# Calculation of PV array combination

The photovoltaic square array connects several components in series and parallel according to the needs of the load, to obtain the output current and voltage required by the design, and to provide power for the load. The output power of the square array is related to the number of series and parallel components. The series connection is to obtain the required operating voltage, and the parallel connection is to obtain the required operating current.

Generally, the voltage of off-grid photovoltaic systems is often designed to correspond to the nominal voltage of the battery or an integer multiple of it, and to be consistent with the voltage level of the electrical appliances, such as 220V, 110V, 48V, 36v, 24V, 12V, etc. For grid-connected photovoltaic power generation systems, the voltage level of the square array is often 110V, 220V, 380V, 500V, etc. For photovoltaic power generation systems with higher voltage levels, multiple square arrays are used in series and parallel connection to form the same voltage level as the grid level, such as 600V, 1KV, etc., and then directly connected to the public grid after passing the inverter, or connect with 3kV, 110kV, 220kV and other high-voltage power transmission and transformation lines after passing through a step-up transformer.

The number of series connected components of the square array is mainly determined by the system working voltage or the rated input voltage of the inverter. Off-grid systems must also consider factors such as battery float voltage, line loss, and temperature changes. Generally, the output voltage of a photovoltaic array with batteries = 1.43 × the nominal voltage of the battery pack. For photovoltaic power generation systems without storage batteries, when calculating the output voltage of the square array, the rated voltage is generally increased by 10%, and then the number of components in series is selected.

For example, the maximum output power of a component in an off-grid system is 245W, and the maximum working voltage is 29.9V. Assuming that the selected inverter is AC three-phase with a rated voltage of 380V, and the inverter adopts a three-phase bridge connection method, the DC output voltage of the photovoltaic array is Up=Uab/0.817=380/0.817≈465V. Considering the voltage margin again, the output voltage of the photovoltaic square array should be increased to 1.1×465≈512V, and the number of modules in series is calculated to be 512V/29.9V≈18.

Next, calculate the total number of battery components from the system output power. Assuming that the required power of the load is 30KW, the total number of components is 30000W/245W≈123, and the number of components in parallel is calculated to be 123/18≈7, and the number of parallel connections can be selected as 7.

Conclusion: The system should select the above-mentioned power components 18 in series and 7 in parallel, the total number of components is 18×7=126, and the maximum output power of the system is 126×245W=30.87KW.