A fault-tolerant control method for inter-turn short-circuit fault of dual three-phase permanent magnet synchronous motor

Abstract

The present invention provides a fault-tolerant control method for a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor, and relates to the field of fault-tolerant control of synchronous motors. The fault-tolerant control method for a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor comprises establishing a transient model for a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor in a stationary coordinate system, analyzing the physical principle of a dual three-phase permanent magnet synchronous motor system under a short-circuit fault between turns, respectively establishing a first-order transient equation characterizing the relationship between the voltage and current changes of the faulty motor in a natural stationary coordinate system and a dual synchronous rotating coordinate system, and then treating the short-circuit current as a sinusoidal variable, and solving to obtain a steady-state model reflecting the relationship between the short-circuit current amplitude and the dq-axis current, on this basis, using permanent magnet charging and demagnetization technology to optimize the rotor flux, and then implementing a three-stage short-circuit fault-tolerant control between turns, respectively controlling the short-circuit current at a target value by applying a weak magnetic current, changing the output ratio of two sets of three-phase windings, and limiting the motor output.

Description

Technical Field

[0001] The present invention relates to the technical field of synchronous motor fault-tolerant control, and specifically to a fault-tolerant control method for inter-turn short-circuit faults of a dual-three-phase permanent magnet synchronous motor. Background Art

[0002] As one of the most common motor faults, the inter-turn short-circuit fault has strong destructiveness. After the motor winding is short-circuited, the induced back electromotive force will generate a fault current far higher than the rated value on the short-circuit loop, which will not only cause the asymmetric operation of the motor, reduce the output torque, generate vibration and noise, but also lead to large copper losses, cause the temperature of the fault part to rise sharply, and the winding insulation to age and damage rapidly. At the same time, the large demagnetizing magnetic field caused by the short-circuit current may also cause irreversible demagnetization of the permanent magnet.

[0003] In order to deeply analyze the characteristics of the inter-turn short-circuit fault and accurately extract the fault features, existing research has established finite element models, equivalent magnetic circuit models, and equivalent circuit models in different coordinate systems of permanent magnet synchronous motors under inter-turn short-circuit faults. Some studies have pointed out that compared with distributed windings, the permanent magnet synchronous motor with fractional-slot concentrated windings has smaller mutual inductance between phases, so it has better operating performance under faults. At the same time, multi-phase motors have higher degrees of freedom in control and are more advantageous in fault-tolerant control.

[0004] In order to effectively suppress the fault current, reduce the torque ripple, and improve the operating performance of the motor under faults, existing research often reduces the synthetic back electromotive force by applying a weak magnetic current to suppress the short-circuit current. At the same time, short-circuiting the faulty phase winding is also a simple and effective method, but it will reduce the motor output and cause serious torque ripple. To solve this problem, some studies suppress the torque ripple caused by motor faults and increase the speed range of operation under faults by injecting zero-sequence voltage, zero-sequence current, or compensating the dq-axis current ripple under faults.

[0005] However, the existing research technologies still have deficiencies. First, there is a lack of research on the equivalent circuit model of dual-three-phase permanent magnet synchronous motors under inter-turn short-circuit faults, which is not conducive to the in-depth analysis and control design of high-fault-tolerant performance motors. Second, the short-circuit current suppression methods by weak magnetic or current injection will increase the copper losses of the motor and reduce the operating efficiency of the motor under faults. Third, the existing methods have limited suppression ability for short-circuit currents and are difficult to meet the control objectives under high fault severity. Summary of the Invention

[0006] (1) Technical Problems to be Solved

[0007] Aiming at the deficiencies of the existing technology, the present invention provides a fault-tolerant control method for inter-turn short-circuit faults of a dual-three-phase permanent magnet synchronous motor. By analyzing the physical principles of the dual-three-phase permanent magnet synchronous motor system under inter-turn short-circuit faults, first-order transient equations characterizing the relationships between the voltages and currents of the faulty motor in the natural stationary coordinate system and the dual synchronous rotating coordinate system are established respectively. Then, regarding the short-circuit current as a sinusoidal variable, a steady-state model reflecting the relationship between the short-circuit current amplitude and the dq-axis currents is solved. On this basis, the rotor magnetic flux is optimized by using the permanent magnet magnetization and demagnetization technology, and then a three-stage inter-turn short-circuit fault-tolerant control is implemented. By applying weak magnetic current, changing the output force ratio of the two sets of three-phase windings, and restricting the motor output force respectively, the short-circuit current is controlled within the target value.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0010] On the one hand, a fault-tolerant control method for inter-turn short-circuit faults of a dual-three-phase permanent magnet synchronous motor is provided, including:

[0011] Based on the physical principles of the dual-three-phase permanent magnet synchronous motor system under inter-turn short-circuit faults, a transient model of inter-turn short-circuit faults of the dual-three-phase permanent magnet synchronous motor in the stationary coordinate system is established, and a first-order transient equation describing the relationships between voltages, currents, and magnetic fluxes in the stationary coordinate system is obtained. On this basis, based on rotor magnetic flux orientation, a coordinate transformation is performed to establish a transient model of inter-turn short-circuit faults of the dual-three-phase permanent magnet synchronous motor in the dual synchronous rotating coordinate system, and a first-order transient equation describing the relationships between voltages, currents, and magnetic fluxes in the dual synchronous coordinate system is obtained;

[0012] Regarding the short-circuit current as a sinusoidal variable, based on the inter-turn short-circuit fault model of the motor in the dual synchronous rotating coordinate system and ignoring the transient change of the current, a steady-state equation describing the relationship between the short-circuit current amplitude and the dq-axis currents is obtained. Further, combined with the motor torque equation, a steady-state equation describing the relationship between the magnitude of the permanent magnet magnetic flux and the motor torque and speed changes is solved, and the short-circuit current reaches the minimum value under this permanent magnet magnetic flux;

[0013] For a variable magnetic flux motor using low coercivity permanent magnets, magnetization and demagnetization optimization is implemented according to its operating conditions to suppress the short-circuit current of the motor under inter-turn short-circuit faults and slow down the severity of the faults;

[0014] According to the characteristics of inter-turn short-circuit faults of the dual-three-phase permanent magnet synchronous motor and the requirements for suppressing short-circuit current, a three-stage inter-turn short-circuit fault-tolerant control is implemented. In the first stage, the short-circuit current is suppressed by applying d-axis weak magnetic current. In the second stage, after the weak magnetic current reaches the maximum value, the short-circuit current is suppressed by changing the output force ratio of the two sets of three-phase windings. In the third stage, after the output of the faulty three phases reaches the minimum, the motor torque output is restricted to further suppress the short-circuit current.

[0015] Preferably, the transient model of the inter-turn short circuit fault of the dual three-phase permanent magnet synchronous motor in the stationary coordinate system specifically includes:

[0016] Based on the physical principle of the dual three-phase permanent magnet synchronous motor system under the inter-turn short circuit fault, a first-order transient equation describing the relationship between voltage, current, and magnetic flux change in the stationary coordinate system is obtained.

[0017]

[0018] ψ sf =L sf i sf +ψ PM F f (θ)

[0019] Among them, assuming that phase A is the inter-turn short circuit fault phase, u sf 、i sf 、ψ sf respectively represent the stator phase voltage matrix, phase current matrix, and winding magnetic flux matrix of the motor under the fault including the short circuit loop; R sf represents the stator resistance matrix under the fault; L sf represents the stator inductance matrix under the fault; ψ PM represents the permanent magnet magnetic flux of the motor.

[0020] Preferably, the first-order transient equation describing the relationship between voltage, current, and magnetic flux change in the stationary coordinate system is specifically:

[0021] i sf =[i a i b i c i d i e i f i af T ;u sf =[u a u b u c u d u e u f 0] T ;

[0022]

[0023]

[0024]

[0025] Based on the symmetry of the motor structure and the relationship between the fault phase inductance, the stator inductance matrix under the fault can be further: ​

[0026]

[0027] Among them, R s represents the stator resistance; L l represents the leakage self-inductance of the stator winding; L ms represents the main self-inductance of the stator winding; L δ represents the reluctance inductance caused by the salient pole effect; M 1 represents the mutual inductance between the three-phase windings; M 2 represents the mutual inductance between two sets of three-phase windings; R f represents the short-circuit resistance; μ represents the turn ratio of the short-circuit winding to the total winding, called the short-circuit turn ratio; c represents the cosine function cos; the parameter m is determined by the inductance of a single coil and is related to the motor structure.

[0028] Preferably, the first-order transient equations for the relationships between voltage, current, and flux linkage changes in the double synchronous coordinate system are specifically as follows

[0029]

[0030] Among them u d1 , u q1 represent the d-axis and q-axis voltages in the first synchronous coordinate system; u d2 , u q2 represent the d-axis and q-axis voltages in the second synchronous coordinate system; i d1 , i q1 represent the d-axis and q-axis currents in the first synchronous coordinate system; i d2 , i q2 represent the d-axis and q-axis currents in the second synchronous coordinate system; L represents the self-inductance of the motor, satisfying L = L l +L ms .

[0031] Preferably, the steady-state equation describing the relationship between the short-circuit current amplitude and the dq-axis current changes is specifically as follows

[0032]

[0033] Among them

[0034] Regarding the short-circuit current as a sinusoidal variable and ignoring the current transient changes, the steady-state equation describing the relationship between the short-circuit current amplitude I af and the dq-axis current changes of two sets can be further derived:

[0035]

[0036] For a given motor, when the speed and fault parameters are determined, the denominator of the above formula is a fixed value, and the numerator is regarded as two orthogonal components Fd With F q The composite value of ,

[0037]

[0038] Preferably, the steady-state equation describing the relationship between the permanent magnet flux size and the motor torque and speed change specifically includes:

[0039] The motor torque equation under normal operation is,

[0040]

[0041] Under the premise that no other fault-tolerant control is implemented, the d-axis current is zero, the q-axis currents of the two sets of three-phase windings are equal, and the influence of short-circuit current on torque is ignored. The torque equation and the short-circuit current steady-state equation are combined to obtain the steady-state equation describing the relationship between the short-circuit current amplitude and the permanent magnet flux change:

[0042]

[0043] Preferably, the steady-state equation describing the relationship between the short-circuit current amplitude and the permanent magnet flux change is solved to obtain the permanent magnet flux calculation formula:

[0044]

[0045] Preferably, the three-stage turn-to-turn short-circuit fault tolerance control specifically includes:

[0046] Based on the short-circuit current suppression target, the PI controller outputs the weak magnetic current reference value i d * ;

[0047] Use the table lookup method to determine the maximum weak magnetic current, make a difference between the weak magnetic current reference value and the maximum value, output ΔK through the proportional controller, and subtract it from the maximum output ratio to obtain the output ratio reference value K, which acts on the q-axis current control closed loop;

[0048] The output ratio reference value is subtracted from the minimum value, and the maximum q-axis current compensation value Δi is obtained through the proportional controller q , use the maximum current limit i max Subtract compensation value Δi q ;

[0049] Get the q-axis current limit value i q_max , considering the output distribution of two sets of three-phase, the maximum limit acting on the q-axis current control closed loop is,

[0050]

[0051] (III) Beneficial effects

[0052] A fault-tolerant control method for inter-turn short circuit of a dual-three-phase permanent magnet synchronous motor. By analyzing the physical principle of the dual-three-phase permanent magnet synchronous motor system under inter-turn short circuit fault, a first-order transient equation is established respectively to characterize the relationship between the voltage and current changes of the faulty motor in the natural stationary coordinate system and the dual synchronous rotating coordinate system. Then, regarding the short-circuit current as a sinusoidal variable, a steady-state model reflecting the relationship between the short-circuit current amplitude and the dq-axis current is solved. On this basis, the rotor flux linkage is optimized by using the permanent magnet magnetization and demagnetization technology, and then a three-stage inter-turn short circuit fault-tolerant control is implemented. By applying weak magnetic current, changing the output force ratio of the two sets of three-phase windings, and restricting the motor output force respectively, the short-circuit current is controlled within the target value. Brief Description of the Drawings

[0053] Figure 1 It is the flowchart of the present invention;

[0054] Figure 2 It is a schematic diagram of the equivalent circuit model of the inter-turn short circuit fault of the dual-three-phase permanent magnet synchronous motor of the present invention;

[0055] Figure 3 It is a schematic diagram of the three-stage inter-turn short circuit fault-tolerant control of the present invention;

[0056] Figure 4 It is the simulation result of the motor temperature change under the three-stage inter-turn short circuit fault-tolerant control of the present invention;

[0057] Figure 5 It is the simulation result of the dq-axis current change under the three-stage inter-turn short circuit fault-tolerant control of the present invention;

[0058] Figure 6 It is the experimental result of the short-circuit current change before and after the demagnetization optimization of the present invention;

[0059] Figure 7 It is the experimental result of the motor temperature change under the three-stage inter-turn short circuit fault-tolerant control of the present invention;

[0060] Figure 8 It is the experimental result of the dq-axis current change under the three-stage inter-turn short circuit fault-tolerant control of the present invention;

[0061] Figure 9 It is the experimental result of the motor loss change before and after the demagnetization optimization of the present invention. Detailed Embodiment

[0062] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0063] Embodiment

[0064] The technical solution adopted by the present invention is a fault-tolerant control method for inter-turn short circuit of a variable permanent magnet flux double-three-phase permanent magnet synchronous motor. The flowchart of this method is as shown in Figure 1 , and specifically includes the following steps:

[0065] S1. Based on the physical principle of the double-three-phase permanent magnet synchronous motor system under inter-turn short circuit fault, establish a transient model of the inter-turn short circuit fault of the double-three-phase permanent magnet synchronous motor in the stationary coordinate system, and obtain a first-order transient equation describing the relationship between voltage, current, and flux linkage change in the stationary coordinate system. On this basis, based on rotor flux linkage orientation, perform coordinate transformation to establish a transient model of the inter-turn short circuit fault of the double-three-phase permanent magnet synchronous motor in the double synchronous rotating coordinate system, and obtain a first-order transient equation describing the relationship between voltage, current, and flux linkage change in the double synchronous coordinate system;

[0066] S2. Regard the short-circuit current as a sinusoidal variable. Based on the motor inter-turn short circuit fault model in the double synchronous rotating coordinate system, ignore the transient change of the current, and obtain a steady-state equation describing the relationship between the short-circuit current amplitude and the dq-axis current change. Further, combine the motor torque equation to solve and obtain a steady-state equation describing the relationship between the optimal permanent magnet flux magnitude and the motor torque and speed change. Under this optimal permanent magnet flux, the short-circuit current can reach the minimum value;

[0067] S3. For a variable flux motor using low coercivity permanent magnets, implement magnetization and demagnetization optimization according to its operating conditions to suppress the short-circuit current of the motor under inter-turn short circuit fault and slow down the severity of the fault.

[0068] S4. According to the inter-turn short circuit fault characteristics of the double-three-phase permanent magnet synchronous motor and the requirements for short-circuit current suppression, implement a three-stage inter-turn short circuit fault-tolerant control. In the first stage, apply a d-axis weak magnetic current to suppress the short-circuit current. In the second stage, after the weak magnetic current reaches the maximum value, suppress the short-circuit current by changing the output force ratio of the two sets of three-phase windings. In the third stage, after the output of the faulty three phases reaches the minimum, limit the motor torque output to further suppress the short-circuit current.

[0069] Furthermore, in the step S1, a transient model of the inter-turn short circuit fault of the double-three-phase permanent magnet synchronous motor in the stationary coordinate system is characterized in that, considering the physical principle of the double-three-phase permanent magnet synchronous motor system under inter-turn short circuit fault, as shown in Figure 2 , a first-order transient equation describing the relationship between voltage, current, and flux linkage change in the stationary coordinate system is obtained:

[0070]

[0071] Among them, assuming that phase A is the inter-turn short circuit fault phase, u sf , i sf , ψ sfrespectively represent the stator phase voltage, phase current, and winding flux linkage matrix of the motor under a fault condition that includes a short - circuit loop; R sf represents the stator resistance matrix under the fault condition; L sf represents the stator inductance matrix under the fault condition; ψ PM represents the permanent - magnet flux linkage of the motor. The detailed expansion of each matrix is as follows:

[0072] i sf =[i a i b i c i d i e i f i af T ; u sf =[u a u b u c u d u e u f 0] T ;

[0073]

[0074]

[0075]

[0076] Considering the symmetry of the motor structure and the relationship between the fault - phase inductances, the stator inductance matrix under the fault condition can be further written as:

[0077]

[0078] where, R s represents the stator resistance; L l represents the self - leakage inductance of the stator winding; L ms represents the main self - inductance of the stator winding; L δ represents the reluctance inductance caused by the salient - pole effect; M 1 represents the mutual inductance between the three - phase windings; M 2 represents the mutual inductance between two sets of three - phase windings; R f represents the short - circuit resistance; μ represents the turn ratio of the short - circuited winding to the total winding, which is called the short - circuit turn ratio; c represents the cosine function cos; the parameter m is determined by the inductance of a single coil and is related to the motor structure.

[0079] ​Further, in the step S1, a transient model of inter-turn short circuit fault of a dual-three-phase permanent magnet synchronous motor in a double synchronous rotating coordinate system is characterized in that a coordinate transformation is performed based on rotor flux orientation to establish a transient model of inter-turn short circuit fault of a dual-three-phase permanent magnet synchronous motor in a double synchronous rotating coordinate system, and a first-order transient equation describing the relationship between voltage, current, and flux linkage change in the double synchronous coordinate system is obtained:

[0080]

[0081] Where u d1 、u q1 represent the d-axis and q-axis voltages in the first synchronous coordinate system; u d2 、u q2 represent the d-axis and q-axis voltages in the second synchronous coordinate system; i d1 、i q1 represent the d-axis and q-axis currents in the first synchronous coordinate system; i d2 、i q2 represent the d-axis and q-axis currents in the second synchronous coordinate system; L represents the self-inductance of the motor, satisfying L = L l +L ms .

[0082] Further, in the step S2, a steady-state model of short-circuit current in a synchronous coordinate system is characterized in that based on the transient model of inter-turn short circuit fault of a dual-three-phase permanent magnet synchronous motor in a double synchronous rotating coordinate system, a first-order transient equation describing the relationship between short-circuit current and the change of two sets of dq-axis currents is sorted out:

[0083]

[0084] Where

[0085] Regarding the short-circuit current as a sinusoidal variable and ignoring the transient change of the current, a steady-state equation describing the relationship between the short-circuit current amplitude I af and the change of two sets of dq-axis currents can be further derived:

[0086]

[0087] For a given motor, when the speed and fault parameters are determined, the denominator of the above formula is a fixed value, and the numerator can be regarded as the combined value of two orthogonal components F d and F q :

[0088]

[0089] It can be seen from the above formula that the short-circuit current amplitude is mainly affected by F d and F qBy applying a weak magnetic current i d1 , can reduce F q component, but it will make F d Component increases; apply weak magnetic current i d2 , can also reduce F q component, but cannot affect F d component. Therefore, the short-circuit current can only be reduced by weakening the magnetic field. q component, the weak magnetic current with suppression effect has a maximum value, which is mainly related to the permanent magnetic flux and inductance parameters of the motor. In order to reduce F d component, under the requirement of ensuring the output torque remains unchanged, the output ratio of the two sets of three-phase can be changed to reduce i q1 And increase i q2 , further suppressing the short-circuit current. This is because the healthy three-phase winding affects the short-circuit current through mutual inductance, and the effect is smaller than that of the faulty three-phase winding.

[0090] Furthermore, in step S2, an optimal permanent magnet flux calculation method under a turn-to-turn short circuit fault is characterized in that the motor torque equation under normal operation is known:

[0091]

[0092] Under the premise that no other fault-tolerant control is implemented, the d-axis current is zero, the q-axis currents of the two sets of three-phase windings are equal, and the influence of short-circuit current on torque is ignored. By combining the torque equation and the short-circuit current steady-state equation, the steady-state equation describing the relationship between the short-circuit current amplitude and the permanent magnet flux change can be obtained:

[0093]

[0094] Solving the above formula, the optimal permanent magnet flux calculation can be obtained as follows:

[0095]

[0096] From the above formula, it can be seen that for a given motor, the optimal permanent magnet flux size has nothing to do with the motor's fault parameters, but only with the motor's operating conditions. Therefore, after the motor's operating conditions are stable, it is possible to perform a charging and demagnetization to optimize the permanent magnet flux, and on this basis implement turn-to-turn short-circuit fault tolerance control.

[0097] Furthermore, the three-stage turn-to-turn short-circuit fault tolerance control strategy in step S4 is characterized by: Figure 3 As shown in the figure, the maximum copper loss P of the faulty coil predicted and controlled based on the model wf_max is the reference value, which is subtracted from the actual fault coil copper loss, and the weak magnetic current reference value i is output through the PI controller d * (i d ​​* ≤ 0). Then, the maximum field-weakening current is determined using a look-up table. The difference between the field-weakening current reference value and the maximum value is taken, and ΔK (ΔK ≥ 0) is output through a proportional controller. After subtracting it from the maximum output ratio K max = 1, the output ratio reference value K is obtained and acts on the q-axis current control closed-loop.

[0098] Furthermore, the difference between the output ratio reference value and the minimum value is taken, and the maximum q-axis current compensation value Δi q (Δi q ≥ 0) is obtained through a proportional controller. To ensure the suppression effect on the short-circuit current, under the requirement of keeping the d-axis current and the motor output ratio unchanged, given the maximum copper loss P wh_max of the normal coil, the maximum q-axis current calculation can be obtained:

[0099]

[0100] The first term of this formula is the maximum q-axis current that does not exceed the limit for the normal coil temperature, and the second term is the maximum q-axis current compensation value that does not exceed the limit for the faulty coil temperature. Therefore, by implementing the limit on the motor output through this formula, it can be ensured that the temperatures of both the normal and faulty parts of the motor are controlled within the limit values. After considering the output ratios of the two sets of three-phase windings, the maximum limit values acting on the q-axis current control closed-loop are as follows:

[0101] i q1_max = Ki q_max

[0102] i q2_max = (2 - K)i q_max

[0103] A simulation model of a dual three-phase permanent magnet synchronous motor under inter-turn short-circuit fault, as well as its loss and thermal network model, are built using Matlab / Simulink software to simulate and verify the three-stage fault-tolerant control strategy of the present invention. The ambient temperature is set to 18°C. Under the fault conditions of a rotational speed of 300 rpm, a load torque of 45 Nm, a short-circuit turn ratio of 0.1, and a short-circuit resistance of 0.15 Ω, when the motor reaches a steady state, the highest temperature is located in the faulty coil, reaching approximately 790°C, and the temperatures of the other parts of the motor reach approximately 400°C, far higher than the safety critical temperature.

[0104] The changes in the dq-axis currents of the motor under the implementation of the three-stage fault-tolerant control strategy are as Figure 4 shown, and the temperature changes are as Figure 5As shown. At 0.4 s, the temperature approaches the limit value and a weak magnetic current is applied. At 0.6 s, the weak magnetic current reaches its maximum and the motor output ratio begins to be adjusted. At 1.6 s, the fault three-phase q-axis current has been controlled to zero, and the motor output is completely provided by the normal three phases, but the temperature control target value still cannot be reached. Therefore, the maximum motor output is limited and the maximum allowable q-axis current is reduced. At 3 s, the maximum allowable value of the q-axis current is lower than the current value required for the original torque output. Therefore, i q2 begins to decrease. While the motor output decreases, the short-circuit current is further suppressed. The temperature of the faulty coil is higher than the limit value for some time because it takes some time to adjust the maximum allowable q-axis current. The final temperature of the faulty coil is stably controlled at 70 °C, and the other normal parts of the motor also remain within the limit temperature.

[0105] The optimization effect of permanent magnet magnetization and demagnetization is verified through experiments. It can be calculated from the optimal magnetic flux that the optimal permanent magnet magnetic flux under the conditions of a rotational speed of 300 rpm and a load of 10 Nm is 0.0697 Wb. However, due to the limited magnetization and demagnetization range of the experimental motor, the magnetic flux can only be demagnetized from 0.096 Wb to 0.0876 Wb. As Figure 6 shown, the amplitude of the short-circuit current decreases after demagnetization. On this basis, weak magnetic fault-tolerant control is implemented. The temperature change of the motor is as shown in Figure 7 shown, and the dq-axis current change is as shown in Figure 8 shown. The temperature of the faulty coil first rises rapidly. When it approaches the limit value, a d-axis weak magnetic current is applied. While suppressing the short-circuit current, it also improves the motor torque output performance. Therefore, the q-axis current decreases somewhat. Finally, the temperature of the faulty coil is stably at 34 °C, and the temperatures of the other parts also remain within the limit values.

[0106] Figure 9 Shown is the change in motor losses under weak magnetic fault-tolerant control before and after demagnetization. Before implementing fault-tolerant control, due to the reduction of the permanent magnet magnetic flux after demagnetization, the copper loss of the faulty coil is smaller and the iron loss is also smaller. However, the larger q-axis current causes an increase in the copper loss of the normal coil. After implementing fault-tolerant control, due to the reduction of the required weak magnetic current after demagnetization, the copper loss of the normal coil is greatly reduced. Although the iron loss increases somewhat, the total motor loss is still smaller. Therefore, implementing demagnetization optimization is beneficial to improving the efficiency of the motor under fault-tolerant operation conditions.

[0107] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or device comprising said element.

Claims

1. A dual three-phase permanent magnet synchronous motor turn-to-turn short-circuit fault tolerance control method, characterized in that: include: Based on the physical principle of the dual three-phase permanent magnet synchronous motor system under inter-turn short-circuit fault, a transient model of the dual three-phase permanent magnet synchronous motor inter-turn short-circuit fault in a stationary coordinate system is established, and the first-order transient equation describing the relationship between voltage, current and flux change in the stationary coordinate system is obtained. On this basis, coordinate transformation is performed based on the rotor flux orientation, and a transient model of the dual three-phase permanent magnet synchronous motor inter-turn short-circuit fault in a dual synchronous rotating coordinate system is established, and the first-order transient equation describing the relationship between voltage, current and flux change in the dual synchronous coordinate system is obtained. The short-circuit current is regarded as a sinusoidal variable. Based on the inter-turn short-circuit fault model of the motor in the dual synchronous rotating coordinate system, the transient change of the current is ignored, and the steady-state equation describing the relationship between the short-circuit current amplitude and the dq-axis current change is obtained. Furthermore, combined with the motor torque equation, the steady-state equation describing the relationship between the permanent magnet flux size and the motor torque and speed change is solved. Under this permanent magnet flux, the short-circuit current reaches the minimum value. For variable flux motors using low coercive force permanent magnets, the charging and demagnetization optimization is implemented according to its operating conditions to suppress the short-circuit current of the motor under turn-to-turn short-circuit faults and reduce the severity of the faults. According to the characteristics of inter-turn short-circuit faults and the requirements for suppressing short-circuit current of dual three-phase permanent magnet synchronous motors, a three-stage inter-turn short-circuit fault tolerance control is implemented. In the first stage, the short-circuit current is suppressed by applying d-axis weak magnetic current. In the second stage, after the weak magnetic current reaches the maximum value, the short-circuit current is suppressed by changing the output ratio of the two sets of three-phase windings. In the third stage, after the output of the faulty three-phase reaches the minimum, the motor torque output is limited to further suppress the short-circuit current. The first-order transient equation of the relationship between voltage, current and flux change in the dual synchronous coordinate system is specifically: in u d1 、u q1 represents the d and q axis voltages in the synchronous coordinate system; u d2 、u q2 represents the d-axis and q-axis voltages in synchronous coordinate system 2; i d1 、i q1 represents the d and q axis currents in the synchronous coordinate system; i d2 、i q2 represents the d and q axis currents in synchronous coordinate system 2; L represents the motor self-inductance, satisfying L=L l +L ms ; R s Indicates stator resistance; L δ represents the magnetic resistance inductance caused by the salient pole effect; M1 represents the mutual inductance between the three-phase windings; M2 represents the mutual inductance between the two sets of three-phase windings; R f represents the short-circuit resistance; μ represents the ratio of the number of turns of the short-circuit winding to the total winding, which is called the short-circuit turns ratio; The steady-state equation describing the relationship between the short-circuit current amplitude and the dq-axis current change is specifically: among them D=mμ(L+L δ cos2θ); The short-circuit current is regarded as a sinusoidal variable, and the transient change of the current is ignored. The short-circuit current amplitude I is further derived. af The steady-state equations related to the changes in the two sets of dq axis currents are: For a given motor, when the speed and fault parameters are determined, the denominator of the above equation is a fixed value, and the numerator is regarded as two orthogonal components F d With F q The composite value of The steady-state equation describing the relationship between the permanent magnet flux size and the motor torque and speed change specifically includes: The motor torque equation under normal operation is: Without implementing other fault-tolerant control, the d-axis current is zero, the q-axis currents of the two sets of three-phase windings are equal, and the influence of short-circuit current on torque is ignored. The torque equation and the short-circuit current steady-state equation are combined to obtain the steady-state equation describing the relationship between the short-circuit current amplitude and the permanent magnet flux change:

2. A dual three-phase permanent magnet synchronous motor turn-to-turn short-circuit fault tolerance control method according to claim 1, characterized in that: The transient model of the inter-turn short-circuit fault of the dual three-phase permanent magnet synchronous motor in the stationary coordinate system specifically includes: Based on the physical principle of the dual three-phase permanent magnet synchronous motor system under turn-to-turn short-circuit fault, the first-order transient equation describing the relationship between voltage, current and flux in the stationary coordinate system is obtained: ψ sf =L sf I sf +ψ PM F f (i) In which, it is assumed that phase A is the phase with turn-to-turn short circuit fault, u sf 、i sf , sf They represent the motor stator phase voltage matrix, phase current matrix and winding flux matrix under the fault condition including the short circuit loop; R sf represents the stator resistance matrix under fault; L sf represents the stator inductance matrix under fault; ψ PM Represents the permanent magnet flux of the motor.

3. A dual three-phase permanent magnet synchronous motor turn-to-turn short-circuit fault tolerance control method according to claim 2, characterized in that: The first-order transient equation describing the relationship between voltage, current and flux in the stationary coordinate system is specifically: and sf =[and a and b and c and d and e and f and af ] T ;in sf =[in a in b in c in d in e in f 0] T ; Based on the symmetry of the motor structure and the relationship between the fault phase inductance, the stator inductance matrix under fault is further: Among them, L l Indicates the stator winding self-leakage inductance; L ms represents the main self-inductance of the stator winding; c represents the cosine function cos; the parameter m is determined by the inductance of a single coil and is related to the motor structure.

4. A dual three-phase permanent magnet synchronous motor turn-to-turn short-circuit fault tolerance control method according to claim 3, characterized in that: Solve the steady-state equation describing the relationship between the short-circuit current amplitude and the permanent magnet flux change to obtain the permanent magnet flux calculation formula:

5. The method for fault-tolerant control of inter-turn short-circuit fault of a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: The three-stage turn-to-turn short-circuit fault tolerance control specifically includes: Based on the short-circuit current suppression target, the PI controller outputs the weak field current reference value i d * ; Use the table lookup method to determine the maximum weak magnetic current, make a difference between the weak magnetic current reference value and the maximum value, output ΔK through the proportional controller, and subtract it from the maximum output ratio to obtain the output ratio reference value K, which acts on the q-axis current control closed loop; Subtract the output ratio reference value from the minimum value, and obtain the maximum q-axis current compensation value Δi through the proportional controller q , use the maximum current limit i max Subtract compensation value Δi q ; Get the q-axis current limit value i q_max , considering the output distribution of two sets of three-phase, the maximum limit value acting on the q-axis current control closed loop is:

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