A target current calculation method, device and motor current control method

Abstract

The embodiment of the application discloses a target current calculation method, device and motor current control method, the target current calculation method comprises the following steps: d and the data relationship table of current value i q and different motor torques T; the data relationship table is based on the maximum power factor γ1 value corresponding to each current value i q selected, the corresponding relationship between current value i d and current value i q is obtained; and the corresponding motor torque T obtained by the corresponding relationship of each group of current value i d and current value i q is obtained; in the actual motor current closed-loop control process, the corresponding target current is obtained by querying the data relationship table according to the obtained motor torque; the target current comprises d-axis target current and q-axis target current. Through the embodiment scheme, the maximum power factor is realized as far as possible while meeting the motor torque demand, the system efficiency is improved, and the efficient use of electric energy is realized.

Description

Technical Field

[0001] This application relates to motor control technology, and more particularly to a target current calculation method, device, and motor current control method. Background Technology

[0002] In an electric drive system, the input current (from the DC bus) and output current (output to the motor) of the motor controller are the main control parameters of the system. By controlling the current, the target torque can be achieved and the system efficiency can be improved.

[0003] Current similar solutions include the following bus current estimation method: select a specified bus voltage value of the motor controller, then take the speed value based on a specific speed interval to obtain each speed point; at each speed point, take the torque value based on a specific torque interval to obtain each torque point. In this way, each speed point and the corresponding torque point under the specified bus voltage are obtained, and these points form a series table. Summary of the Invention

[0004] This application provides a target current calculation method, device, and motor current control method, which can achieve the maximum power factor while meeting the motor torque requirements, thereby improving system efficiency and making efficient use of electrical energy.

[0005] This application provides a method for calculating a target current, the method including:

[0006] Get the current value i d and current value i q A data relationship table relating different motor torques T; the data relationship table is based on each selected current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence is determined; and based on the correspondence, the current value i for each group is calculated. d and current value i q This is obtained from the corresponding motor torque T;

[0007] In the actual closed-loop control process of motor current, the target current is obtained by querying the data relationship table based on the acquired motor torque; the target current includes the d-axis target current and the q-axis target current.

[0008] In an exemplary embodiment of this application, based on each selected current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence is determined; and based on the correspondence, the current value i for each group is calculated. d and current value iq The corresponding motor torque T can include:

[0009] Obtain the steady-state voltage equation of the motor;

[0010] Get any time i s phase angle θ i ,u s and i s Phase difference θ,u s phase angle θ i +θ, and according to u s and i s The power factor is calculated as γ = cosθ based on the phase difference θ.

[0011] Based on the steady-state voltage equation, according to the phase angle θ i The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The first relationship between the power factor γ and the motor torque T;

[0012] Based on the first relationship, select multiple current values ​​i q Based on each current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence is determined; and based on the correspondence, the current value i for each group is calculated. d and current value i q The corresponding motor torque T.

[0013] In an exemplary embodiment of this application, the step is based on the steady-state voltage equation, according to the phase angle θ. i The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The first relationship between the power factor γ and the motor torque T can include:

[0014] Based on the steady-state voltage equation, according to the phase angle θ i The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The power factor is γ = cosθ, the motor torque is T, and the magnetic flux linkage Ψ of the motor rotor permanent magnet is Ψ. p and the inductance values ​​L along the d-axis and q-axis d and Lq The second relation between them;

[0015] The motor rotor permanent magnet flux Ψ in the second relation is obtained according to the preset first method. p Inductance value L along the d-axis d and the inductance value L along the q-axis q The power factor γ is calculated using a pre-defined second method.

[0016] The obtained permanent magnet flux linkage Ψ of the motor rotor p The inductance value L of the d-axis d The inductance value L of the q-axis q And by substituting the power factor γ into the second relational expression, the first relational expression is obtained.

[0017] In an exemplary embodiment of this application, the first method may include a parameter identification method; the second method may include a bench test method.

[0018] In an exemplary embodiment of this application, the step of selecting multiple current values ​​i based on the first relational expression is... q Based on each current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence can include:

[0019] Based on the first relationship, select multiple current values ​​i q Substitute them sequentially into the first relational expression; where 0 q ≤i max Every two current values ​​i q The numerical interval between them is a fixed value Δi q i max This is the preset maximum current value for the q-axis;

[0020] Calculate each current value i q The maximum power factor γ1 corresponding to the value is used to calculate the corresponding current value i based on the first relationship. d With current value i q The correspondence.

[0021] In an exemplary embodiment of this application, the steady-state voltage equation may include:

[0022] u d =R s i d -ωL q i q ;

[0023] u q =R​s i q +ωL d i d +ωΨ p ;

[0024] Among them, u d u q These are the voltage values ​​along the d-axis and q-axis, respectively. s It is a vector-synthesized voltage, and i q These are the current values ​​along the d-axis and q-axis, respectively. s It is a vector-synthesized current, and R s ω is the equivalent resistance of the motor stator winding on the dq axis, and ω is the rotational speed of the motor rotor.

[0025] In an exemplary embodiment of this application, the step is based on the steady-state voltage equation, according to the phase angle θ. i The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The power factor is γ = cosθ, the motor torque is T, and the magnetic flux linkage Ψ of the motor rotor permanent magnet is Ψ. p and the inductance values ​​L along the d-axis and q-axis d and L q The second relation between them can include:

[0026] The steady-state voltage equation and the preset third relation are combined. Substitute into the pre-defined fourth relation Obtain the second relation:

[0027] In an exemplary embodiment of this application, the current value i for each group is calculated based on the correspondence. d and current value i q Before obtaining the corresponding motor torque T, the method may further include: obtaining the calculation formula for the motor torque T;

[0028] The formula for calculating the motor torque T may include:

[0029] T = 1.5p(Ψ) p i q +(L d -L q )i d i q ).

[0030] This application also provides a target current calculation device, characterized in that it includes a processor and a computer-readable storage medium, wherein the computer-readable storage medium stores instructions, and when the instructions are executed by the processor, the target current calculation method is implemented.

[0031] This application embodiment also provides a motor current control method, the method may include:

[0032] In the actual closed-loop control of motor current, the target current is obtained based on the target current calculation method described above; the target current includes the d-axis target current and the q-axis target current.

[0033] Three-phase current i is collected by a current sensor a i b and i c and the three-phase current i a i b and i c The actual current is obtained after conversion; the actual current includes the d-axis actual current and the q-axis actual current.

[0034] The target current and the actual current are subjected to proportional-integral-derivative (PID) control to control the actual current of the motor to approximate the target current.

[0035] Compared with related technologies, the embodiments of this application include: acquiring the current value i d and current value i q A data relationship table relating different motor torques T; the data relationship table is based on each selected current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence is determined; and based on the correspondence, the current value i for each group is calculated. d and current value i q The target current is obtained by referring to the corresponding motor torque T. During the actual closed-loop control of the motor current, the target current is obtained by querying the data relationship table based on the acquired motor torque; the target current includes the d-axis target current and the q-axis target current. This embodiment achieves the maximum power factor while meeting the motor torque requirements, improving system efficiency and realizing efficient use of electrical energy.

[0036] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the solutions described in the description and the accompanying drawings. Attached Figure Description

[0037] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0038] Figure 1 This is a flowchart of the target current calculation method according to an embodiment of this application;

[0039] Figure 2 For obtaining each group of current values ​​i in this application embodiment d and current value i q The corresponding flowchart for the method of controlling the motor torque T;

[0040] Figure 3 i, as an embodiment of this application d Vector diagram of dq-axis voltage and current when <0;

[0041] Figure 4 This is a block diagram of the target current calculation device according to an embodiment of this application;

[0042] Figure 5 This is a flowchart of the motor current control method according to an embodiment of this application;

[0043] Figure 6 This is a schematic diagram of closed-loop control of motor current according to an embodiment of this application. Detailed Implementation

[0044] This application describes several embodiments, but these descriptions are exemplary and not limiting, and it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with or in lieu of any other feature or element in any other embodiment.

[0045] This application includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features, and elements disclosed in this application may also be combined with any conventional features or elements to form a unique inventive scheme as defined by the claims. Any feature or element of any embodiment may also be combined with features or elements from other inventive schemes to form another unique inventive scheme as defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in this application may be implemented individually or in any suitable combination. Therefore, the embodiments are not limited except by the limitations imposed by the appended claims and their equivalents. Furthermore, various modifications and changes may be made within the scope of the appended claims.

[0046] Furthermore, in describing representative embodiments, the specification may have presented methods and / or processes as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that it does not depend on such a specific order. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Moreover, the claims concerning the method and / or process should not be limited to the steps performed in the written order, and those skilled in the art will readily understand that these orders can be varied and still remain within the spirit and scope of the embodiments of this application.

[0047] This application provides a method for calculating a target current, such as... Figure 1 As shown, the method may include steps S101-S102:

[0048] S101, Obtain the current value i d and current value i q A data relationship table relating different motor torques T; the data relationship table is based on each selected current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence is determined; and based on the correspondence, the current value i for each group is calculated. d and current value i q This is obtained from the corresponding motor torque T;

[0049] S102. In the actual motor current closed-loop control process, based on the acquired motor torque, the corresponding target current is obtained by querying the data relationship table; the target current includes the d-axis target current and the q-axis target current.

[0050] In an exemplary embodiment of this application, the motor may include, but is not limited to, a permanent magnet synchronous motor. Based on the steady-state mathematical model of the permanent magnet synchronous motor, considering the power factor γ of the motor, a conversion relationship between the power factor and the dq-axis control current of the motor is established, and then the torque of the motor is associated with it. Finally, a method for estimating the torque and dq-axis current that satisfies the maximum power factor is realized.

[0051] In an exemplary embodiment of this application, in the control of a permanent magnet synchronous motor, the fundamental frequencies of the voltage and current output by the inverter to the motor are both sinusoidal waves; assuming:

[0052] The expression for the fundamental voltage wave is: u(t) = U m sin(ωt);

[0053] Among them, U m Let ω be the voltage amplitude, ω = 2πf = 2π / T, f be the frequency, and T be the period. Assume the initial phase of the voltage is zero.

[0054] The expression for the fundamental current wave is: i(t) = I m sin(ωt+θ);

[0055] Among them, I m ω is the amplitude, θ is the phase difference between the current and voltage; ω = 2πf = 2π / T, f is the frequency, and T is the period;

[0056] The average power in the circuit is:

[0057] in: U and I are the effective values ​​of voltage and current, respectively.

[0058] Based on the definition of power factor, we know that:

[0059] Apparent power is the product of the effective value of voltage and the effective value of current, i.e.: S = UI;

[0060] Active power is the average power of a circuit, i.e.: P = UIcosθ;

[0061] Reactive power is defined as: Q = UIsinθ;

[0062] The power factor γ is defined as the ratio of active power P to apparent power S, i.e.:

[0063] γ = P / S = cosθ; (2)

[0064] The relationship between reactive power Q, active power P, and apparent power S is as follows:

[0065] S 2 =P 2 +Q 2 .

[0066] In the exemplary embodiments of this application, in reality, the power factor is a coefficient that measures the efficiency of a motor. A low power factor indicates that the reactive power used for alternating magnetic field conversion in the circuit is large, which reduces the utilization rate of the motor input voltage and increases energy loss.

[0067] In an exemplary embodiment of this application, it can be seen from equation (2) that the motor control parameter that affects the power factor γ is the phase difference θ between the fundamental current and the fundamental voltage. When θ is zero, γ is at its maximum value of 1. Therefore, in the process of controlling the permanent magnet synchronous motor, ensuring that the fundamental phase difference between the voltage and the current is infinitely close to zero can improve the efficiency of the motor.

[0068] In an exemplary embodiment of this application, this solution provides a method for estimating the control parameters of a motor: the dq-axis current, i.e., idq axis current, based on the control objective that the fundamental phase difference between the voltage and current is zero. d and i q The dq axis belongs to the dq coordinate system in the mathematical model of the motor.

[0069] In exemplary embodiments of this application, as Figure 2 As shown, based on each selected current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence is determined; and based on the correspondence, the current value i for each group is calculated. d and current value i q The corresponding motor torque T may include steps S201-S204:

[0070] S201. Obtain the steady-state voltage equation of the motor.

[0071] In an exemplary embodiment of this application, the steady-state voltage equation may include:

[0072] u d =R s i d -ωL q i q (3)

[0073] u q =R s i q +ωL d i d +ωΨ p (4)

[0074] Among them, u d u q These are the voltage values ​​along the d-axis and q-axis, respectively. sIt is a vector-synthesized voltage, and

[0075] i d i q These are the current values ​​along the d-axis and q-axis, respectively. s It is a vector-synthesized current, and

[0076] R s This is the equivalent resistance of the motor stator winding on the dq axis (usually a very small value);

[0077] ω is the rotational speed of the motor rotor, Ψ p For permanent magnet flux linkage of motor rotor;

[0078] L d L q These are the inductance values ​​along the d-axis and q-axis, respectively; θ is the inductance value of u. s and i s The phase difference.

[0079] In an exemplary embodiment of this application, i is represented by a vector graphic. d dq axis voltage and current when <0, such as Figure 3 As shown.

[0080] S202, Obtain any time i s phase angle θ i ,u s and i s Phase difference θ,u s phase angle θ i +θ, and according to u s and i s The power factor is calculated as γ = cosθ based on the phase difference θ.

[0081] In an exemplary embodiment of this application, at a certain moment i s The phase angle is θ i , θ is u s and i s The phase difference, then u s The phase angle is (θ) i +θ), at this moment the power factor is γ=cosθ;

[0082] but:

[0083] tanθ=tan(cos -1 γ). (7)

[0084] S203. Based on the steady-state voltage equation, according to the phase angle θi The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The first relationship between the power factor γ and the motor torque T.

[0085] In an exemplary embodiment of this application, the step is based on the steady-state voltage equation, according to the phase angle θ. i The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The first relationship between the power factor γ and the motor torque T can include:

[0086] Based on the steady-state voltage equation, according to the phase angle θ i The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The power factor is γ = cosθ, the motor torque is T, and the magnetic flux linkage Ψ of the motor rotor permanent magnet is Ψ. p and the inductance values ​​L along the d-axis and q-axis d and L q The second relation between them;

[0087] The motor rotor permanent magnet flux Ψ in the second relation is obtained according to the preset first method. p Inductance value L along the d-axis d and the inductance value L along the q-axis q The power factor γ is calculated using a pre-defined second method.

[0088] The obtained permanent magnet flux linkage Ψ of the motor rotor p The inductance value L of the d-axis d The inductance value L of the q-axis q And by substituting the power factor γ into the second relational expression, the first relational expression is obtained.

[0089] In an exemplary embodiment of this application, the step is based on the steady-state voltage equation, according to the phase angle θ. i The phase difference θ, the phase angle θ i Using +θ and the power factor γ, calculate the d-axis current value i. d q-axis current value i q The power factor is γ = cosθ, the motor torque is T, and the magnetic flux linkage Ψ of the motor rotor permanent magnet is Ψ. p and the inductance values ​​L along the d-axis and q-axisd and L q The second relation between them can include:

[0090] The steady-state voltage equation and the preset third relation are combined. Substitute into the pre-defined fourth relation Obtain the second relation:

[0091] In an exemplary embodiment of this application, equations (3), (4), and (6) are substituted into equation (5), and the resistance R is ignored. s The following equation (8) can be obtained as the second relation:

[0092]

[0093] In an exemplary embodiment of this application, the first method may include a parameter identification method; the second method may include a bench test method.

[0094] In an exemplary embodiment of this application, p in equation (8) is the number of pole pairs of the motor, Ψ p L d L q These are all parameters of the motor. These three parameters can be obtained using parameter identification methods, meaning they are known parameters. The power factor γ can be obtained through bench testing. (The last part, "i", appears to be a typo and can be omitted.) q The corresponding maximum power factor value γ1, i, is determined through bench testing. q The corresponding data table for γ1.

[0095] S204. Based on the first relationship, select multiple current values ​​i q Based on each current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence is determined; and based on the correspondence, the current value i for each group is calculated. d and current value i q The corresponding motor torque T.

[0096] In an exemplary embodiment of this application, the step of selecting multiple current values ​​i based on the first relational expression is... q Based on each current value i q Calculate the current value i based on the corresponding maximum power factor γ1. d With current value i q The correspondence can include:

[0097] Based on the first relationship, select multiple current values ​​i qSubstitute them sequentially into the first relational expression; where 0 q ≤i max Every two current values ​​i q The numerical interval between them is a fixed value Δi q i max This is the preset maximum current value for the q-axis;

[0098] Calculate each current value i q The maximum power factor γ1 corresponding to the value is used to calculate the corresponding current value i based on the first relationship. d With current value i q The correspondence.

[0099] In an exemplary embodiment of this application, based on the known parameter Ψ p L d L q Substituting into the resulting equation (8), i.e. the first relation, select multiple i q Current point, where 0 q ≤i max Let each i q The interval between the numbers is a fixed Δi q Then based on each i q Find the maximum γ value γ1 corresponding to the value of i. d with i q This will generate a data set in the format of Table 1, corresponding to the list.

[0100] Table 1

[0101]

[0102] In an exemplary embodiment of this application, the current value i for each group is calculated based on the correspondence. d and current value i q Before obtaining the corresponding motor torque T, the method may further include: obtaining the calculation formula for the motor torque T;

[0103] The formula for calculating the motor torque T may include:

[0104] T = 1.5p(Ψ) p i q +(L d -L q )i d i q (9)

[0105] In an exemplary embodiment of this application, i as shown in Table 1 above q i d Based on the array sequence, and combined with equation (9), the array sequence corresponding to the torque T can be obtained, as shown in Table 2:​​

[0106] Table 2

[0107]

[0108] In an exemplary embodiment of this application, the current i is determined by the above scheme. d i q The relationship between torque T and power factor γ can be determined, and the corresponding data relationship tables can be obtained (as shown in Table 1 and Table 2).

[0109] This application also provides a target current calculation device 1, such as... Figure 4 As shown, it includes a processor 11 and a computer-readable storage medium 12, wherein the computer-readable storage medium 12 stores instructions that, when executed by the processor 11, implement the target current calculation method.

[0110] In the exemplary embodiments of this application, any of the embodiments in the foregoing target current calculation method embodiments are applicable to the device embodiments, and will not be described in detail here.

[0111] This application also provides a method for controlling motor current, such as... Figure 5 As shown, the method may include steps S301-S303:

[0112] S301. In the actual closed-loop control process of motor current, the target current is obtained based on the target current calculation method described above; the target current includes the d-axis target current and the q-axis target current.

[0113] S302, Collect three-phase current i through a current sensor a i b and i c and the three-phase current i a i b and i c The actual current is obtained after conversion; the actual current includes the d-axis actual current and the q-axis actual current.

[0114] S303. Perform proportional-integral-derivative (PID) control on the target current and the actual current to control the actual current of the motor to approach the target current.

[0115] In an exemplary embodiment of this application, a correspondence table (i.e., a data relationship table) between torque and dq-axis current is estimated using the method described above. Then, in the actual motor current closed-loop control, as... Figure 6 As shown, based on the above torque and current i q and i d The relationship table is used to look up the current corresponding to the current torque. and The value, used as the target value of the current, i.e., the target current, is the three-phase current i collected from the current sensor. a i b and i c The actual current i is obtained after Clark / Park conversion. q and i d The target current and the actual current are controlled by PID (Proportional Integral Derivative) control, which in turn controls the actual current of the motor to approach the target current.

[0116] In the exemplary embodiments of this application, the solutions of this application include at least the following advantages: while meeting the motor torque requirements, the maximum power factor can be achieved as quickly as possible, thereby improving system efficiency and making efficient use of electrical energy.

[0117] It will be understood by those skilled in the art that all or some of the steps, systems, or apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software may be distributed on a computer-readable medium, which may include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

Claims

1. A method for calculating a target current, characterized in that, The method includes: Obtain current value and current value A data relationship table showing the relationship between different motor torques T; the data relationship table is based on each selected current value. The corresponding maximum power factor 1. Calculate the current value. With current value The correspondence, where each current value The corresponding maximum power factor The value is determined based on bench testing; and based on the aforementioned correspondence, the current value for each group is calculated respectively. and current value This is obtained from the corresponding motor torque T; In the actual closed-loop control process of motor current, the target current is obtained by querying the data relationship table based on the acquired motor torque; the target current includes the d-axis target current and the q-axis target current. Among them, based on each selected current value The corresponding maximum power factor 1. Calculate the current value. With current value The correspondence is determined; and based on the correspondence, the current value for each group is calculated. and current value The corresponding motor torque T includes: Obtain the steady-state voltage equation of the motor; Get any time phase angle , phase difference , phase angle and according to phase difference Calculate the power factor as follows ,in For vector-synthesized voltage, and For vector composite current; Based on the steady-state voltage equation, according to the phase angle The phase difference The phase angle and the power factor Calculate the current value along the d-axis. q-axis current value Power factor is And the first relationship between the motor torque T; Based on the first relationship, multiple current values ​​are selected. Based on each current value The corresponding maximum power factor 1. Calculate the current value. With current value The correspondence is determined; and based on the correspondence, the current value for each group is calculated. and current value The corresponding motor torque T.

2. The target current calculation method according to claim 1, characterized in that, Based on the steady-state voltage equation, according to the phase angle The phase difference The phase angle and the power factor Calculate the current value along the d-axis. q-axis current value Power factor is And the first relationship between the motor torque T and the torque T includes: Based on the steady-state voltage equation, according to the phase angle The phase difference The phase angle and the power factor Calculate the current value along the d-axis. q-axis current value Power factor is Motor torque T, motor rotor permanent magnet flux linkage and the inductance values ​​of the d-axis and q-axis The second relation between them; The permanent magnet flux linkage of the motor rotor is obtained in the second relational formula according to the preset first method. Inductance value of the d-axis Inductance value along the q-axis The power factor was calculated using a bench test method. ; The obtained permanent magnet flux linkage of the motor rotor The inductance value of the d-axis The inductance value of the q-axis and the power factor Substitute the second relation into the first relation to obtain the second relation.

3. The target current calculation method according to claim 2, characterized in that, The first method includes: a parameter identification method.

4. The target current calculation method according to claim 2, characterized in that, Based on the first relationship, multiple current values ​​are selected. Based on each current value The corresponding maximum power factor 1. Calculate the current value. With current value The correspondence includes: Based on the first relationship, multiple current values ​​are selected. Substitute them sequentially into the first relational expression; where Every two current values The numerical intervals between them are fixed values. ; This is the preset maximum current value for the q-axis; Calculate each current value The maximum power factor corresponding to the value 1. Calculate the corresponding current value based on the first relationship. With current value The correspondence.

5. The target current calculation method according to claim 2 or 4, characterized in that, The steady-state voltage equation includes: ; ; in, These are the voltage values ​​along the d-axis and q-axis, respectively. It is a vector-synthesized voltage, and ; These are the current values ​​along the d-axis and q-axis, respectively. It is a vector-synthesized current, and ; Let be the equivalent resistance of the motor stator winding on the dq axis. This refers to the rotational speed of the motor rotor.

6. The target current calculation method according to claim 5, characterized in that, Based on the steady-state voltage equation, according to the phase angle The phase difference The phase angle and the power factor Calculate the current value along the d-axis. q-axis current value Power factor is Motor torque T, motor rotor permanent magnet flux linkage and the inductance values ​​of the d-axis and q-axis The second relation between them includes: The steady-state voltage equation and the preset third relation are combined. Substitute into the preset fourth relation Obtain the second relation: .

7. The target current calculation method according to claim 1, characterized in that, Based on the aforementioned correspondence, the current values ​​for each group are calculated. and current value Before obtaining the corresponding motor torque T, the method further includes: obtaining the calculation formula for the motor torque T; The formula for calculating the motor torque T includes: ,in, It is the magnetic flux linkage of the permanent magnet in the motor rotor. It is the inductance value along the d-axis. It is the inductance value along the q-axis. It is the current value along the d-axis, and This is the current value along the q-axis.

8. A target current calculation device, characterized in that, The device includes a processor and a computer-readable storage medium storing instructions that, when executed by the processor, implement the target current calculation method as described in any one of claims 1-7.

9. A method for controlling motor current, characterized in that, The method includes: In the actual closed-loop control of motor current, the target current is obtained based on the target current calculation method described in any one of claims 1-7; the target current includes the d-axis target current and the q-axis target current. Three-phase current is collected using a current sensor. and the three-phase current The actual current is obtained after conversion. The actual current includes the d-axis actual current and the q-axis actual current; The target current and the actual current are subjected to proportional-integral-derivative (PID) control to control the actual current of the motor to approximate the target current.

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