Photovoltaic module-level micro energy storage system and fireproof safety monitoring method

Abstract

The invention discloses a photovoltaic module-level micro energy storage system and a fireproof safety monitoring method. The photovoltaic module-level micro energy storage system comprises a micro energy storage rod, a string type inverter and a monitoring platform, one micro energy storage rod and one photovoltaic module form an energy storage unit, and a plurality of energy storage units are connected in parallel to a string loop through a direct current side and are connected to a grid through a string inverter; and the monitoring platform is used for performing centralized monitoring on the plurality of micro energy storage rods. Temperature and internal resistance changes of the battery are monitored in real time, a three-level protection mechanism is adopted, and when abnormity is detected, a circuit can be rapidly cut off and reported to a monitoring platform. According to the invention, real-time temperature and internal resistance monitoring can be carried out on each energy storage unit, and the circuit is actively cut off and reported when abnormality is detected, so that the risk of thermal runaway is avoided, and the overall safety of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of new energy storage, specifically to a photovoltaic module-level micro energy storage system and a fire safety monitoring method. Background Technology

[0002] Photovoltaic power generation systems, as an important form of distributed renewable energy utilization, have been widely used in recent years. Existing photovoltaic systems, using string inverters for grid-connected operation, incorporate centralized energy storage devices on the DC side to balance solar radiation fluctuations and load demand. However, the centralized energy storage deployment model suffers from problems such as coarse-grained energy regulation, insufficient system scalability, and a wide impact from single-point failures, which are detrimental to improving the overall operational safety and energy efficiency of the photovoltaic system.

[0003] In terms of safety, electrical anomalies at the module level and thermal runaway of energy storage batteries during the operation of photovoltaic power plants have gradually gained attention. Existing monitoring systems are mostly deployed at the inverter or combiner box level, typically relying on macroscopic electrical parameters such as current and voltage, making it difficult to obtain timely key state parameters of individual modules or battery cells, such as rapid changes in temperature or internal resistance. This results in potential overheating, short circuits, or battery degradation not being identified in a timely manner, posing a risk of fire. Furthermore, the monitoring response time is significant, lacking a refined, tiered handling mechanism, and there are deficiencies in safety protection measures.

[0004] Therefore, how to realize a system structure that combines photovoltaic modules with micro energy storage units and introduce a rapid, hierarchical fire safety monitoring mechanism remains a technical problem that has not yet been effectively solved in this field. Summary of the Invention

[0005] In view of this, the purpose of this invention is to overcome the defects in the prior art and provide a photovoltaic module-level micro energy storage system and a fire safety monitoring method that can monitor the temperature and internal resistance of each energy storage unit in real time, actively cut off the circuit and report when an abnormality is detected, thereby avoiding the risk of thermal runaway and improving the overall safety of the system.

[0006] The photovoltaic module-level micro energy storage system of the present invention includes a micro energy storage rod, a string inverter, and a monitoring platform;

[0007] One of the micro energy storage rods and one photovoltaic module form an energy storage unit. Several of the energy storage units are connected in parallel to a string circuit via the DC side and connected to the grid via a string inverter.

[0008] The monitoring platform is used for centralized monitoring of several micro energy storage rods.

[0009] Furthermore, the micro energy storage rod includes a battery module, a temperature sensor for detecting the temperature of the battery module, a detection module for detecting the internal resistance of the battery module, a circuit breaker connected to the battery module, and a control module for receiving and transmitting data and performing data processing and analysis.

[0010] Furthermore, the micro energy storage rod also includes a bidirectional DC / DC converter; the positive terminal of the battery module is connected to the low-voltage side input terminal LV+ of the bidirectional DC / DC converter through the circuit breaker, the negative terminal of the battery module is connected to the low-voltage side input terminal LV- of the bidirectional DC / DC converter, the high-voltage side port of the bidirectional DC / DC converter is connected to the DC bus where the photovoltaic module is located; the control input terminal of the bidirectional DC / DC converter is connected to the control output terminal of the control module.

[0011] A monitoring method for fire safety monitoring using the aforementioned photovoltaic module-level micro energy storage system includes:

[0012] Collect the temperature and internal resistance of the battery module in the micro energy storage rod;

[0013] When the temperature reaches 55℃ or the rate of change of internal resistance exceeds 10% / min, reduce the charging and discharging power to 50%.

[0014] When the temperature reaches 60℃ or the rate of change of internal resistance exceeds 12% / min, the charging and discharging operation is stopped and an early warning message is sent to the monitoring platform.

[0015] When the temperature exceeds 60℃ or the rate of change of internal resistance exceeds 15% / min, the circuit breaker is immediately triggered to cut off the circuit and send an emergency alarm message to the monitoring platform.

[0016] Furthermore, the monitoring platform includes a data acquisition module, a data analysis module, an alarm processing module, and a user interface module; wherein, the data update interval is ≤5s, and the alarm response time is ≤5s.

[0017] Furthermore, the firmware and data parameters of the control module are updated wirelessly, and a differential upgrade is performed; the upgrade package size is ≤500KB, and the upgrade time is ≤5 minutes.

[0018] Furthermore, each micro energy storage rod is equipped with an independent power management circuit, which enables the target data to be preserved for more than 72 hours in the event of a power outage.

[0019] The beneficial effects of this invention are as follows: This invention discloses a photovoltaic module-level micro energy storage system, which consists of micro energy storage rods, string inverters, and a monitoring platform. Each photovoltaic module is equipped with one micro energy storage rod, forming an independent energy storage unit, and is connected to the string circuit in parallel via the DC side. The micro energy storage rod integrates a battery module, a temperature sensor, an internal resistance detection module, a circuit breaker, and a control module, and is equipped with a bidirectional DC / DC converter to achieve energy interaction with the photovoltaic module and grid-connected operation. The monitoring method of this invention collects battery temperature and internal resistance, and performs power derating, shutdown warning, and circuit breaker protection measures according to threshold levels, and sends alarm information to the monitoring platform.

[0020] This invention achieves an organic integration of component-level energy storage and fire monitoring, possessing refined energy regulation capabilities and effectively preventing the spread of single-point faults; it enhances safety through a graded response mechanism, enabling early warning and rapid circuit disconnection to reduce fire risk; simultaneously, it works with a monitoring platform to achieve centralized monitoring, facilitating remote operation and maintenance and system management, thereby improving the safety and reliability of photovoltaic system operation. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0022] Figure 1 This is a schematic diagram of the structural framework of the micro energy storage system of the present invention;

[0023] Figure 2 This is a schematic diagram of the appearance of the micro energy storage rod of the present invention;

[0024] Figure 3 This is a schematic diagram illustrating the temperature detection principle of the micro energy storage rod of the present invention;

[0025] Figure 4 This is a schematic diagram of the internal battery module fixing of the micro energy storage rod of the present invention;

[0026] Figure 5 This is a schematic diagram of the fire safety monitoring method of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings, as shown in the figures:

[0028] This embodiment discloses a photovoltaic module-level micro energy storage system, including micro energy storage rods, string inverters, and a monitoring platform;

[0029] One of the micro energy storage rods and one photovoltaic module form an energy storage unit. Several of the energy storage units are connected in parallel to a string circuit via the DC side and connected to the grid via a string inverter.

[0030] The monitoring platform is used for centralized monitoring of several micro energy storage rods. The monitoring platform can utilize an existing cloud platform, such as... Figure 1 As shown.

[0031] The micro energy storage system of this invention adopts a distributed structure design, with an independent micro energy storage rod configured on each photovoltaic module side, forming a one-to-one correspondence between photovoltaic modules and energy storage units. Each energy storage unit is connected to the string circuit via parallel DC-side connection, and then connected to the grid via a string inverter. Unlike traditional centralized energy storage methods, by distributing energy storage functions to the module level, each photovoltaic module can both independently store energy and collaboratively output energy.

[0032] The monitoring platform undertakes the tasks of centralized monitoring and unified management. Through data interaction with each micro energy storage rod, the monitoring platform can collect operational status information in real time, complete the storage, analysis, and visualization of operational data, and issue control commands according to actual conditions to achieve overall coordination of multiple energy storage units. This mode ensures that the system has both distributed redundancy characteristics and centralized scheduling through the platform during operation.

[0033] In this embodiment, as Figure 2-4 As shown, the micro energy storage rod includes a battery module, a temperature sensor for detecting the temperature of the battery module, a detection module for detecting the internal resistance of the battery module, a circuit breaker connected to the battery module, and a control module for receiving and transmitting data and performing data processing and analysis.

[0034] The battery module is a lithium iron phosphate battery module, consisting of 6 3.2V / 50Ah cells connected in series, with a rated capacity of 0.96kWh, a rated voltage of 19.2V, and a cycle life of over 4000 cycles.

[0035] The temperature sensor is a high-precision temperature sensor, which is a digital temperature sensor that collects the battery surface temperature in real time. The measurement range is -55℃ to +125℃, the accuracy is ±0.5℃, and the sampling frequency is 1Hz.

[0036] The detection module is an internal resistance detection circuit that uses the AC injection method to measure the battery's internal resistance by injecting a small AC signal. The measurement range is 0.1mΩ to 100mΩ, with an accuracy of ±1% and a sampling interval of 5 minutes.

[0037] The circuit breaker is a fast circuit breaker, which adopts a parallel design of solid-state relay (SSR) and mechanical relay, and can completely cut off the charging and discharging circuit within 10ms.

[0038] The control module uses a domestically produced high-performance MCU with a built-in high-performance processor core, equipped with 256KB Flash and 128KB RAM, for processing sensor data and executing protection logic.

[0039] By configuring high-performance battery modules and multi-dimensional monitoring and protection devices in micro energy storage rods, accurate acquisition of battery operating status and rapid, safe response are achieved. The lithium iron phosphate battery module boasts high cycle life and stability, enhancing system durability; temperature sensors and internal resistance detection modules accurately reflect battery operating conditions in real time; the circuit breaker can disconnect the circuit in milliseconds, reducing the risk of thermal runaway; and the control module possesses high computing power and storage capacity, ensuring efficient execution of protection strategies, thereby significantly improving system safety and reliability.

[0040] In this embodiment, the micro energy storage rod further includes a bidirectional DC / DC converter; the positive terminal of the battery module is connected to the low-voltage input terminal LV+ of the bidirectional DC / DC converter through the circuit breaker, the negative terminal of the battery module is connected to the low-voltage input terminal LV- of the bidirectional DC / DC converter, and the high-voltage port of the bidirectional DC / DC converter is connected to the DC bus where the photovoltaic module is located; the control input terminal of the bidirectional DC / DC converter is connected to the control output terminal of the control module. The bidirectional DC / DC converter has a constant current / constant voltage charging mode and a constant current discharging mode.

[0041] By introducing a bidirectional DC / DC converter into the micro energy storage rod, efficient bidirectional energy flow between the battery module and the DC bus is achieved. It features constant current and constant voltage charging and constant current discharging modes, which can ensure the stability and safety of the battery charging and discharging process and avoid overcharging and over-discharging. At the same time, it can achieve smooth energy regulation under the influence of light fluctuations or load changes, improve grid-connected power quality, and enhance the flexibility and reliability of the system.

[0042] It should be noted that the micro energy storage system of the present invention also includes a communication module, and the signal output terminal of the control module is connected to the monitoring platform through the communication module. The communication module adopts WIoTa wireless communication, operates at a frequency of 470MHz, has a transmission distance of ≥500m (line-of-sight), a transmit power of up to +20dBm, a receive sensitivity of up to -145dBm, and supports Mesh networking functionality.

[0043] This invention also relates to a monitoring method for fire safety monitoring using the micro energy storage system described in the above embodiments, comprising:

[0044] Collect the temperature and internal resistance of the battery module in the micro energy storage rod;

[0045] When the temperature reaches 55℃ or the rate of change of internal resistance exceeds 10% / min, reduce the charging and discharging power to 50%.

[0046] When the temperature reaches 60℃ or the rate of change of internal resistance exceeds 12% / min, the charging and discharging operation is stopped and an early warning message is sent to the monitoring platform.

[0047] When the temperature exceeds 60℃ or the rate of change of internal resistance exceeds 15% / min, the circuit breaker is immediately triggered to cut off the circuit and send an emergency alarm message to the monitoring platform.

[0048] By setting multi-level temperature and internal resistance thresholds, combined with a tiered response mechanism of power derating, shutdown warning, and circuit breaker protection, dynamic control of battery safety status is achieved. The system can mitigate the spread of risk as soon as abnormal signs appear, quickly shut down and issue an alarm if the situation worsens, and promptly disconnect the circuit in extreme cases. This method effectively improves the sensitivity and reliability of fire monitoring, significantly reduces battery thermal runaway and fire hazards, and ensures the safe and stable operation of photovoltaic module-level energy storage systems.

[0049] In this embodiment, the monitoring platform includes a data acquisition module, a data analysis module, an alarm processing module, and a user interface module; wherein the data update interval is ≤5s, and the alarm response time is ≤5s. The monitoring platform is capable of centralized monitoring of up to 10,000 micro energy storage rods.

[0050] By setting up data acquisition, analysis, alarm processing, and user interface modules in the monitoring platform, and achieving a data update interval of ≤5s and an alarm response time of ≤5s, the real-time performance and response efficiency of monitoring can be significantly improved. Simultaneously, the platform has the capability to centrally monitor up to 10,000 micro-energy storage rods, meeting the operational needs of large-scale photovoltaic power plants, enabling unified management and rapid handling of massive amounts of equipment, and enhancing the system's security, scalability, and operational efficiency.

[0051] In this embodiment, OTA remote upgrade is used to update the firmware and data parameters of the control module wirelessly and perform differential upgrade; wherein the upgrade package size is ≤500KB and the upgrade time is ≤5 minutes.

[0052] Differential firmware and parameter upgrades for the control module can be performed wirelessly, enabling remote updates without interrupting system operation. The upgrade package is less than 500KB and the upgrade time is no more than 5 minutes, significantly improving upgrade efficiency and flexibility. This solution not only reduces maintenance costs but also ensures rapid iteration and optimization of security policies and control algorithms, thereby enhancing the system's adaptability and long-term reliability.

[0053] In this embodiment, each micro energy storage rod is equipped with an independent power management circuit, which enables the target data to be preserved for more than 72 hours in the event of a power outage.

[0054] This design ensures that the temperature, internal resistance, and operating status information of the energy storage unit are not lost in the event of an unexpected power outage or system failure, providing a reliable basis for fault analysis, post-event traceability, and safety assessment, and significantly improving the reliability and data integrity of the system.

[0055] To better understand the micro energy storage system and fire safety monitoring method of the present invention, such as Figure 5 As shown, further explanation is provided below:

[0056] In a rooftop photovoltaic project for an office building, a photovoltaic power generation system with a total capacity of 77.85 kWp was deployed. To achieve energy storage and peak shaving, this project adopted the micro-energy storage system described in this invention.

[0057] The system configuration is as follows:

[0058] 1. Select 36 615Wp monocrystalline silicon photovoltaic modules (a total of 2 photovoltaic strings), and install one micro energy storage rod for each photovoltaic module, for a total of 36 energy storage units;

[0059] 2. Each string consists of 18 micro-energy storage rods, for a total of 2 strings;

[0060] 3. Each photovoltaic string is equipped with a 10kW string inverter;

[0061] 4. The monitoring platform is deployed in the park's data center and is equipped with a dual-machine hot standby architecture.

[0062] The implementation process includes the following steps:

[0063] Step 1: Hardware Installation and Deployment

[0064] The micro energy storage rods are mounted on the side beams of the photovoltaic module support using specialized clamps, with the mounting angle consistent with the photovoltaic module (local latitude 29°, installation tilt angle 10°). Each energy storage rod is connected by two 6mm rods. 2 The DC cable is connected in parallel to the corresponding photovoltaic module, and the connector uses an MC4 waterproof interface. A torque wrench is used during installation to ensure reliable connection.

[0065] Step 2: Building the Communication Network

[0066] Employing a WIoTa wireless network architecture, 36 miniature energy storage rods form a subnet, equipped with a communication gateway node. The communication gateway communicates with the monitoring platform via a 4G network, ensuring reliable data transmission.

[0067] Step 3: System Debugging and Parameter Setting

[0068] Each micro energy storage rod automatically performs a self-test procedure after being powered on, including:

[0069] Battery health status detection: measuring parameters such as open circuit voltage, internal resistance, and temperature;

[0070] Communication testing: Establish a connection with the communication gateway and test the communication quality;

[0071] Protection function test: Simulate abnormal situations to verify the reliability of protection functions.

[0072] Parameter settings include:

[0073] Temperature protection thresholds: Twarning = 55℃, Talarm = 60℃, Tshutdown = 60℃

[0074] Thresholds for rate of change of internal resistance: ΔR / Δt_warning = 10% / min, ΔR / Δt_alarm = 12% / min, ΔR / Δt_shutdown = 15% / min

[0075] Data acquisition intervals: temperature 1s, internal resistance 5min, voltage and current 1s.

[0076] Communication reporting interval: 5 minutes in normal state, 1 minute in early warning state, and 10 seconds in alarm state.

[0077] Step 4: Operation Monitoring and Maintenance

[0078] After the system is put into operation, the monitoring platform displays the real-time operating status of each energy storage rod. The platform has the following functions:

[0079] Real-time monitoring: Displays parameters such as voltage, current, temperature, and SOC;

[0080] Historical data query: Saves 365 days of operational data and supports export in multiple formats;

[0081] Alarm Management: Tiered alarm handling, supporting multiple notification methods such as SMS and email push;

[0082] Remote maintenance: Supports remote parameter modification and firmware upgrade.

[0083] At 2:16 PM one afternoon, the ambient temperature on the roof was 41.7℃, the temperature of the photovoltaic modules was 50.2℃, and the irradiance was 891 W / m². 2 The system is operating at near full capacity. The monitoring platform received an alarm message from energy storage rod number 0x568CF:

[0084] 14:16:07 The temperature reached 55℃, entering the first-level warning state, and automatically reducing the charging power to 50%;

[0085] 14:18:15 The temperature continued to rise to 60℃, entering the second-level alarm state, and the charging operation was stopped;

[0086] At 14:21:40, the temperature reached 65℃, and the internal resistance change rate reached 16% / min, triggering the three-level protection and cutting off the circuit.

[0087] At 14:21:45, an emergency alarm message was sent to the monitoring platform and the mobile phones of the maintenance personnel.

[0088] After receiving the alarm, the maintenance personnel viewed the detailed data through the monitoring platform:

[0089] Temperature change curve 3 hours before the anomaly occurred;

[0090] Historical data on internal resistance changes;

[0091] Comparison of operating status of adjacent energy storage rods;

[0092] Ambient temperature and historical operating data.

[0093] On-site inspection revealed that several aluminum plates were temporarily placed near the energy storage rod (stacked by curtain wall maintenance workers). This caused reflected sunlight to be concentrated on the energy storage rod through the aluminum plates, leading to a temperature increase. After the aluminum plates were removed, the system returned to normal operation. Throughout the process, the protection system responded promptly, preventing a potential thermal runaway accident.

[0094] This invention proposes a safety assessment model based on two parameters: temperature and internal resistance, which improves the accuracy and timeliness of fault identification; it designs a three-level protection mechanism to achieve a progressive response from early warning to protection; it develops an efficient communication architecture to support real-time monitoring of large-scale distributed nodes; it achieves a plug-and-play deployment method, which greatly reduces installation and maintenance costs; and it provides a complete system solution, including hardware devices, communication networks, and a monitoring platform.

[0095] It achieves real-time fire safety monitoring of module-level energy storage, and has local diagnostic and protection capabilities; it improves the accuracy of fault identification by judging through dual parameters of temperature and internal resistance; it has a fast response speed and effectively prevents heat spread; it can be seamlessly integrated with existing photovoltaic systems without modifying the original electrical architecture; it supports remote monitoring and maintenance, greatly reducing operation and maintenance costs; and it provides complete data recording and analysis functions to provide data support for system optimization.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A photovoltaic module-level micro energy storage system, characterized in that: This includes micro energy storage rods, string inverters, and a monitoring platform; One of the micro energy storage rods and one photovoltaic module form an energy storage unit. Several of the energy storage units are connected in parallel to a string circuit via the DC side and connected to the grid via a string inverter. The monitoring platform is used for centralized monitoring of several micro energy storage rods.

2. The photovoltaic module-level micro energy storage system according to claim 1, characterized in that: The micro energy storage rod includes a battery module, a temperature sensor for detecting the temperature of the battery module, a detection module for detecting the internal resistance of the battery module, a circuit breaker connected to the battery module, and a control module for receiving and transmitting data and performing data processing and analysis.

3. The photovoltaic module-level micro energy storage system according to claim 2, characterized in that: The micro energy storage rod also includes a bidirectional DC / DC converter; the positive terminal of the battery module is connected to the low-voltage input terminal LV+ of the bidirectional DC / DC converter through the circuit breaker, the negative terminal of the battery module is connected to the low-voltage input terminal LV- of the bidirectional DC / DC converter, the high-voltage port of the bidirectional DC / DC converter is connected to the DC bus where the photovoltaic module is located; the control input terminal of the bidirectional DC / DC converter is connected to the control output terminal of the control module.

4. A monitoring method for fire safety monitoring using a photovoltaic module-level micro-energy storage system as described in any one of claims 1-3, characterized in that: include: Collect the temperature and internal resistance of the battery module in the micro energy storage rod; When the temperature reaches 55℃ or the rate of change of internal resistance exceeds 10% / min, reduce the charging and discharging power to 50%. When the temperature reaches 60℃ or the rate of change of internal resistance exceeds 12% / min, the charging and discharging operation is stopped and an early warning message is sent to the monitoring platform. When the temperature exceeds 60℃ or the rate of change of internal resistance exceeds 15% / min, the circuit breaker is immediately triggered to cut off the circuit and send an emergency alarm message to the monitoring platform.

5. The fire safety monitoring method according to claim 4, characterized in that: The monitoring platform includes a data acquisition module, a data analysis module, an alarm processing module, and a user interface module; wherein, the data update interval is ≤5s and the alarm response time is ≤5s.

6. The fire safety monitoring method according to claim 4, characterized in that: The firmware and data parameters of the control module are updated wirelessly, and a differential upgrade is performed; the upgrade package size is ≤500KB, and the upgrade time is ≤5 minutes.

7. The fire safety monitoring method according to claim 4, characterized in that: Each micro energy storage rod is equipped with an independent power management circuit, which allows the target data to be preserved for more than 72 hours in the event of a power outage.

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