Five-phase induction motor fault-tolerant control method based on virtual vector reconstruction

Abstract

The invention relates to the technical field of motor fault-tolerant control, and discloses a five-phase induction motor fault-tolerant control method based on virtual vector reconstruction, which reduces torque ripple and harmonic content caused by non-uniform voltage vector distribution by reconstructing vector distribution and providing two virtual vector synthesis strategies of uniform angle and constant amplitude. On the basis, in order to realize efficient fault-tolerant operation in a full-speed domain range, an improved ten-virtual-vector fault-tolerant control strategy is provided, and a hysteresis comparator is introduced to improve the steady-state and dynamic performance in a mode switching process, so that the torque ripple under single-phase open-circuit fault operation is remarkably reduced, and the reliability of the system is improved. And smooth switching and effective control between a normal mode and a fault mode are realized in a full-speed domain range.

Description

Technical Field

[0001] The present invention relates to the technical field of motor fault-tolerant control, and in particular to a five-phase induction motor fault-tolerant control method based on virtual vector reconstruction. Background Art

[0002] With the development of AC transmission systems, multiphase motors have shown broad application prospects in aerospace, wind power generation, electric vehicles and other fields due to their advantages such as high power density, high efficiency and low torque ripple. Among them, five-phase motors can achieve low torque pulsation and high-precision control with more control freedom and harmonic decoupling capabilities, and have stronger fault-tolerant control capabilities. The fault-tolerant control of five-phase motors is mainly carried out for open-circuit faults. When a single-phase open-circuit fault occurs in a five-phase motor, the motor operates asymmetrically, and the voltage vector after the open circuit needs to be reconstructed. However, the spatial voltage vector distribution under a single-phase open circuit is uneven, resulting in poor accuracy of predictive control.

[0003] To solve this problem, those skilled in the art have proposed an extended virtual voltage vector MPC fault-tolerant control method, which expands the voltage vector control set, adds additional voltage vectors, and performs equal amplitude processing on all available voltage vectors after a fault. However, this method requires the selection of more voltage vectors, which increases the amount of calculation and also reduces the voltage utilization. In addition, the spatial distribution of the voltage vector in the above-mentioned virtual vector reconstruction-based phase-loss fault-tolerant MPC control method will be significantly offset after a motor fault occurs, and the sectors need to be redivided, making the control process switching from healthy operation to open-circuit fault-tolerant operation more cumbersome, and the stability in the full speed domain during fault-tolerant operation is poor.

[0004] Therefore, those skilled in the art are in urgent need of a stable and reliable five-phase motor single-phase open-circuit fault-tolerant control strategy. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems. A five-phase induction motor fault-tolerant control method based on virtual vector reconstruction is designed to solve the problems of increased harmonic current, increased torque pulsation and complex control caused by single-phase open-circuit fault of the five-phase induction motor.

[0006] To achieve the above object, the technical solution of the present invention is a five-phase induction motor fault-tolerant control method based on virtual vector reconstruction, which comprises the following steps:

[0007] Step 1: by reconstructing the vector distribution, two virtual vector synthesis modes, namely, equal angle and equal amplitude, are set;

[0008] Step 2: construct an improved ten-virtual vector fault-tolerant control method and introduce a hysteresis comparator to improve the steady-state and dynamic performance during mode switching;

[0009] The virtual appropriate synthesis method of the average angle in step 1 is:

[0010] By synthesizing a new vector using three adjacent vectors and combining it with the voltage vector after the fault, the synthesis formula of the fault-tolerant virtual voltage vector can be obtained, namely:

[0011] VV i (u x ,u y ,u z )=D1u x +D2u y +D3u z (1)

[0012] Where: u x 、u y 、u z is the basic voltage vector; D1, D2, D3 are the voltage vector proportions, and they satisfy:

[0013] D1+D2+D3=1,D i ∈[0,1],(i=1,2,3) (2)

[0014] By analogy, 10 virtual voltage vectors are synthesized, including 4 large virtual vectors (VV3, VV4, VV8, VV9, with an amplitude of 0.4642U dc ), 2 medium virtual vectors (VV1, VV6, with an amplitude of 0.4472U dc ), 4 small virtual vectors (VV2, VV5, VV7, VV 10 , the amplitude is 0.3685U dc ).

[0015] The method for synthesizing the medium-amplitude virtual vector in step 1 is:

[0016] Adjust the proportion of zero vector in 10 virtual voltage vectors, with the minimum virtual vector amplitude of 0.3685U dc As a benchmark, the amplitude coefficient d is introduced, and the large virtual vector and the medium virtual vector are reduced to the same amplitude as the small virtual vector through the adjustment of the zero vector, and the new ten virtual vectors V i * (i=1,2...10).

[0017] It should be noted that the equal-amplitude ten-vector has equal amplitude, but the overall amplitude is small, which is suitable for low-speed and light-load conditions; the equal-angle ten-vector has unequal amplitude, but makes full use of the DC voltage, broadens the speed regulation range, and is suitable for high-speed and heavy-load conditions. In order to ensure that the faulty motor can operate stably in each speed range, the present invention proposes an improved ten-virtual vector single-phase open-circuit fault-tolerant control strategy that integrates the equal-amplitude principle and the equal-angle principle. It is divided into a low-speed mode and a high-speed mode. The two modes are based on the amplitude of the equal-amplitude ten-vector (0.3685U dc ) as the boundary, and mode switching is performed when the voltage reaches this threshold boundary point.

[0018] The present invention uses a deadbeat current prediction method to select a vector and control the operation of a motor. The method obtains the position of a reference voltage vector in advance during the control process.

[0019] Therefore, the process of constructing the improved ten-virtual vector fault-tolerant control method in step 2 is:

[0020] Based on the deadbeat idea, the prediction model for a single-phase open-circuit fault in the motor is assumed to be:

[0021]

[0022] Where: σ=1-L 2 m / (L s L r ) is the magnetic leakage coefficient, u dref 、u qref 、u yref are the dq axis and y axis reference voltages respectively, i dref 、i qref 、i yref are the dq axis and y axis reference currents, i d (k), i q (k), i y (k) is the dq axis and y axis current at the current moment k; R s is the stator resistance, L m is the coaxial equivalent magnetizing inductance between the stator and the rotor; L s , L r are the stator self-inductance and rotor self-inductance of the equivalent winding, L m is the coaxial equivalent magnetizing inductance between the stator and the rotor; ω r is the electrical angular velocity, T s is the sampling time, τ r =L r / R r is the rotor time constant of the asynchronous motor;

[0023] Then the voltage cost function is:

[0024]

[0025] Where: λ is the weight coefficient, u d (k) and u q (k) and u y (k) are the dq axis and y axis voltages at the current moment k respectively.

[0026] Take the second sector as an example. Fig. 9 As shown, the virtual voltage vector V2 * Defined as u opt , calculate the duty cycle based on the geometric method, and convert u opt Projected onto the reference voltage vector, the ratio of the projection to the virtual voltage vector amplitude is the action time of the optimal voltage vector:

[0027]

[0028] Where: u opt is the reference voltage vector in case of motor fault, θ u is the angle between the reference voltage vector and the α axis; θ i is the angle between the virtual vector in each sector and the α-axis.

[0029] The required virtual voltage vector and its duty cycle are determined through this process. The vector is selected using the distribution diagram of the equal-amplitude ten vectors at low speeds and the distribution diagram of the equal-angle ten vectors at high speeds.

[0030] The process of introducing the hysteresis comparator in step 2 to improve the steady-state and dynamic performance during the mode switching process is as follows:

[0031] Introduce hysteresis comparator control and set the maximum inverter output voltage to 2U dc / π, the maximum voltage vector amplitude under single-phase open circuit fault is 0.6145U dc , then the threshold stator voltage is:

[0032]

[0033] According to u s1 Design a hysteresis comparator, △u1 represents the hysteresis width, u s (k+1) represents the steady-state amplitude of the stator voltage; when u s (k+1)≤u s1 , S=-1, it is low speed mode; when u s (k+1)≥u s1 , S=1, high speed mode;

[0034] It should be noted that in actual operation, there is still a certain deviation between the actual voltage output value and the reference value, which cannot accurately follow the set current, so the output voltage will fluctuate within a certain range. Since the mode switching is based on whether the output voltage reaches a certain threshold, when the output voltage is close to the maximum voltage of the low-speed mode, the voltage fluctuation will lead to frequent switching between the two modes.

[0035] It should be noted that after the optimization of uniform angle and equal amplitude, the virtual vector distribution in the healthy state and the single-phase open circuit fault state is as follows: Figure 8 As shown in the figure, the synthetic virtual voltage vector in the healthy state is HV i (i=1,2,…,10). It can be seen that after the equal angle and equal amplitude transformation, the 10 reconstructed voltage vectors evenly divide the α-β subspace into 10 sectors, each sector is 36°, and the direction of the reconstructed virtual vector is consistent with the virtual vector in the healthy state, so there is no need to redivide the sectors.

[0036] Therefore, the single-phase open-circuit fault-tolerant control strategy of the five-phase induction motor based on virtual vector reconstruction proposed in this application is basically the same as the model prediction operation control strategy under healthy state. The fault-tolerant control strategy under fault is easier to implement, which simplifies the entire fault-tolerant control switching process. The difference is that the amplitude of the reconstructed virtual voltage vector is reduced.

[0037] Beneficial Effects

[0038] A five-phase induction motor fault-tolerant control method based on virtual vector reconstruction produced by the technical solution of the present invention has the following advantages:

[0039] 1. The present invention needs to re-correct the virtual vector according to the single-phase open-circuit fault-tolerant control of the five-phase induction motor. The corrected virtual vector can effectively suppress the torque pulsation during fault operation and realize effective control after a single-phase open-circuit fault;

[0040] 2. The improved ten-vector strategy proposed in the present invention can obtain two virtual vectors, namely, equal-angle and equal-amplitude vectors, in combination with the operating requirements under different working conditions, thus achieving a performance balance under low-speed and light-load conditions and high-speed and heavy-load conditions;

[0041] 3. The present invention introduces a hysteresis comparator to suppress frequent oscillations during mode switching, further enhancing the dynamic and steady-state response capabilities of the system;

[0042] 4. The method described in the present invention can significantly reduce the torque pulsation under single-phase open circuit fault operation, and realize smooth switching and effective control between normal and fault modes within the full speed range. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1It is a flow chart of a five-phase induction motor fault-tolerant control method based on virtual vector reconstruction according to the present invention;

[0044] Figure 2 is a typical topological diagram of a five-phase induction motor driven by a five-phase two-level voltage source inverter according to the present invention;

[0045] Figure 3 It is a vector composite graph of the eight vectors in the α-β and y subspaces of the present invention;

[0046] Figure 4 is the eight-vector distribution diagram of the present invention;

[0047] Figure 5 It is a vector composite diagram of the nominal angle ten vector in the α-β and y subspaces of the present invention;

[0048] Figure 6 It is the average angle ten-vector distribution diagram of the present invention;

[0049] Figure 7 It is the equal-amplitude ten-vector distribution diagram of the present invention;

[0050] Figure 8 It is a virtual voltage vector distribution diagram under healthy and faulty states of the present invention;

[0051] Fig. 9 It is the optimal voltage vector selection diagram of the present invention;

[0052] Fig.10 It is a general control flow chart of a five-phase induction motor fault-tolerant control method based on virtual vector reconstruction according to the present invention;

[0053] Fig.11 is a schematic diagram of the hysteresis comparator of the present invention;

[0054] Fig.12 This is a physical picture of the five-phase induction motor drive system experimental platform of the present invention;

[0055] Fig.13 is a comparison table of the steady-state experiment described in the present invention;

[0056] Fig.14 is the harmonic analysis diagram of the present invention;

[0057] Fig.15 is the current torque waveform diagram of the present invention;

[0058] Fig.16 is the harmonic analysis diagram of the present invention;

[0059] Fig.17 This is a comparison diagram of the variable speed experiment described in the present invention;

[0060] Fig.18 It is a comparison diagram of the speed mode switching experiment described in the present invention;

[0061] Fig.19 This is a comparison diagram of the variable torque experiment described in the present invention;

[0062] Fig. 20 is the health-fault-tolerance switching diagram of the present invention;

[0063] Fig.21 is the eight-vector synthesis parameter table of the present invention;

[0064] Fig. 22 is the average angle ten-vector synthesis parameter table of the present invention;

[0065] Fig.23 It is the equal-amplitude ten-vector synthesis parameter table of the present invention;

[0066] Fig.24 is the motor parameter table of the present invention;

[0067] Fig.25 It is a table of phase current values ​​under different operating modes described in the present invention;

[0068] Fig.26 It is the voltage vector table under the single-phase open circuit fault of the present invention. DETAILED DESCRIPTION

[0069] The present invention and embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Figure 1-26 As shown;

[0070] Since the voltage vector distribution changes after an open-circuit fault, the virtual voltage vector synthesis method under normal conditions is no longer applicable, and the torque pulsation caused by the fault cannot be effectively suppressed. Therefore, in order to improve the fault-tolerant operation capability of the motor under fault conditions, the virtual voltage vector synthesis method needs to be redesigned.

[0071] In order to reduce the influence of the third harmonic in the y subspace after a fault, the y subspace synthetic voltage vector should be made 0. An eight-voltage vector synthesis method is proposed in the prior art, as shown in the following formula:

[0072] V h (u i ,u j )=Ku i +(1-K)u j

[0073] Where: u i 、u j generation Fig.21 basic voltage vectors; K is the voltage vector ratio. Figure 2 As shown, with u8 and u 13For example, two adjacent vectors have opposite directions in the y subspace. Using this feature, we can find the action time of two basic vectors when the y-axis component is zero, such as Figure 3 As shown, the calculated K value is 0.382, and the new synthesized virtual voltage vector is V2.

[0074] The virtual voltage vectors V1-V8 synthesized according to this principle are as follows: Fig.21 As shown, the amplitude of V1 and V5 is 0.4472U dc ; The amplitude of V3 and V7 is 0.5257U dc ; The amplitude of V2, V4, V6 and V8 is 0.3944U dc The corresponding spatial distribution is as follows: Figure 4 shown.

[0075] As can be seen from the above figure, the vectors generated by the above eight-vector synthesis method are irregularly distributed, and the sectors need to be redivided when switching from normal operating conditions to fault-tolerant control, which will lead to high harmonic content in fault-tolerant operation and excessive current fluctuations during the fault switching process to fault-tolerant control.

[0076] To solve this problem, it is necessary to optimize the synthesis of virtual vectors. This application makes improvements in two aspects: uniform angle of virtual vectors and equal amplitude of virtual vectors, and proposes a ten-vector reconstruction strategy.

[0077] In order to achieve uniform phase angle, unlike the eight-vector synthesis method using two adjacent vectors, the ten-vector reconstruction strategy uses three adjacent vectors to synthesize a new vector. Combined with the voltage vector after the fault, the synthesis formula of the fault-tolerant virtual voltage vector can be obtained, namely:

[0078] VV i (u x ,u y ,u z )=D1u x +D2u y +D3u z (1)

[0079] Where: u x 、u y 、u z generation Fig. 22 Basic voltage vectors; D1, D2, D3 are voltage vector proportions, and satisfy

[0080] D1+D2+D3=1,D i ∈[0,1],(i=1,2,3) (2)

[0081] With u8, u9 and u 13 For example, Figure 2 As shown, since in the y subspace u8, u 13The two vectors are in opposite directions and u9 is a zero vector. Therefore, this feature can be used to make the voltage synthesized on the harmonic plane zero, such as Figure 5 As shown, we can obtain D1=0.4120, D2=0.3334, and D3=0.2546.

[0082] By analogy, 10 virtual voltage vectors can be synthesized, including 4 large virtual vectors (VV3, VV4, VV8, VV9, with an amplitude of 0.4642U dc ), 2 medium virtual vectors (VV1, VV6, with an amplitude of 0.4472U dc ), 4 small virtual vectors (VV2, VV5, VV7, VV 10 , the amplitude is 0.3685U dc ), whose distribution is as follows Figure 5 As shown, the synthesis principle is as follows Fig. 22 shown.

[0083] Depend on Figure 6 It can be seen that the above method achieves uniform distribution of virtual voltage vector amplitude angle and appropriately expands the vector control set. However, unequal amplitudes will still cause large torque pulsation.

[0084] In order to achieve equal amplitude of synthetic virtual vector after fault, the zero vector (u0 and u1) is adjusted in the voltage vector corresponding to the 10 reconstructed virtual vectors. 15 ) proportion, with the minimum virtual vector amplitude of 0.3685U dc As a benchmark, the amplitude coefficient d is introduced, Fig. 22 The large virtual vector and the medium virtual vector in are reduced to the same amplitude as the small virtual vector through the adjustment of the zero vector, and a new ten virtual vectors V i * (i=1,2...10), such as Fig.23 As shown, the corresponding fundamental wave spatial distribution is as follows Figure 7 shown.

[0085] After the optimization of uniform angle and equal amplitude, the virtual vector distribution in the healthy state and the single-phase open circuit fault state is as follows: Figure 8 As shown in the figure, the synthetic virtual voltage vector in the healthy state is HV i(i=1,2,…,10). It can be seen that after the equal angle and equal amplitude transformation, the 10 reconstructed voltage vectors evenly divide the α-β subspace into 10 sectors, each sector is 36°, and the direction of the reconstructed virtual vector is consistent with the virtual vector in the healthy state, and there is no need to redivide the sectors. Therefore, the single-phase open-circuit phase fault-tolerant control strategy of the five-phase induction motor based on virtual vector reconstruction proposed in this application is basically the same as the model predictive runtime control strategy in the healthy state, and the fault-tolerant control strategy under fault is easier to implement, which simplifies the entire fault-tolerant control switching process. The difference is that the amplitude of the reconstructed virtual voltage vector is reduced.

[0086] In order to reduce the burden of traversing all vectors in the calculation of MPC, the deadbeat current prediction method can be used to obtain the position of the reference voltage vector in advance during the control process.

[22] Based on the deadbeat idea, the prediction model for a single-phase open-circuit fault in a motor is:

[0087]

[0088] Where: σ=1-L 2 m / (L s L r ) is the magnetic leakage coefficient, u dref 、u qref 、u yref are the dq axis and y axis reference voltages respectively, i dref 、i qref 、i yref are the dq axis and y axis reference currents, i d (k), i q (k), i y (k) is the dq axis and y axis current at the current moment k; R s is the stator resistance, L m is the coaxial equivalent magnetizing inductance between the stator and the rotor; L s , L r are the stator self-inductance and rotor self-inductance of the equivalent winding, L m is the coaxial equivalent magnetizing inductance between the stator and the rotor; ω r is the electrical angular velocity, T s is the sampling time, τ r =L r / R r is the rotor time constant of the asynchronous motor.

[0089] The voltage cost function is:

[0090]

[0091] Where: λ is the weight coefficient.

[0092] Take the first sector as an example. Fig. 9 As shown, the duty cycle is calculated based on the geometric method, and u opt Projected onto the reference voltage vector, the ratio of the projection to the virtual voltage vector amplitude is the action time of the optimal voltage vector:

[0093]

[0094] Where: u opt is the reference voltage vector in case of motor fault, θ u is the angle between the reference voltage vector and the α axis; θ i is the angle between the virtual vector in each sector and the α-axis.

[0095] The equal-amplitude ten-vector has equal amplitude, but the overall amplitude is small, which is suitable for low-speed and light-load conditions; the equal-angle ten-vector has unequal amplitude, but makes full use of the DC voltage, widens the speed regulation range, and is suitable for high-speed and heavy-load conditions. In order to ensure that the faulty motor can operate stably in each speed range, this application proposes an improved ten-virtual vector single-phase open-circuit fault-tolerant control strategy that integrates the equal-amplitude principle and the equal-angle principle. It is divided into low-speed mode and high-speed mode. The two modes are based on the amplitude of the equal-amplitude ten-vector (0.3685U dc ) as the demarcation point, and the mode switching is performed when the voltage reaches this threshold demarcation point. The overall control process of the proposed fault-tolerant MPC algorithm based on improved ten virtual vectors is as follows: Fig.10 shown.

[0096] In actual operation, there is still a certain deviation between the actual voltage output value and the reference value, which cannot accurately follow the set current, so the output voltage will fluctuate within a certain range. Since the mode switching is based on whether the output voltage reaches a certain threshold, when the output voltage is close to the maximum voltage of the low-speed mode, the voltage fluctuation will lead to frequent switching between the two modes.

[23] Therefore, the present application introduces hysteresis comparator control to effectively avoid frequent switching between the two control modes at the threshold.

[0097] The maximum inverter output voltage is 2U dc / π, by Fig.26 It can be seen that the maximum voltage vector amplitude under single-phase open circuit fault is 0.6145U dc , then the threshold stator voltage can be calculated as:

[0098]

[0099] According to u s1 Design a hysteresis comparator, such as Fig.11 As shown, △u1 represents the hysteresis loop width, u s (k+1) represents the steady-state amplitude of the stator voltage.s (k+1)≤u s1 , S=-1, it is low speed mode; when u s (k+1)≥u s1 , S=1, high speed mode.

[0100] Example 1

[0101] In order to verify the single-phase open-circuit fault-tolerant MPC strategy of the five-phase induction motor based on the improved ten virtual vectors proposed in this application, an experimental platform capable of simulating single-phase open-circuit faults was built based on the dSPACE control system. Fig.12 As shown in the figure, the circuit breaker is used to control the on and off of the A phase circuit to simulate the introduction and removal of faults. The parameters of the tested motor are as follows: Fig.24 shown.

[0102] In order to verify the single-phase open-circuit fault-tolerant control performance of the five-phase induction motor under steady-state conditions, the steady-state performance of the motor under three control modes, namely eight-vector, equal-angle ten-vector and equal-amplitude ten-vector, was tested at low speed (250r / min) and high speed (350r / min), with a load torque of 5N·m.

[0103] The phase current and torque ripple comparison experiments of the three strategies under low speed (250r / min) conditions are as follows: Fig.13 The waveform of the eight-vector strategy is shown in Fig.13 (a) shows that the current distortion of the phase current is large and the torque ripple is 1.9 N·m. The waveform of the equal angle ten-vector strategy is as follows: Fig.13 (b) shows that the sinusoidal degree of the phase current is better and the torque ripple is 1.5N·m. Compared with the eight-vector strategy, the steady-state performance of the motor is improved; the equal-amplitude ten-vector strategy is as follows Fig.13 As shown in (c), the torque ripple is 1.2N·m. Compared with the equal-angle ten-vector strategy, both the current distortion rate and the torque ripple are suppressed. The main reason is that the equal-amplitude ten-vector achieves uniform distribution of the voltage vector under the single-phase open-circuit fault state.

[0104] Harmonic analysis at low speed Fig.14 and Fig.25 As shown, it can be seen that in low-speed mode, the THD of the equal-amplitude ten-vector strategy current is better than that of the other two strategies.

[0105] The phase current and torque ripple comparison experiments of the three strategies under high-speed (350r / min) conditions are as follows: Fig.15 The experimental results show that the equal-amplitude ten-vector strategy has large current and waveform distortion and large torque waveform fluctuation. The equal-amplitude ten-vector strategy cannot operate at high speeds, so only the eight-vector strategy and the equal-angle ten-vector strategy are compared. Among them, the equal-angle ten-vector strategy can still operate stably in the high-speed area, and its steady-state performance is significantly better than that of the eight-vector strategy.

[0106] Harmonic analysis at high speeds Fig.15 and Fig.25 As shown, it can be seen that the harmonic suppression ability of the even-angle ten-vector strategy in the high-speed domain is better than that of the eight-vector strategy. Therefore, the use of the even-angle ten-vector strategy is the best choice in the high-speed domain where the equal-amplitude ten-vector strategy cannot operate.

[0107] In summary, the voltage utilization rate of the equal-angle ten-vector is high, and the equal-amplitude ten-vector has a good control effect at low speed. Therefore, the two are combined to form an improved ten-vector control. Under low-speed operating conditions, the equal-amplitude ten-vector strategy can effectively reduce THD and torque pulsation. Under high-speed operating conditions, the equal-angle ten-vector is used to adapt to stable operation in the full speed range.

[0108] In order to compare the dynamic operation characteristics of the eight-vector and the improved ten-vector, variable torque and variable speed experiments were carried out. The experimental waveforms of the current response, torque and speed when the five-phase induction motor was accelerated from 250r / min to 350r / min with a torque of 5N·m under fault conditions are shown in the following figure. Fig.17 When the speed changes suddenly, the improved ten-vector strategy has a faster response speed than the eight-vector strategy and can quickly stabilize to the set torque.

[0109] In addition, in order to verify the effectiveness of the hysteresis comparator in mode switching, an experiment was conducted under no-load conditions, with the speed stepping from 200r / min to 400r / min. The instantaneous waveform of speed mode switching is shown in Figure 1. Fig.18 As shown, it can be seen that due to the addition of the hysteresis comparator during the switching process, the impact of torque and speed during the switching process is small, there is almost no disturbance, and stable operation in the full speed range is achieved.

[0110] The motor speed is set to 200r / min and the load torque increases from 5N·m to 8N·m. The corresponding current response, torque and speed experimental waveforms are as follows: Fig.19 As shown. When the load changes suddenly, it can also be proved that the improved ten-vector strategy has a faster response speed than the eight-vector strategy, and the torque can be adjusted to a stable state in a short time, quickly following the set value, while the motor speed fluctuation is kept within a small range. This further verifies that the improved ten-vector strategy has good dynamic response performance and strong anti-interference ability.

[0111] The waveforms of the five-phase induction motor switching from normal operation to fault-tolerant operation under the two strategies are shown in the figure below. Fig. 20As shown. When an open circuit fault occurs in phase A, the current of phase A drops to zero and the current of the remaining phases is significantly distorted. Subsequently, the motor switches from fault mode to fault-tolerant control mode. The results show that both fault-tolerant control strategies can effectively improve the current waveform. The improved ten-vector proposed in this application does not require sector switching, so the switching between health-fault-tolerance is smoother.

[0112] The above technical solutions only reflect the preferred technical solutions of the technical solutions of the present invention. Some changes that may be made to certain parts thereof by technicians in this technical field all reflect the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A five-phase induction motor fault-tolerant control method based on virtual vector reconstruction, characterized in that: The method comprises the following steps: Step 1: by reconstructing the vector distribution, two virtual vector synthesis modes, namely, equal angle and equal amplitude, are set; Step 2: construct an improved ten-virtual vector fault-tolerant control method and introduce a hysteresis comparator to improve the steady-state and dynamic performance during mode switching.

2. A five-phase induction motor fault-tolerant control method based on virtual vector reconstruction according to claim 1, characterized in that: The synthesis method of the virtual vector of the average angle in step 1 is: By synthesizing a new vector using three adjacent vectors and combining it with the voltage vector after the fault, the synthesis formula of the fault-tolerant virtual voltage vector can be obtained: VV i (in x ,in y ,in z )=D1u x +D2u y +D3u z (1) Where: u x 、u y 、u z is the basic voltage vector; D1, D2, D3 are the voltage vector proportions, and they satisfy: <h2 style=";text-align:left;direction:ltr">D1+D2+D3 = 1,D<h2 style=";text-align:left;direction:ltr"> i <h2 style=";text-align:left;direction:ltr"> ∈[0,1],(i=1,2,3) (2) In this way, 10 virtual voltage vectors are synthesized, including 4 large virtual vectors, 2 medium virtual vectors, and 4 small virtual vectors.

3. The five-phase induction motor fault-tolerant control method based on virtual vector reconstruction according to claim 2 is characterized in that: The method for synthesizing the medium-amplitude virtual vector in step 1 is: Adjust the proportion of zero vector in 10 virtual voltage vectors, with the minimum virtual vector amplitude of 0.3685U dc As a benchmark, the amplitude coefficient d is introduced, and the large virtual vector and the medium virtual vector are reduced to the same amplitude as the small virtual vector through the adjustment of the zero vector, and the new ten virtual vectors are obtained.

4. The five-phase induction motor fault-tolerant control method based on virtual vector reconstruction according to claim 1 is characterized in that: The process of constructing the improved ten-virtual vector fault-tolerant control method in step 2 includes: The improved ten-virtual vector fault-tolerant control mode is divided into a low-speed mode and a high-speed mode, and the mode is switched when the voltage reaches the threshold dividing point; Assume that the prediction model for a single-phase open circuit fault of the motor is: Where: σ=1-L 2 m / (L s L r ) is the magnetic leakage coefficient, u dref 、u qref 、u yref are the dq axis and y axis reference voltages respectively, i dref 、i qref 、i yref are the dq axis and y axis reference currents, i d (k), i q (k), i y (k) is the dq axis and y axis current at the current moment k; R s is the stator resistance, L m is the coaxial equivalent magnetizing inductance between the stator and the rotor; L s , L r are the stator self-inductance and rotor self-inductance of the equivalent winding, L m is the coaxial equivalent magnetizing inductance between the stator and the rotor; ω r is the electrical angular velocity, T s is the sampling time, τ r =L r / R r is the rotor time constant of the asynchronous motor; Then the voltage cost function is: Where: λ is the weight coefficient, u d (k) and u q (k) and u y (k) are the dq-axis and y-axis voltages at the current moment k; Virtual voltage vector V2 * Defined as u opt , calculate the duty cycle based on the geometric method, and project the reference voltage vector onto u opt The ratio of the projection to the virtual voltage vector amplitude is the action time of the optimal voltage vector: Where: u opt is the reference voltage vector in case of motor fault, θ u is the angle between the reference voltage vector and the α axis; θ i is the angle between the virtual vector in each sector and the α-axis; and then the virtual voltage vector and its duty cycle are determined. In low-speed mode, the distribution diagram of ten equal-amplitude vectors is used to select the vector, and in high-speed mode, the distribution diagram of ten equal-angle vectors is used to select the vector.

5. The five-phase induction motor fault-tolerant control method based on virtual vector reconstruction according to claim 4 is characterized in that: The process of introducing the hysteresis comparator in step 2 to improve the steady-state and dynamic performance during the switching process between the high-speed mode and the low-speed mode is as follows: Introduce hysteresis comparator control and set the maximum inverter output voltage to 2U dc / π, the maximum voltage vector amplitude under single-phase open circuit fault is 0.6145U dc , then the threshold stator voltage is: According to u s1 Design a hysteresis comparator, △u1 represents the hysteresis width, u s (k+1) represents the steady-state amplitude of the stator voltage; when u s (k+1)≤u s1 , S=-1, it is low speed mode; when u s (k+1)≥u s1 , S=1, high speed mode.

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