Composition and principle of solar photovoltaic system
The solar photovoltaic system consists of the following three parts: solar cell module; Charge and discharge controller, inverter, test instrument, computer monitoring and other power electronic equipment and battery or other energy storage and auxiliary power generation equipment.
The solar photovoltaic system has the following characteristics:
-No rotating parts, no noise;
-No air pollution and wastewater discharge;
-No combustion process, no fuel required;
-Simple maintenance and low maintenance cost;
-Good operation reliability and stability;
-As a key component, the service life of solar cells is long, and the service life of crystalline silicon solar cells can reach more than 25 years; It is easy to expand the scale of power generation as required.
Photovoltaic systems are widely used. The basic forms of photovoltaic system application can be divided into two categories: independent power generation system and grid-connected power generation system. The main fields of application are mainly in space vehicles, communication systems, microwave relay stations, television turntables, photovoltaic water pumps and household power supply in areas without electricity and power shortage. With the development of technology and the need for sustainable development of the world economy, developed countries have begun to promote urban photovoltaic grid-connected power generation in a planned way, mainly by building house-top photovoltaic power generation systems and megawatt centralized large-scale grid-connected power generation systems, while vigorously promoting the application of solar photovoltaic systems in transportation vehicles and urban lighting.
The scale and application forms of photovoltaic systems vary, such as the large scale span of the system, which is as small as 0.3~2W solar garden lamps, solar photovoltaic power stations, such as 3.75kWp household rooftop power generation equipment. Its application forms are also diverse, and it can be widely used in many fields such as home use, transportation, communications, space applications, etc. Although the scale of photovoltaic system is different, its composition structure and working principle are basically the same. It includes several main components in the photovoltaic system:
Photovoltaic module array: It is composed of solar cell modules (also known as photovoltaic cell modules) in series and in parallel according to the system requirements. It converts solar energy into electrical energy output under the sunlight. It is the core component of the solar photovoltaic system.
Battery: stores the electric energy generated by the solar cell module. When the light is insufficient or at night, or the load demand is greater than the electric energy generated by the solar cell module, the stored electric energy will be released to meet the energy demand of the load. It is the energy storage component of the solar photovoltaic system. At present, lead-acid batteries are commonly used in solar photovoltaic systems. For systems with higher requirements, deep-discharge valve-regulated sealed lead-acid batteries and deep-discharge liquid-absorbing lead-acid batteries are usually used.
Controller: It regulates and controls the charging and discharging conditions of the battery, and controls the power output of the solar cell module and the battery to the load according to the power demand of the load. It is the core control part of the whole system. With the development of the solar photovoltaic industry, the functions of the controller become more and more powerful. There is a trend to integrate the traditional control part, inverter and monitoring system.
Inverter: In the solar photovoltaic power supply system, if there is an AC load, the inverter equipment shall be used to convert the DC generated by the solar cell module or the DC released by the battery into the AC required by the load.
The basic working principle of the solar photovoltaic power supply system is to charge the battery with the electric energy generated by the solar cell module under the control of the controller or directly supply power to the load if the load demand is met. If the sun is insufficient or at night, the battery will supply power to the DC load under the control of the controller. For the photovoltaic system with AC load, It is also necessary to add an inverter to convert direct current into alternating current. The application of photovoltaic system has many forms, but its basic principles are similar. For other types of photovoltaic systems, the control mechanism and system components are only different according to the actual needs. The following will describe different types of photovoltaic systems in detail.