Method and device for generating duty ratio of motor driving circuit and vehicle

Abstract

The invention discloses a duty ratio generation method and device of a motor drive circuit and a vehicle, the motor drive circuit comprises multiple phases of bridge arms, each phase of bridge arm comprises an upper bridge hybrid switch and a lower bridge hybrid switch, each of the upper bridge hybrid switches and the lower bridge hybrid switches comprises a Si tube and a SiC tube which are connected in parallel, and the method comprises the following steps: for any phase of bridge arm, the Si tube and the SiC tube are connected in parallel; acquiring the bridge arm current and the bridge arm duty ratio of the bridge arm; under the condition that the absolute value of the bridge arm current is greater than a preset bridge arm current threshold value, determining turn-on delay time and turn-off delay time between the Si tube and the SiC tube according to the bridge arm current; and determining the duty ratio of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the bridge arm duty ratio. According to the method provided by the invention, the hybrid switch is applied to the motor driving circuit and is correspondingly controlled, so that the motor can be controlled to operate with higher efficiency, the loss of a power device can be reduced, and the electric driving efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the field of vehicle technology, and in particular to a method for generating a duty cycle of a motor drive circuit, a device for generating a duty cycle of a motor drive circuit, and a vehicle. Background Art

[0002] At present, power electronic power devices generally use Si semiconductor materials. Si-based insulated gate bipolar transistors (Si tubes for short) have the advantages of low on-state voltage drop, large current capacity and low driving loss, and are widely used in new energy, smart grid and other fields. However, Si tubes (such as IGBT) have disadvantages such as high switching loss and low switching frequency, which restrict their application in high power density, high switching frequency and other fields. In recent years, new wide bandgap semiconductor materials suitable for high temperature, high frequency, medium and high power power electronics applications are represented by silicon carbide (SiC) and gallium nitride (GaN). SiC has the advantages of higher withstand voltage, higher switching frequency, lower on-resistance and better heat dissipation, so it has more application prospects in new energy.

[0003] Although the performance of SiC power devices far exceeds that of Si tubes, the limitations of SiC wafer growth process and current carrying capacity of the same chip area result in the single-chip current carrying capacity of SiC devices being inferior to that of Si tubes. In addition, the cost of SiC discrete devices is 2 to 15 times higher than that of Si tubes, and its processing technology is complex, making it difficult to meet the requirements of mass production. In order to solve the contradiction between SiC's high performance and high cost, a hybrid switch (Hybrid Switch) with Si tubes as the main and SiC as the auxiliary has become a feasible technical route, with SiC of small current specifications as auxiliary switch devices.

[0004] In related technologies, hybrid switching devices are mainly used in Buck / Boost and single-phase inverters, and have not been found in electric drive new energy. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the first object of the present invention is to propose a duty cycle generation method for a motor drive circuit, which applies a hybrid switch to the motor drive circuit and performs corresponding control, thereby controlling the motor to operate more efficiently, reducing the loss of power devices, and improving the efficiency of the electric drive.

[0006] A second objective of the present invention is to provide a duty cycle generating device for a motor driving circuit.

[0007] A third object of the present invention is to provide a vehicle.

[0008] To achieve the above-mentioned purpose, an embodiment of the first aspect of the present invention proposes a method for generating a duty cycle of a motor drive circuit, wherein the motor drive circuit includes a multi-phase bridge arm, each phase bridge arm includes an upper bridge hybrid switch and a lower bridge hybrid switch, and the upper bridge hybrid switch and the lower bridge hybrid switch both include a Si tube and a SiC tube connected in parallel. The method includes: for any phase bridge arm, obtaining the bridge arm current and the bridge arm duty cycle of the bridge arm; when the absolute value of the bridge arm current is greater than a preset bridge arm current threshold, determining the turn-on delay time and the turn-off delay time between the Si tube and the SiC tube according to the bridge arm current; and determining the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the bridge arm duty cycle.

[0009] According to the duty cycle generation method of the motor drive circuit of the embodiment of the present invention, for any phase bridge arm, the bridge arm current and bridge arm duty cycle of the bridge arm are first obtained, and when the absolute value of the bridge arm current is greater than the preset bridge arm current threshold, the opening delay time and the closing delay time between the Si tube and the SiC tube are determined according to the bridge arm current, and then the duty cycle of the Si tube and the SiC tube is determined based on the opening delay time, the closing delay time and the bridge arm duty cycle. Therefore, the method can control the motor to operate more efficiently, reduce the loss of power devices, and improve the efficiency of electric drive.

[0010] In addition, the duty cycle generation method of the motor drive circuit according to the above embodiment of the present invention may also have the following additional technical features:

[0011] According to one embodiment of the present invention, the determining the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the bridge arm duty cycle includes: when the turn-on delay time is greater than or equal to zero, taking the bridge arm duty cycle as the duty cycle of the SiC tube, and obtaining the difference between the bridge arm duty cycle and the turn-on delay duty cycle to obtain the duty cycle of the Si tube; wherein the turn-on delay duty cycle is the ratio of the turn-on delay time to the control period; when the turn-on delay time is less than zero, obtaining the bridge arm duty cycle The duty cycle of the SiC tube is obtained by summing the duty cycle of the bridge arm and the turn-on delay duty cycle, and the bridge arm duty cycle is used as the duty cycle of the Si tube; when the turn-off delay time is greater than or equal to zero, the difference between the duty cycle of the Si tube and the turn-off delay duty cycle is obtained to update the duty cycle of the Si tube; wherein the turn-off delay duty cycle is the ratio of the turn-off delay time to the control period; when the turn-off delay time is less than zero, the sum of the duty cycle of the SiC tube and the turn-off delay duty cycle is obtained to update the duty cycle of the SiC tube.

[0012] According to one embodiment of the present invention, the duty cycle of the target tube includes the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube, and the target tube is the Si tube or the SiC tube. The method also includes: obtaining the minimum pulse width and dead time of the target tube; based on the duty cycle, minimum pulse width and dead time of the target tube, determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube.

[0013] According to one embodiment of the present invention, determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle, minimum pulse width and dead time of the target tube includes: determining multiple duty cycle intervals based on the minimum pulse width and the dead time; determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle interval in which the duty cycle of the target tube is located.

[0014] According to an embodiment of the present invention, determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle interval of the target tube includes: a ∈The first duty cycle interval (1-T plsMin / T s , 1], determine D aH =1,D aL =0; where D a is the duty cycle of the target tube, T plsMin is the minimum pulse width of the target tube, T s is the control period, D aH is the duty cycle of the upper bridge target tube, D aL is the duty cycle of the lower bridge target tube; a ∈The second duty cycle interval (1-T plsMin / T s -2*T dead / T s , 1-T plsMin / T s ], determine D aH =D a , D aL =0; where T dead is the dead time of the target tube; a ∈The third duty cycle interval (T plsMin / T s +2*T dead / T s , 1-T plsMin / T s -2*T dead / T s ], determine D aH =D a , DaL =1-D a -2*T dead / T s ; in D a ∈The fourth duty cycle interval (T plsMin / T s , T plsMin / T s +2*T dead / T s ], determine D aH =0,D aL =1-D a ; in D a ∈ the fifth duty cycle interval [0, T plsMin / T s ], determine D aH =0,D aL =1.

[0015] According to one embodiment of the present invention, obtaining the bridge arm duty cycle includes: performing space vector pulse width modulation control on the motor drive circuit to obtain the DC bus voltage, α-axis voltage and β-axis voltage of the motor drive circuit; determining a target voltage based on the α-axis voltage and the β-axis voltage, and determining the sector in which the target voltage is located; determining the bridge arm duty cycle based on the sector in which the target voltage is located, the α-axis voltage, the β-axis voltage and the DC bus voltage.

[0016] According to one embodiment of the present invention, the preset bridge arm current threshold is determined based on the ratio of the threshold voltage of the Si tube to the on-resistance of the SiC tube.

[0017] According to one embodiment of the present invention, the method further includes: when the absolute value of the bridge arm current is less than or equal to the preset bridge arm current threshold, determining that the duty cycle of the SiC tube is the bridge arm duty cycle and the duty cycle of the Si tube is zero.

[0018] To achieve the above-mentioned purpose, the third aspect of the present invention proposes a duty cycle generating device for a motor drive circuit, wherein the motor drive circuit includes a multi-phase bridge arm, each phase bridge arm includes an upper bridge hybrid switch and a lower bridge hybrid switch, and the upper bridge hybrid switch and the lower bridge hybrid switch both include a Si tube and a SiC tube connected in parallel, and the device includes: an acquisition module, for acquiring the bridge arm current and the duty cycle of the bridge arm for any phase bridge arm; a first determination module, for determining the turn-on delay time and the turn-off delay time between the Si tube and the SiC tube according to the bridge arm current when the absolute value of the bridge arm current is greater than a preset bridge arm current threshold; a second determination module, for determining the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the duty cycle of the bridge arm.

[0019] According to the duty cycle generation device of the motor drive circuit of the embodiment of the present invention, the acquisition module acquires the bridge arm current and duty cycle of any phase bridge arm; the first determination module determines the turn-on delay time and turn-off delay time between the Si tube and the SiC tube according to the bridge arm current when the absolute value of the bridge arm current is greater than the preset bridge arm current threshold; the second determination module determines the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the duty cycle of the bridge arm. Thus, the device can control the motor to operate more efficiently, reduce the loss of power devices, and improve the efficiency of electric drive.

[0020] In order to achieve the above-mentioned purpose, a fourth aspect of the present invention provides a vehicle, comprising the duty cycle generating device of the above-mentioned motor drive circuit.

[0021] According to the vehicle of the embodiment of the present invention, the duty cycle generating device of the motor drive circuit can control the motor to operate with higher efficiency, reduce the loss of power devices, and improve the efficiency of electric drive.

[0022] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of a method for generating a duty cycle of a motor driving circuit according to an embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of the structure of a hybrid switch according to an embodiment of the present invention;

[0025] Figure 3 is a flow chart of a method for generating a duty cycle of a motor driving circuit according to another embodiment of the present invention;

[0026] Figure 4 is a schematic diagram of a working mode of a hybrid switch according to an embodiment of the present invention;

[0027] Figure 5 is a schematic diagram of six sectors in an α-β coordinate system according to an embodiment of the present invention;

[0028] Figure 6 is a block diagram of a duty cycle generating device of a motor driving circuit according to an embodiment of the present invention;

[0029] Figure 7 FIG. 4 is a block diagram of a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0031] The following describes a method for generating a duty cycle of a motor drive circuit, a device for generating a duty cycle of a motor drive circuit, and a vehicle according to embodiments of the present invention with reference to the accompanying drawings.

[0032] Figure 1 The figure is a flow chart of a method for generating a duty cycle of a motor driving circuit according to an embodiment of the present invention.

[0033] In some embodiments of the present invention, the motor drive circuit includes a multi-phase bridge arm, each phase bridge arm includes an upper bridge hybrid switch and a lower bridge hybrid switch, the upper bridge hybrid switch and the lower bridge hybrid switch both include a Si tube and a SiC tube connected in parallel, and the structure of the hybrid switch is as follows: Figure 2 As shown, the Si tube can be an IGBT. Due to the difference in the turn-on and turn-off moments of SiC and Si tubes, they show different electrical and thermal characteristics. In order to give full play to the advantages of the two power devices and obtain higher current overload capacity, it is necessary to optimize the gate drive control of the hybrid switch.

[0034] like Figure 1 As shown, the duty cycle generation method of the motor drive circuit of the embodiment of the present invention may include the following steps:

[0035] S1, for any phase bridge arm, obtain the bridge arm current and bridge arm duty cycle of the bridge arm.

[0036] S2, when the absolute value of the bridge arm current is greater than a preset bridge arm current threshold, determining the turn-on delay time and turn-off delay time between the Si tube and the SiC tube according to the bridge arm current.

[0037] Among them, the turn-on delay time and turn-off delay time between the Si tube and the SiC tube under different load currents can be tested under the calibration state, so as to find out the turn-on delay time t between the Si tube and the SiC tube with the minimum power consumption corresponding to different load currents. on_delay and the turn-off delay time t off_delay Therefore, when the absolute value of the bridge arm current is greater than the preset bridge arm current threshold, the table can be looked up according to the bridge arm current to determine the opening delay time t between the Si tube and the SiC tube corresponding to the bridge arm current. on_delay and the turn-off delay time t off_delay .

[0038] S3, determining the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the bridge arm duty cycle.

[0039] Specifically, taking the A-phase bridge arm as an example, the motor controller obtains the bridge arm current of the A-phase bridge arm through the current sensor, and calculates the duty cycle D of the A-phase bridge arm according to the target voltage and the SVPWM (Space Vector Pulse Width Modulation) algorithm. a The motor controller compares the absolute value of the bridge arm current of the phase A bridge arm with the preset bridge arm current threshold. When the absolute value of the bridge arm current is greater than the preset bridge arm current threshold, the motor controller looks up the table according to the bridge arm current of the phase A bridge arm to determine the opening delay time t between the Si tube and the SiC tube corresponding to the bridge arm current. on_delay and the turn-off delay time t off_delay The motor controller is based on the opening delay time t on_delay , turn-off delay time t off_delay and the duty cycle of the bridge arm of phase A D a Calculate to get the duty cycle D of the Si tube of the A phase bridge arm a_igbt and the duty cycle D of the SiC tube a_sic The motor controller is based on the duty cycle D of the Si tube of the A phase bridge arm. a_igbti and the duty cycle D of the SiC tube a_sic Control the Si tube and SiC tube of the A-phase bridge arm.

[0040] Therefore, the method of the present invention applies a hybrid switch to a motor drive circuit for the first time and performs corresponding control to control the motor to operate more efficiently, combines the hybrid switch control strategy with the SVPWM algorithm, and uses different hybrid switch control modes according to different current amplitudes, thereby being able to control the motor to operate more efficiently, reduce the loss of power devices, and improve the efficiency of the electric drive.

[0041] The specific calculation process for determining the duty cycle of Si tubes and SiC tubes is described below in conjunction with specific embodiments.

[0042] According to one embodiment of the present invention, based on the turn-on delay time, the turn-off delay time and the bridge arm duty cycle, the duty cycle of the Si tube and the SiC tube is determined, including: when the turn-on delay time is greater than or equal to zero, the bridge arm duty cycle is used as the duty cycle of the SiC tube, and the difference between the bridge arm duty cycle and the turn-on delay duty cycle is obtained to obtain the duty cycle of the Si tube; wherein the turn-on delay duty cycle is the ratio of the turn-on delay time to the control period; when the turn-on delay time is less than zero, the bridge arm duty cycle is obtained. The duty cycle of the SiC tube is obtained by summing the turn-on delay duty cycles, and the bridge arm duty cycle is used as the duty cycle of the Si tube; when the turn-off delay time is greater than or equal to zero, the difference between the duty cycle of the Si tube and the turn-off delay duty cycle is obtained to update the duty cycle of the Si tube; wherein, the turn-off delay duty cycle is the ratio of the turn-off delay time to the control period; when the turn-off delay time is less than zero, the sum of the duty cycle of the SiC tube and the turn-off delay duty cycle is obtained to update the duty cycle of the SiC tube.

[0043] Specifically, let's take the A-phase bridge arm as an example. The duty cycle of the A-phase bridge arm is D a , assuming that the PWM control period is T s , when the opening delay time t on_delay ≥0, the duty cycle D of the SiC tube a_sic =D a , the duty cycle of the Si tube D a_igbt =D a -t on_delay / T s ; When the opening delay time t on_delay When <0, the duty cycle D of SiC tube a_sic =D a +t on_delay / T s , the duty cycle of the Si tube D a_igbt =D a When the shutdown delay time t off_delay ≥0, the duty cycle of the Si tube is updated to D a_igbt =D a_igbt -t off_delay / T s ; When the shutdown delay time t off_delay When <0, the duty cycle of the SiC tube is updated to D a_sic =D a +t off_delay / T s The specific duty cycle calculation logic is as follows: Figure 3 shown.

[0044] It is important to understand that Figure 4As shown, the hybrid switch has four basic switching modes, where the gate drive signals of SiC tube and Si tube are shown respectively. The waveform can select different switching modes according to different working conditions. Mode I is the control mode under the above ideal condition, t on_delay >0 and t off_delay > 0, the SiC tube bears the turn-on loss and turn-off loss, and the conduction loss is borne by both the Si tube and the SiC tube. In mode II, t on_delay = 0 and t off_delay >0, at this time, the SiC tube and the Si tube are turned on at the same time. Because the SiC tube itself has a long turn-on delay, it is similar to the zero voltage turn-on of the Si tube. Therefore, the SiC tube bears most of the turn-on loss, the Si tube and the SiC tube bear the conduction loss, and the SiC bears the turn-off loss. In mode III, t on_delay <0, t off_delay <0, the Si tube bears the turn-on and turn-off losses, and the conduction losses are shared by the Si tube and the SiC tube. In mode IV, t on_delay <0, t off_delay > 0, the Si tube bears the turn-on loss, the SiC tube and the Si tube bear the conduction loss together, and the SiC tube bears the turn-off loss. Ideally, Figure 4 Mode I, t on_delay and t off_dela y>0, that is, in the hybrid switch, the SiC tube is turned on before the Si tube and turned off after the Si tube. The Si tube is in the state of zero voltage turn-on and turn-off (Zero Voltage Switch) to reduce the switching loss of the Si tube, thereby reducing the total loss of the hybrid switch. However, because the SiC tube has a small current specification, it needs to withstand a conduction current that is several times greater than its rated current in a short period of time when turned on and off, which will cause the SiC tube to heat up and cause damage, so a suitable hybrid switch strategy is needed.

[0045] According to one embodiment of the present invention, the duty cycle of the target tube includes the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube, and the target tube is a Si tube or a SiC tube. The above method also includes: obtaining the minimum pulse width and dead time of the target tube; based on the duty cycle, minimum pulse width and dead time of the target tube, determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube. That is to say, when determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube, the limitation of the minimum pulse width and the influence of the dead time on the duty cycle setting are also considered, so as to ensure that the obtained duty cycle is more reasonable.

[0046] According to one embodiment of the present invention, based on the duty cycle, minimum pulse width and dead time of the target tube, the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube are determined, including: determining multiple duty cycle intervals based on the minimum pulse width and the dead time; determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle interval in which the duty cycle of the target tube is located. Exemplarily, a duty cycle can be determined based on the minimum pulse width, and a duty cycle can be determined based on the dead time, and then the duty cycle interval is divided based on the two duty cycles, and finally the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube are determined based on the duty cycle interval in which the duty cycle of the target tube is located.

[0047] According to one embodiment of the present invention, based on the duty cycle interval of the target tube, the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube are determined, including: a ∈The first duty cycle interval (1-T plsMin / T s , 1], determine D aH =1,D aL =0; where D a is the duty cycle of the target tube, T plsMin is the minimum pulse width of the target tube, T s is the control period, D aH is the duty cycle of the upper bridge target tube, D aL is the duty cycle of the lower bridge target tube; a ∈The second duty cycle interval (1-T plsMin / T s -2*T dead / T s , 1-T plsMin / T s ], determine D aH =D a , D aL =0; where T dead is the dead time of the target tube; a ∈The third duty cycle interval (T plsMin / T s +2*T dead / T s , 1-T plsMin / T s -2*T dead / T s ], determine D aH =D a , D aL =1-D a -2*T dead / T s ; in D a ∈The fourth duty cycle interval (T plsMin / Ts , T plsMin / T s +2*T dead / T s ], determine D aH =0,D aL =1-D a ; in D a ∈ the fifth duty cycle interval [0, T plsMin / T s ], determine D aH =0,D aL =1.

[0048] Specifically, taking the A-phase bridge arm as an example, the minimum pulse width of the Si tube is T plsMin_igbt , the dead time is T dead_igbt ; The minimum pulse width of SiC tube is T plsMin_sic , the dead time is T dead_sic ; The duty cycle of the Si tube of the A phase bridge arm is D a_igbt , the duty ratios of the upper and lower bridge arms of the Si tube are D aH_igbt , D aL_igbt ; The duty cycle of SiC tube is D a_sic , the duty ratios of the upper and lower bridge arms of the SiC tube are D aH_sic , D aL_sic When the absolute value of the A-phase bridge arm current is greater than the preset bridge arm current threshold and the target tube is the Si tube, the Si tube is turned on and the duty cycle D of the Si tube needs to be adjusted. a_igbt Calculation. The specific calculation process is as follows:

[0049] 1) When D a_igbt ∈(1-T plsMin_igbt / T s , 1], ideally D aH_igbt =D a_igbt , D aL_igbt =1-D a_igbt , but in fact, the lower bridge arm is turned on for a long time T s L _igbt <T plsMin_igbt , and the upper bridge arm closing time is less than T plsMin_igbt ; So in this case, let D aH_igbt =1,D aL_igbt =0.

[0050] 2) When D a_igbt ∈(1-T plsMin_igbt / T s -2*T dead_igbt / T s , 1-T plsMin_igbt / T s ], ideally D aH_igbt =Da_igbt , D aL_igbt =1-D a_igbt , at this time, the lower bridge arm is turned on for a long time T s L _igbt <T plsMin_igbt +2*T dead_igbt In actual situations, the lower bridge arm needs to be inserted into the dead zone. After the dead zone is inserted, the duration of the lower bridge arm opening needs to be subtracted from two dead zone times, that is, 2*T dead_igbt At this time, the actual opening time of the lower bridge arm is T s L _igbt <T plsMin_igbt In order to eliminate the above situation, let D aH_igbt =D a_igbt , D aL_igbt =0.

[0051] 3) When D a_igbt ∈(T plsMin_igbt / T s +2*T dead_igbt / T s , 1-T plsMin_igbt / T s -2*T dead_igbt / T s ], the opening and closing time of the upper and lower bridge arms are both > T plsMin_igbt , no additional processing is required, so D aH_igbt =D a_igbt , D aL_igbt =1-D a_igbt -2*T dead_igbt / T s .

[0052] 4) When D a_igbt ∈(T plsMin_igbt / T s , T plsMin_igbt / T s +2*T dead_igbt / T s ], the upper bridge arm is turned on for a long time ∈(T plsMin_igbt , T plsMin_igbt +2*T dead_igbt ], then add the dead zone insertion and the lower bridge arm opening time ∈[T s -T plsMin_igbt , T s -T plsMin_igbt +2*T dead_igbt ); However, in order to increase the symmetry of the wave (symmetric with case 2), reduce the even harmonics, let D aH_igbt =0,D aL_igbt =1-D a_igbt .

[0053] 5) When D a_igbt∈[0,T plsMin_igbt / T s ], let D aH_igbt =0,D aL_igbt =1.

[0054] Based on the same principle, when the target tube is a SiC tube, the calculation process is consistent with that of the Si tube and will not be repeated here.

[0055] According to one embodiment of the present invention, obtaining the bridge arm duty cycle includes: performing space vector pulse width modulation control on the motor drive circuit to obtain the DC bus voltage, α-axis voltage and β-axis voltage of the motor drive circuit; determining the target voltage based on the α-axis voltage and the β-axis voltage, and determining the sector in which the target voltage is located; determining the bridge arm duty cycle based on the sector in which the target voltage is located, the α-axis voltage, the β-axis voltage and the DC bus voltage.

[0056] Specifically, in the vector pulse width modulation algorithm, there are six space vectors (U1~I6), each with a vector amplitude of The 360° space in the α-β coordinate system is divided into six sectors (I to VI), each sector is 60°, such as Figure 5 shown.

[0057] The following takes the first sector as an example to explain the duty ratio of the three phases (A, B, C). s When passing through the first sector, space vectors I4 and I6 are synthesized (according to the volt-second balance principle) as shown in the following equation: Assumption: d4 and d6 are the duty ratios of voltage vectors U4 and U6 respectively.

[0058] U s =U4*d4+U6*d6

[0059] So we get:

[0060]

[0061] After sorting, we get:

[0062]

[0063] Therefore, when the voltage vector U s In the first sector, the duty ratios of phases A, B, and C are: Phase B Phase C

[0064] Similarly, the duty ratios of the other five sectors can be derived. Therefore, the voltage vector action times of the six sectors are obtained, as shown in Table 1.

[0065] Table 1

[0066]

[0067] Define the intermediate variables as follows:

[0068]

[0069] in,

[0070] Therefore, the duty ratio d of the three phases ABC under six sectors is obtained. a ,d b ,d c , see Table 2 for details.

[0071] Table 2

[0072]

[0073] Thus, space vector pulse width modulation control is performed on the motor drive circuit to obtain the DC bus voltage, α-axis voltage and β-axis voltage of the motor drive circuit; the target voltage is determined based on the α-axis voltage and the β-axis voltage, and the sector in which the target voltage is located is determined; based on the sector in which the target voltage is located, the α-axis voltage, the β-axis voltage and the DC bus voltage, the bridge arm duty cycle is determined.

[0074] According to one embodiment of the present invention, the preset bridge arm current threshold is determined based on the ratio of the threshold voltage of the Si tube to the on-resistance of the SiC tube.

[0075] Specifically, assuming that the preset bridge arm current threshold is I1, then Where V th，igbt is the threshold voltage of Si tube, R ds，sic is the on-resistance of the SiC tube, both of which can be found in the data sheet. Thus, the preset bridge arm current threshold can be determined.

[0076] According to one embodiment of the present invention, the method further includes: when the absolute value of the bridge arm current is less than or equal to a preset bridge arm current threshold, determining that the duty cycle of the SiC tube is the bridge arm duty cycle and the duty cycle of the Si tube is zero.

[0077] Specifically, taking the A-phase bridge arm as an example, when the absolute value of the A-phase current is less than or equal to the preset bridge arm current threshold, the motor controller only controls the switch of the SiC tube, and the duty cycle D of the SiC tube is a_sic =D a , the duty cycle of the Si tube D a_igbt =0.

[0078] In summary, the present invention applies a hybrid switch to a motor drive circuit for the first time and performs corresponding control, and proposes a new wave generation strategy in combination with narrow pulses to control the motor to operate with higher efficiency, combines the hybrid switch control strategy with the SVPWM algorithm, and uses different hybrid switch control modes according to different current amplitudes, so as to minimize the loss of power devices and optimize the efficiency; and adjusts the wave generation strategy according to the device's own characteristics (dead zone and narrow pulses), so as to optimize the voltage utilization while meeting NVH, thereby further improving the efficiency of the motor.

[0079] In summary, according to the duty cycle generation method of the motor drive circuit of the embodiment of the present invention, for any phase bridge arm, the bridge arm current and bridge arm duty cycle of the bridge arm are first obtained, and when the absolute value of the bridge arm current is greater than the preset bridge arm current threshold, the turn-on delay time and turn-off delay time between the Si tube and the SiC tube are determined according to the bridge arm current, and then based on the turn-on delay time, turn-off delay time and bridge arm duty cycle, the duty cycle of the Si tube and the SiC tube is determined. Therefore, the method can control the motor to operate more efficiently, reduce the loss of power devices, and improve the efficiency of electric drive.

[0080] Corresponding to the above embodiment, the present invention further proposes a duty cycle generating device for a motor drive circuit.

[0081] Figure 6 4 is a block diagram of a duty cycle generating device of a motor driving circuit according to an embodiment of the present invention.

[0082] like Figure 6 As shown, a duty cycle generating device 100 of a motor drive circuit of an embodiment of the present invention, the motor drive circuit includes a multi-phase bridge arm, each phase bridge arm includes an upper bridge hybrid switch and a lower bridge hybrid switch, the upper bridge hybrid switch and the lower bridge hybrid switch both include parallel Si tubes and SiC tubes, the device 100 includes: an acquisition module 110, a first determination module 120 and a second determination module 130.

[0083] The acquisition module 110 is used to acquire the bridge arm current and duty cycle of the bridge arm for any phase bridge arm. The first determination module 120 is used to determine the turn-on delay time and turn-off delay time between the Si tube and the SiC tube according to the bridge arm current when the absolute value of the bridge arm current is greater than the preset bridge arm current threshold. The second determination module 130 is used to determine the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the duty cycle of the bridge arm.

[0084] According to one embodiment of the present invention, the second determination module 130 determines the duty cycle of the Si tube and the SiC tube based on the opening delay time, the closing delay time and the bridge arm duty cycle, and is specifically used to, when the opening delay time is greater than or equal to zero, use the bridge arm duty cycle as the duty cycle of the SiC tube, and obtain the difference between the bridge arm duty cycle and the opening delay duty cycle to obtain the duty cycle of the Si tube; wherein the opening delay duty cycle is the ratio of the opening delay time to the control period; when the opening delay time is less than zero, obtain The sum of the bridge arm duty cycle and the turn-on delay duty cycle obtains the duty cycle of the SiC tube, and the bridge arm duty cycle is used as the duty cycle of the Si tube; when the turn-off delay time is greater than or equal to zero, the difference between the duty cycle of the Si tube and the turn-off delay duty cycle is obtained to update the duty cycle of the Si tube; wherein, the turn-off delay duty cycle is the ratio of the turn-off delay time to the control period; when the turn-off delay time is less than zero, the sum of the duty cycle of the SiC tube and the turn-off delay duty cycle is obtained to update the duty cycle of the SiC tube.

[0085] According to one embodiment of the present invention, the duty cycle of the target tube includes the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube, the target tube is a Si tube or a SiC tube, and the second determination module 130 is also used to obtain the minimum pulse width and dead time of the target tube; based on the duty cycle, minimum pulse width and dead time of the target tube, determine the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube.

[0086] According to one embodiment of the present invention, the second determination module 130 determines the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle, minimum pulse width and dead time of the target tube, and is specifically used to determine multiple duty cycle intervals based on the minimum pulse width and dead time; determine the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle interval in which the duty cycle of the target tube is located.

[0087] According to an embodiment of the present invention, the second determining module 130 is specifically configured to: a ∈The first duty cycle interval (1-T plsMin / T s , 1], determine D aH =1,D aL =0; where D a is the duty cycle of the target tube, T plsMin is the minimum pulse width of the target tube, T s is the control period, D aH is the duty cycle of the upper bridge target tube, D aL is the duty cycle of the lower bridge target tube; a ∈The second duty cycle interval (1-T plsMin / T s -2*T dead / T s, 1-T plsMin / T s ], determine D aH =D a , D aL =0; where T dead is the dead time of the target tube; a ∈The third duty cycle interval (T plsMin / T s +2*T dead / T s , 1-T plsMin / T s -2*T dead / T s ], determine D aH =D a , D aL =1-D a -2*T dead / T s ; in D a ∈The fourth duty cycle interval (T plsMin / T s , T plsMin / T s +2*T dead / T s ], determine D aH =0,D aL =1-D a ; in D a ∈ the fifth duty cycle interval [0, T plsMin / T s ], determine D aH =0,D aL =1.

[0088] According to one embodiment of the present invention, the second determination module 130 obtains the bridge arm duty cycle, and is specifically used to perform space vector pulse width modulation control on the motor drive circuit, obtain the DC bus voltage, α-axis voltage and β-axis voltage of the motor drive circuit; determine the target voltage based on the α-axis voltage and the β-axis voltage, and determine the sector in which the target voltage is located; determine the bridge arm duty cycle based on the sector in which the target voltage is located, the α-axis voltage, the β-axis voltage and the DC bus voltage.

[0089] According to one embodiment of the present invention, the preset bridge arm current threshold is determined based on the ratio of the threshold voltage of the Si tube to the on-resistance of the SiC tube.

[0090] According to one embodiment of the present invention, the second determination module 130 is further used to determine that the duty cycle of the SiC tube is the bridge arm duty cycle and the duty cycle of the Si tube is zero when the absolute value of the bridge arm current is less than or equal to a preset bridge arm current threshold.

[0091] It should be noted that for details not disclosed in the duty cycle generating device of the motor driving circuit in the embodiment of the present invention, please refer to the details disclosed in the duty cycle generating method of the motor driving circuit in the embodiment of the present invention, and the details will not be repeated here.

[0092] According to the duty cycle generation device of the motor drive circuit of the embodiment of the present invention, the acquisition module acquires the bridge arm current and duty cycle of any phase bridge arm; the first determination module determines the turn-on delay time and turn-off delay time between the Si tube and the SiC tube according to the bridge arm current when the absolute value of the bridge arm current is greater than the preset bridge arm current threshold; the second determination module determines the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the duty cycle of the bridge arm. Thus, the device can control the motor to operate more efficiently, reduce the loss of power devices, and improve the efficiency of electric drive.

[0093] Corresponding to the above embodiment, the present invention also provides a vehicle.

[0094] like Figure 7 As shown, a vehicle 300 according to an embodiment of the present invention includes the duty cycle generating device 100 of the motor driving circuit described above.

[0095] According to the vehicle of the embodiment of the present invention, the duty cycle generating device of the motor drive circuit can control the motor to operate with higher efficiency, reduce the loss of power devices, and improve the efficiency of electric drive.

[0096] 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 specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0097] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0098] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0099] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0100] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0101] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for generating a duty cycle of a motor drive circuit, characterized in that: The motor drive circuit includes a multi-phase bridge arm, each phase bridge arm includes an upper bridge hybrid switch and a lower bridge hybrid switch, the upper bridge hybrid switch and the lower bridge hybrid switch both include a Si tube and a SiC tube connected in parallel, and the method includes: For any phase bridge arm, obtaining the bridge arm current and bridge arm duty cycle of the bridge arm; When the absolute value of the bridge arm current is greater than a preset bridge arm current threshold, determining a turn-on delay time and a turn-off delay time between the Si tube and the SiC tube according to the bridge arm current; Based on the turn-on delay time, the turn-off delay time and the bridge arm duty cycle, the duty cycles of the Si tube and the SiC tube are determined.

2. The method according to claim 1, characterized in that The determining the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the bridge arm duty cycle includes: When the opening delay time is greater than or equal to zero, the bridge arm duty cycle is used as the duty cycle of the SiC tube, and the difference between the bridge arm duty cycle and the opening delay duty cycle is obtained to obtain the duty cycle of the Si tube; wherein the opening delay duty cycle is the ratio of the opening delay time to the control period; When the opening delay time is less than zero, the sum of the bridge arm duty cycle and the opening delay duty cycle is obtained to obtain the duty cycle of the SiC tube, and the bridge arm duty cycle is used as the duty cycle of the Si tube; When the shutdown delay time is greater than or equal to zero, the difference between the duty cycle of the Si tube and the shutdown delay duty cycle is obtained to update the duty cycle of the Si tube; wherein the shutdown delay duty cycle is the ratio of the shutdown delay time to the control period; When the turn-off delay time is less than zero, the sum of the duty cycle of the SiC tube and the turn-off delay duty cycle is obtained to update the duty cycle of the SiC tube.

3. The method according to claim 1 or 2, characterized in that: The duty cycle of the target tube includes the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube, the target tube is the Si tube or the SiC tube, and the method further includes: Obtaining the minimum pulse width and dead time of the target tube; Based on the duty cycle, minimum pulse width and dead time of the target tube, the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube are determined.

4. The method according to claim 3, characterized in that The step of determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle, the minimum pulse width and the dead time of the target tube comprises: determining a plurality of duty cycle intervals based on the minimum pulse width and the dead time; Based on the duty cycle interval in which the duty cycle of the target tube is located, the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube are determined.

5. The method according to claim 4, characterized in that The determining the duty cycle of the upper bridge target tube and the duty cycle of the lower bridge target tube based on the duty cycle interval of the duty cycle of the target tube includes: In D a ∈The first duty cycle interval (1-T plsMin / T s ,1], determine D aH =1,D aL =0; where D a is the duty cycle of the target tube, T plsMin is the minimum pulse width of the target tube, T s is the control period, D aH is the duty cycle of the upper bridge target tube, D aL is the duty cycle of the lower bridge target tube; In D a ∈The second duty cycle interval (1-T plsMin / T s -2*T dead / T s ,1-T plsMin / T s ], determine D aH =D a , D aL =0; where T dead is the dead time of the target tube; In D a ∈The third duty cycle interval (T plsMin / T s +2*T dead / T s ,1-T plsMin / T s -2*T dead / T s ], determine D aH =D a , D aL =1-D a -2*T dead / T s ; In D a ∈The fourth duty cycle interval (T plsMin / T s ,T plsMin / T s +2*T dead / T s ], determine D aH =0,D aL =1-D a ; In D a ∈The fifth duty cycle interval [0,T plsMin / T s ], determine D aH =0,D aL =1.

6. The method according to claim 1, characterized in that Obtaining the bridge arm duty cycle includes: Performing space vector pulse width modulation control on the motor drive circuit to obtain a DC bus voltage, an α-axis voltage, and a β-axis voltage of the motor drive circuit; determining a target voltage based on the α-axis voltage and the β-axis voltage, and determining a sector where the target voltage is located; The bridge arm duty cycle is determined based on the sector where the target voltage is located, the α-axis voltage, the β-axis voltage, and the DC bus voltage.

7. The method according to claim 1, characterized in that The preset bridge arm current threshold is determined based on the ratio of the threshold voltage of the Si tube to the on-resistance of the SiC tube.

8. The method according to claim 1, characterized in that The method further comprises: When the absolute value of the bridge arm current is less than or equal to the preset bridge arm current threshold, it is determined that the duty cycle of the SiC tube is the bridge arm duty cycle, and the duty cycle of the Si tube is zero.

9. A duty cycle generating device for a motor drive circuit, characterized in that: The motor drive circuit includes a multi-phase bridge arm, each phase bridge arm includes an upper bridge hybrid switch and a lower bridge hybrid switch, the upper bridge hybrid switch and the lower bridge hybrid switch both include a Si tube and a SiC tube connected in parallel, and the device includes: An acquisition module, used for acquiring a bridge arm current and a duty cycle of any phase bridge arm; A first determination module is used to determine a turn-on delay time and a turn-off delay time between the Si tube and the SiC tube according to the bridge arm current when the absolute value of the bridge arm current is greater than a preset bridge arm current threshold; The second determination module is used to determine the duty cycle of the Si tube and the SiC tube based on the turn-on delay time, the turn-off delay time and the duty cycle of the bridge arm.

10. A vehicle, characterized in that: A duty cycle generating device comprising the motor driving circuit according to claim 9.

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