A Detection Method and Device for Disconnection of Backup Power Supply of Wind Turbine Pitch

Abstract

This application relates to a method and a device for detecting disconnection of the backup power supply of a wind turbine pitch system. The detection method includes the following steps: introducing a characteristic voltage signal between the positive sampling terminal and the negative sampling terminal; acquiring the voltage waveform and voltage frequency between the positive sampling terminal and the negative sampling terminal; determining whether the voltage waveform and voltage frequency match the characteristic voltage waveform and characteristic voltage frequency; and determining whether the backup power supply is disconnected based on the determination result. This application has the function of being able to detect in real time whether the backup power supply is disconnected, and the detection process has a relatively small impact on the life of the backup power supply, with stable and reliable detection and easy implementation in engineering.

Description

Technical Field

[0001] The present application relates to the technical field of variable pitch control of wind turbine generator sets, and in particular to a method and device for detecting disconnection of a backup power supply for variable pitch of a wind turbine. Background Art

[0002] At present, most of the wind power industry uses three-blade wind turbines, which are mainly composed of three blades, a hub and a tower. The working principle of the wind turbine is that the wind blows on the three blades, driving the blades to rotate, and then driving the hub and the generator to rotate and generate electricity. Since the wind speed in nature changes in real time, in order to keep the generator in a stable full power generation state under changing wind speeds, the pitch angle of the blades is adjusted in real time to change the wind energy absorbed by the blades and the rotation speed of the three blades, thereby controlling the power generation of the generator.

[0003] The wind turbine generator set is equipped with a variable pitch control system to change the position of the three blades in real time, thereby adjusting the full power generation state of the generator. The variable pitch control system is powered by the power grid. If the power grid suddenly becomes abnormal and causes the power supply to become abnormal, the variable pitch control system is likely to lose control of the three blades, causing the three blades to be out of control. When the blades are out of control, the three blades will be at the 0-degree position, at which time the blades absorb the most wind energy and the speed will gradually increase. If the blade rotation speed is greater than the speed that the entire wind turbine can withstand, it will cause the hub to detach from the tower and fly away or the tower to break and collapse.

[0004] In order to avoid major safety accidents such as flying or collapse caused by sudden power outages, the variable pitch control system is generally equipped with a backup power supply as standard. The backup power supply can power the entire variable pitch control system when the power grid fails, and then control the three blades to rotate to the 90-degree position. Since the blades are at the 90-degree position, the blades basically do not absorb wind energy. At this position, the blades and the wind turbine are subjected to the least force and are the safest.

[0005] To avoid safety accidents during power outages, the backup power supply and the pitch control system should always be reliably connected to ensure that the backup power supply can supply power to the pitch control system when the power grid is out of power. For the backup power supply, it is necessary to perform disconnection detection to determine the reliability of the backup power supply connection. At present, the disconnection detection of the backup power supply is generally to detect the charging current and charging voltage when the backup power supply is charged for the first time by the charger to determine whether the backup power supply is disconnected; or when the backup power supply is float charged by the charger, the charging current and charging voltage are increased to detect whether the backup power supply is disconnected. The disconnection detection is performed during the first charging, which is a non-real-time detection method, with a small number of detections. It cannot be detected during subsequent use, which poses a greater risk. When the power supply is float charged, due to the narrow intermittent charging voltage range and small charging current, the changes in charging voltage and charging current are affected by the accuracy of the detection circuit and the temperature characteristics of the device, and there is a possibility of false detection.

[0006] In the related art described above, there is a defect that the detection of whether the backup power supply is disconnected is inaccurate. Summary of the Invention

[0007] In order to improve the accuracy of detecting the disconnection of the backup power supply, the present application provides a method and a detection device for detecting the disconnection of the backup power supply for the pitch of a wind turbine.

[0008] A method for detecting the disconnection of the backup power supply for the pitch of a wind turbine provided by the present application adopts the following technical solutions:

[0009] A method for detecting the disconnection of the backup power supply for the pitch of a wind turbine includes the following steps:

[0010] Introduce a characteristic voltage signal between the positive sampling terminal and the negative sampling terminal;

[0011] Obtain the voltage waveform and voltage frequency between the positive sampling terminal and the negative sampling terminal;

[0012] Judge whether the voltage waveform and voltage frequency match the characteristic voltage waveform and characteristic voltage frequency;

[0013] Based on the judgment result, determine whether the backup power supply is disconnected.

[0014] By adopting the above technical solutions, since the backup power supply belongs to a voltage source and has the characteristic of extremely small internal resistance, after being connected to the positive sampling terminal and the negative sampling terminal, it can change the impedance characteristic between the original positive sampling terminal and the negative sampling terminal, causing the voltage waveform and voltage frequency of the introduced characteristic voltage signal to change. After introducing the characteristic voltage signal between the positive sampling terminal and the negative sampling terminal, if the connection between the backup power supply and the positive sampling terminal or the negative sampling terminal is disconnected, the voltage signal waveform and frequency reflected between the positive sampling terminal and the negative sampling terminal are those of the characteristic voltage signal. If the connection between the backup power supply and the positive sampling terminal or the negative sampling terminal is reliable, the voltage source characteristic of the backup power supply makes the voltage waveform between the positive sampling terminal or the negative sampling terminal a DC voltage waveform, and the voltage frequency also decreases. By detecting the differences in frequency, waveform, and amplitude between the characteristic voltage waveform and the DC voltage waveform in the backup power supply, it is determined whether the backup power supply is disconnected. This detection method provides a real-time function for detecting the disconnection of the backup power supply, has no impact on the life of the backup power supply, and the detection is stable, reliable, free of false detection, low-cost, and easy to be engineered.

[0015] Optionally, the characteristic voltage signal is the voltage signal between the positive bus of the three-phase power supply rectified output and the characteristic terminal, or the voltage signal between the negative bus of the three-phase power supply rectified output and the characteristic terminal, where the characteristic terminal is the ground wire or any one of the phase lines.

[0016] By adopting the above technical solution, since the connection of the backup power supply directly affects the impedance characteristics between the positive sampling terminal and the negative sampling terminal, the voltage between the positive sampling terminal and the negative sampling terminal is maintained at the voltage of the backup power supply. Therefore, when collecting the voltage signal between the positive sampling terminal and the negative sampling terminal, the voltage signals between the positive and negative busbars and the ground wire and between the positive and negative busbars and the phase wire can be changed by the voltage signal of the backup power supply.

[0017] The present application further provides a detection device for open circuit of the backup power supply of the wind turbine pitch, which is used to execute the detection method described in the above solution. The detection device adopts the following technical solution:

[0018] A detection device for open circuit of the backup power supply of the wind turbine pitch includes:

[0019] A three-phase rectification module, the three-phase rectification module is connected to a three-phase power supply, and the output of the three-phase rectification module includes a positive busbar and a negative busbar;

[0020] A backup switch module, the backup switch module is connected to the positive busbar and the negative busbar;

[0021] A backup power supply module, the backup power supply module is connected to the backup switch module, the backup switch module controls the connection or disconnection of the positive electrode of the backup power supply module and the positive busbar, and the backup switch module also controls the connection or disconnection of the negative electrode of the backup power supply module and the negative busbar;

[0022] A resistor voltage division module, the resistor voltage division module is connected to the positive busbar, the negative busbar and a characteristic terminal, the connection point of the resistor voltage division module and the positive busbar is used as the positive sampling terminal, and the connection point of the resistor voltage division module and the negative busbar is used as the negative sampling terminal;

[0023] A differential operation module, the differential operation module includes two input terminals, and the two input terminals are respectively connected to the positive sampling terminal and the negative sampling terminal;

[0024] A main control module, the main control module is connected to the output terminal of the differential operation module.

[0025] By adopting the above technical solution, the backup switch module is used to connect the backup power supply module to the positive sampling terminal and the negative sampling terminal, and the resistor voltage division module is connected between the three-phase rectifier output terminal and the characteristic terminal, while forming the characteristic voltage signal, the voltage value between the positive sampling terminal and the negative sampling terminal is maintained. When the differential operation module samples and obtains the voltages on the positive sampling terminal and the negative sampling terminal, the voltages on the positive sampling terminal and the negative sampling terminal are affected by the DC characteristics of the backup power supply, so that the voltage between the positive sampling terminal and the negative sampling terminal remains a linear voltage. Compared with the original three-phase rectifier output voltage, the sampled frequency characteristics change greatly, and both the amplitude and the waveform change. The main control module can judge whether the backup power supply is disconnected according to the signal output by the differential operation module.

[0026] Optionally, a bus capacitor C1 is provided in the three-phase rectifier module, and the bus capacitor C1 is connected between the positive bus and the negative bus.

[0027] By adopting the above technical solution, the bus capacitor C1 filters the voltage output by the three-phase rectifier, making the finally output voltage smoother and more stable. And the bus capacitor C1 can also play a protective role in the circuit to reduce the impact of load mutation on the circuit.

[0028] Optionally, a first choke diode D2 is also provided in the three-phase rectifier module. The anode of the first choke diode D2 is connected to the output terminal of the three-phase rectifier module where the negative bus is located, and the cathode of the first choke diode D2 is connected to the negative sampling terminal.

[0029] By adopting the above technical solution, the first choke diode D2 is used to limit the current reflux of the negative bus, so that the positive and negative buses of the three-phase rectifier output cannot charge the backup power supply, thereby reducing the impact of detection on the backup power supply.

[0030] Optionally, the resistor voltage division module includes a first resistor R1 and a second resistor R2. The first resistor R1 is connected in series between the positive sampling terminal and the negative sampling terminal, and the second resistor R2 is connected in series between the negative sampling terminal and the characteristic terminal.

[0031] By adopting the above technical solution, the first resistor R1 and the second resistor R2 are connected in series, and the voltage between the positive sampling terminal and the negative sampling terminal is maintained through the first resistor R1. The characteristic voltage signal flows from the positive bus through the first resistor R1 and the second resistor R2, and then returns to the ground wire or any one of the phase wires of the three phases.

[0032] Optionally, a second choke diode D4 is also provided in the three-phase rectifier module. The cathode of the second choke diode D4 is connected to the output terminal of the three-phase rectifier module where the positive bus is located, and the anode of the second choke diode D4 is connected to the negative sampling terminal.

[0033] By adopting the above technical solution, the second choke diode D4 restricts the current on the positive bus, enabling the voltage signal between the negative bus and the characteristic terminal to be introduced onto the resistor voltage division module.

[0034] Optionally, the resistor voltage division module includes a third resistor R3 and a fourth resistor R4. The third resistor R3 is connected in series between the sampling positive terminal and the sampling negative terminal, and the fourth resistor R4 is connected in series between the sampling positive terminal and the characteristic terminal.

[0035] By adopting the above technical solution, the third resistor R3 and the fourth resistor R4 are connected in series, and the voltage between the sampling positive terminal and the sampling negative terminal is maintained through the third resistor R3. The characteristic voltage signal flows from the negative bus, through the third resistor R3 and the fourth resistor R4, and then returns to the ground wire or any one of the phase wires of the three phases.

[0036] In summary, the present application includes at least one of the following beneficial technical effects:

[0037] 1. It has the function of being able to detect in real time whether the backup power supply is disconnected, with stable and reliable detection and easy engineering implementation;

[0038] 2. The detection process does not charge the backup power supply, reducing the impact on the lifespan of the backup power supply;

[0039] 3. The three-phase rectifier circuit has multiple protections, reducing the impact of the load on the circuit during use. Description of the Drawings

[0040] Figure 1 is a flowchart of a method for detecting disconnection of a backup power supply for a wind turbine pitch in Embodiment 1 of the present application.

[0041] Figure 2 is a flowchart structure diagram of a method for detecting disconnection of a backup power supply for a wind turbine pitch in Embodiment 2 of the present application.

[0042] Figure 3 is a flowchart structure diagram of a method for detecting disconnection of a backup power supply for a wind turbine pitch in Embodiment 3 of the present application.

[0043] Description of the reference numerals: 1, three-phase rectification module; 11, positive bus; 12, negative bus; 2, backup switch module; 3, backup power supply module; 4, resistor voltage division module; 5, differential operation module; 6, main control module. Detailed Description of the Embodiment

[0044] The following further describes the present application in detail with reference to the drawings.

[0045] Embodiment 1

[0046] The embodiments of the present application disclose a method for detecting disconnection of the backup power supply for the pitch of a wind turbine. Refer to Figure 1 , the method for detecting disconnection of the backup power supply for the pitch of a wind turbine includes the following steps.

[0047] S1. Introduce a characteristic voltage signal between the positive sampling terminal and the negative sampling terminal.

[0048] Among them, the positive sampling terminal is the connection terminal between the positive pole of the backup power supply and the positive power supply of the rectified output of the three-phase power supply, and the negative sampling terminal is the connection terminal between the negative pole of the backup power supply and the negative power supply of the rectified output of the three-phase power supply. When the backup power supply is not connected, the characteristic voltage signal between the positive sampling terminal and the negative sampling terminal is provided by the voltage rectified and output by the three-phase power supply. Specifically, at this time, the characteristic voltage signal is the voltage signal between the positive busbar of the rectified output of the three-phase power supply and the characteristic terminal, or the voltage signal between the negative busbar of the rectified output of the three-phase power supply and the characteristic terminal, where the characteristic terminal is the ground wire or any one of the phase wires.

[0049] S2. Obtain the voltage waveform and voltage frequency between the positive sampling terminal and the negative sampling terminal.

[0050] Among them, the characteristic voltage signal is the voltage signal rectified and filtered by the three-phase rectifier. The characteristic voltage signal itself has a certain voltage waveform and voltage frequency. The backup power supply belongs to a voltage source and has relatively stable characteristics. If the connection between the backup power supply and the positive sampling terminal and the negative sampling terminal is good, then both the voltage frequency characteristic and the voltage waveform characteristic between the positive sampling terminal and the negative sampling terminal will change greatly.

[0051] S3. Determine whether the voltage waveform and voltage frequency match the characteristic voltage waveform and characteristic voltage frequency.

[0052] Among them, the characteristics of the backup power supply are used to change the voltage characteristics between the positive sampling terminal and the negative sampling terminal. After obtaining the voltage waveform and voltage frequency between the positive sampling terminal and the negative sampling terminal, they are compared with the characteristic voltage signal formed between the power supply terminal of the three-phase rectified output and the characteristic terminal to determine whether the positive sampling terminal and the negative sampling terminal are affected by the backup power supply.

[0053] S4. Based on the judgment result, determine whether the backup power supply is disconnected.

[0054] Among them, the backup power supply directly affects the voltage characteristics between the positive sampling terminal and the negative sampling terminal. Therefore, by judging whether the positive sampling terminal and the negative sampling terminal are affected by the backup power supply, it can be judged whether there is a disconnection between the backup power supply and the power supply terminal of the three-phase rectified output. While realizing the real-time detection function, the influence on the backup power supply is also reduced.

[0055] The implementation principle of the embodiments of this application is as follows: Since the backup power supply belongs to a voltage source and has the characteristic of extremely small internal resistance, after being connected to the sampling positive terminal and the sampling negative terminal, it can change the impedance characteristic between the original sampling positive terminal and the sampling negative terminal, causing the voltage waveform and voltage frequency of the connected characteristic voltage signal to change. After introducing the characteristic voltage signal between the sampling positive terminal and the sampling negative terminal, when the connection between the backup power supply and the sampling positive terminal or the sampling negative terminal is disconnected, the waveform and frequency of the characteristic voltage signal are reflected between the sampling positive terminal and the sampling negative terminal. When the connection between the backup power supply and the sampling positive terminal or the sampling negative terminal is reliable, the voltage source characteristic of the backup power supply makes the voltage waveform between the sampling positive terminal or the sampling negative terminal a DC voltage waveform, and the voltage frequency also decreases. By detecting the differences in the frequency, waveform, and amplitude between the characteristic voltage waveform and the DC voltage waveform in the backup power supply, it is possible to detect whether the backup power supply is disconnected, so as to perform real-time disconnection detection on the backup power supply.

[0056] Embodiment 2

[0057] The embodiments of this application disclose a disconnection detection device for the backup power supply of a wind turbine pitch system. Referring to Figure 2 , the disconnection detection device for the backup power supply of a wind turbine pitch system includes a three-phase rectification module 1, a backup switch module 2, a backup power supply module 3, a resistor voltage division module 4, a differential operation module 5, and a main control module 6. The resistor voltage division module 4 and the backup switch module 2 are sequentially connected between the three-phase rectification module 1 and the backup power supply module 3. The differential operation module 5 is connected to the resistor voltage division module 4, and the main control module 6 is connected to the differential operation module 5. The output of the three-phase rectification module 1 includes a positive bus 11 and a negative bus 12. While the resistor voltage division module 4 is connected to the positive bus 11 and the negative bus 12, it is also connected to a characteristic terminal, and a characteristic signal is formed between the characteristic terminal and the positive bus 11 or the negative bus 12. Among them, the characteristic terminal is the ground wire or any one of the phase wires.

[0058] The connection point between the positive bus 11 of the three-phase rectification module 1 and the resistor voltage division module 4 is used as the sampling positive terminal, and the connection point between the negative bus 12 of the three-phase rectification module 1 and the resistor voltage division module 4 is used as the sampling negative terminal. When the backup switch module 2 is turned on, the DC characteristic of the backup power supply changes the impedance characteristic between the original sampling positive terminal and the sampling negative terminal, thereby changing the voltage amplitude, frequency, and waveform between the sampling positive terminal and the sampling negative terminal. After the operation and processing by the differential operation module 5, the differential operation module 5 outputs operation data to the main control module 6, and the main control module 6 analyzes and processes the operation data to determine whether the backup power supply is connected to the output end of the three-phase rectification module 1.

[0059] The three-phase rectification module 1 is connected to a three-phase power supply and outputs direct current after rectification. In this embodiment, the three-phase rectification module 1 adopts a three-phase semi-controlled rectifier bridge. The upper bridge is a thyristor rectifier for realizing soft start, and the lower bridge is a diode rectifier. The upper bridge is the positive bus 11 of the three-phase rectification output, and the lower bridge is the negative bus 12 of the three-phase rectification output.

[0060] In the three-phase rectification module 1, a bus capacitor C1 and a first choke diode D2 are also provided. Among them, the bus capacitor C1 is connected between the positive bus 11 and the negative bus 12. The voltage of the three-phase rectification output is filtered through the bus capacitor C1, making the DC voltage of the three-phase rectification output smoother and more stable. Therefore, both ends of the bus capacitor C1 serve as the power supply terminals of the three-phase rectification output. When the three-phase rectification output is connected to a driving motor, the bus capacitor C1 can provide a more stable voltage.

[0061] The first choke diode D2 is provided on the negative bus 12. The anode of the first choke diode D2 is connected to the output terminal of the three-phase rectification module 1 where the negative bus 12 is located, and the cathode of the first choke diode D2 is connected to the sampling negative terminal. When the backup power supply is connected to the positive bus 11 and the negative bus 12 of the three-phase rectification output and the backup switch module 2 is turned on, the three-phase rectification output will not charge the backup power supply. Therefore, the backup power supply can be charged using a separate charger. During daily detection, the impact caused by directly charging the backup power supply is reduced, and the service life of the backup power supply is increased.

[0062] The differential operation module 5 includes two input terminals, which are respectively connected to the sampling positive terminal and the sampling negative terminal. The main control module 6 is connected to the output terminal of the differential operation module 5, and analyzes the data processed by the differential operation module 5 to determine whether the backup power supply is disconnected.

[0063] The resistor voltage division module 4 includes a first resistor R1 and a second resistor R2. The first resistor R1 is connected in series between the sampling positive terminal and the sampling negative terminal, and the second resistor R2 is connected in series between the sampling negative terminal and the characteristic terminal. In this embodiment, the characteristic terminal is the ground wire. The voltage between the positive bus 11 and the ground wire is divided by the first resistor R1 and the second resistor R2. That is, the two input terminals of the differential operation module 5 are respectively connected to both ends of the first resistor R1, and the voltage difference between both ends of the first resistor R1 is used for comparison and analysis. Then the differential operation module 5 outputs the calculated and processed data to the main control module 6 for analysis and processing to make a judgment. In other embodiments, the characteristic terminal can also be any one of the phase lines in the three-phase power supply.

[0064] The backup switch module 2 is simultaneously connected to the positive bus 11 and the negative bus 12, and the backup switch module 2 controls the conduction or cut-off between the backup power supply module 3, the positive bus 11, and the negative bus 12. In this embodiment, the backup switch module 2 is a synchronous switch, and the backup switch module 2 is used for debugging and later maintenance; the backup power supply module 3 includes a super capacitor, a lithium battery, and a lead-acid battery; the main control module 6 is an MCU.

[0065] In this embodiment, both the first resistor R1 and the second resistor R2 are high-impedance resistors. When the connection between the backup power supply and the sampling positive terminal and the sampling negative terminal is disconnected, at this time, the first resistor R1 and the second resistor R2 are divided into the 150 Hz characteristic voltage signal between the positive bus 11 and the ground wire, and the voltage difference across the first resistor R1 is a fixed value. When the connection between the backup power supply and the sampling positive terminal and the sampling negative terminal is conductive, since the backup power supply belongs to a voltage source, the voltage across its positive and negative terminals changes very little within the 150 Hz period, and there is a large difference in frequency characteristics from 150 Hz. By using the differential method, the voltage across the first resistor R1 is reduced to the voltage range that can be detected by the MCU. The MCU analyzes the frequency, waveform, and amplitude of the signal based on the detected voltage waveform to achieve the disconnection detection of the backup power supply.

[0066] The implementation principle of the embodiment of the present application is as follows: The first resistor R1 first receives the rectified characteristic signal. By utilizing the DC characteristic of the backup power supply, after being connected in parallel with the first resistor R1, the voltage signal across the first resistor R1 is changed. The voltage signal is analyzed and processed by using the differential method, thereby determining whether the connection of the backup power supply is disconnected and achieving real-time disconnection detection.

[0067] Embodiment 3

[0068] Refer to Figure 3 In this embodiment, the difference between the embodiment of the present application and Embodiment 2 is that a second choke diode D4 is connected in series on the positive bus 11 to limit the current on the positive bus 11, so that the voltage between the negative bus 12 and the characteristic terminal is used as the characteristic voltage signal. The cathode of the second choke diode D4 is connected to the output terminal of the three-phase rectification module 1 where the positive bus 11 is located, and the anode of the second choke diode D4 is connected to the sampling negative terminal.

[0069] And at this time, the resistor voltage division module 4 includes a third resistor R3 and a fourth resistor R4. The third resistor R3 is connected in series between the positive sampling terminal and the negative sampling terminal, and the fourth resistor R4 is connected in series between the positive sampling terminal and the characteristic terminal. In this embodiment, the characteristic terminal is the ground wire. The voltage between the negative bus 12 and the ground wire is divided by the third resistor R3 and the fourth resistor R4. That is, the two input terminals of the differential operation module 5 are respectively connected to both ends of the third resistor R3, and the voltage difference across the third resistor R3 is used for comparison and analysis. Then, the differential operation module 5 outputs the calculated and processed data to the main control module 6 for analysis, processing, and judgment. In other embodiments, the characteristic terminal can also be any one of the phase lines in the three-phase power supply.

[0070] The above are all the preferred embodiments of this application, and the protection scope of this application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A disconnection detection device for the backup power supply of a wind turbine pitch system, characterized in that, The detection device includes: A three-phase rectification module (1), which is connected to a three-phase power supply. The output of the three-phase rectification module (1) includes a positive busbar (11) and a negative busbar (12); A backup switch module (2), which is connected between the positive busbar (11) and the negative busbar (12); A backup power supply module (3), which is connected to the backup switch module (2). The backup switch module (2) controls the connection or disconnection between the positive electrode of the backup power supply module (3) and the positive busbar (11), and the backup switch module (2) also controls the connection or disconnection between the negative electrode of the backup power supply module (3) and the negative busbar (12); A resistor voltage division module (4), which is connected to the positive busbar (11), the negative busbar (12) and the characteristic terminal. The connection point of the resistor voltage division module (4) and the positive busbar (11) is used as the sampling positive terminal, and the connection point of the resistor voltage division module (4) and the negative busbar (12) is used as the sampling negative terminal; A differential operation module (5), which includes two input terminals, and the two input terminals are respectively connected to the sampling positive terminal and the sampling negative terminal; A main control module (6), which is connected to the output terminal of the differential operation module (5).

2. The wind turbine pitch backup power supply disconnection detection device according to claim 1, characterized in that: A bus capacitor C1 is provided in the three-phase rectification module (1), and the bus capacitor C1 is connected between the positive busbar (11) and the negative busbar (12).

3. The wind turbine pitch backup power supply disconnection detection device according to claim 1, characterized in that: A first choke diode D2 is also provided in the three-phase rectification module (1). The anode of the first choke diode D2 is connected to the output terminal of the three-phase rectification module (1) where the negative busbar (12) is located, and the cathode of the first choke diode D2 is connected to the sampling negative terminal.

4. The wind turbine pitch backup power supply disconnection detection device according to claim 3, characterized in that: The resistor voltage division module (4) includes a first resistor R1 and a second resistor R2. The first resistor R1 is connected in series between the sampling positive terminal and the sampling negative terminal, and the second resistor R2 is connected in series between the sampling negative terminal and the characteristic terminal.

5. The pitch backup power supply disconnection detection device for a fan according to claim 1, characterized in that: A second choke diode D4 is also provided in the three-phase rectification module (1). The cathode of the second choke diode D4 is connected to the output terminal of the three-phase rectification module (1) where the positive busbar (11) is located, and the anode of the second choke diode D4 is connected to the sampling negative terminal.

6. The wind turbine pitch backup power supply disconnection detection device according to claim 1, wherein: The resistor voltage division module (4) includes a third resistor R3 and a fourth resistor R4. The third resistor R3 is connected in series between the sampling positive terminal and the sampling negative terminal, and the fourth resistor R4 is connected in series between the sampling positive terminal and the characteristic terminal.

7. A method for detecting disconnection of the backup power supply for a wind turbine pitch system, characterized in that, The detection method is used for the detection device according to any one of claims 1-6, and includes the following steps: Introduce a characteristic voltage signal between the sampling positive terminal and the sampling negative terminal; Obtain the voltage waveform and voltage frequency between the sampling positive terminal and the sampling negative terminal; Judge whether the voltage waveform and voltage frequency match the characteristic voltage waveform and characteristic voltage frequency; Based on the judgment result, determine whether the backup power supply is disconnected.

8. The method for detecting disconnection of the backup power supply for the pitch control of a wind turbine according to claim 7, wherein The characteristic voltage signal is the voltage signal between the positive busbar of the three-phase power supply rectifier output and the characteristic terminal, or the voltage signal between the negative busbar of the three-phase power supply rectifier output and the characteristic terminal, where the characteristic terminal is the ground wire or any one of the phase lines.

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