Variable pitch control method and variable pitch controller for a wind turbine generator system

Abstract

A variable pitch control method and a variable pitch controller of a wind turbine generator system are disclosed. The variable pitch control method comprises: in response to the wind turbine generator system being in a variable pitch state, determining whether a variable pitch direction at a current control time is consistent with a variable pitch direction at a previous control time; in response to the variable pitch direction at the current control time being consistent with the variable pitch direction at the previous control time, correcting a given variable pitch speed at the current control time based on the given variable pitch speed at the current control time, a given variable pitch speed at a previous control time, and a preset correction coefficient; and controlling a variable pitch motor to perform a variable pitch operation based on the corrected given variable pitch speed.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of wind power generation in general, and more particularly, to a variable pitch control method and a variable pitch controller for a wind turbine. BACKGROUND

[0002] Since wind energy is a low-density energy with instability and randomness, the control technology of the wind turbine is the key to safe and efficient operation of the wind turbine. Developing a wind turbine system suitable for wind power conversion, reliable operation, high efficiency, good control performance and power supply performance, and advanced control technology is the key to the promotion and application of wind power.

[0003] With the large-scale of wind turbine capacity, variable pitch control has become the mainstream control method for current wind turbines. From the perspective of aerodynamics, when the wind speed is too high, only by adjusting the pitch angle and changing the angle of attack of the airflow on the blade can the aerodynamic torque obtained by the wind turbine be changed, so that the power output of the wind turbine can be kept stable; according to the Betz theory, if the pitch angle position is over-adjusted, the wind turbine cannot absorb the maximum wind energy, and even the speed of the wind turbine is unstable; if the pitch angle adjustment response time is too slow, the wind turbine cannot execute the pitch according to the control command in time, and also cannot absorb the maximum wind energy, and even the speed of the wind turbine is too fast. In addition, during the process of the wind turbine in the feathering, if the position is over-adjusted, it is possible to trigger the limit switch, or cause the blade position to shake during shutdown, affecting the service life of the pitch motor.

[0004] Therefore, optimizing the variable pitch control of the wind turbine plays a crucial role in the stable operation of the wind turbine and the improvement of the power generation. SUMMARY

[0005] Embodiments of the present disclosure provide a variable pitch control method and a variable pitch controller for a wind turbine, which can make the actual variable pitch speed of the variable pitch system more suitable for the change of the wind speed, especially the change of the speed of the wind turbine, and further make the operation of the wind turbine more stable.

[0006] In one general aspect, there is provided a variable pitch control method for a wind turbine, the variable pitch control method comprising: determining whether a variable pitch direction at a current control time is consistent with a variable pitch direction at a previous control time in response to the wind turbine being in a variable pitch state; correcting a given variable pitch speed at the current control time based on the given variable pitch speed at the current control time, a given variable pitch speed at the previous control time, and a preset correction coefficient in response to the variable pitch direction at the current control time being consistent with the variable pitch direction at the previous control time; and controlling a pitch motor to perform a variable pitch operation based on the corrected given variable pitch speed.

[0007] In another general aspect, there is provided a computer readable storage medium storing a computer program which, when executed by a processor, implements the pitch control method as described above.

[0008] In another general aspect, there is provided a pitch controller comprising: a processor; and a memory storing a computer program which, when executed by the processor, implements the pitch control method as described above.

[0009] In another general aspect, there is provided a wind turbine generator comprising the pitch controller as described above.

[0010] The pitch control method and the pitch controller of the wind turbine generator according to embodiments of the present disclosure can compensate for the lag of the pitch execution caused by the communication data transmission and the lag of the pitch execution to the wind speed change by modifying the given pitch speed, so as to make the pitch execution of the pitch system more match the actual rotational speed of the wind turbine, and improve the pitch response speed and the operation stability of the wind turbine generator. BRIEF DESCRIPTION OF DRAWINGS

[0011] The above and other objects and features of embodiments of the present disclosure will become more apparent from the following description of embodiments of the present disclosure when taken in conjunction with the accompanying drawings, which show, by way of illustration, embodiments of the present disclosure.

[0012] Figure 1 is a diagram showing an example of the rotational speed of the wind turbine and the pitch speed during the pitch operation of the wind turbine generator;

[0013] Figure 2 is a diagram showing another example of the rotational speed of the wind turbine and the pitch speed during the pitch operation of the wind turbine generator;

[0014] Figure 3 is a flowchart showing the pitch control method of the wind turbine generator according to embodiments of the present disclosure;

[0015] Figure 4 is a diagram showing the effect of the pitch control method of the wind turbine generator according to embodiments of the present disclosure;

[0016] Figure 5 is a block diagram showing the controller according to embodiments of the present disclosure. DETAILED DESCRIPTION

[0017] The following detailed description is presented to aid the reader in gaining a thorough understanding of the methods, devices, and / or systems described herein. However, various changes, modifications, and equivalents can be used, and the

[0018] At present, the pitch control of wind turbine mainly adopts PID control mode, that is, the main control system (main controller) of wind turbine group calculates the pitch angle value and transmits the corresponding given pitch speed to the pitch system by making the wind turbine run at constant speed as the control target, and the pitch system performs pitch operation according to the latest given pitch speed. This method can realize constant control of wind turbine speed to a certain extent, but also has the following shortcomings.

[0019] Firstly, since the wind speed is transient, the stability effect of wind turbine speed by simply using PID control mode has certain limitations. Secondly, PID control is based on target difference, that is, after detecting the change of wind turbine speed difference, the pitch operation is started, so it has hysteresis, and when the wind turbine group runs above the rated wind speed, the fluctuation of wind turbine speed will cause large load, affecting the service life of wind turbine group. Thirdly, due to the hysteresis of PID control, when the wind speed suddenly increases, the wind turbine overspeed phenomenon is easy to appear, which will lead to two situations, one is that the generator speed is too high, which increases the fatigue load of wind turbine group, and long-term operation at high speed will cause serious loss of wind turbine group and reduce the service life; the second is that the generator speed is too high, which is easy to trigger overspeed fault and stop. Fourthly, due to the hysteresis of PID control, when the wind speed suddenly decreases, the wind turbine group is easy to frequently switch between power constant region and speed constant region, the torque of the unit will decrease when the unit switches from power constant region to speed constant region, which leads to the decrease of power generation efficiency and affects the power generation of the unit.

[0020] In order to achieve accurate pitch control and reduce the lag of pitch execution to wind speed changes, the main method currently adopted is to predict or measure the wind speed in real time. However, the wind speed predicted by weather forecast information is not accurate due to high blindness, and it is difficult to serve as the basis for pitch control. On the other hand, the wind speed is measured by using a front-mounted wind speed sensor. Since the pitch hub is rotating, the sensor installation is limited, and the addition of a slip ring device easily causes data interference and instability. If the wind speed sensor is installed at the tail of the nacelle, it requires a longer measurement distance, thereby causing cost increase.

[0021] Figure 1 is a diagram showing an example of wind turbine rotor speed and pitch speed during pitch operation of a wind turbine generator.

[0022] Referring to Figure 1 , curve 101 represents the wind turbine rotor speed, curve 102 represents the given pitch speed, curve 103 represents the actual pitch speed executed by the pitch system, and the horizontal axis represents time, and the vertical axis represents the change trend of the three curves only, not the numerical size relationship with each other.

[0023] The principle of pitch control is to take the actual rotor speed and the target rotor speed of the wind turbine generator as input to calculate the pitch speed to be executed. When the actual rotor speed of the wind turbine generator is higher than the target rotor speed, a positive speed is output to pitch in, and when the actual rotor speed of the wind turbine generator is lower than the target rotor speed, a negative speed is output to pitch out, thereby making the wind turbine rotor speed run stably around the target rotor speed.

[0024] However, the existing pitch control method has the following disadvantages. After the wind turbine rotor speed changes, the pitch speed to be executed is calculated, so the calculated pitch speed has a certain lag. On the other hand, since the data transmission between the main control system and the pitch system of the wind turbine generator adopts DP communication mode, the transmission period is generally 20 ms, and the scanning period of the main control system and the pitch controller is generally also 20 ms, so from the calculation of the given pitch speed by the main control system to the execution of the given pitch speed by the pitch controller, there is generally a lag of about 60 ms. The lag of pitch execution caused by the above two factors, combined with the fact that wind speed transients will immediately cause changes in wind turbine rotor speed, makes it difficult for pitch control to match the wind turbine rotor speed.

[0025] As Figure 1As shown, the wind turbine speed (curve 101) increases at time t1, and then the given pitch speed (curve 102) output by the main control system starts to decrease at time t2 after detecting the increase in the wind turbine speed. The main control system calculates the given pitch speed and sends the given pitch speed to the pitch system, but due to the lag in communication data transmission, the pitch system can only receive the given pitch speed at time t3, at which time the given pitch speed is no longer matched to the pitch speed of the wind turbine. Further, the pitch system starts to perform the pitch operation at time t3, but the corresponding wind turbine speed has further increased, which can easily cause fluctuations or instability in the generator speed, and further affect the power generation and load of the wind turbine generator set.

[0026] Figure 2 FIG. 3 is a diagram showing another example of wind turbine speed and pitch speed during pitch operation of a wind turbine generator set.

[0027] Referring to Figure 2 , the abscissa represents the time value, and the ordinate represents the variable value, wherein curve 201 represents the wind turbine speed, curve 202 shows the given pitch speed, and curve 203 represents the actual pitch speed executed by the pitch system. As Figure 2 shown, after the given pitch speed reaches the maximum value, the wind turbine speed is still increasing, and thus a certain pitch deviation occurs. At the same time, there is also a significant time difference between the actual pitch speed and the given pitch speed.

[0028] This situation cannot be solved by adjusting the PID parameters, because the given pitch speed is based on the wind turbine speed, and the wind turbine speed inevitably lags behind the change in wind speed. Therefore, changing the PID parameters can only speed up the response, but cannot solve the problem of pitch execution lag. On the other hand, the PID control has the characteristic that when the PID parameters are increased, the system response speed can be accelerated, but system overshoot can be caused, which is not conducive to the stability of the wind turbine speed.

[0029] Therefore, the pitch control method of the wind turbine generator set according to the embodiments of the present disclosure optimizes the actual pitch speed executed by the pitch system by utilizing the speed change characteristics of the PID control and the communication data transmission time difference between the main control system and the pitch system, so as to accelerate the pitch, make the actual pitch speed executed by the pitch system more adaptive to the change in wind speed, especially the change in wind turbine speed, and further make the operation of the wind turbine generator set more stable.

[0030] Figure 3is a flow chart illustrating a pitch control method of a wind turbine generator according to an embodiment of the present disclosure. The pitch control method can be implemented in a pitch controller of the wind turbine generator, or in a main controller or other dedicated controller of the wind turbine generator.

[0031] Referring to Figure 3 In step S301, in response to the wind turbine generator being in a pitch state, it can be determined whether the pitch direction at the current control time is consistent with the pitch direction at the previous control time. Here, the current control time can be the Nth time to the (N+M)th time in the pitch operation process, where N is an integer greater than 1 and M is an integer greater than or equal to 1. If the pitch control method is performed during the entire pitch operation, the (N+M)th time in the pitch operation process can be a time before the end of the pitch operation.

[0032] According to an embodiment of the present disclosure, it can be determined whether the pitch direction at the current control time is consistent with the pitch direction at the previous control time according to the given pitch speed at the current control time and the given pitch speed at the previous control time. Specifically, if the given pitch speed at the current control time and the given pitch speed at the previous control time are both positive or both negative, it can be determined that the pitch direction at the current control time is consistent with the pitch direction at the previous control time, otherwise it can be determined that the pitch direction at the current control time is not consistent with the pitch direction at the previous control time.

[0033] In response to the pitch direction at the current control time being consistent with the pitch direction at the previous control time, in step S302, the given pitch speed at the current control time can be corrected based on the given pitch speed at the current control time, the given pitch speed at the previous control time and a preset correction coefficient. Specifically, a difference between the given pitch speed at the current control time and the given pitch speed at the previous control time can be calculated first. Then, it can be determined whether the difference is less than a preset threshold. In response to the difference being less than the preset threshold, the given pitch speed at the current control time can be corrected based on the given pitch speed at the current control time, the difference and the preset correction coefficient. For example, a product of the difference and the preset correction coefficient can be calculated, and a sum of the given pitch speed at the current control time and the product is determined as the corrected given pitch speed. According to an embodiment of the present disclosure, the preset correction coefficient can be an integer greater than 1, preferably in the range of 2 to 5, and the preset threshold can be, for example, 6 degrees / second.

[0034] In step S303, the pitch motor can be controlled to perform the pitch operation based on the corrected given pitch speed. However, if the difference between the given pitch speed at the current control time and the given pitch speed at the previous control time is greater than the preset threshold, the pitch control method can be exited, and the pitch motor can be controlled to perform the pitch operation based on the given pitch speed at the current time.

[0035] Alternatively, in response to the pitch direction at the current control moment being inconsistent with the pitch direction at the previous control moment, the pitch motor can be controlled to perform the pitch operation based on the given pitch speed at the current control moment in step S304. That is, when the pitch direction changes, the given pitch speed at the current control moment is directly used to perform the pitch operation without calculating the corrected given pitch speed. Then, the pitch control method can be re-executed.

[0036] The pitch control method of the wind turbine generator unit according to the embodiments of the present disclosure is described below in combination with specific data.

[0037] For example, during the pitch operation, it is assumed that the given pitch speed at the current control moment is 1.151 degrees / second and the given pitch speed at the previous control moment is 1.123 degrees / second. Since the given pitch speeds at the two moments are both positive, it can be determined that the pitch directions at the two moments are consistent, and the difference between the given pitch speeds at the two moments is 0.021 degrees / second. If the preset correction coefficient is 4 (i.e., the given pitch speed will be corrected by 4 periods), the corrected given pitch speed is 1.151+0.021*4=1.235 degrees / second.

[0038] For another example, during the pitch operation, it is assumed that the given pitch speed at the current control moment is 1.123 degrees / second and the given pitch speed at the previous control moment is 1.151 degrees / second. Since the given pitch speeds at the two moments are both positive, it can be determined that the pitch directions at the two moments are consistent, and the difference between the given pitch speeds at the two moments is -0.021 degrees / second. If the preset correction coefficient is 4 (i.e., the given pitch speed will be corrected by 4 periods), the corrected given pitch speed is 1.123+(-0.021*4)=1.039 degrees / second.

[0039] Figure 4 is a diagram showing the effect of the pitch control method of the wind turbine generator unit according to the embodiments of the present disclosure.

[0040] Referring to Figure 4 , curve 401 represents the given pitch speed, curve 402 represents the original actual pitch speed, curve 403 represents the corrected given pitch speed, the horizontal coordinate represents time, and the vertical coordinate represents only the value of the pitch speed. As Figure 4 shown, curve 401 and curve 402 have a large deviation in time, and curve 403 is close to the change of curve 401. It can be seen that the pitch control method can reduce the lag of the given pitch speed and improve the pitch performance of the wind turbine generator unit.

[0041] The variable pitch control method of the wind turbine generator set according to the embodiment of the present disclosure can compensate for the lag of the variable pitch execution caused by the communication data transmission and the lag of the variable pitch execution to the wind speed change by modifying the given variable pitch speed, so as to make the variable pitch execution of the variable pitch system more match the actual rotating speed of the wind turbine generator, improve the variable pitch response speed and the operation stability of the wind turbine generator set.

[0042] Figure 5 is a block diagram illustrating a controller according to an embodiment of the present disclosure.

[0043] Referring to Figure 5 The controller 500 according to the embodiment of the present disclosure can be implemented as a variable pitch controller, a main controller or other special-purpose controller of a wind turbine generator set. The controller 500 can include a processor 510 and a memory 520. The processor 510 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 520 can store a computer program to be executed by the processor 510. The memory 520 can include a high-speed random access memory and / or a non-volatile computer readable storage medium. When the processor 510 executes the computer program stored in the memory 520, the variable pitch control method of the wind turbine generator set as described above can be implemented.

[0044] Alternatively, the controller 500 can communicate with other various components in the wind turbine generator set 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 500 can communicate with devices outside the wind farm in a wired / wireless communication manner.

[0045] The variable pitch control method of a wind turbine generator system according to an embodiment of the 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 variable pitch control method of a wind turbine generator system 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 an 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 a computer so that the processor or the computer can execute the computer program. In one example, the computer program and any associated data, data files, and data structures are distributed over a networked computer system so that the computer program and any associated data, data files, and data structures are stored, accessed, and executed in a distributed manner by one or more processors or computers.

[0046] The variable pitch control method and the variable pitch controller of a wind turbine generator system according to an embodiment of the disclosure can compensate for the lag of variable pitch execution caused by communication data transmission and the lag of variable pitch execution to wind speed changes by modifying a given variable pitch speed, so that the variable pitch execution of the variable pitch system is more matched to the actual rotational speed of the wind turbine generator, and the variable pitch response speed and the operation stability of the wind turbine generator system are improved.

[0047] Although some embodiments of the disclosure have been shown and described, it should be understood by those skilled in the art that modifications can be made to the embodiments without departing from the principles and spirit of the disclosure, which are defined by the scope of the claims and their equivalents.

Claims

1. A method of pitch control of a wind turbine, characterized in that, The variable pitch control method comprises: in response to the wind turbine being in a variable pitch state, determining whether the variable pitch direction at a current control time is consistent with the variable pitch direction at a previous control time; in response to the variable pitch direction at the current control time being consistent with the variable pitch direction at the previous control time, correcting the given variable pitch speed at the current control time based on the given variable pitch speed at the current control time, the given variable pitch speed at the previous control time, and a preset correction coefficient; controlling the variable pitch motor to perform the variable pitch operation based on the corrected given variable pitch speed; wherein the step of correcting the given variable pitch speed at the current control time based on the given variable pitch speed at the current control time, the given variable pitch speed at the previous control time, and the preset correction coefficient comprises: calculating a difference between the given variable pitch speed at the current control time and the given variable pitch speed at the previous control time; determining whether the difference is less than a preset threshold value; in response to the difference being less than the preset threshold value, correcting the given variable pitch speed at the current control time based on the given variable pitch speed at the current control time, the difference, and the preset correction coefficient.

2. The pitch control method of claim 1, wherein, The variable pitch control method further comprises: in response to the variable pitch direction at the current control time being inconsistent with the variable pitch direction at the previous control time, controlling the variable pitch motor to perform the variable pitch operation based on the given variable pitch speed at the current control time.

3. The pitch control method of claim 1, wherein, in response to the given variable pitch speed at the current control time and the given variable pitch speed at the previous control time both being positive values or both being negative values, determining that the variable pitch direction at the current control time is consistent with the variable pitch direction at the previous control time.

4. The pitch control method of claim 1, wherein, The step of correcting the given variable pitch speed at the current control time based on the given variable pitch speed at the current control time, the difference, and the preset correction coefficient comprises: calculating a product of the difference and the preset correction coefficient; determining the sum of the given variable pitch speed at the current control time and the product as the corrected given variable pitch speed.

5. The pitch control method of any one of claims 1-4, wherein, The preset correction coefficient is an integer greater than 1.

6. The pitch control method of any one of claims 1-4, wherein, The current control time is the Nth time to the N+Mth time in the variable pitch operation process, wherein N is an integer greater than 1, and M is an integer greater than or equal to 1.

7. A computer readable storage medium storing a computer program, characterized in that, The computer program, when executed by the processor, implements the variable pitch control method according to any one of claims 1 to 6.

8. A pitch controller characterized by The variable pitch controller comprises: a processor; and a memory storing a computer program, which, when executed by the processor, implements the variable pitch control method according to any one of claims 1 to 6.

9. A wind power unit, characterized in that The wind turbine comprises the variable pitch controller according to claim 8.

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