The inverter is also called the power regulator. According to the use of the inverter in the photovoltaic power generation system, it can be divided into two types: independent power supply and grid connection. According to the waveform modulation method, it can be further divided into a square wave inverter, a staircase wave inverter, a sine wave inverter and a combined three-phase inverter. For inverters used in grid-connected systems, transformer-type inverters and transformerless inverters can be classified according to the presence or absence of transformers.
Photovoltaic inverter structureAs a kind of power regulation device for direct AC conversion, the inverter is divided into two parts: the booster loop and the inverter bridge loop, which are mainly composed of semiconductor devices. The main semiconductor devices are as follows:
1) Current sensor: It requires high precision, fast response, low temperature resistance, high temperature resistance, etc. Different current sensors are used for different powers. Hall current sensors are generally used for current sampling.
2) Current transformer: Wide range of current, generally using BRS series current transformer;
3) Reactor.
The photovoltaic inverter is composed of a booster loop and an inverter bridge loop. The booster loop is mainly used to boost the DC voltage to the DC voltage required for the inverter output, and the inverter bridge loop is mainly used for boosting the loop. The DC voltage is converted to a fixed frequency AC voltage. Therefore, the function of converting direct current into an alternating current point is completed by the boosting loop and the inverter bridge loop.
Photovoltaic inverters have common ten major faults and treatment methods1. Mains abnormality
The mains abnormality is divided into the mains voltage is too low, too high, the mains frequency is too low, too high (corresponding to the error code F00-F03)
1 Confirm that the safety standards selected by the machine meet the local grid requirements.
2 Check if the AC output terminal is connected reliably, and use a multimeter to measure whether the voltage is normal.
3 Disconnect the PV input, restart the machine, and observe if the machine can return to normal.
4 The fault has not been eliminated, contact the distributor.
2, the insulation resistance is too low
Error code F07
1 Disconnect the PV input, restart the machine, and observe if the machine can return to normal.
2 Check if the PV+ and PV-pair earth resistance is greater than 500KΩ.
3 If it is less than 500KΩ, please contact your local inverter distributor for help, or contact the panel supplier for disposal.
3, leakage current is too high
Error code F20
1 Disconnect the PV input, restart the machine, and observe if the machine can return to normal.
2 Failure is not ruled out, contact the distributor.
4, the ambient temperature, the radiator temperature is too high
Error code: F12, F13
1 Disconnect the PV input. After a few minutes of cooling, restart the machine and observe if the machine can return to normal.
2 Check if the ambient temperature is outside the normal operating temperature range of the machine.
3 Failure is not ruled out, contact the distributor.
5, monitoring no data
WiFi monitoring:
Connect the inverter WiFi, check whether there is a connected inverter on the monitoring page. If there is no inverter information, re-plug the built-in WiFi module or check the external WiFi RS485 connection; if you cannot find the inverter WiFi, please check Whether the built-in WiFi module is in poor contact or whether the external WiFi is not powered.
GPRS monitoring:
Test the strength of the Internet signal with the service provider at the inverter installation site, check whether the built-in GPRS module is in poor contact or whether the external GPRS is not powered.
6, low insulation resistance
Use the exclusion method. Unplug all the strings on the input side of the inverter, and then connect them one by one. Use the function of the inverter to detect the insulation resistance, detect the problem string, and find the problem string and check whether the DC connector has the water immersion shorting bracket. Or burn the shorting bracket, and also check whether the component itself has black spots burned at the edge, causing the component to leak through the frame to the ground.
7, leakage current failure
The root cause of this type of problem is the quality of the installation, the choice of the wrong installation location and low quality equipment. There are many fault points: low-quality DC connectors, low-quality components, unqualified component mounting height, low-quality grid-connected equipment or water leakage, but similar problems can be found by polling the powder and doing Good insulation work to solve the problem, if it is the material problem, you can only change the material.
8, the inverter is not responding to boot
Please ensure that the DC input line is not reversed. Generally, the DC connector has a foolproof effect, but the crimp terminal has no foolproof effect. It is important to carefully read the inverter manual to ensure that the positive and negative terminals are then crimped. The inverter has built-in reverse short circuit protection and starts normally after returning to normal wiring.
9, the grid failure
Over-voltage of the power grid: The work of re-surveying the grid heavy load (large power consumption working time) / light load (low power consumption rest time) is reflected here, and the health of the grid voltage is investigated in advance, and the inverter manufacturer Communicating the power grid to do technical integration can ensure that the project design is within a reasonable range. Do not “take it for grantedâ€, especially the rural power grid. The inverter has strict requirements on the grid-connected voltage, grid-connected waveform and grid-connected distance. The main reason for the grid overvoltage problem is that the light load voltage of the original grid exceeds or approaches the safety protection value. If the grid connection line is too long or the crimping is not good, the line impedance/inductance is too large, and the power station cannot operate normally. The solution is to find the power supply bureau to coordinate the voltage or correctly select the grid and strictly control the quality of the power station construction.
Grid undervoltage: This problem is consistent with the grid overvoltage treatment method, but if the independent one-phase voltage is too low, in addition to the original grid load distribution is not complete, the phase grid power failure or open circuit will also cause this problem, appear Virtual voltage.
Grid over/under frequency: If such problems occur in the normal grid, it proves that grid health is very worrying.
There is no voltage in the grid: check the grid connection.
Loss of phase in the grid: Check the phase loss circuit, ie the voltage-free line.
10, DC overvoltage protection
As the component pursues high-efficiency process improvement, the power level is continuously updated and the component open circuit voltage and working voltage are also rising. The temperature coefficient problem must be considered in the design stage to avoid hard damage caused by overvoltage in the low temperature condition.
Trend 1: High-speed development of inverter hardware
The application of various new devices such as SiC, CAN, and excellent DSP and new topologies has led to continuous improvement of the efficiency of inverters. The maximum efficiency of inverters has reached 99%, and the next target is 99.5%. China's efficiency has been A level is reached, the next target is A+, A++.
Trend 2: Centralized inverters increase power, increase efficiency, and increase voltage levels
Larger power class inverters such as 2.5MW will be widely used. Compared with the 1MW square array, the 2.5MW solution can reduce the cost by about 0.1 yuan/W, that is, the 100MW power station can reduce the initial investment by 10 million. In addition, after the cable is matched, the loss of the DC part is guaranteed to be uniform.
It is worth mentioning that the 1500V system will be the development trend of large power plants. Compared with the 1000V system, it can save 0.2 yuan/W investment in addition to components, which is equivalent to saving 20 million investment in 100MW power station. At the same time, system losses can be reduced by approximately 0.27%.
Trend 3: String inverters continue to increase in stand-alone power and increase power density
The power of the string inverter has been continuously increased. At present, the maximum power has been 80 kW, the power density is also constantly increasing, and the weight is continuously reduced to meet the complicated application environment where installation and maintenance are difficult. Sunshine Power's 40kW string inverter has achieved 39kg, which is the lightest 40kW product in the industry. In terms of heat dissipation, Sunshine Power has always adhered to the way of intelligent fan cooling to further reduce the temperature rise of internal components and improve the overload capability of the inverter in high temperature environments. The fan is rated IP65 and has a lifespan of 70,000 hours, while the fan can provide a 20-year warranty.
Trend 4: Component-level products (MLPE) are becoming more and more abundant
There are more and more types of components at the component level, such as the micro inverter represented by Enphase and the power optimizer represented by SolarEdge. According to industry research firm GTM, shipments of component-level power electronics (MLPE) equipment will increase from 1.1 GW in 2013 to more than 5 GW in 2017.
Trend 5: The adaptability of the power grid is continuously enhanced, and various protections are more perfect to ensure safety and reliability.
Leakage current protection, SVG function, LVRT, DC component protection, insulation resistance detection protection, PID protection, lightning protection, PV positive and negative reverse connection protection and other continuous improvement functions, the inverter's adaptability to the power grid is further enhanced and continuously improved. The protection function makes the system more secure and reliable.
Trend 6: The environmental adaptability of the inverter is constantly improving
With the increasing application of photovoltaic power plants in various harsh environments such as coastal areas, deserts, and plateaus, the environmental adaptability of inverters such as corrosion resistance and sand resistance is continuously improved to ensure high reliability in harsh environments.
When talking about the development trend of photovoltaic systems, Zhao Wei said that through the application of various new technologies and new products, the progress of photovoltaic technology is continuously promoted, the system efficiency PR is improved, and the electricity cost (LCOE) in the system life cycle is reduced. Affordable Internet access is the goal of everyone's struggle.
The design of the power station will be more refined; the system integration will be further improved, and the integrated solution of integrated inverter and medium voltage transformer can simplify the system to the extreme, reduce cost, facilitate use, improve efficiency and improve reliability.
The development of the photovoltaic inverter industry is in the ascendant. Various new technologies and new products are changing with each passing day. It can be said that it is suitable for local conditions and a hundred schools of thought contend; in large-scale ground power stations, the initial investment of centralized solutions is lower, and the operation and maintenance cost in the later stage is only 1/3 of the string type. The results of several power station operations show that the string type and centralized power generation are the same, which is the user's first choice; the 2/2.5MW solution will become the mainstream next year; the application of string inverters in distributed is also becoming more and more More, high power, high efficiency, high power density is the future development direction; photovoltaic + Internet is recognized by customers, digital smart power station will become the mainstream; photovoltaic + energy storage application has broad prospects.
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