Solar photovoltaic system classification
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Solar photovoltaic systems have different forms in different applications. Generally, solar photovoltaic systems can be divided into independent photovoltaic systems and grid-connected photovoltaic systems.
- Independent photovoltaic system
Independent photovoltaic system refers to the formation of a solar photovoltaic power generation system into an independently operating power generation system, which directly converts the received solar radiation energy into electrical energy through solar cells, which can be directly provided to the load, or the excess energy can be stored in the battery. For use when needed. Independent photovoltaic systems can be divided into household photovoltaic systems and independent photovoltaic power stations.
1) Household photovoltaic system Household photovoltaic system mainly refers to the photovoltaic power generation system that needs to supply power for the residents themselves, which is generally composed of solar panels, batteries, charge/discharge controllers and inverters. When there is sunlight, the power generation system can directly supply power to the household load or charge the battery; when there is no sunlight, the battery outputs energy, and the inverter realizes power supply to the household load. From an economic and technical point of view, household photovoltaic systems can also be complementary to wind power generation, diesel power generation or city electricity. The application technology of household photovoltaic system is relatively simple, and its power supply reliability and stability requirements are relatively low. The capacity of the DC/DC conversion circuit or the DC/AC conversion circuit of the household photovoltaic system is generally small.
2) Independent photovoltaic power station Independent photovoltaic power station refers to the photovoltaic power generation system that supplies power to regional users. In some non-electricity villages and islands with good lighting conditions, it is suitable to establish independent photovoltaic power stations. The capacity of an independent photovoltaic power plant is generally larger. The independent power station is composed of solar arrays, artemisia batteries, converters, energy managers, power distribution and transmission systems to form a regional power grid. When designing an independent power station, it is important to consider the rational use of batteries. Since independent power stations need to supply power to many loads at the same time, energy managers should be used to rationally plan and manage the energy distribution between the power consumption of each load and the battery charging, so as to make the most reasonable and full use of solar energy. The capacity of DC/AC inverters of independent photovoltaic power plant systems is relatively large.
- Grid-connected photovoltaic system
The grid-connected photovoltaic system converts the direct current generated by the solar cell array into the alternating current that meets the requirements of the mains grid through the grid-connected inverter, and then directly merges it into the public grid. Grid-connected photovoltaic system is the development direction of solar photovoltaic technology in the future. Compared with independent photovoltaic power stations, grid-connected photovoltaic systems have many advantages, such as not having to consider the stability of load power supply and power supply quality; solar cells can always run at the maximum power point, improving the utilization efficiency of photovoltaic systems; using the grid as storage The energy device does not require a battery for energy storage. In addition to reducing the initial investment in the construction of the photovoltaic system, it also reduces the energy loss during the charging/discharging process of the battery, and avoids the operation and maintenance costs of the battery.
Similar to independent photovoltaic systems, grid-connected photovoltaic systems can also be divided into household grid-connected photovoltaic systems and grid-connected photovoltaic power stations.
The grid-connected photovoltaic system consists of a photovoltaic array, a converter, and a controller. The converter inverts the DC power generated by the photovoltaic array into a sinusoidal current and integrates it into the grid; the controller controls the maximum power point tracking of the photovoltaic cell and controls the inverter to connect to the grid The waveform and power of the current balance the power transferred to the grid with the maximum power generated by the photovoltaic array.
Grid-connected photovoltaic systems must also consider a special failure state, that is, islanding. This type of failure will have some adverse effects and must be protected.