Method and device for suppressing rotor eddy current loss of permanent magnet synchronous motor in boost charging mode and vehicle

Abstract

This application provides a method, apparatus, and vehicle for suppressing rotor eddy current losses in a permanent magnet synchronous motor under boost charging mode. The method includes: acquiring the current rotor electrical angle of the motor in boost charging mode; determining the target rotor electrical angle region to which the current rotor electrical angle belongs based on a pre-divided rotor electrical angle region; determining the target switching state combination and target three-phase PWM wave generation mode corresponding to the target rotor electrical angle region; under the target switching state combination and target three-phase PWM wave generation mode, the equivalent d-axis voltage of the three-phase voltage composite vector output by the inverter within one switching cycle is zero; controlling the inverter duty cycle output according to the target switching state combination and target three-phase PWM wave generation mode, controlling the current to generate torque so that the rotor position reaches the reference electrical angle, making the high-frequency ripple amplitude of the three-phase voltage composite vector output by the inverter approach zero on the d-axis, thereby reducing the rotor permanent magnet eddy current losses and rotor temperature rise of the motor.

Description

Technical Field

[0001] This application relates to the field of motor control, specifically to a method, device, and vehicle for suppressing rotor eddy current losses in a permanent magnet synchronous motor under boost charging mode. Background Technology

[0002] With the development of the new energy vehicle industry, in order to solve the problem that the infrastructure construction of DC charging piles for electric vehicles is difficult to popularize rapidly in the short term, high-voltage battery charging systems have begun to develop towards high power density and high integration, and DC boost charging function has gradually become the main focus of electric vehicle charging technology.

[0003] Drive-multiplexing boost charging technology, which integrates the electric drive system and the charging system, achieves boost charging of the battery by multiplexing the drive motor windings and the three-phase inverter to form a DC / DC converter. Essentially, it uses the motor windings as boost inductors and the inverter's switching arms as boost synchronous rectifier bridges. This solution only adds an extra motor winding interface, eliminating the need for separate charging inductors, power devices, and cooling circuits, thus reducing cost and system size, and has become a hot research topic in the industry.

[0004] Electric vehicle drive systems typically use permanent magnet synchronous motors. When using the three-phase windings of the motor for boost charging, a parallel interleaved PWM scheme with three-phase switches interleaved by 120° is usually employed to increase charging power. However, this scheme generates high-frequency voltage ripple, which in turn generates high-frequency current ripple on the motor's d-axis. This d-axis current ripple induces eddy currents in the rotor's permanent magnets, leading to severe rotor overheating. Under certain operating conditions, the rotor temperature may even fail to reach thermal equilibrium, potentially causing demagnetization of the permanent magnets and a decline in motor performance over long-term operation. Summary of the Invention

[0005] This application provides a method, device, and vehicle for suppressing rotor eddy current losses in a permanent magnet synchronous motor under boost charging mode, in order to solve the technical problems in existing drive reuse boost charging technology, such as excessive rotor permanent magnet eddy current losses, excessive rotor temperature rise, and rotor inability to reach thermal equilibrium due to d-axis current ripple.

[0006] The technical solution of this invention is as follows:

[0007] This application provides a method for suppressing rotor eddy current losses in a permanent magnet synchronous motor under boost charging mode, including:

[0008] In boost charging mode, obtain the current rotor electrical angle of the permanent magnet synchronous motor;

[0009] Based on the pre-defined rotor electrical angle regions, determine the target rotor electrical angle region to which the current rotor electrical angle belongs;

[0010] Determine the target switching state combination and target three-phase PWM wave operation mode corresponding to the target rotor electrical angle region; under the target switching state combination and target three-phase PWM wave operation mode, the equivalent d-axis voltage of the three-phase voltage synthesis vector output by the inverter within one switching cycle is zero;

[0011] The inverter's three-phase duty cycle output is controlled according to the target switching state combination and the target three-phase PWM wave generation working mode, so that the high-frequency ripple amplitude of the inverter's output three-phase voltage synthesis vector on the d-axis approaches zero (maximum 1.16%Vdc, typical value less than 0.46%Vdc), thereby reducing the rotor permanent magnet eddy current loss and rotor temperature rise of the permanent magnet synchronous motor.

[0012] Preferably, after the step of controlling the three-phase duty cycle output of the inverter according to the target switching state combination and the target three-phase PWM ripple operation mode, the method further includes:

[0013] Reacquire the current rotor electrical angle of the permanent magnet synchronous motor and the total DC current demand on the inverter side after rectification and boosting by the inverter in the boost charging mode.

[0014] Determine the electrical angle deviation between the newly acquired current rotor electrical angle and the reference electrical angle corresponding to its rotor electrical angle region;

[0015] When the absolute value of the electrical angle deviation is greater than the first threshold, the three-phase current output by the permanent magnet synchronous motor is adjusted according to the electrical angle deviation between the current rotor electrical angle and the reference electrical angle corresponding to its rotor electrical angle region and the total DC current demand on the inverter side, so that the permanent magnet synchronous motor generates torque in the opposite direction to the electrical angle deviation, pulling the rotor electrical angle of the permanent magnet synchronous motor toward the reference electrical angle.

[0016] Preferably, the method further includes:

[0017] When the absolute value of the electrical angle deviation is less than the second threshold, the three-phase current is not adjusted according to the electrical angle deviation and the total DC current demand, and the output of each phase of the permanent magnet synchronous motor is kept to be 1 / 3 of the total DC current demand on the inverter side.

[0018] When the absolute value of the electrical angle deviation is greater than or equal to the second threshold and less than the first threshold, the current three-phase current output by the permanent magnet synchronous motor remains unchanged.

[0019] Wherein, the first threshold is greater than the second threshold.

[0020] Preferably, the step of adjusting the three-phase current output by the permanent magnet synchronous motor based on the electrical angle deviation between the newly acquired current rotor electrical angle and the reference electrical angle corresponding to its rotor electrical angle region, and the total DC current requirement on the inverter side, includes:

[0021] Based on the electrical angle deviation and the total DC current requirement on the inverter side, the reference value of the three-phase current is determined;

[0022] Adjust the three-phase current output of the permanent magnet synchronous motor according to the three-phase current reference value;

[0023] The three-phase current reference value is the sum of the DC charging component and the electrical angle self-locking current component, and the specific calculation formula is as follows:

[0024]

[0025] Among them, i u,ref i v,ref i w,ref These represent the reference values ​​for the three-phase currents of phases U, V, and W, respectively; Iin / 3 is the DC charging component; I in This refers to the total DC current requirement on the inverter side for charging the battery after rectification and boosting by the inverter in boost charging mode; q,ref This is a reference value for the q-axis current related to the electrical angle deviation;

[0026] The q-axis current reference value i related to the electrical angle deviation q,ref Through the formula:

[0027]

[0028] Calculated; △ denoted as , where is the deviation between the current rotor electrical angle and the reference electrical angle, kp is the pre-calibrated proportional gain, and kd is the pre-calibrated differential gain.

[0029] Preferably, the rotor electrical angle region is divided into 6 continuous regions within the range of 0° to 360°, namely: 0°~60°, 60°~120°, 120°~180°, 180°~240°, 240°~300°, and 300°~360°.

[0030] Preferably, the reference electrical angle corresponding to each rotor electrical angle region is the midpoint of that region, which are 30°, 90°, 150°, 210°, 270°, and 330° respectively.

[0031] Preferably, the rotor electrical angle region includes 6 rotor electrical angle regions, wherein:

[0032] The switching state combinations corresponding to the first rotor electrical angle region and the fourth rotor electrical angle region are S2 and S5, and the corresponding three-phase PWM wave generation working modes are U phase and W phase are the same phase, and V phase is 180° different from U phase and W phase.

[0033] The switching state combinations corresponding to the second rotor electrical angle region and the fifth rotor electrical angle region are S3 and S4, and the corresponding three-phase PWM wave generation working modes are V phase and W phase are in phase, and U phase and V phase and W phase are 180° apart.

[0034] The switching state combinations corresponding to the third rotor electrical angle region and the sixth rotor electrical angle region are S1 and S6, respectively. The corresponding three-phase PWM wave generation working modes are U phase and V phase are in phase, and W phase is 180° different from U phase and V phase.

[0035] Preferably, the first threshold is 1° and the second threshold is 0.4°.

[0036] This application also provides a rotor eddy current loss suppression device for a permanent magnet synchronous motor in boost charging mode, comprising:

[0037] The acquisition module is used to acquire the current rotor electrical angle of the permanent magnet synchronous motor in boost charging mode.

[0038] The first determining module is used to determine the target rotor electrical angle region to which the current rotor electrical angle belongs, based on the pre-divided rotor electrical angle region.

[0039] The second determining module is used to determine the target switching state combination and the target three-phase PWM wave operation mode corresponding to the target rotor electrical angle region; under the target switching state combination and the target three-phase PWM wave operation mode, the equivalent d-axis voltage of the three-phase voltage synthesis vector output by the inverter in one switching cycle is zero.

[0040] The control module is used to control the three-phase duty cycle output of the inverter according to the target switching state combination and the target three-phase PWM wave generation working mode, so that the high-frequency ripple amplitude of the three-phase voltage synthesis vector output by the inverter on the d-axis approaches zero, thereby reducing the rotor permanent magnet eddy current loss and rotor temperature rise of the permanent magnet synchronous motor.

[0041] This application also provides a vehicle including the aforementioned rotor eddy current loss suppression device for a permanent magnet synchronous motor in boost charging mode.

[0042] The technical solution of this invention is as follows:

[0043] By acquiring the current rotor electrical angle and determining its corresponding rotor electrical angle region, the corresponding switching state combination and three-phase PWM wave generation mode are selected. The principle is as follows: Existing technologies using a three-phase parallel interleaved PWM scheme generate high-frequency voltage ripple, thus introducing high-frequency current ripple along the d-axis. This d-axis current ripple induces eddy currents in the rotor permanent magnets, leading to severe rotor overheating and an inability to reach thermal equilibrium. This application, by selecting a specific switching state combination and a three-phase PWM wave generation mode, ensures that the equivalent d-axis voltage of the inverter's output three-phase voltage composite vector is zero within one switching cycle. Simultaneously, the output torque moves the rotor to the reference position, making the transient d-axis voltage zero, thus eliminating the high-frequency voltage component along the d-axis at its source. Therefore, the amplitude of the d-axis current ripple approaches zero. With the d-axis current ripple approaching zero, eddy currents are no longer induced in the rotor permanent magnets, significantly reducing rotor eddy current losses and rotor temperature rise, enabling the rotor to reach a steady-state thermal equilibrium. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to an embodiment of this application.

[0045] Figure 2 This is a schematic diagram of the PWM output when UW is in phase in an embodiment of this application;

[0046] Figure 3 This is a schematic diagram of the relationship between rotor position and torque in an embodiment of this application;

[0047] Figure 4 This is an analysis diagram of the d-axis components of the voltage vector. Detailed Implementation

[0048] In existing drive-multiplexed boost charging technology, a parallel interleaved PWM scheme with three-phase switches interleaved by 120° is typically used to improve charging power. In this scheme, the switches of the three-phase bridge arms operate independently with a 120° phase difference, and the duty cycle of each bridge arm varies independently according to a sinusoidal modulation law, without a fixed synchronization relationship between them. Because the three-phase switching actions are staggered in time, the switching states of the three-phase voltages are different at the same moment, causing the component of the three-phase voltage composite vector on the d-axis to be unable to remain constant within a switching cycle. With frequent switching states, the d-axis voltage component exhibits high-frequency fluctuations in each switching cycle, the same frequency as the switching frequency, thus generating a high-frequency voltage ripple on the d-axis. This high-frequency voltage ripple then excites a high-frequency current ripple on the d-axis in the motor windings. When this d-axis current ripple passes through the rotor permanent magnet, according to the principle of electromagnetic induction, it induces high-frequency eddy currents in the permanent magnet, causing severe rotor heating and a continuous rise in rotor temperature, preventing the achievement of steady-state thermal equilibrium.

[0049] To solve the above problems, refer to Figures 1-4 This application provides a method for suppressing rotor eddy current losses in a permanent magnet synchronous motor under boost charging mode, including:

[0050] S101, in boost charging mode, obtain the current rotor electrical angle of the permanent magnet synchronous motor;

[0051] S102, determine the target rotor electrical angle region to which the current rotor electrical angle belongs based on the pre-divided rotor electrical angle region;

[0052] S103, determine the target switching state combination and target three-phase PWM wave generation mode corresponding to the target rotor electrical angle region; under the target switching state combination and target three-phase PWM wave generation mode, the equivalent d-axis voltage of the three-phase voltage synthesis vector output by the inverter in one switching cycle is zero;

[0053] S104, according to the target switching state combination and the target three-phase PWM wave generation working mode, control the three-phase duty cycle output of the inverter so that the high-frequency ripple amplitude of the three-phase voltage synthesis vector output by the inverter on the d-axis approaches zero, thereby reducing the rotor permanent magnet eddy current loss and rotor temperature rise of the permanent magnet synchronous motor.

[0054] The boost charging mode refers to the working mode in which the three-phase inverter of the electric vehicle drive system and the three-phase winding of the permanent magnet synchronous motor are used together to form a DC / DC boost converter, which boosts the low-voltage DC power input from the external DC charging pile to charge the high-voltage power battery on the vehicle.

[0055] In this boost charging mode, the three-phase windings of the permanent magnet synchronous motor act as boost inductors, and the switching arms of the three-phase inverter act as boost synchronous rectifier bridges. By controlling the on / off state of the inverter switching transistors, electrical energy is transferred and the voltage is increased. At this time, the motor winding coils act as energy storage devices, and the current in the three-phase windings is rectified and boosted by the inverter to charge the battery.

[0056] A typical application scenario for boost charging mode is: when the output voltage of a DC charging pile is lower than the battery voltage, the voltage is increased through this boost charging mode to meet the battery charging needs, thereby making it compatible with charging piles of different voltage levels and improving charging convenience.

[0057] In boost charging mode, the rotor's mechanical position signal is acquired in real time by the rotor position sensor integrated into the permanent magnet synchronous motor. This rotor position sensor can be a rotary transformer, Hall sensor, or magnetic encoder, with a measurement accuracy of no less than 0.1° electrical angle. Based on the acquired rotor mechanical position signal and the number of pole pairs of the motor, the controller calculates the current rotor electrical angle θ. eThe rotor electrical angle ranges from 0° to 360°. This angle is used in subsequent steps to determine the current electrical angle region of the rotor and serves as the basic input parameter for electrical angle self-locking control.

[0058] In step S102, the pre-divided rotor electrical angle region is divided into 6 continuous regions within the range of 0° to 360°, namely: 0°~60°, 60°~120°, 120°~180°, 180°~240°, 240°~300°, and 300°~360°.

[0059] The above-mentioned regional division is based on the relationship between the component of the three-phase voltage composite vector on the d-axis and the rotor electrical angle under different switching states, which makes there a specific combination of switching states in each region that can make the equivalent d-axis voltage zero.

[0060] In boost charging mode, the controller acquires the current rotor electrical angle θ. e Then, the angle value is compared with the ranges of the six regions mentioned above one by one to determine its region. For example, if the current rotor electrical angle θ e =45°, then it is determined to belong to the first region; if θ e =210°, then it belongs to the fourth region; the region determined is the target rotor electrical angle region.

[0061] The reference electrical angles corresponding to each rotor electrical angle region are the midpoint positions of that region, specifically: 30°, 90°, 150°, 210°, 270°, and 330°. The rotor electrical angle regions comprise six areas, of which:

[0062] The switch state combinations corresponding to the first and fourth regions are S2 and S5, and the corresponding three-phase PWM wave generation working modes are U phase and W phase are in phase, and V phase is 180° different from U phase and W phase.

[0063] The switching state combinations corresponding to the second and fifth regions are S3 and S4, and the corresponding three-phase PWM wave generation working modes are V phase and W phase are in phase, and U phase and V phase and W phase are 180° apart.

[0064] The switching state combinations corresponding to the third and sixth regions are S1 and S6, and the corresponding three-phase PWM wave generation working modes are U phase and V phase are in phase, and W phase is 180° different from U phase and V phase.

[0065] In this embodiment of the application, the process of pre-dividing the rotor electrical angle region includes:

[0066] Assume the three-phase voltages of the motor are respectively , , According to the equal-amplitude Park transform, the components of the three-phase voltage composite vector on the d-axis are:

[0067] (1)

[0068] Based on the three-phase voltage results under different switching states, the relationship between the d-axis voltage and the rotor electrical angle under different switching states was obtained. To minimize the d-axis voltage... The rotor electrical angle ranges are defined as 60° counterclockwise from 0°, forming electrical angle regions 1 to 6. The midpoint of each electrical angle region is the location of 6 rotor reference electrical angles, as detailed in Table 1.

[0069] Table 1. Rotor Electrical Angle Region and Reference Electrical Angle Definition

[0070]

[0071] In step S103, according to a predefined correspondence, each rotor electrical angle interval corresponds to a set of switching state combinations and a three-phase PWM wave generation mode. Specifically, based on the relationship between the d-axis voltage and the rotor electrical angle under different switching states, the corresponding switching state combinations and three-phase PWM wave generation modes within the rotor electrical angle region are defined, as shown in Table 2:

[0072] Table 2 Definitions of Rotor Electrical Angle Region and Wave Generation Working Mode

[0073]

[0074] In other words, the specific correspondence is as follows:

[0075] The first rotor electrical angle region (0°~60°) and the fourth rotor electrical angle region (180°~240°) correspond to the switch state groups S2(0,1,0) and S5(1,0,1), and the corresponding three-phase PWM wave generation working modes are U phase and W phase are in phase, and V phase is 180° different from U phase and W phase.

[0076] The second rotor electrical angle region (60°~120°) and the fifth rotor electrical angle region (240°~300°) have the corresponding switch state combinations S3(0,1,1) and S4(1,0,0), and the corresponding three-phase PWM wave generation working modes are V phase and W phase are in phase, and U phase and V phase and W phase are 180° apart.

[0077] The third rotor electrical angle region (120°~180°) and the sixth interval (300°~360°) have the corresponding switch state combinations S1(0,0,1) and S6(1,1,0), and the corresponding three-phase PWM wave generation working modes are U phase and V phase are in phase, and W phase is 180° different from U phase and V phase.

[0078] Under the above switching state combination and three-phase PWM wave operation mode, the equivalent d-axis voltage of the inverter output three-phase voltage synthesis vector within one switching cycle is zero, and the d-axis high-frequency ripple amplitude is small. Through actual experiments, the maximum value of the d-axis high-frequency ripple amplitude was determined to be 1.16%*Vd, and the typical value is less than 0.46%*Vd.

[0079] Based on the target rotor electrical angle range determined in step S102, the controller looks up the corresponding relationship in Table 2 above to determine the target switching state combination and the target three-phase PWM wave generation mode corresponding to the range.

[0080] Specifically, based on the rotor electrical angle Taking 45° as an example, this explains why step S104 can achieve a smaller high-frequency ripple amplitude in the d-axis of the three-phase voltage synthesis vector output by the inverter, thereby reducing the eddy current loss of the rotor permanent magnet and the rotor temperature rise of the permanent magnet synchronous motor.

[0081] As shown in Table 2, at this rotor electrical angle When the angle is 45°, make the d-axis voltage... The smallest pair of switch states are S2(0,1,0) and S5(1,0,1). From equation (1), the components of the voltage vector on the d-axis at this time are calculated as follows:

[0082]

[0083] According to Table 2, the three-phase PWM wave generation modes corresponding to S2(0,1,0) and S5(1,0,1) are as follows:

[0084] The U-phase and W-phase switching states are synchronized (in phase), while the V-phase switching state is 180° out of phase with the U and W phases (out of phase).

[0085] When S2(0,1,0) is in effect, , , Substituting into When S5(1,0,1) is active, , , Substituting into Therefore, under the influence of the switching states S2(0,1,0) and S5(1,0,1), the resultant voltage of the three-phase voltage vector on the d-axis within one switching cycle is... They cancel each other out, making The high-frequency ripple amplitude is relatively small.

[0086] Furthermore, as shown in Tables 1 and 2, when the rotor electrical angle is located at one of the six reference electrical angles in Table 1... (30°, 90°, 150°, 210°, 270°, 330°), under the switching state combinations defined in Table 2, the transient voltage projection on the d-axis for each switching state combination is always zero, and the d-axis current ripple is at this time. =0. Therefore, when the rotor electrical angle is at 6 reference electrical angles... When using the switching state combinations and three-phase PWM waveform operation modes defined in Table 2 to control the three-phase duty cycle output, the d-axis voltage can be reduced to the greatest extent during battery boost charging. and d-axis current ripple Therefore, these 6 reference electrical angles The optimal working position minimizes eddy current losses in the rotor permanent magnet and reduces rotor temperature rise.

[0087] Further calculations based on Tables 1 and 2 show that for any rotor electrical angle within these six electrical angle regions, there always exists a pair of switching state combinations such that, under the action of this switching state combination, the equivalent d-axis voltage within one switching cycle... The value is zero. Therefore, based on the region of the rotor's electrical angle, the switching state combination and three-phase PWM wave generation mode defined in Table 2 are used to control the three-phase duty cycle output. This allows for boost charging of the battery. The high-frequency ripple amplitude tends to 0 in order to reduce the eddy current loss of the rotor permanent magnet and reduce the rotor temperature rise.

[0088] Therefore, according to the above steps S101-S104, the equivalent d-axis voltage of the three-phase voltage synthesis vector output by the inverter is zero within one switching cycle, thereby reducing the amplitude of its d-axis high-frequency ripple.

[0089] Furthermore, in order to make the boost charging operate as close as possible to the preset reference electrical angle... Nearby, by redistributing the three-phase current reference values, the torque generated by the operating current forms a reference electrical angle self-locking. When the motor is at the reference electrical angle, the d-axis transient voltage projection is always zero, the d-axis high-frequency voltage component is eliminated, and the d-axis high-frequency current ripple is suppressed, thus preventing the induction of high-frequency eddy currents in the rotor permanent magnet. This fundamentally solves the problem of excessive rotor eddy current losses and excessive rotor temperature rise caused by d-axis current ripple in the prior art, achieving the technical effect of reducing rotor eddy current losses and rotor temperature rise. In this embodiment, after step S104 of controlling the three-phase duty cycle output of the inverter according to the target switching state combination and the target three-phase PWM wave operation mode, the method further includes:

[0090] S105, Reacquire the current rotor electrical angle of the permanent magnet synchronous motor and the total DC current demand on the inverter side of the battery after rectification and boosting by the inverter in the boost charging mode.

[0091] S106, Determine the electrical angle deviation between the newly acquired current rotor electrical angle and the reference electrical angle corresponding to its rotor electrical angle region.

[0092] S107, when the absolute value of the electrical angle deviation is greater than the first threshold, the three-phase current output by the permanent magnet synchronous motor is adjusted according to the electrical angle deviation between the current rotor electrical angle and the reference electrical angle corresponding to the rotor electrical angle region it is in, and the total DC current demand on the inverter side, so that the permanent magnet synchronous motor generates a torque in the opposite direction to the electrical angle deviation, and pulls the rotor electrical angle of the permanent magnet synchronous motor toward the reference electrical angle.

[0093] S108, when the absolute value of the electrical angle deviation is less than the second threshold, the three-phase current is not adjusted according to the electrical angle deviation and the total DC current demand, and the output of each phase of the permanent magnet synchronous motor is kept at 1 / 3 of the total DC current demand of the inverter side charged into the battery after rectification and boosting by the inverter in the boost charging mode.

[0094] S109, when the absolute value of the electrical angle deviation is greater than or equal to the second threshold and less than the first threshold, the current three-phase current output by the permanent magnet synchronous motor remains unchanged;

[0095] Wherein, the first threshold is greater than the second threshold.

[0096] In boost charging mode, the total DC current demand I on the inverter side after rectification and boosting by the inverter to charge the battery is... in The battery controller sends the data to the motor controller via a communication network as input parameters for subsequent calculations of the three-phase current reference values.

[0097] The specific principle behind step S106 is as follows:

[0098] The current rotor electrical angle is reacquired using the rotor position sensor. Determine the current rotor electrical angle based on Table 1. The target rotor electrical angle region is determined, and the reference electrical angle is obtained according to Table 1. As a self-locking target.

[0099] Specifically, step S107 includes:

[0100] Based on the electrical angle deviation and the total DC current requirement on the inverter side, the reference value of the three-phase current is determined;

[0101] Adjust the three-phase current output of the permanent magnet synchronous motor according to the three-phase current reference value;

[0102] The three-phase current reference value is the sum of the DC charging component and the electrical angle self-locking current component, and the specific calculation formula is as follows:

[0103]

[0104] Among them, i u,ref i v,ref i w,ref These represent the reference values ​​for the three-phase currents of phases U, V, and W, respectively; Iin / 3 is the DC charging component; I in This refers to the total DC current requirement on the inverter side for charging the battery after rectification and boosting by the inverter in boost charging mode; q,ref The q-axis current reference value related to the electrical angle deviation; the q-axis current reference value i related to the electrical angle deviation. q,ref Through the formula:

[0105]

[0106] Calculated; △ denoted as , where is the deviation between the current rotor electrical angle and the reference electrical angle, kp is the pre-calibrated proportional gain, and kd is the pre-calibrated differential gain.

[0107] The principle behind steps S107-S109 is as follows:

[0108] The three-phase current is each decomposed into two parts: a DC charging component and an electrical angle self-locking current component. The DC charging component is a fixed value. ,in The total charging magnitude for boost charging is the sum of the DC components of the three-phase currents. This component has a spatially synthesized vector of zero, generating no torque and only providing charging energy. The electrical angle self-locking current components are as follows:

[0109] (1)

[0110] The electrical angle self-locking current component is derived from the q-axis current reference value related to the electrical angle deviation. and the current rotor electrical angle The only certainty is that the sum of the electrical angle self-locking current components is:

[0111] (2)

[0112] Equation (2) shows that the electrical angle self-locking current component does not contain zero-sequence current, ensuring that the total battery charging current is always within the range specified by equation (2). .

[0113] To achieve self-locking of the reference electrical angle, the components of the composite vector of the self-locking current components of the electrical angle along the d and q axes are:

[0114] (3)

[0115] Equation (3) indicates that the torque current component of the resultant vector on the q-axis is a current opposite to the direction of the electrical angle deviation, while maintaining the component of the resultant vector on the d-axis. This avoids generating d-axis current ripple and eddy current losses.

[0116] The further optimized components of the synthesized vector of the self-locking current component at the power extraction angle are as follows:

[0117] (4)

[0118] Equation (4) indicates that the torque current component of the resultant vector on the q-axis is a current opposite to the direction of the electrical angle deviation and the direction of the rotor electrical angular velocity, while maintaining the component of the resultant vector on the d-axis. This avoids generating d-axis current ripple and eddy current losses.

[0119] In equations (3) and (4), For proportional gain, This is the differential gain, and the self-locking adjustment capability of the reference electrical angle can be changed by calibrating this parameter.

[0120] Furthermore, considering the periodicity of the electrical angle within the range of 0~360°, the electrical angle deviation is handled as follows:

[0121] (5)

[0122] The mod operation is a mathematical modulo operation. By processing the electrical angle deviation to (-180°, 180°), the rotor electrical angle returns to the self-locking target position through the shortest path.

[0123] From the torque equation of a permanent magnet synchronous motor:

[0124] (6)

[0125] Equations (3), (4), and (6) show that the component of the composite vector of the self-locking current components at the electrical angle on the q-axis is... This generates a torque opposite to the direction of the deviation, thus achieving self-locking of the reference electrical angle. Specifically, when the actual electrical angle of the rotor... Positive deviation from reference electrical angle ( > This generates negative electromagnetic torque, pulling the rotor back to the target electrical angle; when the actual electrical angle of the rotor... Reverse deviation from reference electrical angle ( < This generates a positive electromagnetic torque, pulling the rotor back to the target electrical angle; when the actual electrical angle of the rotor... Equal to reference electrical angle ( = The combined torque approaches 0, achieving stable locking.

[0126] The final calculated three-phase current reference value is the sum of the DC charging component and the electrical angle self-locking current component. The specific calculation formula is as follows:

[0127] (7)

[0128] To avoid frequent switching near the target electrical angle, the electrical angle hysteresis region strategy is set as follows: when That is, electrical angle deviation The absolute value is greater than the first threshold. When the electrical angle self-locking control is activated, the three-phase current reference values ​​are calculated according to equations (3), (4), (5), and (7); when That is, electrical angle deviation The absolute value is less than the second threshold. At this time, the electrical angle self-locking control is turned off, and the current sharing mode is maintained, that is, the reference values ​​of the three-phase currents are all equal to ;when That is, electrical angle deviation The absolute value is greater than or equal to the second threshold. And less than the first threshold At the same time, the reference values ​​of the three-phase current output by the permanent magnet synchronous motor are kept constant. Among them, ,like =1°, =0.4°.

[0129] In this embodiment, through motor thermal simulation, it is confirmed that the electronic rotor temperature can reach thermal equilibrium, which is different from the previous three-phase parallel interleaved scheme. Temperature sensors monitor the rotor temperature and compare it with the heat generation during normal three-phase parallel interleaved wave generation to confirm that the rotor temperature of the new strategy can reach a steady-state thermal equilibrium.

[0130] By dividing the rotor electrical angle into six self-stabilizing regions, selecting a specific voltage vector combination where the d-axis component is zero, and optimizing the three-phase current magnitude to achieve reference electrical angle self-locking, the system achieves optimal positioning. The high-frequency ripple approaches zero, thereby reducing the d-axis current ripple, reducing the rotor permanent magnet eddy current losses caused by the d-axis current ripple during boost charging, reducing rotor temperature rise, and bringing the rotor temperature from a state below thermal equilibrium to a steady-state thermal equilibrium state. Specifically, compared with the prior art, this invention has the following advantages and positive effects:

[0131] 1. Eddy current losses are significantly reduced.

[0132] By analyzing the relationship between d-axis voltage and rotor electrical angle under different switching states, switching state combinations where the d-axis voltage component is 0 and three-phase PWM waveform generation operating modes are selected in different rotor electrical angle regions, so that... The high-frequency ripple amplitude is reduced by more than 80%, the amplitude of the change in the magnetic field of the rotor permanent magnet is greatly reduced, and the rotor eddy current loss is reduced by 60%-70%.

[0133] 2. Thermal equilibrium is achieved.

[0134] Under the same heat dissipation conditions, after adopting the technical solution of this invention, the rotor temperature is improved from being unable to reach a thermal equilibrium state (continuous temperature rise) with the original technology to reaching a steady-state thermal equilibrium state (temperature stabilized within a safe range). Actual test data shows that after 30 minutes of continuous charging, the rotor temperature stabilizes at 85°C ± 5°C, while under the original technology, the temperature continues to rise to over 120°C. The technical solution of this invention can significantly reduce the rotor temperature rise, which is beneficial for improving the boost charging capability and protecting the motor's lifespan.

[0135] 3. Strong self-locking stability.

[0136] Within the six rotor electrical angle regions, by calculating and allocating the three-phase current reference values, and in conjunction with the reference angle self-locking strategy, the rotor can automatically return to the reference electrical angle position after being subjected to external disturbances, so that boost charging can be performed at the optimal angle, and the position fluctuation range is controlled within ±1° electrical angle.

[0137] 4. High compatibility.

[0138] The embodiments of the present invention are based on the existing electric vehicle electric drive software architecture. Without additional hardware costs, only software algorithm upgrades are needed to achieve the best performance boost charging. It is applicable to boost charging systems that reuse permanent magnet synchronous motor drives.

[0139] 5. Extended lifespan of permanent magnets.

[0140] By selecting switching state combinations where the d-axis voltage component is 0 and three-phase PWM wave operation mode in different rotor electrical angle regions, the rotor eddy current loss caused by d-axis current ripple is significantly reduced, rotor temperature rise is reduced, and rotor thermal balance is improved. This can effectively reduce the risk of rotor permanent magnet demagnetization and is expected to extend the motor service life by more than 30%.

[0141] 6. Room for improvement in charging power.

[0142] With the rotor heating problem resolved, higher boost charging power can be supported under the same temperature rise limit, thereby increasing the charging speed of electric vehicle batteries.

[0143] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Those skilled in the art can understand that implementing all or part of the processes of the above embodiments and making equivalent changes according to the claims of this application still fall within the scope of this application.

Claims

1. A method for suppressing rotor eddy current losses in a permanent magnet synchronous motor under boost charging mode, characterized in that, include: In boost charging mode, obtain the current rotor electrical angle of the permanent magnet synchronous motor; Based on the pre-defined rotor electrical angle regions, determine the target rotor electrical angle region to which the current rotor electrical angle belongs; Determine the target switching state combination and target three-phase PWM wave operation mode corresponding to the target rotor electrical angle region; under the target switching state combination and target three-phase PWM wave operation mode, the equivalent d-axis voltage of the three-phase voltage synthesis vector output by the inverter within one switching cycle is zero; The inverter's three-phase duty cycle output is controlled according to the target switching state combination and the target three-phase PWM wave generation working mode, so that the high-frequency ripple amplitude of the three-phase voltage synthesis vector output by the inverter on the d-axis approaches zero, thereby reducing the rotor permanent magnet eddy current loss and rotor temperature rise of the permanent magnet synchronous motor.

2. The method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to claim 1, characterized in that, After the step of controlling the three-phase duty cycle output of the inverter according to the target switching state combination and the target three-phase PWM waveform operation mode, the method further includes: Reacquire the current rotor electrical angle of the permanent magnet synchronous motor and the total DC current demand on the inverter side after rectification and boosting by the inverter in the boost charging mode. Determine the electrical angle deviation between the newly acquired current rotor electrical angle and the reference electrical angle corresponding to its rotor electrical angle region; When the absolute value of the electrical angle deviation is greater than the first threshold, the three-phase current output by the permanent magnet synchronous motor is adjusted according to the electrical angle deviation and the total DC current demand on the inverter side, so that the permanent magnet synchronous motor generates a torque in the opposite direction to the electrical angle deviation, pulling the rotor electrical angle of the permanent magnet synchronous motor toward the reference electrical angle.

3. The method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to claim 2, characterized in that, The method further includes: When the absolute value of the electrical angle deviation is less than the second threshold, the three-phase current is not adjusted according to the electrical angle deviation and the total DC current demand on the inverter side, and the output of each phase of the permanent magnet synchronous motor is kept at 1 / 3 of the total DC current demand on the inverter side. When the absolute value of the electrical angle deviation is greater than or equal to the second threshold and less than the first threshold, the current three-phase current output by the permanent magnet synchronous motor remains unchanged; Wherein, the first threshold is greater than the second threshold.

4. The method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to claim 2, characterized in that, The steps for adjusting the three-phase current output of the permanent magnet synchronous motor, based on the electrical angle deviation between the re-acquired current rotor electrical angle and the reference electrical angle corresponding to its rotor electrical angle region, and the total DC current requirement on the inverter side, include: Based on the electrical angle deviation and the total DC current requirement on the inverter side, the reference value of the three-phase current is determined; Adjust the three-phase current output of the permanent magnet synchronous motor according to the three-phase current reference value; The three-phase current reference value is the sum of the DC charging component and the electrical angle self-locking current component, and the specific calculation formula is as follows: Among them, i u,ref i v,ref i w,ref These represent the reference values ​​for the three-phase currents of phases U, V, and W, respectively; Iin / 3 is the DC charging component; I in This refers to the total DC current requirement on the inverter side for charging the battery after rectification and boosting by the inverter in boost charging mode; q,ref This is a reference value for the q-axis current related to the electrical angle deviation; The q-axis current reference value i related to the electrical angle deviation q,ref By formula: Calculated; △ denoted as , where is the deviation between the current rotor electrical angle and the reference electrical angle, kp is the pre-calibrated proportional gain, and kd is the pre-calibrated differential gain.

5. The method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to claim 1, characterized in that, The rotor electrical angle region is divided into 6 continuous regions within the range of 0° to 360°, namely: 0°~60°, 60°~120°, 120°~180°, 180°~240°, 240°~300°, and 300°~360°.

6. The method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to claim 5, characterized in that, The reference electrical angles corresponding to each rotor electrical angle region are the midpoint positions of that region, namely: 30°, 90°, 150°, 210°, 270°, and 330°.

7. The method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to claim 5, characterized in that, The rotor electrical angle region includes 6 rotor electrical angle regions, wherein: The switching state combinations corresponding to the first rotor electrical angle region and the fourth rotor electrical angle region are S2 and S5, and the corresponding three-phase PWM wave generation working modes are U phase and W phase are the same phase, and V phase is 180° different from U phase and W phase. The switching state combinations corresponding to the second rotor electrical angle region and the fifth rotor electrical angle region are S3 and S4, and the corresponding three-phase PWM wave generation working modes are V phase and W phase are in phase, and U phase and V phase and W phase are 180° apart. The switching state combinations corresponding to the third rotor electrical angle region and the sixth rotor electrical angle region are S1 and S6, respectively. The corresponding three-phase PWM wave generation working modes are U phase and V phase are in phase, and W phase is 180° different from U phase and V phase.

8. The method for suppressing rotor eddy current losses of a permanent magnet synchronous motor in boost charging mode according to claim 3, characterized in that, The first threshold is 1°, and the second threshold is 0.4°.

9. A device for suppressing rotor eddy current losses in a permanent magnet synchronous motor under boost charging mode, characterized in that, include: The acquisition module is used to acquire the current rotor electrical angle of the permanent magnet synchronous motor in boost charging mode. The first determining module is used to determine the target rotor electrical angle region to which the current rotor electrical angle belongs, based on the pre-divided rotor electrical angle region. The second determining module is used to determine the target switching state combination and the target three-phase PWM wave operation mode corresponding to the target rotor electrical angle region; under the target switching state combination and the target three-phase PWM wave operation mode, the equivalent d-axis voltage of the three-phase voltage synthesis vector output by the inverter in one switching cycle is zero. The control module is used to control the three-phase duty cycle output of the inverter according to the target switching state combination and the target three-phase PWM wave generation working mode, so that the high-frequency ripple amplitude of the three-phase voltage synthesis vector output by the inverter on the d-axis approaches zero (maximum 1.16%Vdc, typical value less than 0.46%Vdc), so as to reduce the rotor permanent magnet eddy current loss and rotor temperature rise of the permanent magnet synchronous motor.

10. A vehicle, characterized in that, Includes the rotor eddy current loss suppression device for permanent magnet synchronous motor in boost charging mode as described in claim 9.

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