Common Faults and Treatment of Photovoltaic Inverter
As the inspection center of the entire power station, the inverter is used for DC components at the top and grid-connected equipment at the bottom. Basically all power station parameters can be detected by the inverter. The basic information of the power station provided by the inverter covers: DC voltage, DC current, DC-to-ground insulation resistance, power station DC-to-AC leakage current detection, AC voltage, AC current, AC frequency, AC phase sequence detection.
Generally, as long as the inverter is in the grid-connected state, the power curve displayed by the monitoring is a normal "hill" line, which proves that the power station is operating stably. If there is an abnormality, you can check the health of the supporting equipment of the power station through the information fed back by the inverter. The basic information and processing methods are listed below:
Basic information and processing methods
1. Low insulation resistance: use the elimination 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 check the insulation resistance to detect the problem string. After finding the problem string, check whether the DC connector has a water-immersed short-circuit bracket. Or fusing and short-circuiting the bracket. In addition, you can also check whether the component itself has black spots burned at the edge, causing the component to leak electricity to the ground grid through the frame.
2. Low bus voltage: If it occurs in the morning/late period, it is a normal problem because the inverter is trying to limit power generation conditions. If it occurs during normal daytime, the detection method is still the exclusion method, and the detection method is the same as item 1.
3. Leakage current failure: The root cause of this type of problem is the installation quality problem, which is caused by the wrong installation location and low-quality equipment. There are many failure points: low-quality DC connectors, low-quality components, unqualified component installation height, low-quality grid-connected equipment, or water leakage. Once similar problems occur, you can find the best points by sprinkling powder and do it. Good insulation work to solve the problem, if it is the problem of the material in the province, you can only replace the material.
4. DC overvoltage protection: As the components pursue high-efficiency process improvement, the power level is constantly updated and increased, and the open circuit voltage and working voltage of the components are also rising. The temperature coefficient must be considered in the design stage to avoid overvoltage caused by low temperature conditions. damage.
5. The inverter does not respond when starting up: Please make sure that the DC input line is not reversed. Generally, the DC connector has fool-proof effect, but the crimping terminal has no fool-proof effect. Read the inverter manual carefully to ensure that the positive and negative poles are crimped afterwards. very important. The inverter has built-in reverse connection short-circuit protection, and it starts normally after normal wiring is restored.
6. Grid failure:
Grid overvoltage: The work of pre-survey of heavy load (large power consumption working time)/light load (less power consumption rest time) of the power grid is reflected here, and the health of the grid-connected point voltage is investigated in advance, and the inverter manufacturer Communicating the power grid situation and combining technology to ensure that the project design is within a reasonable range, do not "take it for granted", especially in rural power grids, inverters have strict requirements on grid-connected voltage, grid-connected waveform, and grid-connected distance. Most of the reasons for grid overvoltage problems are that the original grid light-load voltage exceeds or approaches the safety protection value. If the grid-connected line is too long or the crimping is not good, the line impedance/inductance is too large, the power station will not be able to operate normally and stably. The solution is to find the power supply bureau to coordinate the voltage or correctly select the grid connection and strictly control the construction quality of the power station.
Grid undervoltage: This problem is the same as the processing method of grid overvoltage, but if an independent phase voltage is too low, in addition to the incomplete load distribution of the original grid, the power failure or disconnection of the phase grid will also cause the problem. False voltage.
Grid over/under frequency: If such problems occur in the normal grid, it proves that the health of the grid is very worrying.
The grid has no voltage: just check the grid-connected circuit.
Power grid lack of phase: check the lack of phase circuit, that is, the circuit without voltage.
(Information reference point, inverter AC parameter monitoring page, grid-connected inverter outputs current according to the grid waveform, so the AC information shows the health status of the grid, and the DC information is the health information of the components. As an integrated device of the energy conversion unit and the power station detection unit, the heart deserves its name.)
Three-phase unbalance: The grid-connected lines plus special equipment cause abnormal grid-connected oscillations, ultra-long-distance grid-connected, and the power grid cuts the top and overvoltage and phase shifts.
7. The last point-monitoring overlap: Correctly read each equipment manual, model line crimping, equipment connection, and set the communication address and time of the equipment, which is a guarantee to ensure stable and effective communication!
8. Guarantee of power generation: When you have time to wipe the board, the power generation will be "protruding".
In fact, for a power station, many problems are not caused by the inverter itself, but related to other equipment or installation methods. Therefore, the material selection and installation in the early stage also require everyone's attention.
The design of the inclination and azimuth angle, the design of the component spacing, the selection of the installation site, the health check of the grid voltage, etc. also determine the performance of the power station's operation and power generation in the next 25 years. It can be said that the overall quality of the power station is determined by the power station materials and installation quality!
1. Components: A grade board is selected, the judgment is based on the price, and low-price and low-quality products are rejected, such as poor grid lines. To
2. Bracket: Use anti-corrosion brackets, and the components should be at least 30cm above the ground, for example...
3. Grounding flat steel: It is very important to correctly design and configure the grounding project according to the size of the system
4. DC terminal: a very important material. Terminals with poor quality will often cause overheating and melting due to the single-point contact of the terminal core. Terminals with poor waterproofness will cause false short-circuits and leakage between the terminals and the bracket in extreme rain. The editor does not post the burnt situation, leaving some room for imagination.
5. DC cables: choose the correct size of the cable model, the design honor should not be too small or too large, usually 1.2-1.5 times. Too small current-carrying capacity is not enough, and too large terminal crimping is bad. It is forbidden to "wrap the line" casually.
6. Inverter: Choose an inverter with excellent quality. The installation of inverter must pay attention to heat dissipation. At present, inverters are all IP65 outdoor installations. It is recommended not to install them in narrow rooms, especially residential customers, to avoid heat dissipation problems. For equipment running noise problems, reading the manual correctly is the best choice.
7. AC cable: Choose the correct size of the cable model, the design honor should not be too small or too large, usually 1.2-1.5 times. Too small current-carrying capacity is not enough, and too large terminal crimping is bad.
8. Cable tray: A good power station will never lack neat wiring. Whether it is a cable tray or a simple fixing method, it determines the beauty and durability of the power station.
9. AC grid-connected equipment: to prevent cutting corners, correctly choose grid-connected switches and lightning protection equipment, and correctly design grid-connected lines to ensure the reliable operation of the system.
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