Variable pitch brake detection and protection method based on capacitance detection

Abstract

The invention discloses a variable pitch brake detection and protection method based on capacitance detection, and belongs to the technical field of wind power generation. According to the method, by detecting the charging current of the super capacitor, the speed of the variable-pitch motor during starting is controlled, that is, the given speed of the variable-pitch motor is adjusted in advance according to the charging current of the super capacitor, and it is ensured that the variable-pitch motor is started only after brake release; therefore, the brake valve is prevented from being abraded due to high-speed operation of the variable-pitch motor when the brake release action becomes slow due to aging of a relay of the variable-pitch system or reduction of driving current or reduction of suction force of the electromagnetic brake valve, normal operation of the wind driven generator is guaranteed, the rate after brake release is corrected, and the corresponding speed of the system is guaranteed.

Description

Technical Field

[0001] The invention relates to a pitch brake detection and protection method based on capacitance detection, belonging to the technical field of wind power generation. Background Art

[0002] Wind power generation technology is a renewable energy technology that converts wind energy into electrical energy. The wind drives the windmill blades to rotate, and then the speed of rotation is increased through the speed increaser, thereby prompting the wind turbine to generate electricity. As an important part of the wind power generation system, the variable pitch system is mainly used to adjust the pitch angle (the angle between the windmill blades and the rotating plane of the wind rotor) according to different wind speed conditions to ensure that the wind turbine can operate efficiently under different wind speeds. In addition, the variable pitch system also serves as the main brake system of the wind turbine unit. When shutdown, emergency braking, and high wind speed are required, the variable pitch system adjusts the windmill blades to the feathering position (the position of the windmill blades parallel to the wind direction) to achieve aerodynamic braking, so that the wind turbine unit can be safely shut down.

[0003] In the wind power generation system, any shutdown caused by a fault will cause the pitch system servo motor to release and drive the blades to the 89-degree position. At the same time, since the blade angle range of the pitch system is 0 to 89 degrees, when the blades are aligned to the 89-degree position, the pitch system servo motor needs to stop the pitch motor and apply the brake at the same time. The purpose is to prevent the blade position from sliding under the action of gravity and rotating out of the limit position. This brake protection is especially important for the pitch system where the blades cannot rotate within the range of 0 to 360 degrees.

[0004] At present, the brake function of the servo motor of the variable pitch system is realized by the electromagnetic brake valve, and considering that the working current of the electromagnetic brake valve is generally large, its release output generally requires an external intermediate relay to control the electromagnetic brake valve; as we all know, the electromagnetic brake valve is an automatic actuator that uses the electromagnetic effect generated by the electromagnet to realize braking. It mainly transmits power and controls movement to mechanical equipment. It has the advantages of sensitive response, simple operation, compact structure, reliable use, and easy to achieve remote control. However, after long-term work, the relay and the electromagnetic brake valve will slow down and the suction force will decrease. Moreover, the action and closing time of the external relay itself will also cause further lag in the release. That is, after long-term work, the relay and the electromagnetic brake valve will cause the variable pitch motor to be blocked for a short time at the moment of the electromagnetic brake valve releasing (that is, the variable pitch motor has been started and started to drive the windmill blades to change the pitch angle, but the electromagnetic brake valve is not fully opened); and the stalling of the variable pitch motor will cause the wear of the brake pads, and the accumulated debris after wear will further affect the smooth opening of the brake valve. Severe wear of the brake valve will lead to brake failure. For the pitch control system, brake failure will cause the blades to rotate in a direction greater than 90 degrees under the action of gravity, and the blade position will exceed the limit, often damaging the mechanical parts in the hub; in strong winds, the blades will slide to the parking position due to the wind force, seriously affecting the operation and power generation of the wind turbine. Therefore, it is necessary to test the performance of the electromagnetic brake valve.

[0005] In the existing methods, the performance of the electromagnetic brake valve is generally judged by detecting the pitch motor current or the pitch angle, pitch speed and other information. However, when analyzing the pitch motor current, it is easy to cause false detection or the working conditions cannot be effectively distinguished. The reason is that the stall current of the pitch motor is usually the maximum starting current. In other words, when the pitch motor rubs or stalls, its current is comparable to the starting current. Therefore, it is difficult to accurately locate the fault point. Further troubleshooting of the mechanical components is time-consuming and laborious. In addition, due to the large volatility of the pitch motor current, it is easy to cause false detection during the data analysis process. The analysis algorithm required to obtain accurate results is also relatively complex. The problem with judging the performance of the electromagnetic brake valve by analyzing the pitch angle, pitch speed and other information is that in the early stage of abnormality, , the stalling time is short, and at this time it is not enough to affect the essential change of the pitch angle, that is, the pitch angle can only identify the situation when the brake valve is severely worn, at this time it has affected the operation of the wind turbine, and cannot identify the situation of slight stalling when the pitch motor is started, and cannot perform the protection of the anti-wear control method; and if the detection is performed after the wear is serious, the pitch system blade retraction speed will be too slow, or even slipping will occur ("slipping" usually refers to the failure or malfunction of the pitch system, resulting in the phenomenon that the angle of the wind turbine blades of the wind turbine cannot be correctly adjusted), resulting in unbalanced blades of the wind turbine, and further causing vibration and load increase of the wind turbine, seriously affecting the mechanical life of the wind turbine, and therefore It is necessary to carry out early warning monitoring and safety protection of the electromagnetic brake valve, but the existing technology cannot meet this requirement. Summary of the invention

[0006] In order to solve the current problems, the present invention provides a pitch brake wear protection and control method based on capacitor detection, the basic principle of which is: by detecting the charging current of the supercapacitor, the speed of the pitch motor at startup is controlled, thereby avoiding wear of the brake valve due to the high-speed operation of the pitch motor when the relay of the pitch system is aged, the driving current is reduced, or the suction of the electromagnetic brake valve is reduced, resulting in a slow release action, thereby ensuring the normal operation of the wind turbine and avoiding the occurrence of batch failures.

[0007] The first object of the present application is to provide a pitch brake detection and protection method based on capacitance detection, the method being applied to a pitch controller in a pitch system, the method comprising:

[0008] Step 1, obtaining a given speed v1 and an actual speed v2 of the pitch motor, and judging whether the pitch system is in a brake state according to the given speed v1 and the actual speed v2;

[0009] Step 2: If the pitch control system is in the brake state, the abnormal pitch control process described in the following steps 3 to 6 is executed; otherwise, the normal pitch control process is executed;

[0010] Step 3, adjust the given speed v1 sent to the pitch motor to v3, and output the release command after controlling the delay t1, where v3 is the critical speed of the driver action; t1 is the release time parameter;

[0011] Step 4, after outputting the brake release command, detecting whether the actual speed v2 of the pitch motor becomes a non-zero value;

[0012] Step 5, when it is detected that the actual speed v2 of the variable pitch motor becomes a non-zero value, the charging current of the supercapacitor is detected in real time. When it is detected that the charging current of the supercapacitor is less than 1 / 2 of the stall current, the given speed v3 sent to the variable pitch motor is adjusted to the correction speed v4, and the correction time is set to Δt1; the stall current refers to the current when the variable pitch motor is stalled;

[0013] Step 5: After the correction time Δt1, adjust the given speed sent to the pitch motor to v1 until the pitch adjustment is completed;

[0014] Step 6: After the pitch adjustment is completed, adjust the given speed sent to the pitch motor to zero and apply the brake.

[0015] Optionally, judging whether the pitch control system is in a braking state according to a given speed v1 and an actual speed v2 includes:

[0016] If the actual speed v2 of the pitch motor remains zero after the given speed v1 changes from zero to a non-zero value, and the duration exceeds a predetermined time length, the pitch system is determined to be in a braking state; otherwise, the pitch system is determined not to be in a braking state.

[0017] Optionally, the predetermined time length is 2s.

[0018] Optionally, when the pitch system is in the braking state, assuming that the time length from the given speed v1 changing from zero to a non-zero value to the end of the correction time Δt1 is Δt3, then the correction speed v4 = (v1×Δt3) / Δt1. Optionally, when the pitch system is in the braking state, assuming that the time length from the output of the release command to the detection of the actual speed v2 of the pitch motor changing to a non-zero value is t2, and the time length from the detection of the actual speed v2 of the pitch motor changing to a non-zero value to the detection of the charging current of the supercapacitor being less than 1 / 2 of the stall current is t3, then Δt3 = t1+t2+t3.

[0019] Optionally, the normal pitch control process is: after controlling the pitch motor to work continuously at a given speed v1 for Δt2, the given speed sent to the pitch motor is adjusted to zero and the brake is applied.

[0020] Optionally, the given speed v1 sent to the pitch motor is adjusted to the step of ending the pitch adjustment, and the duration of the given speed v1 is Δt2-Δt3.

[0021] Optionally, the corrected speed v4 meets the limit requirement of the maximum pitch speed.

[0022] Optionally, the brake release time parameter t1 = 200ms.

[0023] A second object of the present application is to provide a pitch controller, which adopts the above-mentioned pitch brake detection and protection method based on capacitance detection to perform pitch control.

[0024] The third object of the present application is to provide a wind power generation system, including a windmill, a speed increaser, a wind turbine, a supercapacitor and a pitch system, wherein the pitch system includes a pitch controller, a pitch drive, a pitch motor, a relay and an electromagnetic brake valve, and the pitch controller adopts the above-mentioned pitch brake detection and protection method based on capacitor detection to perform pitch control.

[0025] The beneficial effects of the present invention are:

[0026] 1) This application scheme can identify the abnormality of the electromagnetic brake valve when an abnormality occurs in the early stage, and notify the operation and maintenance personnel to prepare and replace the components. On the one hand, it can avoid the occurrence of propeller jamming accidents, and on the other hand, it can avoid the extension of downtime caused by serious damage to the brake valve; on the other hand, it can also achieve accurate fault location, so as to "target" and reduce the workload of unnecessary fault point troubleshooting on site (such as disassembling the variable pitch motor).

[0027] 2) Compared with the method of detecting capacitor voltage, the method of this scheme has the following advantages: in the case of short-term stall, the drop in capacitor voltage is generally small and difficult to identify, but this application scheme can detect it. Compared with the method of detecting motor current, the detection accuracy is higher and more timely, because the variable pitch motor is generally an AC motor, and the calculation of the effective value of the current often has a certain time lag.

[0028] 3) Since the stall current of the variable pitch motor is the rated current, this feature ensures the correctness of the detection principle and the correctness of the detection results of the present application.

[0029] 4) Compared with the method of detecting brake release feedback, the present application scheme does not require hardware modification, does not require the installation of detection sensors in the brake valve of the variable pitch motor, and does not require hardware modification such as electrical equipment of the units that are already generating electricity; thus, the cost of technical modification can be reduced.

[0030] 5) Compared with the method of detecting the temperature of the pitch motor, this method can directly locate the brake valve and is not affected by other factors (such as frequent pitch changes, driver parameter errors, encoder abnormalities, and increased loads during strong winds, which can cause the temperature of the pitch motor to rise). The detection result is more accurate. It does not require complex calculations, can simplify the amount of calculations, and is applicable to a variety of different change characteristics.

[0031] 6) The calculation process of the present application does not require the influence of factors such as the pitch motor voltage, pitch motor current, encoder abnormality, etc., so the detection accuracy can be improved, and in the event of early abnormalities in the brake valve, an early warning or diagnosis can be accurately made.

[0032] 7) The method of this scheme will not cause pitch adjustment lag, so it will not affect the response accuracy of the pitch control system and will not affect the power generation of the wind turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 It is a schematic diagram of the hardware composition of the pitch system;

[0035] Figure 2 It is a curve diagram of the angle change of the three blades of the windmill under the action of the pitch motor and the brake valve;

[0036] Figure 3 This is a real shot of the wear of the electromagnetic brake valve in the pitch control system;

[0037] Figure 4 It is a schematic diagram of the feedback angle curve of the pitch motor and the current curve of the supercapacitor when the pitch motor is started and stopped;

[0038] Figure 5 It is the detection and control protection timing diagram;

[0039] Figure 6 It is a speed correction schematic diagram provided by this application;

[0040] Figure 7 This is the overall flow chart of the pitch brake detection and protection method based on capacitance detection provided in this application. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0042] Embodiment 1:

[0043] This embodiment provides a pitch brake wear protection and control method based on capacitance detection. First, the relevant technical terms involved in this application are introduced as follows:

[0044] (1) Feathering refers to the control process of turning the blades of a wind turbine to a state nearly parallel to the wind direction (also known as the safe position, which refers to the position of the blades at about 89 degrees) after a wind turbine fails.

[0045] (2) Loads: Due to direct or indirect action on the structure, internal forces (such as axial force, bending moment, shear force, torque, etc.) and deformations (such as rotation angle and cracks) are generated inside the structure, which are called "structural effects". For wind turbines, it mainly refers to horizontal loads, axial loads, wind loads, etc. when the unit is running.

[0046] (3) Pitch Angle: In a wind turbine, if the plane where the three blades are located is taken as a reference plane, then the angle between any blade and the reference plane is the blade pitch angle. The pitch angle on a wind turbine refers to the angle between the chord line of the airfoil at the top of the blade and the plane of rotation.

[0047] (4) Solenoid valve, an industrial device controlled by electromagnetics, is a basic component used to control fluid automation and is used in industrial control systems to adjust the direction, flow, speed and other parameters of the medium. Solenoid valves can be used in conjunction with different circuits to achieve the desired control.

[0048] Secondly, the hardware composition of the wind power generation system is introduced as follows:

[0049] The wind power generation system includes a windmill, a speed increaser, a wind turbine, a super capacitor and a pitch control system. The wind drives the windmill blades to rotate, and the speed increaser increases the rotation speed, thereby prompting the wind turbine to generate electricity, which is transmitted to the power grid through the charger and charges the super capacitor at the same time. The super capacitor is connected to the pitch control system to provide power for the pitch control system; Figure 1 As shown in FIG. 1 , the pitch control system includes a pitch control controller, a pitch drive, a pitch motor, a relay and an electromagnetic brake valve (the electromagnetic brake valve is not shown in FIG. 1 ). Figure 1 ).

[0050] Under normal working conditions, when the pitch controller receives the pitch speed from the main controller in the wind power generation system, or when the pitch controller detects a fault in the pitch system and autonomously adjusts the pitch, the pitch controller will send a speed command and an enable signal to the pitch driver; after receiving the speed command and the enable signal, the pitch driver will immediately control the coil of the relay to energize, release the electromagnetic brake valve, and output voltage at the power output port to drive the pitch motor to rotate, thereby realizing the pitch adjustment function.

[0051] There is a release time parameter between the release of the electromagnetic brake valve and the rotation of the pitch motor (usually 200ms, so that the electromagnetic brake valve can be completely released), that is, the pitch motor starts again 200ms after the electromagnetic brake valve is released to prevent the pitch motor from starting when the electromagnetic brake valve is not completely released, causing wear of the brake pads; and when the relay and electromagnetic brake valve slow down due to long-term work and the suction force decreases, resulting in release lag (the working current of the electromagnetic coil is proportional to the displacement of the pressure spring; and the working current comes from the contact current of the relay. Therefore, if the relay is not properly attracted, the electromagnetic brake valve will not be able to overcome the elastic force of the spring, and the electromagnetic brake valve will not be able to open smoothly), the electromagnetic brake valve will not be completely released after 200ms, but the pitch motor will start to rotate, which will cause wear of the brake pads. If the release time parameter is simply extended (for example, set to 300ms), the system response will slow down.

[0052] To this end, the present application provides a pitch brake detection and protection method based on capacitance detection, including:

[0053] Step 1, obtaining a given speed v1 and an actual speed v2 of the pitch motor, and judging whether the pitch system is in a brake state according to the given speed v1 and the actual speed v2;

[0054] If the actual speed v2 of the pitch motor remains zero after the given speed v1 changes from zero to a non-zero value, and the duration exceeds a predetermined time length, the pitch system is determined to be in a braking state; otherwise, the pitch system is determined not to be in a braking state.

[0055] Step 2. If the pitch system is in the braking state, execute the abnormal pitch adjustment process described in the following steps 3 to 6, otherwise execute the normal pitch adjustment control process; the normal pitch adjustment control process is: after controlling the pitch motor to work continuously at a given speed v1 for Δt2, adjust the given speed sent to the pitch motor to zero and brake.

[0056] Step 3, adjust the given speed v1 sent to the pitch motor to v3, and output the release command after controlling the delay t1, where v3 is the critical speed of the driver action; t1 is the release time parameter;

[0057] Step 4, after outputting the brake release command, detecting whether the actual speed v2 of the pitch motor becomes a non-zero value;

[0058] Assume that the time length between outputting the brake release command and detecting that the actual speed v2 of the pitch motor becomes a non-zero value is t2.

[0059] Step 5, when it is detected that the actual speed v2 of the variable pitch motor becomes a non-zero value, the charging current of the supercapacitor is detected in real time. When it is detected that the charging current of the supercapacitor is less than 1 / 2 of the stall current, the given speed v3 sent to the variable pitch motor is adjusted to the correction speed v4, and the correction time is set to Δt1; the stall current refers to the current when the variable pitch motor is stalled;

[0060] The time length from when the actual speed v2 of the variable pitch motor is detected to become a non-zero value to when the charging current of the supercapacitor is detected to be less than 1 / 2 of the stall current is t3;

[0061] Corrected speed v4 = (v1×Δt3) / Δt1, where Δt3 = t1+t2+t3.

[0062] Step 5: After the correction time Δt1, adjust the given speed sent to the pitch motor to v1 until the pitch adjustment is completed;

[0063] The duration of the given speed v1 is Δt2-Δt3.

[0064] Step 6: After the pitch adjustment is completed, adjust the given speed sent to the pitch motor to zero and apply the brake.

[0065] Embodiment 2:

[0066] This embodiment provides a pitch brake wear protection and control method based on capacitance detection. Combined with the research on wind power generation system, this application scheme is further described as follows:

[0067] like Figure 2 As shown, it is the angle change curve of the three blades of the wind turbine under the action of the pitch motor and the brake valve. Red, purple and green represent the angle changes of the three blades respectively. It can be seen that when the pitch is retracted, the rate of change of the angle value corresponding to the green curve becomes slower and slower, which eventually leads to the gradual increase of the angle deviation of the three blades and the wind turbine triggers the "angle inconsistency fault".

[0068] like Figure 3 The figure below shows the wear of the brake valve of the pitch motor. There are obvious friction marks on the contact section between the brake pad and the motor, and the magnet can absorb black particles and powder. At the same time, the thickness of the brake pad is seriously consumed.

[0069] From the perspective of physical mechanism, the cause of wear is that when the pitch motor is running at high speed, the electromagnetic brake valve is in the brake state or not fully opened. The control logic of the pitch drive brake is that the actual speed of the pitch motor is 0 for more than 2 seconds before the brake is engaged. Therefore, when the pitch motor stops, it will not cause brake wear. Therefore, the analysis is that when the pitch motor is started, a short-term stall and wear occurred. With the extension of the wind turbine operation time and the accumulation of wear, it eventually leads to severe wear and affects the normal operation of the wind turbine.

[0070] In view of the above problems, the present invention designs a pitch brake detection and protection method based on capacitor detection, which specifically includes: controlling the speed of the pitch motor when it starts by detecting the charging current of the supercapacitor, thereby avoiding wear of the brake valve due to high-speed operation of the pitch motor when the relay of the pitch system ages, the driving current decreases, or the suction of the brake valve decreases, causing the release action to slow down, thereby ensuring the normal operation of the wind turbine and avoiding the occurrence of batch failures.

[0071] See Figure 4 The figure below is a schematic diagram of the current curve when the pitch motor is started and stopped. The blue curve is the feedback angle of the pitch motor (also called the actual angle of the blade, collected by the encoder), and the red curve is the charging current of the supercapacitor. Figure 4 It can be seen that at the moment the pitch motor starts, due to the starting current characteristics of the pitch motor, the charging current of the supercapacitor will also increase instantly and reach -129.8A. At the moment the pitch motor stops, due to the braking effect of the pitch drive on the pitch motor, the supercapacitor current will also increase instantly. Negative values ​​indicate that the supercapacitor is charging, and positive values ​​indicate that the supercapacitor is reversely charged under the action of motor braking.

[0072] like Figure 4 As shown, when the pitch motor is started, the duration of the supercapacitor charging current increasing can be determined to be 240ms (from moment 858 to moment 882, the data sampling period is 10ms), that is, (882-858)*10ms=240ms.

[0073] Under normal circumstances, when the pitch motor is started and stopped, the fluctuation duration of the supercapacitor charging current should be consistent. However, when the electromagnetic relay or electromagnetic brake valve ages, the suction force decreases, and the suction speed slows down, the pitch motor will be blocked for a short time (that is, the driver has issued a speed command, but the electromagnetic brake valve is not fully opened), which will cause the duration of the supercapacitor charging current to increase further. This solution detects this current value to achieve abnormal detection of pitch motor release and anti-wear protection control.

[0074] The control conditions of this scheme are: after the pitch controller receives the given speed and enable signal sent by the main controller in the wind power generation system (specifically, the given speed changes from 0 to non-0), it first determines whether the previous actual pitch speed has been 0 for a long time (i.e., detects whether it is in the release state). If the actual pitch speed is 0 for 2 seconds or more, the detection and control method of this scheme is started. If it is less than 2 seconds, it is determined that the pitch system is not braked, and normal pitch control is performed.

[0075] See Figure 5 The following is the detection and protection timing diagram of this scheme. The horizontal axis is the time value. The detection and protection control logic of this scheme is:

[0076] 1) The pitch controller detects the given speed and the actual speed of the pitch motor during the time period from T0 to T1. If the actual speed of the pitch motor is 0 for 2 seconds or more after the given speed changes from a non-zero value to a non-zero value, the pitch motor is judged to be in the brake state, and the following brake release anti-wear protection logic is executed at this time; otherwise, the pitch motor is judged to be in the brake release state, and normal pitch control is executed;

[0077] 2) T1~T2 is the "speed holding interval", which limits the speed finally sent to the pitch motor to 0.1 degrees / second. This speed value is the critical speed of the driver's action. That is, the driver will control the pitch motor to run only when the speed is greater than this value. After that, the driver outputs the release command after a delay of 200ms.

[0078] 3) After the actual speed of the pitch control becomes non-zero, the controller can delay 200ms to detect whether the charging current of the supercapacitor is greater than 1 / 2 of the maximum value. If the charging current is still large at this time, the pitch control speed is still controlled at a low speed of 0.1 degrees / second, and the deviation is accumulated and calculated according to the time and the given speed value, so that corrections can be made later based on the deviation.

[0079] 4) When the charging current of the supercapacitor is less than 1 / 2 of the maximum value, a certain delay time can be set appropriately, such as the time from T2 to T3 in the figure. At this time, the speed finally sent to the driver is switched to the given speed, and the speed is adjusted appropriately to correct the small deviation of the following position caused by the speed holding interval. That is, the "speed correction interval" from T3 to T4.

[0080] 5) The preset time of the speed correction interval can be set to 500ms, and the maximum pitch speed is limited. When the speed correction time is reached, the "speed recovery interval" is entered and switched to the original given speed value again, as shown in the T4-T5 moment in the figure.

[0081] The maximum pitch speed is the maximum execution speed allowed in a safe state, for example, it cannot be greater than 4 degrees / second.

[0082] 6) When the given speed becomes 0, the actual speed sent to the driver also becomes 0, and the pitch motor stops running.

[0083] The specific detection and control method of this scheme is as follows: when it is identified that the variable pitch system is in a brake state and the given speed is not 0, it is first sent to the driver at a critical speed of 0.1 degrees / second. After 200ms (the release time parameter controlled by the driver), the charging current of the supercapacitor is detected. If the charging current of the supercapacitor is still at a large value after 200ms, it can be determined that a short-term stall has occurred. The control of the variable pitch system then enters the "speed holding interval". At this time, the controller still sends a speed command of 0.1 degrees / second and performs timing t1. When the charging current of the supercapacitor drops to a normal value, it exits the "speed holding interval", and the speed command sent to the driver is then switched to the normal given speed value, and the given speed is compensated according to the timing time t, to speed up the pitch adjustment speed of the variable pitch system and ensure the response speed of the variable pitch system.

[0084] See Figure 6 The figure shows a schematic diagram of speed correction of the present scheme, the purpose of which is to correct the slight deviation between the actual pitch adjustment position and the theoretical (or expected) pitch adjustment position caused by the speed limit in the "speed holding interval". The horizontal axis is time and the vertical axis is blade position.

[0085] Corresponds to Figure 5 , 0~T3 is the "speed holding interval" (the speed is 0.1 degrees / second, so the slope is small), T3~T4 is the "speed correction interval" (the speed increases, and the corresponding slope increases). The compensation method for the pitch speed of this scheme is: within the speed holding interval, the position is accumulated according to the given speed to obtain the position offset S. After exiting the speed holding interval, the given speed value is fine-tuned according to the position offset and the adjustment time t2 (which can be preset to 500ms). The fine-tuning amount is S / (T4-T3), that is, on the basis of the original given speed, s / t2 is increased to correct the position.

[0086] See Figure 7 The figure shows the overall flow chart of the brake valve anti-wear control of this scheme. The detailed control steps are:

[0087] In particular, a 200ms delay time can be set. If the capacitor charging current is small after 200ms, the anti-wear protection control is not performed, so the starting current of the feathering and pitching motor is large (determined by the motor starting characteristics). If the charging current is still large after a certain period of time, it is judged as a short-term stall.

[0088] The "speed holding interval" of this solution needs to be set to a certain duration, for example (500-800ms). If it exceeds this duration, it means that other abnormalities have occurred, such as real stall, encoder abnormality, brake valve disconnection, or mechanical jamming.

[0089] In particular, since the current of the variable pitch motor when starting and stopping is the maximum current, and the brake control logic of the variable pitch system is to brake only when the speed is 0 for 2 seconds or more, that is, the time is long enough, the duration of the supercapacitor current when stopping can be used as the current duration parameter detected during startup.

[0090] In summary:

[0091] 1. This scheme provides a pitch brake wear protection and control method based on capacitor detection. The basic principle is: by detecting the charging current of the supercapacitor, the speed of the pitch motor at startup is controlled, so as to avoid the wear of the brake valve due to the high-speed operation of the pitch motor when the relay of the pitch system is aged, the driving current is reduced, or the suction of the brake valve decreases, resulting in a slow release action, thereby ensuring the normal operation of the wind turbine and avoiding the occurrence of batch failures.

[0092] 2. The detection and anti-wear control protection of this solution are divided into "speed holding interval", "speed correction interval" and "speed recovery interval".

[0093] 3. The technical effect and feasibility of this solution are reflected in: through the charging control principle of supercapacitors and the operating mechanism of the variable pitch system, the brake release feedback, motor temperature and other result quantities that are difficult to detect or do not exist are converted into process quantities of action. This achieves the protection of the variable pitch motor from stalling or wear at the moment of starting.

[0094] 4. The control conditions of this scheme are: after the pitch controller receives the given speed and enable signal sent by the main control (specifically, the given speed changes from 0 to non-0), it first determines whether the previous pitch actual speed has been 0 for a long time (that is, whether it is in the release state). If the pitch actual speed is 0 for 2 seconds or more, the detection and control method of this scheme is started. If it is less than 2 seconds, it is determined that the pitch system is not braked, and normal pitch control is performed.

[0095] 5. The specific detection and control method of this scheme is as follows: when it is identified that the variable pitch system is in a braking state and the given speed is not 0, it is first sent to the driver at a critical speed of 0.1 degrees / second. After 200ms (the release time parameter controlled by the driver), the charging current of the supercapacitor is detected. If after 200ms, the charging current of the supercapacitor is still at a large value, it can be determined that a short-term stall has occurred. The control of the variable pitch system then enters the "speed holding interval". At this time, the controller still sends a speed command of 0.1 degrees / second and performs timing t1. When the charging current of the supercapacitor drops to a normal value, it exits the "speed holding interval", and the speed command sent to the driver is switched to the normal given speed value, and the given speed is compensated according to the timing time t, to speed up the pitch adjustment speed of the variable pitch system and ensure the response speed of the variable pitch system.

[0096] 6. In particular, since the current of the variable pitch motor when starting and stopping is the maximum current, and the brake control logic of the variable pitch system is to brake only when the speed is 0 for 2 seconds or more, that is, the time is long enough, the duration of the supercapacitor current when stopping can be used as the current duration parameter detected during startup.

[0097] 7. The compensation method for the pitch speed of this scheme is: within the speed holding interval, the position is accumulated according to the given speed to obtain the position offset s. After exiting the speed holding interval, the given speed value is fine-tuned according to the position offset and the adjustment time t2 (which can be preset to 500ms). The fine-tuning amount is s / t2, that is, s / t2 is increased on the basis of the original given speed.

[0098] 8. The "speed holding interval" of this solution needs to be set to a certain duration, for example (500-800ms). If it exceeds this duration, it means that other abnormalities have occurred, such as real stall, encoder abnormality, brake valve disconnection, or mechanical jamming.

[0099] Some steps in the embodiments of the present invention may be implemented using software, and the corresponding software program may be stored in a readable storage medium, such as a CD or a hard disk.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pitch brake detection and protection method based on capacitance detection, characterized in that: The method is applied to a pitch controller in a pitch system, and the method comprises: Step 1, obtaining a given speed v1 and an actual speed v2 of the pitch motor, and judging whether the pitch system is in a brake state according to the given speed v1 and the actual speed v2; Step 2: If the pitch control system is in the brake state, the abnormal pitch control process described in the following steps 3 to 6 is executed; otherwise, the normal pitch control process is executed; Step 3, adjust the given speed v1 sent to the pitch motor to v3, and output the brake release command after controlling the delay t1, where v3 is the critical speed of the driver action; Step 4, after outputting the brake release command, detecting whether the actual speed v2 of the pitch motor becomes a non-zero value; Step 5, when it is detected that the actual speed v2 of the variable pitch motor becomes a non-zero value, the charging current of the supercapacitor is detected in real time. When it is detected that the charging current of the supercapacitor is less than 1 / 2 of the stall current, the given speed v3 sent to the variable pitch motor is adjusted to the correction speed v4, and the correction time is set to Δt1; the stall current refers to the current when the variable pitch motor is stalled; Step 5: After the correction time Δt1, adjust the given speed sent to the pitch motor to v1 until the pitch adjustment is completed; Step 6: After the pitch adjustment is completed, adjust the given speed sent to the pitch motor to zero and apply the brake.

2. The method according to claim 1, characterized in that The step of judging whether the pitch control system is in a braking state according to the given speed v1 and the actual speed v2 includes: If the actual speed v2 of the pitch motor remains zero after the given speed v1 changes from zero to a non-zero value, and the duration exceeds a predetermined time length, the pitch system is determined to be in a braking state; otherwise, the pitch system is determined not to be in a braking state.

3. The method according to claim 2, characterized in that When the pitch control system is in the braking state, assuming that the time length from when the given speed v1 changes from a zero value to a non-zero value to when the correction time Δt1 ends is Δt3, the correction speed v4 = (v1×Δt3) / Δt1.

4. The method according to claim 3, characterized in that When the pitch system is in the braking state, assuming that the time length from outputting the release command to detecting that the actual speed v2 of the pitch motor becomes a non-zero value is t2, and the time length from detecting that the actual speed v2 of the pitch motor becomes a non-zero value to detecting that the charging current of the supercapacitor is less than 1 / 2 of the stall current is t3, then Δt3=t1+t2+t3.

5. The method according to claim 4, characterized in that The normal pitch control process is: after controlling the pitch motor to work continuously at a given speed v1 for Δt2, the given speed sent to the pitch motor is adjusted to zero and the brake is applied.

6. The method according to claim 5, characterized in that The given speed v1 sent to the pitch motor is adjusted to the step of ending the pitch adjustment, and the duration of the given speed v1 is Δt2-Δt3.

7. The method according to claim 6, characterized in that The t1 is a brake release time parameter.

8. The method according to claim 7, characterized in that The modified speed v4 meets the limit requirement of the maximum pitch speed.

9. A pitch controller, characterized in that: The pitch controller adopts the pitch brake detection and protection method based on capacitance detection as described in any one of claims 1-8 to perform pitch control.

10. A wind power generation system, comprising a windmill, a speed increaser, a wind turbine, a super capacitor and a pitch control system, characterized in that: The pitch system includes a pitch controller, a pitch driver, a pitch motor, a relay and an electromagnetic brake valve. The pitch controller uses the pitch brake detection and protection method based on capacitance detection as described in any one of claims 1 to 8 to perform pitch control.

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