Photovoltaic string protection switch and method
By introducing a signal detection and control module into the photovoltaic string protection switch, and using Hall sensors and ARM microprocessors for fault analysis, the problems of unreliable detection and delayed response of existing photovoltaic string protection devices are solved, achieving rapid isolation and accurate protection, and reducing the risk of equipment damage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-03-10
AI Technical Summary
Existing photovoltaic string protection devices cannot reliably detect and promptly handle DC fault arcs and insulation damage, leading to equipment burnout and fire risks. Furthermore, existing devices are poorly targeted, have unreliable fault detection, and are slow to adjust.
Design a photovoltaic string protection switch, including a signal detection module, a DC switching module and a control section. It adopts Hall voltage sensor, Hall current sensor, 32-bit ARM microprocessor and 4G/5G communication module. It identifies arcing faults and insulation abnormalities through time domain and frequency domain feature analysis, and realizes rapid disconnection and isolation.
It enables accurate identification and protection of photovoltaic strings, preventing equipment burnout and fires, and has flexible installation and remote operation and maintenance capabilities, improving the accuracy and response speed of fault detection.
Smart Images
Figure CN121642849A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of photovoltaic power generation, and particularly relates to a photovoltaic string protection switch and method. BACKGROUND
[0002] For a photovoltaic string power generation system, the number of solar panel assemblies, combiner boxes, DC cables and other devices is large, the distribution is wide, the operating environment is harsh, hidden dangers are difficult to detect, and DC side insulation damage, electrical short circuit and other faults are prone to occur. When there are series, parallel and ground arc faults, the temperature of the combiner bus is unbalanced, and an arc burning atmosphere is easily formed. Since there is no zero-crossing point feature of alternating current arc, the DC arc is easy to maintain stable combustion. If the arc cannot be detected in time and corresponding protection measures are not taken, the high temperature generated by the continuously burning arc is easy to burn the device and may cause an electrical fire, which may cause a single device to burn, or a large area to catch fire.
[0003] The voltage generated in the photovoltaic string is high, but the current is relatively small, and each branch needs to be connected to the DC input interface of the photovoltaic inverter or connected to the photovoltaic string combiner box. The photovoltaic string combiner box is mainly composed of a DC fuse, an anti-reverse diode, a surge protector, a DC circuit breaker, an isolation switch and the like.
[0004] In actual operation, since the DC system has low inductance and high current deviation characteristics, the current protection device does not have reliable detection and protection means for insulation damage and series, parallel and ground arc hidden dangers. The action criterion of the high-voltage fuse is determined by its fixed protection characteristics, which is prone to misoperation, and it is difficult to distinguish between transient faults and permanent faults of the protection device, and the protection device needs to be replaced in time after protection action. The DC circuit breaker is connected to multiple photovoltaic string loops at the same time, and cannot effectively protect and isolate a single photovoltaic string. Therefore, the existing protection device of the photovoltaic string has defects, and a photovoltaic string protection switch needs to be designed to effectively monitor serious safety hazards such as DC fault arc and insulation characteristic damage and immediately perform disconnection and isolation protection on the device. SUMMARY
[0005] In view of the problems in the prior art, the application provides a photovoltaic string protection switch and method, which has the advantages of being able to individually isolate string faults, accurately identify arcs and insulation abnormalities, be flexible to install and be convenient for remote operation and maintenance, and solves the problems of poor pertinence, unreliable fault detection and lagging regulation and control of the photovoltaic string protection device in the prior art.
[0006] The application is implemented as follows: a photovoltaic string protection switch, comprising a protection switch connected in series between a photovoltaic string and a combiner box / photovoltaic inverter, and comprising a main circuit part and a control part, the main circuit part being composed of a signal detection module and a direct current switch module; the control part being composed of a control power module, a master control module, a signal analysis module, a switch control module, an external communication module and a cloud platform monitoring, the signal detection module being composed of a voltage sensor, a current sensor and a hardware acquisition circuit, for detecting and acquiring input direct current voltage and output direct current current signal of the protection switch, the direct current switch module being used for completing on-off function of the main circuit, having breaking quick arc extinguishing capacity and on-state low loss characteristics, the control power module taking power from the photovoltaic string, having an input voltage range of 300-2000VDC, and outputting a stable 24VDC control power, the signal analysis module being used for signal acquisition, filtering, amplification and analog-digital conversion processing, the switch control module being used for driving the direct current switch module to close / open and feeding back a state, the master control module being used for establishing a fault analysis model, extracting signal features and completing pattern recognition, and outputting an action instruction, the external communication module being used for uploading data to the cloud platform and receiving a remote instruction, and the cloud platform monitoring being used for realizing data storage, fault alarm and remote control.
[0007] As preferred in the application, the voltage sensor adopts a Hall voltage sensor, and the current sensor adopts a Hall current sensor.
[0008] Through the arrangement, the Hall voltage sensor and the current sensor have the characteristics of strong anti-interference ability and high measurement precision, can stably acquire signals under photovoltaic string voltage fluctuation and complex electromagnetic environment, are beneficial to avoiding detection errors, and improve data precision.
[0009] As preferred in the application, the master control module adopts a 32-bit ARM microprocessor.
[0010] Through the arrangement, the 32-bit ARM microprocessor has the advantages of high main frequency and fast data processing speed, can efficiently complete signal feature extraction, fault model operation and action instruction output, and improves timeliness of protection action.
[0011] As preferred in the application, the external communication module adopts a 4G / 5G dual-mode communication module, and is connected with the master control module through a Profinet industrial bus.
[0012] Through the arrangement, the dual-mode communication module can adapt to network environments in different scenes, ensures stability of data transmission, and the Profinet industrial bus realizes high-speed data interaction between the master control module and the communication module, guarantees real-time performance of operation data uploading and remote instruction receiving.
[0013] A photovoltaic string protection method, applicable to the aforementioned photovoltaic string protection switch, includes the following steps: S1, Closing Initialization The control power module starts up and completes the power-on self-test. When the main control module detects that the string voltage is greater than the closing threshold and there is no external closing command, it drives the DC switch to close. S2, Signal Acquisition and Preprocessing The signal detection module collects voltage and current signals, which are then filtered, amplified, and converted from analog to digital by the signal analysis module before being transmitted to the main control module. S3, Fault Diagnosis The main control module performs arcing fault judgment (extracting time domain and frequency domain features) and insulation resistance anomaly judgment (calculating insulation resistance value) in parallel. If the fault judgment conditions are met, an alarm is triggered. S4, Protective Actions The main control module drives the DC switch to trip, achieving electrical isolation, and simultaneously records fault information and uploads it to the cloud platform; S5, Feedback closed loop and reset After troubleshooting, the system is restored by repeating step S1 through local or remote reset.
[0014] In a preferred embodiment of the present invention, step S3 includes calculating the variance and rate of change of voltage and current, performing FFT operation on the collected data, extracting specific spectral information, and determining an arcing fault when the above time-domain and frequency-domain characteristics both meet the fault conditions.
[0015] This setting utilizes dual-dimensional feature analysis in both the time and frequency domains to effectively distinguish between arcing faults and normal signal fluctuations, avoiding false alarms or missed alarms caused by single feature judgments, and ensuring the accuracy of identifying faults such as parallel arcing, series arcing, and grounding arcing.
[0016] As a preferred embodiment of the present invention, in step S4, the tripping trigger conditions include arcing fault, abnormal insulation resistance, string voltage < tripping threshold, output current > overcurrent threshold, and external remote tripping command.
[0017] This setting covers the main safety hazards in the operation of photovoltaic strings, enables multi-condition triggering and all-round protection, and ensures a rapid response when any type of fault occurs, preventing the fault from escalating.
[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The protection switch is installed at the output end of the photovoltaic string, which can isolate and protect the string branch itself from faults and the output line faults. The protection switch can accurately identify fault phenomena such as parallel arcing, series arcing and grounding arcing, and promptly perform protection actions to perform electrical isolation and eliminate potential fault hazards; The protective switch can accurately detect abnormal insulation resistance faults, provide early warnings, and eliminate faults caused by deterioration in insulation performance. Protective switches can accurately detect and analyze signals such as current, voltage, and ambient temperature, and handle various potential faults accurately and flexibly. The protection switch uses wide voltage input and self-powering technology to obtain control power, and also uses a cloud platform for remote communication. It is simple and flexible to install and convenient and intuitive to use. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the photovoltaic string protection switch system provided by the present invention; Figure 2 This is a schematic diagram showing the installation location and protection range of the photovoltaic string protection switch provided by the present invention; Figure 3 This is a flowchart for judging arcing faults in photovoltaic string protection switches provided by the present invention; Figure 4 This is a flowchart for judging abnormal insulation resistance faults in photovoltaic string protection switches provided by the present invention. Figure 5 This is a flowchart of the operation of the photovoltaic string protection switch provided by the present invention. Detailed Implementation
[0020] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given in conjunction with the accompanying drawings.
[0021] The structure of the present invention will now be described in detail with reference to the accompanying drawings.
[0022] refer to Figures 1 to 5As shown in the figure, an embodiment of the present invention provides a photovoltaic string protection switch, which is connected in series between the photovoltaic string and the combiner box / photovoltaic inverter, and includes a main circuit part and a control part. The main circuit part consists of a signal detection module and a DC switch module; the control part consists of a control power supply module, a main control module, a signal analysis module, a switch control module, an external communication module, and a cloud platform monitoring system. The signal detection module consists of voltage and current sensors and hardware acquisition circuitry, used to detect and acquire the input DC voltage and output DC current signals of the protection switch. The DC switch module is used to complete the on / off function of the main circuit. It possesses the ability to quickly extinguish arcs and has low on-state losses. The control power supply module draws power from the photovoltaic string, with an input voltage range of 300-2000VDC, and outputs a stable 24VDC control power supply. The signal analysis module is used for signal acquisition, filtering, amplification, and analog-to-digital conversion. The switch control module is used to drive the DC switch module to close / open and provide status feedback. The main control module is used to establish a fault analysis model, extract signal features, complete pattern recognition, and output action commands. The external communication module is used to upload data to the cloud platform and receive remote commands. The cloud platform monitoring is used to realize data storage, fault alarm, and remote control.
[0023] Specifically, the voltage sensor is a Hall voltage sensor, and the current sensor is a Hall current sensor.
[0024] Using the above scheme, the Hall voltage sensor and current sensor have the characteristics of strong anti-interference ability and high measurement accuracy. They can stably collect signals in photovoltaic string voltage fluctuations and complex electromagnetic environments, which helps to avoid detection errors and improve data accuracy.
[0025] Specifically, the main control module uses a 32-bit ARM microprocessor.
[0026] Using the above scheme, the 32-bit ARM microprocessor has the advantages of high clock frequency and fast data processing speed, which can efficiently complete signal feature extraction, fault model calculation and action command output, and improve the timeliness of protection actions.
[0027] Specifically, the external communication module adopts a 4G / 5G dual-mode communication module and is connected to the main control module through the Profinet industrial bus.
[0028] Using the above solution, the dual-mode communication module can adapt to network environments in different scenarios, ensuring the stability of data transmission. The Profinet industrial bus enables high-speed data interaction between the main control module and the communication module, ensuring the real-time upload of operating data and reception of remote commands.
[0029] A photovoltaic string protection method, applicable to the aforementioned photovoltaic string protection switch, includes the following steps: S1, Closing Initialization The photovoltaic string generates DC voltage output. The control power module draws power directly from the photovoltaic string. When the output voltage of the photovoltaic string reaches the starting operating voltage of the control power module, the control power module starts to work normally. The input voltage range of the control power module is 200VDC-2500VDC. It stably outputs 24V DC and other DC voltage levels as control voltage. The control system performs normal power-on self-test and switch status self-test, and there is no external limiting protection switch closing action command. When the DC voltage output of the photovoltaic string is greater than the protection switch closing action voltage threshold (the parameter is set according to the inverter characteristics), the string protection switch closes, and the photovoltaic string is directly connected to the combiner box or photovoltaic inverter. S2, Signal Acquisition and Preprocessing The signal detection module collects voltage and current signals, which are then filtered, amplified, and converted from analog to digital by the signal analysis module before being transmitted to the main control module. S3, Fault Diagnosis Arc fault diagnosis Current and voltage signals are acquired through current and voltage sensors and hardware circuits. The hardware conditioning circuit filters and amplifies the signals. The signals are then converted from analog to digital by an AD chip. The digital signals are then stored in a microprocessor. The microprocessor establishes an arcing fault analysis model and initializes arcing-related variables. The microprocessor extracts time-domain features such as the variance and rate of change of voltage and current from the acquired data, performs relevant model judgments, and makes a preliminary judgment on whether an arcing phenomenon has occurred. At the same time, the microprocessor performs FFT operations on the acquired data to extract specific spectral information, performs spectral analysis, feature extraction, pattern recognition, and model judgment, and comprehensively judges whether an arcing phenomenon has occurred. If an arcing phenomenon is found, a fault alarm is triggered, and the protective switch is tripped. Insulation resistance abnormality fault diagnosis Voltage sensors and hardware circuits collect positive and negative voltage signals from the string. The insulation resistance sampling hardware circuit processes the signal, and the hardware conditioning circuit filters and amplifies the sampled signal. The signal enters the AD chip for analog-to-digital conversion, and the digital signal enters the microprocessor for data storage. The microprocessor establishes an insulation resistance anomaly analysis model and initializes relevant variables. The microprocessor performs digital signal processing, extracts insulation resistance characteristics, and performs model judgment. If an insulation resistance anomaly is found, a fault alarm is triggered, and the protective switch is tripped. S4, Protective Actions The main control module drives the DC switch to trip. When an external tripping command is sent or the DC voltage output of the photovoltaic string is lower than the tripping action voltage threshold of the protection switch (the parameter is set according to the inverter characteristics), the string protection switch trips normally. When the protection switch detects and determines fault states such as abnormal input / output voltage, abnormal output current, abnormal output power, arc characteristic, insulation resistance, or environmental abnormality through real-time detection, the protection switch immediately performs the tripping action. At the same time, it records and stores the protection action status, triggers event information and fault alarm information, and displays the local fault indicator light on the protection switch. The protection switch uploads data to the cloud platform through the communication module for storage, display, and fault alarm information push. S5, Feedback closed loop and reset After troubleshooting, the system is restored by repeating step S1 through local or remote reset.
[0030] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A photovoltaic string protection switch, characterized by: The photovoltaic string protection switch comprises a protection switch connected in series between a photovoltaic string and a combiner box / photovoltaic inverter, and a main circuit part and a control part, wherein the main circuit part is composed of a signal detection module and a direct current switch module; the control part is composed of a control power module, a main control module, a signal analysis module, a switch control module, an external communication module and a cloud platform monitoring; the signal detection module is composed of a voltage sensor, a current sensor and a hardware acquisition circuit, and is used for detecting and collecting input direct current voltage and output direct current current signals of the protection switch; the direct current switch module is used for completing the on-off function of the main circuit, and has the characteristics of breaking fast arc extinguishing capacity and low on-state loss; the control power module takes power from the photovoltaic string, and has an input voltage range of 300-2000VDC and an output stable 24VDC control power; the signal analysis module is used for signal acquisition, filtering, amplification and analog-digital conversion processing; the switch control module is used for driving the direct current switch module to close / open and feeding back the state; the main control module is used for establishing a fault analysis model, extracting signal features and completing pattern recognition, and outputting an action instruction; the external communication module is used for uploading data to the cloud platform and receiving remote instructions; and the cloud platform monitoring is used for realizing data storage, fault alarm and remote control.
2. A photovoltaic string protection switch as claimed in claim 1, characterized in that: The voltage sensor adopts a Hall voltage sensor, and the current sensor adopts a Hall current sensor.
3. A photovoltaic string protection switch as claimed in claim 1, characterized in that: The main control module adopts a 32-bit ARM microprocessor.
4. A photovoltaic string protection switch as claimed in claim 1, characterized in that: The external communication module adopts a 4G / 5G dual-mode communication module and is connected with the main control module through a Profinet industrial bus.
5. A method of photovoltaic string protection, characterized by, The photovoltaic string protection switch of any one of claims 1-4 comprises the following steps: S1, closing initialization The control power module is started and completes power-on self-test, and when the main control module monitors that the string voltage is greater than the closing threshold value and there is no external opening instruction, the direct current switch is driven to close; S2, signal acquisition and preprocessing The signal detection module collects voltage and current signals, which are transmitted to the main control module after being filtered, amplified and analog-digital converted by the signal analysis module; S3, fault determination The main control module executes arc fault judgment (extracting time domain and frequency domain features) and insulation resistance abnormality judgment (calculating insulation resistance value) in parallel, and triggers an alarm when the fault judgment condition is met; S4, protection action The main control module drives the direct current switch to open, realizes electrical isolation, records fault information and uploads it to the cloud platform at the same time; S5, feedback closed loop and reset After the fault is eliminated, the system is restored by repeating step S1 through local or remote reset.
6. A method of photovoltaic string protection as claimed in claim 5, characterized by: In step S3, the arc fault judgment comprises calculating the variance value and the change rate of voltage and current, performing FFT operation on the collected data, and extracting specific frequency spectrum information, and the arc fault is determined when the time domain and frequency domain features meet the fault condition.
7. A method of protecting a photovoltaic string as defined in claim 5, wherein: In step S4, the opening trigger condition comprises arc fault, insulation resistance abnormality, string voltage < opening threshold value, output current > overcurrent threshold value and external remote opening instruction.