Five Key Technologies of Smart Grid

With the large-scale development and utilization of wind power, photovoltaic power generation and other new energy sources, as well as the rapid development of UHV AC and DC technology, the characteristics of my country's power supply and power grid have undergone major changes. In order to adapt to the new changes in the development of my country's power grid For safe and stable operation, the researchers of State Grid have been working hard to develop a lot of "tall" new grid technologies. Today we will take a look at the five key technologies in the smart grid.

1. Flexible DC technology?

Flexible DC is a new generation of DC transmission technology with voltage source converter as the core after AC and conventional DC. It is currently the transmission technology with the highest controllability and best adaptability in the world. It is suitable for renewable energy grid connection, distributed generation grid connection, island power supply, capacity expansion and transformation of urban distribution network, etc.

The so-called flexibility mainly refers to flexible operation control and a high degree of intelligence. Under the traditional power transmission technology, for example, to solve the problem of decentralized power supply on islands, a "rigid" method of large investment is generally adopted to build long-span cross-sea transmission lines, or simply build large power plants on islands. However, such a rigid investment is not economical, and it is also difficult to accept new energy sources such as wind power generation that the island already has. Flexible DC transmission technology can improve the stability of the power system, enhance the system's ability to absorb clean energy, and improve the reliability and flexibility of the distribution network. If UHV DC is like a large airplane, with large capacity, high efficiency, and long distance, flexible DC is like a helicopter, flexible and convenient.

2. Virtual synchronous machine technology

Clean energy is developing rapidly, but for a long period of time, it is still necessary to track the synchronous power grid to realize its plug-and-play and autonomous coordinated operation. How to ensure that these newly connected distributed energy sources are compatible with the power system has become a top priority.

For more than 100 years, the scale of the power system has continued to increase, which is mainly due to the synchronization mechanism of the synchronous generator. Generally speaking, distributed power is mainly connected to the grid through grid-connected inverters. Grid-connected inverters must be converted to voltage control, and it is difficult to achieve seamless switching. If grid-connected inverters can be made to have operating characteristics similar to synchronous generators, then the grid-connected security and operational adaptability of distributed generation will be greatly improved.

3. Adjustable camera technology

With the rapid development of UHV DC and the large-scale development of clean energy in my country, the problems of declining dynamic reactive power reserves and insufficient voltage support in some areas have become more prominent, and voltage stability has become one of the main issues for the safety and stability of large power grids. This objectively requires DC large-scale active power transmission to match large-scale dynamic reactive power, that is, "large DC power transmission and strong reactive power support". In order to improve the dynamic reactive power compensation capability of the power grid, it is necessary to install dynamic reactive power equipment such as a condenser in the power grid to improve the dynamic reactive power compensation capability of the power grid.

4. Unified Power Flow Controller (UPFC)

Unified Power Flow Controller (UPFC) can solve the problems of power flow control and power supply capacity improvement that are difficult to solve in the construction, transformation and operation of conventional power grids. Through the application of high-power power electronics technology, the power flow of the power grid can be transformed from natural distribution to intelligent. Flexible control can effectively solve the above problems under the premise of keeping the existing grid structure unchanged and not building new transmission channels.

In layman's terms, after the UPFC device is installed on the power grid, it is equivalent to installing a "traffic light" that can adjust the current to pass through it. From point to point, it can realize precise control of power flow, fully tap the power transmission capacity of the existing power grid, and realize power transmission. The intelligent control can greatly improve the power supply capacity under the existing resource conditions, ensure the safe and stable supply of power loads, and effectively reduce power outages for residents during peak power consumption.

5. Half-wavelength technology

It can be known from circuit theory that power transmission is essentially a process of wave propagation. When the line is long enough, there will be many different characteristics from conventional transmission lines in terms of transmission power limit and voltage distribution along the line.

Half-wavelength power transmission is a power transmission method determined according to the characteristic that the transmission power limit can reach infinity when the length of the AC line is equal to a power frequency half-wave, that is, 3000 kilometers (50 Hz) (applicable to ideal lossless lines).

Half-wavelength technology can be used for point-to-network long-distance large-capacity power transmission, without the need to install reactive power compensation equipment, and without setting up intermediate switching stations on the whole line, and can realize point-to-point or point-to-network power transmission like DC transmission systems, but it is not as good as DC transmission in terms of power transmission distance flexible. Half-wavelength technology can also be used for networking between the sending-end power grid and the receiving-end power grid. In addition, half-wavelength lines can be used to construct a "three-dimensional power grid". The "three-dimensional power grid" can greatly change the shape of the power grid, greatly shorten the electrical distance between landing points, significantly change the structure of the synchronous power grid, and significantly improve the stability of the synchronous power grid.