Grid-connected principle of solar photovoltaic power generation

Grid-connected principle of solar photovoltaic power generation. Photovoltaic power generation is a technology that directly converts light energy into electric energy by using photovoltaic effect of semiconductor interface. The key component of this technology is solar cell. Let's take a look at the principle of solar photovoltaic power generation. Grid-connected principle of solar photovoltaic power generation 1

Grid-connected principle of photovoltaic power generation: Relying on solar cell modules and using the electronic characteristics of semiconductor materials, when sunlight shines on the semiconductor PN junction, a strong built-in electrostatic field is generated, and under the action of the built-in electrostatic field, light energy is converted into electric energy.

its working principle is that the direct current generated by the solar cell module is converted into alternating current that meets the requirements of the power grid through the grid-connected inverter, and then directly enters the public power grid. The power generated by the photovoltaic cell array is not only supplied to the alternating current load, but also fed back to the power grid. On rainy days or nights, when the solar cell module does not generate electric energy or the electric energy cannot meet the load demand, it is powered by the power grid.

Because solar power is directly supplied to the power grid, the storage battery is not required, which saves the process of energy storage and release of the storage battery, reduces the energy loss and reduces the cost of the system. However, the system needs a dedicated grid-connected inverter to ensure that the output power meets the requirements of the power grid for voltage, frequency and other indicators. Because of the efficiency of inverter, there will be some energy loss. Grid-connected principle of solar photovoltaic power generation 2

Basic principle of photovoltaic power generation

Independent photovoltaic power generation system consists of solar cell array, storage battery, inverter module, controller and load (DC load and AC load). Because the electric energy generated by the solar cell is DC, but the output voltage of the solar cell is unstable due to the real-time change of the illumination intensity, at this time, the storage battery is also needed to play a filtering role and stabilize the voltage generated by the solar cell at the voltage value of the storage battery. < P > In another sense, the storage battery also has the function of storing energy, and the surplus electric energy can be stored for use when the illumination intensity is low. If it is a DC load, it can be directly connected to the battery to work. If it is an AC load, it needs DC-AC conversion by an inverter to change DC into AC and supply it to the AC load.

Basic principle of grid-connected photovoltaic power generation

Independent photovoltaic power generation system consists of solar cell array, storage battery, inverter module, controller and load. Because the electricity generated by photovoltaic needs to be fed back to the power grid, it is necessary to convert direct current into alternating current of 221V and 51HZ required by the power grid, and connect it to the grid in the same phase, so as to supply power to the power grid.

whether it is an independent photovoltaic power generation system or a grid-connected photovoltaic power generation system, the inverter system is essential for AC load and grid-connected power generation. Next, we mainly study the related design of inverter system in photovoltaic distributed power generation.

composition of photovoltaic power generation inverter system

photovoltaic power generation system is mainly composed of solar cells, main circuit, control circuit and load. The main loop mainly includes DC/DC circuit, DC/AC circuit and filter components. The following mainly introduces the design of the main circuit, including the analysis of the topological structure of the main circuit, and introduces the working principle of the full-bridge inverter circuit, the selection of inverter modules and the design of related protection.

Topology of photovoltaic power generation inverter system

Usually, single-phase voltage-source inverters are mainly divided into three types: push-pull inverter, half-bridge inverter and full-bridge inverter. These three methods are applied to different occasions according to their different characteristics.

the circuit structure of the push-pull inverter circuit is relatively simple, as shown in figure 3-1. The upper circuit only needs two thyristors, and the base drive circuit does not need isolation. The drive circuit is relatively simple, but the thyristors need to bear twice the peak voltage of the line, so it is suitable for low input voltage.

at the same time, there is magnetic bias in the transformer, and the primary winding has a center tap, so the effective value of the current flowing and copper consumption are large, and the primary winding should be closely coupled, so the winding process is complicated. Push-pull inverter circuit is not suitable as the main circuit of photovoltaic power generation system because of its high requirements for thyristor withstand voltage.

compared with the push-pull inverter circuit, the thyristor used in the single-phase half-bridge inverter circuit has relatively low withstand voltage requirements, which will not be twice as much as the peak line voltage, and will never exceed the peak line voltage. The inverted waveform is also close to sine wave compared with push-pull mode, so the requirements of filtering are relatively low. Because the saturation voltage drop of thyristor is minimized, it is not one of the most important factors.

However, due to the structure of the half-bridge inverter circuit, its collector current will double when the thyristor is turned on, so it is inevitable that it is not suitable as the main circuit of the inverter system for photovoltaic power generation because of its high price when considering the situation of large current and high voltage in the selection of thyristor. Grid-connected principle of solar photovoltaic power generation 3

Solar power generation is mainly divided into two types, one is grid-connected power generation and the other is independent photovoltaic system. The main difference between the two is that one needs to be connected to the grid, and the battery is not applicable. The other is self-sufficient and needs a battery, and the others are basically the same.

the basic composition is as follows: the photovoltaic array converts solar energy into DC energy, and after DC and AC inverter, the voltage level of photovoltaic power station connected to the power grid is determined according to the capacity of photovoltaic power station connected to the power grid technology, and then the photovoltaic power station is connected to the medium voltage or high voltage power grid after being boosted by the transformer.

The principle is as follows: Photovoltaic power generation is a technology that directly converts light energy into electric energy by using photovoltaic effect at semiconductor interface. The key component of this technology is solar cell. After the solar cells are connected in series, they can be packaged and protected to form a large-area solar cell module, and then a photovoltaic power generation device is formed with the power controller and other components.

at present, there are usually three "grid-connected modes" of solar photovoltaic power stations in the market: spontaneous self-use surplus electricity grid-connected mode, full grid-connected mode and full self-use mode.

first of all, if you choose one of the three grid-connected modes, you need to choose it according to your own actual situation. For example, like ordinary households, most people choose the mode of spontaneous self-use surplus electricity to access the Internet, which is also the highest proportion of distributed photovoltaic power stations.

The advantage of this mode is that the electricity generated by photovoltaic power plants is given priority to power supply in their own homes, and then it can be automatically merged into the power grid without using excess electricity, so that waste can be avoided and money can be made. This mode is more suitable for ordinary household users to choose, and it is also very economical, because there is no need to spend extra money on batteries to store electricity.

in addition to household electricity consumption, such places as industrial electricity consumption, roofs of factories and industrial and commercial buildings are commercial electricity consumption, and they are also more suitable for spontaneous self-use surplus electricity access mode.

why do you say that? Because the cost of commercial electricity is higher than that of civil electricity, if photovoltaic power stations are installed on the roofs of industrial and commercial buildings and factories, the economic benefits will be greatly increased and the time to return to the capital will be shorter. This choice is very favorable, and the unused electricity will be directly connected to the power grid.