Fault detection method and controller for a variable pitch system encoder

Abstract

A fault detection method and a controller of a variable pitch system encoder are disclosed. The fault detection method comprises: reading a blade angle value at each sampling moment within a preset time period of a variable pitch operation; generating a discrete binary sequence based on the blade angle value at each sampling moment; and in response to the expiration of the preset time period, determining whether a fault occurs in the variable pitch system encoder based on a fluctuation frequency of the discrete binary sequence.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to the field of wind power generation, and more particularly to a method for detecting faults of an encoder of a variable pitch system of a wind turbine generator system and a controller. BACKGROUND

[0002] A wind turbine is a device that converts wind energy into electrical energy, and the wind energy is converted into electrical energy through a hub, a speed increasing box and a generator, and the converted electrical energy is transmitted to a power grid through grid connection control. The variable pitch system of a wind turbine generator system plays a crucial role in tracking the maximum power of the wind turbine and ensuring the safe shutdown of the wind turbine generator system. The variable pitch system controls the rotational speed of the hub (i.e., the rotational speed of the wind turbine) by controlling the angle of the blades, thereby controlling the output power of the wind turbine generator system, and can make the wind turbine generator system stop safely in the form of aerodynamic braking. The blades of the wind turbine generator system are connected to the hub through variable pitch bearings, and each blade has its own relatively independent electrically controlled synchronous variable pitch system. The variable pitch system is connected to the inner teeth of the variable pitch bearing through a small gear. During normal operation of the wind turbine generator system, when the wind speed exceeds the rated wind speed of the system (for example, between 12 m / s and 25 m / s), in order to control the power output, the variable pitch angle is limited between 0 degrees and 30 degrees (the variable pitch angle is automatically adjusted according to the change of the wind speed), and the rotational speed of the wind turbine is kept constant by controlling the angle of the blades. Any situation causing the wind turbine generator system to stop will cause the blades to be pitched to 90 degrees (the blades will be pitched to a 91-degree limit position when an emergency pitch command is executed).

[0003] Currently, the control method of the variable pitch system of the wind turbine generator system is as follows: the actual rotational speed value of the wind turbine is detected by the main controller of the wind turbine generator system, and the target rotational speed value is set according to the characteristics of the model of the system, the deviation between the target rotational speed value and the actual rotational speed value is calculated by PID operation, and the blade angle value is output. After receiving the target angle value issued by the main control, the variable pitch system uses the absolute value signal of the encoder to collect the change of the blade angle value, forms a closed-loop PID negative feedback control with the variable pitch motor, controls the rotational speed and direction of the variable pitch motor, and the variable pitch motor is engaged with the inner gear ring of the hub through the driving gear, directly controls the angle of the blade.

[0004] In addition, the driver (variable pitch driver) of the variable pitch system also needs to collect the incremental signal of the encoder to detect the rotational speed and direction of the variable pitch motor. For example, the forward rotation and reverse rotation of the encoder can be determined by comparing whether the A phase of the incremental signal is in the front or the B phase is in the front, and the zero reference position of the encoder can be obtained through the zero position pulse. The incremental signal of the encoder is a function that can convert rotational motion into an output signal. Combined with mechanical transmission elements (such as gear racks, measuring wheels or spindles), the incremental signal can also measure linear motion. The encoder can convert the incremental form of position change into a continuous square wave signal output.

[0005] The encoder is a relatively precise and sensitive device. Abnormal working environment can cause the encoder to be damaged. Generally, the main reasons for the failure of the encoder are: 1) encoder itself failure or grating contamination, which means that the encoder itself component fails; 2) the encoder cable shielding line is not connected or falls off; 3) the encoder is loose; 4) abnormal voltage fluctuation causes the encoder to burn out.

[0006] Since the driver needs to collect the incremental signal of the encoder, after the encoder is damaged, the position signal detected by the driver will be incorrect, which will cause the pitch motor to operate abnormally, the motor current to become large, and even cause the internal trigger of the driver to stop. After the drive of the pitch system fails, the pitch system will appear to be stuck, at which time the pitch motor cannot drive the blades to the safe position, which will cause great hidden dangers to the safety of the wind turbine generator set. In addition, if it is a single shaft stuck, the impeller of the wind turbine generator set will be in operation due to the different positions of the three blades, and the wind energy acting on it will have a great deviation, that is, the impeller is not balanced, so it will have a great impact on the load of the wind turbine generator set, reducing the service life of the wind turbine generator set.

[0007] However, during troubleshooting, since the encoder (especially the incremental signal of the encoder) has no detection signal and detection device, the existing method for troubleshooting or detecting encoder failure is generally to replace the encoder and then test it. Since the encoder is installed in the pitch motor, disassembly and installation are time-consuming, which will bring great inconvenience to operation and maintenance. In addition, since the encoder signal is a high-frequency signal, there is currently no better device or circuit for detecting the encoder signal, so the troubleshooting of the encoder failure is difficult and time-consuming. SUMMARY

[0008] Embodiments of the present disclosure provide a pitch system encoder failure detection method and a controller, which can reduce the troubleshooting time of the encoder failure, improve the operation and maintenance efficiency, and reduce the downtime of the wind turbine generator set caused by the encoder failure.

[0009] In one general aspect, a pitch system encoder failure detection method is provided, which includes: reading a blade angle value at each sampling time within a preset time period of a pitch operation; generating a discrete binary sequence based on the blade angle value at each sampling time; and determining whether a pitch system encoder fails based on a fluctuation frequency of the discrete binary sequence in response to the expiration of the preset time period.

[0010] Optionally, the fault detection method further comprises: updating a preset angle no change counter, an angle rising counter and an angle falling counter based on the blade angle value at each sampling time; and the step of determining whether the pitch system encoder is faulty based on the fluctuation frequency of the discrete binary sequence comprises: in response to the fluctuation frequency of the discrete binary sequence being greater than a preset threshold, and the count values of the angle no change counter, the angle rising counter and the angle falling counter satisfying a preset condition, determining that the pitch system encoder is faulty.

[0011] Optionally, the preset condition comprises: the count value of the angle rising counter being greater than or equal to the difference between the number of sampling times in the preset time period and the count value of the angle no change counter, and the count value of the angle falling counter being zero; or the count value of the angle falling counter being greater than or equal to the difference between the number of sampling times in the preset time period and the count value of the angle no change counter, and the count value of the angle rising counter being zero.

[0012] Optionally, the step of generating binary discrete data based on the blade angle value at each time comprises: in response to the blade angle value at the current time being different from the angle value at the previous time, setting the position corresponding to the current time in the discrete binary sequence to 1; and in response to the blade angle value at the current time being the same as the angle value at the previous time, setting the position corresponding to the current time in the discrete binary sequence to 0.

[0013] Optionally, the fault detection method further comprises: reading a given pitch speed value at each time within a preset time period; and the step of generating binary discrete data based on the blade angle value at each time comprises: in response to the blade angle value at the current time being different from the angle value at the previous time, setting the position corresponding to the current time in the discrete binary sequence to 1; in response to the blade angle value at the current time being the same as the angle value at the previous time, and the given pitch speed value at the current time being non-zero, setting the position corresponding to the current time in the discrete binary sequence to 0; and in response to the blade angle value at the current time being the same as the angle value at the previous time, and the given pitch speed value at the current time being zero, setting the position corresponding to the current time in the discrete binary sequence to the value of the position corresponding to the previous time.

[0014] Optionally, the fluctuation frequency of the discrete binary sequence is calculated based on the number of times of 0 to 1 changes or the number of times of 1 to 0 changes in the discrete binary sequence and the length of the preset time period.

[0015] Optionally, the step of updating the preset count values of the angle no-change counter, the angle rising counter and the angle falling counter based on the blade angle value at each sampling time comprises: in response to the blade angle value at the current time being different from the angle value at the previous time, increasing the count value of the angle no-change counter by 1, and in response to the blade angle value at the current time being the same as the angle value at the previous time, keeping the count value of the angle no-change counter unchanged; in response to the blade angle value at the current time being greater than the angle value at the previous time, increasing the count value of the angle rising counter by 1, and in response to the blade angle value at the current time being less than or equal to the angle value at the previous time, keeping the count value of the angle rising counter unchanged; in response to the blade angle value at the current time being less than the angle value at the previous time, increasing the count value of the angle falling counter by 1, and in response to the blade angle value at the current time being greater than or equal to the angle value at the previous time, keeping the count value of the angle falling counter unchanged.

[0016] Optionally, in response to the start of the preset time period, the count values of the angle no-change counter, the angle rising counter and the angle falling counter are cleared.

[0017] Optionally, the step of determining that the pitch system encoder has failed comprises: determining that the pitch system encoder has an incremental signal abnormal failure, and outputting alarm information indicating that the incremental signal abnormal failure has occurred.

[0018] According to another aspect of the present disclosure, a computer readable storage medium storing a computer program is provided, when the computer program is executed by a processor, the pitch system encoder failure detection method as described above is implemented.

[0019] According to another aspect of the present disclosure, a controller is provided, the controller comprising: a processor; and a memory storing a computer program, when the computer program is executed by the processor, the pitch system encoder failure detection method as described above is implemented.

[0020] According to another aspect of the present disclosure, a wind turbine generator set is provided, the wind turbine generator set comprising the controller as described above.

[0021] The pitch system encoder failure detection method and the controller according to the present disclosure can directly determine whether the encoder has failed only by the running condition of the blade angle value, are suitable for various types of pitch systems, and have important significance for improving the efficiency of encoder failure elimination and reducing power generation loss.

[0022] In addition, the pitch system encoder failure detection method and the controller according to the present disclosure can realize early warning of encoder failure, so that the pitch system open-loop stall can be triggered in advance to prevent the situation of three-blade angle imbalance caused by short-time pitch locking.

[0023] In addition, according to the fault detection method and the controller of the pitch system encoder of the present disclosure, the encoder fault can be effectively distinguished from mechanical sticking, given speed fluctuation and the like, thereby improving the accuracy of fault detection. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and other objects and features of the present disclosure will become more apparent from the following description of embodiments taken in conjunction with the accompanying drawings, in which:

[0025] Figure 1 is a diagram illustrating a pitch cabinet topology of a wind turbine generator set and encoder signal transmission;

[0026] Figure 2 is a diagram illustrating an example of an incremental signal of an encoder;

[0027] Figure 3 is a diagram illustrating a change curve of an angle value of three blades in the case of an abnormality in the incremental signal of the encoder;

[0028] Figure 4 is a diagram illustrating a curve 301 in the enlarged Figure 3

[0029] Figure 5 is a flowchart illustrating a fault detection method of a pitch system encoder according to an embodiment of the present disclosure;

[0030] Figure 6 is a block diagram illustrating a controller according to an embodiment of the present disclosure;

[0031] Figure 7 is a diagram illustrating an application example of a fault detection method of a pitch system encoder according to an embodiment of the present disclosure;

[0032] Figure 8 is a curve graph illustrating a blade angle value when a pitch system open loop stall is triggered in the case of a fault in a pitch system encoder. DETAILED DESCRIPTION

[0033] The following detailed description is provided to help the reader understand the method, device and / or system described herein. However, various changes, modifications and equivalents can be made to the method, device and / or system described herein after understanding the disclosure of the present application. For example, the order of the operations described herein is only an example, and is not limited to those set forth herein, but can be changed as will be apparent to those skilled in the art after understanding the disclosure of the present application, except for the operations that must occur in a specific order. In addition, the description of features known in the art can be omitted for more clarity and conciseness.

[0034] ​Figure 1 is a diagram showing a topology of a variable pitch cabinet of a wind turbine generator and a signal transmission of an encoder.

[0035] Referring to Figure 1 , the variable pitch controller 11 and the variable pitch driver 12 are arranged inside the variable pitch cabinet 10, while the encoder 13 is arranged outside the variable pitch cabinet 10 and installed inside a variable pitch motor (not shown).

[0036] The signal lines of the encoder 13 are connected to the devices inside the variable pitch cabinet 10 via the wiring plugs on the cabinet body of the variable pitch cabinet 10, respectively. For example, the absolute value signal of the encoder 13 is transmitted to the encoder signal acquisition module of the variable pitch controller 11 for calculating the blade angle value, while the incremental signal of the encoder 13 is transmitted to the variable pitch driver 12 for calculating the rotating speed of the variable pitch motor.

[0037] As mentioned above, since there is no device specially used for detecting the incremental signal of the encoder in the prior art, the existing method for troubleshooting or detecting the fault of the encoder is generally to replace the encoder and make observation, which brings great inconvenience to operation and maintenance. Moreover, when the early slight abnormality of the incremental signal of the encoder occurs, it is also difficult to detect and discover the abnormality in the existing fault detection method.

[0038] Figure 2 is a diagram showing an example of the incremental signal of the encoder.

[0039] Referring to Figure 2 , the encoder directly outputs three groups of square wave pulses, i.e. A-phase, B-phase and Z-phase pulses, by using the photoelectric conversion principle. The phase of the A-phase pulse is 90° different from that of the B-phase pulse, and by judging whether the phase of the A-phase pulse is in the front or the phase of the B-phase pulse is in the front, the rotating direction (forward or reverse) of the encoder (variable pitch motor) can be determined. In addition, the encoder generates a Z-phase pulse every 360° rotation, which is used for reference point positioning. CLK is the clock signal of the encoder, which is used to assist in generating the A-phase, B-phase and Z-phase pulses.

[0040] The rotating speed value of the variable pitch motor is usually calculated according to the number of A-phase pulses and B-phase pulses within a certain time. Assuming that the number of pulses collected by the variable pitch driver within t time is m, and the number of pulses generated by the encoder every 360° rotation is N, then the number of rotations corresponding to the number of pulses m within t time is a = m / N. Accordingly, the rotating speed value n of the variable pitch motor can be calculated as n = 60*1000*m / N*t. Since the frequency of the clock signal of the encoder can reach 4096 or 8192 pulses per rotation, the rotating speed value of the variable pitch motor can also reach very high measurement accuracy.

[0041] From n = 60 * 1000 * m / N * t, it can be seen that the rotation speed value of the pitch motor mainly depends on the number of pulses m in the t time. When the incremental signal of the encoder is abnormal (for example, signal interference, wire breakage), etc., the number of pulses m will decrease, and the calculated rotation speed value will decrease. Since the pitch control requires the measured rotation speed value to track the given target speed, the voltage of the pitch motor will increase, and the reasons are as follows.

[0042] The rotation speed calculation formula of the pitch motor is: n = 60f / p*(1-s), where f is the power frequency of the pitch motor, and s is the rotation speed difference. From the above formula, it can be seen that if it is desired to increase the rotation speed of the pitch motor, the frequency f needs to be increased. Further, in the variable frequency speed regulation process, in order to keep the motor magnetic flux basically unchanged, it is necessary to make u / f≈const(constant), that is, while changing the frequency f, the stator voltage u also needs to be changed. The means to keep unchanged is to keep the voltage regulation ratio ku equal to the frequency regulation ratio kf, that is, ku=kf. Therefore, while adjusting the frequency, the voltage of the pitch motor will also increase. On the other hand, since u / f≈const(constant), in the case of low frequency resulting in insufficient torque, in order to make the pitch motor achieve sufficient output torque and track the given target speed, the current of the pitch motor needs to be increased.

[0043] Figure 3 is a diagram showing the change curve of the angle value of the three blades in the case of abnormal incremental signal of the encoder.

[0044] Referring to Figure 3 , the abscissa represents time, and the ordinate represents the blade angle value, wherein 0 o'clock is the time when the fault is triggered, that is, the blade angle values before and after the fault are around 0 o'clock. Curve 301 is the blade angle value of the shaft of the encoder with a fault. From Figure 3 it can be seen that when the wind turbine generator set triggers a fault and stops, the remaining two blades normally pitch, and the pitch speed shown by curve 301 is slow, and the reason is that when the incremental signal of the encoder is abnormal, the number of pulses in the same time decreases, the pitch control adjustment angle and the number of times of driving the pitch motor to operate decrease, and finally the pitch speed of the shaft of the encoder with a fault slows down.

[0045] Figure 4 is a diagram showing the enlarged Figure 3 curve 301 in

[0046] Referring to Figure 4 , the number of pulses in the same time decreases, the pitch control adjustment angle and the number of times of driving the pitch motor to operate decrease, so the angle value curve will have a continuous, high-frequency intermittent interruption phenomenon, that is, as shown inFigure 4 The horizontal line segment shown in the figure does not change in angle (as indicated by the box in the figure). The fault detection method of the pitch system encoder according to the embodiment of the present disclosure is just based on the working mechanism of the encoder when the incremental signal of the encoder is abnormal to realize the detection and early warning of the abnormality of the incremental signal of the encoder.

[0047] Figure 5 is a flow chart showing the fault detection method of the pitch system encoder according to the embodiment of the present disclosure. The fault detection method of the pitch system encoder according to the embodiment of the present disclosure can be implemented in the pitch controller of the wind turbine generator set, or in the main controller or other special-purpose controller of the wind turbine generator set.

[0048] Referring to Figure 5 In step S501, the blade angle value can be read at each sampling time within a preset time period of the pitch operation. As described above, the blade angle value can be obtained by reading the absolute value signal of the encoder. Alternatively, the preset time period can be repeated periodically during the pitch operation, and the length of the preset time period can be much longer than the scanning period of the pitch controller. For example, the scanning period of the pitch controller is 20 ms, and the length of the preset time period can be 20*20 ms = 400 ms, but is not limited thereto.

[0049] In step S502, a discrete binary sequence can be generated based on the blade angle value at each sampling time. Specifically, if the blade angle value at the current time is different from the angle value at the previous time, the position corresponding to the current time in the discrete binary sequence can be set to 1; if the blade angle value at the current time is the same as the angle value at the previous time, the position corresponding to the current time in the discrete binary sequence can be set to 0.

[0050] Further, in order to effectively distinguish the encoder failure condition from the given speed fluctuation condition, the fault detection method of the pitch system encoder according to the embodiment of the present disclosure can also read the given pitch speed value at each time within the preset time period. In this way, in the step of generating the discrete binary sequence, if the blade angle value at the current time is different from the angle value at the previous time, the position corresponding to the current time in the discrete binary sequence can be set to 1; if the blade angle value at the current time is the same as the angle value at the previous time, and the given pitch speed value at the current time is not zero, the position corresponding to the current time in the discrete binary sequence can be set to 0; if the blade angle value at the current time is the same as the angle value at the previous time, and the given pitch speed value at the current time is zero, the position corresponding to the current time in the discrete binary sequence can be set to the value of the position corresponding to the previous time (i.e., making the value of the position corresponding to the current time the same as the value of the position corresponding to the previous time).

[0051] Next, in step S503, in response to the expiration of the preset time period, it is determined whether the pitch system encoder fails based on the fluctuation frequency of the discrete binary sequence. Here, the fluctuation frequency of the discrete binary sequence can be calculated based on the number of 0-to-1 changes or the number of 1-to-0 changes in the discrete binary sequence and the length of the preset time period. That is, the fluctuation frequency of the discrete binary sequence can be calculated based on the number of pulses in the discrete binary sequence and the length of the preset time period. For example, assuming that the length of the preset time period is 400 ms, if there is only one pulse in the discrete binary sequence during the preset time period, the fluctuation frequency of the discrete binary sequence is 1*2.5 = 2.5 Hz, and if there are three pulses in the discrete binary sequence during the preset time period, the fluctuation frequency of the discrete binary sequence is 3*2.5 = 7.5 Hz. For another example, assuming that the length of the preset time period is 800 ms, if there is only one pulse in the discrete binary sequence during the preset time period, the fluctuation frequency of the discrete binary sequence is 1*1.25 = 1.25 Hz, and if there are eight pulses in the discrete binary sequence during the preset time period, the fluctuation frequency of the discrete binary sequence is 8*1.25 = 10 Hz.

[0052] According to an embodiment of the present disclosure, in order to effectively distinguish the encoder failure from the abnormal pitch adjustment (i.e., the positive transmission-stop-reverse of the pitch motor), the angle non-change counter, the angle rising counter and the angle falling counter can be preset, and the count values of the preset angle non-change counter, the angle rising counter and the angle falling counter can be updated based on the blade angle value at each sampling time. In this case, the pitch system encoder can be determined to be faulty in response to the fluctuation frequency of the discrete binary sequence being greater than a preset threshold value, and the count values of the angle non-change counter, the angle rising counter and the angle falling counter satisfying a preset condition. Further, when the fluctuation frequency of the discrete binary sequence is greater than the preset threshold value, and the count values of the angle non-change counter, the angle rising counter and the angle falling counter satisfy the preset condition, it can be determined that the pitch system encoder has an incremental signal abnormal failure, and alarm information indicating that the incremental signal is abnormal can be output. Here, the preset condition can include that the count value B of the angle rising counter is greater than or equal to the difference between the number D of sampling time points in a preset time period and the count value A of the angle non-change counter, and the count value C of the angle falling counter is zero (i.e., B≥D-A and C=0); or the count value C of the angle falling counter is greater than or equal to the difference between the number D of sampling time points in a preset time period and the count value A of the angle non-change counter, and the count value B of the angle rising counter is zero (i.e., C≥D-A and B=0). Alternatively, the preset threshold value can be set according to actual needs, for example, the preset threshold value can be in the range of 2Hz-5Hz, but is not limited thereto. Generally, in order to effectively distinguish the encoder failure from the mechanical jamming condition, the preset threshold value is generally not too low (for example, not less than 2Hz, but is not limited thereto).

[0053] According to an embodiment of the present disclosure, for the angle non-change counter, in response to the blade angle value at the current time being different from the angle value at the previous time, the count value of the angle non-change counter can be increased by 1, and in response to the blade angle value at the current time being the same as the angle value at the previous time, the count value of the angle non-change counter can be kept unchanged. For the angle rising counter, in response to the blade angle value at the current time being greater than the angle value at the previous time, the count value of the angle rising counter can be increased by 1, and in response to the blade angle value at the current time being less than or equal to the angle value at the previous time, the count value of the angle rising counter can be kept unchanged. For the angle falling counter, in response to the blade angle value at the current time being less than the angle value at the previous time, the count value of the angle falling counter can be increased by 1, and in response to the blade angle value at the current time being greater than or equal to the angle value at the previous time, the count value of the angle falling counter can be kept unchanged. Alternatively, the count values of the angle non-change counter, the angle rising counter and the angle falling counter can be cleared every time a preset time period starts.

[0054] According to the fault detection method of the pitch system encoder of the present disclosure, whether the encoder fails can be directly judged only through the running condition of the blade angle value, which is suitable for various types of pitch systems, and has important significance for improving the troubleshooting efficiency of the encoder failure and reducing the loss of power generation. In addition, according to the fault detection method of the pitch system encoder of the present disclosure, early warning of the encoder failure can be realized, so that the pitch system open-loop stall can be triggered in advance to prevent the imbalance of the three-blade angle caused by short-time pitch jamming. In addition, according to the fault detection method of the pitch system encoder of the present disclosure, the encoder failure can be effectively distinguished from mechanical jamming, given speed fluctuation and other conditions, thereby improving the accuracy of fault detection.

[0055] Figure 6 is a block diagram illustrating a controller according to an embodiment of the present disclosure. The controller according to the embodiment of the present disclosure can be implemented as a pitch controller of a wind turbine generator system, or as a main controller or other special-purpose controller of the wind turbine generator system.

[0056] Referring to Figure 6 The controller 600 disclosed according to the present embodiment can include a processor 610 and a memory 620. The processor 610 can include, but is not limited to, a central processing unit (CPU), a digital signal processor (DSP), a microcomputer, a field programmable gate array (FPGA), a system on chip (SoC), a microprocessor, an application specific integrated circuit (ASIC), etc. The memory 620 can store a computer program to be executed by the processor 610. The memory 620 can include a high-speed random access memory and / or a non-volatile computer readable storage medium. When the processor 610 executes the computer program stored in the memory 620, the wind storage joint frequency modulation method as described above can be implemented.

[0057] Alternatively, the controller 600 can communicate with other various components in the wind storage joint system in a wired / wireless communication manner, and can also communicate with other devices in the wind farm in a wired / wireless communication manner. In addition, the controller 600 can communicate with devices outside the wind farm in a wired / wireless communication manner.

[0058] Figure 7 is a diagram illustrating an application example of the fault detection method of the pitch system encoder according to an embodiment of the present disclosure.

[0059] Referring to Figure 7 The horizontal axis represents the number of scanning periods. The curve 701 represents the blade angle value, and the curve 702 represents the discrete binary sequence generated based on the blade angle value at each sampling time, where TRUE represents high level 1 and FALSE represents low level 0. From Figure 7It can be seen that the fluctuation frequency of the discrete binary sequence (pulse signal) is high, and two groups of obvious pulse signals appear in succession. Curve 703 represents the fluctuation frequency of the discrete binary sequence (pulse signal). From Figure 7 It can be seen that the minimum frequency value is 8 Hz, and the maximum frequency value is 18 Hz, both of which are greater than the preset threshold (for example, 5 Hz). Curve 704 represents the fault detection result of the encoder, where curve 704 is TRUE (high level 1) when the fluctuation frequency of the discrete binary sequence (pulse signal) (that is, the encoder fails) and is FALSE (low level 0) when the encoder does not fail. From Figure 7 It can be seen that the fault detection method of the pitch system encoder according to the embodiment of the present disclosure can accurately detect that the encoder has an incremental signal abnormal failure and realize the function of early warning.

[0060] Further, when the fault detection method of the pitch system encoder according to the embodiment of the present disclosure detects that the encoder has an incremental signal abnormal failure, the pitch system open-loop feathering can be triggered in advance to prevent the imbalance of the three-blade angle caused by short-time pitch sticking.

[0061] Figure 8 FIG. 8 is a curve diagram showing the blade angle value when the pitch system encoder fails and the pitch system open-loop feathering is triggered.

[0062] Referring to Figure 8 , the abscissa represents time, and the ordinate represents the blade angle value, where 0 o'clock is the time when the fault is triggered (that is, the open-loop feathering is triggered), that is, the blade angle values before and after the fault at around 0 o'clock. From Figure 8 It can be seen that at 0 o'clock, the blade angle value (curve 801) of the shaft of the encoder that fails is stuck for about 8 seconds, and then the open-loop feathering is started. During this period of time, since the other two blades normally perform feathering, the angle difference of the three blades becomes larger and larger, causing aerodynamic imbalance of the wind turbine impeller (the angle difference of the three blades reaches 35° at most). However, the fault detection method of the pitch system encoder according to the embodiment of the present disclosure can accurately detect that the encoder has an incremental signal abnormal failure, and trigger the pitch driver to stop urgently, so that the pitch system enters the open-loop feathering state in advance, thereby preventing the blade sticking and three-blade aerodynamic imbalance.

[0063] The failure detection method of the pitch system encoder according to the embodiments of the present disclosure can be written as a computer program and stored on a computer-readable storage medium. When the computer program is executed by a processor, the failure detection method of the pitch system encoder as described above can be implemented. Examples of the computer-readable storage medium include a read-only memory (ROM), a random access programmable read-only memory (PROM), an electrically erasable programmable read-only memory (EEPROM), a random access memory (RAM), a dynamic random access memory (DRAM), a static random access memory (SRAM), a flash memory, a non-volatile memory, a CD-ROM, a CD-R, a CD+R, a CD-RW, a CD+RW, a DVD-ROM, a DVD-R, a DVD+R, a DVD-RW, a DVD+RW, a DVD-RAM, a BD-ROM, a BD-R, a BD-R LTH, a BD-RE, a Blu-ray or optical disc memory, a hard disk drive (HDD), a solid state drive (SSD), a card memory such as a multimedia card, a secure digital (SD) card or an extreme digital (XD) card, a magnetic tape, a floppy disk, a magneto-optical data storage device, an optical data storage device, a hard disk, a solid state disk, and any other device configured to store a computer program and any associated data, data files and data structures in a non-transitory manner and provide the computer program and any associated data, data files and data structures to a processor or computer so that the processor or computer can execute the computer program. In one example, the computer program and any associated data, data files and data structures are distributed on a networked computer system, so that the computer program and any associated data, data files and data structures are stored, accessed and executed by one or more processors or computers in a distributed manner.

[0064] The failure detection method and controller of the pitch system encoder according to the present disclosure can directly determine whether the encoder has failed only by the running condition of the blade angle value, are suitable for various types of pitch systems, and have important significance for improving the efficiency of encoder failure elimination and reducing power generation loss. In addition, the failure detection method and controller of the pitch system encoder according to the present disclosure can realize early warning of encoder failure, so as to trigger the open-loop stall of the pitch system in advance and prevent the imbalance of the three-blade angle caused by short-time pitch sticking. In addition, the failure detection method and controller of the pitch system encoder according to the present disclosure can effectively distinguish the encoder failure from mechanical sticking, given speed fluctuation and other conditions, thereby improving the accuracy of failure detection.

[0065] While certain embodiments of the disclosure have been described and shown, those skilled in the art will understand that modifications can be made without departing from the principles and spirit of the disclosure, which is defined by the following claims and their equivalents.

Claims

1. A method of fault detection for a pitch system encoder, the method comprising: The fault detection method comprises: reading a blade angle value at each sampling time within a preset time period of a variable pitch operation; generating a discrete binary sequence based on the blade angle value at each sampling time; in response to the expiration of the preset time period, determining whether a variable pitch system encoder fails based on a fluctuation frequency of the discrete binary sequence; wherein the fault detection method further comprises: updating a preset angle no-change counter, an angle rising counter and an angle falling counter based on the blade angle value at each sampling time, wherein the step of determining whether the variable pitch system encoder fails based on the fluctuation frequency of the discrete binary sequence comprises: in response to the fluctuation frequency of the discrete binary sequence being greater than a preset threshold, and the count values of the angle no-change counter, the angle rising counter and the angle falling counter satisfying a preset condition, determining that the variable pitch system encoder fails; wherein the preset condition comprises: the count value of the angle rising counter is greater than or equal to the difference between the number of sampling times within the preset time period and the count value of the angle no-change counter, and the count value of the angle falling counter is zero; or the count value of the angle falling counter is greater than or equal to the difference between the number of sampling times within the preset time period and the count value of the angle no-change counter, and the count value of the angle rising counter is zero.

2. The fault detection method of claim 1, wherein, The step of generating binary discrete data based on the blade angle value at each time comprises: in response to the blade angle value at the current time being different from the angle value at the previous time, setting the position corresponding to the current time in the discrete binary sequence to 1; in response to the blade angle value at the current time being the same as the angle value at the previous time, setting the position corresponding to the current time in the discrete binary sequence to 0.

3. The fault detection method of claim 1, wherein, The fault detection method further comprises: reading a given variable pitch speed value at each time within a preset time period, wherein the step of generating binary discrete data based on the blade angle value at each time comprises: in response to the blade angle value at the current time being different from the angle value at the previous time, setting the position corresponding to the current time in the discrete binary sequence to 1; in response to the blade angle value at the current time being the same as the angle value at the previous time, and the given variable pitch speed value at the current time being non-zero, setting the position corresponding to the current time in the discrete binary sequence to 0; in response to the blade angle value at the current time being the same as the angle value at the previous time, and the given variable pitch speed value at the current time being zero, setting the position corresponding to the current time in the discrete binary sequence to the value of the position corresponding to the previous time.

4. The fault detection method according to claim 2 or 3, characterized in that, The fluctuation frequency of the discrete binary sequence is calculated based on the number of times of changes from 0 to 1 or the number of times of changes from 1 to 0 in the discrete binary sequence and the length of the preset time period.

5. The fault detection method of claim 1, wherein, The step of updating the preset angle no-change counter, the angle rising counter and the angle falling counter based on the blade angle value at each sampling time comprises: in response to the blade angle value at the current moment being different from the angle value at the previous moment, increasing the count value of the angle non-change counter by 1, and in response to the blade angle value at the current moment being the same as the angle value at the previous moment, keeping the count value of the angle non-change counter unchanged; in response to the blade angle value at the current moment being greater than the angle value at the previous moment, increasing the count value of the angle rise counter by 1, and in response to the blade angle value at the current moment being less than or equal to the angle value at the previous moment, keeping the count value of the angle rise counter unchanged; in response to the blade angle value at the current moment being less than the angle value at the previous moment, increasing the count value of the angle drop counter by 1, and in response to the blade angle value at the current moment being greater than or equal to the angle value at the previous moment, keeping the count value of the angle drop counter unchanged.

6. The fault detection method of claim 1, wherein, in response to the start of the preset time period, clearing the count values of the angle non-change counter, the angle rise counter and the angle drop counter.

7. The fault detection method of claim 1, wherein, The step of determining that the pitch system encoder has a fault comprises: determining that the pitch system encoder has an incremental signal abnormal fault, and outputting alarm information indicating that the incremental signal abnormal fault has occurred.

8. A computer readable storage medium storing a computer program, characterized in that, The computer program, when executed by a processor, implements the fault detection method of the pitch system encoder according to any one of claims 1 to 7.

9. A controller characterized by comprising: The controller comprises: a processor; and a memory storing a computer program, which, when executed by the processor, implements the fault detection method of the pitch system encoder according to any one of claims 1 to 7.

10. A wind power unit, characterized in that The wind turbine generator set comprises the controller according to claim 9.

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