1. Analysis of lithium-ion battery capacity attenuation Positive and negative electrodes, electrolytes and diaphragms are important components of lithium-ion batteries. The positive and negative electrodes of lithium-ion batteries undergo lithium insertion and extraction reactions respectively, and the amount of lithium inserted in the positive and negative electrodes becomes the main factor affecting the capacity of lithium-ion batteries. Therefore, the balance of the positive and negative electrode capacities of lithium-ion batteries must be maintained to ensure that the battery has optimal performance.   2. Overcharge 2.1 Negative electrode overcharge reaction There are many types of active materials that can be used as negative electrodes of lithium-ion batteries, with carbon-based negative electrode materials, silicon-based, tin-based negative electrode materials, lithium titanate negative electrode materials, etc. as the main materials. Different types of carbon materials have different electrochemical properties. Among them, graphite has the advantages of high conductivity, excellent layered structure and high crystallinity, which is more suitable for lithium insertion and extraction. At the same time, graphite materials are affordable and have a large stock, so they are widely used.   When a lithium-ion battery is charged and discharged for the first time, solvent molecules will decompose on the graphite surface and form a passivation film called SEI. This reaction will cause battery capacity loss and is an irreversible process. During the overcharging process of a lithium-ion battery, metal lithium deposition will occur on the negative electrode surface. This situation is prone to occur when the positive electrode active material is excessive relative to the negative electrode active material. At the same time, metal lithium deposition may also occur under high rate conditions.   Generally speaking, the reasons for the formation of metal lithium leading to the change in lithium battery capacity decay mainly include the following aspects: first, it leads to a decrease in the amount of circulatory lithium in the battery; second, metal lithium reacts with electrolytes or solvents to form other by-products; third, metal lithium is mainly deposited between the negative electrode and the diaphragm, causing the pores of the diaphragm to be blocked, resulting in an increase in the internal resistance of the battery. The influencing mechanism of lithium-ion battery capacity decay varies depending on the graphite material. Natural graphite has a high specific surface area, so the self-discharge reaction will cause the lithium battery capacity loss, and the electrochemical reaction impedance of natural graphite as the negative electrode of the battery is also higher than that of artificial graphite. In addition, factors such as the dissociation of the negative electrode layered structure during the cycle, the dispersion of the conductive agent during the production of the pole piece, and the increase in the impedance of the electrochemical reaction during storage are all important factors that lead to the loss of lithium battery capacity.   2.2 Positive electrode overcharge reaction Positive electrode overcharge mainly occurs when the proportion of positive electrode material is too low, resulting in an imbalance in the capacity between the electrodes, causing irreversible loss of lithium battery capacity, and the coexistence and continuous accumulation of oxygen and combustible gases decomposed from the positive electrode material and the electrolyte may bring safety hazards to the use of lithium batteries.   2.3 Electrolyte reacts at high voltage If the charging voltage of the lithium battery is too high, the electrolyte will undergo an oxidation reaction and generate some by-products, which will block the electrode micropores and hinder the migration of lithium ions, thereby causing the cycle capacity to decay. The change trend of the electrolyte concentration and the stability of the electrolyte is inversely proportional. The higher the electrolyte concentration, the lower the electrolyte stability, which in turn affects the capacity of the lithium-ion battery. During the charging process, the electrolyte will be consumed to a certain extent. Therefore, it needs to be supplemented during assembly, resulting in a reduction in battery active materials and affecting the initial capacity of the battery.   3. Decomposition of electrolyte The electrolyte includes electrolytes, solvents and additives, and its properties will affect the service life, specific capacity, rate charge and discharge performance and safety performance of the battery. The decomposition of electrolytes and solvents in the electrolyte will cause the battery capacity to be lost. During the first charge and discharge, the formation of SEI film on the surface of the negative electrode by solvents and other substances will cause irreversible capacity loss, but this is inevitable. If there are impurities such as water or hydrogen fluoride in the electrolyte, the electrolyte LiPF6 may decompose at high temperatures, and the generated products will react with the positive electrode material, resulting in the battery capacity being affected. At the same time, some products will also react with the solvent and affect the stability of the SEI film on the surface of the negative electrode, causing the performance of the lithium-ion battery to decay. In addition, if the products of the electrolyte decomposition are not compatible with the electrolyte, they will block the positive electrode pores during the migration process, resulting in battery capacity decay. In general, the occurrence of side reactions between the electrolyte and the positive and negative electrodes of the battery, as well as the generated by-products, are the main factors causing battery capacity decay.   4. Self-discharge Lithium-ion batteries generally experience capacity loss, a process called self-discharge, which is divided into reversible capacity loss and irreversible capacity loss. The solvent oxidation rate has a direct impact on the self-discharge rate. The positive and negative active materials may react with the solute during the charging process, resulting in capacity imbalance and irreversible attenuation of lithium ion migration. Therefore, it can be seen that reducing the surface area of ​​the active material can reduce the capacity loss rate, and the decomposition of the solvent will affect the storage life of the battery. In addition, diaphragm leakage can also lead to capacity loss, but this possibility is low. If the self-discharge phenomenon exists for a long time, it will lead to the deposition of metallic lithium and further lead to the attenuation of the positive and negative electrode capacities.   5. Electrode instability During the charging process, the active material of the positive electrode of the battery is unstable, which will cause it to react with the electrolyte and affect the battery capacity. Among them, structural defects of the positive electrode material, excessive charging potential, and carbon black content are the main factors affecting battery capacity.

                                                                                                Preface As an important equipment in the field of modern energy conversion and transmission, the careful design and reasonable composition of the inverter-boost integrated silo are the key to achieving efficient and stable operation. The inverter-boost integrated cabin, as the name suggests, integrates the two key functions of PCS and boost into a compact and efficient cabin. This integrated design brings many significant advantages. The following takes a 2MW inverter-boost integrated silo as an example to analyze the internal composition and design. 1. Composition of the inverter-boost integrated warehouse The inverter-boost integrated warehouse adopts a standard container design, which is flexible in deployment and convenient for operation and maintenance. It can generally adapt to 500kW and 630kW energy storage converter PCS. The built-in transformer can adapt to voltage levels of 35kV and below, and supports local and remote monitoring. The inverter-boost integrated warehouse integrates energy storage converters, boost transformers, high-voltage ring network cabinets, low-voltage distribution boxes and other equipment in one container. It has a high degree of integration, reduces the difficulty of on-site construction, and is easy to transport, install, use and maintain. It has built-in emergency lighting system, fire protection system, access control system, and heat dissipation system. There are fireproof partitions inside the box, ventilation openings on both sides of the box, and heat dissipation ducts specially designed for PCS, which can effectively ensure the normal operation and safety of the equipment inside the boost integrated warehouse. 2. Design of the main circuit of the inverter-boost integrated warehouse From the perspective of space utilization, the integrated cabin greatly saves the floor space required for equipment installation. Compared with traditional distributed inverter and boost equipment, it integrates complex circuits and components into a cabin, which not only reduces the connection lines between equipment and reduces line losses, but also makes the entire system more concise and beautiful, and is easy to layout in a limited space. The 2 MW containerized energy storage boost transformer system mainly consists of a container body, four 500kW energy storage bidirectional converters, a 1250 kVA, 10 kV/0.38 kV transformer, a 1250 kVA, 10 kV/0.38 kV transformer, a 250 kVA, 10kV/0.38 kV isolation transformer, and supporting high-voltage switch cabinets, low-voltage distribution cabinets, and local monitoring system cabinets.   Two energy storage bidirectional converters are used as a group. The DC side of each group of energy storage bidirectional converters is connected to the energy storage system, and the AC side is connected to the secondary side of the 1250 kVA, 10 kV/0.38 kV transformer. The high voltage side of two 1250kVA transformers are connected in parallel to a 10kV high voltage switchgear. The total output of the system is 2MW, 10 kV three-phase AC, and energy can flow in both directions on the DC side and the AC side. 3. The high-voltage side of the high-voltage system uses a 10kV high-voltage switch cabinet to access the park's 10kV busbar, with one in and two out. One way is to supply power to two 1250 kVA transformers in parallel through a high-voltage circuit breaker, and the other way is to supply power to a 250kVA isolation transformer through a load isolation switch plus a fuse. The ring network cabinet is equipped with an isolation switch, a fuse, a circuit breaker, a lightning protection device, a live indication device, a fault indication device, a current transformer, and a comprehensive protection device. The comprehensive protection device controls the circuit breaker tripping by monitoring system parameters to achieve local and remote operation. 4. Local monitoring system The local monitoring system is installed in the local monitoring cabinet, with a programmable controller as the core, and is used to realize the status acquisition and system communication of transformers, high and low voltage switches, converters, fire equipment, air conditioners, lighting equipment, security equipment, etc. It has a human-computer interaction interface to display the status and parameters of the 2 MW container-type energy storage booster system. 5. Energy Storage Bidirectional Converter The energy storage bidirectional converter is the core component and is an important guarantee for achieving efficient, stable, safe and reliable operation of the 2 MW containerized energy storage boost converter system and maximizing the utilization of wind and solar energy. Combined with the on-site use environment and actual operation requirements, the energy storage bidirectional converter is designed to achieve grid-connected and off-grid operation functions.   The energy storage bidirectional converter is connected to the large power grid for a long time. The battery system is charged when the park load is small, and the battery is discharged when the park load is large. The energy storage bidirectional converter is required to have the function of grid-connected operation, realize independent decoupling control of active power and reactive power, and be able to coordinate with the superior monitoring system to realize various applications of the power grid system in the park.

The full name of the energy storage battery BMS management system is Battery Management System. The energy storage battery BMS management system is one of the core subsystems of the battery energy storage system, responsible for monitoring the operating status of each battery in the battery energy storage unit to ensure the safe and reliable operation of the energy storage unit. The BMS battery management system unit includes a BMS battery management system, a control module, a display module, a wireless communication module, electrical equipment, a battery pack for powering electrical equipment, and a collection module for collecting battery information of the battery pack. Generally, BMS is presented as a circuit board, that is, a BMS protection board, or a hardware box. The basic framework of the battery management system (BMS) includes a power battery pack housing and a sealed hardware module, a high-voltage analysis box (BDU) and a BMS controller. 1. BMU master controller Battery Management Unit (BMU for short) refers to a system for monitoring and managing battery packs. That is, the BMS motherboard that is often said, its function is to collect the adoption information from each slave board. BMU management units are usually used in electric vehicles, energy storage systems and other applications that require battery packs. BMU monitors the status of the battery pack by collecting data on the battery's voltage, current, temperature and other related parameters. BMU can monitor the battery's charging and discharging process, as well as control the rate and method of charging and discharging to ensure the safe operation of the battery pack. BMU can also diagnose and troubleshoot faults in the battery pack and provide various protection functions, such as overcharge protection, over-discharge protection and short-circuit protection. 2. CSC slave controller The CSC slave controller is used to monitor the module's single cell voltage and single cell temperature problems, transmit information to the main board, and has a battery balancing function. It includes voltage detection, temperature detection, balancing management and corresponding diagnosis. Each CSC module contains an analog front-end chip (Analog Front End, AFE) chip. 3. BDU battery energy distribution unit The battery energy distribution unit (BDU for short), also called the battery junction box, is connected to the vehicle's high-voltage load and fast-charging harness through a high-voltage electrical interface. It includes a pre-charging circuit, a total positive relay, a total negative relay, and a fast-charging relay, and is controlled by the main board. 4. High-voltage controller The high-voltage controller can be integrated into the mainboard or can be independent, real-time monitoring of batteries, current, voltage, and also includes pre-charge detection. The BMS management system can monitor and collect the state parameters of the energy storage battery in real time (including but not limited to single cell voltage, battery pole temperature, battery loop current, battery pack terminal voltage, battery system insulation resistance, etc.), and perform necessary analysis and calculation on the relevant state parameters to obtain more system state evaluation parameters, and realize effective control of the energy storage battery body according to specific protection and control strategies to ensure the safe and reliable operation of the entire battery energy storage unit. At the same time, BMS can exchange information with other external devices (PCS, EMS, fire protection system, etc.) through its own communication interface and analog/digital input and input interface to form linkage control of each subsystem in the entire energy storage power station, ensuring the safe, reliable and efficient grid-connected operation of the power station.

How do photovoltaic power stations deal with high temperature weather? On August 5, the Central Meteorological Observatory continued to issue an orange high temperature warning. According to data from China Weather Network, southern my country is experiencing a round of fierce high temperature and hot weather. Large-scale high temperature weather in the south will continue, with the core area remaining in the Jiangsu, Zhejiang and Shanghai areas. With strong sunlight and high temperatures, will the power generation efficiency of photovoltaic power stations that use solar energy to generate electricity also increase? The answer is no. Under normal circumstances, the ideal operating temperature of photovoltaic power generation components is about 25℃. For every 1℃ increase in temperature, the output power will decrease by about 0.35%, and the power generation of photovoltaic power stations will also decrease by about 0.35%. That is, after the temperature exceeds 25℃, the higher the temperature, the lower the output power, and the power generation will also decrease accordingly. In addition to photovoltaic components, the high temperature caused by the weather will also cause the efficiency of inverters and other electrical components to decrease. Generally, the operating temperature range of civilian-grade electronic components is -35℃～70℃, and the operating temperature of most photovoltaic inverters is -30～60℃. Improper installation or heat dissipation will force the inverter and electrical components to start  derating operation or even shut down for maintenance, resulting in power generation loss. Due to the influence of weathering and ultraviolet radiation, electrical components installed outdoors will also age quickly. To ensure that photovoltaic modules have good power generation in hot weather, the first thing is to maintain air circulation for modules, inverters, distribution boxes and other equipment. Avoid excessive number of modules blocking each other, which will affect the ventilation and heat dissipation of the photovoltaic array. At the same time, ensure that the area around photovoltaic modules, inverters, distribution boxes and other equipment is open and free of debris to avoid affecting the heat dissipation of the power station. If there are debris piled up next to the equipment that blocks or oppresses the power station, it must be removed in time. When installing a photovoltaic power station, the inverter and distribution box are installed in a shaded and rainproof place. If there is no shelter in the actual environment, they can be equipped with a canopy to avoid direct sunlight, which will cause the equipment temperature to be too high, affecting the power generation and equipment life. At the same time, a cooling fan can be installed on the equipment. In order to ensure the safety of photovoltaic power stations and avoid equipment failures and possible disasters caused by high temperatures, regular inspections of photovoltaic power stations are also essential. It is necessary to pay attention to the temperature difference problem that causes hidden cracks in components when cleaning components in high temperatures in summer. It is necessary to avoid high temperature periods and clean them in the early morning or evening when the temperature is lower.

Positive electrode materials The method of using materials with excellent conductivity to coat the surface of the active material body to improve the conductivity of the positive electrode material interface, reduce the interface impedance, and reduce the side reactions between the positive electrode material and the electrolyte to stabilize the material structure. The material body is bulk-doped with elements such as Mn, Al, Cr, Mg, and F to increase the interlayer spacing of the material to increase the diffusion rate of Li+ in the body, reduce the diffusion impedance of Li+, and thus improve the low-temperature performance of the battery. Reduce the particle size of the material and shorten the migration path of Li+. It should be pointed out that this method will increase the specific surface area of ​​the material and thus increase the side reactions with the electrolyte.   Electrolyte Improve the low-temperature conductivity of the electrolyte by optimizing the solvent composition and using new electrolyte salts. Use new additives to improve the properties of the SEI film to facilitate the conduction of Li+ at low temperatures.   Negative electrode materials Selecting appropriate negative electrode materials is a key factor in improving the low-temperature performance of batteries. Currently, the low-temperature performance is mainly optimized through negative electrode surface treatment, surface coating, doping to increase interlayer spacing, and controlling particle size.

The PCS (Power Conversion System) energy storage converter is a bidirectional current controllable conversion device that connects the energy storage battery system and the power grid/load. Its core function is to control the charging and discharging process of the energy storage battery, perform AC/DC conversion, and directly supply power to the AC load without a power grid. The working principle is a four-quadrant converter that can control the AC and DC sides to achieve bidirectional conversion of AC/DC power. The principle is to perform constant power or constant current control through microgrid monitoring instructions to charge or discharge the battery, while smoothing the output of fluctuating power sources such as wind power and solar energy. The PCS energy storage converter can convert the DC power output by the battery system into AC power that can be transmitted to the power grid and other loads to complete the discharge; at the same time, it can rectify the AC power of the power grid into DC power to charge the battery. It consists of power, control, protection, monitoring and other hardware and software appliances. Power electronic devices are the core component of the energy storage converter, which mainly realizes the conversion and control of electric energy. Common power electronic devices include thyristors (SCR), thyristors (BTR), relays, IGBTs, MOSFETs, etc. These devices realize the flow and conversion of electric energy by controlling the switching state of current and voltage. The control circuit is used to achieve precise control of power electronic devices. The control circuit generally includes modules such as signal acquisition, signal processing, and control algorithm. The signal acquisition module is used to collect input and output current, voltage, temperature and other signals. The signal processing module processes and filters the collected signals to obtain accurate parameters; the control algorithm module calculates the control signal based on the input signal and the set value, which is used to control the switching state of the power electronic device. Electrical connection components are used to connect energy elements and external systems. Common electrical connection components include cables, plugs and sockets, and wiring terminals. The electrical connection components must have good conductivity and reliable contact performance to ensure the effective transmission of electric energy and safe and reliable. The grid-connected mode of the energy storage converter PCS is to achieve bidirectional energy conversion between the battery pack and the grid. It has the characteristics of a grid-connected inverter, such as anti-islanding, automatic tracking of grid voltage phase and frequency, low voltage ride-through, etc. According to the requirements of grid dispatch or local control, PCS converts the AC power of the grid into DC power during the low load period of the grid to charge the battery pack, and has the function of battery charging and discharging management; during the peak load period of the grid, it inverts the DC power of the battery pack into AC power and feeds it back to the public grid; when the power quality is poor, it feeds or absorbs active power to the grid and provides reactive power compensation. Off-grid mode is also called isolated grid operation, that is, the energy conversion system (PCS) can be disconnected from the main grid according to actual needs and meet the set requirements, and provide AC power that meets the power quality requirements of the grid to some local loads.   Hybrid mode means that the energy storage system can switch between grid-connected mode and off-grid mode. The energy storage system is in the microgrid, which is connected to the public grid and operates as a grid-connected system under normal working conditions. If the microgrid is disconnected from the public grid, the energy storage system will work in off-grid mode to provide the main power supply for the microgrid. Common applications include filtering, stabilizing the grid, and adjusting power quality.

01What is a photovoltaic cable?   Photovoltaic cables are mainly used to connect solar panels and various solar system equipment, and are the basis of supporting electrical equipment in solar systems. The basic structure of photovoltaic cables consists of conductors, insulation layers, and sheaths.   Photovoltaic cables are divided into DC cables and AC cables: Photovoltaic DC cables are mainly used for connection between modules, parallel connection between strings and between strings and DC distribution boxes (combiner boxes), and between DC distribution boxes and inverters. Photovoltaic AC cables are mainly used for connection between inverters and low-voltage distribution systems, connection between low-voltage distribution systems and transformers, and connection between transformers and power grids or users.   Photovoltaic cables need to withstand long-term erosion from natural conditions such as wind and rain, day and night exposure, frost, snow, ice, and ultraviolet rays. Therefore, they need to have characteristics such as ozone resistance, UV resistance, acid and alkali resistance, high temperature resistance, severe cold resistance, dent resistance, halogen-free, flame retardant, and compatibility with standard connectors and connection systems. The service life can generally reach more than 25 years.   02What is a bidirectional meter?   A bidirectional meter refers to a bidirectional meter, which is a meter that can measure electricity consumption and power generation.   In a solar system, both power and electric energy have directions. From the perspective of electricity consumption, power consumption is counted as positive power or positive electric energy, and power generation is counted as negative power or negative electric energy. The meter can read the positive and reverse electric energy through the display screen and store the electric energy data. The reason for installing a bidirectional meter in a household solar system is that the electricity generated by photovoltaics cannot be consumed by all users, and the remaining electric energy needs to be transmitted to the power grid, and the meter needs to measure a number; When solar power generation cannot meet user needs, it is necessary to use the power of the power grid, which requires another number to be measured. Ordinary single meters cannot meet this requirement, so it is necessary to use smart meters with bidirectional metering functions.

Lithium-ion batteries (LIBs), which store energy leveraging the reversible reduction of lithium ions, power most devices and electronics on the market today. Due to their wide range of operating temperatures, long lifespan, small size, fast charging times, and compatibility with existing manufacturing processes, these rechargeable batteries can greatly contribute to the electronics industry, while also supporting ongoing efforts towards carbon neutrality.     The affordable and eco-friendly recycling of used LIBs is a long sought-after goal in the energy sector, as it would improve the sustainability of these batteries. Existing methods, however, are often ineffective, expensive, or harmful to the environment.   Moreover, LIBs heavily rely on materials that are becoming less abundant on Earth, such as cobalt and lithium. Approaches that enable the reliable and cost-effective extraction of these materials from spent batteries would drastically reduce the need to source these materials elsewhere, thus helping to meet the growing LIB demand.   Researchers at the Chinese Academy of Sciences recently devised a new approach based on so-called contact-electro-catalysis, which could enable the recycling of spent LIB cells. Their method, introduced in Nature Energy, leverages the transfer of electrons that takes place during liquid-solid contact electrification to generate free radicals that initiate desired chemical reactions.   "With the global trend towards carbon neutrality, the demand for LIBs is continuously increasing," Huifan Li, Andy Berbille, and their colleagues wrote in their paper. "However, current recycling methods for spent LIBs need urgent improvement in terms of eco-friendliness, cost, and efficiency. We propose a mechano-catalytic method, dubbed contact-electro-catalysis, utilizing radicals generated by contact electrification to promote the metal leaching under the ultrasonic wave. We also use SiO2 as a recyclable catalyst in the process."   As part of their recent study, Li, Berbille and their colleagues set out to explore the possibility that contact-electro-catalysis could replace chemical agents typically used to recycle LIBs. To do this, they used the technique to elicit continuous solid-liquid contact and separation through cavitation bubbles, under ultrasound waves.   This enabled the constant generation of reactive oxygen through the electrification of contacts. They then assessed the effectiveness of this strategy for recycling lithium and cobalt in worn-out LIBs.   "For lithium cobalt (III) oxide batteries, the leaching efficiency reached 100% for lithium and 92.19% for cobalt at 90°C within six hours," Li, Berbille, and their colleagues wrote in their paper. "For ternary lithium batteries, the leaching efficiencies of lithium, nickel, manganese, and cobalt reached 94.56%, 96.62%, 96.54%, and 98.39% at 70°C, respectively, within six hours."   In initial tests, the approach proposed by this team of researchers achieved highly promising results, highlighting its potential for supporting the low-cost, sustainable, and large-scale recycling of the expensive and highly sought-after materials inside LIBs. Future studies could help to perfect this method, while further assessing its advantages and limitations, potentially paving the way towards its deployment in real-world settings.   "We anticipate that this method can provide a green, high efficiency and economic approach for LIB recycling, meeting the exponentially growing demand for LIB productions," the researchers wrote in their paper.    

No.1 The symbol for the isolating switch is QS and the symbol for the circuit breaker is QF. In terms of function and structure, the main differences between isolating switches and circuit breakers are as follows: 1. Function: The circuit breaker has an arc extinguishing device and can operate with load, including load current and fault current; the isolating switch does not have an arc extinguishing device and is usually used to isolate the power supply and cannot be used to cut off or put in load currents and faults above a certain capacity. current. 2. Structure: The structure of the circuit breaker is relatively complex, usually composed of contacts, operating mechanism, tripping device, etc.; the structure of the isolation switch is relatively simple, mainly composed of a knife switch and an operating mechanism. No.2  In terms of usage occasions and operation methods, the main differences between isolating switches and circuit breakers are as follows: 1. Usage occasions: Circuit breakers are usually used in high-voltage power systems, such as substations, transmission lines, etc.; isolation switches are usually used in low-voltage power systems, such as distribution boxes, switch cabinets, etc. 2. Operation mode: Most circuit breakers are operated by remote electric control; most isolating switches are operated by local manual operation. To sum up, the circuit breaker is more powerful in function and can provide overload protection and short-circuit protection, while the isolating switch is mainly used to isolate the power supply to ensure safety during inspection, maintenance or other operations.  

BackgroundFire risk: Fire is the biggest economic loss of photovoltaic power plants. If it is installed on the roof of a factory or residential building, it can easily endanger personal safety.In general centralized photovoltaic systems, there are tens of meters of high-voltage DC lines between 600V and 1000V between the photovoltaic module array and the inverter, which can be regarded as a potential safety hazard for people and buildings. There are many factors causing fire accidents in photovoltaic power stations. According to statistics, more than 80% of fire accidents in photovoltaic power stations are caused by DC side faults, and DC arcing is the main reason.2. ReasonsIn the entire photovoltaic system, the DC side voltage is usually as high as 600-1000V. DC arcing can easily occur due to loose joints of photovoltaic module joints, poor contact, moisture in the wires, ruptured insulation, etc.DC arcing will cause the temperature of the contact part to rise sharply. Continuous arcing will produce a high temperature of 3000-7000℃, accompanied by high temperature carbonization of surrounding devices. In the least case, fuses and cables will be blown. In the worst case, components and equipment will be burned and cause fires. Currently, UL and NEC safety regulations have mandatory requirements for arc detection functions for DC systems above 80V.Since a fire in a photovoltaic system cannot be extinguished directly with water, early warning and prevention are very important. Especially for color steel tile roofs, it is difficult for maintenance personnel to check fault points and hidden dangers, so it is necessary to install an inverter with arc detection function. Very necessary.3. SolutionsIn addition to high-voltage direct current easily causing fires, it is also difficult to put out fires when a fire occurs. According to the national standard GB/T18379 DC voltage specification for building electrical equipment, for home rooftop photovoltaic systems, system solutions with a DC side voltage not exceeding 120V are preferred.For photovoltaic systems with a DC side voltage exceeding 120V, it is recommended to install protection devices such as arc fault interrupters (AFCI) and DC switches; if the DC cable from the photovoltaic module to the inverter exceeds 1.5 meters, it is recommended to add a quick shutdown device, or use Optimizer, so that when a fire occurs, the high-voltage direct current can be cut off in time to extinguish the fire.AFCI: (Arc-Fault Circuit-Interrupter) is a protection device that disconnects the power circuit before the arc fault develops into a fire or a short circuit occurs by identifying the arc fault characteristic signal in the circuit.As a circuit protection device, AFCI's main function is to prevent fires caused by fault arcs and can effectively detect loose screws and poor contacts in the DC loop. At the same time, it has the ability to detect and distinguish between normal arcs and fault arcs generated by the inverter when starting, stopping or switching, and promptly cuts off the circuit after detecting fault arcs.In addition, AFCI has the following characteristics:1. It has effective DC arc identification capability, allowing the maximum DC current to reach 60A;2. It has a friendly interface and can be remotely connected to control circuit breakers or connectors;3. It has RS232 to 485 communication function and can monitor the module status in real time;4. LED and buzzer can be used to quickly identify the working status of the module and provide sound and light alarms;5. Functional modularization, easy to transplant to various series of productsIn terms of arc fault protection of photovoltaic systems, we give full play to the role of photovoltaic clean energy and develop special AFCI for photovoltaic DC systems, involving series DC arc fault protection of photovoltaic inverters, combiner boxes, and photovoltaic battery modules.To meet the new requirements of smart grid for switching appliances and realize the communication and networking of AFCI, intelligence and related bus technology, communication and networking and other technologies will play a greater role. In terms of AFCI product serialization and standardization, AFCI's serialization, standardization, and accessory modularization will greatly increase its application scope in terminal power distribution.

Ongrid solar inverters have high working efficiency and reliable performance. They are suitable for installation in remote areas where no one is maintaining or on duty. They can maximize the use of solar energy, thus improving the efficiency of the system. Below I will introduce to you the installation precautions for installing grid-connected inverters.   1. Before installation, you should first check whether the inverter has been damaged during transportation. 2. When selecting an installation site, make sure there is no interference from other power electronic equipment in the surrounding area. 3. Before making electrical connections, be sure to cover the photovoltaic panels with opaque materials or disconnect the DC side circuit breaker. When exposed to sunlight, photovoltaic arrays will generate dangerous voltages. 4. All installation operations must be completed by professional technicians only. 5. The cables used in the photovoltaic system power generation system must be firmly connected, well insulated and of appropriate specifications. 6. All electrical installations must meet local and national electrical standards. 7. The inverter can only be connected to the grid after obtaining permission from the local power department and after professional technicians have completed all electrical connections. 8. Before performing any maintenance work, you should first disconnect the electrical connection between the inverter and the grid, and then disconnect the DC side electrical connection. 9. Wait at least 5 minutes until the internal components are discharged before performing maintenance work. 10. Any fault that affects the safety performance of the inverter must be eliminated immediately before the inverter can be turned on again. 11. Avoid unnecessary circuit board contact. 12. Comply with electrostatic protection regulations and wear an anti-static bracelet. 13. Pay attention to and obey the warning labels on the product. 14. Conduct a preliminary visual inspection of the equipment for damage or other dangerous conditions before operation. 15. Pay attention to the hot surface of the inverter. For example, the radiator of power semiconductors will still maintain a high temperature for a period of time after the inverter is powered off.

The DC input of the photovoltaic grid-connected inverter mainly includes the maximum input voltage, starting voltage, rated input voltage, MPPT voltage, and the number of MPPTs. Among them, the MPPT voltage range determines whether the voltage after the photovoltaic strings are connected in series meets the optimal voltage input range of the inverter. The number of MPPTs and the maximum number of input strings for each MPPT determine the series-parallel design method of photovoltaic modules. The maximum input current determines the maximum string input current value of each MPPT, and is an important determining condition for photovoltaic module selection. The AC output of the photovoltaic grid-connected inverter mainly includes rated output power, maximum output power, maximum output current, rated grid voltage, etc. The output power of the inverter under normal working conditions cannot exceed the rated power. When sunshine resources are abundant, the inverter's output can work within the maximum output power for a short period of time. In addition, the power factor of the inverter is the ratio of the output power to the apparent power. The closer this value is to 1, the higher the efficiency of the inverter. The protection functions of photovoltaic grid-connected inverters mainly include DC reverse polarity protection, AC short circuit protection, anti-islanding protection, surge protection, AC and DC over-voltage and under-voltage protection, leakage current protection, etc. 1. DC reverse connection protection: prevent AC short circuit when the positive input terminal and negative input terminal of the inverter are reversely connected. 2. AC short-circuit protection: Prevent the AC output side of the inverter from short-circuiting. At the same time, when a short-circuit occurs in the power grid, the inverter protects itself. 3. Anti-islanding protection: When the power grid loses power and loses voltage, the inverter stops working due to the loss of voltage. 4. Surge protection: Protects the inverter from transient overvoltage.