MTPA control method for interior permanent magnet synchronous motor based on virtual signal injection

Abstract

The present invention discloses a control method for an internal permanent magnet synchronous motor (MTPA) using virtual signal injection. The method specifically comprises the following steps: Step 1: establishing a mathematical model of the electromagnetic torque after injecting a virtual DC signal; Step 2: calculating the partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis using the electromagnetic torque mathematical model obtained in Step 1; and Step 3: calculating the d-axis and q-axis stator current setpoints using the partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis obtained in Step 2. The present invention solves the problem that conventional virtual injection methods ignore the high-order partial derivatives of the torque and the angle between the current vector and the d-axis, causing the MTPA current trajectory to deviate from the optimal trajectory.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet synchronous motor control, and relates to a virtual signal injection built-in permanent magnet synchronous motor MTPA control method. Background Art

[0002] Interior permanent magnet synchronous motors (IPMSMs) are widely used in military, aerospace, industrial, medical, and civilian applications due to their compact structure, high power density, and wide magnetic weakening range. To improve motor efficiency and fully utilize reluctance torque, maximum torque-to-current (MTPA) control is typically employed in the constant torque region. MTPA requires accurate motor parameters to obtain a current reference value. However, due to variations in motor parameters caused by magnetic saturation and cross-coupling effects, the MTPA current trajectory deviates from the optimal trajectory, making accurate MTPA impossible. Therefore, achieving accurate MTPA under conditions of varying motor parameters is key to improving IPMSM efficiency.

[0003] Currently, in the IPMSM MTPA method, the virtual signal injection method injects a virtual signal to obtain the partial derivatives of the torque and current vector with the d-axis angle, thereby achieving MTPA. Since the virtual signal is not actually injected into the motor, additional losses are avoided, and this has led to extensive research and application. Traditional virtual injection methods ignore the higher-order partial derivatives of the torque and current vector with the d-axis angle. However, the magnitude of these higher-order partial derivatives is related to the stator current and the amplitude of the injected signal. The larger the stator current and the amplitude of the injected signal, the larger the higher-order partial derivatives. This results in inaccurate partial derivatives of the torque and current vector with the d-axis angle, which in turn causes the MTPA current trajectory to deviate from the optimal trajectory, making it impossible to accurately achieve maximum torque-to-current ratio control. Summary of the Invention

[0004] The purpose of the present invention is to provide a built-in permanent magnet synchronous motor (MTPA) control method using virtual signal injection, which solves the problem that the existing traditional virtual injection method ignores the high-order partial derivatives of the angle between the torque and the current vector and the d-axis, causing the MTPA current trajectory to deviate from the optimal trajectory, thereby achieving accurate control of the maximum torque-to-current ratio.

[0005] The technical solution adopted by the present invention is a method for controlling an internal permanent magnet synchronous motor (MTPA) with virtual signal injection, which specifically includes the following steps:

[0006] Step 1, establishing a mathematical model of electromagnetic torque after injecting a virtual DC signal;

[0007] Step 2, calculating the partial derivative of the electromagnetic torque and the angle between the stator current vector and the d-axis using the electromagnetic torque mathematical model obtained in step 1;

[0008] Step 3: Calculate the given values ​​of the d-axis and q-axis stator currents from the partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis obtained in step 2.

[0009] The present invention is also characterized in that:

[0010] The specific process of step 1 is:

[0011] The torque equation of IPMSM in dq-axis synchronous coordinates is expressed as:

[0012]

[0013] Among them, T e is the electromagnetic torque; i d and i q are the d-axis stator current and the q-axis stator current respectively; L d and L q are the d-axis stator inductance and the q-axis stator inductance respectively; f is the permanent magnet flux amplitude; p is the number of pole pairs;

[0014] The relationship between the stator current vector and the d-axis and q-axis stator current components is:

[0015]

[0016] Among them, I s is the amplitude of the current vector; β is the current vector angle, that is, the angle between the current vector and the d-axis;

[0017] When the amplitude of the current vector is constant, there is an optimal current angle that maximizes the output torque of the IPMSM;

[0018] During steady-state operation, the voltage equation is expressed as:

[0019]

[0020] Among them, u d and u q are the d-axis stator voltage and the q-axis stator voltage respectively; R is the stator resistance; ω e is the rotor angular frequency;

[0021] According to formula (1), the electromagnetic torque after injecting the constant signal A is:

[0022]

[0023] in, is the electromagnetic torque after the constant signal A is injected into the d-axis, It is the electromagnetic torque after the constant signal A is injected into the q-axis; A is the injected constant signal.

[0024] The specific process of step 2 is:

[0025] Calculate the electromagnetic torque T by formula (1) e The derivative with respect to β is expressed as:

[0026]

[0027] Combining formula (2), formula (5) can be further expressed as

[0028]

[0029] According to formula (1), we can get T e to i d and i q The partial derivative of is shown in the following formula (7):

[0030]

[0031] Then equations (1), (4) and (7) can be expressed as follows:

[0032]

[0033] According to formula (8), T e to i d The partial derivative of is expressed as:

[0034]

[0035] According to formula (9), T e to i q The partial derivative of is expressed as:

[0036]

[0037] Substituting equations (10) and (11) into equation (6), we get T e Partial derivative with respect to β

[0038]

[0039] From formula (12), we can conclude that by controlling The optimal current vector angle when the motor is running at the MTPA operating point can be obtained by approaching zero. The d-axis and q-axis current given values ​​are set by this current angle. From formula (3), we can get:

[0040]

[0041] Among them, the stator resistance R is a constant;

[0042] Substitute equation (13) into equation (1), T e Expressed as:

[0043]

[0044] Substitute equation (13) into equation (4), Expressed as:

[0045]

[0046] Substituting equations (14), (15), and (16) into equation (12), we can obtain the partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis:

[0047]

[0048] In step 2, due to f changes with temperature, so through i d Yes f Make the corrections as follows:

[0049]

[0050] Among them, f0 K is the offline self-learning permanent magnet flux; p is the proportional gain, K i is the integral gain; i dref is the stator current reference; α1 and α2 are the characteristic angular frequencies of the low-pass filter, and s is the complex frequency.

[0051] The specific process of step 3 is:

[0052] The setting method of d-axis given current is:

[0053] When the motor runs below the reference speed, the d-axis reference current is obtained by integrating the calculated formula (17), as shown in the following formula (19):

[0054]

[0055] The setting method of q-axis given current is:

[0056] When the d-axis current and q-axis current are given currents and the electromagnetic torque is given torque, i qref Expressed as:

[0057]

[0058] The q-axis current reference obtained by equation (20) cannot obtain the required torque. Combining equations (7) and (20), i qref Expressed as:

[0059]

[0060] Among them, i qref is the q-axis current reference value; T e-ref is the electromagnetic torque reference value.

[0061] The beneficial effect of the present invention is that, compared with the conventional virtual injection MPTA method, the acquisition of partial derivative information by the present method avoids the influence of higher-order partial derivatives ignored by conventional methods of injecting virtual signals along the current angle. It accurately extracts the partial derivatives of torque and the angle between the current vector and the d-axis, enabling accurate maximum torque-to-current ratio control. By using partial derivative information of torque with respect to the q-axis current, it is possible to set a q-axis current reference value that is independent of motor parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a block diagram of a vector control system used in the MTPA control method for a built-in permanent magnet synchronous motor with virtual signal injection according to the present invention;

[0063] Figure 2 This is a block diagram of the MTPA control method for generating d-axis and q-axis reference currents used in the interior permanent magnet synchronous motor MTPA control method with virtual signal injection of the present invention;

[0064] Figure 3 This is a block diagram of the online correction of permanent magnet flux linkage used in the MTPA control method of the interior permanent magnet synchronous motor with virtual signal injection of the present invention;

[0065] Figure 4 This is a simulation diagram of the current vector angle waveform of the interior permanent magnet synchronous motor MTPA control method without using the virtual signal injection of the present invention;

[0066] Figure 5 This is a simulation diagram of the current vector angle waveform of the MTPA control method for a built-in permanent magnet synchronous motor using the virtual signal injection of the present invention. DETAILED DESCRIPTION

[0067] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] Example 1

[0069] The vector control system block diagram of the MTPA control method for the virtual signal injection of the present invention is as follows: Figure 1 As shown in the figure, the system consists of three PI regulators, forming a double closed-loop control of the speed loop and the current loop. The output of the speed loop PI regulator is T e ; Mechanical angular frequency ω detected by the encoder m and the current value i in the two-phase synchronous rotating coordinate system d 、i q and the voltage u of the d-axis and q-axisd 、u q As Figure 2 Given the values ​​of the d-axis and q-axis current reference generation schematic shown, the output of the d-axis and q-axis current reference generation schematic is i dref and i qref ; d-axis reference current i dref and q-axis reference current i qref As the input of the current loop PI regulator, the output of the current regulator controls the power electronic converter.

[0070] The mechanical angular frequency ω of the rotor is detected by installing an encoder on the rotor shaft of the high-speed permanent magnet synchronous motor. m , set the given mechanical angular frequency of the speed loop The mechanical angular frequency ω detected by the encoder m The output of the speed loop PI regulator is T e ; Mechanical angular frequency ω detected by the encoder m and the current value i in the two-phase synchronous rotating coordinate system d 、i q and the voltage u of the d-axis and q-axis d 、u q As Figure 2 The input of the d-axis and q-axis current reference generation schematic is shown, and the output of the d-axis and q-axis current reference generation schematic is i dref and i qref ; d-axis reference current i dref and q-axis reference current i qref As the input of the current loop PI regulator, the stator current i of the permanent magnet synchronous motor in the three-phase stationary coordinate system is detected by the current Hall sensor. a 、i b 、i c ; Detected three-phase stator current i a 、i b 、i c Through abc / αβ transformation, the current value i is converted to the two-phase stationary coordinate system α 、i β ;i α 、i β Through αβ / dq transformation, the current value i is converted to the two-phase synchronous rotating coordinate system d 、i q ; d-axis reference current i dref With the feedback current i d The PI controller outputs the d-axis voltage u through the current loop. d , q-axis reference current i qref With the feedback current i q The PI controller outputs the q-axis voltage u through the current loop. q ;ud 、u q After dq / αβ transformation, the two-phase voltage u in the two-phase stationary coordinate system is obtained α 、u β , then the three-phase inverter is controlled through SVPWM modulation, and finally the permanent magnet synchronous motor is driven to work.

[0071] Example 2

[0072] The MTPA control method of the interior permanent magnet synchronous motor with virtual signal injection of the present invention is specifically implemented according to the following steps:

[0073] Step 1: Establish a mathematical model of electromagnetic torque after injecting a virtual DC signal, specifically:

[0074] The torque equation of IPMSM in dq-axis synchronous coordinates can be expressed as:

[0075]

[0076] Among them, T e is the electromagnetic torque; i d and i q are the d-axis stator current and the q-axis stator current respectively; L d and L q are the d-axis stator inductance and the q-axis stator inductance respectively; f is the magnetic flux amplitude of the permanent magnet; p is the number of pole pairs.

[0077] The relationship between the stator current vector and the d-axis and q-axis stator current components is:

[0078]

[0079] Among them, I s is the amplitude of the current vector; β is the current vector angle, that is, the angle between the current vector and the d-axis.

[0080] When the amplitude of the current vector is constant, there is an optimal current angle that can maximize the output torque of the IPMSM.

[0081] During steady-state operation, the voltage equation can be expressed as:

[0082]

[0083] Among them, u d and u q are the d-axis stator voltage and the q-axis stator voltage respectively; R is the stator resistance; ω e is the rotor angular frequency;

[0084] According to formula (1), the electromagnetic torque after injecting the constant signal A is:

[0085]

[0086] in, is the electromagnetic torque after the constant signal A is injected into the d-axis, It is the electromagnetic torque after the constant signal A is injected into the q-axis; A is the injected constant signal.

[0087] Step 2: Calculate the electromagnetic torque mathematical model obtained in step 1 as follows: Figure 2 The partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis are shown as follows:

[0088] Calculate the electromagnetic torque T by formula (1) e The derivative with respect to β can be expressed as:

[0089]

[0090] Combined with formula (2), formula (5) can be further expressed as

[0091]

[0092] According to formula (1), we can get T e to i d and i q The partial derivative of

[0093]

[0094] Then from formula (1), formula (4) and formula (7), we can get

[0095]

[0096] From formula (8), we can get T e to i d The partial derivative of can be expressed as:

[0097]

[0098] From formula (9), we can get T e to i q The partial derivative of can be expressed as:

[0099]

[0100] Substituting equations (10) and (11) into equation (6), we can get T e Partial derivative with respect to β:

[0101]

[0102] From formula (12), we can see that by controlling The optimal current vector angle when the motor is running at the MTPA operating point can be obtained by approaching zero. The d-axis and q-axis current given values ​​are set by this current angle. From formula (3), we can get

[0103]

[0104] Since the stator resistance is very small and does not change with the current, the stator resistance R can be regarded as a constant. Substituting equation (13) into equation (1), T e It can be expressed as:

[0105]

[0106] Substitute equation (13) into equation (4), It can be expressed as

[0107]

[0108] Substituting equations (14), (15), and (16) into equation (12), we can calculate the partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis.

[0109]

[0110] Ψ f Mainly changes with the change of temperature, the present invention through i d Yes f Make corrections, such as Figure 3 shown.

[0111]

[0112] Among them, f0 K is the offline self-learning permanent magnet flux; p is the proportional gain, K i is the integral gain; i dref is the stator current reference; α1 and α2 are the characteristic angular frequencies of the low-pass filter, α1 is 10*2Πrad / s, α2 is 5*2Πrad / s; s is the complex frequency.

[0113] Step 3: Calculate the partial derivative of the electromagnetic torque and the angle between the stator current vector and the d-axis obtained in step 2 as follows: Figure 2 The d-axis and q-axis stator current given values ​​are shown as follows:

[0114] The setting method of d-axis given current is:

[0115] When the motor runs below the reference speed, the d-axis reference current is obtained by integrating the formula (17):

[0116]

[0117] The setting method of q-axis given current is:

[0118] When the d-axis current and q-axis current are given currents and the electromagnetic torque is given torque, i qref It can be expressed as:

[0119]

[0120] However, the parameters of the motor are uncertain during operation, and the q-axis current reference obtained by equation (20) cannot obtain the required torque. Combining equations (7) and (20), i qref It can be expressed as:

[0121]

[0122] Among them, i qref is the q-axis current reference; T e-ref is the electromagnetic torque reference.

[0123] Figure 4 is the current vector angle waveform when the method of the present invention is not adopted; Figure 5 : is the current vector angle waveform using the method of the present invention.

[0124] Example 3

[0125] The parameters of the permanent magnet synchronous motor are set according to Table 1 below, and the method in Example 2 is simulated. The motor speed is set to a rated speed of 500 rpm, and the load dragged by the motor is a rated load of 10 N.m.

[0126] Table 1 Parameters of permanent magnet synchronous motor

[0127] parameter Numerical parameter Numerical Rated power 3kW Rated torque 10N.m Pole pairs 4 Rated current 9.6A Rated speed 500rpm Rated frequency 500Hz

[0128] The simulation results are as follows:

[0129] from Figure 4 It can be seen that the actual MTPA point deviates from the ideal MTPA point; Figure 5 As can be seen from the figure, the actual MTPA angle quickly tracks the ideal MTPA point; Figure 4 and Figure 5 It can be found that the method proposed in the present invention can significantly improve the MTPA tracking accuracy. The above simulation results show that the MTPA control method of the built-in permanent magnet synchronous motor with virtual signal injection in the present invention can solve the problem of the MTPA current trajectory deviating from the optimal trajectory and realize accurate control of the maximum torque-to-current ratio.

Claims

1. A virtual signal injection control method for an interior permanent magnet synchronous motor (MTPA) is characterized by: The specific steps include: Step 1: Establish a mathematical model of electromagnetic torque after injecting a virtual DC signal; the specific process of step 1 is: the torque equation of IPMSM in dq axis synchronous coordinates is expressed as: （1） in, T e is the electromagnetic torque; i d and i q are the d-axis stator current and the q-axis stator current respectively; and are the d-axis stator inductance and the q-axis stator inductance respectively; Ψ f is the permanent magnet flux amplitude; p is the number of pole pairs; the relationship between the stator current vector and the d-axis and q-axis stator current components is: （2） in, I s is the amplitude of the current vector; is the current vector angle, that is, the angle between the current vector and the d-axis; When the amplitude of the current vector is constant, there is an optimal current angle that maximizes the output torque of the IPMSM. During steady-state operation, the voltage equation is expressed as: （3） in, u d and u q are the d-axis stator voltage and the q-axis stator voltage respectively; R is the stator resistance; ω e is the rotor angular frequency; according to formula (1), the electromagnetic torque after injecting the constant signal A is （4） in, is the electromagnetic torque after the constant signal A is injected into the d-axis, is the electromagnetic torque after the constant signal A is injected into the q-axis; A is the injected constant signal; Step 2, calculate the partial derivative of the electromagnetic torque and the angle between the stator current vector and the d-axis using the electromagnetic torque mathematical model obtained in step 1; the specific process of step 2 is: calculate the electromagnetic torque by formula (1) T e right The derivative of is expressed as: （5） Combining formula (2), formula (5) is expressed as （6） According to formula (1), we can get T e right i d and i q The partial derivative of is shown in the following formula (7): （7） Then equations (1), (4) and (7) are expressed as follows: （8） （9） From formula (8), we can get: T e right i d The partial derivative of is expressed as: （10） From formula (9), we can get: T e right i q The partial derivative of is expressed as: （11） Substituting equations (10) and (11) into equation (6), we get T e right The partial derivative of : （12） From formula (12), we can conclude that by controlling The optimal current vector angle when the motor is running at the MTPA operating point can be obtained by approaching zero. The d-axis and q-axis current given values ​​are set by this current angle. From formula (3), we can get: （13） Among them, the stator resistance R is a constant; Substitute equation (13) into equation (1), T e Expressed as: （14） Substitute equation (13) into equation (4), 、 Expressed as: （15） （16） Substituting equations (14), (15), and (16) into equation (12), we can obtain the partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis: : （17）； Step 3, calculating the given values ​​of the d-axis and q-axis stator currents from the partial derivatives of the electromagnetic torque and the angle between the stator current vector and the d-axis obtained in step 2; the specific process of step 3 is: The setting method of d-axis given current is: When the motor runs below the reference speed, the d-axis reference current is obtained by integrating the calculated formula (17), as shown in the following formula (18): （18） The setting method of q-axis given current is: when d-axis current and q-axis current are given currents and electromagnetic torque is given torque, i qref Expressed as: （19） The q-axis current reference obtained by equation (20) cannot obtain the required torque. Combining equations (7) and (20), i qref Expressed as: （20） in, is the q-axis current reference value; is the electromagnetic torque reference value.

2. The method for controlling an interior permanent magnet synchronous motor (MTPA) with virtual signal injection according to claim 1, wherein: In step 2, due to f changes with temperature, so i d Yes f Make the corrections as follows: （21） in, Ψ f0 For offline self-learning of permanent magnet flux; K p is the proportional gain, K i is the integral gain; i dref is the stator current reference; α1 and α2 are the characteristic angular frequencies of the low-pass filter, and s is the complex frequency.

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