CN117013482A

CN117013482A - Photovoltaic system direct current parallel arc protection and positioning system with reverse perfusion function

Info

Publication number: CN117013482A
Application number: CN202211702881.2A
Authority: CN
Inventors: 陈维; 宋悦
Original assignee: Jiangsu Xumax Power Technology Co ltd; Shenzhen Zhongxu New Energy Co ltd
Current assignee: Jiangsu Xumax Power Technology Co ltd; Shenzhen Zhongxu New Energy Co ltd
Priority date: 2022-12-29
Filing date: 2022-12-29
Publication date: 2023-11-07

Abstract

The invention discloses a photovoltaic system direct current parallel arc protection and positioning system with a reverse perfusion function, and belongs to the technical field of photovoltaic equipment protection. When the system detects that the parallel arc fault occurs in the photovoltaic power generation system, the photovoltaic power optimizer correspondingly controls the front-stage power optimizer of the fault point location to switch from the MPPT working mode to the safe working mode, after the control action is completed, the running mode information of the power optimizer is sent to the central controller, the position of the power optimizer which is carried in the running mode information and is in the safe working mode is analyzed by the central controller to realize the positioning of the fault point location, and the reverse perfusion and the parallel arc protection are automatically carried out. The invention realizes the reverse-filling protection of the photovoltaic string in a mode different from adding the anti-reverse diode in the branch of the photovoltaic string, can rapidly realize the cutting off of the parallel arc when the parallel arc or the short circuit fault occurs, and rapidly positions the position where the parallel arc or the short circuit fault occurs.

Description

Photovoltaic system direct current parallel arc protection and positioning system with reverse perfusion function

Technical Field

The invention relates to the technical field of photovoltaic equipment protection, in particular to a photovoltaic system direct current parallel arc protection and positioning system with a reverse perfusion function.

Background

The system voltage of the photovoltaic power generation system powered by direct current is usually up to 1000V or even 1500V, if phenomena such as contact drop, device aging, insulation breakage, poor grounding and the like occur, direct current arc faults (including series arcs and parallel arcs) are easy to occur, and the direct current arc faults can cause fire accidents, so that the photovoltaic power generation system can be damaged, and meanwhile, the safety of residential buildings, industrial and commercial facilities, public facilities and the like is threatened. In view of the hazard of dc arc faults in photovoltaic power generation systems, safety regulations generally require that rooftop photovoltaic power generation systems having dc voltages above 80V must be equipped with series dc arc fault breakers to break the circuit upon occurrence of a dc arc to reduce the fire hazard due to the arc fault. However, when a series arc or a parallel arc is generated, the current of the photovoltaic power generation system generally cannot reach the tripping current of an arc protection device such as a direct current arc fault circuit breaker, so that the arc cannot be extinguished in time.

Series arcs, also known as arcing, are often caused by poor contact of the inter-component cable plugs, poor connection of the series cables to the combiner box or inverter, and the like. The parallel arc is mainly caused by the short circuit of positive and negative polarity conductors caused by line breakage or the short circuit between photovoltaic string cables. When the string cable is mechanically squeezed or worn out, arcing can occur between the positive and negative electrodes, or between different strings, which is a parallel arc fault. There is also a situation that can lead to parallel arcs, and when the system has a series arc that is not handled in time, the heat of the series arc burns out the cable insulation, and the parallel arc is also generated. The series fault arc can be extinguished by cutting off the direct current bus or the corresponding photovoltaic group string of the photovoltaic power generation system, but the parallel fault arc cannot be extinguished, and even larger current can be caused to pass through an arc passage, so that the arc burns more severely.

At present, a plurality of groups of serial photovoltaic inverter suppliers in the market all push out photovoltaic inverter products with built-in AFCI (Arc-Fault Circuit-Interrupter) functions, and a photovoltaic inverter with built-in AFCI Arc detection identifies direct current Arc faults by detecting Arc noise, breaks a direct current Circuit and eliminates arcs. An AFCI, i.e., an arc fault circuit interrupter, is a protection device that, by identifying an arc fault signature in a circuit, opens a power circuit before the arc fault develops into a fire or the circuit becomes shorted. It is noted that the AFCI of current photovoltaic inverters can typically detect and extinguish only series arcs, while parallel arcs cannot be detected and eliminated by current AFCI functions. Although the module-level quick turn-off technology can disconnect each module in the photovoltaic power generation system, thereby eliminating direct-current high-voltage and series-parallel arc faults existing in the photovoltaic power generation system array, the current module-level quick turn-off technology cannot quickly realize the elimination of parallel arcs because the AFCI function of the current photovoltaic inverter cannot detect the parallel arcs, the destructive power of the parallel arcs is often 10 times or more than that of the series arcs, and the potential safety hazard is larger.

In order to solve the problem that AFCI cannot detect parallel arcs, in the scheme provided by the patent with publication number CN102472789B entitled "method for detecting arcs in photovoltaic system and photovoltaic system thereof", an arc detection signal is detected from a direct current path by digital low-pass filtering, and a series arc and a parallel arc are distinguished according to the detection signal. If a series arc is detected, the working state of the photovoltaic inverter is changed to a safe state, the photovoltaic inverter basically generates no alternating current, and the current flowing in the direct current path is blocked, so that the series arc is extinguished. On the other hand, if a parallel arc is detected, the dc path is shorted by one switch, and thus the parallel arc voltage becomes substantially zero, thereby extinguishing the arc. However, the method needs to distinguish and detect parallel arcs from serial arcs, and additional hardware components are required, which can cause additional cost, meanwhile, various noises and interferences in the normal running state of the photovoltaic power generation system can also bring influence to detection, and experiments show that various noises and interferences in a direct current loop are enough to cause misjudgment and misoperation of fault arc detection equipment when the photovoltaic power generation system is in normal running, so that the fault detection equipment is difficult to perform normal functions, if the fault arc detection equipment cannot guarantee the accuracy of arc fault judgment, particularly for parallel arc faults with larger harm, unnecessary power generation loss can be caused, the benefits of the photovoltaic power station are influenced, and serious consequences such as fire disaster can be caused.

And when a parallel arc or short circuit fault occurs in one of the parallel multi-path photovoltaic module strings, current of other groups of strings in the parallel multi-path photovoltaic module strings can flow back, and then the parallel arc or short circuit fault also occurs, so that the fault range is enlarged, and the whole power generation amount of the photovoltaic power station is reduced. At present, a method for avoiding current backflow of multiple parallel photovoltaic module strings generally adopts anti-reflection diodes, namely anti-reflection diodes are added in each photovoltaic module string branch, however, the anti-reflection diodes can increase certain electric loss, and the failed photovoltaic module string cannot be accurately positioned.

CN 211127119U provides a current anti-backflow protection circuit and a photovoltaic grid-connected device, which accurately detect each path of series current signal through a high-precision direct current sensor, when a fault is detected, the direct current breaking switch can be actively controlled, trip protection and active alarm are carried out in a short time, and series anti-backflow protection is realized.

Therefore, in summary, there is an urgent need for a dc parallel arc protection and positioning system with a reverse current function for a photovoltaic system, which does not need to add a reverse current protection detection and switch protection circuit with a reverse current protection and high accuracy in a string branch of the photovoltaic system, and can realize quick turn-off of the parallel arc and accurate positioning of the parallel arc or a short circuit fault occurrence position, and start the anti-current protection, so that the operation of the photovoltaic power generation system can be quickly recovered after the parallel arc and the short circuit fault occur under the premise of ensuring the safety of photovoltaic power generation.

Disclosure of Invention

The invention aims to realize the reverse-perfusion protection of the photovoltaic string in a mode of being different from adding an anti-reverse diode and other isolation devices in a photovoltaic string branch, and can rapidly realize the cutting off of parallel arcs and rapidly positioning the parallel arcs or the short-circuit faults when the parallel arcs or the short-circuit faults occur, and provides a photovoltaic system direct-current parallel arcs protection and positioning system with a reverse-perfusion function.

To achieve the purpose, the invention adopts the following technical scheme:

the utility model provides a take photovoltaic system direct current parallel arc protection and positioning system of anti-perfusion function, with the power optimizer after the access photovoltaic power generation unit is a unit, a plurality of the unit establish ties each other and constitute a photovoltaic group cluster, one or a plurality of the output of photovoltaic group cluster is connected in photovoltaic dc-to-ac converter and is constituteed photovoltaic system, including be used for when detecting that photovoltaic power generation system takes place parallel arc trouble, the power optimizer of corresponding control fault point's front stage switches over to safe operating mode's a plurality of sub control module from MPPT operating mode, and with each sub control module communication connection's central controller, the sub control module is accomplished and is carried out the control action of safe operating mode switching back, will correspond the operating mode information of control the power optimizer is sent to central controller, central controller is solved the operating mode information carries the position that has been in the power optimizer under the safe operating mode and is located the fault point position realizes the location to the anti-perfusion and parallel arc protection voluntarily.

Preferably, the method for controlling the power optimizer in the photovoltaic string branch of the fault point and/or generating the current reverse irrigation by the sub-control module to switch to the safe working mode is that the power optimizer in the photovoltaic power generation system detects that the output voltage is lower than a preset voltage threshold value, and/or detects that the current reverse irrigation occurs in the photovoltaic string branch where the power optimizer is located, and when the reverse irrigation current is higher than the preset reverse irrigation current threshold value, the parallel arc fault occurs in the judging circuit, and then the sub-control module controls the power optimizer to switch to the safe working mode by the sub-control module per se, and the method for switching to the safe working mode is as follows:

the sub-control module of the power optimizer drives a first switch in the power optimizer to be turned off and drives a second switch to be turned on so as to control a photovoltaic power generation unit connected with the power optimizer to stop outputting photovoltaic power, and therefore the operation state of the power optimizer is switched to a safe working mode.

Preferably, the power optimizer includes the sub-control module, the first switch, the second switch, an input capacitor Cin, an output capacitor Cout and a storage inductor L; the grid electrode of the first switch is connected with an HD-driver pin of the sub-control module; the grid electrode of the second switch is connected with an LD-driver pin of the sub-control module; one end of the energy storage inductor L is connected with the source electrode of the first switch, the other end of the energy storage inductor L is connected with one end of the output capacitor Cout, and the other end of the output capacitor Cout is connected with the source electrode of the second switch; the input capacitor Cin is connected in parallel between the positive output end and the negative output end of the photovoltaic power generation unit.

Preferably, the protection method for controlling parallel arc and current reverse perfusion to occur among components in an array of a photovoltaic string in a parallel photovoltaic string branch by the sub-control module comprises the following steps:

s1, when a power optimizer in a photovoltaic power generation system detects that the output voltage is lower than a preset voltage threshold, judging that a parallel arc fault occurs in a circuit, then controlling the power optimizer to switch to a safe working mode by a sub-control module of the power optimizer, and after the sub-control module finishes a control action of executing the safe working mode switching, sending running mode information of the power optimizer which is correspondingly controlled to the central controller;

s2, after the central controller receives the operation mode information, the central controller analyzes the position of the power optimizer in a safe working mode carried in the operation mode information to position the fault point, and stops sending heartbeat packets to the photovoltaic string branches of the power optimizer corresponding to the sub-control module sending the operation mode information;

s3, the safety correction control module in the power optimizer judges whether the heartbeat packet is abnormal or not,

If yes, stopping generating a trimming instruction to control a trimming switch to be closed, and maintaining the trimming switch in a closed state until the heartbeat packet is judged to be received and recovered to be normal, wherein after the trimming switch is closed, the output voltage of the power optimizer is pulled down below a preset voltage threshold value, and the sub-control module of the power optimizer uses the trimming instruction as an instruction to control the power optimizer to be switched and maintained in a safe working mode;

if not, the sub-control module controls the power optimizer to be maintained in the current running working mode;

s4, after all power optimizers of the photovoltaic string branches with parallel arc faults enter a safe working mode, other photovoltaic strings without parallel arc faults in the parallel photovoltaic strings enter the safe working mode because the power optimizers in the strings detect that the output voltage of the power optimizers is lower than a preset voltage threshold value due to short circuit; all power optimizers with parallel photovoltaic strings enter a safe working mode, and parallel arcs and reverse perfusion states in arrays of the photovoltaic strings in parallel photovoltaic string branches disappear until faults are relieved and a heartbeat packet is restored to be sent by the central controller.

Preferably, in step S1, the method for switching the power optimizer to the safe operation mode includes:

Preferably, the sub-control module is a dual-operation mode BUCK power optimization ASIC chip, the inside of the ASIC chip comprises a maximum power tracking circuit, a reference voltage generating circuit, a mode control circuit, a driving control circuit, a communication interface circuit and an internal power supply circuit,

the maximum power tracking circuit comprises a voltage and current detection unit, a multiplier and a maximum power tracking processing unit, wherein the voltage and current detection unit is used for collecting the output voltage and the output current of the accessed photovoltaic power generation unit;

the multiplier is used for multiplying the output voltage acquired by the voltage and current detection unit by the output current to obtain the output power of the photovoltaic power generation unit;

The input end of the maximum power tracking processing unit is connected with the output end of the multiplier and is used for tracking the maximum power point of the photovoltaic power generation unit;

the power optimizer is used for controlling the on-off of the first switch and the second switch according to the duty ratio signal when the power optimizer operates in an MPPT working mode so as to realize the maximum power tracking of the accessed photovoltaic power generation unit;

the signal output end of the Mode control circuit is connected with the Mode pin of the double-working Mode BUCK power optimization ASIC chip, the first signal input end of the low-voltage protection and safety trimming circuit at the periphery of the chip is connected with the Mode pin, the second signal input end is connected with the VDD pin of the chip, the signal output end is connected with the safety trimming control module, when the output voltage of the power optimizer is lower than the reference voltage and reaches a first threshold value, the sub-control module controls the power optimizer to operate in a safe working Mode, and when the output voltage of the power optimizer is higher than the reference voltage and reaches a second threshold value, the sub-control module controls the power optimizer to operate in an MPPT working Mode;

The drive control circuit comprises a logic control unit, a first drive unit and a second drive unit, wherein a first input end of the logic control unit is connected with a signal output end of the mode control circuit, a second input end of the logic control unit is connected with a signal output end of the maximum power tracking unit, the first output end and the second output end are respectively connected with signal input ends of the first drive unit and the second drive unit, the signal output ends of the first drive unit and the second drive unit are respectively connected with an HD-driver pin and an LD-driver pin of the sub control module, and the drive control circuit is used for controlling the on-off of the first switch and the second switch according to preset control logic;

the communication interface circuit is used for providing a communication interface for connecting the external equipment with the sub-control module.

Preferably, the low-voltage protection and safety trimming circuit comprises a trimming switch piece, resistors R1 and R2, a diode VD, a capacitor Cx and a safety trimming control module, wherein the trimming switch piece is a normally-closed PMOS (P-channel metal oxide semiconductor) tube, a forward body diode is connected between a source electrode and a drain electrode of the PMOS tube, the source electrode of the trimming switch piece is grounded, the drain electrode is connected with a Mode pin of a chip after being connected with the resistor R1 in series, and the grid electrode is connected with a signal input end of the safety trimming control module; one end of the resistor R2 is connected with a VDD pin of the chip, and the other end of the resistor R2 is connected with the drain electrode of the PMOS tube and is grounded after being connected with the capacitor Cx; the anode of the diode VD is connected with the drain electrode of the PMOS tube, and the cathode of the diode VD is connected with the V0 pin of the chip;

The safety trimming control module is used for obtaining working voltage by taking electricity from the photovoltaic power generation unit through an auxiliary power supply, detecting output current of the power optimizer, judging that the power optimizer does not generate current counter-current when detecting that the output current of the power optimizer is smaller than a preset counter-current threshold, and generating a trimming instruction to control a normally-closed trimming switch element in the low-voltage protection and safety trimming circuit to be disconnected and maintain the normally-closed trimming switch element in an disconnected state;

when the output current of the power optimizer is detected to be higher than the preset counter-current threshold, the power optimizer is judged to generate current counter-current, and the safety trimming control module stops generating trimming instructions to control the trimming switch piece to be closed and maintain the trimming switch piece in a closed state.

Preferably, the safety trimming control module is further used for detecting whether the heartbeat packet communication signal generated by the central controller is normal,

if the heartbeat packet communication signal is normal, generating a trimming instruction to control the trimming switch piece to be disconnected and maintain the trimming switch piece in a disconnected state until the heartbeat packet communication signal is judged to be abnormal;

and if the heartbeat packet communication signal is abnormal, stopping generating a trimming instruction to control the trimming switch piece to be closed and maintaining the trimming switch piece in the closed state until the heartbeat packet communication signal is judged to be normal.

Preferably, the central controller includes a communication module and a decision module, where the communication module is configured to establish communication connection with each of the sub-control modules disposed at the corresponding current detection point, so as to receive the operation mode information of the corresponding power optimizer sent by each of the sub-control modules, and further is configured to send a heartbeat packet communication signal to the corresponding sub-control module;

the decision module is in communication connection with the communication module and is used for judging whether the photovoltaic power generation system has a direct current parallel arc fault or not and positioning fault points according to the received operation mode information, and deciding whether to send the heartbeat packet communication signal to the sub-control module of the corresponding photovoltaic string branch.

Preferably, the power optimizer after being connected into the photovoltaic power generation unit is used as a unit, a plurality of units are mutually connected in series to form a photovoltaic group string, the output ends of the photovoltaic group strings are connected to a direct current bus of the photovoltaic inverter in parallel, an alternating current side of the photovoltaic inverter is connected to a power grid to form a photovoltaic power generation system, an isolating switch device is arranged in a path of each photovoltaic group string connected with the direct current bus, each isolating switch device is in communication connection with the central controller, after the central controller receives the operation mode information, the central controller analyzes the position of the power optimizer in a safe operation mode carried in the operation mode information to realize the positioning of the fault point, then a switch control signal is generated and sent to the corresponding isolating switch device, and the isolating switch device receives the switch control signal and then controls the disconnection between the corresponding photovoltaic group string with the fault and the photovoltaic inverter.

The invention has the following beneficial effects:

the scheme can realize the automatic reverse perfusion and parallel arc fault protection of the photovoltaic system of the parallel photovoltaic string, can realize the automatic protection aiming at the automatic reverse perfusion and the parallel arc fault, and then positions the arc fault point, and has high safety, reliability and convenience. When the power optimizer in the photovoltaic power generation system detects that the output voltage is lower than a preset voltage threshold value and/or detects that the current of the string branch of the photovoltaic group where the power optimizer is located is reversely irrigated, and the reversely irrigated current is higher than the preset reversely irrigated current threshold value, the parallel arc fault of the circuit is judged, and then the sub-control module of the power optimizer controls the power optimizer to switch the power optimizer to a safe working mode. The invention realizes the reverse irrigation protection of the photovoltaic string in a mode of being different from adding the anti-reverse diode in the branch of the photovoltaic string, can rapidly realize the disconnection of the parallel arc when the parallel arc or the short circuit fault occurs, can rapidly position the parallel arc or the short circuit fault, and can generate a switch control signal to be sent to the corresponding isolating switch device, and the isolating switch device can control the disconnection of the connection between the corresponding photovoltaic string with the arc fault and the photovoltaic inverter after receiving the switch control signal, so that the operation of the photovoltaic power generation system can be rapidly recovered after the parallel arc and the short circuit fault occur on the premise of ensuring the safety of the photovoltaic power generation.

Drawings

In order to more clearly illustrate the technical solution of the embodiments of the present invention, the drawings that are required to be used in the embodiments of the present invention will be briefly described below. It is evident that the drawings described below are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.

Fig. 1 is a schematic structural diagram of a photovoltaic power generation system with a photovoltaic system dc parallel arc protection and positioning system with a reverse perfusion function according to embodiment 1 of the present invention;

FIG. 2 is a schematic diagram of the internal architecture of a power optimizer;

FIG. 3 is a schematic diagram of the internal circuit structure of the sub-control module;

fig. 4 is a circuit diagram of a schematic architecture of a photovoltaic power generation system provided in embodiment 1 of the present invention;

fig. 5 is a schematic view of the state of the photovoltaic power generation system according to embodiment 1 of the present invention when parallel arcs are generated;

FIG. 6 (a) is a schematic diagram showing a state of generating parallel arcs on the series-parallel bus bar provided in embodiment 1 of the present invention;

FIG. 6 (b) is an I-V graph of the output voltage variation for each string of photovoltaic groups of the system of FIG. 6 (a) before and after parallel arcs are generated;

fig. 7 (a) is a schematic view of a state of parallel arc generation outside the photovoltaic modules in the string of the photovoltaic string provided in embodiment 1 of the present invention;

FIG. 7 (b) is an I-V graph of the output voltage variation for each string of photovoltaic groups of the system of FIG. 7 (a) before and after parallel arcs are generated;

fig. 8 (a) is a schematic diagram of a state in which parallel arcs are generated between photovoltaic modules in a string of photovoltaic strings provided in embodiment 1 of the present invention;

FIG. 8 (b) is an I-V graph of the output voltage variation for each string of photovoltaic groups of the system of FIG. 8 (a) before and after parallel arcs are generated;

fig. 9 is a circuit diagram of a schematic architecture of a photovoltaic power generation system provided in embodiment 2 of the present invention;

fig. 10 is a schematic view of the state of the photovoltaic power generation system according to embodiment 2 of the present invention when parallel arcs are generated;

FIG. 11 (a) is a schematic view showing a state of generating parallel arcs on the series-parallel bus bars provided in embodiment 2 of the present invention;

FIG. 11 (b) is an I-V graph of the output voltage variation for each string of photovoltaic groups of the system of FIG. 11 (a) before and after parallel arcs are generated;

fig. 12 (a) is a schematic view of a state in which parallel arcs are generated outside the photovoltaic modules in the string of the photovoltaic string provided in embodiment 2 of the present invention;

FIG. 12 (b) is an I-V graph of the output voltage variation for each string of photovoltaic groups of the system of FIG. 12 (a) before and after parallel arcs are generated;

fig. 13 is a circuit diagram of a schematic architecture of a photovoltaic power generation system provided in embodiment 3 of the present invention;

Fig. 14 is a schematic view of a state of the photovoltaic power generation system according to embodiment 3 of the present invention when parallel arcs are generated;

FIG. 15 (a) is a schematic view showing a state of generating parallel arcs on the series-parallel bus bar provided in embodiment 3 of the present invention;

FIG. 15 (b) is an I-V graph of the output voltage variation for each string of photovoltaic groups of the system of FIG. 15 (a) before and after parallel arcs are generated;

fig. 16 (a) is a schematic view of a state of parallel arc generation outside the photovoltaic modules in the strings of the photovoltaic strings provided in embodiment 3 of the present invention;

FIG. 16 (b) is an I-V graph of the output voltage variation for each string of photovoltaic groups of the system of FIG. 16 (a) before and after parallel arcs are generated;

fig. 17 (a) is a schematic view of a state in which parallel arcs are generated between photovoltaic modules in a string of photovoltaic strings provided in embodiment 3 of the present invention;

fig. 17 (b) is an I-V plot of the output voltage variation for each string of photovoltaic cells of the system of fig. 17 (a) before and after parallel arcs are generated.

Detailed Description

The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings.

Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to be limiting of the present patent; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, only for convenience in describing the present invention and simplifying the description, rather than indicating or implying that the apparatus or elements being referred to must have a specific orientation, be constructed and operated in a specific orientation, so that the terms describing the positional relationships in the drawings are merely for exemplary illustration and should not be construed as limiting the present patent, and that the specific meaning of the terms described above may be understood by those of ordinary skill in the art according to specific circumstances.

In the description of the present invention, unless explicitly stated and limited otherwise, the term "coupled" or the like should be interpreted broadly, as it may be fixedly coupled, detachably coupled, or integrally formed, as indicating the relationship of components; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between the two parts or interaction relationship between the two parts. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

Example 1

The dc parallel arc protection and positioning system with the reverse current function provided in the embodiment 1 of the present invention, as shown in fig. 1, includes a plurality of sub-control modules (denoted by reference numeral "10" in fig. 2) for switching the MPPT (maximum power point tracking) operation mode to the safe operation mode of the power optimizer 2 at the front stage corresponding to the control failure point when the parallel arc fault is detected to occur in the current detection point 1 of the photovoltaic power generation system (when the current value of the current detection point changes), and a central controller 3 communicatively connected to each sub-control module 10, where the sub-control modules 10 send the operation mode information of the power optimizer 2 corresponding to the control to the central controller 3 after executing the control action of the safe operation mode switching, and the central controller 3 analyzes the position of the power optimizer 2 in the safe operation mode carried in the operation mode information to realize the positioning of the failure point.

In this embodiment, the method for controlling the power optimizer 2 in the photovoltaic string branch of the previous stage of the fault point and/or the current reverse-flowing generation by the sub-control module 10 to switch to the safe working mode includes a first method and a second method, as shown in fig. 2, where the first method is as follows:

The power optimizer in the photovoltaic power generation system detects that the output voltage is lower than a preset voltage threshold value, or detects that the current of the string branch of the photovoltaic group where the power optimizer is located is reversely irrigated, and the reversely irrigated current is higher than the preset reversely irrigated current threshold value, and judges that a parallel arc fault occurs in the circuit, and then the power optimizer is controlled by the sub-control module 10 to switch to a safe working mode under the control of the power optimizer, the method for switching to the safe working mode is as follows:

the sub-control module 10 of the power optimizer drives the first switch 20 in the power optimizer 2 to be turned off and drives the second switch 30 to be turned on so as to control the photovoltaic power generation unit 4 connected to the power optimizer 2 to stop outputting photovoltaic power, thereby realizing that the operation state of the power optimizer 2 is switched from the MPPT working mode to the safe working mode.

The second method comprises the steps of:

s1, when a power optimizer in a photovoltaic power generation system detects that the output voltage is lower than a preset voltage threshold, judging that a parallel arc fault occurs in a circuit, then controlling the power optimizer to switch to a safe working mode by a sub-control module of the power optimizer, and after the sub-control module finishes a control action of executing the safe working mode switching, sending operation mode information of the power optimizer correspondingly controlled to a central controller;

s3, the safety maintenance control module in the power optimizer judges whether the received heartbeat packet is abnormal,

if yes, stopping generating the trimming command to control and close the trimming switch piece 103 shown in fig. 2, and maintaining the trimming switch piece 103 in a closed state until the heartbeat packet is judged to be recovered to be normal, and after the trimming switch piece 103 is closed, pulling down the output voltage of the power optimizer to be below a preset voltage threshold value, wherein a sub-control module of the power optimizer uses the trimming command to control the power optimizer to switch and maintain in a safe working mode;

The power optimizer 2 includes the sub-control module 10, the first switch 20, the second switch 30, the input capacitor Cin, the output capacitor Cout and the energy storage inductor L shown in fig. 2, where the first switch 20 and the second switch 30 are NMOS tubes with body diodes connected in parallel between source and drain, the drain of the first switch 20 is connected to the positive output end of the photovoltaic power generation unit 4, the source is connected to the drain of the second switch 30, and the source of the second switch 30 is connected to the negative output end of the photovoltaic power generation unit; the grid of the first switch 20 is connected with an HD-driver pin of the sub-control module; the grid electrode of the second switch 30 is connected with an LD-driver pin of the sub-control module; one end of the energy storage inductor L is connected with the source electrode of the first switch 20, the other end of the energy storage inductor L is connected with one end of the output capacitor Cout, and the other end of the output capacitor Cout is connected with the source electrode of the second switch 30; the input capacitor Cin is connected in parallel between the positive output end and the negative output end of the photovoltaic power generation unit.

The sub-control module 10 is an ASIC chip with a dual-operation mode BUCK type power optimization function shown in fig. 2, and the inside of the chip is shown in fig. 3, and includes a maximum power tracking circuit, a reference voltage generating circuit, a mode control circuit, a drive control circuit, a communication interface circuit and an internal power supply circuit;

the multiplier is used for multiplying the output voltage and the output current acquired by the voltage and current detection unit to obtain the output power of the photovoltaic power generation unit;

the reference voltage generating circuit is used for providing a reference voltage for determining a duty ratio signal for the maximum power tracking circuit by utilizing the power supply of the power supply circuit in the chip and providing a reference voltage for mode control for the mode control circuit, and when the power optimizer operates in the MPPT working mode, the sub-control module controls the on-off of the first switch 20 and the second switch 30 according to the duty ratio signal so as to realize the maximum power tracking of the accessed photovoltaic power generation unit;

the signal output end of the Mode control circuit is connected with a Mode pin of the dual-working Mode BUCK power optimization ASIC chip, the first signal input end 101 of the low-voltage protection and safety trimming circuit 100 at the periphery of the chip is connected with the Mode pin, the second signal input end 102 is connected with a VDD pin of the chip, the signal output end is connected with the safety trimming control module, when the output voltage of the power optimizer is lower than the reference voltage and reaches a first threshold value, the sub control module controls the power optimizer to operate in the safety working Mode, and when the output voltage of the power optimizer is higher than the reference voltage and reaches a second threshold value, the sub control module controls the power optimizer to operate in the MPPT working Mode;

The drive control circuit comprises a logic control unit, a first drive unit and a second drive unit, wherein a first input end of the logic control unit is connected with a signal output end of the mode control circuit, a second input end of the logic control unit is connected with a signal output end of the maximum power tracking unit, the first output end and the second output end are respectively connected with signal input ends of the first drive unit and the second drive unit, the signal output ends of the first drive unit and the second drive unit are respectively connected with an HD-driver pin and an LD-driver pin of the sub control module, and the drive control circuit is used for controlling the on-off of the first switch 20 and the second switch 30 according to preset control logic;

the communication interface circuit is used for providing a communication interface for the external equipment to connect with the sub-control module.

Referring to fig. 3, the low voltage protection and safety trimming circuit 100 includes a trimming switch 103, resistors R1 and R2, a diode VD, a capacitor Cx, and a safety trimming control module 200, wherein the trimming switch 103 is a normally-closed PMOS tube, a forward body diode is connected between a source and a drain of the PMOS tube, the source of the trimming switch 103 is grounded, the drain is connected to a Mode pin of the chip after being connected in series with the resistor R1, and the gate is connected to a signal input end of the safety trimming control module; one end of the resistor R2 is connected with the VDD pin of the chip, and the other end of the resistor R2 is connected with the drain electrode of the PMOS tube and is grounded after being connected with the capacitor Cx; the anode of the diode VD is connected with the drain electrode of the PMOS tube, and the cathode of the diode VD is connected with the V0 pin of the chip;

The safety trimming control module is used for obtaining working voltage by taking electricity from the photovoltaic power generation unit through the auxiliary power supply, detecting output current of the power optimizer, judging that the power optimizer does not generate current reverse-pouring when detecting that the output current of the power optimizer is smaller than a preset reverse-pouring current threshold value, and generating a trimming instruction to control the normally-closed trimming switch element 103 in the low-voltage protection and safety trimming circuit 100 to be disconnected and maintain the normally-closed trimming switch element in a disconnected state;

when the output current of the power optimizer is detected to be higher than a preset counter-current threshold, it is determined that the power optimizer generates a current counter-current, and then the safety trimming control module stops generating a trimming command to control the trimming switch 103 to be closed and maintain the trimming switch in an on state.

The safety trimming control module is further configured to detect whether a heartbeat packet communication signal generated by the central controller is normal, and if so, generate a trimming instruction to control the trimming switch element 103 to be turned off and maintain the trimming switch element in a turned-off state until it is determined that the heartbeat packet communication signal is abnormal; if the heartbeat packet communication signal is abnormal, stopping generating the trimming instruction to control the trimming switch piece 103 to be closed and maintaining the trimming switch piece in the closed state until the heartbeat packet communication signal is judged to be normal.

The central controller 3 comprises a communication module and a decision module, wherein the communication module is used for establishing communication connection with each sub-control module arranged at the corresponding current detection point to receive the operation mode information of the corresponding power optimizer sent by each sub-control module and sending heartbeat packet communication signals to the corresponding sub-control module;

the decision module is in communication connection with the communication module and is used for judging whether the photovoltaic power generation system has a direct current parallel arc fault or not and positioning fault points according to the received operation mode information, and deciding whether to send heartbeat packet communication signals to the sub-control modules of the corresponding photovoltaic group string branches or not.

In order to facilitate a quick turn-off of each photovoltaic string in fig. 1, preferably, an isolation device is provided in the path of each photovoltaic string that is connected to the dc bus of the photovoltaic inverter. Specifically, the power optimizer after being connected to the photovoltaic power generation unit as shown in fig. 2 is used as a unit, a plurality of units are mutually connected in series to form a photovoltaic string 300 shown in fig. 1, the output ends of the photovoltaic strings 300 are connected in parallel to the alternating-current side of the photovoltaic inverter and connected to the power grid to form a photovoltaic power generation system, an isolation device is arranged in the path of each photovoltaic string connecting a direct-current bus, each isolation device is in communication connection with a central controller, the isolation device is used for monitoring the output current of the corresponding photovoltaic string and sending the output current to the central controller, the central controller is used for positioning the photovoltaic string with the arc fault according to the monitored current change, then a switch control signal is generated and sent to the corresponding isolation device, and the isolation device is used for controlling to disconnect the corresponding photovoltaic string with the arc fault from being connected with the direct-current bus after receiving the switch control signal.

As shown in fig. 4, the multiple photovoltaic groups are connected in series-parallel and centrally into the photovoltaic inverter.

Fig. 5 is a schematic view of a state of the photovoltaic power generation system in this embodiment when parallel arcs are generated, which shows a position where parallel arcs may be generated, including parallel arcs generated on buses connected in series and parallel, parallel arcs outside photovoltaic modules in a series of photovoltaic series, and parallel arcs between photovoltaic modules in a series of photovoltaic series.

Fig. 6 (a) and fig. 6 (b) are schematic diagrams of a state of generating parallel arcs on the parallel-series bus provided by the present embodiment, where the system generates an I-V graph of each photovoltaic string output voltage change before and after parallel arcs, 11 points are maximum operating points of the photovoltaic string, 10 points are output voltages of the photovoltaic string after parallel arcs at the above positions occur, and the voltage value is an arc voltage value of 10V-20V; the number of the photovoltaic power optimizers connected in series on the photovoltaic group string is 30, and the average output voltage of each photovoltaic power optimizer is less than 1V. After all power optimizers after parallel arc is generated detect that the output voltage is lower than the preset voltage threshold value by 2.5V, all power optimizers of the parallel photovoltaic string enter a safe working mode until the fault is relieved.

Fig. 7 (a) and fig. 7 (b) are schematic diagrams of a state of generating parallel arcs outside the photovoltaic modules in the strings of the photovoltaic strings according to the present embodiment, where the system is an I-V graph of each photovoltaic string output voltage change before and after generating the parallel arcs, 11 points are maximum operating points of the photovoltaic strings, and 10 points are output voltages of the photovoltaic strings after generating the parallel arcs at the above positions, and the voltage value is an arc voltage value of 10V-20V. The number of the photovoltaic power optimizers connected in series on the photovoltaic group string is 30, and the average output voltage of each photovoltaic power optimizer is less than 1V. After all power optimizers after parallel arc is generated detect that the output voltage is lower than the preset voltage threshold value by 2.5V, all power optimizers of the parallel photovoltaic string enter a safe working mode until the fault is relieved.

Fig. 8 (a) and fig. 8 (b) are schematic diagrams of a state of generating parallel arcs between photovoltaic modules in strings of the photovoltaic strings provided in this embodiment, and I-V graphs of output voltage changes of each photovoltaic string before and after generating parallel arcs in the system, wherein 11 points are maximum operating points of the photovoltaic strings, 12 points are operating points of the photovoltaic strings after generating parallel arcs in the above positions, and output voltage values of voltages of the maximum operating points of the photovoltaic strings after generating parallel arcs in other strings without generating parallel arcs; and 13 points are working points of the photovoltaic string after parallel arcs at the positions do not occur, and the output voltage of the working points is the voltage value of the maximum working point of the photovoltaic string after reverse current occurs. After parallel arcs are generated, a photovoltaic power optimizer at the front end of the parallel arcs in a photovoltaic group string branch which generates parallel arcs among photovoltaic assemblies in the parallel photovoltaic assembly string enters a safe mode. When other photovoltaic power optimizers of the photovoltaic group string branches generating parallel arcs among the photovoltaic modules detect that current reverse-irrigation occurs to the photovoltaic group string branches where the photovoltaic group string branches are located, and the reverse-irrigation current is higher than a preset reverse-irrigation current threshold value, the judgment circuit generates parallel arc faults, and then the sub control module controls the sub control module to switch the sub control module to a safe working mode. After all power optimizers of the photovoltaic string branches with parallel arc faults enter a safe working mode, other photovoltaic strings without parallel arc faults in the parallel photovoltaic strings are short-circuited, so that the power optimizers in the strings detect that the output voltage of the power optimizers is lower than a preset voltage threshold value and enter the safe working mode; all power optimizers with parallel photovoltaic strings enter a safe working mode, and parallel arcs and reverse perfusion states in the arrays of the photovoltaic strings in the parallel photovoltaic string branches disappear.

Example 2

This embodiment is substantially the same as embodiment 1 described above, except that: and a plurality of groups of strings are connected into the photovoltaic system direct current parallel arc protection and positioning system with the reverse perfusion function of the photovoltaic inverter in a concentrated way through the intelligent isolating switch.

As shown in fig. 9, the strings are centrally connected to the photovoltaic inverter through the intelligent isolating switch.

Fig. 10 is a schematic view of a state of the photovoltaic power generation system provided in this embodiment when parallel arcs are generated, which shows a position where parallel arcs may be generated, including parallel arcs generated on buses connected in series and parallel, parallel arcs outside photovoltaic modules in a series of photovoltaic series, and parallel arcs between photovoltaic modules in a series of photovoltaic series.

Fig. 11 (a) and 11 (b) are schematic diagrams of a state of generating parallel arcs on the parallel-series bus provided by the present embodiment, and an I-V graph of a system of the state of generating parallel arcs on each photovoltaic string output voltage change before and after generating parallel arcs, wherein 11 points are maximum operating points of the photovoltaic strings, 10 points are output voltages of the photovoltaic strings after generating parallel arcs at the above positions, and the voltage value is an arc voltage value of 10V-20V; the number of the photovoltaic power optimizers connected in series on the photovoltaic group string is 30, and the average output voltage of each photovoltaic power optimizer is less than 1V. After all power optimizers after parallel arc is generated detect that the output voltage is lower than the preset voltage threshold value by 2.5V, all power optimizers of the parallel photovoltaic string enter a safe working mode until the fault is relieved.

Fig. 12 (a) and fig. 12 (b) are schematic diagrams of a state of parallel arc generation outside the photovoltaic modules in the strings of the photovoltaic strings provided in this embodiment, and I-V graphs of output voltage changes of each photovoltaic string before and after parallel arc generation in the system thereof. The 11 points are the maximum working points of the photovoltaic string, and the 10 points are the output voltages of the photovoltaic string after parallel arcs at the positions occur, and the voltage values are arc voltage values of 10V-20V. The number of the photovoltaic power optimizers connected in series on the photovoltaic group string is 30, and the average output voltage of each photovoltaic power optimizer is less than 1V. After the parallel arc is generated here, all power optimizers of the parallel photovoltaic string will enter a safe mode of operation. In this embodiment, an isolating switch device is disposed in a path where each photovoltaic string is connected to the dc bus, each isolating switch device is in communication connection with the central controller, after the central controller receives the operation mode information, the central controller analyzes the position of the power optimizer in the safe operation mode carried in the operation mode information to realize positioning of the fault point, then generates a switch control signal and sends the switch control signal to the corresponding isolating switch device, and the isolating switch device receives the switch control signal and then controls to disconnect the connection between the photovoltaic string with the corresponding arc fault and the photovoltaic inverter, so that the operation of the photovoltaic power generation system can be quickly recovered after parallel arc and short circuit fault occur under the premise of ensuring the safety of photovoltaic power generation.

Example 3

This embodiment is substantially the same as embodiment 1 described above, except that: the photovoltaic system direct current parallel arc protection and positioning system with the reverse perfusion function is commonly connected with the DC-AC bus side of the photovoltaic inverter through the BOOST circuit of the BOOST;

as shown in fig. 13, the strings are commonly connected to the DC-AC bus side of the photovoltaic inverter through a BOOST circuit.

Fig. 14 is a schematic view of a state of a photovoltaic power generation system when parallel arcs are generated, showing positions where parallel arcs may be generated, including parallel arcs generated on buses connected in series and parallel, parallel arcs outside photovoltaic modules in a group of photovoltaic group strings, and parallel arcs between photovoltaic modules in a group of photovoltaic group strings.

Fig. 15 (a) and 15 (b) are schematic diagrams of a state of generating parallel arcs on the series-parallel buses provided in this embodiment, and I-V graphs of output voltage changes of each photovoltaic series before and after generating parallel arcs. The 11 points are the maximum working points of the photovoltaic string, the 10 points are the output voltages of the photovoltaic string after parallel arcs at the positions occur, and the voltage value is 10V-20V arc voltage value; the number of the photovoltaic power optimizers connected in series on the photovoltaic group string is 30, and the average output voltage of each photovoltaic power optimizer is less than 1V. After all power optimizers after parallel arc is generated detect that the output voltage is lower than the preset voltage threshold value by 2.5V, all power optimizers of the parallel photovoltaic string enter a safe working mode until the fault is relieved.

Fig. 16 (a) and 16 (b) are schematic diagrams of a state of generating parallel arcs outside the photovoltaic modules in the strings of the photovoltaic strings and I-V graphs of the system thereof for each photovoltaic string output voltage variation before and after generating the parallel arcs, respectively. The 11 points are the maximum working points of the photovoltaic string, and the 10 points are the output voltages of the photovoltaic string after parallel arcs at the positions occur, and the voltage values are arc voltage values of 10V-20V. The number of the photovoltaic power optimizers connected in series on the photovoltaic group string is 30, and the average output voltage of each photovoltaic power optimizer is less than 1V. After all power optimizers after parallel arc is generated detect that the output voltage is lower than the preset voltage threshold value by 2.5V, all power optimizers of the parallel photovoltaic string enter a safe working mode until the fault is relieved.

Fig. 17 (a) and 17 (b) are schematic diagrams of a state of generating parallel arcs between photovoltaic modules in strings of photovoltaic strings and I-V graphs of output voltage changes of each photovoltaic string before and after generating parallel arcs in the system according to the present embodiment. The 11 points are the maximum working points of the photovoltaic string, the 12 points are the working points of the parallel photovoltaic string branches after parallel arcs at the positions, and the reverse voltage value of the voltage of the maximum working points of the photovoltaic string which does not generate parallel arcs after parallel arcs occur in other strings is output; and 13 points are working points of other photovoltaic group strings under the BOOST circuit of the parallel arc branch after the parallel arc at the position does not occur, and the output voltage of the working points is the voltage value of the maximum working point of the photovoltaic group string after the reverse current occurs. After parallel arcs are generated, a photovoltaic power optimizer at the front end of the parallel arcs in a photovoltaic group string branch which generates parallel arcs among photovoltaic assemblies in the parallel photovoltaic assembly string enters a safe mode. When other photovoltaic power optimizers of the photovoltaic group string branches generating parallel arcs among the photovoltaic modules detect that current reverse-irrigation occurs to the photovoltaic group string branches where the photovoltaic group string branches are located, and the reverse-irrigation current is higher than a preset reverse-irrigation current threshold value, the judgment circuit generates parallel arc faults, and then the sub control module controls the sub control module to switch the sub control module to a safe working mode. After all power optimizers of the photovoltaic string branches with parallel arc faults enter a safe working mode, other photovoltaic strings without parallel arc faults in the parallel photovoltaic strings are short-circuited, so that the power optimizers in the strings detect that the output voltage of the power optimizers is lower than a preset voltage threshold value and enter the safe working mode; all power optimizers with parallel photovoltaic strings enter a safe working mode, and parallel arcs and reverse perfusion states in the arrays of the photovoltaic strings in the parallel photovoltaic string branches disappear. The remaining operating point 11 of the other strings of photovoltaic strings that do not have parallel arcs is the maximum operating point of the strings of photovoltaic strings.

In summary, the application realizes the reverse-filling protection of the photovoltaic string in a mode of being different from adding the anti-reverse diode in the branch of the photovoltaic string, can rapidly realize the cutting of the parallel arc when the parallel arc or the short circuit fault occurs, and rapidly positions the position where the parallel arc or the short circuit fault occurs.

It should be understood that the above description is only illustrative of the preferred embodiments of the present application and the technical principles employed. It will be apparent to those skilled in the art that various modifications, equivalents, variations, and the like can be made to the present application. However, such modifications are intended to fall within the scope of the present application without departing from the spirit of the present application. In addition, some terms used in the description and claims of the present application are not limiting, but are merely for convenience of description.

Claims

1. The photovoltaic system direct current parallel arc protection and positioning system with the anti-perfusion function is characterized by comprising a plurality of sub-control modules which are used for switching a power optimizer of a front stage corresponding to a control fault point position from an MPPT working mode to a safe working mode when the parallel arc fault of the photovoltaic system is detected, and a central controller which is in communication connection with each sub-control module, wherein the sub-control modules are used for sending operation mode information of the corresponding controlled power optimizers to the central controller after completing control actions of executing the safe working mode switching, and the central controller is used for resolving out the position of the power optimizers which are in the safe working mode and are carried in the operation mode information to realize the positioning of the fault point position and automatically anti-perfusion and anti-perfusion protection of the fault point position.

2. The system according to claim 1, wherein the method for controlling the power optimizer in the photovoltaic string branch with reverse current filling to switch to the safe operation mode by the sub-control module to control the pre-stage of the parallel arc fault point and/or the current reverse filling is that the power optimizer in the photovoltaic power generation system detects that the output voltage is lower than a preset voltage threshold value, and/or detects that the current reverse filling occurs in the photovoltaic string branch with reverse current filling is higher than a preset reverse current threshold value, and when the reverse filling current is higher than the preset reverse current threshold value, the determining circuit generates a parallel arc fault, and then the sub-control module controls the sub-control module to switch to the safe operation mode by itself, the method for switching to the safe operation mode is that:

the sub-control module (10) of the power optimizer drives a first switch (20) in the power optimizer to be turned off and drives a second switch (30) to be turned on so as to control a photovoltaic power generation unit connected with the power optimizer to stop outputting photovoltaic power, and therefore the operation state of the power optimizer is switched to a safe working mode.

3. The photovoltaic system direct current parallel arc protection and positioning system with reverse current function according to claim 2, wherein the power optimizer comprises the sub-control module (10), the first switch (20), the second switch (30), an input capacitor Cin, an output capacitor Cout and an energy storage inductor L; the grid electrode of the first switch (20) is connected with an HD-driver pin of the sub-control module; the grid electrode of the second switch (30) is connected with an LD-driver pin of the sub control module; one end of the energy storage inductor L is connected with the source electrode of the first switch (20), the other end of the energy storage inductor L is connected with one end of the output capacitor Cout, and the other end of the output capacitor Cout is connected with the source electrode of the second switch (30); the input capacitor Cin is connected in parallel between the positive output end and the negative output end of the photovoltaic power generation unit.

4. The dc parallel arc protection and positioning system with anti-current function according to claim 1, wherein the sub-control module controls the protection method of parallel arcs and current anti-current between components inside an array of a photovoltaic string in a parallel photovoltaic string branch, comprising the steps of:

if yes, stopping generating a trimming instruction to control to close a trimming switch piece (103), and maintaining the trimming switch piece (103) in a closed state until the fact that the heartbeat packet is received is judged to be normal is judged, after the trimming switch piece (103) is closed, the output voltage of the power optimizer is pulled down to be below a preset voltage threshold value, and the sub-control module of the power optimizer uses the trimming switch piece as an instruction to control the power optimizer to switch and maintain in a safe working mode;

5. The photovoltaic system direct current parallel arc protection and positioning system with reverse perfusion function according to claim 4, wherein in step S1, the method for switching the power optimizer to the safe working mode is as follows:

the sub-control module of the power optimizer drives a first switch (20) in the power optimizer to be turned off and drives a second switch (30) to be turned on so as to control a photovoltaic power generation unit connected with the power optimizer to stop outputting photovoltaic power, and therefore the operation state of the power optimizer is switched to a safe working mode.

6. The photovoltaic system direct current parallel arc protection and positioning system with the reverse perfusion function according to claim 2 or 4, wherein the sub-control module is a dual-operation mode BUCK power optimization ASIC chip, and the inside of the ASIC chip comprises a maximum power tracking circuit, a reference voltage generating circuit, a mode control circuit, a driving control circuit, a communication interface circuit and an internal power supply circuit;

the reference voltage generating circuit is used for providing a reference voltage for determining a duty ratio signal for the maximum power tracking circuit and providing a reference voltage for mode control for the mode control circuit by utilizing the power supply of the chip internal power supply circuit, and when the power optimizer operates in an MPPT working mode, the sub-control module controls the on-off of the first switch (20) and the second switch (30) according to the duty ratio signal so as to realize the maximum power tracking of the accessed photovoltaic power generation unit;

the signal output end of the Mode control circuit is connected with a Mode pin of the double-working-Mode BUCK power optimization ASIC chip, a first signal input end (101) of a low-voltage protection and safety trimming circuit (100) at the periphery of the chip is connected with the Mode pin, a second signal input end (102) is connected with a VDD pin of the chip, the signal output end is connected with a safety trimming control module, when the output voltage of the power optimizer is lower than the reference voltage and reaches a first threshold value, the sub control module controls the power optimizer to operate in a safety working Mode, and when the output voltage of the power optimizer is higher than the reference voltage and reaches a second threshold value, the sub control module controls the power optimizer to operate in an MPPT working Mode;

The drive control circuit comprises a logic control unit, a first drive unit and a second drive unit, wherein a first input end of the logic control unit is connected with a signal output end of the mode control circuit, a second input end of the logic control unit is connected with a signal output end of the maximum power tracking unit, the first output end and the second output end are respectively connected with signal input ends of the first drive unit and the second drive unit, the signal output ends of the first drive unit and the second drive unit are respectively connected with an HD-driver pin and an LD-driver pin of the sub control module, and the drive control circuit is used for controlling on-off of the first switch (20) and the second switch (30) according to preset control logic;

7. The photovoltaic system direct current parallel arc protection and positioning system with the reverse perfusion function according to claim 6, wherein the low voltage protection and safety trimming circuit (100) comprises a trimming switch element (103), a resistor R1, a resistor R2, a diode VD, a capacitor Cx and a safety trimming control module (200), the trimming switch element (103) is a normally closed PMOS tube, a forward body diode is connected between a source electrode and a drain electrode of the PMOS tube, the source electrode of the trimming switch element (103) is grounded, the drain electrode is connected to a Mode pin of a chip after being connected in series with the resistor R1, and a grid electrode is connected with a signal input end of the safety trimming control module; one end of the resistor R2 is connected with a VDD pin of the chip, and the other end of the resistor R2 is connected with the drain electrode of the PMOS tube and is grounded after being connected with the capacitor Cx; the anode of the diode VD is connected with the drain electrode of the PMOS tube, and the cathode of the diode VD is connected with the V0 pin of the chip;

The safety trimming control module is used for obtaining working voltage by taking electricity from the photovoltaic power generation unit through an auxiliary power supply, and is used for detecting output current of the power optimizer, when the output current of the power optimizer is detected to be smaller than a preset counter-current threshold value, the power optimizer is judged not to have current counter-current, and a trimming instruction is generated to control a normally-closed trimming switch element (103) in the low-voltage protection and safety trimming circuit (100) to be disconnected and maintain the normally-closed trimming switch element in a disconnected state;

when the output current of the power optimizer is detected to be higher than the preset reverse current threshold, the power optimizer is judged to generate current reverse current, and the safety repair control module stops generating a repair instruction to control the repair switch (103) to be closed and maintain the repair switch in a closed state.

8. The photovoltaic system direct current parallel arc protection and positioning system with reverse perfusion function according to claim 7, wherein the safety trimming control module is further used for detecting whether the heartbeat packet communication signal generated by the central controller is normal,

if the heartbeat packet communication signal is normal, generating a trimming instruction to control the trimming switch piece (103) to be disconnected and maintain the disconnection state until the heartbeat packet communication signal is judged to be abnormal;

9. The photovoltaic system direct current parallel arc protection and positioning system with the reverse perfusion function according to claim 1, wherein the central controller comprises a communication module and a decision module, wherein the communication module is used for establishing communication connection with each sub-control module arranged at a corresponding current detection point position so as to receive the operation mode information of the corresponding power optimizer sent by each sub-control module, and is also used for sending heartbeat packet communication signals to the corresponding sub-control module;

10. The photovoltaic system direct current parallel arc protection and positioning system with the reverse perfusion function according to claim 1, wherein the power optimizer connected into the photovoltaic power generation unit is used as a unit, a plurality of units are mutually connected in series to form a photovoltaic group string, the output ends of the photovoltaic group strings are connected onto a direct current bus of a photovoltaic inverter in parallel, the alternating current side of the photovoltaic inverter is connected to a power grid to form the photovoltaic power generation system, an isolating switch device is arranged in a path of each photovoltaic group string connected with the direct current bus, each isolating switch device is in communication connection with the central controller, after the central controller receives the operation mode information, the central controller analyzes the position of the power optimizer in a safe operation mode carried in the operation mode information to realize the positioning of the fault point, then a switch control signal is generated and sent to the corresponding isolating switch device, and the isolating switch device receives the switch control signal and controls the disconnection of the photovoltaic inverter string with the fault.