A method for controlling the speed of a wind turbine generator set

Abstract

The present invention provides a method for switching the speed control of a wind turbine generator set, comprising the following steps: detecting the current operating state of the wind turbine generator set, including a standby state, a start-up state, an acceleration operating state, a grid-connected operating state, and a fault shutdown state; switching the controller speed input strategy based on the current operating state, wherein the controller speed input strategy includes using the generator speed measured by the proximity switch as the current wind turbine generator set controller input speed, or using the generator speed calculated by the converter as the current wind turbine generator set controller input speed. When the wind turbine generator set is in operation, the input speed of the pitch angle and torque reference control instruction of the wind turbine generator set, combined with the control characteristics of the wind turbine generator set, adopts an automatic and effective switching strategy between the speed calculated by the converter and the speed measured by the proximity switch, replacing the original incremental photoelectric encoder measured speed, effectively reducing the procurement cost of the wind turbine generator set speed measuring device without affecting the operating stability and reliability of the wind turbine generator set.

Description

Technical Field

[0001] The invention relates to the technical field of wind power generation, and in particular to a speed control switching method for a wind power generator set. Background Art

[0002] As the country vigorously supports the development of new energy, wind turbines, as an important part of new energy, are also expanding rapidly. In the face of the development needs of offshore and onshore parity wind turbine models, higher requirements are placed on the production cost, operation stability, and reliability of wind turbines.

[0003] In a wind turbine generator set, the generator speed is one of the most important control targets. Due to the high requirements for the accuracy and reliability of the speed measurement equipment, the current mainstream wind turbines in China generally use incremental photoelectric encoders as wind turbine generator speed measurement devices. However, the procurement cost of this device is high and cannot meet the demand for reducing the development cost of wind turbines. If only proximity switches are used as wind turbine generator speed measurement devices, the device cannot meet the accuracy and resolution requirements for generator speed measurement under the grid-connected operation of the wind turbine, which will directly affect the stability and reliability of the wind turbine operation. Therefore, in order to ensure the reliable and stable operation of the wind turbine at a reduced cost, it is necessary to combine the control characteristics of the wind turbine set and carry out the design of the wind turbine set input speed control switching method in a targeted manner, so as to achieve the cost reduction design requirements without affecting the stability and reliability of the wind turbine operation. Summary of the invention

[0004] In view of the defects in the prior art, the present invention provides a wind turbine generator set speed control switching method to solve the technical problems that the existing wind turbine generator set controller speed input strategy does not combine the wind turbine generator set control characteristics, has high cost or lacks stability and reliability.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0006] A method for controlling the speed of a wind turbine generator set comprises the following steps:

[0007] Detecting the current operating state of the wind turbine generator set, wherein the current operating state of the wind turbine generator set includes a standby state, a startup state, an accelerated operating state, a grid-connected operating state, and a fault shutdown state;

[0008] The controller speed input strategy is switched based on the current operating state of the wind turbine group. The controller speed input strategy includes using the generator speed measured by the proximity switch as the input speed of the current wind turbine group controller, or using the generator speed calculated by the converter as the input speed of the current wind turbine group controller.

[0009] Optionally, the controller speed input strategy is switched based on the current operating state of the wind turbine generator set, including:

[0010] If the wind turbine set is in a standby state or a start-up state, the generator speed measured by the proximity switch is switched to be the input speed of the current wind turbine set controller; or

[0011] If the wind turbine is in an accelerated running state, and the maximum value between the rotational speed measured by the proximity switch and the rotational speed calculated by the converter exceeds a first set threshold, the generator rotational speed calculated by the converter is switched to be the input rotational speed of the current wind turbine controller; or

[0012] If the wind turbine is in a grid-connected operation state, the generator speed calculated by the converter is switched to be the input speed of the current wind turbine controller; or

[0013] If the wind turbine is in a fault shutdown state and the maximum value between the speed measured by the proximity switch and the speed calculated by the converter is less than a second set threshold, the generator speed measured by the proximity switch is switched as the input speed of the current wind turbine controller.

[0014] Optionally, the controller speed input strategy is switched based on the current operating state of the wind turbine generator set, further comprising:

[0015] When the wind turbine set is in an accelerated operation state, a grid-connected operation state or a fault shutdown state, the generator speed calculated by the converter, the generator speed measured by the proximity switch and the wind wheel speed*gear box ratio measured by the proximity switch are compared with each other. If the absolute value of the difference between the two exceeds the set value, the speed measurement signal abnormal fault shutdown is triggered.

[0016] Optionally, the controller speed input strategy is switched based on the current operating state of the wind turbine generator set, further comprising:

[0017] Based on the generator speed calculated by the converter, the generator speed measured by the proximity switch and the wind wheel speed measured by the proximity switch * gearbox ratio, the maximum speed of the generator is calculated. If the maximum speed exceeds the third set threshold, the unit fault shutdown is triggered.

[0018] Optionally, before switching the controller speed input strategy based on the current operating state of the wind turbine generator set, the method further includes:

[0019] The input speed of the wind turbine set before switching is compared with the input speed of the wind turbine set to be switched. If the absolute value of the difference between the two is greater than a fourth set threshold, filtering is performed on the input speed of the wind turbine set to be switched.

[0020] Optionally, filtering the input rotation speed of the switched wind turbine generator set includes:

[0021] The filtered input speed is given by the following formula:

[0022] The input speed after filtering = weight value * input speed of the wind turbine before switching + (1-weight value) * input speed of the wind turbine to be switched; wherein the weight value changes from 1 to 0 at a uniform speed.

[0023] Optionally, the controller speed input strategy is switched based on the current operating state of the wind turbine generator set, further comprising:

[0024] The instantaneous data of the generator input shaft speed converted from the converter feedback speed and the generator rotor speed detected by the main control are compared and the following judgments are made:

[0025] If the difference between the two exceeds a third set threshold and is delayed for a set time, the wind turbine generator set is triggered to shut down due to a fault.

[0026] Optionally, the controller speed input strategy is switched based on the current operating state of the wind turbine generator set, further comprising:

[0027] Compare the feedback speed of the converter with the speed data of the generator detected by the main control and make the following judgments:

[0028] If the difference between the two exceeds a third set threshold and is delayed for a set time, the wind turbine generator set is triggered to shut down due to a fault.

[0029] Optionally, the controller speed input strategy is switched based on the current operating state of the wind turbine generator set, further comprising:

[0030] The generator rotor speed detected by the main control is converted into the generator input shaft speed and compared with the generator speed data detected by the main control to make the following judgment:

[0031] If the difference between the two exceeds a third set threshold and is delayed for a set time, the wind turbine generator set is triggered to shut down due to a fault.

[0032] It can be seen from the above technical solution that the beneficial effects of the present invention are:

[0033] The present invention provides a method for switching the speed control of a wind turbine generator set, comprising the following steps: detecting the current operating state of the wind turbine generator set, wherein the current operating state of the wind turbine generator set includes a standby state, a start-up state, an acceleration operation state, a grid-connected operation state, and a fault shutdown state; switching the controller speed input strategy based on the current operating state of the wind turbine generator set, wherein the controller speed input strategy includes using the generator speed measured by the proximity switch as the input speed of the current wind turbine generator set controller, or using the generator speed calculated by the converter as the input speed of the current wind turbine generator set controller. When the wind turbine generator set is in operation, the input speed of the pitch angle and torque reference control instruction of the wind turbine generator set adopts an automatic and effective switching strategy between the speed calculated by the converter and the speed measured by the proximity switch, replacing the original incremental photoelectric encoder measured speed. The speed switching involves the entire process of the wind turbine generator set standby, start-up, power generation, and shutdown, fully combining the control characteristics of the wind turbine generator set, and effectively reducing the procurement cost of the wind turbine generator set speed measuring device without affecting the operating stability and reliability of the wind turbine generator set. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0035] Figure 1 The present invention is a step diagram of a method for switching the speed control of a wind turbine generator set. DETAILED DESCRIPTION

[0036] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0037] See also Figure 1 The present invention provides a method for switching the speed control of a wind turbine generator set, comprising the following steps:

[0038] S1, detecting the current operating status of the wind turbine;

[0039] The current operating state of the wind turbine generator set includes a standby state, a startup state, an accelerated operating state, a grid-connected operating state, and a fault shutdown state;

[0040] S2, switching the controller speed input strategy based on the current operating state of the wind turbine generator set;

[0041] The controller speed input strategy includes using the generator input shaft speed measured by the proximity switch as the input speed of the current wind turbine controller, or using the generator speed calculated by the converter as the input speed of the current wind turbine controller. The full power converter calculates the generator speed by voltage, and the converter can calculate when the speed reaches a certain value, generally above 50rpm.

[0042] In this method, the original sampled generator speed is processed by Outlier filter. Outlier filter is used to remove the deviation value / burr in the speed encoder measurement signal. This filter is a causal median filter and does not bring any phase shift. The filter is determined by a threshold value and filter time length value:

[0043] Threshold value: the rejection threshold of the signal deviating from the median value;

[0044] Filter time: 100ms;

[0045] The filter calculates the median (not the average) of the last 10 inputs, and the number of data = filter time / sampling time (10ms). If the value of the last input to the outlier filter exceeds the threshold value than the median, the median is used as the output of the outlier filter, otherwise the last input is used as the output of the outlier filter.

[0046] Note: In the following text, the generator speed measured by the proximity switch and the generator speed calculated by the converter are the output values ​​of the original sampled speed after being filtered by the outlier filter.

[0047] The core of this method is the switching between the generator proximity switch measuring the generator speed and the converter calculating the generator speed, which involves the entire process of wind turbine standby, start-up, power generation, and shutdown, as follows:

[0048] 1. Standby and startup status

[0049] If the wind turbine is in standby or startup state, in this state, the generator speed value calculated by the converter has a large error and cannot be used for control and monitoring. Therefore, in this state, the generator speed measured by the proximity switch is used for related monitoring and control, which mainly involves the self-test of wind turbine startup, that is, after the blades are opened, the generator input shaft brake release state is judged based on the generator speed measured by the proximity switch, and the brake engagement state is judged in the standby state of the wind turbine;

[0050] 2. Acceleration running state

[0051] The target speed of the wind turbine in the accelerated operation state is the cut-in speed. In this state, when the maximum value between the generator speed measured by the proximity switch and the generator speed calculated by the converter is greater than 0.5 times the cut-in speed, the controller input speed is switched to the generator speed calculated by the converter as the current wind turbine controller input speed;

[0052] 3. Grid-connected operation status

[0053] When the wind turbine is in grid-connected operation, the wind turbine speed is running within the cut-in speed and rated speed range, and the converter calculates the speed as the controller input speed and participates in the wind turbine torque controller and pitch angle controller output calculation;

[0054] 4. Fault shutdown status

[0055] If any fault is triggered by the wind turbine, the torque will decrease as the speed decreases during the shutdown process. When the maximum value between the generator speed calculated by the converter and the generator speed measured by the proximity switch is less than the mechanical speed low speed setting value, the proximity switch will be used to measure the generator speed to continue the shutdown action.

[0056] As a further improvement to the above scheme, the controller speed input strategy switching based on the current operating state of the wind turbine set also includes: when the wind turbine set is in an accelerated operating state, a grid-connected operating state or a fault shutdown state, the generator speed calculated by the converter, the generator speed measured by the proximity switch and the wind rotor main shaft speed * gear box ratio measured by the proximity switch (that is, the generator input shaft speed is indirectly obtained by calculation) are compared with each other. If the absolute value of the difference between the two exceeds the set value, the speed measurement signal abnormal fault shutdown is triggered.

[0057] As a further improvement to the above scheme, the proximity switch measuring the generator speed, the converter calculating the generator speed, and the proximity switch generator speed all have the risk of failure. This method also proposes that after some speed measuring components fail, the wind turbine can still complete the speed switching and execute the shutdown action in the first time to achieve the purpose of protecting the safe operation of the wind turbine. The specific method is as follows:

[0058] 1) Maximum speed measurement protection method

[0059] Compare the generator speed calculated by the converter, the generator speed measured by the proximity switch, and the wind wheel speed measured by the proximity switch * gearbox ratio. The maximum value of the three is regarded as the maximum speed of the generator. If the maximum speed exceeds 115% * rated generator speed, a fault shutdown is triggered.

[0060] 2) Method to solve the speed fluctuation when switching between the generator speed measured by the proximity switch and the generator speed calculated by the converter

[0061] Before switching the controller speed input strategy based on the current operating state of the wind turbine, compare the input speed of the wind turbine before switching with the input speed of the wind turbine to be switched. If the absolute value of the difference between the two is greater than 0.2rpm*gearbox ratio, filter the input speed of the wind turbine to be switched. Since there is a certain static difference between the speed of the proximity switch and the speed of the converter, a jump in the control speed will inevitably occur when the speed is switched. At this time, the strategy algorithm is already in a closed-loop control state, which may cause disturbances in the output torque setting and the pitch angle setting. To solve this problem, the following method is proposed:

[0062] A variable weighted first-order low-pass algorithm can be used. After the trigger condition is met, the speed signal is filtered, and the weight changes from 1 to 0 at a constant speed. When the weight becomes 0, it is equivalent to not filtering. The input speed after filtering uses the following formula:

[0063] Input speed after filtering = weight value * input speed of wind turbine before switching + (1-weight value) * input speed of wind turbine after switching;

[0064] 3) Speed ​​difference comparison monitoring and protection method

[0065] In order to ensure the safe and stable operation of wind turbines and prevent the converter feedback speed distortion and rotor speed measurement distortion during the whole operation cycle of wind turbines, the following protection methods are proposed:

[0066] A. Comparison between converter feedback speed and rotor speed

[0067] The instantaneous data of the generator input shaft speed converted from the converter feedback speed and the generator rotor speed detected by the main control are compared and the following judgments are made:

[0068] If the difference between the two exceeds 5%*rated generator speed and lasts for 100ms, the wind turbine fault shutdown is triggered;

[0069] B. Comparison of converter feedback speed and main control generator speed data

[0070] Compare the feedback speed of the converter with the speed data of the generator detected by the main control and make the following judgments:

[0071] If the difference between the two exceeds 5%*rated generator speed and lasts for 100ms, the wind turbine fault shutdown is triggered;

[0072] C. Comparison of rotor speed and speed data of main control generator

[0073] The generator rotor speed detected by the main control is converted into the generator input shaft speed and compared with the generator speed data detected by the main control to make the following judgment:

[0074] If the difference between the two exceeds 5%*rated generator speed and lasts for 100ms, the wind turbine will be triggered to shut down.

[0075] In summary, the purpose of the present invention is to use an automatic and effective switching strategy between the input speed of the pitch angle and torque reference control instruction of the wind turbine when the wind turbine is running, and the speed calculated by the converter and the speed measured by the proximity switch to replace the original incremental photoelectric encoder to measure the speed. The speed switching involves the entire process of the wind turbine standby, start-up, power generation, and shutdown, which fully combines the control characteristics of the wind turbine and effectively reduces the purchase cost of the wind turbine speed measuring device. At the same time, the wind turbine generator speed failure protection method is adopted to effectively solve the impact caused by the wind turbine control speed switching under the premise of ensuring the stability and reliability of the wind turbine operation, and ensure the stable operation of the wind turbine.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for switching the speed control of a wind turbine generator set, characterized in that: The following steps are included: Detecting the current operating state of the wind turbine generator set, wherein the current operating state of the wind turbine generator set includes a standby state, a startup state, an accelerated operating state, a grid-connected operating state, and a fault shutdown state; The controller speed input strategy is switched based on the current operating state of the wind turbine generator set. The controller speed input strategy includes using the generator speed measured by the proximity switch as the input speed of the current wind turbine generator set controller, or using the generator speed calculated by the converter as the input speed of the current wind turbine generator set controller. Specifically, it includes: If the wind turbine is in a standby state or a start-up state, the generator speed measured by the proximity switch is switched to be the input speed of the current wind turbine controller; If the wind turbine is in an accelerated running state, and the maximum value between the rotation speed measured by the proximity switch and the rotation speed calculated by the converter exceeds a first set threshold, the generator rotation speed calculated by the converter is switched to be the input rotation speed of the current wind turbine controller; If the wind turbine is in a grid-connected operation state, the generator speed calculated by the converter is switched to be the input speed of the current wind turbine controller; If the wind turbine is in a fault shutdown state and the maximum value between the speed measured by the proximity switch and the speed calculated by the converter is less than a second set threshold, the generator speed measured by the proximity switch is switched as the input speed of the current wind turbine controller.

2. A method for controlling the speed of a wind turbine generator set according to claim 1, characterized in that: The controller speed input strategy is switched based on the current operating state of the wind turbine generator set, and further includes: When the wind turbine set is in an accelerated operation state, a grid-connected operation state or a fault shutdown state, the generator speed calculated by the converter, the generator speed measured by the proximity switch and the wind wheel speed*gear box ratio measured by the proximity switch are compared with each other. If the absolute value of the difference between the two exceeds the set value, the speed measurement signal abnormal fault shutdown is triggered.

3. A method for controlling and switching the speed of a wind turbine generator set according to claim 1 or 2, characterized in that: The controller speed input strategy is switched based on the current operating state of the wind turbine generator set, and further includes: Based on the generator speed calculated by the converter, the generator speed measured by the proximity switch and the wind wheel speed measured by the proximity switch * gearbox ratio, the maximum value of the three is regarded as the maximum speed value of the generator. If the maximum speed value exceeds the third set threshold, the unit fault shutdown is triggered.

4. A method for controlling and switching the speed of a wind turbine generator set according to claim 3, characterized in that: Before switching the controller speed input strategy based on the current operating state of the wind turbine generator set, the method further includes: The input speed of the wind turbine set before switching is compared with the input speed of the wind turbine set to be switched. If the absolute value of the difference between the two is greater than a fourth set threshold, filtering is performed on the input speed of the wind turbine set to be switched.

5. A method for controlling and switching the speed of a wind turbine generator set according to claim 4, characterized in that: The filtering process of the input speed of the switched wind turbine generator set includes: The filtered input speed is given by the following formula: The input speed after filtering = weight value * input speed of the wind turbine before switching + (1-weight value) * input speed of the wind turbine to be switched; wherein the weight value changes from 1 to 0 at a uniform speed.

6. A method for controlling and switching the speed of a wind turbine generator set according to claim 1, characterized in that: The controller speed input strategy is switched based on the current operating state of the wind turbine generator set, and further includes: The instantaneous data of the generator input shaft speed converted from the converter feedback speed and the generator rotor speed detected by the main control are compared and the following judgments are made: If the difference between the two exceeds the fifth set threshold and lasts for a set time, the wind turbine generator set is triggered to shut down due to a fault.

7. A method for controlling and switching the speed of a wind turbine generator set according to claim 1, characterized in that: The controller speed input strategy is switched based on the current operating state of the wind turbine generator set, and further includes: Compare the feedback speed of the converter with the speed data of the generator detected by the main control and make the following judgments: If the difference between the two exceeds the fifth set threshold and lasts for a set time, the wind turbine generator set is triggered to shut down due to a fault.

8. A method for controlling and switching the speed of a wind turbine generator set according to claim 1, characterized in that: The controller speed input strategy is switched based on the current operating state of the wind turbine generator set, and further includes: The generator rotor speed detected by the main control is converted into the generator input shaft speed and compared with the generator speed data detected by the main control to make the following judgment: If the difference between the two exceeds the fifth set threshold and lasts for a set time, the wind turbine generator set is triggered to shut down due to a fault.

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