Grid-connected photovoltaic power generation system is to directly connect the DC power generated by the battery components or the square array to the public grid after being converted into AC power that meets the requirements of the mains power grid through the grid-connected inverter. Grid-connected photovoltaic power generation systems include centralized large-scale ground photovoltaic power station systems and distributed photovoltaic power station systems. Large-scale ground photovoltaic power stations are generally national-level power stations. The main feature is that the generated energy is directly transmitted to the grid, and the grid is uniformly deployed to supply power to users. This kind of power station has a large investment, a long construction period, a large area, complex control equipment and long-distance high-voltage transmission and distribution systems, and its power generation cost is more than double the cost of traditional energy power generation. It is currently widely used in western China Some projects are still at the stage of state policy subsidies. Distributed photovoltaic power plants, especially rooftop photovoltaic power generation systems combined with buildings and integrated photovoltaic power generation systems, have the advantages of small investment, fast construction, small footprint or even no land occupation, and large policy support. It is the mainstream of grid-connected photovoltaic power generation applications at present and in the future.
So, what is distributed photovoltaic power generation? Distributed photovoltaic power generation mainly refers to the construction and grid-connected operation on the user’s site or near the site. It does not aim at large-scale long-distance transmission. A photovoltaic power generation facility that operates on the power grid and is balanced and regulated in the distribution network system.
Distributed photovoltaic power generation systems are generally connected to the grid below 10kV, and the total installed capacity of a single grid connection point does not exceed 6MW. For the system connected to the 220V voltage level, the total installed capacity of a single grid connection point does not exceed 8kW.
In the “Notice on Further Implementing Relevant Policies on Distributed Photovoltaic Power Generation”, the National Energy Administration has also extended the definition of distributed photovoltaic power generation to include: a distributed photovoltaic power generation project constructed on the roof of a building and auxiliary sites. Choose one of the modes of “spontaneous self-use, surplus electricity to the Internet” or “full-amount Internet”. Constructed on the ground or using agricultural greenhouses and other non-power consumption facilities, connected to the grid at a voltage level of 35kV and below (66kV and below in the Northeast), the capacity of a single project does not exceed 20,000 kW (20MW), and the power generation is mainly changed at the grid connection point The photovoltaic power station projects consumed in the station area can be included in the management of distributed photovoltaic power generation scale indicators.
The document pointed out that the state encourages the development of various forms of distributed photovoltaic power generation applications. Make full use of qualified building roof (including auxiliary free space) resources, and encourage development zones and large-scale industrial and commercial enterprises with large roof areas, large power loads, and high grid power supply prices to take the lead in developing photovoltaic power generation applications. Encourage local governments at all levels to formulate supporting financial subsidy policies on the basis of state subsidies, and appropriately increase support for public institutions, affordable housing and rural areas. Encourage the promotion of photovoltaic power generation in public facilities systems such as railway stations (including high-speed rail stations), expressway service areas, airport terminals, large-scale integrated transportation hub buildings, large-scale stadiums and parking lots, and the planning and design of related buildings and other facilities The application of photovoltaic power generation is regarded as an important element, and large enterprise groups are encouraged to uniformly organize and build distributed photovoltaic power generation projects for their subsidiaries. According to local conditions, use abandoned land, barren hills and slopes, agricultural greenhouses, beaches, fish ponds, lakes, etc. to build distributed photovoltaic power plants that can be absorbed on the spot. Encourage the integration of distributed photovoltaic power generation with rural poverty alleviation, new rural construction, and agricultural facilities to promote the improvement of rural residents’ lives and the development of rural agriculture.
Distributed photovoltaic power generation advocates the principle of nearby power generation, nearby grid connection, nearby conversion, and nearby use. It can not only effectively increase the power generation of photovoltaic power stations of the same scale, but also effectively solve the problem of power loss during boosting and long-distance transportation. Its high energy efficiency and flexible construction methods will become the main direction of China’s photovoltaic applications. At present, the most widely used distributed photovoltaic power generation system is the photovoltaic power generation project built on the roofs of various buildings, agricultural facilities and homes. The requirements for the application of these projects are that it must be connected to the public power grid, or together with the public power grid to provide power to nearby users, and the generated power is generally directly fed into the low-voltage distribution network or the medium-high-voltage power grid of 35kV and below.
Several general forms of common grid-connected photovoltaic power generation systems will be introduced in detail in the next article.