In recent years, the world's wind turbines have developed very rapidly,
with their capacity increasing at a rate of 30% every year. According to the
latest statistics, the world's installed wind turbine capacity in 1998 was
9839MW, an increase of 29.6% from 7588MW in 1997. In April 1999, the installed
capacity of wind turbines worldwide exceeded 10,000 MW.
1. The main regulating technologies for wind turbines currently on the
world market
1.1 Home pitch regulation wind turbine technology (Stallregulation)
This technology is the core of the so-called typical Danish wind power
technology. Its basic principle is to utilize the stall characteristics of the
blade airfoil itself. Its advantages are: the adjustment is simple and reliable,
and the control can be greatly simplified; its disadvantages are: the stress on
main stress-bearing components such as blades, hubs, and towers increases.
Nowadays, most of the 600kW and above units in the world still use this
technology. Famous manufacturers such as MFG-MICON, BONUS, and NORDEX all use
this technology.
1.2 The main representative of variable pitch wind turbine technology
(Pitchregulation) is Vestas.
The main advantages of variable pitch adjustment are: the blades are less
stressed, the blades can be made lighter, and the structural components of the
wind turbine can be made lighter; its disadvantages are: the structure is
complex.
1.3 Active pitch regulation technology (Active stall regulation)
This adjustment method is a combination of the two aforementioned methods.
At present, several major international wind turbine manufacturers, such as
MFGMICON, BONUS, etc., all use this technology for wind turbines larger than
600kW. The main benefits of this adjustment method are: it has the
characteristics of the fixed pitch adjustment method, the output power changes
little, and the wheel is stable.
1.4 Variable speed constant frequency (Viarablespeed)
This adjustment method is theoretically the optimal adjustment method. The
manufacturers currently using this technology are mainly Enercon of Germany and
Largeway of the Netherlands.
This adjustment method can maximize efficiency before the output power
drops below the rated power. But when the output power is greater than the rated
power, that is, the wind speed is greater than the rated wind speed, the
adjustment method is the same as the pitch method. Constant frequency devices
are expensive, which is why this technology is only widely used in Germany and
is rarely used in other countries.
2 Main trends in the current development of wind turbine technology in the
world
Since onshore wind turbines are restricted by transportation, installation
and other conditions, a single unit capacity of 2MW is the limit for the
development of wind turbines. This is mainly because after the wind turbine
capacity reaches 2MW, the blade length will reach 60-70m, making land
transportation extremely difficult and installation The crane capacity used will
exceed 1200-1400t. Cranes with this capacity are basically unavailable in other
regions except in developed areas such as Europe and the United States (where
there are only a few units). At the same time, in developed areas such as
Western Europe, the population is relatively dense and the locations for
installing wind turbines are greatly restricted. People naturally focus on
offshore wind farms. In order to adapt to the development of offshore wind
farms, the European Union released the 2000-2010 Energy White Paper in Amsterdam
in June 1999, which included the development of wind turbines with a capacity of
3-5MW as one of its priorities.
Many universities, research institutes, and manufacturers in Europe have
introduced various new offshore wind turbine concepts. Among them, the most
widely noticed is the wind turbine that combines the following technologies: 3
blades, downwind direction; no gearbox; multi-pole generator and wind turbine
Wheel direct connection; airfoil tower (wind tower); steering system at the
bottom of the tower; variable speed constant frequency, etc.
The main features of 3-5MW offshore wind turbines are: transportation
problems can be directly transported by sea (the manufacturing plant is located
on the seaside), and installation can be solved by large-capacity offshore
floating cranes. Offshore floating cranes have large capacities, and floating
cranes exceeding 1,500t are common.
Usually, the cost structure of an onshore wind farm is: wind turbines
account for about 70%, and infrastructure (basic power grids, roads, etc.)
account for about 30%. The cost structure of offshore wind farms is about 30%
for wind turbines and about 70% for infrastructure (foundation, submarine
cables, etc.). However, due to the good wind resources of offshore wind farms,
the annual power generation can be 50% higher than that of onshore wind farms.
At the same time, due to the adoption of the above new technologies,
large-capacity offshore wind turbines have reduced costs, increased operational
reliability, and reduced operating costs, so that the cost of power generation
can be equal to or lower than that of onshore wind farms.
3 Current development status and gaps of wind turbine technology in my
country
The current status of wind turbine technology development in my country is:
200kW/250kW wind turbines with independent intellectual property rights have
been successfully developed with the support of the Ministry of Science and
Technology.
The successful development of this unit marks the technical success of the
fixed-pitch stall-adjustable wind turbine. The capacity of this type of wind
turbine can be expanded to 750kW.
In addition, Xinjiang Wind Energy Corporation has introduced German Jacobs
600kW technology (also a fixed-pitch stall-adjustable type) and is in the
process of localizing components. The first batch of 2 units has a localization
rate of 40% (including towers and nacelles), and the localization of generators,
gearboxes, and controllers is in progress.
Two joint ventures (Nordex and MADE) are introducing 300kW/600kW wind
turbine technology, both of which are wind turbines with fixed pitch stall
regulation.
In the mid-1980s, my country developed 20kW, 30kW, 40kW and 50kW wind
turbines with variable pitch adjustment. Due to the low level of mechanical
foundation and regulation and control in my country at that time, the
reliability of the units developed was poor, especially the variable pitch
system with a high failure rate. The units often broke down and were basically
out of service by the end of the 1980s, without industrialization.
4 Conclusion
my country's wind turbine technology development is still at a low level.
Currently, my country has only mastered one of several popular wind turbine
technologies in the world. The other three technologies, namely active stall
adjustment, variable pitch adjustment and variable speed constant frequency
adjustment, are not involved, let alone offshore wind turbines with a capacity
of 3-5MW. Judging from the current world development trends, wind turbines with
a capacity less than 750kW can still use fixed pitch stall adjustment
technology, while wind turbines with a capacity greater than 750kW mostly use
active stall adjustment, variable pitch adjustment and variable speed constant
frequency adjustment technology. Therefore, our country should carry out
research on these technologies during the Tenth Five-Year Plan period.
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