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.

1. What is photovoltaic power generation? Photovoltaic power generation refers to a power generation method that uses solar radiation to directly convert into electrical energy. Photovoltaic power generation is the mainstream of solar power generation today. Therefore, what people often call solar power generation now is photovoltaic power generation.   2. Do you know the historical origin of photovoltaic power generation? In 1839, 19-year-old Becquerel of France discovered the "photovoltaic effect" while doing physical experiments when he discovered that the current would increase when two metal electrodes in a conductive liquid were irradiated with light. In 1930, Lange first proposed using the "photovoltaic effect" to manufacture solar cells to turn solar energy into electrical energy. In 1932 Odubot and Stola made the first "cadmium sulfide" solar cell. In 1941 Audu discovered the photovoltaic effect on silicon. In May 1954, Chapin, Fuller and Pierson of Bell Labs in the United States launched a monocrystalline silicon solar cell with an efficiency of 6%. This was the first solar cell with practical value in the world. In the same year, Wick first discovered the photovoltaic effect of nickel arsenide, and deposited a nickel sulfide film on glass to create a solar cell. Practical photovoltaic power generation technology that converts sunlight into electrical energy was born and developed.   3. How do photovoltaic solar cell generate electricity? Photovoltaic solar cell is a semiconductor device with light and electricity conversion characteristics. It directly converts solar radiation energy into direct current. It is the most basic unit of photovoltaic power generation. The unique electrical characteristics of photovoltaic cells are achieved by incorporating certain elements into crystalline silicon. Elements (such as phosphorus or boron, etc.), thereby causing a permanent imbalance in the molecular charge of the material, forming a semiconductor material with special electrical properties. Free charges can be generated in semiconductors with special electrical properties under sunlight. These free charges Directional movement and accumulation, thus generating electrical energy when its two ends are closed, this phenomenon is called the "photovoltaic effect"   4. What components does a photovoltaic power generation system consist of? The photovoltaic power generation system consists of a solar panel array, a controller, a battery pack, a DC/AC inverter, etc. The core component of the photovoltaic power generation system is solar panel, It is composed of photovoltaic solar cells connected in series, parallel and packaged. It converts the sun's light energy directly into electrical energy. The electricity generated by solar panel is direct current. We can use it or use an inverter to convert it into alternating current for use. From one perspective, the electric energy generated by the photovoltaic solar system can be used immediately, or the electric energy can be stored using energy storage devices such as batteries and released for use at any time as needed.

There are many factors that affect the power generation and efficiency of a solar station with the same capacity. Today SAIL SOLAR will lead you to have a studying.   1. Solar Radiation When the conversion efficiency of solar panel is constant, the power generation of the solar system is determined by the intensity of solar radiation. Normally, the utilization efficiency of solar radiation by solar systems is only about 10%. Therefore, solar radiation intensity, spectral characteristics, and climate conditions must be taken into consideration. If the current year's power generation exceeds or falls short of the standard, it is likely that the overall solar radiation for that year deviates from the average.   2. Tilt angle of solar panel The azimuth angle of solar panel is generally selected in the south direction to maximize the power generation per unit capacity of solar station. As long as it is within ±20° of due south, it will not have much impact on the power generation. If conditions permit, it should be as far as 20° to the southwest. The above angle recommendations are based on installation in the Northern Hemisphere, and vice versa for the Southern Hemisphere. Tilt angles vary from place to place, and local installers are more familiar with the optimal tilt angle for components. If it is a pitched roof, in order to save brackets, many of them will be laid flat on the roof, regardless of the tilt angle, for the sake of beauty.   3. Solar panel efficiency and quality There are many solar panel types to choose from on the market, such as polycrystalline silicon, monocrystalline silicon solar panel, etc. Different solar panels have different power generation efficiency, attenuation and quality. The most important thing is must purchase them from regular channels at a reasonable market price. Only in this way can you ensure stable and reliable power generation for 25 years.   4. Solar panel matching loss Any series connection will cause current loss due to the current difference of solar panels, and any parallel connection will cause voltage loss due to the voltage difference of solar panels. Losses may reach more than 8%. In order to reduce the matching loss and increase the power generation capacity of the solar  station, we should pay attention to the following aspects: 1)To reduce matching losses, try to use solar panels with consistent current in series; 2)The attenuation of solar panels should be kept as consistent as possible; 3)Isolation diode.   5. Temperature (ventilation) Data shows that when the temperature rises by 1°C, the output power of crystalline silicon solar panel decreases by 0.04%. Therefore, it is necessary to avoid the impact of temperature on power generation and maintain good ventilation conditions for the solar panels.    6. Effect of dust The crystalline silicon solar panel is made of tempered glass. If it is exposed to the air for a long time, organic matter and a large amount of dust will naturally accumulate. Dust falling on the surface blocks the light, which will reduce the output efficiency of the solar panels and directly affect the power generation. At the same time, it may also cause a "hot spot" effect on the solar panels, causing damage to the components. solar panel station must be cleaned in time.   7.Shadows, snow cover During the site selection process of the solar solution, attention must be paid to the light shielding. Avoid areas where light may be blocked. According to the circuit principle, when solar panels are connected in series, the current is determined by the smallest solar panels Therefore, if there is a shadow on one solar panels, it will affect the power generation of this solar panels. Therefore, when installing a solar power station, you must not be greedy for large capacity. You must consider the area of the roof and whether there is any obstruction around the roof.   8. Maximum output power tracking (MPPT) MPPT efficiency is a key factor in determining the power generation of solar inverters, and its importance far exceeds the efficiency of the solar inverter itself. MPPT efficiency is equal to hardware efficiency times software efficiency. Hardware efficiency is mainly determined by the accuracy of the current sensor and the accuracy of the sampling circuit; software efficiency is determined by the sampling frequency. There are many ways to implement MPPT, but no matter which method is used, the solar panel power changes must first be measured and then react to the changes. The key component here is the current sensor. Its accuracy and linear error will directly determine the hard efficiency, and the sampling frequency of the software is also determined by the accuracy of the hardware.   9. Reduce line losses In solar systems, cables account for a small part, but the impact of cables on power generation cannot be ignored. It is recommended that the line loss of the system's DC and AC loops be controlled within 5%. The cables in the system must be well prepared, including the insulation performance of the cable, the heat-resistant and flame-retardant performance of the cable, the moisture-proof and light-proof performance of the cable, the type of cable core, and the size and specification of the cable. Therefore, in daily operation and maintenance, we need to check whether the lines are damaged and whether there is leakage or other conditions. Especially after every typhoon or hailstorm, it is essential to check whether the lines and connectors are loose.   10. Inverter efficiency The solar inverter is the main component and important component of the solar system. In order to ensure the normal operation of the power station, the correct configuration and selection of the inverter is particularly important. In addition to the various technical indicators of the entire solar power generation system and the product sample manual provided by the manufacturer, the configuration of the inverter generally needs to consider the following technical indicators: 1. Rated output power 2. Output voltage adjustment performance 3,Overall machine efficiency 4.Start-up performance. There are not many daily environments that affect the efficiency of the inverter. Pay attention to installing the inverter in a cool place and keep the surroundings ventilated to facilitate the heat dissipation of the inverter. Especially in summer and autumn, normal heat dissipation can maintain the power generation efficiency of the inverter.

With rainy season coming, the weather will become increasingly hot and humid. For photovoltaic power plants, on the one hand, the peak period of power generation is ushered in; on the other hand, the fluctuating temperature and frequent thunderstorms also pose a lot of challenges to the safe and efficient operation of the power plant. Take you from the following Starting from several aspects, learn more about the precautions for photovoltaic power plants: 1. Anti-high temperature 2. Anti-storm 3. Anti-lightning   1. How to prevent high temperature? Ensure air flow: ensure smooth air circulation around the inverter. Do not install the inverter in a narrow and closed environment. If multiple inverters are installed on the same plane, it is necessary to ensure that there is enough space between This not only ensures the ventilation and heat dissipation of the inverter, but also has enough operating space for later maintenance.   Avoid wind and sun: Although the protection level of our inverter meets the requirements for long-term use in outdoor environments, reducing the chance of the inverter being exposed to wind, sun, and rain can prolong the service life of the inverter. When installing the inverter, you can choose to install it at the bottom of the module or under the eaves. If the inverter is installed outdoors, it is recommended to install an awning at the same time, which can not only provide shelter from wind and rain, but also reduce direct sunlight, reduce the temperature of the inverter, avoid load reduction caused by overheating of the inverter, and ensure power generation efficiency.   2. How to prevent heavy rain? Rainstorms are frequent in summer, and the main impact on photovoltaic power plants is that a large amount of rainwater soaks cables and components, and the insulation performance is degraded or even damaged, causing the inverter to detect a fault and fail to generate electricity.   The sloping roof itself has strong drainage capacity, and generally there will be no excessive water accumulation; if the lower edge of the module is low on the flat roof, it may be soaked by rainwater; for photovoltaic power plants installed on the ground, rainwater washing the ground may cause module imbalance .   If the roof where the photovoltaic power station is installed is a sloping roof, there is basically no need to worry about heavy rain. If it is a flat roof, it is best to consider the drainage problem during the design and installation of the photovoltaic power station. It should be avoided that the photovoltaic modules are soaked by rainwater due to the relatively low bracket installation of the flat roof when the rainfall is too heavy.   Specific measures to prevent rainstorms in power stations: a. When designing a power station, geographical and geological factors should be taken into consideration, such as the orientation of the selected terrain, the degree of slope fluctuation, hidden dangers of geological disasters, depth of accumulated water, flood water level, drainage conditions, etc. b. For the power stations that have already been built, scientifically add drainage systems. Note: During inspection and maintenance in rainy days, avoid bare-handed electrical operations and do not directly touch the inverter, components, cables and terminals with your hands. You need to wear rubber gloves and rubber boots to reduce the risk of electric shock.   3. How to prevent from lightning? For the lightning protection of photovoltaic power stations, in addition to the conventional protective grounding on the component side, support side and distribution box side, the inverter, as the core electrical equipment of the photovoltaic power station, should also be well protected against lightning protection. Electrical grounding and protective grounding for protection.   Electrical grounding: Generally, the electrical grounding will be connected to the PE row of the electric box, and then grounded through the distribution box. The electrical grounding point is generally located at the AC terminal of the inverter, and there is a PE ( Ground) symbol identification.   Protective grounding: The inverter body has a grounding hole for grounding to protect the safety of the inverter and operators. The protective grounding point of the inverter is located on the body of the inverter and has a grounding mark. It is generally recommended to only connect to the protective ground (because lightning current discharge, faults and static electricity all go to the protective ground).   Protection against direct lightning strikes: set up metal lightning protection grounding conductors on tall buildings, including lightning rods, lightning protection belts, and grounding devices, which can release the huge thunderstorm cloud charge. All electrical equipment in the photovoltaic system cannot protect against direct lightning strikes.   Inductive lightning protection: Photovoltaic systems have lightning protection modules in electrical equipment such as combiner boxes and inverters to protect against indirect lightning strikes. The inverter has two levels of lightning protection and three levels of lightning protection. The second level of lightning protection uses lightning protection modules, which are generally used in medium and large photovoltaic power plants. There are no tall buildings around the power station. The third level of lightning protection uses lightning protection devices. It is used for household small-scale photovoltaic power plants, and there are tall buildings around the power plant.   The photovoltaic power generation system is equipped with lightning protection devices, and the Deye inverter has a built-in secondary lightning protection module, so it does not need to be disconnected in normal lightning weather. If there is a strong thunderstorm, for safety reasons, it is recommended to disconnect the DC switch of the inverter or the combiner box, and cut off the circuit connection with the photovoltaic module to avoid damage caused by induced lightning.

In solar system, though the cost of the cable is not high, as the "blood vessel" of the pv system, it plays an important role in connecting pv modules, inverters, distribution boxes and the grid, and also plays an important role in the operation safety of the whole system, which even influences the overall profitability of the power station. Therefore, the cable selection in system design process is very critical.   1. Types of pv cables From the perspective of different functions, the cables in the pv system can be mainly divided into two types: DC cables and AC cables.   1.1 DC cable ① Serial cables between pv modules. ② Parallel cables between strings and between strings and DC distribution box (combiner box). ③ Cables between the DC distribution box and the inverter. The above cables are all DC cables, and they are often laid outdoors. They need to be protected from moisture, sun exposure, cold, heat, and ultraviolet rays. In some special environments, they also need to be resistant to chemical substances such as acids and alkalis.   1.2 AC cable ① Connecting cables from the inverter to the step-up transformer. ② Connecting cables from the step-up transformer to the power distribution unit ③ Connecting cables from the power distribution device to the power grid or users The above cables are all AC load cable, which are often laid in the indoor environment, and can be selected according to the general power cable selection requirements.   2. Why choose dedicated pv cable? Under much circumstance, DC cables need to be laid outdoors. The cable materials should be determined according to the resistance to ultraviolet rays, ozone, severe temperature changes and chemical erosion. The long-term use of ordinary material cables in this environment will cause the cable sheath to break and even decompose the cable insulation layer. These conditions will directly damage the cable system, and will also increase the risk of system short circuit. In the medium and long term, the possibility of fire or personal injury is also higher, which greatly affects the lifespan of the system. Therefore, it is very necessary to use dedicate pv cables and modules. Solar-specific cables and modules not only have the best weather resistance, UV and ozone resistance, but also can withstand a wider range of temperature changes.   3. Principles of cable design and selection ① The withstand voltage of the cable should be greater than the maximum voltage of the system. For example, for AC cables with 380V output, 450/750V cables would be selected. ② For the connection inside and between the system arrays, the rated current of the selected cable is 1.56 times the maximum continuous current in the calculated cable. ③ For the connection of AC loads, the rated current of the selected cable is 1.25 times of the calculated maximum continuous current in the cable. ④ For the connection of the inverter, the rated current of the selected cable is 1.25 times of the calculated maximum continuous current in the cable. ⑤ Consider the influence of temperature on the performance of cable. The higher the temperature, the less the current carrying capacity of the cable, and the cable should be installed in a ventilated and heat-dissipating place as much as possible. ⑥ Consider that the voltage drop should not exceed 2%.   4. The DC circuit is often affected by various unfavorable factors during operation and causes grounding, which makes the system unable to work. Such as extrusion, poor cable manufacturing, unqualified insulation materials, low insulation performance, DC system insulation aging, or some damage defects, can cause ground faults or become a grounding hazard. In addition, the intrusion or biting of wild animals in the outdoor environment will also cause a DC ground fault. In this case, armored cables with rodent-proof functional sheaths are generally necessary.   5. Summary: Select the appropriate cable according to the grid form supported by inverter and data of the maximum continuous current in the cable.