Hydraulic pitch drive system

Abstract

One aspect of the present invention relates to a hydraulic pitch drive system for controlling the pitch angle of blades on a rotor of a wind turbine. The pitch drive system includes a hydraulic cylinder having a piston side A and a connecting rod side B. The hydraulic cylinder is arranged to actuate blade pitch rotation. The pitch drive system also includes a first hydraulic proportional valve V3, which is arranged to control the flow of hydraulic oil from a pressure port P to the hydraulic cylinder in response to a primary control signal S3. In the hydraulic cylinder's extend mode, the pressure port P is connected to the piston side A of the hydraulic cylinder via the first hydraulic proportional valve V3. The connecting rod side B of the hydraulic cylinder is connected to the pressure port P via a check valve V6. The pitch drive system also includes a first control module configured to provide a primary control signal S3 in response to a blade pitch angle positioning request. The pitch drive system also includes: a second hydraulic proportional valve V4, which is arranged to control the flow of hydraulic oil from the connecting rod side B to the tank port T in response to the secondary control signal S4 without relying on the first hydraulic valve V3; and a second control valve, which is configured to provide the secondary control signal S4 so as to control the second proportional valve V4 in the extension mode of the hydraulic cylinder according to the control scheme.

Description

Technical Field

[0001] In one aspect, the present invention relates to a hydraulic pitch drive system for controlling the pitch angle of blades on a wind turbine rotor. In another aspect, the present invention relates to a wind turbine comprising a rotor having one or more blades and a hydraulic pitch drive system for controlling the pitch angle of the rotor blades. In yet another aspect, the present invention relates to a method for controlling a hydraulic pitch drive system for controlling the pitch angle of blades on a wind turbine rotor. Background Art

[0002] A wind turbine has a rotor that converts wind energy into rotational motion about a rotor axis. The energy from this rotational motion can be converted into useful energy via a converter, typically a generator, which produces electrical energy for supply to the power grid. Typically, the converter and other equipment are housed in a nacelle at the top of the tower. The rotor has a hub mounted on the rotor shaft and at least one blade mounted on the hub. The hub includes a hub shell that is typically accessible from the inside for servicing and maintenance. Modern wind turbines often feature a pitch system that allows the blades to rotate relative to the hub about the blade axis to control the blade pitch angle β relative to the hub. The blade axis extends radially outward from the rotor axis and follows the longitudinal axis of the blade. The root of one or more blades is mounted to an attachment flange on the hub shell via the pitch system. A typical pitch system includes a pitch bearing, whose fixed portion is configured to couple the bearing to the hub and whose movable portion is configured to couple the blade to the bearing. Furthermore, the pitch system typically comprises an actuator for driving the pitch motion and a pitch control system for controlling the pitch motion according to a blade pitch request from a wind turbine controller. The blade pitch motion request may comprise a command for setting the blade pitch angle β and / or its time derivative (i.e., velocity dβ / dt and / or acceleration d 2 β0 / dt 2 Such instructions may typically include target values for blade pitch positioning, such as a target blade pitch angle β0 and / or its time derivative, i.e. a target speed dβ0 / dt and / or a target acceleration d of the requested blade pitch movement. 2 β0 / dt 2 .

[0003] An important class of modern pitch drive systems uses hydraulic actuation to control the pitch angle of adjustable blades on a wind turbine comprising a rotor having one or more, or at least two, and typically three blades. A hydraulic pitch drive is located at the root of each blade. The pitch drive provides a rotatable bearing for pitch rotation about the longitudinal axis of the blade. The pitch rotation of each blade is hydraulically actuated by means of one or more, typically one or two, linear hydraulic cylinders, each of which is attached to the rotor hub at one end and to the blade at the other. By expanding and contracting the hydraulic cylinders, a bearing element fixed to the blade can be rotated relative to a bearing element fixed to the rotor hub, thereby adjusting the blade pitch.

[0004] Proper sizing of hydraulic components and design pressures for hydraulic pitch drive systems are considered critical to the safe, reliable, and efficient operation of wind turbines with adjustable blade pitch angles. However, selecting the sizing of components in the system and the corresponding design pressures can involve balancing competing criteria. Furthermore, the design of the hydraulic pitch drive directly impacts the initial component cost as well as the operating and ownership costs of the wind turbine. Therefore, there is a need for increased design flexibility for designers of hydraulic pitch drive systems.

[0005] US 2019 / 0055922 A1 discloses a pitch control system for wind turbine blade pitch control. US2019 / 0055922A1 describes an auxiliary pitch force subsystem that can increase the pitch force of the hydraulic piston controlled by the main pitch force subsystem. However, starting the auxiliary subsystem described in US 2019 / 0055922 A1 will shorten the life of the hydraulic piston unless it is started based on a prediction of future excessive loads and before the excessive load is predicted to occur. Therefore, the system requires an additional control layer with a prediction module, which increases the complexity of the system. In addition, when the control system cannot correctly predict a specific excessive load situation and operates in a response mode, starting the auxiliary subsystem described in US 2019 / 0055922 A1 will still shorten the life of the hydraulic piston.

[0006] EP2458201A1 discloses another hydraulic blade pitch system for controlling the pitch of a single blade of a wind turbine rotor. The hydraulic blade pitch system can have redundant linear hydraulic actuators that are arranged to operate in parallel. In one embodiment, the system described in EP2458201A1 provides a one-way valve that can be controlled to an open position so that the liquid contents of the piston connecting rod chamber of the hydraulic actuator can be discharged to the low-pressure oil tank line through the main control valve, rather than recirculating the hydraulic oil from the piston connecting rod chamber to the high-pressure return line to prevent a higher pressure difference from being required on the piston of the hydraulic actuator. In any case, EP2458201A1 does not address the problem of shortened life of the hydraulic cylinder caused by such operating mode.

[0007] Therefore, there remains a need for a hydraulic pitch drive system with higher efficiency, higher response speed and / or reduced cost without sacrificing safety and reliability.

[0008] In view of these needs, it is an object of the present invention to improve a hydraulic pitch drive system compared to known hydraulic pitch drive systems with auxiliary pitch force arrangements, or at least to provide an alternative. Summary of the Invention

[0009] According to one aspect, the object of the invention is achieved by a hydraulic pitch drive system for controlling the pitch angle of blades on a rotor of a wind turbine according to claim 1 , advantageous embodiments of the hydraulic pitch drive system being as defined in the dependent claims and as disclosed herein.

[0010] According to one broad aspect, there is provided a hydraulic pitch drive system for controlling the pitch angle of blades on a rotor of a wind turbine, the pitch drive system comprising:

[0011] a hydraulic cylinder having a piston side A and a connecting rod side B, the hydraulic cylinder being arranged to actuate the pitch rotation of the blades;

[0012] a first hydraulic proportional valve V3, arranged to control the flow of hydraulic oil from a pressure port P to the hydraulic cylinder in response to a primary control signal S3; wherein in an extension mode of the hydraulic cylinder, the pressure port P is connected to the piston side A of the hydraulic cylinder via the first hydraulic proportional valve V3; wherein the connecting rod side B of the hydraulic cylinder is connected to the pressure port P via a valve V6;

[0013] A first control module, the first control module being configured to provide the primary control signal S3 in response to a blade pitch angle positioning request;

[0014] a second hydraulic proportional valve V4 arranged to control the flow of the hydraulic oil from the connecting rod side B to the tank port T in response to a secondary control signal S4, independently of the first hydraulic valve V3; and

[0015] The second control module is configured to provide the secondary control signal S4 so as to control the second hydraulic proportional valve V4 in the extension mode of the hydraulic cylinder.

[0016] The second hydraulic proportional valve V4 is controlled according to a control scheme that can be implemented in the second control module.

[0017] The hydraulic control logic thus implemented provides two operating modes in the extension mode of the hydraulic cylinder. In the primary extension operating mode, pressurized hydraulic oil from the connecting rod side B is regenerated to the pressure port P of the hydraulic pitch drive system through valve V6. In the primary extension operating mode, the connecting rod side pressure P3 substantially corresponds to the first pressure at the pressure port P. Thus, efficient operation under normal load conditions is ensured. In the secondary extension operating mode, the connecting rod side pressure P3 is reduced in a controlled manner according to the secondary control signal S4, which is generated in the second control module according to the control scheme. Typically, the control scheme identifies a situation where a high load is present or expected, or equivalently a situation where a rapid extension is required or expected. Once this situation is determined, the secondary valve (boost valve) can be controlled to reduce the connecting rod side pressure accordingly by returning the hydraulic oil to the tank port in a controlled manner. Thus, a boost mode is provided in the extension mode of the hydraulic cylinder, thereby improving system performance, for example in terms of responsiveness and the peak load that a given hydraulic pitch drive system can handle. During the design phase, when designing a hydraulic pitch drive system based on given design performance specifications, performance improvements provide sizing advantages, enabling system cost reduction and / or performance improvement.

[0018] The need for increasing the pitch force can be determined by processing measured parameters from the hydraulic pitch system, such as hydraulic pressure values, cylinder position, velocity or acceleration, actual spool position of the primary valve V3, or similar parameters indicating the state of a time-dependent load curve on the hydraulic pitch drive system. Processing can include accumulating a history of measured data and applying estimation algorithms, such as those involving interpolation, extrapolation, or more complex prediction algorithms. Alternatively or in addition, the need for force boost can also be determined from commands or positioning requests received by the hydraulic pitch drive system from the wind turbine controller, as also described in further detail below.

[0019] The boosted, two-stage extension mode of operation is not always active but can be temporarily applied as needed according to a control scheme, for example, based on a parameter indicative of cylinder load. Thus, a surprising discovery of the present invention is that the highly efficient, regenerative, primary extension mode of operation can be maintained active most of the time, while the boosted, two-stage extension mode of operation is only activated transiently for brief periods of time. Thus, surprisingly, the aforementioned performance / sizing advantages do not come at the expense of hydraulic efficiency, becoming a viable design option.

[0020] By providing the second hydraulic valve V4 as a hydraulic proportional valve, dynamic control of the connecting rod side pressure under high load (or high speed) conditions during the extension movement can be achieved, as described in further detail below.

[0021] One advantageous aspect of the present invention provides a hydraulic pitch drive system for controlling the blade pitch angle of one or more blades on a rotor of a wind turbine, the pitch drive system comprising:

[0022] a hydraulic cylinder having a piston side A and a connecting rod side B, the hydraulic cylinder being arranged to actuate the pitch rotation of the blades;

[0023] a first hydraulic proportional valve V3 configured to control the flow of hydraulic oil from the pressure port P to the hydraulic cylinder in response to a primary control signal S3; wherein in an extension mode of the hydraulic cylinder, the pressure port P is connected to the piston side A of the hydraulic cylinder via the first hydraulic proportional valve V3;

[0024] a first control module configured to generate a primary control signal S3 in response to a blade pitch angle positioning request; wherein a rod side B of the hydraulic cylinder is connected to a pressure port P via a check valve V6 for regeneration of pressurized hydraulic oil; wherein the rod side B is further connected to a tank port T via a second hydraulic proportional valve V4; wherein the second hydraulic proportional valve V4 is configured to control the flow of hydraulic oil from the rod side B to the tank port T in response to the secondary control signal S4, independently of the first hydraulic valve V3; and

[0025] The second control module is configured to provide the secondary control signal S4 so as to control the second hydraulic proportional valve V4 in the extension mode of the hydraulic cylinder.

[0026] The primary control signal S3 is used to control the first hydraulic proportional valve V3 to operate the hydraulic cylinder according to the blade pitch angle positioning request received by the pitch drive system. Depending on the valve position of the first hydraulic proportional valve V3, the hydraulic cylinder is pressurized to extend or retract it, thereby meeting the positioning request, whether for position, positioning speed and / or acceleration. The hydraulic cylinder is mounted on a rotatable pitch bearing in a known manner to actuate the rotation of the movable blade side part relative to the fixed hub side part. The extension and retraction of the hydraulic cylinder causes the movable part to rotate relative to the fixed part. Therefore, the linear position x of the hydraulic cylinder is directly mapped to the corresponding rotation angle, or blade pitch angle β. Therefore, the first control module of the hydraulic pitch drive system is suitable for controlling the blade pitch angle by generating the primary control signal S3 in response to the blade pitch angle positioning request, typically from the wind turbine controller of the wind turbine.

[0027] The second control module is adapted to generate a control signal S4 and apply the control signal S4 to the second hydraulic proportional valve V4 during extension of the hydraulic cylinder, i.e., in extend mode. Thus, the system is further configured to open and close the second proportional valve V4 in a controlled manner during the extension movement of the hydraulic cylinder according to a control scheme implemented in the second control module. During retract mode, the secondary valve V4 is closed.

[0028] In extend mode, the pressure port pressurizes the piston side of the hydraulic cylinder. When the secondary proportional valve V4 is closed in extend mode, the pressurized hydraulic oil is regenerated from the piston side through the check valve to the pressure port, typically to an accumulator arrangement connected to the pressure port, allowing the blade pitch actuation to respond well under normal operating conditions and loads, achieving efficient operation.

[0029] When the secondary proportional valve is opened in the extend mode in response to the secondary control signal received from the second control module, the pressure on the rod side of the hydraulic cylinder is reduced, thereby increasing the maximum force that the hydraulic cylinder can provide. However, in contrast to an emergency stop, such as an on / off valve or a safety valve, which activates and quickly drains the rod-side hydraulic oil to the tank, the secondary valve of the present invention is conceived as a proportional valve that opens (and closes) in a controlled manner to meter the flow according to the control scheme in a manner that allows continuous, stable and responsive operation according to the kinematic constraints of the blade pitch system, even when the hydraulic blade pitch system is in the continuous blade pitch control operating mode. To allow for simple and predictable control, during the extend mode, the flow from the rod side B to the tank port T through the second proportional valve V4 does not pass through V3, i.e., it bypasses V3 and is therefore independent of the first hydraulic proportional valve V3.

[0030] The second control module distinguishes between normal load operation and high load operation. During normal load operation, the secondary valve remains closed, and hydraulic oil is regenerated from the connecting rod side to the pressure port. During high load operation, the secondary valve is controlled to meter the flow of hydraulic fluid from the connecting rod side to the tank port through the second hydraulic proportional valve. Specifically, the second control module is adapted to set the secondary signal S4 in extend mode to meter leakage flow from the connecting rod side to the tank when the cylinder load is in the opposite direction of the cylinder's extension, i.e., when the cylinder is operating in the first quadrant of hydraulic operation.

[0031] Advantageously, the second control signal is adapted to meter the flow of fluid from the connecting rod side to the tank port through the second hydraulic proportional valve when the second control module determines that the external load on the hydraulic cylinder is oriented opposite to the extension direction of the hydraulic cylinder, more particularly, when the determined load or a load parameter indicative of the cylinder load exceeds a predetermined threshold. Advantageously, the flow rate and / or amount of fluid from the connecting rod side to the tank port is adjusted according to a control scheme. The control scheme advantageously includes a predetermined control stabilization rule for setting the flow rate and / or amount of fluid leakage to the tank through the secondary control valve V4.

[0032] One advantage of this system is that it allows the hydraulic components to be sized based on, for example, normal operating loads determined over a longer timeframe, but also provides a dynamic reserve to cope with high load conditions, which are often transient, i.e., lasting only a short time compared to normal operation. Transient peak loads can be predictable and handled in a predetermined manner, or they can occur randomly but be detected and handled dynamically during operation.

[0033] For example, in a regenerative system without a two-stage proportional valve, the following two parameters are crucial for determining hydraulic cylinder sizing: the maximum extension force F_op,ext during regenerative operation; and the maximum extension force F_em,ext during an emergency stop. During the extension motion under normal load regenerative operation, the pressure on the connecting rod side corresponds to the pressure at the pressure port, and the maximum force F_op,ext can be determined as the product of the pressure P1 supplied at pressure port P and the cross-sectional area of the hydraulic cylinder's connecting rod position: A_rod.F_op,ext = P1.A_rod. However, during an emergency stop, the oil on the connecting rod side is drained to the tank port, and the pressure on the connecting rod side can drop to tank pressure. During an emergency stop, the maximum extension force F_em,ext can then be determined as the product of the pressure P1 supplied at pressure port P and the cross-sectional area of the hydraulic cylinder's cylinder bore: A_bore.F_em,ext = P1.A_bore. The difference between the cylinder bore area A_bore and the connecting rod area A_rod is represented as the annular area A_ring. A_ring is also a decisive parameter for the maximum retraction force that can be achieved, wherein a relatively larger ring area relative to the connecting rod location area provides a greater maximum retraction force.

[0034] For a given design specification for a hydraulic pitch drive system, the active metering control of the leakage flow from the connecting rod side directly to the tank port according to an embodiment of the present invention allows the size of the hydraulic cylinder to be set more advantageously than would otherwise be possible. By providing additional dynamic force reserve for handling high load conditions as discussed above, the size of the hydraulic cylinder can be set according to lower requirement values for normal load operation without affecting the efficient and responsive operation required for continuous blade pitch control operation. In particular, for a given annular area determined by the retraction force requirement, the smaller the maximum extension force during operation, the smaller the connecting rod diameter that can be used, thereby allowing the use of a cylinder body with a smaller cylinder bore. Therefore, the sizing advantage of the present invention also facilitates the opposite situation, that is, for a given cylinder bore size of the cylinder body, reducing the diameter of the connecting rod correspondingly increases the annular area, thereby achieving an increase in retraction force.

[0035] As already noted, the hydraulic pitch drive system is particularly useful when in a continuous blade pitch control mode. This mode is particularly useful for controlling blade pitch during wind turbine energy production. In this mode, varying positioning requests are continuously received to continuously optimize production during wind turbine operation. By regenerating pressurized oil under normal operating conditions and metering a controlled amount of leakage fluid to the reservoir port only during high load conditions encountered during the extension movement, improved responsiveness can be achieved for a given size of hydraulic cylinder.

[0036] As mentioned above, the hydraulic oil flow from the connecting rod side B, metered by the second hydraulic valve V4 to the tank port T, does not pass through the first hydraulic proportional valve V3 and is therefore independent of the first hydraulic proportional valve V3. Nevertheless, for example, in conjunction with a parameter indicative of parallel cylinder extension motion, the actual valve spool position of V3 can be measured and used to determine whether an overload condition exists. Thus, the valve spool position of V3 can advantageously serve as a sensor input for determining a load parameter indicative of cylinder load, which can then be used to generate an appropriate secondary control signal S4.

[0037] Valve V6 is used to prevent a hydraulic short circuit between the pressure port P and the tank port T. At the same time, V6 allows hydraulic oil to flow from the rod side B of the hydraulic cylinder to the pressure port P so that the pressurized hydraulic oil can be recirculated to the pump and / or accumulator arrangement of the hydraulic pitch drive system. The valve arrangement of valve V6 and the second hydraulic proportional valve V4 is configured in combination so that when the second hydraulic proportional valve V4 is opened to discharge the proportionally controlled hydraulic oil flow to the tank port, once the rod side pressure P3 drops below a predetermined value corresponding to the pressure port pressure P1 plus an optional valve bias, the return flow of hydraulic oil from the rod side B to the pressure port P via valve V6 is normally stopped. This can be achieved in any suitable way. For example, the check valve V6 can be a one-way valve or a biased one-way valve. Valve V6 can also be provided as an actively controlled on / off valve, which can also be controlled by the second control module, for example, in response to an input parameter indicating a pressure difference across valve V6; or it can also be provided as any other check valve that allows hydraulic oil to flow from rod side B to pressure port P only when rod side pressure P3 exceeds pressure port pressure P1 at least (plus an optional valve bias), and prevents any reverse flow from pressure port P to rod side B when rod side pressure falls below this threshold pressure. When hydraulic oil from the rod side is metered by the second hydraulic proportional valve V4, rod side pressure P3 drops below pressure port pressure P1, and flow from rod side B to pressure port P stops. Instead, hydraulic oil flows to the tank sump through the tank port.

[0038] Furthermore, the inlet of V4 is split between the connecting rod-side port B and valve V6. Therefore, when the connecting rod-side pressure falls below the threshold pressure P_th, the combined arrangement of V4 and V6 prevents any short-circuiting of the flow from pressure port P to tank port T, while also effectively controlling the reduction in connecting rod-side pressure P3 to provide a sufficiently enhanced pitch force reserve. The excellent pressure control achieved by this arrangement avoids sudden changes in the pressure differential across the hydraulic actuators in the system while ensuring reliable and rapid tracking of the actual actuator position relative to the reference position targeted by the pitch controller in response to blade pitch angle requests.

[0039] The amount and rate of hydraulic oil flowing through the second proportional valve V4 to the reservoir is controlled by a secondary control signal S4 according to a predetermined control scheme. This control scheme can be any suitable control scheme, such as an open-loop or closed-loop scheme. For example, in an open-loop control scheme, the second proportional valve V4 can be opened within a controlled time interval, triggered by a control event / satisfied criterion, and the valve opening of the second proportional valve V4 can be controlled to allow fluid to flow at a given flow rate for a given period of time. The flow rate and / or time period can be dynamically determined based on any one or more input parameters, such as hydraulic pressure, actual and target values for a positioning parameter, the position of the first proportional valve, and the vane angle. In a closed-loop control scheme, the opening of the second proportional valve V4 can be controlled and dynamically adjusted based on an error signal determined by comparing the current value with a reference value of the control parameter, wherein the control parameter is determined based on any one or more input parameters, such as hydraulic pressure, actual and target values for a positioning parameter, the position of the first proportional valve, and the vane angle.

[0040] Further, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 is determined to control the set point of the second hydraulic proportional valve V4 in response to one or more parameters indicating a current operating state of the hydraulic pitch drive system.

[0041] The system can include a device suitable for monitoring one or more real-time parameters indicating the current operating state of the hydraulic pitch drive system, the parameters being one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or its time derivative dx / dt or d 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt or d 2 β0 / dt 2, or blade azimuth angle α. Alternatively or in addition, the system may be adapted to communicate with one or more external monitoring devices so as to receive such real-time parameters as input. Thus, real-time operating state parameters can be provided to the first and second control modules of the hydraulic pitch drive system. By controlling the set point of the second hydraulic proportional valve V4 in response to real-time parameters indicative of the current operating state, the hydraulic pitch drive system is able to respond to any external load scenario, including excessive load scenarios caused by external events (whether or not these events are predictable). As further mentioned below, it is particularly advantageous if the second hydraulic proportional valve V4 is opened in response to one or more operating state parameters or quantitative derivatives derived therefrom exceeding a threshold value, which represents a cylinder load F below the maximum force level F_op of the given hydraulic pitch drive system at the rated accumulator operating pressure P1 of the given hydraulic pitch drive system. L . Thus, a sufficient pitch force reserve can be maintained in a continuous manner, thereby allowing a stable and precise tracking response of the hydraulic pitch drive system without undesirable and dangerous interruptions to the blade pitch actuation movement. As is also described in detail below, this is further achieved by embodiments of the present invention without the occurrence of harmful pressure jumps that would significantly affect the service life of the hydraulic components in the system. Thus, the present invention provides a stable and precise tracking hydraulic pitch force system that can be used continuously without being hampered by the need to predict future loads on the hydraulic pitch force system compared to known systems. In particular, embodiments that support and / or contribute to these advantages may include one or more of the embodiments discussed below.

[0042] Further, according to some embodiments of the hydraulic pitch drive system, the control signal S4 is determined based on the cylinder load on the hydraulic cylinder. The secondary control signal S4 can be determined based on the operating state parameters of the pitch drive system during extension of the hydraulic cylinder. Therefore, based on the value of the operating state parameter, the fluid flow through the second hydraulic proportional valve V4 can be controlled. The operating state parameter is a parameter indicating the load acting on the hydraulic cylinder during extension. The load parameter representing the cylinder load can be determined in any suitable manner, for example, based on measured, estimated and / or predetermined operating parameters of the hydraulic pitch drive system, as further described in detail below. By actively controlling the second proportional valve V4 based on the cylinder load, the dynamic force reserve can be controlled in an optimized manner so that the amount of hydraulic oil leaking to the tank port is kept to a minimum.

[0043] Further, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 can be determined with respect to one or more thresholds.

[0044] Further, according to some embodiments of the hydraulic pitch drive system, the threshold value can be set for one or more real-time parameters monitored by the system, or any combination thereof.

[0045] Further, according to some embodiments of the hydraulic pitch drive system, the one or more threshold values can be determined based on one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or a time derivative dx / dt or d 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt or d 2 β0 / dt 2 , or the blade azimuth angle α.

[0046] Further, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 can be configured so that in response to the cylinder load F L When the parameter exceeds the first threshold value, the second hydraulic proportional valve V4 is opened.

[0047] Further, according to some embodiments of the hydraulic pitch drive system, the control signal S4 can be based on an indication of the cylinder load F L The difference between the parameter and the first threshold is determined.

[0048] Further, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 can be configured so that in response to the cylinder load F L When the parameter falls below the first threshold, the second hydraulic proportional valve V4 is closed.

[0049] Further, according to some embodiments of the hydraulic pitch drive system, the first threshold value can represent a load less than the maximum cylinder load F L,max The first threshold cylinder load F L,open , such as at the maximum cylinder load F L,max A first threshold cylinder load F in the range of 50%-90%, or 55%-85%, or 60%-80% L,open .

[0050] Further, according to some embodiments of the hydraulic pitch drive system, the second threshold value can represent a cylinder load F that is less than the first threshold value. L,open The second threshold cylinder load F L,close .

[0051] Further, according to some embodiments of the hydraulic pitch drive system, the second threshold value can represent a cylinder load F that is less than the first threshold value. L,open The second threshold cylinder load F L,close, such as at the maximum cylinder load F L,max The second threshold cylinder load F is within the range of 1%-20%, or 5%-25%, or 10%-20% of L,close and the first threshold cylinder load F L,open The difference between .

[0052] Further, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 is determined based on one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or its time derivative dx / dt or d 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt or d 2 β0 / dt 2 , or the blade azimuth angle α.

[0053] Using a single parameter as the control parameter for determining the secondary control signal provides a simple and effective control scheme that is particularly useful for relatively straightforward operating conditions, which can further reduce the accuracy requirements of the control. For example, assuming that the first pressure P1 remains relatively stable across operating modes, a high load situation can be determined based on an increase in the second pressure P2 or a higher value, such as exceeding a given threshold. Another simple parameter, which is determined solely by the geometry of the actuator, is the target blade pitch angle at which the linear extension force of the hydraulic cylinder is known to result in low torque. The second control module can then determine the secondary control signal in response to this target blade pitch angle to open the second proportional valve accordingly. Similarly, a target speed request indicating a higher blade pitch control speed, or a blade azimuth angle indicating a high load in the pitch bearing due to gravity or aerodynamic forces, can be used to determine a corresponding secondary control signal for opening the second proportional valve to address this situation in a more efficient and responsive manner.

[0054] Further, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 is determined based on a combination of two or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or its time derivative dx / dt or d 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt, d 2 β0 / dt 2 , or the blade azimuth angle α.

[0055] By using a combination of two or more parameters to determine the secondary control signal, more precise control of the flow through the second proportional valve is achieved. Furthermore, a parameter indicative of the current load can be more accurately determined and used to dynamically control the second proportional valve to reduce the connecting rod-side pressure P3 in a controlled manner, thereby improving positioning response.

[0056] For example, the difference between the observed target value and the actual value of the connecting rod position and / or velocity, or the corresponding blade pitch angle, can also be used to control the second proportional valve to achieve more sensitive and precise control behavior. Furthermore, for example, in the absence of load, a comparison of the observed valve spool position y of the first proportional valve V3 with the actual value of the connecting rod velocity or the corresponding blade pitch angle based on a reference map of the system behavior can reveal significant deviations from the reference map. This observed deviation can then be used as a parameter indicative of the cylinder load in a relatively simple, low-cost, yet precise control scheme.

[0057] Furthermore, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 is determined based on the difference between the first pressure P1 at the pressure port P and the second pressure P2 at the piston side A of the hydraulic cylinder. Determining the difference between the first and second pressures P1 and P2, when measured during the extension of each side of the first proportional valve V3, provides an accurate indication of the current load in the system. Thus, in response to the control signal S4 indicating the difference, the connecting rod-side pressure P3 is adjusted accordingly by controlling the opening of the second proportional valve V4, thereby achieving precise and responsive control of the hydraulic pitch drive system.

[0058] Further, according to some embodiments of the hydraulic pitch drive system, determining the secondary control signal S4 includes measuring one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or its time derivative dx / dt or d 2 x / dt 2 , the valve spool position y of the first hydraulic proportional valve V3, the blade pitch angle β and / or its time derivative dβ / dt, d 2 β / dt 2 , or the blade azimuth angle α. For example, in a closed-loop control scheme, measuring one or more input parameters used to determine the secondary control signal allows the valve setting of the second proportional valve V4 to be dynamically controlled during the extension movement based on the measured operating parameters. This allows for a highly precise dynamic response to the control action.

[0059] Further, according to some embodiments of the hydraulic pitch drive system, determining the control signal S4 includes estimating one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or its time derivative dx / dt or d 2 x / dt 2 , blade pitch angle β and / or its time derivative dβ / dt, d 2 β / dt 2 , or the blade azimuth angle α. Thus, an improvement in the responsiveness in the control behavior of a hydraulic pitch drive system is achieved using a relatively simple approach.

[0060] The estimation may include any suitable estimation technique, such as interpolation, extrapolation, prediction algorithms, training algorithms, learning algorithms, calculations and / or approximations using predetermined functions (such as parameterized functions). The estimation may take as input one or more of the above parameters, such as a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or its time derivative dx / dt or d 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt or d 2 β0 / dt 2 , the input value of one or more of the slide position of the first hydraulic valve V3, or the blade azimuth angle α.

[0061] Furthermore, according to some embodiments of the hydraulic pitch drive system, control signal S4 is determined based on a comparison between an actual value and a predetermined reference value of a parameter indicative of the cylinder load. Thus, using a predetermined mapping of parameter values to reference values, a deviation can be determined in a simple manner during the extension mode, and this deviation can be used to distinguish between a normal operating mode in which the second proportional valve is closed and a high-load condition in which the second proportional valve is opened based on the observed deviation. This enhances the responsiveness of the hydraulic pitch drive system in a simple, yet reliable and efficient manner.

[0062] Furthermore, according to some embodiments of the hydraulic pitch drive system, the secondary control signal S4 is selectively determined in response to a predetermined operating command, such as a blade pitch feathering command, thereby improving the responsiveness of the hydraulic pitch drive system in a particularly simple manner for predictable load conditions.

[0063] The following is an advantageous embodiment of a hydraulic pitch drive system having a different advantageous valve arrangement for implementing the second proportional valve V4 and further realizing an emergency function in order to flush the hydraulic oil directly from the connecting rod side to the tank port in case of an emergency stop.

[0064] Furthermore, according to some embodiments of the hydraulic pitch drive system, the second hydraulic proportional valve V4 is one of the following: a normally open flow control valve, a normally closed flow control valve, a normally open pressure control valve, or a normally closed pressure control valve. This provides a simple and cost-effective implementation that can also be flexibly configured through software control.

[0065] Furthermore, according to some embodiments of the hydraulic pitch drive system, the second hydraulic proportional valve V4 is a normally open valve configured to provide a fully open connection from the connecting rod side B to the tank port T when power is lost. This open connection is suitable for emergency shutdown. This achieves a simple and cost-effective implementation and reduces system complexity.

[0066] Furthermore, according to some embodiments of the hydraulic pitch drive system, the second hydraulic proportional valve V4 is a normally closed valve V4b, and the hydraulic pitch drive system further includes a bypass valve structure V4a. When the bypass valve structure V4a is de-energized, the bypass valve structure V4a provides an open connection from the connecting rod side B to the hydraulic oil port T, in parallel with the second hydraulic proportional valve V4b. This open connection is suitable for emergency stopping. Thus, since the valve functions are separated into separate valve components, an implementation with improved reliability is achieved.

[0067] Furthermore, according to some embodiments of the hydraulic pitch drive system, the second hydraulic proportional valve V4 is a hydraulic pilot pressure control valve, such as a hydraulic logic element, an eccentric valve, a counterbalance valve, a sequence valve, a pilot-assisted relief valve, or the like. The pilot pressure used to control the hydraulic pilot pressure control valve can be generated in any suitable manner. This provides significant flexibility in system design, for example, allowing the advantages of hydraulic and electric control logic to be combined.

[0068] For example, the pilot pressure can be provided by an electrically controlled proportional valve, especially during normal operation. This allows for great flexibility in optimizing and adapting the control concept thanks to the digital control logic.

[0069] In some embodiments, the pilot pressure can also be provided by hydraulic components. Therefore, it can be noted that the control signal for controlling the hydraulic proportional valve arrangement can also be derived via hydraulic logic. This allows for a non-electrical implementation that is robust to electrical failures, but at the expense of less flexible implementation.

[0070] Furthermore, according to some embodiments of the hydraulic pitch drive system, the second hydraulic proportional valve V4 is a combination of a hydraulic proportional valve and a pilot-controlled hydraulic logic element, an eccentric valve, or similar component. This allows for both non-electrical operation, such as for emergency shutdown, and electric control, such as for non-emergency operation.

[0071] Furthermore, according to some embodiments of the hydraulic pitch drive system, the hydraulic logic element is controlled by a first pressure P1 at the pressure port P and a second pressure P2 at the hydraulic cylinder piston. Thus, the advantages of reliable operation that is robust to electrical failures are synergistically combined with the advantages of using the observed pressure difference between the first and second pressures as an indicator of cylinder load, wherein the observation of the first and second pressures is directly obtained through the corresponding pilot pressure lines.

[0072] Advantageously, according to some embodiments of the hydraulic pitch drive system, the blade pitch system includes a pitch controller, which is configured to generate a primary control signal S3 for controlling a first hydraulic proportional valve V3 to operate a hydraulic cylinder according to a blade pitch angle positioning request of the pitch drive system; wherein the pitch controller is further configured to generate a secondary control signal S4 for controlling the second hydraulic proportional valve V4 according to a predetermined control scheme.

[0073] According to other aspects of the present invention, a wind turbine includes a rotor having one or more blades and a hydraulic pitch drive system for controlling blade pitch angles of the rotor blades according to any of the embodiments disclosed herein.

[0074] According to further aspects of the present invention, a control method of a hydraulic pitch drive system for controlling the pitch angle of blades on a wind turbine rotor performs steps related to the disclosure of operating the hydraulic pitch drive system according to any embodiment disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] The preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings, in which

[0076] Figure 1 shows a perspective view of a portion of a hub of a wind turbine housing a hydraulic pitch drive system according to one embodiment;

[0077] Figure 2 A hydraulic pitch drive system for a rotor blade according to one embodiment is shown;

[0078] Figure 3 、 Figure 4 shows an elevation view of a hydraulic pitch drive of a hydraulic pitch drive system according to one embodiment in two operating states;

[0079] Figure 5 shows a schematic diagram of a hydraulic pitch drive system according to one embodiment;

[0080] Figure 6shows a schematic diagram of a hydraulic pitch drive system according to another embodiment;

[0081] Figure 7 The on / off valve arrangement is shown;

[0082] Figures 8 to 12 as well as Figure 22 An embodiment of a second hydraulic proportional valve is shown in a different valve arrangement;

[0083] Figure 13 shows a simplified schematic diagram of a hydraulic control circuit of a hydraulic pitch drive system in an extended operating mode according to one embodiment; and

[0084] Figures 14 to 21 Examples of simulated system parameter variations over time for different hydraulic pitch drive systems are shown. DETAILED DESCRIPTION

[0085] refer to Figures 1 to 4 , an embodiment of a hydraulic pitch drive system 20 for use on a rotor of a wind turbine is described. Figure 1 A perspective view of a hub 1 of a wind turbine housing a hydraulic pitch drive system 20 according to one embodiment is shown. The hub 1 is adapted to be connected to a nacelle (not shown) at a flange indicated at 9. The rotor blades 2 are connected at flange 3b. Further flanges 3, 3a are used to connect further blades (not shown). Each blade has a hydraulic pitch drive system 20 comprising at least one hydraulic drive component 5, a so-called pitch cylinder. Each pitch cylinder is connected to a fixed part 7 at a connection point 4, which is capable of receiving a corresponding mounting eyelet of the pitch cylinder (see Figures 2 to 4 The other end of the pitch cylinder is connected to the movable part 6 via a corresponding cylinder bearing 18. An inspection hole 8 can be provided at the windward end of the hub, typically covered by a closure. A bridge 13 is mounted on the fixed part 7. The fixed part 7 is suitable for mounting mechanical, pneumatic, and electric devices, such as the accumulator 10, electrical components 11, and hydraulic components 12 of the hydraulic control system. These devices can be collected on the bridge 13. Figure 3 and Figure 4 Elevation views of the hydraulic pitch drive are shown in two different operating states. Figure 3 The hydraulic pitch drive is shown in the feathering position, with the hydraulic cylinder 5 fully extended. Figure 4 The hydraulic pitch drive is shown in the operating position at the other end of the cylinder stroke, with the hydraulic cylinder fully retracted. Due to the geometry, the conversion of the hydraulic cylinder force into rotational torque becomes increasingly unfavorable when approaching the feathering position from the operating position. Figures 1 to 4In the present invention, although the hydraulic pitch drive system for controlling the pitch angle of blades on the rotor of a wind turbine is shown here with one specific mechanical actuator arrangement, it should be noted that the hydraulic control of the present invention can also be used in the extended mode for other embodiments of the hydraulic pitch drive having different mechanical arrangements of the pitch rotation actuator parts. For example, the movable part for receiving the root of the blade can be formed as a ring instead of a disk. In addition, the movable part can be an outer ring instead of an inner disk or inner ring. In addition, the number of hydraulic cylinders can be different. For example, the number of hydraulic cylinders in the blade pitch actuator arrangement for each blade can be one instead of two, for example, in order to reduce the system complexity and cost of small wind turbines; or the number can be, for example, three, in order to increase the redundancy of the system at the expense of increased system complexity.

[0086] Accordingly, in the following schematics, wherever a single pitch cylinder or hydraulic cylinder is shown or mentioned, this is intended to represent one or more blade pitch actuator arrangements of a wind turbine, each arrangement may comprise one hydraulic cylinder or a plurality of hydraulic cylinders operating in parallel.

[0087] Figure 5 A schematic diagram of a hydraulic pitch drive system 500 according to one embodiment is shown. The schematic diagram provides three basic hydraulic blade pitch drive modes typically provided in a wind turbine with adjustable blade pitch: an extend mode for controlling the extension movement of a hydraulic cylinder during normal operation of the wind turbine; a retract mode for controlling the retract movement of a hydraulic cylinder during normal operation of the wind turbine; and an emergency stop mode for moving the blades to an emergency stop position in an emergency.

[0088] The hydraulic pitch drive system includes a hydraulic cylinder C1 having a piston side A and a connecting rod side B. The hydraulic cylinder is arranged to actuate blade pitch rotation with the aid of a blade pitch brake arrangement (such as the arrangement discussed above). The hydraulic pitch drive system also includes a pressure port P, which provides pressurized hydraulic oil to the hydraulic pitch drive system from a hydraulic pressure unit (not shown) at a first pressure P1, and a tank port T, which is used to collect the hydraulic oil into a tank sump (not shown). The pressure at tank port T is at or near the tank pressure, which is the lowest pressure in the system and typically corresponds to ambient pressure. An accumulator A1 is connected to pressure port P for storing pressurized oil that can be regenerated to the hydraulic pitch drive during operation. Pressure port P is typically connected to tank port T via a safety valve V2 and a service valve V5. Valve V2 is normally closed during operation unless the pressure on the pressure port side exceeds an unsafe level. Valve V5 is also normally closed during operation and is only opened during inspection and maintenance procedures. The schematic shows the de-energized state, with all actuated valves in their default positions. This de-energized state also corresponds to the system state during an emergency stop. In the de-energized state, valve V1 is fully open to supply pressurized oil to the piston side through port O1; valve V4 is fully open to discharge hydraulic oil from the connecting rod side B through port O2 to the tank port T; and valves V3, V6, and V7 are closed. In emergency mode, the hydraulic cylinder fully extends at the full speed determined by ports O1 and O2, with pressurized oil from the connecting rod side normally sent to the tank port without pressure regeneration. After an emergency stop, the system must be restored before normal operation can resume.

[0089] In the retract mode under normal operation, valves V1 and V4 are closed. Pressurized oil is then metered from pressure port P to rod side B via check valve V7 in a cross-connect configuration (crossed arrow symbol) via the first proportional valve V3. Correspondingly, hydraulic oil is metered from piston side A to tank port T via the first proportional valve V3. The flow through the first proportional valve V3 is controlled in response to a primary control signal S3 provided by the first control module 111. The first control module is configured to provide this primary control signal S3 in response to a blade pitch angle positioning request from a wind turbine controller (not shown). As a result, the rod end is retracted into the cylinder in a controlled manner.

[0090] In the extend mode under normal operation, valve V1 is closed, and under normal load conditions, valve V4 is also closed. In the extend mode, pressure port P is connected to the piston side A of the hydraulic cylinder via the first hydraulic proportional valve V3 in a parallel connection configuration (anti-parallel arrow symbols), and the rod side B of the hydraulic cylinder is connected to pressure port P and accumulator A1 via check valve V6, where pressurized hydraulic oil can be stored in accumulator A1 for regeneration. Flow through the first proportional valve V3 is again controlled in response to a primary control signal S3 provided by the first control module 111, which is configured to provide the primary control signal S3 in response to blade pitch angle positioning requests from a wind turbine controller (not shown). Thus, hydraulic oil flowing from pressure port P via the first hydraulic valve V3 to the piston side B of the cylinder is metered and correspondingly regenerated from the rod side B back to pressure port P via check valve V6. Check valve V7 prevents any flow from the rod side B through the first proportional valve V3 to the tank port T. As a result, under normal load conditions, the extension movement of the connecting rod end from the cylinder body takes place in a controlled manner. For a simplified schematic diagram of the system in the extension mode of operation (in which components relevant only to the retraction mode of operation are omitted), see also Figure 13 , wherein corresponding reference numerals identify corresponding parts.

[0091] To drive the extension movement, hydraulic oil must flow through the first proportional valve. To support this flow, the second pressure P2 on piston side A, downstream of the first proportional valve V3, must be lower than the first pressure P1 upstream of it. When the cylinder body experiences a gradually increasing load in the extension mode, opposing the extension movement (the first quadrant of the hydraulic cylinder's operation), the second pressure P2 approaches P1, and in extreme cases, the extension movement may stall. Throughout the extension movement, which regenerates the pressurized hydraulic oil through the check valve V6, the third pressure P3 on the connecting rod side B essentially corresponds to the first pressure P1.

[0092] The system of the present invention identifies a high load condition during the extension movement and generates a secondary control signal S4 based on the identified cylinder load condition. The secondary control signal S4 is provided to the second proportional valve V4. The second hydraulic proportional valve V4 is configured to control the flow of hydraulic oil from the connecting rod side B to the tank port T in response to the secondary control signal S4, independently of the first hydraulic valve V3. The second control module 112 is configured to provide the secondary control signal S4 to control the second proportional valve V4 in the extension mode of the hydraulic cylinder, thereby reducing the third pressure P3 in a controlled manner. As a result of the reduction in the third pressure P3 on the connecting rod side B, the second pressure P2 on the piston side also decreases compared to the first pressure P1, thereby reestablishing or at least increasing the flow through the first proportional valve V3, bringing it closer to the flow corresponding to the valve position y under low or no load conditions.

[0093] like Figure 5 As indicated, the hydraulic pitch system 500 can be equipped with a sensor suitable for measuring the first pressure P1, the second pressure P2, the third pressure P3, the spool position y of the first hydraulic proportional valve V3, the cylinder position x and / or its time derivative, or the equivalent actual blade pitch angle corresponding to the cylinder position. Based on one or more combinations of these measurements, the current hydraulic operating state of the hydraulic pitch drive system can be determined. The hydraulic operating state may include a load parameter indicating the current cylinder load. The load parameter or corresponding information can be provided to the second control module, which then provides a secondary control signal S4 to control the leakage flow from the connecting rod side B to the tank port T through the second hydraulic proportional valve V4, thereby reducing the pressure P3 accordingly.

[0094] As mentioned above, the flow through the first proportional valve V3, and thus the extension speed dx / dt of the hydraulic cylinder C1, generally depends on the difference between the first and second pressures P1 and P2 in the first quadrant of hydraulic operation. This can be described, for example, as dx / dt = y·c·sqrt(P1-P2), where y is the spool position of the first proportional valve V3 and c is a constant that characterizes the first proportional valve. Therefore, the maximum speed of the hydraulic cylinder (which can be considered a parameter indicative of the responsiveness of the hydraulic pitch drive system) is limited by the value of this pressure difference. In a known system, this limitation can be overcome by using a first proportional valve V3 that is larger in size to achieve a larger constant c. However, by reducing the operating pressure in the hydraulic cylinder during the extension operation via controlled leakage through the second proportional valve V4 as a function of load, the size of the first proportional valve V3 can be kept smaller without affecting the responsiveness of the hydraulic pitch drive system or the like, achieving higher responsiveness for the extension movement for a given selected first proportional valve V3. Thus, the sizing advantages of the hydraulic components of the hydraulic pitch drive system also apply to the first proportional valve V3.

[0095] Figure 6 A schematic diagram of a hydraulic pitch drive system 600 is shown according to another embodiment. Figure 6 The hydraulic pitch drive system 600 is generally similar to Figure 5 . However, the second control module 112 of the hydraulic pitch drive system 600 is directly connected to the sensors for measuring the first and second pressures P1 and P2. The second control module can then be configured to directly determine a load parameter indicative of the cylinder load from a comparison of the observed values of the first and second pressures. Typically, the load parameter is determined based on the difference between the first and second pressures. Therefore, based on the measured value indicative of the current cylinder load, a secondary control signal S4 can be directly generated in order to reduce the third pressure by means of a controlled leakage flow through the second proportional valve V4. In Figure 6In FIG. 6 , the hydraulic pitch drive system 600 is shown having a general proportional valve arrangement 124 including a second proportional valve V4. As further described below, the proportional valve arrangement 124 can advantageously be implemented in many different ways, with advantageous embodiments 724, 824, 924, 1024, 1124, 1224, 1324, 1424 being described below with reference to FIG. Figures 7 to 14 given.

[0096] Figure 7 A valve arrangement 724 is shown having a pulse width modulation (PWM) controlled on / off valve that enables the metered flow to be proportional to the duty cycle of the pulse width modulated signal controlling the valve spool. Figure 7 Valve V4 in the circuit is normally open, providing an emergency stop function. By providing orifice O2 in series with the PWM-controlled valve V4, the flow path is adapted for emergency stop flow. When valve V4 is de-energized, i.e., in the "open" position, orifice O2 determines the maximum flow rate required for emergency operation.

[0097] Figure 8 A valve arrangement 824 is shown having a normally open proportional flow control valve V4. When energized, under normal operation, valve V4 is capable of controlling the leakage flow therethrough in proportion to the applied control signal. Figure 8 When the proportional flow control valve V4 is de-energized, the flow is restricted only by orifice O2, thereby providing the emergency stop function as discussed above.

[0098] Figure 9 A valve arrangement 924 is shown comprising two valves V4a and V4b operating in parallel. Valve V4b is a normally closed proportional flow control valve adapted to control the flow therethrough in proportion to an applied control signal. Figure 9 Valve V4b is closed when power is lost and therefore does not provide an emergency stop flow path. Instead, the emergency stop function is implemented in a simple normally open on-off valve V4a, which is arranged in parallel with proportional flow control valve V4b. When power is lost, V4a is open, and the flow rate through the valve arrangement is determined by orifice O2, which is located on the same branch as valve V4a and connected in series with it.

[0099] Figure 10 A valve arrangement 1024 is shown having a normally open proportional pressure control valve V4. When energized, under normal operation, valve V4 is capable of controlling the upstream pressure (i.e., the third pressure P3) in a manner proportional to the applied control signal. Figure 10 When the proportional pressure control valve V4 is de-energized, the flow is essentially restricted only by orifice O2, thereby providing the emergency stop function discussed above.

[0100] Figure 11A valve arrangement 1124 is shown comprising two valves V4a and V4b operating in parallel. Valve V4b is a normally closed proportional pressure control valve adapted to control an upstream pressure (ie a third pressure P3) in proportion to an applied control signal. Figure 11 Valve V4b is closed when de-energized and therefore does not provide an emergency stop flow path. Instead, the emergency stop function is implemented in a simple normally open on-off valve V4a, which is arranged in parallel with proportional pressure control valve V4b. When de-energized, V4a is open, and the flow rate through the valve arrangement is determined by orifice O2, which is located on the same branch as valve V4a and connected in series with it.

[0101] Figure 12 A valve arrangement 1224 with hydraulic logic is shown, in which the valve opening is directly controlled in response to an applied hydraulic pilot signal. Advantageously, valve spool V4 can be connected to receive first and second pressures P1 and P2 via valve ports 3 and 4 as pilot pressures, with the pilot pressure deviation adjustable to control the pressure difference between first and second pressures P1 and P2, thereby regulating the valve opening for the flow path from port 2 to port 1 of the valve. Load-dependent in-situ control of the third pressure P3 on the connecting rod side is thus achieved directly and hydraulically. It should be noted that control signal S4 for controlling the hydraulic proportional valve arrangement can also be derived via hydraulic logic.

[0102] exist Figure 22 , a further valve arrangement 2224 is shown, in which this solution is achieved by controlling the pilot pressure of an eccentric valve 2226 using a proportional control valve 2225. In this solution, the flow from the rod side B of the hydraulic cylinder to the tank port T no longer passes through the proportional control valve 2225, but instead passes through the eccentric valve 2226. However, this flow, and the resulting pressure P3 on the rod side B of the hydraulic cylinder, is still controlled by the control signal S4 via the proportional control valve 2225.

[0103] Examples

[0104] Now go to Figures 14 to 21 The following example illustrates the comparison of the simulated system performance of four different hydraulic pitch drive systems in the extension mode of the hydraulic cylinder. Figure 13 The simplified schematic diagram of the hydraulic control circuit of the hydraulic pitch drive system shown and described above is discussed, and the corresponding modifications will be described in further detail below.

[0105] All systems are considered to be subject to Figure 14 The external load versus time curves shown in Figure 15 The curve of the reference position changing with time is shown. For the convenience of comparison, the external load value FL The values are scaled relative to the maximum force level F_op of a given hydraulic pitch drive system at nominal accumulator operating pressure P1, where the maximum force level F_op corresponds to 100%. Positive values of the external load correspond to forces directed in the direction opposite to the extension actuation motion of the hydraulic cylinder, while negative values of the external load correspond to forces directed in the direction parallel to the extension actuation motion of the hydraulic cylinder. The position value x is scaled relative to the maximum cylinder stroke, where the maximum stroke length corresponds to 100%. Figure 14 and Figure 15 The simulated curves shown represent the time dependence of the external loads and the reference positions requested by the wind turbine controller, as can be observed during actual typical operation of a wind turbine, and these curves include a period of excessive load between t=1.9 s and t=2.9 s, during which the maximum force level F_op is exceeded, with the maximum external load reaching 120% at t=2.4 s.

[0106] In order to evaluate the system performance of four different hydraulic pitch drive systems, the system performance of each of these systems is simulated for three real-time parameters, namely the connecting rod side pressure P3 at the connecting rod side B of the hydraulic cylinder, the piston side pressure P2 at the piston side A of the hydraulic cylinder, and the connecting rod position x of the hydraulic cylinder. Figure 14 External load curve and Figure 15 The simulated response of the reference position curve is shown in Figure 2. The pressure values for the connecting rod pressure P3 and the piston pressure P2 are scaled relative to the accumulator operating pressure P1 (corresponding to 100%). The connecting rod position values are scaled relative to the maximum cylinder stroke (just like the reference position values), where the length of the maximum cylinder stroke corresponds to 100%.

[0107] Example 1 is marked as "no control" here, which is for Figure 13 The hydraulic pitch drive system is schematically shown, with the modification that valve V4 is not present or at least remains closed throughout the monitoring period. Figure 16 The corresponding pressure curves of the connecting rod side pressure P3 and the piston side pressure P2 during the monitoring period are shown. Figure 17 Shown again Figure 15reference position and schematically shows the actual position of the cylinder piston during the monitoring time period in the "no control" arrangement. The connecting rod side pressure P3 is consistent with the rated operating pressure P1 of the accumulator, where the hydraulic oil is recirculated from the connecting rod side B to the pressure port P through the check valve V6. As long as the external load is below 100%, the piston side pressure P2 is basically consistent with the external load curve. However, when the external load approaches and exceeds 100%, the piston side pressure also approaches the rated operating pressure P1 of the accumulator and reaches saturation there. Therefore, the flow of hydraulic oil on the primary hydraulic proportional valve V3 from pressure port P to piston side A stagnates. The piston cannot maintain any further extension actuation movement. Since friction is a significant part of the external load, the hydraulic pitch drive system pauses until the external load drops below 100% again, the piston side pressure P2 drops below, and the extension movement can be resumed, as shown Figure 17 The open circle marking the actual piston position x is shown schematically.

[0108] Example 2 is labeled "Independent Proportional Control" and is for Figure 13 The hydraulic pitch drive system according to one embodiment of the present invention is schematically shown in FIG. 1 , wherein the secondary valve V4 is a hydraulic proportional valve controlled in response to the secondary signal S4, such as Figures 8 to 12 The valve arrangement of any one of the embodiments shown in . Figure 18 The corresponding pressure curves for the rod-side pressure P3 and the piston-side pressure P2 during the monitoring period are shown. As in Example 1, the piston-side pressure P2 initially largely corresponds to the external load profile, as the hydraulic pitch system is controlled to track the reference position requested by the wind turbine controller via the primary hydraulic proportional valve V3. However, in response to detecting that the piston-side pressure P2 exceeds a threshold of 80%, a secondary control signal S4 is generated, causing the second hydraulic proportional valve V4 to gradually open. The set point of the second hydraulic proportional valve V4 can be determined based on the difference between the piston-side pressure P2 and the threshold. When the piston-side pressure P2 again drops below the threshold, the second hydraulic proportional valve V4 can be closed again. By gradually opening the second hydraulic proportional valve, hydraulic oil is discharged directly to the tank port T in a well-controlled manner, independent of the setting of the primary hydraulic proportional valve V3. Therefore, depending on the setting of the second hydraulic proportional valve V4, the rod-side pressure P3 can be reduced in a well-controlled manner, independent of the flow control of the pressurized hydraulic oil from the pressure port P to the piston side A via the first hydraulic proportional valve V3. Compared to the "uncontrolled" configuration in Example 1, the piston side pressure P2 is also gradually controlled to a lower value and no longer reaches saturation in the excessive external load region. As a result, the hydraulic pitch drive system of Example 2 reliably maintains the pitch force reserve, allowing the hydraulic cylinder to maintain uninterrupted extension actuation movement even in the excessive external load region.

[0109] Example 3 is labeled "Digital Control" and is for Figure 13 The hydraulic pitch drive system shown in FIG. 1 is modified in that the second valve V4 is a hydraulic switch valve controlled in response to the secondary signal S4, such as Figure 7 Valve arrangement. Figure 19 The corresponding pressure curves of the connecting rod side pressure P3 and the piston side pressure P2 during the monitoring period are shown. As in Examples 1 and 2, the piston side pressure P2 initially essentially corresponds to the external load curve because the hydraulic pitch system is controlled by means of the primary hydraulic proportional valve V3 to track the reference position requested by the wind turbine controller. However, in response to monitoring that the piston side pressure P2 exceeds the threshold of 80%, a secondary control signal S4 is generated, instructing the switching valve to open, thereby allowing the hydraulic oil to be drained from the connecting rod side to the tank port. As a result, the connecting rod side pressure P3 drops rapidly, and the piston side pressure also drops rapidly. As a result, a large pitch force reserve is provided almost instantaneously, facilitating controlled extension actuation of the hydraulic cylinder even in the excessive external load range.

[0110] Example 4 is labeled "Dependent Proportional Control" and is for Figure 13 The hydraulic pitch drive system schematically shown in FIG. 1 is modified in that the second valve V4 is a hydraulic switching valve controlled in response to the secondary signal S4, such as according to Figure 7 The valve arrangement of Example 4 can be viewed as corresponding to the configuration of Example 4, with the additional modification that the drain line from the second valve V4 to the tank port T passes through the parallel port of the first hydraulic proportional valve V3. Figure 5 or Figure 6 The arrangement of the valve V7 in FIG. 1 is further modified in that, when the hydraulic pitch system is in the extended operating mode, V7 can be controlled to the open position and the second valve arrangement V4 is omitted. Figure 20The corresponding pressure curves for the rod-side pressure P3 and the piston-side pressure P2 during the monitoring period are shown. As in the previous example, as long as the second valve V4 remains closed, the piston-side pressure P2 essentially reflects the external load curve for external loads below the maximum force level F_op. Accordingly, the rod-side pressure P3 reaches 100% saturation within the same range. Once the piston-side pressure P2 exceeds the 80% threshold, the second valve V4 is controlled to the open position. As in Example 3, when the first proportional valve V3 is mostly open, the "dependent proportional control" valve arrangement of Example 4 provides a nearly instantaneous auxiliary pitch force reserve. Adjusting the set point of the first hydraulic proportional valve V3 allows the extension actuation movement of the hydraulic cylinder to be controlled even in the excessive external load range, where the amount of hydraulic oil flowing from the rod side B to the tank will also depend on the set point of the first hydraulic proportional valve V3. Similar to the pressure curves seen in Example 3, opening and closing the second valve V4 results in significant jumps in the rod-side pressure P3 and the piston-side pressure P2. Reducing the pressures P3 , P2 on the connecting rod side and the piston side in this way allows the extension actuation movement to be controlled also in the area of excessive external loads.

[0111] Figure 21 The actual position of the cylinder piston and the position of the valve arrangement of Examples 2, 3 and 4 during the entire monitoring period are shown. Figure 15 Comparison of the reference position, Figure 21 Also included Figure 15 The comparison shows that for the three valve arrangements of Examples 2, 3 and 4, an overall satisfactory tracking performance can actually be achieved. However, significant pressure jumps (such as at Figure 19 and Figure 20 The jumps seen in Examples 3 and 4 in the present invention are harmful to the hydraulic components in the hydraulic pitch drive system and may therefore significantly affect the service life of these components, and in particular the service life of the hydraulic cylinders. In contrast, the arrangement of Example 2, which corresponds to an embodiment of the present invention, does not have such harmful pressure jumps and thus provides good tracking performance in a surprisingly gentle manner, i.e., without sacrificing the service life and durability of the hydraulic pitch drive system. As a result, it is possible to maintain a sufficient pitch force reserve in a continuous and gentle manner, thereby allowing the hydraulic pitch drive system to perform a stable and rapid tracking response without causing undesirable and dangerous interruptions to the blade pitch actuation motion.

[0112] From this comparison, it is apparent that embodiments of the present invention, such as the embodiment illustrated herein by Example 2, can be routinely employed as part of ongoing blade pitch adjustment during normal operation of a wind turbine, whereas the solutions exemplified by Examples 3 and 4 sacrifice reliability and therefore cannot be used in the same manner continuously during normal operation. Thus, embodiments of the present invention, such as the embodiment illustrated herein by Example 2, can achieve the aforementioned system sizing advantages. Thus, the present invention provides a stable and accurate tracking-assisted hydraulic pitch force system that, in contrast to known systems, can be used continuously without being hampered by the need to predict future loads on the hydraulic pitch force system.

Claims

1. A hydraulic pitch drive system for controlling the pitch angle of blades on a rotor of a wind turbine, the pitch drive system comprising: a hydraulic cylinder having a piston side A and a connecting rod side B, the hydraulic cylinder being arranged to actuate the pitch rotation of the blades; a first hydraulic proportional valve V3, arranged to control the flow of hydraulic oil from a pressure port P to the hydraulic cylinder in response to a primary control signal S3; wherein in an extension mode of the hydraulic cylinder, the pressure port P is connected to the piston side A of the hydraulic cylinder via the first hydraulic proportional valve V3; wherein the connecting rod side B of the hydraulic cylinder is connected to the pressure port P via a recirculation line including a check valve V6, wherein the check valve V6 is arranged for flow from the connecting rod side B of the hydraulic cylinder to the pressure port P; a first control module configured to provide the primary control signal S3 in response to a blade pitch angle positioning request; a second hydraulic proportional valve V4 arranged to control the flow of the hydraulic oil from the connecting rod side B to the tank port T in response to a secondary control signal S4 without relying on the first hydraulic proportional valve V3; and The second control module is configured to provide the secondary control signal S4 to control a set point of the second hydraulic proportional valve V4, thereby controlling the second hydraulic proportional valve V4 in an extension mode of the hydraulic cylinder.

2. The hydraulic pitch drive system according to claim 1, wherein the secondary control signal S4 is determined to control the set point of the second hydraulic proportional valve V4 in response to one or more parameters indicating a current operating state of the hydraulic pitch drive system.

3. The hydraulic pitch drive system according to claim 1 or claim 2, wherein the secondary control signal S4 is a signal generated by the cylinder load on the hydraulic cylinder. F L Sure. 4 . The hydraulic pitch drive system according to claim 3 , wherein the secondary control signal S4 is determined relative to one or more threshold values.

5. The hydraulic pitch drive system according to claim 4, wherein the one or more threshold values are determined based on one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or a time derivative dx / dt or d 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt or d 2 β0 / dt 2 , or the blade azimuth angle α.

6. The hydraulic pitch drive system according to claim 3, wherein the secondary control signal S4 is configured so that in response to the indication of the cylinder load F L When the parameter exceeds the first threshold value, the second hydraulic proportional valve V4 is opened.

7. The hydraulic pitch drive system according to claim 6, wherein the secondary control signal S4 is based on an indication of the cylinder load F L The difference between the parameter and the first threshold is determined.

8. The hydraulic pitch drive system according to claim 6, wherein the secondary control signal S4 is configured such that in response to an indication of the cylinder load F L When the parameter falls below the first threshold, the second hydraulic proportional valve V4 is closed.

9. The hydraulic pitch drive system according to claim 8, wherein the secondary control signal S4 is determined based on one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or a time derivative dx / dt or d 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt or d 2 β0 / dt 2 , or the blade azimuth angle α.

10. The hydraulic pitch drive system according to claim 8, wherein the secondary control signal S4 is determined based on a combination of two or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or a time derivative dx / dt or dx / dt thereof; 2 x / dt 2 , target blade pitch angle β0 and / or its time derivative dβ0 / dt, d 2 β0 / dt 2 , or the blade azimuth angle α.

11. The hydraulic pitch drive system according to any one of claims 1-2, wherein the secondary control signal S4 is determined based on a difference between a first pressure P1 at the pressure port P and a second pressure P2 at the piston side A of the hydraulic cylinder.

12. The hydraulic pitch drive system according to claim 11, wherein determining the secondary control signal S4 comprises measuring one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or a time derivative dx / dt or d 2 x / dt 2 , the valve slot position y of the first hydraulic proportional valve V3, the blade pitch angle β and / or its time derivative dβ / dt, d 2 β / dt 2 , or the blade azimuth angle α.

13. The hydraulic pitch drive system according to claim 11, wherein determining the secondary control signal S4 comprises estimating one or more of the following: a first pressure P1 at the pressure port P, a second pressure P2 at the piston side A, a third pressure P3 at the connecting rod side B, a connecting rod position x of the hydraulic cylinder and / or a time derivative dx / dt or d 2 x / dt 2 , blade pitch angle β and / or its time derivative dβ / dt, d 2 β / dt 2 , or the blade azimuth angle α. 14 . The hydraulic pitch drive system according to claim 3 , wherein the secondary control signal S4 is determined based on a comparison between an actual value and a predetermined reference value of a parameter indicative of the cylinder load.

15. The hydraulic pitch drive system according to any one of claims 1-2, wherein the secondary control signal S4 is in response to a predetermined operation instruction.

16. The hydraulic pitch drive system according to claim 1, wherein the second hydraulic proportional valve V4 is one of the following: a normally open flow control valve, a normally closed flow control valve, a normally open pressure control valve, a normally closed pressure control valve, or a pulse width modulation control on / off valve.

17. The hydraulic pitch drive system according to claim 16, wherein the second hydraulic proportional valve V4 is a normally open valve configured to provide an open connection from the connecting rod side B to the tank port T when power is off, the open connection being suitable for emergency stop.

18. The hydraulic pitch drive system according to claim 16, wherein the second hydraulic proportional valve V4 is a normally closed valve V4b, and wherein the hydraulic pitch system further comprises a bypass valve structure V4a, which, when the bypass valve structure V4a is de-energized, provides an open connection from the connecting rod side B to the tank port T in parallel with the normally closed valve V4b, and the open connection is suitable for emergency stop.

19. The hydraulic pitch drive system according to claim 1, wherein the second hydraulic proportional valve V4 is a hydraulic pilot pressure control valve.

20. The hydraulic pitch drive system of claim 19, wherein the pilot pressure for controlling the hydraulic pilot pressure control valve is provided by one of the following: an electrically controlled proportional valve, a hydraulic component, or a combination of an electrically controlled proportional valve and a hydraulic component.

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