CN116517789A - Method and system for identifying failure of variable pitch control requirement of wind generating set - Google Patents

Abstract

The invention belongs to the technical field of pitch control of wind turbines, and particularly relates to a method for identifying failure of pitch control requirements of a wind turbine generator system, wherein a comparison threshold value is obtained through processing a second input parameter, if the first input parameter is larger than the comparison threshold value, the magnitude of a small pitch angle overspeed rotating speed pitch angle threshold value and a current pitch requirement average angle is judged, and if the small pitch angle overspeed rotating speed pitch angle threshold value is larger than the current pitch requirement average angle, time accumulation is started to obtain a time accumulation value; and judging whether the failure of the variable pitch control requirement of the wind generating set is in an instantaneous state or in a long-term state by adopting a mode of accumulated time timing, and if the failure is judged to be in a non-instantaneous state, indicating that the failure of the variable pitch control requirement is caused, performing protection operation to ensure the normal and safe operation of the wind generating set.

Description

Method and system for identifying failure of variable pitch control requirement of wind generating set

Technical Field

The invention belongs to the technical field of variable pitch control of wind turbines, and particularly relates to a method and a system for identifying failure of variable pitch control requirements of a wind turbine generator set.

Background

The wind wheel of the horizontal axis wind driven generator absorbs wind energy to rotate, and then drives the connected generator to rotate for power generation. According to different wind speeds, the control targets of the wind generating set are different. Above rated wind speed, the control target is to control the rotating speed of the unit to be near the rated rotating speed through pitch control, so that the output power of the unit is near the rated power, and the mechanical and electrical components of the wind generating unit can be ensured to normally operate within the design range.

The traditional generator rotating speed-variable pitch control loop control input is the difference between the actually detected generator rotating speed and the set value of the generator rotating speed, the corresponding variable pitch angle is given through PI or PID control, and the variable pitch angle can limit or absorb wind energy to control the generator rotating speed. The traditional generator rotating speed-pitch control ring is closed-loop control, but the pitch control command is given to the pitch actuating mechanism to execute and then the whole wind wheel is limited to absorb or release wind energy due to the pitch action so as to control the generator rotating speed, and as the wind wheel of the wind generating set is a huge inertia component, a certain time is required from the pitch control command to the actual generator rotating speed control target to achieve, so that the problem that the pitch demand command is not matched with the generator rotating speed exists, for example, when a larger pitch angle is required to adjust larger rotating speed fluctuation, the given pitch control command is small enough to adjust the larger rotating speed fluctuation, so that intervention is not performed, and the generator rotating speed control target cannot be achieved.

Disclosure of Invention

The invention aims to provide a method for identifying failure of a pitch control demand of a wind generating set, which is used for finding out the problem that the matching of a pitch demand instruction and a generator rotating speed cannot be analyzed in the prior art, so that the problem that the failure of the pitch control demand of the wind generating set cannot be identified is solved more pertinently.

The invention is realized by the following technical scheme:

a method for identifying failure of pitch control requirements of a wind generating set specifically comprises the following steps:

s1, acquiring a first input parameter and a second input parameter;

preprocessing a second input parameter to obtain a comparison threshold;

if the first input parameter is smaller than or equal to the comparison threshold value, ending the control flow;

if the first input parameter is greater than the comparison threshold, starting S2;

s2, acquiring a small pitch angle overspeed rotating speed pitch angle threshold value and a blade pitch changing demand instruction;

obtaining the current variable pitch demand average angle according to the blade variable pitch demand instruction;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the current pitch-changing demand average angle, starting time accumulation to obtain a time accumulation value;

s3, acquiring a small pitch angle overspeed rotating speed time keeping threshold value;

judging whether the time accumulated value is larger than a small pitch angle overspeed rotation speed time keeping threshold value or not;

if the time accumulated value is smaller than or equal to the small pitch angle overspeed rotating speed time keeping threshold value, the control flow is terminated;

and if the time accumulated value is larger than the small pitch angle overspeed rotating speed time keeping threshold value, indicating that the pitch control requirement of the wind generating set is invalid, executing a protection operation by the pitch control system.

Further, when the obtained first input parameter is the generator rotating speed, the second input parameter is the current rated generator rotating speed;

s1 specifically comprises the following steps:

1.1. acquiring the current generator rotating speed and acquiring the current generator rated rotating speed;

1.2 multiplying the rated rotating speed of the current generator by a small pitch angle overspeed rotating speed gain coefficient to obtain a small pitch angle overspeed rotating speed judgment value omega_rate factor_spo;

1.3. judging whether the current generator rotating speed is larger than a small pitch angle overspeed rotating speed judgment value omega_speed;

if the current generator rotating speed is less than or equal to a small pitch angle overspeed rotating speed judgment value omega_speed_factor_spo, ending the control flow;

if the current generator speed is greater than the small pitch angle overspeed speed judgment value omega_rate_factor_spo, starting time accumulation to obtain a time accumulation value.

Further, when the obtained blade pitch demand command is a three-blade pitch demand command, in S2, the current pitch demand angles of the three blades are averaged to obtain a current pitch demand average angle of the three blades;

judging whether the current pitch demand average angle of the three blades is smaller than a small pitch angle overspeed rotating speed pitch angle threshold value or not;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is smaller than or equal to the current pitch-changing demand average angle of the three blades, the control flow is terminated;

and if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the current pitch-changing demand average angle of the three blades, starting time accumulation to obtain a time accumulation value.

Further, the current pitch demand angles of the three blades are averaged to obtain the current pitch demand average angle of the three blades, and the specific process is as follows:

summing the current variable pitch demand angles of the three blades, wherein the expression is as follows:

pitch_demand_sum＝pitch_demand1+pitch_demand2+pitch_demand3；

wherein, 1pitch_demand1 is the current pitch demand angle of the first blade; pitch_demand2 is the current pitch demand angle of the second blade; 3pitch_demand3 is the current pitch demand angle of the third blade;

dividing pitch_demand_sum by 3 yields the three-blade current pitch demand average angle pitch_demand_avg.

Further, when the acquired blade pitch demand command is a single blade pitch demand command, in S2, judging whether the current pitch demand angle of a certain blade is smaller than a small pitch angle overspeed rotating speed pitch angle threshold value;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is smaller than or equal to the average angle of the current pitch changing requirement of a certain blade, the control flow is terminated;

and if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the average angle of the current pitch changing requirement of a certain blade, starting time accumulation to obtain a time accumulation value.

Further, in S3, the mode of performing the protection operation by the pitch system adopts a shutdown mode, a power limiting mode or a rotation speed limiting mode.

Further, when the stopping operation of the pitch system is performed in a stopping mode, the method specifically comprises the following steps:

and the pitch system receives the pitch to a final position according to the pitch rate requirement, and the generator torque gives a generator torque command in a generator rotating speed table look-up mode.

Further, when the pitch system performs a shutdown operation in a power-limited manner, the method specifically includes: the power set point is set to be 50% -80% of rated power, and the pitch control loop and the torque control loop operate in a power-limited mode according to the power set point.

Further, when the stopping operation of the variable pitch system is performed in a rotation speed limiting mode, the method specifically comprises the following steps: the rotating speed set point is set to 70% -90% of the rated rotating speed, and the variable pitch control loop operates at the limited rotating speed according to the rotating speed set point.

A system for identifying failure of pitch control requirements of a wind generating set specifically comprises:

the acquisition module is used for acquiring a first input parameter, a second input parameter, a small pitch angle overspeed rotating speed time keeping threshold value and a blade pitch demand instruction;

the preprocessing module is used for preprocessing the second input parameters to obtain comparison thresholds;

the first comparison module is used for comparing the first input parameter with a comparison threshold value;

if the first input parameter is smaller than or equal to the comparison threshold value, ending the control flow;

if the first input parameter is larger than the comparison threshold value, a second comparison module is started;

the calculation module is used for obtaining the current pitch requirement average angle according to the blade pitch requirement instruction;

the second comparison module is used for judging the magnitude of the threshold value of the low pitch angle overspeed rotating speed pitch angle and the current average pitch changing demand angle;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the average angle of the current pitch changing requirement, starting a time accumulation module;

the time accumulation module is used for carrying out time accumulation to obtain a time accumulation value;

the third comparison module is used for judging whether the time accumulated value is larger than a small pitch angle overspeed rotation speed time keeping threshold value or not;

if the time accumulated value is smaller than or equal to the small pitch angle overspeed rotating speed time keeping threshold value, the control flow is terminated;

and if the time accumulated value is larger than the small pitch angle overspeed rotating speed time keeping threshold value, indicating that the pitch control requirement of the wind generating set is invalid, executing a protection operation by the pitch control system.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention discloses a method for identifying failure of variable pitch control requirements of a wind generating set, which comprises the steps of obtaining a comparison threshold value through processing a second input parameter, if the first input parameter is larger than the comparison threshold value, starting to judge the magnitude of a small pitch angle overspeed rotating speed pitch angle threshold value and a current variable pitch requirement average angle, and if the small pitch angle overspeed rotating speed pitch angle threshold value is larger than the current variable pitch requirement average angle, starting to perform time accumulation to obtain a time accumulation value; and judging whether the failure of the variable pitch control requirement of the wind generating set is in an instantaneous state or in a long-term state by adopting a mode of accumulated time timing, and if the failure is judged to be in a non-instantaneous state, indicating that the failure of the variable pitch control requirement is caused, performing protection operation to ensure the normal and safe operation of the wind generating set.

The variable pitch requirement control instruction is used as a condition input for identifying whether the variable pitch control requirement of the wind generating set is invalid, and no detection hardware is required to be added; when the failure of the pitch control requirement is identified, the shutdown protection is immediately carried out, so that the failure of the control target caused by the wrong pitch control requirement is prevented.

Furthermore, if the rotation speed of the generator continuously rises, the continuous rising of the rotation speed by the pitch control command can cause serious consequences such as overspeed galloping, so the invention takes the rotation speed of the generator as the condition input for identifying whether the pitch control requirement of the wind generating set is invalid, when the rotation speed of the generator exceeds a comparison threshold value, time accumulation is started, and when the accumulated time is greater than a small pitch angle overspeed rotation speed time keeping threshold value, the failure is judged to be immediately subjected to shutdown protection.

Drawings

Fig. 1 is a flowchart of embodiment 1 of the present invention.

Detailed Description

The objects, technical solutions and advantages of the present invention will be more apparent from the following detailed description with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention, i.e., the embodiments described are merely some, but not all, of the embodiments of the invention.

The components illustrated in the figures and described and shown in the embodiments of the invention may be arranged and designed in a wide variety of different configurations, and thus the detailed description of the embodiments of the invention provided in the figures below is not intended to limit the scope of the invention as claimed, but is merely representative of selected ones of the embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present invention, based on the figures and embodiments of the present invention.

It should be noted that: the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, element, method, article, or apparatus.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

As shown in fig. 1, the invention discloses a method for identifying failure of pitch control requirements of a wind generating set, which specifically comprises the following steps:

1. acquiring the current rated rotation speed omega_rated of the generator; acquiring a small pitch angle overspeed rotating speed gain coefficient factor_spo;

2. multiplying the current rated rotation speed omega_speed of the generator by a small pitch angle overspeed rotation speed gain coefficient factor_spo to obtain omega_rated factor_spo, wherein the Chinese name is a small pitch angle overspeed rotation speed judgment value;

3. acquiring the current generator rotation speed omega;

4. judging whether the current generator rotation speed omega is greater than omega_rated factor_spo;

if the current generator rotation speed omega is less than or equal to omega_rated factor_spo, ending the control flow;

5. if the current generator rotating speed omega is larger than omega_rated factor_spo, acquiring a small pitch angle overspeed rotating speed pitch angle threshold value and current pitch changing demand angles of three blades;

summing the current pitch demand angles of the three blades to obtain:

pitch_demand_sum＝pitch_demand1+pitch_demand2+pitch_demand3；

wherein, 1pitch_demand1 is the current pitch demand angle of the first blade; pitch_demand2 is the current pitch demand angle of the second blade; 3pitch_demand3 is the current pitch demand angle of the third blade; dividing the pitch_demand_sum by 3 to obtain a three-blade current pitch demand average angle pitch_demand_avg;

6. judging the magnitude of an average angle between a small pitch angle overspeed rotating speed pitch angle threshold and the current pitch changing requirement of the three blades;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the current pitch-changing demand average angle, starting to perform time accumulation timer, wherein the timer is initially set to 0, and accumulating time;

7. acquiring a small pitch angle overspeed rotation speed time keeping threshold value durationthreshold_spo;

judging whether the timer is greater than the reducing threshold_spo;

if the timer is less than or equal to the reducing threshold_spo, the control flow is terminated;

if the timer is greater than the reducing threshold_spo, the pitch system performs a shutdown operation;

the stopping operation of the variable pitch system is specifically as follows: the pitch rate demand is given by the pitch rate demand through the pitch system to the final position, and the generator torque command torque_demand is given by the generator torque through the generator speed table look-up mode.

Example 2

As shown in fig. 1, the invention discloses a method for identifying failure of pitch control requirements of a wind generating set, which specifically comprises the following steps:

1. acquiring the current rated rotation speed omega_rated of the generator; acquiring a small pitch angle overspeed rotating speed gain coefficient factor_spo;

2. multiplying the current rated rotation speed omega_speed of the generator by a small pitch angle overspeed rotation speed gain coefficient factor_spo to obtain omega_rated factor_spo, wherein the Chinese name is a small pitch angle overspeed rotation speed judgment value;

3. acquiring the current generator rotation speed omega;

4. judging whether the current generator rotation speed omega is greater than omega_rated factor_spo;

if the current generator rotation speed omega is less than or equal to omega_rated factor_spo, ending the control flow;

5. if the current generator rotating speed omega is larger than the omega_rated factor_spo, acquiring a small pitch angle overspeed rotating speed pitch angle threshold value pitchthreshold_spo and a current pitch demand angle of a single blade;

6. judging whether the current pitch demand angle of a single blade is smaller than a small pitch angle overspeed rotating speed pitch angle threshold value pitch threshold_spo;

if the current pitch demand angle of the single blade is greater than or equal to a small pitch angle overspeed rotating speed pitch angle threshold value pitch threshold_spo, the control flow is terminated;

if the current pitch demand angle of a single blade is smaller than the small pitch angle overspeed rotating speed pitch angle threshold value pitch threshold_spo, starting to perform time accumulation timer, wherein the timer is initially set to 0, and accumulating time;

7. acquiring a small pitch angle overspeed rotation speed time keeping threshold value durationthreshold_spo;

judging whether the timer is greater than the reducing threshold_spo;

if the timer is less than or equal to the reducing threshold_spo, the control flow is terminated;

if the timer is greater than the reducing threshold_spo, the pitch system performs a shutdown operation;

the stopping operation of the variable pitch system is specifically as follows: the pitch rate demand is given by the pitch rate demand through the pitch system to the final position, and the generator torque command torque_demand is given by the generator torque through the generator speed table look-up mode.

The invention adopts the rotation speed of the generator and the pitch control instruction as control input, and judges whether the rotation speed of the generator and the pitch control instruction are matched or not by judging the relation between the rotation speed of the generator and the pitch control instruction and the threshold value.

The invention adopts the mode of shutdown protection, but is not limited to the mode, and other modes such as power limiting, rotating speed limiting and the like are adopted.

When the pitch system executes the shutdown operation in a power limiting mode, the method specifically comprises the following steps: the power set point is set to be 50% -80% of rated power, and the pitch control loop and the torque control loop operate in a power-limited mode according to the power set point.

When the stopping operation of the variable pitch system is performed in a rotation speed limiting mode, the method specifically comprises the following steps: the rotating speed set point is set to 70% -90% of the rated rotating speed, and the variable pitch control loop operates at the limited rotating speed according to the rotating speed set point.

The invention also discloses a system for identifying the failure of the pitch control requirement of the wind generating set, which specifically comprises the following steps:

the acquisition module is used for acquiring a first input parameter, a second input parameter, a small pitch angle overspeed rotating speed time keeping threshold value and a blade pitch demand instruction;

the preprocessing module is used for preprocessing the second input parameters to obtain comparison thresholds;

the first comparison module is used for comparing the first input parameter with a comparison threshold value;

if the first input parameter is smaller than or equal to the comparison threshold value, ending the control flow;

if the first input parameter is larger than the comparison threshold value, a second comparison module is started;

the calculation module is used for obtaining the current pitch requirement average angle according to the blade pitch requirement instruction;

the second comparison module is used for judging the magnitude of the threshold value of the low pitch angle overspeed rotating speed pitch angle and the current average pitch changing demand angle;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the average angle of the current pitch changing requirement, starting a time accumulation module;

the time accumulation module is used for carrying out time accumulation to obtain a time accumulation value;

the third comparison module is used for judging whether the time accumulated value is larger than a small pitch angle overspeed rotation speed time keeping threshold value or not;

if the time accumulated value is smaller than or equal to the small pitch angle overspeed rotating speed time keeping threshold value, the control flow is terminated;

and if the time accumulated value is larger than the small pitch angle overspeed rotating speed time keeping threshold value, indicating that the pitch control requirement of the wind generating set is invalid, executing a protection operation by the pitch control system.

Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.

Claims (10)

1. The method for identifying the failure of the pitch control requirement of the wind generating set is characterized by comprising the following steps of:

s1, acquiring a first input parameter and a second input parameter;

preprocessing a second input parameter to obtain a comparison threshold;

if the first input parameter is smaller than or equal to the comparison threshold value, ending the control flow;

if the first input parameter is greater than the comparison threshold, starting S2;

s2, acquiring a small pitch angle overspeed rotating speed pitch angle threshold value and a blade pitch changing demand instruction;

obtaining the current variable pitch demand average angle according to the blade variable pitch demand instruction;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the current pitch-changing demand average angle, starting time accumulation to obtain a time accumulation value;

s3, acquiring a small pitch angle overspeed rotating speed time keeping threshold value;

judging whether the time accumulated value is larger than a small pitch angle overspeed rotation speed time keeping threshold value or not;

if the time accumulated value is smaller than or equal to the small pitch angle overspeed rotating speed time keeping threshold value, the control flow is terminated;

and if the time accumulated value is larger than the small pitch angle overspeed rotating speed time keeping threshold value, indicating that the pitch control requirement of the wind generating set is invalid, executing a protection operation by the pitch control system.

2. The method for identifying a failure in pitch control demand of a wind turbine generator set according to claim 1, wherein when the obtained first input parameter is a generator speed, the second input parameter is a current generator rated speed;

s1 specifically comprises the following steps:

1.1. acquiring the current generator rotating speed and acquiring the current generator rated rotating speed;

1.2 multiplying the rated rotating speed of the current generator by a small pitch angle overspeed rotating speed gain coefficient to obtain a small pitch angle overspeed rotating speed judgment value omega_rate factor_spo;

1.3. judging whether the current generator rotating speed is larger than a small pitch angle overspeed rotating speed judgment value omega_speed;

if the current generator rotating speed is less than or equal to a small pitch angle overspeed rotating speed judgment value omega_speed_factor_spo, ending the control flow;

if the current generator speed is greater than the small pitch angle overspeed speed judgment value omega_rate_factor_spo, starting time accumulation to obtain a time accumulation value.

3. The method for identifying failure of pitch control requirements of a wind generating set according to claim 1, wherein when the obtained blade pitch requirement instruction is a three-blade pitch requirement instruction, in S2, current pitch requirement angles of three blades are averaged to obtain current pitch requirement average angles of three blades;

judging whether the current pitch demand average angle of the three blades is smaller than a small pitch angle overspeed rotating speed pitch angle threshold value or not;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is smaller than or equal to the current pitch-changing demand average angle of the three blades, the control flow is terminated;

and if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the current pitch-changing demand average angle of the three blades, starting time accumulation to obtain a time accumulation value.

4. The method for identifying failure of pitch control requirements of a wind generating set according to claim 3, wherein the method comprises the steps of averaging current pitch demand angles of three blades to obtain an average current pitch demand angle of three blades, and comprises the following specific steps:

summing the current variable pitch demand angles of the three blades, wherein the expression is as follows:

pitch_demand_sum＝pitch_demand1+pitch_demand2+pitch_demand3；

wherein, 1pitch_demand1 is the current pitch demand angle of the first blade; pitch_demand2 is the current pitch demand angle of the second blade; 3pitch_demand3 is the current pitch demand angle of the third blade;

dividing pitch_demand_sum by 3 yields the three-blade current pitch demand average angle pitch_demand_avg.

5. The method for identifying failure of pitch control requirements of a wind turbine generator system according to claim 1, wherein when the obtained blade pitch demand command is a single blade pitch demand command, in S2, it is determined whether a current pitch demand angle of a certain blade is smaller than a small pitch angle overspeed rotational speed pitch angle threshold;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is smaller than or equal to the average angle of the current pitch changing requirement of a certain blade, the control flow is terminated;

and if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the average angle of the current pitch changing requirement of a certain blade, starting time accumulation to obtain a time accumulation value.

6. The method for identifying failure of pitch control demand of a wind turbine according to claim 1, wherein in S3, a mode of performing a protecting operation by the pitch system is a shutdown mode, a power-limiting mode or a rotational speed-limiting mode.

7. The method for identifying failure of pitch control demand of a wind turbine according to claim 6, wherein when a shutdown mode is adopted for performing a shutdown operation of the pitch system, the method specifically comprises:

and the pitch system receives the pitch to a final position according to the pitch rate requirement, and the generator torque gives a generator torque command in a generator rotating speed table look-up mode.

8. The method for identifying failure of pitch control demand of a wind turbine according to claim 6, wherein when the pitch system performs a shutdown operation in a power-limited manner, the method specifically comprises: the power set point is set to be 50% -80% of rated power, and the pitch control loop and the torque control loop operate in a power-limited mode according to the power set point.

9. The method for identifying failure of pitch control demand of a wind turbine according to claim 6, wherein when the pitch system performs a shutdown operation in a speed limited manner, the method specifically comprises: the rotating speed set point is set to 70% -90% of the rated rotating speed, and the variable pitch control loop operates at the limited rotating speed according to the rotating speed set point.

10. A system for identifying a failure in pitch control demand of a wind turbine, comprising:

the acquisition module is used for acquiring a first input parameter, a second input parameter, a small pitch angle overspeed rotating speed time keeping threshold value and a blade pitch demand instruction;

the preprocessing module is used for preprocessing the second input parameters to obtain comparison thresholds;

the first comparison module is used for comparing the first input parameter with a comparison threshold value;

if the first input parameter is smaller than or equal to the comparison threshold value, ending the control flow;

if the first input parameter is larger than the comparison threshold value, a second comparison module is started;

the calculation module is used for obtaining the current pitch requirement average angle according to the blade pitch requirement instruction;

the second comparison module is used for judging the magnitude of the threshold value of the low pitch angle overspeed rotating speed pitch angle and the current average pitch changing demand angle;

if the threshold value of the small pitch angle overspeed rotating speed pitch angle is larger than the average angle of the current pitch changing requirement, starting a time accumulation module;

the time accumulation module is used for carrying out time accumulation to obtain a time accumulation value;

the third comparison module is used for judging whether the time accumulated value is larger than a small pitch angle overspeed rotation speed time keeping threshold value or not;

if the time accumulated value is smaller than or equal to the small pitch angle overspeed rotating speed time keeping threshold value, the control flow is terminated;

and if the time accumulated value is larger than the small pitch angle overspeed rotating speed time keeping threshold value, indicating that the pitch control requirement of the wind generating set is invalid, executing a protection operation by the pitch control system.