# PV Grid-Connected Cabinet

## Main Functions of PV Grid-Connected Cabinet

1. Grid Connection and Power Transmission
As a critical interface between the photovoltaic power station and the power grid, the primary function of the PV grid-connected cabinet is to realize grid-connected power transmission. It connects the alternating current converted by inverters from the direct current generated by the photovoltaic power system to the power grid, laying the foundation for power supply and electricity revenue.
2. Multi-protection Functions

– Islanding Protection: Real-time monitoring of grid voltage and frequency. It rapidly disconnects the grid connection point in case of abnormalities to prevent islanding effect which endangers the power grid and equipment.
– Overvoltage/Undervoltage Protection: Detects grid fluctuations to avoid impacts on the system caused by abnormal voltage.
– Anti-reflux Protection: Prevents grid current from flowing backward into the photovoltaic system to ensure the safety of maintenance personnel.
– Harmonic Control and Reactive Power Compensation: Improves power quality via APF (Active Power Filter) and SVG (Static Var Generator) to ensure grid connection compliance.

3. Real-time Monitoring and Metering
Integrated power quality monitoring devices (such as Class A on-line monitors) conduct real-time monitoring of parameters including voltage, current, power and harmonics. Data is uploaded through communication interfaces (e.g. RS485) to support remote operation and maintenance.
4. Adaptation to Diverse Scenarios
From commercial and industrial rooftops to agrivoltaic projects, the modular design of the PV grid-connected cabinet (e.g. IP65 protection, dual-channel MPPT input) enables it to adapt to harsh environments with high humidity and heavy dust, improving system reliability and efficiency.

## Working Principle of PV Grid-Connected Cabinet

1. Grid Connection Control Logic

– Close breaker upon voltage detection: Automatically closes the circuit breaker after confirming normal grid voltage to achieve grid connection.
– Open breaker upon loss of voltage: Quickly disconnects when the power grid loses power to prevent reverse power feeding.

2. Coordination of Key Equipment
The anti-islanding protection device triggers a tripping signal by detecting deviations in voltage and frequency, decoupling the system from the power grid.

– Circuit breakers and disconnecting switches: Provide physical isolation points to guarantee operation and maintenance safety (e.g. visible break design).
– Smart energy meter: Measures power generation and supports bidirectional power statistics (e.g. surplus power feed-in to grid).

3. Dynamic Response Mechanism
When grid faults or abnormalities occur on the photovoltaic side, rapid disconnection (millisecond-level response) and redundant protection (such as overcurrent protection) reduce risks. It also supports switching between off-grid and grid-connected modes (e.g. for energy storage system applications).

## Summary

Supported by three technical pillars: power quality control, linkage of protection devices and intelligent monitoring, the PV grid-connected cabinet realizes safe grid connection and efficient operation & maintenance. It acts as an indispensable “intelligent gateway” in photovoltaic systems.