is shown in fig. 11, and specifically includes: a grid-side switching device 100, at least one pv string 40 (only two pv strings 40 are shown in fig. 11 as an example), and an inverter 200 provided in the above embodiment; the connection relationship between the devices is as follows:

at least one dc side of the inverter 200 is connected with the pv string 40 (only two dc sides are connected with the pv string 40 in fig. 11 as an example), but at most one pv string 40 can be connected to each dc side of the inverter 200, and the dc sides of the inverter correspond to the pv strings 40 one by one; the ac side of the inverter 100 is connected to a grid 300 (only shown as grid in fig. 11) or a load via the grid-side switching device 100.

In a specific example, as shown in fig. 12, the photovoltaic power generation system further includes: and the two poles of each energy storage device 400 are respectively connected with the two poles of the output end of the corresponding photovoltaic string 40.

In the above description of the disclosed embodiments, features described in various embodiments in this specification can be substituted for or combined with each other to enable those skilled in the art to make or use the present application. The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make many possible variations and modifications to the disclosed solution, or to modify equivalent embodiments, without departing from the scope of the solution, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. The MPPT optimization method of the inverter is characterized in that at least one direct current side of the inverter is connected with a photovoltaic string; the MPPT optimization method of the inverter comprises the following steps:

if all the optimizers in the preset path of photovoltaic group string do not work in the through area currently, increasing the current value of the output voltage of the preset path of photovoltaic group string by a preset value, and returning to execute the step of judging whether all the optimizers in the preset path of photovoltaic group string do not work in the through area currently;

2. The MPPT optimization method for an inverter according to claim 1, wherein if all dc sides of the inverter are connected to the pv strings, determining whether a total number of the pv strings connected to each dc side of the inverter is less than 2 includes:

judging whether the total number of the photovoltaic group strings is larger than the MPPT number of the inverter or not; the MPPT paths are the maximum paths of the inverter which can enable the photovoltaic string to realize MPPT;

3. The method of claim 2, wherein determining whether a total number of strings of pv strings is greater than the number of MPPT strings for the inverter comprises:

4. The MPPT optimizing method for an inverter according to claim 1, further comprising, before the increasing of the preset value to a preset path of the photovoltaic string,:

5. The method for MPPT optimization of an inverter according to claim 1, further comprising, before the increasing of the preset value to the preset string, the steps of:

judging whether all the optimizers in the preset path of photovoltaic group strings do not work in the through area within a first preset time;

6. The MPPT optimization method for an inverter according to claim 1, further comprising, before the current value of the output voltage of the preset path of the photovoltaic string is not adjusted:

judging whether all the optimizers working in the through area in the photovoltaic group strings of a preset path work in the through area within second preset time or not;

7. The method for MPPT optimization of an inverter according to any one of claims 1 to 6, wherein the preset value is a fixed value or a variable value.

8. The method of claim 7, wherein the predetermined value is proportional to a current value of the output voltage of the predetermined string if the predetermined value is a variable value.

9. An inverter, comprising: the controller, the inverter circuit and at least one DCDC conversion circuit; wherein:

the inverter circuit and all the DCDC conversion circuits are controlled by the controller, the controller is in communication connection with a remote platform through communication equipment, the controller is used for obtaining the output current and the output voltage of each optimizer in each optimizer, and the controller is further used for respectively executing the MPPT optimization method of the inverter according to any one of claims 1 to 8 on at least one photovoltaic string connected with the inverter.

10. The inverter of claim 9, wherein the communication device is integrated within the controller.

11. The inverter of claim 9, wherein the remote platform is a cloud.

12. The inverter according to any one of claims 9 to 11, wherein the controller includes: a first controller and a second controller; wherein:

the first controller and all of the second controllers are configured to collectively perform an MPPT optimization method of the inverter according to any one of claims 1 to 8.

13. The inverter of claim 12, wherein each of the second controllers is integrated into the corresponding inverter circuit.

14. A photovoltaic power generation system, comprising: grid-side switching means, at least one string of photovoltaic strings and an inverter as claimed in any one of claims 9 to 13; wherein:

15. The photovoltaic power generation system of claim 14, further comprising: at least one energy storage device; wherein: