A field weakening control method and related equipment for permanent magnet synchronous motors

Abstract

This application relates to a field weakening control method and related equipment for a permanent magnet synchronous motor (PMSM). The method includes: obtaining the initial value of the phase current of the stator coil of the PMSM, the initial value being equal to the initial quadrature-axis current value of the stator coil; when the phase current has not reached a current threshold, performing field weakening control on the stator coil based on a preset negative direct-axis current compensation method; when the phase current reaches the current threshold, determining the stop angle of the stator coil's lead angle based on the current speed of the PMSM, the initial quadrature-axis current value, the current threshold, and the voltage threshold of the stator coil; and performing field weakening control on the stator coil based on a preset current lead angle control method until the lead angle reaches the stop angle. This solves the problem that when the phase current of the PMSM reaches the current threshold of the stator coil, the quadrature-axis current is limited by the current threshold, resulting in overshoot and reduced accuracy of field weakening control.

Description

Technical Field

[0001] This application relates to the field of field weakening control technology, and in particular to a field weakening control method and related equipment for permanent magnet synchronous motors. Background Technology

[0002] When a permanent magnet synchronous motor (PMSM) operates at high speeds, its back electromotive force exceeds the bus voltage. To further increase the motor speed, field weakening control is required. The conventional field weakening control method is generally the negative direct-axis current compensation method. However, once the phase current of the PMSM reaches the current threshold of the stator coil, if the direct-axis current is still adjusted using the negative direct-axis current compensation method, the quadrature-axis current, limited by the current threshold, will exhibit overshoot, reducing the accuracy of field weakening control. Summary of the Invention

[0003] To overcome the problem that when the phase current of a permanent magnet synchronous motor reaches the current threshold of the stator coil, if the direct-axis current is still adjusted according to the negative direct-axis current compensation method, but the quadrature-axis current is limited by the current threshold and overshoot occurs, thus reducing the accuracy of field weakening control, this application provides a field weakening control method and related equipment for permanent magnet synchronous motors.

[0004] Firstly, in order to solve the above-mentioned technical problems, this application provides a field weakening control method for a permanent magnet synchronous motor, comprising:

[0005] Obtain the initial value of the phase current of the stator coil of the permanent magnet synchronous motor. The initial value is equal to the initial cross-axis current value of the cross-axis current of the stator coil.

[0006] When the phase current does not reach the current threshold of the stator coil, the stator coil is subjected to field weakening control based on the preset negative direct axis current compensation method and the quadrature axis initial current value.

[0007] When the phase current reaches the current threshold, the current speed of the permanent magnet synchronous motor is obtained;

[0008] Based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil, determine the stop angle of the stator coil's lead angle;

[0009] The stator coil is subjected to field weakening control based on the preset current lead angle control method and the initial cross-axis current value until the lead angle reaches the stop angle.

[0010] Secondly, this application also provides a field weakening control system for a permanent magnet synchronous motor, comprising:

[0011] The first acquisition module is used to acquire the initial value of the phase current of the stator coil of the permanent magnet synchronous motor. The initial value is equal to the initial cross-axis current value of the cross-axis current of the stator coil.

[0012] The first field weakening control module is used to perform field weakening control on the stator coil based on the preset negative direct axis current compensation method and quadrature axis initial current value when the phase current does not reach the current threshold of the stator coil.

[0013] The second acquisition module is used to acquire the current speed of the permanent magnet synchronous motor when the phase current reaches the current threshold.

[0014] The calculation module is used to determine the stop angle of the stator coil lead angle based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil.

[0015] The second field weakening control module is used to perform field weakening control on the stator coil based on a preset current lead angle control method and the initial cross-axis current value until the lead angle reaches the stop angle.

[0016] Thirdly, this application also provides a computing device, including a memory, a processor, and a program stored in the memory and running on the processor, wherein the processor executes the program to implement the steps of the field weakening control method for a permanent magnet synchronous motor as described above.

[0017] Fourthly, this application also provides a computer-readable storage medium storing instructions that, when executed on a terminal device, cause the terminal device to perform the steps of a field weakening control method for a permanent magnet synchronous motor.

[0018] The beneficial effects of this application are as follows: When the phase current of the stator coil of the permanent magnet synchronous motor has not reached the current threshold, a preset negative direct-axis current compensation method is used to perform field weakening control on the stator coil. When the phase current reaches the current threshold, a stop angle for the lead angle that can simultaneously satisfy the current threshold and voltage threshold is determined, and the preset current lead angle control method is used to perform field weakening control on the stator coil until the lead angle reaches the stop angle. In this way, by performing corresponding field weakening control on the stator coil at different stages, the overshoot phenomenon that occurs after the quadrature-axis current is limited by the current threshold can be avoided, thereby improving the accuracy of field weakening control. At the same time, by using the pre-determined stop angle for the lead angle, the lead angle can be increased to a maximum of that stop angle, thereby improving the safety of field weakening control. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of a field weakening control method for a permanent magnet synchronous motor according to this application.

[0020] Figure 2 This is a schematic diagram illustrating the calculation of the leading angle in this application;

[0021] Figure 3 This is a circuit schematic diagram of the field weakening control in this application;

[0022] Figure 4 Curves showing the variation of direct-axis and quadrature-axis currents when performing field weakening control using existing technologies;

[0023] Figure 5 The graphs showing the changes in direct-axis current and quadrature-axis current during field weakening control in this application;

[0024] Figure 6 This is a schematic diagram of a field weakening control system for a permanent magnet synchronous motor according to this application. Detailed Implementation

[0025] The following embodiments are further explanations and supplements to this application and do not constitute any limitation on this application.

[0026] The following describes, with reference to the accompanying drawings, a field weakening control method and related equipment for a permanent magnet synchronous motor according to an embodiment of this application.

[0027] This application discloses a field weakening control method for a permanent magnet synchronous motor. The method is applied to a terminal device. This application uses the terminal device as the execution subject to describe the solution. The terminal device is used to execute the steps of a field weakening control method for a permanent magnet synchronous motor.

[0028] like Figure 1 As shown, this application provides a field weakening control method for a permanent magnet synchronous motor, comprising:

[0029] Step S1: Obtain the initial value of the phase current of the stator coil of the permanent magnet synchronous motor. The initial value is equal to the initial cross-axis current value of the cross-axis current of the stator coil.

[0030] Step S2: When the phase current does not reach the current threshold of the stator coil, the stator coil is subjected to field weakening control based on the preset negative direct axis current compensation method and the quadrature axis initial current value.

[0031] Step S3: When the phase current reaches the current threshold, obtain the current speed of the permanent magnet synchronous motor;

[0032] Step S4: Based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil, determine the stop angle of the stator coil's lead angle;

[0033] Step S5: Based on the preset current lead angle control method and the initial cross-axis current value, the stator coil is subjected to field weakening control until the lead angle reaches the stop angle.

[0034] This embodiment provides a field weakening control method for a permanent magnet synchronous motor. When the phase current of the stator coil of the permanent magnet synchronous motor has not reached a current threshold, a preset negative direct-axis current compensation method is used to weaken the stator coil. When the phase current reaches the current threshold, a stop angle for the lead angle that simultaneously satisfies the current threshold and the voltage threshold is determined, and the stator coil is weakened using a preset current lead angle control method until the lead angle reaches the stop angle. In this way, by performing corresponding field weakening control on the stator coil at different stages, the overshoot phenomenon that occurs when the quadrature-axis current is limited by the current threshold can be avoided, thereby improving the accuracy of field weakening control. At the same time, by using the pre-determined stop angle for the lead angle, the lead angle can be increased to a maximum of that stop angle, thereby improving the safety of field weakening control.

[0035] Optionally, based on a preset negative direct-axis current compensation method and quadrature-axis initial current value, field weakening control is performed on the stator coils, including:

[0036] The quadrature-axis current is kept at the initial quadrature-axis current value, and the direct-axis current of the stator coil is adjusted according to the preset adjustment rule until the phase current reaches the current threshold. The preset adjustment rule is to reduce the direct-axis current by a preset difference every first preset time interval.

[0037] In this embodiment, when the quadrature-axis current is maintained at its initial value, field weakening control of the stator coil can be achieved simply by adjusting the direct-axis current. Stopping the adjustment of the direct-axis current when the phase current reaches the current threshold avoids the overshoot of the quadrature-axis current caused by the negative direct-axis current compensation method when the phase current reaches the current threshold, thereby improving the accuracy of field weakening control.

[0038] Optionally, based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil, the stop angle of the stator coil's lead angle is determined, including:

[0039] Based on the current speed and voltage threshold, the first voltage limit circle of the permanent magnet synchronous motor is obtained;

[0040] The formula for calculating the first voltage limit circle is as follows:

[0041]

[0042] In the formula, i d Indicates the direct-axis current, i q L represents the quadrature-axis current. d L represents direct-axis inductance. q Indicates quadrature axis inductance. Represents magnetic flux linkage, ω e Indicates the current rotational speed, u max This indicates the voltage threshold.

[0043] Based on the current threshold, the current limit circle of the permanent magnet synchronous motor is obtained;

[0044] Based on the current limiting circle and the first voltage limiting circle, the stop angle of the lead angle is obtained.

[0045] In this embodiment, the quadrature-axis current and direct-axis current are limited by the voltage threshold, current speed, and current threshold of the stator coil. Therefore, a first voltage limit circle is determined based on the current speed and voltage threshold, and a current limit circle is determined based on the current threshold. This allows us to understand the quadrature-axis stopping current of the quadrature-axis current and the direct-axis stopping current of the direct-axis current when using the current lead angle control method to control overshoot of the stator coil, thereby determining the stopping angle of the lead angle. This facilitates timely stopping of field weakening adjustment when using the preset current lead angle control method to control the field weakening of the stator coil, avoiding overshoot of the lead angle and improving the safety of the stator coil during the field weakening control process.

[0046] Optionally, such as Figure 2 As shown, based on the current limiting circle and the first voltage limiting circle, the stopping angle of the lead angle is obtained, including:

[0047] Establish a rectangular coordinate system based on the direct axis and quadrature axis of the stator coil;

[0048] Draw the current limiting circle on the rectangular coordinate system with the origin of the rectangular coordinate system as the center.

[0049] Based on the magnetic flux linkage and direct-axis inductance of the stator coil, the center of the first voltage limit circle is determined in the rectangular coordinate system, and the first voltage limit circle is drawn in the rectangular coordinate system.

[0050] The center of the first limit circle is represented as: L d Indicates direct-axis inductance. Indicates magnetic flux;

[0051] Find the intersection point of the first voltage limit circle and the current limit circle in the rectangular coordinate system;

[0052] Obtain the line connecting the intersection point and the origin in the rectangular coordinate system;

[0053] The angle between the connecting line and the Y-axis in the rectangular coordinate system is taken as the stopping angle of the lead angle.

[0054] In this embodiment, a rectangular coordinate system is established based on the direct and quadrature axes of the stator coils. The current limiting circle and the first voltage limiting circle are plotted in this rectangular coordinate system. The intersection point of the first voltage limiting circle and the current limiting circle can be intuitively obtained from this rectangular coordinate system. This intersection point represents the values ​​of the quadrature axis current and the direct axis current that simultaneously satisfy the current threshold and the voltage threshold corresponding to the current speed. It also indicates that the advance angle can only be and must be rotated to the angle formed by the line containing this intersection point and the Y-axis. This included angle is taken as the final value angle of the advance angle, which facilitates the direct control of the advance angle to be adjusted to the maximum stop angle during subsequent field weakening control, thus avoiding overshoot of the advance angle.

[0055] Figure 2 This is a schematic diagram illustrating the calculation of the leading angle in this application, as shown below. Figure 2 As shown, the positive direction of the direct-axis current is taken as the positive direction of the X-axis of the rectangular coordinate system, and the positive direction of the quadrature-axis current is taken as the positive direction of the Y-axis of the rectangular coordinate system. The current threshold I is plotted on this rectangular coordinate system. max The corresponding current limiting circle, the first voltage limiting circle corresponding to the current speed ω2, and the second voltage limiting circle corresponding to the first speed ω1 when the direct-axis current is equal to OA. Among them, the first speed ω1 is less than the current speed ω2, OA represents the initial value of the phase current, the first angle of the lead angle β is angle AOB, and the stopping angle of the lead angle β is angle AOE.

[0056] With the quadrature-axis current maintained at the same initial value, the phase current reaches the current threshold I. max Subsequently, if the negative direct-axis current compensation method is still used to negatively increase the direct-axis current to reach point C, although it can satisfy the first voltage limit circle corresponding to the current speed, it does not satisfy the current limit circle. The current limit circle will cause the quadrature-axis current to decrease, resulting in quadrature-axis current overshoot and reducing the accuracy of this method for field weakening control. Here, Δβ is not calculated using the conventional PI method, but rather using Δi corresponding to the negative direct-axis current compensation method for field weakening control. d Calculations show that when the angle is small, it can be approximated as:

[0057]

[0058]

[0059] In the formula, Δi d U represents the negatively increasing direct-axis current. max Indicates the voltage threshold, u d Represents direct-axis voltage, u q Represents the quadrature-axis voltage, ω e I represents the electrical frequency of the phase current, Δβ represents the angular increment of the lead angle corresponding to the first voltage limit circle corresponding to the current speed after the negative direct-axis current compensation method exceeds the current limit circle.s Indicates phase current, i q This represents the quadrature-axis current.

[0060] When a permanent magnet synchronous motor performs field weakening control, the phase current i s With cross-axis current i q The included angle between them is the lead angle β. Phase current i s Cross-axis current i q Direct-axis current i d The relationship between the leading angle β and the leading angle β is as follows:

[0061]

[0062] In the formula, i d Indicates the direct-axis current, i q i represents the quadrature-axis current. s β represents the phase current, and β represents the lead angle.

[0063] Optionally, the stator coil is subjected to field weakening control based on a preset current lead angle control method and the quadrature axis initial current value until the lead angle reaches the stop angle, including:

[0064] Based on the initial cross-axis current value and the current threshold, the direct-axis current value is obtained, and the direct-axis current value is used as the first direct-axis stop current value of the direct-axis current.

[0065] Based on the initial current value of the quadrature axis and the stopping current value of the first straight axis, the first angle of the lead angle is obtained;

[0066] Based on the current threshold, the leading angle is adjusted from the first angle to the stop angle according to the preset rotation rule; wherein, the preset rotation rule is the rule of rotating a preset incremental angle at preset time intervals.

[0067] In this embodiment, when the phase current reaches the current threshold, the negative direct-axis current compensation method needs to be stopped to avoid overshoot caused by the quadrature-axis current. Therefore, the direct-axis current value corresponding to the initial quadrature-axis current value and the current threshold is the first direct-axis stopping current value. The quadrature and direct axes of the stator coil intersect perpendicularly. The first stopping angle of the lead angle under the negative direct-axis current compensation method can be directly calculated using the initial quadrature-axis current value and the first direct-axis stopping current value. When the phase current reaches the current threshold, the current lead angle control method is switched to. Based on the current threshold, the lead angle is adjusted from the first angle to the stopping angle according to the preset rotation rules, which can avoid overshoot of the lead angle and thus improve the safety of the stator coil when performing field weakening control.

[0068] Optionally, the stator coil is subjected to field weakening control based on a preset current lead angle control method and the quadrature axis initial current value until the lead angle reaches the stop angle, including:

[0069] Based on the initial cross-axis current value, current threshold, and voltage threshold, the second voltage limit circle of the permanent magnet synchronous motor is obtained;

[0070] Based on the current threshold, the current limit circle of the permanent magnet synchronous motor is obtained;

[0071] Based on the second voltage limit circle and the current limit circle, the first angle of the lead angle is obtained;

[0072] Based on the current limit circle, the lead angle is adjusted from the first angle to the stop angle according to the preset rotation rules.

[0073] In this embodiment, the second voltage limit circle of the permanent magnet synchronous motor is determined by the initial cross-axis current value, current threshold, and voltage threshold. The current limit circle is also determined based on the current threshold. This allows us to understand the cross-axis stopping current of the cross-axis current and the direct-axis stopping current of the direct-axis current when using the negative direct-axis current compensation method for field weakening control of the stator coils to prevent overshoot. This allows us to determine the first angle at which the lead angle stops adjusting under the negative direct-axis current compensation method. This facilitates timely switching from the negative direct-axis current compensation method to the current lead angle control method when the lead angle reaches the first angle, avoiding overshoot of the cross-axis current when the phase current reaches the current threshold. This improves the stability and safety of the stator coils during field weakening control. Furthermore, by using this current lead angle control method to promptly control the lead angle from the first angle to the stopping angle, overshoot can be avoided, further enhancing the safety of the stator coils during field weakening control.

[0074] Optionally, based on the initial quadrature-axis current value, current threshold, and voltage threshold, the second voltage limit circle of the permanent magnet synchronous motor is obtained, including:

[0075] Based on the initial cross-axis current value, current threshold, and voltage threshold, the first speed of the permanent magnet synchronous motor corresponding to the initial cross-axis current value is obtained; wherein, the first speed is less than the current speed.

[0076] The formula for calculating the first rotational speed is as follows:

[0077]

[0078] In the formula, ω1 represents the first rotational speed, u max L represents the voltage threshold. q I represents quadrature axis inductance. max Indicates the current threshold, i q L represents the quadrature-axis current. d Indicates direct-axis inductance. Indicates magnetic flux;

[0079] Based on the first rotational speed and voltage threshold, the second voltage limit circle of the permanent magnet synchronous motor is obtained.

[0080] In this embodiment, when no overshoot occurs in the quadrature-axis current, each value of the quadrature-axis current of the stator coil is based on a first rotational speed corresponding to the adjustment amount of a direct-axis current, using a current threshold and a voltage threshold. This first rotational speed and voltage threshold allow for understanding the voltage limitations of the direct-axis and quadrature-axis. This voltage limitation can be represented as a second voltage limit circle, which facilitates the subsequent determination of the first angle corresponding to when the lead angle stops increasing during field weakening control using the negative direct-axis current compensation method. This allows for timely switching to the current lead angle control method for field weakening control of the stator coil when the lead angle reaches the first angle, i.e., when the phase current reaches the current threshold, thus avoiding quadrature-axis current overshoot during field weakening control.

[0081] Figure 3 The circuit schematic for field weakening control in this application is shown below. Figure 3 As shown, the direct-axis voltage ud and quadrature-axis voltage uq of the DC-side voltage Udc of the three-level inverter are collected, and the direct-axis voltage ud and quadrature-axis voltage uq are combined with the calculation formula and input into the first PI controller to obtain the output direct-axis current Δi. d And based on the phase current I s Cross-axis current i q Direct-axis current i d The phase current I is obtained by calculating the relationship between the phase current and the lead angle β. s If the calculated phase current I s Less than the current threshold I max Then, the negative direct-axis current compensation method is selected for field weakening control. If the calculated phase current I... s Equal to current threshold I max Then, the current lead angle control method is selected for field weakening control, utilizing the negative increment Δi of the direct-axis current. d Calculate the current lead angle increment Δβ for field weakening control, and then process the lead angle increment Δβ through a phase-locked loop to obtain the actual output lead angle stop angle β.

[0082] When performing field weakening control, the three-phase current i in the three-level inverter is first collected. u i v i w , change i u i y i w Perform CLARK transform to obtain i α i β , change i α i β The direct-axis current i is obtained after PARK transformation. d and cross-axis current i q .

[0083] When using the negative direct-axis current compensation method for field weakening control, the initial direct-axis current value of the setpoint is used. and direct-axis current Δi d Calculate the current direct-axis current And an initial quadrature-axis current value is given. In cross-axis current If it remains unchanged, that is Maintain current quadrature axis current When, the current direct-axis current is negatively increased. Then calculate the current direct-axis current. and direct-axis current i d The first error, and calculate the current quadrature axis current. and cross-axis current i q The second error. The first and second errors are respectively input into the second PI controller, which outputs the corresponding current direct-axis voltage. and current quadrature axis voltage and respectively for the current direct-axis voltage and current quadrature axis voltage Perform the inverse PARK transform to obtain the corresponding u α and ux, will u α and u β The voltage space vector is synthesized and SVPWM modulation is performed, while the switching states of the three half-bridges of the three-level inverter at that moment are output.

[0084] When using the current lead angle control method for field weakening control, the lead angle is rotated according to a preset rotation rule to control the current direct-axis current. and current quadrature axis current Simultaneous modulation is used to achieve field weakening control of the stator coils. During modulation, the current direct-axis current is calculated. and direct-axis current i d The first error, and calculate the current quadrature axis current. and cross-axis current i q The second error. The first and second errors are respectively input into the second PI controller, which outputs the corresponding current direct-axis voltage. and current quadrature axis voltage And respectively for the current direct-axis voltage and current quadrature axis voltage Perform the inverse PARK transform to obtain the corresponding u α and u β , will u α and u β The voltage space vector is synthesized and SVPWM modulation is performed, while the switching states of the three half-bridges of the three-level inverter at that moment are output.

[0085] Figure 4The graphs showing the variation of direct-axis and quadrature-axis currents when performing field weakening control using existing technologies are shown below. Figure 4 As shown, the horizontal axis represents time t (s), and the vertical axis represents current (A). Figure 4 The data recorded shows the change in direct-axis current i over time during field weakening control using the negative direct-axis current compensation method. d and cross-axis current i q The measured variation curves are shown. Specifically, when the phase current exceeds the current threshold during field weakening control, the direct-axis current i... d and cross-axis current i q The given instructions are provided by the algorithm corresponding to the negative direct-axis current compensation method, but for the direct-axis current i d The command is calculated from the voltage threshold, and the quadrature-axis current i q The commands are calculated from the current threshold, causing asynchronous responses and resulting in cross-axis current i. q Overshoot occurs (i in the diagram) q (Fall). That is, due to the direct-axis current i during field weakening control. d The voltage threshold limitation results in a slow response speed, preventing it from promptly following the quadrature-axis current i, which is limited by the current threshold. q The change in current leads to a significant overshoot in the quadrature-axis current and a torque drop. Specifically, the quadrature-axis current i is limited using a current threshold. q The amplitude limiting formula is as follows:

[0086]

[0087] Among them, i d Indicates the direct-axis current, i q I represents the quadrature-axis current. max This indicates the current threshold.

[0088] Figure 5 The graphs showing the changes in direct-axis and quadrature-axis currents during field weakening control in this application are shown below. Figure 5 As shown, the horizontal axis represents time t (s), and the vertical axis represents current (A). Figure 5 The data recorded shows the change in direct-axis current i over time when the negative direct-axis current compensation method is used before the phase current reaches the current threshold, and the current lead angle control method is used for field weakening control after the phase current reaches the current threshold. d and cross-axis current i q The measured variation curve. Because in the field weakening control stage of the negative direct-axis current compensation method and the field weakening control stage of the lead angle control method, the direct-axis current i... d and cross-axis current i q Both can simultaneously meet the current threshold and voltage threshold restrictions, avoiding quadrature-axis current i q Overshoot occurs when the phase current reaches the current threshold, thereby improving the accuracy of field weakening control.

[0089] The method in this application utilizes a permanent magnet synchronous motor with negative direct-axis current compensation for field weakening control, and the phase current reaches the current threshold I. max Then, a smooth transition is made to the lead angle control method for field weakening control, so that the direct-axis current i d It can be limited by a voltage threshold, while the quadrature-axis current i q Limited by a current threshold, i.e., simultaneously providing a direct-axis current i that satisfies the constraint conditions. d and cross-axis current i q The instruction causes the direct-axis current i to... d and cross-axis current i q Maintain synchronous changes and avoid direct-axis current i limited only by voltage limits. d For quadrature axis current i q Limiting causes quadrature axis current i q Overshooting has occurred.

[0090] like Figure 6 As shown, this application provides a field weakening control system for a permanent magnet synchronous motor, comprising:

[0091] The first acquisition module is used to acquire the initial value of the phase current of the stator coil of the permanent magnet synchronous motor. The initial value is equal to the initial cross-axis current value of the cross-axis current of the stator coil.

[0092] The first field weakening control module is used to perform field weakening control on the stator coil based on the preset negative direct axis current compensation method and quadrature axis initial current value when the phase current does not reach the current threshold of the stator coil.

[0093] The second acquisition module is used to acquire the current speed of the permanent magnet synchronous motor when the phase current reaches the current threshold.

[0094] The calculation module is used to determine the stop angle of the stator coil lead angle based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil.

[0095] The second field weakening control module is used to perform field weakening control on the stator coil based on a preset current lead angle control method and the initial cross-axis current value until the lead angle reaches the stop angle.

[0096] Optionally, the first field weakening control module is specifically used for:

[0097] The quadrature-axis current is kept at the initial quadrature-axis current value, and the direct-axis current of the stator coil is adjusted according to the preset adjustment rules until the phase current reaches the current threshold.

[0098] Optionally, the calculation module is specifically used for:

[0099] Based on the current speed and voltage threshold, the first voltage limit circle of the permanent magnet synchronous motor is obtained;

[0100] Based on the current threshold, the current limit circle of the permanent magnet synchronous motor is obtained;

[0101] Based on the current limiting circle and the first voltage limiting circle, the stop angle of the lead angle is obtained.

[0102] Optionally, the calculation module is specifically used for:

[0103] Establish a rectangular coordinate system based on the direct axis and quadrature axis of the stator coil;

[0104] Draw the current limiting circle on the rectangular coordinate system with the origin of the rectangular coordinate system as the center.

[0105] Based on the magnetic flux linkage and direct-axis inductance of the stator coil, the center of the first voltage limit circle is determined in the rectangular coordinate system, and the first voltage limit circle is drawn in the rectangular coordinate system.

[0106] Find the intersection point of the first voltage limit circle and the current limit circle in the rectangular coordinate system;

[0107] Obtain the line connecting the intersection point and the origin in the rectangular coordinate system;

[0108] The angle between the connecting line and the Y-axis in the rectangular coordinate system is taken as the stopping angle of the lead angle.

[0109] Optionally, the second field weakening control module is specifically used for:

[0110] Based on the initial cross-axis current value and the current threshold, the direct-axis current value is obtained, and the direct-axis current value is used as the first direct-axis stop current value of the direct-axis current.

[0111] Based on the initial current value of the quadrature axis and the stopping current value of the first straight axis, the first angle of the lead angle is obtained;

[0112] Based on the current threshold, the lead angle is adjusted from the first angle to the stop angle according to the preset rotation rules.

[0113] Optionally, the second field weakening control module is specifically used for:

[0114] Based on the initial cross-axis current value, current threshold, and voltage threshold, the second voltage limit circle of the permanent magnet synchronous motor is obtained;

[0115] Based on the current threshold, the current limit circle of the permanent magnet synchronous motor is obtained;

[0116] Based on the second voltage limit circle and the current limit circle, the first angle of the lead angle is obtained;

[0117] Based on the current limit circle, the lead angle is adjusted from the first angle to the stop angle according to the preset rotation rules.

[0118] Optionally, the second field weakening control module is specifically used for:

[0119] Based on the initial cross-axis current value, current threshold, and voltage threshold, the first speed of the permanent magnet synchronous motor corresponding to the initial cross-axis current value is obtained; wherein, the first speed is less than the current speed.

[0120] Based on the first rotational speed and voltage threshold, the second voltage limit circle of the permanent magnet synchronous motor is obtained.

[0121] A computing device according to an embodiment of this application includes a memory, a processor, and a program stored in the memory and running on the processor. When the processor executes the program, it implements some or all of the steps of the field weakening control method for a permanent magnet synchronous motor described above.

[0122] The computing device can be a computer, and the corresponding program is computer software. The parameters and steps in the computing device described above can be referred to the parameters and steps in the embodiment of the field weakening control method for permanent magnet synchronous motor described above, and will not be repeated here.

[0123] This application embodiment provides a computer-readable storage medium storing instructions that, when executed, perform the steps of the aforementioned field weakening control method for a permanent magnet synchronous motor.

[0124] The computer-readable storage medium may be a transient computer-readable storage medium or a non-transitory computer-readable storage medium.

[0125] The technical solutions of this disclosure can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes one or more instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of this disclosure. The aforementioned computer-readable storage medium can be a non-transitory computer-readable storage medium, including: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks, and other media capable of storing program code; it can also be a transient computer-readable storage medium.

[0126] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. Each block in a flowchart or block diagram may represent a module, segment, or portion of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0127] Those skilled in the art will recognize that this application can be implemented as a system, method, or computer program product. Therefore, this disclosure can be implemented in the following forms: it can be entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software, generally referred to herein as a "circuit," "module," or "system." Furthermore, in some embodiments, this application can also be implemented as a computer program product contained in one or more computer-readable media, which contains computer-readable program code. Computer-readable storage media can be, for example, but not limited to—electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any combination thereof.

[0128] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0129] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A field weakening control method for a permanent magnet synchronous motor, characterized in that, include: Obtain the initial value of the phase current of the stator coil of the permanent magnet synchronous motor, wherein the initial value is equal to the initial cross-axis current value of the cross-axis current of the stator coil; When the phase current does not reach the current threshold of the stator coil, the stator coil is subjected to field weakening control based on the preset negative direct axis current compensation method and the initial cross axis current value. When the phase current reaches the current threshold, the current speed of the permanent magnet synchronous motor is obtained; Based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil, the stop angle of the stator coil's lead angle is determined; The stator coil is subjected to field weakening control based on the preset current lead angle control method and the initial cross-axis current value until the lead angle reaches the stop angle.

2. The method according to claim 1, characterized in that, The method of field weakening control of the stator coil based on the preset negative direct-axis current compensation method and the initial quadrature-axis current value includes: The quadrature-axis current is maintained at the initial quadrature-axis current value, and the direct-axis current of the stator coil is adjusted according to a preset adjustment rule until the phase current reaches the current threshold.

3. The method according to claim 1, characterized in that, The determination of the stop angle of the stator coil's lead angle based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil includes: Based on the current rotational speed and the voltage threshold, the first voltage limit circle of the permanent magnet synchronous motor is obtained; Based on the current threshold, the current limit circle of the permanent magnet synchronous motor is obtained; Based on the current limiting circle and the first voltage limiting circle, the stopping angle of the lead angle is obtained.

4. The method according to claim 3, characterized in that, The stopping angle for obtaining the lead angle based on the current limiting circle and the first voltage limiting circle includes: A rectangular coordinate system is established based on the direct axis and quadrature axis of the stator coil; The origin of the rectangular coordinate system is used as the center of the current limiting circle, and the current limiting circle is drawn on the rectangular coordinate system. Based on the magnetic flux linkage and direct-axis inductance of the stator coil, the center of the first voltage limit circle is determined in the rectangular coordinate system, and the first voltage limit circle is drawn on the rectangular coordinate system. Obtain the intersection point of the first voltage limit circle and the current limit circle in the rectangular coordinate system; Obtain the line connecting the intersection point and the origin in the rectangular coordinate system; The angle between the connecting line and the Y-axis in the rectangular coordinate system is taken as the stopping angle of the leading angle.

5. The method according to any one of claims 1 to 4, characterized in that, The method of field weakening control of the stator coil based on the preset current lead angle control method and the initial cross-axis current value until the lead angle reaches the stop angle includes: Based on the initial cross-axis current value and the current threshold, the direct-axis current value is obtained, and the direct-axis current value is used as the first direct-axis stop current value of the direct-axis current. Based on the initial cross-axis current value and the first direct-axis stop current value, the first angle of the lead angle is obtained; Based on the current threshold, the advance angle is adjusted from the first angle to the stop angle according to the preset rotation rules.

6. The method according to any one of claims 1 to 4, characterized in that, The method of field weakening control of the stator coil based on the preset current lead angle control method and the initial cross-axis current value until the lead angle reaches the stop angle includes: Based on the initial cross-axis current value, the current threshold, and the voltage threshold, the second voltage limit circle of the permanent magnet synchronous motor is obtained; Based on the current threshold, the current limit circle of the permanent magnet synchronous motor is obtained; Based on the second voltage limit circle and the current limit circle, the first angle of the lead angle is obtained; Based on the current limit circle, the advance angle is adjusted from the first angle to the stop angle according to the preset rotation rules.

7. The method according to claim 6, characterized in that, The process of obtaining the second voltage limit circle of the permanent magnet synchronous motor based on the initial cross-axis current value, the current threshold, and the voltage threshold includes: Based on the initial cross-axis current value, the current threshold, and the voltage threshold, the first rotational speed of the permanent magnet synchronous motor corresponding to the initial cross-axis current value is obtained; wherein, the first rotational speed is less than the current rotational speed; Based on the first rotational speed and the voltage threshold, the second voltage limit circle of the permanent magnet synchronous motor is obtained.

8. A field weakening control system for a permanent magnet synchronous motor, characterized in that, include: The first acquisition module is used to acquire the initial value of the phase current of the stator coil of the permanent magnet synchronous motor, wherein the initial value is equal to the cross-axis initial current value of the cross-axis current of the stator coil. The first field weakening control module is used to perform field weakening control on the stator coil based on a preset negative direct axis current compensation method and the quadrature axis initial current value when the phase current does not reach the current threshold of the stator coil. The second acquisition module is used to acquire the current speed of the permanent magnet synchronous motor when the phase current reaches the current threshold. The calculation module is used to determine the stop angle of the stator coil's lead angle based on the current rotational speed, the initial cross-axis current value, the current threshold, and the voltage threshold of the stator coil; The second field weakening control module is used to perform field weakening control on the stator coil based on a preset current lead angle control method and the initial cross-axis current value until the lead angle reaches the stop angle.

9. A computing device, comprising a memory, a processor, and a program stored in the memory and running on the processor, characterized in that, When the processor executes the program, it implements the steps of a field weakening control method for a permanent magnet synchronous motor as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed on a terminal device, cause the terminal device to perform the steps of a field weakening control method for a permanent magnet synchronous motor as described in any one of claims 1 to 7.

Images