Hydraulic system for adjusting the pitch angle of the rotor blades of a wind turbine and wind turbine having such a hydraulic system

Abstract

This invention relates to a hydraulic system (10) for adjusting the pitch angle of the rotor blades (108) of a wind turbine (100). The hydraulic system (10) includes a variable displacement pump (12), a hydraulic accumulator (14), a dynamic valve (16), a control valve (18), a tank (20), and a pitch cylinder (22). The invention also relates to a wind turbine having such a hydraulic system (10).

Description

Technical Field

[0001] The present invention relates to a hydraulic system for adjusting the pitch angle of the rotor blades of a wind turbine generator, and a wind turbine generator having such a hydraulic system. Background Technology

[0002] This type of hydraulic system is known in the prior art and is also called a blade adjustment system. These hydraulic systems are configured to adjust the aerodynamic angle of attack of one or more rotor blades of a wind turbine, thereby setting the so-called pitch angle. For this purpose, the rotor blades are rotatably mounted on the rotor of the wind turbine via pitch bearings and a pitch gearbox. The rotor is in turn rotatably mounted on the nacelle of the wind turbine via a hub. The hydraulic system changes the angle of attack of the rotor blades according to the current wind speed in order to operate the wind turbine at optimal efficiency and thus at a substantially constant rated power. The angle of attack of the rotor blades is adjusted for a variety of purposes to achieve the desired blade lift, such as bringing the rotor to a standstill, limiting the energy supply of the wind to the blades, and performing maintenance work. In other words, the angle of attack is adapted to the wind direction.

[0003] In addition, the hydraulic system is configured to prevent the wind turbine from being damaged in strong winds by turning the rotor blades outward, i.e., in the so-called "feed position." This interrupts the lift of the rotor blades, and the rotor may come to a stop with the support of the brakes.

[0004] For this purpose, hydraulic systems typically have pitch cylinders that engage with the rotor blades, and the pitch angle of the rotor blades relative to the hub can be changed by retracting or extending the pitch cylinders. A hydraulic accumulator supplies pressure to the pitch cylinders, thereby pressurizing the accumulator via a suitable and simple device (usually a fixed displacement pump) located in the nacelle. Since this device is only used to pressurize the accumulator, its efficiency is not considered in detail in these systems. Furthermore, the heat that may be generated by this device, located in the nacelle, is a concern.

[0005] However, a drawback of the known solutions is that, since the hydraulic accumulator only supplies pressure to the pitch cylinder, this (high) pressure will also remain permanently on the rod side of the pitch cylinder. Furthermore, a correspondingly large accumulator must be selected to provide the necessary pressure and the required amount of hydraulic fluid. In addition, the rotary feedthrough required for accumulator pressurization is expensive, complex, and requires extensive maintenance. Therefore, for efficiency reasons, it is desirable to address the pitch angle adjustment problem in a different way and, where possible, eliminate the rotary feedthrough. However, due to the heat generated, it is impossible to install a fixed displacement pump inside the rotary hub. Due to the complex hydraulic design, using a variable displacement pump is not economical for pure accumulator pressurization operations. Furthermore, variable displacement pumps are not suitable for direct control of the pitch cylinder because there is a certain time required for the variable displacement pump to provide the required flow or pressure after swinging out. Summary of the Invention

[0006] Therefore, an object of the present invention is to provide an improved hydraulic system for adjusting the pitch angle of the rotor blades of a wind turbine. Another object of the present invention is to provide a wind turbine having such a hydraulic system.

[0007] According to the present invention, a hydraulic system for adjusting the pitch angle of rotor blades of a wind turbine is provided. The hydraulic system includes a variable displacement pump, a hydraulic accumulator, a dynamic valve, a control valve, a tank, and a pitch cylinder. Preferably, the control valve is configured as a proportional valve, and more preferably a spool valve. The variable displacement pump is connected to the control valve via a first connecting line without a rotating oil seal, and the control valve is connected to the tank via a second connecting line without a rotating oil seal. The control valve is also connected to the piston side of the pitch cylinder via a third connecting line without a rotating oil seal, and the control valve is connected to the rod side of the pitch cylinder via a fourth connecting line without a rotating oil seal. Therefore, in a first switching position of the control valve, the first connecting line is connected to the third connecting line, and in a second switching position of the control valve, the first connecting line is connected to the fourth connecting line, and the second connecting line is connected to the third connecting line. The hydraulic accumulator is connected to the first connecting line via a fifth connecting line, wherein the fifth connecting line leads to the first connecting line at an interface. The dynamic valve is located in the fifth connecting line, and in a first switching position, it blocks the fifth connecting line along the flow direction from the hydraulic accumulator to the first connecting line. In a second switching position, the dynamic valve releases the fifth connecting line.

[0008] In principle, the hydraulic system according to the invention is used to regulate the pitch angle via a flow rate supplied by a variable displacement pump. A hydraulic accumulator and a dynamic valve are used to compensate for any design delay in the flow rate supplied by the variable displacement pump. To set the pitch angle, the control valve is switched to the corresponding switching position, and the variable displacement pump is swung out. Simultaneously, the dynamic valve opens, thereby connecting the hydraulic accumulator to the control valve via a fifth connecting line and a first connecting line. Once sufficient capacity is obtained through the variable displacement pump, the dynamic valve closes again, disconnecting the hydraulic accumulator from the control valve. The capacity is then entirely supplied by the variable displacement pump.

[0009] The advantages of this approach are that by using a variable displacement pump to improve efficiency and by placing the hydraulic system within the hub, heat generation is significantly reduced. This eliminates the need for a rotary oil seal. Furthermore, since initial supply is only required through an accumulator, the hydraulic accumulator can be configured with a smaller storage capacity and higher storage pressure, significantly improving the overall cost-effectiveness of the accumulator. Additionally, this allows for pressure to be applied as needed, thus relieving the rod side of the pitch cylinder from prolonged high pressure.

[0010] Preferably, a first check valve that opens in the flow direction from the variable pump to the control valve is located upstream of the interface in the first connecting line. When the dynamic valve is in the second switching position, the first check valve prevents hydraulic oil in the accumulator from flowing in the direction of the variable pump.

[0011] Preferably, the hydraulic accumulator is connected to the fourth connecting line via a sixth connecting line, wherein the control valve blocks the fourth connecting line in the first switching position. This means that when pressure is applied to the piston side of the pitch cylinder, hydraulic oil discharged from the rod side is loaded into the hydraulic accumulator. In this case, preferably, a second check valve that opens in the flow direction from the fourth connecting line to the hydraulic accumulator is provided in the sixth connecting line. This prevents hydraulic oil from accidentally flowing out of the hydraulic accumulator through the sixth connecting line.

[0012] Preferably, the hydraulic system includes a control unit. The control unit can also be a more advanced control unit of the wind turbine or a separate control unit for the hydraulic system.

[0013] Preferably, the dynamic valve is preloaded to the first switching position and can be activated by the control unit to switch to the second switching position. Once pitch angle adjustment is performed, the control unit switches the dynamic valve to the second switching position, thereby connecting the hydraulic accumulator to the control valve via the first connecting line. Once sufficient capacity is provided by the variable pump, the signal from the control unit is interrupted, and the dynamic valve switches back to the first switching position due to preloading, disconnecting the hydraulic accumulator from the first connecting line. The dynamic valve can be configured, for example, as an electromagnetically actuated 2 / 2-way valve that switches accordingly when energized by the control unit.

[0014] Preferably, the control valve can be switched to either the first switching position or the second switching position via the control unit. Also preferably, the control valve can be switched to the accumulator charging position. In the accumulator charging position of the control valve, the first connecting line, the second connecting line, the third connecting line, and the fourth connecting line are all blocked. This means that when the control valve is in the accumulator charging position, the hydraulic accumulator can be charged via the fifth connecting line. It is conceivable to switch the dynamic valve to the second switching position to charge the hydraulic accumulator. Furthermore, the dynamic valve can also be configured such that in the first switching position of the dynamic valve, the check valve allows flow from the first connecting line to the hydraulic accumulator.

[0015] Preferably, a first pilot control line branches off from the first connecting line and is connected to the variable pump in such a way that a pilot control pressure signal can be applied to the variable pump. Preferably, a pilot control valve is disposed in the first pilot control line, whereby the pilot control valve is configured to block or release the pilot control line. Furthermore, the pilot control valve can be configured to release the pilot pressure signal applied to the variable pump to the oil tank. Preferably, the first pilot control valve is actuated by the control system.

[0016] In the first embodiment, when the control valve is in the accumulator pressurization position, the pilot control valve for pressurizing the accumulator opens. This ensures that the variable pump swings out and increases the flow rate according to the pilot pressure signal sent through the first pilot control line at that time. Preferably, the first embodiment is an embodiment with a load pressure signaling circuit.

[0017] In this configuration, preferably, the hydraulic system has a second pilot control line, which is connected to the first pilot control line via a first reciprocating valve. In the first switching position of the control valve, the second pilot control line is connected to either the first or third connecting line, while in the second switching position of the control valve, the second pilot control line is connected to the fourth connecting line. Therefore, the load pressure applied to the pitch cylinder is signaled via the second pilot control line and can thus be transmitted as a pilot pressure signal to the load pressure regulator via the first reciprocating valve, thereby operating the variable pump accordingly.

[0018] The hydraulic system includes a third pilot control line branching off from the first pilot control line between the control valve and the pilot control valve, and extending via a second reciprocating valve to the first pilot control line between the pilot control valve and the variable pump. A preload valve is disposed in the third pilot control line, thereby preloading the pilot pressure signal in the first pilot control line to a predetermined pressure. This arrangement ensures that the pilot pressure signal is always kept at a minimum level, thus ensuring that the variable pump is always partially disengaged.

[0019] Preferably, the first pilot control line depressurizes to the oil tank via a pressure relief line, whereby a pressure relief element is disposed. The pressure relief element is preferably a pressure relief valve. Alternatively, a throttle valve or similar device can be used to provide a leak point as the pressure relief element. This ensures that the pressure in the first pilot control line is not locked but decreases over time, allowing the variable pump to safely return to zero when needed.

[0020] In the second embodiment, no load pressure signaling circuit is provided; instead, the system is controlled entirely by the control unit. For this purpose, it is preferable to provide appropriate sensors in the hydraulic system, such as position sensors on the pitch cylinder. Also preferably, the control system can utilize other sensor data from the wind turbine to adjust the pilot pressure signal of the pump. Preferably, the pilot control valve is configured as a proportional 3 / 3 directional control valve to block the first pilot control line or connect it to the variable pump, or to release the pilot control pressure signal applied to the variable pump to the tank, thereby causing the variable pump to rotate in the zero-position direction.

[0021] Preferably, the flow control element is disposed in the third connecting line. Preferably, the flow control element is configured as a pressure valve and a bypass line bypassing the pressure valve along the flow direction from the control valve to the pitch cylinder. This ensures unimpeded pressurization on the piston side of the pitch cylinder, but the flow rate can be regulated when pressure is applied on the rod side.

[0022] According to the present invention, a wind turbine is also provided, the wind turbine having a tower, a nacelle disposed on the tower, and a rotor rotatably mounted on the nacelle via a hub, at least one rotor blade being rotatably disposed on the rotor at a pitch angle relative to the hub, the wind turbine including the aforementioned hydraulic system for adjusting the pitch angle, the hydraulic system being entirely disposed in the hub. Attached Figure Description

[0023] The present invention will now be described in more detail with reference to the embodiments shown in the accompanying drawings. In the drawings: Figure 1 This is a side view of a wind turbine. Figure 2 This is a hydraulic circuit diagram of a hydraulic system according to a first exemplary embodiment of the present invention; Figure 3 This is a hydraulic circuit diagram of a hydraulic system according to a second exemplary embodiment of the present invention; and Figure 4 This is a hydraulic circuit diagram of a hydraulic system according to a third exemplary embodiment of the present invention. Detailed Implementation

[0024] Figure 1 A side view of a wind turbine 100 according to the present invention is shown. The wind turbine 100 has a tower 102 and a nacelle 104 attached to the tower 102. A rotor 106 is rotatably mounted on the nacelle 104 via a hub 112. The wind turbine 100 also includes a plurality of rotor blades 108 attached to the rotor 106. Furthermore, a hydraulic system 10 (see [reference needed]) is provided for each rotor blade 108, fully disposed in the hub 112. Figures 2 to 4The hydraulic system 10 is configured to adjust the aerodynamic angle of attack of the corresponding rotor blades 108 of the wind turbine 100. The hydraulic system changes the angle of attack of the rotor blades 108 according to the current wind speed in order to operate the wind turbine 100 with optimal efficiency and thus substantially constant rated power. For this purpose, the angular position of the rotor blades 108 relative to the hub 112, the so-called pitch angle, is adjusted by the corresponding hydraulic system 10 in a manner that generates the required lift. The hydraulic system 10 is also configured to prevent damage to the wind turbine 100 in strong winds by turning the rotor blades 108 out of the wind, into a so-called feathering position. This interrupts the lift of the rotor blades 108, and the rotor 106 stops rotating.

[0025] Figure 2 A first exemplary embodiment of a hydraulic system 10 for adjusting the pitch angle of individual rotor blades 108 according to the present invention is shown. The hydraulic system 10 includes a variable displacement pump 12, a hydraulic accumulator 14, a control valve 18, a tank 20, and a pitch cylinder 22. In this exemplary embodiment, the control valve 18 is configured as a proportional three-way controller. The variable displacement pump 12 draws hydraulic oil through the tank 20 in a known manner and is connected to the control valve 18 via a first connecting line 24. The control valve 18 is also connected to the tank 20 via a second connecting line 26. The pitch cylinder 22 is connected to the piston-side control valve 18 via a third connecting line 28. On the rod side, the pitch cylinder 22 is connected to the control valve 18 via a fourth connecting line 30. The control valve can be switched to a first switching position RV1, a second switching position RV2, and an accumulator charging position RV3. In the first switching position RV1, the first connecting line 24 is connected to the third connecting line 28, and the second connecting line 26 and the third connecting line 30 are blocked. In the second switching position, the first connecting line 24 is connected to the fourth connecting line 30, and the second connecting line 26 is connected to the third connecting line 28. In the accumulator pressurization position RV3, the first connecting line 24, the second connecting line 26, the third connecting line 28, and the fourth connecting line 30 are all blocked.

[0026] Hydraulic accumulator 14 is connected via a fifth connecting line 32, which leads at interface 34 to a first connecting line 24 between variable pump 12 and control valve 18. A dynamic valve 16 is disposed in the fifth connecting line 32. The dynamic valve 16 is biased to a first switching position DV1, in which the fifth connecting line 32 is blocked in the flow direction from hydraulic accumulator 14 to interface 34. A first check valve 36 is disposed in the first connecting line 24 between variable pump 12 and interface 34. The first check valve 36 prevents flow in the direction of variable pump 12. Furthermore, hydraulic accumulator 14 is connected to a fourth connecting line 30 via a sixth connecting line 38. A second check valve 40, which opens in the direction of flow towards hydraulic accumulator 14, is disposed in the sixth connecting line 38.

[0027] The dynamic valve 16 can be actuated by the control unit 42 to switch it to a second switching position DV2, in which the fifth connecting line 32 is released. In this exemplary embodiment, the dynamic valve 16 is therefore configured as a solenoid-actuated 2 / 2-way valve. The control unit 42 can be a separate control unit 42 for the hydraulic system 10, or it can be part of a higher-level control unit of the wind turbine 100. The control unit 42 is also configured to switch the control valve 18 between a first switching position RV1, a second switching position RV2, and an accumulator pressurization position RV3. The control unit is also connected to the wind turbine's sensor system 110 and the position sensor 64 of the pitch cylinder 22. The control unit 42 processes sensor data and takes the sensor data into account when controlling the hydraulic system 10.

[0028] A flow control element 62 is disposed in the third connecting line 28. In this exemplary embodiment, the flow control element 62 is configured as a pressure valve and a bypass line bypassing the pressure valve. Hydraulic oil can flow unimpeded from the control valve 18 to the piston side of the pitch cylinder 22 through the flow control element 62, but the flow rate from the piston side of the pitch cylinder 22 to the control valve 18 is controlled by the pressure valve. As shown, the pressure in the fourth connecting line 30 acts on the pressure valve on the control side.

[0029] exist Figure 2 In the exemplary embodiment shown, the load pressure signaling circuit for applying a pilot pressure signal to the variable pump 12 includes a first pilot control line 44 and a second pilot control line 48. The first pilot control line 44 branches off from the first connecting line 24 between the variable pump 12 and the first check valve 36 and is connected to the variable pump 12 via a load pressure regulator 74. The pilot pressure signal in the first pilot control line 44 determines the extension and retraction of the variable pump 12 by receiving the pilot pressure from the first connecting line 24 via a fourth pilot control line 76 and sending the signal to the variable pump 12 via the load pressure regulator 74. As shown, the load pressure regulator 74 is configured as a proportional 3 / 2-way valve, wherein the pressure in the fourth pilot control line 76 acts on the load pressure regulator 74 in the opening direction. The pressure in the first pilot control line 44 acts on the load pressure regulator 74 in the closing direction. Furthermore, the load pressure regulator 74 is preloaded by a spring in the closing direction. Therefore, based on the pilot pressure signal, the pressure signal is transmitted to the variable pump 12 through the load pressure regulator 74 to achieve oscillation, or the pressure signal is released to the oil tank 20 through the load pressure regulator 74.

[0030] A pilot control valve 46, actuated by a control unit 42, is provided in the first pilot control line 44. As shown, in this exemplary embodiment, the pilot control valve 46 is configured as a solenoid-actuated 2 / 2-way valve. The pilot control valve 46 is biased to a switching position that blocks the first pilot control line 44 in the direction of flow toward the variable pump 12. The control unit 42 can be used to switch the pilot control valve 46 to a switching position that releases the first pilot control line 44.

[0031] In this exemplary embodiment, in the first switching position RV1 of the control valve 18, the second pilot control line 48 is connected to the third connecting line 28. In the second switching position RV2 of the control valve 18, the second pilot control line 48 is connected to the fourth connecting line 30. In the accumulator pressurization position RV3 of the control valve 18, the second pilot control line 48 is blocked. The second pilot control line 48 leads via the first reciprocating valve 50 to the first pilot control line 44 between the pilot control valve 46 and the variable pump 12.

[0032] A first branch line 70 branches off from the third connecting line 28 between the pitch cylinder 22 and the flow control element 62. The first branch line 70 leads to either the fifth connecting line 32 or the sixth connecting line 38. A first emergency valve 66 is disposed in the first branch line 70. In this exemplary embodiment, the first emergency valve 66 is configured as a solenoid-actuated 2 / 2-way valve. The first emergency valve 66 is biased to a position that releases the switching of the first branch line 70. The control unit 42 can be used to switch the first emergency valve 66 to a position that blocks the switching of the first branch line 70.

[0033] The second branch line 72 branches off from the fourth connecting line 30 between the pitch cylinder 22 and the control valve 18. The second branch line 72 leads directly to the second connecting line 26, wherein the second emergency valve 68 is disposed in the second branch line. In this exemplary embodiment, the second emergency valve 68 is configured as an electromagnetically actuated proportional 2 / 2-way valve. The second emergency valve 68 is biased to a position that releases the switching of the second branch line 72. The control unit 42 can be used to switch the second emergency valve to a position that blocks the switching of the second branch line 72.

[0034] The first emergency valve 66 and the second emergency valve 68 are configured in a known manner for emergency control of the hydraulic system 10, for example, in the event of a power outage. Therefore, during normal operation, the first emergency valve 66 and the second emergency valve 68 are energized via the control unit 42.

[0035] The operation of the hydraulic system 10 for setting the pitch angle will be described below.

[0036] To adjust the pitch angle by extending the pitch cylinder 22, control valve 18 is switched to the first switching position RV1 via control unit 42. Simultaneously, control unit switches dynamic valve 16 to the second switching position DV2, thereby connecting hydraulic accumulator 14 to the first connecting line 23. At this time, variable pump 12 has not yet swung out, only providing dp pressure. In the first switching position RV1 of control valve 18, hydraulic accumulator 14 pressurizes the first connecting line 24 and the third connecting line 28 connected to the first connecting line 24, causing pitch cylinder 22 to extend. The load pressure signal of the third connecting line 28 is received via the second pilot control line 48 and fed to the first pilot control line 44 via the first reciprocating valve 50. Therefore, a pilot pressure signal is applied to variable pump 12, causing variable pump 12 to swung out. Once variable pump 12 supplies sufficient quantity, dynamic valve 16 is switched to the first switching position DV1 via control unit 42 due to preload, and hydraulic accumulator 14 is disconnected from the first connecting line 24. Currently, only variable pump 12 supplies oil to pitch cylinder 22. The hydraulic oil discharged from the rod side of pitch cylinder 22 flows out through the fourth connecting line 30 and is guided to hydraulic accumulator 14 through the sixth connecting line 38.

[0037] To adjust the pitch angle by retracting the pitch cylinder 22, control valve 18 is switched to the second switching position RV2 via control unit 42. Simultaneously, control unit switches dynamic valve 16 to the second switching position DV2, thereby connecting hydraulic accumulator 14 to the first connecting line 23. At this time, variable pump 12 has not yet swung out, only providing dp pressure. In the second switching position RV2 of control valve 18, hydraulic accumulator 14 pressurizes the first connecting line 24 and the fourth connecting line 30 connected to the first connecting line 24, causing pitch cylinder 22 to begin retracting. The load pressure signal of the fourth connecting line 30 is received via the second pilot control line 48 and fed to the first pilot control line 44 via the first reciprocating valve 50. Therefore, a pilot pressure signal is applied to variable pump 12, causing variable pump 12 to swung out. Once variable pump 12 supplies sufficient quantity, dynamic valve 16 is switched to the first switching position DV1 via control unit 42 due to preloading, and hydraulic accumulator 14 is disconnected from the first connecting line 24. Currently, only variable pump 12 supplies oil to pitch cylinder 22. Hydraulic oil discharged from the piston side of pitch cylinder 22 flows out in a controlled manner through third connecting line 28 and flow control element 62, and is discharged to oil tank 20 through second connecting line 26.

[0038] To pressurize the hydraulic accumulator 14, control valve 18 is switched to the accumulator pressurization position RV3 via control unit 42. Simultaneously, pilot control valve 46 is switched to the switching position of releasing the first pilot control line 44 via control unit 42. The dP pressure received from the first connecting line 24 is transmitted to the variable pump 12 as a pilot pressure signal, causing the variable pump 12 to swing out. Then, increasing pressure is supplied to the hydraulic accumulator 14 via the fifth connecting line 32, which is provided by the variable pump 12. As shown, to achieve this, dynamic valve 16 is configured such that flow toward the hydraulic accumulator 14 can also be achieved in the first switching position DV1 of dynamic valve 16. Of course, during the accumulator pressurization operation, dynamic valve 16 can also be switched to the second switching position DV2 via control unit 42.

[0039] Figure 3 A second exemplary embodiment of the hydraulic system 10 according to the present invention is shown. The second exemplary embodiment is... Figure 2 The exemplary embodiments shown differ in that the configuration of the load pressure signaling circuit is different.

[0040] In this exemplary embodiment, the load pressure signaling circuit has a third pilot control line 52, which branches off from the first pilot control line 44 between the control valve 18 and the pilot control valve 46. The third pilot control line 52 then flows back through the second reciprocating valve 54 to the first pilot control line 44 between the pilot control valve 46 and the variable pump 12. A preload valve 56 is provided in the third pilot control line 52. The pressure in the first pilot control line 44 can be preloaded to a defined pressure level by the preload valve 56, thus allowing a larger pilot pressure signal to be applied to the variable pump 12 compared to the first exemplary embodiment. Therefore, the swing amplitude of the variable pump 12 is greater.

[0041] Furthermore, the load pressure signaling circuit has a pressure relief line 58 that branches off from the first pilot control line 44 between the variable pump 12 and the first reciprocating valve 50. The pressure relief line 58 is connected to the tank 20 to release any residual pressure that may be trapped in the first pilot control line 44, allowing the variable pump 12 to safely swing back to the zero position. For this purpose, a pressure relief element 60 is provided in the pressure relief line 58. In this exemplary embodiment, the pressure relief element 60 is configured as a pressure relief valve to throttle and reduce the pressure in the first pilot control line 44, preventing unexpected collapse of the pilot control pressure signal in the first pilot control line 44.

[0042] Figure 4A third exemplary embodiment of the hydraulic system 10 according to the present invention is shown. The hydraulic system 10 according to the third exemplary embodiment does not have a load pressure signaling circuit. Instead, the pilot control valve 46 is configured as an electromagnetically actuated proportional 3 / 3 directional control valve, which can be controlled by the control unit 42 in such a way that the first pilot control line 44 is blocked or connected to the variable pump 12. Furthermore, the pilot control valve 46 can also be switched to a switching position by the control unit 42, in which the pilot pressure signal applied to the variable pump 12 is released to the tank 20. This ensures that there is no residual pressure between the pilot control valve 46 and the variable pump 12, preventing the variable pump 12 from swinging back.

[0043] It should also be noted that the various components in different embodiments can be combined together. For example, it is conceivable that a pressure relief line with a pressure relief element may also be provided in the first or third embodiment. Furthermore, it should be noted that numbers such as "first" and "second" are used only for distinction and do not specify a mandatory order.

[0044] List of reference numerals 10 Hydraulic System 12 variable pump 14 Hydraulic accumulators 16 dynamic valves 18 control valves 20 fuel tanks 22 pitch cylinder 24 First connecting pipeline 26 Second connecting pipeline 28 Third connecting pipeline 30 Fourth connecting pipeline 32 Fifth connecting pipeline 34-interface 36 First check valve 38 Sixth connecting pipeline 40 Second check valve 42 control units 44 First pilot control line 46 pilot control valve 48 Second pilot control line 50 First reciprocating valve 52 Third Pilot Control Line 54 Second reciprocating valve 56 Preload Valve 58 Pressure Relief Pipeline 60 pressure relief element 62 Flow control elements 64 position sensors 66 First Emergency Valve 68 Second Emergency Valve 70 First Branch Pipeline 72 Second Branch Pipeline 74 Load Pressure Regulator 76 Fourth Pilot Control Line First switching position of DV1 dynamic valve The second switching position of the DV2 dynamic valve First switching position of RV1 control valve The second switching position of the RV2 control valve RV3 control valve accumulator charging position 100 wind turbine 102 towers Cabin 104 106 rotor 108 rotor blades 110 sensor system 112 rims

Claims

1. A hydraulic system (10) for adjusting the pitch angle of the rotor blades (108) of a wind turbine (100), the hydraulic system (10) comprising a variable pump (12), a hydraulic accumulator (14), a dynamic valve (16), a control valve (18), an oil tank (20), and a pitch cylinder (22). in, The variable pump (12) is connected to the control valve (18) via a first connecting line (24) without a rotational feedthrough. The control valve (18) is connected to the oil tank (20) via a second connecting line (26) without a rotational feedthrough. The control valve (18) is connected to the piston side of the pitch cylinder (22) via a third connecting line (28) without a rotational feedthrough. The control valve (18) is also connected to the rod side of the pitch cylinder (22) via a fourth connecting line (30) without a rotational feedthrough. This causes the first connecting line (24) to be connected to the third connecting line (28) in the first switching position (RV1) of the control valve (18), and In the second switching position (RV2) of the control valve (18), the first connecting line (24) is connected to the fourth connecting line (30), and the second connecting line (26) is connected to the third connecting line (28). The hydraulic accumulator (14) is connected to the first connecting pipeline (24) via a fifth connecting pipeline (32), and the fifth connecting pipeline (32) leads to the first connecting pipeline (24) at an interface (34). The dynamic valve (16) is located in the fifth connecting pipeline (32), and The dynamic valve (16) blocks the fifth connecting line (32) along the flow direction from the hydraulic accumulator (14) to the first connecting line (24), and releases the fifth connecting line (32) at the second switching position (DV2). The hydraulic accumulator and dynamic valve are used to compensate for the delay in the flow rate provided by the variable pump.

2. The hydraulic system (10) according to claim 1. Its features are, The control valve (18) is a proportional control valve.

3. The hydraulic system (10) according to claim 1. Its features are, A first check valve (36) that opens in the flow direction from the variable pump (12) to the control valve (18) is located upstream of the interface (34) in the first connecting line (24).

4. The hydraulic system (10) according to any one of claims 1 to 3. Its features are, The hydraulic accumulator (14) is connected to the fourth connecting line (30) via the sixth connecting line (38), wherein the control valve (18) blocks the fourth connecting line (30) in the first switching position (RV1).

5. The hydraulic system (10) according to claim 4. Its features are, in, A second check valve (40) that opens in the flow direction from the fourth connecting line (30) to the hydraulic accumulator (14) is provided in the sixth connecting line (38).

6. The hydraulic system (10) according to claim 1. Its features are, The hydraulic system (10) includes a control unit (42).

7. The hydraulic system (10) according to claim 6. Its features are, The dynamic valve (16) is biased to a first switching position (DV1) and can be actuated by the control unit (42) to switch to a second switching position (DV2).

8. The hydraulic system (10) according to claim 6 or 7. Its features are, The control valve (18) can be switched to the first switching position (RV1) or the second switching position (RV2) by the control unit.

9. The hydraulic system (10) according to claim 8. Its features are, The control valve (18) can be switched to the accumulator charging position (RV3), and the first connecting line (24), the second connecting line (26), the third connecting line (28) and the fourth connecting line (30) are all blocked in the accumulator charging position (RV3). When the control valve (18) is in the accumulator charging position (RV3), the hydraulic accumulator (14) can be charged through the fifth connecting line (32).

10. The hydraulic system (10) according to claim 6. Its features are, A first pilot control line (44) branches out from the first connecting line (24), wherein a pilot control pressure signal can be applied to the variable pump (12) through the first pilot control line (44).

11. The hydraulic system (10) according to claim 10. Its features are, A pilot control valve (46) is disposed in the first pilot control line (44), and the pilot control valve (46) is configured to block or release the first pilot control line (44) and / or release the pilot control pressure signal applied to the variable pump (12) to the oil tank (20).

12. The hydraulic system (10) according to claim 11. Its features are, The pilot control valve (46) can be actuated by the control unit to block or release the first pilot control line (44) or release pressure to the oil tank (20).

13. The hydraulic system (10) according to any one of claims 11 to 12. Its features are, The hydraulic system includes a second pilot control line (48), which is connected to the first pilot control line (44) via a first reciprocating valve (50). In the first switching position (RV1) of the control valve (18), the second pilot control line (48) is connected to the first connecting line (24) or the third connecting line (28), and In the second switching position (RV2) of the control valve (18), the second pilot control line (48) is connected to the fourth connecting line (30).

14. The hydraulic system (10) according to claim 13. Its features are, The hydraulic system (10) includes a third pilot control line (52) that branches off from the first pilot control line (44) between the control valve (18) and the pilot control valve (46) and connects to the first pilot control line (44) between the pilot control valve (46) and the variable pump (12) via a second reciprocating valve (54). A preload valve (56) is provided in the third pilot control line (52) to preload the pilot control pressure signal in the first pilot control line (44) to a defined pressure.

15. The hydraulic system (10) according to claim 14. Its features are, The first pilot control line (44) depressurizes the oil tank (20) through the pressure relief line (58), wherein the pressure relief element (60) is disposed in the pressure relief line (58).

16. The hydraulic system (10) according to claim 15. Its features are, The pressure relief element (60) is a pressure relief valve (60).

17. The hydraulic system (10) according to claim 1. Its features are, The flow control element (62) is disposed in the third connecting line (28).

18. The hydraulic system (10) according to claim 17. Its features are, The flow control element (62) is configured as a pressure valve and a bypass line that bypasses the pressure valve along the flow direction from the control valve (18) to the pitch cylinder (22).

19. A wind turbine (100) comprising a tower (102), a nacelle (104) disposed on the tower, and a rotor (106) rotatably mounted on the nacelle (104) via a hub (112), at least one rotor blade (108) being rotatably disposed on the rotor (106) at a pitch angle relative to the hub (112), the wind turbine (100) having a hydraulic system (10) for changing the pitch angle according to any one of claims 1-18, the hydraulic system (10) being disposed in the hub (112).

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