Method and device for controlling a three-phase motor

Abstract

The present invention relates to a device and method for controlling a motor using a maximum torque / current field module and a direct flux vector control module. The invention involves determining a reference voltage in an fτ framework with a direct flux vector control module, driving the motor with the summed voltage, measuring the motor current vector, determining a high frequency injection voltage such that the motor's high frequency current response to the high frequency injection voltage is perpendicular to the measured motor current vector, determining an estimated flux from the measured motor current and the reference voltage, and determining a reference flux from the estimated flux and a high frequency sinusoidal signal such that the high frequency flux response to the injected voltage is aligned with the measured current vector.

Description

[Technical field]

[0001] The present invention relates generally to methods and devices for controlling a three-phase motor. [Background technology]

[0002] Electric machines are widely used in either factory automation or transportation industries. Many control techniques for machines such as Permanent Magnet Synchronous Machines (PMSM), Synchronous Reluctance Machines (SyncRM), Wound Rotor Synchronous Machines (WRSM), etc. often use rotary encoders to provide feedback on the speed and position of the machine.

[0003] The demand for low-cost, robust motor drives is driving the development of sensorless controls. Their lack of sensors makes mechanical drives cheaper and more robust to dusty and harsh environments.

[0004] Many techniques have been proposed for sensorless control. These techniques are based on estimating the machine's position and speed, but one aspect of sensorless controllers that is often neglected is the strategy of choosing the reference currents of FOC (Field Oriented Control) controllers from a given desired torque reference. In CVC (Current Vector Control) controllers, the reference quantities are the current levels in the dq axes in the rotor reference frame, whose position must be estimated. In DFVC (Direct Flux Vector Control), the reference quantities are the norm of the flux and one current component. The latter technique is attractive because it also applies to the stator flux reference frame, which does not require position estimation.

[0005] The best current trajectory is the MTPA (Maximum Torque / Current (Maximum Torque Per Current)) which chooses a combination of criteria to maximize the torque for a given current level (and given copper loss). In the literature, various techniques have been proposed to track the MTPA using one or more look-up tables (LUTs) or injection-based techniques. In the case of look-up tables, the torque is measured as a function of the Idq current to derive the ideal MTPA trajectory. This trajectory can be stored with varying torque levels and can be used dynamically. However, certain measurements are required before operating the MTPA mode. This is the most common way to track the MTPA trajectory.

[0006] These methods have significant limitations. It is generally difficult for a general purpose inverter (GPI) to establish a look-up table of MTPA for an unknown motor. An alternative to direct measurement of the MTPA LUT is to manipulate the flux linkage or inductance map LUT, but this also requires a dedicated test or self-commissioning session. For CVC controllers, the MTPA representation requires knowledge of the incremental and code inductances in both the d-axis and q-axis. In general, MTPA control tends to require knowledge of the inductance LUT. Uncertainty in inductance results in position errors and risks of instability and deviations from MTPA, which in turn result in energy abuse in addition to possible loss of control.

[0007] Techniques have been proposed in the literature to track the MTPA and MTPV of a DFVC controller, but these techniques rely on measured inductance LUTs for MTPA tracking.

[0008] Although injection methods for online tracking of MTPA have already been proposed in the literature, those methods are generally used for CVC controllers and cannot be applied to DFVC controllers. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a sensorless control method and device using DFVC control techniques, which reaches the MTPA optimum operating state without any a priori information about the motor being controlled. [Means for solving the problem]

[0010] To this end, the present invention provides a method for controlling a motor using a maximum torque / current field module and a direct flux vector control module, comprising the steps of: The direct flux vector control module estimates the flux

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[0011] The present invention also provides a device for controlling a motor using a maximum torque / current field module and a direct flux vector control module, comprising: The direct flux vector control module estimates the flux

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[0012] Thus, the motor is controlled on the MTPA trajectory without the need for a look-up table. LUT-less MTPA is applied directly to flux-vector control. The overall stability of sensorless control is improved because there is no need to estimate the rotor position and the MTPA criterion is met in any saturation condition.

[0013] According to a particular feature, the high frequency injection voltage

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[0014] Therefore, the HF (high frequency) injection voltage is set to drive the HF change in current coefficient to 0. The HF response of the machine to the HF injection voltage is then orthogonal to the measured fundamental current vector.

[0015] According to a particular feature, the maximum torque / current module comprises: The flux estimated in the j-axis to provide the reference flux

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[0016] It is therefore possible to estimate the HF component of the estimated flux, which is perpendicular to the current. A proportional integral produces a reference flux that can make this HF component zero. In the absence of HF variations in the current amplitude, the resulting reference flux necessarily meets the MTPA criterion.

[0017] According to a particular feature, the direct flux vector control module comprises: Reference current i on the τ axis * τ to the measured current i on the τ axis τ and performing a first proportional-integral adjustment of the result of the subtraction. Reference magnetic flux λ * MTPA and means for subtracting the estimated flux norm from the input signal and performing a second proportional-integral adjustment of the result of the subtraction. a first summing means for summing a result of the second proportional-integral adjustment to a result of the first proportional-integral adjustment; means for adding a result of the first addition to a first value that depends on the stator resistance of the motor, the estimated motor speed, and a reference current in the τ-axis; means for performing a second summation for adding a result of the second proportional-integral adjustment to a second value that is dependent on the stator resistance of the motor and a reference current in the f-axis; Equipped with.

[0018] The machine can therefore be controlled directly by the estimated flux and the measured motor currents without requiring a priori knowledge of the machine rotor position or of the motor saturation state, which changes with torque conditions.

[0019] According to a particular feature, the flux estimation module comprises: load angle

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[0020] Therefore, the estimated load angle can be calculated without the need for a position sensor.

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[0021] The characteristics of the invention will emerge more clearly from a reading of the following description of an exemplary embodiment, the said description being produced with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 illustrates a first example of direct flux vector control of a motor using maximum torque / current in accordance with the present invention. [Diagram 2] FIG. 2 is a block diagram of a direct flux vector control module according to the present invention; [Diagram 3] FIG. 2 illustrates an example block diagram of a magnetic flux estimation module in accordance with the present invention. [Figure 4] FIG. 2 illustrates an example of a block diagram of a maximum torque / current module in accordance with the present invention. [Diagram 5] FIG. 2 illustrates an example block diagram of an injection block module in accordance with the present invention. [Figure 6] FIG. 13 illustrates a second example of direct flux vector control of a motor using maximum torque / current in accordance with the present invention. [Figure 7] FIG. 1 illustrates a motor framework for use with the present invention. [Figure 8] FIG. 4 is a diagram showing an example of an algorithm for controlling a motor according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] FIG. 1 shows a first example of direct flux vector control of a motor using maximum torque / current according to the invention.

[0024] In the system shown in Figure 1, the reference torque T * is the reference magnetic flux λ provided by the MTPA tracking module 155. * MTPA and the number of pole pairs of the motor 135 multiplied by 3 / 2 are supplied to the divider 100, and the reference current i in the τ axis is provided to the DFVC module 110. * τ get.

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[0025] The DFVC module 110 calculates a reference current i * τ and the estimated magnetic flux

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[0026] The reference voltage v in the fτ framework * fτ is provided to the framework transformation module 115, which converts the estimated load angle

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[0027] Reference voltage v in the αβ framework * αβ is provided to the summing module 120. The summing module 120 receives the reference voltage v * αβ The high frequency injection voltage in the αβ framework

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[0028] The reference voltage v in the modified αβ framework ** αβ is provided to a voltage source inverter VSI 130 connected to a motor 135. The motor current vector i measured in the three phases abc is abc is provided to the framework conversion module 140.

[0029] The framework transformation module 140 converts the motor current i measured in the three phases a,b,c into abc Let i be the measured motor current vector in the αβ framework. αβ Convert to.

[0030] Measured motor current vector i in the αβ framework αβ is provided to the flux estimation module 150, the j-axis injection module 125 and the framework transformation module 145.

[0031] The framework transformation module 145 converts the estimated load angle

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[0032] Measured current vector i on the fτ axis fτ is provided to the DFVC module 110.

[0033] The j-axis injection module 125 receives the measured motor current vector i in the αβ framework. αβ and high frequency sinusoidal signal i δ sin(ω h t) to the injection voltage in the αβ framework

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[0034] High frequency injection voltage

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[0035] High frequency injection voltage

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[0036] The flux estimation module 150 estimates the measured motor current vector i in the αβ framework. αβ and the reference voltage v * αβ From the estimated magnetic flux in the αβ framework,

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[0037] The speed estimation module 152 determines the speed of the motor 135 from the estimated load angle.

[0038] For example, speed

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[0039] Magnetic flux in the estimated αβ framework

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[0040] The MTPA tracking module 155 calculates the flux in the estimated αβ framework.

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[0041] In accordance with the present invention, a system includes: The direct flux vector control module estimates the flux

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[0042] Torque is T=i dq T J dq where J is the matrix

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[0043] The MTPA rule states:

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[0044] MTPA, (i dq a ) T Ji dq At λ = 0, the auxiliary flux λ dq a =JLi dq -lJi dq is aligned with the measured current vector.

[0045] The i-axis is i dq In the ij framework aligned with ij =e -Jγ Le Jγ i ij The derivative of is given by:

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[0046] The MTPA condition is, λ j a = 0, this condition is satisfied, so dλ j = 0.

[0047] Therefore, the present invention provides ij = 0, and zero HF flux response dλ on the j axis j This is constructed by injecting a small HF current excitation into the j axis to obtain λ = 0. j a When =0 is achieved, then the flux perturbation vector is aligned with the current vector and the MTPA condition is satisfied.

[0048] In one variant, once the MTPA law is obtained, the high frequency injection is switched off. The magnetic flux is then adapted to the torque conditions according to the MTPA law just obtained.

[0049] In yet another variation, the injection can be turned on sporadically to assess changes in the machine over time and reset the MTPA law.

[0050] FIG. 2 illustrates an example block diagram of a direct flux vector control module according to the present invention.

[0051] The direct flux vector control module 110 calculates a reference current i * τ to the measured current i on the τ axis τ The subtraction module 220 subtracts

[0052] The output of the subtraction module 220 is provided to a PI regulator 225. The output of the PI regulator 225 is provided to a multiplication module 230. The multiplication module 230 multiplies the output of the PI regulator 225 by a decoupling constant value 1 / b.

[0053] The direct flux vector control module 110 calculates the estimated flux norm

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[0054] The outputs of multiplication modules 230 and 210 are added by addition module 235 .

[0055] The output of the summation module 235 is provided to the summation module 240. The summation module 240 converts the result of the summation performed by the summation module 235 into

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[0056] Stator resistance R s is obtained, for example, from a self-commissioning procedure. The motor speed is determined by the load angle of the estimated flux vector.

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[0057] The output of the PI regulator 205 is provided to a summing module 215. The summing module 215 sums the result of the output of the PI regulator 205 with R s i f Add to the reference voltage v on the f axis * f to provide.

[0058] FIG. 3 illustrates an example block diagram of a flux estimation module according to the present invention.

[0059] The flux estimation module 150 estimates the current i α Resistance to R s The reference voltage v on the α axis is * α The signal processing device includes a subtraction module 300 for subtracting from the

[0060] The result of subtraction module 300 is provided to subtraction module 305 .

[0061] The subtraction module 305 subtracts the result provided by the multiplication module 315 from the result of the subtraction module 300 .

[0062] The output of the subtraction module 305 is provided to an integrator 310, which calculates the estimated magnetic flux in the α-axis

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[0063] Estimated magnetic flux in the α-axis

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[0064] The flux estimation module 150 estimates the current i β The resistance R of the motor 135 s This is multiplied by the reference voltage v on the β axis. * β The subtraction module 330 subtracts from

[0065] The result of subtraction module 330 is provided to subtraction module 335 .

[0066] The subtraction module 335 subtracts the result provided by the multiplication module 345 from the result of the subtraction module 330 .

[0067] The output of the subtraction module 335 is provided to an integrator 340, which calculates the estimated magnetic flux in the β axis.

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[0068] Estimated magnetic flux in the β axis

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[0069] The division module 320 divides the estimated magnetic flux in the β-axis by

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[0070] The result of the division module 320 is the estimated load angle

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[0071] FIG. 4 illustrates an example block diagram of a maximum torque / current module according to the present invention.

[0072] The maximum torque / current module 155 determines the angle γ between the measured current and the α axis of the αβ framework. s Using the estimated flux in the αβ framework,

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[0073] Estimated magnetic flux in the j-axis

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[0074] The output of the multiplication module 415 is processed by a low pass filter 420 .

[0075] Modules 415 and 420 form the heterodyne demodulation 410 .

[0076] The output of the heterodyne modulator 410 has an integral gain k λ and a proportional gain of 0. The PI regulator 425 is * MTPA to provide.

[0077] Reference magnetic flux λ * MTPA is therefore controlled to ensure that the flux response to the high frequency injected voltage is null on the j-axis and only on the i-axis. The high frequency flux response to the injected voltage is aligned with the measured current vector.

[0078] FIG. 5 illustrates an example block diagram of an injection block module according to the present invention.

[0079] The injection module 125 calculates the fundamental current vector i αβ_LF As an example, the basic current vector i αβ_LF is the measured current vector i αβ As another example, the fundamental current vector i αβ_LF is the past stored current vector.

[0080] The injection module 125 calculates the measured motor current vector i in the αβ framework. αβ Let i be the measured motor current vector in the ij framework. ij The ij framework includes a framework transformation module 501 for transforming the ij vector into an angle γ s , i.e.

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[0081] The output of the framework transformation module 501 is provided to a high pass filter HPF 510. The output of the high pass filter 510 is provided to a subtraction module 515. The subtraction module 515 subtracts a high frequency sinusoidal signal i δ sin(ω h t) is subtracted from the output of the high pass filter 510.

[0082] The output of the subtraction module 515 is provided to a PI regulator 520 to obtain a voltage injection signal in the ij framework. The voltage injection signal in the ij framework is provided to a framework transformation module 525. The framework transformation module 525 transforms the voltage injection signal in the ij framework into a voltage injection signal in the αβ framework.

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[0083] The high frequency current response to the high frequency injection voltage is therefore controlled to follow a criterion that lies solely on the j-axis: the high frequency current response of the motor to the high frequency injection voltage is perpendicular to the measured motor current vector.

[0084] FIG. 6 illustrates a second example of direct flux vector control of a motor using maximum torque / current according to the present invention.

[0085] The direct flux vector control of the motor device 60 using maximum torque / current has, for example, an architecture based on components connected by a bus 601 and a processor 600 controlled by a program as disclosed in FIG.

[0086] The bus 601 links the processor 600 to a read-only memory ROM 602 , a random access memory RAM 603 and an input / output interface I / O IF 605 .

[0087] The input / output interface I / O IF 605 allows a device that monitors the condition of the motor 135 to sense a signal representative of the current flowing through the motor 135 .

[0088] The memory 603 includes registers intended to receive the variables and instructions of the program related to the algorithm such as that disclosed in FIG.

[0089] The read-only memory ROM 602, or possibly the flash memory, contains instructions of a program related to an algorithm such as that disclosed in Figure 8, which is loaded into the random access memory RAM 603 when the device 60 is powered on. Alternatively, the program can be executed directly from the ROM 602.

[0090] The calculations performed by device 60 may be realized in software by execution of a set of instructions or programs by a programmable computing machine such as a PC (personal computer), DSP (digital signal processor) or microcontroller, or in hardware by a machine or dedicated components such as an FPGA (field programmable gate array) or ASIC (application specific integrated circuit).

[0091] In other words, the device 60 comprises circuitry, or an apparatus comprising circuitry, that causes the device 60 to execute a program associated with an algorithm such as that disclosed in FIG.

[0092] FIG. 7 illustrates the motor framework used by the present invention.

[0093] The αβ two-phase stator framework is depicted in Figure 7. The αβ framework is static with respect to the stator of the motor.

[0094] The dq two-phase rotor framework is depicted in Figure 7. The dq framework is dynamic and tracks the rotor position θ.

[0095] In Fig. 7, the ij two-phase current framework is represented. The i-axis follows the current vector and forms an angle γ with the α-axis. s while the j-axis is perpendicular to the current vector.

[0096] The fτ two-phase flux framework is shown in Figure 7. The f axis tracks the estimated flux vector and is at an angle δ with the α axis. s while the τ axis is perpendicular to the estimated flux vector.

[0097] Figure 7 shows the HF current response to high-frequency voltage injection i HF is shown. HF current response i HF is perpendicular to the i-axis and therefore perpendicular to the measured current vector.

[0098] Figure 7 shows the HF response of the estimated magnetic flux to the high-frequency injected voltage, λ HF is shown. HF response λ HF is aligned with the i-axis and therefore with the measured current vector. The j-axis flux is constant.

[0099] FIG. 8 shows an example of an algorithm for controlling a motor according to the present invention.

[0100] The algorithm is disclosed in an example of direct flux vector control of the motor device 60 executed by the processor 600 .

[0101] In step S800, the processor 600 calculates the reference magnetic flux λ * MTPAand the number of pole pairs of the motor 135 multiplied by 3 / 2, together with the reference torque T * Using the above, the reference current i * τ is calculated as follows:

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[0102] In step S801, the processor 600 calculates a reference current i * τ and the estimated magnetic flux

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[0103] In step S802, the processor 600 calculates the estimated load angle

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[0104] At step S803, the processor 600 calculates the reference voltage v in the modified αβ framework. ** αβ To obtain the reference voltage v in the αβ framework, * αβ is the injection voltage in the αβ framework

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[0105] At step S804, the processor 600 calculates the reference voltage v in the modified αβ framework. ** αβ to a voltage source inverter VSI connected to the motor 135.

[0106] At step S805, the processor 600 calculates the motor current vector i abc Measure.

[0107] In step S806, the processor 600 calculates the motor current vector i measured in the three phases abc. abc Let i be the measured motor current vector in the αβ framework. αβ Convert to.

[0108] At step S807, the processor 600 calculates the measured motor current vector i in the αβ framework. αβ Let i be the measured motor current vector in the fτ framework. fτ Convert to.

[0109] At step S808, the processor 600 calculates the measured motor current vector i in the αβ framework. αβ and high frequency sinusoidal signal i δ sin(ω h t), the injection voltage in the αβ framework

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[0110] At step S809, the processor 600 calculates the measured current vector i αβ and the reference voltage v * αβ From the estimated magnetic flux in the αβ framework,

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[0111] At step S810, the processor 600 calculates the flux in the estimated αβ framework

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[0112] Naturally, many modifications can be made to the embodiment of the invention described above without departing from the scope of the invention.

Claims

1. 1. A method of controlling a motor using a maximum torque / current field module and a direct flux vector control module, comprising: determining, by the direct flux vector control module, a reference voltage in the fτ framework from the estimated flux norm, a reference flux, a measured motor current vector in the fτ framework using the estimated load angle, and a reference torque and a reference current in the τ axis obtained from the reference flux; determining a summed voltage by summing a high frequency injection voltage to the reference voltage transformed in a stator αβ framework; driving the motor with the summed voltage; measuring a motor current vector; determining the high frequency injection voltage from the measured motor current vector and a high frequency sinusoidal current signal such that a high frequency current response of the motor to the high frequency injection voltage is perpendicular to the measured motor current vector; determining an estimated magnetic flux from the measured motor current vector and the reference voltage; determining, by the maximum torque / current field module, from the estimated flux and a high frequency sinusoidal signal, the reference flux provided to the direct flux vector control module such that a high frequency flux response to an injected voltage matches the measured motor current vector; A method comprising:

2. 1. A device for controlling a three-phase motor using a maximum torque / current field module and a direct flux vector control module, comprising: means for determining, by the direct flux vector control module, a reference voltage in the fτ framework from a measured motor current vector in the fτ framework using the estimated flux norm, a reference flux, an estimated load angle, and a reference torque and a reference current in the τ axis obtained from the reference flux; means for determining a summed voltage by summing a high frequency injection voltage to the reference voltage transformed in a stator αβ framework; means for driving the three-phase motor using the summed voltage; means for measuring a motor current vector of the three-phase motor; means for determining the high frequency injection voltage from the measured motor current vector and a high frequency sinusoidal signal such that a high frequency current response of the three-phase motor to the high frequency injection voltage is perpendicular to the measured motor current vector; means for determining an estimated magnetic flux from the measured motor current vector and the reference voltage; means for determining the reference flux provided by the maximum torque / current field module from the estimated flux and the high frequency sinusoidal signal such that a high frequency flux response to an injected voltage corresponds to the measured motor current vector; and A device comprising:

3. The means for determining the high frequency injection voltage includes: A means for determining a fundamental current vector; means for converting the motor current vectors measured in a stator framework into current vectors in a current framework aligned with the determined fundamental current vectors; means for obtaining a filtered current vector by high frequency filtering of the current vector; means for subtracting a high frequency sinusoidal signal in the j-axis of the current framework from the filtered current vector and performing proportional-integral adjustment to obtain a voltage injection signal in the current framework; means for converting the voltage injection signal in the current framework into the high frequency injection voltage in the stator framework; The device according to claim 2, characterized in that it comprises:

4. The maximum torque / current field module comprises: means for performing a heterodyne modulation of the estimated magnetic flux in the j-axis and performing a proportional-integral adjustment of a result of the heterodyne demodulation to provide the reference magnetic flux; 4. A device according to claim 2 or 3, characterized in that it comprises:

5. The direct flux vector control module includes: The measured current i on the τ axis from the reference current on the τ axis τ and performing a first proportional-integral adjustment of the result of said subtraction. means for subtracting the estimated flux norm from the reference flux and performing a second proportional-integral adjustment of the result of the subtraction; a first summing means for summing a result of the second proportional-integral adjustment to a result of the first proportional-integral adjustment; means for adding a result of the first summation to a first value that depends on a stator resistance of the three-phase motor, an estimated motor speed, and the reference current in the τ-axis; means for performing a second summation for adding a result of the second proportional-integral adjustment to a second value that depends on a stator resistance of the three-phase motor and the reference current in an f-axis; 4. A device according to claim 2 or 3, characterized in that it comprises:

6. The means for determining the estimated magnetic flux includes: means for subtracting a motor current on the α-axis multiplied by a stator resistance of the three-phase motor from a reference voltage on the α-axis; a means for subtracting a result of multiplying the estimated magnetic flux in the α-axis by a coefficient from a result of subtracting a product of the motor current in the α-axis and the stator resistance from a reference voltage in the α-axis to obtain an estimated magnetic flux in the α-axis, and performing a third proportional-integral adjustment of the result of the subtraction; means for subtracting a motor current on the β-axis multiplied by the stator resistance from a reference voltage on the β-axis; a means for subtracting a result of multiplying the estimated magnetic flux in the β-axis by the coefficient from a result of subtracting a result of multiplying the motor current in the β-axis by the stator resistance from a reference voltage in the β-axis, to obtain an estimated magnetic flux in the β-axis, and performing a fourth proportional-integral adjustment of the result of the subtraction; 4. A device according to claim 2 or 3, characterized in that it comprises:

7. The magnetic flux estimation module, which is a means for determining the estimated magnetic flux, means for dividing the estimated flux in the β-axis by the estimated flux in the α-axis to provide an estimated tangent of the load angle; The device of claim 6 further comprising:

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