Safe photovoltaic power generation system

Abstract

The present invention discloses a safe photovoltaic power generation system, which relates to the field of photovoltaic grid-connected power generation. The present invention can solve the shutdown control problem at the component level. It configures a shutdown circuit corresponding to each photovoltaic DC source in a series circuit. The shutdown circuit is independently adjusted by the state of a sub-control module and is configured with a central control module that can send an excitation communication signal to the sub-control module. The sub-control module can automatically operate in a safety protection mode controlled by the excitation communication signal and a normal working mode that does not need to be controlled by the excitation communication signal according to the current situation of the shutdown circuit. During power generation, the present invention can avoid power generation losses caused by communication stability between the central control module and the sub-control module in the high-current power generation interval. At the same time, in the event of external disasters, system failures and installation and maintenance, the voltage drop of the string can be automatically reduced to a safe range, and the power generation in the morning and evening can be increased, thereby comprehensively achieving safety, low cost and high power generation.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic grid-connected power generation, and in particular to a safe photovoltaic power generation system for reducing the open-circuit voltage of a photovoltaic string in a series circuit (photovoltaic string) composed of photovoltaic direct current sources (photovoltaic modules) that can be individually and controllably connected in series, as well as an operation and maintenance method for the safe photovoltaic power generation system and an optimizer that can be configured in the safe photovoltaic power generation system. Background Art

[0002] Current photovoltaic power generation systems still lack specific safety protection measures. Typically, the output terminals of individual photovoltaic modules are connected in series to form a series circuit. Under normal power generation conditions, the output voltage of this series circuit often exceeds 200V, and some large-scale photovoltaic power station projects even exceed 1000V, constituting a dangerous voltage. This is particularly true during the construction of photovoltaic projects, as well as during the inspection and maintenance of photovoltaic power stations, where there is a risk of electric shock for construction and maintenance personnel.

[0003] To address safety issues in photovoltaic power generation systems, US Patent No. US10312857B2 discloses a watchdog-type shutoff device that continuously monitors signals from a central controller. To ensure the watchdog shutoff device receives signals from the central controller safely and reliably, current PV module shutdown solutions generally employ power line carrier communication (PLC). Both of these solutions require not only the addition of a corresponding transmitter module to the PV inverter system, but also an additional receiver module in the PV module's rapid shutoff device or power optimizer. Because these systems rely on PLC, signal transmission attenuation is a concern. This limits the number and length of PV module strings that can be affected by each rapid shutdown device. Furthermore, because PLC transmission is not transmitted via a busbar, it is not suitable for use in combiner boxes in centralized PV power plants. Consequently, PLC not only increases the cost and power consumption of the PV system, but also increases the number of signal source transmitters and receivers that may fail.

[0004] In addition, in the prior art, China's patent number CN201710114503.5 discloses a command sending device and a photovoltaic module shutdown system. The system controls the shutdown and opening of each photovoltaic module through a wireless communication command sending device. However, the shutdown device corresponding to the photovoltaic module is prone to wireless communication disconnection, which in turn affects the reliability of the shutdown operation due to the failure to receive the shutdown command, or triggering and other situations will affect the normal operation of the entire photovoltaic power generation system.

[0005] In summary, the issue of PV module-level shutdown inevitably presents a difficult balance between cost and reliability. Consequently, these safe PV power generation systems have been difficult to commercialize in China, leading to significant safety risks in my country's PV power generation industry. Summary of the Invention

[0006] In order to address the defects of the existing technology, the main purpose of the present invention is to provide a safe photovoltaic power generation system, and to provide an operation and maintenance method and a photovoltaic power optimizer in conjunction with it, which can realize the series circuit (photovoltaic string) composed of photovoltaic DC sources (photovoltaic modules) in the system that are individually connected in a controlled manner. It can solve the problem that various distributed control schemes in traditional photovoltaic power generation systems are difficult to balance safety, cost and power generation efficiency.

[0007] In order to embody the characteristics of the above-mentioned safe photovoltaic power generation system, the present invention further provides an operation and maintenance method of the safe photovoltaic power generation system, and an optimizer that can be configured in the safe photovoltaic power generation system.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] In a first aspect, embodiments of the present application provide a safe photovoltaic power generation system, which includes a power acquisition circuit and a control circuit;

[0010] The power acquisition circuit is a series circuit formed by connecting the output ends of multiple shutdown circuits in series, and the input end of each shutdown circuit is connected to a photovoltaic DC source, so as to safely acquire power from each photovoltaic DC source in a distributed manner and output it to the output end of the series circuit;

[0011] The control circuit includes: a central control module and a sub-control module;

[0012] The sub-control module is used to adjust the corresponding shutdown circuit to switch between a connected state and a disconnected state. The disconnected state of the shutdown circuit means that the corresponding photovoltaic DC source is individually disconnected from the series circuit by means of the corresponding shutdown circuit. The connected state of the shutdown circuit means that the solar current generated by the photovoltaic DC source is exported to the series circuit through the corresponding shutdown circuit.

[0013] The central control module is used to send an excitation communication signal to the sub-control module, and is used to stop sending the excitation communication signal;

[0014] The sub-control module of the shutdown circuit is used to obtain the current parameter signal of the shutdown circuit corresponding to the shutdown circuit; when the current parameter signal of the shutdown circuit changes to the range of, the sub-control module is used to operate in the corresponding working mode;

[0015] The working modes include normal working mode and safety protection mode; the safety protection mode means that the sub-control module receives the excitation communication signal from the central control module, and adjusts the state of the shutdown circuit according to whether the excitation communication signal is detected within a certain time period. If so, the sub-control module is used to adjust the shutdown circuit to a connected state or maintain a connected state; if not, the sub-control module is used to adjust the shutdown circuit to a disconnected state or maintain a disconnected state; the normal working mode refers to a working mode other than the safety protection mode.

[0016] The above-mentioned safe photovoltaic power generation system may optionally include: when the current parameter signal of the shutdown circuit changes to a range, the sub-control module is used to operate in the corresponding working mode including:

[0017] When the current parameter signal changes to below the preset current threshold, the working mode of the sub-control module is adjusted from the normal working mode to the safety protection mode; correspondingly, when the current parameter signal changes to not below the preset current threshold, the working mode of the sub-control module is adjusted from the safety protection mode to the normal working mode.

[0018] The above-mentioned safe photovoltaic power generation system may optionally include that when the current parameter signal changes to below the preset current threshold, it at least includes: the continuous change of the current parameter signal approaches the preset current threshold, or the current parameter signal remains below the preset current threshold.

[0019] The above-mentioned safe photovoltaic power generation system may optionally include: the central control module is used to send the excitation communication signal via a wireless signal, and the sub-control module is used to receive the wireless signal.

[0020] The above-mentioned safe photovoltaic power generation system may optionally include:

[0021] In the connected state of the corresponding shutdown circuit, the sub-control module is used to maintain the shutdown circuit in the connected state if the excitation communication signal is detected within a certain period of time, and is used to adjust the shutdown circuit to the disconnected state if the excitation communication signal is not detected within a certain period of time;

[0022] In the disconnected state of the corresponding shutdown circuit, the sub-control module is used to adjust the shutdown circuit to the connected state when the excitation communication signal is detected within a certain period of time, and to maintain the shutdown circuit in the disconnected state when the excitation communication signal is not detected within a certain period of time.

[0023] The above-mentioned safe photovoltaic power generation system may optionally include that the normal operating mode includes: the corresponding shutdown circuit is in a connected state, and the sub-control module is used to independently adjust the state transition of the corresponding shutdown circuit without responding to the excitation communication signal from the central control module.

[0024] The above-mentioned safe photovoltaic power generation system may optionally include an inverter, wherein the output end of one of the series circuits is connected to the inverter, or the output end of a series-parallel circuit composed of at least two mutually parallel series circuits is connected to the inverter; the central control module obtains operating power from the output end of the inverter, accompanied by simultaneous opening of both sides of the power supply point of the central control module, so that the central control module will lose power supply and stop sending excitation communication signals.

[0025] Specifically, the central control module obtains operating power from the output end of the inverter, and can obtain power from the grid side or the inverter side. In the event of a short circuit on the grid side, the central control module stops sending the excitation communication signal due to loss of power supply.

[0026] The above-mentioned safe photovoltaic power generation system may optionally include that the inverter is configured with a control interface, which is connected to and receives instructions from a system fault detection device, and / or a user command input device, and / or a remote control gateway; the control interface is used to receive and respond to a shutdown instruction to the inverter, and in response to the shutdown instruction, the central control module stops sending the excitation communication signal.

[0027] Specifically, when the inverter is shut down due to a shutdown command, the central control module stops sending the excitation communication signal; when the inverter is shut down due to a shutdown command, the series circuit corresponding to the inverter will be switched to an open circuit, and the sub-control module will be set in a safety protection mode because the current of the shutdown circuit will be lower than the preset current threshold, and the shutdown circuit will be adjusted to a disconnected state because no excitation communication signal is detected, so that the inverter is shut down at least due to the above-mentioned shutdown command, and the output end voltage of the series circuit is reduced to within a safe voltage range.

[0028] Specifically, when the photovoltaic power station is undergoing component replacement, maintenance, or cleaning and operation, when the grid-connected side of the grid-connected photovoltaic inverter is disconnected, the central control module stops sending the excitation communication signal due to the loss of power supply; the sub-control module will be set in a safety protection mode because the current of the shutdown circuit will be lower than the preset current threshold, and the shutdown circuit will remain disconnected because no excitation communication signal is detected, so that the output end voltage of the series circuit is reduced to a safe voltage range, until the replacement component maintenance, cleaning and operation of the above-mentioned photovoltaic power station is completed, the central control module resumes power supply and sends the excitation communication signal, and the output voltage of the series circuit returns to normal.

[0029] In a second aspect, embodiments of the present application provide an operation and maintenance method for a safe photovoltaic power generation system, which is applied to a safe photovoltaic power generation system including a power acquisition circuit and a control circuit, wherein the power acquisition circuit is a series circuit formed by connecting the output ends of multiple shutdown circuits in series, and the input end of each shutdown circuit is respectively connected to a photovoltaic DC source, so as to safely acquire power from each photovoltaic DC source in a distributed manner and output it to the output end of the series circuit;

[0030] The control circuit includes: a central control module and a sub-control module; the sub-control module is used to adjust the corresponding shutdown circuit to switch between a connected state and a disconnected state. The disconnected state of the shutdown circuit refers to disconnecting the corresponding photovoltaic DC source from the series circuit by means of the corresponding shutdown circuit. The connected state of the shutdown circuit refers to exporting the solar current generated by the photovoltaic DC source to the series circuit through the corresponding shutdown circuit; the central control module is used to send an excitation communication signal to the sub-control module, and to stop sending the excitation communication signal. The method includes the steps of:

[0031] The sub-control module of the shutdown circuit obtains a current parameter signal of the corresponding shutdown circuit;

[0032] When the current parameter signal of the shutdown circuit changes to the range of, the sub-control module operates in the corresponding working mode; the working mode includes a normal working mode and a safety protection mode:

[0033] The safety protection mode means that the sub-control module receives an excitation communication signal from the central control module and adjusts the state of the shutdown circuit according to whether the excitation communication signal is detected within a certain period of time. If so, the sub-control module adjusts the shutdown circuit to a connected state or maintains the connected state; if not, the sub-control module adjusts the shutdown circuit to a disconnected state or maintains the disconnected state;

[0034] The normal operating mode refers to an operating mode other than the safety protection mode.

[0035] In a third aspect, an embodiment of the present application provides an optimizer that can be configured in a safe photovoltaic power generation system, the optimizer comprising a shutdown circuit and a sub-control module, the shutdown circuit comprising an input terminal for connecting to at least one photovoltaic DC source, and an output terminal for connecting in series to form a series circuit;

[0036] The sub-control module is used to adjust the corresponding shutdown circuit to switch between a connected state and a disconnected state. The disconnected state of the shutdown circuit means that the corresponding photovoltaic DC source is individually disconnected from the series circuit by means of the corresponding shutdown circuit. The connected state of the shutdown circuit means that the solar current generated by the photovoltaic DC source is exported to the series circuit through the corresponding shutdown circuit.

[0037] The sub-control module includes:

[0038] A sampling unit, used to obtain a current parameter signal of a corresponding shutdown circuit;

[0039] A mode setting unit, configured to cause the sub-control module to operate in a corresponding working mode when the current parameter signal of the shutdown circuit changes to a range;

[0040] The working mode includes a normal working mode and a safety protection mode: the safety protection mode means that the sub-control module receives an excitation communication signal from outside the optimizer, and adjusts the state of the shutdown circuit according to whether the excitation communication signal is detected within a certain time period. If so, the sub-control module adjusts the shutdown circuit to a connected state or maintains a connected state; if not, the sub-control module adjusts the shutdown circuit to a disconnected state or maintains a disconnected state; the normal working mode refers to a working mode other than the safety protection mode.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The safe photovoltaic power generation system of the present invention is mainly configured by configuring a shutdown circuit for each photovoltaic DC source in the series circuit, and the shutdown circuit is adjusted by the sub-control module to switch between the shutdown state and the connected state, and is configured with a central control module that can send an excitation communication signal to the sub-control module. The sub-control module is correspondingly set to a safety protection mode controlled by the central control module and a normal working mode not required to be controlled by the central control module according to the current parameter of the shutdown circuit. When the series circuit is in an open circuit low current state, each DC source under it is automatically shut down, so that the series circuit can maintain power generation under the low current state of low radiation in the morning and evening, thereby increasing the power generation; and avoiding the power generation loss caused by the unstable transmission of the excitation communication signal between the central control module and the sub-control module in the medium and high current power generation range (accounting for more than 98.8% of the total power generation).

[0043] (2) The present invention can circumvent the high requirements of the watchdog type fast shutdown device for the continuous reliability of heartbeat signal acquisition. There is no need to continuously send heartbeat communication signals through the PLC circuit, and there is no need to send periodic excitation pulse sources on the DC bus, which reduces the use of special signal receivers. The signal transmission between the central control module and the sub-control module can be completed using a wireless communication method with lower stability, and is not restricted by the number and length of photovoltaic component strings and the parallel connection of the strings. At the same time, since the excitation signal can be transmitted wirelessly, it is particularly suitable for large-scale, low-cost, reliable and safe applications in large and medium-sized industrial and commercial rooftop distributed power stations and floating photovoltaic power stations in simple terrain.

[0044] (3) The safe photovoltaic power generation system of the present invention also has the beneficial effect of stopping the transmission of the excitation communication signal of the central control module during the stage of installation and maintenance, thereby stably, safely and reliably disconnecting each DC source from the series circuit and reducing the voltage of the series circuit to a safe range, thereby ensuring the safety of the installation and maintenance personnel.

[0045] (4) The safe photovoltaic power generation system of the present invention also has the following beneficial effects: in emergency situations such as fire, earthquake, flood, hurricane, or when the photovoltaic power generation system is detected to have an arc, leakage or other faults causing the photovoltaic string to open, the inverter is shut down and the output end of the series line is switched to an open circuit, and the excitation communication signal of the central control module is automatically stopped, and the DC sources configured with the disconnect circuit are automatically disconnected, so that the voltage of the series line is reduced to a safe range, thereby ensuring the safety of the photovoltaic power generation system.

[0046] The present invention will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of the circuit structure of a safe photovoltaic power generation system according to an embodiment;

[0048] Figure 2 A schematic diagram of a partial structure of a safe photovoltaic power generation system including an off-state switch in an embodiment;

[0049] Figure 3 A schematic diagram of a partial structure of a safe photovoltaic power generation system including a connected state switch in an embodiment;

[0050] Figure 4 A schematic diagram of a partial structure of a safe photovoltaic power generation system including an optimizer according to an embodiment;

[0051] Figure 5 Schematic diagram of the circuit and program structure of the sub-control module of the embodiment;

[0052] Figure 6Schematic diagram of the operation flow of the sub-control module of the operation and maintenance method of the photovoltaic power generation system according to the embodiment.

[0053] The accompanying drawings are marked as follows: 11, photovoltaic module; 20, shutdown circuit; 201, positive line; 202, negative line; S, switch; D, diode; 21, sub-control module; 211, microcontroller; 212, drive unit; 213, power supply unit; 214, sampling unit; 215, wireless receiving unit; 216, mode setting unit; 22, junction box; 23, conversion circuit; M1, first switch tube; M2, second switch tube; L1, power supply Sensor; C1, input capacitor; C2, output capacitor; D1, freewheeling diode; D2, bypass diode; 2a, shutdown device; 2b, optimizer; 30, series line; 40, central control module; 41, auxiliary power supply; 42, wireless transmission unit; 50, inverter; 51, inverter circuit; 52, inverter controller; 53, fault detection device; 54, emergency shutdown button; 55, gateway; 56, output relay; 60, grid-side circuit breaker. DETAILED DESCRIPTION

[0054] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the specific embodiments of the present invention are described in further detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0055] like Figure 1 As shown, according to an embodiment of the present invention, a circuit structure of a safe photovoltaic power generation system is disclosed.

[0056] The safe photovoltaic power generation system of this embodiment includes, on one hand, a power acquisition system. In a typical embodiment, the power acquisition circuit includes a plurality of photovoltaic modules 11, junction boxes 22 corresponding to the output ends of the photovoltaic modules 11, a series circuit 30 that connects the output ends of each junction box 22 in series to collect power, and an inverter 50 that acquires power from the output end of the series circuit 30 and converts it. Each junction box 22 is equipped with a disconnect circuit 20, and the disconnect circuit 20 has an on state and an off state. The on state means that the photovoltaic module 11 is individually disconnected from the module series circuit 30, while the off state means that the electrical energy generated by the photovoltaic module 11 is exported to the series circuit 30. It can be seen that the power acquisition system can safely acquire power from each photovoltaic DC source 10 in a distributed manner and output it to the output end of the series circuit 30.

[0057] The photovoltaic power generation system of this embodiment also includes a control circuit for ensuring the safe and reliable operation of the power acquisition circuit. In a typical embodiment, this control circuit includes a central control module 40 and sub-control modules 21 connected to the shutdown circuits 20. Each sub-control module 21 is housed in a junction box 22 and is used to adjust the switching between connected and disconnected states of the connected shutdown circuits 20 and to obtain current parameters of the shutdown circuits 20. A communication connection is established between the central control module 40 and the sub-control modules 21. The central control module 40 can periodically send or stop sending excitation communication signals; the sub-control modules 21 can also detect and receive these excitation communication signals. When the current in the shutdown circuits 20 is low, the sub-control modules 21 automatically operate in a safety protection mode. When the current in the shutdown circuits 20 is high, the sub-control modules 21 automatically operate in a normal operating mode. The logic used by the sub-control modules 21 to adjust the state of the shutdown circuits 20 differs depending on the mode. In the safe operating mode, the sub-control module 21 adjusts the state of the shutdown circuit 20 based on whether the excitation communication signal is currently detected. If so, the shutdown circuit 20 is adjusted to the connected state or maintained in the connected state; if not, the shutdown circuit 20 is adjusted to the disconnected state or maintained in the disconnected state. In the normal operating mode, the sub-control module 21 independently adjusts the state of its corresponding shutdown circuit 20 without detecting the excitation communication signal. If it adjusts the shutdown circuit 20 to the disconnected state, it is not related to whether the central control module 40 is currently sending the excitation communication signal.

[0058] During the operation of the safe photovoltaic power generation system of this embodiment, the central control module 40 adjusts the on or off of the shutdown circuits 20 distributed in the photovoltaic components 11 in the system by sending an excitation communication signal. In coordination, each sub-control module 21 can also intelligently choose to respond to the excitation communication signal of the central control module 40 when there is a risk, or intelligently and autonomously adjust the shutdown circuit 20 when it is safer, based on the current current range. Combined with the startup and shutdown of the inverter 50 due to various factors, it can affect the change of the current in the series line 30, and correspondingly affect the mode switching of each sub-control module 21, thereby realizing on or off adjustment at the component level and realizing the functions of safe and reliable installation, maintenance and daily operation of the photovoltaic power generation system.

[0059] Still refer to Figure 1 , and refer to Figure 1 Partially enlarged Figure 2 and 3The power acquisition system of this embodiment specifically comprises at least two photovoltaic strings, each containing n photovoltaic modules 11. Each photovoltaic module 11 is provided with a junction box 22, and each junction box 22 is provided with a shutdown circuit 20 and a sub-control module 21. The shutdown circuit 20 comprises a positive line 201 and a negative line 202. The positive line 201 and the negative line 202 can be electrically connected to the positive and negative output terminals of the photovoltaic modules 11 via connectors at the input of the junction box 22, thereby forming a distributed power acquisition system for the photovoltaic DC source 10. The positive line 201 and the negative line 202 can be electrically connected to other adjacent photovoltaic modules 11 connected in series via connectors at the output of the junction box 22, or can serve as the output terminals of the photovoltaic string, thereby forming a series circuit 30 composed of the output terminals of multiple shutdown circuits 20 connected in series. At least one switch element S (connected in series to the positive line 201 in the figure) is provided on either the positive line 201 or the negative line 202. The sub-control module 21 controls the switch S connected to the switch. Figure 2 As shown, the switch S is disconnected by the sub-control module 21, and the photovoltaic assembly 11 is individually disconnected from the series circuit 30, and then the shutdown circuit 20 is adjusted to the disconnected state or maintained in the disconnected state; Figure 3 As shown, when the switch element S is connected by the sub-control module 21, the photovoltaic assembly 11 can normally extract solar energy to the series circuit 30, and the shutdown circuit 20 is adjusted to the connected state or maintained in the connected state. Each sub-control module 21 has the function of detecting the current parameter on the positive line 201 or negative line 202 of the corresponding shutdown circuit 20 and operates in the corresponding mode based on the current. Each sub-control module 21 has the function of detecting the excitation communication signal, allowing it to detect whether the excitation communication signal is present in the safety protection mode.

[0060] It will be appreciated that, in a preferred embodiment, a diode D is connected in parallel to the output side of the positive circuit 201 and the negative circuit 202 to bypass the current when the circuit is turned off. In another preferred embodiment (not shown in the figure), another switch is connected in parallel between the positive circuit 201 and the negative circuit 202 to conduct when the series switch is disconnected, thereby maintaining smooth flow of the bypass current.

[0061] Regarding the specific structure of the power acquisition circuit, it can be understood that in other embodiments, the power acquisition circuit can also be that the output end of the above-mentioned series circuit 30 of a single string, or the output end of the above-mentioned series circuit 30 of multiple strings connected in parallel is connected to a DC combiner box, and the output end of the DC combiner box is connected to the input end of the photovoltaic inverter 50, so that after the convergence, the AC-DC conversion is uniformly performed in the photovoltaic inverter 50.

[0062] Regarding the corresponding configuration relationship between the photovoltaic module 11 and the shutdown circuit 20, it can be understood that the photovoltaic module 11 is a type of photovoltaic DC source 10. The input end of the shutdown circuit 20 can be connected to other devices that can obtain solar radiation and convert it into electrical energy. The output end of the photovoltaic module 11 is connected to the input end of the shutdown circuit 20, which refers to the output end of the plurality of solar cells in the array after being integrally packaged. In other embodiments, the output ends of some solar cell strings in a photovoltaic module 11 connected in series / parallel / series-parallel are independently configured with a shutdown circuit 20, or the output ends of a plurality of photovoltaic modules 11 connected in series / parallel / series-parallel are configured with a shutdown circuit 20.

[0063] Regarding signal exchange between the central control module 40 and each sub-control module 21, in a preferred embodiment, the central control module 40 utilizes a wireless signal transmission function based on one of Bluetooth, Zigbee, and Wi-Fi, while the sub-control modules 21 utilize a corresponding wireless signal reception function. This allows the central control module 40 to transmit excitation communication signals via wireless communication and receive them from the sub-control modules 21. In other embodiments, the central control module 40 and its sub-control modules 21 may transmit excitation communication signals via wired communication or other wireless communication methods.

[0064] It should be noted that, in a typical aspect, reference Figure 2 and 3 The shutdown circuit 20 and the sub-control module 21 are combined to form a shutdown device 2a, which is configured in the junction box 22 of the photovoltaic module 11.

[0065] In another preferred aspect of this embodiment, the shutdown circuit 20 and sub-control module 21 are combined to form a photovoltaic power optimizer 2b, which is disposed within the junction box 22 of the photovoltaic module 11. This photovoltaic power optimizer 2b comprises a shutdown circuit 20 that controls the connection and disconnection between the input and output terminals of the optimizer 2b. It also comprises a DC-DC converter circuit 23 and a control circuit that coordinately adjusts the duty cycle of the converter circuit 23. Adjusting the duty cycle ensures that the current flowing through the series line 30 connected to the output terminal of the optimizer 2b matches the current flowing through the series line 30. Furthermore, the photovoltaic power optimizer 2b is configured to obtain input current and voltage parameters at the input terminal of the optimizer 2b, i.e., the output side of the photovoltaic module 11, and to track the obtained parameters to the maximum power point (MPP) of the corresponding photovoltaic module 11. Furthermore, the converter circuit 23 is driven to perform DC power conversion via a pulse-width modulated (PWM) control signal.

[0066] Reference again Figure 4The optimizer 2b in the safe photovoltaic power generation system of this embodiment includes a conversion circuit 23, a shutdown circuit 20, and a sub-control module 21. The conversion circuit 23 is a Buck-type DC chopper circuit structure, which includes: an input capacitor C1, a first switch tube M1, an inductor L1, a freewheeling diode D1, an output capacitor C2, and a bypass diode D2. Among them, the shutdown circuit 20 includes a second switch tube M2. Specifically, the first switch tube M1 and the second switch tube M2 are n-type normally open switch field effect transistors. The first switch tube M1, the inductor L1, and the second switch tube M2 are connected in series in the positive line 201 in sequence, and the controlled gates of the first switch tube M1 and the second switch tube M2 are respectively connected to the sub-control module 21. Input capacitor C1 (positive and negative) circuits 202 are connected in parallel between the input of optimizer 2b and the first switch M1, filtering the pre-conversion current at the input of optimizer 2b. Freewheeling diode D1 (positive and negative) circuits 202 are connected in parallel between the first switch M1 and inductor L1. This circuit primarily maintains the continuity between inductor L1 and series circuit 30 when the first switch M1 is off, and is replaceable by a different switch. Output capacitor C2 (positive and negative) circuits 202 are connected in parallel between inductor L1 and the second switch M2, filtering the converted power at the output of optimizer 2b. Sub-control module 21 is configured to control the operation of first switch M1 via a pulse width modulation (PWM) control signal and to control the switching of first switch M1 between on and off using a switch control signal, thereby adjusting the switching between the disconnected and connected states of optimizer 2b. It is understandable that the conversion circuit 23 may also be a boost type DC chopper circuit structure, or a Buck-Boost DC chopper circuit structure.

[0067] The photovoltaic power generation system of this embodiment is preferably equipped with an optimizer 2b. Compared to conventional junction boxes 22 equipped with only bypass diodes, the photovoltaic power optimizer 2b can adjust the duty cycle to ensure consistent current at the output terminals of each optimizer 2b in the series circuit 30. Furthermore, the duty cycle can be adjusted to track the voltage at the input terminal of the optimizer 2b, ensuring operation at the maximum power point and improving the power generation efficiency of the photovoltaic assembly 11. Furthermore, a shutdown circuit 20 is provided within the optimizer 2b. This shutdown circuit 20 utilizes the optimizer 2b's own control circuitry for data acquisition, logic operation, judgment, driving, and communication, operating under a logic program designed for safe and reliable on / off control.

[0068] It is understood that the shutdown circuit 20 can include two or more switches connected in series to ensure safety when the shutdown circuit 20 is disconnected. The shutdown circuit 20 can also utilize the switches in the conventional optimizer 2b circuit structure, namely, utilizing the first switch M1 in the conversion circuit 23 to control the connection or disconnection of the positive line 201, without providing the second switch M2. It is understood that the sub-control module 21 configured in the optimizer 2b can utilize the control components in the optimizer 2b circuit structure. Specifically, the sub-control module 21 can be used to drive the operation of the first switch M1 in the conversion circuit 23 to balance the output current by adjusting the duty cycle and tracking the maximum power point of the photovoltaic module 11. It is understood that the freewheeling diode D1 can be replaced by a switch and controlled by a control signal opposite to that of the first switch M1. When the first switch M1 is disconnected, the switch is switched to a connected state, thereby short-circuiting the input terminal of the inductor L1; when the first switch M1 is turned on, the switch is switched to a disconnected state, thereby disconnecting the short circuit.

[0069] refer to Figure 5 , is a hardware-level implementation of the sub-control module 21 in this embodiment. The sub-control module 21 includes at least a sampling unit 214 for measuring current parameters, a driving unit 212 for driving the switch with appropriate power, a receiving unit for detecting wireless signals, a power supply unit 213 for providing power to the sub-control module 21, and a microcontroller 211 for calculating the results of the sampling unit 214, outputting control signals to the driving unit 212, and setting the operating mode. The above hardware-level structure of the sub-control module 21 is similarly applicable to the example of the circuit breaker 2a. In the example of the optimizer 2b, the sub-control module 21 also includes a collection unit for measuring the input and output currents of the optimizer 2b, as well as a sampling unit 214 for measuring the output current of the optimizer 2b. It should be noted that in the circuit structure of the optimizer 2b, due to the presence of inductor L1, the currents on both sides of inductor L1 will be different. The optimizer 2b of this embodiment switches to a corresponding operating mode based on the current parameter on its output side. In other embodiments, it may also be based on the current parameter on the side of the inductor L1 close to the input end of the optimizer 2b.

[0070] Reference again Figure 1In the photovoltaic power generation system of this embodiment, the photovoltaic inverter 50 is a device used to convert the DC power generated by the photovoltaic modules 11 into constant-frequency AC power. It includes an inverter circuit 51 and an inverter controller 52. The inverter circuit 51 includes a DC input side for connecting to the output end of the series circuit 30 and an AC output side for connecting to the power grid. The inverter controller 52 is connected to the inverter circuit 51, and the inverter circuit 51 converts the DC power output of the series circuit 30 into AC power for output on the AC side of the inverter circuit 51. The AC side of the inverter circuit 51 is equipped with an output relay 56. By turning off the output relay 56, the series circuit 30 on the DC side of the inverter circuit 51 is disconnected. The AC side of the inverter circuit 51 is connected to the grid-connected box, which is equipped with a grid-side circuit breaker 60. By turning off the grid-side circuit breaker 60, the AC side of the inverter current is disconnected from the grid.

[0071] Typically, the central control module 40 of this embodiment also includes an auxiliary power supply 41 to provide operating power, and a wireless transmission unit 42 for transmitting communication signals. The auxiliary power supply 41 draws power from an output relay 56 on the AC side of the inverter circuit 51 and a grid-side circuit breaker 60 of the grid-connected box. The auxiliary power supply 41 can draw power from the inverter circuit 51. When the output relay 56 of the inverter circuit 51 is disconnected, the auxiliary power supply 41 can draw power from the grid-connected box. When both the output relay 56 and the grid-side circuit breaker 60 are disconnected, the input voltage of the auxiliary power supply 41 falls below operating requirements, causing the central control module 40 to shut down and become unable to transmit excitation communication signals.

[0072] In a typical operation of the central control module 40, when the AC side of the inverter 50 is disconnected, the series line 30 is consequently opened, causing the current to drop to or near zero amperes, causing the sub-control module 21 to enter a safe mode. The central control module 40 can then draw power from the grid and controllably transmit or cease energizing communication signals. When both the output relay 56 and the grid-side circuit breaker 60 are closed, the central control module 40 loses power and ceases transmitting energizing communication signals. The inverter controller 52 is equipped with a control interface. In response to control commands from this control interface, the inverter controller 52 and the central control module 40 perform corresponding operations.

[0073] In a first preferred aspect, the control interface is connected to a system fault detection device 53, which is configured to detect faults including insulation resistance, leakage current (residual current detector, RCD), arcing (AFCI), or a combination thereof. When the control interface receives a shutdown control command due to a detected fault, the output relay 56 is turned off and the central control module 40 is prevented from transmitting energizing communication signals.

[0074] In a second preferred aspect, the control interface is connected to an emergency shutdown button 54 serving as a user command input device. Once the emergency shutdown button 54 is pressed, the control interface receives a shutdown control instruction, which turns off the output relay 56 and stops the central control module 40 from sending an excitation communication signal.

[0075] In a third preferred aspect, the control interface is connected to the power station's power supply and is controlled by remote commands from the gateway 55. When the control interface receives a shutdown control command from the gateway 55, the output relay 56 will be shut down and the central control module 40 will stop sending the excitation communication signal.

[0076] In a fourth preferred aspect, upon receiving the shutdown instruction, the control interface shuts down the output relay 56 and simultaneously shuts down the grid-side circuit breaker 60 , so that the central control module 40 stops sending the excitation communication signal due to power loss.

[0077] In this embodiment, whether the shutdown circuit 20 is configured in the example of the circuit breaker 2a or the example of the optimizer 2b, it functions to ensure the safe and reliable installation, maintenance, and daily operation of the photovoltaic power generation system. Embodiments of the present invention also include the safe operation and maintenance method of the photovoltaic power generation system described above, which includes operating logic provided in the sub-control module 21 and corresponding operating logic provided in the central control module 40.

[0078] The safe photovoltaic power generation system according to the present invention also has a corresponding operation and maintenance method. Figure 6 , and auxiliary reference Figure 5 , the operating logic of the sub-control module according to the present invention includes:

[0079] (1) Working mode setting

[0080] - Periodically acquire the electrical signal of the acquisition unit and obtain the current parameter Ao at the output end of the optimizer 2b;

[0081] -Compare the current parameter Ao with a preset current threshold (e.g. 0.4A);

[0082] - If the current parameter is less than the preset current threshold, the sub-control module 21 operates in a safety protection mode;

[0083] If the current parameter is not less than the preset current threshold, the sub-control module 21 is operated in the normal operating mode.

[0084] It should be noted that there are multiple ways to set the operating mode of the sub-control module 21 based on the current parameter. To avoid frequent mode switching, the current parameter signal can also continuously change and approach a preset current threshold. For example, when the current parameter is greater than the preset 0.4A, if it changes within a short period of time to less than the preset 0.4A, the sub-control module 21 will still be in the safety protection mode. Only when the current parameter exceeds 0.4A for a preset number of consecutive times within the detection cycle will the mode be adjusted to the normal operation mode.

[0085] It will be appreciated that, in a typical example, the current parameter is an electrical signal from a current sensor connected in series to the positive line 201 or the negative line 202 of the shutdown circuit 20. In other examples, the basis for adjusting the operating mode of the determination sub-control module 21 may also refer to changes in electrical signals from other devices configured on the interrupter 2a or optimizer 2b. For example, when the output end of the series circuit 30 is switched to an open circuit, the electrical signal of this device may be zero or near zero.

[0086] (1a) Security protection mode

[0087] The control logic of the sub-control module 21 for the shutdown circuit 20 in the safety protection mode (also the operation logic of the shutdown device 2a or the optimizer 2b) includes:

[0088] - detecting a periodic excitation communication signal;

[0089] - Determining whether a periodic excitation communication signal is detected;

[0090] - If the excitation communication signal is detected, a control signal indicating a connection instruction is output to the shutdown circuit 20 (to adjust the shutdown circuit 20 in the disconnected state to the connected state; to maintain the shutdown circuit 20 in the connected state in the connected state);

[0091] - If no excitation communication signal is detected, a control signal indicating a shutdown instruction is output to the shutdown circuit 20 (the shutdown circuit 20 in the disconnected state is maintained in the off state; the shutdown circuit 20 in the connected state is adjusted to the disconnected state);

[0092] - Again, according to the change of the current parameter Ao, the working mode of the sub-control module 21 is set accordingly.

[0093] (1b) Normal operating mode

[0094] In a typical example, the control logic of the sub-control module 21 for the shutdown circuit 20 in the normal working mode (also the operating logic of the optimizer 2b or the shutdown device 2a) includes:

[0095] - outputting a control signal indicating a connection instruction to the shutdown circuit 20 (to maintain the shutdown circuit 20 in a connection state);

[0096] - Again, according to the change of the current parameter Ao, the working mode of the sub-control module 21 is set accordingly.

[0097] In another preferred example, again referring to Figure 6 The control logic of the sub-control module 21 for the shutdown circuit 20 in the normal working mode (which is also the operating logic of the optimizer 2b or the shutdown device 2a) includes:

[0098] - outputting a control signal indicating a connection instruction to the shutdown circuit 20 (to maintain the shutdown circuit 20 in a connection state);

[0099] - Detection of electrical parameters of optimizer 2b;

[0100] -Determine whether the electrical parameters meet the fault conditions;

[0101] If a fault is detected, a control signal indicating a shutdown instruction is output to the shutdown circuit 20 (to adjust the shutdown circuit 20 from the on state to the off state).

[0102] If no fault is detected, a control signal indicating a connection instruction is output to the shutdown circuit 20 (so that the shutdown circuit 20 remains connected).

[0103] - Again, according to the change of the current parameter Ao, the working mode of the sub-control module 21 is set accordingly.

[0104] It should be noted that optimizer 2b typically monitors voltage, current, and even temperature, and has a maximum power point tracking function. This tracking function encompasses both the calculation of these parameters and the fault determination at the output of either circuit breaker 2a or optimizer 2b. For example, if sub-control module 21 detects an overcurrent fault at the output of optimizer 2b, it can shut down the corresponding circuit breaker 20 based on its determination, without relying on the determination or control of central control module 40 or other devices.

[0105] In this embodiment, in the above-mentioned safe operation and maintenance method of the photovoltaic power generation system, the operation logic of the central control module 40 includes:

[0106] - When the input voltage of the auxiliary power supply 41 is lower than the operating voltage, the periodic transmission of the communication signal is stopped;

[0107] - When the input voltage of the auxiliary power supply 41 is not lower than the operating voltage, the excitation communication signal is sent periodically in a controlled manner;

[0108] - When the input voltage of the auxiliary power supply 41 is not lower than the operating voltage, the periodic transmission of the excitation communication signal is stopped in a controlled manner.

[0109] Accordingly, in this embodiment, the above-mentioned safe operation and maintenance method of the photovoltaic power generation system can be applied to the existing inverter 50 operation logic:

[0110] - In response to the shutdown control signal from the emergency shutdown button 54, the output relay 56 and the grid-side circuit breaker 60 are turned off, the output end of the series line 30 is opened, and the central control module 40 is controlled to stop sending the excitation signal;

[0111] - In response to the shutdown control signal of the fault detection module, the output relay 56 is turned off, the output end of the series line 30 is open, and the central control module 40 is controlled to stop sending the excitation signal;

[0112] - In response to the remote shutdown control signal from the gateway 55, the output relay 56 is turned off, the output end of the series line 30 is opened, and the grid-side circuit breaker 60 is turned off. The central control module 40 stops periodically sending signal communication signals due to power loss;

[0113] In response to the reset of the emergency shutdown button 54 , the output relay 56 and the grid-side circuit breaker 60 are connected for the first time or again, the output end of the series line 30 is connected, and the central control module 40 periodically sends an excitation communication signal.

[0114] Still refer to Figure 1 In order to further understand the safe photovoltaic power generation system in the embodiment of the present invention, the following describes the operation process of the safe photovoltaic power generation system in various scenarios during the operation of the whole day, including the operation process of the photovoltaic power generation system in normal operation, installation, maintenance, failure, etc.

[0115] The embodiments of the present invention are applied in a first application scenario: power plant installation, fault repair, or cleaning and maintenance. During this process, manual operation can cause the output relay 56 and the grid-side circuit breaker 60 to shut down, disconnecting the inverter 50 from the grid and opening the output end of the series line 30. Due to the loss of power, the central control module 40 does not send an excitation communication signal, and the series line 30 has no current. Even if the photovoltaic assembly 11 can power its circuit breaker or optimizer 2b, its sub-control module 21 will automatically be set to a safe operating mode. Due to the lack of an excitation communication signal, its shutdown circuit 20 remains disconnected, keeping the voltage of the entire photovoltaic power generation system within a safe range and ensuring the safety of the operator. After the power plant installation, fault repair, or cleaning and maintenance task is completed, the grid-side circuit breaker 60 is connected for the first time or again, and the central control module 40 can obtain power from the grid-connected side and operate, sending an excitation communication signal, and further the photovoltaic power generation system can resume or resume operation.

[0116] The embodiment of the present invention applies to a second application scenario: a photovoltaic power generation system that normally captures solar energy and supplies power to the grid. The output inverter 50 and the grid-side circuit breaker 60 are closed and connected, and the central control module 40 receives power and operates. It periodically sends an excitation communication signal. The sub-control modules 21 within each optimizer 2b detect that the current exceeds 0.4A and operate in normal operating mode. They control their corresponding shutdown circuits 20 to remain connected. The sub-control modules 21 do not detect the excitation communication signal, thus preventing the photovoltaic modules 11 from being disconnected from the series circuit 30 due to communication interference, thereby reducing power generation losses. In the evening (similar to the early morning), when solar radiation intensity decreases, causing the current in the series circuit 30 to fall below 0.4A, each sub-control module 21 will correspondingly switch from normal operating mode to safety protection mode. If there are no other instructions to shut down the central control module 40, the sub-control modules 21 detect the excitation communication signal and maintain the shutdown circuits 20 connected, enabling early startup and late shutdown of the photovoltaic power generation system. When the string line voltage falls below the operating range due to reduced irradiation, the inverter controller 52 automatically controls the output relay 56 to open, allowing the central control module 40 to draw power from the grid to maintain operation. Therefore, in the early morning and evening, the sub-control module 21 can automatically maintain connectivity under the excitation communication signal and complete the early startup and late shutdown of the inverter 50. It is understood that the central control module 40 can periodically stop sending the excitation communication signal at night.

[0117] In a third application scenario, an embodiment of the present invention involves a photovoltaic power generation system in a power generation state and experiencing an anomaly requiring system shutdown. In this scenario, the output relay 56 and the grid-side circuit breaker 60 are closed, the series line 30 has a current exceeding 0.4 amps, and each sub-control module 21 is set to normal operating mode, not detecting the excitation signal. When the emergency shutdown button 54 is pressed, or the fault detection device 53 detects a fault, or a remote shutdown command is received, the inverter controller 52 shuts off the output relay 56, opening the output end of the series line 30 and causing the current to drop below or near 0 amps. Simultaneously, the central control module 40 stops sending the excitation communication signal. Because the current drops below 0.4 amps, each sub-control module 21 is set to safety protection mode and detects the excitation communication signal. If no excitation signal is detected, the optimizer 2b or the shutdown circuit 20 within the circuit breaker is controlled to open.

[0118] A specific example of the third application scenario can be seen: for example, when a fire occurs at the location where the photovoltaic power generation system is deployed, firefighters can press the emergency shutdown button 54 to shut down the grid-side circuit breaker 60 and output relay 56. Without power, the central control module 40 will stop sending the excitation communication signal, reducing the open-circuit voltage of the series circuit 30 of the modules to a safe range of 0 volts or close to 0 volts, allowing firefighters to safely carry out firefighting operations. For example, in emergencies such as fires, earthquakes, floods, and hurricanes, the inverter controller 52 will receive a remote shutdown command and shut down the grid-side circuit breaker 60 and output relay 56. Without power, the central control module 40 will stop sending the excitation communication signal, reducing the open-circuit voltage of the series circuit 30 of the modules to a safe range of 0 volts or close to 0 volts, thus preventing further damage to the circuit breaker. For example, if arcing, leakage or other faults occur in the photovoltaic power generation system, these faults will be detected by the fault detection device 53, causing the output relay 56 to be turned off. The synchronous central control module 40 can draw power from the grid-connected side and stop sending the excitation communication signal in a controlled manner. The control circuit is in a standby detection state, and the power acquisition system is shut down and waits for maintenance personnel to repair it.

[0119] In summary, in various application scenarios, based on the safe power generation system of the present invention, it is possible to achieve that in normal operation scenarios, the series circuit 30 of each component continues to generate electricity at high current, does not detect the excitation communication signal, and avoids the instability of the excitation communication signal and causing false shutdown; and still maintains operation and power generation at low current, that is, it has the characteristics of early startup and late shutdown, thereby extending the power generation time; and in the scenario of system installation or maintenance, it has the characteristic of absolute safety; in the scenario of sudden disasters, when the system has arcing, leakage and other faults, the voltage of the series circuit 30 of each component is automatically adjusted to a safe range; the comprehensive realization can intelligently ensure safety in various scenarios.

[0120] The above embodiments primarily illustrate the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A safe photovoltaic power generation system, comprising a power acquisition circuit and a control circuit; the power acquisition circuit is a series circuit (30) formed by connecting the output ends of multiple shutdown circuits (20) in series, and the input end of each shutdown circuit (20) is respectively connected to a photovoltaic DC source (10), so as to safely acquire power from each photovoltaic DC source (10) in a distributed manner and output it to the output end of the series circuit (30); characterized in that The control circuit comprises: a central control module (40) and a sub-control module (21); The sub-control module (21) is used to adjust the corresponding shutdown circuit (20) to switch between a connected state and a disconnected state, wherein the disconnected state of the shutdown circuit (20) means that the photovoltaic DC source (10) is individually disconnected from the series circuit (30) by means of the corresponding shutdown circuit (20), and the connected state of the shutdown circuit (20) means that the solar current generated by the photovoltaic DC source (10) is exported to the series circuit (30) through the corresponding shutdown circuit (20); The central control module (40) is used to send an excitation communication signal to the sub-control module (21), and is used to stop sending the excitation communication signal; The sub-control module (21) is used to obtain a current parameter signal of a corresponding shutdown circuit (20); when the current parameter signal changes to be lower than a preset current threshold, the working mode of the sub-control module (21) is adjusted from a normal working mode to a safety protection mode; correspondingly, when the current parameter signal changes to not lower than the preset current threshold, the working mode of the sub-control module (21) is adjusted from the safety protection mode to the normal working mode; The safety protection mode means that the sub-control module (21) receives an excitation communication signal from the central control module (40), and adjusts the state of the shutdown circuit (20) according to whether the excitation communication signal is detected within a certain period of time. If so, the sub-control module (21) is used to adjust the shutdown circuit (20) to a connected state or maintain the connected state; if not, the sub-control module (21) is used to adjust the shutdown circuit (20) to a disconnected state or maintain the disconnected state; The normal operating mode refers to the sub-control module (21) being used to independently adjust the state transition of the corresponding shutdown circuit (20) without responding to the excitation communication signal from the central control module (40); The security protection mode includes: In the connected state of the corresponding shutdown circuit (20), the sub-control module (21) is used to detect the excitation communication signal within a certain period of time and maintain the shutdown circuit (20) in the connected state, and is used to adjust the shutdown circuit (20) to the disconnected state if the excitation communication signal is not detected within a certain period of time; In the disconnected state of the corresponding shutdown circuit (20), the sub-control module (21) is used to adjust the shutdown circuit (20) to the connected state when the excitation communication signal is detected within a certain period of time, and to maintain the shutdown circuit (20) in the disconnected state when the excitation communication signal is not detected within a certain period of time.

2. The safe photovoltaic power generation system according to claim 1, characterized in that: The current parameter signal changes to be lower than the preset current threshold value, which at least includes: the current parameter signal continuously changes and approaches the preset current threshold value, or the current parameter signal remains lower than the preset current threshold value.

3. The safe photovoltaic power generation system according to claim 1, characterized in that: The central control module (40) is used to send the excitation communication signal via a wireless signal, and the sub-control module (21) is used to receive the wireless signal.

4. The safe photovoltaic power generation system according to claim 1, characterized in that: The system further comprises an inverter (50), wherein the output end of one of the series circuits (30) is connected to the inverter (50), or the output end of a series-parallel circuit formed by at least two series circuits (30) connected in parallel is connected to the inverter (50); the central control module (40) obtains operating power from the output end of the inverter (50), and when the power grid side of the central control module (40) is disconnected, the central control module (40) stops sending the excitation communication signal due to the loss of power supply.

5. The safe photovoltaic power generation system according to claim 4, characterized in that: The inverter (50) is equipped with a control interface, the control interface is connected to and receives instructions from a system fault detection device (53), and / or a user command input device, and / or a remote control gateway (55); the control interface is used to receive and respond to a shutdown instruction to the inverter (50), and in response to the shutdown instruction, the central control module (40) stops sending the excitation communication signal.

6. A safe operation and maintenance method, characterized in that: The invention is applied to a safe photovoltaic power generation system including a power acquisition circuit and a control circuit, wherein the power acquisition circuit is a series circuit (30) formed by connecting the output ends of multiple shutdown circuits (20) in series, and the input end of each shutdown circuit (20) is respectively connected to a photovoltaic DC source (10), so as to safely acquire power from each photovoltaic DC source (10) in a distributed manner and output the power to the output end of the series circuit (30); The control circuit comprises: a central control module (40) and a sub-control module (21); the sub-control module (21) is used to adjust the corresponding shutdown circuit (20) to switch between a connected state and a disconnected state, the disconnected state of the shutdown circuit (20) means that the photovoltaic DC source (10) is disconnected from the series circuit (30) by means of the corresponding shutdown circuit (20), and the connected state of the shutdown circuit (20) means that the solar current generated by the photovoltaic DC source (10) is exported to the series circuit (30) through the corresponding shutdown circuit (20); the central control module (40) is used to send an excitation communication signal to the sub-control module (21), and to stop sending the excitation communication signal; the method comprises the steps of: The sub-control module (21) of the shutdown circuit (20) obtains a current parameter signal of the corresponding shutdown circuit (20); when the current parameter signal changes to be lower than a preset current threshold, the working mode of the sub-control module (21) is adjusted from a normal working mode to a safety protection mode; correspondingly, when the current parameter signal changes to not lower than the preset current threshold, the working mode of the sub-control module (21) is adjusted from the safety protection mode to the normal working mode: The safety protection mode means that the sub-control module (21) receives an excitation communication signal from the central control module (40), and adjusts the state of the shutdown circuit (20) according to whether the excitation communication signal is detected within a certain period of time. If so, the sub-control module (21) adjusts the shutdown circuit (20) to a connected state or maintains the connected state; if not, the sub-control module (21) adjusts the shutdown circuit (20) to a disconnected state or maintains the disconnected state; The normal operating mode refers to the sub-control module (21) being used to independently adjust the state transition of the corresponding shutdown circuit (20) without responding to the excitation communication signal from the central control module (40); The security protection mode includes: In the connected state of the corresponding shutdown circuit (20), the sub-control module (21) is used to detect the excitation communication signal within a certain period of time and maintain the shutdown circuit (20) in the connected state, and is used to adjust the shutdown circuit (20) to the disconnected state if the excitation communication signal is not detected within a certain period of time; In the disconnected state of the corresponding shutdown circuit (20), the sub-control module (21) is used to adjust the shutdown circuit (20) to the connected state when the excitation communication signal is detected within a certain period of time, and to maintain the shutdown circuit (20) in the disconnected state when the excitation communication signal is not detected within a certain period of time.

7. An optimizer that can be configured in a safe photovoltaic power generation system, characterized in that: The optimizer (2b) comprises a shutoff circuit (20) and a sub-control module (21), wherein the shutoff circuit (20) comprises an input terminal for connecting to at least one photovoltaic DC source (10), and an output terminal for connecting in series to form a series circuit (30); The sub-control module (21) is used to adjust the corresponding shutdown circuit (20) to switch between a connected state and a disconnected state, wherein the disconnected state of the shutdown circuit (20) means that the photovoltaic DC source (10) is individually disconnected from the series circuit (30) by means of the corresponding shutdown circuit (20), and the connected state of the shutdown circuit (20) means that the solar current generated by the photovoltaic DC source (10) is exported to the series circuit (30) through the corresponding shutdown circuit (20); The sub-control module (21) comprises: A sampling unit (214) is used to obtain a current parameter signal of a corresponding shutdown circuit (20); A mode setting unit (216) is used to adjust the working mode of the sub-control module (21) from the normal working mode to the safety protection mode when the current parameter signal changes to below the preset current threshold; correspondingly, when the current parameter signal changes to not below the preset current threshold, the working mode of the sub-control module (21) is adjusted from the safety protection mode to the normal working mode: the safety protection mode means that the sub-control module (21) receives an excitation communication signal from outside the optimizer (2b), and adjusts the state of the shutdown circuit (20) according to whether the excitation communication signal is detected within a certain time period, if so, the sub-control module (21) adjusts the shutdown circuit (20) to a connected state or maintains a connected state, if not, the sub-control module (21) adjusts the shutdown circuit (20) to a disconnected state or maintains a disconnected state; the normal working mode means that the sub-control module (21) is used to independently adjust the state conversion of the corresponding shutdown circuit (20) without responding to the excitation communication signal from the central control module (40); The security protection mode includes: In the connected state of the corresponding shutdown circuit (20), the sub-control module (21) is used to detect the excitation communication signal within a certain period of time and maintain the shutdown circuit (20) in the connected state, and is used to adjust the shutdown circuit (20) to the disconnected state if the excitation communication signal is not detected within a certain period of time; In the disconnected state of the corresponding shutdown circuit (20), the sub-control module (21) is used to adjust the shutdown circuit (20) to the connected state when the excitation communication signal is detected within a certain period of time, and to maintain the shutdown circuit (20) in the disconnected state when the excitation communication signal is not detected within a certain period of time.

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