A Method and Device for Suppressing Inter-turn Short-circuit Fault Current of a Permanent Magnet Wind Turbine Generator

Abstract

The present invention belongs to the field of permanent magnet generator fault diagnosis and control, and provides a method and device for suppressing the inter-turn short-circuit fault current of a permanent magnet wind generator. Generally, the present invention is divided into three steps, namely, the working principle of the damping winding, fault detection, and fault current control; according to the signal provided by the fault detection unit, it can be preliminarily judged whether the stator inter-turn short circuit occurs in the generator; a thermal resistance sensor for measuring temperature is placed in each stator slot to judge the position of the faulty winding. When the position of the faulty winding is detected, the magnitude of the current in the damping winding above the corresponding slot and the impedance of the damping winding itself are controlled, and the circuit parameters of the damping winding are adjusted in real time through the control unit to suppress the short-circuit current so as to make the short-circuit current value less than or equal to the normal winding current; the present invention can effectively suppress the fault current, prevent the fault from deteriorating and causing more serious losses, and improve the reliability of the permanent magnet generator.

Description

Technical Field

[0001] The present invention belongs to the field of fault diagnosis and control of permanent magnet generators, and particularly relates to a method and device for suppressing the inter-turn short-circuit fault current of a permanent magnet wind generator. Background Art

[0002] The stator winding is a key component for energy conversion in an offshore permanent magnet wind generator. The working environment of the offshore permanent magnet generator is harsh, and the operating conditions are complex and changeable. The insulation of the winding not only bears a great electromagnetic load, but also faces a series of severe tests such as overheating aging and wear. Therefore, the winding insulation is very likely to be damaged, resulting in a short-circuit fault. Among them, the inter-turn short-circuit fault occurs frequently in the faults of permanent magnet wind generators. When the fault occurs, the main insulation outside the stator winding remains good, but the insulation layer between adjacent coils of the same-phase winding is damaged, and some coils are in contact short-circuit, and the short-circuit current is very large, which will cause a local temperature spike, and then exacerbate the damage to the adjacent insulation system. When the fault is severe, the motor will be burned out, causing huge economic losses.

[0003] It should be noted that when an inter-turn short-circuit fault occurs in a permanent magnet generator, there is a short-circuit current higher than the rated value inside the faulty winding. The faulty winding will generate too much heat and heat severely, and then the thermal stress of the insulation of the faulty winding will be greatly increased. The insulation of the faulty winding may be accelerated due to high temperature. Damaged, thus further exacerbating the inter-turn short-circuit fault. Therefore, it is necessary to take some measures to reduce the current of the faulty winding of the generator, prevent the fault from deteriorating and causing more serious losses, and improve the reliability of the generator. Most of the reported short-circuit current suppression methods start from the perspective of optimizing the body structure of the generator by adjusting the winding layout, winding shape, slot-pole matching, stator structure and air-gap length of the generator to achieve the suppression of the faulty winding current. Although the short-circuit current under the inter-turn short-circuit fault can be suppressed by adjusting the body structure of the permanent magnet generator to increase the impedance of the short-circuit winding and reduce the back electromotive force of the short-circuit loop, the high-impedance design will inevitably lead to a loss of power density and reduce the energy conversion efficiency of the generator. In addition, the short-circuit fault current suppression effect of high-impedance motors is limited, and it is difficult to reduce the short-circuit fault current below the rated value.

[0004] In view of the deficiencies of the above methods, the present invention proposes a method and device for suppressing the inter-turn short-circuit fault current of a permanent magnet generator based on a damping winding. This method and device not only have a low accuracy requirement for fault detection technology, but also can effectively suppress the fault current, prevent the fault from deteriorating and causing more serious losses, and improve the reliability of the permanent magnet generator. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method and device for suppressing the inter-turn short-circuit fault current of a permanent magnet wind generator to solve the problems in the prior art. The technical solution adopted by the present invention is as follows:

[0006] A method for suppressing the inter-turn short-circuit fault current of a permanent magnet wind generator includes:

[0007] The first step: Open damping slots in the yoke of the stator core of the permanent magnet generator for placing damping windings;

[0008] The second step: Number the stator windings respectively, and install a thermal resistance sensor in each stator winding;

[0009] The third step: Measure the electromagnetic torque signal of the permanent magnet generator, perform FFT transformation on the measured electromagnetic torque signal. If the second harmonic component appears in the spectrum of the electromagnetic torque and the amplitude of the DC component of the electromagnetic torque decreases, it is determined that the stator inter-turn short-circuit fault has occurred in the permanent magnet generator;

[0010] The fourth step: Determine the position of the short-circuited winding through the thermal resistance sensor inside the stator winding;

[0011] The fifth step: When the temperature of a certain stator winding rises rapidly, control the AC power switch of the damping winding corresponding to the corresponding short-circuited winding, and control the impedance of the damping winding to dynamically adjust the magnitude of the short-circuit current to make its value less than or equal to the normal winding phase current.

[0012] Further, the third step includes:

[0013] The air-gap flux density of the permanent magnet generator is obtained by multiplying the air-gap magnetomotive force by the air-gap permeance. The short-circuit loop current generated by the fault winding after inter-turn short circuit will generate a pulsating magnetic field that changes cosinusoidally, and this magnetic field is expressed as:

[0014] ;

[0015] Wherein, F d is the amplitude of the pulsating magnetomotive force generated by the short-circuit current;

[0016] According to the product-to-sum formula, Equation (1) is expressed as:

[0017] ;

[0018] Wherein, F d+ is the magnetomotive force induced by the short-circuit current in the same direction as the rotation direction of the main magnetic field, F d- is the magnetomotive force induced by the short-circuit current in the opposite direction to the rotation direction of the main magnetic field;

[0019] The armature reaction magnetic potential before and after the turn-to-turn short circuit is expressed as:

[0020] ;

[0021] Among them, F s is the fundamental wave armature reaction magnetic potential of the generator stator under normal conditions, F PM is the magnetic potential of the permanent magnet, ω is the electrical angle, θ is the mechanical angle of the air gap, ψ is the internal power angle, F s+ is the fundamental wave armature reaction magnetic potential of the stator rotating forward after the short circuit, F s- is the fundamental wave armature reaction magnetic potential of the stator rotating backward after the short circuit;

[0022] Multiply Equation (3) by the air gap permeance to obtain the air gap magnetic flux density before and after the short circuit:

[0023] ;

[0024] The air gap magnetic energy is expressed as:

[0025] ;

[0026] If there is an internal power angle difference Δ ψ in the rotor magnetic potential, an electromagnetic torque will be generated, which is expressed as:

[0027] ;

[0028] Substitute Equation (3) and Equation (4) into Equation (5) and Equation (6) to obtain the electromagnetic torque expressions before and after the short circuit:

[0029] ;

[0030] Among them, p is the number of pole pairs of the generator, l is the length of the stator core, R is the inner diameter of the stator core;

[0031] The DC component of the electromagnetic torque after the short circuit decreases and a new second harmonic component appears. The changes in these two components are used as the basis for judging the short circuit fault.

[0032] Furthermore, the fifth step includes: obtaining the temperature in each stator slot through a thermal resistance sensor. If the temperature in the stator slot of the permanent magnet generator rises rapidly, suppressing the short circuit current by adjusting the control damping winding current and impedance magnitude. When the fault current is less than or equal to the normal winding current, the control ends.

[0033] A device for suppressing the inter-turn short-circuit fault current of a permanent magnet wind power generator, comprising a damping winding, a permanent magnet generator, a thermal resistance sensor, a torque sensor, a driving motor, a torque collector, a monitoring and control system, an RL circuit, an AC power supply, an AC power supply switch, a stator core, damping slots and a stator winding;

[0034] Damping slots are opened on the stator core for installing the damping winding;

[0035] The permanent magnet generator is connected to the driving motor through a coupling. The torque sensor is connected to the rotating shafts of the permanent magnet generator and the driving motor. The torque collector is connected to the torque sensor. The thermal resistance sensor is placed in the stator winding of the permanent magnet generator. The monitoring and control system is connected to the thermal resistance sensor. The RL circuit is connected to the damping winding. When receiving an inter-turn short-circuit signal, the RL circuit is connected to the damping winding to control the impedance of the damping winding;

[0036] The damping winding is connected to the AC power supply. The monitoring and control system is connected to the AC power supply and the AC power supply switch. When an inter-turn short-circuit occurs, the switch for controlling the corresponding damping winding to be energized with the AC power supply is opened.

[0037] The present invention has the following beneficial effects: When a short-circuit fault occurs, there is no need to stop the machine immediately. The stable operation of the generator can be guaranteed by suppressing the short-circuit current in real time, thereby avoiding economic losses caused by shutdown maintenance and significantly improving the reliability of the wind power generation system; At the same time, in the initial stage of the inter-turn short-circuit fault, the short-circuit current in the faulty winding can be quickly suppressed by dynamic reactance regulation, avoiding the further expansion of the short-circuit current and effectively protecting the winding and other key components of the permanent magnet wind power generator. Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the magnetic flux distribution of the winding in the fault slot;

[0039] Figure 2 It is the magnetic flux distribution of the winding in the fault slot when using the damping winding: Figure 2 (a) The current direction of the damping winding is opposite to that of the faulty winding, Figure 2 (b) The current direction of the faulty winding is the same as that of the damping winding;

[0040] Figure 3 It is the judgment flow of the stator inter-turn short circuit;

[0041] Figure 4 It is the dynamic regulation flow chart of the damping winding of the present invention;

[0042] Figure 5 It is the overall structure diagram of suppressing the inter-turn short-circuit current;

[0043] Figure 6 It is the installation schematic diagram of the thermal resistance sensor and the damping winding;

[0044] Figure 7 Schematic diagram of damping winding current and impedance control circuit

[0045] In the figure: 1 - damping winding, 2 - permanent magnet generator, 3 - thermal resistance sensor, 4 - torque sensor, 5 - drive motor, 6 - torque collector, 7 - monitoring and control system, 8 - RL circuit, 9 - AC power supply, 10 - AC power switch, 11 - stator core, 12 - damping slot, 13 - stator winding Specific implementation manner

[0046] The following will combine with the Figures 1 - 7 in the embodiments of the present invention, and clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. If not specifically specified, the technical means used in the embodiments are conventional means well known to those skilled in the art

[0047] The technical solutions of the present invention generally include the working principle of the damping winding, fault detection, and fault current control. Specifically as follows

[0048] Working principle of the damping winding: A damping winding 1 is arranged in the stator core 11 of the permanent magnet generator 2. The damping winding 1 has a relatively high resistance and inductance value, and the damping winding 1 will not significantly weaken the stator phase current and reduce the power generation output during the normal operation of the generator. Only when the permanent magnet generator 2 has an inter-turn short circuit fault, the damping winding 1 will work to generate a magnetic field opposite to the short circuit current to suppress the short circuit current

[0049] First, analyze the magnetic flux distribution of the winding in the fault slot. When an inter-turn short circuit fault occurs, the magnetic flux distribution in the stator fault slot is as Figure 1 shown. Since the fault winding current consists of two parts: the phase current and the additional circulating current (short circuit path current), the fault winding magnetic flux also includes two parts: the main magnetic flux of the phase current and the magnetic flux of the additional circulating current. Different from this, there is only the phase current in the normal winding, so there is only the main magnetic flux of the phase current in the normal winding. The directions of the fault winding magnetic flux and the normal winding magnetic flux are the same. When the fault winding current and the normal winding current are both in the clockwise direction, both the fault winding magnetic flux and the normal winding magnetic flux are in the BA direction. Therefore, the resultant magnetic flux in the fault slot is also in the BA direction

[0050] The inter-turn short circuit fault current suppression method proposed by the present invention is that after the damping winding 1 is energized, an induced electromotive force will be generated in the fault loop composed of the fault winding and the short circuit path, and then an induced current will be generated. As long as the direction of the induced current is controlled to be opposite to the fault current, the fault current can be effectively reduced. When the damping winding 1 is used, the magnetic flux distribution of the winding in the fault slot is as Figure 2As shown. When both the fault current and the normal winding current are in the clockwise direction, if the fault current is to be reduced, the induced current in the fault winding should be in the counterclockwise direction. According to Ampere's rule, the magnetic field direction of the induced current is the BA direction. Further analysis shows that according to Lenz's law, the effect of the induced current always opposes the cause of the induced current. Therefore, when the magnetic field along the BA direction weakens or the magnetic field along the AB direction strengthens, a counterclockwise induced current can be generated in the fault winding. If the magnetic field along the BA direction is to be weakened, the current in the damper winding 1 should be in the counterclockwise direction and decrease with time. At this time, the current in the damper winding 1 is in the opposite direction to the fault winding current, as shown in Figure 2 (a). Similarly, if the magnetic field along the AB direction is to be strengthened, the current in the damper winding should be in the clockwise direction and increase with time. At this time, the current in the damper winding is in the same direction as the fault winding current, as shown in Figure 2 (b). In addition, induced current will also be generated in the normal winding. Since the number of turns of the normal winding is much larger than that of the damper winding, the damper winding has little effect on the phase current.

[0051] Fault detection: The permanent magnet wind turbine is prone to inter-turn short circuit faults in the high-salt and high-humidity offshore environment, which will reduce the operation reliability of the generator and may lead to serious consequences such as winding burnout. Therefore, it is extremely important to find suitable fault indication parameters, and the electromagnetic torque of the generator that is not easily affected by external interference can be used as the target parameter for detecting the inter-turn short circuit fault of the generator. Next, the change of the electromagnetic torque before and after the short circuit will be specifically analyzed.

[0052] The air-gap flux density of the permanent magnet generator can be obtained by multiplying the air-gap magnetomotive force by the air-gap permeance. The inter-turn short circuit mainly affects the air-gap magnetomotive force and has no effect on the air-gap permeance. The short-circuit loop current generated by the fault winding after the inter-turn short circuit will generate a pulsating magnetic field that changes cosinusoidally. This magnetic field can be expressed as:

[0053] ;

[0054] where, F d is the amplitude of the pulsating magnetomotive force generated by the short-circuit current.

[0055] According to the product-to-sum formula, Equation (1) can be expressed as:

[0056] ;

[0057] where, F d+ is the magnetomotive force induced by the short-circuit current in the same direction as the rotation direction of the main magnetic field, F d- is the magnetomotive force induced by the short-circuit current in the opposite direction to the rotation direction of the main magnetic field.

[0058] Therefore, the air-gap magnetomotive force before and after the turn-to-turn short circuit can be expressed as:

[0059] ;

[0060] Among them, F s is the fundamental magnetomotive force of the generator stator under normal conditions, F PM is the magnetomotive force of the permanent magnet, ω is the electrical angle, θ is the mechanical angle of the air gap, ψ is the internal power angle, F s1+ is the fundamental magnetomotive force of the forward-rotating stator after the short circuit, F s1- is the fundamental magnetomotive force of the backward-rotating stator after the short circuit.

[0061] Multiplying Equation (3) by the air-gap permeance, the air-gap flux density before and after the short circuit can be obtained:

[0062] ;

[0063] During the electromechanical energy conversion process of the generator, most of the energy is stored in the air-gap magnetic field. The air-gap magnetic energy can be expressed as:

[0064] ;

[0065] According to the principle of virtual displacement, if there is an internal power angle difference Δ ψ in the rotor magnetomotive force, an electromagnetic torque will be generated, which can be expressed as:

[0066] ;

[0067] Substituting Equation (3) and Equation (4) into Equation (5) and Equation (6), the electromagnetic torque expressions before and after the short circuit can be obtained:

[0068] ;

[0069] Among them, p is the number of pole pairs of the generator, l is the length of the stator iron core, R 0 is the inner diameter of the stator iron core.

[0070] It can be seen from Equation (7) that a new second-harmonic component appears after the short circuit, and the DC component of the electromagnetic torque will decrease. The changes in these two components can be used as the basis for judging the short circuit fault. According to the above principle, the basic flow of turn-to-turn short circuit judgment is as Figure 3As shown: First, measure the electromagnetic torque signal of the generator and perform FFT transformation on the electromagnetic torque signal. If the DC component of the electromagnetic torque spectrum decreases and a second harmonic signal appears, it is determined that the generator has a turn-to-turn short circuit fault. If the DC component of the electromagnetic torque spectrum remains unchanged and there is no second harmonic component, it is determined that the generator is operating normally without a turn-to-turn short circuit fault.

[0071] Such as Figures 5 - 6 , a method for suppressing the turn-to-turn short circuit fault current of a permanent magnet wind generator, the specific steps are as follows:

[0072] Step 1: Open damping slots 12 in the yoke of the stator core 11 of the permanent magnet generator for placing damping windings 1, which are d1, d2, d3, d4, d5, d6, d7, d8, d9, d 10 , d 11 , d 12 , d 13 , d 14 , d 15 , d 16 , d 17 , d 18 , d 19 , d 20 , d 21 , d 22 , d 23 , d 24 , d 25 , d 26 , d 27 , d 28 , d 29 , d 30 , d 31 , d 32 , d 33 , d 34 , d 35 , d 36 , d 37 , d 38 , d 39 , d 40 , d 41 , d 42 , d 43 , d 44 , d 45 .

[0073] Step 2: Number the stator windings 13 as w1, w2, w3, w4, w5, w6, w7, w8, w9, w 10 , w 11 , w 12 , w 13 , w 14 , w 15 , w 16 , w17 , w 18 , w 19 , w 20 , w 21 , w 22 , w 23 , w 24 , w 25 , w 26 , w 27 , w 28 , w 29 , w 30 , w 31 , w 32 , w 33 , w 34 , w 35 , w 36 , w 37 , w 38 , w 39 , w 40 , w 41 , w 42 , w 43 , w 44 , w 45 , A thermal resistance sensor 3 is installed in each stator winding 13, namely t1, t2, t3, t4, t5, t6, t7, t8, t9, t 10 , t 11 , t 12 , t 13 , t 14 , t 15 , t 16 , t 17 , t 18 , t 19 , t 20 , t 21 , t 22 , t 23 , t 24 , t 25 , t 26 , t 27 , t 28 , t 29 , t 30 , t 31 , t 32 , t 33 , t 34 , t 35 , t 36 , t 37 , t 38 , t 39 , t 40 , t 41 , t 42 , t 43 , t44 , t 45 is used to measure the winding temperature.

[0074] The third step: Measure the electromagnetic torque signal of the permanent magnet generator 2, perform FFT transformation on the measured electromagnetic torque signal. If a second-harmonic component appears in the spectrum of the electromagnetic torque and the amplitude of the DC component of the electromagnetic torque decreases, it is determined that the stator inter-turn short circuit fault has occurred in the permanent magnet generator 2. The specific process is as Figure 3 shown.

[0075] The fourth step: Since the huge short-circuit current after the inter-turn short circuit will generate a large amount of heat at the short-circuit winding, resulting in a sharp rise in the temperature of the faulty winding, the specific short-circuit winding position can be judged by the thermal resistance sensor 3 installed inside the stator winding 13 in the second step.

[0076] The fifth step: In the monitoring and control system 7, when it is found that the temperature of a certain stator winding 13 rises rapidly, turn on the AC power switch 10 of the damping winding 1 corresponding to the corresponding short-circuit winding, and control the impedance of the damping winding 1 to dynamically adjust the magnitude of the short-circuit current so that its value is less than or equal to the normal winding phase current, as Figure 7 shown.

[0077] As Figure 4 , first obtain the temperature in each stator slot of the permanent magnet generator 2 through the thermal resistance sensor 3. If the temperature in the stator slot rises rapidly within a short time, and combined with the previous fault detection, it is determined that the permanent magnet generator 2 has an inter-turn short circuit fault, then the position of the faulty winding can be determined. The temperature signal generated by the faulty winding will be collected and the damping winding 1 corresponding to the stator fault slot will be controlled to work. By adjusting the current and impedance of the damping winding 1, the short-circuit current is suppressed. When the fault current is less than or equal to the normal winding current, the control ends. If there is no rapid rise in the temperature in the stator slot within a short time, it is judged that the generator is operating normally.

[0078] The present invention also relates to a device for suppressing the inter-turn short circuit fault current of a permanent magnet wind generator, including a damping winding 1, a permanent magnet generator 2, a thermal resistance sensor 3, a torque sensor 4, a drive motor 5, a torque collector 6, a monitoring and control system 7, an RL circuit 8, an AC power supply 9, an AC power switch 10, a stator core 11, a damping slot 12 and a stator winding 13;

[0079] The permanent magnet generator 2 is connected to the drive motor 5 through a coupling. The two ends of the torque sensor 4 are respectively connected to the rotating shafts of the permanent magnet generator 2 and the drive motor 5. The torque acquisition instrument 6 is used to measure and judge the electromagnetic torque characteristic signal of the permanent magnet generator for inter-turn short circuit fault. A thermal resistance sensor 3 for measuring the winding temperature is also placed in the stator winding 13 of the permanent magnet generator 2. The monitoring and control system 7 is used to detect the temperature signal transmitted by the thermal resistance sensor 3 and judge the specific inter-turn short circuit position. The RL circuit 8 is connected to the damper winding 1. When receiving the inter-turn short circuit signal, the RL circuit 8 will be connected to the damper winding 1 to control the impedance of the damper winding.

[0080] In addition, the damper winding 1 is connected to the AC power supply 9. The monitoring and control system 7 also controls an AC power supply 9 and an AC power switch 10. When an inter-turn short circuit occurs, the AC power supply 9 operates to control the opening of the switch 10 for the corresponding damper winding 1 to be energized with the AC power supply 9. The specific working process is as follows: A damper slot 12 is pre-opened on the stator core 11 of the permanent magnet generator to install the damper winding 1. The permanent magnet generator 2 is driven to rotate by the drive motor 5. The torque sensor 4 is used to detect the electromagnetic torque signal and collect it through the torque acquisition instrument 6. If the DC component of the electromagnetic torque decreases and a second harmonic component appears, it is determined that the permanent magnet generator 2 has an inter-turn short circuit fault. After the short circuit occurs, the temperature of the corresponding winding will rise rapidly in a short time. The specific position of the inter-turn short circuit fault winding can be accurately located through the thermal resistance sensor 3. After the short circuit winding position can be viewed in the monitoring and control system 7, the RL circuit 8 is controlled to be connected to the damper winding 1 to adjust the impedance of the damper winding circuit. In addition, the monitoring and control system 7 will also accurately control the magnitude of the current flowing into the damper winding through the AC power supply 9 and the switch 10.

[0081] The embodiments described above are only for describing the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, variations, modifications, and substitutions made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for suppressing inter-turn short-circuit fault current of a permanent magnet wind turbine generator, characterized in that: include: The first step is to open a damping groove (12) on the yoke of the stator core (11) of the permanent magnet generator for accommodating the damping winding (1); Step 2: Number the stator windings (13) respectively, and place a thermal resistance sensor (3) in each stator winding (13); Step 3: Measure the electromagnetic torque signal of the permanent magnet generator (2), perform FFT transformation on the measured electromagnetic torque signal, and if a double frequency harmonic component appears in the spectrum of the electromagnetic torque and the amplitude of the DC component of the electromagnetic torque decreases, it is determined that a stator turn-to-turn short circuit fault occurs in the permanent magnet generator (2); Step 4: Determine the short-circuit winding position by using a thermal resistance sensor (3) inside the stator winding (13); Step 5: When the temperature of a stator winding (13) rises rapidly, the AC power switch (10) of the damping winding (1) corresponding to the corresponding short-circuit winding is controlled, and the impedance of the damping winding (1) is controlled to dynamically adjust the magnitude of the short-circuit current so that its value is less than or equal to the normal winding phase current; The third step includes: The air gap flux density of the permanent magnet generator (2) is obtained by multiplying the air gap magnetomotive force and the air gap permeance. The short-circuit loop current generated by the faulty winding after the turn-to-turn short circuit will generate a pulsating magnetic field with a cosine variation, which is expressed as: ； in, F d is the amplitude of the pulsating magnetic potential generated by the short-circuit current; According to the product-to-difference formula, equation (1) can be expressed as: ； in, F d+ It is the short-circuit current induced magnetomotive force with the same direction of rotation as the main magnetic field. F d- It is the short-circuit current induced magnetomotive force that rotates in the opposite direction to the main magnetic field; The air gap magnetomotive force before and after the turn-to-turn short circuit is expressed as: ； in, F s is the fundamental magnetomotive force of the generator stator under normal conditions, F PM is the magnetomotive force of the permanent magnet, ω is the electrical angle, θ is the air gap mechanical angle, ψ is the internal angle, F s1+ is the fundamental magnetomotive force of the stator rotating in the forward direction after short circuit, F s1- It is the fundamental wave magnetomotive force of the stator rotating in the opposite direction after short circuit; Multiplying equation (3) by the air gap permeance yields the air gap flux density before and after the short circuit: ； The air gap magnetic energy is expressed as: ； If the rotor magnetomotive force has an internal power angle difference Δ ψ , an electromagnetic torque will be generated, which can be expressed as: ； Substituting equations (3) and (4) into equations (5) and (6), we can obtain the expression of electromagnetic torque before and after short circuit: ； in, p is the number of generator pole pairs, l is the stator core length, R 0 is the inner diameter of the stator core; After the short circuit, the DC component of the electromagnetic torque decreases and a new double frequency component appears. The changes in these two components serve as the basis for judging the short circuit fault.

2. A method for suppressing inter-turn short-circuit fault current of a permanent magnet wind turbine generator according to claim 1, characterized in that: The fifth step includes: obtaining the temperature in each stator slot through a thermal resistor sensor (3); if the temperature in the stator slot of the permanent magnet generator (2) rises rapidly, the short-circuit current is suppressed by adjusting the current and impedance of the damping winding (1); when the fault current is less than or equal to the normal winding current, the control ends.

3. A device for suppressing inter-turn short-circuit fault current of a permanent magnet wind generator, adopting a method for suppressing inter-turn short-circuit fault current of a permanent magnet wind generator as claimed in any one of claims 1 to 2, comprising a damping winding (1), a permanent magnet generator (2), a thermal resistor sensor (3), a torque sensor (4), a drive motor (5), a torque acquisition instrument (6), a monitoring and control system (7), an RL circuit (8), an AC power supply (9), an AC power switch (10), a stator core (11), a damping slot (12) and a stator winding (13); The stator core (11) is provided with a damping slot (12) for mounting a damping winding (1); The permanent magnet generator (2) is connected to the drive motor (5) through a coupling, the torque sensor (4) is connected to the rotating shaft of the permanent magnet generator (2) and the rotating shaft of the drive motor (5), the torque collector (6) is connected to the torque sensor (4), a thermal resistor sensor (3) is placed in the stator winding (13) of the permanent magnet generator (2), and the monitoring and control system (7) is connected to the thermal resistor sensor (3); the RL circuit (8) is connected to the damping winding (1), and when a turn-to-turn short-circuit signal is received, the RL circuit (8) is connected to the damping winding (1) to control the impedance of the damping winding; The damping winding (1) is connected to an AC power source (9), and the monitoring and control system (7) is connected to the AC power source (9) and an AC power switch (10). When an inter-turn short circuit occurs, the AC power source (9) controls the corresponding damping winding (1) to pass through the AC power switch (10) and turn on.

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