Nowadays, photovoltaic power generation is a very common new energy source. Compared with hydropower and wind power, there is no strict location selection for its construction. Hydropower should be built in areas with abundant water resources, such as river sections with large water flows.
Wind power is usually built in open areas such as mountains and hills, and there is wind all year round. However, PV systems are different. There are centralized large-area PV systems built in areas such as deserts like the Gobi to make full use of abandoned land resources.
In general, distributed photovoltaics are built on places such as building roofs, factory roofs, and vegetable greenhouses to make full use of space. Therefore, what are the similarities and differences between distributed and centralized PV systems?
(1) They have the same principle to use solar energy to convert into electrical energy, and then the generated electricity is connected to the grid and sent to the grid for production and life use.
(2) They have the same components even though they are different types of solar pv system. In general, monocrystalline silicon panels or solar thin films are commonly used.
(3) The primary equipment of distributed PV systems and centralized PV systems are basically the same, which includes inverters, transformers, combiner boxes and other equipment.
The role of the inverter is to convert the generated direct current into alternating current. The role of the transformer is to boost the alternating current converted by the inverter. The role of the combiner box is to gather the direct current from the sunrise solar panel and transfer it to the inverter together.
(1) Different installation locations: Distributed PV systems are mainly installed on the roof of agricultural greenhouses. Centralized PV systems are mainly installed in the Gobi and other deserts, and they are usually installed in remote and desolate areas where the land is relatively cheap.
(2) Different grid-connected voltage levels: In general, distributed PV systems with 380V voltage are connected to the grid, and low-voltage tripping devices are usually used to connect to the grid. Also, the number of distributed grid-connected points depends on the actual situation.
The voltage of centralized PV system connected to grid power stations is usually 35KV or 110KV. If the power station is 30 MW or less, the main transformer usually will not be installed.
For centralized PV systems power stations above 30 MW, the main transformer is usually installed and connected to the grid after rising to 110KV voltage level through the main transformer.
(3) Different secondary equipment used in the power station: Since the distributed photovoltaic power station is connected to the grid at low voltage 380V, it is less used for primary equipment and secondary equipment.
Among them, the inverter is usually a wall-mounted inverter, which is small in size and simple to install. The transformer is also small in size. Distributed PV systems are commonly used in power quality monitoring, anti-islanding protection devices, and fault disassembly devices.
The requirements for equipment and technical parameters are different from regions. But for now, it is a must for every distributed PV device.
In general, centralized photovoltaic power stations have their own substations since they have relatively high voltage levels. The inverter has a large size and is usually located in the substation room. The boost function is completed by a box transformer, and centralized PV systems can usually be raised to 35KV.
There is a lot of equipment in the booster station, including primary equipment such as the station transformer, switch cabinet, various transformers, arc suppression coil, and main transformer. And the secondary equipment includes microcomputer protection, watt-hour meter, dispatching data screen, etc., which is relatively complicated. Dispatching can directly implement centralized management of the power station.
At the same time, a power control system is required in the station, which is much more complicated than distributed PV systems.
(4) Different transmission distances: In general, the electricity generated by the distributed PV systems can be connected to the grid locally, and there are low or no losses. They can supplement local electricity for local and nearby users.
The electricity generated by the centralized photovoltaic power station is connected to the grid at high voltage and transmitted to a higher voltage level layer by layer.