Method and system for calculating three-phase maximum asc current trajectory of permanent magnet synchronous motor

Abstract

The application provides a method and system for calculating three-phase maximum ASC current trajectory of a permanent magnet synchronous motor, the method comprising the following steps: solving d-axis voltage U d and q-axis voltage U q as differential equations of d-axis current i d and q-axis current i q ; establishing current trajectory expression of d-axis current i d and q-axis current i q transformed into three-phase current; deriving the current trajectory expression of three-phase current with respect to rotor angle to obtain extreme point expression; establishing three-phase ASC current trajectory expression, determining that three-phase current is at a peak value at the n sampling interval, and corresponding d-axis current i d and q-axis current i q ; calculating initial phase of the permanent magnet synchronous motor after entering ASC, and determining three-phase maximum ASC current trajectory under the current working condition. After the above technical scheme is adopted, a large amount of test resources such as test benches and manpower can be saved to estimate the three-phase maximum ASC current trajectory of the permanent magnet synchronous motor.

Description

Technical Field

[0001] This invention relates to the field of motor control, and in particular to a method and system for calculating the maximum ASC current trajectory of a three-phase permanent magnet synchronous motor. Background Technology

[0002] Active short circuit (ASC) primarily involves short-circuiting the three phases (UVW) of the motor (achieved through IGBT switching, either by short-circuiting the upper or lower three bridge arms) and serves as a safety protection mechanism for motor systems. In severe fault conditions, ASC three-phase short circuits protect or prevent further damage to the controller's electrical system.

[0003] When a permanent magnet synchronous motor enters ASC (Automatic Current Surge) mode, a large transient current is generated. The largest transient current may damage the IGBT module of the controller. Therefore, if the specific magnitude of the maximum transient current can be estimated based on the motor parameters, it can be determined whether the currently used IGBT module can withstand the maximum ASC transient current. However, in existing technology, the maximum ASC transient current cannot be obtained by general calibration methods.

[0004] Therefore, it is necessary to predict and calculate the maximum ASC current trajectory of the three phases after the permanent magnet synchronous motor enters ASC, so as to obtain the maximum ASC current at any time under actual working conditions. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a method and system for calculating the maximum three-phase ASC current trajectory of a permanent magnet synchronous motor, which can save a lot of testing resources such as test benches and manpower to estimate the maximum three-phase ASC current trajectory of a permanent magnet synchronous motor.

[0006] This invention discloses a method for calculating the maximum ASC current trajectory of a three-phase permanent magnet synchronous motor, comprising the following steps:

[0007] The d-axis voltage U of the permanent magnet synchronous motor in the rotor orientation d-axis and q-axis coordinate system is... d and q-axis voltage U q The solution is to determine the d-axis current i in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC (Automatic Stability Control) mode. d and q-axis current i q The differential equations are: the transient d-axis current, the transient q-axis current, and the speed of the permanent magnet synchronous motor when entering ASC.

[0008] Establish the d-axis current i of the permanent magnet synchronous motor after entering ASC d and q-axis current i qThe current trajectory expression is transformed into a three-phase current expression, where the rotor angle of the permanent magnet synchronous motor when entering the ASC is regarded as a variable in the current trajectory expression;

[0009] Differentiate the expression for the current trajectory of the three-phase current with respect to the rotor angle to obtain the expression for the extreme points of the three-phase current with respect to the rotor angle;

[0010] Based on d-axis current I d and q-axis current I q The differential equations, current trajectory expressions, and extreme point expressions are used to establish the three-phase ASC current trajectory expression. A rotational speed, sampling interval, and transient d-axis and q-axis currents are selected. The peak values ​​of the three-phase currents at the nth sampling interval and the corresponding d-axis currents i at these peak values ​​are determined. d and q-axis current i q ;

[0011] The initial phase of the permanent magnet synchronous motor after entering ASC is calculated based on the sampling duration determined by the nth sampling interval and the selected speed. The maximum three-phase ASC current trajectory under the current operating condition is determined based on the initial phase, sampling duration, selected speed, transient d-axis current, transient q-axis current and differential equation.

[0012] Preferably, the d-axis voltage U of the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate system is... d and q-axis voltage U q Solve for the d-axis current I in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC. d and q-axis current I q The steps for solving a differential equation include:

[0013] Establish the d-axis voltage U of the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate system. d and q-axis voltage U q The following voltage equation:

[0014]

[0015] Where L d L is the stator inductance on the d-axis. q Ψ is the stator inductance on the q-axis. f R is the rotor flux linkage of a permanent magnet synchronous motor. s The stator resistance of a permanent magnet synchronous motor, where ω is the speed of the permanent magnet synchronous motor;

[0016] Based on the d-axis voltage U d and q-axis voltage U q Since both are 0, the voltage equation is transformed into the following differential equation concerning the current:

[0017] in

[0018] Set up the following auxiliary variable

[0019] This allows the differential equation to be simplified to the following homogeneous equation:

[0020]

[0021] Transform matrix A into Jordan canonical form: in:

[0022]

[0023]

[0024] J and T can be approximated by the following expression:

[0025] Make auxiliary variables Approximately expressed as

[0026] Simplify auxiliary variables The approximate expression for the d-axis current i is obtained as follows: d and q-axis current i q Differential equations:

[0027] in This refers to the transient d-axis current when entering ASC. This is the transient q-axis current when entering ASC.

[0028] Preferably, the d-axis current i of the permanent magnet synchronous motor after entering ASC is established. d and q-axis current i q The steps to transform the current trajectory expression into a three-phase current expression include:

[0029] Establish the following d-axis current i d and q-axis current i q The following are the current trajectory expressions for the three-phase currents after inverse Park transform and inverse Clarke transform:

[0030] Where θ is the rotor angle of the permanent magnet synchronous motor when entering ASC, and the rotor angle is the sum of the product of the rotational speed and time and the initial angle;

[0031] The steps to differentiate the expression for the current trajectory of the three-phase current with respect to the rotor angle to obtain the expression for the extreme points of the three-phase current with respect to the rotor angle include:

[0032] Differentiating the current trajectory expression with the rotor angle as the variable, we obtain the following extreme point expression:

[0033]

[0034] Preferably, based on the d-axis current I d and q-axis current I q The differential equations, current trajectory expressions, and extreme point expressions are used to establish the three-phase ASC current trajectory expression. A rotational speed, sampling interval, and transient d-axis and q-axis currents are selected. The peak values ​​of the three-phase currents at the nth sampling interval and the corresponding d-axis currents i at these peak values ​​are determined. d and q-axis current i q The steps include:

[0035] Substituting the extreme point expression into the current trajectory expression, we obtain the following three-phase ASC current trajectory expressions for the d-axis current in the time domain, id(t), and the q-axis current in the time domain:

[0036]

[0037] Select a rotational speed, sampling interval, transient d-axis current, and transient q-axis current, and statistically analyze the three-phase current at its peak value at the nth sampling interval, and the corresponding d-axis current i at the peak value. d and q-axis current i q The value of .

[0038] Preferably, the steps of calculating the initial phase of the permanent magnet synchronous motor after entering ASC based on the sampling duration determined by the nth sampling interval and the selected speed, and determining the three-phase maximum ASC current trajectory under the current operating condition based on the initial phase, sampling duration, selected speed, transient d-axis current, transient q-axis current, and differential equation include:

[0039] The d-axis current i corresponding to the three-phase current d and q-axis current i q The value of the value, the selected speed, and the sampling duration determined by the nth sampling interval are substituted into the extreme point expression and the speed-angle relationship to calculate the initial phase InitTheat of the permanent magnet synchronous motor after entering ASC;

[0040] Substituting the initial phase InitTheat into the three-phase ASC current trajectory expression based on the speed-angle relationship, we obtain the following information regarding the d-axis current i under the current operating condition. d and q-axis current i q The expression for the maximum three-phase ASC current trajectory is:

[0041]

[0042] Preferably, the d-axis voltage U of the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate system is... d and q-axis voltage U q The solution is to determine the d-axis current i in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC (Automatic Stability Control) mode. d and q-axis current i q After the steps of solving the differential equation, the following steps are also included:

[0043] Select the simulated d-axis current, simulated q-axis current, and simulated rotational speed under specific operating conditions;

[0044] Substitute the simulated d-axis current, simulated q-axis current, and simulated rotational speed into the differential equation, and fit to obtain the simulated ASC current waveform based on the differential equation;

[0045] The simulated ASC current waveform is compared with the actual ASC current waveform under specific operating conditions to verify the differential equation through simulation.

[0046] This invention also discloses a calculation system for the maximum ASC current trajectory of a three-phase permanent magnet synchronous motor, including a calculation module, which includes:

[0047] The solution element calculates the d-axis voltage U of the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate systems. d and q-axis voltage U q The solution is to determine the d-axis current i in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC (Automatic Stability Control) mode. d and q-axis current i q The differential equations are: the transient d-axis current, the transient q-axis current, and the speed of the permanent magnet synchronous motor when entering ASC.

[0048] Establish a unit to establish the d-axis current i of the permanent magnet synchronous motor after it enters ASC. d and q-axis current i q The current trajectory expression is transformed into a three-phase current expression, where the variable in the current trajectory expression is the rotor angle of the permanent magnet synchronous motor when entering the ASC.

[0049] The differentiation unit differentiates the current trajectory expression of the three-phase current with respect to the rotor angle to obtain the extreme point expression of the three-phase current with respect to the rotor angle.

[0050] Processing unit, based on d-axis current I d and q-axis current I qThe differential equations, current trajectory expressions, and extreme point expressions are used to establish the three-phase ASC current trajectory expression. A rotational speed, sampling interval, and transient d-axis and q-axis currents are selected. The peak values ​​of the three-phase currents at the nth sampling interval and the corresponding d-axis currents i at these peak values ​​are determined. d and q-axis current i q ;

[0051] The plotting unit calculates the initial phase of the permanent magnet synchronous motor after entering ASC based on the sampling duration determined by the nth sampling interval and the selected speed, and determines the trajectory of the maximum three-phase ASC current under the current operating condition based on the initial phase, sampling duration, selected speed, transient d-axis current, transient q-axis current and differential equation.

[0052] Compared with existing technologies, the above technical solution has the following advantages:

[0053] 1. Only motor parameters are needed to quickly and iteratively calculate the maximum three-phase ASC current trajectory at various speeds;

[0054] 2. The maximum ASC current trajectory of three phases can be quickly fitted without requiring a large number of test benches and manpower. Attached Figure Description

[0055] Figure 1 A flowchart illustrating the calculation method in a preferred embodiment of the present invention;

[0056] Figure 2 This is a schematic diagram comparing the maximum ASC current trajectories of the three phases under the first simulated operating condition in a preferred embodiment of the present invention. Detailed Implementation

[0057] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0058] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0059] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0060] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0061] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0062] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0063] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0064] See Figure 1 To illustrate the flowchart of the calculation method for the maximum three-phase ASC current trajectory of a permanent magnet synchronous motor in a preferred embodiment of the present invention, the calculation method includes the following steps in this embodiment:

[0065] S100: The d-axis voltage U of the permanent magnet synchronous motor in the rotor orientation d-axis and q-axis coordinate system. d and q-axis voltage U qThe solution is to determine the d-axis current i in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC (Automatic Stability Control) mode. d and q-axis current i q The differential equations are: the transient d-axis current, the transient q-axis current, and the speed of the permanent magnet synchronous motor when entering ASC.

[0066] After the permanent magnet synchronous motor enters the active short-circuit state, the d-axis voltage U input to the motor in the rotor-oriented d-axis and q-axis coordinate system is... d and q-axis voltage U q When the current changes to 0, the vehicle's inertia is relatively large, and the motor speed changes slowly. Relative to the change in current, the speed can be approximated as constant. Therefore, the d-axis voltage U can be... d and q-axis voltage U q Transform into d-axis current i in the d-axis and q-axis coordinate system d and q-axis current i q The differential equation contains only the transient d-axis current, transient q-axis current, and the speed of the permanent magnet synchronous motor (electric angular velocity of the rotor) when entering ASC. Therefore, given a given speed, the d-axis current i is searched throughout. d and q-axis current i q Various combinations can integrate discrete data into a current trajectory composed of all ASC currents.

[0067] S200: Establish the d-axis current i after the permanent magnet synchronous motor enters ASC. d and q-axis current i q The current trajectory expression is transformed into a three-phase current expression, where the rotor angle of the permanent magnet synchronous motor when entering the ASC is regarded as a variable in the current trajectory expression;

[0068] Differentiate the expression for the current trajectory of the three-phase current with respect to the rotor angle to obtain the expression for the extreme points of the three-phase current with respect to the rotor angle;

[0069] Since a brief large current is generated when active short-circuit protection is activated, the peak current entering ASC under the same operating condition is crucial for the controller's drive module. Therefore, it is necessary to estimate the trajectory of the three-phase maximum value among all ASC currents. Consequently, the dq-axis coordinate system needs to be transformed into a current trajectory expression for the three-phase current, i.e., establishing the d-axis current i after the permanent magnet synchronous motor enters ASC. d and q-axis current i q Transform the current trajectory into a three-phase current expression (e.g., based on the inverse Park transform and the inverse Clarke transform). Based on the transformed expression, the d-axis current i can be... d and q-axis current i qIf we consider it a constant, then the rotor angle of the permanent magnet synchronous motor when entering ASC can be regarded as a variable in the current trajectory expression. Then, we differentiate the current trajectory expression of the three-phase current with respect to the rotor angle to obtain the extreme point expression of the three-phase current with respect to the rotor angle. This extreme point expression is for different d-axis currents i d and q-axis current i q The rotor angle corresponding to the maximum value of a certain phase in the three-phase current.

[0070] It is understandable that the transient currents of the ASC current trajectories obtained by coordinate transformation using different rotor angles are different, while the steady-state currents are basically the same. For example, when the speed is 4000 rpm, after 0.3 seconds of simulation, the simulated rotor angle should be near 0. Therefore, it can be observed that when the rotor angle is π / 15, the estimated trajectory is basically consistent with the simulated trajectory. At the same speed, different coordinate transformation rotor angles result in the same oscillation frequency and amplitude change rate of the ASC phase current trajectory, but the ASC current amplitude will shift vertically. It can be considered that the coordinate transformation rotor angle determines the maximum amplitude of the ASC phase current. Therefore, it is necessary to determine the rotor angle corresponding to the instant the simulation enters ASC protection to ensure that the estimated maximum amplitude of the ASC phase current is the same as the simulated ASC phase current.

[0071] S300: Based on d-axis current I d and q-axis current I q The differential equations, current trajectory expressions, and extreme point expressions are used to establish the three-phase ASC current trajectory expression. A rotational speed, sampling interval, and transient d-axis and q-axis currents are selected. The peak values ​​of the three-phase currents at the nth sampling interval and the corresponding d-axis currents i at these peak values ​​are determined. d and q-axis current i q ;

[0072] Since the variables in this differential equation are the transient d-axis current, transient q-axis current, and speed of the permanent magnet synchronous motor when entering the ASC, the variable in the current trajectory expression is the rotor angle of the permanent magnet synchronous motor when entering the ASC, and the extreme point expression is the rotor angle with respect to the d-axis current I. d and q-axis current I q The function expression, then, with a selected rotational speed, transient d-axis current, and transient q-axis current (representing the d-axis current I just entering ASC), d and q-axis current I q The value of the three-phase current is taken as constant under test conditions. After determining a sampling interval (i.e., how often to sample the three-phase current), the maximum value of the three-phase current at the peak position of the waveform at the moment of the nth sampling interval can be obtained, as well as the d-axis current I at this time. d and q-axis current I qThe value of . In other words, when designing various operating conditions, the rotational speed, sampling interval, and transient d-axis current and transient q-axis current can be manually determined, thereby obtaining the d-axis current i with respect to time. d and q-axis current i q The ASC current trajectory.

[0073] S400: Calculate the initial phase of the permanent magnet synchronous motor after entering ASC based on the sampling duration determined by the nth sampling interval and the selected speed, and determine the three-phase maximum ASC current trajectory under the current operating condition based on the initial phase, sampling duration, selected speed, transient d-axis current, transient q-axis current and differential equation.

[0074] For example, sampling the three-phase maximum ASC current trajectory in the dq coordinate system at 100µs intervals yields i d and i q Find the value of i corresponding to the maximum value of the current trajectory. d and i q Value, using this i d and i q The rotor angle is calculated by taking the value, and finally a coordinate transformation rotor angle is obtained, so that the trajectory of the maximum three-phase ASC current can be obtained.

[0075] S500: Finally, based on the sampling duration determined by the nth sampling interval (i.e., when the above peak occurs), the initial phase of the permanent magnet synchronous motor after entering ASC is calculated using the selected speed (this initial phase is related to the speed and rotor angle; for example, the initial phase is equal to the rotor angle minus the product of the speed and the sampling duration). When the variable is finally transformed into the rotor angle, and this rotor angle can be calculated based on the selected parameters, the maximum three-phase ASC current trajectory under the current operating condition can be finally determined based on the initial phase, sampling duration, selected speed, transient d-axis current, transient q-axis current, and differential equations.

[0076] In other words, in this step, i d and i q A rotor angle is determined, which is defined as ω*t + initial angle φ. The electrical angular velocity ω is an assumed rotational speed, and t is obtained by multiplying the sampling time by the corresponding data set. Finally, the initial angle φ is obtained. The trigonometric function in the coordinate transformation should specifically be Cos(w*t+φ).

[0077] In a preferred embodiment, step S100 includes:

[0078] S110: Establish the d-axis voltage U of the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate systems. d and q-axis voltage U q The following voltage equation:

[0079]

[0080] Where L d L is the stator inductance on the d-axis. q Ψ is the stator inductance on the q-axis. f R is the rotor flux linkage of a permanent magnet synchronous motor. s The stator resistance of a permanent magnet synchronous motor, where ω is the speed of the permanent magnet synchronous motor;

[0081] S120: Due to the large inertia of electric vehicles and the slow change in motor speed, the speed can be approximated as constant relative to the change in current. Therefore, the d-axis voltage U is based on... d and q-axis voltage U q Since both are 0, the voltage equation above can be transformed into a differential equation concerning the current:

[0082] in

[0083] S130: To facilitate solving the differential equation of the current, the above differential equation can be simplified into a homogeneous equation, that is, by setting an auxiliary variable as follows.

[0084] This allows the differential equation to be simplified to the following homogeneous equation, which is the homogeneous differential equation expression of the permanent magnet synchronous motor in ASC state:

[0085]

[0086] Under ASC, the time-domain response of the motor current can be expressed as:

[0087] S140: Thus, in this step, matrix A can be transformed into Jordan canonical form: in:

[0088]

[0089]

[0090] S150: In electric vehicles, the motor speed is generally on the order of magnitude much larger than the motor's resistance and inductance. Therefore, J and T can be approximated by the following expression:

[0091] Make auxiliary variables Approximately expressed as

[0092] S160: As can be seen from the above formula, after entering ASC, the current oscillation decays, and the smaller amplitude part of the current response can be ignored, thus simplifying the auxiliary variables. The following approximate representation:

[0093] Substitute the formula into the auxiliary variable The definition formula is used to obtain the following d-axis current i d and q-axis current i q Differential equations:

[0094] in This refers to the transient d-axis current when entering ASC. This is the transient q-axis current when entering ASC.

[0095] In a preferred embodiment, step S200 includes:

[0096] S210: Establish the following d-axis current i d and q-axis current i q The following are the current trajectory expressions for the three-phase currents after inverse Park transform and inverse Clarke transform:

[0097] Where θ is the rotor angle of the permanent magnet synchronous motor when entering the ASC;

[0098] Meanwhile, step S300 includes:

[0099] S310: Treating the above current trajectory expression as a function of the rotor angle, we can differentiate the current trajectory expression with the rotor angle as the variable to obtain the following extreme point expression:

[0100]

[0101] Further, step S400 includes:

[0102] S410: Substitute the extreme point expression as the rotor angle corresponding to the extreme point into the current trajectory expression to obtain the following three-phase ASC current trajectory expressions for the d-axis current in the time domain and the q-axis current in the time domain:

[0103]

[0104] S420: From the current trajectory expression, it can be seen that all motor parameters determined by the motor's inherent properties are known parameters. Only four unknowns exist: the transient d-axis current and transient q-axis current when entering ASC state, the speed, and time t. Therefore, in this step, a speed, sampling interval, transient d-axis current, and transient q-axis current can be selected to replace all unknowns with known values. The nth sampling interval (where each sampling interval forms a sampling moment) is defined as the time when the three-phase current reaches its peak value across all sampling moments (making this sampling moment the moment the peak value occurs; for example, when the sampling interval is 100μs, the 5th sampling interval means the peak value occurs at 500μs). The three-phase current at the peak value and the corresponding d-axis current i are then calculated. d and q-axis current i q The value of .

[0105] Furthermore, step S500 includes:

[0106] S510: The d-axis current i corresponding to the three-phase current (specifically, the peak current of each phase). d and q-axis current i q Substituting the value of the value, the selected speed, and the sampling duration determined by the nth sampling interval into the extreme point expression and the speed-angle relationship, we can calculate the initial phase InitTheat of the coordinate transformation corresponding to the maximum ASC current trajectory after the permanent magnet synchronous motor enters ASC.

[0107] S520: Based on the speed-angle relationship, the initial phase InitTheat is substituted into the three-phase ASC current trajectory expression to obtain the following information about the d-axis current i under the current operating condition. d and q-axis current i q The expression for the maximum three-phase ASC current trajectory:

[0108] In summary, by selecting a rotational speed and providing a set of... and This allows us to determine the trajectory of the maximum three-phase Asc current. Then, at the selected speed, by searching through all the dq current combinations within the current limit range, we can obtain the trajectory of the maximum three-phase Asc current under all operating conditions at the selected speed. Similarly, by searching through all the dq current combinations at all speeds, we can obtain the trajectory of the maximum three-phase Asc current at each speed.

[0109] In the above steps, the initial phases of the coordinate transformation of the three-phase currents are different. To obtain the maximum ASC current trajectory of a particular phase, simply substitute the corresponding initial phase of the coordinate transformation into the formula for the inverse Park coordinate transformation. The formula for the inverse Park transformation is shown below:

[0110]

[0111] See Figure 2 In a preferred embodiment, step S100 may further include a simulation verification process for the differential equation, specifically including:

[0112] Select the simulated d-axis current, simulated q-axis current and simulated speed under specific working conditions. For example, in one embodiment, the simulated d-axis current can be -100A, the simulated q-axis current can be 180A and the simulated speed can be 5000rpm.

[0113] Substituting the simulated d-axis current, simulated q-axis current, and simulated rotational speed into the differential equation, and fitting the result, we obtain the simulated ASC current waveform based on the differential equation. This simulated ASC current waveform is in the form of discrete points spaced apart from each other.

[0114] By comparing the simulated ASC current waveform with the actual ASC current waveform under the specific operating condition, simulation verification revealed that the peak value and oscillation frequency of the dq-axis ASC current trajectory were basically consistent with the simulation results. Therefore, the differential equation can be applied to subsequent steps.

[0115] Furthermore, since the simulation does not consider electromagnetic saturation, which occurs in actual motor control, the dq-axis inductance changes with the current. As the current increases, the d-axis inductance initially remains constant, then decreases slowly with increasing current; the q-axis inductance initially remains constant, then decreases rapidly with increasing current, but the d-axis inductance is always less than the q-axis inductance. In a preferred embodiment, considering the impact of electromagnetic saturation under actual operating conditions, the relationship between the dq-axis inductance and dq-axis current can be obtained first using motor simulation software based on electromagnetic parameters. Then, before performing ASC trajectory estimation, the corresponding dq-axis inductance can be obtained by looking up the current dq-axis current in a table, thereby reducing the impact of electromagnetic saturation on the maximum ASC trajectory estimation accuracy.

[0116] This invention also discloses a calculation system for the maximum ASC current trajectory of a three-phase permanent magnet synchronous motor, characterized in that the calculation module includes: a solution unit, which calculates the d-axis voltage U of the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate systems. d and q-axis voltage U q The solution is to determine the d-axis current i in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC (Automatic Stability Control) mode. d and q-axis current i q The differential equations are given, where the variables are the transient d-axis current, transient q-axis current, and speed of the permanent magnet synchronous motor upon entering the ASC. A unit is established to define the d-axis current i of the permanent magnet synchronous motor after entering the ASC. d and q-axis current i qThe process transforms the current trajectory expression into a three-phase current expression, where the variable in the current trajectory expression is the rotor angle of the permanent magnet synchronous motor when entering the ASC (Automatic Stability Control) state; the differentiation unit differentiates the three-phase current trajectory expression with respect to the rotor angle to obtain the extreme point expression of the three-phase current with respect to the rotor angle; the processing unit, based on the d-axis current I... d and q-axis current I q The differential equations, current trajectory expressions, and extreme point expressions are used to establish the three-phase ASC current trajectory expression. A rotational speed, sampling interval, and transient d-axis and q-axis currents are selected. The peak values ​​of the three-phase currents at the nth sampling interval and the corresponding d-axis currents i at these peak values ​​are determined. d and q-axis current i q The plotting unit calculates the initial phase of the permanent magnet synchronous motor after entering ASC based on the sampling duration determined by the nth sampling interval and the selected speed, and determines the trajectory of the three-phase maximum ASC current under the current operating condition based on the initial phase, sampling duration, selected speed, transient d-axis current, transient q-axis current and differential equation.

[0117] Smart terminals can be implemented in various forms. For example, the terminals described in this invention may include smart terminals such as mobile phones, smartphones, laptops, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), navigation devices, etc., as well as fixed terminals such as digital TVs, desktop computers, etc. Hereinafter, it is assumed that the terminal is a smart terminal. However, those skilled in the art will understand that, in addition to elements specifically designed for mobile purposes, the construction according to embodiments of the present invention can also be applied to fixed-type terminals.

[0118] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method of calculating three-phase maximum ASC current trajectory of a permanent magnet synchronous motor, characterized by, The method comprises the following steps: The d-axis voltage U of the permanent magnet synchronous motor in the rotor orientation d-axis and q-axis coordinate system is... d and q-axis voltage U q The solution is to determine the d-axis current i in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC (Automatic Stability Control) mode. d and q-axis current i q The differential equations, wherein the variables in the differential equations are the transient d-axis current, the transient q-axis current, and the speed of the permanent magnet synchronous motor when entering ASC; establishing the d-axis current i d and the q-axis current i q transforming the current trajectory expression into a three-phase current, wherein the rotor angle of the permanent magnet synchronous machine at the entry into the ASC is considered as a variable of the current trajectory expression; deriving the current trajectory expression of the three-phase current with respect to the rotor angle to obtain an extreme point expression of the three-phase current with respect to the rotor angle; differential equations of the d-axis current I d and q-axis current I q , current trajectory expressions, and extreme point expressions to establish three-phase ASC current trajectory expressions, and select a rotational speed, a sampling interval, a transient d-axis current, and a transient q-axis current to determine that the three-phase current is at a peak value at the nth sampling interval, and the d-axis current i d and q-axis current i q corresponding to the peak value three-phase current; the step of calculating the initial phase of the permanent magnet synchronous motor after entering the ASC based on the sampling duration determined in the n sampling interval, the selected rotating speed, the transient d-axis current, the transient q-axis current and the differential equation comprises:

2. The computing method of claim 1, wherein, The d-axis voltage U of the permanent magnet synchronous motor in the rotor orientation d-axis and q-axis coordinate system is... d and q-axis voltage U q Solve for the d-axis current I in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC. d and q-axis current I q The steps for solving a differential equation include: The following voltage equations are established for the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate system: d and q-axis voltages U q ​ where Ld d is the stator inductance on the d-axis, Lq q is the stator inductance on the q-axis, Ψ f is the rotor flux of the permanent magnet synchronous machine, R s is the stator resistance of the permanent magnet synchronous machine, and ω is the rotational speed of the permanent magnet synchronous machine. The d-axis voltage U d and the q-axis voltage U q are both zero, the voltage equations are transformed into the following differential equations with respect to the currents: wherein Let us set an auxiliary variable This allows the differential equation to be reduced to a homogeneous equation of the form Convert the matrix A to the Jordan canonical form: where: J and T are approximately expressed as follows: such that the auxiliary variable is approximated as Simplified auxiliary variable The approximate representation of the d-axis current i d and the q-axis current i q is obtained as follows: wherein is the transient d-axis current at the entry into the ASC, is the transient q-axis current at the entry into the ASC.

3. The computing method of claim 2, wherein, establishing a d-axis current i d and a q-axis current i q The step of transforming the current trajectory expression into a three-phase current comprises: The d-axis current i d and q-axis current i q The following current locus expression of the three-phase current after inverse Park transformation and inverse Clarke transformation: where θpm is the rotor angle of the θpermanent magnet synchronous motor at entering the ASC, where the rotor angle is the product of the rotational speed and time and the initial angle; The step of deriving the current trajectory expression of the three-phase current with respect to the rotor angle to obtain an extreme point expression of the three-phase current with respect to the rotor angle comprises: The extreme point expression is substituted into the current trajectory expression to obtain the following three-phase ASC current trajectory expression of the expression id(t) of the d-axis current in the time domain and the expression iq(t) of the q-axis current in the time domain:

4. The computing method of claim 3, wherein, based on the d-axis current I d and the q-axis current I q differential equations, current trajectory expressions, and extreme point expressions to establish a three-phase ASC current trajectory expression, and selecting a rotational speed, a sampling interval, a transient d-axis current, and a transient q-axis current to determine that the three-phase current is at a peak value at the nth sampling interval and the d-axis current i d and the q-axis current i q at the peak value correspond to the three-phase current. The step of calculating the initial phase of the permanent magnet synchronous motor after entering the ASC based on the sampling duration determined in the n sampling interval, the selected rotating speed, the transient d-axis current, the transient q-axis current and the differential equation comprises: Select a rotational speed, a sampling interval, a transient d-axis current and a transient q-axis current, and count the n sampling interval at which the three-phase current is at a peak value at all sampling time points, and the values of the peak value of the three-phase current, the d-axis current i d and the q-axis current i q corresponding to the three-phase current.

5. The computing method of claim 4, wherein, The simulated d-axis current, the simulated q-axis current and the simulated rotating speed in a specific working condition are selected; The values of the d-axis current i d and q-axis current i q corresponding to the three-phase current, the selected rotational speed, and the sampling duration determined by the n-th sampling interval are substituted into the extreme point expression and the rotational speed-angle relationship to calculate an initial phase InitTheat of the permanent magnet synchronous motor after entering the ASC. The initial phase InitTheat is substituted into the three-phase ASC current trajectory expression based on the speed-angle relationship to obtain the three-phase maximum ASC current trajectory expression about d-axis current i d and q-axis current i q in the current working condition as follows:

6. The computing method of claim 1, wherein, solving the differential equations for the d-axis current i d and the q-axis current i q after the step of entering the ASC for the permanent magnet synchronous motor, the d-axis voltage U d and the q-axis voltage U q in the d-axis and q-axis coordinate system of the permanent magnet synchronous motor. The simulated ASC current waveform based on the differential equation is fitted by substituting the simulated d-axis current, the simulated q-axis current and the simulated rotating speed into the differential equation; The simulated ASC current waveform is compared with the actual ASC current waveform in the specific working condition to simulate and verify the differential equation. The method comprises a calculation module, and the calculation module comprises:

7. A system for calculating three-phase maximum ASC current trajectories of a permanent magnet synchronous machine, characterized by, The drawing unit calculates the initial phase of the permanent magnet synchronous motor after entering the ASC based on the sampling duration determined in the n sampling interval, the selected rotating speed, the transient d-axis current, the transient q-axis current and the differential equation, and determines the three-phase maximum ASC current trajectory in the current working condition based on the initial phase, the sampling duration, the selected rotating speed, the transient d-axis current, the transient q-axis current and the differential equation. The solution element calculates the d-axis voltage U of the permanent magnet synchronous motor in the rotor-oriented d-axis and q-axis coordinate systems. d and q-axis voltage U q The solution is to determine the d-axis current i in the d-axis and q-axis coordinate systems after the permanent magnet synchronous motor enters ASC (Automatic Stability Control) mode. d and q-axis current i q The differential equations, wherein the variables in the differential equations are the transient d-axis current, the transient q-axis current, and the speed of the permanent magnet synchronous motor when entering ASC; The establishing unit establishes a d-axis current i d and a q-axis current i q into a current trajectory expression of three-phase currents, where a variable of the current trajectory expression is a rotor angle of the permanent magnet synchronous motor at entering the ASC; the deriving unit derives the current trajectory expression of the three-phase currents with respect to the rotor angle to obtain an extreme point expression of the three-phase currents with respect to the rotor angle; a processing unit configured to establish a three-phase ASC current trajectory expression based on a differential equation of the d-axis current I d and the q-axis current I q , a current trajectory expression, and an extreme point expression, select a rotational speed, a sampling interval, a transient d-axis current, and a transient q-axis current, determine that the three-phase current is at a peak value at an nth sampling interval, and determine a d-axis current i d and a q-axis current i q corresponding to the peak value of the three-phase current. ​

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