Method and device for rotational speed control in high gear ratio transmissions

(54)

PATENT HOLDER Roland INVENTOR Roland

Davidson, 45 Oskarsgatan

Davidson, Hultsfred SE

577 31 Hultsfred SE (56) (57)

AGENCY Stored District R

NAME Method and apparatus for speed control in high speed gearbox transmissions

CALLED PUBLICATIONS: - SUMMARY:

The present invention relates to a method and apparatus for speed control in high speed gear transmissions, where one side's speed is very low and off should be variable while the other side's speed is high. The method and apparatus according to the invention provide stepless control of the input shaft (1) as a function of an external parameter, at the same time as a very high exchange between the input shaft (1) and the two output shafts (6 and 8). The task is solved by arranging all three shafts to be able to rotate simultaneously, and by controlling the speed of a secondary output shaft (6) by an external parameter to vary about a nominal speed as a constant factor, equal to the gear ratio of the two shafts. times a primary output shaft (8) speed, (6, 8) such that the speed of the input shaft (1) becomes a function of the difference between the speeds of the shaft (6, 8).

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The numbers in brackets indicate international identification code, IDN code. Letters in clamps indicate international document code.

TECHNICAL FIELD

The present invention relates to methods and devices for speed control and to achieve high speed gearing (about 50: 1 to 100: 1) in transmissions, and more particularly to such transmissions where one side speed is very low and can be varied for various reasons. , while the speed of the other side is substantially high and often preferably constant. The most suitable gearbox for such a transmission is the planetary gearbox, and the present invention therefore preferably relates to methods and devices for speed control and to provide high speed gearing for planetary gearboxes.

A typical application for a transmission of the above type is wind turbines, and the description below will therefore be concretized with wind turbines as an example.

BACKGROUND

Wind turbines, which are today one of the world's fastest expanding industries, need gearboxes with high gearing. A wind turbine typically operates at a speed of about 15-20 rpm, while a generator to get out of standard design and thus reasonably inexpensive to produce should run at least 1500 rpm. This means a ratio of 75 to 100: 1. A gearbox with this gear ratio is usually carried out as a multi-stage planetary gear, yet becomes large and heavy. To slightly adjust the turbine's speed to different wind speeds, generators with two fixed speeds are often used today, which makes the gearbox even bigger and heavier. Since the gearbox is located at the top of the wind turbine's blank, this size and weight becomes a problem in both assembly and maintenance work.

Another alternative is to run the generator at the slow speed of the wind turbine. In order to then reach the network frequency 50 Hz, the generator must have many poles and / or a large diameter in order to reach a sufficiently high peripheral speed. Since the generator sits at the top of the wind turbine, behind the wind turbine itself, there are physical limitations to its size, and both size and weight become a problem, for the same reason as for the gearbox. In addition, in this case, it will be a custom-made generator, which makes it expensive. In many cases, therefore, frequency converters are used to reach the right frequency. The frequency converter can also be used to vary the wind turbine speed with the wind power, but still be able to deliver 50 Hz via the frequency converter.

Thus, there is a need in the market for a transmission and a way to control this transmission which means that e.g. a wind turbine can rotate at a low and in addition continuously variable speed, in order to be able to adapt momentarily to the wind speed and thereby optimally utilize the wind's energy content, while the driven generator can run at as high a speed as possible, without the transmission therefore being large and heavy. By momentarily adjusting the speed to the wind speed, there is a theoretical possibility to increase the efficiency of the wind turbine by about 7%. It is also possible to influence the sound level of the wind turbine via the speed variation.

There is also a need, since wind turbines are always placed at the top on a high void, and often in inaccessible places, such as at sea, to minimize the weight and space requirements of the power plant's components, and to reduce the need for and simplify work on service and maintenance. .

The above objects are achieved by the method and apparatus for regulating speed and providing high speed gearing in transmissions, according to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a very schematic principle view of how known components can be connected according to the method according to the invention to a device according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT EXAMPLE

In the following, a preferred embodiment of the invention will be described, with reference to the figure. The description is in no way limiting as to the scope of the invention, which is solely determined by the appended claims.

In Fig. 1 is shown a planetary gear having an input shaft 1 which is firmly connected to the inner gear of the planetary gear 2. The planetary gear has in a known manner a number of planetary gears 3 which sit on a planet holder 5 and rotate in gear contact with the inner gear 2 and a sun gear 4.

The sun gear is connected to an electrical primary generator via a shaft 8. The planet holder 5 is connected to an electric secondary generator 7 via a hollow shaft 6.

The primary generator 9 is frequency-connected directly to a frequency-stable three-phase power grid 12, and may be of the new high-voltage type developing 10000 volts, whereby it can be directly connected to the grid as Fig. 1 shows. The generator 9 can also be of a conventional lower voltage generator type, which in this case is known in the known way to the grid via a transformer (not shown). The secondary generator 7 is connected to the frequency stable electricity grid 12 via a frequency converter 10 and a transformer 11. However, the secondary generator can also be of a high voltage type, whereby the need for the transformer 11 lapses.

If the primary drive source in this embodiment is a wind turbine, then it is known in the known manner to the input shaft 1 of the planetary gear, which in this embodiment is connected to the inner gear of the planetary gearbox 2. Between the wind turbine and the input shaft 1 of the planetary gearbox to be able to brake and lock the wind turbine in a stationary position. The wind turbine and the braking device are not shown.

In order to facilitate the understanding of the operation of the device, we hereby assume certain parameter values ​​of the constituent components. These values, as those skilled in the art will readily recognize, may be altered to optimize the device, as long as the changes are coordinated so as to achieve the equation described below in the ratio of the speed of the generators to the gear ratio of the planetary gear.

The planetary gearbox is assumed to have a ratio of 1: 3 between the speed of the planet holder 5 and the speed of the sun wheel 4 if the inner gear ring 2 is stationary. The primary generator 9 is assumed to have only one pair of pairs and then rotates in phased state on a 50Hz network at 3000 rpm. The secondary generator 7 is assumed to have three poles and would then rotate at 1000 rpm when directly phased into a 50Hz network. However, since the secondary generator is connected to the 50Hz network via a variable frequency converter, the phases of the secondary generator in phased state can be caused to vary within a range of about 1000 rpm.

Assume that the sun gear 1, which is connected to the electric primary generator 9, of the stable grid 12 and the phased primary generator 9 is rotated clockwise by 3000 rpm. At the same time, suppose that the frequency converter 10 is set to a conversion factor 1, ie no conversion, and the planet holder 5, connected to the secondary generator 7, of the stable network 12 and the phased secondary generator 7 is rotated clockwise by 1000 rpm. The inner gear ring 2 will then, since the gear ratio between the planet holder 5 and the sun gear 4 is 1: 3 and the ratio of their rotational speed is also 1: 3, to remain completely still.

Consequently, if one increases or decreases the conversion factor of the frequency converter 10, the phased speed of the secondary generator will increase or decrease from 1000 rpm. This also means that the planetary gearbox 2 will start to rotate at a speed that will vary with the difference between the primary generator 9 speed and the secondary generator 7 speed multiplied by the planetary gear ratio of the planetary gear to the gearbox. In a planetary gear with the gear ratio 1: 3 between the planet holder 5 and the sun gear 4, the gear ratio between the inner gear ring 2 and the planet holder 5 equals 2: 3.

Thus, if the phased speed of the secondary generator 9 through the frequency converter 10 is increased to 1030 rpm clockwise, the internal gearing will also move clockwise, but with the rpm only (1030-1000) / 1.5 = 20 rpm. If secondary generating phases 9 of phased 9 through the frequency converter 10 are instead lowered to 970 turns clockwise, the internal gearing will instead move counterclockwise, with the speed (1000970) / 1.5 = 20 rpm.

Thus, in the illustrated embodiment of the method and apparatus according to the invention, the very frequency-stable electricity network 12 is used to hold one of the three movable main parts of the planetary gearbox (the sun gear 4 / the primary output shaft 8) at a constant, relatively high speed, instead of as is usually the case, hold a main part at a standstill, ie at the constant speed of zero. Another of the main parts of the gearbox (the planet holder 5 / the secondary output shaft 6) is allowed to rotate at a speed which is also very stable (through the mains 12) but adjustable (through the frequency converter 10) around the nominal speed where the speed of the two main parts concerned ( 4, 5) in the gearbox, taking into account the gears, take each other off, so that the third main component (inner gear ring 2 / input shaft 1) is stationary. The speed of the input shaft 1 can thus be adjusted steplessly in both directions about zero, by varying the setting of the frequency converter 10. The setting of the frequency converter 10 can be easily and in a known manner, via, for example, a microprocessor-based control system, controlled by an external parameter, in the described embodiment, for example, by the wind speed, so that the speed of the wind turbine can thereby be adjusted steplessly to the wind speed.

Thus, in accordance with this method of the invention, a very high gear ratio has been obtained between the input shaft 1 and the output primary generator shaft 8, in the illustrated embodiment as a whole 3000: 20 or 150: 1, and between the input shaft 1 and the output secondary generator shaft 6. 1030: 20 or 51.5: 1, on the other hand, an elegant possibility for stepless speed control of the input drive shaft 1, in both clockwise and counterclockwise directions. The regulation becomes due to the stability of the mains 12 independent of changes in the input power on the input shaft 1, if this increases, both generators 7 and 9 will simply generate higher electrical power to the mains 12. We naturally assume that all parts of the device are adapted to its required effects, speed, torque, etc.

In the illustrated embodiment with a wind generator, the device is started as follows:

a. The wind turbine shaft 1 is initially braked and stationary in the initial position.

b. The secondary generator 7 is started unmagnetized (at idle) by controlling the frequency converter 10 from the frequency zero upwards and is phased in to the grid at its nominal speed, ie 1000 rpm.

c. Since the wind turbine is stationary, the planetary gearbox 2 is stationary. This means that as the secondary generator 7 starts to rotate, the rotation of the planet holder 5 will also rotate the sun gear 4 and thus the primary generator 9, which is also started and phased unmagnetized (at idle) at the grid at its 3000 rpm.

d. When both generators are phased in, they are magnetized, while releasing the brake of the wind turbine and adjusting the frequency converter 10 to such a frequency conversion factor that a speed occurs at the secondary generator 7 which deviates from the nominal (1000 rpm) in such a direction and so much that the wind turbine rotates in its normal operating direction at a speed adapted to the wind speed.

e. The wind turbine speed can now easily be adjusted to the wind power in an optimal way by measuring the wind speed in a known manner and controlling the conversion factor of the frequency converter 10 thereafter, for example via a microcomputer, so that the wind turbine continuously adjusts its rotational speed optimally to the wind speed.

The method and apparatus according to the invention can also be applied in the event that a shaft speed cannot be maintained at a stable and constant speed. In this case, the speed of one of the main parts of the gearbox (eg the planet holder 5 / the secondary output shaft 6) can be controlled by both an external parameter (eg a wind speed) and by another main part (e.g. the speed of the secondary gear 4 / the primary output shaft 8), so that the speed of the secondary output shaft 6 varies around a nominal speed which is a constant factor of the speed of the primary output shaft 8, the constant factor being equal to the gear ratio of the two shafts. 6, and 8. If the outer parameter remains constant, a constant speed will appear on the third of the main parts of the gearbox (e.g. the internal gear ring 2 / the input shaft 1) is still maintained, although the speed of the primary output shaft 8 is varied, since the speed of the secondary output shaft 6 of the outer parameter, via the control system, is simultaneously varied by one, taking into account the gearbox ratio, corresponding amount.

Thus, the method and apparatus according to the invention provide, inter alia, one of the delivered power to the input shaft 1 completely independent stepless control of the speed of this shaft as a function of an external parameter, at the same time as a very high exchange between the input shaft 1 and the two output shafts. 6 and 8, without therefore requiring a larger and heavier gearbox, whereby a large generator diameter and high generator weight can be avoided and costs can be kept down.

Those of ordinary skill in the art will certainly be able to recognize a variety of modifications and modifications to the method and apparatus of the invention without, therefore, going beyond the scope of the invention, which is limited only by the appended claims.