In the era of parity, the three major trends of China's wind power development

The impeller of the doubly-fed unit is connected to the generator rotor through a growth gear box. Due to the support of the growth gear box, the wind turbine does not need to speed regulate when sending power to the constant frequency grid, the active and reactive power can be adjusted independently, and the capacity of the rotor excitation converter is small. At present, most units in the world use doubly-fed technology.

However, the disadvantages of doubly-fed technology are also obvious, that is, the wind speed is very high, it is easy to occur off-grid phenomenon, if the wind speed is very low, even if there is gear acceleration, it is difficult to generate power, there are certain limitations. At the same time, due to the existence of the gear box, the repair cost is increased.

The impeller of the direct drive technology is directly connected to the generator, eliminating the need for an acceleration gearbox, and the rotor is excited by the permanent magnet, without the need for an external excitation power supply. The generator of direct drive unit is connected to the grid through the full power converter, which has the advantages of high efficiency, low noise and strong low voltage crossing ability.

Disadvantages, the motor and electronic device cost is high, the motor weight is large, in order to adapt to low wind speed need to be equipped with a lot of logpole, resulting in a large motor volume, and can only be cooled by water cooling.

The location of offshore wind power is special and the wind is changeable, which greatly increases the maintenance cost. Therefore, doubly-fed units with high maintenance cost are not suitable for offshore scenarios. Although the direct drive unit can generate electricity normally, it is too heavy, and there are problems in installation and transportation. Therefore, doubly-fed units and direct-drive units are not the best choice for offshore scenarios.

At present, the iterative direction of fan technology is semi-direct drive motor. Semi-direct drive combines the advantages of direct drive and doubly-fed, avoiding the disadvantages of both sides, and is recognized by the industry as the next generation of wind turbine technology.

The impeller of the semi-direct drive unit is connected with the rotor of the permanent magnet synchronous generator through the medium speed gearbox, and the full power converter is connected. Compared with direct drive, semi-direct drive increases the medium-speed gearbox, and the rotor speed of the generator is higher than that of the permanent magnet direct drive, which can reduce the magnetic pole number of the rotor of the permanent magnet synchronous generator, and is conducive to reducing the volume and mass of the generator.

Nowadays, semi-direct drive has become a must-have for wind turbine manufacturers, and even who can do a good job of semi-direct drive may become the leader of the future.

Focusing on domestic companies, Goldwind Technology is the absolute leader, ranking second only to Vestas in global shipments, with a market share of 12.8%. However, the stock price trend of Goldwind technology in the past year has been exploded by Yang Mingzhi, the reason is that the research and development of semi-direct drive units.

Mingyang Intelligent is the first company to lay out semi-direct drive technology in China. In 2008, Mingyang Intelligent introduced semi-direct drive technology from aerodyn, a European wind power design company, which began the semi-direct drive layout.

Since 2015, Mingyang Intelligent has gradually replaced the past double-fed units with semi-direct drive products. The 2020 annual report shows that Mingyang Intelligent has sold a total of 5658MW units, of which the sales capacity of semi-direct drive products accounts for 93%.

It is thanks to the success of semi-direct drive technology that Mingyang Intelligent is expected to launch a strong challenge to Goldwind Technology. Of course, Goldwind Technology has also had a reserve in semi-direct drive technology, but the product volume still needs time to precipitate.

04 Model iteration: The imagination of decentralized wind power

Wind power generation has high geographical requirements, so the wind power is mainly concentrated in the north of China.

With the continuous improvement of the penetration rate of the domestic onshore wind power industry, the excellent tuyere location has been rapidly reduced. In the future, there will have to be fewer large centralized wind power plants, which are likely to be replaced by decentralized wind power.

The so-called distributed wind power refers to the layout of wind power around the power load center, not for the purpose of long-distance transportation. These distributed wind power is often distributed near key cities, using the nearest approach to the network, real-time rapid consumption.

From 2012 to 2019, the cumulative installed capacity of decentralized wind power in China increased from 60MW to 935MW, with a compound annual growth rate of nearly 41%. In 2019, the newly installed decentralized wind power capacity in China was 300MW, accounting for only about 1% of the new domestic suspended wind power scale, which shows that distributed wind power is in the embryonic stage.