A typical solar photovoltaic power generation system consists of solar arrays (modules), cables, power electronic converters (inverters), energy storage devices (cells), loads that are users, etc. Among them, the solar cell array and energy storage device are the power supply system, the controller and power electronic converter are the control and protection system, and the load is the system terminal.
- Solar arrays
The smallest unit used for photoelectric conversion is the solar cell cell. Its size is 4~100cm2, the working voltage is 0.45~0.50V, and the working current is 20~25mA/cm2, so it can not be used as a power supply alone. In the photovoltaic power generation system, it is necessary to series, parallel and package the solar cell monomer to form a solar cell module. Its power can range from a few watts to several hundred watts and can be used as a power source alone. Solar cell array is the solar cell module after series, parallel and installed on the bracket, it can output hundreds of watts, a few kilowatts or even greater power, is the power generator of photovoltaic power generation system.
According to the type of solar cell, it can be divided into: monocrystalline silicon module, polycrystalline silicon module, gallium arsenide module, amorphous silicon thin film cell module, etc., of which crystalline silicon (including monocrystalline silicon and multi-product silicon) solar cell module accounts for about 80% to 90% of the market.
The packaging materials and processes of crystalline silicon are also different, mainly divided into epoxy resin sealing, lamination packaging silicone packaging and so on. At present, the most widely used is the vacuum laminate packaging method, which is suitable for industrial packaging of large-area cells.
Independent photovoltaic power generation systems rely on cells to store excess electrical energy, so cells play an important role in independent photovoltaic power generation systems. As the price of solar modules falls, the proportion of cell costs in the total investment of the system will gradually increase.
In addition, in the operation of independent photovoltaic power generation systems, the normal operation of the system will be affected by cell failure, which will occupy a large proportion. Therefore, in the system design, selecting the appropriate cell type, determining the appropriate cell capacity, accurately implementing the installation, operation, and careful maintenance are very important for the normal operation of independent solar photovoltaic power generation systems.
3.Power electronic converter (photovoltaic inverter)
The inverter in the photovoltaic power generation system is a converter circuit, whose role is to convert the direct current emitted by the solar array into alternating current with different required frequencies and voltage values. Inverter can be divided into passive and active two types, passive inverter refers to the direct current through the inverter to supply energy to the load, the active inverter refers to the direct current through the inverter to AC power supply.
The necessity of DC to AC is also reflected in that when the power supply system needs to raise or lower the voltage, the AC system only needs to add a transformer, and the technology and equipment in the DC system are much more complex. Therefore, in addition to special users, in the photovoltaic power generation system need to be equipped with inverters.
In addition, the inverter also has automatic voltage regulation or manual voltage regulation function, which can improve the power supply quality of the photovoltaic power generation system. It is obvious that the inverter is an indispensable supporting equipment in the photovoltaic power generation system.