Common-mode voltage suppression motor controller and power assembly

Abstract

The invention provides a motor controller with common-mode voltage suppression and a power assembly, the motor controller comprises an inverter circuit, the inverter circuit comprises three phases of switch tube bridge arms, the bridge arm midpoint of each phase of switch tube bridge arm is used for being connected with a phase winding of a motor, and the bridge arm midpoint of each phase of switch tube bridge arm is used for being connected with a phase winding of the motor. The motor controller is used for controlling the midpoint of each phase of bridge arm of a three-phase switch tube bridge arm of the inverter circuit to output phase voltage, and the phase voltage is used for generating phase current on a winding of the motor to drive the motor to output torque, the phase voltage generated by the bridge arm midpoint of at least one phase of bridge arm in the three-phase switch tube bridge arms is different from the phase voltage generated by the bridge arm midpoints in other switch tube bridge arms in direction, or the phase voltage generated by each group of bridge arms in the three-phase switch tube bridge arms is zero. By controlling the connection or disconnection mode of the three-phase bridge arm in the inverter circuit, the phase voltage output by the bridge arm midpoint of the three-phase bridge arm is adjusted, and the common-mode voltage of the inverter circuit is further reduced.

Description

Technical Field

[0001] The present application relates to the field of electric vehicles, and particularly to a motor controller for common mode voltage suppression and a powertrain. Background Art

[0002] With the exacerbation of energy shortage and environmental pollution problems in modern society, electric vehicles, as new energy vehicles, have received extensive attention from all walks of life. Since the electric drive system of electric vehicles directly affects the safety and efficiency of electric vehicles, the electric drive system has always been a research hotspot.

[0003] The electric drive system mainly uses the pulse width modulation method (PWM) to control the inverter circuit in the motor controller, so that the voltage output by the inverter circuit to the three-phase windings of the motor is a rectangular wave voltage, thereby adjusting the speed, which results in the existence of a common mode voltage (CMV) at the neutral point position of the three-phase windings of the motor.

[0004] The common mode voltage will generate electromagnetic interference (EMI) on the loop between the power battery - inverter circuit - motor. This electromagnetic interference will be reflected in the form of high-frequency current or high-frequency voltage. The high-frequency current will excite a high-frequency electric field in space, and the high-frequency voltage will excite a high-frequency magnetic field in space. For the motor, the above electromagnetic interference will specifically induce a high-amplitude shaft voltage on the motor shaft and form bearing current at the same time. The bearing current will corrode the motor bearing and shorten the service life of the motor.

[0005] At present, the common mode voltage suppression scheme can be to add a conductive structure on the motor shaft or add a common mode magnetic ring (magnetic core) between the connection path of the inverter circuit and the motor winding.

[0006] Among them, the scheme of adding a conductive structure to solve the common mode voltage has poor effect on motors that require high-voltage drive and cannot meet the service life requirements of the motor either. For the scheme of using a common mode magnetic ring, due to the high magnetic induction characteristic of the common mode magnetic ring, it is easy to cause magnetic saturation and high temperature rise, and better heat dissipation conditions are required. Moreover, after adding the common mode magnetic ring, the weight and volume of the electric drive system both increase, and the overall cost of the system will also increase. The above schemes only reduce the common mode voltage from the propagation path, and the suppression effect of the common mode voltage is poor. Summary of the Invention

[0007] The present application provides a motor controller for common mode voltage suppression and a powertrain, which can better reduce the common mode voltage of the inverter circuit by adjusting the modulation mode of the switching tubes of each bridge arm on the inverter circuit, so as to extend the service life of the motor.

[0008] In a first aspect, the present application provides a motor controller for suppressing common-mode voltage. The motor controller includes an inverter circuit, and the inverter circuit includes three-phase switch tube arms. The midpoints of each phase of the switch tube arms are respectively used to connect one phase winding of the motor. The inverter circuit is used to connect to a power battery through a DC bus. The motor controller is configured to: control the phase voltage output at the midpoint of each phase of the three-phase switch tube arms of the inverter circuit. The phase voltage is used to generate a phase current in the winding of the motor to drive the motor to output torque. Among them, the phase voltage generated at the midpoint of at least one phase of the three-phase switch tube arms is different in direction from the phase voltage generated at the midpoint of the other switch tube arms, or the phase voltage generated by each group of arms in the three-phase switch tube arms is zero.

[0009] By controlling the conduction or cutoff mode of the three arms in the inverter circuit, the phase voltages output by the three arms are adjusted, thereby reducing the common-mode voltage of the inverter circuit. When the phase voltages output at the midpoints of each switch tube arm are all greater than zero, it can be equivalent to the case where the common-mode voltage of the inverter circuit is Vdc / 2. When the phase voltages output at the midpoints of each switch tube arm are all less than zero, it can be equivalent to the case where the common-mode voltage of the inverter circuit is -Vdc / 2. The above two cases are both cases with a relatively large common-mode voltage. To avoid the occurrence of the above situations, the motor controller of the present application is configured to control the phase voltage generated at the midpoint of at least one phase of the three-phase switch tube arms to be different in direction from the phase voltage generated at the midpoint of the other switch tube arms, or the phase voltage generated by each group of arms in the three-phase switch tube arms is zero, thereby reducing the common-mode voltage of the inverter circuit.

[0010] As a possible implementation, the phase voltage output at the midpoint of each phase of the three-phase switch tube arms of the inverter circuit includes: a first voltage, a second voltage, or a third voltage. The first voltage is greater than zero, the second voltage is equal to zero, and the third voltage is less than zero. The first voltage is Vdc / 2, the third voltage is -Vdc / 2, and Vdc is the voltage value of the power battery.

[0011] The voltage of the power battery is a voltage greater than zero. The first voltage is a voltage vector in the same direction as the power battery, and the third voltage is a voltage vector in the opposite direction to the power battery.

[0012] As a possible implementation, the motor controller is configured to control the three-phase switch tube arms to make the common-mode voltage of the inverter circuit not greater than a preset value. The common-mode voltage is determined according to the phase voltages output at the midpoints of each switch tube arm.

[0013] As a possible implementation, during the process of the motor controller outputting the phase voltage, the motor controller is configured to: control the direction of the phase voltage output at the midpoint of any one phase of the switch tube arms of the inverter circuit to remain unchanged.

[0014] As a possible implementation, during the process of the motor controller outputting the phase voltage, the motor controller is configured to: at most control the direction of the phase voltage output at the midpoint of the bridge arm of any phase of the switching tube bridge arm in the inverter circuit to change.

[0015] As a possible implementation, in response to there being multiple different magnitudes of common-mode voltages that can be output by the inverter circuit, control the three-phase switching tube bridge arms to make the common-mode voltage output by the inverter circuit be the minimum value among the multiple different magnitudes of common-mode voltages that can be output. The values of the multiple different magnitudes of common-mode voltages include any two of the following: ±Vdc / 6, ±Vdc / 3, ±Vdc / 2, and zero.

[0016] As a possible implementation, the motor controller includes a control circuit, and the control circuit is configured to output a control signal to the inverter circuit. The control signal is used to control the phase voltage output at the midpoint of each phase of the three-phase switching tube bridge arms in the inverter circuit. Among them, the control signal is used to indicate that the phase voltage generated at the midpoint of at least one phase of the three-phase switching tube bridge arms is different in direction from the phase voltage generated at the midpoint of other switching tube bridge arms, or to indicate that the phase voltage generated by each group of bridge arms in the three-phase switching tube bridge arms is zero.

[0017] As a possible implementation, the inverter circuit includes three-phase switching tube bridge arms, a first capacitor, and a second capacitor. Each switching tube bridge arm includes a first switching tube, a second switching tube, a third switching tube, and a fourth switching tube, a first diode, and a second diode. The first end of the first capacitor is connected to the positive electrode of the power battery, the second end of the first capacitor is connected to the first end of the second capacitor, the second end of the second capacitor is connected to the negative electrode of the power battery, and the connection point between the first capacitor and the second capacitor is the connection midpoint. The first end of the first switching tube is connected to the positive electrode of the power battery, the second end of the first switching tube is connected to the first end of the second switching tube, the second end of the second switching tube is connected to the connection midpoint, the second end of the second switching tube is connected to the first end of the third switching tube, the second end of the third switching tube is connected to the first end of the fourth switching tube, the second end of the fourth switching tube is connected to the negative electrode of the power battery, the anode of the first diode and the cathode of the second diode are connected to the connection midpoint, the cathode of the first diode is connected to the second end of the first switching tube, the anode of the second diode is connected to the second end of the third switching tube, and the connection point between the second switching tube and the third switching tube is the midpoint of the bridge arm of this phase of the switching tube bridge arm.

[0018] As a possible implementation, when the first switch tube in the switch tube leg is conducting, the second switch tube is conducting, the third switch tube is off, and the fourth switch tube is off, the phase voltage output by the phase switch tube leg is the first voltage. When the first switch tube in the switch tube leg is off, the second switch tube is conducting, the third switch tube is conducting, and the fourth switch tube is off, the phase voltage output by the phase switch tube leg is the second voltage. When the first switch tube in the switch tube leg is off, the second switch tube is off, the third switch tube is conducting, and the fourth switch tube is conducting, the phase voltage output by the phase switch tube leg is the third voltage. Among them, the first voltage is Vdc / 2, the third voltage is -Vdc / 2, and Vdc is the voltage value of the power battery.

[0019] As a possible implementation, when the switch state of the switch tube in any one of the switch tube legs changes, the phase voltage output by each switch tube leg switches between the first voltage and the second voltage, or when the switch state of the switch tube in any one of the switch tube legs changes, the phase voltage output by each switch tube leg switches between the second voltage and the third voltage.

[0020] Since the amplitude of the common-mode voltage is determined by the off states of the switching devices on the three-phase legs, the more the number of off state changes of the switching devices on the three-phase legs, the greater the amplitude of the common-mode voltage. Therefore, compared with the phase voltage output at the midpoint of the switch tube leg of any phase of the inverter circuit switching between the first voltage and the third voltage, switching between the first voltage and the second voltage, and switching between the second voltage and the third voltage, it is possible to minimize the number of switching devices whose off states change, so as to ensure that the common-mode voltage output on the inverter circuit is reduced, thereby extending the service life of the motor.

[0021] As a possible implementation, at most two-phase switch tube legs in the inverter circuit have their switch states changed, or at most one-phase switch tube leg in the inverter circuit has its switch state changed.

[0022] The amplitude of the common-mode voltage is determined by the off states of the switching devices on the three-phase legs. Therefore, the motor controller provided by the present application can further reduce the number of legs whose off states are switched simultaneously in the inverter circuit, and further reduce the number of switching devices on the three-phase legs whose off states change, thereby reducing the common-mode voltage to extend the service life of the motor.

[0023] As a possible implementation, the vectors of the phase voltages output at the midpoints of the three-phase switch tube legs are used to synthesize the target vector. The control circuit is configured to: when there are multiple phase voltage synthesis methods to synthesize the target vector, select the phase voltage synthesis method with the minimum common-mode voltage and adjust the switch states of the switch tubes in the three-phase switch tube legs.

[0024] When each bridge arm of the inverter circuit outputs different synthesized target vectors of phase voltages, the corresponding common-mode voltages are not the same. When synthesizing the target vector, if there are multiple phase voltage synthesis methods, the phase voltage synthesis method with the minimum common-mode voltage can be selected from the multiple phase voltage synthesis methods for synthesis, so as to reduce the common-mode voltage of the inverter circuit and extend the service life of the motor.

[0025] As a possible implementation manner, the control circuit is configured to: when the target vector is a zero vector, control the midpoints of each switch tube bridge arm to output a second voltage.

[0026] The situation where the phase voltages output by the midpoints of each switch tube bridge arm are all the first voltage can be equivalent to the situation where the common-mode voltage of the inverter circuit is Vdc / 2. The situation where the phase voltages output by the midpoints of each switch tube bridge arm are all the third voltage can be equivalent to the situation where the common-mode voltage of the inverter circuit is -Vdc / 2. The situation where the phase voltages output by the midpoints of each switch tube bridge arm are all the second voltage can be equivalent to the situation where the common-mode voltage of the inverter circuit is 0. Although the above three situations are all synthesized into a zero vector, since the common-mode voltage is the lowest when the midpoints of each switch tube bridge arm output the second voltage, therefore, using this control method can reduce the common-mode voltage.

[0027] As a possible implementation manner, the common-mode voltage of the inverter circuit conforms to the following formula:

[0028]

[0029] where U com is the common-mode voltage of the inverter circuit, U1 is the phase voltage output by the midpoint of the first group of bridge arms, U2 is the phase voltage output by the midpoint of the second group of bridge arms, and U3 is the phase voltage output by the midpoint of the third group of bridge arms.

[0030] In a second aspect, the present application provides a powertrain, the powertrain includes a motor and a motor controller, the motor controller includes an inverter circuit, the inverter circuit includes three-phase switch tube bridge arms, the midpoint of each phase switch tube bridge arm is respectively used to connect a phase winding of the motor, the inverter circuit is used to connect to a power battery through a DC bus, and the motor controller is configured to: control the phase voltage output by the midpoint of each phase of the three-phase switch tube bridge arms of the inverter circuit, and the phase voltage is used to generate a phase current on the winding of the motor to drive the motor to output torque, wherein, the phase voltage generated by the midpoint of at least one phase of the three-phase switch tube bridge arms is different from the phase voltage generated by the midpoint of other switch tube bridge arms, or, the phase voltage generated by each group of bridge arms in the three-phase switch tube bridge arms is zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of an electric vehicle provided by an embodiment of the present application;

[0032] Figure 2 Schematic diagram of the powertrain provided by the embodiment of the present application;

[0033] Figure 3 Schematic diagram of the motor controller provided by the embodiment of the present application;

[0034] Figure 4 Vector distribution diagrams corresponding to 27 output states of the inverter circuit;

[0035] Figure 5 Schematic diagram of the synthesis of reference voltage vectors;

[0036] Figure 6 Schematic diagram of the timing of the control period;

[0037] Figure 7 Schematic diagram of the control of the first phase leg;

[0038] Figure 8A Schematic diagram of the synthesis vector sequence and common-mode voltage of the existing first typical modulation strategy;

[0039] Figure 8B Schematic diagram of the synthesis vector sequence and common-mode voltage of the existing second typical modulation strategy;

[0040] Figure 8C Schematic diagram of the synthesis vector sequence and common-mode voltage of the existing third typical modulation strategy;

[0041] Figure 8D Schematic diagram of the synthesis vector sequence and common-mode voltage of the existing fourth typical modulation strategy;

[0042] Figure 9 Schematic diagram of the synthesis vector sequence and common-mode voltage of the modulation strategy provided by the present application;

[0043] Figure 10 Schematic flowchart of a motor drive method. Specific embodiments

[0044] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and appended claims of the present application, the singular forms "a", "an", "", "the foregoing", "said", and "such" are also intended to include, for example, the expression "one or more", unless the context clearly indicates otherwise.

[0045] References to "one embodiment" or "some embodiments" etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. appearing at different places in this specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in another way. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in another way.

[0046] Below, some of the terms involved in the embodiments of the present application are explained to facilitate easy understanding by those skilled in the art.

[0047] Figure 1 A schematic diagram of an electric vehicle provided in an embodiment of the present application. Figure 1 The electric vehicle 10 includes a powertrain 11, wheels 12, and a power battery 13. The powertrain 11 is used to receive power from the power battery 13 to drive the wheels 12. The power battery 13 provided in the present application may be a lithium-ion battery, a lead-acid battery, a solar cell, etc., and the present application does not limit the type of the power battery.

[0048] Figure 2 Schematic diagram of the powertrain provided in the embodiment of the present application. The powertrain 11 includes a motor 111 and a motor controller 112. The motor controller 112 receives direct current from the power battery 13 and converts the direct current into three-phase alternating current to power the motor 111. The motor 111 and the wheel 12 are connected through a reducer or a transmission. During the driving process of the electric vehicle 10, the torque of the motor 111 is transmitted to the wheel 12 to provide power for the electric vehicle 10.

[0049] The topology of the motor controller 112 mostly adopts the three-phase full-bridge inverter circuit structure, and the modulation method mostly adopts space vector pulse width modulation (SVPWM). However, in the application process, the three-phase full-bridge inverter circuit can only output voltages of two levels, and the output voltage harmonics and current harmonics are relatively high, resulting in an increase in the losses of the motor 111. Moreover, when the motor 111 is in the low-torque region, the power is small, the proportion of switching losses is large, and the efficiency is low. The output voltage of the three-phase full-bridge inverter circuit can include two levels. By controlling each switch on each bridge arm, the inverter circuit converts the direct current provided by the power battery 13 into alternating current. During the control of the inverter circuit, for the two switches of each bridge arm, one switch is in the on state and the other switch is in the off state at the same time. In one bridge arm, when the upper-bridge-arm switch is in the on state and the lower-bridge-arm switch is in the off state, the output voltage is +Vdc, where Vdc is the voltage of the power battery 13. When the upper-bridge-arm switch is in the off state and the lower-bridge-arm switch is in the on state, the output voltage is 0. It can be seen that the three-phase full-bridge inverter circuit can output voltages of two levels when working.

[0050] Due to the relatively large output voltage and current harmonics of the three-phase full-bridge inverter circuit, the torque ripple of the motor becomes larger and the noise becomes larger. Therefore, a circuit with a three-level inverter circuit structure is proposed. The output voltage of the three-level inverter circuit can include three levels, and the output voltage waveform is closer to the ideal sine waveform. Compared with the three-phase full-bridge inverter circuit, the three-level inverter circuit has smaller output current harmonics and can improve the operating efficiency of the motor. Among them, the three-level inverter circuit can include a T-type three-level inverter and an I-type three-level inverter.

[0051] Figure 3 Schematic diagram of the motor controller provided by the embodiment of the present application. Figure 3 The inverter circuit 121 in is a schematic diagram of the structure of a neutral-point-clamped I-type three-level inverter circuit.

[0052] Among them, the inverter circuit 121 includes a three-phase switch tube bridge arm, a first capacitor C1, and a second capacitor C2. Each switch tube bridge arm includes a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a first diode D1, and a second diode D2. The first end of the first capacitor C1 is connected to the positive pole of the power battery 13, the second end of the first capacitor C1 is connected to the first end of the second capacitor C2, the second end of the second capacitor C2 is connected to the negative pole of the power battery 13, and the connection point between the first capacitor C1 and the second capacitor C2 is the connection midpoint. The first end of the first switch tube S1 is connected to the positive pole of the power battery 13, the second end of the first switch tube S1 is connected to the first end of the second switch tube S2, the second end of the second switch tube S2 is connected to the connection midpoint, the second end of the second switch tube S2 is connected to the first end of the third switch tube S3, the second end of the third switch tube S3 is connected to the first end of the fourth switch tube S4, the second end of the fourth switch tube S4 is connected to the negative pole of the power battery 13, the anode of the first diode D1 and the cathode of the second diode D2 are connected to the connection midpoint, the cathode of the first diode D1 is connected to the second end of the first switch tube S1, the anode of the second diode D2 is connected to the second end of the third switch tube S3, and the connection point between the second switch tube S2 and the third switch tube S3 is the bridge arm midpoint of this phase of the switch tube bridge arm.

[0053] Each bridge arm in the inverter circuit 121 can output three levels with different amplitudes. Taking the first-phase bridge arm among the three bridge arms as an example. In the first-phase bridge arm, when the first switch tube S1 and the second switch tube S2 are in the on state and the third switch tube S3 and the fourth switch tube S4 are in the off state, regardless of whether the current direction is forward or reverse, the phase voltage output by the first-phase bridge arm is +Vdc / 2. When the second switch tube S2 and the third switch tube S3 are in the on state and the first switch tube S1 and the fourth switch tube S4 are in the off state, regardless of whether the current direction is forward or reverse, the output terminal voltage of the first-phase bridge arm is 0. When the third switch tube S3 and the fourth switch tube S4 are in the on state and the first switch tube S1 and the second switch tube S2 are in the off state, regardless of whether the current direction is forward or reverse, the output terminal voltage of the first-phase bridge arm is -Vdc / 2.

[0054] Continue to refer to Figure 3 As shown, the motor controller 112 may further include a control circuit 122. The input side of the inverter circuit 121 is connected to the power battery 13, and the output side of the inverter circuit 121 is connected to the motor 111. The control circuit 122 may be connected to each switching device in the inverter circuit 121 to control the states of each switching device. For example, it controls the switching device to be in the on state or the open state.

[0055] The above control circuit 122 may include, but is not limited to, a central processing unit (CPU), other general-purpose processors, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The control circuit 122 can control the switches in each arm to turn on or off by outputting control signals to each arm of the inverter circuit 121. Among them, the control signal can be a pulse width modulation (PWM) signal.

[0056] The switching devices in the inverter circuit 121 may include, but are not limited to, insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), silicon carbide (SiC)-based power switching devices, gallium nitride (GaN)-based power switching devices, etc.

[0057] The control circuit 122 can select a target operating mode from multiple operating modes and drive the inverter circuit 121 using the selected target operating mode. In other words, the control circuit 122 can determine the operating mode for driving the inverter circuit 121 according to the motor operating condition signal. In the embodiments of the present application, the motor operating condition signal may include, but is not limited to, the operating current, torque, etc. of the motor 111. Among them, the motor operating condition signal can be the current at one or more phase input terminals of the motor. By collecting the current at one or more phase input terminals of the motor 111, the collected current is provided to the control circuit 122. The motor operating condition signal may also include the torque parameter of the motor 111.

[0058] The three bridge arms in the inverter circuit 121 are respectively denoted as the first-phase bridge arm, the second-phase bridge arm, and the third-phase bridge arm. The three bridge arms respectively correspond to the three-phase windings of the motor 111, and the midpoints of the three bridge arms are respectively connected to one of the corresponding phases of the windings in the motor 111. Taking one of the bridge arms as an example, when the first switch tube S1 and the second switch tube S2 are in the conducting state, and the third switch tube S3 and the fourth switch tube S4 are in the off state, the phase voltage output by this bridge arm is +Vdc / 2, and the output state of this bridge arm can be denoted as "P". When the second switch tube S2 and the third switch tube S3 are in the conducting state, and the first switch tube S1 and the fourth switch tube S4 are in the open state, the phase voltage output by this bridge arm is 0, and the output state of this bridge arm can be denoted as "O". When the third switch tube S3 and the fourth switch tube S4 are in the conducting state, and the first switch tube S1 and the second switch tube S2 are in the open state, the phase voltage output by this bridge arm is -Vdc / 2, and the output state of this bridge arm can be denoted as "N".

[0059] If one bridge arm can have three output states, then the three bridge arms of the inverter circuit 121 can have 3 3 = 27 different output states. Each output state of the inverter circuit 121 can be represented by a basic voltage vector. A basic voltage vector can include the desired output voltages of each bridge arm. Figure 4 The vector distribution diagram corresponding to the 27 output states of the inverter circuit 121 is shown. For example, for the basic voltage vector PPN, the first-phase bridge arm is in the output state P, the second-phase bridge arm is in the output state P, and the third-phase bridge arm is in the output state N.

[0060] The space vector diagram formed by the 27 basic voltage vectors of the inverter circuit 121. Among them, the basic voltage vectors NNN, OOO, and PPP are vectors at the same position in the space vector diagram (zero vectors). The basic voltage vectors PPO and OON are vectors at the same position in the space vector diagram (i.e., the same basic effective vector). The basic voltage vectors POO and ONN are vectors at the same position in the space vector diagram (i.e., the same basic effective vector). The basic voltage vectors POP and ONO are vectors at the same position in the space vector diagram (i.e., the same basic effective vector). The basic voltage vectors OOP and NNO are vectors at the same position in the space vector diagram (i.e., the same basic effective vector). The basic voltage vectors OPP and NOO are vectors at the same position in the space vector diagram (i.e., the same basic effective vector). The basic voltage vectors OPO and NON are vectors at the same position in the space vector diagram (i.e., the same basic effective vector). It can be seen that the 27 basic voltage vectors of the inverter circuit 121 correspond to 18 basic effective vectors and 3 zero vectors.

[0061] Figure 4 The vector distribution diagram shown can be divided into six large sectors, which can be denoted as Sector I, Sector II, Sector III, Sector IV, Sector V, and Sector VI respectively. The angle of each sector is 60°. Continuing to refer to Figure 4 , in the two-phase orthogonal coordinate system (αβ coordinate system), the sectors do not overlap with each other, and each sector has a corresponding α-axis coordinate range and β-axis coordinate range.

[0062] Each large sector can include multiple triangular regions. As Figure 5 shown, taking Sector I as an example, Sector I can include 6 triangular regions, which can be denoted as Region 1, Region 2, Region 3, Region 4, Region 5, and Region 6 respectively. Each region has a corresponding basic voltage vector, such as the vector with the vertex of the region as the vector vertex, which is the corresponding basic voltage vector of the region. For example, the corresponding basic effective vectors of Region 3 are the basic voltage vector PON, the basic voltage vector POO (or the basic voltage vector ONN), and the basic voltage vector PPO (or the basic voltage vector OON). The control circuit can select multiple basic effective vectors from the basic voltage vectors corresponding to the region where the reference voltage vector V ref belongs, and synthesize the reference voltage vector V ref . For example, the control circuit can select four or five basic voltage vectors from 27 basic voltage vectors to synthesize the reference voltage vector V ref .

[0063] Generally, the motor controller 112 controls the motor 111 in a closed-loop control manner. The motor controller 112 can obtain the target current to be output to the motor and the actual current output to the motor 111. The motor controller 112 can determine the reference voltage vector V ref according to the target current and the actual current.

[0064] The motor controller 112 can determine the region where the reference voltage vector V ref is located based on the component of the reference voltage vector V ref on the α-axis and the component on the β-axis. As Figure 5 shown, assume that the motor controller 112 uses the component V ref of the reference voltage vector V α on the α-axis and the component V β on the β-axis to determine that the reference voltage vector is in Region 3 of Sector I. The motor controller 112 can determine at least one vector (basic effective vector and / or zero vector) from the basic voltage vectors corresponding to Region 3 to synthesize the reference voltage vector V ref .

[0065] The motor controller 112 synthesizes the reference voltage vector V ref This may include two processes, namely determining the action duration of the vector and determining the basic voltage vector and the corresponding action period.

[0066] Suppose the control circuit 122 selects three vectors (basic effective vectors and / or zero vectors) adjacent to the reference voltage vector V ref from the basic voltage vectors corresponding to the region where the reference voltage vector V ref is located, and they are denoted as V1, V2, and V3 respectively. The control circuit can calculate the action times of the three vectors adjacent to the reference voltage vector V ref according to the volt-second balance principle. See the following formula:

[0067] V ref ×TS = V1×t1 + V2×t2 + V3×t3

[0068] V α ×TS = V1 α ×t1 + V2 α ×t2 + V3 α ×t3

[0069] V β ×TS = V1 β ×t1 + V2 β ×t2 + V3 β ×t3

[0070] Ts = t1 + t2 + t3

[0071] where Ts is the control cycle duration, V ref is the reference voltage vector, t1 is the action duration of V1 (the action duration in one control cycle), t2 is the action duration of V2, t3 is the action duration of V3, V1 α is the component of V1 on the α-axis, V2 α is the component of V2 on the α-axis, V2 α is the component of V2 on the α-axis, V1 β is the component of V1 on the β-axis, V2 β is the component of V2 on the β-axis, V3 β is the component of V3 on the β-axis. For easy distinction, the determined vectors can be denoted as selected vectors. The control circuit 122 can determine the action duration corresponding to each selected vector.

[0072] Based on the principle of quarter wave symmetry (QWS), in the seven-segment symmetric SVPWM mode, the PWM waveforms corresponding to the output states (desired output voltage information) of each branch in each control period are symmetric about the middle moment of the control period, as Figure 6 shown in the example. A control period can be divided into seven segments. The vector corresponding to the first segment and the vector corresponding to the seventh segment are the same basic voltage vector, and the action durations corresponding to the first segment and the seventh segment are the same. Similarly, the vector corresponding to the second segment and the vector corresponding to the sixth segment are the same basic vector, and the action durations corresponding to the second segment and the sixth segment are the same. The vector corresponding to the third segment and the vector corresponding to the fifth segment are the same basic voltage vector, and the action durations corresponding to the third segment and the fifth segment are the same.

[0073] If two reference vectors in a sector are symmetric about the middle of the sector, then the switching sequence for synthesizing these two reference voltage vectors is also symmetric about the middle of the sector. When the synthesis vector sequence of the first reference voltage vector in Sector I is synthesized by POO - PON - PNN, according to the spatial vector symmetry relationship, the seventh reference vector symmetric to the first reference voltage vector about the middle of the sector can be obtained. The synthesis vector sequence of the fifth reference vector is synthesized by PPN - PON - OON.

[0074] Under the constraint of the QWS principle, the switching sequence in the first half of Sector I and the synthesis vector sequence in the second half of Sector I satisfy the symmetric relationship shown in the table. Therefore, when designing the synthesis vector sequence, only the synthesis vector sequence of the first half of the vectors needs to be designed, thus simplifying the synthesis process.

[0075] To facilitate understanding of the above process, an example is used for illustration. Assume that the reference voltage vector V ref belongs to Region 3 in Sector I. As Figure 6 shown, after the control circuit 122 determines at least one vector (at least one selected vector) from the basic voltage vectors corresponding to Region 3 and the action durations corresponding to each selected vector, the seven-segment symmetric PWM mode can be used to determine the selected vectors and action durations corresponding to each segment. The synthesized reference voltage vector V corresponding to Region 3 refAmong the vectors, vector V1 corresponds to multiple basic voltage vectors, namely basic voltage vector ONN and basic voltage vector POO, vector V2 corresponds to basic voltage vector OON, and vector V3 corresponds to basic voltage vector PON. The control circuit selects basic voltage vector ONN and basic voltage vector POO from the multiple basic voltage vectors corresponding to vector V1. The control circuit can determine that in one control period, the corresponding vector in the first segment is basic voltage vector ONN, the corresponding vector in the second segment is basic voltage vector OON, the corresponding vector in the third segment is basic voltage vector PON, the corresponding vector in the fourth segment is basic voltage vector PNN, the corresponding vector in the fifth segment is basic voltage vector PON, the corresponding vector in the sixth segment is basic voltage vector OON, and the corresponding vector in the seventh segment is basic voltage vector NOO.

[0076] The control circuit 122 can determine the drive signals of each switching device in each bridge arm during the corresponding action period of each segment according to the phase voltages of the expected outputs of each bridge arm included in the corresponding basic voltage vector of each segment. For example, after determining the basic voltage vector and the corresponding action period, the control circuit 122 can determine the phase voltages of the expected outputs of each bridge arm corresponding to the basic voltage vector during the corresponding action period of the basic voltage vector, and can determine the modulation signals corresponding to each bridge arm.

[0077] The control circuit 122 can modulate the carrier based on the modulation waves corresponding to each bridge arm to generate the drive signals of the switches on each bridge arm. Taking the first segment as an example, as Figure 7 shown, the corresponding vector in the first segment is basic voltage vector ONN, that is, the output voltage state of the first-phase bridge arm is "O", and the corresponding voltage is 0. Then the control circuit 122 can control the second switch tube S2 and the third switch tube S3 in the first-phase bridge arm to be in the on state, and the first switch tube S1 and the fourth switch tube S4 to be in the off state. The drive signals T1 of the second switch tube S2 and the third switch tube S3 generated by the control circuit 122 are high-level signals corresponding to the duration, which can drive the second switch tube S2 and the third switch tube S3 to be in the on state during the corresponding action duration T1 of the first segment in one control period. The drive signals T1 of the first switch tube S1 and the fourth switch tube S4 generated by the control circuit are low-level signals corresponding to the duration, which can make the first switch tube S1 and the fourth switch tube S4 be in the off state during the action duration T1 of the first segment in one control period.

[0078] Among them, when the control circuit 122 controls the inverter circuit 121 using the space vector pulse width modulation (SVPWM) method to output three-phase current to the motor 111, it will cause the neutral point position of the three-phase windings of the motor 111 to have a common-mode voltage with respect to the reference potential. The common-mode voltage refers to the voltage between the neutral point of the three-phase windings and the reference potential. The neutral point refers to the common point of the star connection in a three-phase or polyphase AC motor. The common-mode voltage will generate electromagnetic interference on the loop between the power battery 13 - inverter circuit 121 - motor 111. For the motor 111, the electromagnetic interference will specifically induce a high-amplitude shaft voltage on the shaft of the motor 111 and simultaneously form a bearing current. The bearing current will corrode the bearings of the motor 111 and shorten the service life of the motor.

[0079] Currently, the solutions for suppressing the common-mode voltage are to add a conductive structure on the shaft of the motor 111 or add a common-mode magnetic ring between the connection path of the inverter circuit 121 and the windings of the motor 111. The above solutions all reduce the common-mode voltage from the propagation path and do not reduce the common-mode voltage from the fundamental source.

[0080] To solve the above problems, this application reduces the common-mode voltage of the inverter circuit 121 by adjusting the magnitudes of the phase voltages output by each bridge arm on the inverter circuit 121.

[0081] The three-phase phase voltages of the inverter circuit 121 are respectively:

[0082]

[0083] In the above formula (1), i1, i2, and i3 are the three-phase currents of the three-phase bridge arms, L s is the load inductance, R s is the load resistance, U COM is the common-mode voltage.

[0084] For a three-phase symmetric motor, the condition i1 + i2 + i3 = 0 is satisfied. Substituting the above condition into the above formula (1), the common-mode voltage U COM can be calculated as:

[0085] The common-mode voltage of the inverter circuit conforms to the following formula:

[0086]

[0087] Among them, U com is the common-mode voltage of the inverter circuit, U1 is the phase voltage output at the midpoint of the first group of bridge arms, U2 is the phase voltage output at the midpoint of the second group of bridge arms, and U3 is the phase voltage output at the midpoint of the third group of bridge arms.

[0088] Among them, taking the three-level inverter circuit 121 as an example, if one arm has three output states, then the three arms of the inverter circuit 121 can have 3^ 3 = 27 output states. Classified and represented by the basic voltage vectors, the 27 basic voltage vectors that the inverter circuit 121 can output can be specifically divided into four vector types according to the vector magnitude, including: large vectors, medium vectors, small vectors, and zero vectors.

[0089] Among them, the large vectors include: PNN, PPN, NPN, NPP, NNP, PNP.

[0090] The medium vectors include: PON, OPN, NPO, NOP, ONP, PNO.

[0091] The small vectors include: POO, OON, OPO, NOO, OOP, ONO, ONN, PPO, NON, OPP, NNO, POP.

[0092] The zero vectors include: OOO, PPP, NNN.

[0093] Among the vectors of various magnitudes above, the common-mode voltages corresponding to each vector output on the inverter circuit 121 are not the same.

[0094] Among them, the common-mode voltages corresponding to the zero vector OOO and the medium vectors PON, OPN, NPO, NOP, ONP, PNO are all 0.

[0095] The common-mode voltages corresponding to the large vectors PNN, PPN, NPN, NPP, NNP, PNP and the small vectors POO, OON, OPO, NOO, OOP, ONO are all ±Vdc / 6.

[0096] The common-mode voltages corresponding to the small vectors ONN, PPO, NON, OPP, NNO, POP are all ±Vdc / 3.

[0097] The common-mode voltages corresponding to the zero vectors PPP, NNN are all ±Vdc / 2.

[0098] As we know, the control circuit 122 can select multiple basic effective vectors from the basic voltage vectors corresponding to the region where the reference voltage vector V ref belongs, and synthesize the reference voltage vector V ref to implement the modulation strategy.

[0099] Moreover, when performing vector synthesis, the synthesis method is not unique. That is to say, there will be multiple combination methods to synthesize the reference voltage vector V ref , and synthesize the reference voltage vector V refEach target vector among the various target vectors is not unique either. Among them, the vectors of the phase voltages output at the midpoints of the bridge arms of the three-phase switch tube bridge arms are used to synthesize the target vector, and there are various phase voltage synthesis methods to synthesize the target vector.

[0100] Based on this idea, when selecting the basic effective vectors, we can preferentially select the basic effective vectors with smaller corresponding common-mode voltages on the premise that the magnitudes of the selected vectors are the same. That is to say, different vector synthesis methods can be achieved by controlling the on or off modes of the three bridge arms in the inverter circuit 121, so as to adjust the phase voltages output by the three bridge arms, and further reduce the common-mode voltage of the inverter circuit 121.

[0101] Among them, the zero vector PPP can correspond to the situation where the phase voltages output at the midpoints of the bridge arms of each switch tube bridge arm are all greater than zero, and the zero vector NNN can correspond to the situation where the phase voltages output at the midpoints of the bridge arms of each switch tube bridge arm are all less than zero. When the output voltage state of the bridge arm is "P", the phase voltage output by this bridge arm is Vdc / 2. When the output voltage state of the bridge arm is "N", the phase voltage output by this bridge arm is -Vdc / 2. Therefore, in other words, the situation where the phase voltages output at the midpoints of the bridge arms of each switch tube bridge arm are all greater than zero can be equivalent to the situation where the phase voltages output at the midpoints of the bridge arms of each switch tube bridge arm are all Vdc / 2 at the same time, and the situation where the phase voltages output at the midpoints of the bridge arms of each switch tube bridge arm are all less than zero can be equivalent to the situation where the phase voltages output at the midpoints of the bridge arms of each switch tube bridge arm are all -Vdc / 2 at the same time.

[0102] When the zero vector PPP and the zero vector NNN are required as the basic voltage vectors to synthesize the reference voltage vector V ref then the zero vector OOO can be used to replace the zero vector PPP or the zero vector NNN for synthesis. That is, when the zero vector PPP and the zero vector NNN are required to participate in the synthesis of the reference voltage vector V ref the motor controller 112 can use the zero vector OOO for replacement.

[0103] Constraint 1: The motor controller 112 uses the above principle as a constraint condition to synthesize the reference voltage vector V ref to reduce the maximum amplitude of the common-mode voltage of the inverter circuit 121, so as to ensure that the common-mode voltage output on the inverter circuit 121 is always less than ±Vdc / 2, thereby extending the service life of the motor 111.

[0104] As a possible implementation, the motor controller 112 is used to control the phase voltage output at the midpoint of each switched leg of the inverter bridge to be: a first voltage, a second voltage, or a third voltage, where the first voltage is greater than zero, the second voltage is equal to zero, and the third voltage is less than zero. The first voltage is Vdc / 2, the third voltage is -Vdc / 2, and Vdc is the voltage value of the power battery. The voltage of the power battery is a voltage greater than zero. The first voltage is a voltage vector in the same direction as the power battery, and the third voltage is a voltage vector in the opposite direction of the power battery.

[0105] When the phase voltage output at the midpoint of the switched leg of the inverter bridge is the first voltage, it can correspond to the case where the output voltage state of the leg is "P". When the phase voltage output at the midpoint of the switched leg of the inverter bridge is the second voltage, it can correspond to the case where the output voltage state of the leg is "O". When the phase voltage output at the midpoint of the switched leg of the inverter bridge is the third voltage, it can correspond to the case where the output voltage state of the leg is "N".

[0106] To further reduce the common-mode voltage, the motor controller 112 is used to control the phase voltage output at the midpoint of any switched leg of the inverter circuit 121 to switch between the first voltage and the second voltage, or to control the phase voltage output at the midpoint of any switched leg of the inverter circuit 121 to switch between the second voltage and the third voltage.

[0107] As we have learned in the above formula (2), the magnitude of the common-mode voltage is determined by the off states of the switching devices on the three-phase legs. The more the number of changes in the off states of the switching devices on the three-phase legs, the greater the magnitude of the common-mode voltage.

[0108] Taking the first-phase leg as an example, when the output voltage state of the first-phase leg is "P", it corresponds to the state where the switching device first switch S1 is on, the switching device second switch S2 is on, the switching device third switch S3 is off, and the switching device fourth switch S4 is off. When the output voltage state of the first-phase leg is "O", it corresponds to the state where the switching device first switch S1 is off, the switching device second switch S2 is on, the switching device third switch S3 is on, and the switching device fourth switch S4 is off. When the output voltage state of the first-phase leg is "N", it corresponds to the state where the switching device first switch S1 is off, the switching device second switch S2 is off, the switching device third switch S3 is on, and the switching device fourth switch S4 is on.

[0109] When the phase voltage output at the midpoint of any switched leg of the inverter bridge switches between the first voltage and the second voltage (i.e., when the output voltage state of the leg changes from "P" to "O"), only two switches of the single-phase switched leg change (the state change of the switching device first switch S1 and the state change of the switching device third switch S3).

[0110] When the phase voltage output at the midpoint of the bridge arm of any phase switch tube bridge arm switches between the second voltage and the third voltage (i.e., the output voltage state of the bridge arm changes from "O" to "N"), only two switches of the single-phase switch tube bridge arm change (the state of the second switch tube S2 changes, and the state of the fourth switch tube S4 changes).

[0111] When the phase voltage output at the midpoint of the bridge arm of any phase switch tube bridge arm switches between the first voltage and the third voltage (i.e., the output voltage state of the bridge arm changes from "P" to "N"), four switches of the single-phase switch tube bridge arm change (the state of the first switch tube S1 changes, the state of the second switch tube S2 changes, the state of the third switch tube S3 changes, and the state of the fourth switch tube S4 changes).

[0112] Therefore, in order to minimize the number of switching devices whose turn-off state changes as much as possible, the motor controller 112 can control the phase voltage output at the midpoint of the bridge arm of any phase switch tube bridge arm of the inverter circuit 121 to switch between the first voltage and the second voltage. Or, control the phase voltage output at the midpoint of the bridge arm of any phase switch tube bridge arm of the inverter circuit 121 to switch between the second voltage and the third voltage. In this way, the common-mode voltage can also be reduced, and the service life of the motor 111 can be extended.

[0113] Constraint condition 2: The motor controller 112 uses the above principle as a constraint condition to synthesize the reference voltage vector V ref to minimize the number of switching devices whose turn-off state changes as much as possible, so as to ensure that the common-mode voltage output on the inverter circuit 121 is reduced, thereby extending the service life of the motor 111.

[0114] To reduce the common-mode voltage, the motor controller 122 is used to:

[0115] Simultaneously control multiple switch tubes in at most two-phase switch tube bridge arms of the inverter circuit 121 to perform on-off state switching.

[0116] Similarly, since the magnitude of the common-mode voltage is determined by the turn-off states of the switching devices on the three-phase bridge arms, therefore, the motor controller 112 provided in this application can minimize the number of bridge arms that simultaneously switch the turn-off state in the inverter circuit 121, and further reduce the number of switching devices that switch the turn-off state on the three-phase bridge arms, thereby reducing the common-mode voltage and extending the service life of the motor 111.

[0117] In the three-phase bridge arm, if only the switches of two-phase switch tube bridge arms change, at least four switching devices will change their states, and at most eight switching devices will change their states. Compared with the situation where all the switches of the three-phase switch tube bridge arm change simultaneously, the common-mode voltage can be reduced, and the service life of the motor 111 can be extended.

[0118] Exemplarily, if the state of the inverter circuit 121 is PPP, the state of the inverter circuit 121 after switching can be selected from the following several: OOP, ONP, NOP, NNP, NPN, OPO, OPN, NPO, POO, PNN, PON, PNO.

[0119] In order to further reduce the common-mode voltage, the motor controller 122 is used to: simultaneously control multiple switching devices in one-phase switch tube bridge arm of the inverter circuit 121 to perform the switching of the on or off state.

[0120] Similarly, since the magnitude of the common-mode voltage is determined by the off states of the switching devices on the three-phase bridge arm, therefore, the method provided in this application can further reduce the number of switching devices on the three-phase bridge arm where the off state switching occurs, thereby reducing the common-mode voltage and extending the service life of the motor 111.

[0121] In the three-phase bridge arm, if only the switches of two-phase switch tube bridge arms change, at least two switching devices will change their states, and at most four switching devices will change their states. Compared with the situation where the switches of the three-phase or two-phase switch tube bridge arms change simultaneously, the common-mode voltage can be reduced, and the service life of the motor 111 can be extended. Exemplarily, if the state of the inverter circuit 121 is PPP, the state of the inverter circuit 121 after switching can be selected from the following several: OPP, NPP, POP, PNP, PPO, PPN.

[0122] Since when performing vector synthesis, the way of selecting multiple basic effective vectors for synthesis is not unique. As a possible implementation manner, when the motor controller 112 responds to the existence of multiple optional common-mode voltages in the inverter circuit 121, the motor controller 112 is used to control the three-phase switch tube bridge arm to make the common-mode voltage of the inverter circuit the minimum value among the multiple optional common-mode voltages.

[0123] Constraint condition 3: The motor controller 112 uses the above principle as a constraint condition to synthesize the reference voltage vector V ref to minimize the number of switching devices that change their off states as much as possible, so as to ensure that the common-mode voltage output on the inverter circuit 121 is reduced, thereby extending the service life of the motor 111.

[0124] Among them, in each vector type, the common-mode voltage output by each vector on the inverter circuit 121 is not the same. When selecting multiple basic effective vectors from the basic voltage vectors to synthesize the reference voltage vector V ref if there are multiple optional basic voltage vectors, the basic voltage vector with the minimum common-mode voltage can be selected from the multiple optional basic voltage vectors for synthesis, so as to reduce the common-mode voltage of the inverter circuit 121 and extend the service life of the motor 111.

[0125] Constraint condition 4: The motor controller 112 uses the above principle as a constraint condition to synthesize the reference voltage vector V ref When small-vector basic vectors are needed for synthesis, small vectors with a smaller common-mode voltage can be preferentially selected for vector synthesis to ensure that the common-mode voltage output on the inverter circuit 121 is reduced, thereby extending the service life of the motor 111.

[0126] Compared with various existing modulation strategies, the modulation strategy provided by this application can significantly reduce the common-mode voltage. Exemplarily, when the modulation index is the same, four existing typical modulation strategies are shown in the following figure. The modulation index is an important parameter of the modulated wave, which reflects the degree to which the amplitude, frequency or phase of the carrier is controlled by the low-frequency modulation signal. Figure 8A is the synthetic vector sequence of the first existing typical modulation strategy. There are zero vectors PPP and NNN in the first typical modulation strategy. Therefore, continue to refer to Figure 8A shown, and the maximum amplitude of the common-mode voltage output by it is Vdc / 2. Refer to Figure 8B shown, Figure 8B is the synthetic vector sequence of the second existing typical modulation strategy. There is also a zero vector PPP in the second typical modulation strategy. Therefore, continue to refer to Figure 8B shown, and the maximum amplitude of the common-mode voltage output by it is Vdc / 2. Refer to Figure 8C shown, Figure 8C is the synthetic vector sequence of the third existing typical modulation strategy. There is also a zero vector NNN in the third typical modulation strategy. Therefore, continue to refer to Figure 8C shown, and the maximum amplitude of the common-mode voltage output by it is Vdc / 2. Refer to Figure 8D shown, Figure 8D is the synthetic vector sequence of the third existing typical modulation strategy. There are also zero vectors PPP and NNN in the third typical modulation strategy. Therefore, continue to refer to Figure 8D shown, and the maximum amplitude of the common-mode voltage output by it is Vdc / 2. In the above typical modulation strategies, when selecting zero vectors, zero vectors PPP and NNN with a relatively large common-mode voltage are used.

[0127] When using the modulation strategy provided by this application, refer toFigure 9 As shown Figure 9 This is the synthetic vector sequence of the modulation strategy provided by this application. Continue to refer to Figure 9 As shown, within the entire modulation region, the maximum amplitude of the common-mode voltage of the inverter circuit 121 is Vdc / 6. Compared with the existing four typical modulation strategies, the common-mode voltage of the modulation strategy provided by this application is significantly reduced, thereby extending the service life of the motor 111.

[0128] Refer to Figure 10 As shown, the process of driving each switching device in the inverter circuit 121 by using the modulation strategy provided by this application will be introduced. Figure 10 It includes the following steps:

[0129] Step S1001, drive each switching device in the inverter circuit 121 by using a three-level operating mode.

[0130] The motor controller 112 can adopt the three-level operating mode provided by the above embodiment to generate drive signals for each switch. And output the generated drive signals for each switch to the corresponding switching device to achieve the drive of each switching device.

[0131] Step S1002, the motor controller 112 can obtain the target current to be output to the motor and the actual current output to the motor 111, and determine the reference voltage vector V ref .

[0132] Step S1003, the motor controller 112 segments the modulation degree according to the sector distribution of the reference voltage vector V ref .

[0133] Step S1004, the motor controller 112 determines the starting basic voltage vector within each segment.

[0134] Step S1005, the motor controller 112 determines the synthetic vector sequence corresponding to the reference voltage vector V ref according to the sector where the reference voltage vector V ref is located and the starting basic voltage vector.

[0135] Step S1006, the motor controller 112 uses the basic voltage vector at the end of the synthetic vector sequence as the basic voltage vector at the start of the next synthetic vector sequence, and repeats the above steps S1004 and step S1005 until the synthetic vector sequences of each reference voltage vector V ref in the first half of sector I are designed.

[0136] Step S1007: The motor controller 112 determines the synthetic vector sequence in the latter half of Sector I based on the QWS principle.

[0137] Step S1008: The motor controller 112 determines the synthetic vector sequences in Sectors II - VI based on the above Constraints 1 - 4.

[0138] Step S1009: The motor controller 112 drives the switching devices in the three bridge arms by using the synthetic vector sequences in Sectors I - VI.

[0139] Based on the same concept, an embodiment of the present application further provides a powertrain, which includes a motor and a motor controller. The motor controller includes an inverter circuit. The inverter circuit includes three - phase switch - tube bridge arms. The mid - points of each phase of the switch - tube bridge arms are respectively used to connect one phase winding of the motor. The inverter circuit is used to connect to a power battery through a DC bus. The motor controller is configured to: control the phase voltage output at the mid - point of each phase of the three - phase switch - tube bridge arms of the inverter circuit. The phase voltage is used to generate a phase current on the winding of the motor to drive the motor to output torque. Among them, the phase voltage generated at the mid - point of at least one phase of the three - phase switch - tube bridge arms is different in direction from the phase voltage generated at the mid - points of the other switch - tube bridge arms, or the phase voltage generated by each group of bridge arms in the three - phase switch - tube bridge arms is zero. An embodiment of the present application further provides an electric vehicle, and the electric vehicle may include the motor controller provided in the above - mentioned embodiment.

[0140] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the protection scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these changes and modifications.

Claims

1. A motor controller for common-mode voltage suppression, characterized in that The motor controller includes an inverter circuit. The inverter circuit includes three-phase switch tube arms. The midpoints of each phase of the switch tube arms are respectively used to connect one phase winding of the motor. The inverter circuit is used to connect to the power battery through a DC bus. The motor controller is used for: Controlling the phase voltage output at the midpoint of each phase of the three-phase switch tube arms of the inverter circuit. The phase voltage is used to generate a phase current in the winding of the motor to drive the motor to output torque. Among them, the phase voltage generated at the midpoint of at least one phase of the three-phase switch tube arms is different in direction from the phase voltage generated at the midpoints of the other switch tube arms, or the phase voltage generated by each group of arms in the three-phase switch tube arms is zero.

2. The motor controller according to claim 1, characterized in that The phase voltage output at the midpoint of each phase of the three-phase switch tube arms of the inverter circuit includes: a first voltage, a second voltage or a third voltage. The first voltage is greater than zero, the second voltage is equal to zero, the third voltage is less than zero. The first voltage is Vdc / 2, the third voltage is -Vdc / 2, and Vdc is the voltage value of the power battery.

3. The motor controller according to claim 1 or 2, characterized in that, During the process of the motor controller outputting the phase voltage, the motor controller is used for: Controlling the direction of the phase voltage output at the midpoint of any one phase switch tube arm of the inverter circuit to remain unchanged.

4. The motor controller according to any one of claims 1-3, characterized in that During the process of the motor controller outputting the phase voltage, the motor controller is used for: At most controlling the direction of the phase voltage output at the midpoint of any one phase switch tube arm of the inverter circuit to change.

5. The motor controller according to any one of claims 1-4, characterized in that, The motor controller is used for: Controlling the three-phase switch tube arms to make the common-mode voltage of the inverter circuit not greater than a preset value. The common-mode voltage is the voltage difference between the neutral point of the motor winding and the reference potential.

6. The motor controller according to claim 5, characterized in that, The motor controller is used for: In response to the existence of multiple different magnitudes of available common-mode voltages in the inverter circuit, controlling the three-phase switch tube arms to make the common-mode voltage output by the inverter circuit the minimum value among the multiple different magnitudes of available common-mode voltages. The values of the multiple different magnitudes of available common-mode voltages include any two of the following: ±Vdc / 6, ±Vdc / 3, ±Vdc / 2, and zero.

7. The motor controller according to any one of claims 1-6, characterized in that, The motor controller includes a control circuit. The control circuit is used to output a control signal to the inverter circuit. The control signal is used to control the phase voltage output at the midpoint of each phase of the three-phase switch tube arms of the inverter circuit. Among them: The control signal is used to indicate that the phase voltage generated at the midpoint of at least one phase of the three-phase switch tube arms is different in direction from the phase voltage generated at the midpoints of the other switch tube arms, or to indicate that the phase voltage generated by each group of arms in the three-phase switch tube arms is zero.

8. The motor controller according to claim 7, characterized in that The inverter circuit includes a three-phase switch tube bridge arm, a first capacitor, and a second capacitor. Each switch tube bridge arm includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first diode, and a second diode. The first end of the first capacitor is connected to the positive electrode of the power battery, the second end of the first capacitor is connected to the first end of the second capacitor, the second end of the second capacitor is connected to the negative electrode of the power battery, and the connection point between the first capacitor and the second capacitor is the connection midpoint. The first end of the first switch tube is connected to the positive electrode of the power battery, the second end of the first switch tube is connected to the first end of the second switch tube, the second end of the second switch tube is connected to the connection midpoint, the second end of the second switch tube is connected to the first end of the third switch tube, the second end of the third switch tube is connected to the first end of the fourth switch tube, and the second end of the fourth switch tube is connected to the negative electrode of the power battery. The anode of the first diode and the cathode of the second diode are connected to the connection midpoint, the cathode of the first diode is connected to the second end of the first switch tube, and the anode of the second diode is connected to the second end of the third switch tube. The connection point between the second switch tube and the third switch tube is the midpoint of the bridge arm of this phase switch tube bridge arm.

9. The motor controller according to claim 8, characterized in that When the first switch tube, the second switch tube, the third switch tube is off, and the fourth switch tube is off in the switch tube bridge arm, the phase voltage output by this phase switch tube bridge arm is the first voltage; When the first switch tube is off, the second switch tube is on, the third switch tube is on, and the fourth switch tube is off in the switch tube bridge arm, the phase voltage output by this phase switch tube bridge arm is the second voltage; When the first switch tube is off, the second switch tube is off, the third switch tube is on, and the fourth switch tube is on in the switch tube bridge arm, the phase voltage output by this phase switch tube bridge arm is the third voltage, where the first voltage is Vdc / 2, the third voltage is -Vdc / 2, and the Vdc is the voltage value of the power battery.

10. The motor controller according to claim 8 or 9, characterized in that, When the switch state of the switch tube in any one of the switch tube bridge arms changes, the phase voltage output by each switch tube bridge arm switches between the first voltage and the second voltage; or When the switch state of the switch tube in any one of the switch tube bridge arms changes, the phase voltage output by each switch tube bridge arm switches between the second voltage and the third voltage.

11. The motor controller according to any one of claims 8-10, characterized in that, At most two-phase switch tube bridge arms in the inverter circuit have the switch state of the switch tube changed; or At most one-phase switch tube bridge arm in the inverter circuit has the switch state of the switch tube changed.

12. The motor controller according to any one of claims 8-11, characterized in that, The vector of the phase voltage output at the midpoint of the bridge arm of the three-phase switch tube bridge arm is used to synthesize the target vector. The control circuit is configured to: when there are multiple phase voltage synthesis methods to synthesize the target vector, select the phase voltage synthesis method with the minimum common-mode voltage and adjust the switch state of the switch tubes in the three-phase switch tube bridge arm.

13. The motor controller according to claim 12, characterized in that, The control circuit is configured to: when the target vector is a zero vector, control the midpoints of each switch tube arm to output a second voltage.

14. The motor controller according to any one of claims 1-13, characterized in that, The common-mode voltage of the inverter circuit conforms to the following formula: where Ucom is the common-mode voltage of the inverter circuit, U1 is the phase voltage output by the midpoint of the first set of arms, U2 is the phase voltage output by the midpoint of the second set of arms, and U3 is the phase voltage output by the midpoint of the third set of arms.

15. A powertrain, characterized in that, The powertrain includes a motor and a motor controller. The motor controller includes an inverter circuit. The inverter circuit includes three-phase switch tube arms. The midpoint of each switch tube arm of each phase is respectively used to connect a phase winding of the motor. The inverter circuit is used to connect to the power battery through a DC bus. The motor controller is configured to: control the midpoint of each phase of the three-phase switch tube arms of the inverter circuit to output a phase voltage, and the phase voltage is used to generate a phase current on the winding of the motor to drive the motor to output torque. Among them, the phase voltage generated by the midpoint of at least one phase of the three-phase switch tube arms is different in direction from the phase voltage generated by the midpoint of other switch tube arms, or the phase voltage generated by each group of arms in the three-phase switch tube arms is zero.

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