Looking at the current development trend of nuclear power at home and abroad, large centralized nuclear power plants are still the mainstream, and small and medium-sized nuclear power plants are regarded as a good supplement to the current large nuclear power. Although small and medium-sized nuclear power plants have not yet reached the stage of large-scale commercialization and practicality, in the long run, centralized nuclear power plants are the mainstay, and the moderate development of small and medium-sized nuclear power plants will be an important direction for the future development of nuclear power.

"Backyard nuclear power plant" potential advantages are obvious

At present, China's nuclear power plants in operation are basically large units in terms of design and scale. Compared with these large nuclear power plants with an installed capacity of one million kilowatts, small and medium-sized nuclear power plants are usually designed to supply power to small and medium-sized towns or some large industrial facilities. Small and medium-sized power stations called "backyard nuclear power plants" often do not require much money, and their safety can also be guaranteed, such as modular small pressurized water reactors and pebble bed module high-temperature gas-cooled reactor power stations.

Small and medium-sized nuclear power plants themselves have many advantages: the total project investment is low, which can reduce capital investment and power plant occupation, and shorten the construction period; it has good flexibility, and the potential safety hazard is also small, and the comprehensive energy utilization is improved through the cascade utilization of energy Efficiency; it is easier to control, and the nuclear power plant can be located in an area closer to the city, saving the cost of long-distance transportation. In addition, the use of clean energy provided by small and medium-sized nuclear power plants to promote CCPH can reduce fossil energy consumption, reduce local pollutant emissions, and bring into play energy-saving and environmental protection benefits.

Broad market prospects, diversified customers, good equipment sealing, and continuous energy supply have made some companies compete fiercely in the field of small and medium-sized nuclear power design and development, such as Westinghouse, Areva, China National Nuclear Corporation, Huaneng Group, Toshiba, etc. At present, the United States, China, Japan and other countries are committed to the development and construction of small and medium-sized nuclear power plants. U.S. President Barack Obama recently proposed to build 500 small nuclear power units to replace the old thermal power units, and plans to invest US $0.453 billion in 5 years to support the research and development of modular small nuclear power. China Huaneng Shidao Bay High Temperature Gas Cooled Reactor Nuclear Power Demonstration Project (200MW unit) has been started in December 2012. Toshiba Company of Japan once proposed that the 10MW small reactor it developed need not change fuel within 30 years and can supply about 3000 households.

However, small and medium-sized nuclear power plants are also facing some practical problems, such as increased investment per unit capacity, high technical requirements, and public doubts about the safety of nuclear power. However, with the large-scale deployment of smart grid, small and medium-sized nuclear power plants can use this technology to overcome the problems faced by their development, so as to obtain greater development prospects.

Complementary advantages of coordinated operation with large power stations

In order to meet the demand for electricity in the future social and economic development, the development of nuclear power in my country will continue to be dominated by large nuclear power units in the medium and long term. In the context of smart grid, the development of small and medium-sized nuclear power plants while developing large-scale nuclear power plants can promote the coordinated operation of centralized power supply and distributed power supply, comprehensively improve the performance of the power grid and realize diversified services.

After the completion of the smart grid, breakthroughs will be made in the technical fields of rapid adjustment of regular units, power prediction and dynamic modeling of intermittent energy sources, and the safe, stable and economic operation level of the energy base will be improved. Large-capacity energy storage technology will also be promoted and applied, and clean energy power generation including nuclear power and its grid-connected operation control capabilities will be significantly improved. The large nuclear power plant power capacity, can be used for system power support, and small and medium-sized nuclear power in the smart grid under the complementary advantages.

For large nuclear power plants, the use of advanced technology in the power generation link under the smart grid can promote the intensification of nuclear power development, scientific structural layout, standardization of grid-connected access, intelligent operation control, and greatly strengthen the power support capacity. The coordination technology of regular power supply network plant can realize on-line monitoring of the main equipment working conditions of large units in the main regular power plant through the measurement of excitation and speed control system parameters, and effectively cover all aspects of nuclear power units. The intelligent upgrade of large nuclear power units can effectively improve the coordination level of the network plant, ensure the safety and stability of the system, and realize the optimal allocation of resources.

For small and medium-sized nuclear power plants, they can play a role similar to distributed generation in the smart grid. In the future, a large number of distributed clean energy power generation and other forms of power generation will be connected to the grid, requiring the distribution network to have flexible reconfiguration, power flow optimization, and clean energy acceptance capacity. The smart grid adopts the simplified interconnection mode of "plug and play", which can seamlessly connect with various power generation modes (including centralized power generation and distributed power generation) and energy storage devices, and realize the coordinated operation of centralized power supply and distributed power supply.

Realize flexible accommodation and flexible power distribution unification

The characteristics of centralized nuclear power development in China require the improvement of the large-capacity transmission capacity of the power grid, as well as the flexibility of power grid voltage and power flow control, while the smart grid provides the feasibility of large-scale nuclear power access and random power grid connection. At the same time, through the smart grid platform, it provides auxiliary services for the grid connection of clean energy, including nuclear power, to achieve complementarity and balance between different energy sources and improve its availability.

In addition to large-scale centralized development and utilization, nuclear power can be directly connected to the local distribution network through small-scale development with decentralized layout. Due to the small power supply capacity and proximity to the load, small nuclear power plants can strengthen the electrical connection between power generation and electricity consumption in the system to meet the requirements of flexible access and nearby consumption of power supply under the smart grid. After small and medium-sized nuclear power plants are connected to the distribution network, the original radial distribution network structure becomes a multi-terminal structure with multiple power points, which changes the trend distribution of the distribution network, and puts forward higher requirements for the reactive power balance, voltage regulation, relay protection, control, measurement and other technologies of the distribution network.

In order to meet the needs of decentralized access of small and medium-sized nuclear power plants, through the comprehensive construction of practical distribution automation system, we can build an efficient, flexible and reasonable distribution network, and have the ability of flexible reconstruction and power flow optimization, and realize the compatible access and unified control of centralized/decentralized energy storage devices and small and medium-sized nuclear power plants by using key technologies such as coordinated operation of small and medium-sized nuclear power plants and main network. In addition, the use of intelligent power technology to build an intelligent two-way interaction system can realize the two-way interaction between the power grid and users, improve the quality of user service, promote the rational allocation of electricity, and meet the diversified needs of users.