1, the composition and principle of solar photovoltaic system
Solar photovoltaic system consists of the following three parts: solar cell modules; charging and discharging controllers, inverters, test instruments and computer monitoring and other power electronics equipment and batteries or other energy storage and auxiliary power generation equipment.
Solar photovoltaic systems have the following characteristics.
- No rotating parts, no noise;
- No air pollution, no waste water emissions;
- No combustion process, no fuel required;
- Simple maintenance and low maintenance costs;
- Good operational reliability and stability;
- Long service life of solar cell as a key component, crystalline silicon solar cell life can reach more than 25 years;
It is easy to expand the scale of power generation as needed.
Photovoltaic systems are widely used, and the basic forms of photovoltaic system applications can be divided into two categories: stand-alone power generation systems and grid-connected power generation systems. The main areas of application are mainly in spacecraft, communication systems, microwave relay stations, TV relay stations, PV pumps and household power supply in areas without electricity. With the development of technology and the need for sustainable development of the world economy, developed countries have begun to systematically promote urban photovoltaic grid-connected power generation, mainly by building household rooftop photovoltaic power generation systems and MW-level centralized large-scale grid-connected power generation systems, etc., while vigorously promoting the application of solar photovoltaic systems in transportation and urban lighting, etc.
The scale and application forms of photovoltaic systems vary, such as the system scale spans a wide range of small to 0.3 ~ 2W solar garden lights, large to MW-class solar photovoltaic power plants, such as 3.75kWp household-type rooftop power generation equipment, Dunhuang 10MW project. Its application form is also diverse, in the home, transportation, communications, space applications and many other fields can be widely used. Although the size of PV systems varies, their composition structure and working principle are basically the same. Figure 4-1 shows a schematic diagram of a typical PV system supplying a DC load. It contains several major components of a PV system.
Photovoltaic module square array: made of solar cell elements (also known as photovoltaic modules) in series and parallel according to system requirements, under the sunlight irradiation will convert solar energy into electrical output, it is the core component of the solar photovoltaic system.
The battery: the solar cell components will produce the electrical energy stored, when the light is not enough or night, or load demand is greater than the power generated by the solar cell components, the stored electrical energy will be released to meet the load energy demand, it is the solar photovoltaic system energy storage components. At present, solar photovoltaic system is commonly used lead-acid battery, for the higher requirements of the system, usually using deep-discharge valve-regulated sealed lead-acid battery, deep-discharge liquid-absorbing lead-acid battery, etc.
Controller: It regulates and controls the charging and discharging conditions of the battery, and controls the solar cell components and the electrical output of the battery to the load according to the power demand of the load, which is the core control part of the whole system. With the development of solar photovoltaic industry, the controller is becoming more and more powerful, and there is a trend to integrate the traditional control part, inverter and monitoring system, such as AES's SPP and SMD series of controllers integrate the above three functions.
Inverter: In a solar PV power supply system, if it contains an AC load, then an inverter device is used to convert the DC power generated by the solar cell elements or the DC power released from the battery into the AC power needed by the load.
The basic working principle of solar photovoltaic power supply system is that under the sunlight, the electrical energy generated by the solar cell elements will be charged to the battery through the control of the controller or directly to the load if the load demand is met. For PV systems with AC loads, an inverter is required to convert the DC power into AC power. The application of photovoltaic systems has many forms, but the basic principles are similar. For other types of photovoltaic systems only in the control mechanism and system components according to the actual needs of different, the following will be described in detail for different types of photovoltaic systems.
2, the classification and introduction of photovoltaic systems
Generally the PV system is divided into independent system, grid-connected system and mixed system. If the application of photovoltaic systems based on the form, application scale and type of load, photovoltaic power supply system for a more detailed division, can be divided into the following six types of photovoltaic systems: small solar power system (Small DC); simple DC system (Simple DC); large solar power system (Large DC); AC, DC power supply system (AC/DC); Grid-connected system (Utility Grid Connect); Hybrid power supply system (Hybrid); Grid-connected hybrid system.
Photovoltaic power generation is an electronic component technology that uses the photovoltaic effect of the semiconductor interface to convert light energy directly into electricity. Solar cells are connected in series and then encapsulated and protected to form large-area solar cell elements, which are combined with power controllers and other components to form a photovoltaic power generation device. The advantages of photovoltaic power generation are that it is less restricted by geography because the sun shines on the earth; photovoltaic system also has the advantages of safety and reliability, no noise, low pollution, no need to consume fuel and set up transmission lines to generate power in situ and short construction period.
Photovoltaic power generation is based on the principle of photovoltaic effect, using solar cells to convert sunlight energy directly into electricity. Regardless of whether it is used independently or grid-connected, photovoltaic power generation system mainly consists of solar panels (components), controllers and inverters, which are mainly composed of electronic components and do not involve mechanical parts, therefore, photovoltaic power generation equipment is extremely refined, reliable, stable and long-lived, easy to install and maintain. Theoretically speaking, photovoltaic power generation technology can be used in any situation where power is needed, from spacecraft to household power, from megawatt-class power plants to toys, photovoltaic power is everywhere. The most basic component of solar photovoltaic power generation is the solar cell (sheet), there are monocrystalline silicon, polycrystalline silicon, amorphous silicon and thin film cells. At present, the largest amount of monocrystalline and polycrystalline cells, amorphous cells are used in some small systems and calculators auxiliary power.
