Demagnetization judgment method of permanent magnet synchronous motor and vehicle-mounted controller

Abstract

The invention provides a demagnetization judgment method of a permanent magnet synchronous motor and a vehicle-mounted controller. The demagnetization judgment method of the permanent magnet synchronous motor comprises the following steps: establishing a current model and a voltage model; on the basis of the current model, according to a first system parameter and a real-time current, a current d-axis expected flux linkage is obtained through calibration on the basis of the current model, and dynamic voltage compensation information is output; based on the voltage model, according to a second system parameter, an instruction voltage, a real-time current, a real-time angular velocity and the dynamic voltage compensation information, a current d-axis observation flux linkage is obtained through observation based on the voltage model; and calculating a difference value between the d-axis expected flux linkage and the d-axis observation flux linkage, and if the difference value exceeds a preset threshold value, determining that a rotor permanent magnet is demagnetized. Therefore, whether the rotor of the permanent magnet synchronous motor is demagnetized or not in the normal operation process of a vehicle can be judged on the premise of not disassembling and damaging the motor and on the basis of not increasing extra hardware cost.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a demagnetization judgment method for a permanent magnet synchronous motor and an on-vehicle controller. Background Art

[0002] The electric drive system of new energy vehicles (primarily pure electric or hybrid vehicles) mainly consists of a motor, controller, and related control circuits. The most commonly used motor types are permanent magnet synchronous motors (PMSM) and asynchronous motors (ASM).

[0003] Permanent magnet synchronous motors (PMSMs) are widely used in electric drive applications due to their high efficiency, high torque-to-weight ratio, and high power density. The flux density of the permanent magnets in the rotor of a PMSM directly affects torque control. Magnetic field fluctuations and demagnetization of the permanent magnets interact with the current, temperature rise, and power angle within the motor, leading to overheating and reduced torque performance. In severe cases, the motor may even fail.

[0004] In practical applications, electric drive systems may operate for extended periods of time. Compared to motor controllers, motors are equipped with fewer sensors, making it difficult to communicate their true status to higher-level controllers. After prolonged and harsh operating conditions such as high currents and high temperatures, it's difficult to determine whether the motor has internal damage or irreversible demagnetization, other than through disassembly and measurement of static parameters. Summary of the Invention

[0005] The object of the present invention is to provide a demagnetization judgment method for a permanent magnet synchronous motor and an on-vehicle controller, so as to solve the problem in the prior art that it is difficult to judge the demagnetization of the rotor permanent magnet without adding hardware.

[0006] In order to solve the above technical problems, the present invention provides a demagnetization judgment method for a permanent magnet synchronous motor, which comprises:

[0007] Establish current model and voltage model;

[0008] Based on the current model, according to the first system parameter and the real-time current, calibrate the current model to obtain the current d-axis expected flux linkage, and output dynamic voltage compensation information;

[0009] Based on the voltage model, according to the second system parameter, the command voltage, the real-time current, the real-time angular velocity and the dynamic voltage compensation information, a current d-axis observed flux is obtained based on the voltage model observation;

[0010] A difference between the expected d-axis flux and the observed d-axis flux is calculated, and if the difference exceeds a preset threshold, it is determined that the rotor permanent magnet is demagnetized.

[0011] Optionally, the first system parameter includes the d-axis inductance L d , q-axis inductance L q , the reference flux of the rotor permanent magnet ψ f .

[0012] Optionally, the d-axis expected magnetic flux is obtained based on the following formula:

[0013] ψ d,I =L d i d +ψ f

[0014] Among them, ψ d,I is the expected flux linkage along the d axis, i d is the d-axis real-time current.

[0015] Optionally, the step of obtaining the dynamic voltage compensation information includes:

[0016] Based on the current model calibration, the current q-axis expected flux is obtained.

[0017] ψ q,I =L q i q

[0018] Among them, ψ q,I is the expected flux linkage along the q axis, i q is the q-axis real-time current;

[0019] The dynamic voltage compensation information is obtained based on the rate of change of the q-axis expected flux linkage over time,

[0020]

[0021] Among them, u q Dyn is the dynamic voltage compensation information.

[0022] Optionally, the second system parameters include stator resistance R, d-axis inductance L d , q-axis inductance L q , the reference flux of the rotor permanent magnet ψ f .

[0023] Optionally, the reference flux ψ f Calibrated according to the rotor temperature.

[0024] Optionally, the d-axis observed magnetic flux is obtained based on the following formula:

[0025] ψ d,U =(u q -Ri q -u q Dyn) / ω

[0026] Among them, ψ d,U is the d-axis observed magnetic flux, u q is the q-axis command voltage, i q is the q-axis real-time current, and ω is the angular velocity.

[0027] Optionally, the q-axis command voltage

[0028] Optionally, the angular velocity is configured to be no less than a preset rotation speed threshold.

[0029] In order to solve the above technical problems, the present invention also provides a vehicle-mounted controller, which is used to execute the steps of the demagnetization judgment method of the permanent magnet synchronous motor as described above.

[0030] To summarize, in the demagnetization judgment method of the permanent magnet synchronous motor and the on-board controller provided by the present invention, the demagnetization judgment method of the permanent magnet synchronous motor includes: establishing a current model and a voltage model; based on the current model, according to the first system parameter and the real-time current, the current d-axis expected magnetic flux is obtained based on the current model calibration, and dynamic voltage compensation information is output; based on the voltage model, according to the second system parameter, the instruction voltage, the real-time current, the real-time angular velocity and the dynamic voltage compensation information, the current d-axis observed magnetic flux is obtained based on the voltage model observation; the difference between the d-axis expected magnetic flux and the d-axis observed magnetic flux is calculated, and if the difference exceeds a preset threshold, it is determined that the rotor permanent magnet is demagnetized.

[0031] With this configuration, it is possible to determine whether the rotor of the permanent magnet synchronous motor is demagnetized during normal operation of the vehicle without disassembling or damaging the motor and without increasing additional hardware costs. It can further accurately identify magnetic flux anomalies under different speed and torque conditions and specific voltage values, and has high diagnostic robustness for demagnetization detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Those skilled in the art will appreciate that the drawings are provided for a better understanding of the present invention, but do not constitute any limitation on the scope of the present invention.

[0033] Figure 1 1 is a schematic diagram of a vector control process of a permanent magnet synchronous motor according to an embodiment of the present invention.

[0034] Figure 2 4 is a flow chart of a method for determining demagnetization of a permanent magnet synchronous motor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] To make the objects, advantages, and features of the present invention more clearly apparent, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale. They are only used to conveniently and clearly assist in illustrating the purposes of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structure. In particular, different drawings may need to illustrate different focuses and sometimes use different scales.

[0036] As used in the present invention, the singular forms "a", "an", "one" and "the" include plural objects, the term "or" is generally used in a sense including "and / or", the term "several" is generally used in a sense including "at least one", and the term "at least two" is generally used in a sense including "two or more". In addition, the terms "first", "second" and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. In addition, directional terms such as above, below, up, down, upward, downward, left, right, etc. are used relative to the exemplary embodiments as they are shown in the figures, with the upward or upper direction being toward the top of the corresponding figure and the downward or lower direction being toward the bottom of the corresponding figure.

[0037] The present invention aims to provide a method for determining demagnetization of a permanent magnet synchronous motor and an on-vehicle controller to address the prior art problem of difficulty in determining the demagnetization of the rotor permanent magnet without adding additional hardware. The following description is made with reference to the accompanying drawings.

[0038] Please refer to Figure 1 This figure shows a vector control process for a permanent magnet synchronous motor (PMSM). The main control flow is: desired torque → desired current → command voltage → coordinate transformation → SVPWM → inverter → measured current → coordinate transformation → real-time current → closed-loop feedback. The forward control chain is from desired torque to inverter output, while the feedback control chain is from measured current to closed-loop feedback.

[0039] First, based on the desired torque TrqDes (which can be obtained based on the throttle request or the predicted trajectory of the advanced driver assistance system ADS), the d-axis desired current i is obtained through the torque equation d Des and q-axis desired current i q Des. Then, according to the control algorithm, the d-axis command voltage u is obtained. d and q-axis command voltage u q Then, after the inverse Park coordinate transformation (2r / 2s transformation), the voltage vector u in the stationary coordinate system is converted to α 、u βPerform space vector pulse width modulation (SVPWM) and convert it into the switching signal of the inverter (such as six basic vector combinations), control the inverter to output three-phase voltage (U, V, W), and drive the permanent magnet synchronous motor (PMSM).

[0040] Furthermore, it is necessary to monitor the real-time current to perform closed-loop control on the torque. Specifically, the real-time three-phase output current of the inverter can be monitored (due to i U +i V +i W =0, in practice, any two-phase current can be detected, for example, i U 、i V ), after Clarke transformation (3s / 2s transformation) and Park transformation (2s / 2r transformation), the real-time current (d-axis real-time current i d and q-axis real-time current i q ), fed back to the desired d-axis current i d Des and q-axis desired current i q Des, thus forming a closed-loop control to ensure that the actual torque tracks the desired torque Tr q Des.

[0041] Based on the above vector control process, please refer to Figure 1 and Figure 2 , an embodiment of the present invention provides a demagnetization determination method for a permanent magnet synchronous motor, which includes:

[0042] Step S1: constructing a current model based on the motor calibration state, and constructing a voltage model based on the motor real-time operating state;

[0043] Step S2: Based on the current model, according to the first system parameter and the real-time current, the current d-axis expected flux is calibrated based on the current model, and dynamic voltage compensation information is output;

[0044] Step S3: Based on the voltage model, according to the second system parameter, the command voltage, the real-time current, the real-time angular velocity and the dynamic voltage compensation information, a current d-axis observed flux is obtained based on the voltage model observation;

[0045] Step S4: Calculate the difference between the expected d-axis flux and the observed d-axis flux. If the difference exceeds a preset threshold, determine that the rotor permanent magnet is demagnetized.

[0046] The current model in step S1 is constructed based on the motor calibration state, and its input information includes the real-time current in the feedback control chain (referring to the current obtained by actual monitoring in the torque closed-loop control, including the d-axis real-time current i d and q-axis real-time current i q). The calculation of magnetic flux is based on magnetic circuit analysis and is a static characteristic.

[0047] The voltage model is based on the real-time operating status of the motor. Its input information includes the command voltage in the forward control chain (the command voltage calculated based on the expected current) and dynamic voltage compensation information obtained based on the current model. Its flux calculation is a dynamic feature.

[0048] Permanent magnet demagnetization primarily affects the d-axis flux. When demagnetized, the actual d-axis flux decreases. By observing the actual d-axis flux, we can determine whether the permanent magnet has demagnetized. However, the d-axis flux is dependent on the current motor operating conditions (such as temperature and speed). When observing the actual d-axis flux, it is difficult to find a constant reference for comparison. Therefore, a current model is needed as a reference.

[0049] There is no order relationship between step S2 and step S3, and both obtain their own d-axis flux outputs based on their own inputs. Since the current model is constructed based on the motor calibration state, the d-axis flux obtained can be considered as an expected value based on the calibration. The voltage model is constructed based on the real-time operating state of the motor. Its input information includes the command voltage in the forward control chain and also includes dynamic voltage compensation information. Therefore, the d-axis flux output by the voltage model is equivalent to the actual value. If the rotor permanent magnet does not demagnetize, the d-axis flux output by the current model and the voltage model should be the same, and the difference between the two should be zero. If the rotor permanent magnet demagnetizes, the d-axis flux obtained based on the voltage model will decrease. If the difference between the d-axis flux output by the current model and the voltage model exceeds the preset threshold, it can be determined that the rotor permanent magnet is demagnetized.

[0050] Optionally, the first system parameter in step S2 includes the d-axis inductance L d , q-axis inductance L q , the reference flux of the rotor permanent magnet ψ f The second system parameters in step S3 include stator resistance R, d-axis inductance L d , q-axis inductance L q , the reference flux of the rotor permanent magnet ψ f . Wherein the d-axis inductance L d and q-axis inductance L q The reference flux ψ can be determined based on calibration or calculation. f It reflects the initial flux linkage value when the rotor permanent magnet is not demagnetized. It is the d-axis inductance L d and q-axis inductance L q and reference flux ψ f It is not a fixed value, it will change with the working conditions (such as the d-axis real-time current i d and q-axis real-time current i qThe d-axis inductance L d and q-axis inductance L q and reference flux ψ f All of these can be determined by calibration, etc. Therefore, in step S2, as long as the current real-time current is known, the expected flux linkage can be obtained based on the corresponding first system parameter.

[0051] The dynamic voltage equation in motor control is shown in equation (1):

[0052]

[0053] Among them, u d is the d-axis command voltage, R is the stator resistance, i d is the d-axis real-time current, L d is the d-axis inductance, L q is the q-axis inductance, ω is the real-time angular velocity of the rotor, u q is the q-axis command voltage, i q is the real-time current of q axis, ψ f is the reference flux of the rotor permanent magnet.

[0054] From formula (1), we can deduce:

[0055]

[0056] In formula (2), ψ q is the q-axis magnetic flux, ψ d is the d-axis magnetic flux.

[0057] According to equations (1) and (2), the expected d-axis flux linkage ψ based on the current model can be obtained: d,I and the expected magnetic flux ψ on the q axis q,I :

[0058] ψ d,I =L d i d +ψ f (3)

[0059] ψ q,I =L q i q (4)

[0060] Furthermore, the step of obtaining the dynamic voltage compensation information includes: obtaining the current q-axis expected flux ψ based on the current model calibration q,i , based on the formula (4) q,i The dynamic voltage compensation information u is obtained by the rate of change over time q Dyn:

[0061]

[0062] The dynamic voltage compensation information u q Dyn is used for output to voltage models.

[0063] Based on equations (1), (2) and (5), the d-axis observed flux ψ based on the voltage model can be obtained d,U :

[0064] ψ d,U =(u q -Ri q -u q Dyn) / ω (6)

[0065] Finally, according to equations (3) and (6), step S4 only needs to compare the d-axis observed flux ψ d,U Expected magnetic flux linkage ψ with d-axis d,I Whether the difference exceeds a preset threshold value can be used to determine whether the rotor permanent magnet has demagnetized. Those skilled in the art can set the preset threshold value based on different motors, which will not be elaborated here. Of course, if the difference does not exceed the preset threshold value, it is determined that the rotor permanent magnet has not demagnetized, or the demagnetization is not significant and does not affect normal operation.

[0066] In the above calculation, the L d 、L q and ψ f It will change according to different working conditions or temperature changes. Among them, the d-axis inductance L d and q-axis inductance L q There are two ways to get it. One is to get it directly from the simulation data of the motor. When the motor is designed, the d-axis inductance L under different d-axis currents and q-axis currents will be given. d and q-axis inductance L q , can be used directly. Another way is to use the voltage equation obtained during the motor calibration process. The steady-state voltage equation in motor control is shown in the following equation (7):

[0067]

[0068] Define L q SubL d =L q -L d , L q SubL d During the motor calibration process, the torque L is obtained based on the motor torque measured on the test bench and the torque calculated by the torque equation. q SubL d , calibrate to obtain L under different d-axis current and q-axis current q SubL d This is a mature technical means in the industry and will not be elaborated here.

[0069] Furthermore, for formula (7) and L q SubL d After sorting, the d-axis inductance L under different d-axis currents and q-axis currents is obtained by calculation. d and q-axis inductance L q , specifically as shown in the following formula (8) and formula (9):

[0070]

[0071] Among them, i s is the effective value of the motor phase current,

[0072] Optionally, the reference flux linkage ψ of the rotor permanent magnet f According to the rotor temperature t R Calibration is obtained. Reference flux ψ f It will change with the change of temperature, the reference magnetic flux ψ f and rotor temperature t R There is a certain functional relationship, ψ f =f(t R ), reference flux ψ f With the rotor temperature t R decreases with the increase.

[0073] In an alternative example, the rotor temperature t R It can be calculated based on the rotor temperature model. The input information of the rotor temperature model includes bus voltage information Udc, phase current effective value I, rotor angular velocity ω, ambient temperature hot node te, coolant temperature hot node tc, stator temperature hot node ts. The rotor temperature t under different working conditions can be obtained through the rotor temperature model algorithm. R The specific setting of the rotor temperature model can refer to the existing technology.

[0074] The rotor temperature model is used to predict and estimate the temperature change of the rotor during operation. R When the temperature is too high, it will give warning and protection. R and the reference flux linkage ψ of the rotor permanent magnet f Has a corresponding functional change relationship. Usually the rotor temperature t R For every 10℃ rise, the reference magnetic flux ψ f In order to obtain an accurate relationship between the rotor flux and temperature, we can select characteristic points at different temperatures to perform curve fitting (such as a quadratic function), thereby obtaining a quadratic function of the rotor flux-temperature relationship, and thus accurately locating the t at different rotor temperatures. R The reference flux ψ f size.

[0075] Optionally, the angular velocity ω is configured to be not less than a preset speed threshold. According to formula (6), the d-axis observed magnetic flux ψ d,U It is linearly related to the angular velocity ω. In order to provide robustness for demagnetization judgment, the angular velocity ω should not be too small. A preset speed threshold can be set. The preset speed threshold can be obtained by converting the angular velocity into a threshold speed such as 4500 rpm or 6000 rpm.

[0076] An embodiment of the present invention further provides a vehicle-mounted controller, which is used to execute the steps of the above-mentioned method for determining the demagnetization of a permanent magnet synchronous motor, so as to determine in real time whether the permanent magnet of the rotor is demagnetized during the operation of the electric drive system. It can be understood that the execution carrier of the above-mentioned method for determining the demagnetization of a permanent magnet synchronous motor can be software, such as a program, or physical hardware, such as a readable storage medium storing a program. The vehicle-mounted controller contains these software, programs or readable storage media, so that it can be used to execute the above-mentioned method for determining the demagnetization of a permanent magnet synchronous motor. Furthermore, the vehicle-mounted controller can be integrated into the electric drive system, or integrated into the ECU, or independently set, and this embodiment does not limit this.

[0077] In summary, in the demagnetization determination method and vehicle-mounted controller for a permanent magnet synchronous motor provided by the present invention, the demagnetization determination method for a permanent magnet synchronous motor includes: establishing a current model and a voltage model; based on the current model, according to a first system parameter and real-time current, calibrating the current d-axis expected flux based on the current model and outputting dynamic voltage compensation information; based on the voltage model, according to a second system parameter, a command voltage, real-time current, real-time angular velocity, and the dynamic voltage compensation information, observing the current d-axis observed flux based on the voltage model; calculating the difference between the d-axis expected flux and the d-axis observed flux, and determining that the rotor permanent magnet is demagnetized if the difference exceeds a preset threshold. With such a configuration, it is possible to determine whether the rotor of the permanent magnet synchronous motor is demagnetized during normal vehicle operation without disassembling or damaging the motor and without incurring additional hardware costs. Furthermore, it is possible to accurately identify flux anomalies under different speed and torque conditions and specific voltage values, thereby providing high diagnostic robustness for demagnetization detection.

[0078] It should be noted that the above embodiments can be combined with each other. The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure are within the scope of protection of the present invention.

Claims

1. A method for determining demagnetization of a permanent magnet synchronous motor, characterized in that: include: Establish current model and voltage model; Based on the current model, according to the first system parameter and the real-time current, calibrate the current model to obtain the current d-axis expected flux linkage, and output dynamic voltage compensation information; Based on the voltage model, according to the second system parameter, the command voltage, the real-time current, the real-time angular velocity and the dynamic voltage compensation information, a current d-axis observed flux is observed based on the voltage model; a difference between the expected d-axis flux and the observed d-axis flux is calculated, and if the difference exceeds a preset threshold, it is determined that the rotor permanent magnet is demagnetized.

2. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 1, wherein: The first system parameters include the d-axis inductance L d , q-axis inductance L q , the reference flux of the rotor permanent magnet ψ f .

3. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 2, wherein: The expected d-axis flux linkage is obtained based on the following formula: ψ d,I =L d I d +ψ f Among them, ψ d,I is the expected flux linkage along the d axis, i d is the d-axis real-time current.

4. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 2, wherein: The step of obtaining the dynamic voltage compensation information includes: Based on the current model calibration, the current q-axis expected flux is obtained. ψ q,I =L q I q Among them, ψ q,I is the expected flux linkage along the q axis, i q is the real-time current of q axis; The dynamic voltage compensation information is obtained based on the rate of change of the q-axis expected flux linkage over time, Among them, u q Dyn is the dynamic voltage compensation information.

5. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 1, wherein: The second system parameters include stator resistance R, d-axis inductance L d , q-axis inductance L q , the reference flux of the rotor permanent magnet ψ f .

6. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 2 or 5, wherein: The reference flux ψ f Calibrated according to the rotor temperature.

7. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 5, wherein: The d-axis observed magnetic flux is obtained based on the following formula: ψ d,U (u q -Country q -he q Dyn) / ω Among them, ψ d,U is the d-axis observed magnetic flux, u q is the q-axis command voltage, i q is the q-axis real-time current, and ω is the angular velocity.

8. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 7, wherein: The q-axis command voltage 9. The method for determining demagnetization of a permanent magnet synchronous motor according to claim 1, wherein: The angular velocity is configured to be no less than a preset rotation speed threshold.

10. A vehicle-mounted controller, characterized in that: The method is used to execute the demagnetization determination method of the permanent magnet synchronous motor according to any one of claims 1 to 9.

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