Open-winding electric machine and control method thereof

Abstract

The application discloses an open-winding motor and a control method thereof. The method comprises the following steps: obtaining a zero-axis voltage instruction value of the motor, and obtaining a sector in which a reference voltage vector of the motor is located; obtaining a basic voltage vector of the motor according to the sector, and obtaining an action time of the basic voltage vector, wherein the basic voltage vector is a voltage vector that generates motor voltage and does not generate zero-axis voltage; selecting an auxiliary voltage vector inserted between the basic voltage vector and a zero voltage vector of the motor according to the sector, the zero-axis voltage instruction value and the action time of the basic voltage vector, wherein the auxiliary voltage vector is a voltage vector that generates motor inter-phase interference voltage and generates zero-axis voltage; obtaining duty cycles of a first inverter and a second inverter according to the basic voltage vector, the zero voltage vector and the auxiliary voltage vector, and controlling the motor according to the duty cycles, so that not only the zero-axis current can be effectively inhibited, but also the motor has higher working efficiency.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to an open-winding motor and its control method. Background Technology

[0002] Compared to a Y-type motor driven by a single inverter without a boost function, an open-winding motor driven by dual inverters can obtain 1.5 to 1.6 times the high voltage at the motor input, thereby expanding the motor's speed range and thus finding wide application in some scenarios.

[0003] For open-winding motors with a common bus (i.e., dual inverters connected to the same DC bus), voltage vector control is typically used. However, when outputting zero-axis voltage, a zero-axis current is generated, with all three phases flowing in the same direction. Related technologies aim to suppress this zero-axis current by inserting the voltage vector corresponding to the reverse-phase zero-axis current between the torque generation vectors. However, this affects motor torque generation and motor efficiency. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art. Therefore, the first objective of the present invention is to propose a control method for an open-winding motor that can not only effectively suppress zero-axis current but also improve the motor's operating efficiency.

[0005] The second objective of this invention is to provide an open-winding motor.

[0006] To achieve the above objectives, a first aspect of the present invention provides a control method for an open-winding motor. The open-winding motor includes a three-phase winding, with the two ends of the three-phase winding connected to a first inverter and a second inverter, respectively. The first inverter and the second inverter share a DC bus. The method includes: acquiring the zero-axis voltage command value of the motor and acquiring the sector where the reference voltage vector of the motor is located; acquiring the basic voltage vector of the motor based on the sector and acquiring the duration of the basic voltage vector, wherein the basic voltage vector is a voltage vector that generates motor voltage but does not generate zero-axis voltage; selecting and inserting an auxiliary voltage vector between the basic voltage vector and the zero-axis voltage vector of the motor based on the sector, the zero-axis voltage command value, and the duration of the basic voltage vector, wherein the zero-axis voltage vector is a voltage vector that does not generate interphase interference voltage and does not generate zero-axis voltage, and the auxiliary voltage vector is a voltage vector that generates interphase interference voltage and generates zero-axis voltage; acquiring the duty cycle of the first inverter and the second inverter based on the basic voltage vector, the zero-axis voltage vector, and the auxiliary voltage vector, and controlling the motor based on the duty cycle.

[0007] According to the control method of the open-winding motor of the present invention, based on the sector, the zero-axis voltage command value and the duration of the basic voltage vector, an auxiliary voltage vector is selected and inserted between the basic voltage vector and the zero-axis voltage vector of the motor. The basic voltage vector is a voltage vector that generates motor voltage but does not generate zero-axis voltage, the zero-axis voltage vector is a voltage vector that does not generate interphase interference voltage and does not generate zero-axis voltage, and the auxiliary voltage vector is a voltage vector that generates interphase interference voltage and generates zero-axis voltage. This not only effectively suppresses zero-axis current but also improves the motor's operating efficiency.

[0008] According to one embodiment of the present invention, the reference voltage vector of the motor is divided into 6 sectors with the zero voltage vector as the center point and the basic voltage vector as the vertex. The center point includes two zero voltage vectors and each vertex includes two basic voltage vectors.

[0009] According to one embodiment of the present invention, selecting and inserting an auxiliary voltage vector between the basic voltage vector and the zero voltage vector of the motor based on the sector, the zero-axis voltage command value, and the duration of the basic voltage vector includes: when the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, if the duration of the first basic voltage vector is greater than or equal to the duration of the second basic voltage vector, then inserting a first auxiliary voltage vector between the first zero voltage vector and the first basic voltage vector, and inserting a second auxiliary voltage vector between the first basic voltage vector and the second basic voltage vector; if the duration of the first basic voltage vector is less than the duration of the second basic voltage vector, then inserting a second auxiliary voltage vector between the first basic voltage vector and the second basic voltage vector, and inserting a third auxiliary voltage vector between the second basic voltage vector and the second zero voltage vector.

[0010] According to one embodiment of the present invention, an auxiliary voltage vector is selected to be inserted between the basic voltage vector and the zero voltage vector of the motor based on the sector, the zero-axis voltage command value and the duration of the basic voltage vector. The method further includes: when the sector is sector 0, 2, or 4 and the zero-axis voltage command value is greater than or equal to 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is less than 0, a first auxiliary voltage vector is inserted between the first zero voltage vector and the first basic voltage vector, a second auxiliary voltage vector is inserted between the first basic voltage vector and the second basic voltage vector, and a third auxiliary voltage vector is inserted between the second basic voltage vector and the second zero voltage vector.

[0011] According to one embodiment of the present invention, obtaining the duty cycle of a first inverter and a second inverter based on a basic voltage vector, a zero voltage vector, and an auxiliary voltage vector includes: obtaining the duration of the zero voltage vector based on the duration of the basic voltage vector; obtaining the duration of the zero-axis voltage command value; and obtaining the duty cycle of the first inverter and the second inverter in the order following the insertion of the auxiliary voltage vector, based on the duration of the basic voltage vector, the duration of the zero voltage vector, and the duration of the zero-axis voltage command value.

[0012] According to one embodiment of the present invention, when the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, the duty cycle of the first inverter and the second inverter is obtained according to the action time of the basic voltage vector, the action time of the zero voltage vector, and the action time of the zero-axis voltage command value, in the order after the insertion of the auxiliary voltage vector. This includes: if the action time of the first basic voltage vector is greater than or equal to the action time of the second basic voltage vector, then obtaining the difference between the action time of the zero voltage vector and the action time of the zero-axis voltage command value to obtain the inverter to be turned on corresponding to the first auxiliary voltage vector. The first duty cycle of the phase is obtained; the sum of the first duty cycle and the duration of the first auxiliary voltage vector is obtained to obtain the second duty cycle of the inverter phase to be turned on corresponding to the first basic voltage vector; the sum of the second duty cycle and the duration of the first basic voltage vector is obtained to obtain the third duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector; the sum of the third duty cycle and the duration of the second auxiliary voltage vector is obtained to obtain the fourth duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector; the sum of the fourth duty cycle and the duration of the second basic voltage vector is obtained to obtain the fifth and sixth duty cycles of the inverter phase to be turned on corresponding to the second zero voltage vector, where the fifth duty cycle is equal to the sixth duty cycle.

[0013] According to one embodiment of the present invention, when the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, the duty cycle of the first inverter and the second inverter is obtained according to the action time of the basic voltage vector, the action time of the zero voltage vector, and the action time of the zero-axis voltage command value, in the order after the insertion of the auxiliary voltage vector. This includes: if the action time of the first basic voltage vector is less than the action time of the second basic voltage vector, then the difference between the action time of the zero voltage vector and the action time of the zero-axis voltage command value is obtained to obtain the first basic voltage vector corresponding to the inverter phase to be turned on. The seventh duty cycle and the eighth duty cycle are equal; the sum of the seventh duty cycle and the duration of the first basic voltage vector is obtained to get the ninth duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector; the sum of the ninth duty cycle and the duration of the second auxiliary voltage vector is obtained to get the tenth duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector; the sum of the tenth duty cycle and the duration of the second basic voltage vector is obtained to get the eleventh duty cycle of the inverter phase to be turned on corresponding to the third auxiliary voltage vector; the sum of the eleventh duty cycle and the duration of the third auxiliary voltage vector is obtained to get the twelfth duty cycle of the inverter phase to be turned on corresponding to the second zero voltage vector.

[0014] According to one embodiment of the present invention, when the sector is sector 0, 2, or 4 and the zero-axis voltage command value is greater than or equal to 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is less than 0, the duty cycle of the first inverter and the second inverter is obtained according to the action time of the basic voltage vector, the action time of the zero voltage vector, and the action time of the zero-axis voltage command value, in the order after the insertion of the auxiliary voltage vector. This includes: obtaining the difference between the action time of the zero voltage vector and the action time of the zero-axis voltage command value to obtain the thirteenth duty cycle of the phase to be turned on in the inverter corresponding to the first auxiliary voltage vector; obtaining the sum of the thirteenth duty cycle and the action time of the first auxiliary voltage vector to obtain the first... The fourteenth duty cycle of the inverter phase to be turned on is obtained by the basic voltage vector; the sum of the fourteenth duty cycle and the duration of the first basic voltage vector is obtained to obtain the fifteenth duty cycle of the inverter phase to be turned on is obtained by the second auxiliary voltage vector; the sum of the fifteenth duty cycle and the duration of the second auxiliary voltage vector is obtained to obtain the sixteenth duty cycle of the inverter phase to be turned on is obtained by the second basic voltage vector; the sum of the sixteenth duty cycle and the duration of the second basic voltage vector is obtained to obtain the seventeenth duty cycle of the inverter phase to be turned on is obtained by the third auxiliary voltage vector; the sum of the seventeenth duty cycle and the duration of the third auxiliary voltage vector is obtained to obtain the eighteenth duty cycle of the inverter phase to be turned on is obtained by the second zero voltage vector.

[0015] According to one embodiment of the present invention, when the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, the action time of the first auxiliary voltage vector, the second auxiliary voltage vector, and the third auxiliary voltage vector is 1 / 2 of the action time of the zero-axis voltage command value; when the sector is sector 0, 2, or 4 and the zero-axis voltage command value is greater than or equal to 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is less than 0, the action time of the first auxiliary voltage vector, the second auxiliary voltage vector, and the third auxiliary voltage vector is 1 / 3 of the action time of the zero-axis voltage command value.

[0016] According to one embodiment of the present invention, obtaining the zero-axis voltage command value of a motor includes: obtaining the d, q and zero-axis current command values, the zero-axis current feedback value and the fundamental harmonic current frequency of the motor; obtaining a first voltage value based on the zero-axis current command value, the zero-axis current feedback value and the fundamental harmonic current frequency, and obtaining a second voltage value based on the d and q-axis current command values; and obtaining the zero-axis voltage command value based on the first voltage value and the second voltage value.

[0017] According to one embodiment of the present invention, obtaining a first voltage value based on a zero-axis current command value, a zero-axis current feedback value, and a fundamental harmonic current frequency includes: obtaining a first difference between the zero-axis current command value and the zero-axis current feedback value; multiplying the first difference by a first proportional gain to obtain a first value; multiplying the first difference by a first resonant gain to obtain a second value, and obtaining a second difference between the second value and a first integral result; and integrating the second difference to obtain a second integral result, wherein the first integral result is obtained by multiplying the fundamental harmonic current frequency and the second integral result corresponding to the previous moment; and summing the second integral result and the first value to obtain the first voltage value.

[0018] According to one embodiment of the present invention, the second voltage value is calculated according to the following formula:

[0019] V off =-3ωA(L q -L d (I) dref sin3θ-I qref cos3θ)

[0020] Among them, V off The second voltage value is given, 3ω is the fundamental harmonic current frequency, and L is the voltage value. q L is the q-axis inductance of the motor. d I is the d-axis inductance of the motor. dref I is the d-axis current command value. qref Here, θ is the q-axis current command value, θ is the rotor position of the motor, and A is a coefficient.

[0021] According to one embodiment of the present invention, determining the sector where the reference voltage vector of the motor is located includes: acquiring the α and β axis voltage command values ​​of the motor; and determining the sector where the reference voltage vector is located based on the α and β axis voltage command values.

[0022] According to one embodiment of the present invention, determining the sector where the reference voltage vector is located based on the α and β axis voltage command values ​​includes: obtaining a first polarity determination coefficient based on the α axis voltage command value, and obtaining a second polarity determination coefficient and a third polarity determination coefficient based on the α and β axis voltage command values; determining the sector where the reference voltage vector is located based on the relationship between the first polarity determination coefficient, the second polarity determination coefficient, the third polarity determination coefficient and zero.

[0023] To achieve the above objectives, a second aspect of the present invention provides an open-winding motor, comprising: a three-phase winding, a first inverter, a second inverter, and a control device, wherein the two ends of the three-phase winding are respectively connected to the first inverter and the second inverter, and the first inverter and the second inverter share a DC bus; the control device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the aforementioned method.

[0024] According to the embodiments of the present invention, the open-winding motor, through the aforementioned control method, can not only effectively suppress zero-axis current, but also improve the motor's operating efficiency.

[0025] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an open-winding motor according to an embodiment of the present invention;

[0027] Figure 2 A flowchart of a control method for an open-winding motor according to an embodiment of the present invention;

[0028] Figure 3 This is a control diagram of an open-winding motor according to an embodiment of the present invention;

[0029] Figure 4 The above are waveforms of the three-phase current and zero-axis current without zero-axis current suppression according to an embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram illustrating the acquisition of the zero-axis voltage command value according to an embodiment of the present invention;

[0031] Figure 6 A schematic diagram of zero-axis voltage generation according to an embodiment of the present invention;

[0032] Figure 7 This is a traditional space voltage vector diagram;

[0033] Figure 8 A spatial voltage vector diagram of an open-winding motor according to an embodiment of the present invention;

[0034] Figure 9 This is a spatial voltage vector diagram of an open-winding motor after segmentation according to an embodiment of the present invention;

[0035] Figures 10a-15b This is a control timing diagram for an open-winding motor according to an embodiment of the present invention;

[0036] Figure 16 This is a spatial voltage vector diagram of an open-winding motor after segmentation according to another embodiment of the present invention;

[0037] Figures 17a-22b This is a control timing diagram for an open-winding motor according to another embodiment of the present invention. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0039] Compared to a Y-type motor driven by a single inverter without a boost function, an open-winding motor driven by dual inverters can obtain 1.5 to 1.6 times the high voltage at the motor input, thereby expanding the motor's speed range. At the same time, dual inverters have hardware redundancy characteristics, which greatly improves the fault tolerance and reliability of the system. Therefore, open-winding motors driven by dual inverters are widely used in some application scenarios.

[0040] For open-winding motors with a common bus (i.e., dual inverters connected to the same DC bus), voltage vector control is typically used. However, when outputting zero-axis voltage, a zero-axis current is generated, with all three phases flowing in the same direction. Related technologies aim to suppress this zero-axis current by inserting the voltage vector corresponding to the reverse-phase zero-axis current between the torque generation vectors. However, this affects motor torque generation and motor efficiency.

[0041] To address the aforementioned technical problems, this application provides an open-winding motor and its control method, which not only effectively suppresses zero-axis current but also improves the motor's operating efficiency. The open-winding motor and its control method according to embodiments of the present invention are described below with reference to the accompanying drawings.

[0042] In this application, the open-winding motor includes: a three-phase winding, one end of which is connected to a first inverter and the other end of which is connected to a second inverter. The two inverters share a DC bus, that is, they share the same DC power supply.

[0043] Specifically, refer to Figure 1 As shown, the open-winding motor includes three-phase stator windings (referred to as three-phase windings), denoted as U-phase winding, V-phase winding, and W-phase winding. Both ends of the three-phase windings are open, meaning they are not connected to each other, thus forming six winding terminals, denoted as Ua, Va, Wa, Ub, Vb, and Wb. The two inverters can be three-phase full-bridge inverters composed of six power switching transistors. The input terminals of both the first and second inverters are connected to the DC buses DC+ and DC-. The three output terminals of the first inverter are connected to the corresponding three-phase windings of the open-winding motor through winding terminals Ua, Va, and Wa, respectively. The three output terminals of the second inverter are connected to the corresponding three-phase windings of the open-winding motor through winding terminals Ub, Vb, and Wb, respectively. The DC voltage on the DC buses DC+ and DC- can be obtained from a DC power supply or by converting AC power from a switching power supply. It should be noted that the open-winding motor in this application can be a three-phase permanent magnet synchronous motor.

[0044] Figure 2 This is a schematic flowchart illustrating a control method for an open-winding motor according to an embodiment of the present invention. (Reference) Figure 2 As shown, the control method may include the following steps:

[0045] In step S101, the zero-axis voltage command value of the motor is obtained, and the sector where the reference voltage vector of the motor is located is obtained.

[0046] In step S102, the basic voltage vector of the motor is obtained according to the sector, and the duration of the basic voltage vector is obtained.

[0047] In step S103, an auxiliary voltage vector is selected between the basic voltage vector and the motor's zero voltage vector based on the sector, the zero-axis voltage command value, and the duration of the basic voltage vector.

[0048] In step S104, the duty cycles of the first inverter and the second inverter are obtained based on the basic voltage vector, the zero voltage vector and the auxiliary voltage vector, and the motor is controlled according to the duty cycles.

[0049] It should be noted that, in this application, the basic voltage vector is a voltage vector that generates motor voltage but does not generate zero-axis voltage; the zero voltage vector is a voltage vector that does not generate motor phase-to-phase interference voltage and does not generate zero-axis voltage; and the auxiliary voltage vector is a voltage vector that generates motor phase-to-phase interference voltage and generates zero-axis voltage.

[0050] Specifically, the open-winding motor of this application can be controlled using voltage vector control. During control, reference is made to... Figure 3 As shown, a position sensor can be installed at the corresponding position of the open-winding motor to detect the motor's position information in real time. At the same time, the three-phase current of the motor can be detected in real time by a current sensor installed between the first inverter and the motor (or by a current sensor installed between the second inverter and the motor), which are denoted as U-phase current Iu, V-phase current Iv, and W-phase current Iw, respectively. At the same time, the voltage of the DC bus DC+ and DC- can be detected in real time by voltage sensors installed at the DC bus DC+ and DC-, which are denoted as DC bus voltage Vdc.

[0051] The speed and position detection unit obtains the motor speed feedback value ω and rotor position θ based on the position information detected by the position sensor, and transmits the speed feedback value ω to the speed control unit for closed-loop speed control. Simultaneously, it transmits the rotor position θ to the first coordinate transformation unit and the second coordinate transformation unit for corresponding calculations. Of course, the speed and position detection unit can also obtain the motor speed feedback value ω and rotor position θ based on the motor's voltage and current, etc., but this is not a limitation.

[0052] The speed control unit uses the rotational speed command value ω ref Combined with the speed feedback value ω, closed-loop speed control is performed to obtain the q-axis current command value I. qref For example, the speed control unit first calculates the speed command value ω. ref The difference between the current and the speed feedback value ω is used to obtain the q-axis current command value I by performing proportional-integral adjustment on this difference. qref .

[0053] The first coordinate transformation unit can perform Clark coordinate transformation on the three-phase currents Iu, Iv, and Iw of the motor based on the rotor position θ, and then perform Park coordinate transformation to obtain the q-axis current feedback value I of the motor. q d-axis current feedback value I d And the zero-axis current feedback value I0, in specific implementation, can be directly calculated using the following formula (1):

[0054]

[0055] The d-axis current command generation unit generates the motor's d-axis current command value I based on the DC bus voltage Vdc and the voltage amplitude Vdq of the dq axis. dref For example, the d-axis current command generation unit first calculates the difference between the DC bus voltage Vdc and the voltage amplitude Vdq of the dq axis, and then performs proportional-integral adjustment on this difference to obtain the d-axis current command value I. dref .

[0056] The current control unit uses the q-axis current command value I. qref d-axis current command value I dref Zero-axis current command value I 0ref q-axis current feedback value I q d-axis current feedback value I d And the zero-axis current feedback value I0 is used for current closed-loop control to obtain the q-axis voltage command value V. q d-axis voltage command value V d The zero-axis voltage command value V0 will be obtained in detail later.

[0057] The second coordinate transformation unit adjusts the q-axis voltage command value V based on the motor's rotor position θ. q and d-axis voltage command value V d Perform a Park inverse coordinate transformation (i.e., perform a Park reverse transformation) to obtain the α-axis voltage command value V. α and β-axis voltage command value V β Specifically, it can be calculated using the following formula (2):

[0058]

[0059] It should be noted that the zero-axis voltage command value V0 is output as is, without any coordinate transformation.

[0060] The space vector modulation unit operates according to the α-axis voltage command value V. α β-axis voltage command value V β Space voltage vector calculations are performed using the zero-axis voltage command value V0 to generate the U-phase duty cycle Du1, V-phase duty cycle Dv1, and W-phase duty cycle Dw1 of the first inverter, and the U-phase duty cycle Du2, V-phase duty cycle Dv2, and W-phase duty cycle Dw2 of the second inverter. The specific generation process will be explained in detail later.

[0061] The PWM (Pulse Width Modulation) signal generation unit generates control signals U1+, U1-, V1+, V1-, W1+, and W1- for each switch in the first inverter based on the duty cycles Du1, Dv1, and Dw1 of each phase. Simultaneously, it generates control signals U2+, U2-, V2+, V2-, W2+, and W2- for each switch in the second inverter based on the duty cycles Du2, Dv2, and Dw2 of each phase. The generated control signals are then output to both the first and second inverters to control the individual switches in both inverters, thereby achieving motor speed control.

[0062] from Figure 3As can be seen, since the two inverters share the same DC bus, a zero-axis current will be generated where all three phase currents flow in the same direction. This zero-axis current can be divided into two categories: one is a low-frequency current flowing at three times the fundamental frequency of the phase current energizing the motor (referred to as fundamental harmonic current, and the frequency of this harmonic current is three times the fundamental frequency of the motor); the other is a current with a carrier frequency component flowing synchronously with the switching of the first and second inverters (referred to as carrier harmonic current). Furthermore, Figure 4 The waveforms of the three-phase currents Iu, Iv, and Iw, as well as the zero-axis current I0, of the motor are given without suppression of the zero-axis current. Figure 4 It can be seen that the zero-axis current I0 pulsates with a component three times the fundamental frequency of the phase current, and this current also flows to the three-phase windings, causing severe distortion of the currents Iu, Iv and Iw in each phase winding; at the same time, each phase current Iu, Iv and Iw and the zero-axis current I0 have synchronously changing ripple currents, which are the zero-axis currents of the carrier frequency component.

[0063] To address the aforementioned problem of zero-axis current, this application controls these two types of zero-axis current separately, thereby achieving effective control of zero-axis current across the entire frequency band.

[0064] The suppression of zero-axis current flowing at a frequency three times that of the fundamental frequency will be explained below.

[0065] First, formula (3) gives the relationship between the d-axis voltage, q-axis voltage, zero-axis voltage and the d-axis current, q-axis current and zero-axis current of the motor:

[0066]

[0067] In this formula, L d L is the d-axis inductance of the motor. q L is the q-axis inductance of the motor. c R is the zero-axis inductance of the motor, and R is the stator resistance. This represents the fundamental component of the rotor flux linkage of the motor. This is the third harmonic component of the rotor flux linkage of the motor.

[0068] When current flows along the d-axis and q-axis, the zero-axis voltage is generated due to the influence of the diagonal terms in equation (3), which in turn leads to the generation of a zero-axis current. To solve this problem, Figure 5 A control strategy for suppressing this zero-axis current is given. Specifically, refer to... Figure 5 As shown, the current control unit is mainly divided into two parts: one part is used to control the d-axis current and the q-axis current, and the other part is used to suppress the zero-axis current.

[0069] In controlling the d-axis current and q-axis current, the d-axis current command value I can be calculated first. dref With d-axis current feedback value I d The difference between them is then adjusted using a proportional-integral method, as shown in the formula (K). pd *S+K id Adjust the voltage by ) / S to obtain the d-axis voltage command value V of the motor. d , where k pd and K id These are all adjustment coefficients, which can be set according to actual conditions; at the same time, the q-axis current command value I can be calculated first. qref With q-axis current feedback value I q The difference between them is then adjusted using a proportional-integral method, as shown in the formula (K). pd *S+K iq The voltage is adjusted by ) / S to obtain the q-axis voltage command value V of the motor. q , where k pd and K iq These are all adjustment coefficients, which can be set according to the actual situation.

[0070] When suppressing zero-axis current, the zero-axis voltage command value V0 can be obtained in the following way: Obtain the d-axis current command value I of the motor. dref q-axis current command value I qref Zero-axis current command value I 0ref The zero-axis current feedback value I0 and the fundamental harmonic current frequency (it is understood that, based on the foregoing, the zero-axis current to be suppressed in this application includes a current at 3 times the fundamental frequency, therefore the fundamental harmonic current frequency here is 3ω); according to the zero-axis current command value I... 0ref The first voltage value V is obtained from the zero-axis current feedback value I0 and the fundamental harmonic current frequency 3ω. s Simultaneously, based on the d-axis current command value I dref and q-axis current command value I qref Obtain the second voltage value V off Finally, based on the first voltage value V s Second voltage value V off Obtain the zero-axis voltage command value V0.

[0071] Furthermore, based on the zero-axis current command value I 0ref The first voltage value V is obtained by using the zero-axis current feedback value I0 and the fundamental harmonic current frequency (3ω here). s This may include: first obtaining the zero-axis current command value I 0refThe first difference between the zero-axis current feedback value I0 and the first value is obtained. Then, the first difference is multiplied by the first proportional gain Kp0 to obtain the first value. At the same time, the first difference is multiplied by the first resonant gain Kr to obtain the second value. The second difference between the second value and the first integral result is obtained, and the second difference is integrated to obtain the second integral result. The first integral result is obtained by multiplying the fundamental harmonic current frequency ω and the second integral result corresponding to the previous moment. Finally, the second integral result and the first value are summed to obtain the first voltage value V. s .

[0072] Furthermore, the second voltage value V can be calculated according to the following formula (4). off :

[0073] V off =-3ωA(L q -L d (I) dref sin3θ-I qref cos3θ) (4)

[0074] Where A is a coefficient, which can be set according to the actual situation. This formula can suppress the interference components of the d and q axes with the zero axis.

[0075] The first voltage value V is obtained through the aforementioned method. s and the second voltage value V off Then, the zero-axis voltage command value V0 of the motor can be obtained by summing the two. The zero-axis voltage command value V0 can be used to suppress the zero-axis current flowing with a component three times the fundamental frequency.

[0076] Therefore, by tracking a specific frequency, which here refers to three times the fundamental frequency of the motor phase current, and suppressing the interference components of the d-axis and q-axis on the zero axis, it is possible to effectively suppress the zero-axis current flowing at three times the fundamental frequency of the motor phase current.

[0077] The suppression of zero-axis current in the carrier frequency component will be explained below.

[0078] First, let's explain the principle of generating zero-axis current with carrier frequency components. Figure 6 The waveforms of the switching signals U1+, V1+, and W1+ of the three upper-arm switches of the first inverter, the switching signals U2+, V2+, and W2+ of the three upper-arm switches of the second inverter, the three-phase currents Iu, Iv, and Iw of the motor, and the zero-axis current I0 are given. The waveform of the zero-axis voltage V0_rip is also given. The zero-axis voltage V0_rip can be calculated using the following formula (5):

[0079]

[0080] Among them, V u1 V v1 and V w1 These are the U-phase voltage, V-phase voltage, and W-phase voltage of the first inverter, respectively. u2 V v2 and V w2 These are the U-phase voltage, V-phase voltage, and W-phase voltage of the second inverter, respectively.

[0081] from Figure 6 As can be seen, the waveform of the zero-axis voltage V0_rip fluctuates back and forth in the positive and negative directions depending on the switching states of the two inverters' switching transistors. Specifically, the zero-axis current I0 increases in the positive direction and decreases in the negative direction. When the zero-axis voltage V0_rip is zero, the variation in the carrier frequency component of the zero-axis current disappears. Furthermore, the generation state of the zero-axis voltage V0_rip depends on the number of active phases of the two inverters' switching transistors. For example, when the number of active phases of the two inverters is the same, the zero-axis voltage V0_rip is zero. When the number of active phases of the two inverters is different, the difference will produce a positive or negative variation. In other words, if the number of active phases of the first and second inverters can be aligned, then the zero-axis voltage V0_rip can be prevented, thereby suppressing the zero-axis current.

[0082] To achieve the above objectives, space voltage vector control can be used. Specifically, Figure 7 The space voltage vector diagram of a traditional Y-type or star-type motor is given. As can be seen from the figure, there are a total of 6 basic voltage vectors (also called effective voltage vectors) from V1 (100) to V6 (101) and two zero voltage vectors V7 (111) and V0 (000). Among them, the basic voltage vector V1 (100) indicates that the upper bridge arm of the U phase is open and the upper bridge arms of the V and W phases are closed; the basic voltage vector V2 (110) indicates that the upper bridge arms of the U and V phases are open and the upper bridge arm of the W phase is closed; the basic voltage vector V3 (010) indicates that the upper bridge arm of the V phase is open and the upper bridge arms of the U and W phases are closed; the basic voltage vector V4 (011) indicates that the upper bridge arms of the V and W phases are open and the upper bridge arm of the U phase is closed; the basic voltage vector V5 (001) indicates that the upper bridge arm of the W phase is open and the upper bridge arms of the U and V phases are closed; the basic voltage vector V6 (101) indicates that the upper bridge arms of the U and W phases are open and the upper bridge arm of the V phase is closed. It should be noted that the meaning of voltage vector described here also applies to open-winding motors.

[0083] Because the open-winding motor has two inverters, it has 8×8=64 switching modes (i.e., voltage vectors), such as... Figure 8 As shown, for convenience, Figure 8 The "V" markings for each voltage vector are omitted.

[0084] exist Figure 8In this context, V35 represents the combination of the voltage vector V3 (010) of the first inverter and the voltage vector V5 (001) of the second inverter; V26 represents the combination of the voltage vector V2 (110) of the first inverter and the voltage vector V6 (101) of the second inverter; and so on. It should be noted that in the voltage vectors of an open-winding motor, outputting a specific command voltage can often be achieved through a combination of multiple voltage vectors. For example, to output... Figure 8 The reference voltage vector Vx indicated by the arrow can be adjusted by changing the duration of voltage vectors V21, V30, V45 or V76, as well as the duration of voltage vectors V32, V47, V56 or V01.

[0085] Furthermore, by analyzing the relationship between zero-axis voltage and voltage vectors, among the aforementioned 64 voltage vectors, the voltage vectors that generate the voltage applied to the motor but do not produce the same zero-axis voltage affecting the three phases—that is, the voltage vectors where the number of activated phases of the two inverters is the same, and at least two of the activated phases are different—are V15, V24, V26, V35, V31, V46, V42, V51, V53, V62, V64, and V13, totaling 12. These 12 voltage vectors are called basic voltage vectors, and these 12 voltage vectors are located in pairs at the vertices of a regular hexagon, such as... Figure 8 The area circled in the small and medium circles can then be divided into 6 sectors, using the center point and vertices of the regular hexagon as a reference: Sector 0, Sector 1, Sector 2, Sector 3, Sector 4, Sector 5, and Sector 6. Specifically, as shown below... Figure 9 As shown on the left, the center points of the regular hexagon are two zero-voltage vectors, V00 and V77. That is, the reference voltage vector of the motor can be divided into 6 sectors with the zero-voltage vector as the center point and the basic voltage vector as the vertex. The center point includes two zero-voltage vectors, V00 and V77 (in this application, V00 is denoted as the first zero-voltage vector and V77 as the second zero-voltage vector), and each vertex includes two basic voltage vectors, namely V15 and V24, V26 and V35, V31 and V46, V42 and V51, V53 and V62, and V64 and V13.

[0086] In practical use, for example when outputting something like... Figure 9When the reference voltage vector in sector 0 is shown, it can be achieved by adjusting the duration of the basic voltage vectors V13 and V24. V13 represents the combination of the voltage vector V1 (100) of the first inverter and the voltage vector V3 (010) of the second inverter, that is, the upper arm of the U phase of the first inverter is open, while the upper arms of the V and W phases are closed, and the upper arm of the V phase of the second inverter is open, while the upper arms of the U and W phases are closed. V24 represents the combination of the voltage vector V2 (110) of the first inverter and the voltage vector V4 (011) of the second inverter, that is, the upper arms of the U and V phases of the first inverter are open, while the upper arm of the W phase is closed, and the upper arms of the V and W phases of the second inverter are open, while the upper arm of the U phase is closed. Simultaneously, two zero-voltage vectors, V00 and V77, are added. V00 represents the combination of the voltage vector V0(000) of the first inverter and the voltage vector V0(000) of the second inverter, meaning that the upper arms of the U-phase, V-phase, and W-phase of the first inverter are all off, and the upper arms of the U-phase, V-phase, and W-phase of the second inverter are also all off. V77 represents the combination of the voltage vector V7(111) of the first inverter and the voltage vector V7(111) of the second inverter, meaning that the upper arms of the U-phase, V-phase, and W-phase of the first inverter are all on, and the upper arms of the U-phase, V-phase, and W-phase of the second inverter are also all on. The specific waveforms are as follows: Figure 9 As shown on the right. From Figure 9 As can be seen from the waveforms shown, the number of active phases of the first transformer is exactly the same as that of the second transformer, therefore no zero-axis voltage is generated. In other words, with... Figure 9 The control method shown can effectively suppress the pulsating current of the carrier component of the zero-axis current.

[0087] However, if only the basic voltage vectors that do not generate zero-axis voltage, namely the aforementioned 12 basic voltage vectors, are used, it is impossible to generate the zero-axis voltage command value V0 desired for suppressing the zero-axis current flowing at three times the fundamental frequency. Therefore, in this application, the following voltage vectors are used to simultaneously satisfy the suppression of the two zero-axis currents mentioned above:

[0088] The first and second basic voltage vectors specifically refer to the voltage vectors that generate the voltage applied to the motor and do not generate the zero-axis voltage that has the same effect on the three phases. In simple terms, they are the voltage vectors that generate the motor voltage and do not generate the zero-axis voltage, which are two of the aforementioned 12 basic voltage vectors.

[0089] The first and second zero voltage vectors specifically refer to voltage vectors that do not generate voltages that affect the phases of the motor and do not generate zero-axis voltages that have the same effect on all three phases. In simple terms, they are voltage vectors that do not generate inter-phase interference voltages and do not generate zero-axis voltages, namely the aforementioned first zero voltage vector V00 and second zero voltage vector V77.

[0090] The first to third auxiliary voltage vectors specifically refer to the voltage vectors that generate voltages that affect the phase-to-phase interaction of the motor and also generate zero-axis voltages that have the same effect on all three phases. In simple terms, they are voltage vectors that generate inter-phase interference voltages and zero-axis voltages, which are related to the aforementioned 12 basic voltage vectors and have a difference of 1 between the number of active phases of the two inverters.

[0091] In practical applications, auxiliary voltage vectors can be inserted between the second basic voltage vector and the first basic voltage vector, between the first basic voltage vector and the first zero voltage vector, and between the second basic voltage vector and the second zero voltage vector, so as to achieve uniform control of the zero-axis voltage and simultaneously suppress the two types of zero-axis currents mentioned above.

[0092] Specifically, when it is sector 0 (Sector0), the basic voltage vectors corresponding to this sector are V13 and V24, referencing... Figure 10a As shown, when a negative zero-axis voltage needs to be applied to this sector to reduce the zero-axis current (i.e., V0 < 0), V03 (first auxiliary voltage vector) can be inserted between V00 (first zero voltage vector) and V13 (first basic voltage vector). Simultaneously, V14 (second auxiliary voltage vector) can be inserted between V24 (second basic voltage vector) and V13 (first basic voltage vector), and V27 (third auxiliary voltage vector) can be inserted between V24 (second basic voltage vector) and V77 (second zero voltage vector). The final voltage vectors are V00, V03, V13, V14, V24, V27, and V77, respectively. It should be noted that voltage vectors V03, V14, and V27 are all voltage vectors where the number of active phases in the second inverter is one more than the number of active phases in the first inverter. This reduces the zero-axis current, and the total number of active phases decreases by one each time the voltage vectors are switched.

[0093] refer to Figure 10bAs shown, when a positive zero-axis voltage needs to be applied to this sector to increase the zero-axis current (i.e., V0 ≥ 0), V10 (first auxiliary voltage vector) can be inserted between V00 (first zero voltage vector) and V13 (first basic voltage vector). Simultaneously, V23 (second auxiliary voltage vector) can be inserted between V24 (second basic voltage vector) and V13 (first basic voltage vector), and V74 (third auxiliary voltage vector) can be inserted between V24 (second basic voltage vector) and V77 (second zero voltage vector). The final voltage vectors are V00, V10, V13, V23, V24, V74, and V77, respectively. It should be noted that voltage vectors V10, V23, and V74 are all voltage vectors where the number of active phases in the first inverter is one more than the number of active phases in the second inverter. This increases the zero-axis current, and the total number of active phases decreases by one each time the voltage vectors are switched.

[0094] In other words, when a negative zero-axis voltage is applied, the three auxiliary voltage vectors inserted are selected only from those where the number of active phases of the second inverter is greater than that of the first inverter. Conversely, when a positive zero-axis voltage is applied, the three auxiliary voltage vectors inserted are selected only from those where the number of active phases of the first inverter is greater than that of the second inverter. This allows for the continuous generation of zero-axis voltages in either the positive or negative direction within the PWM carrier cycle, thus preventing the generation of zero-axis currents that fluctuate between positive and negative directions, thereby suppressing both types of zero-axis currents.

[0095] Similarly, when it is Sector 1, the basic voltage vectors corresponding to this sector are V15 and V26. When it is necessary to apply a negative zero-axis voltage to this sector to reduce the zero-axis current, such as... Figure 11a As shown, the corresponding voltage vectors are V00, V05, V15, V16, V26, V27, and V77, respectively. When a positive zero-axis voltage needs to be applied to this sector to increase the zero-axis current, as shown... Figure 11b As shown, the corresponding voltage vectors are V00, V10, V15, V25, V26, V76 and V77, respectively.

[0096] When it is sector 2, the basic voltage vectors corresponding to this sector are V35 and V46. When it is necessary to apply a negative zero-axis voltage to this sector to reduce the zero-axis current, such as... Figure 12a As shown, the corresponding voltage vectors are V00, V05, V35, V36, V46, V47, and V77, respectively. When a positive zero-axis voltage needs to be applied to this sector to increase the zero-axis current, as shown... Figure 12b As shown, the corresponding voltage vectors are V00, V30, V35, V45, V46, V76 and V77, respectively.

[0097] When it is sector 3, the basic voltage vectors corresponding to this sector are V31 and V42. When it is necessary to apply a negative zero-axis voltage to this sector to reduce the zero-axis current, such as... Figure 13a As shown, the corresponding voltage vectors are V00, V01, V31, V32, V42, V47, and V77, respectively. When a positive zero-axis voltage needs to be applied to this sector to increase the zero-axis current, as shown... Figure 13b As shown, the corresponding voltage vectors are V00, V30, V31, V41, V42, V72 and V77, respectively.

[0098] When it is sector 4, the basic voltage vectors corresponding to this sector are V51 and V62. When it is necessary to apply a negative zero-axis voltage to this sector to reduce the zero-axis current, such as... Figure 14a As shown, the corresponding voltage vectors are V00, V01, V51, V52, V62, V67, and V77, respectively. When a positive zero-axis voltage needs to be applied to this sector to increase the zero-axis current, as shown... Figure 14b As shown, the corresponding voltage vectors are V00, V50, V51, V61, V62, V72 and V77, respectively.

[0099] When it is sector 5, the basic voltage vectors corresponding to this sector are V53 and V64. When it is necessary to apply a negative zero-axis voltage to this sector to reduce the zero-axis current, such as... Figure 15a As shown, the corresponding voltage vectors are V00, V03, V53, V54, V64, V67, and V77, respectively. When a positive zero-axis voltage needs to be applied to this sector to increase the zero-axis current, as shown... Figure 15b As shown, the corresponding voltage vectors are V00, V50, V53, V63, V64, V74 and V77, respectively.

[0100] Therefore, by generating the zero-axis voltage command value V0 in the aforementioned manner, and by inserting auxiliary voltage vectors between the two basic voltage vectors, between the first basic voltage vector and the first zero voltage vector, and between the second basic voltage vector and the second zero voltage vector, the purpose of effectively suppressing the low-frequency current flowing at three times the frequency of the fundamental frequency of the phase current energizing the motor, as well as the current flowing at the carrier frequency component synchronously with the switching of the two inverters, is achieved. This results in low current and low loss in the first inverter, the second inverter, and the open-winding motor.

[0101] Furthermore, considering that although the purpose of inserting auxiliary voltage vectors in the above three locations is to suppress the zero-axis current of the motor, this will also unintentionally affect the torque of the motor. In order to minimize this effect, in this application, auxiliary voltage vectors can be selectively inserted between the second basic voltage vector and the first basic voltage vector, between the first basic voltage vector and the first zero voltage vector, and between the second basic voltage vector and the second zero voltage vector.

[0102] In practical implementation, the sector where the motor's reference voltage vector is located can be determined first. After determination, two basic voltage vectors and their corresponding durations can be obtained based on the sector. At the same time, the zero-axis voltage command value V0 can be obtained through the aforementioned method. Finally, auxiliary voltage vectors can be selectively inserted at the above three locations based on the sector, the zero-axis voltage command value V0, the duration of the first basic voltage vector, and the duration of the second basic voltage vector.

[0103] Optionally, when determining the sector, the α-axis voltage command value V of the motor can be obtained first using the aforementioned method. α and β-axis voltage command value V β Then, based on the α-axis voltage command value V α and β-axis voltage command value V β This determines the sector where the reference voltage vector is located. Furthermore, based on the α-axis voltage command value, the first polarity determination coefficient f1 can be obtained, such as f1 = V. α And according to the α-axis voltage command value V α and β-axis voltage command value V β Obtain the second polarity determination coefficient f2 and the third polarity determination coefficient f3, such as the second polarity determination coefficient... Third polarity determination coefficient Then, based on the relationship between the calculated first polarity determination coefficient f1, second polarity determination coefficient f2, and third polarity determination coefficient f3 and zero, the sector where the reference voltage vector is located is determined, as shown in Table 1:

[0104] Table 1

[0105] Sector0 ＞0 ≤0 ≤0 Sector1 ＞0 ≤0 ＞0 Sector2 ≤0 ≤0 ＞0 Sector3 ≤0 ＞0 ＞0 Sector4 ≤0 ＞0 ≤0 Sector5 ＞0 ＞0 ≤0

[0106] It should be noted that in practical applications, it can also be directly calculated using the formula n = 4 * f3' + 2 * f2' + f1', where f1' = 1 when f1 > 0 and f1' = 0 when f1 ≤ 0; f2' = 1 when f2 > 0 and f2' = 0 when f2 ≤ 0; f3' = 1 when f3 > 0 and f3' = 0 when f3 ≤ 0.

[0107] After obtaining the sector, the corresponding first basic voltage vector Vn, the duration Tn of the first basic voltage vector, the second basic voltage vector Vn+1, and the duration Tn+1 of the second basic voltage vector can be obtained based on Table 2:

[0108] Table 2

[0109]

[0110]

[0111] in,

[0112] Furthermore, the duration of the first zero voltage vector V00 and the duration of the second zero voltage vector V77 can be obtained based on the duration of the first basic voltage vector Vn (Tn) and the duration of the second basic voltage vector Vn+1 (Tn+1). For example, both are Vnul = 0.5*(1-(Tn+Tn+1)). That is, for the same sector, the duration of the two zero voltage vectors is the same, but for different sectors, the duration of the zero voltage vectors is different.

[0113] It should be noted that the duration of the zero-axis voltage command value V0 is... Here, abs represents the absolute value function, which is the absolute value of the zero-axis voltage command value V0.

[0114] Furthermore, after obtaining the sector, zero-axis voltage command value V0, and the duration of the basic voltage vector as described above, auxiliary voltage vectors can be selectively inserted at the above three locations in the following manner:

[0115] When the sector is any one of sector 0, sector 2, and sector 4, and the zero-axis voltage command value V0 < 0; or when the sector is any one of sector 1, sector 3, and sector 5, and the zero-axis voltage command value V0 ≥ 0, if Tn > Tn+1 (i.e., the duration Tn of the first basic voltage vector Vn is greater than or equal to the duration Tn+1 of the second basic voltage vector Vn), then a first auxiliary voltage vector is inserted between the first zero voltage vector V00 and the first basic voltage vector Vn, and a second auxiliary voltage vector is inserted between the first basic voltage vector Vn and the second basic voltage vector Vn+1. The voltage vector, optionally, has the same duration of action for the first and second auxiliary voltage vectors, both being half the duration of action of the zero-axis voltage command value V0 Vz; otherwise, a second auxiliary voltage vector is inserted between the first basic voltage vector Vn and the second basic voltage vector Vn+1, and a third auxiliary voltage vector is inserted between the second basic voltage vector Vn+1 and the second zero voltage vector V77. Optionally, the duration of action for both the second and third auxiliary voltage vectors is the same, both being half the duration of action of the zero-axis voltage command value V0 Vz. That is, auxiliary voltage vectors are selectively and equally inserted between two of the above three locations.

[0116] When the sector is any one of sector 0, sector 2, and sector 4, and the zero-axis voltage command value V0 ≥ 0; or when the sector is any one of sector 1, sector 3, and sector 5, and the zero-axis voltage command value V0 < 0, a first auxiliary voltage vector is directly inserted between the first zero voltage vector V00 and the first basic voltage vector Vn; a second auxiliary voltage vector is inserted between the first basic voltage vector Vn and the second basic voltage vector Vn+1; and a third auxiliary voltage vector is inserted between the second basic voltage vector Vn+1 and the second zero voltage vector V77. Optionally, the duration of the first, second, and third auxiliary voltage vectors is the same, and each is 1 / 3 of the duration Vz of the zero-axis voltage command value V0. That is, in this case, auxiliary voltage vectors are inserted equally in three locations.

[0117] Specifically, taking sector 0 (Sector0) as an example, refer to... Figures 10a-10bAs shown, the basic voltage vectors corresponding to this sector are V13 and V24. The auxiliary voltage vectors inserted when reducing the zero-axis current are V03, V14, and V27, respectively, and the auxiliary voltage vectors inserted when increasing the zero-axis current are V10, V23, and V74, respectively. Although the three auxiliary voltage vectors are inserted in three different places to suppress the zero-axis current, they will also affect the motor torque. To minimize this effect, the duration of the three auxiliary voltage vectors V03, V14, and V27 inserted when reducing the zero-axis current can be set to 1 / 3 of the duration of the zero-axis voltage command value V0. This makes the additive vector of auxiliary voltage vectors V03, V14, and V27 become V14*1 / 2*Vz. V14 will then become the direction of the average torque vector (center of gravity direction) of the entire field of Sector 0, thereby minimizing the impact on the torque variation of the motor. Since the three auxiliary voltage vectors V10, V23, and V74 inserted when increasing the zero-axis current are in the same direction, their summation vector becomes V14*1 / 2*Vz, which also becomes the direction of the average torque vector (center of gravity direction) across the entire range of Sector 0. This minimizes the impact on torque variations generated by the motor. It should be noted that for the analysis of other sectors, please refer to the analysis of Sector 0; they will not be analyzed individually here.

[0118] Furthermore, the directions of the three inserted auxiliary voltage vectors may be consistent or inconsistent. For example, in sector 0, the directions of the three inserted auxiliary voltage vectors V10, V23 and V74 are consistent when the zero-axis current is increased, while the directions of the three inserted auxiliary voltage vectors V03, V14 and V27 are not completely consistent when the zero-axis current is decreased.

[0119] In the latter case, sector 0 can be further divided into sector 0a and sector 0b, as follows: Figure 16 As shown, the duration of V13 (the first fundamental voltage vector) corresponding to sector 0a is greater than or equal to the duration of V24 (the second fundamental voltage vector), while the opposite is true for sector 0b. Furthermore, for sector 0a, as... Figure 17a As shown, V03 (first auxiliary voltage vector) is inserted only between V00 (first zero voltage vector) and V13 (first basic voltage vector), and V14 (second auxiliary voltage vector) is inserted between V13 (first basic voltage vector) and V24 (second basic voltage vector), while V27 (third auxiliary voltage vector) is not inserted. The duration of action for both the first and second auxiliary voltage vectors is 1 / 2 * Vz. For sector 0b, as... Figure 17bAs shown, V14 (second auxiliary voltage vector) is inserted only between V13 (first basic voltage vector) and V24 (second basic voltage vector), and V27 (third auxiliary voltage vector) is inserted between V24 (second basic voltage vector) and V77 (second zero voltage vector), while V03 (first auxiliary voltage vector) is not inserted, and the duration of action of the second and third auxiliary voltage vectors is 1 / 2*Vz.

[0120] In other words, when it is sector 0, V0 < 0, and Tn ≥ Tn+1, only the first auxiliary voltage vector V03 and the second auxiliary voltage vector V14 are inserted, and their duration is 1 / 2 * Vz. When it is sector 0, V0 < 0, and Tn < Tn+1, only the second auxiliary voltage vector V14 and the third auxiliary voltage vector V27 are inserted, and their duration is 1 / 2 * Vz. In this way, the additive composite vector of the auxiliary voltage vectors (i.e., the zero-axis voltage vector command value) becomes V03 * 1 / 2 * Vz + V14 * 1 / 2 * Vz. Compared with the method of inserting three auxiliary voltage vectors, although the additive composite vector increases V03 * 1 / 2 * Vz, the increased part contributes to the motor torque, thus improving the motor efficiency.

[0121] It should be noted that in sector 0, since the three auxiliary voltage vectors V10, V23 and V74 inserted when the zero-axis current is increased are in the same direction, the auxiliary voltage vectors can be inserted at the aforementioned three locations respectively.

[0122] Further reference Figure 18a As shown, when it is Sector 1, and V0≥0, and Tn≥Tn+1, only the first auxiliary voltage vector V10 and the second auxiliary voltage vector V25 are inserted, and their action time is 1 / 2*Vz. However, when it is Sector 1, and V0≥0, and Tn<Tn+1, refer to... Figure 18b As shown, only the second auxiliary voltage vector V25 and the third auxiliary voltage vector V76 are inserted, and their application time is 1 / 2*Vz.

[0123] refer to Figure 19a As shown, when it is the second sector (Sector2), and V0 < 0, and Tn ≥ Tn+1, only the first auxiliary voltage vector V05 and the second auxiliary voltage vector V36 are inserted, and their action time is 1 / 2*Vz. However, when it is the second sector (Sector2), and V0 < 0, and Tn < Tn+1, as shown... Figure 19b As shown, only the second auxiliary voltage vector V36 and the third auxiliary voltage vector V47 are inserted, and their application time is 1 / 2*Vz.

[0124] refer to Figure 20aAs shown, when it is the 3rd sector (Sector 3), and V0≥0, and Tn≥Tn+1, only the first auxiliary voltage vector V30 and the second auxiliary voltage vector V41 are inserted, and their action time is 1 / 2*Vz. However, when it is the 3rd sector (Sector 3), and V0≥0, and Tn<Tn+1, as shown... Figure 20b As shown, only the second auxiliary voltage vector V41 and the third auxiliary voltage vector V72 are inserted, and their application time is 1 / 2*Vz.

[0125] refer to Figure 21a As shown, when it is sector 4, and V0 < 0, and Tn ≥ Tn+1, only the first auxiliary voltage vector V01 and the second auxiliary voltage vector V52 are inserted, and their action time is 1 / 2*Vz. However, when it is sector 4, and V0 < 0, and Tn < Tn+1, as shown... Figure 21b As shown, only the second auxiliary voltage vector V52 and the third auxiliary voltage vector V67 are inserted, and their application time is 1 / 2*Vz.

[0126] refer to Figure 22a As shown, when it is sector 5, and V0≥0, and Tn≥Tn+1, only the first auxiliary voltage vector V50 and the second auxiliary voltage vector V63 are inserted, and their action time is 1 / 2*Vz. However, when it is sector 5, and V0≥0, and Tn<Tn+1, as shown... Figure 22b As shown, only the second auxiliary voltage vector V63 and the third auxiliary voltage vector V74 are inserted, and their application time is 1 / 2*Vz.

[0127] Based on the above, in sectors 0, 2, and 4, the sectors are further divided only when a negative zero-axis voltage is applied to reduce the zero-axis current. A partial insertion of auxiliary voltage vectors is used to effectively suppress the zero-axis current while improving motor efficiency. Similarly, in sectors 1, 3, and 5, the sectors are further divided only when a positive zero-axis voltage is applied to increase the zero-axis current. Again, a partial insertion of auxiliary voltage vectors is used to effectively suppress the zero-axis current while improving motor efficiency. Furthermore, the duration of each inserted auxiliary voltage vector is the same and half the duration of the zero-axis voltage command value, thus minimizing the impact on motor torque.

[0128] Furthermore, after inserting the auxiliary voltage vector in the aforementioned manner, the duty cycle of each phase in the first inverter and the duty cycle of each phase in the second inverter can be obtained based on the determined basic voltage vector, auxiliary voltage vector, and zero voltage vector, in the following manner:

[0129] First, based on the duration of the basic voltage vector, obtain the duration of the zero voltage vector Vnul. As mentioned above, the duration of the first zero voltage vector V00 is the same as the duration of the second zero voltage vector V77, and both are 0.5*(1-(Tn+Tn+1)). Simultaneously, obtain the duration of the zero-axis voltage command value V0 Vz, as mentioned above. Then, based on the action times Tn and Tn+1 of the basic voltage vector, the action time Vnul of the zero voltage vector, and the action time Vz of the zero-axis voltage command value V0, as shown in Table 2 above, the duty cycles of each phase in the first inverter and the duty cycles of each phase in the second inverter are obtained in sequence after the auxiliary voltage vectors are inserted.

[0130] Specifically, when the sector is sector 0, sector 2, or sector 4 and the zero-axis voltage command value V0 < 0, or when the sector is sector 1, sector 3, or sector 5 and the zero-axis voltage command value V0 ≥ 0, the duty cycle of each phase in the two inverters is obtained in the following manner:

[0131] If the duration Tn of the first basic voltage vector Vn is greater than or equal to the duration Tn+1 of the second basic voltage vector Vn+1 (i.e., Tn ≥ Tn+1), then the difference between the duration Vnul of the zero voltage vector and the duration Vz of the zero-axis voltage command value V0 is obtained to get the duty cycle of the inverter phase to be turned on corresponding to the first auxiliary voltage vector (denoted as the first duty cycle); the sum of the first duty cycle and the duration of the first auxiliary voltage vector is obtained to get the duty cycle of the inverter phase to be turned on corresponding to the first basic voltage vector Vn (denoted as the second duty cycle); the sum of the second duty cycle and the duration of the first auxiliary voltage vector is obtained. The sum of the duration Tn of the first basic voltage vector Vn is used to obtain the duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector (denoted as the third duty cycle); the sum of the duration of the third duty cycle and the second auxiliary voltage vector is used to obtain the duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector Vn+1 (denoted as the fourth duty cycle); the sum of the duration Tn+1 of the fourth duty cycle and the second basic voltage vector Vn+1 is used to obtain the duty cycle of the inverter phase to be turned on corresponding to the second zero voltage vector (denoted as the fifth duty cycle and the sixth duty cycle, respectively, and the two are equal).

[0132] If the duration Tn of the first basic voltage vector Vn is less than the duration Tn+1 of the second basic voltage vector Vn+1, i.e., Tn < Tn+1, then the difference between the duration Vnul of the zero voltage vector and the duration Vz of the zero-axis voltage command value V0 is obtained to get the duty cycle of the inverter phase to be turned on corresponding to the first basic voltage vector Vn (denoted as the seventh duty cycle and the eighth duty cycle, respectively, and the two are equal); the sum of the seventh duty cycle and the duration Tn of the first basic voltage vector Vn is obtained to get the duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector (denoted as...). (This is the ninth duty cycle); obtain the sum of the ninth duty cycle and the duration of the second auxiliary voltage vector to obtain the duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector Vn+1 (denoted as the tenth duty cycle); obtain the sum of the tenth duty cycle and the duration of the second basic voltage vector Vn+1 Tn+1 to obtain the duty cycle of the inverter phase to be turned on corresponding to the third auxiliary voltage vector (denoted as the eleventh duty cycle); obtain the sum of the eleventh duty cycle and the duration of the third auxiliary voltage vector to obtain the duty cycle of the inverter phase to be turned on corresponding to the second zero voltage vector (denoted as the twelfth duty cycle).

[0133] It should be noted that the first to twelfth duty cycles mentioned above are for ease of description only and are not specific limitations on the duty cycles. These duty cycles can be the same or different. Furthermore, it can be understood that the inverter phase to be turned on corresponding to the voltage vector refers to a phase of the inverter that will be turned on when the corresponding voltage vector is applied. This phase is the phase to be turned on, and before turning it on, the duty cycle for the current voltage vector's corresponding phase is calculated based on the previous voltage vector. In other words, the duty cycle calculation follows the order after the auxiliary voltage vector is inserted.

[0134] Specifically, when it is sector 0, V0 < 0, and Tn ≥ Tn+1, refer to Figure 17a As shown,

[0135] Step ① calculates the V-phase duty cycle of the second inverter: Dv2=Vnul–Vz;

[0136] Step 2 calculates the u-phase duty cycle of the first inverter: Du1=Dv2+1 / 2*Vz;

[0137] Step ③ calculates the duty cycle of the W phase of the second inverter: Dw2=Du1+Tn;

[0138] Step 4 calculates the V-phase duty cycle of the first inverter: Dv1=Dw2+1 / 2*Vz;

[0139] Step 5 calculates the u-phase duty cycle of the second inverter: Du2=Dv1+Tn+1;

[0140] Step 6 calculates the duty cycle of phase w of the first inverter: Dw1 = Du2.

[0141] When it is sector 0, V0 < 0, and Tn < Tn+1, refer to Figure 17b As shown,

[0142] Step ① calculates the V-phase duty cycle of the second inverter: Dv2=Vnul–Vz;

[0143] Step ② calculates the u-phase duty cycle of the first inverter: Du1 = Dv2;

[0144] Step ③ calculates the duty cycle of the W phase of the second inverter: Dw2=Du1+Tn;

[0145] Step 4 calculates the V-phase duty cycle of the first inverter: Dv1=Dw2+1 / 2*Vz;

[0146] Step 5 calculates the u-phase duty cycle of the second inverter: Du2=Dv1+Tn+1;

[0147] Step 6 calculates the duty cycle of phase W of the first inverter: Dw1 = Du2 + 1 / 2 * Vz.

[0148] When it is sector 1, V0≥0, and Tn≥Tn+1, refer to Figure 18a As shown,

[0149] Step ① calculates the u-phase duty cycle of the first inverter: Du1=Vnul–Vz;

[0150] Step ② calculates the duty cycle of phase W of the second inverter: Dw2=Du1+1 / 2*Vz;

[0151] Step ③ calculates the V-phase duty cycle of the first inverter: Dv1=Dw2+Tn;

[0152] Step 4 calculates the u-phase duty cycle of the second inverter: Du2=Dv1+1 / 2*Vz;

[0153] Step 5 calculates the duty cycle of phase w of the first inverter: Dw1=Du2+Tn+1;

[0154] Step 6 calculates the duty cycle of phase v of the second inverter: Dv2 = Dw1.

[0155] When it is sector 1, V0≥0, and Tn<Tn+1, refer to Figure 18b As shown,

[0156] Step ① calculates the u-phase duty cycle of the first inverter: Du1=Vnul–Vz;

[0157] Step ② calculates the duty cycle of phase W of the second inverter: Dw2 = Du1;

[0158] Step ③ calculates the V-phase duty cycle of the first inverter: Dv1=Dw2+Tn;

[0159] Step 4 calculates the u-phase duty cycle of the second inverter: Du2=Dv1+1 / 2*Vz;

[0160] Step 5 calculates the duty cycle of phase w of the first inverter: Dw1=Du2+Tn+1;

[0161] Step 6 calculates the V-phase duty cycle of the second inverter: Dv2 = Dw1 + 1 / 2 * Vz.

[0162] When it is the second sector (Sector2), and V0 < 0, and Tn ≥ Tn+1, refer to Figure 19a As shown,

[0163] Step ① calculates the w-phase duty cycle of the second inverter: Dw2=Vnul–Vz;

[0164] Step ② calculates the V-phase duty cycle of the first inverter: Dv1=Dw2+1 / 2*Vz;

[0165] Step ③ calculates the u-phase duty cycle of the second inverter: Du2=Dv1+Tn;

[0166] Step 4 calculates the duty cycle of phase W of the first inverter: Dw1=Du2+1 / 2*Vz;

[0167] Step 5 calculates the duty cycle of phase v of the second inverter: Dv2=Dw1+Tn+1;

[0168] Step 6 calculates the u-phase duty cycle of the first inverter: Du1 = Dv2.

[0169] When it is sector 2, and V0 < 0, and Tn < Tn+1, refer to Figure 19b As shown,

[0170] Step ① calculates the w-phase duty cycle of the second inverter: Dw2=Vnul–Vz;

[0171] Step 2 calculates the duty cycle of phase v of the first inverter: Dv1 = Dw2;

[0172] Step ③ calculates the u-phase duty cycle of the second inverter: Du2=Dv1+Tn;

[0173] Step 4 calculates the duty cycle of phase W of the first inverter: Dw1=Du2+1 / 2*Vz;

[0174] Step 5 calculates the duty cycle of phase v of the second inverter: Dv2=Dw1+Tn+1;

[0175] Step 6 calculates the u-phase duty cycle of the first inverter: Du1 = Dv2 + 1 / 2 * Vz.

[0176] When it is sector 3, and V0≥0, and Tn≥Tn+1, refer to Figure 20a As shown,

[0177] Step ① calculates the duty cycle of phase v of the first inverter: Dv1=Vnul–Vz;

[0178] Step ② calculates the u-phase duty cycle of the second inverter: Du2=Dv1+1 / 2*Vz;

[0179] Step ③ calculates the duty cycle of phase W of the first inverter: Dw1=Du2+Tn;

[0180] Step 4 calculates the V-phase duty cycle of the second inverter: Dv2=Dw1+1 / 2*Vz;

[0181] Step 5 calculates the u-phase duty cycle of the first inverter: Du1 = Dv2 + Tn + 1;

[0182] Step 6 calculates the duty cycle of phase W of the second inverter: Dw2 = Du1.

[0183] When it is sector 3, V0≥0, and Tn<Tn+1, refer to Figure 20b As shown,

[0184] Step ① calculates the duty cycle of phase v of the first inverter: Dv1=Vnul–Vz;

[0185] Step ② calculates the u-phase duty cycle of the second inverter: Du2 = Dv1;

[0186] Step ③ calculates the duty cycle of phase W of the first inverter: Dw1=Du2+Tn;

[0187] Step 4 calculates the V-phase duty cycle of the second inverter: Dv2=Dw1+1 / 2*Vz;

[0188] Step 5 calculates the u-phase duty cycle of the first inverter: Du1 = Dv2 + Tn + 1;

[0189] Step 6 calculates the duty cycle of phase W of the second inverter: Dw2 = Du1 + 1 / 2 * Vz.

[0190] When it is sector 4, V0 < 0, and Tn ≥ Tn+1, refer to Figure 21a As shown,

[0191] Step ① calculates the u-phase duty cycle of the second inverter: Du2=Vnul–Vz;

[0192] Step ② calculates the duty cycle of phase W of the first inverter: Dw1=Du2+1 / 2*Vz;

[0193] Step ③ calculates the v-phase duty cycle of the second inverter: Dv2=Dw1+Tn;

[0194] Step 4 calculates the u-phase duty cycle of the first inverter: Du1=Dv2+1 / 2*Vz;

[0195] Step 5 calculates the duty cycle of phase w of the second inverter: Dw2=Du1+Tn+1;

[0196] Step 6 calculates the duty cycle of phase v of the first inverter: Dv1 = Dw2.

[0197] When it is sector 4, V0 < 0, and Tn ≥ Tn+1, refer to Figure 21b As shown,

[0198] Step ① calculates the u-phase duty cycle of the second inverter: Du2=Vnul–Vz;

[0199] Step ② calculates the duty cycle of phase W of the first inverter: Dw1 = Du2;

[0200] Step ③ calculates the v-phase duty cycle of the second inverter: Dv2=Dw1+Tn;

[0201] Step 4 calculates the u-phase duty cycle of the first inverter: Du1=Dv2+1 / 2*Vz;

[0202] Step 5 calculates the duty cycle of phase w of the second inverter: Dw2=Du1+Tn+1;

[0203] Step 6 calculates the duty cycle of phase V of the first inverter: Dv1 = Dw2 + 1 / 2 * Vz.

[0204] When it is sector 5, and V0≥0, and Tn≥Tn+1, refer to Figure 22a As shown,

[0205] Step ① calculates the w-phase duty cycle of the first inverter: Dw1=Vnul–Vz;

[0206] Step ② calculates the V-phase duty cycle of the second inverter: Dv2=Dw1+1 / 2*Vz;

[0207] Step ③ calculates the u-phase duty cycle of the first inverter: Du1=Dv2+Tn;

[0208] Step 4 calculates the duty cycle of phase W of the second inverter: Dw2=Du1+1 / 2*Vz;

[0209] Step 5 calculates the duty cycle of phase v of the first inverter: Dv1 = Dw2 + Tn + 1;

[0210] Step 6 calculates the u-phase duty cycle of the second inverter: Du2 = Dv1.

[0211] When it is sector 5, V0≥0, and Tn<Tn+1, refer to Figure 22b As shown,

[0212] Step ① calculates the w-phase duty cycle of the first inverter: Dw1=Vnul–Vz;

[0213] Step ② calculates the duty cycle of phase v of the second inverter: Dv2 = Dw1;

[0214] Step ③ calculates the u-phase duty cycle of the first inverter: Du1=Dv2+Tn;

[0215] Step 4 calculates the duty cycle of phase W of the second inverter: Dw2=Du1+1 / 2*Vz;

[0216] Step 5 calculates the duty cycle of phase v of the first inverter: Dv1 = Dw2 + Tn + 1;

[0217] Step 6 calculates the u-phase duty cycle of the second inverter: Du2 = Dv1 + 1 / 2 * Vz.

[0218] Furthermore, when the sector is any one of sector 0, sector 2, and sector 4, and the zero-axis voltage command value V0 ≥ 0, or when the sector is any one of sector 1, sector 3, and sector 5, and the zero-axis voltage command value V0 < 0, the duty cycle of each phase in the two inverters can be obtained in the following way:

[0219] The difference between the action time Vnul of the zero-voltage vector and the action time Vz of the zero-axis voltage command value V0 is obtained to get the duty cycle of the inverter phase to be turned on corresponding to the first auxiliary voltage vector (denoted as the thirteenth duty cycle); the sum of the thirteenth duty cycle and the action time of the first auxiliary voltage vector is obtained to get the duty cycle of the inverter phase to be turned on corresponding to the first basic voltage vector Vn (denoted as the fourteenth duty cycle); the sum of the fourteenth duty cycle and the action time Tn of the first basic voltage vector Vn is obtained to get the duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector (denoted as the fifteenth duty cycle). (Duty cycle); obtain the sum of the fifteenth duty cycle and the action time of the second auxiliary voltage vector to obtain the duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector Vn+1 (denoted as the sixteenth duty cycle); obtain the sum of the sixteenth duty cycle and the action time Tn+1 of the second basic voltage vector Vn+1 to obtain the duty cycle of the inverter phase to be turned on corresponding to the third auxiliary voltage vector (denoted as the seventeenth duty cycle); obtain the sum of the seventeenth duty cycle and the action time of the third auxiliary voltage vector to obtain the duty cycle of the inverter phase to be turned on corresponding to the second zero voltage vector (denoted as the eighteenth duty cycle).

[0220] It should be noted that the duty cycles from the thirteenth to the eighteenth mentioned above are for ease of description only and are not specific limitations on the duty cycles. These duty cycles can be the same or different. Furthermore, it can be understood that the inverter phase to be turned on corresponding to the voltage vector refers to a phase of the inverter that will be turned on when the corresponding voltage vector is applied. This phase is the phase to be turned on, and before turning it on, the duty cycle for the current voltage vector's corresponding phase is calculated based on the previous voltage vector. In other words, the duty cycle calculation follows the order after the auxiliary voltage vector is inserted.

[0221] Specifically, when it is sector 0 and V0≥0, refer to Figure 10b As shown,

[0222] Step ① calculates the u-phase duty cycle of the first inverter: Du1=Vnul–Vz;

[0223] Step 2 calculates the V-phase duty cycle of the second inverter: Dv2=Du1+1 / 3*Vz;

[0224] Step ③ calculates the duty cycle of phase v of the first inverter: Dv1=Dv2+Tn;

[0225] Step 4 calculates the duty cycle of phase W of the second inverter: Dw2=Dv1+1 / 3*Vz;

[0226] Step 5 calculates the w-phase duty cycle of the first inverter: Dw1 = Dw2 + Tn + 1;

[0227] Step 6 calculates the u-phase duty cycle of the second inverter: Du2 = Dw1 + 1 / 3 * Vz.

[0228] When it is sector 1 and V0 < 0, refer to Figure 11a As shown,

[0229] Step ① calculates the w-phase duty cycle of the second inverter: Dw2=Vnul–Vz;

[0230] Step 2 calculates the u-phase duty cycle of the first inverter: Du1=Dw2+1 / 3*Vz;

[0231] Step ③ calculates the u-phase duty cycle of the second inverter: Du2=Du1+Tn;

[0232] Step 4 calculates the V-phase duty cycle of the first inverter: Dv1=Du2+1 / 3*Vz;

[0233] Step 5 calculates the v-phase duty cycle of the second inverter: Dv2 = Dv1 + Tn + 1;

[0234] Step 6 calculates the duty cycle of phase w of the first inverter: Dw1 = Dv2 + 1 / 3 * Vz.

[0235] When it is sector 2 and V0≥0, refer to Figure 12b As shown,

[0236] Step ① calculates the duty cycle of phase v of the first inverter: Dv1=Vnul–Vz;

[0237] Step 2 calculates the w-phase duty cycle of the second inverter: Dw2=Dv1+1 / 3*Vz;

[0238] Step ③ calculates the w-phase duty cycle of the first inverter: Dw1=Dw2+Tn;

[0239] Step 4 calculates the u-phase duty cycle of the second inverter: Du2=Dw1+1 / 3*Vz;

[0240] Step 5 calculates the u-phase duty cycle of the first inverter: Du1 = Du2 + Tn + 1;

[0241] Step 6 calculates the V-phase duty cycle of the second inverter: Dv2 = Du1 + 1 / 3 * Vz.

[0242] When it is sector 3 and V0 < 0, refer to Figure 13a As shown,

[0243] Step ① calculates the u-phase duty cycle of the second inverter: Du2=Vnul–Vz;

[0244] Step 2 calculates the V-phase duty cycle of the first inverter: Dv1=Du2+1 / 3*Vz;

[0245] Step ③ calculates the v-phase duty cycle of the second inverter: Dv2=Dv1+Tn;

[0246] Step 4 calculates the duty cycle of phase W of the first inverter: Dw1=Dv2+1 / 3*Vz;

[0247] Step 5 calculates the w-phase duty cycle of the second inverter: Dw2 = Dw1 + Tn + 1;

[0248] Step 6 calculates the u-phase duty cycle of the first inverter: Du1 = Dw2 + 1 / 3 * Vz.

[0249] When it is sector 4 and V0≥0, refer to Figure 14b As shown,

[0250] Step ① calculates the w-phase duty cycle of the first inverter: Dw1=Vnul–Vz;

[0251] Step ② calculates the u-phase duty cycle of the second inverter: Du2=Dw1+1 / 3*Vz;

[0252] Step ③ calculates the u-phase duty cycle of the first inverter: Du1=Du2+Tn;

[0253] Step 4 calculates the V-phase duty cycle of the second inverter: Dv2=Du1+1 / 3*Vz;

[0254] Step 5 calculates the duty cycle of phase v of the first inverter: Dv1 = Dv2 + Tn + 1;

[0255] Step 6 calculates the duty cycle of phase W of the second inverter: Dw2 = Dv1 + 1 / 3 * Vz.

[0256] When it is sector 5 and V0 < 0, refer to Figure 15a As shown,

[0257] Step ① calculates the v-phase duty cycle of the second inverter: Dv2=Vnul-Vz;

[0258] Step 2 calculates the duty cycle of phase w of the first inverter: Dw1=Dv2+1 / 3*Vz;

[0259] Step ③ calculates the w-phase duty cycle of the second inverter: Dw2=Dw1+Tn;

[0260] Step 4 calculates the u-phase duty cycle of the first inverter: Du1 = Dw2 + 1 / 3 * Vz;

[0261] Step 5 calculates the u-phase duty cycle of the second inverter: Du2 = Du1 + Tn + 1;

[0262] Step 6 calculates the duty cycle of phase V of the first inverter: Dv1 = Du2 + 1 / 3 * Vz.

[0263] Using the above method, the duty cycle of each phase in the first inverter and the duty cycle of each phase in the second inverter can be calculated. Then, based on the duty cycle of each phase, the PWM control signal for the corresponding switch can be obtained. This PWM control signal is then used to control the switches in the first and second inverters, thereby controlling the motor speed. It should be noted that the method for calculating the PWM control signal based on the duty cycle can be implemented using existing technology, which will not be elaborated upon here.

[0264] In summary, the control method for an open-winding motor according to embodiments of the present invention, by selectively inserting an auxiliary voltage vector between the basic voltage vector and the motor's zero voltage vector based on the sector, the zero-axis voltage command value, and the duration of the basic voltage vector, can not only effectively suppress the zero-axis current and achieve low current and low loss, but also ensure that the motor has high operating efficiency. At the same time, the duration of the inserted auxiliary voltage vectors is the same and is 1 / 2 or 1 / 3 of the duration of the zero-axis voltage command value, thus minimizing the impact on the generation of motor torque.

[0265] In addition, embodiments of the present invention also provide an open-winding motor, such as... Figure 1 As shown, the open-winding motor may include: a three-phase winding, a first inverter, a second inverter, and a control device (not shown in the figure).

[0266] In this configuration, one end of the three-phase winding is connected to the first inverter, and the other end is connected to the second inverter. The first and second inverters share a common DC bus, meaning they share the same DC power supply. Specifically, refer to... Figure 1As shown, the open-winding motor includes three-phase stator windings (referred to as three-phase windings), denoted as U-phase winding, V-phase winding, and W-phase winding. Both ends of the three-phase windings are open, meaning they are not connected to each other, thus forming six winding terminals, denoted as Ua, Va, Wa, Ub, Vb, and Wb. The two inverters can be three-phase full-bridge inverters composed of six power switching transistors. The input terminals of both the first and second inverters are connected to the DC buses DC+ and DC-. The three output terminals of the first inverter are connected to the corresponding three-phase windings of the open-winding motor through winding terminals Ua, Va, and Wa, respectively. The three output terminals of the second inverter are connected to the corresponding three-phase windings of the open-winding motor through winding terminals Ub, Vb, and Wb, respectively. The DC voltage on the DC buses DC+ and DC- can be obtained from a DC power supply or by converting AC power from a switching power supply. It should be noted that the open-winding motor in this application can be a three-phase permanent magnet synchronous motor.

[0267] The control device includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the aforementioned control method. The specific process is described above and will not be repeated here.

[0268] According to the open-winding motor of the present invention, by means of the aforementioned control method, auxiliary voltage vectors are selectively inserted between the basic voltage vector and the zero voltage vector of the motor based on the sector, the zero-axis voltage command value and the duration of the basic voltage vector. This not only effectively suppresses the zero-axis current and achieves low current and low loss, but also ensures that the motor has high operating efficiency. At the same time, the duration of the inserted auxiliary voltage vectors is the same and is 1 / 2 or 1 / 3 of the duration of the zero-axis voltage command value, thus minimizing the impact on the generation of motor torque.

[0269] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0270] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0271] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0272] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0273] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0274] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A control method for an open-winding motor, characterized in that, The open-winding motor includes a three-phase winding, with both ends of the three-phase winding connected to a first inverter and a second inverter, respectively. The first inverter and the second inverter share a DC bus. The method includes: Obtain the zero-axis voltage command value of the motor, and obtain the sector where the reference voltage vector of the motor is located; The basic voltage vector of the motor is obtained according to the sector, and the duration of the basic voltage vector is obtained, wherein the basic voltage vector is a voltage vector that generates motor voltage but does not generate zero-axis voltage; Based on the sector, the zero-axis voltage command value, and the duration of the basic voltage vector, an auxiliary voltage vector is selected and inserted between the basic voltage vector and the zero-axis voltage vector of the motor. The zero-axis voltage vector is a voltage vector that does not generate inter-phase interference voltage and does not generate zero-axis voltage, while the auxiliary voltage vector is a voltage vector that generates inter-phase interference voltage and generates zero-axis voltage. The duty cycles of the first inverter and the second inverter are obtained based on the basic voltage vector, the zero voltage vector, and the auxiliary voltage vector, and the motor is controlled according to the duty cycles. With the zero voltage vector as the center point and the basic voltage vector as the vertex, the reference voltage vector of the motor is divided into 6 sectors, wherein the center point includes two zero voltage vectors and each vertex includes two basic voltage vectors; The step of selecting and inserting an auxiliary voltage vector between the basic voltage vector and the motor's zero voltage vector based on the sector, the zero-axis voltage command value, and the duration of the basic voltage vector includes: When the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, if the duration of the first basic voltage vector is greater than or equal to the duration of the second basic voltage vector, then a first auxiliary voltage vector is inserted between the first zero voltage vector and the first basic voltage vector, and a second auxiliary voltage vector is inserted between the first basic voltage vector and the second basic voltage vector; if the duration of the first basic voltage vector is less than the duration of the second basic voltage vector, then a second auxiliary voltage vector is inserted between the first basic voltage vector and the second basic voltage vector, and a third auxiliary voltage vector is inserted between the second basic voltage vector and the second zero voltage vector.

2. The method according to claim 1, characterized in that, The step of selecting and inserting an auxiliary voltage vector between the basic voltage vector and the zero-axis voltage vector of the motor based on the sector, the zero-axis voltage command value, and the duration of action of the basic voltage vector, further includes: When the sector is sector 0, 2, or 4 and the zero-axis voltage command value is greater than or equal to 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is less than 0, the first auxiliary voltage vector is inserted between the first zero voltage vector and the first basic voltage vector, the second auxiliary voltage vector is inserted between the first basic voltage vector and the second basic voltage vector, and the third auxiliary voltage vector is inserted between the second basic voltage vector and the second zero voltage vector.

3. The method according to claim 2, characterized in that, The step of obtaining the duty cycles of the first inverter and the second inverter based on the basic voltage vector, the zero voltage vector, and the auxiliary voltage vector includes: The duration of the zero voltage vector is obtained based on the duration of the basic voltage vector. The duration of the zero-axis voltage command value is obtained; Based on the duration of the basic voltage vector, the duration of the zero voltage vector, and the duration of the zero-axis voltage command value, the duty cycles of the first inverter and the second inverter are obtained in the order following the insertion of the auxiliary voltage vector.

4. The method according to claim 3, characterized in that, When the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, the step of obtaining the duty cycle of the first inverter and the second inverter according to the action time of the basic voltage vector, the action time of the zero voltage vector, and the action time of the zero-axis voltage command value, in the order after inserting the auxiliary voltage vector, includes: If the duration of action of the first basic voltage vector is greater than or equal to the duration of action of the second basic voltage vector, then the difference between the duration of action of the zero voltage vector and the duration of action of the zero-axis voltage command value is obtained, and the first duty cycle of the inverter phase to be turned on corresponding to the first auxiliary voltage vector is obtained. The sum of the first duty cycle and the duration of the first auxiliary voltage vector is obtained to obtain the second duty cycle of the inverter phase to be turned on corresponding to the first basic voltage vector; The sum of the second duty cycle and the duration of the first basic voltage vector is obtained to obtain the third duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector; The sum of the third duty cycle and the duration of the second auxiliary voltage vector is obtained to obtain the fourth duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector; The sum of the fourth duty cycle and the duration of the second basic voltage vector is obtained to obtain the fifth and sixth duty cycles of the inverter phase to be turned on corresponding to the second zero voltage vector, wherein the fifth duty cycle is equal to the sixth duty cycle.

5. The method according to claim 3, characterized in that, When the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, the step of obtaining the duty cycle of the first inverter and the second inverter according to the action time of the basic voltage vector, the action time of the zero voltage vector, and the action time of the zero-axis voltage command value, in the order after inserting the auxiliary voltage vector, includes: If the duration of the first basic voltage vector is less than the duration of the second basic voltage vector, then the difference between the duration of the zero voltage vector and the duration of the zero-axis voltage command value is obtained to obtain the seventh and eighth duty cycles of the inverter phase to be turned on corresponding to the first basic voltage vector, wherein the seventh duty cycle is equal to the eighth duty cycle. The sum of the seventh duty cycle and the duration of the first basic voltage vector is obtained to obtain the ninth duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector; The sum of the ninth duty cycle and the duration of the second auxiliary voltage vector is obtained to get the tenth duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector; The sum of the tenth duty cycle and the duration of the second basic voltage vector is obtained to obtain the eleventh duty cycle of the inverter phase to be turned on corresponding to the third auxiliary voltage vector; The sum of the eleventh duty cycle and the duration of the third auxiliary voltage vector is obtained to obtain the twelfth duty cycle of the inverter phase to be turned on corresponding to the second zero voltage vector.

6. The method according to claim 3, characterized in that, When the sector is sector 0, 2, or 4 and the zero-axis voltage command value is greater than or equal to 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is less than 0, the step of obtaining the duty cycle of the first inverter and the second inverter according to the action time of the basic voltage vector, the action time of the zero voltage vector, and the action time of the zero-axis voltage command value, in the order after inserting the auxiliary voltage vector, includes: The difference between the duration of the zero voltage vector and the duration of the zero-axis voltage command value is obtained to obtain the thirteenth duty cycle of the inverter phase to be turned on corresponding to the first auxiliary voltage vector; The sum of the thirteenth duty cycle and the duration of the first auxiliary voltage vector is obtained to obtain the fourteenth duty cycle of the inverter phase to be turned on corresponding to the first basic voltage vector. The sum of the fourteenth duty cycle and the duration of the first basic voltage vector is obtained to get the fifteenth duty cycle of the inverter phase to be turned on corresponding to the second auxiliary voltage vector; The sum of the fifteenth duty cycle and the duration of the second auxiliary voltage vector is obtained to get the sixteenth duty cycle of the inverter phase to be turned on corresponding to the second basic voltage vector; The sum of the sixteenth duty cycle and the duration of the second basic voltage vector is obtained to get the seventeenth duty cycle of the inverter phase to be turned on corresponding to the third auxiliary voltage vector; The sum of the seventeenth duty cycle and the duration of the third auxiliary voltage vector is obtained to obtain the eighteenth duty cycle of the inverter phase to be turned on corresponding to the second zero voltage vector.

7. The method according to any one of claims 3-6, characterized in that, When the sector is sector 0, 2, or 4 and the zero-axis voltage command value is less than 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is greater than or equal to 0, the duration of action of the first auxiliary voltage vector, the second auxiliary voltage vector, and the third auxiliary voltage vector is 1 / 2 of the duration of action of the zero-axis voltage command value. When the sector is sector 0, 2, or 4 and the zero-axis voltage command value is greater than or equal to 0, or when the sector is sector 1, 3, or 5 and the zero-axis voltage command value is less than 0, the duration of action of the first auxiliary voltage vector, the second auxiliary voltage vector, and the third auxiliary voltage vector is 1 / 3 of the duration of action of the zero-axis voltage command value.

8. The method according to claim 1, characterized in that, The step of obtaining the zero-axis voltage command value of the motor includes: Obtain the d, q, and zero-axis current command values, zero-axis current feedback value, and harmonic current frequency of the motor; The first voltage value is obtained based on the zero-axis current command value, the zero-axis current feedback value, and the harmonic current frequency; and the second voltage value is obtained based on the d-axis and q-axis current command values. The zero-axis voltage command value is obtained based on the first voltage value and the second voltage value.

9. The method according to claim 8, characterized in that, The step of obtaining the first voltage value based on the zero-axis current command value, the zero-axis current feedback value, and the harmonic current frequency includes: Obtain the first difference between the zero-axis current command value and the zero-axis current feedback value; Multiply the first difference by the first proportional gain to obtain the first value; The first difference is multiplied by the first resonance gain to obtain the second value, and the second difference between the second value and the first integral result is obtained. The second difference is then integrated to obtain the second integral result, wherein the first integral result is obtained by multiplying the harmonic current frequency and the second integral result corresponding to the previous moment. The first voltage value is obtained by summing the second integral result and the first value.

10. The method according to claim 8, characterized in that, The second voltage value is calculated using the following formula: in, This is the second voltage value. The frequency of the harmonic current. Let be the q-axis inductance of the motor. Let be the d-axis inductance of the motor. This is the d-axis current command value. This is the q-axis current command value. Let A be the rotor position of the motor, and A be a coefficient.

11. The method according to claim 1, characterized in that, The step of obtaining the sector where the reference voltage vector of the motor is located includes: Obtain the motor , Shaft voltage command value; According to the above , The axis voltage command value determines the sector where the reference voltage vector is located.

12. The method according to claim 11, characterized in that, According to the , The shaft voltage command value determines the sector where the reference voltage vector is located, including: according to The first polarity determination coefficient is obtained from the shaft voltage command value, and according to the... , The axis voltage command value is used to obtain the second polarity determination coefficient and the third polarity determination coefficient; The sector where the reference voltage vector is located is determined based on the relationship between the first polarity determination coefficient, the second polarity determination coefficient, the third polarity determination coefficient, and zero.

13. An open-winding motor, characterized in that, include: The system comprises a three-phase winding, a first inverter, a second inverter, and a control device. The two ends of the three-phase winding are respectively connected to the first inverter and the second inverter, and the first inverter and the second inverter share a DC bus; The control device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method according to any one of claims 1 to 12.

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