A low vibration fault-tolerant control method for dual three-phase motors

Abstract

The present invention provides a low-vibration fault-tolerant control method for a dual three-phase motor. First, the reference current of the controller harmonic plane is changed according to the coupling relationship after the dual three-phase motor has a circuit breaker fault, so that the torque output is stable. Secondly, a modulation method for multiplying the carrier harmonic frequency is designed. In each control cycle, a traditional centralized modulation method or a carrier harmonic frequency multiplication method is selected by random numbers to realize random modulation, and a comparison value of pulse width modulation of each phase is calculated. Finally, the comparison value of pulse width modulation of each phase is compared with a fixed carrier period of T. s The carrier value of the triangular carrier is compared to obtain a dual three-phase pulse width modulation signal, and the signal is output to the dual three-phase motor through the inverter. The present invention reduces the amplitude of high-frequency harmonics while keeping the control frequency fixed, so that the high-frequency vibration of the motor is suppressed, and finally realizes low-vibration fault-tolerant control of the dual three-phase motor.

Description

Technical Field

[0001] The invention relates to the field of multi-phase motors, and in particular to a low-vibration fault-tolerant control method for dual three-phase motors. Background Art

[0002] The dual three-phase motor drive system with two sets of three-phase windings that are 30° out of phase has the advantages of high power output, multiple control degrees of freedom, and excellent fault tolerance performance. Therefore, it has good application prospects in aerospace, ship propulsion and other fields. The fault-tolerant control of dual three-phase motors has always been valued by scholars at home and abroad. Some scholars have achieved fault tolerance by deriving the reduced-order decoupling matrix after the fault, some scholars have improved the torque capacity after the fault by using the harmonic injection method, and some scholars have achieved the reduction of losses under the fault by modulating the current of the remaining non-fault phases. However, the vibration problem under fault operation has not been effectively solved.

[0003] When a dual three-phase motor is driven by a six-phase voltage source inverter, the opening and closing of the power device will generate concentrated high-frequency harmonics at the switching frequency, which will cause high-frequency vibration of the motor. The high-frequency vibration of the motor will affect the stability of the control system and damage the motor structure. There are two main ways to suppress high-frequency vibration: hardware and software. The hardware method will increase the volume and cost of the system. The software methods mainly include random switching frequency and random zero vector. The random switching frequency is achieved by changing the control cycle. Its essence is to expand the concentrated high-frequency fundamental wave to a wider frequency band. Its high-frequency vibration suppression effect depends on the range of control cycle variation. The larger the range of control cycle variation, the better the high-frequency vibration suppression effect, but it will bring larger current harmonics and torque pulsation, and deteriorate the fault-tolerant operation performance. The random zero vector is achieved by randomly allocating the action time of the middle zero vector and the zero vector on both sides. However, in order to achieve a higher voltage utilization rate, the motor usually works in the high modulation area. The zero vector action time in the high modulation area is short, so the high-frequency vibration suppression effect of the random zero vector is poor. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a low-vibration fault-tolerant control method for dual three-phase motors.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A dual three-phase motor low vibration fault tolerance control method comprises the following steps:

[0007] Step (1), according to the coupling relationship after the dual three-phase motor is broken, the reference current of the controller harmonic plane is changed so that the output torque of the dual three-phase motor is stable;

[0008] Step (2), dividing the duty cycle of each phase in the traditional centralized modulation method into two equal parts, respectively allocating them in the first and second half of the carrier cycle, so that the carrier harmonics are doubled;

[0009] Step (3), allocating the action time of the 77 vector in the carrier harmonic frequency multiplication modulation method to the 00 vector, thereby reducing the switching loss in the carrier harmonic frequency multiplication modulation;

[0010] Step (4), according to the component u of the reference voltage vector in the fundamental wave space α 、u β , determine the sector corresponding to the reference voltage vector in the fundamental wave space;

[0011] Step (5), according to the sector corresponding to the reference voltage vector in the fundamental wave space, select the maximum four vectors corresponding to the sector, and calculate the action time T1, T2, T3, T4 of the maximum four vectors in one control cycle and the action time T 00 ;

[0012] Step (6), using a linear congruential method to generate a random number, implementing random modulation according to a traditional centralized modulation method or a carrier harmonic frequency multiplication modulation method randomly selected by the random number, and calculating a comparison value of pulse width modulation of each phase; wherein the random number ranges from 0 to 1;

[0013] Step (7), compare the comparison value of each phase pulse width modulation with the fixed carrier period T s The carrier value of the triangular carrier is compared to obtain the switching signal of the switching device, and then the dual three-phase pulse width modulation signal is obtained, and then output to the dual three-phase motor through the inverter.

[0014] According to a further technical solution, after the carrier harmonics are frequency-multiplied, the carrier harmonic frequency is twice the carrier frequency.

[0015] A further technical solution is that in step (3), the 77 vector is cancelled and the action time of the 77 vector is allocated to the 00 vector; the switching times of sectors Ⅰ, Ⅱ, Ⅴ, Ⅵ, Ⅸ and Ⅹ are reduced from 12 times to 10 times, and the switching times of sectors Ⅲ, Ⅳ, Ⅶ, Ⅷ, Ⅺ and Ⅻ are reduced from 12 times to 8 times.

[0016] In a further technical solution, in step (4), firstly according to the component u of the reference voltage vector in the fundamental wave space α 、u β The current reference electrical angle is calculated, and then the sector corresponding to the reference voltage vector in the fundamental wave space is determined according to the reference electrical angle.

[0017] In a further technical solution, the calculation formula of the reference electrical angle is:

[0018] θ ref= atan2(u α ,u β )

[0019] Among them, θ ref Represents the reference electrical angle, and atan2 is the inverse tangent function.

[0020] Further technical solution, the action time of the maximum four vectors is calculated as:

[0021]

[0022] Where, T y It represents the time that the yth reference voltage vector acts in one switching cycle, U xy represents the projection of the yth reference voltage vector on the x-axis, and y = 1, 2, 3, 4; x = α, β, z1, z2, α, β represent the coordinate axes of the fundamental wave space, z1, z2 represent the coordinate axes of the harmonic wave space, μ α , μ β , μ z1 , μ z2 Respectively represent the components of the reference voltage vector under the α, β, z1, and z2 coordinate axes;

[0023] Zero vector action time T 00 =T 00 =T s -T1-T2-T3-T4.

[0024] In a further technical solution, the random number is calculated as follows:

[0025]

[0026] Among them, R represents a random number, mod is a modulus operation, λ and m are constants, y is an intermediate variable, and the subscripts n and n-1 represent the current moment and the previous moment respectively.

[0027] A further technical solution is that when the random number is greater than 0.5, the carrier harmonic frequency doubling modulation method is selected; when the random number is less than 0.5, the traditional centralized modulation method is selected.

[0028] A further technical solution is that in step (7), when the carrier value is equal to the comparison value 1, the switch signal S changes from 0 to 1; when the carrier value is equal to the comparison value 2, the switch signal S changes from 1 to 0; thereby obtaining a dual three-phase pulse width modulation signal.

[0029] The beneficial effects of the present invention are:

[0030] 1. The present invention divides the duty cycle of each phase in the traditional centralized modulation method into two equal parts, which are respectively allocated in the first and second half of the carrier cycle, so that the carrier harmonics are doubled.

[0031] 2. The present invention selects the traditional centralized modulation method and the carrier harmonic frequency doubling modulation method through random numbers. When the random number is greater than 0.5, the carrier harmonic frequency doubling modulation method is selected; when the random number is less than 0.5, the traditional centralized modulation method is selected, forming a random modulation strategy and realizing random modulation, thereby suppressing vibration under fault-tolerant working conditions.

[0032] 3. The present invention allocates the action time of the 77 vector in the carrier harmonic frequency doubling modulation method to the 00 vector, thereby reducing the switching loss in the carrier frequency doubling modulation.

[0033] 4. The present invention maintains a fixed carrier period while suppressing high-frequency harmonics, without affecting the fault-tolerant control performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a block diagram of the low vibration fault-tolerant control method for dual three-phase motors of the present invention;

[0035] FIG2( a ) is a fundamental wave spatial voltage vector diagram of a dual three-phase motor according to the present invention;

[0036] FIG2( b ) is a harmonic space voltage vector diagram of a dual three-phase motor according to the present invention;

[0037] Figure 3 It is a schematic diagram of PWM waveform and phase voltage of the conventional centralized modulation method of sector I of the present invention;

[0038] Figure 4 It is a schematic diagram of PWM waveform and phase voltage of the carrier harmonic frequency multiplication modulation method of sector I of the present invention;

[0039] Figure 5 It is a schematic diagram of PWM waveform and phase voltage of the carrier harmonic frequency multiplication modulation method after reducing the switching action in sector I of the present invention;

[0040] FIG6( a ) is a schematic diagram of a comparison value and a triangular carrier wave opened once in one control cycle of the present invention;

[0041] FIG6( b ) is a schematic diagram of opening the comparison value and the triangular carrier twice within one control cycle of the present invention;

[0042] FIG6( c ) is a schematic diagram of the present invention in which the comparison value and the triangular carrier are not enabled within one control cycle;

[0043] Figure 7 The waveform diagram of phase voltage, phase current, speed and torque using only the fault-tolerant method in the present invention;

[0044] Figure 8 The waveform diagram of phase voltage, phase current, speed and torque of the low vibration fault-tolerant control of the present invention;

[0045] FIG9( a ) is a diagram showing the phase current harmonic distribution when only the fault-tolerant method is used in the present invention;

[0046] FIG9( b ) is a diagram showing the phase current harmonic distribution of the present invention;

[0047] FIG. 10( a ) is a diagram of acceleration data using only the fault-tolerant method in the present invention;

[0048] FIG. 10( b ) is a diagram showing vibration acceleration data of the present invention. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0050] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0051] like Figure 1 As shown in the structural block diagram, the low-vibration fault-tolerant control method for dual three-phase motors of the present invention mainly includes reference current modification of the harmonic plane, design of a carrier harmonic frequency multiplication modulation method, and suppressing the high-frequency vibration of the motor by selecting different modulation methods through random numbers.

[0052] The present invention takes a dual three-phase motor as the control object and performs low vibration fault-tolerant control on it. The specific measures are as follows:

[0053] Step 1: According to the coupling relationship after the dual three-phase motor circuit breaker fault, change the reference current of the harmonic plane so that the magnetomotive force remains unchanged and the output torque is stable.

[0054] The coupling relationship under double three motor fault can be expressed as:

[0055]

[0056] Among them, i β 、i y and i O2 They represent the currents of the β-axis, y-axis and O2-axis in the space vector decoupling coordinate system respectively; i B 、i C 、i D and i E They respectively represent the currents of the B-axis, C-axis, D-axis and E-axis in the natural coordinate system.

[0057] Since the sum of the currents of each set of windings is 0, the coupling relationship under the double three motor fault can be expressed as:

[0058]

[0059] In order to maintain the decoupling matrix and modulation method of the dual-three motor under normal operation and minimize the reconstruction of the controller, the maximum torque output mode is adopted, and the reference current of the controller harmonic plane can be expressed as:

[0060]

[0061] Among them, i x * and i y * They represent the reference current of the harmonic plane, i α Represents the current of the α-axis in the space vector decoupling coordinate system.

[0062] Step 2: Divide the duty cycle of each phase in the traditional centralized modulation method into two equal parts, and distribute them in the first and second half of the carrier cycle respectively, so that the carrier harmonics are doubled.

[0063] Figure 2 (a) and (b) are the voltage vector distribution diagrams of the fundamental space / harmonic space of the dual three-phase motor. In the traditional centralized modulation method, four vectors are selected for modulation and the PWM wave is centralized. The PWM waveform and phase voltage waveform of the first sector in the traditional centralized modulation method are as follows: Figure 3 The carrier harmonic frequency multiplication modulation does not change the selected vector and the vector action time, but only divides the duty cycle of each phase into two parts, and acts on the first and second half of the carrier cycle respectively. The carrier harmonic frequency multiplication PWM waveform and phase voltage waveform are shown in Figure 4 As shown. The phase voltage of the dual three-phase motor can be expressed as:

[0064] U X (t+0.5T s )=U X (t)

[0065] Among them, X can be any phase among A, B, C, D, E, F, T s represents the carrier period, and t represents any time point.

[0066] The carrier harmonic frequency can be expressed as:

[0067]

[0068] Among them, f c It is expressed as the carrier period, m is a constant;

[0069] After the carrier harmonic is modulated by frequency doubling, the high-frequency harmonic frequency is twice the carrier frequency.

[0070] Step 3: Allocate the action time of the 77 vector in the carrier harmonic frequency doubling modulation method to the 00 vector to reduce the switching loss in the carrier frequency doubling modulation.

[0071] Carrier harmonic frequency doubling modulation can make the high-frequency harmonic frequency twice the carrier frequency, but the number of switching times will also become twice that of the traditional centralized modulation method; in order to reduce the number of switching times, the 77 vector is cancelled and the action time of the 77 vector is allocated to the 00 vector; the number of switching times of sectors Ⅰ, Ⅱ, Ⅴ, Ⅵ, Ⅸ and Ⅹ is reduced from 12 times to 10 times, and the number of switching times of sectors Ⅲ, Ⅳ, Ⅶ, Ⅷ, Ⅺ and Ⅻ is reduced from 12 times to 8 times. The PWM waveform and phase voltage waveform of the carrier harmonic frequency doubling modulation after reducing the number of switching times are shown in the figure below. Figure 5 shown.

[0072] Step 4: According to the component u of the reference voltage vector in the fundamental wave space α 、u β Determine the sector to which the reference voltage vector corresponds in the fundamental wave space.

[0073] First, according to the component u of the reference voltage vector in the fundamental wave space α 、u β Calculate the current reference electrical angle, and then determine the sector corresponding to the reference voltage vector in the fundamental wave space based on the reference electrical angle. ref The calculation can be expressed as:

[0074] θ ref = atan2(u α ,u β )

[0075] Among them, atan2 is the inverse tangent function.

[0076] Step 5: According to the sector where the reference voltage vector is located in the fundamental wave space, select the maximum four vectors corresponding to the sector, and calculate the action time T1, T2, T3, T4 of the maximum four vectors in one control cycle, as well as the action time T of the zero vector. 00 .

[0077] According to the sector where the reference voltage vector is located in the fundamental wave space, the maximum four vectors corresponding to the sector are selected. Then, the action time T1, T2, T3, T4 of the maximum four vectors in one control cycle and the action time T of the zero vector are calculated respectively. 00 , so that the voltage vector acting in a control cycle is consistent with the reference voltage vector in both the fundamental wave space and the harmonic wave space. The action time calculation of the maximum four vectors can be expressed as:

[0078]

[0079] Where, T y(y=1, 2, 3, 4) represents the time during which the yth reference voltage vector acts in one switching cycle; U xy (x=α, β, z1, z2; α, β represent the coordinate axes of the fundamental wave space, z1, z2 represent the coordinate axes of the harmonic wave space) represents the projection of the y-th reference voltage vector on the x-axis; μ α , μ β , μ z1 , μ z2 They represent the components of the reference voltage vector on the α, β, z1, and z2 coordinate axes respectively.

[0080] Zero vector action time T 00 It can be expressed as:

[0081] T 00 =T s -T1-T2-T3-T4

[0082] Step 6: Use the linear congruential method to generate random numbers, the range of which is 0 to 1. According to one of the two modulation methods randomly selected by the random number, random modulation is implemented, and the comparison value of the pulse width modulation of each phase is calculated.

[0083] The random number R obtained by the linear congruential method can be expressed as:

[0084]

[0085] Among them, mod is the modulo operation, λ and m are constants, y is an intermediate variable, and the subscripts n and n-1 represent the current moment and the previous moment respectively.

[0086] When the random number is greater than 0.5, the carrier harmonic frequency multiplication modulation method is selected; when the random number is less than 0.5, the traditional centralized modulation method is selected to form a random modulation strategy. The comparison value of each phase pulse width modulation is calculated according to the selected modulation method and vector action time, and recorded as comparison value 1 and comparison value 2.

[0087] Step 7: Compare the pulse width modulation comparison value of each phase with the fixed carrier period T s The carrier value of the triangular carrier is compared to obtain the switching signal of the switching device, and then the dual three-phase pulse width modulation signal is obtained, which is output to the dual three-phase motor through the inverter.

[0088] When the carrier value is equal to the comparison value 1, the switch signal S changes from 0 to 1; when the carrier value is equal to the comparison value 2, the switch signal S changes from 1 to 0; thus, a dual three-phase pulse width modulation signal is obtained, which is output to the dual three-phase motor through the inverter. As shown in Figures 6(a), (b), and (c), there are three different switching times of a certain phase in a control cycle. 6(a) means that there are two switching actions in a control cycle, and both comparison values ​​are less than 1; 6(b) means that there is one switching action in a control cycle, at this time, one comparison value is less than 1 and the other comparison value is equal to 1; 6(c) means that there is no switching action in a control cycle, and both comparison values ​​are equal to 1.

[0089] Figure 7 The waveforms of phase voltage, phase current, speed and torque during fault-tolerant operation show that the total harmonic distortion (THD) of the phase current is 11.4% and the torque ripple is 4.4Nm. Figure 8 The waveforms of phase voltage, phase current, speed and torque during low vibration fault-tolerant operation show that the total harmonic distortion (THD) of the phase current is 10.3% and the torque ripple is 4.3Nm.

[0090] After the present invention adopts the low-vibration fault-tolerant control strategy, the fault-tolerant performance is not deteriorated. On the contrary, due to the increase in switching frequency, the fault-tolerant performance is improved. Figures 9 (a) and (b) are comparison diagrams of the phase voltage spectrum analysis of the fault-tolerant method alone and the low-vibration fault-tolerant method of the present invention. The voltage at the 2k switching frequency when the fault-tolerant method alone is used is 26.4V, and the vibration at the 2k switching frequency of the present invention is 13.1V. Figures 10 (a) and (b) are comparison diagrams of the vibration spectrum analysis of the fault-tolerant method alone and the low-vibration fault-tolerant method of the present invention. The vibration at the 2k switching frequency when the fault-tolerant method alone is used is 0.8m / s 2 The vibration at the 2k switching frequency of the present invention is 0.4m / s 2 The present invention realizes low-vibration operation while realizing fault-tolerant control, and improves the fault-tolerant function to fault-tolerant performance.

[0091] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0092] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A low vibration fault-tolerant control method for dual three-phase motors, characterized in that: The steps include: Step (1), according to the coupling relationship after the dual three-phase motor is broken, the reference current of the controller harmonic plane is changed so that the output torque of the dual three-phase motor is stable; Step (2), dividing the duty cycle of each phase in the traditional centralized modulation method into two equal parts, respectively allocating them in the first and second half of the carrier cycle, so that the carrier harmonics are doubled; Step (3), allocating the action time of the 77 vector in the carrier harmonic frequency multiplication modulation method to the 00 vector, thereby reducing the switching loss in the carrier harmonic frequency multiplication modulation; Step (4), according to the component u of the reference voltage vector in the fundamental wave space α 、u β , determine the sector corresponding to the reference voltage vector in the fundamental wave space; Step (5), according to the sector corresponding to the reference voltage vector in the fundamental wave space, select the maximum four vectors corresponding to the sector, and calculate the action time T1, T2, T3, T4 of the maximum four vectors in one control cycle and the action time T of the zero vector respectively. 00 ; Step (6), using a linear congruential method to generate a random number, implementing random modulation according to a traditional centralized modulation method or a carrier harmonic frequency multiplication modulation method randomly selected by the random number, and calculating a comparison value of pulse width modulation of each phase; The random number ranges from 0 to 1; Step (7), compare the comparison value of each phase pulse width modulation with the fixed carrier period T s The carrier value of the triangular carrier is compared to obtain the switching signal of the switching device, and then the dual three-phase pulse width modulation signal is obtained, and then output to the dual three-phase motor through the inverter.

2. The dual three-phase motor low vibration fault-tolerant control method according to claim 1, characterized in that: After the carrier harmonic is frequency-multiplied, the carrier harmonic frequency is twice the carrier frequency.

3. The dual three-phase motor low vibration fault-tolerant control method according to claim 1, characterized in that: In the step (3), the 77 vector is cancelled and the action time of the 77 vector is allocated to the 00 vector; the switching times of sectors Ⅰ, Ⅱ, Ⅴ, Ⅵ, Ⅸ and Ⅹ are reduced from 12 times to 10 times, and the switching times of sectors Ⅲ, Ⅳ, Ⅶ, Ⅷ, Ⅺ and Ⅻ are reduced from 12 times to 8 times.

4. The dual three-phase motor low vibration fault-tolerant control method according to claim 1, characterized in that: In the step (4), firstly, according to the component u of the reference voltage vector in the fundamental wave space α 、u β The current reference electrical angle is calculated, and then the sector corresponding to the reference voltage vector in the fundamental wave space is determined according to the reference electrical angle.

5. The dual three-phase motor low vibration fault-tolerant control method according to claim 4, characterized in that: The calculation formula of the reference electrical angle is: θ ref =attach2(u α ,the β ) Among them, θ ref Represents the reference electrical angle, and atan2 is the inverse tangent function.

6. The dual three-phase motor low vibration fault-tolerant control method according to claim 1, characterized in that: The action time of the maximum four vectors is calculated as: Where, T y It represents the time that the yth reference voltage vector acts in one switching cycle, U xy represents the projection of the yth reference voltage vector on the x-axis, and y = 1, 2, 3, 4; x = α, β, z1, z2, α, β represent the coordinate axes of the fundamental wave space, z1, z2 represent the coordinate axes of the harmonic wave space, μ α , μ β , μ z1 , μ z2 Respectively represent the components of the reference voltage vector under the α, β, z1, and z2 coordinate axes; Zero vector action time T 00 =T 00 =T s -T1-T2-T3-T4.

7. The dual three-phase motor low vibration fault-tolerant control method according to claim 1, characterized in that: The random number is calculated as follows: Among them, R represents a random number, mod is a modulus operation, λ and m are constants, y is an intermediate variable, and the subscripts n and n-1 represent the current moment and the previous moment respectively.

8. The dual three-phase motor low vibration fault-tolerant control method according to claim 7, characterized in that: When the random number is greater than 0.5, the carrier harmonic frequency multiplication modulation method is selected; when the random number is less than 0.5, the traditional centralized modulation method is selected.

9. The dual three-phase motor low vibration fault-tolerant control method according to claim 1, characterized in that: In the step (7), when the carrier value is equal to the comparison value 1, the switch signal S changes from 0 to 1; when the carrier value is equal to the comparison value 2, the switch signal S changes from 1 to 0; thereby a dual three-phase pulse width modulation signal is obtained.

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