Working principle of DC combiner box

1、 Working principle and process
Current input and anti backflow protection
The direct current generated by Photovoltaic modules is connected to the combiner box through the input terminal. To ensure stable operation of the system, each input is equipped with anti reverse diodes. This device can effectively resist the problem of reverse current backflow caused by local obstruction and faults of components. At this stage, it is necessary to strictly control the fluctuation range of the current to ensure that it is within 5%, in order to maintain stable transmission of the current. ​
Overcurrent protection and circuit breaker mechanism
Each branch is equipped with dedicated fuses designed specifically for photovoltaic systems, with a rated current accurately designed at 1.56 times the component short-circuit current (Isc). Taking the 24 channel combiner box as an example, when a short circuit fault occurs in a single channel, the fuse of this branch needs to withstand the reverse current surge generated by the other 23 parallel components, that is, a current load of up to 23 × Isc, in order to timely cut off the abnormal current path and protect the system safety. ​
Current convergence and output
Multiple currents are efficiently integrated through a copper busbar, and then output to the inverter through a DC circuit breaker. The DC circuit breaker adopts a multi pole series structure (such as 4P or 3P), which can meet the high withstand voltage requirements of 1000-1500V, ensuring safe and reliable transmission of electrical energy in high voltage environments. ​

2、 Core protection mechanism
Lightning protection system
Equipped with T1 grade composite lightning arresters, such as the high-performance DEHNguard series products. The lightning arrester has an extremely fast response speed, with a response time of less than 25ns, and can effectively discharge lightning overvoltage with an amplitude of not less than 15kA, providing a solid lightning protection barrier for the system. ​
Insulation monitoring
Based on the principle of unbalanced bridge, real-time accurate detection of positive and negative pole to ground impedance. The system has a sensitivity of up to 500k Ω, which can timely capture subtle insulation abnormalities and always control the risk of leakage within a safe range, ensuring the safety of personnel and equipment. ​
Temperature monitoring
Install temperature sensors inside the combiner box to continuously monitor the temperature inside the box. Once the temperature exceeds the threshold of 55 ℃, the system will immediately trigger an alarm mechanism for operation and maintenance personnel to promptly investigate and handle potential overheating risks. ​
3、 Intelligent monitoring expansion
Modern photovoltaic combiner boxes integrate high-precision Hall sensors (with an accuracy of ± 1%) and RS485 communication modules, which can collect real-time and accurate current, voltage data, and environmental parameters of each branch. By seamlessly integrating with the SCADA system, remote fault warning and energy efficiency analysis functions can be achieved, helping operation and maintenance personnel to timely grasp the system operation status and improve the intelligent management level of photovoltaic power plants. ​
Summary of Key Principles
The photovoltaic combiner box adopts a three-level progressive protection system of anti backflow, melting, and lightning protection, combined with an intelligent monitoring system, to build a comprehensive safety protection network, realizing the safe and efficient collection and transmission of photovoltaic array energy, ensuring that the system always maintains stable and reliable operation under complex and changing working conditions.