Unlocking rotor of wind turbine

Abstract

There is described a method of assisting in unlocking and in particular unlocking a rotor of a wind turbine (1570) locked by a locking system (1575), the rotor coupled to an electric machine (1571) and rotatably supported by a rotor bearing, the method comprising: providing a torque reference (100, 200, 300, 700, 1100) or an equivalent current reference (1300); controlling the electric machine (1571) based on the torque reference (100); according to the torque reference, mechanical torque acting on the rotor is generated through the motor; wherein the torque reference (100) defines a time course (t1, t2) of a target torque (tt1, t2).

Description

Technical Field

[0001] The present invention relates to a method and a device for assisting unlocking, and in particular unlocking a rotor of a wind turbine locked by a locking system. The invention also relates to a wind turbine comprising such a device. Background Art

[0002] During repair or maintenance on a wind turbine, it may be necessary to lock the wind turbine rotor using a locking pin inserted between the rotor (or a brake disk that rotates with the rotor) and the stator to secure the rotor from unintended movement. For turbines with roller or ball bearings supporting the rotor, the locking pin can typically be released by moving the rotor by yaw and then extracting the pin using a hydraulic or electric mechanism.

[0003] However, for certain types of bearings, such as fluid film bearings (FFB bearings), after long periods of stationary time, friction can build up quite high and the rotor can become stuck, pressed against the surface of the brake disc bore, and the locking pins may not be removed using hydraulic or electric mechanisms. For certain types of rotor bearings, if the rotor has been locked for a significant period of time, rotor bearing friction can be relatively high and the rotor will not be able to be moved by applying conventional yaw (and blade pitch) methods.

[0004] Conventional closed-loop position control methods may not be applicable to rotor movement in a straightforward manner due to the stick-slip effect of bearing loads. Therefore, conventional lock pin extraction or unlocking methods may not be sufficient.

[0005] Therefore, there may be a need for a method and a corresponding device for assisting unlocking and in particular unlocking a rotor of a wind turbine locked by a locking system, wherein reliable and safe unlocking of the rotor locked by the locking system is achieved without risking damage to components of the wind turbine. Summary of the Invention

[0006] This need is met by the subject matter according to the independent claim. Advantageous embodiments of the invention are described by the dependent claims.

[0007] According to one embodiment of the present invention, a method is provided for assisting unlocking, and in particular unlocking a rotor of a wind turbine locked by a locking system (e.g., relative to a stator), the rotor being coupled to an electric machine (e.g., a generator system) (e.g., an electric machine of the wind turbine) and rotatably supported by a rotor bearing (e.g., relative to the stator), the method comprising: providing (e.g., accessing or generating) a torque reference; controlling the electric machine based on the torque reference; generating, by the electric machine, a mechanical torque acting on the rotor according to the torque reference; wherein the torque reference defines a time course of a target torque.

[0008] At the beginning of the application of the method, the rotor can be locked to, for example, a stator or a fixed part of the motor by means of a locking system.The rotor can thus be stationary and can be mechanically fixed to the stator or the fixed part of the motor (by means of the locking system).

[0009] The locking system may include one or more mechanical locking elements, such as bolts and / or pins. The locking system may include one or more openings or through-holes or holes (in the fixed part and / or the rotor), and may include additional through-holes or holes (in the fixed part and / or the rotor). The locking system may also include several locking members that can be inserted into one or more locking holes in the fixed part and the rotor part. To lock the rotor to the fixed part, the corresponding locking holes (on the rotor, on the one hand, and on the fixed part, on the other hand) may need to be aligned to substantially coincide or have an overlapping alignment of the corresponding locking openings. To lock, the one or more locking members may then be inserted into both the locking holes in the stator shaft and the aligned locking holes in the rotor part. When locked, the locking members, in particular locking pins or bolts, may be slightly displaced within the locking holes to be pressed against a restricted surface area of ​​the corresponding locking holes, for example due to torque or forces acting on the rotor and / or the mounted rotor blades.

[0010] When locked, the rotor may have one or more wind turbine blades installed.According to an embodiment, one or more wind turbine blades may be missing, for example due to replacement work or assembly / disassembly work.

[0011] The method may be performed during assembly / disassembly of a wind turbine, in particular during mounting of one or more rotor blades to the rotor or during any maintenance work and may require (temporarily) fixing the rotor relative to a fixed part of the generator for any type of repair or maintenance work.

[0012] The electric machine may be primarily designed to operate in generator mode, generating or producing electrical energy when the rotor is rotated by wind impacting the rotor blades mounted thereon. The electric machine may be configured, for example, as a synchronous machine, in particular a permanent magnet synchronous machine. The electric machine may provide multiple electrical phases, such as three electrical phases. The electric machine may include a multi-phase electrical winding set for each of one or potentially multiple stator segments. Each or one or more of the winding sets may be connected to one or more converters.

[0013] The rotor bearing may be configured to rotatably support the rotor relative to a stationary part of the generator, in particular relative to a stator of the electrical machine.

[0014] The torque reference may define a plurality of target torque values ​​for a plurality of subsequent time points. For example, the torque reference may be defined or represented as an electronic data structure, such as stored in an electronic memory. Providing the torque reference may involve accessing electronic data from the electronic memory. In other embodiments, the torque reference may be calculated (online).

[0015] The torque reference (also referred to as a target torque time course) may have been precalculated or predetermined based on the configuration of the wind turbine, in particular in view of or taking into account the mechanical configuration of the rotor (including one or more installed wind turbine blades), and also taking into account the friction properties of the rotor bearings, in particular also taking into account the stationary time of the rotor bearings, i.e. the time during which the rotor has been locked.

[0016] Therefore, the specific torque reference used during the method can be dynamically selected based on specific state information and / or one or more operating parameters of the wind turbine, and in particular the state of the rotor bearings and / or the mechanical state of the entire drive train (including the rotor, rotor blades, possible gearbox, and other components that affect the mechanical configuration of the drive train). In particular, the azimuthal position of the rotor can also be taken into account.

[0017] For example, multiple torque reference instances may be referenced by one or more operating parameters or state parameters, such as by looking up using a lookup table.

[0018] Controlling the motor based on a torque reference may involve providing control signals to the motor, in particular via a control module and / or a converter. The converter may include a plurality of controllable switches, such as power transistors (e.g., IGBTs), having discrete gates to which gate control signals may be provided from the control module. The controllable switches may be controlled by corresponding gate drive signals such that the motor generates a mechanical torque according to a given torque reference. This allows, in particular, the motor to generate a mechanical torque at multiple points in time, i.e., a target torque for each of these multiple points in time, in accordance with the torque reference.

[0019] When the electric machine is controlled according to a torque reference (in particular instead of controlling the rotor position), situations can be handled in an improved manner in which, for example, the rotor bearing is stuck, for example due to a long standstill period, and in which, further, the rotor bearing can be suddenly released from the stuck state due to a sudden reduction in friction.

[0020] The method may or may not require any input of a quantity indicative of the rotor position. In particular, turbines having fluid film bearings as rotor bearings can be processed by the method.

[0021] According to one embodiment of the invention, the method comprises performing open-loop control based on a torque reference; and / or wherein the method is not based on a target rotor position; and / or wherein the torque reference is generated such that the target torque acts in a direction that relieves the pressure acting on the locking system, in particular in a direction that moves at least one locking pin away from an edge of the lock hole.

[0022] The torque generated by the motor may not be measured and may not be fed back to the control portion used to perform the method. Thus, the open-loop control may simply involve providing a torque reference to the motor or motor system (e.g., including other control portions and / or a converter or converters).

[0023] The torque reference may also include the definition of an upper torque limit (e.g., limiting the absolute value of the target torque to below this upper torque limit). In other embodiments, the upper torque limit may be a separate quantity from the torque reference. However, the torque reference may maintain its value below the upper torque limit for all values ​​of the target torque.

[0024] The method of assisting unlocking may not rely on or require a target rotor position as an input. In other embodiments, the method may require a target rotor position as an input, such as to adjust, and in particular, stop, control of the motor to generate torque if it is detected that the rotor has actually begun to move or has moved an amount greater than a threshold rotor movement amount.

[0025] During locking (i.e., when the rotor is stationary), one or more components of the locking system may have been positioned or moved to a position such that the locking element is pressed against a specific locking edge. This locking edge may be the one that is contacted or pressed due to any mechanical torque or force acting on the entire drive train and exerting any torque or force on the rotor.

[0026] A torque reference can be generated that acts in a direction opposite to the mechanical torque or force applied to the rotor. This can reduce the applied torque or move the locking pin slightly away from the edge of the locking hole in which it rests when the rotor is locked and stationary. Locking may still occur due to the presence of the locking member, in particular the presence of the inserted locking pin (which is still inserted into the corresponding locking hole), thereby still locking the rotor relative to the stationary part of the motor. However, by acting in a direction that relieves the pressure on the locking system, the removal of the locking member, or in particular the locking pin, from the corresponding locking hole can be simplified.

[0027] The direction in which the torque reference acts (e.g. in a clockwise or counterclockwise manner) can be automatically identified or set, for example, by a maintenance person who observes and / or checks the manner or locking state of the locking pin, in particular how the corresponding locking member occupies the corresponding locking hole.

[0028] In other embodiments, the direction may be determined automatically, such as by analyzing the mechanical configuration of the drive train.

[0029] According to one embodiment of the present invention, the torque reference includes the magnitude (or absolute value) of the increase of the target torque in the first time span.

[0030] Torque can have a positive or negative sign, and the magnitude of the torque can be considered as the absolute value of the torque.

[0031] The target torque may be increased linearly over time, or may be increased according to a curve segment, a plurality of curve segments, or a plurality of straight line segments with varying inclinations over time. This provides for considerable flexibility. Increasing the target torque may be particularly advantageous if the friction provided by the bearings is not precisely known from the outset. The method may particularly involve observing when the rotor begins to move or rotate.

[0032] According to one embodiment of the present invention, the torque reference comprises a target torque whose magnitude is maintained below an upper torque limit, wherein in particular the upper torque limit is estimated and / or calculated and / or predicted based on at least one of: a type and / or configuration and / or state of a rotor bearing; a rotor bearing stationary time span; an azimuthal position of the rotor; a gravity-induced torque acting on the rotor taking into account the weight of one or more mounted rotor blades; an aerodynamic-induced torque acting on the rotor.

[0033] The upper torque limit can be determined so that when the torque actually generated by the motor has a magnitude that does not exceed the upper torque limit, the rotor is expected to move or is not expected to move. The upper torque limit can be determined or estimated so that it can substantially balance the mechanical torque acting on the drive train, or in particular, the rotor. When the torque generated by the motor and the mechanical torque applied to the rotor due to the mechanical mass to which the rotor is connected are balanced (i.e., opposite and have approximately the same magnitude), it can facilitate the release of the locking system components.

[0034] In other embodiments, the upper torque limit may be determined or estimated such that it may substantially exceed the mechanical torque acting on the drive train or in particular the rotor in order to move the rotor or apply a short stroke.

[0035] An embodiment of the present invention provides a method for assisting unlocking without rotor movement, which will be explained and described in detail below.

[0036] According to one embodiment of the present invention, the torque reference includes the target torque increasing to an upper torque limit without moving the rotor.

[0037] When the torque generated by the motor is applied to the rotor and reaches the upper torque limit, it can specifically balance the torque acting on the rotor due to the mechanical configuration and state of the rotor (including the rotor blades).When the rotor is not moving, safety can be improved.

[0038] According to an embodiment of the invention, the torque reference comprises a target torque which increases to an upper torque limit and remains substantially constant thereafter, in particular in the second time span.

[0039] It may be advantageous to keep the torque generated by the electric machine substantially constant at an upper torque limit in order to maintain a balanced torque such that the resulting (net or total) torque acting on the rotor is substantially zero.

[0040] Embodiments of the present invention provide a method for assisted unlocking in which the rotor moves a specific amount. Similarly, in these embodiments, the motor is controlled based on a torque reference. Similarly, for these embodiments, position may not be a controlled variable. However, rotor position can be used as an input, for example, to detect rotor movement.

[0041] According to one embodiment of the invention, the method further comprises detecting when the rotor starts to move or rotate, in particular detecting a target torque, at a first time instance, the target torque thereby having a first torque value; wherein the torque reference comprises a reduction of the target torque in a second time span after the first time instance, in particular a reduction to a value less than the first torque value, wherein in particular the first time instance defines the end of the first time span and the beginning of the second time span.

[0042] Because the target torque (magnitude) generated by the motor is greater than the torque due to gravity and / or friction acting on the rotor, the rotor may begin to move or rotate. Therefore, lowering the target torque or defining the torque reference such that the target torque is lower after the first time instance may advantageously resist further movement or rotation of the rotor. The target torque after the first time instance may be lowered to substantially zero, or to any value greater than zero but less than the first torque value.

[0043] According to an embodiment of the invention, the torque reference comprises a target torque that is substantially zero at the first time instance and / or during the second time span.Thereby, the method may be simplified.

[0044] According to one embodiment of the present invention, the method further includes at least one of: the torque reference includes the target torque decreasing in the second time span but remaining above zero; and the torque reference includes the target torque remaining substantially constant above zero in a third time span after the second time span.

[0045] After the first time instance, the target torque may be reduced in any manner, such as a linear manner or a curve manner according to several curve segments or according to several linear segments.

[0046] According to one embodiment of the invention, the electric machine can be operated in generator mode or in motor mode and / or controlled by an electric machine controller, in particular a converter and a converter controller.The electric machine can generate a torque acting on the rotor according to a torque reference.

[0047] According to one embodiment of the present invention, the method further comprises at least one of: determining a rotor position indication, in particular by adopting or using at least one of at least one encoder, at least one Hall sensor, at least one HFI sensorless observer; and / or determining the movement of the rotor based on the rotor position indication; and / or applying vector control of the motor.

[0048] At least one Hall sensor can detect a magnetic field or flux caused by a rotating rotor (particularly having a plurality of permanent magnets mounted thereon). Based on the observed or measured flux or magnetic field values, a processing section can determine the rotor position, such as the electrical position.

[0049] The HFI sensorless observer can employ high-frequency current or voltage injection into a generator or motor. During high-frequency current or voltage injection, the voltage or current measured at the motor can depend on the rotor's rotational electrical position. The rotor's rotational position can then be determined based on multiple current and / or voltage measurements and processing of the resulting measurements.

[0050] Vector control of a motor may involve transforming electrical quantities (such as phase voltages and / or currents in a stationary reference frame) into quantities in a rotating coordinate system that rotates synchronously with the motor's rotor. This rotating coordinate system may be referred to as a dq coordinate system. Quantities that actually oscillate at a fundamental frequency in the stationary reference frame may be essentially DC quantities in the synchronously rotating dq coordinate system, simplifying control.

[0051] According to an embodiment of the invention, the method further comprises: unlocking the locking system in the second time span; and / or applying brakes to the rotor in the second time span; wherein unlocking the locking system comprises extracting the locking pin from the locking hole.

[0052] During the second time span, the corresponding locking system can be in a relaxed state, wherein one or more locking pins are not pressed against the corresponding locking hole edge. Unlocking the locking system may involve withdrawing one or more locking members (such as locking pins) from the locking hole. This also allows for the use of specialized unlocking tools, particularly hydraulic ones. This can improve the safety of the method when applying rotor braking.

[0053] According to one embodiment of the present invention, the rotor bearing includes or comprises at least one of the following: a fluid film bearing; a roller bearing; a ball bearing.

[0054] It should be understood that according to embodiments of the present invention, features disclosed, described or applied individually or in any combination to a method for assisting unlocking and in particular unlocking a rotor of a wind turbine may also be applied individually or in any combination to a corresponding device for assisting unlocking a rotor, and vice versa.

[0055] According to one embodiment of the present invention, a device is provided for assisting unlocking, and in particular unlocking, a rotor of a wind turbine locked by a locking system, the rotor being coupled to a motor of the wind turbine and rotatably supported by a rotor bearing, the device comprising: a torque reference module for providing a torque reference; a motor; a motor controller connected and adapted to control the motor so as to generate a mechanical torque acting on the rotor according to the torque reference; wherein the torque reference defines a time course of a target torque, the device in particular comprising: an unlocking tool adapted to unlock the locking system.

[0056] The device may be configured to control or execute the assisted unlocking method according to an embodiment of the present invention.

[0057] According to one embodiment of the present invention, a wind turbine is provided, comprising: a rotor; a locking system adapted to lock the rotor (to prevent rotation relative to a stator); a rotor bearing, by which the rotor is rotatably supported (relative to the stator); and a device according to the preceding embodiments for assisting unlocking, and in particular unlocking the rotor.

[0058] The above-defined aspects of the present invention as well as further aspects will be apparent from the examples of embodiment described hereinafter and will be explained with reference to these examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment, but the invention is not limited to these examples of embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Embodiments of the present invention will now be described with reference to the accompanying drawings. The present invention is not limited to the embodiments shown or described.

[0060] Figure 1 illustrates a reference torque applied according to one embodiment of the present invention; Figure 2 illustrates a reference torque applied according to another embodiment of the present invention; Figure 3 illustrates a reference torque applied according to yet another embodiment of the present invention; Figure 4 Schematically illustrates a functional diagram employed in a method and apparatus for assisting in unlocking a rotor according to one embodiment of the present invention; Figure 5 The load on the rotor bearings after different standstill times is shown; Figure 6 、 Figure 7 Graphs show test results of applying a method for unlocking or assisting in unlocking a rotor including rotor movement according to one embodiment of the present invention; Figure 8 、 Figure 9 Graphs show test results of applying a method for unlocking or assisting in unlocking a rotor including rotor movement according to another embodiment of the present invention; Figure 10 、 Figure 11 FIGURES illustrate test results of a method for assisting in unlocking a rotor without rotor movement according to one embodiment of the present invention; Figure 12 A part of a wind turbine according to an embodiment of the present invention is illustrated in a partial cross-sectional view, comprising a device for assisting unlocking of a rotor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The drawings are schematic. Note that in different drawings, elements that are similar or identical in structure and / or function are given the same reference numerals or reference numerals that differ only in the first digit. A description of an element not described in one embodiment can be obtained from the description of that element in another embodiment.

[0062] Figure 1 A torque reference 100 is schematically illustrated in a coordinate system having an abscissa 101 indicating time and an ordinate 102 indicating torque. The torque reference 100 is used in a method for assisting unlocking a rotor of a wind turbine according to an embodiment of the present invention. According to the method, an electric machine is controlled based on the torque reference 100 to assist unlocking a rotor of a wind turbine that is locked by a locking system (e.g., relative to a stator of the electric machine).

[0063] The motor then generates a mechanical torque acting on the rotor according to the torque reference 100. Figure 1 As can be appreciated, torque reference 100 defines the time course of a target torque. For example, at time t1, torque reference 100 defines target torque tt1, and at time t2, torque reference 100 defines target torque tt2. Target torque tt2 is greater than target torque tt1. Torque reference 100 includes an increasing target torque over a first time span 103 from time t0 to time t3. In the illustrated embodiment, this increase is a linear increase in target torque over time.

[0064] The torque reference 100 is limited by the torque upper limit 104. Therefore, the target torque is always kept below or at most at the torque upper limit 104. The horizontal line indicated by reference numeral 105 indicates the gravity load acting on the rotor. The torque upper limit is greater than the gravity load 105.

[0065] The interval 106 indicates the error margin allowed for the generator torque for a specific rotor bearing (eg, FFB) installed at the wind turbine.The target torque defined by the reference torque 100 is equal to the upper torque limit 104 for times greater than t3.

[0066] At or after time t4, the locked rotor locking system may be unlocked, specifically within a second time span 107 starting at time t3 when the target torque reaches the upper torque limit 104. When applying this method to unlock the rotor, the target torque is increased to the upper torque limit 104 without moving the rotor.

[0067] In addition, as from Figure 1 As can be appreciated, the target torque increases to the upper torque limit 104 and remains substantially constant thereafter, particularly during the second time span 107 .

[0068] Figure 1 The torque reference (time course of the target torque defined) 100 shown in can also be referred to as an unlocking method without rotor movement, in which a balancing torque is applied. Therefore, as long as the pressure on the locking pin can be significantly reduced, the locking pin can be pulled out without moving the pin away from the edge of the locking hole. According to the horizontal line 105, there is a load in the unbalanced rotor due to gravity. For example, based on the rotor standstill time, the bearing static friction that causes the rotor to jam can be estimated. For example, based on the rotor mechanical position (azimuth angle), the blade gravity load of the unbalanced rotor can be estimated. These estimates can be used as the value of the generator torque limit 104. Increasing the generator torque towards this limit 104 can reduce the pressure on the locking pin. If the estimate of the torque upper limit 104 is correct, the influence of the pressure load will be completely removed. However, a certain level of error 106 can be allowed in the load estimate. First, even if a small amount of pressure remains on the locking pin, it can be pulled out. Moreover, in the case of FFB, the possible high static friction will tolerate more errors in the gravity load estimate, since the bearing static friction will resist the rotor movement. When applying Figure 1 When the reference torque is 100 as shown in Figure 1, it may not be necessary or desirable to monitor rotor movement, thus simplifying the method. One particular advantage may be the ability to reliably apply low-resolution Hall-effect sensors, as they can be used solely for generator torque control without having to monitor their state changes for rotor movement. In this case, torque production may be reduced by approximately 14%, whereas using angle adjustment methods (which are not part of the present invention), torque production can be as high as 100%.

[0069] Figure 2 and Figure 3 Torque references 200 and 300 , respectively, which are applied during a method of assisting unlocking a rotor of a wind turbine according to an embodiment of the invention, are also illustrated in a graph with abscissas 201 , 301 indicating time and ordinates 202 and 302 indicating torque. Figure 2 and Figure 3 The torque references 200 and 300 shown in also define the time course of a target torque to be generated by the electrical machine, in particular the generator system, of the wind turbine in order to enable or assist unlocking of the rotor starting from a situation in which the rotor is locked by the locking system.

[0070] However, according to Figure 2 and Figure 3 In the embodiment of the reference torque shown in FIG, the rotor can be moved at least slightly. Figure 2 and Figure 3 , the respective reference torques 200, 300 comprise an increased target torque in the first time span 203. This increase depends linearly on time. According to other embodiments, the increased target torque may be increased according to one or more curve segments and / or one or more straight line segments having, for example, different inclinations.

[0071] At time t5, rotor movement can be detected. Time t5 can be considered a first time instance. At this first time instance t5, the target torque has a value tt5, which is a first torque value. After the first time instance t5, the torque reference defines a target torque decrease, specifically a decrease in the second time intervals 207 and 307, respectively. The target torque decreases to a value less than the first torque value tt5.

[0072] exist Figure 2 In the example shown in , the torque reference is reduced to substantially zero at a first time instance t5. In a second time interval 207, the brake may be applied and / or the locking pin may be unlocked in order to unlock the rotor.

[0073] according to Figure 3 In the example shown in , the magnitude of the torque reference defined target torque decreases during the second time span 307 but remains above zero. Figure 3 It can be seen that the magnitude of the target torque decreases from the first torque value tt5 at the first time instance t5 to a value 310 above zero.

[0074] During the third time interval 311, the target torque is kept constant at a value 310, which is reached at the end of the second time interval 307. At or after the first time point t5, or within the second and / or third time intervals 307, 311, the brakes may be applied and / or the locking system may be unlocked in order to unlock the rotor. Figure 2 、 Figure 3 The reference torques 200 , 300 shown in FIG always remain respectively below the upper torque limits 204 , 304 .

[0075] according to Figure 2 and Figure 3 The torque references 200 and 300 shown in FIG. allow for short strokes (pushing) of the rotor using torque management. Testing has shown that the FBB load does not change much with small rotor position shifts. This property of viscous loads can be exploited for latch release control. Essentially, the rotor can be pushed a short distance, and then, by removing the moving force, the rotor will come to rest at its stop.

[0076] At approximately 20 hours of standstill, the FFB static friction was measured to be approximately 70% of its maximum value when the bearing is completely dry. After some small rotor movement in the forward and reverse directions within the keyhole, the rotor was activated, and the bearing starting torque was measured at a similar level to that observed previously. This indicates that the bearing static friction will hardly change due to the small rotor movement. Given the viscous nature of the FFB bearing load, a generator torque higher than the bearing static friction can be applied to at least slightly move or rotate the rotor. Once the rotor has moved the desired distance, the generator torque can be switched off or at least reduced. Due to the high bearing viscosity, the rotor will stop almost immediately and will maintain its position. This task is simplified by only loosening the locking pin, eliminating the need to move the rotor to the middle of the keyhole.

[0077] Since FFB static friction may vary with several factors such as stationary time and bearing temperature, the generator torque can be increased until the rotor is observed to move or begin to move. The torque can then be cut off (e.g., at Figure 2 or Figure 3 ) or at least decreases, such as Figure 3 As shown in .

[0078] If there is some gravity loading in an unbalanced rotor condition, e.g. for a single blade mounted application, then the generator torque can be maintained during rotor pin pullout (e.g. see Figure 3). As a result, the generator torque increases slowly to limit the acceleration torque. Once the rotor has moved or rotated slightly the desired distance, the generator torque can be maintained and the turbine brake can be applied simultaneously. Thus, by balancing the torque from the generator, the bearing static friction, the gravity load, and the wind aerodynamic load, the rotor will remain stationary. In practice, the generator torque can be reduced to a positive level within the braking torque capacity to save some current and / or prevent the rotor from moving further than strictly required, such as Figure 3 This solution can also be based on the observation that for the locking pin to be extracted, the pin does not have to be at the dead centre of the lock hole, ie there is a margin for small deviations and positions, or that the rotor does not have to be absolutely stationary when the brake is applied.

[0079] exist Figure 2 In , the torque cut-off at the first time instance t5 may not take into account the gravity load. Figure 3 In the embodiment, the torque is reduced according to the reference torque 300 after the first time instance t5 not to zero, but to a positive torque value in order to counteract any possible gravity load. Figure 2 The examples shown in or Figure 3 The example in may depend on the gravity load and in particular the azimuthal position of the rotor and whether all rotor blades or only some are installed.

[0080] Figure 4 The functional scheme for implementing the method of unlocking the rotor is illustrated, such as Figure 1 、 Figure 2 or Figure 3 Those methods with corresponding reference torques are illustrated in . Figure 4 The device 450 for assisting unlocking of a rotor of a wind turbine according to an embodiment of the present invention is illustrated as a functional diagram. Figure 4 Or the device 450 may be configured to apply a torque reference, such as Figure 1 、 Figure 2 or Figure 3 As shown in curves 200, 300, and 100 in FIG.

[0081] The apparatus 450 comprises a torque reference module 451 for providing a torque reference 400. For example, the torque reference may be Figure 1 、 Figure 2 、 Figure 3 The apparatus 450 further includes an electrical drive train (including an electric motor) 452 and a motor controller 460 including a plurality of functional blocks. The motor controller 460 is connected and adapted to control the electric motor 452 so as to generate a mechanical torque acting on the rotor according to the torque reference 400.

[0082] In the illustrated embodiment of the device 450, the device includes a lock pin release control block 453 that receives the torque reference 400, the torque upper limit 404, and the rotor position 454. In addition, the module 453 receives the rotor's azimuthal position 455 as an alternative to 454 in order to detect rotor movement. The rotor position 454 represents the electrical rotor position, which is typically obtained from an HFI observer and encoder or a set of Hall effect sensors; the azimuthal position 455 represents the mechanical rotor position, which is typically measured by the turbine controller.

[0083] Based on the input signals, the latch control release module 453 determines a torque demand 456, which is provided to a conversion module 457. The conversion module calculates a corresponding current demand 458, which is provided to a vector control module 459. The vector control module also receives the electrical rotor position 454 to perform the transformation into and out of the dq rotating reference frame. The vector control module 459 outputs a voltage demand 461, which is provided to the motor 452.

[0084] The motor 452 can be considered to include the generator and converter, as well as the entire drive train including the bearings and inertial system. Bearing loads 462, gravity loads 463, and braking torques 464 act on the generator system or motor 452. Measurement sensors 465, such as encoders and / or Hall sensors and / or sensorless HFI, determine the electrical position 454 of the motor 452.

[0085] It should be understood that Figure 4 A functional diagram 450 of an apparatus for assisted unlocking is provided. The functions shown may be provided by modules different from those shown. The entire apparatus 450 may be considered to implement a converter control.

[0086] For example, for a lock pin release, a torque reference 400 may be issued from the turbine controller. This torque reference may typically be presented as a time-based ramp signal. Upon receiving the torque reference, the converter control 450 may convert it into a generator torque producing current 458, i.e., the generator Iq current, which will be controlled by standard vector control. For example, the torque or current reference may also be obtained from an internal controller in the converter control, or a signal generator. The rotor electrical angle required for vector control 459 may be provided by a variety of source options, such as an HFI sensorless observer, a Hall effect sensor, or an encoder. A key part of this technology may be the torque management for lock pin release control. When it is identified that the rotor has moved a desired distance along an angle (e.g., applied to Figure 2 and Figure 3 When the torque reference 200, 300 shown in FIG is reached, the torque reference can be terminated or maintained or reduced, and the rotor will stop moving with assistance from bearing static friction and / or braking torque. At this time or a later time, the lock pin can be pulled out to complete the lock pin release.

[0087] Figure 4 Detection of rotor movement within the lock hole in module 465 can be supported by various sources, such as rotor azimuth, HFI sensorless observer, Hall effect sensor, or encoder. The HFI (High Frequency Injection) sensorless observer provides the best solution for both generator vector control and lock pin release control. The encoder can be permanently installed in the turbine or used as a portable kit when lock pin release is to be performed. The Hall effect sensor can be of analog or digital type. With the former, the generator position can be obtained with high resolution for generator control and lock pin release control. The latter provides a robust and low-cost solution for torque control, however, the angular resolution may be too coarse for lock pin release control.

[0088] Using alternative techniques, such as balancing the generator torque Figure 1 With the method shown in , no rotor movement detection is required, and a Hall effect sensor can be reliably applied for latch release.

[0089] Thus, according to this embodiment, a torque reference can be applied without the intention of moving the rotor (and without actually moving the rotor), but rather to relieve pressure between the lock pin and the lock hole. This approach will simplify lock pin unlocking and may not require high resolution and high dynamic position feedback.

[0090] The conversion from torque demand to generator Iq current (in rms) can be expressed as follows: Where p is the number of motor pole pairs, ψ is the motor air gap flux from the permanent magnets, and γ is a factor that depends on the position feedback for vector control. For example, in the case of an HFI observer, γ = 1, and when using a digital Hall effect sensor, γ = cos (30°)~1, depending on the rotor electrical position within the sensor's measurement range of 60 electrical degrees.

[0091] Figure 5The loads generated by the rotor bearings, in particular the FFBs, are illustrated, where the abscissa 80 indicates the rotor angular movement and the ordinate 81 indicates the bearing load. Curves 82, 83, 84 indicate the loads after a stationary period of 1 hour, 24 hours, and 7 days, respectively. The longer the stationary period, the greater the bearing static friction will be. As soon as a small angular movement is made, the bearing friction decreases sharply. These characteristics will generally cause difficulties for position control. For example, when a conventional position controller attempts to move the rotor, a large motor torque (or current) will be required to overcome the high static friction of the bearing. Therefore, conventional controllers need to have a high bandwidth to avoid overshoot during position control. Otherwise, the controller will need to move the rotor backwards, and the torque required to overcome the static friction of the bearing will change sign. This stick-slip load will add challenges to position control, and conventional positioning control methods are expected to have other problems. Embodiments of the present invention can handle such situations by basing the control of the unlocking process on a torque reference. Figure 5 The characteristics of the bearing load shown in , as explained below and above.

[0092] Figure 6 、 Figure 7 The time progression of a torque reference 700 and electrical angles 843 a, b, c (obtained respectively by HFI, encoder or Hall sensor) is schematically illustrated in a coordinate system having time as abscissa 701 , 801 and torque and electrical angle as ordinate 702 , 841 .

[0093] At a first time point t5, the rotor is observed to move or begin to move via the encoder. At this first time point, torque reference 700 drops to zero, or the target torque drops to zero. If no rotor movement was detected at the first time point t5, the target torque would follow the progression defined by torque reference 700 according to the solid line. However, since the rotor begins to move, the target torque drops to zero at the first time point t5.

[0094] Figure 8 、 Figure 9 The time progression of a torque reference 1100 and electrical angles 1143 a, b, c (obtained respectively by HFI, encoder or Hall sensor) is schematically illustrated in a coordinate system having time as abscissa 1001 , 1101 and torque and electrical angle as ordinate 1002 , 1141 .

[0095] At a first time point t5, the HFI observer detects that the rotor begins to move. Therefore, at this first time point t5, the torque is cut off, i.e., the target torque is set to zero. During a second time span 1007, the locking pin may be released or removed and / or the brake may be applied.

[0096] In accordance with Figure 6 、 Figure 7 In the test results, the encoder was used for vector control and the azimuth position was used for rotor movement detection and, therefore, torque management for lock pin release. A ramp torque of 700° was applied, and when the level was sufficient to break the bearing static friction and cause a rotor movement of approximately 0.3°, the generator torque was cut off.

[0097] In such Figure 8 、 Figure 9 In the test shown in Figure 1, HFI position feedback was used for motor vector control and torque management of the lock pin release. The rotor had moved approximately 0.14°, and the lock pin release could therefore be well controlled. Due to the high friction in the bearings, the rotor stayed where it stopped, allowing the lock pin to release and be easily removed.

[0098] Figure 1 The method for torque reference 100 shown in the figure can also be achieved by Figure 4 In the case where the azimuth or motor electrical angle is not used to manage the release of the locking pin, a torque limitation can be applied (see Figure 1 , reference numeral 104), the torque limit can be derived based on load estimation by taking into account bearing static friction and / or the torque due to blade weight in the case of an unbalanced rotor. An advantage of this technique is that there is no need to monitor precise rotor movement and therefore no need to monitor rotor position, and therefore, simple low-resolution position feedback such as a digital Hall effect sensor can be used.

[0099] The test results for this auxiliary unlocking without rotor movement are shown by Figure 10 、 Figure 11 The test results are shown in the figure. Figure 10 、 Figure 11 The time course of the current (reference) 1300 ′ and the electrical angle 1443 a, b (derived from the HFI and the encoder, respectively) is schematically illustrated in a coordinate system having time as the abscissa and current Iq and electrical angle as the ordinates 1302, 1441. Curve 1443 c represents the rotor speed, indicating the rotor movement after the locking system has been unlocked.

[0100] It should be understood that torque can be related to Figure 10The current amplitude shown in is proportional to the current amplitude shown in . In this test, the turbine was installed with a single blade, and the rotor was locked at a 60° position, where the torque due to the weight of the blade would be approximately 87% of the maximum value. To generate the balancing torque, the torque can be increased through closed-loop control, but the rotor will not move due to the torque limit. A stable balancing torque will be generated, and the rotor will no longer be firmly seated on the locking pin. At this point, the locking pin can be successfully removed without difficulty. Braking can also be applied, which will allow for a little more tolerance in the torque limit estimate without moving the rotor.

[0101] Embodiments of the present invention may provide: - Simple lock pin release control technology, which can be applied in the case of FFB bearings and / or in cases with high gravitational loads due to unbalanced rotors; - A method of small rotor angular movement by using short pulses of generator torque while exploiting high bearing static friction; - A method with balanced generator torque but no rotor movement, where precise position feedback is not required for torque management; - less likelihood of exciting vibrations in the blades and tower compared to solutions with rotor positioning; - Implementation using position feedback from rotor azimuth, generator HFI sensorless observer, Hall effect sensor management or encoder measurement.

[0102] The embodiments are also applicable to turbines having roller bearings or ball bearings.

[0103] Figure 12 A portion of a wind turbine 1570 according to an embodiment of the present invention is schematically illustrated, including an apparatus for assisting rotor unlocking according to an embodiment of the present invention. Wind turbine 1570 includes a rotor (not shown) of a generator 1571. Generator 1571 includes a stator 1572, which includes a multi-phase winding set (not shown in detail). A rotor 1573 is rotatably supported relative to stator 1572 and a rotor bearing (not shown in detail). A brake disk 1574 is mounted on rotor 1573. Therefore, during normal operation, brake disk 1574 rotates relative to stator 1572.

[0104] For maintenance operations, wind turbine 1570 includes a locking system 1575. In the illustrated embodiment, the locking system is implemented via locking holes 1576 within stator 1572 and brake disc 1574. A locking pin 1577 can be inserted into the locking hole to lock rotor 1573 relative to stator 1572. A locking pin actuator 1578 is provided for inserting and withdrawing locking pin 1577. To release or unlock locking system 1575, a method for assisting in unlocking the locking system according to an embodiment of the present invention can be performed.

[0105] It should be noted that the term "comprising" does not exclude other elements or steps, and the wording "a", "an" or "an" does not exclude a plurality. Furthermore, elements described in connection with different embodiments may also be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method for assisting unlocking, and in particular unlocking, a rotor of a wind turbine (1570) locked by a locking system (1575), the rotor being coupled to a motor (1571) and rotatably supported by a rotor bearing, the method comprising: Providing a torque reference (100, 200, 300, 700, 1100) or an equivalent current reference (1300) indicative of the torque reference; controlling the motor (1571) based on the torque reference or the current reference (100); generating a mechanical torque acting on the rotor by the electric motor according to the torque reference; Therein, the torque reference (100) defines the time course (t1, t2) of the target torque (tt1, tt2).

2. The method according to the preceding claim, comprising performing open loop control based on the torque reference (100); and / or in, The method is not based on closed-loop position control; and / or The torque reference (100) is generated so that the target torque acts in a direction that relieves the pressure acting on the locking system (1575), in particular in a direction that moves at least one locking pin away from the edge of the lock hole.

3. The method according to any one of the preceding claims, in, The torque reference (100) includes a magnitude of an increase in the target torque in a first time span (103, 203, 303).

4. The method according to any one of the preceding claims, in, The torque reference (100) includes the magnitude of the target torque being maintained below the torque upper limit (104, 204, 304), In particular, the torque upper limit is estimated and / or calculated and / or predicted based on at least one of the following: the type and / or configuration and / or condition of the rotor bearings; rotor bearing stationary time span; the azimuthal position of the rotor; the gravity-induced torque acting on the rotor, taking into account the weight of one or more mounted rotor blades; Aerodynamically induced torque acting on the rotor.

5. The method according to any one of the preceding claims, in, The torque reference (100) includes the magnitude of the target torque increasing to the upper torque limit (104) without moving the rotor.

6. The method according to the preceding claim, in, The torque reference (100) includes the magnitude of the target torque increasing to the upper torque limit (104) and then remaining substantially constant, particularly during a second time span (107).

7. The method according to any one of the preceding claims 1 to 4, further comprising: At a first time instance (t5), detecting when the rotor starts to move or rotate, in particular detecting the target torque, the target torque thereby having a first torque value (tt5); wherein the magnitude of the torque reference including the target torque decreases in a second time span (207, 307) after the first time instance (t5), in particular decreases to an absolute value less than the first torque value, Therein, in particular, the first time instance (t5) defines the end of the first time span (203, 303) and the beginning of the second time span (207, 307).

8. The method according to the preceding claim, in, The magnitude of the torque reference (200) including the target torque drops substantially to zero at the first time instance (t5) and / or remains at zero during the second time span (207).

9. The method according to any one of the preceding claims, further comprising at least one of the following: The magnitude of the torque reference (300) including the target torque decreases during the second time span (307), but remains above zero; and The torque reference is included in a third time span (311) after the second time span (307), and the magnitude of the target torque remains substantially constant above zero.

10. The method according to any one of the preceding claims, in, The electric machine (1571) can be operated in generator mode or motor mode and / or controlled by an electric machine controller, in particular a converter and a converter controller.

11. The method according to any one of the preceding claims, further comprising at least one of the following: Determining the rotor position indicator, in particular by adopting or using at least one of the following: at least one encoder; at least one Hall sensor; at least one HFI observer; determining movement of the rotor based on the indication of rotor position; determining movement of the rotor based on a measurement of an azimuthal position of the rotor position; and / or Vector control of the motor is applied.

12. The method according to any one of the preceding claims, further comprising: unlocking the locking system (1575) during the second time span (107, 207, 307); and / or applying braking to the rotor during the second time span; Wherein, unlocking the locking system includes pulling out a locking pin from a locking hole.

13. A method according to any one of the preceding claims, wherein The rotor bearing includes or comprises at least one of the following: Fluid film bearings; Roller bearings; Ball bearings.

14. A device (450) for assisting unlocking, in particular unlocking, a rotor of a wind turbine locked by a locking system (1575), the rotor being coupled to a motor of the wind turbine and rotatably supported by a rotor bearing, the device comprising: A torque reference module (451) for providing a torque reference (400) or an equivalent current reference; said motor (452, 1571); a motor controller connected and adapted to control the motor to generate a mechanical torque acting on the rotor in accordance with the torque reference; wherein the torque reference (400) defines the time course of the target torque, The device comprises in particular: An unlocking tool (1578) adapted to unlock the locking system.

15. Wind turbine (1570), including: rotor; a locking system (1578) adapted to lock the rotor; a rotor bearing, by which the rotor is rotatably supported (relative to the stator), The device (450) according to the preceding claim for assisting unlocking and in particular unlocking the rotor.

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