Wind turbines are the key equipment of wind power systems. Many countries have invested heavily in research on materials, structures, generator control technologies, power capacity and reliability of wind turbines. progress. However, there are still some shortcomings in the design, development, operation and maintenance of domestic generator sets. The following is a domestic mainstream model as an example to analyze and explore the summer high temperature limited power phenomenon of wind turbines.
After more than a decade of rapid development, China's wind power installed capacity ranks first in the world's installed capacity, and also has the world's first need to maintain wind power installed capacity. For wind power operation and maintenance, time and experience accumulation are important. There are many problems encountered in the operation and maintenance of wind farms. The high temperature limit power of wind turbines in summer is one of the representative problems.
1 phenomenon of running high temperature limit power in summer
The models of today's mainstream wind turbines are roughly divided into two types, one is the traditional three-blade horizontal-axis variable-speed pitch constant-frequency doubly-fed asynchronous wind turbine; the other is the three-blade horizontal-axis variable-speed pitch constant-frequency direct drive. Permanent magnet wind turbine. Both models have their own characteristics due to the different power generation structures. However, in the face of high-temperature operation in summer, limited power operation, and even the phenomenon of shutdown and shutdown have occurred from time to time.
1.1 Three-blade horizontal axis variable-speed pitch constant-frequency doubly-fed asynchronous wind turbine generator, which converts wind energy into electric energy in the form of impeller, gear box and generator speed increasing transmission. In its transmission chain, the gearbox is a key link, and the speed of 9-17.5 rpm is increased by about 104 times, which is the speed of 1300-1800 rpm required for the doubly-fed asynchronous generator. The corresponding friction of the high speed will increase. The gearbox has an independent cooling system to cool the transmission shaft by cooling the lubricating medium oil. However, in the hot Gobi in summer, the gearbox will still appear. Gear oil, high-speed shaft high-temperature limited power operation, and even reported the phenomenon of downtime. In addition, the high temperature of the generator on the drive side and the non-drive side during summer operation will also affect the power output of the wind turbine. The above two phenomena have caused the summer wind farm to abandon the wind due to the problems of the equipment in the field. According to the statistics of the wind in the field due to the high temperature in more than ten wind farms in a domestic wind power base from 2011 to 2013, the doubly-fed asynchronous The phenomenon of high-temperature limited power of wind turbines starts from the beginning of May every year and lasts until the end of September, which lasts for 5 months, especially in July and August. For the 200MW wind farm, when it is the most serious, it reaches the full wind speed. At the time, the total output of the wind farm can only reach 70MW, which is equivalent to one-third of the total output.
1.2 Three-blade horizontal axis variable-speed pitch constant-frequency direct-drive permanent-magnet wind turbine generator set. This model reduces the link of the gearbox. The generator is directly driven by the impeller, and the speed range is 7-17 rpm. The transmission chain structure is simple, and the mechanical loss is one of its characteristics. However, since the generator is a direct-drive permanent magnet generator, the electric energy generated needs to be completed by a full-power inverter to perform rectification, chopper-boost-inverter, etc. Process to meet the requirements of grid connection. Under normal circumstances, the full-power inverter used in this type of model is completed by the on-off function of the insulated gate bipolar transistor IGBT. Due to the frequent switching of the IGBT, the IGBT will be heated and harmonic current will be generated. Power quality is also poor. Although the IGBT has two large fans to cool it, it will run under high temperature in summer, and there will be a shutdown due to high temperature. According to the statistics of the operation of a wind farm, during the high temperature in summer, it is necessary to limit the power in advance to achieve the effect of controlling the temperature of the IGBT. Although the operation is better than the doubly-fed asynchronous wind turbine, the problem of running high-temperature limited power in summer has always existed.
