阅读说明：本技术 一种光伏组串并联失配优化方法、电力设备和光伏系统 (Photovoltaic group series-parallel mismatch optimization method, power equipment and photovoltaic system ) 是由 云平 孙帅 陈鹏 徐君 于 2021-08-13 设计创作，主要内容包括：本申请公开了一种光伏组串并联失配优化方法、电力设备和光伏系统,以降低电力设备下总的光伏组串并联失配损失。该方法包括：预判组串优化分配策略能否使电力设备下总的光伏组串并联失配损失降低第一阈值以上,如果能,发出实施所述组串优化分配策略的指示信号；其中,所述组串优化分配策略,是指按光伏组串的最大功率点电压对所述电力设备的全部或部分MPPT单元下的光伏组串进行重新分配与组合。(The application discloses a photovoltaic string series-parallel mismatch optimization method, power equipment and a photovoltaic system, so as to reduce total photovoltaic string series-parallel mismatch loss under the power equipment. The method comprises the following steps: the method comprises the steps that whether a group string optimization distribution strategy can reduce the total photovoltaic group string parallel mismatch loss under the power equipment by more than a first threshold value is judged in advance, and if yes, an indication signal for implementing the group string optimization distribution strategy is sent out; the photovoltaic string optimization allocation strategy is to reallocate and combine the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings.)

1. A photovoltaic group series-parallel mismatch optimization method is characterized by comprising the following steps:

the method comprises the steps that whether a group string optimization distribution strategy can reduce the total photovoltaic group string parallel mismatch loss under the power equipment by more than a first threshold value is judged in advance, and if yes, an indication signal for implementing the group string optimization distribution strategy is sent out;

the photovoltaic string optimization allocation strategy is to reallocate and combine the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings.

2. The pv string series-parallel mismatch optimization method of claim 1, wherein the redistributing and combining pv strings under all or some MPPT units of the power plant according to their maximum power point voltages comprises:

redistributing and combining the photovoltaic strings under the MPPT units in the 1 st to s th paths, so that the dispersion degree of the MPPT units in the k th path does not exceed a preset degree; the dispersion of the MPPT unit refers to the dispersion of the maximum power point voltage of each photovoltaic group string under the MPPT unit of the current path; k is 1, 2, …, s-1, s is more than or equal to 2 and less than or equal to n, and n is the number of MPPT units of the power equipment.

3. The pv string series-parallel mismatch optimization method of claim 1, wherein the redistributing and combining pv strings under all or some MPPT units of the power plant according to their maximum power point voltages comprises:

obtaining a curve of the maximum power point voltage of each photovoltaic group string under the MPPT units of the 1 st to s paths along with the time change, and redistributing and combining the photovoltaic group strings under the MPPT units of the 1 st to s paths according to the curve, so that the curve coincidence degree of each photovoltaic group string under the MPPT units of the k path exceeds a preset degree; k is 1, 2, …, s-1, s is more than or equal to 2 and less than or equal to n, and n is the number of MPPT units of the power equipment.

4. The photovoltaic string series-parallel mismatch optimization method according to claim 2 or 3, wherein the 1 st to s-th MPPT units are s-th MPPT units with the highest dispersion in the power equipment.

5. The pv string mismatch optimization method according to claim 1, further comprising, when it is determined in advance that the string optimization allocation policy cannot reduce the overall pv string mismatch loss of the power equipment by more than a first threshold, and/or after the sending of the indication signal for implementing the string optimization allocation, the method further comprising:

respectively aiming at each path of MPPT unit in all or part of MPPT units, locating the pathSatisfies | V under MPPT unit_i-V₀If the photovoltaic string is greater than the second threshold value, | sending an indication signal for maintaining the currently positioned photovoltaic string;

V_ithe maximum power point voltage of the ith photovoltaic string under the MPPT unit of the current path is i ═ 1, 2, … and m, m is the number of the photovoltaic strings under the MPPT unit of the current path, and V₀The maximum power point voltage of the m photovoltaic groups under the MPPT unit of the current path after series-parallel connection.

6. The photovoltaic string series-parallel mismatch optimization method of claim 1, wherein the maximum power point voltage of the photovoltaic string is obtained by an IV scan technique.

7. The photovoltaic string series-parallel mismatch optimization method according to claim 6, wherein when obtaining the maximum power point voltage of the photovoltaic string by the IV scanning technique, the IV scanning is performed on each photovoltaic string one by one or simultaneously on a plurality of photovoltaic strings.

8. The photovoltaic string series-parallel mismatch optimization method according to claim 1, wherein said signaling an indication to implement the string-optimized assignment strategy comprises:

sending a trigger signal to a reconstruction unit; the reconstruction unit is connected between all the MPPT units and all the photovoltaic string, and according to the received signals, the reconstruction unit performs switching of the MPPT units accessed to the photovoltaic string through switch control.

9. The photovoltaic string series-parallel mismatch optimization method according to claim 1, wherein said signaling an indication to implement the string-optimized assignment strategy comprises: and instructing a worker to manually switch the MPPT unit accessed by the photovoltaic group string.

10. An electrical power plant comprising a main circuit and a controller for running a program, wherein the program when running performs the method of photovoltaic string series parallel mismatch optimization according to any of claims 1-9.

11. The electrical power apparatus of claim 10, wherein the electrical power apparatus is an inverter or a combiner box.

12. A photovoltaic system comprising the power plant of claim 10 or 11.

Technical Field

The invention relates to the technical field of power electronics, in particular to a photovoltaic group series-parallel mismatch optimization method, power equipment and a photovoltaic system.

Background

The photovoltaic group is mismatched in series-parallel connection, which means that: the multiple photovoltaic strings are connected in parallel to the same MPPT (maximum power Point Tracking) unit of the power equipment such as the inverter or the combiner box, but the maximum power Point voltages of the photovoltaic strings in the same MPPT unit cannot be completely consistent due to inconsistency generated in the production and use processes of the photovoltaic strings, and at this time, the individual photovoltaic strings cannot work at the maximum power Point, so that power loss is generated.

The total photovoltaic group series-parallel mismatch loss under the power equipment is reduced, and the aim of the photovoltaic industry is always pursued.

Disclosure of Invention

In view of this, the invention provides a photovoltaic string series-parallel mismatch optimization method, power equipment and a photovoltaic system, so as to reduce the total photovoltaic string series-parallel mismatch loss under the power equipment.

A photovoltaic group series-parallel mismatch optimization method comprises the following steps:

the method comprises the steps that whether a group string optimization distribution strategy can reduce the total photovoltaic group string parallel mismatch loss under the power equipment by more than a first threshold value is judged in advance, and if yes, an indication signal for implementing the group string optimization distribution strategy is sent out;

the photovoltaic string optimization allocation strategy is to reallocate and combine the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings.

Optionally, the redistributing and combining the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings includes:

redistributing and combining the photovoltaic strings under the MPPT units in the 1 st to s th paths, so that the dispersion degree of the MPPT units in the k th path does not exceed a preset degree; the dispersion of the MPPT unit refers to the dispersion of the maximum power point voltage of each photovoltaic group string under the MPPT unit of the current path; k is 1, 2, …, s-1, s is more than or equal to 2 and less than or equal to n, and n is the number of MPPT units of the power equipment.

Or, the redistribution and combination of the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings includes:

obtaining a curve of the maximum power point voltage of each photovoltaic group string under the MPPT units of the 1 st to s paths along with the time change, and redistributing and combining the photovoltaic group strings under the MPPT units of the 1 st to s paths according to the curve, so that the curve coincidence degree of each photovoltaic group string under the MPPT units of the k path exceeds a preset degree; k is 1, 2, …, s-1, s is more than or equal to 2 and less than or equal to n, and n is the number of MPPT units of the power equipment.

Optionally, the 1 st to s th MPPT units are s MPPT units with the highest dispersion in the power equipment.

Optionally, when it is determined in advance that the string optimal allocation policy cannot reduce the overall photovoltaic string parallel mismatch loss of the power equipment by more than a first threshold, and/or after the indication signal for implementing the string optimal allocation is sent, the method further includes:

respectively aiming at each path of MPPT unit in all or part of MPPT units, positioning that the MPPT unit of the path meets the condition of | V_i-V₀If the photovoltaic string is greater than the second threshold value, | sending an indication signal for maintaining the currently positioned photovoltaic string;

V_ithe maximum power point voltage of the ith photovoltaic string under the MPPT unit of the current path is i ═ 1, 2, … and m, m is the number of the photovoltaic strings under the MPPT unit of the current path, and V₀The maximum power point voltage of the m photovoltaic groups under the MPPT unit of the current path after series-parallel connection.

Optionally, the maximum power point voltage of the photovoltaic string is obtained by an IV scanning technique.

Optionally, when the maximum power point voltage of the photovoltaic group strings is obtained through the IV scanning technology, the IV scanning is performed on each photovoltaic group string one by one or performed on a plurality of photovoltaic group strings simultaneously.

Optionally, the sending the indication signal for implementing the group string optimization allocation policy includes:

sending a trigger signal to a reconstruction unit; the reconstruction unit is connected between all the MPPT units and all the photovoltaic string, and according to the received signals, the reconstruction unit performs switching of the MPPT units accessed to the photovoltaic string through switch control.

Or, the sending the indication signal for implementing the group string optimization allocation policy includes: and instructing a worker to manually switch the MPPT unit accessed by the photovoltaic group string.

An electric power device comprises a main circuit and a controller, wherein the controller is used for running a program, and the program executes any one of the photovoltaic string series-parallel mismatch optimization methods disclosed above during running.

Optionally, the power equipment is an inverter or a combiner box.

A photovoltaic system comprising any of the above disclosed power devices.

According to the technical scheme, when the photovoltaic string parallel-series mismatch occurs in the electric power equipment, the invention judges whether the total power loss of the photovoltaic side of the electric power equipment can be obviously reduced by reallocating and combining the photovoltaic string in advance, and if so, reallocating and combining the photovoltaic string so as to solve the problems in the prior art.

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 description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of a photovoltaic string series-parallel mismatch optimization method disclosed in an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a photovoltaic system according to an embodiment of the present invention;

fig. 3 is a flowchart of another photovoltaic string series-parallel mismatch optimization method disclosed in the embodiment of the present invention;

fig. 4 is a flowchart of another photovoltaic string series-parallel mismatch optimization method disclosed in the embodiment of the present invention;

fig. 5 is a flowchart of another photovoltaic string series-parallel mismatch optimization method disclosed in the embodiment of the present invention;

FIG. 6 shows a specific implementation of step S02 in FIG. 3;

FIG. 7 illustrates yet another specific implementation of step S02 in FIG. 3;

fig. 8 is a schematic structural diagram of another photovoltaic system disclosed in the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, an embodiment of the present invention discloses a photovoltaic string series-parallel mismatch optimization method, including:

step S01: whether the pre-judgment group string optimal distribution strategy can reduce the total photovoltaic group series-parallel mismatch loss under the power equipment by a first threshold value epsilon₁(first threshold value ε₁Greater than zero), if so, proceed to step S02, if not, return to said step S01.

Step S02: and sending an indication signal for implementing the string optimization allocation strategy, and then restarting the photovoltaic string parallel mismatch optimization method.

Specifically, the embodiment of the invention is applied to the power equipment with n MPPT units, n is more than or equal to 2, and multiple photovoltaic strings are connected in parallel under each MPPT unit. The power device may be an inverter or a combiner box, and the inverter may be a string inverter or a centralized inverter, but is not limited thereto.

Supposing that m photovoltaic strings are connected in parallel under one path of MPPT unit of the power equipment, wherein m is more than or equal to 2, and the maximum power point voltage of each photovoltaic string under the MPPT unit is V₁、V₂、…、V_mThe maximum power point voltage of each photovoltaic group after series-parallel connection under the MPPT unit of the current path is V₀And then: satisfies V under this way MPPT unit_i＝V₀The photovoltaic string has no power loss, | V_i-V₀The greater the | the greater the power loss of the photovoltaic string; if each photovoltaic group string under the MPPT unit of the current path meets | V_i-V₀| < second threshold epsilon₂(first stepTwo threshold values epsilon₂Equal to or slightly greater than zero; i is 1, 2, … and m), which shows that the maximum power point voltages of the photovoltaic group strings under the MPPT unit are basically consistent, and the parallel-parallel mismatch of the photovoltaic group strings does not exist or is not obvious and can be ignored under the MPPT unit; on the contrary, if at least one photovoltaic string under the MPPT unit of the path meets the | V |_i-V₀| > second threshold ε₂The maximum power point voltage consistency of each photovoltaic group string under the MPPT unit is poor, and the photovoltaic group string parallel mismatch is obvious under the MPPT unit.

Optionally, V under the same way of MPPT unit₁、V₂、…、V_mAnd V₀Under the MPPT control, the acquisition is directly obtained by the IV scanning technology. As shown in fig. 2 (fig. 2 only takes the power equipment with two MPPT units and one inverter unit as an example), by controlling the MPPT units to scan the pv strings IV, the real-time current a in each pv string under the same MPPT unit is recorded₁、A₂、A3、…、A_mAnd acquiring the real-time voltage V of each photovoltaic string, and calculating the V under the same MPPT unit according to the IV data₁、V₂、…、V_mAnd V₀. Of course, when performing IV scanning, IV scanning may be performed on a plurality of photovoltaic group strings simultaneously or performed on each photovoltaic group string one by one, which is not limited.

In order to reduce the total mismatch loss of the photovoltaic strings in series and parallel connection under the power equipment, a string optimization distribution strategy can be adopted, photovoltaic modules with more similar maximum power point voltages of the photovoltaic strings are distributed under more MPPT units, and the condition that the dispersion degree of the maximum power point voltages of the photovoltaic modules under the same MPPT unit is too high is avoided as much as possible. The string optimization allocation strategy is to reallocate and combine the photovoltaic strings under the 1 st to s th MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings, wherein s is more than or equal to 2 and less than or equal to n, so that the consistency of the maximum power point voltage of the photovoltaic strings under the s th MPPT units is improved on the whole (that is, the consistency of the maximum power point voltage of the photovoltaic strings under the 1 st MPPT unit is improved)The maximum power point voltage of the pv string in the 2 nd MPPT unit + … + the maximum power point voltage of the pv string in the s nd MPPT unit). For example: redistributing and combining the photovoltaic strings under the MPPT units of the 1 st to s th paths of the power equipment to ensure that the dispersion of the MPPT units of the k th path does not exceed a preset degree; the dispersion of the MPPT unit refers to the dispersion of the maximum power point voltage of each photovoltaic string in the MPPT unit, that is, the dispersion of the maximum power point voltage of each photovoltaic string in the MPPT unit in the MPPT₁、V₂、…、V_mRelative to V₀The degree of deviation of; k is 1, 2, …, s-1. For another example: obtaining a curve of the maximum power point voltage of each photovoltaic group string under the MPPT units of the 1 st to s paths along with the time change, and redistributing and combining the photovoltaic group strings under the MPPT units of the 1 st to s paths according to the curve, so that the curve coincidence degree of each photovoltaic group string under the MPPT unit of the k path exceeds a preset degree (at the moment, the curve coincidence degree is considered to be relatively close); k is 1, 2, …, s-1.

Before implementing the string optimal allocation strategy, the feasibility of the string optimal allocation strategy needs to be pre-judged, that is: obtaining the total photovoltaic string series-parallel mismatch loss under the power equipment after implementing the string optimization distribution strategy through theoretical analysis in advance, comparing the total photovoltaic string series-parallel mismatch loss under the power equipment with the total photovoltaic string series-parallel mismatch loss under the power equipment before implementing the string optimization distribution strategy, and if the total photovoltaic string series-parallel mismatch loss is obviously reduced compared with the total photovoltaic string series-parallel mismatch loss under the power equipment before implementing the string optimization distribution strategy, considering that the string optimization distribution strategy is feasible, and starting to implement; otherwise, it is not put into practice.

Of course, when the photovoltaic strings are redistributed and combined, the number of the photovoltaic strings distributed under each MPPT unit is necessarily performed under the condition that the number of the photovoltaic strings allowed to be accessed under the MPPT unit of the current path is ensured.

The more significant MPPT unit of the string-parallel mismatch of the photovoltaic strings, the more the redistribution and combination of the photovoltaic strings should be performed. Based on this, the embodiments of the present invention may set the 1 st to s-th MPPT units as the s-th MPPT units with the highest dispersion in the power equipment. Wherein, considering that the more MPPT units for the redistribution and combination of the photovoltaic string, the more the MPPT units are distributedThe richer the photovoltaic string resource is, the easier it is to achieve the first threshold epsilon for reducing the total photovoltaic string parallel mismatch loss under the power equipment₁Therefore, the embodiments of the present invention recommend that the MPPT units on the 1 st to s th routes are all MPPT units under the power equipment.

To sum up, when the photovoltaic strings are in series-parallel mismatch in the power equipment, the embodiment of the invention pre-judges whether the total power loss of the photovoltaic side of the power equipment can be obviously reduced by performing the redistribution and the combination of the photovoltaic strings through theoretical analysis, and if so, performs the redistribution and the combination of the photovoltaic strings so as to solve the problems in the prior art; on the contrary, if the total power loss on the photovoltaic side of the power equipment can only be slightly reduced or no change is made before and after the redistribution and combination of the photovoltaic string, the redistribution and combination of the photovoltaic string is not necessary at present.

Optionally, referring to fig. 3, fig. 4, or fig. 5, when it is determined in advance that the string optimal allocation policy cannot reduce the overall photovoltaic string parallel mismatch loss of the power equipment by more than a first threshold, and/or after the sending of the indication signal for implementing the string optimal allocation policy, the method further includes:

step S03: respectively aiming at each path of MPPT unit in all or part of MPPT units, positioning that the MPPT unit of the path meets the condition of | V_i-V₀| > second threshold ε₂The photovoltaic string sending out the maintenance of the current positioned photovoltaic string.

Wherein, V_iThe maximum power point voltage of the ith photovoltaic string under the MPPT unit of the current path is i ═ 1, 2, … and m, m is the number of the photovoltaic strings under the MPPT unit of the current path, and V₀The maximum power point voltage of the m photovoltaic groups under the MPPT unit of the current path after series-parallel connection.

After the maximum power point voltage of the photovoltaic string to be maintained is increased, the photovoltaic string parallel mismatch optimization method can be restarted.

Optionally, based on any of the embodiments disclosed above, the instruction signal for implementing the group string optimization assignment sent in step S02 may be used to notify a worker to manually switch the MPPT unit for accessing the photovoltaic group string (as shown in fig. 6, fig. 6 is obtained based on fig. 3 only as an example), or may send a trigger signal to the reconfiguration unit to automatically complete switching the MPPT unit for accessing the photovoltaic group string (as shown in fig. 7, fig. 7 is obtained based on fig. 3 only as an example). The reconstruction unit is connected between all MPPT units and all photovoltaic string, and according to the received signal, the reconstruction unit performs switching of the MPPT unit to which the photovoltaic string is connected through switching control, for example, as shown in fig. 8.

In addition, the embodiment of the invention also discloses power equipment which comprises a main circuit and a controller, wherein the controller is used for running a program, and the following photovoltaic group series-parallel mismatch optimization method is executed when the program runs:

the method comprises the steps that whether a group string optimization distribution strategy can reduce the total photovoltaic group string parallel mismatch loss under the power equipment by more than a first threshold value is judged in advance, and if yes, an indication signal for implementing the group string optimization distribution strategy is sent out;

the photovoltaic string optimization allocation strategy is to reallocate and combine the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings.

Optionally, the redistributing and combining the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings includes: redistributing and combining the photovoltaic strings under the MPPT units in the 1 st to s th paths, so that the dispersion degree of the MPPT units in the k th path does not exceed a preset degree; the dispersion of the MPPT unit refers to the dispersion of the maximum power point voltage of each photovoltaic group string under the MPPT unit of the current path; k is 1, 2, …, s-1, s is more than or equal to 2 and less than or equal to n, and n is the number of MPPT units of the power equipment.

Or, the redistribution and combination of the photovoltaic strings under all or part of the MPPT units of the power equipment according to the maximum power point voltage of the photovoltaic strings includes: obtaining a curve of the maximum power point voltage of each photovoltaic group string under the MPPT units of the 1 st to s paths along with the time change, and redistributing and combining the photovoltaic group strings under the MPPT units of the 1 st to s paths according to the curve, so that the curve coincidence degree of each photovoltaic group string under the MPPT units of the k path exceeds a preset degree; k is 1, 2, …, s-1, s is more than or equal to 2 and less than or equal to n, and n is the number of MPPT units of the power equipment.

Optionally, the 1 st to s th MPPT units are s MPPT units with the highest dispersion in the power equipment.

Optionally, for any of the above-disclosed power devices, when it is determined in advance that the string optimal allocation policy cannot reduce the overall photovoltaic string parallel mismatch loss of the power device by more than a first threshold, and/or after the sending of the indication signal for implementing the string optimal allocation, the method further includes:

respectively aiming at each path of MPPT unit in all or part of MPPT units, positioning that the MPPT unit of the path meets the condition of | V_i-V₀If the photovoltaic string is greater than the second threshold value, | sending an indication signal for maintaining the currently positioned photovoltaic string;

V_ithe maximum power point voltage of the ith photovoltaic string under the MPPT unit of the current path is i ═ 1, 2, … and m, m is the number of the photovoltaic strings under the MPPT unit of the current path, and V₀The maximum power point voltage of the m photovoltaic groups under the MPPT unit of the current path after series-parallel connection.

Optionally, for any of the above-disclosed power devices, the maximum power point voltage of each photovoltaic string in the same MPPT unit is obtained by an IV scanning technique.

Optionally, when the maximum power point voltage of the photovoltaic group strings is obtained through the IV scanning technology, the IV scanning is performed on each photovoltaic group string one by one or performed on a plurality of photovoltaic group strings simultaneously.

Optionally, for any of the power devices disclosed above, the sending an indication signal for implementing the group string optimized allocation policy includes: sending a trigger signal to a reconstruction unit; the reconstruction unit is connected between all the MPPT units and all the photovoltaic string, and according to the received signals, the reconstruction unit performs switching of the MPPT units accessed to the photovoltaic string through switch control.

Or, the sending the indication signal for implementing the group string optimization allocation policy includes: and instructing a worker to manually switch the MPPT unit accessed by the photovoltaic group string.

Optionally, any of the above-disclosed power devices is an inverter or a combiner box, and the like, and is not limited.

In addition, the embodiment of the invention also discloses a photovoltaic system which comprises any one of the power equipment disclosed above.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the power equipment and the photovoltaic system disclosed by the embodiment, the description is relatively simple because the method corresponds to the method disclosed by the embodiment, and the relevant points can be obtained by referring to the description of the method part.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.