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CN114157231A - Photovoltaic inverter and control method thereof - Google Patents

Photovoltaic inverter and control method thereof Download PDF

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Publication number
CN114157231A
CN114157231A CN202111440118.2A CN202111440118A CN114157231A CN 114157231 A CN114157231 A CN 114157231A CN 202111440118 A CN202111440118 A CN 202111440118A CN 114157231 A CN114157231 A CN 114157231A
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CN
China
Prior art keywords
output
apparent power
voltage
maximum
circuit
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Pending
Application number
CN202111440118.2A
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Chinese (zh)
Inventor
张健华
周党生
曾建友
王光伟
文熙凯
黄太军
刘永桥
章伟
李达
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Shenzhen Hopewind Electric Co Ltd
Original Assignee
Shenzhen Hopewind Electric Co Ltd
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Filing date
Publication date
Application filed by Shenzhen Hopewind Electric Co Ltd filed Critical Shenzhen Hopewind Electric Co Ltd
Priority to CN202111440118.2A priority Critical patent/CN114157231A/en
Publication of CN114157231A publication Critical patent/CN114157231A/en
Pending legal-status Critical Current

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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02SGENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S40/00Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/30Electrical components
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381Dispersed generators
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02SGENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S40/00Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/30Electrical components
    • H02S40/32Electrical components comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20The dispersed energy generation being of renewable origin
    • H02J2300/22The renewable source being solar energy
    • H02J2300/24The renewable source being solar energy of photovoltaic origin
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/56Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The application discloses a photovoltaic inverter and a control method thereof, wherein the photovoltaic inverter comprises a DC/DC circuit and a DC/AC circuit which are sequentially connected between a photovoltaic panel and a power grid, and the DC/AC circuit comprises a switching tube device; the method comprises the following steps: and adjusting the output voltage of the photovoltaic panel according to the comparison result of the maximum allowable output apparent power and the actual output apparent power of the DC/AC circuit, so that the switching device works in a safe voltage and safe current range. The method and the device can control the switching device of the DC/AC circuit to work in a safe voltage and current range, enable the actual output apparent power to reach the maximum allowable output apparent power, and improve the reliability of the photovoltaic inverter under the over-distribution condition.

Description

Photovoltaic inverter and control method thereof
Technical Field
The application relates to the technical field of photovoltaic power generation, in particular to a photovoltaic inverter and a control method thereof.
Background
With the urgent need for new clean energy, photovoltaic power stations are increasingly developed. The photovoltaic inverter is used as electrical equipment of the core of the photovoltaic power station, and the stability of the photovoltaic inverter is related to whether the photovoltaic power station can normally operate.
At present, the string-type inverter is commonly used in a photovoltaic power station, and the improvement of the stability of the string-type inverter is of great significance. As shown in fig. 1, a string-type photovoltaic inverter generally includes two stages, a DC/DC circuit at a front stage and a DC/AC circuit at a rear stage. The "preceding stage DC/DC circuit" is generally a boost circuit, i.e. the output voltage is higher than the input voltage. For the over-distribution condition existing in a photovoltaic field, for example, the optimal output power of a photovoltaic panel is higher than the maximum allowable operating power of the inverter, because the inverter operates under the working conditions of high input voltage and high input power, the direct current bus voltage (the output voltage of a front-stage DC/DC circuit) of the inverter is high and the alternating current output current is large, and the switching device of the DC/AC inverter circuit is high in voltage bearing capacity and large in current bearing capacity. The stress requirement of the working condition on the switching tube device of the DC/AC inverter circuit is high, and the switching tube device is easy to damage. In order to operate stably under the over-matched condition, the switching device capability of the 'DC/AC circuit' needs to be improved, however, the mode increases the cost and cannot adapt to the over-matched condition.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a photovoltaic inverter and a control method thereof, which can control a switching device of a DC/AC circuit to operate in a safe voltage and safe current range under an over-load condition, and enable an actual output apparent power to reach an allowable output maximum apparent power.
According to an aspect of the present application, there is provided a control method of a photovoltaic inverter including a DC/DC circuit and a DC/AC circuit connected in sequence between a photovoltaic panel and a grid, the DC/AC circuit including a switching device; the method comprises the following steps:
and adjusting the output voltage of the photovoltaic panel according to the comparison result of the maximum allowable output apparent power and the actual output apparent power of the DC/AC circuit, so that the switching device works in a safe voltage and safe current range.
In one example, the adjusting the output voltage of the photovoltaic panel according to the comparison result of the maximum allowable output apparent power and the actual output apparent power of the DC/AC circuit includes:
if the maximum allowable output apparent power is larger than the actual output apparent power, reducing the output voltage of the photovoltaic panel to improve the actual output apparent power;
and if the maximum allowable output apparent power is smaller than the actual output apparent power, the output voltage of the photovoltaic panel is increased to reduce the actual output apparent power.
In an example, the method further comprises:
and within the allowable range of the direct-current bus voltage, controlling the direct-current bus voltage to be reduced along with the reduction of the output voltage of the photovoltaic panel or be increased along with the increase of the output voltage of the photovoltaic panel.
In one example, if the maximum allowable output apparent power is greater than the actual output apparent power, decreasing the output voltage of the photovoltaic panel to increase the actual output apparent power includes:
and when the actual output apparent power reaches the maximum value of the actual output apparent power, if the maximum allowable output apparent power is still larger than the actual output apparent power, maintaining the voltage of the direct-current bus unchanged.
In one example, the increasing the output voltage of the photovoltaic panel to decrease the actual output apparent power if the allowed output maximum apparent power is smaller than the actual output apparent power includes:
and when the actual value of the direct current bus voltage reaches the maximum direct current bus voltage, if the maximum allowable output apparent power is still smaller than the actual output apparent power, maintaining the direct current bus voltage unchanged.
In one example, the dc bus voltage is maintained at a preset value; the preset value is within the allowable range of the direct-current bus voltage, and the maximum allowable output apparent power corresponding to the preset value is the same as the actual output apparent power.
In one example, the maximum apparent power allowed to be output is obtained according to a relation curve between the actual value of the direct-current bus voltage and the maximum apparent power allowed to be output.
In one example, a relation curve between the direct current bus voltage and the maximum output allowable alternating current is obtained according to a relation curve between the direct current bus voltage and the maximum output allowable alternating current and the alternating current side power grid voltage.
In one example, according to the hardware characteristics of the switching device, a relation curve between the direct current bus voltage and the maximum output allowable alternating current is obtained.
According to another aspect of the present application, there is provided a photovoltaic inverter comprising a DC/DC circuit and a DC/AC circuit connected in series between a photovoltaic panel and an electrical grid, the DC/AC circuit comprising a switching device; the photovoltaic inverter further comprises a controller;
the controller is configured to adjust the output voltage of the photovoltaic panel according to the comparison result of the maximum allowable output apparent power and the actual output apparent power of the DC/AC circuit, so that the switching device operates in a safe voltage and safe current range.
According to the photovoltaic inverter and the control method thereof, the switching device of the DC/AC circuit can be controlled to work in a safe voltage and current range, the actual output apparent power reaches the maximum allowable output apparent power, and the reliability of the photovoltaic inverter under the over-distribution condition is improved.
Drawings
Fig. 1 is a schematic diagram of a photovoltaic inverter provided in an embodiment of the present application;
fig. 2 is a schematic diagram illustrating a relationship between a dc bus voltage and a maximum ac current allowed to be output according to an embodiment of the present disclosure;
FIG. 3 is a graph illustrating a relationship between a DC bus voltage and a maximum apparent power allowed to be output according to an embodiment of the present disclosure;
fig. 4 is a schematic diagram of a control process of a photovoltaic inverter provided in an embodiment of the present application;
fig. 5 is a schematic diagram illustrating a relationship between a dc bus voltage and an input active power according to an embodiment of the present disclosure;
FIG. 6 is a schematic diagram of a control process for allowing the maximum output apparent power to be smaller than the actual output apparent power according to an embodiment of the present application;
fig. 7 is a schematic diagram of a control process for allowing the maximum output apparent power to be greater than the actual output apparent power according to an embodiment of the present application.
The implementation, functional features and advantages of the objectives of the present application will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer and clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Fig. 2 is a schematic diagram of a relationship between a dc bus voltage and a maximum ac current allowed to be output according to an embodiment of the present disclosure.
As shown in fig. 2, according to the hardware characteristics of the switching device of the "DC/AC circuit" of the string-type photovoltaic inverter, the "DC bus voltage" U can be obtained when the switching device of the "DC/AC circuit" is operated in the safe voltage and safe current rangedcAnd "maximum allowed AC Current output" ILimitThe relationship between them. The abscissa in FIG. 2 represents the "DC bus voltage" UdcThe ordinate represents the maximum permissible output AC current ILimit. Wherein, IMaxUpper limit value, U, for maximum AC current allowed to be output by the systemMaxThe upper limit value of the allowed direct current bus voltage of the system. The switch tube device in the curve range, namely the DC/AC circuit, works in a safe voltage and safe current range.
Fig. 3 is a graph illustrating a relationship between a dc bus voltage and a maximum apparent power allowed to be output according to an embodiment of the present disclosure.
According to the "DC bus voltage" U, as shown in FIG. 3dcAnd "maximum allowed AC Current output" ILimitCurve of the relation between, and "AC-side grid voltage" VgCan obtain 'DC bus voltage' UdcAnd "maximum apparent power allowed to output" SLimitThe relationship of (1). Wherein S isMaxUpper limit value, U, for maximum apparent power output allowed by the systemMaxThe upper limit value of the allowed direct current bus voltage of the system.
In an implementation, the photovoltaic inverter further comprises a controller;
the controller is configured to adjust the output voltage of the photovoltaic panel according to the comparison result of the maximum allowable output apparent power and the actual output apparent power of the DC/AC circuit, so that the switching device of the DC/AC circuit works in a safe voltage and safe current range.
Specifically, first, according to the "DC bus voltage" U shown in FIG. 3dcAnd "maximum apparent power allowed to output" SLimitAnd the relation curve of (1) and the actual value of the DC bus voltage (U) obtained by actual samplingActThe corresponding 'maximum apparent power allowed to be output' S can be obtainedLimit
Then, in the closed-loop control as shown in FIG. 4, the step of "allowing the output of the maximum apparent power" S "is realized by" the controller 1LimitGreater than "actual output apparent power" SActIn time, the 'output voltage' U of the photovoltaic panel is controlledpv(the input voltage of the "DC/DC circuit") decreases; when "maximum apparent power allowed to output" SLimitLess than "actual output apparent power" SActIn time, the 'output voltage' U of the photovoltaic panel is controlledpvThe input voltage of the ("DC/DC circuit") rises. Realizing ' DC bus voltage ' U by ' controller 2dcAccording to the "output voltage" U of the photovoltaic panel within the permitted range of the DC bus voltage of the systempvThe input voltage of the ("DC/DC circuit") rises linearly and falls linearly. DC bus voltage Udc"output voltage" U with photovoltaic panelpvThe relationship between the input voltage of the "DC/DC circuit" is shown in FIG. 5. The abscissa in FIG. 5 is "DC bus voltage" UdcAnd the ordinate is the inverter input active power P. As shown in FIG. 5, "DC bus Voltage" UdcMinimum DC bus voltage U allowed in systemLowAnd the maximum DC bus voltage UMaxIn between, following the "output voltage" U of the photovoltaic panelpvRaised and linearly raised, lowered and linearly lowered.
Fig. 6 is a schematic diagram of a control process for allowing the maximum output apparent power to be smaller than the actual output apparent power according to an embodiment of the present application.
As shown in FIG. 6, the current "actual value of DC bus voltage" UAct1Can be based on the 'DC bus voltage' UdcAnd "allow maximum apparent work to be outputRate "SLimitObtaining corresponding 'maximum apparent power allowed to output' SLimit1. Due to "maximum apparent power allowed to output" SLimit1Less than "actual output apparent power" SAct1Then the "output voltage" U of the photovoltaic panel needs to be adjustedpvThe input voltage of the "DC/DC circuit" rises, thereby reducing the "output power" of the photovoltaic panel. I.e. "actual output apparent power" S of the photovoltaic inverterActWith the decrease of the 'DC bus voltage' UdcAnd then raised.
With "actual output apparent Power" SActGradually decreasing, "DC bus voltage" UdcGradually raised and can be connected with the DC bus voltage UdcAnd "maximum apparent power allowed to output" SLimitHas an intersection point (U)Act2,SAct2) The system can stably and safely work at the intersection. Namely, the DC bus voltage is maintained to be UAct2(ii) a At this intersection point, the maximum apparent power S is allowed to be outputLimitAnd actual output apparent power SActAre identical, i.e. are all SAct2
Further, the actual value of the direct current bus voltage reaches the maximum direct current bus voltage UMaxIf "allow to output maximum apparent power" SLimitAnd if the output voltage is still less than the actual output apparent power, the direct current bus voltage is kept unchanged. I.e. working at maximum dc bus voltage UMax
Fig. 7 is a schematic diagram of a control process for allowing the maximum output apparent power to be greater than the actual output apparent power according to an embodiment of the present application.
As shown in FIG. 7, the current "actual value of DC bus voltage" UAct3Corresponding to an "allowable output maximum apparent power" of SLimit2. Due to "maximum apparent power allowed to output" SLimit2Greater than "actual output apparent power" SAct3Then the "output voltage" U of the photovoltaic panel needs to be adjustedpvDecreasing to gradually reach the optimum operating point. With "output voltage" U of the photovoltaic panelpvGradually decreasing "DC bus voltage" UdcWithin the allowable rangeThe internal voltage gradually decreases, and the system realizes that the allowable maximum power is output in the safe working current range of the safe working voltage of the switching device of the 'DC/AC inverter circuit'.
Further, when the actual output apparent power reaches the maximum value of the actual output apparent power, if the maximum allowed output apparent power is still greater than the actual output apparent power, the dc bus voltage is maintained unchanged (the dc bus voltage corresponding to point a in the figure).
The preferred embodiments of the present application have been described above with reference to the accompanying drawings, and are not intended to limit the scope of the claims of the application accordingly. Any modifications, equivalents and improvements which may occur to those skilled in the art without departing from the scope and spirit of the present application are intended to be within the scope of the claims of the present application.

Claims (10)

1. A control method of a photovoltaic inverter, the photovoltaic inverter comprises a DC/DC circuit and a DC/AC circuit which are sequentially connected between a photovoltaic panel and a power grid, wherein the DC/AC circuit comprises a switching device; characterized in that the method comprises:
and adjusting the output voltage of the photovoltaic panel according to the comparison result of the maximum allowable output apparent power and the actual output apparent power of the DC/AC circuit, so that the switching device works in a safe voltage and safe current range.
2. The method of claim 1, wherein said adjusting the output voltage of the photovoltaic panel based on the comparison of the allowed output maximum apparent power and the actual output apparent power of the DC/AC circuit comprises:
if the maximum allowable output apparent power is larger than the actual output apparent power, reducing the output voltage of the photovoltaic panel to improve the actual output apparent power;
and if the maximum allowable output apparent power is smaller than the actual output apparent power, the output voltage of the photovoltaic panel is increased to reduce the actual output apparent power.
3. The method of claim 2, further comprising:
and within the allowable range of the direct-current bus voltage, controlling the direct-current bus voltage to be reduced along with the reduction of the output voltage of the photovoltaic panel or be increased along with the increase of the output voltage of the photovoltaic panel.
4. The method of claim 3, wherein the reducing the output voltage of the photovoltaic panel to boost the actual output apparent power if the allowed output maximum apparent power is greater than the actual output apparent power comprises:
and when the actual output apparent power reaches the maximum value of the actual output apparent power, if the maximum allowable output apparent power is still larger than the actual output apparent power, maintaining the voltage of the direct-current bus unchanged.
5. The method of claim 3, wherein the step of boosting the output voltage of the photovoltaic panel to reduce the actual output apparent power if the allowed output maximum apparent power is less than the actual output apparent power comprises:
and when the actual value of the direct current bus voltage reaches the maximum direct current bus voltage, if the maximum allowable output apparent power is still smaller than the actual output apparent power, maintaining the direct current bus voltage unchanged.
6. The method of claim 3, wherein the DC bus voltage is maintained at a preset value; the preset value is within the allowable range of the direct-current bus voltage, and the maximum allowable output apparent power corresponding to the preset value is the same as the actual output apparent power.
7. The method according to claim 1, wherein the maximum apparent power allowed to be output is obtained according to a relation curve between the actual value of the direct current bus voltage and the maximum apparent power allowed to be output.
8. The method according to claim 7, wherein the relation between the DC bus voltage and the maximum apparent power allowed to be output is obtained according to the relation between the DC bus voltage and the maximum AC current allowed to be output and the AC side grid voltage.
9. The method of claim 8, wherein a relationship between the dc bus voltage and the maximum ac current allowed to be output is obtained according to hardware characteristics of the switching device.
10. A photovoltaic inverter, characterized in that it comprises a DC/DC circuit and a DC/AC circuit connected in sequence between a photovoltaic panel and an electric grid, the DC/AC circuit comprising switching devices; the photovoltaic inverter further comprises a controller;
the controller is configured to adjust the output voltage of the photovoltaic panel according to the comparison result of the maximum allowable output apparent power and the actual output apparent power of the DC/AC circuit, so that the switching device operates in a safe voltage and safe current range.
CN202111440118.2A 2021-11-27 2021-11-27 Photovoltaic inverter and control method thereof Pending CN114157231A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111440118.2A CN114157231A (en) 2021-11-27 2021-11-27 Photovoltaic inverter and control method thereof

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Application Number Priority Date Filing Date Title
CN202111440118.2A CN114157231A (en) 2021-11-27 2021-11-27 Photovoltaic inverter and control method thereof

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CN114157231A true CN114157231A (en) 2022-03-08

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106972772A (en) * 2017-05-08 2017-07-21 阳光电源股份有限公司 A kind of inversion system and its operating voltage control method
CN111668868A (en) * 2020-05-08 2020-09-15 华为技术有限公司 Photovoltaic power generation system and method
CN111799837A (en) * 2020-07-09 2020-10-20 深圳市禾望科技有限公司 Photovoltaic system and control method thereof
CN112242712A (en) * 2019-07-17 2021-01-19 株洲中车时代电气股份有限公司 Power control method for two-stage photovoltaic inverter system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106972772A (en) * 2017-05-08 2017-07-21 阳光电源股份有限公司 A kind of inversion system and its operating voltage control method
CN112242712A (en) * 2019-07-17 2021-01-19 株洲中车时代电气股份有限公司 Power control method for two-stage photovoltaic inverter system
CN111668868A (en) * 2020-05-08 2020-09-15 华为技术有限公司 Photovoltaic power generation system and method
CN111799837A (en) * 2020-07-09 2020-10-20 深圳市禾望科技有限公司 Photovoltaic system and control method thereof

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