Method and system for testing doubly-fed motor and method and system for testing rotor

Abstract

The embodiment of the invention relates to the field of fan testing, and discloses a doubly-fed motor testing method and system and a rotor testing method and system. In the invention, a stator winding of the doubly-fed motor is configured to be in an open circuit state, a rotor shaft of the doubly-fed motor is mechanically connected with a dragging device, and a rotor slip ring of the doubly-fed motor is electrically connected with a variable-frequency power supply device; the method comprises the following steps: controlling the dragging device to drive a rotor of the doubly-fed motor to rotate so as to apply a mechanical load, and controlling the variable-frequency power supply device to inject alternating current into the rotor so as to apply an electric heating load; wherein the mechanical load and the electric heating load of the rotor are mutually decoupled based on the open circuit state of the stator winding; and monitoring state parameters of the doubly-fed motor. Therefore, the problems that the test cost is high, the energy consumption is large, the test working condition simulation of a single part is not real, and the fatigue failure risk of the rotor system cannot be fully identified in the prior art are solved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of wind turbine testing, and particularly to the test methods and systems for doubly fed motors and rotors. Background Technology

[0002] Doubly-fed induction generators (DFIGs) are among the most widely used types of generators in the wind power industry. As wind turbines become larger, the requirements for generator reliability are increasing. The generator's rotor system (including the rotor core, windings, leads, and slip ring system) is subjected to complex mechanical, thermal, and electrical stresses, making it a key component determining the overall reliability of the DFIG. To ensure product reliability, thorough testing and verification of the generator rotor are necessary during the development process.

[0003] In related technologies, the verification of doubly-fed induction generators mainly includes the following methods: The first is whole-machine type testing, which involves full-power grid-connected operation testing on a professional type test bench. While this method can simulate actual operating conditions well, it suffers from high investment costs in test bench construction, extremely high electricity costs for long-term load testing, and limited test bench resources. The second is individual simulation testing of the slip ring system, which involves testing the slip rings separately. However, this method typically suffers from problems such as excessively low test voltage, limited adjustable current frequency range, and significant differences between the vibration environment and cooling conditions and the actual whole-machine operating environment. This results in the slip ring system's failure risk not being accurately reflected, further affecting the fatigue failure risk assessment of the rotor system under complex operating conditions. The third is conventional no-load testing. Although simple to operate, the rotor side is usually supplied with DC or a small current at a constant speed, which cannot simulate the complex coupled operating conditions of speed fluctuations and large current impacts under real wind conditions, and it is also difficult to effectively assess the durability of the rotor insulation system.

[0004] Therefore, how to achieve long-term reliability verification of doubly fed motor rotors under near-real operating conditions with low testing costs and energy consumption is an urgent problem to be solved in the industry. Summary of the Invention

[0005] The purpose of this invention is to provide a testing method and system for a doubly-fed motor and a testing method and system for the rotor, in order to solve the problems of high testing costs, high energy consumption, and unrealistic simulation of individual component test conditions, which cannot fully identify the risk of fatigue failure of the rotor system in related technologies.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a testing method for a doubly-fed induction generator (DFIG), wherein the stator winding of the DFIG is configured in an open-circuit state, the rotor shaft of the DFIG is mechanically connected to a drive device, and the rotor slip rings of the DFIG are electrically connected to a frequency converter. The method includes: controlling the drive device to drive the rotor of the DFIG to rotate to apply a mechanical load, and controlling the frequency converter to inject alternating current into the rotor to apply an electrothermal load; wherein, based on the open-circuit state of the stator winding, the mechanical load and the electrothermal load of the rotor are decoupled from each other; and monitoring the state parameters of the DFIG.

[0007] An embodiment of the present invention also provides a test method for the rotor of a doubly-fed induction generator (DFIG), wherein the rotor shaft of the DFIG is mechanically connected to a drive device, and the rotor slip ring of the DFIG is electrically connected to a frequency converter; the method includes: controlling the drive device to drive the rotor of the DFIG to rotate to apply a mechanical load, and controlling the frequency converter to inject alternating current into the rotor to apply an electrothermal load; and monitoring the state parameters of the DFIG.

[0008] Embodiments of the present invention also provide a test system for a doubly-fed induction generator (DFIG), comprising: a drive device, the output of which is connected to the rotor shaft of the DFIG and configured to drive the rotor to rotate to apply a mechanical load; a frequency converter, the output of which is connected to the rotor slip ring of the DFIG and configured to inject alternating current into the rotor to apply an electrothermal load; and a control device, communicatively connected to both the drive device and the frequency converter, and configured to perform operations controlling the drive device and the frequency converter. The stator windings of the DFIG are configured in an open-circuit state; based on the open-circuit state of the stator windings, the mechanical load and the electrothermal load of the rotor are decoupled from each other.

[0009] An embodiment of the present invention provides a test system for the rotor of a doubly-fed induction generator (DFIG), comprising: a drive device whose output end is connected to the rotor shaft of the DFIG and configured to drive the rotor to rotate to apply a mechanical load; a frequency converter whose output end is connected to the rotor slip ring of the DFIG and configured to inject alternating current into the rotor to apply an electrothermal load; and a control device communicatively connected to the drive device and the frequency converter, respectively, and configured to perform operations controlling the drive device and the frequency converter.

[0010] In this embodiment of the invention, by configuring the stator windings of the doubly-fed generator to an open-circuit state, the electromagnetic coupling loop between the stator, the power grid, and the rotor is severed, thereby eliminating the electromagnetic induction effect during conventional generator operation. Based on this, the mechanical speed (mechanical load) of the rotor is controlled independently using a drive device, and AC current (electrothermal load) is injected into the rotor independently through slip rings using a frequency converter. This design achieves complete decoupling of the mechanical load and the electrothermal load, allowing testers to arbitrarily combine speed and current conditions, such as applying rated current at low speeds, to flexibly simulate various extreme or specific fatigue conditions. Simultaneously, since the stator is open-circuited and unloaded, the drive device only needs to overcome the mechanical friction loss and wind resistance loss during rotor rotation, without needing to provide the enormous mechanical power required for power generation, significantly reducing energy consumption and the requirements for test bench infrastructure. Furthermore, this method does not require expensive type test benches, offers flexible start-stop functionality, and significantly reduces the cost of long-term reliability verification.

[0011] Furthermore, the control of the drive device to rotate the rotor of the doubly-fed motor to apply mechanical load, and the control of the variable frequency power supply to inject AC current into the rotor to apply electrothermal load, includes: controlling the drive device to operate according to a preset speed curve to apply mechanical load; controlling the variable frequency power supply to adjust the AC current injected into the rotor according to a preset current curve to apply electrothermal load; and simulating the operating state of the doubly-fed motor under various working conditions by combining speed parameters and current parameters. Thus, by combining speed parameters and current parameters, the specific loading curve of "speed fluctuation + current frequency fluctuation" under real wind conditions can be reproduced, for example, simulating the "high wind, high power generation" working condition of a real wind turbine, or simulating the coupling effect of mechanical fatigue caused by alternating speed and thermal fatigue caused by current surge, improving the authenticity and effectiveness of the test results.

[0012] In addition, voltage sensors are configured at the three-phase ends of the stator windings. Monitoring the state parameters of the doubly-fed induction generator includes: acquiring the induced voltage of the stator windings through the voltage sensors; and assessing the inter-turn short-circuit fault status of the rotor windings based on the induced voltage. Thus, by using the open-circuit stator windings as a non-contact "fault probe," when an inter-turn short circuit or insulation degradation occurs in the rotor windings, the stator induced voltage will exhibit three-phase imbalance or specific harmonics. This method can capture early faults inside the rotor in real time and with high sensitivity during testing, without requiring disassembly for inspection, thus improving the efficiency of fault monitoring.

[0013] Furthermore, the variable frequency power supply device is a voltage source type variable frequency converter; controlling the variable frequency power supply device to inject AC current into the rotor to apply an electrothermal load includes: controlling the variable frequency power supply device to output a pulse width modulation waveform voltage to the rotor; and verifying the insulation performance of the rotor based on the voltage change rate of the pulse width modulation waveform. Therefore, compared to traditional power frequency sinusoidal power supplies, the introduction of a PWM wave containing abundant high-frequency harmonics and an extremely high voltage change rate reproduces the high-frequency pulse voltage impact environment experienced by the rotor insulation system under actual variable frequency converter power supply, enabling more effective assessment of the rotor insulation system's tolerance and reliability.

[0014] Furthermore, the doubly-fed motor is mounted on a test base, and the stator core of the doubly-fed motor under test is retained on the test base; a cooling fan is also configured on the test base; the ventilation slots of the stator core are used to cooperate with the cooling fan to form a ventilation duct for the rotor; the method further includes: controlling the cooling fan to drive the hot airflow generated by the rotor through the ventilation duct. Thus, by utilizing the retained stator core as a necessary physical airflow boundary, the airflow is forced to flow along a preset path (such as radial or axial ventilation slots), effectively preventing airflow dispersion or leakage (i.e., "air leakage") when the stator is removed. This design successfully constructs a heat dissipation flow field environment consistent with the actual operation of the doubly-fed motor under the special test condition of open stator windings, ensuring the accuracy and reference value of the rotor system temperature rise test data.

[0015] In addition, the doubly-fed motor is connected to the test base via an elastic support; the method further includes: collecting vibration data of the doubly-fed motor and evaluating the mechanical reliability of the rotor under a simulated nacelle elastic support environment. Thus, the elastic support environment within the wind turbine nacelle can be simulated, making the vibration modes and responses of the doubly-fed motor during the test closer to the actual installed state, thereby accurately evaluating the mechanical reliability of the rotor under a simulated nacelle vibration environment. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0017] Figure 1 This is a diagram of the test environment used in the test method for a doubly fed motor provided in this application; Figure 2 This is a flowchart of a test method for a doubly fed motor according to the present application. Detailed Implementation

[0018] As mentioned in the background technology, related technologies mainly suffer from high costs and huge energy consumption in whole-machine type testing, while the simulated test conditions for individual components (such as slip rings) are unrealistic and cannot fully identify failure risks. The inventors discovered that the root causes of the above problems are the following two points: First, in the normal operation or closed-loop testing of a doubly-fed generator, there is strong electromagnetic coupling between the stator and rotor. This means that the electrical load (current / heat) and the mechanical load (torque / power) are deeply bound together. If the rated current is applied to the rotor to assess thermal fatigue, it will inevitably be accompanied by huge electromagnetic torque, which requires the driven equipment to provide matching huge mechanical power (active power). This directly leads to high barriers to the construction of test benches and staggering electricity costs. At the same time, this coupling characteristic also limits the degree of freedom of the test, making it difficult to simulate specific decoupled conditions such as "low speed + high current". Second, for the individual-level test scheme, its physical isolation leads to the lack of a multi-physics environment. The slip ring system is separated from the huge rotor core and stator entity and cannot simulate the electromagnetic stress environment coupled by the rotor in actual operation, resulting in a serious deviation between the test boundary conditions and the real operating conditions, causing "simulation distortion".

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the various embodiments of the present invention to facilitate a better understanding of this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0020] One embodiment of the present invention relates to a testing method for a doubly-fed induction generator (DFIG), which is mainly applied to the reliability verification stage in the research and development or production process of wind turbine generator sets. The specific executing entity can be a dedicated test bench system comprising a drive device (such as a small-power servo motor), a frequency converter (such as a four-quadrant frequency converter), and a central control unit. In this embodiment, the stator winding of the DFIG is configured to be open-circuit, the rotor shaft of the DFIG is mechanically connected to the drive device, and the rotor slip rings of the DFIG are electrically connected to the frequency converter. The method includes: controlling the drive device to drive the rotor of the DFIG to rotate to apply a mechanical load, and controlling the frequency converter to inject AC current into the rotor to apply an electrothermal load; wherein, based on the open-circuit state of the stator winding, the mechanical load and the electrothermal load of the rotor are decoupled from each other; and monitoring the state parameters of the DFIG. In this embodiment, by configuring the stator winding of the DFIG to be open-circuit, the electromagnetic coupling loop between the stator and the power grid and the rotor is cut off, thereby eliminating the electromagnetic induction effect during conventional generator operation. Building upon this, the mechanical speed (mechanical load) of the rotor is controlled independently using a drive device, while an AC current (electrothermal load) is injected into the rotor independently through slip rings using a variable frequency power supply. This design achieves complete decoupling of the mechanical and electrothermal loads, allowing testers to arbitrarily combine speed and current conditions, such as applying rated current at low speeds, thereby flexibly simulating various extreme or specific fatigue conditions. Simultaneously, since the stator is open-circuited and unloaded, the drive device only needs to overcome the mechanical friction and wind resistance losses during rotor rotation, without needing to provide the enormous mechanical power required for power generation, significantly reducing energy consumption and the requirements for test bench infrastructure. Furthermore, this method eliminates the need for expensive type test benches, offers flexible start-stop functionality, and significantly reduces the cost of long-term reliability verification.

[0021] The following is a detailed description of the implementation details of the test method for the doubly fed motor according to an embodiment of the present invention. The following content is only for the convenience of understanding the implementation details and is not necessary for implementing this solution.

[0022] The testing environment for this invention embodiment is as follows: Figure 1 As shown in the figure. In this case, the stator winding of the doubly-fed motor is configured to be in an open-circuit state, the rotor shaft of the doubly-fed motor is mechanically connected to the drive device, and the rotor slip ring of the doubly-fed motor is electrically connected to the frequency converter.

[0023] In a specific example, the three-phase ends of the stator winding are configured to be unconnected and suspended. Specifically, by configuring the stator winding in an open-circuit state, the electromagnetic coupling loop between the stator and the power grid and the rotor is cut off, thereby eliminating the electromagnetic induction effect during conventional generator operation. Based on this, the mechanical speed of the rotor (mechanical load) is controlled independently using a drive device, and AC current (electrothermal load) is injected independently into the rotor through slip rings using a frequency converter. This design achieves complete decoupling of the mechanical load and the electrothermal load, allowing testers to arbitrarily combine speed and current conditions, such as applying rated current at low speeds, thereby flexibly simulating various extreme or specific fatigue conditions.

[0024] In an optional embodiment, the stator core of the doubly-fed induction generator under test is retained on the test base, serving both to form a ventilation duct in conjunction with the cooling fan and as part of the magnetic circuit (or a simulation component). It is worth noting that the material of the stator core can be flexibly selected within a certain range, depending on the magnitude of the injected current on the rotor side during the test and the emphasis of the test.

[0025] 1. Non-magnetic or low-permeability materials: When test conditions require injecting extremely high currents into the rotor (e.g., overload thermal tests of several thousand amperes), if conventional high-permeability silicon steel sheets are used, the stator core is prone to magnetic saturation because the open circuit of the stator windings cannot generate a demagnetizing magnetomotive force, preventing the rotor current from reaching the target value. In this case, it is preferable to use non-magnetic materials such as epoxy resin or high-strength plastics, or low-permeability materials such as stator emulators, to fabricate the stator core. This reduces the magnetic flux density, ensuring that the magnetic circuit remains unsaturated under high-current conditions, thus allowing the intended electrothermal load to be applied smoothly.

[0026] 2. High permeability materials: When the expected test current is small and has not reached the core saturation limit, or when the focus of the test is to use the stator winding induced voltage to highly sensitively monitor rotor inter-turn short-circuit faults, high permeability materials can be selected. High permeability can enhance the mutual inductance between the stator and rotor, so that under the same rotor fault, the stator side can induce a voltage signal (or harmonic component) with a higher amplitude, thereby improving the signal-to-noise ratio and sensitivity of fault monitoring.

[0027] 3. Medium permeability materials: In practical applications, materials with permeability between the two mentioned above can be selected based on calculation results, or a balance can be achieved between preventing magnetic saturation and retaining a certain induced voltage amplitude by adjusting the geometric dimensions of the stator core (such as the air gap length).

[0028] In a specific example, the rated power of the drive device is less than that of the doubly-fed induction generator (DFIG). The drive device provides the mechanical energy needed to overcome the mechanical friction and wind resistance losses during rotor rotation. Specifically, since the stator is open-circuited and unloaded, there is no electromagnetic torque braking effect in the system. The drive device (e.g., a small variable frequency motor) only needs to overcome bearing friction and fan wind resistance to drive the rotor to its rated speed. Typically, the power of this drive device is only about 10% (or even less) of the rated power of the DFIG under test. This design eliminates the need to provide the huge mechanical power required for power generation, significantly reducing the energy consumption of the test and the requirements for test bench infrastructure (such as foundation and power distribution capacity).

[0029] In a specific example, the doubly-fed motor is mounted on a test base, and the stator core of the doubly-fed motor under test remains on the test base; a cooling fan is also configured on the test base; the ventilation slots of the stator core are used to cooperate with the cooling fan to form a ventilation duct for the rotor; the method also includes: controlling the cooling fan to drive the hot airflow generated by the rotor through the ventilation duct. Thus, on the one hand, the stator core located on the outside of the rotor acts as a key physical airflow boundary (or airflow barrier), which forcibly confines the airflow generated by the rotor rotation within the preset ventilation slot path (e.g., Figure 1 The ventilation path in the cooling equipment ensures that the airflow trajectory under test conditions is completely consistent with the hydrodynamic characteristics of the complete motor during actual operation, effectively preventing airflow dispersion or ineffective leakage into open spaces due to stator removal. On the other hand, the active design of the cooling fan introduces a controllable heat dissipation regulation mechanism. By controlling the fan's operating state, the flow rate and velocity of the hot airflow passing through the motor can be precisely adjusted, so that the heat dissipation conditions of the rotor system no longer solely depend on the rotor's rotational speed, achieving decoupling of heat dissipation capacity from mechanical speed. This design, under the special test condition of open stator windings, not only constructs a high-fidelity heat dissipation flow field environment but also provides flexible thermal management methods, thereby greatly ensuring the accuracy and engineering reference value of the rotor system temperature rise test data.

[0030] In a specific example, the doubly-fed induction generator (DFIG) is connected to the test base via a flexible support. By collecting vibration data from the DFIG, the mechanical reliability of the rotor can be assessed under a simulated nacelle flexible support environment. Specifically, by introducing the flexible support, the flexible installation environment under wind load within the wind turbine nacelle can be simulated, making the vibration modes and responses of the DFIG during testing closer to the actual installed state. This helps to more accurately induce and assess the mechanical resonance risk and fatigue life of the rotor system at specific frequencies.

[0031] In an optional example, the drive device used in this embodiment of the invention can be, but is not limited to, a DC motor, an AC asynchronous motor with a frequency converter, or a permanent magnet synchronous servo motor. Specifically, although the drive device in this solution only needs to provide torque to overcome friction and wind resistance, different types of motors can be adapted to different testing requirements. For example, using a DC motor can achieve smooth stepless speed regulation by utilizing its excellent speed regulation performance; using an AC asynchronous motor with a general-purpose frequency converter has the advantages of low cost and simple maintenance, making it suitable for large-scale testing in industrial settings; and in situations requiring extremely high speed control accuracy (such as simulating small wind speed fluctuations), a permanent magnet synchronous servo motor can be selected. This diverse selection scheme allows the test system to be flexibly configured according to the existing equipment resources on site, further reducing the hardware threshold for test bench construction.

[0032] In an optional example, the variable frequency power supply device used in the embodiments of the present invention can be, but is not limited to, a four-quadrant frequency converter, a matrix converter, or a programmable AC power supply. Specifically, a four-quadrant frequency converter can achieve bidirectional energy flow, feeding energy back to the grid when the rotor is in a generating state, offering advantages in energy saving and environmental protection; a matrix converter, due to the elimination of intermediate DC energy storage, is smaller in size and has better output waveform quality; while a programmable AC power supply has stronger waveform editing capabilities, not only outputting standard sine waves or PWM waves, but also directly generating complex waveforms with specific harmonics (such as the 5th and 7th harmonics) or voltage drop characteristics through software programming. This flexible power supply selection allows the test system to not only perform conventional temperature rise tests, but also to conduct in-depth research on rotor tolerance under power quality disturbances.

[0033] Applied to the above-mentioned test environment, the test method of this embodiment of the invention is as follows: Figure 2 As shown, it includes: Step S101: Control the drive device to drive the rotor of the doubly fed motor to rotate to apply mechanical load, and control the frequency converter to inject AC current into the rotor to apply electrothermal load.

[0034] In a specific example, controlling the drive device to rotate the rotor of the doubly-fed induction generator (DFIG) to apply a mechanical load, and controlling the variable frequency power supply to inject AC current into the rotor to apply an electrothermal load, includes: controlling the drive device to operate according to a preset speed curve to apply the mechanical load; controlling the variable frequency power supply to adjust the AC current injected into the rotor according to a preset current curve to apply the electrothermal load; and simulating the operating state of the DFIG under various working conditions by combining speed and current parameters. Specifically, based on the aforementioned decoupling characteristics, the test system can construct a flexible "multi-physics coupling" test pattern. For example, a specific loading curve of "speed fluctuation + current frequency fluctuation" can be set to simulate the "high wind, high power generation" scenario of a real wind turbine under gust conditions; or the superimposed effect of mechanical fatigue caused by alternating speed and thermal fatigue caused by current surge can be simulated. This combined loading method greatly improves the authenticity and effectiveness of the test results, filling the gap in traditional single-unit tests that cannot simulate coupled stress.

[0035] In a specific example, controlling the variable frequency power supply to adjust the AC current injected into the rotor according to a preset current curve includes at least: controlling the frequency of the AC current within a preset slip frequency range to test the electrical performance of the rotor under near-rated operating conditions, and / or continuously sweeping the frequency of the AC current within the preset range to test the electrical performance of the rotor at different slip frequencies. Specifically, utilizing the frequency adjustment capability of the variable frequency power supply, an AC current at a slip frequency (e.g., 5Hz-10Hz) corresponding to the rated speed can be injected. Under this "near-rated operating" condition, the electromagnetic force state of the rotor in actual wind farm operation can be simulated more realistically. Simultaneously, continuous frequency sweeping can cover the slip frequency range (typically 0-15Hz) corresponding to different wind speeds of the rotor, comprehensively assessing the reliability of electrical connections under electromagnetic forces at different frequencies.

[0036] In a specific example, the frequency converter is a voltage source inverter. Controlling the frequency converter to inject AC current into the rotor to apply an electrothermal load includes: controlling the frequency converter to output a pulse-width modulated (PWM) voltage to the rotor; and verifying the rotor's insulation performance based on the voltage change rate of the PWM waveform. Specifically, compared to the power frequency sinusoidal power supply (such as a voltage regulator) used in traditional tests, this embodiment introduces a PWM wave containing abundant high-frequency harmonics and an extremely high voltage change rate (dv / dt). This waveform realistically reproduces the high-frequency pulse voltage impact environment experienced by the rotor insulation system when powered by the grid-side frequency converter in an actual wind turbine. Through this "qualitative change" of stress application, potential defects in the rotor insulation can be more effectively stimulated and eliminated, thereby improving the reliability verification level of the insulation system.

[0037] In a specific example, controlling the drive device to operate according to a preset speed curve includes at least: controlling the drive device to drive the rotor to accelerate from a standstill to a rated speed within a preset time, and / or, performing alternating cycles between multiple speeds to test the rotor's mechanical performance. Specifically, by controlling the drive device to perform rapid acceleration / deceleration or periodic speed fluctuations, alternating centrifugal force loads can be generated at the rotor end windings and lead positions. Combined with the simultaneously applied current thermal effect, this "mechanical-thermal" dual fatigue test can accelerate the aging process and effectively identify early failure modes such as rotor end clamp loosening, lead wear, or insulation cracking.

[0038] Step S102: Monitor the status parameters of the doubly fed motor.

[0039] In a specific example, voltage sensors are configured at the three-phase ends of the stator windings to monitor the status parameters of the doubly-fed induction generator (DFIG), including: acquiring the induced voltage of the stator windings through the voltage sensors; and assessing the inter-turn short-circuit fault status of the rotor windings based on the induced voltage. Specifically, the open-circuit stator windings are used as a non-contact "fault probe." When the rotor is energized and rotates, the rotating magnetic field it generates induces a voltage on the stator side. If the rotor windings are healthy, the three-phase induced voltages in the stator should be symmetrical; if an inter-turn short circuit or insulation degradation occurs in the rotor windings, the air gap magnetic field will be distorted, resulting in a three-phase imbalance or specific harmonics in the stator induced voltage. This method can capture early faults inside the rotor in real time and with high sensitivity during testing, without requiring shutdown and disassembly for inspection, significantly improving the efficiency and safety of fault monitoring.

[0040] It should be noted that the amplitude of the stator induced voltage is closely related to the magnetic permeability of the stator core. When a non-magnetic material is used to make the stator core to prevent saturation, the amplitude of the induced voltage will decrease accordingly. However, the symmetry and harmonic characteristics of its three-phase waveform can still be used to qualitatively identify inter-turn short circuits or insulation abnormalities in the rotor winding. When a magnetic material (such as silicon steel sheet) or a material with higher magnetic permeability is used to make the stator core, the amplitude of the induced voltage in the stator winding will be relatively high. However, under high current conditions, the voltage monitoring threshold needs to be set in conjunction with the magnetic saturation characteristics of the core.

[0041] In a specific example, monitoring the state parameters of a doubly-fed induction generator (DFIG) also includes: real-time monitoring of the rotor temperature, the operating parameters of the rotor slip ring system, and the vibration parameters of the DFIG; combining temperature, operating parameters, and vibration parameters to assess the rotor reliability of the DFIG. Specifically, the assessment process includes: process monitoring, real-time monitoring of rotor temperature and vibration values ​​to ensure they do not exceed limits, and monitoring the operating status of the slip ring system (such as carbon brush temperature and the formation of oxide film on the slip ring surface); post-test inspection, after the test, disassembling or visually inspecting the rotor to confirm whether there are cracks, deformations, or ablation marks on the rotor surface, lead connectors, and insulation structure. Combining the above process data and physical inspection results, a comprehensive judgment is made on the product reliability.

[0042] In an optional embodiment, the test method further includes grid fault ride-through simulation. Specifically, the variable frequency power supply is controlled to instantaneously increase the current amplitude injected into the rotor (e.g., to 2-3 times the rated current) for a very short time, and then restore it after several seconds, to simulate the overcurrent impact experienced by the rotor side of the doubly-fed induction generator during grid low-voltage ride-through. Based on this, the temperature rise and contact stability of the rotor lead joints and slip ring brush holders under high current impact are observed, thereby verifying the fault ride-through capability of the rotor system in advance under laboratory conditions.

[0043] In this embodiment of the invention, by configuring the stator windings of the doubly-fed generator to an open-circuit state, the electromagnetic coupling loop between the stator, the power grid, and the rotor is severed, thereby eliminating the electromagnetic induction effect during conventional generator operation. Based on this, the mechanical speed (mechanical load) of the rotor is controlled independently using a drive device, and AC current (electrothermal load) is injected into the rotor independently through slip rings using a frequency converter. This design achieves complete decoupling of the mechanical load and the electrothermal load, allowing testers to arbitrarily combine speed and current conditions, such as applying rated current at low speeds, to flexibly simulate various extreme or specific fatigue conditions. Simultaneously, since the stator is open-circuited and unloaded, the drive device only needs to overcome the mechanical friction loss and wind resistance loss during rotor rotation, without needing to provide the enormous mechanical power required for power generation, significantly reducing energy consumption and the requirements for test bench infrastructure. Furthermore, this method does not require expensive type test benches, offers flexible start-stop functionality, and significantly reduces the cost of long-term reliability verification.

[0044] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0045] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0046] The steps described above are for clarity only. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they include the same logical relationship, they are all within the protection scope of this invention. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, without changing the core design of the algorithm and process, are also within the protection scope of this invention.

[0047] Furthermore, the examples mentioned in the above embodiments can be freely combined, and any combination can be understood as an embodiment. The terms "embodiment" or "example" appearing in various locations in the specification do not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand that the embodiments described herein can be combined with other embodiments.

[0048] Another embodiment of the present invention relates to a testing method for the rotor of a doubly-fed induction generator (DFIG). The rotor shaft of the DFIG is mechanically connected to a drive device, and the rotor slip rings of the DFIG are electrically connected to a frequency converter. The method includes: controlling the drive device to drive the rotor of the DFIG to rotate to apply a mechanical load, and controlling the frequency converter to inject AC current into the rotor to apply an electrothermal load; and monitoring the state parameters of the DFIG. Thus, in a hardware structure that only configures the rotor, the mechanical speed (mechanical load) of the rotor is controlled independently by the drive device, and AC current (electrothermal load) is injected independently into the rotor through the slip rings by the frequency converter. This design achieves complete decoupling of the mechanical load and the electrothermal load, allowing testers to arbitrarily combine speed and current conditions, such as applying rated current at low speeds, thereby flexibly simulating various extreme or specific fatigue conditions. Furthermore, this method does not require expensive type testing equipment, offers flexible start-stop functionality, and significantly reduces the cost of long-term reliability verification.

[0049] In some embodiments, controlling the drive device to drive the rotor of the doubly fed motor to rotate to apply a mechanical load, and controlling the variable frequency power supply device to inject AC current into the rotor to apply an electrothermal load, includes: controlling the drive device to operate according to a preset speed curve to apply a mechanical load; controlling the variable frequency power supply device to adjust the AC current injected into the rotor according to a preset current curve to apply an electrothermal load; and simulating the operating state of the doubly fed motor under various operating conditions by combining speed parameters and current parameters.

[0050] In some embodiments, controlling the variable frequency power supply device to adjust the AC current injected into the rotor according to a preset current curve includes at least: controlling the frequency of the AC current to be within a preset slip frequency range to test the electrical performance of the rotor under near-rated operating conditions, and / or controlling the frequency of the AC current to continuously sweep the frequency within a preset range to test the electrical performance of the rotor at different slip frequencies.

[0051] In some embodiments, controlling the drive device to operate according to a preset speed curve includes at least: controlling the drive device to drive the rotor to accelerate from a stationary state to a rated speed within a preset time, and / or, performing alternating cycles between multiple speeds to test the mechanical performance of the rotor.

[0052] In some embodiments, the variable frequency power supply device is a voltage source type variable frequency converter; controlling the variable frequency power supply device to inject AC current into the rotor to apply an electrothermal load includes: controlling the variable frequency power supply device to output a voltage of a pulse width modulated waveform to the rotor; and verifying the insulation performance of the rotor based on the voltage change rate of the pulse width modulated waveform.

[0053] In some embodiments, the rated power of the drive device is less than the rated power of the doubly fed motor, and the drive device is used to provide the mechanical energy required to overcome the mechanical friction loss and wind resistance loss during rotor rotation.

[0054] In some embodiments, monitoring the state parameters of the doubly-fed motor further includes: real-time monitoring of the rotor temperature, the operating parameters of the rotor slip ring system, and the vibration parameters of the doubly-fed motor; and evaluating the rotor reliability of the doubly-fed motor by combining the temperature, operating parameters, and vibration parameters.

[0055] Another embodiment of the present invention relates to a test system for a doubly-fed induction generator (DFIG), comprising: a drive device whose output end is connected to the rotor shaft of the DFIG and configured to drive the rotor to rotate to apply a mechanical load; a frequency converter whose output end is connected to the rotor slip ring of the DFIG and configured to inject alternating current into the rotor to apply an electrothermal load; and a control device communicatively connected to the drive device and the frequency converter, respectively, and configured to perform operations controlling the drive device and the frequency converter; wherein the stator winding of the DFIG is configured to be in an open-circuit state; based on the open-circuit state of the stator winding, the mechanical load and the electrothermal load of the rotor are decoupled from each other.

[0056] In some embodiments, the control device is specifically used to control the drive device to operate according to a preset speed curve to apply mechanical load; to control the variable frequency power supply device to adjust the AC current injected into the rotor according to a preset current curve to apply electrothermal load; and to simulate the operating state of the doubly fed motor under various working conditions by combining speed parameters and current parameters.

[0057] In some embodiments, the control device is further configured to control the frequency of the alternating current to be within a preset slip frequency range in order to test the electrical performance of the rotor under near-rated operating conditions, and / or to control the frequency of the alternating current injected by the frequency converter to continuously sweep the frequency within a preset range in order to test the electrical performance of the rotor at different slip frequencies.

[0058] In some embodiments, the control device is further configured to control the drive device to accelerate the rotor from a stationary state to a rated speed within a preset time, and / or to perform alternating cycles between multiple speeds to test the mechanical performance of the rotor.

[0059] In some embodiments, voltage sensors are provided at the three-phase ends of the stator winding, and the voltage sensors are connected to the control device; the control device is also used to acquire the induced voltage of the stator winding through the voltage sensors; and to evaluate the inter-turn short-circuit fault status of the rotor winding based on the induced voltage.

[0060] In some embodiments, the frequency converter is a voltage source type frequency converter, and the control device is also used to control the frequency converter to output a voltage of pulse width modulation waveform to the rotor; and to verify the insulation performance of the rotor based on the voltage change rate of the pulse width modulation waveform.

[0061] In some embodiments, the doubly fed motor is mounted on a test base, and the stator core of the doubly fed motor under test is retained on the test base; a cooling fan is also configured on the test base; the ventilation slots of the stator core are used to cooperate with the cooling fan to form a ventilation duct for the rotor; the cooling fan is connected to a control device; the control device is also used to control the cooling fan to drive the hot airflow generated by the rotor through the ventilation duct.

[0062] In some embodiments, the doubly-fed motor is connected to the test base via an elastic support; the control device is also used to collect vibration data of the doubly-fed motor and evaluate the mechanical reliability of the rotor in a simulated cabin elastic support environment.

[0063] In some embodiments, the rated power of the drive device is less than the rated power of the doubly fed motor, and the drive device is used to provide the mechanical energy required to overcome the mechanical friction loss and wind resistance loss during rotor rotation.

[0064] In some embodiments, the control device is also used to monitor the rotor temperature, the operating parameters of the rotor slip ring system, and the vibration parameters of the doubly fed motor in real time; and to evaluate the rotor reliability of the doubly fed motor by combining the temperature, operating parameters, and vibration parameters.

[0065] Another embodiment of the present invention relates to a test system for a rotor of a doubly fed motor, comprising: a drive device having an output end for connecting to the rotor shaft of the doubly fed motor and configured to drive the rotor to rotate to apply a mechanical load; a frequency converter having an output end for connecting to the rotor slip ring of the doubly fed motor and configured to inject alternating current into the rotor to apply an electrothermal load; and a control device communicatively connected to the drive device and the frequency converter, respectively, and configured to perform operations controlling the drive device and the frequency converter.

[0066] In some embodiments, the control device is specifically used to control the drive device to operate according to a preset speed curve to apply mechanical load; to control the variable frequency power supply device to adjust the AC current injected into the rotor according to a preset current curve to apply electrothermal load; and to simulate the operating state of the doubly fed motor under various working conditions by combining speed parameters and current parameters.

[0067] In some embodiments, the control device is further configured to control the frequency of the alternating current to be within a preset slip frequency range in order to test the electrical performance of the rotor under near-rated operating conditions, and / or to control the frequency of the alternating current injected by the frequency converter to continuously sweep the frequency within a preset range in order to test the electrical performance of the rotor at different slip frequencies.

[0068] In some embodiments, the control device is further configured to control the drive device to accelerate the rotor from a stationary state to a rated speed within a preset time, and / or to perform alternating cycles between multiple speeds to test the mechanical performance of the rotor.

[0069] In some embodiments, the frequency converter is a voltage source type frequency converter, and the control device is also used to control the frequency converter to output a voltage of pulse width modulation waveform to the rotor; and to verify the insulation performance of the rotor based on the voltage change rate of the pulse width modulation waveform.

[0070] In some embodiments, the rated power of the drive device is less than the rated power of the doubly fed motor, and the drive device is used to provide the mechanical energy required to overcome the mechanical friction loss and wind resistance loss during rotor rotation.

[0071] In some embodiments, the control device is also used to monitor the rotor temperature, the operating parameters of the rotor slip ring system, and the vibration parameters of the doubly fed motor in real time; and to evaluate the rotor reliability of the doubly fed motor by combining the temperature, operating parameters, and vibration parameters.

[0072] It is not difficult to see that this embodiment is a device embodiment corresponding to the above method embodiments, and this embodiment can be implemented in conjunction with the above method embodiments. The relevant technical details mentioned in the above method embodiments are still valid in this embodiment, and will not be repeated here to reduce repetition. Accordingly, the relevant technical details mentioned in this embodiment can also be applied to the above method embodiments.

[0073] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this invention, this embodiment does not introduce units that are not closely related to solving the technical problem proposed by this invention; however, this does not mean that other units are absent from this embodiment.

[0074] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A method of testing a doubly-fed electrical machine, characterized in that, The stator winding of the double-fed motor is configured in an open circuit state, a rotor shaft of the double-fed motor is mechanically connected with a drag device, and a rotor slip ring of the double-fed motor is electrically connected with a variable frequency power supply device; the method comprises: controlling the drag device to drive the rotor of the double-fed motor to rotate to apply a mechanical load, and controlling the variable frequency power supply device to inject an alternating current into the rotor to apply an electrical heat load; wherein, based on the open circuit state of the stator winding, the mechanical load and the electrical heat load of the rotor are decoupled from each other; monitoring a state parameter of the double-fed motor.

2. A test method for a doubly-fed electrical machine according to claim 1, characterized in that, The control of the drag device to drive the rotor of the double-fed motor to rotate to apply a mechanical load, and the control of the variable frequency power supply device to inject an alternating current into the rotor to apply an electrical heat load, comprises: controlling the drag device to operate according to a preset speed curve to apply a mechanical load; controlling the variable frequency power supply device to adjust the alternating current injected into the rotor according to a preset current curve to apply an electrical heat load; by combining the speed parameter and the current parameter, the running state of the double-fed motor under multiple working conditions is simulated.

3. A test method for a doubly-fed electrical machine according to claim 2, characterized in that, The control of the variable frequency power supply device to adjust the alternating current injected into the rotor according to a preset current curve at least comprises: controlling the frequency of the alternating current to be in a preset slip frequency range to test the electrical performance of the rotor under an approximate rated running working condition, and / or controlling the frequency of the alternating current to be continuously swept within a preset range to test the electrical performance of the rotor under different slip frequencies.

4. The test method of a doubly-fed electric machine according to claim 2, characterized in that, The control of the drag device to operate according to a preset speed curve at least comprises: controlling the drag device to drive the rotor to accelerate from a stationary state to a rated speed within a preset time, and / or to perform an alternating cycle between multiple speeds to test the mechanical performance of the rotor.

5. The test method of a doubly-fed electric machine according to claim 1, characterized in that, The three-phase end of the stator winding is configured with a voltage sensor, and the monitoring of the state parameter of the double-fed motor comprises: collecting an induced voltage of the stator winding through the voltage sensor; based on the induced voltage, evaluating the turn-to-turn short circuit fault state of the rotor winding.

6. The test method of a doubly-fed electric machine according to claim 1, characterized in that, The variable frequency power supply device is a voltage source type frequency converter; The control of the variable frequency power supply device to inject an alternating current into the rotor to apply an electrical heat load comprises: controlling the variable frequency power supply device to output a voltage of a pulse width modulation waveform to the rotor; based on the voltage variation rate of the pulse width modulation waveform, verifying the insulation performance of the rotor.

7. The test method of a doubly-fed electric machine according to claim 1, characterized in that, The double-fed motor is installed on a test base, and a stator core of the double-fed motor to be tested is retained on the test base; a cooling fan is further configured on the test base; a ventilation slot of the stator core is used to cooperate with the cooling fan to form a ventilation air duct of the rotor; The method further comprises: controlling the cooling fan to drive the hot air flow generated by the rotor to pass through the ventilation air duct.

8. A test method of a doubly-fed electrical machine according to claim 7, characterized in that, The double-fed motor is connected to the test base through an elastic support seat; the method further comprises: collecting vibration data of the double-fed motor to evaluate the mechanical reliability of the rotor in a simulated cabin elastic support environment.

9. The test method of a doubly-fed electric machine according to claim 1, characterized in that, The drag device has a rated power less than a rated power of the doubly-fed motor, and is configured to provide mechanical energy required to overcome mechanical friction loss and windage loss when the rotor rotates.

10. The test method of a doubly-fed electric machine according to claim 1, characterized in that, The method further comprises: monitoring a temperature of the rotor, an operating parameter of the rotor slip ring system, and a vibration parameter of the doubly-fed motor in real time; evaluating rotor reliability of the doubly-fed motor in combination with the temperature, the operating parameter, and the vibration parameter.

11. A method of testing a rotor of a doubly-fed electrical machine, characterized in that, The rotor shaft of the doubly-fed motor is mechanically connected with a drag device, and the rotor slip ring of the doubly-fed motor is electrically connected with a variable frequency power supply device; the method comprises: controlling the drag device to drive the rotor of the doubly-fed motor to rotate to apply a mechanical load, and controlling the variable frequency power supply device to inject an alternating current into the rotor to apply an electrical heat load; monitoring a state parameter of the doubly-fed motor.

12. A test system for a doubly-fed electrical machine, characterized in that The method comprises: a drag device having an output end configured to be connected with a rotor shaft of a doubly-fed motor, and configured to drive the rotor to rotate to apply a mechanical load; a variable frequency power supply device having an output end configured to be connected with a rotor slip ring of the doubly-fed motor, and configured to inject an alternating current into the rotor to apply an electrical heat load; a control device communicatively connected with the drag device and the variable frequency power supply device respectively, and configured to perform the controlling of the drag device and the variable frequency power supply device. The stator winding of the doubly-fed motor is configured to be in an open circuit state; based on the open circuit state of the stator winding, the mechanical load and the electrical heat load of the rotor are decoupled from each other.

13. A test system for a rotor of a doubly-fed electrical machine, characterized in that, The method comprises: a drag device having an output end configured to be connected with a rotor shaft of a doubly-fed motor, and configured to drive the rotor to rotate to apply a mechanical load; a variable frequency power supply device having an output end configured to be connected with a rotor slip ring of the doubly-fed motor, and configured to inject an alternating current into the rotor to apply an electrical heat load; a control device communicatively connected with the drag device and the variable frequency power supply device respectively, and configured to perform the controlling of the drag device and the variable frequency power supply device.

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