Photovoltaic combiner box refers to an electrical device that connects the DC power of several photovoltaic module strings in parallel in the photovoltaic power generation system, and mainly plays a role of current collection.
Photovoltaic lightning protection combiner boxes are divided into DC combiner boxes and AC combiner boxes according to different access methods.
(1) DC combiner box
The main function of the DC combiner box is to reduce the connection between the photovoltaic string array and the inverter in the solar photovoltaic power generation system. According to the input DC voltage range of the inverter, a certain number of photovoltaic modules with the same specifications are connected in series. Form a photovoltaic module string, and then connect several photovoltaic strings to the photovoltaic array lightning protection combiner box, and output after passing through the circuit breaker to facilitate the access of the downstream inverter.
According to the electrical design requirements, the photovoltaic DC combiner box has multiple wiring methods of 8 in and 1 out or 16 in and 1 out. The wiring method of each branch of the combiner box is the same. Figure 1 shows a 16-in-1 DC combiner box, and Figure 2 shows the internal wiring diagram of the DC combiner box.
In order to improve the reliability and practicability of the photovoltaic power generation system, photovoltaic lightning protection combiner boxes are equipped with photovoltaic special DC and DC fuses and circuit breakers to provide lightning protection and overcurrent protection, and monitor the single string current and voltage of the photovoltaic array And the state of the lightning protection device, the state of the circuit breaker. Using the non-contact measurement method of the DC current transformer, it is convenient for the operation and maintenance personnel to grasp the working condition of the string in a timely and accurate manner, and measure the string current value output by the photovoltaic module in the combiner box without affecting the output power of the string. The solar photovoltaic power generation system exerts its maximum efficiency.
The technical parameters of the photovoltaic combiner box stipulate the maximum number of parallel input channels of the photovoltaic array in the combiner box, the maximum current of each photovoltaic array, the voltage range of the photovoltaic array and other important parameters, which become requirements in the final inverter analysis and string troubleshooting Reference basis (see Table 1).
|PV array voltage range||200~1000||DC circuit breaker|
|Maximum number of parallel input channels of photovoltaic array||16||Photovoltaic special lightning protection module|
|Maximum current of each photovoltaic array (A)||10|
|Output terminal size||PG21||Serial current monitoring|
|Protection level||IP65||Lightning protection monitoring|
|Environment temperature (℃)||-25~60||Communication module interface|
(2) AC combiner box
The photovoltaic AC combiner box is applied to the photovoltaic power generation system of the string inverter and is installed between the AC output side of the inverter and the low voltage side of the photovoltaic box transformer.
At the photovoltaic power station site, the AC combiner box is an AC output device that inverts the string inverter into a rated voltage level. The interior of the AC combiner box is equipped with input circuit breakers, output circuit breakers, and AC lightning protection devices. Intelligent monitoring instruments with signal functions such as monitoring system voltage, current, power, and energy can be optionally equipped. Figure 3 shows the installation position of the AC combiner box, and Figure 4 shows the internal configuration of the AC combiner box.
The main function of the AC combiner box is to converge the output current of multiple inverters, and at the same time protect the inverter from the harm from the AC grid-connected side/load, as the inverter output disconnection point, improve the safety of the system, and protect the installation Maintain the safety of personnel.
(1) AC input circuit breaker: The output terminal of the inverter is directly connected to the 3P circuit breaker, and the circuit breaker can quickly cut off the fault current.
(2) AC output circuit breaker: The total circuit breaker after the 6 inverters are combined is a molded case circuit breaker with a rated current of 350A. The cables connected to the circuit breaker are connected by copper bars with a wire diameter of 150mm².
(3) Lightning protection fuse: A fuse (commonly known as a fuse) is an over-current protector. When the current of the protected circuit exceeds the specified value, the fuse will blow off and the circuit will be disconnected to protect it. It is generally used for lightning protection. Only after the surge fails, you can choose a 100A fuse.