In order to support the clean transformation of energy structure and the revolution of energy consumption, the national key R & D plan has launched the implementation of the key special project of “smart grid technology and equipment”. In order to improve the full consumption and utilization efficiency of distributed energy, a multi energy complementary distributed energy supply and microgrid technology direction has been set. As an important practice of this technology, in early 2016, State Grid Jiangsu Electric Power Co., Ltd. cooperated with Lianyungang border defense detachment to plan and build an “AC / DC hybrid” island smart microgrid on cheniushan island in Lianyungang. It was put into trial operation in December 2017 and officially put into operation through acceptance on April 25, 2018. The project is equipped with the first AC / DC hybrid and three port converter in China, which provides an effective solution for the high-quality power consumption of offshore islands.

Up to now, the micro grid in cheniushan island has generated 57600 kwh, purified 61 tons of fresh water, and achieved self-sufficiency in power and water supply, changing the history of regular delivery of diesel power generation by supply ships. The project is a successful preliminary study of “Research on AC / DC hybrid distributed renewable energy technology based on power electronic transformer”. It is also a substantive promotion of the implementation project of the national key R & D plan. It is of great significance to the sustainable and reliable use of electricity in all “high coastal areas” (high altitude, islands, border defense and no man’s land) in China.

At present, China has 6536 islands with an area of more than 500 square meters, of which more than 400 are inhabited, mostly small and medium-sized islands far from land. For these islands, a sustained and stable power supply has always been a luxury.

“The island we are stationed on is far away from the mainland, and all the usual supplies depend on land transportation. It is very inconvenient to use water and electricity. In order to solve this problem, our detachment has installed wind and photovoltaic generators on the island. Now with smart microgrid, power supply and water supply are no longer a problem. In good weather, we can generate more than 400 kwh of electricity a day. High-power appliances such as air conditioner and electric water heater have no problem in use, but To enjoy the same life as land. ” When it comes to the improvement of life on the island, Sun Quan, director of cheniushan Island border police station in Lianyungang, said with emotion. Cheniushan Island stationed by Sun Quan is located in the northeast of Lianyungang, 47.5 kilometers away from the land, with a total area of 0.06 square kilometers. The mobile communication base stations, maritime signal stations and border defense forces on the island have long relied on diesel engines and photovoltaic to supply electric energy. Like other domestic islands far from the mainland, there are problems such as insufficient power supply stability, low automation level and shortage of drinking water.

“The cheniushan Island microgrid project makes full use of the AC / DC hybrid distributed renewable energy technology based on power electronic transformer. The ‘three port converter’ is the biggest highlight of this project. With it, the microgrid on the island has a thinking ‘brain’ and can intelligently dispatch the wind power, photovoltaic, battery and other electric energy on the island, making the power consumption on the island as stable and reliable as that on land.” Yuan Xiaodong of State Grid Jiangsu Electric Power Research Institute said.

“In the past, the power supply was unstable. In winter, on average, only about 3 hours of electricity was used every day. The water mainly depended on regular supply and rainwater collection, barely meeting the basic domestic water demand. Now the power supply is stable and sufficient, and a seawater desalination system is installed, so you can take a hot bath every day.” Chen Hu, a recruit, didn’t adapt to the life of guarding the island at first, but being able to take a hot bath every day made him feel at home. “Moreover, in the weather with a large amount of photovoltaic and wind power generation, he can also use excess electric energy to desalinate seawater and store it. It’s really convenient!”

After the completion of the smart microgrid in cheniushan Island, the interconnection between power supply points and electrical equipment on the island has been realized. Under different weather conditions, the electric energy between different users can complement each other, realizing the comprehensive utilization of island energy with 50 kW wind turbine, 30 kW photovoltaic, 100 kW diesel engine and 450 kwh energy storage on the island.

It is understood that the AC / DC hybrid smart microgrid in cheniushan island is based on a variety of green energy such as photovoltaic and wind power, and takes the “three port converter” as the core to build an AC / DC hybrid microgrid composed of frontier defense, mobile and maritime. It uses the energy management system to accurately coordinate and control power generation, energy storage and power consumption, flexibly allocate the connection mode of each user, and realize the coordinated control and economic operation of “source network load storage”.

As the core of AC / DC hybrid smart microgrid, the “three port converter” also provides the island power grid with a “remote controller” for remote operation and maintenance. The power grid professional operation and maintenance personnel tens of kilometers away can carry out real-time monitoring and remote diagnosis of the power grid and electrical equipment on the island without leaving home, effectively solving the problems that the island is far away from the mainland, there is a lack of professional power grid operation and maintenance personnel, and the island power grid cannot be monitored and operated in time.

It is understood that State Grid Jiangsu electric power is developing the first four port microgrid router in China. The technology is currently at the leading level in the world. It will be pilot applied in Tongli new energy town in Suzhou to build a modern energy system with “cleaning as the direction, electricity as the center, power grid as the platform and electric energy substitution as the focus”, and a variety of energy synergy and complementarity, so as to lead the development direction of modern urban energy.

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