An on-line insulation detection method and device for a generator of a doubly-fed wind turbine

Abstract

The present invention provides an on-line insulation detection method for a generator of a doubly-fed wind turbine, comprising the following steps: the main control system sends a generator winding insulation detection command to the converter, and the converter switches to the generator winding insulation detection working mode; the converter sends an excitation signal to the generator, and then collects the detection signal fed back by the generator; the converter transmits the collected detection signal to the main control system and switches to the normal working mode; the main control system transmits the detection signal to the data acquisition and monitoring control system; the data acquisition and monitoring control system stores, analyzes and determines the detection signal, identifies possible insulation faults of the generator and gives an early warning; the present invention also provides an on-line insulation detection device for a generator of a doubly-fed wind turbine; the present invention can solve the technical problems that the prior art cannot realize the real-time detection of the insulation performance of the generator winding and cannot more accurately predict the working health state of the generator.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and particularly relates to an online insulation detection method and device for a generator of a doubly-fed wind turbine generator set. Background Art

[0002] As a key component in a wind turbine generator set, the generator undertakes the function of converting mechanical energy into electrical energy, and its health state is one of the key factors affecting the normal operation of the wind turbine generator set. The insulation performance of the generator winding is the core parameter reflecting the health state of the generator. Detecting the insulation performance of the generator winding can judge the health state of the generator.

[0003] Currently, the conventional detection method is to remove the power cable of the generator outlet under the shutdown state of the wind turbine generator set, and use insulation detection instruments and meters to measure parameters such as the dielectric loss angle, partial discharge amount, DC withstand voltage value, polarization index, and discharge index of the generator winding, so as to judge the health state of the insulation system. The disadvantage of this method is that it is necessary to shut down the wind turbine generator set and remove the power cable of the outlet for detection. Therefore, this method cannot realize the real-time detection of the insulation performance of the generator winding.

[0004] Because when early faults occur in the stator and rotor windings of the generator, the wind turbine generator set can still continue to operate. If the faults cannot be detected as early as possible, it will lead to an increase in the stator and rotor currents and a rise in temperature, exacerbating the faults, and ultimately causing the wind turbine generator set to be forced to shut down. Therefore, it is necessary to perform real-time detection on the insulation performance of the generator winding, so as to more accurately predict the working health state of the generator. This can avoid the situation where no abnormality is found during the previous shutdown detection, but after the wind turbine generator set has been operating for a period of time, before the next shutdown detection, a fault occurs in the generator winding, affecting the normal operation of the wind turbine generator set. Summary of the Invention

[0005] Aiming at the defects in the prior art, the present invention provides an online insulation detection method and device for a generator of a doubly-fed wind turbine generator set to solve the technical problems existing in the prior art that the real-time detection of the insulation performance of the generator winding cannot be realized and the working health state of the generator cannot be more accurately predicted.

[0006] The technical solution adopted by the present invention is as follows:

[0007] In the first aspect, an online insulation detection method for a generator of a doubly-fed wind turbine generator set is provided;

[0008] In the first implementable manner, it includes the following steps:

[0009] The main control system sends a generator winding insulation detection command to the converter, and the converter switches to the generator winding insulation detection working mode;

[0010] The converter sends an excitation signal to the generator and then collects the detection signal fed back by the generator.

[0011] The converter transmits the collected detection signal to the main control system. After receiving the detection signal, the main control system sends a normal operation command to the converter, and the converter switches to the normal operation mode.

[0012] The main control system transmits the detection signal to the data acquisition and monitoring control system.

[0013] The data acquisition and monitoring control system stores, analyzes, and determines the detection signal, identifies possible insulation faults of the generator, and issues early warnings.

[0014] Combined with the first implementation method, in the second implementation method, the converter switches to the generator winding insulation detection operation mode, which is achieved by the following method: the converter control unit controls to disconnect the grid-connected contactor of the converter and close the main contactor and main circuit breaker of the converter.

[0015] Combined with the first implementation method, in the third implementation method, the following method is used to obtain the excitation signal: the converter control unit controls to adjust the frequency and carrier ratio of the converter modulation signal, and change the waveform, frequency, and amplitude of the converter output voltage.

[0016] Combined with the first implementation method, in the fourth implementation method, the detection signal fed back by the generator includes a voltage signal and a current signal. The converter collects the voltage signal fed back from one side of the generator stator through a voltage transformer, and collects the current signals fed back from one side of the generator stator and one side of the generator rotor respectively through current transformers.

[0017] Combined with the first implementation method, in the fifth implementation method, the data acquisition and monitoring control system analyzes the detection signal, including performing multiple Fourier transforms on the data of the detection signal after preprocessing, and using time-domain analysis and frequency-domain analysis methods to extract insulation state parameters reflecting the insulation performance of the generator.

[0018] Combined with the fifth implementation method, in the sixth implementation method, the insulation state parameters include the polarization index of the winding insulation, the partial discharge amount, the phase angle between voltage and current, and the characteristic frequency of current or voltage.

[0019] Combined with the first implementation method, in the seventh implementation method, a temperature sensor is used to monitor the real-time temperature of the generator, and the data acquisition and monitoring control system determines the detection signal in combination with the real-time temperature.

[0020] In the second aspect, an on-line insulation detection device for the generator of a doubly-fed wind turbine generator set is provided.

[0021] In the eighth implementation manner, any one method among the first to seventh implementation manners is used to perform on-line insulation detection on the generator of a doubly-fed wind turbine unit, including: a generator, a converter, a main control system, and a data acquisition and monitoring control system;

[0022] The generator includes a stator and a rotor;

[0023] The converter is used to change the waveform, frequency, and amplitude of the converter output voltage by adjusting the frequency and carrier ratio of the modulation signal to obtain an excitation signal; it is used to send the excitation signal to the generator, collect the detection signal fed back by the generator, and also transmit the collected detection signal to the main control system;

[0024] The main control system is used to control the switching of the working mode of the converter; it is also used to receive the detection signal and transmit the detection signal to the data acquisition and monitoring control system;

[0025] The data acquisition and monitoring control system is used to store, analyze, and judge the detection signal, identify possible insulation faults of the generator, and give an early warning.

[0026] Combined with the eighth implementation manner, in the ninth implementation manner, the converter includes a converter control unit, a grid-connected contactor, a main circuit breaker, a main contactor, a power module, a voltage transformer, and a current transformer;

[0027] The converter control unit is respectively connected to the grid-connected contactor, the main circuit breaker, the main contactor, the power module, the voltage transformer, and the current transformer;

[0028] The grid-connected contactor is connected to the stator of the generator, and the power module is connected to the rotor of the generator;

[0029] The grid-connected contactor, the main circuit breaker, and the main contactor are used to switch the working mode of the converter;

[0030] The voltage transformer and the current transformer are used to collect the detection signal;

[0031] Combined with the ninth implementation manner, in the tenth implementation manner, the voltage transformer is arranged between the rotor and the power module, and is also arranged between the stator and the grid-connected contactor; the current transformer is arranged between the stator and the grid-connected contactor.

[0032] As can be seen from the above technical solutions, the beneficial technical effects of the present invention are as follows:

[0033] 1. Disconnect the generator from the power grid by using a grid-connected contactor, a main circuit breaker, and a main contactor; use the converter as a waveform generator to generate the excitation signal required for insulation detection; collect the detection signal fed back after passing through the generator rotor winding through a voltage transformer and a current transformer; analyze and determine the detection signal through the SCADA system (Supervisory Control and Data Acquisition System); in this way, the on-line insulation performance detection of the generator of the doubly-fed wind turbine can be realized when the wind turbine is starting up, standby, or shutting down without removing the generator outgoing cable.

[0034] 2. Combine the method of simulating generator faults, establish a fault model of the doubly-fed motor in the SIMULINK simulation environment, and obtain the simulation parameters used to determine whether the generator has a fault or a risk of failure through pre-fault simulation and modeling and simulation, which can make the determination of the detection signal by the SCADA system more accurate.

[0035] 3. Make full use of the existing equipment and components of the wind turbine itself, without the need to add other equipment additionally, which is economical and practical.

[0036] 4. The converter can be set to two working modes. When insulation detection is to be carried out, the converter is switched to the generator winding insulation detection working mode. After the converter completes the functions of sending the excitation signal and data acquisition, it is immediately switched to the normal working mode, and then the detection signal is analyzed and processed in the SCADA system, which will not affect the normal operation of the wind turbine for a long time.

[0037] 5. The SCADA system can query the mapping relationship curve according to the measured value of the generator temperature measured by the temperature sensor, obtain the calibrated simulation parameters at this measured temperature through the mapping relationship, and then use the calibrated simulation parameters to determine the insulation fault of the generator, so as to make the determination result more accurate. Description of the Drawings

[0038] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or 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 do not necessarily draw according to the actual scale.

[0039] Figure 1 It is the flowchart of the method of Embodiment 1 of the present invention.

[0040] Figure 2 It is the voltage waveform diagram of the excitation signal emitted by the converter of the present invention.

[0041] Figure 3 It is the flowchart of the method for the SCADA system of the present invention to establish a fault information database.

[0042] Figure 4 The simulated spectrum diagram of the rotor current when establishing the fault information database for the SCADA system of the present invention.

[0043] Figure 5 The simulated spectrum diagram of the stator current when establishing the fault information database for the SCADA system of the present invention.

[0044] Figure 6 The flowchart of the method for analyzing and determining the insulation fault of the generator by the SCADA system of the present invention.

[0045] Figure 7 The structural block diagram of the device system in Embodiment 3 of the present invention. Detailed implementation manners

[0046] Next, embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, so they are only examples and cannot be used to limit the protection scope of the present invention.

[0047] It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should have the ordinary meanings understood by those skilled in the art to which the present invention belongs.

[0048] Embodiment 1

[0049] As Figure 1 shown, the present invention provides an on-line insulation detection method for a doubly-fed wind turbine generator, including the following steps:

[0050] The main control system sends a generator winding insulation detection command to the converter, and the converter switches to the generator winding insulation detection working mode;

[0051] The converter sends an excitation signal to the generator and then collects the detection signal fed back by the generator;

[0052] The converter transmits the collected detection signal to the main control system; after receiving the detection signal, the main control system sends a normal working command to the converter, and the converter switches to the normal working mode;

[0053] The main control system transmits the detection signal to the data acquisition and monitoring control system;

[0054] The data acquisition and monitoring control system stores, analyzes and determines the detection signal, identifies the possible insulation faults of the generator and gives an early warning.

[0055] The working principle of Embodiment 1 will be described in detail below. As Figure 1 shown, for on-line insulation detection of a doubly-fed wind turbine generator, the following steps are carried out:

[0056] 1. The main control system sends a generator winding insulation detection command to the converter, and the converter switches to the generator winding insulation detection working mode.

[0057] In this embodiment, during the startup, standby or shutdown of the wind turbine generator set, the insulation performance of the generator winding can be detected online. Before the online detection of the insulation performance, it is necessary to disconnect the generator from the power grid and also use the converter. Therefore, the staff needs to disconnect the generator from the power grid and switch the working mode of the converter through the main control system of the wind turbine generator set. By setting in the main control system of the wind turbine generator set, a generator winding insulation detection working mode can be added to the converter, and this working mode and the normal working mode can be switched online under the control of the main control system. Specifically, when it is necessary to switch the working model of the converter, after the main control system sends a generator winding insulation detection command to the converter, the control unit of the converter will control to disconnect the grid-connected contactor of the converter and close the main contactor and main circuit breaker of the converter, so as to switch the working mode of the converter to the generator winding insulation detection working mode. In this working mode, it is possible to disconnect the generator from the power grid without removing the power cable of the generator output.

[0058] 2. The converter sends an excitation signal to the generator; then the detection signal fed back by the generator is collected.

[0059] In this embodiment, using the control principle of the converter, including SPWM (Pulse Width Modulation) or SVPWM (Space Vector Pulse Width Modulation), the converter is used as a waveform generator. After the main control system sends a generator winding insulation detection command to the converter, the control unit of the converter will control the converter to adjust the frequency and carrier ratio of the modulation signal, change the waveform, frequency and amplitude of the output voltage of the converter, so as to generate the excitation signal required for the detection of the generator insulation performance. Taking the excitation signal as an example, in this embodiment, the generator of the doubly-fed wind turbine generator set is a doubly-fed asynchronous wind generator, and the parameters are as follows: stator base frequency 50Hz, stator resistance 1.115Ω, rotor resistance 1.083Ω; stator inductance 0.005974H, rotor inductance 0.005974H, mutual inductance 0.2037H; rotor fault resistance 0.001Ω, rotor fault inductance 0.0001H. When detecting the insulation performance of the generator, the converter provides an excitation signal to the rotor, as Figure 2 shown, the voltage amplitude of the excitation signal is 1V and the frequency is 30Hz.

[0060] Then, the converter control unit controls the converter to use the power module to transmit an excitation signal to the generator rotor winding through the power cable on the generator rotor side. When the generator rotor winding receives the excitation signal, after the excitation signal passes through the generator rotor winding, detection signals will be generated on the rotor side and stator side of the generator respectively. The detection signals include voltage signals and current signals. The converter collects the voltage signal feedback from the generator stator side through a PT (voltage transformer), and the converter collects the current signal feedback from the generator stator side and the current signal feedback from the generator rotor side through a CT (current transformer).

[0061] 3. The converter transmits the collected detection signals to the main control system; after receiving the detection signals, the main control system sends a normal operation command to the converter, and the converter switches to the normal operation mode

[0062] The converter transmits the collected signals, including the voltage signal and current signal feedback from the generator stator side and the current signal feedback from the generator rotor side, to the main control system. After receiving the signals collected by the converter, the main control system sends a normal operation command to the converter; the converter control unit controls to turn on the grid-connected contactor of the converter, open the main contactor and main circuit breaker of the converter, and switch the converter to the normal operation mode. In this way, when the converter completes the excitation signal transmission and data acquisition functions, it immediately switches to the normal operation mode, without affecting the normal operation of the wind turbine for a long time.

[0063] 4. The main control system transmits the detection signals to the Supervisory Control and Data Acquisition (SCADA) system

[0064] The main control system transmits the received detection signals to the SCADA system (Supervisory Control and Data Acquisition system). The transmission method is not limited, and it can be wired transmission or wireless transmission. Since the SCADA system is usually deployed in the cloud and remotely controlled, in this embodiment, the wireless transmission method is adopted, and wireless transmission is performed in any implementable manner in the prior art, such as 4G communication.

[0065] 5. The Supervisory Control and Data Acquisition system stores, analyzes, and determines the detection signals, identifies possible insulation faults in the generator, and issues early warnings

[0066] The SCADA system stores, analyzes, and determines the received detection signals, identifies possible insulation faults in the generator, and issues early warnings. In order to determine the detection signals, a reference value for determination is first required. For example Figure 3As shown in the figure, the SCADA system establishes a fault information database as follows: Through laboratory fault simulation and generator modeling and simulation calculations, the characteristic frequencies of the current and voltage of the generator stator and rotor, as well as the changes in the amplitudes at the characteristic frequencies, are obtained under different insulation fault types; Through laboratory thermal aging and electrical aging tests, the relationship curves between the insulation state and life of the generator winding and the partial discharge amount, polarization index, and dielectric loss angle are obtained. Specifically, in combination with the method of simulating generator faults, a fault model of a doubly-fed motor is established in the SIMULINK simulation environment. Through pre-fault simulation and modeling and simulation, the simulation parameters for determination are obtained. The simulation parameters are the insulation performance standard values used as references during determination, and the simulation parameters include data values and relationship curves. For example: When a fault occurs in the rotor winding of a doubly-fed generator, the fault characteristic frequency component is kf, where k = 3, 5, 7…, and f is the fundamental frequency (10 Hz). As Figure 4 、 Figure 5 shown: Figure 4 (a) represents the current simulation spectrum diagram of the rotor in the normal state, Figure 4 (b) represents the current simulation spectrum diagram of the rotor in the fault state; Figure 5 (a) represents the current simulation spectrum diagram of the stator in the normal state, Figure 5 (b) represents the current simulation spectrum diagram of the stator in the fault state. By comparing the two figures, it can be seen that the change in the rotor current in the fault characteristic frequency 3f is 30.78 dBm, and the change in the stator current is 30.96 dBm. Therefore, both the stator current signal and the rotor current signal can be used as characteristic signals for short-circuit diagnosis of doubly-fed wind turbines. The simulation parameters obtained through the above technical solutions are closer to the actual situation than the conventional mapping relationship standards refined according to human experience. When used for subsequent determination of generator insulation faults based on detection signals, the SCADA system can make more accurate determinations of detection signals.

[0067] As Figure 6 shown, the SCADA system analyzes and determines the possible insulation faults of the generator as follows:

[0068] (1) The SCADA system preprocesses the received detection signals to remove interference data and invalid data; The main method of preprocessing is data cleaning.

[0069] (2) The preprocessed data is subjected to multiple Fourier transforms, and time-domain analysis and frequency-domain analysis methods are used to extract insulation state parameters that reflect the insulation performance of the generator. In this embodiment, the insulation state parameters include the polarization index, partial discharge amount of the winding insulation, phase angle between voltage and current, characteristic frequency of current or voltage, and so on. The process of extracting insulation state parameters in this step is the analysis process of the detection signal.

[0070] (3) Compare the extracted insulation state parameters with the simulation parameters (including data values and relationship curves) to obtain a determination result. When the difference between the insulation state parameters and the simulation parameters exceeds the preset threshold, it indicates that the insulation performance of the generator at this time exceeds the range allowed by the insulation performance standard value, indicating that there may be an insulation fault in the generator winding. This fault may be an early fault or a more serious fault that may cause the wind turbine unit to shut down. At this time, the determination result of the SCADA system is that there is a risk of failure. This step is the determination process of the detection signal. In this embodiment, the threshold value is set to not exceed ±5% of the simulation parameters (i.e., the insulation performance standard value); for the relationship curve, it is ±5% of the value of the corresponding point on the curve. When the preset threshold is not exceeded, it indicates that the fault characteristic values do not match, and the insulation performance of the generator is normal at this time.

[0071] (4) The SCADA system issues a warning according to the determination result

[0072] When the determination result is that there is a risk of failure, the SCADA system will give a warning prompt on the system interface, including in the form of display or by emitting an alarm sound to remind the staff to pay attention. After receiving the warning, the staff will determine whether to shut down the wind turbine unit for maintenance.

[0073] Through the technical solution in this embodiment, it is possible to realize the on-line detection of the insulation performance of the generator of the doubly-fed wind turbine unit without removing the outgoing cable of the generator. At the same time, make full use of the existing equipment and components of the wind turbine unit itself, without the need to add other equipment additionally, which is economical and practical.

[0074] Embodiment 2

[0075] The insulation performance of the generator has a certain relationship with temperature; for example, when the external temperature rises or the temperature of the generator itself rises due to work, the insulation resistance of the generator will decrease; when the external temperature drops or the temperature of the generator itself drops due to the stop of work, the insulation resistance of the generator will increase.

[0076] In Embodiment 1, by combining the method of simulating generator faults, a fault model of the doubly-fed motor is established in the SIMULINK simulation environment. Through pre-fault simulation and modeling and simulation, the simulation parameters for determination reference are obtained. The temperature value corresponding to the simulation parameters is generally under room temperature conditions, that is, 25 degrees Celsius. When the generator is performing insulation detection, since it has been in a working state before shutdown, its temperature is much higher than 25 degrees Celsius in a short time after just shutting down, and may be close to or even exceed 100 degrees Celsius. In this embodiment, 100 degrees Celsius is used as an example for illustration. At this time, using the simulation parameters obtained under the condition of 25 degrees Celsius to determine the insulation fault of the generator at 100 degrees Celsius will produce a certain error.

[0077] In order to solve the above technical problems, the following technical solution is adopted: a temperature sensor is set on the generator to monitor the real-time temperature of the generator, and the SCADA system judges the detection signal in combination with the real-time temperature. Specifically, the SCADA system calibrates the simulation parameters obtained under the condition of 25 degrees Celsius by the real-time temperature, obtains the calibrated simulation parameters, and then uses the calibrated simulation parameters to judge the insulation fault of the generator.

[0078] The working principle of Example 2 is described in detail below:

[0079] A temperature sensor is provided on the generator, and the location of the setting can be on the rotor of the generator or on the stator; however, because the stator temperature of the generator is generally higher than the rotor temperature, the temperature sensor is provided on the stator in this embodiment. The temperature sensor can use the temperature sensor provided by the generator, or a new one can be provided, and the model can be the DJNTC1 series; in this embodiment, the temperature sensor provided by the generator is used for temperature monitoring. The real-time temperature measured by the temperature sensor is transmitted to the SCADA system through the main control system. Because under different temperature conditions, the insulation performance parameters of the generator will form a mapping relationship curve with the temperature value, and this curve can be obtained through actual measurement. Therefore, during calibration, the SCADA system can query the mapping relationship curve according to the actual value of the generator temperature measured by the temperature sensor, and obtain the calibrated simulation parameters at this measured temperature through the mapping relationship. The SCADA system then uses the calibrated simulation parameters to determine the insulation fault of the generator, so that the determination result is more accurate.

[0080] Example 3

[0081] In this example, an online insulation detection device for a double-fed wind turbine generator is provided. Figure 7 As shown, it includes: generator, converter, main control system and data acquisition and monitoring control system;

[0082] The generator includes a stator and a rotor;

[0083] The converter is used to send an excitation signal to the generator, to collect the detection signal fed back by the generator, and to transmit the collected detection signal to the main control system;

[0084] The main control system is used to control the switching of the converter working mode; it is also used to receive the detection signal and transmit the detection signal to the data acquisition and monitoring control system;

[0085] The data acquisition and monitoring control system is used to store, analyze and judge the detection signals, identify possible insulation faults in the generator and issue early warnings.

[0086] The converter includes a converter control unit, a grid-connected contactor, a main circuit breaker, a main contactor, a power module, a voltage transformer, and a current transformer; the converter control unit is respectively connected to the grid-connected contactor, the main circuit breaker, the main contactor, the power module, the voltage transformer, and the current transformer; the grid-connected contactor of the converter is connected to the stator of the generator, and the power module of the converter is connected to the rotor of the generator; the grid-connected contactor, the main circuit breaker, and the main contactor are used to switch the working mode of the converter; the voltage transformer and the current transformer are used to collect detection signals; the voltage transformer is arranged between the rotor and the power module, and is also arranged between the stator and the grid-connected contactor; the current transformer is arranged between the stator and the grid-connected contactor.

[0087] In this embodiment, the online insulation detection device for the generator of the doubly-fed wind turbine uses the method in Embodiment 1 or Example 2 to perform online insulation detection on the generator of the doubly-fed wind turbine. When performing online insulation detection on the generator, Figure 7 each grid-side PT and grid-side CT in does not work, and when the wind turbine switches the converter to the normal working mode, each grid-side PT and grid-side CT starts to work.

[0088] 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 foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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 covered by the scope of the claims and the description of the present invention.

Claims

1. An on-line insulation detection method for the generator of a doubly-fed wind turbine, characterized in that The method includes the following steps: The main control system sends a generator winding insulation detection command to the converter, and through the converter control unit, controls the disconnection of the grid-connected contactor of the converter, closes the main contactor and the main circuit breaker of the converter; the converter switches to the generator winding insulation detection working mode, and conducts on-line detection of the insulation performance of the generator winding when the wind turbine is starting up, on standby or shutting down; The converter sends an excitation signal to the generator, and then collects the detection signals fed back by the generator; the detection signals fed back by the generator include voltage signals and current signals, and the converter collects the voltage signals fed back on the stator side of the generator through a voltage transformer, and collects the current signals fed back on the stator side and the rotor side of the generator respectively through a current transformer; The converter transmits the collected detection signals to the main control system; after receiving the detection signals, the main control system sends a normal operation command to the converter, and the converter switches to the normal operation mode; The main control system transmits the detection signals to the data acquisition and monitoring control system; The data acquisition and monitoring control system stores, analyzes and determines the detection signals, identifies possible insulation faults of the generator and issues early warnings.

2. The on-line insulation detection method for the generator of a doubly-fed wind turbine set according to claim 1, characterized in that The excitation signal is obtained in the following manner: the converter control unit adjusts the frequency and carrier ratio of the converter modulation signal to change the waveform, frequency and amplitude of the converter output voltage.

3. The on-line insulation detection method for the generator of a doubly-fed wind turbine set according to claim 1, characterized in that: The data acquisition and monitoring control system analyzes the detection signals, including performing multiple Fourier transforms on the data of the detection signals after preprocessing, and using time-domain analysis and frequency-domain analysis methods to extract insulation state parameters reflecting the insulation performance of the generator.

4. The on-line insulation detection method for the generator of a doubly-fed wind turbine set according to claim 3, wherein: The insulation state parameters include the polarization index of the winding insulation, the partial discharge amount, the phase angle between voltage and current, and the characteristic frequency of current or voltage.

5. The on-line insulation detection method for the generator of a doubly-fed wind turbine set according to claim 1, wherein: A temperature sensor is used to monitor the real-time temperature of the generator, and the data acquisition and monitoring control system determines the detection signals in combination with the real-time temperature.

6. An on-line insulation detection device for the generator of a doubly-fed wind turbine, characterized in that: The on-line insulation detection of the generator of a doubly-fed wind turbine is performed by using any one of the methods of claims 1-5, including: a generator, a converter, a main control system and a data acquisition and monitoring control system; The generator includes a stator and a rotor; The converter is used to obtain an excitation signal by adjusting the frequency and carrier ratio of the modulation signal, change the waveform, frequency and amplitude of the output voltage; used to send an excitation signal to the generator, used to collect the detection signals fed back by the generator, and also used to transmit the collected detection signals to the main control system; The main control system is used to control the switching of the working mode of the converter; and is also used to receive the detection signals and transmit the detection signals to the data acquisition and monitoring control system; The data acquisition and monitoring control system is used to store, analyze and determine the detection signals, identify possible insulation faults of the generator and issue early warnings.

7. The on-line insulation detection device for the generator of a doubly-fed wind turbine according to claim 6, characterized in that: The converter includes a converter control unit, a grid-connected contactor, a main circuit breaker, a main contactor, a power module, a voltage transformer and a current transformer; The converter control unit is respectively connected to the grid-connected contactor, the main circuit breaker, the main contactor, the power module, the voltage transformer and the current transformer; The grid-connected contactor is connected to the stator of the generator, and the power module is connected to the rotor of the generator; The grid-connected contactor, the main circuit breaker and the main contactor are used to switch the operating mode of the converter; The voltage transformer and the current transformer are used to collect detection signals.

8. The on-line insulation detection device for the generator of a doubly-fed wind turbine according to claim 7, characterized in that: The voltage transformer is arranged between the rotor and the power module, and is also arranged between the stator and the grid-connected contactor; the current transformer is arranged between the stator and the grid-connected contactor.

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