Control method of dual three-phase permanent magnet synchronous motor in low modulation ratio region

Abstract

The invention relates to a control method of a dual three-phase permanent magnet synchronous motor in a low-modulation-ratio region, solves the problem that the existing dual three-phase permanent magnet synchronous motor needs two sets of three-phase windings to work together in the low-modulation-ratio region, and is low in operation efficiency, and belongs to the field of motor driving. The method comprises the steps that in a low modulation ratio area, three-phase windings A, B and C operate independently, the sum of B-phase lower bridge arm current and C-phase lower bridge arm current is sampled, and three-phase current reconstruction is carried out; the reconstructed three-phase current and the sampling rotating speed are sent into a loop for operation to obtain three-phase modulation reference voltage, and power module driving is completed through pulse width modulation; in a modulation ratio normal area, the two sets of three-phase windings operate cooperatively, the sum of B, C, Y and Z phase lower bridge arm currents in the two sets of three-phase windings is sampled at different sampling vector combination positions, six-phase current reconstruction is carried out, the reconstructed six-phase current and the sampling rotating speed are sent into a loop to be calculated, modulation reference voltage is obtained, after amplitude limiting is carried out, pulse width modulation is carried out, and the modulation reference voltage is obtained. And completing power module driving.

Description

Technical Field

[0001] The invention relates to a control method for a dual three-phase permanent magnet synchronous motor in a low modulation ratio area, and belongs to the field of motor driving. Background Art

[0002] To fully utilize the bus voltage without introducing overmodulation safety hazards, the static operating point of a dual three-phase permanent magnet synchronous motor (DTP-PMSM) is generally set within the normal modulation ratio range. However, during transitional situations such as motor startup, sudden load addition, and forward / reverse switching, the motor enters a low modulation ratio operating region. Although open-loop startup transition solutions exist in this low modulation ratio region, to ensure system stability, the motor must always operate under closed-loop control. Therefore, eliminating the phase current reconstruction blind spot in this low modulation ratio region is essential.

[0003] In the low modulation ratio region, motor output is low. Traditional solutions for low modulation ratios modify PWM, construct sampling vectors, and perform current reconstruction. This traditional approach significantly impacts current harmonics and may increase the number of switching cycles, thereby increasing inverter drive losses. For DTP-PMSMs, using traditional PWM modification in the low modulation ratio region requires modifications to both three-phase windings. The negative impact of these two windings on the electric drive system is exacerbated by the combined effects of these two windings, and this approach underutilizes the characteristics of the DTP-PMSM. Because motor output and speed requirements are lower in the low modulation ratio region, using two three-phase windings to drive the DTP-PMSM in this low modulation ratio region reduces system drive efficiency and wastes system resources. Furthermore, the vector coupling caused by the two three-phase windings operating in this low modulation ratio region further complicates reconstruction. When the current reconstruction schemes differ between the low modulation ratio region and the normal region, a clear and efficient switching control method is needed. Traditional current reconstruction schemes switching between different modulation ratios can make phase current reconstruction difficult over a wide modulation ratio range, leaving room for further optimization.

[0004] Different voltage vectors cause current to flow through different paths, and the sampling branches corresponding to the current sensors in these paths have different phase current information. Single-path sampling limits phase current information, so some researchers have replaced the zero vector with the opposite effective vector to construct reconstruction conditions. This method can lead to large current reconstruction errors during sector switching. The traditional solution is to use predictive control to estimate the sampled current, which is computationally complex and wastes controller resources. Summary of the Invention

[0005] In view of the problem that two sets of three-phase windings need to work together in the low modulation ratio region of the DTP-PMSM vector control frequency conversion system, which leaves room for optimizing the operating efficiency, the present invention provides a control method for a dual three-phase permanent magnet synchronous motor in the low modulation ratio region.

[0006] A control method for a dual three-phase permanent magnet synchronous motor in a low modulation ratio region of the present invention comprises:

[0007] Step 1: In the low modulation ratio region, the three-phase winding ABC operates independently, and the three-phase winding XYZ is subjected to wave sealing processing. The sum of the lower arm currents of phases B and C in the three-phase winding ABC is sampled, and the low modulation ratio three-phase current reconstruction is completed according to the three-phase current reconstruction expression in the low modulation ratio region. The reconstructed three-phase current and the sampled speed are sent into the loop for calculation to obtain the three-phase modulation reference voltage, and the power module is driven by low modulation ratio hybrid pulse width modulation.

[0008] Step 2: Calculate the minimum sampling vector |U according to the minimum sampling time Min |, determine the reference voltage modulus of the three-phase winding ABC|u ref-ABC |Is it satisfied? |u ref-ABC |≤2.1|U Min If yes, go back to step 1, if no, go to step 3;

[0009] Step 3: In the normal modulation ratio region, the two sets of three-phase windings operate in coordination, and the sum of the lower arm currents of the B, C, Y, and Z phases in the two sets of three-phase windings is sampled at different sampling vector combinations. The six-phase current reconstruction expression in the normal modulation ratio region is used to complete the six-phase current reconstruction. The reconstructed six-phase current and the sampled speed are sent into the loop for calculation to obtain the modulation reference voltage, and the modulation reference voltage of the quadrature axis is limited. All modulation reference voltages are subjected to hybrid pulse width modulation (RHPWM) to complete the power module drive.

[0010] Step 4: Determine the three-phase winding XYZ reference voltage modulus |u ref-ABC |Is it satisfied? |u ref-ABC |≤1.1|U Min If yes, go to step 1, if no, go to step 3.

[0011] Preferably, the method for obtaining the reconstruction expression of the three-phase current in the low modulation ratio area includes:

[0012] Construct a low modulation ratio reconstruction area:

[0013] S A 、S B 、S C 、S X 、S Y 、S ZThey are the six-phase bridge arm switching functions of the dual three-phase permanent magnet synchronous motor, where a value of 0 represents that the lower bridge arm is turned on, and a value of 1 represents that the upper bridge arm is turned on;

[0014] When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z =0 corresponds to voltage vector U0;

[0015] When S A =1, S B =0, S C =0 or S X =1, S Y =0, S Z =0 corresponds to voltage vector U1;

[0016] When S A =1, S B =1, S C =0 or S X =1, S Y =1, S Z =0 corresponds to voltage vector U2;

[0017] When S A =0, S B =1, S C =0 or S X =0, S Y =1, S Z =0 corresponds to voltage vector U3;

[0018] When S A =0, S B =1, S C =1 or S X =0, S Y =1, S Z =1 corresponds to voltage vector U4;

[0019] When S A =0, S B =0, S C =1 or S X =0, S Y =0, S Z =1 corresponds to voltage vector U5;

[0020] When S A =1, S B =0, S C =1 or S X =1, S Y =0, S Z=1 corresponds to voltage vector U6;

[0021] When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z =1 corresponds to voltage vector U7;

[0022] The area enclosed by the voltage vector U1 and the voltage vector U2 in space is the low modulation ratio reconstruction area L1;

[0023] The area enclosed by the voltage vector U2 and the voltage vector U3 in space is the low modulation ratio reconstruction area L2;

[0024] The area enclosed by the voltage vector U3 and the voltage vector U4 in space is the low modulation ratio reconstruction area L3;

[0025] The area enclosed by the voltage vector U4 and the voltage vector U5 in space is the low modulation ratio reconstruction area L4;

[0026] The area enclosed by the voltage vector U5 and the voltage vector U6 in space is the low modulation ratio reconstruction area L5;

[0027] The area enclosed by the voltage vector U6 and the voltage vector U1 in space is the low modulation ratio reconstruction area L6;

[0028] According to the different low modulation ratio reconstruction regions where the reference voltage vector is located, the three-phase current reconstruction expression is:

[0029]

[0030] Among them, 0T s , 0.5T s Represents one switching cycle T s Two sampling moments within;

[0031] i A Represents the current of phase A in the three-phase winding ABC; i B Represents the current of phase B in three-phase winding ABC; i C Represents the current of phase C in the three-phase winding ABC.

[0032] Preferably, the low modulation ratio hybrid pulse width modulation comprises:

[0033] When the reference voltage vector is in the low modulation ratio reconstruction area L1 or L4, SVPWM modulation is normally used, and then the A and C phase drive signals are inverted and swapped;

[0034] When the reference voltage vector is in the low modulation ratio reconstruction region L2, SVPWM modulation is normally used, and then the B-phase drive signal is inverted and used for C-phase drive;

[0035] When the reference voltage vector is in the low modulation ratio reconstruction area L3 or L6, SVPWM modulation is normally used, and then the A and B phase drive signals are inverted and then swapped;

[0036] When the reference voltage vector is located in the low modulation ratio reconstruction region L5, SVPWM modulation is normally adopted, and then the C-phase drive signal is inverted and used for B-phase drive.

[0037] Preferably, the method for obtaining the six-phase current expression in the normal modulation ratio region includes:

[0038] S A 、S B 、S C 、S X 、S Y 、S Z They are the six-phase bridge arm switching functions of the dual three-phase permanent magnet synchronous motor, where a value of 0 represents that the lower bridge arm is turned on, and a value of 1 represents that the upper bridge arm is turned on;

[0039] When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z =0 corresponds to voltage vector U0;

[0040] When S A =1, S B =0, S C =0 or S X =1, S Y =0, S Z =0 corresponds to voltage vector U1;

[0041] When S A =1, S B =1, S C =0 or S X =1, S Y =1, S Z =0 corresponds to voltage vector U2;

[0042] When S A =0, S B =1, S C =0 or S X =0, S Y =1, S Z =0 corresponds to voltage vector U3;

[0043] When S A =0, S B =1, S C =1 or S X =0, S Y =1, S Z =1 corresponds to voltage vector U4;

[0044] When S A =0, S B =0, S C =1 or S X =0, S Y =0, S Z =1 corresponds to voltage vector U5;

[0045] When S A =1, S B =0, S C =1 or S X =1, S Y =0, S Z =1 corresponds to voltage vector U6;

[0046] When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z =1 corresponds to voltage vector U7;

[0047] The area enclosed by the voltage vector U1 and the voltage vector U2 in space is sector I;

[0048] The area enclosed by the voltage vector U2 and the voltage vector U3 in space is sector II;

[0049] The area enclosed by the voltage vector U3 and the voltage vector U4 in space is sector III;

[0050] The area enclosed by the voltage vector U4 and the voltage vector U5 in space is sector IV;

[0051] The area enclosed by the voltage vector U5 and the voltage vector U6 in space is sector V;

[0052] The area enclosed by the voltage vector U6 and the voltage vector U1 in space is sector VI;

[0053] For sectors I to VI, the midline within each sector is taken, and the area surrounded by the midline of sector I and the midline of sector VI is the normal modulation ratio area G1;

[0054] The area enclosed by the midline of sector II and the midline of sector I is the normal modulation ratio area G2;

[0055] The area enclosed by the midline of sector II and the midline of sector III is the normal modulation ratio area G3;

[0056] The area enclosed by the midline of sector III and the midline of sector IV is the normal modulation ratio area G4;

[0057] The area enclosed by the midline of sector IV and the midline of sector V is the normal modulation ratio area G5;

[0058] The area enclosed by the midline of sector V and the midline of sector VI is the normal modulation ratio area G6;

[0059] Among them, the normal modulation ratio region G1 and the normal modulation ratio region G4 are zero vector modification regions, the normal modulation ratio region G1 includes the normal modulation ratio region G1-Ⅰ and the normal modulation ratio region G1-Ⅱ, the region surrounded by the midline of sector VI and the voltage vector U1 is the normal modulation ratio region G1-Ⅰ, and the region surrounded by the midline of sector I and the voltage vector U1 is the normal modulation ratio region G1-Ⅱ;

[0060] The normal modulation ratio region G4 includes the normal modulation ratio region G4-I and the normal modulation ratio region G4-II. The region surrounded by the midline of sector III and the voltage vector U4 is the normal modulation ratio region G4-I, and the region surrounded by the midline of sector IV and the voltage vector U4 is the normal modulation ratio region G4-II.

[0061] According to the normal modulation ratio region of the reference voltage vector, the six-phase current reconstruction expression is:

[0062]

[0063]

[0064]

[0065] Among them, ABC-U i XYZ-U j Indicates the switching period T s The voltage vector corresponding to the inner three-phase winding ABC is U i , the voltage vector corresponding to the three-phase winding XYZ is U j , i=0,1,2,3,4,5,6,7, j=0,1,2,3,4,5,6,7;

[0066] I1, I2, I3, and I4 represent the currents sampled by the four sampling vector combinations; i X Indicates the current of phase X in the three-phase winding XYZ; i Y Indicates the current of phase Y in the three-phase winding XYZ; iZ Indicates the current of phase Z in the three-phase winding XYZ; i A Represents the current of phase A in the three-phase winding ABC; i B Represents the current of phase B in three-phase winding ABC; i C Represents the current of phase C in the three-phase winding ABC.

[0067] Preferably, the hybrid pulse width modulation RHPWM comprises:

[0068] Shift the carrier of three-phase winding XYZ by 0.25T s SVPWM modulation is adopted in the modulation ratio normal region G1-Ⅰ and the modulation ratio normal region G4-Ⅰ, and then the A and B phase drive signals in the three-phase winding ABCZ are inverted and swapped, and the voltage vectors U0 and U7 are replaced by the voltage vectors U2 and U5 respectively;

[0069] In the modulation ratio normal region G1-Ⅱ and the modulation ratio normal region G4-Ⅱ, SVPWM modulation is adopted, and then the A and C phase drive signals in the three-phase winding ABCZ are inverted and swapped, and the voltage vectors U0 and U7 are replaced by the voltage vectors U6 and U3 respectively;

[0070] In the normal modulation ratio area G2, G3, G5, and G6 all use SVPWM for modulation.

[0071] As a preference, in the normal modulation ratio region, when switching from the zero vector transition boundary to the normal modulation ratio region, the calculation method of the sampled currents I1 and I3 is changed;

[0072] The zero vector transition boundary includes the center lines of sectors I, III, IV, and V, voltage vector U1, and voltage vector U4;

[0073] When the reference voltage vector crosses the center line of sector I and switches from the normal modulation ratio region G1-II to the normal modulation ratio region G2, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0074]

[0075] Where i' A represents the current of phase A in the three-phase winding ABC of the dual three-phase permanent magnet synchronous motor in the last switching cycle, i' B Indicates the current of phase B in the three-phase winding ABC in the last switching cycle, i' C Indicates the current of phase C in the three-phase winding ABC in the last switching cycle, i' X Indicates the current of phase X in the three-phase winding XYZ in the last switching cycle, i' YIndicates the current of phase Y in the three-phase winding XYZ in the last switching cycle, i' Z Indicates the current of phase Z in the three-phase winding XYZ in the previous switching cycle;

[0076] When the reference voltage vector crosses the center line of sector III and switches from the normal modulation ratio region G3 to the normal modulation ratio region G4-I, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0077]

[0078] When the reference voltage vector passes through the voltage vector U4 and switches from the normal modulation ratio region G4-I to the normal modulation ratio region G4-II, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0079]

[0080] When the reference voltage vector crosses the center line of sector IV and switches from the normal modulation ratio region G4-II to the normal modulation ratio region G5, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampled currents I1 and I3 are updated as follows:

[0081]

[0082] When the reference voltage vector crosses the midline of sector VI and switches from the normal modulation ratio region G6 to the normal modulation ratio region G1-I, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0083]

[0084] When the reference voltage vector passes through the voltage vector U1 and switches from the normal modulation ratio region G1-I to the normal modulation ratio region G1-II, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0085]

[0086] As a preference, the modulation reference voltage of the quadrature axis is limited:

[0087]

[0088] Among them, U q To represent the modulation reference voltage of the quadrature axis, T s represents the switching period, Tmin Indicates the minimum sampling time, U dc Indicates the bus voltage.

[0089] The beneficial effects of the present invention are as follows: only one set of three-phase windings is required for operation in the low modulation ratio region, thereby improving system operation efficiency and reducing control complexity; the present invention can realize phase current reconstruction in a wide range of low modulation ratio regions and normal modulation ratio regions of the DTP-PMSM drive system; and the present invention provides a convenient and fast method for suppressing sector switching reconstruction errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 The control principle diagram of the dual three-phase permanent magnet synchronous motor DTP-PMSM is shown in Figure 1, where θ is the DTP-PMSM electrical angle, ω is the DTP-PMSM speed, and I SAMPLE is the current Hall sampling value;

[0091] Figure 2 Control flow chart of DTP-PMSM under different modulation ratios;

[0092] Figure 3 Reconstruct the topology diagram for DTP-PMSM low modulation ratio current;

[0093] Figure 4 Reconstructing regions for low and normal modulation ratios;

[0094] Figure 5(a) shows the carrier and PWM waveforms of the L1 region of the three-phase winding XYZ low modulation ratio reconstruction;

[0095] Figure 5(b) shows the carrier and PWM waveforms of the L2 region of the three-phase winding XYZ low modulation ratio reconstruction;

[0096] Figure 5(c) shows the carrier and PWM waveforms of the low modulation ratio reconstruction area L3 of the three-phase winding XYZ;

[0097] Figure 5(d) is a schematic diagram of the zero vector transition boundary sampling from the modulation ratio normal region G1-II to the modulation ratio normal region G2.

[0098] Figure 6 The waveform diagram of the sampling current in the low modulation ratio area and the real phase current of the three-phase winding ABC;

[0099] Figure 7(a) is the real phase current waveform of three-phase winding ABC;

[0100] Figure 7(b) is the reconstructed phase current waveform of three-phase winding ABC;

[0101] Figure 7(c) shows the error between the true current and the reconstructed current of phase A in the three-phase winding ABC in the low modulation ratio region;

[0102] Figure 8(a) shows the waveforms of the real phase current and reconstructed phase current of the three-phase winding ABC when switching between different modulation ratio regions;

[0103] Figure 8(b) shows the waveforms of the real phase current and reconstructed phase current of the three-phase winding XYZ when switching between different modulation ratio regions;

[0104] Figure 8(c) shows the error between the real current and the reconstructed current of phase A in the three-phase winding ABC with different modulation ratio switching.

[0105] Figure 9(a) shows the real phase current waveform of the three-phase winding ABC of the motor starting in the low modulation ratio area;

[0106] Figure 9(b) shows the waveform of the reconstructed phase current of the three-phase winding ABC in the low modulation ratio area when the motor starts;

[0107] Figure 9(c) shows the error between the true current and the reconstructed current of phase A in the three-phase winding ABC of the motor starting in the low modulation ratio region. DETAILED DESCRIPTION

[0108] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0109] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0110] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0111] The control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio region of this embodiment includes:

[0112] Step 1: In the low modulation ratio region, the three-phase winding ABC operates independently, and the three-phase winding XYZ is subjected to wave sealing processing. The sum of the lower arm currents of phases B and C in the three-phase winding ABC is sampled, and the low modulation ratio three-phase current reconstruction is completed according to the three-phase current reconstruction expression in the low modulation ratio region. The reconstructed three-phase current and the sampled speed are sent into the loop for calculation to obtain the three-phase modulation reference voltage, and the power module is driven by low modulation ratio hybrid pulse width modulation.

[0113] In the low modulation operation area, the three-phase windings ABC operate independently. At this time, the corresponding relationship between the current sensor sampling results and the phase current under different voltage vectors is calculated by formula (1):

[0114] I SAMPLE=(1-S B )i B +(1-S C )i C (1)

[0115] Where S A 、S B 、S C 、S X 、S Y 、S Z are the six-phase bridge arm switching functions respectively, a value of 0 represents the lower bridge arm is turned on, and a value of 1 represents the upper bridge arm is turned on; i A Represents the current of phase A in the three-phase winding ABC; i B Represents the current of phase B in three-phase winding ABC; i C Represents the current of phase C in three-phase winding ABC; i X Indicates the current of phase X in the three-phase winding XYZ; i Y Indicates the current of phase Y in the three-phase winding XYZ; i Z Indicates the current of phase Z in the three-phase winding XYZ; I SAMPLE is the current sensor sampling value.

[0116] When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z =0 corresponds to voltage vector U0;

[0117] When S A =1, S B =0, S C =0 or S X =1, S Y =0, S Z =0 corresponds to voltage vector U1;

[0118] When S A =1, S B =1, S C =0 or S X =1, S Y =1, S Z =0 corresponds to voltage vector U2;

[0119] When S A =0, S B =1, S C =0 or S X =0, S Y =1, S Z =0 corresponds to voltage vector U3;

[0120] When S A =0, S B =1, S C =1 or S X =0, S Y =1, S Z =1 corresponds to voltage vector U4;

[0121] When S A =0, S B =0, S C =1 or S X =0, S Y =0, S Z =1 corresponds to voltage vector U5;

[0122] When S A =1, S B =0, S C =1 or S X =1, S Y =0, S Z =1 corresponds to voltage vector U6;

[0123] When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z =1 corresponds to voltage vector U7;

[0124] The area enclosed by the voltage vector U1 and the voltage vector U2 in space is the low modulation ratio reconstruction area L1;

[0125] The area enclosed by the voltage vector U2 and the voltage vector U3 in space is the low modulation ratio reconstruction area L2;

[0126] The area enclosed by the voltage vector U3 and the voltage vector U4 in space is the low modulation ratio reconstruction area L3;

[0127] The area enclosed by the voltage vector U4 and the voltage vector U5 in space is the low modulation ratio reconstruction area L4;

[0128] The area enclosed by the voltage vector U5 and the voltage vector U6 in space is the low modulation ratio reconstruction area L5;

[0129] The area enclosed by the voltage vector U6 and the voltage vector U1 in space is the low modulation ratio reconstruction area L6;

[0130] In the low modulation ratio area, low modulation ratio hybrid pulse width modulation LHPWM is used for modulation. LHPWM is:

[0131] When the reference voltage vector is in the low modulation ratio reconstruction area L1 or L4, SVPWM modulation is normally used, and then the A and C phase drive signals are inverted and then swapped;

[0132] When the reference voltage vector is in the low modulation ratio reconstruction region L2, SVPWM modulation is normally used, and then the B-phase drive signal is inverted and used for C-phase drive;

[0133] When the reference voltage vector is in the low modulation ratio reconstruction area L3 or L6, SVPWM modulation is normally used, and then the A and B phase drive signals are inverted and then swapped;

[0134] When the reference voltage vector is located in the low modulation ratio reconstruction region L5, SVPWM modulation is normally adopted, and then the C-phase drive signal is inverted and used for B-phase drive.

[0135] Sampling is performed at the beginning (0Ts) and midpoint (0.5Ts) of the switching cycle Ts to obtain the sampling current I L1 with I L2 Substitute the sampled current into the current reconstruction expression in Table 1 to complete the ABC three-phase current reconstruction.

[0136] Table 1 Correspondence between the current sensor sampling results and the three-phase current in the low modulation ratio reconstruction area

[0137]

[0138]

[0139] The simulation experiment was conducted using a 30-pole, rated speed 125rpm, motor flux 0.89Wb, quadrature and direct axis inductance 7.1mH, and stator excitation inductance 5.1mH. A dual three-phase permanent magnet synchronous motor with a phase shift angle of 0° was used for the simulation experiment. The switching period was 40us, and the two sets of three-phase windings were independently connected in star configuration. Figure 1 As shown, the main control loop adopts dual DQ closed-loop control, and the control loop is reorganized according to the switching controller instructions.

[0140] Start the motor at a speed of 40r / min (0.32pu). Figure 2 From the motor switching control flow chart, it can be seen that when the motor starts, it first runs in the low modulation ratio area. Figure 1 In the low modulation ratio area shown, the independent three-phase windings ABC are working, the XYZ drive is closed, and the torque current given value is 0.

[0141] In the low modulation ratio area, LHPWM modulation is used to replace the zero vector with the opposite effective vector. Sampling is performed at 0Ts and 0.5Ts to obtain the sampling current I L1 with I L2According to the reconstruction area where the reference voltage is located, the corresponding reconstruction expression can be obtained by querying Table 1. The sampled current is brought into the reconstruction expression to complete the ABC low modulation ratio phase current reconstruction. Taking the low modulation ratio reconstruction area L1 as an example, the reconstruction process is explained. As shown in Figure 5(a), sampling is performed at 0Ts and 0.5Ts to obtain I L1 , I L2 From Table 1, we can see that the reconstruction expression of the low modulation ratio reconstruction area L1 is formula (2), and the XYZ three-phase current can be reconstructed by substituting the sampled current.

[0142]

[0143] Figure 7(a) to Figure 7(c) The phase current reconstruction results for operation in the low modulation ratio region are shown. Under this condition, the three-phase reconstructed current still maintains good sinusoidal properties. The comparison of the reconstructed current of phase A with the measured current, as well as the error curve shown in Figure 7(c), also show that the reconstructed current fundamental wave still closely follows the actual current in the low modulation ratio region.

[0144] During the starting process of the motor, it will inevitably pass through the low modulation ratio area, so it is necessary to verify the accuracy of the DTP-PMSM phase current reconstruction technology under this dynamic process.

[0145] Figure 9(a) to Figure 9(c) The phase current reconstruction results of the motor from zero speed and zero load to 40r / min (0.32pu) speed and 110N·m load are given, where Figure 9(a) and Figure 9(b) are the actual and reconstructed current waveforms of the ABC three-phase at this time respectively. Figure 9(a) to Figure 9(c) It can be seen that this embodiment effectively eliminates the low modulation ratio reconstruction blind area. During the entire dynamic process, the three-phase reconstructed current of the DTP-PMSM can be smoothly started from the low modulation ratio area.

[0146] The three-phase current is sent to the Clark-Park transformation of formula (3) to obtain the ABC winding torque current feedback value i q1 and the excitation current feedback value i d1 .

[0147]

[0148] The motor speed and angular position are collected and sent to the speed loop for calculation to obtain the torque current setting. The difference between the given current and the feedback current is sent to the current loop, and the three-phase modulation reference voltage U is obtained through the current loop calculation. d1 U q1 . Set the reference voltage U d1 U q1The three-phase space vector pulse width modulation is input to calculate the specific driving information of each power module to complete the wave transmission. In addition, the three-phase winding XYZ drive signal is set low to perform wave sealing processing on the power module.

[0149] Step 2: Bus voltage U dc Sampling is performed and the modulus of the minimum sampling vector is calculated according to formula (4):

[0150]

[0151] Where U Min is the minimum sampling vector; T Min is the minimum sampling time.

[0152] In this embodiment, the motor speed is set to 40 r / min (0.32 pu), the load torque is 110 N·m, and the DC bus voltage is 550 V. At this time, the XYZ three-phase winding reference voltage amplitude is 55 V, the minimum sampling time is 2 μs, and the switching period corresponding to a 25 kHz switching frequency is 40 μs.

[0153]

[0154] According to the quadrature axis voltage u output by the ABC current loop q1 and direct axis voltage u d1 Calculate the ABC reference voltage modulus |u ref-ABC |

[0155]

[0156] The switching state is judged according to formula (6). When formula (6) is satisfied, the state variable Mode = 0 and the system continues to operate in the low modulation ratio area, returning to step 1 to complete the ABC three-phase winding drive.

[0157] |u ref-ABC |≤2.1|U Min | (6)

[0158] When equation (6) is not satisfied, the state variable Mode=1 and the system enters the normal modulation ratio region and proceeds to step 3.

[0159] In this embodiment, |u ref-ABC |=55≤2.1|U Min |=2.1×37=74V; In this state, the switching condition is not met, so the state variable Mode=0. The system maintains operation in the low modulation ratio area and adopts a single three-phase winding operation drive scheme.

[0160] The motor suddenly increases from the low-modulation operating region (40 r / min (0.32 pu) and 110 N·m load) to the normal modulation ratio operating region (125 r / min (1 pu) and 1069 N·m load). At this point, Equation (6) is no longer satisfied, so the state variable system enters the normal modulation ratio region. At this point, a drive scheme with two sets of three-phase windings operating in coordination is adopted, using RHPWM for modulation.

[0161] Step 3: In the normal modulation ratio region, the two sets of three-phase windings operate in coordination, and the sum of the lower arm currents of the B, C, Y, and Z phases in the two sets of three-phase windings is sampled at different sampling vector combinations. The six-phase current reconstruction expression in the normal modulation ratio region is used to complete the six-phase current reconstruction. The reconstructed six-phase current and the sampled speed are sent into the loop for calculation to obtain the modulation reference voltage, and the modulation reference voltage of the quadrature axis is limited. All modulation reference voltages are subjected to hybrid pulse width modulation (RHPWM) to complete the power module drive.

[0162] The area enclosed by the voltage vector U1 and the voltage vector U2 in space is sector I;

[0163] The area enclosed by the voltage vector U2 and the voltage vector U3 in space is sector II;

[0164] The area enclosed by the voltage vector U3 and the voltage vector U4 in space is sector III;

[0165] The area enclosed by the voltage vector U4 and the voltage vector U5 in space is sector IV;

[0166] The area enclosed by the voltage vector U5 and the voltage vector U6 in space is sector V;

[0167] The area enclosed by the voltage vector U6 and the voltage vector U1 in space is sector VI;

[0168] For sectors I to VI, the midline within each sector is taken, and the area surrounded by the midline of sector I and the midline of sector VI is the normal modulation ratio area G1;

[0169] The area enclosed by the midline of sector II and the midline of sector I is the normal modulation ratio area G2;

[0170] The area enclosed by the midline of sector II and the midline of sector III is the normal modulation ratio area G3;

[0171] The area enclosed by the midline of sector III and the midline of sector IV is the normal modulation ratio area G4;

[0172] The area enclosed by the midline of sector IV and the midline of sector V is the normal modulation ratio area G5;

[0173] The area enclosed by the midline of sector V and the midline of sector VI is the normal modulation ratio area G6;

[0174] Among them, the normal modulation ratio region G1 and the normal modulation ratio region G4 are zero vector modification regions, the normal modulation ratio region G1 includes the normal modulation ratio region G1-Ⅰ and the normal modulation ratio region G1-Ⅱ, the region surrounded by the midline of sector VI and the voltage vector U1 is the normal modulation ratio region G1-Ⅰ, and the region surrounded by the midline of sector I and the voltage vector U1 is the normal modulation ratio region G1-Ⅱ;

[0175] The normal modulation ratio region G4 includes the normal modulation ratio region G4-I and the normal modulation ratio region G4-II. The region surrounded by the midline of sector III and the voltage vector U4 is the normal modulation ratio region G4-I, and the region surrounded by the midline of sector IV and the voltage vector U4 is the normal modulation ratio region G4-II.

[0176] Shift the carrier of three-phase winding XYZ by 0.25T s In the normal modulation ratio area G1-Ⅰ and the normal modulation ratio area G4-Ⅰ, SVPWM modulation is normally adopted, and then the A and B phase drive signals are inverted and interchanged, and the zero vectors U0 and U7 are replaced by the opposite effective vectors U2 and U5 respectively; in the normal modulation ratio area G1-Ⅱ and the normal modulation ratio area G4-Ⅱ, SVPWM modulation is normally adopted, and then the A and C phase drive signals are inverted and interchanged, and the zero vectors U0 and U7 are replaced by the opposite effective vectors U6 and U3 respectively.

[0177] In the normal modulation ratio area G2, G3, G5, and G6 all use SVPWM for modulation.

[0178] When the reference voltage vector is located at G1-Ⅰ, sampling is performed at the switching vector combinations ABC-U2 XYZ-U1, ABC-U5XYZ-U1, ABC-U1 XYZ-U2, and ABC-U1 XYZ-U5 to obtain the sampling currents I1I2I3I4.

[0179] When the reference voltage vector is located at G1-II, sampling is performed at the switching vector combinations ABC-U6 XYZ-U1, ABC-U3XYZ-U1, ABC-U1 XYZ-U6, and ABC-U1 XYZ-U3 to obtain the sampling currents I1I2I3I4.

[0180] When the reference voltage vector is located at G2, sampling is performed at the switching vector combinations ABC-U0 XYZ-U2, ABC-U7 XYZ-U2, ABC-U2 XYZ-U0, and ABC-U2 XYZ-U7 to obtain the sampling currents I1I2I3I4.

[0181] When the reference voltage vector is located at G3, sampling is performed at the switching vector combinations ABC-U0 XYZ-U3, ABC-U7 XYZ-U3, ABC-U3 XYZ-U0, and ABC-U3 XYZ-U7 to obtain the sampling currents I1I2I3I4.

[0182] When the reference voltage vector is located at G4-Ⅰ, sampling is performed at the switching vector combinations ABC-U2 XYZ-U4, ABC-U5XYZ-U4, ABC-U4 XYZ-U2, and ABC-U4 XYZ-U5 to obtain the sampling currents I1I2I3I4.

[0183] When the reference voltage vector is located at G4-II, sampling is performed at the switching vector combinations ABC-U2 XYZ-U1, ABC-U5XYZ-U1, ABC-U1 XYZ-U2, and ABC-U1 XYZ-U5 to obtain the sampling currents I1I2I3I4.

[0184] When the reference voltage vector is located at G5, sampling is performed at the switching vector combinations ABC-U0 XYZ-U5, ABC-U7 XYZ-U5, ABC-U5 XYZ-U0, and ABC-U5 XYZ-U7 to obtain the sampling currents I1I2I3I4.

[0185] When the reference voltage vector is located at G6, sampling is performed at the switching vector combinations ABC-U0 XYZ-U6, ABC-U7 XYZ-U6, ABC-U6 XYZ-U0, and ABC-U6 XYZ-U7 to obtain the sampling currents I1I2I3I4.

[0186] According to the operating voltage vectors of the two sets of three-phase windings at the sampling location, the corresponding relationship between the sampling current and the phase current is obtained by querying Table 2. Combined with the current constraint relationship (7), the six-phase current reconstruction expression can be solved.

[0187]

[0188] Table 2 Correspondence between current sensor sampling results and phase current under different voltage vectors

[0189] <![CDATA[U i ]]> <![CDATA[U0]]> <![CDATA[U7]]> <![CDATA[U1]]> <![CDATA[U2]]> <![CDATA[U3]]> <![CDATA[U4]]> <![CDATA[U5]]> <![CDATA[U6]]> Isum-ABC <![CDATA[-i A ]]> 0 <![CDATA[-i A ]]> <![CDATA[i C ]]> <![CDATA[i C ]]> 0 <![CDATA[i B ]]> <![CDATA[i B ]]> Isum-XYZ <![CDATA[-i X ]]> 0 <![CDATA[-i X ]]> <![CDATA[i Z ]]> <![CDATA[i Z ]]> 0 <![CDATA[i Y ]]> <![CDATA[i Y ]]>

[0190] Taking the modulation ratio normal region G1-I as an example, during the time period when the switching vector combination's first three-phase winding ABC voltage vector U2 overlaps with the XYZ voltage vector U1, sampling is performed to obtain sampled current I1. During the time period when the switching vector combination's first three-phase winding ABC voltage vector U5 overlaps with the XYZ voltage vector U1, sampling is performed to obtain sampled current I2. During the time period when the switching vector combination's first three-phase winding ABC voltage vector U1 overlaps with the XYZ voltage vector U2, sampling is performed to obtain sampled current I3. During the time period when the switching vector combination's first three-phase winding ABC voltage vector U1 overlaps with the XYZ voltage vector U5, sampling is performed to obtain sampled current I4.

[0191] According to the operating voltage vectors of the two sets of three-phase windings at the sampling location, the corresponding relationship between the sampled current and the phase current is obtained by querying Table 2, and the phase current matrix is ​​solved to complete the six-phase current reconstruction. Take the modulation ratio normal area G1-Ⅰ as an example:

[0192] The sampled current I1 is obtained by sampling during the period when the ABC voltage vector U2 overlaps with the XYZ voltage vector U1. From Table 2, it can be seen that the current generated by the ABC voltage vector U2 in the current sensor is i C , XYZ voltage vector U1 in current sensor -i X , the two are superimposed and we can see that the sampling current i C -i X .

[0193] The sampled current I2 is obtained by sampling during the period when the ABC voltage vector U5 overlaps with the XYZ voltage vector U1. From Table 2, it can be seen that the current generated by the ABC voltage vector U5 in the current sensor is i B , XYZ voltage vector U1 in current sensor -i X , the two are superimposed and we can see that the sampling current i B -i X .

[0194] The sampled current I3 is obtained by sampling during the period when the ABC voltage vector U1 overlaps with the XYZ voltage vector U2. From Table 2, it can be seen that the current generated by the ABC voltage vector U1 in the current sensor is -i A , XYZ voltage vector U2 in the current sensor i Z , the two are superimposed and we can see that the sampling current -i A +i Z .

[0195] The sampled current I4 is obtained by sampling during the period when the ABC voltage vector U1 overlaps with the XYZ voltage vector U5. From Table 2, it can be seen that the current generated by the ABC voltage vector U1 in the current sensor is -i A , XYZ voltage vector U5 in current sensor -iY , the two are superimposed and we can see that the sampling current -i A -i Y .

[0196] Therefore, the corresponding relationship between the sampling current and the phase current is:

[0197]

[0198] In combination with the current constraint equation (7), the following corresponding relationship can be obtained:

[0199]

[0200] By inverting equation (8), we can get the current reconstruction expression at this time:

[0201]

[0202] According to the above solution process, the current reconstruction expressions of different reconstruction groups are summarized in Table 3;

[0203] Table 3 Current sensor sampling results and current reconstruction expressions for different reconstruction groups

[0204]

[0205]

[0206]

[0207] Substituting the sampled current into Table 3 can complete the six-phase current reconstruction.

[0208] In the normal modulation ratio area, when switching from the zero vector transition boundary to the normal modulation ratio area, the calculation method of the sampling currents I1 and I3 is changed;

[0209] The zero vector transition boundary includes the center lines of sectors I, III, IV, and V, voltage vector U1, and voltage vector U4;

[0210] When the reference voltage vector crosses the center line of sector I and switches from the normal modulation ratio region G1-II to the normal modulation ratio region G2, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0211]

[0212] Where i' A represents the current of phase A in the three-phase winding ABC of the dual three-phase permanent magnet synchronous motor in the last switching cycle, i' B Indicates the current of phase B in the three-phase winding ABC in the last switching cycle, i' CIndicates the current of phase C in the three-phase winding ABC in the last switching cycle, i' X Indicates the current of phase X in the three-phase winding XYZ in the last switching cycle, i' Y Indicates the current of phase Y in the three-phase winding XYZ in the last switching cycle, i' Z Indicates the current of phase Z in the three-phase winding XYZ in the previous switching cycle;

[0213] When the reference voltage vector crosses the center line of sector III and switches from the normal modulation ratio region G3 to the normal modulation ratio region G4-I, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0214]

[0215] When the reference voltage vector passes through the voltage vector U4 and switches from the normal modulation ratio region G4-I to the normal modulation ratio region G4-II, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0216]

[0217] When the reference voltage vector crosses the center line of sector IV and switches from the normal modulation ratio region G4-II to the normal modulation ratio region G5, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampled currents I1 and I3 are updated as follows:

[0218]

[0219] When the reference voltage vector crosses the midline of sector VI and switches from the normal modulation ratio region G6 to the normal modulation ratio region G1-I, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0220]

[0221] When the reference voltage vector passes through the voltage vector U1 and switches from the normal modulation ratio region G1-I to the normal modulation ratio region G1-II, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

[0222]

[0223] The following uses the zero vector transition boundary from the modulation ratio normal region G6 to the modulation ratio normal region G1-I as an example to explain the reconstruction error suppression method when switching sectors at the zero vector transition boundary:

[0224] As shown in Figure 5(d), when the reference voltage vector switches from the modulation ratio normal region G6 to the modulation ratio normal region G1-I, the reference voltage crosses the dividing line in sector VI. In the first switching cycle of the modulation ratio normal region G1-I, its I1 sampling vector combination becomes the ABC three-phase winding U0 and the XYZ three-phase winding U1, which is inconsistent with the vector combination of the ABC three-phase winding U2 and the XYZ three-phase winding U1 corresponding to the modulation ratio normal region G1-I sampling current I1. At the same time, the I3 sampling vector combination becomes the ABC three-phase winding U1 and the XYZ three-phase winding U0, which is inconsistent with the vector combination of the ABC three-phase winding U1 and the XYZ three-phase winding U2 corresponding to the modulation ratio normal region G1-I sampling current I1. If the sampling currents I1 and I3 are continued to be used to complete the current reconstruction at this time, it will bring about a large reconstruction error. Therefore, according to formula (11), I1 and I3 are corrected and combined with the actual sampling I2 and I4 to complete the six-phase current reconstruction. While reducing the reconstruction error, a large number of prediction operations are saved.

[0225] Substitute the reconstructed current into equation (3) in units of three phases to complete the Clark-Park transformation, and obtain two sets of torque current feedback values ​​i q1 i q2 and the excitation current feedback value i d1 i d2 The difference between the current feedback value and the set value is fed into the current loop for calculation. The output reference quadrature-axis voltage is limited to a minimum sampling voltage vector of 37V. The current loop then calculates the six-phase modulation reference voltage. This reference voltage is fed into the RHPWM to drive the power module.

[0226] The angular speed is sampled and sent to the speed loop for calculation to obtain the torque current setting. The torque current setting of the two sets of three-phase windings is equal, and the six-phase current coordinate transformation is reconstructed to obtain the quadrature and direct axis current feedback i d1 i q1 i d2 i q2 Combined with the torque given current, the current loop operation is performed to obtain the six-phase modulation reference voltage U d1 U q1 U d2 U q2 At the same time, to prevent the given voltage from being less than the minimum sampling vector in transient transition, the lower limit of the output reference quadrature-axis voltage is limited by equation (17). The reference voltage is sent to the six-phase modulation to complete the power module drive.

[0227]

[0228] Step 4: Judge the switching state according to formula (18). When formula (18) is satisfied, the state variable Mode = 1 and the system continues to operate in the normal modulation ratio area, completing the drive of two sets of three-phase windings.

[0229] |u ref-ABC |≤1.1|U Min | (18)

[0230] When equation (18) is not satisfied, the system re-enters the low modulation ratio region and proceeds to step 1.

[0231] In this embodiment, the system operates at a rated operating reference voltage of 183V. Equation (18) is not satisfied, so the state variable remains at Mode = 1. The system maintains operation in the positive modulation ratio constant modulation region, using a drive scheme that uses two sets of three-phase windings to operate in coordination. When Equation (18) is satisfied again, the system re-enters the single three-phase winding operation state and initializes the loop parameters corresponding to ABC.

[0232] Figure 8(a) to Figure 8(c) The waveforms of ABC three-phase actual current, ABC three-phase reconstructed current, XYZ three-phase actual current and XYZ three-phase reconstructed current are given in the dynamic switching process. Figure 8(a) to Figure 8(c) As can be seen, the proposed method effectively eliminates the low-modulation-ratio reconstruction blind zone. Throughout the dynamic process, the DTP-PMSM's three-phase reconstructed current can smoothly transition from the low-modulation-ratio region to the normal-modulation-ratio region. Furthermore, the reconstructed current of phase A closely follows the measured current.

[0233] Because the reconstruction method of the present invention only involves low-modulation-ratio current reconstruction, reconstruction topology, and switching control methods, this implementation imposes no constraints on the controller, DTP-PMSM phase angle, and other factors. This embodiment is also applicable to applications where a 30° phase-shift DTP-PMSM speed loop controller uses an active disturbance rejection controller, and a current loop controller uses a proportional resonant controller.

[0234] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A control method for a dual three-phase permanent magnet synchronous motor in a low modulation ratio region, characterized in that: The method comprises: Step 1: In the low modulation ratio area, the three-phase winding ABC operates independently, the three-phase winding XYZ performs wave sealing processing, and the sum of the lower bridge arm currents of the two phases B and C in the three-phase winding ABC is sampled. The low modulation ratio three-phase current reconstruction is completed according to the three-phase current reconstruction expression in the low modulation ratio area; the reconstructed three-phase current and the sampled speed are sent into the loop for calculation to obtain the three-phase modulation reference voltage, and the power module is driven by low modulation ratio hybrid pulse width modulation; Step 2: Calculate the minimum sampling vector |U according to the minimum sampling time Min |, determine the reference voltage modulus of the three-phase winding ABC |u ref-ABC |Is it satisfied? |u ref-ABC |≤2.1|U Min |, if yes, return to step 1, if no, go to step 3; Step 3: In the normal modulation ratio area, the two sets of three-phase windings are operated in coordination, and the sum of the lower bridge arm currents of the B, C, Y, and Z phases in the two sets of three-phase windings is sampled at different sampling vector combinations. The six-phase current reconstruction is completed according to the six-phase current reconstruction expression in the normal modulation ratio area, and the reconstructed six-phase current and the sampling speed are sent into the loop for calculation to obtain the modulation reference voltage, and the modulation reference voltage of the quadrature axis is limited. All modulation reference voltages are subjected to hybrid pulse width modulation RHPWM to complete the power module drive; Step 4: Determine the reference voltage modulus of the three-phase winding XYZ |u ref-ABC |Is it satisfied? |u ref-ABC |≤1.1|U Min |, if yes, go to step 1, if no, go to step 3.

2. The control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio area according to claim 1 is characterized in that: The method for obtaining the three-phase current reconstruction expression in the low modulation ratio area includes: Construct a low modulation ratio reconstruction area: S A , S B , S C , S X , S Y , S Z They are the six-phase bridge arm switching functions of the dual three-phase permanent magnet synchronous motor, a value of 0 represents the lower bridge arm is turned on, and a value of 1 represents the upper bridge arm is turned on; When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z =0 corresponds to voltage vector U0; When S A =1, S B =0, S C =0 or S X =1, S Y =0, S Z =0 corresponds to voltage vector U1; When S A =1, S B =1, S C =0 or S X =1, S Y =1, S Z =0 corresponds to voltage vector U2; When S A =0, S B =1, S C =0 or S X =0, S Y =1, S Z =0 corresponds to voltage vector U3; When S A =0, S B =1, S C =1 or S X =0, S Y =1, S Z =1 corresponds to voltage vector U4; When S A =0, S B =0, S C =1 or S X =0, S Y =0, S Z =1 corresponds to voltage vector U5; When S A =1, S B =0, S C =1 or S X =1, S Y =0, S Z =1 corresponds to voltage vector U6; When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z =1 corresponds to voltage vector U7; The area enclosed by the voltage vector U1 and the voltage vector U2 in space is the low modulation ratio reconstruction area L1; The area surrounded by the voltage vector U2 and the voltage vector U3 in space is the low modulation ratio reconstruction area L2; The area surrounded by the voltage vector U3 and the voltage vector U4 in space is the low modulation ratio reconstruction area L3; The area surrounded by the voltage vector U4 and the voltage vector U5 in space is the low modulation ratio reconstruction area L4; The area surrounded by the voltage vector U5 and the voltage vector U6 in space is the low modulation ratio reconstruction area L5; The area surrounded by the voltage vector U6 and the voltage vector U1 in space is the low modulation ratio reconstruction area L6; According to the different low modulation ratio reconstruction regions where the reference voltage vector is located, the three-phase current reconstruction expression is: Among them, 0T s , 0.5T s Represents a switching cycle T s Two sampling moments within ; i A Represents the current of phase A in the three-phase winding ABC; i B Represents the current of phase B in three-phase winding ABC; i C Represents the current of phase C in the three-phase winding ABC.

3. The control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio area according to claim 2 is characterized in that: Low modulation ratio hybrid pulse width modulation includes: When the reference voltage vector is located in the low modulation ratio reconstruction area L1 or L4, SVPWM modulation is normally adopted, and then the A and C phase drive signals are inverted and then interchanged; When the reference voltage vector is located in the low modulation ratio reconstruction area L2, SVPWM modulation is normally adopted, and then the B phase drive signal is inverted and used for C phase drive; When the reference voltage vector is located in the low modulation ratio reconstruction area L3 or L6, SVPWM modulation is normally adopted, and then the A and B phase drive signals are inverted and then interchanged; When the reference voltage vector is located in the low modulation ratio reconstruction region L5, SVPWM modulation is normally adopted, and then the C-phase driving signal is inverted and used for B-phase driving.

4. The control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio area according to claim 1 is characterized in that: The method for obtaining the six-phase current expression in the normal modulation ratio region includes: S A , S B , S C , S X , S Y , S Z They are the six-phase bridge arm switching functions of the dual three-phase permanent magnet synchronous motor, a value of 0 represents the lower bridge arm is turned on, and a value of 1 represents the upper bridge arm is turned on; When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z =0 corresponds to voltage vector U0; When S A =1, S B =0, S C =0 or S X =1, S Y =0, S Z =0 corresponds to voltage vector U1; When S A =1, S B =1, S C =0 or S X =1, S Y =1, S Z =0 corresponds to voltage vector U2; When S A =0, S B =1, S C =0 or S X =0, S Y =1, S Z =0 corresponds to voltage vector U3; When S A =0, S B =1, S C =1 or S X =0, S Y =1, S Z =1 corresponds to voltage vector U4; When S A =0, S B =0, S C =1 or S X =0, S Y =0, S Z =1 corresponds to voltage vector U5; When S A =1, S B =0, S C =1 or S X =1, S Y =0, S Z =1 corresponds to voltage vector U6; When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z =1 corresponds to voltage vector U7; The area enclosed by the voltage vector U1 and the voltage vector U2 in space is sector I; The area enclosed by the voltage vector U2 and the voltage vector U3 in space is sector II; The area enclosed by the voltage vector U3 and the voltage vector U4 in space is sector III; The area enclosed by the voltage vector U4 and the voltage vector U5 in space is sector IV; The area enclosed by the voltage vector U5 and the voltage vector U6 in space is sector V; The area enclosed by the voltage vector U6 and the voltage vector U1 in space is sector VI; Take the midline of sectors I to VI respectively, and the area surrounded by the midline of sector I and the midline of sector VI is the normal modulation ratio area G1; The area surrounded by the midline of sector II and the midline of sector I is the normal modulation ratio area G2; The area surrounded by the midline of sector II and the midline of sector III is the modulation ratio normal area G3; The area surrounded by the midline of sector III and the midline of sector IV is the modulation ratio normal area G4; The area surrounded by the midline of sector IV and the midline of sector V is the modulation ratio normal area G5; The area surrounded by the midline of sector V and the midline of sector VI is the normal modulation ratio area G6; Among them, the normal modulation ratio region G1 and the normal modulation ratio region G4 are zero vector modification regions, the normal modulation ratio region G1 includes the normal modulation ratio region G1-Ⅰ and the normal modulation ratio region G1-Ⅱ, the region surrounded by the middle dividing line of sector VI and the voltage vector U1 is the normal modulation ratio region G1-Ⅰ, and the region surrounded by the middle dividing line of sector Ⅰ and the voltage vector U1 is the normal modulation ratio region G1-Ⅱ; The normal modulation ratio region G4 includes the normal modulation ratio region G4-Ⅰ and the normal modulation ratio region G4-Ⅱ. The region surrounded by the middle dividing line of the sector III and the voltage vector U4 is the normal modulation ratio region G4-Ⅰ, and the region surrounded by the middle dividing line of the sector IV and the voltage vector U4 is the normal modulation ratio region G4-Ⅱ. According to the normal area of ​​different modulation ratios of the reference voltage vector, the six-phase current reconstruction expression is: Among them, ABC-U i XYZ-U j Represents the switching period T s The voltage vector corresponding to the inner three-phase winding ABC is U i , the voltage vector corresponding to the three-phase winding XYZ is U j , i=0,1,2,3,4,5,6,7, j=0,1,2,3,4,5,6,7; I1, I2, I3, and I4 represent the currents sampled by the four sampling vector combinations; i X Represents the current of phase X in the three-phase winding XYZ; i Y Represents the current of phase Y in the three-phase winding XYZ; i Z Represents the current of phase Z in the three-phase winding XYZ; i A Represents the current of phase A in the three-phase winding ABC; i B Represents the current of phase B in three-phase winding ABC; i C Represents the current of phase C in the three-phase winding ABC.

5. The control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio region according to claim 4 is characterized in that: Hybrid pulse width modulation RHPWM includes: Shift the carrier of three-phase winding XYZ by 0.25T s SVPWM modulation is adopted in the modulation ratio normal region G1-Ⅰ and the modulation ratio normal region G4-Ⅰ, and then the A-phase and B-phase drive signals in the three-phase winding ABCZ are inverted and then interchanged, and the voltage vectors U0 and U7 are replaced by the voltage vectors U2 and U5 respectively; In the modulation ratio normal area G1-Ⅱ and the modulation ratio normal area G4-Ⅱ, SVPWM modulation is adopted, and then the A and C phase drive signals in the three-phase winding ABCZ are inverted and then interchanged, and the voltage vectors U0 and U7 are replaced by the voltage vectors U6 and U3 respectively; In the normal modulation ratio area G2, G3, G5, and G6, SVPWM is used for modulation.

6. The control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio region according to claim 4 is characterized in that: In the normal modulation ratio area, when switching from the zero vector transition boundary to the normal modulation ratio area, the calculation method of the sampling currents I1 and I3 is changed; The zero vector transition boundary includes the center line of sectors Ⅰ, Ⅲ, Ⅳ, and Ⅴ, the voltage vector U1, and the voltage vector U4; When the reference voltage vector crosses the center line of sector I and switches from the normal modulation ratio region G1-II to the normal modulation ratio region G2, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows: In the formula, i' A represents the current of phase A in the three-phase winding ABC of the double three-phase permanent magnet synchronous motor in the last switching cycle, i' B represents the current of phase B in three-phase winding ABC in the last switching cycle, i' C represents the current of phase C in the three-phase winding ABC in the last switching cycle, i' X represents the current of phase X in the three-phase winding XYZ in the previous switching cycle, i' Y Indicates the current of phase Y in the three-phase winding XYZ in the previous switching cycle, i' Z Indicates the current of phase Z in the three-phase winding XYZ in the previous switching cycle; When the reference voltage vector crosses the center line of sector III, it switches from the modulation ratio normal region G3 to the modulation ratio normal region G4-Ⅰ. In the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows: When the reference voltage vector passes through the voltage vector U4, it switches from the normal modulation ratio region G4-I to the normal modulation ratio region G4-II. In the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows: When the reference voltage vector crosses the center line of sector IV, it switches from the normal modulation ratio region G4-II to the normal modulation ratio region G5. In the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows: When the reference voltage vector crosses the middle line of sector VI and switches from the modulation ratio normal region G6 to the modulation ratio normal region G1-I, in the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows: When the reference voltage vector passes through the voltage vector U1, it switches from the normal modulation ratio region G1-I to the normal modulation ratio region G1-II. In the current reconstruction of the first switching cycle after the switch, I2 and I4 use the current real sampling values, and the sampling currents I1 and I3 are updated as follows:

7. The control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio region according to claim 1, characterized in that: Limit the modulation reference voltage of the quadrature axis: Among them, U q is the modulation reference voltage of the quadrature axis, T s represents the switching period, T min Indicates the minimum sampling time, U dc Indicates the bus voltage.

8. A computer-readable storage device storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the control method of a dual three-phase permanent magnet synchronous motor in a low modulation ratio region as claimed in any one of claims 1 to 7 are implemented.

9. A control device for a dual three-phase permanent magnet synchronous motor in a low modulation ratio region, comprising a storage device, a processor, and a computer program stored in the storage device and executable on the processor, characterized in that: The processor executes the computer program to implement the steps of the control method of the dual three-phase permanent magnet synchronous motor in the low modulation ratio area according to any one of claims 1 to 7.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the control method of a dual three-phase permanent magnet synchronous motor in a low modulation ratio region as claimed in any one of claims 1 to 7 are implemented.

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