A method and apparatus for smooth switching of variable sampling period and current controller

Abstract

The application discloses a variable sampling period smooth switching method and device and a current controller. A beat before sampling period switching is the kth beat. When a sampling period switching instruction is received, the original output voltage of the current controller in a synchronous rotating coordinate system after kth beat angle compensation is determined. When the original output voltage is transformed from the synchronous rotating coordinate system to a stationary coordinate system, preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after the kth beat angle compensation. The target output voltage is used for motor control. Since the preset compensation angle is determined based on the rotor electric angular velocity of the motor, the sampling period before switching and the sampling period after switching, the preset compensation angle is used for transformation compensation when the original output voltage is transformed in the coordinate conversion, the output voltage of the current controller after the sampling period switching is completed is prevented from being suddenly changed, and the smooth switching of the variable sampling period is realized.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor technology, and more specifically, to a smooth switching method, device, and current controller with variable sampling period. Background Technology

[0002] Currently, the highest operating frequency of automotive-mounted permanent magnet synchronous motors has exceeded 1000Hz. Z However, due to switching losses, the switching frequency of the inverter connected to the permanent magnet synchronous motor (PMSM) is difficult to increase accordingly, resulting in a very low carrier ratio (the ratio of switching frequency to fundamental frequency) in the PMSM current control system. Under low carrier ratio conditions, the discretization error of the traditional continuous domain-based current controller increases when it is digitally implemented, leading to a significant reduction in system performance and even instability.

[0003] To address the aforementioned issues, a direct discrete control method for permanent magnet synchronous motors (PMSMs) has been proposed. This method effectively ensures the control performance of the current control system under low carrier ratio conditions. However, existing discrete control methods assume a constant sampling period for the current control system. In practical applications, however, the sampling period of the current control system adjusts with the fundamental frequency of the PMSM. Therefore, during field tests using the direct discrete control method, variations in the sampling period often cause transient current runaway and sudden torque changes, exposing the current control system to overcurrent risks and impacting road safety and driving comfort. Summary of the Invention

[0004] In view of this, the present invention discloses a method, device and current controller for smooth switching of variable sampling period, so as to achieve smooth switching of variable sampling period, ensure that the stator current and output torque of the motor do not change suddenly before and after the sampling period switching, effectively avoid the risk of overcurrent in the current control system, and improve road safety and driving comfort.

[0005] A smooth switching method with a variable sampling period, applied to a current controller, the smooth switching method comprising:

[0006] When a sampling period switching command is received, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th cycle is determined, wherein the k-th cycle is the cycle before the sampling period switching, and k is a positive integer;

[0007] When the original output voltage is transformed from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation. The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching. The target output voltage is used for motor control.

[0008] Optionally, when a sampling period switching command is received, determining the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation for the k-th cycle includes:

[0009] When the sampling period switching instruction is received, the relevant data of the period switching is acquired, wherein the relevant data of the period switching includes: rotor electric angular velocity, sampling period before switching, sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation;

[0010] Based on the switching-related data, the original output voltage of the current controller is determined.

[0011] Optionally, determining the original output voltage of the current controller based on the switching-related data includes:

[0012] The original output voltage of the current controller is determined based on the rotor electric angular velocity, the sampling period before switching, the sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation.

[0013] Optionally, the target output voltage is determined based on the rotor electrical angular velocity sampled in the k-th cycle, the preset compensation angle, and the original output voltage.

[0014] Optionally, after determining the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame when the sampling period switching command is received, the step further includes:

[0015] Determine the initial value of the integral in the (k+1)th step based on the original output voltage;

[0016] The initial integral value of the (k+1)th cycle is used as the initial integral value of the cycle after the sampling period switching is completed. The output of the integral link of the current controller is reset, and non-sampling period switching control is performed after the reset is completed.

[0017] Optionally, determining the initial value of the integral in the (k+1)th step based on the original output voltage includes:

[0018] The initial value of the (k+1)th integral is determined based on the identity matrix, the current controller delay output feedback coefficient matrix, the rotor electric angular velocity, the sampling period after switching, the original output voltage, the proportional coefficient matrix, the given current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, the stator current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, and the current feedback coefficient matrix.

[0019] Optionally, the preset compensation angle is obtained based on the rotor electric angular velocity, the sampling period before switching, and the sampling period after switching.

[0020] A smooth switching device with a variable sampling period, applied to a current controller, the smooth switching device comprising:

[0021] The original output voltage determination unit is used to determine the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame when a sampling period switching command is received, wherein the k-th frame is the frame before the sampling period switching, and k is a positive integer;

[0022] The target output voltage determination unit is used to transform the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system by using a preset compensation angle to perform transformation compensation, so as to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation. The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching and the sampling period after switching. The target output voltage is used for motor control.

[0023] Optionally, the original output voltage determination unit is specifically used for:

[0024] When the sampling period switching instruction is received, the relevant data of the period switching is acquired, wherein the relevant data of the period switching includes: rotor electric angular velocity, sampling period before switching, sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation;

[0025] Based on the switching-related data, the original output voltage of the current controller is determined.

[0026] Optional, also includes:

[0027] The determination unit is used to determine the original output voltage of the current controller in the synchronous rotating coordinate system after the k-th frame angle compensation when the original output voltage determination unit receives the sampling period switching instruction, and then determine the initial value of the integral in the (k+1)-th frame based on the original output voltage.

[0028] The reset unit is used to reset the output of the current controller's integral stage by taking the (k+1)th integral initial value as the integral initial value of the next stage after the sampling period switching is completed, and to perform non-sampling period switching control after the reset is completed.

[0029] A current controller includes the aforementioned smooth switching device with variable sampling period.

[0030] As can be seen from the above technical solution, this invention discloses a smooth switching method, device, and current controller for variable sampling periods. Taking the period before switching as the k-th period, when a sampling period switching command is received, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th period is determined. When transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after angle compensation in the k-th period. This target output voltage is used for motor control. Since the preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching, using the preset compensation angle for transformation compensation when transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system ensures that the output voltage of the current controller in the stationary coordinate system will not change abruptly after the sampling period switching is completed. This achieves smooth switching of variable sampling periods, ensuring that the stator current and output torque of the motor do not change abruptly before and after the sampling period switching, effectively avoiding the risk of overcurrent in the current control system, and improving road safety and driving comfort. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the published drawings without creative effort.

[0032] Figure 1 This is a flowchart of a smooth switching method with a variable sampling period disclosed in an embodiment of the present invention;

[0033] Figure 2 This is a flowchart of a method for determining the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame when a sampling period switching command is received, as disclosed in an embodiment of the present invention.

[0034] Figure 3 This is a flowchart of another smooth switching method with variable sampling period disclosed in an embodiment of the present invention;

[0035] Figure 4This is a block diagram of a current loop control for a permanent magnet synchronous motor disclosed in an embodiment of the present invention;

[0036] Figure 5 The figure shows the simulation results of the current closed-loop control before and after the sampling period switching of a motor controller disclosed in the existing scheme.

[0037] Figure 6 The figure shows the simulation results of current closed-loop control before and after the sampling period switching of a motor controller, as disclosed in an embodiment of the present invention.

[0038] Figure 7 This is a current waveform diagram before and after switching the sampling period of a motor controller, as disclosed in an embodiment of the present invention.

[0039] Figure 8 This is a schematic diagram of the structure of a smooth switching device with a variable sampling period disclosed in an embodiment of the present invention;

[0040] Figure 9 This is a schematic diagram of another smooth switching device with variable sampling period disclosed in an embodiment of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention discloses a method, apparatus, and current controller for smooth switching of variable sampling periods. Taking the period before switching as the k-th period, when a sampling period switching command is received, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th period is determined. When transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after angle compensation in the k-th period. This target output voltage is used for motor control. Since the preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching, using the preset compensation angle for transformation compensation when transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system ensures that the output voltage of the current controller in the stationary coordinate system does not change abruptly after the sampling period switching is completed. This achieves smooth switching of variable sampling periods, ensuring that the stator current and output torque of the motor do not change abruptly before and after the sampling period switching, effectively avoiding the risk of overcurrent in the current control system, and improving road safety and driving comfort.

[0043] See Figure 1 The present invention discloses a flowchart of a smooth switching method with a variable sampling period, which is applied to a current controller. The method includes:

[0044] Step S101: When the sampling period switching command is received, determine the original output voltage of the current controller in the synchronous rotating coordinate system after the angle compensation of the kth frame.

[0045] For ease of subsequent description, this invention defines the k-th sampling period as the period before the sampling period switch, where k is a positive integer. Correspondingly, the period after the sampling period switch is k+1.

[0046] "Beat" is a concept in discrete control. The current controller controls the required output voltage, which is actually updated once by calculating the sampling period. In this embodiment, the kth beat refers to the kth sampling period.

[0047] Step S102: When transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation.

[0048] In this embodiment, the transformation compensation is preferably Ipark transformation compensation.

[0049] The Ipark transformation converts a rotating dq coordinate system into a stationary αβ coordinate system.

[0050] The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching.

[0051] Specifically, the expression for the preset compensation angle is as follows:

[0052] Δθ=ω e (T s1 -T s2 );

[0053] In the formula, Δθ represents the preset compensation angle, ω e T represents the rotor's electrical angular velocity. s1 T represents the sampling period before the switch. s2 This indicates the sampling period after the switch.

[0054] To ensure that the motor's current loop idq(t) does not change abruptly before and after the sampling period switching, the output voltage udq(t) of the current controller needs to remain stable. In this embodiment, angle compensation is performed when the original output voltage is transformed from the synchronous rotating coordinate system to the stationary coordinate system. This ensures that the output voltage of the current controller in the stationary coordinate system does not change abruptly before and after the sampling period switching, thereby ensuring that the current does not change abruptly.

[0055] It should be noted that the target output voltage obtained in this embodiment is used for motor control. Specifically, the current controller inputs the target output voltage to the SVPWM module for space vector pulse width modulation and outputs a PWM (Pulse Width Modulation) wave to the inverter module. The inverter module then processes the PWM wave and applies it to the motor to achieve motor control.

[0056] The motor involved in this embodiment mainly refers to a permanent magnet synchronous motor.

[0057] In summary, this invention discloses a smooth switching method for variable sampling periods. Taking the period before switching as the k-th period, when a sampling period switching command is received, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th period is determined. When transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after angle compensation in the k-th period. This target output voltage is used for motor control. Since the preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching, using the preset compensation angle for transformation compensation when transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system ensures that the output voltage of the current controller in the stationary coordinate system does not change abruptly after the sampling period switching is completed. This achieves smooth switching of variable sampling periods, ensuring that the stator current and output torque of the motor do not change abruptly before and after the sampling period switching, effectively avoiding the risk of overcurrent in the current control system, and improving road safety and driving comfort.

[0058] To further optimize the above embodiments, see [link to relevant documentation]. Figure 2 The present invention discloses a method for determining the original output voltage of the current controller in a synchronous rotating coordinate system after angle compensation in the k-th frame when a sampling period switching command is received. The method includes:

[0059] Step S201: When a sampling period switching instruction is received, acquire relevant data for period switching;

[0060] The data related to the periodic switching include: rotor electric angular velocity, sampling period before switching, sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after angle compensation for the (k-1)th cycle.

[0061] In this invention, the k-th sampling period is the sampling period before the switching, and the (k-1)-th sampling period is the previous sampling period before the switching. When determining the original output voltage of the current controller corresponding to the k-th sampling period, it is necessary to determine it based on the output voltage of the current controller corresponding to the (k-1)-th sampling period. See the calculation formula for the original output voltage for details.

[0062] Step S202: Determine the original output voltage of the current controller based on the switching related data.

[0063] In this embodiment, the original output voltage of the current controller is determined based on the rotor electric angular velocity, the sampling period before switching, the sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation.

[0064] Specifically, the expression for calculating the original output voltage is as follows:

[0065]

[0066] In the formula, This represents the d-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame. This represents the q-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame. The original output voltage includes: and ω e T represents the rotor's electrical angular velocity. s1 Indicates the sampling period before switching, T s2 Indicates the sampling period after the switch. This represents the d-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the (k-1)th cycle. This represents the q-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the (k-1)th cycle. The output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the (k-1)th cycle includes: and

[0067] Based on the above discussion, the original output voltage includes: and This invention transforms the original output voltage from a synchronous rotating coordinate system to a stationary coordinate system by using a preset compensation angle to perform transformation compensation, thereby obtaining the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation. The target output voltage is determined based on the rotor electric angular velocity sampled in the k-th frame, the preset compensation angle, and the original output voltage.

[0068] The formula for calculating the target voltage is as follows:

[0069]

[0070] In the formula, u α (k) represents the α-axis voltage output by the current controller in the stationary coordinate system after angle compensation at the k-th beat. β(k) represents the β-axis voltage output by the current controller in the stationary coordinate system after angle compensation at the k-th beat. The target output voltage includes: u α (k) and u β (k), θ e (k) represents the rotor electric angular velocity sampled in the k-th time step, and Δθ is the preset compensation angle. This represents the d-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame. This represents the q-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame.

[0071] In practical applications, after determining the original output voltage of the current controller in the synchronous rotating coordinate system after the k-th frame angle compensation, in addition to performing the transformation compensation shown in step S102, it is also necessary to reset the output of the current controller's integral element based on the original output voltage. That is, using the original output voltage of the current controller in the synchronous rotating coordinate system after the k-th frame angle compensation, the output of the original integral element is solved in reverse. In practical applications, the integral output needs to be reset according to the specific structure of the current controller. Different current controllers have slight differences, but the general idea is universal.

[0072] Taking the discrete-domain current controller of a permanent magnet synchronous motor as an example, see [link / reference]. Figure 3 The present invention discloses another smooth switching method with variable sampling period, which is applied to a current controller and includes:

[0073] Step S301: When a sampling period switching command is received, determine the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation for the kth frame.

[0074] For ease of subsequent description, this invention defines the k-th sampling period as the period before the sampling period switch, where k is a positive integer. Correspondingly, the period after the sampling period switch is the (k+1)-th sampling period.

[0075] Step S302: When transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation.

[0076] In this embodiment, steps S301 and S302 are the same as... Figure 1 Steps S101 and S102 in the illustrated embodiment are the same; for details on the working principle, please refer to [link / reference needed]. Figure 1 The embodiments shown are not described in detail here.

[0077] Step S303: Determine the initial value of the integral in the (k+1)th step based on the original output voltage;

[0078] It should be noted that step S303 is executed after step S301.

[0079] In this embodiment, the initial value of the (k+1)th integral is determined based on the identity matrix, the current controller delay output feedback coefficient matrix, the rotor electric angular velocity, the sampling period after switching, the original output voltage, the proportional coefficient matrix, the given current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, the stator current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, and the current feedback coefficient matrix.

[0080] Specifically, the expression for the initial value of the integral in the (k+1)th cycle is as follows:

[0081]

[0082] In the formula, U I_d (k) represents the initial value of the d-axis integral in the (k+1)th step, U I_q (k) represents the initial value of the q-axis integral at the (k+1)th step, I represents the identity matrix, A represents the delay output feedback coefficient matrix of the current controller, and ω e T represents the rotor's electrical angular velocity. s2 This indicates the sampling period after the switch. This represents the d-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame. K represents the q-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame. p Represents the scaling factor matrix, i d,ref (k) represents the d-axis current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, i q,ref (k) represents the q-axis current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, i d (k) represents the d-axis component of the stator current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, i q (k) represents the q-axis component of the stator current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, and M represents the current feedback coefficient matrix.

[0083] Step S304: Use the initial value of the integral in the (k+1)th cycle as the initial value of the integral in the cycle after the sampling period switching is completed, reset the output of the integral link of the current controller, and perform non-sampling period switching control after the reset is completed.

[0084] In summary, the smooth switching method for variable sampling periods disclosed in this invention, since the preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching, can ensure that the output voltage of the current controller in the stationary coordinate system will not change abruptly after the sampling period switching is completed. This achieves smooth switching of variable sampling periods, ensures that the stator current and output torque of the motor do not change abruptly before and after the sampling period switching, effectively avoids the risk of overcurrent in the current control system, and improves road safety and driving comfort.

[0085] Taking the period before the sampling period switching as the kth period, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the kth period is used to determine the initial value of the integral in the (k+1)th period after the sampling period switching is completed. The output of the integral link of the current controller is then reset using the initial value of the integral in the (k+1)th period, thereby realizing the conversion from sampling period switching control to non-sampling period switching control.

[0086] against Figure 3 The illustrated embodiment, in conjunction with the smooth switching strategy for variable sampling periods disclosed in this invention, see [link to relevant documentation]. Figure 4 The present invention also discloses a current loop control block diagram for a permanent magnet synchronous motor, wherein the kth step is defined as the step before the sampling period switching and the step after the sampling period switching is the (k+1)th step.

[0087] Figure 4 in,i d,ref (k) represents the d-axis current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, i q,ref (k) represents the q-axis current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, i d (k) represents the d-axis component of the stator current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, i q (k) represents the q-axis component of the stator current of the permanent magnet synchronous motor in the synchronous rotating coordinate system.

[0088] (1) When non-sampling cycle switching control is required, the current controller outputs: and This represents the d-axis voltage output by the current controller in a synchronous rotating coordinate system, and This represents the q-axis voltage output by the current controller in a synchronous rotating coordinate system. The general calculation formula for representing the coordinate transformation process is as follows: ω e T represents the rotor electrical angular velocity of a permanent magnet synchronous motor. s The sampling period is represented by J, and the orthogonal matrix is ​​represented by J. and The results were obtained through the coordinate rotation transformation process. and This represents the d-axis voltage output by the current controller in a synchronous rotating coordinate system. This represents the q-axis voltage output by the current controller in a synchronous rotating coordinate system. and The output voltage u of the current controller is obtained by transforming from a synchronous rotating coordinate system to a stationary coordinate system. α and u β .

[0089] (2) When sampling period switching control is required, according to step S301, This represents the d-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame. This represents the q-axis voltage output by the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame. The original output voltage includes: and According to step S302, when the original output voltage is transformed from the synchronous rotating coordinate system to the stationary coordinate system, Ipark transformation compensation is performed using a preset compensation angle Δθ (that is, the preset compensation angle Δθ is added to θ). e (middle), to obtain the target output voltage of the current controller in the stationary coordinate system after angle compensation in the k-th frame, including: u α (k) represents the α-axis voltage output by the current controller in the stationary coordinate system after angle compensation in the k-th frame. β (k) represents the β-axis voltage output by the current controller in the stationary coordinate system after angle compensation in the k-th frame.

[0090] When performing non-sampling cycle switching control, the output voltage u of the current controller α and u β The output is sent to the SVPWM module 11 for space vector pulse width modulation, and then outputs a PWM (Pulse Width Modulation) wave to the inverter module 12. The inverter module 12 further processes the PWM wave and applies it to the permanent magnet synchronous motor 13 to control the permanent magnet synchronous motor 13. The three-phase current i output by the permanent magnet synchronous motor 13 is... a i b and i c i is obtained by transforming from the abc stationary coordinate system to the αβ stationary coordinate system. α and i β i α and i β i is obtained by transforming from the αβ stationary coordinate system to the synchronous rotating coordinate system. d and iq .

[0091] When performing sampling period switching control, the output voltage u of the current controller α (k) and u β (k) The output is sent to the SVPWM module 11 for space vector pulse width modulation, and the PWM wave is output to the inverter module 12. The inverter module 12 then processes the PWM wave and applies it to the permanent magnet synchronous motor 13 to achieve control of the permanent magnet synchronous motor 13. The three-phase current i output by the permanent magnet synchronous motor 13 is... a i b and i c i is obtained by transforming from the abc stationary coordinate system to the αβ stationary coordinate system. α and i β i α and i β i is obtained by transforming from the αβ stationary coordinate system to the synchronous rotating coordinate system. d and i q .

[0092] To illustrate how this invention achieves smooth switching of the variable sampling period, simulation tests were performed on both the current closed-loop control before and after the sampling period switching of the existing motor controller and the current closed-loop control before and after the sampling period switching of the motor controller of this invention. The motor parameters used are: stator resistance R... s =0.05Ω, d-axis inductance L d =0.14mH, q-axis inductance L q =0.3mH, permanent magnet flux linkage The motor's base frequency is gradually increased from 297Hz to 303Hz. A sampling period switch occurs when the base frequency reaches 300Hz. The output electromagnetic torque T during the test is recorded. e Stator current i dq and three-phase current i abc Record them separately.

[0093] See details Figure 5 The simulation results of the current closed-loop control before and after the switching of the sampling period of the motor controller in the existing scheme are shown, and Figure 6 The simulation results of the current closed-loop control before and after the switching of the sampling period of the motor controller in this invention are shown below. Figure 5 As can be seen, there is a transitional process of current runaway after the sampling period is switched in the existing scheme. This will cause sudden changes in the torque and stator current of the output permanent magnet synchronous motor, leading to the risk of overcurrent and runaway of the current control system, which affects road safety and driving comfort.

[0094] contrast Figure 5 ,from Figure 6As can be seen, the smooth switching strategy of variable sampling period disclosed in this invention can achieve smooth switching of variable sampling period. Before and after the sampling period switching, the stator current and output torque of the motor have almost no oscillation or distortion, which effectively avoids the risk of overcurrent in the current control system and improves road safety and driving comfort.

[0095] Furthermore, the control effects before and after the application of the switching strategy proposed in this invention were tested on the HIL (Hardware-in-the-Loop) platform, with the same motor parameters as in the simulation. The maximum motor torque was always given during the test, and the current reference was obtained by looking up a table. The motor's fundamental frequency was gradually increased until it reached 300Hz, at which point the sampling period was switched from 1 / 3000s to 1 / 6000s. The stator current amplitude before and after the switch was approximately 350A. The phase current data from the DSP (Digital Signal Processing) was exported via the host computer software, and the current waveforms before and after the switch are shown below. Figure 7 As shown, without applying the variable sampling period switching strategy disclosed in this invention, the stator current of the motor exhibits a significant period of uncontrolled operation after the sampling period switching, with marked current waveform distortion. The maximum current during the transition process approaches 400A, greatly increasing the risk of overcurrent. Furthermore, sudden current changes can cause torque surges and impact on the mechanical system. However, with the variable sampling period switching strategy disclosed in this invention, almost no current distortion or oscillation is observed, effectively reducing the risk of current runaway caused by sampling period switching.

[0096] Corresponding to the above method embodiments, the present invention also discloses a smooth switching device with variable sampling period.

[0097] See Figure 8 The present invention discloses a schematic diagram of a smooth switching device with a variable sampling period, which is applied to a current controller. The device includes:

[0098] The original output voltage determination unit 401 is used to determine the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame when a sampling period switching command is received, wherein the k-th frame is the frame before the sampling period switching, and k is a positive integer;

[0099] The target output voltage determination unit 402 is used to transform the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system by using a preset compensation angle to perform transformation compensation, so as to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation. The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching and the sampling period after switching. The target output voltage is used for motor control.

[0100] In this embodiment, the preferred transformation compensation is Ipark transformation compensation.

[0101] The Ipark transformation converts a rotating dq coordinate system into a stationary αβ coordinate system.

[0102] The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching.

[0103] Specifically, the expression for the preset compensation angle is as follows:

[0104] Δθ=ω e (T s1 -T s2 );

[0105] In the formula, Δθ represents the preset compensation angle, ω e T represents the rotor's electrical angular velocity. s1 T represents the sampling period before the switch. s2 This indicates the sampling period after the switch.

[0106] To ensure that the motor's current loop idq(t) does not change abruptly before and after the sampling period switching, the output voltage udq(t) of the current controller needs to remain stable. In this embodiment, angle compensation is performed when the original output voltage is transformed from the synchronous rotating coordinate system to the stationary coordinate system. This ensures that the output voltage of the current controller in the stationary coordinate system does not change abruptly before and after the sampling period switching, thereby ensuring that the current does not change abruptly.

[0107] It should be noted that the target output voltage obtained in this embodiment is used for motor control. Specifically, the current controller inputs the target output voltage to the SVPWM module for space vector pulse width modulation and outputs a PWM (Pulse Width Modulation) wave to the inverter module. The inverter module then processes the PWM wave and applies it to the motor to achieve motor control.

[0108] The motor involved in this embodiment mainly refers to a permanent magnet synchronous motor.

[0109] In summary, this invention discloses a smooth switching device for variable sampling periods. Taking the period before switching as the k-th period, when a sampling period switching command is received, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th period is determined. When transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after angle compensation in the k-th period. This target output voltage is used for motor control. Since the preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching, using the preset compensation angle for transformation compensation when transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system ensures that the output voltage of the current controller in the stationary coordinate system does not change abruptly after the sampling period switching is completed. This achieves smooth switching of the variable sampling period, ensuring that the stator current and output torque of the motor do not change abruptly before and after the sampling period switching, effectively avoiding the risk of overcurrent in the current control system, and improving road safety and driving comfort.

[0110] To further optimize the above embodiments, the original output voltage determination unit 401 can specifically be used for:

[0111] When the sampling period switching instruction is received, the relevant data of the period switching is acquired, wherein the relevant data of the period switching includes: rotor electric angular velocity, sampling period before switching, sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation;

[0112] Based on the switching-related data, the original output voltage of the current controller is determined.

[0113] Taking the discrete-domain current controller of a permanent magnet synchronous motor as an example, see [link / reference]. Figure 9 The present invention discloses a schematic diagram of a smooth switching device with a variable sampling period, which is applied to a current controller. The device includes:

[0114] The original output voltage determination unit 501 is used to determine the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame when a sampling period switching command is received, wherein the k-th frame is the frame before the sampling period switching, and k is a positive integer;

[0115] The target output voltage determination unit 502 is used to transform the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system by using a preset compensation angle to perform transformation compensation, so as to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation. The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching and the sampling period after switching. The target output voltage is used for motor control.

[0116] The determining unit 503 is used to determine the initial value of the integral of the (k+1)th step based on the original output voltage after the original output voltage determines the original output voltage of the current controller in the synchronous rotating coordinate system after the kth step angle compensation when the original output voltage determining unit 501 receives the sampling period switching instruction.

[0117] The reset unit 504 is used to reset the output of the current controller integral stage by taking the initial integral value of the (k+1)th cycle as the initial integral value of the cycle after the sampling period switching is completed, and to perform non-sampling period switching control after the reset is completed.

[0118] In summary, the smooth switching device for variable sampling period disclosed in this invention, since the preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching, can perform transformation compensation by using the preset compensation angle when transforming the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system. This ensures that the output voltage of the current controller in the stationary coordinate system will not change abruptly after the sampling period switching is completed, thereby achieving smooth switching of variable sampling period. This ensures that the stator current and output torque of the motor do not change abruptly before and after the sampling period switching, effectively avoiding the risk of overcurrent in the current control system and improving road safety and driving comfort.

[0119] Taking the period before the sampling period switching as the kth period, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the kth period is used to determine the initial value of the integral in the (k+1)th period after the sampling period switching is completed. The output of the integral link of the current controller is then reset using the initial value of the integral in the (k+1)th period, thereby realizing the conversion from sampling period switching control to non-sampling period switching control.

[0120] It should be noted that the specific working principles of each component in the device embodiment can be found in the corresponding section of the method embodiment, and will not be repeated here.

[0121] The present invention also discloses a current controller, which includes the variable sampling period smooth switching device in the above embodiments. For its specific working principle, please refer to the corresponding part of the above embodiments, which will not be repeated here.

[0122] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0123] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0124] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for smooth switching of variable sampling periods, characterized in that, Applied to a current controller, the smooth switching method includes: When a sampling period switching command is received, the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th cycle is determined, wherein the k-th cycle is the cycle before the sampling period switching, and k is a positive integer; When the original output voltage is transformed from the synchronous rotating coordinate system to the stationary coordinate system, a preset compensation angle is used for transformation compensation to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation. The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching, and the sampling period after switching. The target output voltage is used for motor control. The step, after determining the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation for the k-th time step upon receiving the sampling period switching command, further includes: Determine the initial value of the integral in the (k+1)th step based on the original output voltage; The initial integral value of the (k+1)th cycle is used as the initial integral value of the cycle after the sampling period switching is completed. The output of the integral link of the current controller is reset, and non-sampling period switching control is performed after the reset is completed.

2. The smooth switching method according to claim 1, characterized in that, When a sampling period switching command is received, determining the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation for the k-th cycle includes: When the sampling period switching instruction is received, the relevant data of the period switching is acquired, wherein the relevant data of the period switching includes: rotor electric angular velocity, sampling period before switching, sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation; Based on the switching-related data, the original output voltage of the current controller is determined.

3. The smooth switching method according to claim 2, characterized in that, Determining the original output voltage of the current controller based on the switching-related data includes: The original output voltage of the current controller is determined based on the rotor electric angular velocity, the sampling period before switching, the sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation.

4. The smooth switching method according to claim 1, characterized in that, The target output voltage is determined based on the rotor electric angular velocity sampled in the kth step, the preset compensation angle, and the original output voltage.

5. The smooth switching method according to claim 1, characterized in that, The determination of the initial value of the integral in the (k+1)th step based on the original output voltage includes: The initial value of the (k+1)th integral is determined based on the identity matrix, the current controller delay output feedback coefficient matrix, the rotor electric angular velocity, the sampling period after switching, the original output voltage, the proportional coefficient matrix, the given current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, the stator current of the permanent magnet synchronous motor in the synchronous rotating coordinate system, and the current feedback coefficient matrix.

6. The smooth switching method according to claim 1, characterized in that, The preset compensation angle is obtained based on the rotor electric angular velocity, the sampling period before switching, and the sampling period after switching.

7. A smooth switching device with a variable sampling period, characterized in that, The smooth switching device, applied to a current controller, includes: The original output voltage determination unit is used to determine the original output voltage of the current controller in the synchronous rotating coordinate system after angle compensation in the k-th frame when a sampling period switching command is received, wherein the k-th frame is the frame before the sampling period switching, and k is a positive integer; The target output voltage determination unit is used to transform the original output voltage from the synchronous rotating coordinate system to the stationary coordinate system by using a preset compensation angle to perform transformation compensation, so as to obtain the target output voltage of the current controller in the stationary coordinate system after the k-th frame angle compensation. The preset compensation angle is determined based on the rotor electric angular velocity of the permanent magnet synchronous motor, the sampling period before switching and the sampling period after switching. The target output voltage is used for motor control. Also includes: The determination unit is used to determine the original output voltage of the current controller in the synchronous rotating coordinate system after the k-th frame angle compensation when the original output voltage determination unit receives the sampling period switching instruction, and then determine the initial value of the integral in the (k+1)-th frame based on the original output voltage. The reset unit is used to reset the output of the current controller's integral stage by taking the (k+1)th integral initial value as the integral initial value of the next stage after the sampling period switching is completed, and to perform non-sampling period switching control after the reset is completed.

8. The smooth switching device according to claim 7, characterized in that, The original output voltage determination unit is specifically used for: When the sampling period switching instruction is received, the relevant data of the period switching is acquired, wherein the relevant data of the period switching includes: rotor electric angular velocity, sampling period before switching, sampling period after switching, and the output voltage of the current controller in the synchronous rotating coordinate system after the (k-1)th frame angle compensation; Based on the switching-related data, the original output voltage of the current controller is determined.

9. A current controller, characterized in that, Includes the smooth switching device with variable sampling period as described in any one of claims 7 to 8.

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