Closed type electro-hydraulic variable pitch system for wind power generation

Abstract

The application discloses a closed electro-hydraulic variable-pitch system for wind power generation, which comprises a variable-pitch cylinder, an opening and closing pitch unit arranged between a first oil port and a second oil port of the variable-pitch cylinder, a motor, a hydraulic pump, a proportional valve and a connecting pipe for conveying hydraulic oil, the motor is used for driving the hydraulic pump to work, an oil outlet of the hydraulic pump is communicated with a P port of the proportional valve, a T port of the proportional valve is communicated with an oil suction port of the hydraulic pump, and A and B ports of the proportional valve are respectively communicated with the first oil port and the second oil port of the variable-pitch cylinder; internal passages between the A and B ports and the P and T ports of the proportional valve can be cross-converted, and the flow directions of the oil inlet and outlet passages of the hydraulic oil between the first oil port and the second oil port are switched through the proportional valve. The variable-pitch system of the application has the advantages of traditional electric variable-pitch and hydraulic variable-pitch, greatly simplifies the hydraulic oil conveying pipeline, has fewer components, saves installation space, has high safety and has great cost advantage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wind power generation, and relates to the structure and performance improvement of a variable pitch system, in particular to a closed electro-hydraulic variable pitch system for wind power generation. BACKGROUND

[0002] With the rapid development of wind power generation technology, wind turbines are developing from constant speed and constant frequency to variable speed and constant frequency, and from fixed pitch to variable pitch. Variable pitch wind turbines have become the mainstream of current wind turbines because they can maximize the capture of wind energy, output stable power, and have small forces on the unit. As one of the core parts of the control system of large wind turbines, the variable pitch system plays a very important role in the safe, stable and efficient operation of the unit.

[0003] Variable pitch is simply adjusting the pitch angle of the blade, i.e. controlling the position angle of the blade relative to the rotation plane, thereby changing the angle of attack of the airflow on the blade, and then controlling the aerodynamic torque and aerodynamic power captured by the blade to stabilize the output power of the generator. Currently, variable pitch systems can be generally divided into two types, one is an electric variable pitch system driven by a motor actuator, and the other is a hydraulic variable pitch system driven by a hydraulic actuator.

[0004] The electric variable pitch system uses a servo motor to drive a reducer gear, which in turn drives the blade gear to realize variable pitch, and cooperates with an angle sensor / encoder to realize closed-loop angle control of the blade. Three blades, three electric drive devices, each set of electric drive device corresponds to a blade. When emergency feathering, the backup power drives the servo motor to push the blade to a safe position. The traditional electric variable pitch system is a rigid structure with pure mechanical transmission, which rotates the gear of the reducer box by the motor. However, the gear will be impacted greatly due to frequent reversing, and has poor shock resistance. This leads to serious wear of the gear, large gear gap, and further delay or even failure of the variable pitch response. The gear life is short, and the maintenance cost is extremely high.

[0005] The hydraulic variable pitch system includes a hydraulic pump station, a slip ring, a variable pitch valve group, an accumulator, a hydraulic cylinder, a variable pitch controller and other main components in structure. The proportional directional valve drives the cylinder to push the blade bearing to rotate. Three groups of driving devices, each group of driving device corresponds to a blade. The cylinder matches with a displacement sensor to form a closed-loop angle control with the proportional directional valve. When emergency feathering, the accumulator drives the cylinder to push the blade to a safe position, without backup power supply.

[0006] And the traditional hydraulic variable pitch system is an open system, including pump station, proportional control valve group, multiple accumulators and many other components, which has large volume, complex connection pipeline, high manufacturing and assembly requirements, high cost, complex system, many leakage points and difficult maintenance. Moreover, the blade is constantly rotating, and a rotating joint must be used to introduce the hydraulic oil pipeline from the hydraulic station in the cabin to the rotating hub. The pressure of the hydraulic oil is above 20 MPa, so the manufacturing process is required to be high and the difficulty is relatively large.

[0007] For example, Chinese patent (authorized announcement number CN113323950 B) discloses a "digital control type electro-hydraulic direct drive variable pitch system", a drive cylinder is connected with a load, two cavities of the drive cylinder are connected to two oil ports of a double-direction gear pump through a hydraulic control assembly, and the double-direction gear pump is connected with a servo motor and a controller. The hydraulic control assembly includes a double-direction flow control valve, a two-position two-way electromagnetic valve, a safety valve and an oil supplement valve. The cavity of the drive cylinder is communicated with a hydraulic oil port of the double-direction flow control valve. The top oil port of the double-direction flow control valve is connected to the oil port of the double-direction gear pump through the two-position two-way electromagnetic valve, the safety valve and the oil supplement valve in sequence. The oil path between the two-position two-way electromagnetic valve and the safety valve is connected to the bottom oil port of the double-direction flow control valve.

[0008] For example, Chinese patent (CN101813066B) discloses a "direct drive type volume control variable pitch system of wind driven generator", which relates to the technical field of fan variable pitch system and solves the technical problem of ensuring the response speed of feathering while reducing the cost. The variable pitch system includes an energy storage circuit and a blade pump control circuit. The energy storage circuit includes a hydraulic control safety valve, an energy storage pump motor, an energy storage pump, an oil storage accumulator, a high-pressure accumulator and a quick closing electromagnetic valve. The blade pump control circuit includes a servo motor, a variable pitch cylinder, a double-direction pump and five hydraulic control check valves. The variable pitch cylinder is used to drive the blade of the wind driven generator to change pitch. The servo motor controls the operation of the variable pitch cylinder through the double-direction pump, thereby controlling the normal variable pitch of the wind driven generator. When the wind driven generator needs to be feathered quickly, the energy storage circuit directly supplies oil to each variable pitch cylinder. The variable pitch system provided by the application has fast response speed and low system cost.

[0009] The technical solutions of the above variable pitch systems have improved the structure and performance, but the hydraulic delivery pipeline is relatively complex and has many components. The system has large volume and occupies large space, and cannot be integrated into the blade hub, so there are still leakage risks. SUMMARY

[0010] The purpose of the present application is to provide a closed electro-hydraulic variable pitch system for wind power generation, which solves the defects in the prior art.

[0011] In order to achieve the purpose of the present application, the following technical solutions are adopted:

[0012] The closed type electro-hydraulic variable pitch system for wind power generation comprises a variable pitch cylinder with a first oil port, a second oil port and a piston rod, an opening and closing pitch unit is arranged between the first oil port and the second oil port of the variable pitch cylinder, the opening and closing pitch unit comprises a motor, a hydraulic pump, a proportional valve and a connecting pipe for conveying hydraulic oil, the motor is used for driving the hydraulic pump to work, an oil outlet of the hydraulic pump is communicated with a P port of the proportional valve, a T port of the proportional valve is communicated with an oil suction port of the hydraulic pump, and A and B ports of the proportional valve are respectively communicated with the first oil port and the second oil port of the variable pitch cylinder; a fluid passage between the A and B ports and the P and T ports in the proportional valve can be cross-converted, a differential bypass with a fifth one-way valve is arranged between the P and B ports outside the proportional valve; the flow direction of the hydraulic oil between the first oil port and the second oil port is switched through the proportional valve, so that the piston rod of the variable pitch cylinder is extended or retracted to complete the variable pitch adjustment of the blade.

[0013] In order to further realize the purpose of the application, the following technical solutions can also be used:

[0014] The closed type electro-hydraulic variable pitch system for wind power generation as described above, the opening and closing pitch unit is provided with an oil supply and return cooling module for filtering and cooling the circulating hydraulic oil.

[0015] The closed type electro-hydraulic variable pitch system for wind power generation as described above, the oil supply and return cooling module comprises a positive pressure oil tank, a cooler and a filter, the filter and the cooler are installed between the T port of the proportional valve and the oil suction port of the hydraulic pump, the oil port of the positive pressure oil tank is communicated with the oil suction port of the hydraulic pump, and the working pressure range of the positive pressure oil tank is between 2 and 10 bar.

[0016] The closed type electro-hydraulic variable pitch system for wind power generation as described above, the oil supply and return cooling module comprises an oil tank, a circulating motor, a circulating hydraulic pump, a filter, a cooler, a slip ring, a first one-way valve, a second one-way valve and a branch pipe for connection, the circulating motor is used for driving the circulating hydraulic pump to work, the oil supply port of the oil tank is communicated with the oil suction port of the circulating hydraulic pump, the cooler and the filter are installed in front of the oil return port of the oil tank, and the inlet and outlet of one side of the slip ring are respectively communicated with the oil suction port of the hydraulic pump and the T port of the proportional valve.

[0017] The closed type electro-hydraulic variable pitch system for wind power generation as described above, a first two-position two-way electromagnetic reversing valve is installed between the A port of the proportional valve and the first oil port of the variable pitch cylinder, and a second two-position two-way electromagnetic reversing valve is installed between the P port of the proportional valve and the oil outlet of the hydraulic pump.

[0018] The wind power closed hydraulic electric variable pitch system as described above, the opening and closing paddle unit is provided with an emergency feathering module, the emergency feathering module comprises a third two-position two-way electromagnetic reversing valve, a third check valve, an accumulator, a fourth two-position two-way electromagnetic reversing valve, a fourth check valve and a backup power supply, the third check valve, the third two-position two-way electromagnetic reversing valve and the fourth check valve are sequentially installed between the first oil port of the variable pitch cylinder and the oil outlet of the hydraulic pump, the accumulator is installed between the fourth check valve and the third two-position two-way electromagnetic reversing valve, the fourth two-position two-way electromagnetic reversing valve is in communication with the B and T interfaces of the proportional valve at both ends, and the backup power supply supplies power to the motor.

[0019] The wind power closed hydraulic electric variable pitch system as described above, the opening and closing paddle unit is provided with a blade lock module for locking or unlocking the paddle, the blade lock module comprises a two-position three-way electromagnetic reversing valve and a blade lock, one-way port of the two-position three-way electromagnetic reversing valve is in communication with the connecting pipe between the accumulator and the fourth two-position two-way electromagnetic reversing valve, the other way port is in communication with the connecting pipe in front of the oil suction port of the hydraulic pump, and the third way port is in communication with the oil inlet and outlet port of the oil cylinder of the blade lock.

[0020] The wind power closed hydraulic electric variable pitch system as described above, a branch with an overflow valve is arranged between the oil suction port and the oil outlet port of the hydraulic pump.

[0021] The wind power closed hydraulic electric variable pitch system as described above, a first pressure sensor is installed between the accumulator and the third two-position two-way electromagnetic reversing valve.

[0022] The wind power closed hydraulic electric variable pitch system as described above, a second pressure sensor is installed between the two-position three-way electromagnetic reversing valve and the oil suction port of the hydraulic pump.

[0023] The innovation of the present application lies in that the opening and closing paddle unit composed of the proportional valve, the motor and the hydraulic pump can be transformed in the hydraulic oil circulation passage between the first oil port and the second oil port of the variable pitch cylinder through the internal passage switching of the proportional valve, so that the components can be greatly reduced, and the hydraulic oil delivery pipeline can be optimized. The oil supply and return cooling module, the emergency feathering module and the blade lock module are arranged in the opening and closing paddle unit, and the above key components can be integrated into the paddle hub and rotate with the blades, so that the stability of the structure is improved, and the leakage risk is reduced.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. The closed-loop electro-hydraulic pitch system of the present invention combines the advantages of traditional electro-pitch and hydraulic pitch systems, maintaining the flexibility and small size of servo electric motion control. The entire system also has the advantage of small space occupation of electro-pitch systems. Compared with traditional hydraulic pitch systems, the pitch adjustment unit is a closed-loop hydraulic system, eliminating the need for an oil source pump station; it greatly simplifies the hydraulic oil delivery pipeline and reduces the number of components; thus resulting in extremely low leakage points, saving installation space, and having a significant cost advantage.

[0026] 2. The key components of this closed electro-hydraulic pitch system can be placed inside the hub and rotate with the blades. Therefore, with the positive pressure oil tank, the slip ring can be eliminated, which better ensures the system stability and sealing, and reduces the risk of leakage.

[0027] 3. This closed-loop electro-hydraulic pitch system achieves emergency feathering by configuring an accumulator and a backup power supply for the motor. Simultaneously, the backup power supply occupies little space, and the hydraulic accumulator is safe and reliable, meeting the harsh operating environment of the wind turbine. The introduction of the accumulator can provide some high-pressure oil, operating simultaneously with the motor and hydraulic pump to achieve rapid action, reduce the power consumption of the motor and hydraulic pump, and extend the service life of the equipment. The motor uses a servo motor or a variable frequency motor, maintaining high pressure in the accumulator during normal operation to meet instantaneous high-speed requirements. Proportional valves or servo valves are used to achieve high dynamic response of the system.

[0028] 4. With the use of an atmospheric pressure oil tank, the supply and return oil cooling module of this closed-loop electro-hydraulic pitch system allows the motor to be placed inside the hub, while the slip rings and corresponding valve assemblies can be placed inside the wind turbine nacelle. Furthermore, the use of low-pressure hydraulic slip rings avoids the high-pressure slip rings of traditional hydraulic pitch systems; it offers lower cost, higher reliability, and is less prone to oil leakage, avoiding the numerous problems associated with longer pipelines and high-pressure slip rings.

[0029] 5. This invention offers high safety. When the pitch cylinder is in the maximum feathering position, the hydraulic oil inside can be sealed off using a corresponding valve group to prevent the pitch from opening. The blade lock ensures safety and reliability; a solenoid valve is installed before the oil port of the blade lock cylinder to ensure the cylinder's locking function during installation, maintenance, pitch control, and other shutdown conditions. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0031] Figure 1 This is the system schematic diagram of Embodiment 1;

[0032] Figure 2 yes Figure 1 A schematic diagram of the hydraulic oil flow direction during the pitching action;

[0033] Figure 3 is Figure 1 a schematic diagram of the hydraulic oil flow direction when the emergency feathering action of the

[0034] Figure 4 is Figure 1 a schematic diagram of the hydraulic oil flow direction when the emergency feathering action of the

[0035] Figure 5 is the system principle diagram of embodiment two;

[0036] Figure 6 is Figure 5 a schematic diagram of the hydraulic oil flow direction when the opening action of the

[0037] Figure 7 is Figure 5 a schematic diagram of the hydraulic oil flow direction when the closing action of the

[0038] Figure 8 is Figure 5 a schematic diagram of the hydraulic oil flow direction when the emergency feathering action of the

[0039] Fig. 1 is a schematic diagram of the hydraulic oil flow direction when the opening action of the DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application.

[0041] In the description of the embodiments of the present application, the words such as setting, installing and connecting should be understood broadly unless otherwise explicitly limited, and the person skilled in the art can determine the specific meaning of the above words in the present application in combination with the specific content of the technical scheme.

[0042] Embodiment one:

[0043] As Figures 1-4As shown, the closed electric-hydraulic variable pitch system for wind power generation disclosed in the embodiment mainly comprises a positive pressure oil tank 1, a backup power supply 2, a motor 3, a hydraulic pump 4, a cooler 5, a filter 6, an accumulator 11, a variable pitch cylinder 13, a blade lock 14, a third one-way valve 17, a fourth one-way valve 18, an overflow valve 101, a proportional valve 102, a first pressure sensor 103, a second pressure sensor 104, a first two-position two-way electromagnetic directional valve 105, a second two-position two-way electromagnetic directional valve 106, a third two-position two-way electromagnetic directional valve 107, a fourth two-position two-way electromagnetic directional valve 108, a first two-position three-way electromagnetic directional valve 130, and the like.

[0044] The variable pitch cylinder 13 is provided with a first oil port, a second oil port, and a piston mechanism composed of a piston and a piston rod. The first oil port can serve as an oil inlet or an oil outlet, and correspondingly, the second oil port can serve as an oil outlet or an oil inlet.

[0045] Therefore, by feeding or discharging hydraulic oil through the first oil port and the second oil port, different pressure differences are formed in the cylinder bodies on both sides of the piston, which drives the piston and the piston rod to move, so that the piston rod extends or retracts relative to the cylinder body, and drives the paddle to complete the variable pitch adjustment as an actuator.

[0046] Continuing to refer to Figure 1 Between the first oil port and the second oil port of the variable pitch cylinder 13, an opening and closing unit is arranged. The opening and closing unit is used for opening or retracting the paddle.

[0047] The opening and closing unit comprises the motor 3, the hydraulic pump 4, the proportional valve 102, the first two-position two-way electromagnetic directional valve 105, the second two-position two-way electromagnetic directional valve 106, and a connecting pipe for conveying hydraulic oil.

[0048] The motor 3 is used to drive the hydraulic pump 4 to work as a hydraulic oil pressurization. The proportional valve 102 has four interfaces of A, B, P, and T. Inside the proportional valve 102, the passages between A, B and P, T interfaces can be cross-converted.

[0049] The oil outlet of the hydraulic pump 4 is in communication with the P interface of the proportional valve 102, the T interface of the proportional valve 102 is in communication with the oil suction port of the hydraulic pump 4, and the A and B interfaces of the proportional valve 102 are in communication with the first oil port and the second oil port of the variable pitch cylinder 13, respectively. Therefore, by switching the passages inside the proportional valve 102, the flow direction of the hydraulic oil inlet and outlet between the first oil port and the second oil port can be converted, and in turn, the piston rod of the variable pitch cylinder 13 is extended or retracted to complete the variable pitch adjustment of the paddle.

[0050] The proportional valve is externally provided with a differential bypass with a fifth one-way valve between the P and B interfaces. When the rod cavity and the rodless cavity of the pitch cylinder 13 are simultaneously connected to the P interface of the proportional valve 102, the pitch cylinder 13 will perform an extension movement, and the extension thrust is the product of the sectional area of the piston rod and the pressure of the P interface, which is smaller than the thrust in the non-differential state. This mode of operation is referred to as the differential operation mode of the cylinder. Although the thrust is reduced, the speed will be increased under the condition that the flow of the hydraulic system is the same.

[0051] At the same time, in order to ensure the safety of the hydraulic oil delivery and the linkage with the emergency feathering module and the blade locking module, a first two-position two-way electromagnetic reversing valve 105 is installed on the connecting pipe between the A interface of the proportional valve 102 and the first oil port of the pitch cylinder 13, and a second two-position two-way electromagnetic reversing valve 106 is installed on the connecting pipe between the P interface of the proportional valve 102 and the oil outlet of the hydraulic pump 4.

[0052] The first two-position two-way electromagnetic reversing valve 105 and the second two-position two-way electromagnetic reversing valve 106 are powered on during the pitch opening or closing operation. During the emergency feathering operation, the power is turned off to stop the hydraulic oil delivery before and after.

[0053] The pitch opening and closing unit is provided with a blade locking module for locking or releasing the blades, which includes a two-position three-way electromagnetic reversing valve 130 and a blade lock 14. One port of the two-position three-way electromagnetic reversing valve 130 is in communication with the connecting pipe between the accumulator 11 and the fourth two-position two-way electromagnetic reversing valve 108, the other port is in communication with the connecting pipe before the oil suction port of the hydraulic pump 4, and the third port is in communication with the oil inlet and outlet ports of the blade lock 14.

[0054] The oil supply and return cooling module in the embodiment includes a positive pressure tank 1, a cooler 5 and a filter 6. The cooler 5 and the filter 6 are installed on the connecting pipe between the T interface of the proportional valve 102 and the oil suction port of the hydraulic pump 4, and the oil inlet and outlet ports of the positive pressure tank 1 are in communication with the connecting pipe before the oil suction port of the hydraulic pump 4.

[0055] The positive pressure tank is a low-pressure container, and the working pressure range is between 2 and 10 bar. The internal volume is adapted to the sum of the hydraulic oil capacity of all the accumulators and the hydraulic oil volume changed by the pitch cylinder 13.

[0056] The positive pressure tank 1 is filled with low-pressure gas inside, which serves as a hydraulic oil buffer area, can store the excess hydraulic oil returned, and can provide the required hydraulic oil medium for the hydraulic pump 4 in time. The cooler 5 is used to cool the returned hydraulic oil medium, to ensure the stability of the pitch opening and closing unit and the safety performance of the system.

[0057] As shown in FIG. 1, Figure 2 As shown in FIG. 1,

[0058] The flow process of hydraulic oil in the vane lock module is as follows:

[0059] The hydraulic pump 4 pressurizes the hydraulic oil and outputs it from the oil outlet. The hydraulic oil enters the cylinder of the vane lock 14 through the fourth one-way valve 18 and the two-position three-way electromagnetic reversing valve 130, pushes the vane lock 14 to move inward, and separates from the blade to ensure the normal opening of the blade.

[0060] The flow process of hydraulic oil between the first oil port and the second oil port of the pitch cylinder 13 is as follows:

[0061] The hydraulic pump 4 pressurizes the hydraulic oil and outputs it from the oil outlet. The hydraulic oil flows into the P port of the proportional valve 102 from the A port after passing through the fourth one-way valve 18 and the second two-position two-way electromagnetic reversing valve 106, and then enters the cylinder of the pitch cylinder 13 through the first two-position two-way electromagnetic reversing valve 105 and the first oil port. At this time, the first oil port serves as the oil inlet. After the hydraulic oil enters the cylinder, it pushes the piston and piston rod to extend. During this process, the force area of the first oil port of the pitch cylinder 13 is greater than that of the second oil port of the cylinder, and the hydraulic oil measured at the second oil port is discharged into the P port of the proportional valve 102 through the one-way valve 19. During this process, the piston rod of the pitch cylinder 13 differentially extends. At this time, the second oil port serves as the oil outlet.

[0062] Figure 2 The one-way arrow shown in the figure indicates the direction of movement of the hydraulic oil, the piston rod, and the vane lock 14. The bidirectional arrow indicates that the accumulator 11 and the positive pressure tank 1 can both output and input. The cross indicates that the component or pipeline is blocked. Figures 3-4 、 Figures 6-8 The meanings of the one-way arrow, bidirectional arrow, and cross shown in the figure are the same as those in Figure 2 , and will not be described again.

[0063] As shown in Figure 3 , the opening and closing blade unit is in the closing action, and the vane lock module is in the state of releasing the blade.

[0064] The flow process of hydraulic oil in the vane lock module is as follows:

[0065] The hydraulic pump 4 pressurizes the hydraulic oil and outputs it from the oil outlet. The hydraulic oil enters the cylinder of the vane lock 14 through the fourth one-way valve 18 and the two-position three-way electromagnetic reversing valve 130, pushes the vane lock 14 to move inward, and separates from the blade to ensure the normal opening of the blade.

[0066] The flow process of hydraulic oil between the second oil port and the first oil port of the pitch cylinder 13 is as follows:

[0067] The hydraulic pump 4 pressurizes the hydraulic oil and outputs it from the oil outlet. The hydraulic oil flows from the P port of the proportional valve 102 to the B port, passes through the second two-position two-way electromagnetic switching valve 106, and then flows into the cylinder of the variable-pitch cylinder 13 from the second oil port. At this time, the second oil port serves as an oil inlet, so the piston and the piston rod can be extended and retracted. After the hydraulic oil in the cylinder on the side of the first oil port is discharged, the hydraulic oil flows from the T port of the proportional valve 102 to the A port, passes through the first two-position two-way electromagnetic switching valve 105, and then flows into the positive pressure tank 1 or the suction port of the hydraulic pump 4 from the first oil port. At this time, the first oil port serves as an oil outlet.

[0068] As shown in FIG. 6, in the emergency feathering operation, the blade locking module pushes out the locking blades. Figure 4

[0069] The flow process of the hydraulic oil in the blade locking module is as follows:

[0070] The third port of the two-position three-way electromagnetic switching valve 130 is opened, the spring in the cylinder of the blade lock 14 pushes out the locking tongue or the locking rod, and the locking tongue or the locking rod is in contact with the locking blades in the emergency feathering process. The hydraulic oil in the cylinder of the blade lock 14 is discharged and then flows back to the positive pressure tank 1 or the suction port of the hydraulic pump 4 through the two-position three-way electromagnetic switching valve 130.

[0071] The flow process of the hydraulic oil between the first oil port and the second oil port of the variable-pitch cylinder 13 is as follows:

[0072] The hydraulic pump 4 pressurizes the hydraulic oil and outputs it from the oil outlet. The hydraulic oil flows from the P port of the proportional valve 102 to the B port, passes through the second two-position two-way electromagnetic switching valve 106, and then flows into the cylinder of the variable-pitch cylinder 13 from the second oil port. At this time, the second oil port serves as an oil inlet, so the piston and the piston rod can be extended and retracted. After the hydraulic oil in the cylinder on the side of the first oil port is discharged, the hydraulic oil flows from the T port of the proportional valve 102 to the A port, passes through the first two-position two-way electromagnetic switching valve 105, and then flows into the positive pressure tank 1 or the suction port of the hydraulic pump 4 from the first oil port. At this time, the first oil port serves as an oil outlet.

[0073] In the emergency feathering operation, the A, B, P, and T ports of the proportional valve 102 are all closed, that is, the hydraulic oil does not flow through the proportional valve 102.

[0074] In this embodiment, the backup power supply 2 and the accumulator 11 are configured. The backup power supply 2 and the accumulator 11 can provide sufficient amount of hydraulic oil to realize the full stroke extension operation of the variable-pitch cylinder 13.

[0075] ​The backup power supply 2 can provide driving power for the motor 3 in emergency situations such as power failure, so as to ensure the overall safety performance of the system. The accumulator 11 can provide part of the high-pressure oil, and simultaneously act with the motor 3 and the hydraulic pump 4, so as to realize rapid action, reduce the power of the motor 3 and the hydraulic pump 4, and prolong the service life of the equipment. The branch pipe with the overflow valve 101 is arranged between the oil suction port and the oil outlet port of the hydraulic pump 4. The oil return of the overflow valve 101 can be collected into the positive pressure tank 1.

[0076] Meanwhile, in order to monitor the pressure of the hydraulic oil on the connecting pipe, the first pressure sensor 103 is arranged on the connecting pipe between the accumulator 11 and the third two-position two-way electromagnetic reversing valve 108. The second pressure sensor 104 is arranged on the connecting pipe between the two-position three-way electromagnetic reversing valve 130 and the oil suction port of the hydraulic pump 4.

[0077] Embodiment two:

[0078] As shown in Figures 5-8 , the closed electric-hydraulic variable pitch system for wind power generation disclosed in the embodiment mainly comprises a normal pressure tank 7, a circulating motor 8, a circulating hydraulic pump 9, a slip ring 10, a first one-way valve 15, a second one-way valve 16, a backup power supply 2, a motor 3, a hydraulic pump 4, a cooler 5, a filter 6, an accumulator 11, a variable pitch cylinder 13, a blade lock 14, a third one-way valve 17, a fourth one-way valve 18, an overflow valve 101, a proportional valve 102, a first pressure sensor 103, a second pressure sensor 104, a first two-position two-way electromagnetic reversing valve 105, a second two-position two-way electromagnetic reversing valve 106, a third two-position two-way electromagnetic reversing valve 107, a fourth two-position two-way electromagnetic reversing valve 108, a first two-position three-way electromagnetic reversing valve 130, and the like.

[0079] Embodiment two and embodiment one are mainly different in the oil supply and return cooling module.

[0080] Continuing to refer to Figure 5 , the oil supply and return cooling module of the embodiment comprises a normal pressure tank 7, a circulating motor 8, a circulating hydraulic pump 9, a cooler 5, a filter 6, a slip ring 10, a first one-way valve 15, a second one-way valve 16, and a branch pipe for connection. The circulating motor 8 is used to drive the circulating hydraulic pump 9 to work.

[0081] The oil supply port of the normal pressure tank 7 is in communication with the oil suction port of the circulating hydraulic pump 9, the oil return port of the normal pressure tank 7 is provided with the cooler 5 and the filter 6 in front, and the inlet and outlet of the slip ring 10 are respectively in communication with the oil suction port of the hydraulic pump 4 and the T-shaped port of the proportional valve 102.

[0082] The slip ring 10 and the corresponding valve group in the system can be placed in the fan cabin. Low-pressure slip ring 10 is adopted, avoiding the high-pressure slip ring 10 of the traditional hydraulic variable pitch. The cost is reduced, the reliability is high, the oil leakage is not easy, and the problems existing in the long pipeline and the high-pressure slip ring 10 are avoided.

[0083] As shown in Figures 6-8 , in the opening, closing and emergency feathering actions of the embodiment, except that the oil path and the path of the hydraulic oil in the oil supply and return cooling module are different from the positive pressure tank 1 part of the embodiment one, the others are the same as the opening, closing and emergency feathering action process of the embodiment one shown in Figure 2 、 Figure 3 、 Figure 4 , hereinafter, the description is not repeated.

[0084] In addition, it should be noted that the piston rod of the variable pitch cylinder 13 in the embodiment one and the embodiment two can also adopt a double-sided structure, or a plurality of variable pitch cylinders 13 can be combined. Figures 1-8 The variable pitch cylinder 13 and the piston rod structure, the number and the like shown in the embodiment one are only for the description and explanation of the technical scheme, and are not limited to the specific number.

[0085] The technical contents not described in detail in the application are all known technologies.

Claims

1. A closed-loop electro-hydraulic pitch control system for wind power generation, comprising a pitch cylinder with a first oil port, a second oil port, and a piston rod, characterized in that, A pitch control unit is installed between the first and second ports of the pitch cylinder. This unit includes a motor, a hydraulic pump, a proportional valve, and a connecting pipe for supplying hydraulic oil. The motor drives the hydraulic pump. The hydraulic pump outlet is connected to the P port of the proportional valve, and the proportional valve T port is connected to the hydraulic pump inlet. The proportional valve A and B ports are connected to the first and second ports of the pitch cylinder, respectively. The fluid channels between the A and B ports and the P and T ports within the proportional valve can be interchanged. A differential bypass with a fifth check valve is installed between the P and B ports externally to the proportional valve. By switching the flow direction of the hydraulic oil between the first and second ports using the proportional valve, the piston rod of the pitch cylinder extends or retracts to adjust the pitch of the blades. A first two-position, two-way solenoid valve is installed between the A port of the proportional valve and the first port of the pitch cylinder, and a second two-position, two-way solenoid valve is installed between the P port of the proportional valve and the hydraulic pump outlet. The pitch control unit is equipped with an emergency feathering module, which includes a third two-position two-way solenoid valve, a third check valve, an accumulator, a fourth two-position two-way solenoid valve, a fourth check valve, and a backup power supply. The third check valve, the third two-position two-way solenoid valve, and the fourth check valve are sequentially installed between the first oil port of the pitch cylinder and the outlet of the hydraulic pump. The accumulator is installed between the fourth check valve and the third two-position two-way solenoid valve. The two ends of the fourth two-position two-way solenoid valve are respectively connected to the B and T ports of the proportional valve. The backup power supply is for motor power supply. The pitch control unit is also equipped with a blade locking module for locking or releasing the blades. The blade locking module includes a two-position three-way solenoid valve and a blade lock. One port of the two-position three-way solenoid valve is connected to the connecting pipe between the accumulator and the fourth two-position two-way solenoid valve, and its other port is connected to the connecting pipe before the hydraulic pump suction port. Its third port is connected to the inlet and outlet ports of the blade lock cylinder.

2. The closed-loop electro-hydraulic pitch system for wind power generation according to claim 1, characterized in that, The propeller unit is equipped with a supply and return oil cooling module for filtering and cooling the circulating hydraulic oil.

3. The closed-loop electro-hydraulic pitch system for wind power generation according to claim 2, characterized in that, The oil supply and return cooling module includes a positive pressure oil tank, a cooler, and a filter. The filter and cooler are installed between the T-port of the proportional valve and the oil inlet of the hydraulic pump. The oil port of the positive pressure oil tank is connected to the oil inlet of the hydraulic pump. The working pressure range of the positive pressure oil tank is 2... Between 10 bar.

4. The closed-loop electro-hydraulic pitch system for wind power generation according to claim 2, characterized in that, The oil supply and return cooling module includes an oil tank, a circulating motor, a circulating hydraulic pump, a filter, a cooler, a slip ring, a first check valve, a second check valve, and branch pipes for connection. The circulating motor drives the circulating hydraulic pump. The oil supply port of the oil tank is connected to the oil suction port of the circulating hydraulic pump. A cooler and a filter are installed in front of the oil return port of the oil tank. The inlet and outlet on one side of the slip ring are connected to the oil suction port of the hydraulic pump and the T-port of the proportional valve, respectively.

5. The closed-loop electro-hydraulic pitch system for wind power generation according to claim 1, characterized in that, A branch line with an overflow valve is provided between the oil inlet and outlet of the hydraulic pump.

6. The closed-loop electro-hydraulic pitch system for wind power generation according to claim 1, characterized in that, A first pressure sensor is installed between the accumulator and the third two-position two-way solenoid directional valve.

7. The closed-loop electro-hydraulic pitch system for wind power generation according to claim 1, characterized in that, A second pressure sensor is installed between the two-position three-way solenoid directional valve and the hydraulic pump suction port.

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