System for improving multi-series parallel power generation of photovoltaic cells

Abstract

The invention discloses a system for improving multi-series parallel power generation of photovoltaic cells, and relates to the technical field of photovoltaic power supply, the system comprises photovoltaic panels, photovoltaic optimizers, a photovoltaic gateway and an inverter, the power output of a photovoltaic array is optimized through a multi-stage cooperative control strategy, each photovoltaic panel is connected with an independent photovoltaic optimizer, and the photovoltaic panels are connected with the photovoltaic gateways. A working point is dynamically adjusted by adopting an MPPT algorithm, real-time data interaction with a photovoltaic gateway is carried out in a wireless or wired communication mode, the photovoltaic gateway automatically detects open-circuit voltage differences of parallel strings, dynamically adjusts the MPPT voltage range of each string and ensures the overlapping proportion of output voltages, the photovoltaic gateway monitors the duty ratio change of the strings, and when shielding is detected, the photovoltaic gateway is switched on and switched off. The MPPT parameters of the affected string are automatically adjusted, and the generating capacity of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power supply, and particularly relates to a system for improving the multi-series and parallel power generation of photovoltaic cells. Background Art

[0002] Photovoltaic systems are mainly divided into several types: centralized, string-type, and micro-inverters. In centralized and string-type systems, the photovoltaic optimizer adopts buck, boost, or buck-boost topologies. When working, it tracks the maximum power point MPPT of the photovoltaic modules it is connected to in real time. Generally, perturbation, constant voltage, conductance increment, or global MPPT scanning algorithms are used. These algorithms only target the photovoltaic modules they are connected to and do not pay attention to the total power after series and parallel connections. Since the inverter itself has an MPPT function, it is very easy to generate conflicts during the final cooperation, resulting in a good local MPPT effect but a poor overall MPPT effect. Therefore, it is particularly important to invent a system for improving the multi-series and parallel power generation of photovoltaic cells.

[0003] The prior art, such as the invention patent application with the publication number CN217116023U, discloses a high-power-generation photovoltaic system. By setting reflection structures between high-power-generation modules and at both ends of the photovoltaic array, the light in the gaps between high-power-generation modules is directionally reflected onto the modules on both sides by using the reflection structures, increasing the current of the battery strings on both sides of the reflection structure. The battery modules on both sides are designed with a parallel circuit. Under the condition of constant voltage, the currents of the battery modules on both sides are superimposed, improving the power generation of the system.

[0004] The prior art also has the following defects, specifically: 1. In the prior art, in centralized or string-type systems, the MPPT algorithms such as perturbation and constant voltage adopted by the photovoltaic optimizer only target the photovoltaic modules they are connected to and do not pay attention to the total power after series and parallel connections. At the same time, the inverter itself also has an MPPT function, and the two are prone to conflicts during cooperation, resulting in a good local MPPT effect but a poor overall MPPT effect.

[0005] 2. In the prior art, the adaptability of the MPPT algorithm to environmental changes is poor. The output power of photovoltaic cells is significantly affected by factors such as ambient temperature fluctuations, light intensity changes, and solar incident angle offsets. However, the existing algorithms cannot quickly respond to these dynamic changes and cannot accurately capture the optimal energy output state at each moment, resulting in energy waste. Summary of the Invention

[0006] The purpose of the present invention is to provide a system for improving the multi-series and parallel power generation of photovoltaic cells, which solves the problems existing in the background art.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a system for improving the multi-string parallel power generation of photovoltaic cells, including: photovoltaic panels, photovoltaic optimizers, photovoltaic gateways, and inverters.

[0008] The photovoltaic panels are used to directly convert solar energy into direct current.

[0009] The photovoltaic optimizers are used to improve the power generation efficiency of each photovoltaic panel.

[0010] The photovoltaic gateways are used to connect the photovoltaic system to the cloud platform to achieve data monitoring and intelligent management.

[0011] The inverters are used to convert the direct current generated by the photovoltaic panels into alternating current and have the MPPT function.

[0012] Preferably, the input of the photovoltaic optimizer is connected one-to-one with the output of the photovoltaic panel, the output of the photovoltaic optimizer is connected in series to the photovoltaic gateway, and the photovoltaic gateway is then connected to the inverter.

[0013] Preferably, the photovoltaic optimizer is of buck, boost or buck-boost topology and communicates bidirectionally with the photovoltaic gateway through wireless or wired transmission methods. At the same time, the photovoltaic gateway has the functions of real-time monitoring of the bus voltage and bus current of each photovoltaic string.

[0014] Preferably, the photovoltaic optimizer records the maximum input voltage, that is, the open-circuit voltage, and supports MPPT algorithms such as perturbation and conductance increment. However, when running the MPPT algorithm, there is a certain voltage range limit, that is, when it exceeds the upper limit, it maintains at the upper limit, and when it is lower than the lower limit, it maintains at the lower limit. This range setting can be modified in real time by the photovoltaic gateway.

[0015] Preferably, when the system is working, the photovoltaic gateway obtains the data of all photovoltaic optimizers in real time, including the current open-circuit voltage, input voltage, input current, output voltage, output current, real-time power, duty cycle, and working status, and combines its own acquisition function to summarize the open-circuit voltage, real-time voltage, real-time current, and real-time power of each string of components.

[0016] Preferably, the photovoltaic gateway automatically identifies the number of series strings. If there are currently two series strings connected in parallel to the inverter, namely series string 1 and series string 2, with their open circuit voltages being OpenV1 and OpenV2 respectively, and real-time voltages being V1 and V2 respectively. When the system starts working, first calculate the difference between OpenV1 and OpenV2, and determine whether the difference between OpenV1 and OpenV2 is within a reasonable range. If the difference between OpenV1 and OpenV2 is within a reasonable range, it is determined that the current two strings of components are matched, and the two strings of components work with the same set of starting parameters. The starting parameters mainly refer to the upper and lower limits of MPPT of each optimizer, that is, the duty cycle or output voltage. If the difference between OpenV1 and OpenV2 is not within a reasonable range, it is determined that the current two strings of components are not matched, and then different MPPT upper and lower limits are used to forcibly set a differentiated MPPT voltage range.

[0017] Preferably, the differentiated MPPT voltage range needs to satisfy that the upper and lower limits of the output voltage V1 of series string 1 and the upper and lower limits of the output voltage V2 of series string 2 overlap by more than or equal to a preset overlap percentage threshold.

[0018] Preferably, during the operation of the system, the photovoltaic gateway detects the working voltages of each series string and the duty cycle status of each optimizer in real time. If the sum of the duty cycles of series string 1 minus the sum of the duty cycles of series string 2 is greater than a preset threshold, it is considered that series string 2 is shaded, and at this time the gateway starts to execute MPPT at the series string level.

[0019] Preferably, when the gateway starts to execute MPPT at the series string level, the specific process is as follows: slowly increase the upper and lower limits of series string 2, and slowly decrease the upper and lower limits of series string 1. Each time of increasing or decreasing, the gateway records the power of the two strings, and finally stabilizes it near the maximum power point.

[0020] The beneficial effects of the present invention are as follows: 1. On the basis of each photovoltaic component executing MPPT, the present invention adds MPPT control at the series string level. By comparing the difference in the open circuit voltages of the series strings to determine whether the components are matched, different strategies are adopted for the matched and unmatched series strings to set the MPPT upper and lower limits, realizing the optimization of the overall power of the series strings and improving the overall MPPT effect of the photovoltaic system.

[0021] 2. In the present invention, the PV optimizer supports MPPT algorithms such as perturbation and incremental conductance, and the voltage range during operation can be modified in real time by the gateway. When the system detects that the duty cycle difference of the series strings exceeds a certain value and determines that there is an occlusion, the gateway can timely adjust the upper and lower limits of the voltage of the series strings. The PV gateway has a powerful real-time monitoring function, can obtain various data such as the open-circuit voltage, input voltage, and current of all optimizers, and summarize the relevant information of each string of components. Based on these data, the gateway can accurately judge the working state of the series strings, timely discover problems and perform intelligent management, realizing refined control of the entire PV system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic connection diagram of the system structure of the present invention.

[0024] Figure 2 It is a schematic flow diagram of the implementation steps of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] Refer to Figure 1 As shown, the present invention provides a system for improving the multi-string parallel power generation of PV cells, including:

[0027] PV panels, PV optimizers, PV gateways, and inverters.

[0028] The PV panels, several in number, are used to directly convert solar energy into direct current.

[0029] The PV optimizers, several in number, are used to improve the power generation efficiency of each PV panel.

[0030] The PV gateway is used to connect the PV system to the cloud platform to realize data monitoring and intelligent management.

[0031] The inverter is used to convert the direct current generated by the PV panels into alternating current and has an MPPT function.

[0032] In a specific embodiment, the input of the PV optimizer is connected one-to-one with the output of the PV panel, the output of the PV optimizer is connected in series to the PV gateway, and the PV gateway is then connected to the inverter.

[0033] In a specific embodiment, the PV optimizer is of buck, boost or buck-boost topology and communicates bidirectionally with the PV gateway through wireless or wired transmission means such as ZigBee, Bluetooth, Sub1G, PLC, etc. At the same time, the PV gateway has the functions of real-time monitoring of the bus voltage and bus current of each PV string.

[0034] In a specific embodiment, the PV optimizer records the maximum input voltage, i.e., the open-circuit voltage, and supports MPPT algorithms such as perturbation and incremental conductance. However, when running the MPPT algorithm, there are certain voltage range limitations, that is, when exceeding the upper limit, it is maintained at the upper limit, and when lower than the lower limit, it is maintained at the lower limit. This range setting can be modified in real time by the PV gateway.

[0035] In a specific embodiment, when the system is working, the PV gateway obtains the data of all PV optimizers in real time, including the current open-circuit voltage, input voltage, input current, output voltage, output current, real-time power, duty cycle, and working status, and combines its own acquisition function to summarize the open-circuit voltage, real-time voltage, real-time current, and real-time power of each string of components.

[0036] In a specific embodiment, the PV gateway automatically identifies the number of strings and refers to Figure 2 , if there are currently two strings connected in parallel to the inverter, namely string 1 and string 2, and their open-circuit voltages are OpenV1 and OpenV2 respectively, and the real-time voltages are V1 and V2 respectively. When the system starts to work, first calculate the difference between OpenV1 and OpenV2, and determine whether the difference between OpenV1 and OpenV2 is within a reasonable range. If the difference between OpenV1 and OpenV2 is within a reasonable range, it is determined that the current two strings of components are matched, and the two strings of components work with the same set of starting parameters. The starting parameters mainly refer to the upper and lower limits of MPPT of each optimizer, that is, the duty cycle or output voltage. If the difference between OpenV1 and OpenV2 is not within a reasonable range, it is determined that the current two strings of components are not matched, and then different MPPT upper and lower limits are used to forcibly set different MPPT voltage ranges.

[0037] It should be noted that the reasonable range is set by professionals. Here, regardless of whether the open-circuit voltages match, it is necessary to ensure that the voltage ranges between the strings overlap sufficiently. The difference in open-circuit voltages is the trigger condition, and the percentage of voltage range overlap is the ultimate basis. When several strings are connected in parallel to the inverter, the analysis method is the same, and the upper and lower limits of the MPPT will determine the output voltage of each bus.

[0038] Based on the implementation of MPPT for each photovoltaic module in the present invention, MPPT control at the string level is added. By comparing the differences in open-circuit voltages of the strings to determine whether the modules match, different strategies are adopted to set the upper and lower limits of the MPPT for the matching and non-matching strings respectively, achieving the optimization of the overall power of the strings and enhancing the overall MPPT effect of the photovoltaic system.

[0039] In a specific embodiment, the differentiated MPPT voltage ranges need to satisfy that the upper and lower limits of the output voltage V1 of string 1 and the upper and lower limits of the output voltage V2 of string 2 overlap by greater than or equal to a preset overlap percentage threshold.

[0040] It should be noted that the preset overlap percentage threshold is set by professionals, for example, 15%.

[0041] In a specific embodiment, during the operation of the system, the photovoltaic gateway detects the operating voltages of each string and the duty cycle status of each optimizer in real time. If the difference between the sum of the duty cycles of string 1 and the sum of the duty cycles of string 2 is greater than a preset threshold, it is considered that string 2 is shaded, and at this time, the gateway starts to execute MPPT at the string level.

[0042] In a specific embodiment, when the gateway starts to execute MPPT at the string level, the specific process is as follows: slowly increase the upper and lower limits of string 2, and slowly decrease the upper and lower limits of string 1. Each time of increasing or decreasing, the gateway records the power of the two strings, and finally stabilizes it near the maximum power point.

[0043] It should be noted that as a variant, it is also possible to fix the parameters of string 1 and slowly adjust the upper and lower limits of string 2 to find the maximum power point; or fix the parameters of string 2 and slowly adjust the upper and lower limits of string 1.

[0044] In the present invention, the photovoltaic optimizer supports MPPT algorithms such as perturbation and incremental conductance, and the voltage range during operation can be modified in real time by the gateway. When the system detects that the difference in the duty cycles of the strings exceeds a certain value and determines that there is a shading situation, the gateway can timely adjust the upper and lower limits of the voltage of the strings. The photovoltaic gateway has a powerful real-time monitoring function, can obtain various data such as the open-circuit voltage, input voltage, and current of all optimizers, and summarizes the relevant information of each string of components. Based on these data, the gateway can accurately judge the operating status of the strings, timely discover problems and perform intelligent management, realizing the refined control of the entire photovoltaic system.

[0045] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications, supplements, or use similar methods to replace the specific embodiments described. As long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, they should fall within the protection scope of the present invention.

Claims

1. A system for improving the multi - series and parallel power generation of photovoltaic cells, characterized in that, Including: Photovoltaic panels, photovoltaic optimizers, photovoltaic gateways, inverters; The photovoltaic panels are used to directly convert solar energy into direct current; The photovoltaic optimizers are used to improve the power generation efficiency of each photovoltaic panel; The photovoltaic gateways are used to connect the photovoltaic system to the cloud platform to achieve data monitoring and intelligent management; The inverters are used to convert the direct current generated by the photovoltaic panels into alternating current and have the MPPT function.

2. The system for improving the multi-string parallel power generation of a photovoltaic cell according to claim 1, wherein, The input of the photovoltaic optimizer is connected one-to-one with the output of the photovoltaic panel, the output of the photovoltaic optimizer is connected in series to the photovoltaic gateway, and the photovoltaic gateway is then connected to the inverter.

3. A system for improving the multi - series and parallel power generation of photovoltaic cells according to claim 1, characterized in that, The photovoltaic optimizer is of buck, boost or buck-boost topology and communicates bidirectionally with the photovoltaic gateway through wireless or wired transmission methods. At the same time, the photovoltaic gateway has the functions of real-time monitoring of the bus voltage and bus current of each photovoltaic string.

4. A system for improving the multi - string parallel power generation of photovoltaic cells according to claim 1, characterized in that, The photovoltaic optimizer will record the maximum input voltage, that is, the open-circuit voltage, and supports MPPT algorithms such as perturbation and conductance increment. However, when running the MPPT algorithm, there is a certain voltage range limit, that is, when it exceeds the upper limit, it is maintained at the upper limit, and when it is lower than the lower limit, it is maintained at the lower limit. This range setting can be modified in real time by the photovoltaic gateway.

5. A system for improving the multi - series and parallel power generation of photovoltaic cells according to claim 1, characterized in that, The photovoltaic gateway, when the system is working, obtains the data of all photovoltaic optimizers in real time, including the current open-circuit voltage, input voltage, input current, output voltage, output current, real-time power, duty cycle, and working status, and combines its own acquisition function to summarize the open-circuit voltage, real-time voltage, real-time current, and real-time power of each string of components.

6. The system for improving the multi-string parallel power generation of a photovoltaic cell according to claim 1, characterized in that, The photovoltaic gateway automatically identifies the number of strings. If there are currently two strings connected in parallel to the inverter, namely string 1 and string 2, and their open-circuit voltages are OpenV1 and OpenV2 respectively, and the real-time voltages are V1 and V2 respectively. When the system starts to work, first calculate the difference between OpenV1 and OpenV2, and judge whether the difference between OpenV1 and OpenV2 is within a reasonable range. If the difference between OpenV1 and OpenV2 is within a reasonable range, it is determined that the current two strings of components are matched, and the two strings of components work with the same set of starting parameters. The starting parameters mainly refer to the upper and lower limits of MPPT of each optimizer, that is, the duty cycle or output voltage. If the difference between OpenV1 and OpenV2 is not within a reasonable range, it is determined that the current two strings of components are not matched, and then different MPPT upper and lower limits are used to forcibly set different MPPT voltage ranges.

7. A system for improving the multi - series and parallel power generation of photovoltaic cells according to claim 6, wherein, The different MPPT voltage ranges need to satisfy that the overlap of the upper and lower limits of the output voltage V1 of string 1 and the upper and lower limits of the output voltage V2 of string 2 is greater than or equal to the preset overlap percentage threshold.

8. A system for improving the multi - series and parallel power generation of photovoltaic cells according to claim 7, characterized in that, The photovoltaic gateway, during the working process of the system, real-time detects the working voltage of each string and the duty cycle status of each optimizer. If the sum of the duty cycles of string 1 minus the sum of the duty cycles of string 2 is greater than the preset threshold, it is considered that string 2 is shaded, and at this time the gateway starts to execute string-level MPPT.

9. A system for improving the multi - string parallel power generation of a photovoltaic cell according to claim 8, characterized in that, The specific process for the gateway to start executing string-level MPPT is as follows: Slowly increase the upper and lower limits of string 2 and slowly decrease the upper and lower limits of string 1. Each time of increase or decrease, the gateway records the power of the two strings and finally stabilizes it near the maximum power point.

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