Load reduction method and system for low-voltage ride-through working condition of wind generating set

Abstract

The invention discloses a low-voltage ride-through working condition load reduction method and system for a wind generating set. The method comprises the steps that firstly, whether the wind generating set enters a low-voltage ride-through mode or not is judged; when it is judged that the wind generating set enters the low-voltage ride-through mode, the variable pitch rate a is superimposed on the original variable pitch rate; and after the preset time is continued, the superposition of the variable pitch speed is canceled, and the variable pitch action is executed according to the original variable pitch speed. When it is detected that the wind generating set enters the low-voltage ride-through state, a constant variable-pitch rate is superposed on the original variable-pitch rate, when the superposed variable-pitch rate reaches the set time, the superposed variable-pitch rate is cancelled, and the variable-pitch action is executed according to the variable-pitch rate calculated by the controller; and the hub limit load in the low-voltage ride-through transient process of the wind generating set can be effectively reduced.

Description

Technical Field

[0001] The present invention mainly relates to the field of wind power technology, and in particular to a method and system for reducing load in low-voltage ride-through conditions of a wind turbine generator set. Background Art

[0002] With the continuous increase in the unit capacity of wind turbines and the scale of wind farms, in order to avoid large-scale wind turbine disconnection accidents in the event of grid failure and reduce the impact on grid stability, the low voltage ride-through capability of wind turbines is an indispensable condition and requirement for large-scale grid-connected operation of wind power, and is the guarantee of the uninterrupted operation capability of wind turbines under external fault conditions. During the low voltage ride-through process of wind turbines, the transient adjustment process of wind turbines will cause the hub load of the turbine to exceed the limit, bringing great risks to the safety of the turbines.

[0003] The invention patent with application publication number CN112072694A analyzes the active and reactive output characteristics of wind turbines during low voltage ride-through and recovery, explores the impact mechanism of wind turbine low voltage ride-through on system transient overvoltage, and on this basis compares and analyzes the impact of different low voltage ride-through performance on wind turbine power characteristics and system transient overvoltage levels, points out the key influencing factors, and provides optimization suggestions for low voltage ride-through control during actual operation of wind turbines.

[0004] The invention patent CN112952850A enables the grid voltage to recover faster by enhancing the reactive current provided by the converter during fault ride-through, thereby reducing the probability of the unit voltage being disconnected from the grid due to long-term failure to recover.

[0005] However, the above-mentioned method of increasing reactive power will lead to low energy conversion efficiency, increase the difficulty of voltage fluctuation control and have a negative impact on the stability of the power grid. Summary of the invention

[0006] In view of the technical problems existing in the prior art, the present invention provides a method and system for reducing load in low-voltage ride-through conditions of a wind turbine generator set with fast response and precise control.

[0007] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0008] A load reduction method for a wind turbine generator set in a low-voltage ride-through condition, firstly judging whether the wind turbine generator set has entered a low-voltage ride-through mode; when judging that the wind turbine generator set has entered the low-voltage ride-through mode, superimposing a pitch change rate on the original pitch change rate; after a preset time has passed, canceling the superimposed pitch change rate, and performing the pitch change action at the original pitch change rate.

[0009] Preferably, whether the wind turbine generator set enters the low voltage ride-through mode is determined by monitoring the voltage level of the grid connection point; when the grid connection voltage is lower than a preset threshold, it is determined that the wind turbine generator set enters the low voltage ride-through mode.

[0010] Preferably, the pitch rate a is a constant pitch rate.

[0011] Preferably, the value range of a is 1-3° / s.

[0012] Preferably, the preset time is 1-2s.

[0013] Preferably, a new pitch rate obtained by superimposing the pitch rate a on the original pitch rate will not exceed the design limit of the pitch rate.

[0014] The present invention also discloses a load reduction system for a wind turbine generator set in a low voltage ride-through condition, comprising:

[0015] A judgment module, used to judge whether the wind turbine generator set enters the low voltage ride-through mode;

[0016] The control module is used to superimpose a pitch rate a on the original pitch rate when the wind turbine generator set enters the low-voltage ride-through mode; after a preset time, the superimposed pitch rate is cancelled and the pitch action is performed at the original pitch rate.

[0017] The present invention also discloses a computer program product, comprising a computer program, wherein the computer program executes the steps of the method described above when executed by a processor.

[0018] The present invention further discloses a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described above are executed.

[0019] The present invention also discloses a computer device, comprising a memory and a processor connected to each other, wherein a computer program is stored in the memory, and when the computer program is run by the processor, the steps of the method described above are executed.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] When the present invention detects that the wind turbine generator set enters a low-pressure ride-through state, a constant pitch rate is superimposed on the original pitch rate. When the superimposed pitch rate reaches a set time, the superimposed pitch rate is canceled and the pitch action is performed according to the pitch rate calculated by the controller, which can effectively reduce the hub limit load of the wind turbine generator set during the low-pressure ride-through transient process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flow chart of a method for reducing load in a low voltage ride-through condition of a wind turbine generator set in an embodiment. Specific embodiments

[0023] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0024] As Figure 1 shown, the method for reducing the load of a wind turbine generator under low-voltage ride-through conditions provided by an embodiment of the present invention includes the steps:

[0025] Judge whether the wind turbine generator enters the low-voltage ride-through mode through the low-voltage flag bit of the converter; wherein the converter continuously monitors the voltage level of the grid connection point. When the voltage drops below the specified threshold, it indicates that a low-voltage situation occurs, and a low-voltage flag bit signal will be sent; of course, it can also be based on the voltage and the unit

[0026] When it is judged that the wind turbine generator enters the low-voltage ride-through mode, on the basis of the power adjustment in the original low-voltage ride-through mode, a pitch rate of a is superimposed on the original pitch rate. The superimposed pitch rate can quickly increase the pitch angle to reduce the hub ultimate load during the transient process of the unit's low-voltage ride-through; where 0 < a < 4, and the unit of the pitch rate is ° / s; the most direct way to quickly adjust the pitch angle is to change the pitch rate in time; of course, the adjusted pitch rate will not exceed the design limit of the blade control system.

[0027] After a duration of b seconds, cancel the superimposed pitch rate and perform the pitch action according to the pitch rate originally calculated by the controller; the pitch rate a and the duration b are selected according to the load requirement; specifically, the pitch rate a can be a constant speed; the time b is generally adjusted according to the load situation, and the duration b < 3s. When the load is large, the duration is longer; however, the transient process of low-voltage ride-through is relatively short, generally 2 - 3 seconds, so the time b is generally selected to be about 1s.

[0028] When the present invention detects that the wind turbine generator enters the low-voltage ride-through state, a constant pitch rate is superimposed on the original pitch rate. When the superimposed pitch rate reaches the set time, cancel the superimposed pitch rate and perform the pitch action according to the pitch rate calculated by the controller, which can effectively reduce the hub ultimate load during the transient process of the wind turbine generator's low-voltage ride-through.

[0029] Compared with the current method of adjusting reactive power, the present invention has the following advantages:

[0030] Fast response: The adjustment of the pitch rate can directly affect the aerodynamic characteristics of the blade, thereby quickly changing the aerodynamic load of the wind turbine, which helps to respond more quickly to the low-voltage condition of the power grid. In contrast, adjusting reactive power may take longer to achieve the desired effect because the adjustment of reactive power usually involves the stability consideration of the entire power grid.

[0031] Control accuracy: The adjustment of the pitch rate can control the angle of the blades very accurately, thereby precisely controlling the aerodynamic load of the wind turbine. However, the adjustment of reactive power may involve multiple nodes of the entire power grid, and the control accuracy may be lower.

[0032] Reducing mechanical stress: By adjusting the pitch rate to reduce the load on the wind turbine, mechanical stress can be reduced without changing the wind turbine output power, which helps to extend the life of the wind turbine. Adjusting the reactive power may cause the active power output of the wind turbine to change, thus affecting the mechanical stress.

[0033] Improve grid stability: Rapid response to low voltage conditions helps improve grid stability and reduces the risk of voltage collapse. Although reactive power regulation also helps grid stability, it requires more time and resources to coordinate the response of the entire grid.

[0034] Reduce the impact on the power grid: The adjustment of pitch speed is mainly aimed at the internal parameters of the wind turbine, and the impact on the power grid is relatively small. The adjustment of reactive power will have an impact on other parts of the power grid and requires more coordination and control.

[0035] Taking a certain model as an example, when it is judged that the wind turbine generator set enters the low-voltage ride-through mode, while the wind turbine generator set adjusts the power in the original low-voltage ride-through mode, the pitch rate is superimposed on the original rate by 2° / s, and the duration is 1 second, so as to reduce the hub load in the low-voltage ride-through transient process.

[0036] The present invention determines that when a wind turbine generator set enters a low voltage ride-through mode by voltage, the ultimate load of the set is reduced by increasing the pitch rate of the low voltage ride-through transient process, thereby improving the safety of the set operation; the above method is easy to use, has strong versatility, and can be applied on multiple power platforms.

[0037] The present invention also discloses a load reduction system for a wind turbine generator set in a low voltage ride-through condition, comprising:

[0038] A judgment module, used to judge whether the wind turbine generator set enters the low voltage ride-through mode;

[0039] The control module is used to superimpose a pitch rate a on the original pitch rate when the wind turbine generator set enters the low-voltage ride-through mode; after a preset time, the superimposed pitch rate is cancelled and the pitch action is performed at the original pitch rate.

[0040] The embodiment of the present invention further discloses a computer program product, including a computer program, which executes the steps of the above method when executed by a processor. The embodiment of the present invention further discloses a computer-readable storage medium, on which a computer program is stored, which executes the steps of the above method when executed by a processor. The embodiment of the present invention further discloses a computer device, including a memory and a processor connected to each other, on which a computer program is stored, which executes the steps of the above method when executed by the processor.

[0041] The system, medium, product and equipment of the present invention all correspond to the above method and also have the advantages described in the above method.

[0042] The present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned method embodiment when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. Computer-readable storage media include: any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. The memory is used to store computer programs and / or modules, and the processor implements various functions by running or executing computer programs and / or modules stored in the memory, and calling data stored in the memory. The memory may include high-speed random access memory and may also include non-volatile memory, such as a hard disk, an internal memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0043] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for reducing load in low voltage ride-through condition of a wind turbine generator set, characterized in that: First, determine whether the wind turbine generator set has entered the low-voltage ride-through mode; when it is determined that the wind turbine generator set has entered the low-voltage ride-through mode, superimpose a pitch rate on the original pitch rate; after a preset time has passed, cancel the superimposed pitch rate and execute the pitch action at the original pitch rate.

2. The method for reducing load in low voltage ride-through condition of a wind turbine generator set according to claim 1, characterized in that: By monitoring the voltage level at the grid connection point, it is determined whether the wind turbine generator set has entered the low voltage ride-through mode; when the grid connection voltage is lower than the preset threshold, it is determined that the wind turbine generator set has entered the low voltage ride-through mode.

3. The method for reducing load in low voltage ride-through condition of a wind turbine generator set according to claim 1 or 2, characterized in that: The pitch rate a is a constant pitch rate.

4. The method for reducing load in low voltage ride-through condition of a wind turbine generator set according to claim 3, characterized in that: The value range of a is 1-3° / s.

5. The method for reducing load in low voltage ride-through condition of a wind turbine generator set according to claim 1 or 2, characterized in that: The preset time is 1-2s.

6. The method for reducing load in low voltage ride-through condition of a wind turbine generator set according to claim 1 or 2, characterized in that: The new pitch rate after the pitch rate a is superimposed on the original pitch rate will not exceed the design limit of the pitch rate.

7. A load shedding system for low voltage ride-through conditions of a wind turbine generator set, characterized in that: include: A judgment module, used to judge whether the wind turbine generator set enters the low voltage ride-through mode; A control module, used for superimposing a pitch change rate a on the original pitch change rate when the wind turbine generator set enters the low voltage ride-through mode; After the preset time has passed, the superimposed pitch rate is cancelled and the pitch action is performed at the original pitch rate.

8. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are performed.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the computer program performs the steps of the method according to any one of claims 1 to 5.

10. A computer device comprising a memory and a processor connected to each other, wherein a computer program is stored in the memory, characterized in that: When the computer program is executed by a processor, the computer program performs the steps of the method according to any one of claims 1 to 5.

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