This chapter introduces the arrangement of photovoltaic array.
Each solar cell can only generate a DC voltage of about 0.5V, which is far lower than the voltage required for actual use. In order to meet the needs of practical applications, solar cells need to be connected in series into modules. The solar cell module contains a certain number of solar cells, which are connected by wires. The modules for large photovoltaic power plants usually encapsulate 72 solar cells, and the normal output voltage is about 35V. When the application field requires higher voltage and current, a single module When the requirements cannot be met, multiple modules can be connected in series and parallel to form a solar cell array to obtain the required voltage and current. The square array of solar cell modules in series and parallel is designed according to the performance parameters of solar cell modules and inverters and the checking temperature of -20~70℃. If 280Wp polycrystalline silicon solar cell modules are used, it is calculated that 18 modules are suitable in series. Two component strings form a square array, which can be installed on a set of brackets. There are 102 sets of brackets, that is, there are 204 component strings in common, and the power of 1028.16kW forms a power generation unit of 1 MWp. To build a 20MWp grid-connected photovoltaic power station, it can be divided into 20 1MWp power generation units, and a box-type transformer is installed in the middle of each power generation unit to reduce the length of the inverter DC and AC cables, while reducing losses and occupying less land. To improve efficiency.
If 240Wp modules are used, according to the performance parameters of the modules and the input voltage requirements of the inverter, after optimization and matching, 20 modules should be connected in series to form a string; if 260Wp modules are used, 12 modules should be connected in series to form a string.
The matching of string and inverter mainly considers two factors under extreme conditions:
① The maximum working voltage of the string does not exceed the MPPT range of the inverter.
②The open circuit voltage of the string does not exceed the requirement of the maximum DC voltage of the inverter.
In order to improve the combined efficiency coefficient of the photovoltaic array (η combination = the sum of the effective power of the square array / the nominal power of each module), the working voltage and working current of each module must be strictly screened, that is, the IV curves of the modules are required to be as consistent as possible. Reduce the power loss caused by series and parallel components. In the design of the photovoltaic array, there are the following considerations.
① Array inclination angle design, azimuth angle design, and array spacing design should be carried out according to specific conditions such as overall technical requirements, geographic location, climatic conditions, solar radiant energy resources, and site conditions.
②Try to ensure that each row of modules in the north-south direction is on the same axis, so that the solar cell modules are arranged neatly, standardized and beautifully, the effect of receiving solar radiation is the best, and the land use is more compact and economical.
③The spacing between each two columns of modules must be set to ensure that all modules still have more than 6 hours of sunshine on the winter solstice day when the sun altitude is the lowest.