A fire alarm device for a solar photovoltaic system

Abstract

The utility model relates to a fire alarm device for solar photovoltaic system relates to alarm device technical field for monitoring solar photovoltaic system. Including monitoring device, monitoring device include: fire automatic identification monitoring camera, temperature cable formula detector, direct current fault arc detector to direct current residual current detector, monitoring device signal output end is connected with electrical fire monitoring equipment, and the signal output end of electrical fire monitoring equipment is connected with monitoring alarm main control platform, and monitoring alarm main control platform output control signal controls the on-off of solar photovoltaic system. The utility model discloses a kind of fire alarm device capable of effectively avoiding fire hazard by the above structure.

Description

Technical Field

[0001] This utility model patent relates to the field of alarm device technology, and in particular to a fire alarm device for a solar photovoltaic system. Background Technology

[0002] Photovoltaic power generation, as a highly efficient new technology that directly converts solar energy into electrical energy, is gradually gaining attention worldwide. In recent years, photovoltaic power generation technology has continuously improved globally, with increased conversion efficiency and decreased manufacturing costs, leading to rapid development of the photovoltaic market. Over the past decade, photovoltaic systems have been widely installed on the roofs of various residential and commercial buildings. In my country, photovoltaic power generation is the most important new energy source. By the end of 2023, the newly added grid-connected capacity of solar power generation nationwide reached 216.3 GW, with a cumulative grid-connected capacity of 609 million kilowatts. In a photovoltaic power generation system, photovoltaic modules are connected in series to form a photovoltaic array, which converts solar energy into electrical energy, outputting it as direct current (DC) to a junction box. The DC power is then converted into lower-voltage three-phase alternating current (AC) by an inverter, and then converted into AC power that meets the requirements of the public power grid by a step-up transformer before being connected to the grid.

[0003] The performance and reliability of photovoltaic (PV) modules remain potential issues due to field failures and degradation. PV systems are typically installed outdoors, subjecting PV modules to various environmental loads and harsh conditions throughout their lifespan, jeopardizing their reliable and long-term operation. Field-installed PV modules, building-integrated photovoltaics (BIPV), and building-integrated photovoltaics (BIPV) modules also pose fire risks because the base of the modules contains flammable materials, namely encapsulants and backsheets. The fire risk of PV power plants is high due to their specific characteristics and application scenarios. The presence of numerous flammable materials and high-voltage sources in PV systems can lead to serious fire accidents. For example, ethylene-vinyl acetate (EVA) used in PV backsheet assembly has been proven to be flammable. Furthermore, the junction boxes, packaging materials, and backsheets of solar PV modules are also flammable. The installation of PV panels introduces multiple electrical components into the building envelope, potentially increasing the risk of fires due to overload and short circuits. Ignition sources for PV fires are typically electric arcs and hot spots. Since PV systems generally operate at 300 to 1000 volts DC, they can generate electric arcs, igniting surrounding flammable materials. Furthermore, the presence of hot spots can cause localized increases in current and voltage within the photovoltaic module, leading to a rise in localized temperature and potentially spontaneous combustion. Therefore, there is an urgent need for a fire alarm device suitable for solar photovoltaic systems. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, this utility model provides a fire alarm device for solar photovoltaic systems.

[0005] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0006] A fire alarm device for a solar photovoltaic system is provided for monitoring the solar photovoltaic system. The device includes a monitoring unit comprising: an automatic fire identification monitoring camera, a heat-sensing cable detector, a DC fault arc detector, and a DC residual current detector. The signal output terminal of the monitoring device is connected to an electrical fire monitoring device, and the signal output terminal of the electrical fire monitoring device is connected to a monitoring and alarm main control platform. The monitoring and alarm main control platform outputs control signals to control the on / off state of the solar photovoltaic system.

[0007] The automatic fire identification monitoring camera is installed at the location of the solar photovoltaic system's solar panels, and the signal output terminal of the automatic fire identification monitoring camera outputs the coordinate information corresponding to the fire occurrence area;

[0008] The temperature-sensing cable detector is installed next to the solar panel connection cable of the solar photovoltaic system and below the solar panel. The temperature-sensing cable detector outputs a temperature signal to the electrical fire monitoring equipment.

[0009] The DC fault arc detector is installed at the input end of the photovoltaic string in the combiner box of the solar photovoltaic system, and the DC fault arc detector outputs a current signal to the electrical fire monitoring equipment.

[0010] The DC residual current detector is installed at the input end of each photovoltaic string in the combiner box of the solar photovoltaic system to monitor the residual current of each photovoltaic string to ground. The DC residual current detector connects the leakage current signal to the electrical fire monitoring equipment through the communication CAN bus.

[0011] The aforementioned automatic fire identification monitoring cameras consist of N cameras, completely covering the monitoring area of ​​the solar panel. These cameras are based on AI algorithms.

[0012] There are N temperature-sensing cable detectors, and a temperature-sensing cable detector is installed at each solar panel location in the solar photovoltaic system.

[0013] The monitoring device and the electrical fire monitoring equipment are connected via a CAN bus.

[0014] There are N DC fault arc detectors. The combiner box of the solar photovoltaic system consists of N photovoltaic strings forming an input branch. Each input branch is equipped with a DC fault arc detector to monitor the fault arc generated in each input branch in real time.

[0015] The DC fault arc detector includes a fluxgate current sensor. The signal output terminal of the fluxgate current sensor passes through a low-pass filter, a high-pass filter, and a differential amplifier in sequence, and is connected to an MCU processing unit. The output signal of the MCU processing unit is connected to an electrical fire monitoring device. The signal output terminal of the low-pass filter is connected to an ADC sampling trigger unit, and the signal output terminal of the ADC sampling trigger unit is connected to the MCU processing unit.

[0016] The DC residual current detector includes a DC residual current sensor. The signal output terminal of the DC residual current sensor is connected in sequence to a differential amplifier and a low-pass filter. The signal output terminal of the low-pass filter is connected to the signal input terminal of the MCU processing unit.

[0017] The beneficial effects of this invention are as follows: In the event of a fire hazard or fire in a solar photovoltaic system, this invention employs various types of electrical fire detectors to detect the fire hazard in the solar photovoltaic system in real time and sends the detected results to the electrical fire monitoring equipment for fire determination and confirmation. Upon confirmation of a fire hazard, the electrical fire monitoring equipment sends an alarm signal to the monitoring and alarm control platform. After receiving the confirmed alarm message, the alarm control platform sends a power-off control command to the solar photovoltaic system, thereby realizing the fire protection function of the solar photovoltaic system. Attached Figure Description

[0018] Figure 1 : Block diagram of this utility model;

[0019] Figure 2 Connection diagram of the monitoring device of this utility model;

[0020] Figure 3 Electrical connection diagram of the combiner box of a solar photovoltaic system;

[0021] Figure 4 : Block diagram of DC fault arc detector;

[0022] Figure 5 : Figure 4 Circuit diagrams of low-pass filters, high-pass filters, and differential amplifiers;

[0023] Figure 6 : Figure 4 Circuit diagram of the ADC sampling trigger unit;

[0024] Figure 7 : Figure 4 Circuit diagram of the power supply unit;

[0025] Figure 8 : Figure 4 Circuit diagram of the MCU processing unit;

[0026] Figure 9 : Block diagram of DC residual current detector;

[0027] Figure 10 : Figure 9 Circuit diagram of a differential amplifier and a low-pass filter. Detailed Implementation

[0028] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0029] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this disclosure, are intended to cover non-exclusive inclusion.

[0030] In this disclosure, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for better description of the embodiments of this disclosure and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this disclosure according to the specific circumstances.

[0031] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0032] like Figure 1 This diagram illustrates a fire alarm device for a solar photovoltaic system, used to monitor the solar photovoltaic system. It includes a monitoring device, as shown in the diagram. Figure 2As shown, the system includes an automatic fire detection monitoring camera, a temperature-sensing cable detector, a DC fault arc detector, and a DC residual current detector. The monitoring devices and the electrical fire monitoring equipment are connected via a CAN bus. The signal output terminal of the monitoring device is connected to the electrical fire monitoring equipment, and the signal output terminal of the electrical fire monitoring equipment is connected to the monitoring and alarm main control platform. The monitoring and alarm main control platform outputs control signals to control the on / off state of the solar photovoltaic system. The electrical fire monitoring equipment is an existing device, specifically manufactured by Beijing Mingri Power Electronics Co., Ltd., with product specification model BMF-J1A.

[0033] The electrical connections between the monitoring device and the combiner box of the solar photovoltaic system are as follows: Figure 3 As shown in the diagram. FU1 is a DC fuse; CT1-A is a DC residual current detector; CT1-B is a DC fault arc current detector; D1 is a power diode; QF is a DC circuit breaker with shunt trip; SPD is a surge protector; and LCP is a linkage control output module. LCP connects the linkage control output module to the signal output terminal of the monitoring and alarm main control platform.

[0034] Automatic fire detection monitoring cameras are installed at the locations of the solar panels in the solar photovoltaic system. There are N cameras, completely covering the monitoring area of ​​the solar panels. When a fire occurs, the system can automatically identify and confirm the fire using AI algorithms and upload the coordinates of the fire location. These cameras are AI-based. The system uses Hikvision's JTT-U-HK142-P image-type fire detector, which supports multi-level flame detection sensitivity adjustment and has a response time as short as 2 seconds. It supports flame detection, covering a maximum distance of 150 meters, and supports temperature anomalies. The detection uses a non-contact detection scheme, making it virtually unaffected by turbulence or smoke obstructions, ensuring safety, reliability, and ease of use. This new type of fusion intelligent camera uses a dual-spectral architecture of high-definition visible light and high-sensitivity thermal imaging, combined with AI deep learning algorithms and real-time fusion processing technology, to analyze fire characteristics such as fire point, smoke, and temperature, and provide timely alarms. It can also provide video verification for accurate fire detection.

[0035] The aforementioned temperature-sensing cable detectors are N in number, with one detector installed at each solar panel location in the solar photovoltaic system. The temperature-sensing cable detectors are installed beside the solar panel connection cables and below the solar panels. They monitor abnormal temperature changes of the solar panels in real time and connect to the electrical fire monitoring equipment via the CAN bus. The temperature-sensing cable detectors output temperature signals to the electrical fire monitoring equipment. This system uses the JBF4310 resettable, differential temperature, distributed location, detection type, and intelligent cable-type linear temperature-sensing fire detector from Qingniao Fire Protection. The JBF4310 cable-type linear temperature-sensing fire detector has thermally sensitive and heat-conducting materials distributed along the cable, and a chip system is distributed along the cable. The chip system calculates the real-time temperature field along the cable and realizes functions such as differential temperature alarm.

[0036] The DC fault arc detector is installed at the input end of the photovoltaic string in the combiner box of the solar photovoltaic system; one combiner box has multiple input branches for the photovoltaic strings. Each branch is equipped with an independent DC fault arc detector to monitor the fault arc generated in each branch in real time. The DC fault arc detector outputs a current signal, which is connected to the electrical fire monitoring equipment via a communication CAN bus.

[0037] DC fault arc detectors, such as Figure 4 As shown, the device includes a fluxgate current sensor. The signal output terminal of the fluxgate current sensor passes through a low-pass filter, a high-pass filter, and a differential amplifier in sequence, and is connected to an MCU processing unit. The output signal of the MCU processing unit is connected to an electrical fire monitoring device. The signal output terminal of the low-pass filter is connected to an ADC sampling trigger unit, and the signal output terminal of the ADC sampling trigger unit is connected to the MCU processing unit.

[0038] The fluxgate current sensor AFDD uses the arc detection current sensor SCT-CTS / P6 from Xici Technology. This series of products has a built-in arc detection function, which can detect weak high-frequency current signals within the aperture. The sensor's frequency response covers the range of 10kHz-200kHz, which can meet the requirements for detecting DC fault arcs in solar photovoltaic cells.

[0039] The low-pass filter, high-pass filter, and differential amplifier of a DC fault arc detector are as follows: Figure 5 As shown. Capacitors C14 and C15, resistors R34 and R36, and operational amplifier U8B together constitute a second-order high-pass filter. Capacitors C19 and C21, resistors R30 and R31, and operational amplifier U9A together constitute a second-order low-pass filter. Resistors R39, R37, and R33, capacitors C18 and C20, and operational amplifier U9B together constitute a differential amplifier.

[0040] ADC sampling trigger unit signal such as Figure 6 As shown, this circuit mainly consists of operational amplifiers U1A and U1B, comparators U2A and U2B, diode D1, resistors, and capacitors, used to trigger the ADC sampling. Comparators U2A and U2B are MCP602; they do not measure the current signal of the DC fault arc when it is less than a given threshold. Data acquisition and calculation are only performed when the energy of the fault arc exceeds a given value, thus reducing the impact on the MCU's processing energy during signal processing. The circuit's signal input ARC-IN takes the output of the filter unit, and the signal output ARC-OUT is connected to the interrupt input pin of the MCU processing unit.

[0041] The power supply unit circuit of the DC fault arc detector is as follows: Figure 7 As shown, a DC 350-DC 450V power supply is connected to terminal P1, and then through a step-down voltage regulator circuit consisting of resistors R9, R10, R11, R12, varistor RV1, capacitors C6-C15, inductor L1, and a step-down controller U3, it outputs 5V to power the various units in the circuit. The LDO controller U4 converts the input 5V voltage to 3.3V to power the MCU. U5, along with R11, C13, and C14, forms a 1.24V bandgap reference source, which serves as the reference source for the filter unit.

[0042] MCU processing unit such as Figure 8 As shown, the MCU processing unit uses STMicroelectronics' STM32G431R6TB.

[0043] The aforementioned DC residual current detector is installed at the input terminal of each photovoltaic string in the combiner box of the solar photovoltaic system to monitor its residual current to ground. The DC residual current detector outputs a leakage current signal to the electrical fire monitoring equipment. The current signal sensor of the DC residual current detector (DRCD) uses the SFG-5.0P / N1 DC leakage current sensor from Xici Technology. This sensor is a current sensor designed based on fluxgate technology and closed-loop principle, capable of measuring DC, AC, pulse, and various irregular waveform currents under isolated conditions. The current measurement range is ±10A, and the frequency response is 0-15kHz. It can meet the requirements for detecting DC leakage current in solar photovoltaic cells.

[0044] DC residual current detector, such as Figure 9 As shown, the system includes a DC residual current sensor. The signal output of the DC residual current sensor is connected in sequence to a differential amplifier and a low-pass filter. The output of the low-pass filter is connected to the signal input of the MCU processing unit. The MCU processing unit is the same as that of the DC fault arc detector. The differential amplifier and low-pass filter are as follows... Figure 10As shown, the current signal collected by the DC residual current sensor is connected to resistors R61 and R67 through the JH6 terminal. Then, the signal is amplified by the amplifier circuit composed of operational amplifiers U10A and U11B. After being filtered by the second-order low-pass filter composed of resistors R65 and R66, capacitors C63 and C64, and operational amplifier U10B, the signal is connected to the ADC sampling terminal of the MCU processing unit for sampling.

[0045] In use: When the automatic fire detection monitoring camera detects a fire, or the temperature detected by the heat-sensing cable detector exceeds the preset value, or the DC fault arc detector detects the presence of a fault arc, or the DC residual current detector detects the presence of residual power, the electrical fire monitoring equipment judges the above signals and reports the alarm signal to the monitoring alarm main control platform for alarm activation; at the same time, the monitoring alarm main control platform outputs a power-off signal to the solar photovoltaic system to control the solar photovoltaic system to cut off power.

Claims

1. A fire alarm device for a solar photovoltaic system, used to monitor the solar photovoltaic system, characterized in that: The monitoring device includes: an automatic fire identification monitoring camera, a heat-sensing cable detector, a DC fault arc detector, and a DC residual current detector; the signal output terminal of the monitoring device is connected to the electrical fire monitoring equipment, the signal output terminal of the electrical fire monitoring equipment is connected to the monitoring and alarm main control platform, and the monitoring and alarm main control platform outputs control signals to control the on / off state of the solar photovoltaic system. The automatic fire identification monitoring camera is installed at the location of the solar photovoltaic system's solar panels, and the signal output terminal of the automatic fire identification monitoring camera outputs the coordinate information corresponding to the fire occurrence area; The temperature-sensing cable detector is installed next to the solar panel connection cable of the solar photovoltaic system and below the solar panel. The temperature-sensing cable detector outputs a temperature signal to the electrical fire monitoring equipment. The DC fault arc detector is installed at the input end of the photovoltaic string in the combiner box of the solar photovoltaic system, and the DC fault arc detector outputs a current signal to the electrical fire monitoring equipment. The DC residual current detector is installed at the input end of each photovoltaic string in the combiner box of the solar photovoltaic system to monitor the residual current of each photovoltaic string to ground. The DC residual current detector connects the leakage current signal to the electrical fire monitoring equipment through the communication CAN bus.

2. A fire alarm device for a solar photovoltaic system according to claim 1, characterized in that: The aforementioned automatic fire identification monitoring cameras consist of N cameras, completely covering the monitoring area of ​​the solar panel. These cameras are based on AI algorithms.

3. A fire alarm device for a solar photovoltaic system according to claim 1, characterized in that: There are N temperature-sensing cable detectors, and a temperature-sensing cable detector is installed at each solar panel location in the solar photovoltaic system.

4. A fire alarm device for a solar photovoltaic system according to claim 1, characterized in that: The monitoring device and the electrical fire monitoring equipment are connected via a CAN bus.

5. A fire alarm device for a solar photovoltaic system according to claim 1, characterized in that: There are N DC fault arc detectors. The combiner box of the solar photovoltaic system consists of N photovoltaic strings forming an input branch. Each input branch is equipped with a DC fault arc detector to monitor the fault arc generated in each input branch in real time.

6. A fire alarm device for a solar photovoltaic system according to claim 1, characterized in that: The DC fault arc detector includes a fluxgate current sensor. The signal output terminal of the fluxgate current sensor passes through a low-pass filter, a high-pass filter, and a differential amplifier in sequence, and is connected to an MCU processing unit. The output signal of the MCU processing unit is connected to an electrical fire monitoring device. The signal output terminal of the low-pass filter is connected to an ADC sampling trigger unit, and the signal output terminal of the ADC sampling trigger unit is connected to the MCU processing unit.

7. A fire alarm device for a solar photovoltaic system according to claim 1, characterized in that: The DC residual current detector includes a DC residual current sensor. The signal output terminal of the DC residual current sensor is connected in sequence to a differential amplifier and a low-pass filter. The signal output terminal of the low-pass filter is connected to the signal input terminal of the MCU processing unit.

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