The photovoltaic grid-connected power generation system is a process of realizing power supply by solar cells and grid-connected inverters. The photovoltaic grid-connected power generation system is widely used in today's life. The light energy of the photovoltaic grid-connected power generation system is converted into electrical energy. Various advantages and functions are supported and studied by professionals and the national government. Our research direction also revolves around Grid-tied inverters and photovoltaic cells. Their equipment has also been very popular in the market, and now solar energy products have been popularized to household users, so they explained some basic concepts and principles.
1. Photovoltaic grid-connected power generation system
1. The photovoltaic grid-connected power generation system is that the direct current generated by solar products is converted into alternating current by the grid-connected inverter and then directly connected to the public power grid. Simply put, it is converted from light energy into electrical energy for users to use.
Because the electric energy can be directly input to the grid, the PV-independent system existing in all batteries will be replaced by the grid-connected system, so there is no need to install batteries, which can reduce costs. However, the grid-connected inverter required by the system must ensure that the power can meet the frequency, frequency and other performance of the grid.
Advantage:
(1) The use of non-polluting, renewable solar power generation can also quickly reduce non-renewable. The consumption of energy with limited resources, the emission of greenhouse gases and polluting gases at noon during use, in harmony with the ecological environment, is to promote the development of sustainable development!
(2) The generated electric energy is directly fed into the grid through the inverter, saving the battery, which can reduce the construction investment by 35% to 45% compared with the photovoltaic independent system, which greatly reduces the production cost. It can also remove the battery to avoid secondary pollution of the battery, and can increase the service life and normal use time of the system.
(3) Photovoltaic building-integrated power generation system, due to the small investment, fast construction, small footprint, high technology content in the building, and enhanced building selling points
(4) Distributed construction, decentralized construction near various places, making it convenient to enter the power grid, not only good at increasing the defense capability of the system and resisting natural disasters, but also good at balancing the load of the power system and reducing line losses.
(5) It can play the role of peak regulation. The grid-connected solar photovoltaic system is the key object and supported project of many developed countries. It is the main development trend of solar power generation system. The market capacity is large and the development space is large.
2. Grid-connected inverter
There are roughly the following types of grid-connected inverters:
(1) Centralized inverter
(2) String inverter
(3) Component inverter
If the main circuits of the above inverters are implemented by control circuits, we can divide them into two control methods: square wave and sine wave.
Square wave output inverter: Most of the square wave output inverters use pulse width modulation integrated circuits, such as TL494. The fact shows that the use of SG3525 integrated circuit to take the power FET as the switching power element can meet the ultra-high performance ratio requirements of the inverter, because the SG3525 is very effective in driving the power FET and has an internal reference source and operational amplifier. And under-voltage protection function, all relative peripheral circuits are also very simple.
Inverter with sine wave output: Schematic diagram of sine wave inverter, there is a difference between square wave output and sine wave output. The inverter with square wave output has high efficiency, but it is not suitable for electrical appliances designed for sine wave power supply. It is said that it is always uneasy to use. Although it can be applied to many electrical appliances, some electrical appliances are not suitable, or the indicators of electrical appliances will change. The inverter with sine wave output does not have this disadvantage, but it has low efficiency. shortcoming.
The principle of grid-connected inverter: We convert AC current into DC current, which is rectification. The circuit process that completes this rectification function is called rectifier circuit. The realization process of the entire rectifier circuit device becomes a rectifier. Compared with it, the current that can convert DC current into AC is reverse current. The circuit that completes the entire reverse current function is called an inverter circuit. The realization process of the entire inverter device is called an inverter.
Function:
a. Automatic switch: According to the work and rest time of the sun, the function of automatic switch machine is realized.
b. Maximum power point tracking control: When the surface temperature of photovoltaic modules and the temperature of solar radiation change, the voltage and current generated by the photovoltaic modules also change, and it can track these changes to ensure maximum power output.
c. Prevent islanding effect: Passive detection can determine whether islanding effect occurs by detecting the power grid, active detection forms positive feedback by actively introducing small-amplitude disturbance, and uses cumulative effect to infer whether islanding occurs. It is through the combination of passive detection and active detection that the effect of anti-islanding effect can be controlled.
d. Automatically adjust the voltage. When too much current flows back into the grid, the voltage at the transmission point rises due to the reverse transmission of power, which may exceed the operating range of the voltage. In order to maintain the normal operation of the grid, the grid-connected inverter should be able to automatically prevent the voltage from rising.
Installation: If it is a centralized inverter, if there is an electric meter nearby, install it near the electric meter. If the conditions and environment are good, it is also possible to install it near the photovoltaic wiring cabinet, which greatly reduces the loss of lines and equipment. Large central inverters are usually installed in an inverter box with other equipment (such as electricity meters, circuit breakers, etc.). More and more distributed inverters are installed on roofs, but experiments have found that protection measures should be taken for the inverters to avoid direct sunlight and rain. When choosing an installation site, it is very important to meet the temperature, humidity and other requirements recommended by the inverter manufacturer. At the same time, the influence of the noise of the inverter on the surrounding environment should also be considered.
Daily use of solar energy in life
Solar energy has many uses and functions in life. It is a kind of radiation energy, pollution-free and pollution-free.
1. Power generation: that is, directly convert solar energy into electrical energy, and store the electrical energy in capacitors for use when needed.
Such as solar street light, solar street light is a kind of street light that does not need power supply and uses solar energy to generate electricity. Such street lights do not need power supply or wires, which is relatively economical and can be used normally as long as the sun is relatively abundant, because such products are widely concerned and liked by the public, not to mention that they do not pollute the environment, so This can become a green product, solar street lights can be used in parks, towns, lawns. It can also be used in areas with small population density, inconvenient transportation, underdeveloped economy, lack of conventional fuels, and it is difficult to use conventional energy to generate electricity, but solar energy resources are abundant to solve the household lighting problems of people in these areas.
2. Heating energy: that is, the heat energy that solar energy converts into water, example: solar water heater.
Solar energy used to heat water a long time ago, and now there are millions of solar installations around the world. The main components of the solar water heating system include three parts: collector, storage device and circulation pipeline. It mainly includes temperature difference control heat collection cycle and floor heating pipeline circulation system. Solar water heating projects are increasingly used in residential, villas, hotels, tourist attractions, science and technology parks, hospitals, schools, industrial plants, agricultural planting and breeding areas and other major fields.
Others, such as electrical energy can be converted into various mechanical energy, thermal energy can be converted into electrical energy, and electrical energy can also be converted into thermal energy.