Typical solar photovoltaic power generation system consists of solar cell array (module), cable, power electronic converter (inverter), energy storage device (battery), load namely user, etc. The solar 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 terminal of the system.
The smallest unit used for photoelectric conversion is a solar cell. Its size is 4~100cm2, working voltage is 0.45~0.50V, working current is 20~25mA/cm2, so it cannot be used as a power supply alone. In the photovoltaic power generation system, solar cells need to be connected in series, in parallel and packaged to form solar cell modules. It can range in power from a few watts to several hundred watts and can be used as a separate power source. 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 more power, is the photovoltaic power generation system electricity generator.
There are various types of solar cell modules, which can be divided into monocrystalline silicon modules, polycrystalline silicon modules, gallium arsenide modules and amorphous silicon thin film cell modules according to the types of solar cells. Crystalline silicon (including monocrystalline silicon and multiproduct silicon) solar cell modules account 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, laminated packaging silicone packaging, etc. At present, the most widely used method is vacuum lamination packaging, which is suitable for industrial packaging of large area battery cells.
2, solar battery
The independent photovoltaic power generation system relies on the battery to store excess electric energy, so the battery plays an important role in the independent photovoltaic power generation system. As the price of solar modules falls, the cost of batteries will gradually increase as a proportion of total system investment. In addition, in the operation of the independent photovoltaic power generation system, the normal operation of the system will be affected by the failure of the battery will occupy a large proportion. Therefore, in the system design, it is very important to choose the appropriate battery type, determine the appropriate battery capacity, accurately implement the installation, operation and careful maintenance for the normal operation of the independent solar photovoltaic power generation system.
3, power electronic converter (photovoltaic inverter)
The inverter in the photovoltaic power generation system is a current-changing circuit, whose function is to convert the direct current generated by the solar cell array into the alternating current of different frequency and voltage values. Specifically, the inverter can be divided into passive and active. Passive inverter refers to the direct supply of energy to the load through the inverter, while active inverter refers to the direct supply of energy to the AC power supply through the inverter.
The necessity of switching from DC to AC is also reflected in the fact that when the power supply system needs to raise or lower the voltage, ac system only needs to add a transformer, whereas in dc system technology and equipment are much more complex. Therefore, in addition to special users, in the photovoltaic power generation system need to be equipped with inverter.
In addition, the inverter also has automatic or manual voltage regulation function, which can improve the power supply quality of photovoltaic power generation system. Obviously, inverter is an indispensable and important supporting equipment in photovoltaic power generation system.