An online parameter identification method for interior permanent magnet synchronous motor

Abstract

The application discloses an online parameter identification method for an interior permanent magnet synchronous motor. Firstly, a motor steady-state model considering the change rate of equivalent loss resistance of the motor is provided; secondly, a motor parameter identification method based on direct current signal injection is provided, and online identification of the equivalent loss resistance base value, the resistance change rate, the direct-axis inductance, the cross-axis inductance and the permanent magnet flux linkage of the motor is realized. The model is simple in form and convenient to calculate. The application is suitable for the parameter identification application field of the interior permanent magnet synchronous motor.

Description

TECHNICAL FIELD

[0001] The application relates to an online parameter identification method for an interior permanent magnet synchronous motor and belongs to the fields of electrical engineering, motor modeling and motor control. BACKGROUND

[0002] The interior permanent magnet synchronous motor is excited by a permanent magnet, and the motor does not have a brush and a slip ring, so that the motor has a simple structure and a higher energy density than other types of motors with the same capacity, and thus the motor has been widely applied in various fields in recent years. However, the high-performance operation of the motor requires accurate equivalent loss resistance, cross-axis inductance and permanent magnet flux linkage and other parameters, but these electromagnetic parameters change with the load and temperature of the motor, and therefore, the online accurate identification of the motor parameters plays a crucial role in the safe and reliable operation and high-performance control of the motor.

[0003] Because the number of motor parameters to be identified is greater than the number of steady-state voltage and current equations of the motor, the online identification of the motor parameters always faces an underdetermined problem. To this end, an online motor parameter identification method based on signal injection is proposed, which adds a voltage and current equation corresponding to the signal to solve the underdetermined problem. At present, the online motor parameter identification method based on signal injection can be roughly divided into two categories: sinusoidal signal injection and direct current signal injection. It is worth mentioning that the motor parameters to be solved are all the motor parameters at the fundamental frequency. However, the existing sinusoidal signal injection method only adds a voltage and current equation at the injection frequency, ignores the difference between the resistance at the injection frequency and the fundamental resistance to be solved, and does not fundamentally solve the underdetermined problem of the fundamental motor parameter identification. The direct current signal injection directly adds a voltage and current equation at the fundamental frequency, and thus has higher accuracy. However, because the traditional parallel iron loss resistance model considering iron loss has a complex structure and a large online calculation burden, the existing online identification method based on direct current signal injection usually identifies based on the traditional model ignoring the iron loss, and does not consider the total loss of the motor including the iron loss and the change of the total loss with the current, and thus ignores the change of the equivalent total loss resistance with the current and does not involve the online identification of the resistance change rate with the current. However, the iron loss is an important part of the total loss of the motor, and the proportion of the iron loss in the total loss may exceed 50% in some working conditions, and if the iron loss is ignored, the accuracy of the motor parameter identification will be affected. Therefore, although the existing method can reduce the online calculation burden, it also causes the problem of reduced accuracy. SUMMARY

[0004] The application aims at: considering the equivalent loss resistance of the embedded permanent magnet synchronous motor changes with current, proposing a new motor steady-state model considering motor loss including iron loss, with small online calculation burden, using the change rate of motor equivalent loss resistance, and based on the steady-state model, proposing a motor parameter identification method based on DC current signal injection, which can realize online identification of motor equivalent loss resistance base value, resistance change rate, direct-axis inductance, cross-axis inductance and permanent magnet flux linkage.

[0005] To solve the above problems, the technical scheme adopted by the application is:

[0006] Firstly, a motor steady-state model considering the change rate of motor equivalent loss resistance is proposed.

[0007]

[0008] In the above equation, i d0 and i q0 are the base values of direct-axis current and cross-axis current respectively, and Δi d is the change amount of direct-axis current. When the direct-axis current and cross-axis current of the motor are i d0 + Δi d and i q0 , the direct-axis end voltage and cross-axis end voltage of the motor are defined as u d1 and u q1 . R0 is the base value of the equivalent loss resistance of the motor; R' is the change rate of the equivalent loss resistance of the motor; L d and L q are the direct-axis inductance and cross-axis inductance of the motor respectively; ψ f is the permanent magnet flux linkage; and ω is the angular velocity of the motor.

[0009] Secondly, based on the proposed motor steady-state model considering the change rate of the equivalent loss resistance of the motor, a motor parameter identification method based on DC current signal injection is proposed to realize online identification of the base value of the equivalent loss resistance of the motor, the change rate of the resistance, the direct-axis inductance, the cross-axis inductance and the permanent magnet flux linkage. The specific steps are as follows:

[0010] (1) Control the direct-axis current and cross-axis current of the motor to be i d0 and i q0 respectively, at this time, the change amount of the direct-axis current Δi d = 0, so the proposed motor steady-state model can be simplified as:

[0011]

[0012] In the above equation, when the direct-axis current and cross-axis current of the motor are i d0 and i q0At this time, the direct-axis end voltage and the quadrature-axis end voltage of the motor are defined as u d0 and u q0 ;...

[0013] (2) Control the direct-axis current and the quadrature-axis current of the motor as i d1 =i d0 +Δi d and i q1 =i q0 , at this time, the motor voltage and the current satisfy the equation:

[0014]

[0015] (3) Control the direct-axis current and the quadrature-axis current of the motor as i d2 =i d0 -Δi d and i q2 =i q0 , at this time, the motor voltage and the current satisfy the equation:

[0016]

[0017] (4) Based on the three groups of voltage and current equations in the direct-current steady state working conditions obtained by steps (1), (2) and (3), the equivalent loss resistance base value R0, the resistance change rate R', the direct-axis inductance L d , the quadrature-axis inductance L q and the permanent magnet flux linkage ψ f can be calculated:

[0018]

[0019] The invention principle of the application is:

[0020] Since the loss of the motor includes copper loss and iron loss, when the motor current changes, the equivalent resistance of the motor, i.e. the copper loss, will be offset due to the proximity effect; at the same time, since the motor iron loss is closely related to the magnetic field distribution inside the motor, and the current change will directly affect the magnetic field distribution, therefore, the iron loss will also change with the current. In summary, the total loss and the equivalent loss resistance of the motor will change with the distribution of the current, and the corresponding change rate is defined as the equivalent loss resistance change rate of the motor.

[0021] The motor model widely used at present which considers the copper loss and the iron loss of the motor is a parallel iron loss resistance model, since a parallel resistance branch is added in the equivalent circuit, the calculation formula becomes more complex, the order is increased, and the calculation pressure is increased. In view of this, the iron loss is equivalent to the resistance in series in the application, which can avoid adding a parallel resistance branch, so as to achieve the purpose of simplifying the model and reducing the calculation pressure.

[0022] The motor parameters under five basic wave frequencies to be measured include: motor equivalent loss resistance base value, resistance change rate, direct-axis inductance, cross-axis inductance and permanent magnet flux linkage, the application constructs three groups of motor steady operation conditions with different direct-axis currents and same cross-axis currents through direct current signal injection, and six linearly independent voltage and current equations can be obtained.

[0023] The application has the advantages that:

[0024] 1. The steady voltage model considering the motor resistance change rate is proposed, the model is more in line with the actual motor physical characteristics than the traditional motor steady model, has more rigorous physical meaning and application value, and the model has smaller online operation pressure than the traditional motor steady model and is more beneficial to online parameter identification.

[0025] 2. The motor parameter online identification method based on the direct current signal injection increases the identification of the motor equivalent loss resistance change rate, can further improve the accuracy of the motor parameter online identification, and has very important engineering application value for improving the control performance and reliable operation of the embedded permanent magnet synchronous motor. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Equivalent circuit diagram of the embedded permanent magnet synchronous motor under the direct-axis current signal injection. DETAILED DESCRIPTION

[0027] The application will be further described below in combination with the drawings and specific embodiments.

[0028] Let i d0 and i q0 be the direct-axis current base value and the cross-axis current base value respectively, and Δi d be the change amount of the direct-axis current. Figure 1 When the direct current signal Δi d is injected into the direct-axis current, that is, the direct-axis current and the cross-axis current are i d0 + Δi d and i q0 respectively, the voltage and current steady model of the motor is specifically as follows:

[0029]

[0030] In the above equation, u d1 and u q1 are respectively when the motor outputs i d0 + Δi d and i q0and u are defined as u and u respectively. R0 is the base value of the equivalent loss resistance of the motor; R' is the change rate of the equivalent loss resistance of the motor; L and L are the direct-axis inductance and the quadrature-axis inductance of the motor respectively; ψ is the permanent magnet flux linkage; and ω is the angular velocity of the motor. d and L q are the direct-axis inductance and the quadrature-axis inductance of the motor respectively; ψ f is the permanent magnet flux linkage; and ω is the angular velocity of the motor.

[0031] The application proposes a motor steady-state model considering the change rate of the equivalent loss resistance of the motor, and specifically comprises the following steps:

[0032]

[0033] In the above equation, i d0 and i q0 are the base values of the direct-axis current and the quadrature-axis current respectively, and Δi d is the change amount of the direct-axis current. When the direct-axis current and the quadrature-axis current of the motor are i d0 + Δi d and i q0 , the direct-axis end voltage and the quadrature-axis end voltage of the motor are defined as u d1 and u q1 respectively. R0 is the base value of the equivalent loss resistance of the motor; R' is the change rate of the equivalent loss resistance of the motor; L d and L q are the direct-axis inductance and the quadrature-axis inductance of the motor respectively; ψ f is the permanent magnet flux linkage; and ω is the angular velocity of the motor.

[0034] Then, based on the proposed motor steady-state model, a motor parameter identification method based on direct current signal injection is proposed to realize online identification of the base value of the equivalent loss resistance, the change rate of the resistance, the direct-axis inductance, the quadrature-axis inductance and the permanent magnet flux linkage of the motor. The specific steps are as follows:

[0035] (1) The direct-axis current and the quadrature-axis current of the motor are controlled to be i d0 and i q0 respectively, at this time, the motor voltage and the current satisfy the equation:

[0036]

[0037] In the above equation, when the direct-axis current and the quadrature-axis current of the motor are i d0 and i q0 , the direct-axis end voltage and the quadrature-axis end voltage of the motor are defined as u d0 and u q0 respectively.

[0038] (2) The direct-axis current and the quadrature-axis current of the motor are controlled to be i d1 = i d0 + Δi d and i q1= i q0 At this time, the motor voltage and current satisfy the equation:

[0039]

[0040] (3) Control the direct-axis and quadrature-axis currents of the motor to be i d2 = i d0 - Δi d and i q2 = i q0 At this time, the motor voltage and current satisfy the equation:

[0041]

[0042] (4) Based on the voltage and current equations obtained in steps (1), (2), and (3) under three groups of direct-current steady-state working conditions, the equivalent loss resistance base value R0, the resistance variation rate R', the direct-axis inductance L d , the quadrature-axis inductance L q , and the permanent magnet flux linkage ψ f can be calculated.

[0043]

[0044] For a sample embedded permanent magnet synchronous motor, the online identification accuracy of the equivalent loss resistance base value R0 under different working conditions is compared among the method of the application, the traditional high-frequency sinusoidal signal injection method, and the traditional direct-current signal injection method. The comparison results are shown in Table 1.

[0045] Note: Because the models based on the three methods and the parameters identified are different, only the equivalent loss resistance base value R0 common to the three methods is selected for accuracy comparison.

[0046] Table 1: Accuracy comparison results of the three methods

[0047]

[0048] As can be seen from the comparison results, compared with the traditional high-frequency sinusoidal signal injection method and the traditional direct-current signal injection method, the equivalent loss resistance can be identified with higher accuracy using the method of the application.

Claims

1. A method for online parameter identification of an interior permanent magnet synchronous motor, characterized in that, The steps are as follows: First, a motor steady-state model considering the change rate of motor equivalent loss resistance is proposed, specifically: In the above equation, i d0 and i q0 are the direct-axis current base value and the quadrature-axis current base value, respectively, and Δi d is the change in the direct-axis current; When the direct-axis current and the quadrature-axis current of the motor are i d0 + Δi d and i q0 , the direct-axis end voltage and the quadrature-axis end voltage of the motor are defined as u d1 and u q1 , respectively; R0 is the base value of the equivalent loss resistance of the motor; R' is the change rate of the equivalent loss resistance of the motor; L d and L q are the direct-axis inductance and the quadrature-axis inductance of the motor, respectively; ψ f is the permanent magnet flux linkage; and ω is the angular velocity of the motor. Next, based on the motor steady-state model considering the change rate of motor equivalent loss resistance, a motor parameter identification method based on direct current signal injection is proposed, which realizes online identification of motor equivalent loss resistance base value, resistance change rate, direct-axis inductance, cross-axis inductance and permanent magnet flux linkage, the specific steps are as follows: (1) Control the direct and quadrature axis currents of the motor to be i d0 and i q0 respectively, at which time the motor voltage and current satisfy the equation: In the above equations, when the direct-axis current and the quadrature-axis current of the motor are i d0 and i q0 , respectively, the direct-axis terminal voltage and the quadrature-axis terminal voltage of the motor are defined as u d0 and u q0 , respectively. (2) Control the direct and quadrature axis currents of the motor to be i d1 = i d0 + Δi d and i q1 = i q0 At this time, the motor voltage and current satisfy the equation: (3) Control the direct and quadrature axis currents of the motor to be i d2 = i d0 - Δi d and i q2 = i q0 , at which time the motor voltage and current satisfy the equation: (4) Based on the three groups of voltage and current equations under the direct current steady state working conditions obtained in steps (1), (2), and (3), the equivalent loss resistance base value R0, the resistance variation rate R', the direct axis inductance L d , the quadrature axis inductance L q , and the permanent magnet flux linkage ψ f are calculated.

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