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

Abstract

The application discloses a control method of a dual three-phase permanent magnet synchronous motor in a low modulation ratio region, and belongs to the field of motor driving. The application comprises the following steps: in the low modulation ratio region, three-phase windings ABC are independently operated, the sum of the currents of the B and C phase lower bridge arms is sampled, three-phase current reconstruction is performed, the reconstructed three-phase current and the sampling rotating speed are input into a loop for operation to obtain three-phase modulation reference voltage, and then the three-phase modulation reference voltage is sent to a power module for driving after pulse width modulation; in the normal modulation ratio region, two sets of three-phase windings are cooperatively operated, the sum of the currents of the B, C, Y and Z phase lower bridge arms in the two sets of three-phase windings is sampled at different sampling vector combinations, six-phase current reconstruction is performed, the reconstructed six-phase current and the sampling rotating speed are input into a loop for operation to obtain modulation reference voltage, and then the modulation reference voltage is sent to a power module for driving after amplitude limiting and pulse width modulation.

Description

Technical Field

[0001] This invention relates to a control method for a dual three-phase permanent magnet synchronous motor in a low modulation ratio region, belonging to the field of motor drive. Background Technology

[0002] To fully utilize the bus voltage without introducing over-modulation 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 increases, and forward / reverse switching, the motor will enter a low modulation ratio operating region. Although open-loop start-up transition schemes exist for the low modulation ratio region, to ensure system stability, the motor should always operate under closed-loop control. Therefore, eliminating the phase current reconfiguration dead zone in the low modulation ratio region is also essential.

[0003] In the low modulation ratio region, the motor output is relatively low. Traditional solutions for low modulation ratio motors involve modifying the PWM, constructing a sampling vector, and reconfiguring the current. However, this traditional approach significantly impacts current harmonics and may increase switching frequency, thus increasing inverter drive losses. For DTP-PMSM motors, modifying the PWM in the low modulation ratio region using the traditional method requires modifying both sets of three-phase windings. The combined effect of these two sets of windings exacerbates the negative impact on the drive system, and this solution does not fully utilize the characteristics of DTP-PMSM. Since the motor output and speed requirements are lower in the low modulation ratio region, using two sets of three-phase windings to drive the DTP-PMSM in this region reduces system drive efficiency and wastes system resources. Furthermore, the vector coupling introduced by the two sets of three-phase windings operating in the low modulation ratio region further increases the reconfiguration difficulty. When the current reconfiguration scheme differs between the low modulation ratio region and the normal region, a clear and efficient switching control method is needed for different reconfiguration schemes. Traditional current reconfiguration scheme switching under different modulation ratios may lead to difficulties in reconfiguring phase currents over a wide modulation ratio range, indicating room for further optimization.

[0004] The current flows through different paths under different voltage vectors, and the sampling branches corresponding to the current sensors have different phase current information under different paths. Single-path sampling will limit the phase current information. To address this, some researchers have changed the zero vector to the opposite effective vector to construct the reconstruction conditions. This method suffers from large current reconstruction errors during sector switching. The traditional solution is to use predictive control to estimate the sampled current, but this method is computationally complex and wastes controller resources. Summary of the Invention

[0005] To address the issue that DTP-PMSM vector control frequency converter systems require two sets of three-phase windings to work together in the low modulation ratio region, resulting in room for efficiency optimization, this invention provides a control method for dual three-phase permanent magnet synchronous motors in the low modulation ratio region.

[0006] The present invention provides a control method for a low modulation ratio region dual three-phase permanent magnet synchronous motor, comprising:

[0007] Step 1: In the low modulation ratio region, the three-phase windings ABC operate independently, and the three-phase windings XYZ are subjected to wave blocking. The sum of the currents of the lower bridge arms of phases B and C in the three-phase windings 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 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. The power module is driven by low modulation ratio mixed pulse width modulation.

[0008] Step 2: Calculate the minimum sampling vector |U| based on the minimum sampling time. Min | Determine the reference voltage magnitude of the three-phase windings ABC |u ref-ABC |Does it satisfy|u ref-ABC |≤2.1|U Min If yes, return to step 1; otherwise, proceed to step 3.

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

[0010] Step 4: Determine the reference voltage magnitude |u of the three-phase winding XYZ ref-ABC |Does it satisfy|u ref-ABC |≤1.1|U Min If yes, proceed to step 1; otherwise, proceed to step 3.

[0011] As a preferred method, the method for obtaining the three-phase current reconstruction expression in the low modulation ratio region includes:

[0012] Constructing a low modulation ratio reconstruction region:

[0013] S A S B S C S X S Y S ZThese are the six-phase bridge arm switching functions for a dual three-phase permanent magnet synchronous motor. A value of 0 indicates that the lower bridge arm is on, and a value of 1 indicates that the upper bridge arm is on.

[0014] When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z When = 0, the corresponding voltage vector is U0;

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

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

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

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

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

[0020] When S A =1, S B =0, S C =1 or S X =1, S Y =0, S ZWhen = 1, the corresponding voltage vector is U6;

[0021] When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z When = 1, the corresponding voltage vector is U7;

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

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

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

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

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

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

[0028] Based on 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 T represents one switching cycle. s Two sampling times within;

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

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

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

[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 located in the low modulation ratio reconstruction region L3 or L6, SVPWM modulation is normally used, and then the A and B phase drive signals are inverted and interchanged.

[0036] When the reference voltage vector is in the low modulation ratio reconstruction region L5, SVPWM modulation is normally used, 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 of the modulation ratio normal region includes:

[0038] S A S B S C S X S Y S Z These are the six-phase bridge arm switching functions for a dual three-phase permanent magnet synchronous motor. A value of 0 indicates that the lower bridge arm is on, and a value of 1 indicates that the upper bridge arm is on.

[0039] When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z When = 0, the corresponding voltage vector is U0;

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

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

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

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

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

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

[0046] When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z When = 1, the corresponding voltage vector is U7;

[0047] The region enclosed by voltage vectors U1 and U2 in space is sector I;

[0048] The region enclosed in space by voltage vectors U2 and U3 is sector II;

[0049] The region enclosed in space by voltage vectors U3 and U4 is sector III;

[0050] The region enclosed in space by voltage vectors U4 and U5 is sector IV;

[0051] The region enclosed in space by voltage vectors U5 and U6 is sector V;

[0052] The region enclosed in space by voltage vectors U6 and U1 is sector VI;

[0053] For sectors I to VI, take the midpoint line within each sector. The area enclosed by the midpoint line of sector I and the midpoint line of sector VI is the normal modulation ratio region G1.

[0054] The region enclosed by the midpoint line of sector II and the midpoint line of sector I is the normal modulation ratio region G2;

[0055] The region enclosed by the midpoint line of sector II and the midpoint line of sector III is the normal modulation ratio region G3;

[0056] The region enclosed by the midpoint line of sector III and the midpoint line of sector IV is the normal modulation ratio region G4;

[0057] The region enclosed by the midpoint line of sector IV and the midpoint line of sector V is the normal modulation ratio region G5;

[0058] The region enclosed by the midpoint of sector V and the midpoint of sector VI is the normal modulation ratio region 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 enclosed by the midpoint of sector VI and the voltage vector U1 is the normal modulation ratio region G1-Ⅰ, and the region enclosed by the midpoint 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 enclosed by the midline of sector Ⅲ and the voltage vector U4 is the normal modulation ratio region G4-Ⅰ, and the region enclosed by the midline of sector Ⅳ and the voltage vector U4 is the normal modulation ratio region G4-Ⅱ.

[0061] Based on the normal region of different modulation ratios where the reference voltage vector is located, 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 three-phase windings 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 combination of four sampling vectors; i X This represents the current in phase X of the three-phase winding XYZ; i Y This represents the current in the Y phase of a three-phase winding XYZ; iZ This represents the current in phase Z of the three-phase winding XYZ; i A This represents the current in phase A of the three-phase winding ABC; i B This represents the current in phase B of a three-phase winding ABC; i C This represents the current in phase C of the three-phase winding ABC.

[0067] Preferably, hybrid pulse width modulation (RHPWM) includes:

[0068] The carrier wave of the three-phase winding XYZ is shifted by 0.25T. s In the normal modulation ratio region G1-Ⅰ and the normal modulation ratio region G4-Ⅰ, SVPWM modulation is used. Then, the A and B phase drive signals in the three-phase winding ABCZ are inverted and interchanged, and the voltage vectors U0 and U7 are replaced with voltage vectors U2 and U5 respectively.

[0069] SVPWM modulation is used in the normal modulation ratio region G1-Ⅱ and the normal modulation ratio region G4-Ⅱ. Then, the A and C phase drive signals in the three-phase winding ABCZ are inverted and interchanged, and the voltage vectors U0 and U7 are replaced with voltage vectors U6 and U3 respectively.

[0070] In the modulation ratio normal regions G2, G3, G5, and G6, SVPWM modulation is used.

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

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

[0073] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0074]

[0075] In the formula, i' A i' represents the current in phase A of the three-phase winding ABC of the dual three-phase permanent magnet synchronous motor during the previous switching cycle. B i' represents the current in phase B of the three-phase winding ABC in the previous switching cycle. C i' represents the current in phase C of the three-phase winding ABC in the previous switching cycle. X i' represents the current in phase X of the three-phase winding XYZ in the previous switching cycle. Yi' represents the current in the Y phase of the three-phase winding XYZ in the previous switching cycle. Z This represents the current in phase Z of the three-phase winding XYZ in the previous switching cycle;

[0076] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0077]

[0078] When the reference voltage vector passes through the voltage vector U4, switching 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0079]

[0080] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0081]

[0082] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0083]

[0084] When the reference voltage vector passes through the voltage vector U1, switching 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0085]

[0086] Preferably, 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 T represents the switching period.min U represents the minimum sampling time. dc This indicates the bus voltage.

[0089] The beneficial effects of this invention are that only one set of three-phase windings is required to operate in the low modulation ratio region, which improves the system operating efficiency and reduces the control complexity; this invention can realize phase current reconstruction over a wide range in both the low modulation ratio region and the normal modulation ratio region of the DTP-PMSM drive system; this invention provides a convenient and quick method for suppressing sector switching reconstruction errors. Attached Figure Description

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

[0091] Figure 2 Control flowcharts for DTP-PMSM under different modulation ratios;

[0092] Figure 3 DTP-PMSM low modulation ratio current reconstruction topology;

[0093] Figure 4 This is the reconstruction region between low modulation ratio and normal modulation ratio;

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

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

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

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

[0098] Figure 6 The waveforms of the sampled current and the actual phase currents of the three-phase windings ABC in the low modulation ratio region are shown.

[0099] Figure 7(a) shows the actual phase current waveforms of the three-phase windings ABC;

[0100] Figure 7(b) shows the phase current waveforms of the three-phase winding ABC reconfiguration.

[0101] Figure 7(c) shows the error between the actual current and the reconfigured 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 with different modulation ratios during region switching;

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

[0104] Figure 8(c) Error between the actual current and the reconfigured current of phase A in three-phase winding ABC with different modulation ratios;

[0105] Figure 9(a) shows the actual phase current waveforms of the three-phase windings ABC during motor startup in the low modulation ratio region.

[0106] Figure 9(b) shows the waveform of the three-phase winding ABC reconfiguration phase current during motor startup in the low modulation ratio region.

[0107] Figure 9(c) shows the error between the actual current and the reconfigured current of phase A in the three-phase winding ABC of the motor starting in the low modulation ratio region. Detailed Implementation

[0108] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0109] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

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

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

[0112] Step 1: In the low modulation ratio region, the three-phase windings ABC operate independently, and the three-phase windings XYZ are subjected to wave blocking. The sum of the currents of the lower bridge arms of phases B and C in the three-phase windings 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 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. The power module is driven by low modulation ratio mixed pulse width modulation.

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

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

[0115] In the formula, S A S B S C S X S Y S Z These are the switching functions for the six-phase bridge arms, where a value of 0 indicates that the lower bridge arm is on, and a value of 1 indicates that the upper bridge arm is on; i A This represents the current in phase A of the three-phase winding ABC; i B This represents the current in phase B of a three-phase winding ABC; i C This represents the current in phase C of a three-phase winding ABC; i X This represents the current in phase X of the three-phase winding XYZ; i Y This represents the current in the Y phase of a three-phase winding XYZ; i Z I represents the current in phase Z of a three-phase winding XYZ; SAMPLE This is the sampled value from the current sensor.

[0116] When S A =0, S B =0, S C =0 or S X =0, S Y =0, S Z When = 0, the corresponding voltage vector is U0;

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

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

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

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

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

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

[0123] When S A =1, S B =1, S C =1 or S X =1, S Y =1, S Z When = 1, the corresponding voltage vector is U7;

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

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

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

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

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

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

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

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

[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 located in the low modulation ratio reconstruction region L3 or L6, SVPWM modulation is normally used, and then the A and B phase drive signals are inverted and interchanged.

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

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

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

[0137]

[0138]

[0139] A 30-pole, rated speed of 125 rpm, motor flux linkage of 0.89 Wb, direct-axis and quadrature-axis inductance of 7.1 mH, and stator excitation inductance of 5.1 mH were used in a simulation experiment. A dual three-phase permanent magnet synchronous motor with a 0° phase shift angle was employed, with a switching cycle of 40 μs and two sets of three-phase windings connected in an independent 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 command.

[0140] Start the motor at a set speed of 40 r / min (0.32 pu), according to Figure 2 As shown in the motor switching control flowchart, the motor initially operates in the low modulation ratio region upon startup. For example... Figure 1 The independent three-phase windings ABC in the low modulation ratio region are operating, with XYZ driving the wave blocking, and the torque current setpoint is 0.

[0141] LHPWM modulation is used in the low modulation ratio region, replacing the zero vector with the opposite effective vector. Sampling is performed at two times, 0Ts and 0.5Ts, to obtain the sampled current I. L1 with I L2Based on the reconstruction region where the reference voltage is located, the corresponding reconstruction expression can be found in Table 1. Substituting the sampled current into the reconstruction expression completes the ABC low modulation ratio phase current reconstruction. Taking the low modulation ratio reconstruction region L1 as an example, the reconstruction process is explained as shown in Figure 5(a). I is obtained by sampling at 0Ts and 0.5Ts respectively. L1 I L2 According to Table 1, the reconstruction expression for the low modulation ratio reconstruction region L1 is Equation (2). Substituting the sampling current, the XYZ three-phase current can be reconstructed.

[0142]

[0143] Figures 7(a) to 7(c) The phase current reconstruction results are presented when operating in the low modulation ratio region. Under this condition, the three-phase reconstruction current still maintains good sinusoidal characteristics. As can be seen from the comparison results of the phase A reconstruction current and the measured current and the error curve given in Figure 7(c), the fundamental frequency of the reconstruction current can still follow the actual current well in the low modulation ratio region.

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

[0145] Figures 9(a) to 9(c) The phase current reconstruction results are presented during the dynamic process of the motor moving from zero speed and zero load to a speed of 40 r / min (0.32 pu) and a load of 110 N·m. Figures 9(a) and 9(b) show the actual and reconstructed current waveforms of the three phases A, B, and C at this point, respectively. Figures 9(a) to 9(c) It can be seen that this implementation effectively eliminates the low modulation ratio reconfiguration blind zone. Throughout the dynamic process, the three-phase reconfiguration current of the DTP-PMSM can be smoothly started from the low modulation ratio region.

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

[0147]

[0148] Motor speed and rotational angle are collected. The collected speed data is fed into the speed loop to obtain the torque current command. The difference between the command current and the feedback current is fed into the current loop, and the three-phase modulation reference voltage U is obtained through current loop calculation. d1 U q1 The reference voltage U d1 U q1The three-phase space vector pulse width modulation is input to calculate the specific drive information of each power module, and the waveform is generated. In addition, the XYZ drive signal of the three-phase winding is set low to perform waveform blocking processing on the power module.

[0149] Step 2, check the bus voltage U dc Sampling is performed, and the magnitude of the minimum sampled vector is calculated according to equation (4):

[0150]

[0151] In the formula U Min T is the minimum sampled vector; Min This 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 reference voltage amplitude of the XYZ three-phase windings is 55 V, the minimum sampling time is 2 μs, and the switching cycle corresponds to a 25 kHz switching frequency of 40 μs.

[0153]

[0154] Based on the quadrature-axis voltage u output by the ABC current loop q1 With direct-axis voltage u d1 Calculate the magnitude of the ABC reference voltage |u ref-ABC |

[0155]

[0156] The switching state is judged according to equation (6). When equation (6) is satisfied, the state variable Mode = 0. The system continues to operate in the low modulation ratio region and returns 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 system with state variable Mode = 1 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 region and adopts a drive scheme with single three-phase winding operation.

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

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

[0162] The region enclosed by voltage vectors U1 and U2 in space is sector I;

[0163] The region enclosed in space by voltage vectors U2 and U3 is sector II;

[0164] The region enclosed in space by voltage vectors U3 and U4 is sector III;

[0165] The region enclosed in space by voltage vectors U4 and U5 is sector IV;

[0166] The region enclosed in space by voltage vectors U5 and U6 is sector V;

[0167] The region enclosed in space by voltage vectors U6 and U1 is sector VI;

[0168] For sectors I to VI, take the midpoint line within each sector. The area enclosed by the midpoint line of sector I and the midpoint line of sector VI is the normal modulation ratio region G1.

[0169] The region enclosed by the midpoint line of sector II and the midpoint line of sector I is the normal modulation ratio region G2;

[0170] The region enclosed by the midpoint line of sector II and the midpoint line of sector III is the normal modulation ratio region G3;

[0171] The region enclosed by the midpoint line of sector III and the midpoint line of sector IV is the normal modulation ratio region G4;

[0172] The region enclosed by the midpoint line of sector IV and the midpoint line of sector V is the normal modulation ratio region G5;

[0173] The region enclosed by the midpoint of sector V and the midpoint of sector VI is the normal modulation ratio region 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 enclosed by the midpoint of sector VI and the voltage vector U1 is the normal modulation ratio region G1-Ⅰ, and the region enclosed by the midpoint 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 enclosed by the midline of sector Ⅲ and the voltage vector U4 is the normal modulation ratio region G4-Ⅰ, and the region enclosed by the midline of sector Ⅳ and the voltage vector U4 is the normal modulation ratio region G4-Ⅱ.

[0176] The carrier wave of the three-phase winding XYZ is shifted by 0.25T. s In the normal modulation ratio regions G1-Ⅰ and G4-Ⅰ, SVPWM modulation is normally used. Then, the A and B phase drive signals are inverted and interchanged, and the zero vectors U0 and U7 are replaced with the opposite effective vectors U2 and U5, respectively. In the normal modulation ratio regions G1-Ⅱ and G4-Ⅱ, SVPWM modulation is normally used. Then, the A and C phase drive signals are inverted and interchanged, and the zero vectors U0 and U7 are replaced with the opposite effective vectors U6 and U3, respectively.

[0177] In the modulation ratio normal regions G2, G3, G5, and G6, SVPWM modulation is used.

[0178] When the reference voltage vector is located at G1-Ⅰ, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U2 XYZ-U1, ABC-U5XYZ-U1, ABC-U1 XYZ-U2, and ABC-U1 XYZ-U5 respectively.

[0179] When the reference voltage vector is located at G1-II, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U6 XYZ-U1, ABC-U3XYZ-U1, ABC-U1 XYZ-U6, and ABC-U1 XYZ-U3 respectively.

[0180] When the reference voltage vector is located at G2, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U0 XYZ-U2, ABC-U7 XYZ-U2, ABC-U2 XYZ-U0, and ABC-U2 XYZ-U7 respectively.

[0181] When the reference voltage vector is located at G3, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U0 XYZ-U3, ABC-U7 XYZ-U3, ABC-U3 XYZ-U0, and ABC-U3 XYZ-U7 respectively.

[0182] When the reference voltage vector is located at G4-Ⅰ, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U2 XYZ-U4, ABC-U5XYZ-U4, ABC-U4 XYZ-U2, and ABC-U4 XYZ-U5 respectively.

[0183] When the reference voltage vector is located at G4-II, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U2 XYZ-U1, ABC-U5XYZ-U1, ABC-U1 XYZ-U2, and ABC-U1 XYZ-U5 respectively.

[0184] When the reference voltage vector is located at G5, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U0 XYZ-U5, ABC-U7 XYZ-U5, ABC-U5 XYZ-U0, and ABC-U5 XYZ-U7 respectively.

[0185] When the reference voltage vector is located at G6, the sampling currents I1I2I3I4 are obtained by sampling at the switch vector combinations ABC-U0 XYZ-U6, ABC-U7 XYZ-U6, ABC-U6 XYZ-U0, and ABC-U6 XYZ-U7 respectively.

[0186] Based on the operating voltage vectors of the two sets of three-phase windings at the sampling point, the corresponding relationship between the sampling current and the phase current can be obtained from 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 normal modulation ratio region G1-Ⅰ as an example, sampling current I1 is obtained during the time period when the voltage vector U2 of the first three-phase winding ABC of the switching vector combination overlaps with the voltage vector U1 of the XYZ. Sampling current I2 is obtained during the time period when the voltage vector U5 of the first three-phase winding ABC of the switching vector combination overlaps with the voltage vector U1 of the XYZ. Sampling current I3 is obtained during the time period when the voltage vector U1 of the first three-phase winding ABC of the switching vector combination overlaps with the voltage vector U2 of the XYZ. Sampling current I4 is obtained during the time period when the voltage vector U1 of the first three-phase winding ABC of the switching vector combination overlaps with the voltage vector U5 of the XYZ.

[0191] Based on the operating voltage vectors of the two sets of three-phase windings at the sampling point, the correspondence between the sampling current and the phase current is obtained from Table 2. Solving for the phase current matrix completes the six-phase current reconstruction. Taking the normal modulation ratio region G1-Ⅰ as an example:

[0192] The sampling current I1 obtained during the time period when the ABC voltage vector U2 and the XYZ voltage vector U1 overlap is shown in Table 2. The current i generated by the ABC voltage vector U2 in the current sensor is... C The XYZ voltage vector U1 in the current sensor is -i X By superimposing the two, we can see that the sampling current i C -i X .

[0193] The sampling current I2 obtained during the time period when the ABC voltage vector U5 and the XYZ voltage vector U1 overlap, according to Table 2, is the current i generated by the ABC voltage vector U5 in the current sensor. B The XYZ voltage vector U1 in the current sensor is -i X By superimposing the two, we can see that the sampling current i B -i X .

[0194] The sampling current I3 obtained during the time period when the ABC voltage vector U1 and the XYZ voltage vector U2 overlap is shown in Table 2. The current generated by the ABC voltage vector U1 in the current sensor is -i. A The XYZ voltage vector U2 in the current sensor i Z By superimposing the two, we can see that the sampling current -i A +i Z .

[0195] The sampling current I4 obtained during the time period when the ABC voltage vector U1 and the XYZ voltage vector U5 overlap, according to Table 2, is -i. A The XYZ voltage vector U5 in the current sensor is -iY By superimposing the two, we can see that the sampling current -i A -i Y .

[0196] Therefore, the relationship between the sampling current and the phase current at this time is:

[0197]

[0198] Combining the current constraint relationship (7), the following correspondence can be obtained:

[0199]

[0200] Inverting equation (8) yields the current reconstruction expression at this point:

[0201]

[0202] Based on the above solution process, the current reconstruction expressions for different reconstruction groups are summarized in Table 3;

[0203] Table 3. Sampling results of current sensors in different reconstruction groups and current reconstruction expressions.

[0204]

[0205]

[0206]

[0207] The six-phase current reconstruction can be completed by substituting the sampled current into Table 3.

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

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

[0210] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0211]

[0212] In the formula, i' A i' represents the current in phase A of the three-phase winding ABC of the dual three-phase permanent magnet synchronous motor during the previous switching cycle. B i' represents the current in phase B of the three-phase winding ABC in the previous switching cycle. Ci' represents the current in phase C of the three-phase winding ABC in the previous switching cycle. X i' represents the current in phase X of the three-phase winding XYZ in the previous switching cycle. Y i' represents the current in the Y phase of the three-phase winding XYZ in the previous switching cycle. Z This represents the current in phase Z of the three-phase winding XYZ in the previous switching cycle;

[0213] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0214]

[0215] When the reference voltage vector passes through the voltage vector U4, switching 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0216]

[0217] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0218]

[0219] When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0220]

[0221] When the reference voltage vector passes through the voltage vector U1, switching 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows:

[0222]

[0223] The following example, using the zero-vector transition boundary from the normal modulation ratio region G6 to the normal modulation ratio region G1-Ⅰ, illustrates 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 normal modulation ratio region G6 to the normal modulation ratio region G1-Ⅰ, the reference voltage crosses the branch line of sector VI. In the first switching cycle of the normal modulation ratio region G1-Ⅰ, the I1 sampling vector combination becomes the ABC three-phase winding U0 and the XYZ three-phase winding U1, which does not match the vector combination of the sampling current I1 in the normal modulation ratio region G1-Ⅰ, the ABC three-phase winding U2 and the XYZ three-phase winding U1; at the same time, the I3 sampling vector combination becomes the ABC three-phase winding U1 and the XYZ three-phase winding U0, which does not match the vector combination of the sampling current I1 in the normal modulation ratio region G1-Ⅰ, the ABC three-phase winding U1 and the XYZ three-phase winding U2. If the sampling currents I1 and I3 are used to complete the current reconstruction at this time, it will bring a large reconstruction error. Therefore, I1 and I3 are corrected according to equation (11) and combined with the actual sampled I2 and I4 to complete the six-phase current reconstruction, which reduces the reconstruction error and saves a lot of prediction calculations.

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

[0226] The rotational speed is sampled and fed into the speed loop to obtain the torque current command. Since the torque current commands of the two sets of three-phase windings are equal, the six-phase current coordinate transformation is reconstructed to obtain the quadrature-direct axis current feedback i. d1 i q1 i d2 i q2 The six-phase modulated reference voltage U is obtained by combining the torque reference current with the current loop operation. d1 U q1 U d2 U q2 To prevent the given voltage from falling below the minimum sampling vector during transient transitions, the lower limit of the output reference quadrature-axis voltage is limited by equation (17). The reference voltage is then fed into the six-phase modulation to drive the power module.

[0227]

[0228] Step 4: Judge the switching state according to equation (18). When equation (18) is satisfied, the state variable Mode = 1. The system continues to operate in the normal modulation ratio region and completes the driving 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 condition reference voltage of 183V, which does not satisfy equation (18). Therefore, the state variable remains Mode = 1, and the system maintains operation in the positive modulation ratio versus normal modulation region, employing a drive scheme with two sets of three-phase windings operating in coordination. When equation (18) is satisfied again, the system will re-enter the state of single three-phase winding operation, and at the same time, the loop parameters corresponding to ABC will be initialized.

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

[0233] Since the reconstruction method of this invention only involves low modulation ratio current reconstruction methods, reconstruction topologies, and switching control methods, this embodiment does not impose constraints on the controller, DTP-PMSM phase band angle, etc. This embodiment is also applicable to applications such as 30° phase-shifted DTP-PMSM speed loop controllers using active disturbance rejection controllers and current loop controllers using proportional resonant controllers.

[0234] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A control method for a dual three-phase permanent magnet synchronous motor in the low modulation ratio region, characterized in that, The method includes: Step 1: In the low modulation ratio region, the three-phase windings ABC operate independently, and the three-phase windings XYZ are subjected to wave blocking. The sum of the currents of the lower bridge arms of phases B and C in the three-phase windings 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 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. The power module is driven by low modulation ratio mixed pulse width modulation. Step 2: Calculate the minimum sampling vector based on the minimum sampling time. Determine the reference voltage magnitude of the three-phase winding ABC Does it meet the requirements? If yes, return to step 1; otherwise, proceed to step 3. Step 3: In the normal modulation ratio region, the two sets of three-phase windings operate in coordination. The sum of the lower bridge arm currents of phases B, C, Y, and Z 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 of the normal modulation ratio region. The reconstructed six-phase current and the sampling speed are sent into the loop for calculation to obtain the modulation reference voltage. The modulation reference voltage of the quadrature axis is limited. All modulation reference voltages are driven by hybrid pulse width modulation (RHPWM) to complete the power module drive. Step 4: Determine the reference voltage magnitude of the three-phase windings ABC Does it meet the requirements? If yes, proceed to step 1; otherwise, proceed to step 3. Methods for obtaining the three-phase current reconstruction expression in the low modulation ratio region include: Constructing a low modulation ratio reconstruction region: S A S B S C S X S Y S Z These are the six-phase bridge arm switching functions for a dual three-phase permanent magnet synchronous motor. A value of 0 indicates that the lower bridge arm is on, and a value of 1 indicates that the upper bridge arm is on. When S A =0、S B =0、S C =0 or S X =0、S Y =0、S Z When = 0, the corresponding voltage vector is U0; When S A =1、S B =0、S C =0 or S X =1、S Y =0、S Z When = 0, the corresponding voltage vector is U1; When S A =1、S B =1、S C =0 or S X =1、S Y =1、S Z When = 0, the corresponding voltage vector is U2; When S A =0、S B =1、S C =0 or S X =0、S Y =1、S Z When = 0, the corresponding voltage vector is U3; When S A =0、S B =1、S C =1 or S X =0、S Y =1、S Z When =1, the corresponding voltage vector is U4; When S A =0、S B =0、S C =1 or S X =0、S Y =0、S Z When =1, the corresponding voltage vector is U5; When S A =1、S B =0、S C =1 or S X =1、S Y =0、S Z When =1, the corresponding voltage vector is U6; When S A =1、S B =1、S C =1 or S X =1、S Y =1、S Z When =1, the corresponding voltage vector is U7; The region enclosed in space by voltage vectors U1 and U2 is the low modulation ratio reconstruction region L1; The region enclosed in space by voltage vectors U2 and U3 is the low modulation ratio reconstruction region L2; The region enclosed in space by voltage vectors U3 and U4 is the low modulation ratio reconstruction region L3; The region enclosed in space by voltage vectors U4 and U5 is the low modulation ratio reconstruction region L4; The region enclosed in space by voltage vectors U5 and U6 is the low modulation ratio reconstruction region L5; The region enclosed in space by voltage vectors U6 and U1 is the low modulation ratio reconstruction region L6; Based on the different low modulation ratio reconstruction regions where the reference voltage vector is located, the three-phase current reconstruction expression is: in, , Indicates one switching cycle Two sampling times within; i A This represents the current in phase A of the three-phase winding ABC; i B This represents the current in phase B of a three-phase winding ABC; i C This represents the current in phase C of the three-phase winding ABC; Low modulation ratio hybrid pulse width modulation includes: When the reference voltage vector is located in the low modulation ratio reconstruction region L1 or L4, SVPWM modulation is normally used, and then the A and C phase drive signals are inverted and interchanged. 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. When the reference voltage vector is located in the low modulation ratio reconstruction region L3 or L6, SVPWM modulation is normally used, and then the A and B phase drive signals are inverted and interchanged. When the reference voltage vector is in the low modulation ratio reconstruction region L5, SVPWM modulation is normally used, and then the C-phase drive signal is inverted and used for B-phase drive.

2. The control method for a dual three-phase permanent magnet synchronous motor in the low modulation ratio region according to claim 1, characterized in that, Methods for obtaining the six-phase current expression in the modulation ratio normal region include: S A S B S C S X S Y S Z These are the six-phase bridge arm switching functions for a dual three-phase permanent magnet synchronous motor. A value of 0 indicates that the lower bridge arm is on, and a value of 1 indicates that the upper bridge arm is on. When S A =0、S B =0、S C =0 or S X =0、S Y =0、S Z When = 0, the corresponding voltage vector is U0; When S A =1、S B =0、S C =0 or S X =1、S Y =0、S Z When = 0, the corresponding voltage vector is U1; When S A =1、S B =1、S C =0 or S X =1、S Y =1、S Z When = 0, the corresponding voltage vector is U2; When S A =0、S B =1、S C =0 or S X =0、S Y =1、S Z When = 0, the corresponding voltage vector is U3; When S A =0、S B =1、S C =1 or S X =0、S Y =1、S Z When =1, the corresponding voltage vector is U4; When S A =0、S B =0、S C =1 or S X =0、S Y =0、S Z When =1, the corresponding voltage vector is U5; When S A =1、S B =0、S C =1 or S X =1、S Y =0、S Z When =1, the corresponding voltage vector is U6; When S A =1、S B =1、S C =1 or S X =1、S Y =1、S Z When =1, the corresponding voltage vector is U7; The region enclosed by voltage vectors U1 and U2 in space is sector I; The region enclosed in space by voltage vectors U2 and U3 is sector II; The region enclosed in space by voltage vectors U3 and U4 is sector III; The region enclosed in space by voltage vectors U4 and U5 is sector IV; The region enclosed in space by voltage vectors U5 and U6 is sector V; The region enclosed in space by voltage vectors U6 and U1 is sector VI; For sectors I to VI, take the midpoint line within each sector. The area enclosed by the midpoint line of sector I and the midpoint line of sector VI is the normal modulation ratio region G1. The region enclosed by the midpoint line of sector II and the midpoint line of sector I is the normal modulation ratio region G2; The region enclosed by the midpoint line of sector II and the midpoint line of sector III is the normal modulation ratio region G3; The region enclosed by the midpoint line of sector III and the midpoint line of sector IV is the normal modulation ratio region G4; The region enclosed by the midpoint line of sector IV and the midpoint line of sector V is the normal modulation ratio region G5; The region enclosed by the midpoint of sector V and the midpoint of sector VI is the normal modulation ratio region 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 enclosed by the midpoint of sector VI and the voltage vector U1 is the normal modulation ratio region G1-Ⅰ, and the region enclosed by the midpoint 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 enclosed by the midline of sector Ⅲ and the voltage vector U4 is the normal modulation ratio region G4-Ⅰ, and the region enclosed by the midline of sector Ⅳ and the voltage vector U4 is the normal modulation ratio region G4-Ⅱ. Based on the normal region of different modulation ratios where the reference voltage vector is located, the six-phase current reconstruction expression is: Among them, ABC-U i XYZ-U j Indicates the switching cycle The voltage vector corresponding to the three-phase windings 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 combination of four sampling vectors; i X This represents the current in phase X of the three-phase winding XYZ; i Y This represents the current in the Y phase of a three-phase winding XYZ; i Z This represents the current in phase Z of the three-phase winding XYZ; i A This represents the current in phase A of the three-phase winding ABC; i B This represents the current in phase B of a three-phase winding ABC; i C This represents the current in phase C of the three-phase winding ABC.

3. The control method for a dual three-phase permanent magnet synchronous motor in the low modulation ratio region according to claim 2, characterized in that, Hybrid pulse width modulation (RHPWM) includes: Phase shift of the carrier wave in the three-phase windings XYZ In the normal modulation ratio region G1-Ⅰ and the normal modulation ratio region G4-Ⅰ, SVPWM modulation is used. Then, the A and B phase drive signals in the three-phase winding ABCZ are inverted and interchanged, and the voltage vectors U0 and U7 are replaced with voltage vectors U2 and U5 respectively. SVPWM modulation is used in the normal modulation ratio region G1-Ⅱ and the normal modulation ratio region G4-Ⅱ. Then, the A and C phase drive signals in the three-phase winding ABCZ are inverted and interchanged, and the voltage vectors U0 and U7 are replaced with voltage vectors U6 and U3 respectively. In the modulation ratio normal regions G2, G3, G5, and G6, SVPWM modulation is used.

4. The control method for a dual three-phase permanent magnet synchronous motor in the low modulation ratio region according to claim 2, characterized in that, In the normal modulation ratio region, when switching from the zero vector transition boundary to the normal modulation ratio region, the calculation method of sampling currents I1 and I3 is changed; The zero-vector transition boundary includes the midpoint of sectors I, III, IV, and V, voltage vector U1, and voltage vector U4; When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows: In the formula, i ' A i represents the current in phase A of the three-phase winding ABC of the dual three-phase permanent magnet synchronous motor during the previous switching cycle. ' B i represents the current in phase B of the three-phase winding ABC in the previous switching cycle. ' C i represents the current in phase C of the three-phase winding ABC in the previous switching cycle. ' X i represents the current in phase X of the three-phase winding XYZ in the previous switching cycle. ' Y i represents the current in the Y phase of the three-phase winding XYZ in the previous switching cycle. ' Z This represents the current in phase Z of the three-phase winding XYZ in the previous switching cycle; When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows: When the reference voltage vector passes through the voltage vector U4, switching 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows: When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows: When the reference voltage vector crosses the midpoint 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows: When the reference voltage vector passes through the voltage vector U1, switching 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 adopt the current true sampled values, and the sampled currents I1 and I3 are updated as follows: 。 5. The control method for a 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: in, To represent the modulation reference voltage of the quadrature axis, Indicates the switching cycle. Indicates the minimum sampling time. This indicates the bus voltage.

6. A computer-readable storage device storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the control method for a low modulation ratio region dual three-phase permanent magnet synchronous motor as described in any one of claims 1 to 5.

7. A control device for a low modulation ratio region dual three-phase permanent magnet synchronous motor, 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 for a low modulation ratio region dual three-phase permanent magnet synchronous motor as described in any one of claims 1 to 5.

8. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the control method for a low modulation ratio region dual three-phase permanent magnet synchronous motor as described in any one of claims 1 to 5.

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