Method for injecting harmonics in a current-regulated or flux-regulated permanent magnet synchronous machine

Abstract

The invention relates to a method for injecting harmonics in a current-regulated or flux-regulated permanent magnet synchronous machine, the current regulator or flux regulator calculating an output voltage for a reference current or a reference flux, the permanent magnet synchronous machine being supplied with an input voltage related to the calculated output voltage, the current regulator obtaining a desired fundamental current as reference current, so that the current regulator regulates the fundamental current, the measured current being modified by subtracting the desired current harmonics, so that in an ideal case only the fundamental current remains, the output voltage of the current regulator being the desired fundamental voltage, the voltage harmonics belonging thereto being subsequently added to the fundamental voltage in a forward direction after the current regulator and before the permanent magnet synchronous machine, or the flux regulator operating in a similar manner, and to an electric or hybrid vehicle comprising a current-regulated or flux-regulated permanent magnet synchronous machine as drive motor and a control device, the control device being configured for implementing such a method.

Description

Technical Field

[0001] This invention relates to a method for injecting harmonics into a permanent magnet synchronous motor with current regulation or flux regulation. Background Technology

[0002] It is known that permanent magnet synchronous motors (PMSMs) can be used as drive motors, for example, in motor vehicles. To control a permanent magnet synchronous motor, methods can be applied to adjust the current or magnetic flux of the motor.

[0003] During operation, permanent magnet synchronous motors can generate unpleasant vibrations, resulting in noise. For applications such as noise reduction, it is known to inject pre-calculated current harmonics—or equivalently, pre-calculated flux harmonics—into the permanent magnet synchronous motor, thereby reducing the harmonics of torque or radial forces that cause mechanical vibrations.

[0004] Desired current harmonics can be introduced in either a closed-loop or open-loop control loop. In the first case, the current harmonics are provided to the current regulator as the desired value. In the second case, the desired current harmonics are converted into corresponding voltage harmonics based on the motor model, and these voltage harmonics are added to the fundamental voltage provided by the current regulator. That is, the current regulator only obtains the desired fundamental current as the desired value, while the harmonics are introduced in a feedforward manner.

[0005] If a desired current harmonic is preset as the expected value for the current regulator, the regulator's tracking performance must be fast enough to achieve the harmonic with acceptable quality. Therefore, depending on the harmonic order considered, this approach is only achievable below a certain speed limit, which is determined by the regulator's bandwidth.

[0006] If harmonics are introduced solely via the corresponding voltage harmonics through feedforward, a high bandwidth of the current regulator is not required. The quality of the resulting current harmonics is primarily related to the quotient of the switching frequency and the electrical fundamental frequency, as well as the accuracy of the motor model used to calculate the required voltage harmonics based on the desired current harmonics.

[0007] However, if the current regulator only obtains the desired fundamental current as a reference and compares that desired fundamental current with the measured current, the current regulator will attempt to eliminate all harmonics. In other words, the voltage harmonic feedforward works in opposition to the current regulator. If the current regulator has a high bandwidth, the quality of the generated current harmonics will deteriorate particularly at low speeds.

[0008] For example, a method for modulating torque ripples and / or radial forces of an electric drive motor, particularly an electric drive motor of a drivetrain of an electrically driven motor operating in a three-phase motor, is known from DE 10 2020 122 099 A1. The method includes the steps of: selecting at least one harmonic in the torque of the motor and / or selecting at least one harmonic in the load of the drivetrain coupled to the motor, and modulating at least one selected harmonic by applying at least one selected harmonic to a d current and / or a q current or a variable associated therewith to generate a desired variable for controlling the motor, wherein the phase angles of the harmonics in the d current and / or the harmonics in the q current are at least temporarily set differently relative to the rotor angle. Summary of the Invention

[0009] The object of this invention is to provide a method for injecting harmonics into a current-regulated or flux-regulated permanent magnet synchronous motor, which reduces harmonics in a permanent magnet synchronous motor in an efficient and cost-effective manner, thereby reducing undesirable noise characteristics. Another object of this invention is to provide an electric or hybrid vehicle including a permanent magnet synchronous motor with improved noise characteristics.

[0010] The solution aims to achieve this by a method for injecting harmonics into a current-regulated or flux-regulated permanent magnet synchronous motor (PMSM), wherein a current regulator or flux regulator calculates an output voltage for a reference current or reference flux; an input voltage related to the calculated output voltage is applied to the PMSM; the current regulator obtains a desired fundamental current as a reference current, causing the current regulator to regulate the fundamental current; the measured current is modified by subtracting desired current harmonics, so that ideally only the fundamental current is retained, and the output voltage of the current regulator is the desired fundamental voltage; and the voltage harmonics are subsequently added in the positive direction, after the current regulator and before the PMSM, to the fundamental voltage.

[0011] Alternatively, the flux regulator obtains the desired fundamental flux as a reference flux, such that the flux regulator adjusts the fundamental flux by subtracting the desired flux harmonics to modify the measured flux, so that ideally only the fundamental flux is retained, and the output voltage of the flux regulator is the desired fundamental voltage, wherein subsequent voltage harmonics are added to the fundamental voltage in the positive direction, after the flux regulator and before the permanent magnet synchronous motor.

[0012] According to the present invention, current regulation or flux regulation is performed on a permanent magnet synchronous motor. Here, on one hand, a preset reference variable, i.e., a reference current or a reference flux, is set as the desired fundamental variable (Grundgröße) by the regulator, while harmonics are not considered, so that the regulator only regulates the fundamental variable. Additionally, the measured value, especially the measured current or flux, is modified at the regulator by subtracting the desired harmonics, and on the output side of the regulator, the corresponding voltage harmonics are subsequently added to the obtained fundamental voltage.

[0013] Therefore, this invention improves harmonic injection. The most important innovation lies in combining harmonic injection via feedforward with current regulation or flux regulation, so that they operate without antagonism. The interaction between feedforward and current or flux regulation is improved.

[0014] Since the fundamental current is constant in the dq coordinate system, the proposed solution does not require a special current regulator or flux regulator with fast tracking performance for harmonic injection. A standard regulator is sufficient.

[0015] The terms “fundamental current”, “fundamental voltage” and “fundamental flux” can also be referred to as “fundamental frequency current”, “fundamental frequency voltage” and “fundamental frequency flux”, whereby these are constant in the dq coordinate system within the scope of this invention.

[0016] When no harmonics other than the desired harmonics appear in the measured current or magnetic flux, it satisfies the condition of retaining only the fundamental current or fundamental magnetic flux.

[0017] The phrase "in an ideal situation" refers to the desired ideal situation, that is, the desired harmonics are consistent with the actual harmonics.

[0018] The use of the plural form of "harmonics" in the described solution, such as in "current harmonics" and "voltage harmonics," refers to: on the one hand, i d and i q The harmonics can be completely independent of each other in amplitude and phase, and in addition, multiple harmonics, i.e. multiple orders, can usually be considered simultaneously. However, this method is not limited to injecting harmonics of multiple orders.

[0019] Improvements to the present invention are given in the specification and accompanying drawings.

[0020] Preferably, the desired current harmonic or the desired magnetic flux harmonic and its associated voltage harmonic are obtained from a lookup table.

[0021] For current harmonics or flux harmonics, and for voltage harmonics, the amplitude and phase are preferably obtained from a lookup table. Particularly preferably, the lookup table is parameterized by torque and speed.

[0022] Preferably, the desired current harmonics or desired magnetic flux harmonics and their associated voltage harmonics stored in a lookup table are calculated using a permanent magnet synchronous motor model that takes into account the correlation between flux linkage and rotor electrical angle.

[0023] Preferably, during operation, the current or flux harmonics and voltage harmonics in the lookup table, together with the rotor electrical angle, are used to reconstruct the corresponding harmonics in the time domain. As described, the lookup table preferably stores the amplitude and phase of the harmonics, from which the signal can be reconstructed in the time domain using the rotor electrical angle.

[0024] The current regulator or flux regulator is preferably implemented in a time-discrete manner, such that the current regulator or flux regulator uses or outputs a constant value over the sampling interval, wherein preferably, the current harmonics or flux harmonics and / or voltage harmonics are composed of the average values ​​over the sampling interval.

[0025] Preferably, the average value is calculated in the dq coordinate system, or in the phase coordinate system UVW fixed to the stator.

[0026] The electric or hybrid vehicle according to the invention includes a permanent magnet synchronous motor with current regulation or flux regulation as a drive motor and a control device, wherein the control device is configured to implement the method described above. Attached Figure Description

[0027] The invention will now be described by way of example with reference to the accompanying drawings.

[0028] Figure 1 A block diagram of the method according to the present invention is shown. Detailed Implementation

[0029] First, the theoretical background of this invention is described, especially regarding one aspect of the permanent magnet synchronous motor 1 (PMSM), namely voltage harmonics (Spannungsharmonischen), i.e., voltage harmonic u. dq,h On the other hand, it is a current harmonic or magnetic flux harmonic. dq,h ψ dq,h The relationship between them. Even though this is usually ignored in regulator design schemes, the flux linkage ψ of the PMSM d and ψ q Not only with current i d and i q It is related to, and also to, the rotor electrical angle φ el Related. This angular correlation is relevant to the applied voltage harmonic u. dq,h =[u d,h u q,h ] T With the generated current harmonics i dq,h= [i d,h i q,h ] T The relationship between them is crucial.

[0030] If we consider the angular dependence of the flux linkage, we obtain the differential equation describing the behavior of the PMSM in the dq coordinate system fixed to the rotor:

[0031] .

[0032] At a given electric angular velocity ω el Under these conditions, the steady-state operating point of the PMSM can be equivalently obtained through the fundamental voltage u. dq,f =[u d,f u q,f ] T or fundamental current i dq,f = [i d,f i q,f ] T To describe this, both are constant in the dq coordinate system fixed to the rotor. For each operating point, the above differential equation establishes the additional applied voltage harmonic u. dq,h With the resulting steady-state current harmonics i dq,h There is a one-to-one correspondence between them. That is, if, for example, one wishes to introduce a specific current harmonic at a particular operating point to reduce torque or radial force harmonics and thus improve the NVH characteristics of the PMSM, then the required voltage harmonic that must be applied can be uniquely determined. This also applies if magnetic flux harmonics are given instead of current harmonics. To derive the relationship between voltage harmonics and their corresponding current or magnetic flux harmonics, it may be appropriate to linearize the above differential equations near the operating point under consideration, as this simplifies the calculation of the system's steady-state behavior.

[0033] The following describes the integration of harmonic injection into the control loop more precisely. Figure 1 The block diagram illustrates the proposed harmonic injection method.

[0034] Desired current harmonics i dq,h and the corresponding voltage harmonic u dq,h The values ​​are stored in lookup tables 3 and 4, which contain the amplitude and phase of the harmonics for the considered operating point range. The operating point can be parameterized, for example, by torque τ and speed—this is relative to using the fundamental current i. dq,f This is advantageous in terms of rotational speed, as rotational speed will add one dimension to lookup tables 3 and 4.

[0035] During operation, refer to Tables 3 and 4 for the amplitude and phase values ​​and the rotor electrical angle φ. el (t) together are used to reconstruct the voltage harmonic u in the time domain.dq,h (t) and current harmonics i dq,h (t). The relationship between the amplitude and phase values ​​of the harmonics under consideration and the time-domain signal generated by superimposing these harmonics has the following form:

[0036]

[0037] The amplitude and phase can be different for the d and q directions, and at least theoretically, any number of harmonics (index j) can be considered simultaneously. However, in practice, such as in noise reduction applications, the goal is usually to reduce the 6th and 12th electrical harmonics of torque and / or radial force, so typically only the corresponding 6th and 12th voltage and current harmonics need to be considered. Therefore, preferably, only the 6th and 12th harmonics are stored in lookup tables 3 and 4, while all other harmonics in the above formulas except for j = 6 and j = 12 are zero.

[0038] The key to the method according to the present invention is that the current regulator 2 regulates only the fundamental current i. dq,f (Or the flux regulator can be configured to adjust only the fundamental flux.) More precisely, the current regulator 2 obtains the desired reference fundamental current i. dq,f,ref For reference, and by subtracting the desired current harmonic i dq,h To modify the measured current i dq This ensures that, under ideal conditions—that is, when the actual current harmonics match the desired current harmonics—only the fundamental current i remains. dq,f Therefore, the output of current regulator 2 is only the desired fundamental voltage u. dq,f voltage harmonics u dq,h It is then added in the positive direction. Since the fundamental current is constant in the dq coordinate system, the proposed harmonic injection method does not require a special current regulator with fast tracking performance—a standard current regulator is sufficient. If a flux regulator is used instead of a current regulator, this method can be easily adjusted by replacing the current with magnetic flux.

[0039] like Figure 1 As can be seen from the fundamental voltage u dq,f and the added voltage harmonics u dq,h The voltage value u obtained in the dq coordinate system dq After being converted from dq / UVW, the voltage is supplied to the permanent magnet synchronous motor 1. UVW The voltage generated from the DC voltage supplied by the battery can be obtained using appropriate modulation methods, such as space vector pulse width modulation, and an inverter. This voltage can then be supplied to the permanent magnet synchronous motor (PMSM). The phase current i appearing at point 1 of the PMSM... UVWAfter UVW / dq transformation 7, it is then used to create the current fundamental current i. dq,f The base value is fed back to the current regulator 2.

[0040] Note: Current regulators typically include a feedforward section based on the requested reference current i. dq,f,ref Directly calculate the output voltage. It might be a mistake to assume that using a lookup table is detrimental to both current and voltage harmonics, and that simply adding the desired current harmonic to the reference current would suffice. Apply the reference signal i to the current regulator. dq,ref = i dq,f,ref + i dq,h —and compare it with the complete measured current i dq The comparison will not yield the same voltage u as our method. dq = u dq,f + u dq,h The reason is that the current harmonics i dq,h With voltage harmonics u dq,h The relationship between them is preferably calculated based on the PMSM model, which considers the magnetic flux linkage ψ. d and ψ q With rotor electrical angle φ el This is a very important correlation. Due to limitations in storage and computational costs, it is usually impossible to incorporate this accurate, angle-dependent model into the current regulator. Without this angle-dependent motor model, the current regulator cannot calculate the correct voltage harmonics.

[0041] The implementation aspects of the time-discrete control loop are then described. On a microcontroller, only time-discrete control loops can be implemented, which means that the voltage u to be applied to PMSM 1... dq (t) cannot change continuously. Instead, the voltage is kept constant piecewise over each sampling interval. This leads to the question of how to evaluate voltage harmonics u. dq,h The problem with (t) is that only u is applied. dq,h,k = u dq,h (kT a ) from t = kT a up to t = (k + 1)T a Errors will be introduced within the sampling interval. A more accurate representation of the desired voltage harmonics can be achieved by applying the desired average value.

[0042] .

[0043] By converting the desired voltage harmonics into the phase coordinate system u fixed to the stator UVW,hHigher accuracy can be achieved by applying the expected average value in (t):

[0044] .

[0045] Of course, this is on the premise that the fundamental voltage and the desired harmonic in the current regulator are also summed in the phase coordinate system.

[0046] Regarding the desired current harmonics i dq,h The evaluation of (t) has a similar problem. For example, if the current is measured at the beginning of each sampling interval, it should be based on i dq,h,k = i dq,h (kT a This is used to evaluate current harmonics. However, if current oversampling is used, the resulting current value approximately represents the average value over the previous sampling interval. In this case, the desired current harmonics are evaluated by determining the average value over that sampling interval, based on...

[0047]

[0048] Or even according to

[0049]

[0050] It can be performed more precisely in the phase coordinate system fixed to the stator.

[0051] The proposed harmonic injection method generally achieves precise injection of desired harmonics over a wide speed range using a feedforward approach, ensuring that the current regulator does not intervene undesirably. A typical application is noise shaping, which aims to introduce harmonics to improve the NVH characteristics of permanent magnet synchronous motors. This noise shaping or reduction can be very helpful in meeting specific NVH requirements without requiring costly hardware changes, such as modifications to the motor's structural design or even NVH coverings.

[0052] This patent application claims priority to German patent application 102025112624.0, the disclosure of which is incorporated herein by reference.

[0053] List of reference numerals

[0054] 1. Permanent magnet synchronous motor

[0055] 2 Current regulator

[0056] 3. Current Harmonic Lookup Table

[0057] 4. Voltage Harmonic Lookup Table

[0058] 5. Angular velocity calculation

[0059] 6 dq / UVW transformation

[0060] 7 UVW / dq conversion

[0061] i d Current (d-coordinate)

[0062] i q Current (q-coordinate)

[0063] i dq Current (fixed to the rotor's dq coordinate)

[0064] i dq,f Fundamental current

[0065] i dq,f,ref Reference fundamental current

[0066] i dq,h Current harmonics

[0067] i UVW Phase current

[0068] t time

[0069] u d Voltage (d-coordinate)

[0070] u q Voltage (q-coordinate)

[0071] u dq Voltage (fixed to the rotor's dq coordinates)

[0072] u dq,f Fundamental voltage

[0073] u dq,f,ref Reference fundamental voltage

[0074] u dq,h Voltage harmonics

[0075] u UVW Phase voltage

[0076] ψ d Magnetic flux (d-coordinate)

[0077] ψ q Magnetic flux (q-coordinate)

[0078] ψ dq Magnetic flux (fixed to the rotor's dq coordinates)

[0079] ψ dq,f Fundamental flux q

[0080] ψ dq,f,ref Reference fundamental magnetic flux

[0081] ψ dq,h magnetic flux harmonics

[0082] τ ref Reference torque

[0083] φ el Rotor electrical angle

[0084] ω el electric angular velocity

Claims

1. A method for injecting harmonics into a permanent magnet synchronous motor (1) with current regulation or flux regulation, The current regulator (2) or flux regulator calculates the output voltage for a reference current or reference flux, wherein an input voltage related to the calculated output voltage is applied to the permanent magnet synchronous motor (1). Its features are, The current regulator (2) obtains the desired fundamental current (i dq,f,ref ) as a reference current, so that the current regulator (2) adjusts the fundamental current (i dq,f,ref ), where by subtracting the desired current harmonics (i dq,h To modify the measured current (i) dq ), so that under ideal conditions only the fundamental current (i) is retained. dq,f ), and the output voltage of the current regulator (2) is the desired fundamental voltage (u). dq,f ), wherein subsequently in the positive direction, after the current regulator (2) and before the permanent magnet synchronous motor (1), the corresponding voltage harmonics (u) will be dq,h ) is applied to the fundamental voltage (u dq,f )superior, Alternatively, the flux regulator can obtain the desired fundamental flux (ψ). dq,f,ref Using ψ as a reference magnetic flux, the flux regulator adjusts the fundamental magnetic flux (ψ). dq,f,ref ), where by subtracting the desired magnetic flux harmonics (ψ) dq,h To modify the measured magnetic flux (ψ) dq This ensures that, ideally, only the fundamental magnetic flux (ψ) is retained. dq,f ), and the output voltage of the flux regulator is the desired fundamental voltage (u). dq,f ), wherein subsequently in the positive direction, after the flux regulator and before the permanent magnet synchronous motor (1), the associated voltage harmonics (u dq,h ) is applied to the fundamental voltage (u dq,f )superior.

2. The method according to claim 1, Its features are, Obtain the desired current harmonics (i) from lookup table (3, 4). dq,h ) or the desired magnetic flux harmonic (ψ) dq,h ) and the voltage harmonics to which they belong (u dq,h ).

3. The method according to claim 2, Its features are, For the desired current harmonics (i dq,h ) or the desired magnetic flux harmonic (ψ) dq,h ) and the voltage harmonics to which they belong (u dq,h The amplitude and phase are obtained from the lookup table (3, 4), wherein preferably the lookup table (3, 4) is obtained through torque (τ). ref The parameters are parameterized for the rotational speed.

4. The method according to claim 2, Its features are, The desired current harmonics (i) in the lookup table (3, 4) are calculated using a permanent magnet synchronous motor model. dq,h ) or the desired magnetic flux harmonic (ψ) dq,h ) and the voltage harmonics to which they belong (u dq,h The permanent magnet synchronous motor model described above considers magnetic flux linkage (ψ). d ) and (ψ q ) and rotor electrical angle (φ) el The correlation of ).

5. The method according to claim 2, Its features are, During operation, the current harmonics (i) in the lookup table (3, 4) will be... dq,h ) or the magnetic flux harmonics (ψ) dq,h ) and the voltage harmonics (u dq,h ) and the rotor electrical angle (φ) el (t) together are used to reconstruct the current harmonics (i) in the time domain. dq,h (t) or the magnetic flux harmonic (ψ) dq,h (t) and the voltage harmonics (u) dq,h (t)).

6. The method according to at least claim 1 or 2, Its features are, The current regulator (2) or the flux regulator is implemented in a time-discrete manner, such that the current regulator or the flux regulator uses a constant value within the sampling interval, wherein the current harmonics (i dq,h ) or the magnetic flux harmonics (ψ) dq,h ) and / or the voltage harmonics (u dq,h It is composed of the average value over the sampling interval.

7. The method according to claim 6, Its features are, The average value can be obtained in the dq coordinate system or in the phase coordinate system UVW fixed to the stator.

8. An electric or hybrid vehicle, comprising a permanent magnet synchronous motor (1) with current regulation or flux regulation as a drive motor and a control device, wherein the control device is configured to perform the method according to at least one of the preceding claims.

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