Individual cells can be connected to form a photovoltaic module, and photovoltaic modules are connected to form a photovoltaic array.
The wiring of the array needs to match the load characteristics. Generally speaking, the load is a set of storage batteries used to store DC power of 12V, 24V or higher. The above-mentioned voltage is called the system nominal voltage. Therefore, the output of the array must be higher than the battery voltage to ensure that the battery pack can be charged by the photovoltaic array under different radiation levels.
Each battery can generate a voltage of 0.5 to 0.6V under standard conditions. Generally, 36 or 72 batteries are connected in series to form a component to generate enough voltage and current to charge the battery pack at the desired operating temperature.
A photovoltaic array consists of a series of photovoltaic modules connected in series to meet the system voltage, and the series are connected in parallel to provide sufficient charging current for the battery. The group string, array diagram is shown as in Figure 1.
If the output of a single photovoltaic module is 4A, 12V (rated), then under the same conditions, the output of the string formed by connecting 3 identical photovoltaic modules in series is 4A, 36V (3×12V); 4 photovoltaic modules are connected in parallel The output of the resulting array is 16A, 36V.
This principle will be explained in detail in the following.
1. Photovoltaic modules are connected in parallel
Photovoltaic parallel module means that in the circuit, the components are connected in parallel. In the photovoltaic module shown in Figure 2, if the output of a single photovoltaic module is Ump=17V and Imp=4A, then under the same conditions, the output of an array formed by three identical photovoltaic modules in parallel is still 17V. The output current Imp will increase from 4A to 12A.
2. PV modules in series
Photovoltaic module series connection is in the photovoltaic power generation system, multiple photovoltaic modules are connected in series to form the smallest unit with the required DC output voltage. . In the photovoltaic module shown in Figure 3, the conditions remain unchanged. After the same photovoltaic modules are connected in series, the output voltage Ump=51V, and the output current Imp is still 4A.
3. PV modules in series and parallel
In order to meet the DC voltage and current requirements of the load in a large array, series and parallel are usually used in combination with photovoltaics.
The output voltage and current of the array follow the following guidelines:
(1) The strings are connected in series and the voltage increases.
(2) The current increases when the strings are connected in parallel.