According to Sudianying [2014] No. 365 document, there are two types of distributed power sources (excluding small hydropower):
(1) Distributed power supply with a voltage level of 10 kV and below, and the total installed capacity of a single grid connection point does not exceed 6 MW.
(2) Distributed power supply with 35 kV voltage level access and annual spontaneous self-consumption ratio greater than 50%; or 10 kV voltage level access and the total installed capacity of a single grid connection exceeds 6 MW, and the annual spontaneous self-consumption ratio is greater than 50% Distributed Power.
In the above definition of “Sudianying”, for existing users, the proportion of self-generated electricity consumption = the total electricity consumption of the user in the previous year (rated output of distributed power × the average annual power generation hours of local distributed power in the previous year); for newly installed users, the proportion of self-generated electricity consumption = annual electricity consumption converted into the load reported by the user (rated output of distributed power × local average annual generation hours of distributed power in the previous year).
In recent years, distributed power sources have been used more and more widely, and their research has become more and more extensive. There are many research reports on distributed power sources. These reports summarize the characteristics and evaluation criteria of distributed power sources, including the following aspects:
(1) Good economic adaptability. Small scale, small device capacity, small floor space, small initial investment, reduced long-distance transportation losses and corresponding investment in transmission and distribution systems, and can meet the needs of special occasions. Distributed power sources are set up nearby as needed and cooperate with users as much as possible. Compared with centralized power generation, there is no transmission and distribution loss caused by long-distance power transmission, saving transmission and distribution system investment, and providing end users with flexible, energy-saving and economical power transmission services. For remote areas in western China that are not suitable for laying power grids, scattered users can use residual pressure, waste heat, and combustible waste gas to generate electricity. The development of distributed power generation is of great significance.
(2) Improve the reliability of power supply for users and make up for the shortcomings of the large power grid in terms of safety and stability. In recent years, there have been several major blackouts around the world, such as the “311 Great Earthquake” in Japan in 2011 caused nuclear power plants to shut down one after another, causing significant economic losses, reflecting that the power supply system based on the centralized power supply mode is not completely reliable. Install distributed power sources close to users and cooperate with large power grids to generate power. In the event of grid collapse or unexpected disasters (such as earthquakes, snowstorms, man-made damage, and wars), it can still maintain the power supply of important users, greatly improving the reliability of power supply.
(3) The energy utilization efficiency is high, and it has a very good energy-saving effect. The conventional centralized power supply mode is relatively single, and it is difficult to meet the cascade utilization of energy, such as heating and cooling, by power supply alone. Distributed power supply is small in scale and flexible. Through the organic integration of different cycles, it can meet the needs of users and overcome the difficulty of long-distance transmission of cold and heat, realize the cascade utilization of energy, and greatly improve the power generation efficiency of power plants.
(4) Protect the environment and open up a new direction for the use of renewable energy. Distributed power sources generally use clean fuels as energy sources to improve environmental protection benefits with their high efficiency. According to the description of the US Department of Energy’s “CCHP2020 Program”, after some new buildings adopt the combined production of cold, heat and electricity, the CO2 in the United States can be reduced by 19%. Compared with fossil energy, renewable energy has low energy density, is scattered, and the current utilization scale is small, energy efficiency is low, and centralized power supply cannot be realized. Therefore, distributed power is suitable for combining with renewable energy.
