In the context of today's energy transition, photovoltaic power generation, as a clean and renewable form of energy, is being more and more widely used. The grid-connected cabinet of photovoltaic power station is the key equipment for the connection of photovoltaic system and power grid, and its importance is self-evident.

First, the working principle of the grid-connected cabinet of photovoltaic power station
Electrical energy conversion and transmission
Solar panels in photovoltaic power plants convert solar energy into direct current. After the DC is collected through the bus box, it enters the inverter. The inverter converts direct current to alternating current, and its output alternating current has the same frequency and phase as the power grid.
The AC power converted by the inverter enters the grid-connected cabinet of the photovoltaic power station. The circuit breaker and isolation switch in the grid-connected cabinet are responsible for controlling the transmission path of electric energy. When everything is normal, the circuit breaker is closed, and the alternating current is transmitted to the grid through the grid cabinet.
 
Implementation of protection function
Overcurrent protection: When the current exceeds the set value, the overcurrent protection device will quickly act to cut off the circuit. This is usually through the current transformer to detect the current size, when the current exceeds the set threshold, triggering the circuit breaker trip.
Overvoltage protection: When the power grid voltage is too high, the overvoltage protection device will start to prevent the equipment from being damaged due to overvoltage. Overvoltage protection can detect the power grid voltage through the voltage transformer, when the voltage exceeds the set value, trigger the circuit breaker trip or send an alarm signal.
Undervoltage protection: In contrast to overvoltage protection, when the grid voltage is too low, the undervoltage protection device will operate to protect the stable operation of the equipment and the grid. Similarly, undervoltage protection also detects the power grid voltage through the voltage transformer, and triggers the corresponding protection action when the voltage is lower than the set value.
Short-circuit protection: When a short-circuit fault occurs in the circuit, the short-circuit protection device will immediately cut off the circuit to prevent the expansion of the fault. Short circuit protection is usually achieved with fast fuses or circuit breakers.
 
Monitoring and control functions
The grid-connected cabinet of photovoltaic power station is equipped with various instruments and sensors for real-time monitoring of voltage, current, power, frequency and other parameters. These parameters can be displayed to the operator through the display screen or remote communication system in order to timely understand the operating status of the photovoltaic power station.
The control system can remotely control and adjust the photovoltaic power station according to the monitored parameters. For example, when the grid voltage is too high, the output power of the photovoltaic power station can be reduced through the control system; When the grid frequency is unstable, the output frequency of the inverter can be adjusted to keep it consistent with the grid frequency.
Second, the connection mode of the grid-connected cabinet of the photovoltaic power station and the power grid
 
Direct grid connection
Direct grid connection is the most common type of connection. In this connection mode, the grid-connected cabinet of the photovoltaic power station is directly connected to the medium or low voltage line of the power grid through the circuit breaker, isolation switch and other equipment.
The advantages of direct grid connection are simple structure, low cost and high efficiency. However, this connection mode has high requirements for the output power quality of photovoltaic power stations, and must meet the technical specifications and requirements of the grid. At the same time, direct grid connection also needs to consider the stability and reliability of the power grid to avoid adverse effects on the power grid.
 
Connected to the grid by transformer
The transformer connection is to connect a transformer between the photovoltaic power station and the power grid. Transformers can raise or lower the output voltage of a photovoltaic power station to a voltage level that matches the grid.
The advantage of connecting the grid through the transformer is that it can improve the output voltage of the photovoltaic power station, reduce the line loss, and also play the role of isolation and protection. However, this connection method is costly, occupies a large area, and the loss of the transformer will also reduce the overall efficiency of the photovoltaic power station.
 
Microgrid connection
Microgrid is a small power system composed of distributed power supply, energy storage device and load. The photovoltaic power station can be connected to the microgrid through the grid-connected cabinet and become part of the microgrid.
The microgrid connection method can improve the reliability and stability of photovoltaic power stations, but also can achieve efficient use and management of energy. In microgrids, photovoltaic plants can work in concert with other distributed power sources to meet the needs of local loads. When the microgrid is connected to the main grid, the bidirectional flow of power can also be realized to improve the efficiency of energy utilization.
 
Installation and maintenance of grid-connected cabinet of photovoltaic power station
Installation requirements
The installation of grid-connected cabinets of photovoltaic power stations shall comply with the relevant electrical safety codes and standards. The installation location should be in a dry, well-ventilated place that is easy to operate and maintain.
The grid-connected cabinet should be securely installed and well grounded. Cables should be connected correctly to avoid faults such as short circuit and grounding.
During the installation process, attention should be paid to protecting the equipment and meters in the grid-connected cabinet to avoid damage. At the same time, strict electrical testing and debugging should also be carried out to ensure that the functions of the grid-connected cabinet are normal.
maintenance
Check and maintain the grid-connected cabinet of the photovoltaic power station regularly, including cleaning equipment, checking cable connections, testing protection devices, etc.
Observe the running status of the grid-connected cabinet. If any abnormal situation is found, handle it in time. For example, when the circuit breaker is tripped, the instrument display is abnormal, etc., it should be inspected and repaired immediately.
The equipment and instruments in the grid-connected cabinet are calibrated and tested regularly to ensure their accuracy and reliability.
Strengthen the safety management of grid-connected cabinets to prevent non-professionals from misoperating or damaging equipment.