Vertical rotary frequency conversion unit

Abstract

The invention discloses a vertical rotary frequency conversion unit which is used for frequency raising and grid connection of low-frequency electric energy of offshore wind power. The generator layer is provided with an upper rack, a power grid side generator and an upper guide bearing, the motor layer is provided with a middle rack, an offshore wind power side motor and a middle guide bearing, and the lower rack layer is provided with a lower rack and a lower guide bearing; the generator layer is located above the motor layer, the vertical shaft system penetrates through and drives a generator rotor and a motor rotor to rotate synchronously, and the two rotors are limited between the upper-middle guide bearing and the middle-lower guide bearing respectively. The motor and the generator synchronously rotate through a shaft system, and low frequency of an offshore wind power side is converted into power frequency of a power grid side; a thrust bearing is arranged on the upper portion or the lower portion of the vertical shaft system to support rotating weight, and a brake device is arranged on the lower rack and forms a friction pair with a motor rotor brake ring to achieve shutdown. The unit is reasonable in space layout, stable in shafting and suitable for offshore wind power medium and long distance conveying scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of variable frequency unit, in particular to a vertical rotary variable frequency unit. BACKGROUND

[0002] With the development of offshore wind power from near shore to far shore, how to realize low-loss long-distance submarine power transmission of large-capacity concentrated offshore wind power is facing great technical challenges. Research shows that low-frequency AC power transmission has good technical and economic performance in the medium and long distance (50-150km) range. The submarine cable needs to be upgraded to the power frequency and connected to the grid after being sent to the shore. At present, there are two ways to realize frequency conversion: power electronic devices and rotary motor variable frequency.

[0003] Among them, due to the low voltage and current resistance of power electronic devices (converters), large-scale off-grid accidents often occur at new energy stations under grid fault conditions, and the reactive power control capability of new energy converters is small, which cannot provide sufficient voltage support. The rotary variable frequency unit (motor-generator variable frequency system) connects the motor to the low-frequency power supply and drives the generator to rotate through the shaft system, and the generator generates power frequency power and is connected to the grid. By setting different numbers of magnetic poles of the motor and the generator, the conversion between different frequencies of the input power supply and the grid is realized. Rotary motor frequency conversion can provide large reactive power support for the wind power side and the grid side.

[0004] A vertical pulse generator set structure was disclosed in Chinese patent document CN103036389A on May 24, 2012; the scheme is composed of an AC speed-regulating asynchronous motor and an AC synchronous generator, adopts a vertical shaft semi-umbrella type two-guide structure, the upper guide bearing is arranged in the upper rack center body, the lower guide bearing and the thrust bearing form a composite bearing structure and are installed in the lower rack center body, the motor drives the generator to rotate, and the generator pulse working mode is used to supply power to the test device. However, this scheme cannot realize the continuous and stable conversion of low-frequency power from the offshore wind power side to power frequency power from the grid side; the two-guide layout of the composite structure of the upper guide bearing, the lower guide bearing and the thrust bearing is difficult to adapt to the high-speed 500r / min and above and the medium and low-speed 428.6r / min and below working conditions, and is easy to cause excessive shaft vibration due to high-speed centrifugal force or medium and low-speed heavy load, affecting the variable frequency precision and equipment life; at the same time, it lacks a layered independent operation and maintenance channel, cannot meet the operation and maintenance requirements in the high-humidity and high-salt fog environment of offshore wind power, and cannot provide reactive power support for the wind power side and the grid side and realize grid fault isolation, which is difficult to adapt to the low-frequency frequency conversion and grid connection scene of offshore wind power.

[0005] Therefore, with the in-depth development of offshore wind energy resources, offshore wind power gradually presents the development trend of large-scale, clustering and far-sea. Under this background, for the low-loss long-distance submarine power transmission of large-scale offshore wind power, a motor-generator frequency conversion system is needed as an optimization scheme to provide reliable technical support for efficient grid connection of offshore wind power in the middle and far sea. SUMMARY

[0006] In view of the above problems of the prior art, the present application provides a vertical rotary frequency conversion unit with stability, convenient operation and maintenance, and suitable for large-scale offshore wind power in the middle and far sea.

[0007] To solve the above technical problems, the present application adopts the following technical scheme: a vertical rotary frequency conversion unit, comprising a generator layer arranged as a vertical shaft, a motor layer and a lower rack layer, the generator layer comprising an upper rack, a generator connected with a power grid side and an upper guide bearing installed in the upper rack, the motor layer comprising a middle rack, a motor connected with an offshore wind power side and a middle guide bearing installed in the middle rack, and the lower rack layer comprising a lower rack and a lower guide bearing installed in the lower rack; wherein the generator layer is arranged above the motor layer, the vertical shaft system penetrates the generator rotor and the motor rotor and drives the generator rotor and the motor rotor to rotate synchronously, the generator rotor is located between the upper guide bearing and the middle guide bearing, and the motor rotor is located between the middle guide bearing and the lower guide bearing; the motor and the generator rotate synchronously through the vertical shaft system, and after the input frequency of the offshore wind power side is frequency-converted to the output frequency of the power grid side, the offshore wind power side is connected to the power grid side, the input frequency of the offshore wind power side is less than the output frequency of the power grid side; the vertical shaft system is provided with a thrust bearing, and the thrust bearing is used to bear the rotating weight; a brake device is arranged on the lower rack, and the brake device forms a friction pair with a brake ring of the motor rotor.

[0008] Further, the thrust bearing is arranged above the vertical shaft system located above the upper guide bearing.

[0009] Further, the thrust bearing is arranged below the vertical shaft system located below the lower guide bearing.

[0010] Further, the lower top end of the vertical shaft system is provided with a motor current collecting ring, and the upper top end of the vertical shaft system is provided with a generator current collecting ring.

[0011] Further, the rotational speed of the generator and the motor is the same, and the number of pole pairs of the motor and the number of pole pairs of the generator are arranged in proportion.

[0012] Further, the inner diameter of the generator stator is greater than or equal to the inner diameter of the motor stator.

[0013] Furthermore, the upper frame, middle frame, and lower frame all adopt a central body plus radial support arm structure, with the radial support arms evenly distributed along the circumference of the central body; the number of radial support arms on the upper frame is the same as the number of upper supports on the generator stator; the number of radial support arms on the middle frame is the same as the number of upper supports on the motor stator.

[0014] Furthermore, the upper frame is radially connected to the generator foundation and axially fixed to the upper support of the generator stator. The generator stator is axially fixed to the cantilevered bracket of the generator foundation via the lower support of the generator stator. The middle frame is radially connected to the cantilevered bracket of the generator foundation and axially fixed to the upper support of the motor stator. The motor stator is fixed to the motor foundation via the lower support of the generator stator. The lower frame is radially connected to the motor foundation.

[0015] Furthermore, the cantilever bracket of the generator foundation extends towards the vertical axis of the unit, and the circular diameter formed by the cantilever end of the generator foundation cantilever bracket on the horizontal plane is larger than the outer diameter of the motor stator.

[0016] Furthermore, the generator layer, motor layer, and lower frame layer all have foundation access doors.

[0017] In summary, the present invention has the following beneficial effects: (1) By arranging the generator layer, motor layer and lower frame layer in a vertical axis layer, the vertical axis unit addresses the problems of poor shaft system stability, low frequency conversion efficiency and unreliable shutdown control encountered in the current trend of offshore wind power low frequency up-frequency grid connection. When constructing vertical axis variable frequency unit facilities, the generator and motor are divided into upper and lower sections, and the generator is placed above the motor. This not only meets the compact space requirements of offshore wind power stations, but also facilitates layered installation and inspection. The unit equipment can be constructed in layers, reducing the interference of cross-layer operation and maintenance.

[0018] (2) Utilizing a combination structure of layered support by guide bearings and load-bearing by thrust bearings, the upper, middle, and lower guide bearings respectively limit the radial displacement of the generator rotor, the middle of the vertical shaft system, and the motor rotor. Combined with the synchronous rotation of the vertical shaft system, the thrust bearing bears the rotational weight of the unit. The mechanical shaft does not transmit electrical signals or electrical shocks. When a short circuit or voltage drop occurs on the grid side connected to the generator, the instantaneous large current and abnormal frequency fluctuations generated by the fault only act on the generator side. The mechanical shaft can physically isolate such electrical shocks, preventing them from being transmitted to the offshore wind power motor and new energy power station, thus structurally eliminating the risk of large-scale grid disconnection of energy equipment due to grid faults. Therefore, the system retains the inherent inertial response, damping characteristics, and excitation control capability of the synchronous motor, and also protects the new energy power plant from the impact of grid faults through the isolation effect of the mechanical shaft.

[0019] (3) The thrust bearing is set at the upper end to form a vertical shaft suspended rotary frequency converter, which is suitable for high-speed frequency converters, such as 500r / min and above; the thrust bearing is set at the lower end to form a vertical shaft semi-umbrella rotary frequency converter, which is suitable for medium and low speed frequency converters, such as 428.6r / min and below.

[0020] (4) The generator and motor collector systems are set up independently, which is beneficial for the generator and motor to perform excitation and reactive power regulation separately. The motor collector ring and the generator collector ring are respectively set at the excitation end of the motor shaft and the excitation end of the generator shaft. The two collector systems operate independently. The motor collector ring is adapted to the low-frequency input of the wind power side for excitation regulation, and the generator collector ring is adapted to the power frequency input of the grid side for excitation regulation. The motor requires a low-frequency magnetic field, while the generator requires a high-frequency magnetic field. This independent adapted excitation regulation can avoid mutual magnetic field interference and ensure smooth and accurate frequency conversion.

[0021] (5) The generator floor, motor floor and lower frame floor of the vertical unit have independent foundation access doors. Maintenance personnel can directly reach the target floor through the corresponding foundation access door without having to disassemble components across floors. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a vertical shaft suspended rotary frequency converter unit.

[0023] Figure 2 This is a schematic diagram of the structure of a vertical shaft semi-umbrella type rotary frequency converter.

[0024] The reference numerals in the attached drawings are explained as follows: 1. Generator layer; 11. Upper frame; 12. Generator; 121. Generator rotor; 122. Generator stator; 13. Upper guide bearing; 14. Generator slip ring; 15. Generator housing; 16. Generator top cover; 17. Generator foundation; 18. Generator foundation cantilever bracket; 2. Motor layer; 21. Middle frame; 22. Motor; 221. Motor rotor; 222. Motor stator; 23. Middle guide bearing; 24. Braking device; 25. Motor slip ring; 26. Motor foundation; 3. Lower frame layer; 31. Lower frame; 32. Lower guide bearing; 4. Thrust bearing; 5. Foundation access door. Detailed Implementation The present invention will be further described in detail below with reference to the embodiments.

[0025] Example 1: Vertical rotary inverter units are classified into suspended and umbrella types according to the different positions of the thrust bearing 4. This embodiment provides a vertical shaft suspended rotary inverter unit, specifically implemented as follows: Figure 1As shown, the system includes a generator layer 1, a motor layer 2, and a lower frame layer 3 arranged vertically. The generator layer 1 includes an upper frame 11, a generator 12 connected to the grid side, and an upper guide bearing 13 installed within the upper frame 11. The motor layer 2 includes a middle frame 21, a motor 22 connected to the offshore wind power side, and a middle guide bearing 23 installed within the middle frame 21. The lower frame layer 3 includes a lower frame 31 and a lower guide bearing 32 installed within the lower frame 31. A thrust bearing 4 is provided on the vertical shaft system to bear the rotational weight and vibration of the generator rotor 121, motor rotor 221, etc. To achieve low-loss, long-distance submarine power transmission for large-scale offshore wind power, the economic cost and construction difficulty of building a vertical rotating frequency converter unit are considered. Therefore, in order to facilitate the construction, installation, and inspection of large-scale equipment in layers and reduce the interference of cross-layer operation and maintenance, a vertical shaft layered layout is adopted, with generator layer 1, motor layer 2 and lower frame layer 3 being independently partitioned. The upper guide bearing 13, lower guide bearing 32 and middle guide bearing 23 are used to limit the radial displacement of generator 12 and motor 22 respectively. Combined with the synchronous rotation design of the vertical shaft system, the vibration amplitude during shaft rotation can be greatly reduced, mechanical wear can be reduced, and the shaft life can be extended.

[0026] The generator layer 1 is positioned above the motor layer 2. A vertical shaft system passes through the generator rotor 121 and the motor rotor 221, driving them to rotate synchronously. The generator rotor 121 is located between the upper guide bearing 13 and the middle guide bearing 23, while the motor rotor 221 is located between the middle guide bearing 23 and the lower guide bearing 32. The motor 22 and generator 12 rotate synchronously via the vertical shaft system, converting the input frequency of the offshore wind power side to the grid output frequency before connecting it to the grid. The input frequency of the offshore wind power side is lower than the output frequency of the grid side. A braking device 24 is installed on the lower frame 31. This braking device 24 forms a friction pair with the brake ring of the motor rotor 221, thereby achieving deceleration and braking.

[0027] A motor slip ring 25 is installed at the lower top of the vertical shaft system, and a generator slip ring 14 is installed at the upper top of the vertical shaft system. The leads of the magnetic pole excitation winding are connected to each slip ring. The generator slip ring 14 corresponds to the grid-side excitation demand, and the motor slip ring 25 corresponds to the offshore wind power-side excitation demand. Both are powered by independent carbon brush assemblies, and the excitation current can be adjusted separately to achieve independent control of grid-side reactive power support and wind power-side voltage stability, avoiding frequency conversion accuracy degradation caused by mutual interference.

[0028] In practice, the generator 12 and the motor 22 rotate at the same speed, and the number of pole pairs of the motor 22 and the number of pole pairs of the generator 12 are set proportionally.

[0029] High-speed vertical shaft turbine units have high centrifugal force and require high shaft stability. Thrust bearing 4 is located at the upper end of the vertical shaft system. A rotary frequency converter unit with thrust bearing 4 at the upper end of the vertical shaft system is called a vertical shaft suspended rotary frequency converter unit. It is suitable for high-speed frequency converter units, such as those with a speed of 500 r / min and above. According to the synchronous motor frequency formula f = pn / 60, where f is the frequency, p is the number of pole pairs, and n is the rotational speed, when the rotational speed n is the same, the frequency is directly proportional to the number of pole pairs. For example, when switching from 20Hz on the wind power side to 50Hz on the grid side, the number of pole pairs of the motor p1 = 4 and the number of pole pairs of the generator p2 = 10, a ratio of 2:5, which can achieve low frequency conversion error and meet the grid connection frequency accuracy requirements.

[0030] Example 2: Vertical rotary inverter units are classified into suspended and umbrella types according to the different positions of the thrust bearing 4. This embodiment provides a vertical shaft semi-umbrella type rotary inverter unit. In specific implementation: as follows: Figure 2 As shown, the system includes a generator layer 1, a motor layer 2, and a lower frame layer 3 arranged vertically. The generator layer 1 includes an upper frame 11, a generator 12 connected to the grid side, and an upper guide bearing 13 installed within the upper frame 11. The motor layer 2 includes a middle frame 21, a motor 22 connected to the offshore wind power side, and a middle guide bearing 23 installed within the middle frame 21. The lower frame layer 3 includes a lower frame 31 and a lower guide bearing 32 installed within the lower frame 31. A thrust bearing 4 is located at the lower end of the vertical shaft system. A rotary inverter unit with the thrust bearing 4 located below the vertical shaft system is called a vertical shaft umbrella-type rotary inverter unit.

[0031] The generator layer 1 is positioned above the motor layer 2. A vertical shaft system passes through the generator rotor 121 and the motor rotor 221, driving them to rotate synchronously. The generator rotor 121 is located between the upper guide bearing 13 and the middle guide bearing 23, while the motor rotor 221 is located between the middle guide bearing 23 and the lower guide bearing 32. The motor 22 and generator 12 rotate synchronously via the vertical shaft system, converting the input frequency of the offshore wind power side of the motor 22 to the grid-side output frequency before connecting it to the grid. The input frequency of the offshore wind power side is lower than the output frequency of the grid side. A braking device 24 is installed on the lower frame 31, forming a friction pair with the brake ring of the motor rotor 221.

[0032] Vertical shaft semi-umbrella type rotary frequency converter is suitable for medium and low speed frequency converters, such as units with a speed of 428.6 r / min and below.

[0033] A motor slip ring 25 is installed at the lower top of the vertical shaft system, and a generator slip ring 14 is installed at the upper top of the vertical shaft system. The leads of the magnetic pole excitation winding are connected to the slip rings. The generator slip ring 14 corresponds to the grid-side excitation demand, and the motor slip ring 25 corresponds to the offshore wind power-side excitation demand. The two are powered by independent carbon brush assemblies, and the excitation current can be adjusted separately to achieve independent control of grid-side reactive power support and wind power-side voltage stability, avoiding the decrease in frequency conversion accuracy caused by mutual interference.

[0034] In practice, the generator 12 and the motor 22 rotate at the same speed, and the number of pole pairs of the motor 22 and the number of pole pairs of the generator 12 are set proportionally.

[0035] GD rotating components of low-speed vertical shaft unit 2 Large frame with high load-bearing requirements (the radial span of the lower frame is smaller than that of the upper frame, and the lower frame is directly fixed axially to the foundation, resulting in good frame rigidity and strong load-bearing capacity), the thrust bearing 4 is located at the lower end of the vertical shaft system. Rotary frequency converters with the thrust bearing 4 located at the lower end of the vertical shaft system are called vertical shaft umbrella-type rotary frequency converters. Suitable for medium and low speed frequency converters, such as those with a speed of 428.6 r / min and above.

[0036] In the above embodiment, the inner diameter of the generator stator 122 is greater than or equal to the inner diameter of the motor stator 222. This facilitates maintenance of the motor rotor 221 without removing the generator stator 122; that is, the motor rotor 221 can be lifted out of the machine pit from the inner diameter of the generator stator 122 for equipment maintenance.

[0037] The upper frame 11, middle frame 21, and lower frame 31 all adopt a central body plus radial support arm structure, with the radial support arms evenly distributed along the circumference of the central body. The number of radial support arms on the upper frame 11 is the same as the number of upper supports on the generator stator 122; the number of radial support arms on the middle frame 21 is the same as the number of upper supports on the motor stator. Bearings are installed inside the central body. A generator upper cover plate 16 is installed above the upper frame 11, between the generator outer cover 15 and the generator foundation 17.

[0038] In the suspended type, the thrust bearing 4 and the upper guide bearing 13 are installed in the center of the upper frame 11; in the umbrella type, the thrust bearing 4 and the lower guide bearing 32 are installed in the center of the lower frame 31.

[0039] Each of the generator level 1, motor level 2, and lower frame level 3 has a foundation access door 5, with an independent access door for each level, allowing maintenance personnel direct access to the target level. The upper frame 11 is radially connected to the generator foundation 17 and axially fixed to the upper support of the generator stator 122. The generator stator 122 is axially fixed to the generator foundation cantilever bracket 18 via the generator stator lower support. The middle frame 21 is radially connected to the generator foundation cantilever bracket 18 and axially fixed to the upper support of the motor stator. The motor stator 222 is fixed to the motor foundation 26 via the generator stator lower support. The lower frame 31 is radially connected to the motor foundation 26. The generator foundation cantilever bracket 18 extends towards the vertical axis of the unit. The circular diameter formed by the cantilever end of the generator foundation cantilever bracket 18 on the horizontal plane is larger than the outer diameter of the motor stator 222. This facilitates the overall lifting of the motor stator 222 into or out of the pit, meeting the needs of unit installation and maintenance.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A vertical rotary variable frequency unit, characterized in that, The system comprises a generator layer (1), a motor layer (2), and a lower frame layer (3) arranged vertically. The generator layer (1) includes an upper frame (11), a generator (12) connected to the grid side, and an upper guide bearing (13) installed in the upper frame (11). The motor layer (2) includes a middle frame (21), a motor (22) connected to the offshore wind power side, and a middle guide bearing (23) installed in the middle frame (21). The lower frame layer (3) includes a lower frame (31) and a lower guide bearing (32) installed in the lower frame (31). The generator layer (1) is located above the motor layer (2), and the vertical shaft system passes through the generator rotor (121) and the motor rotor (221) and drives the generator rotor (121). The generator rotor (121) and the motor rotor (221) rotate synchronously. The generator rotor (121) is located between the upper guide bearing (13) and the middle guide bearing (23), and the motor rotor (221) is located between the middle guide bearing (23) and the lower guide bearing (32). The motor (22) and the generator (12) rotate synchronously through the vertical shaft system. The input frequency of the offshore wind power side is converted to the output frequency of the grid side and then connected to the grid side. The input frequency of the offshore wind power side is less than the output frequency of the grid side. The vertical shaft system is equipped with a thrust bearing (4), which is used to bear the rotational weight. The lower frame (31) is equipped with a braking device (24), which forms a friction pair with the brake ring of the motor rotor (221).

2. A vertical rotary variable frequency unit according to claim 1, characterized in that, The thrust bearing (4) is located above the upper guide bearing (13) in the vertical shaft system.

3. A vertical rotary variable frequency unit according to claim 1, characterized in that, The thrust bearing (4) is located below the lower guide bearing (32) in the vertical shaft system.

4. A vertical rotary variable frequency unit according to claim 2 or 3, characterized in that, The lower top end of the vertical shaft system is provided with a motor slip ring (25), and the upper top end of the vertical shaft system is provided with a generator slip ring (14).

5. A vertical rotary variable frequency unit according to claim 4, characterized in that, The generator (12) and the motor (22) have the same rotational speed, and the number of pole pairs of the motor (22) and the number of pole pairs of the generator (12) are set proportionally.

6. A vertical rotary variable frequency unit according to claim 2 or 3, characterized in that, The inner diameter of the generator stator (122) is greater than or equal to the inner diameter of the motor stator (222).

7. A vertical rotary variable frequency unit according to claim 2 or 3, characterized in that, The upper frame (11), middle frame (21) and lower frame (31) all adopt a central body plus radial support arm structure, and the radial support arms are evenly distributed along the circumference of the central body; the number of radial support arms of the upper frame (11) is the same as the number of upper supports of the generator stator; The number of radial supports of the middle frame (21) is the same as the number of supports on the stator of the motor.

8. A vertical rotary frequency converter unit according to claim 2 or 3, characterized in that, The upper frame (11) is radially connected to the generator foundation (17) and axially fixed to the upper support of the generator stator. The generator stator (122) is axially fixed to the cantilever bracket (18) of the generator foundation through the lower support of the generator stator. The middle frame (21) is radially connected to the cantilever bracket (18) of the generator foundation and axially fixed to the upper support of the motor stator. The motor stator (222) is fixed to the motor foundation (26) through the lower support of the generator stator. The lower frame (31) is radially connected to the motor foundation (26).

9. A vertical rotary frequency converter unit according to claim 8, characterized in that, The generator foundation cantilever bracket (18) extends toward the vertical axis of the generator unit. The diameter of the circle formed by the cantilever end of the generator foundation cantilever bracket (18) on the horizontal plane is larger than the outer diameter of the motor stator (222).

10. A vertical rotary variable frequency unit according to claim 8, characterized in that, The generator layer (1), motor layer (2) and lower frame layer (3) are all equipped with foundation access doors (5).

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