In the solar power supply system, several photovoltaic cells are usually connected in series into solar modules with a certain voltage, then several solar modules are connected in series, and the solar modules connected in series are sent to the converter through the DC bus and converted into AC for power supply.
A bypass diode is connected in parallel next to each photocell group in the solar module to conduct when the photocell group is shielded or damaged, so that the current of other photocell groups can pass through, so as to export the current of the solar module.
However, if multiple photocells in the solar module are abnormal, multiple bypass diodes will be turned on, which will cause large loss.
In view of this, it is necessary to provide a junction box with small conduction loss of bypass diode. The utility model relates to a junction box, which is placed in a solar module and connected with a plurality of photovoltaic cells in series.
The junction box comprises a first bypass diode string and at least one second bypass diode. The first bypass diode string includes a plurality of first bypass diodes connected in series in the same direction. The first bypass diode is connected in parallel with the photocell pack one by one, which is respectively used to conduct when the corresponding photocell pack is abnormal to bypass the corresponding photocell pack.
The at least one second bypass diode is connected in parallel with at least two adjacent photocell packs for conducting and bypassing the at least two adjacent abnormal photocell packs when the at least two adjacent photocell packs are abnormal at the same time.
The first bypass diode is different from the second bypass diode. It also includes two interfaces connecting both ends of the first bypass diode string for outputting the current generated by the photocell pack.
The interface includes a positive interface and a negative interface, the positive interface is connected with the cathode of the first bypass diode string for outputting the positive current generated by the photocell pack, and the negative interface is connected with the anode of the first bypass diode string for outputting the negative current generated by the photocell pack.
The junction box is additionally connected in parallel with at least one second bypass diode on two or more adjacent photocells. In this way, when two or more adjacent photocells are abnormal at the same time, a parallel second bypass diode replaces a plurality of first bypass diodes connected in parallel with two or more adjacent photocells, thereby reducing the number of conducting diodes, It can effectively reduce the conduction loss of bypass diode, so as to effectively reduce the temperature in parts and junction box, avoid unsafe problems such as shell deformation and cracking caused by excessive temperature, and prolong the service life of the product.
