1. Daily inspection of centralized grid-connected inverter
In daily inspections, check that the inverter‘s various operating parameters are within the specified range, and check whether the data is consistent with the background monitoring data. Check the DC voltage, DC current, DC power, AC voltage, AC current, power generation, grid power generation, and cumulative power generation from the inverter panel. Check that the deviation between the output power of the inverter and the output power of the inverter of the same model is ≤3%.
In addition, the following inspections should be carried out:
(1) Check the appearance/cleanliness of the cabinet, ventilation system and all exposed surfaces.
(2) Check, clean/replace the components of the air filter.
(3) Check that the inverter cabinet door is locked normally.
(4) The dust-proof net of the inverter is clean and intact without damage.
(5) The equipment identification label is complete and the handwriting is clear.
(6) When the inverter is running, the indicator lights work normally and there is no fault signal.
(7) Check that there is no abnormal sound when the inverter is running.
(8) Check that the connection of the primary circuit of the inverter is tight, and there is no looseness, no peculiar smell, and no abnormal temperature rise.
(9) Check that each module of the inverter is operating normally, and the operating temperature is within the normal range.
(10) Check the DC side and AC side cables of the inverter for no signs of aging, heat generation, or discharge.
(11) Check that the switch positions on the DC side and AC side of the inverter are correct, and there is no heat generation.
(12) Check that the ambient temperature of the inverter room is within the normal range and the ventilation system is normal.
(13) Check that the inverter’s power supply switching circuit is working normally, and if necessary, perform a power switching test.
(14) Use an infrared thermometer to measure the temperature of the incoming and outgoing cables of the inverter in the cable trench.
2. Centralized grid-connected inverter power outage process
The inverter needs to go to the site for power-off and transmission operations before and after the initial grid connection and maintenance. Standardized and correct operation can not only avoid accidents, but also protect the equipment from wear and aging.
The specific operation process of the inverter on site is as follows:
(1) Power transmission from the inverter.
1) Step 1: turn on the control power switch.
A. Before powering on, check to confirm that the AC side has been powered on and there is no abnormal phenomenon;
B. After closing, you need to wait for the control touch screen to start and check that the touch screen is normal before proceeding to the next operation.
2) Step 2: Close the AC side circuit breaker.
A. Before closing the circuit breaker, check whether the circuit breaker is intact, whether the cable phase sequence is correct and reliably connected;
B. Use professional tools and equipment to enter the site for operation;
C. After closing, observe whether the AC voltage is normal on the touch screen.
3) Step 3: Close the DC side circuit breaker.
A. Check that the confluence cables of each branch on the DC side are not damaged, the positive and negative poles are reversed, and the grounding phenomenon;
B. Check that the DC side circuit breaker is intact;
C. Turn on the DC side circuit breakers one by one, and observe whether the voltage on the display screen of the inverter is normal, whether there are faults and alarms.
4) Step 4: Turn the grid-connected knob “OFF” to “ON”.
A. There is no fault warning information on the touch screen, and the AC and DC voltages are normal before operation.
B. Keep a safe distance after closing, about 5~10s, the internal grid-connected contactor of the inverter will be closed, and the inverter will be connected to the grid to generate electricity.
C. In case of emergency, you can directly press the “Emergency Stop Knob”.
After the inverter runs normally, the inverter will automatically run and de-load according to the set MPPT voltage range:
The inverter runs automatically: no human intervention is required. When the input voltage is within the rated DC voltage range and the grid voltage is within the normal operating range, it will be automatically connected to the grid.
The inverter automatically disassembles: no need for manual intervention. When the input DC voltage exceeds the rated DC voltage range, and the grid voltage is abnormal, it will be automatically de-serialized.
(2) The inverter is out of power.
The power-off operation sequence of the inverter is opposite to the power-transmission sequence. During the operation, the power is cut off strictly in accordance with the sequence. Before disconnection, it is necessary to confirm that the DC and AC side circuit breakers have been disconnected and there is no abnormal phenomenon; if there is any abnormality after disconnection For maintenance work, wait for 15-20min before proceeding with other operations.
3. Spot inspection and maintenance of centralized grid-connected inverters
(1) Guidelines for cleaning and general inspection.
Pay attention when cleaning the dust inside the photovoltaic inverter. First blow low-pressure compressed air into the inverter from the bottom of the device, and then blow low-pressure compressed air from the top of the device. The inverter should be kept in a good energized state to prevent the danger caused by equipment damage.
Check the cables regularly to prevent damage to the insulation layer and contactors, and immediately replace or repair the cracked or worn cables.
Do not overload the cable; do not touch the output terminals when the device is powered on.
(2) Maintenance guidance for power supply components.
Use low-pressure compressed air or a soft brush to clean the radiator to keep the power supply components clean, free from dirt and blockage, which will avoid leakage and heat accumulation, thereby increasing the life of the equipment.
Check the wiring terminals for signs of overheating caused by loose electrical connections; check whether the electrical connections and mechanical connections are tight, carefully check all compression interfaces; check all wires, wires and cables; check for cuts, scratches, and damage. Signs of overheating; check whether the terminal wire is broken; check the door hinge (if any), if the door hinge is too tight and difficult to operate, spray high-quality silicone oil lubricating spray on the door hinge.
Thermal expansion and vibration during operation can loosen fasteners. After the initial commissioning period (3 months), check and re-torque the following components: all clamps; all power bolt connections; all logic screw connections; rectifier diodes/insulating bipolar transistors (IGBT) mounting fasteners. Ensure that the torque specifications of the equipment are met. It should be done at least once a year.
(3) Printed circuit board maintenance.
Keep the printed circuit board clean, free of dirt and foreign matter. Ensure that electrostatic materials are never placed near the inverter circuit (whether in the cabinet or will be stored), be careful when approaching or handling the circuit board, and ensure that the correct electrostatic discharge (ESD) measures are taken to avoid the appearance of the PCB Fault. Keep all logic controls clean, free of dirt or foreign matter (except for maintaining a good clean environment, no special maintenance is required), all printed circuit boards and logic components are susceptible to thermal degradation, and a good clean environment can ensure that the above devices are under their design parameters Operation, and increase the mean time between failures (MTBF) value of the equipment.
(4) Fan maintenance.
If you need to replace the cabinet cooling fan, you should follow the following procedures: take out the cooling fan shell panel; disconnect the wire of the wiring port; loosen the floating nut that fastens the fan platform and base; remove the fixing used to fasten the fan plate and the cabinet top Bolts; remove the loose fasteners; remove the fan accessories; remove the fasteners that fasten the fan motor and the metal plate; install a new fan.