Maximum torque current ratio control method of permanent magnet synchronous motor considering core loss

Abstract

This application provides a maximum torque-to-current ratio control method for permanent magnet synchronous motors that considers core losses. It comprehensively considers the effects of core losses, winding losses, and magnetic saturation effects, making the established model and corresponding derivation process more consistent with the actual working conditions of permanent magnet synchronous motors. In the control, it can make full use of the stator current of permanent magnet synchronous motors, improve the control accuracy and motor efficiency, and also help reduce motor heating. Thus, it effectively overcomes the shortcomings of the prior art in not considering the above-mentioned important losses and influencing factors.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet synchronous motor control technology, and specifically relates to a maximum torque-to-current ratio control strategy for permanent magnet synchronous motors that comprehensively considers core losses, winding losses, and magnetic saturation effects. Background Technology

[0002] In existing technologies, the maximum torque-to-current ratio control strategy for permanent magnet synchronous motors (PMSMs) generally assumes that core losses and the magnetic saturation effect of the motor core material are ignored, and calculates the maximum output torque under minimum current with the goal of minimizing winding losses (i.e., copper losses). However, with the development of PMSMs, their speed and torque ranges have continued to expand. Under high-speed and high-load conditions, core losses will gradually surpass winding losses to become the dominant losses in PMSMs. Ignoring core losses and the magnetic saturation effect of the core material will inevitably lead to significant calculation errors. The main electromagnetic losses of PMSMs include winding losses and core losses, which not only directly determine the motor's efficiency but are also closely related to the motor's heat generation, thus affecting the motor's power density and torque density. Therefore, they should not be ignored in the control strategy. Thus, how to fully consider the influence of core losses, winding losses, and magnetic saturation effects in the maximum torque-to-current ratio control strategy for PMSMs and establish a more scientific and reasonable model is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] To address the aforementioned technical problems in this field, this application provides a method for controlling the maximum torque-to-current ratio of a permanent magnet synchronous motor considering core losses, specifically including the following steps:

[0004] Step 1: Considering core losses, winding losses, and magnetic saturation effects, establish equivalent circuit models of the permanent magnet synchronous motor along the d-axis and q-axis in a rotating coordinate system. In the equivalent circuit models, the topology of the d-axis is determined by the phase winding internal resistance R. s d-axis inductance L d With rotating electromotive force ω e L q I q First connect the two in series, then connect the equivalent load iron loss resistor R in parallel. i The circuit is formed by connecting the components sequentially, with the voltage V across the circuit being the d-axis voltage. d The topology of the q-axis is determined by the phase winding internal resistance R. s q-axis inductance L q With rotating electromotive force ω e L d I d First connect the two in series, then connect the equivalent load iron loss resistor R in parallel. i Equivalent abnormal loss resistance R in parallel anEquivalent eddy current loss resistance R e Equivalent hysteresis loss resistance R h and back electromotive force ω e λ f The circuit is formed by connecting the elements sequentially, with the q-axis voltage V at both ends. q ; where ω e I is the rotor's electric angular velocity. d I q These are the d-axis and q-axis currents, respectively, λ f For permanent magnet flux linkage;

[0005] Step 2: For the maximum torque-to-current ratio control of the permanent magnet synchronous motor, the following stator current optimization target is set:

[0006]

[0007] And construct the following auxiliary function F:

[0008]

[0009] In the formula, P is the number of poles of the permanent magnet synchronous motor, and χ is the Lagrange multiplier;

[0010] Step 3: Calculate the partial derivatives of the auxiliary function F with respect to the d-axis current, q-axis current, and the Lagrange operator, respectively.

[0011]

[0012]

[0013]

[0014] Set all partial derivatives to 0 and base them on L in the permanent magnet synchronous motor d <L q The relationship is as follows: solve for the q-axis current and the d-axis current sequentially.

[0015]

[0016]

[0017] The optimal stator current is obtained by combining the stator current optimization objective, and the corresponding electromagnetic torque of the permanent magnet synchronous motor is calculated.

[0018] Furthermore, based on the topology of the d-axis and q-axis of the equivalent circuit model in step one, the mathematical model of the permanent magnet synchronous motor is obtained:

[0019]

[0020]

[0021] In the formula, I cd I cq These are the iron loss currents of the d-axis and q-axis loads, respectively; I md I mq I oq These are the magnetizing currents along the d-axis and q-axis, respectively; I can I ce I ch For no-load iron loss current, corresponding to no-load abnormal loss, no-load eddy current loss, and no-load hysteresis loss, respectively.

[0022] The current in each branch can be obtained separately:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031] The electromagnetic torque of a permanent magnet synchronous motor, taking into account core losses, winding losses, and magnetic saturation effects, is calculated as follows:

[0032]

[0033] Furthermore, in step three, after solving for the optimal stator current, substituting the d-axis current expression into the electromagnetic torque expression, we can obtain the electromagnetic torque in the following form:

[0034]

[0035] In the formula,

[0036]

[0037]

[0038]

[0039] The maximum torque-to-current ratio control method for permanent magnet synchronous motors considering core losses provided in this application comprehensively considers the effects of core losses, winding losses, and magnetic saturation effects. This makes the established model and corresponding derivation process more closely match the actual working conditions of permanent magnet synchronous motors. In the control process, it can make full use of the stator current of the permanent magnet synchronous motor, improve the control accuracy and motor efficiency, and also help reduce motor heating. Thus, it effectively overcomes the shortcomings of the prior art in not considering the above-mentioned important losses and influencing factors. Attached Figure Description

[0040] Figure 1 The topology of the d-axis equivalent circuit model established in the method provided by this invention;

[0041] Figure 2 The topology of the q-axis equivalent circuit model established in the method provided by this invention;

[0042] Figure 3 This is the structural framework of the maximum torque-current ratio control system corresponding to the method provided by the present invention. Detailed Implementation

[0043] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The maximum torque-to-current ratio control method for permanent magnet synchronous motors considering core losses provided in this application specifically includes the following steps:

[0045] Step 1: Considering core losses, winding losses, and magnetic saturation effects, establish equivalent circuit models of the permanent magnet synchronous motor along the d-axis and q-axis in a rotating coordinate system; the topology of the d-axis in the equivalent circuit model is as follows: Figure 1 As shown, the phase winding internal resistance R s d-axis inductance L d With rotating electromotive force ω e L q I q First connect the two in series, then connect the equivalent load iron loss resistor R in parallel. i The circuit is formed by connecting the components sequentially, with the voltage V across the circuit being the d-axis voltage. d The topology of the q-axis is as follows: Figure 2 As shown, the phase winding internal resistance R s q-axis inductance L q With rotating electromotive force ω e L d I dFirst connect the two in series, then connect the equivalent load iron loss resistor R in parallel. i Equivalent abnormal loss resistance R in parallel an Equivalent eddy current loss resistance R e Equivalent hysteresis loss resistance R h and back electromotive force ω e λ f The circuit is formed by connecting the elements sequentially, with the q-axis voltage V at both ends. q ; where ω e I is the rotor's electric angular velocity. d I q These are the d-axis and q-axis currents, respectively, λ f For permanent magnet flux linkage;

[0046] Step 2: For the maximum torque-to-current ratio control of the permanent magnet synchronous motor, the following stator current optimization target is set:

[0047]

[0048] And construct the following auxiliary function F:

[0049]

[0050] In the formula, P is the number of poles of the permanent magnet synchronous motor, and χ is the Lagrange multiplier;

[0051] Step 3: Calculate the partial derivatives of the auxiliary function F with respect to the d-axis current, q-axis current, and the Lagrange operator, respectively.

[0052]

[0053]

[0054]

[0055] Set all partial derivatives to 0 and base them on L in the permanent magnet synchronous motor d <L q The relationship is as follows: solve for the q-axis current and the d-axis current sequentially.

[0056]

[0057]

[0058] The optimal stator current is obtained by combining the stator current optimization objective, and the corresponding electromagnetic torque of the permanent magnet synchronous motor is calculated.

[0059] In a preferred embodiment of the present invention, in step one, a mathematical model of the permanent magnet synchronous motor is obtained based on the topology of the d-axis and q-axis of the equivalent circuit model:

[0060]

[0061]

[0062] In the formula, I cd I cq These are the iron loss currents of the d-axis and q-axis loads, respectively; I md I mq I oq These are the magnetizing currents along the d-axis and q-axis, respectively; I can I ce I ch For no-load iron loss current, corresponding to no-load abnormal loss, no-load eddy current loss, and no-load hysteresis loss, respectively.

[0063] The current in each branch can be obtained separately:

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] The electromagnetic torque of a permanent magnet synchronous motor, taking into account core losses, winding losses, and magnetic saturation effects, is calculated as follows:

[0073]

[0074] In a preferred embodiment of the present invention, after solving for the optimal stator current in step three, the expression for the d-axis current is substituted into the expression for the electromagnetic torque to obtain the electromagnetic torque in the following form:

[0075]

[0076] In the formula,

[0077]

[0078]

[0079]

[0080] Figure 3 The block diagram of the maximum torque-to-current ratio control system built based on the method of this invention is shown. The outer loop of the control system adopts a motor speed loop, using a PI controller to dynamically adjust the stator current. The inner loop of the control system adopts a dq-axis current loop. For any given torque, the reference value of the dq-axis current is calculated by the maximum torque-to-current ratio controller (Improved MTPA) established by this invention. The error between the reference value and the sampled value of the dq-axis current is fed into two PI controllers and generates dq-axis voltage signals. Finally, the switching signal of the inverter is calculated by the space vector pulse width modulation module (SVPWM), which drives the permanent magnet synchronous motor. Compared with the traditional maximum torque-to-current ratio control strategy, this invention not only considers the winding losses of the motor, but also accurately calculates the core losses of the motor and the influence of magnetic saturation effect on the core losses and electromagnetic torque of the motor, thus achieving better accuracy and reliability.

[0081] It should be understood that the sequence number of each step in the embodiments of the present invention does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0082] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for controlling the maximum torque-to-current ratio of a permanent magnet synchronous motor considering core losses, characterized in that: Specifically, the following steps are included: Step 1: Considering core losses, winding losses, and magnetic saturation effects, establish equivalent circuit models of the permanent magnet synchronous motor along the d-axis and q-axis in a rotating coordinate system. In the equivalent circuit models, the topology of the d-axis is determined by the phase winding internal resistance R. s d-axis inductance L d With rotating electromotive force ω e L q I q First connect the two in series, then connect the equivalent load iron loss resistor R in parallel. i The circuit is formed by connecting the components sequentially, with the voltage V across the circuit being the d-axis voltage. d The topology of the q-axis is determined by the phase winding internal resistance R. s q-axis inductance L q With rotating electromotive force ω e L d I d First connect the two in series, then connect the equivalent load iron loss resistor R in parallel. i Equivalent abnormal loss resistance R in parallel an Equivalent eddy current loss resistance R e Equivalent hysteresis loss resistance R h and back electromotive force ω e λ f The circuit is formed by connecting the elements sequentially, with the q-axis voltage V at both ends. q ; where ω e I is the rotor's electric angular velocity. d I q These are the d-axis and q-axis currents, respectively, λ f For permanent magnet flux linkage; Step 2: For the maximum torque-to-current ratio control of the permanent magnet synchronous motor, the following stator current optimization target is set: And construct the following auxiliary function F: In the formula, P is the number of poles of the permanent magnet synchronous motor, and χ is the Lagrange multiplier; Step 3: Calculate the partial derivatives of the auxiliary function F with respect to the d-axis current, q-axis current, and the Lagrange operator, respectively. Set all partial derivatives to 0 and base them on L in the permanent magnet synchronous motor d <L q The relationship is as follows: solve for the q-axis current and the d-axis current sequentially. The optimal stator current is obtained by combining the stator current optimization objective, and the corresponding electromagnetic torque of the permanent magnet synchronous motor is calculated.

2. The method as described in claim 1, characterized in that: In step one, based on the topology of the d-axis and q-axis of the equivalent circuit model, the mathematical model of the permanent magnet synchronous motor is obtained: In the formula, I cd I cq These are the d-axis and q-axis load iron loss currents, respectively; I md I mq I oq These are the magnetizing currents along the d-axis and q-axis, respectively; I can I ce I ch denoted as no-load iron loss current, corresponding to no-load abnormal loss, no-load eddy current loss, and no-load hysteresis loss, respectively; p is the differential operator d / dt, and t is the time variable. The current in each branch can be obtained separately: The electromagnetic torque of a permanent magnet synchronous motor, taking into account core losses, winding losses, and magnetic saturation effects, is calculated as follows:

3. The method as described in claim 1, characterized in that: In step three, after solving for the optimal stator current, substituting the d-axis current expression into the electromagnetic torque expression, we can obtain the electromagnetic torque in the following form: In the formula,

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