In order to support the clean transformation of the energy structure and the energy consumption revolution, the national key research and development plan has launched the key project of "smart grid technology and equipment", and set the distributed energy supply and micro-grid technology direction of multi-energy complementary in order to improve the full consumption and utilization efficiency of distributed energy. As an important practice of this technology, at the beginning of 2016, Jiangsu Electric Power of State Grid and Lianyungang Border defense Team cooperated to plan the construction of an "AC-DC hybrid" island smart microgrid on Cheniushan Island in Lianyungang, which was put into trial operation in December 2017 and officially put into operation on April 25, 2018 through acceptance. The project is equipped with the first AC-DC hybrid, three-port converter in China, providing an effective solution for high-quality electricity consumption in offshore islands.

Up to now, the Cheniushan Island microgrid has generated 57,600 KWH of electricity, purified 61 tons of fresh water, and achieved self-sufficiency in power supply and water supply, changing the history of regularly transporting diesel power generation by supply ships. This project is a successful exploration of "AC-DC hybrid distributed renewable energy technology research based on power electronic transformers", and is also a substantial promotion of the implementation project of the national key research and development plan, and is of great significance for the sustainable and reliable electricity consumption of all the "high sea without" (high altitude, island, border defense, no man's land) areas in the country.

At present, there are 6,536 islands in China with an area of more than 500 square meters, of which more than 400 are inhabited, mostly small and medium-sized islands far from the land, for which continuous and stable power supply has been a luxury.

Yuan Xiaodong of the State Grid Jiangsu Institute of Electrical Science and Technology said, "Cheniushan Island microgrid project makes full use of AC-DC hybrid distributed renewable energy technology based on power electronics transformers, 'three-port converter' is the biggest highlight of this project, with its island microgrid has a thinking 'brain', It can intelligently dispatch the wind power, photovoltaic, battery and other electric energy on the island, making the electricity consumption on the island as stable and reliable as that on land."

After the completion of the smart microgrid on Cheniushan Island, the interconnection between various power points and electrical equipment on the island has been realized. Under different weather conditions, the electric energy between different users can complement each other, and the comprehensive utilization of island energy including 50 kW fan, 30 kW photovoltaic, 100 kW diesel engine and 450 KWH energy storage has been realized on the island.

It is understood that the AC-DC hybrid intelligent microgrid of Cheuniushan Island is based on a variety of green energy sources such as photovoltaic and wind power, and takes "three-port converters" as the core to build an AC-DC hybrid microgrid composed of border defense, mobile and maritime, using energy management systems to precisely coordinate and control power generation, energy storage and electricity consumption, and flexibly deploy the connection modes of each user. It realizes the coordinated control and economic operation of "source-network-charge-storage".

As the core of AC-DC hybrid intelligent microgrid, the "three-port converter" also enables the island power grid to have a remote "remote control" for remote operation and maintenance. Professional power grid operation and maintenance personnel who are tens of kilometers away from the island can carry out real-time monitoring and remote diagnosis of the island's power grid and electrical equipment without leaving their homes, effectively solving the problem of the lack of professional power grid operation and maintenance personnel who are far away from the mainland. Island power grid can not be timely monitoring and operation and maintenance problems.