Method and apparatus for controlling electric motor using direct flux vector control module and constant current angular trajectory module

Abstract

The present invention relates to an apparatus and a method for controlling an electric motor using a DFVC module and a CCAL module. In the present invention, a torque reference is determined, a magnetic flux reference and a current reference are determined by a CCAL module according to the torque reference and a predetermined angle, the magnetic flux reference and the current reference are provided to a DFVC module to obtain a reference voltage provided to a motor, a high frequency signal is injected to the reference voltage, an estimated value of the direction of the magnetic flux of the motor is determined from the motor current vector, and an estimated value of the magnetic flux and an estimated value of the current flowing perpendicular to the estimated direction of the magnetic flux are determined from the estimated value of the direction of the magnetic flux. The estimated value of the magnetic flux and the estimated value of the current flowing perpendicular to the estimated direction of the magnetic flux are supplied to the DFVC module.

Description

Technical Field

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

[0002] Electric machines are widely used in industry for factory automation or transportation. Many control technologies for machines such as permanent magnet synchronous machines (PMSM), synchronous reluctance machines (SyncRM), and wound rotor synchronous machines (WRSM) often use rotary encoders to obtain the speed and position of the machine as feedback.

[0003] The need for low-cost and durable motor drives has led to the development of sensorless control. Without these sensors, machine drives become cheaper and more durable in dusty and harsh environments.

[0004] Many techniques for sensorless control have been proposed. These techniques are based on an inference of the position and speed of the machine, but one aspect of sensorless controllers that is often overlooked is the strategy used to select the current reference for the FOC (field oriented control) controller from a given required torque reference. MTPA (maximum torque per ampere) operation uses the minimum level of current that can produce a given torque, thus minimizing the level of current induction losses (inverter and motor losses) in the motor drive.

[0005] In a CVC controller (current vector control), the reference quantity is the coordinate of the current vector in the rotor (dq) axis frame. In this frame, the MTPA condition is satisfied only in a specific direction of the current vector. The ideal direction depends on the machine's parameters, which vary on the d-axis and q-axis as a function of the current coordinate.

[0006] To achieve the MTPA condition, the inductance level and rotor position must be estimated. To address this problem, some machine controllers are equipped with a self-tuning routine to obtain and store a lookup table (LUT) of inductance versus current. In the absence of a previously prepared test load, it is difficult to obtain an inductance table that is valid for full load conditions, so the disadvantages of this method are related to the discovery time before the driven machine is used for the first time, the memory required, and the accuracy.

[0007] In DFVC (Direct Flux Vector Control), the reference quantities are the flux norm and a current component. The technique operates in the stator flux framework where no estimation of the rotor position is required. Instead, DFVC operation requires the estimation of the flux norm and the current component perpendicular to the flux. Operating DFVC under MTPA conditions at a given torque also requires the determination of the optimal flux norm. For example, for high speeds, it is believed that the optimal flux norm is achieved when the HF current response of the machine to an HF voltage pattern injected in the direction of the current vector is perpendicular to the current vector.

[0008] The main problem with using DFVC is its reliance on a flux estimator. In the absence of a LUT, a typical flux estimator is based on BEMF sensing (back electromotive force field), which is the product of speed and flux linkage. However, for low and zero speed conditions, the flux cannot be properly estimated from the BEMF. As a result, sensorless DFVC tends to have stability issues at low speeds and in the absence of a LUT. Summary of the invention

[0009] The present invention is directed to providing a sensorless control method and apparatus using sensorless DFVC control that is effective for low speed and without a LUT.

[0010] To this end, the present invention relates to a method for controlling an electric motor using a direct flux vector control module and a constant current angle trajectory module,

[0011] Characterized in that the method comprises the following steps:

[0012] Determine the torque reference;

[0013] Determining a flux reference and a current reference by the constant current angle trajectory module according to the torque reference and a predetermined angle;

[0014] providing the flux reference and the current reference to the direct flux vector control module to obtain a reference voltage provided to the motor;

[0015] injecting a high frequency signal into the reference voltage;

[0016] determining an estimate of the direction of the magnetic flux of the motor based on the motor current vector;

[0017] determining an estimated value of a norm of the magnetic flux and an estimated value of a current flowing perpendicularly to the estimated direction of the magnetic flux based on the estimated value of the direction of the magnetic flux; and

[0018] The estimated value of the norm of the magnetic flux and the estimated value of the current flowing perpendicular to the estimated direction of the magnetic flux are provided to the direct flux vector control module.

[0019] The invention also relates to a device for controlling an electric motor using a direct flux vector control module and a constant current angle trajectory module,

[0020] The device comprises a unit for performing the following processing:

[0021] Determine the torque reference;

[0022] Determining a flux reference and a current reference by the constant current angle trajectory module according to the torque reference and a predetermined angle;

[0023] providing the flux reference and the current reference to the direct flux vector control module to obtain a reference voltage provided to the motor;

[0024] injecting a high frequency signal into the reference voltage;

[0025] determining an estimate of the direction of the magnetic flux of the motor based on the motor current vector;

[0026] determining an estimated value of a norm of the magnetic flux and an estimated value of a current perpendicular to the estimated direction of the magnetic flux based on the estimated value of the direction of the magnetic flux; and

[0027] The estimated value of the norm of the magnetic flux and the estimated value of the current flowing perpendicular to the estimated direction of the magnetic flux are provided to the direct flux vector control module.

[0028] Therefore, the flux reference and the current reference perpendicular to the flux can be determined under any conditions including low speed conditions. Since the angle between the estimated current and the estimated flux is stabilized, the generated torque is stable. Even when the quality of the flux estimation is poor, stability is maintained at low speeds.

[0029] The proposed sensorless control is also effective at low speeds and at standstill. Since the scheme works well at low speeds, a similar control structure can also be applied at high speeds (e.g., above 200 rpm) using an accurate BEMF-based flux estimator with a smooth transition between the low and high speed regions (e.g., 200 rpm). Since the DFVC controller does not require an estimation of the rotor angle, the controller structure does not have the tendency to become unstable due to inaccurate estimation of the rotor position.

[0030] According to a specific feature, a flux reference is determined using a first function that is a square root of a value obtained by multiplying a nominal parameter of the motor by the product of the torque divided by the tangent of a reference angle, and a current reference is determined using a second function that is a square root of a value obtained by multiplying a nominal parameter of the motor by the product of the torque reference multiplied by the tangent of the reference angle.

[0031] Therefore, the flux reference and current reference used in DFVC ensure that DFVC control using a fixed angle between the flux vector and the current vector is achieved under any torque condition.

[0032] According to a specific feature, the first function is And the second function is Among them, λ n is the nominal magnetic flux of the motor, I n is the nominal current of the motor, sin(φ n ) is based on the nominal power factor of the motor cos(φ n ) is determined by, p is the number of electrode pairs of the motor.

[0033] Therefore, the torque generated by the DFVC controller is a good approximation of the reference torque under nominal conditions. Under other torque conditions, the generated torque may deviate from the reference torque level. However, even at low speeds, the level of the generated torque is stable and the level of the torque reference can be adjusted.

[0034] In the presence of errors in the flux estimation, the DFVC trajectory adopted by the DFVC controller does not deviate significantly from the optimal maximum torque per ampere (MTPA) condition. Therefore, the CCAL controller is stable but also efficient at low speeds.

[0035] According to a specific characteristic, the flux reference λ is determined according to the following formula * and the current reference i τ * :

[0036]

[0037] Among them, λ n is the nominal magnetic flux of the motor, I n is the nominal current of the motor, sin(φ n ) is based on the nominal power factor of the motor cos(φ n ), p is the number of electrode pairs of the motor, T * is the torque reference and γ λ * is a predetermined angle.

[0038] According to a particular feature, the predetermined angle falls between 30° and 45°.

[0039] Therefore, the DFVC trajectory does not deviate significantly from the MTPA trajectory. In addition, angles that deviate from this range may cause problems such as instability of the DFVC controller (in the case of larger angles) or undesirable motor losses (in the case of smaller angles).

[0040] According to a particular feature, the predetermined angle is And it is determined that, and is the nominal inductance estimated from the motor's nameplate characteristics, and or larger.

[0041] Hence, the controller trajectory is better matched to the MTPA conditions.The predetermined angle may be adapted to the nominal saliency of the machine according to its nameplate characteristics.

[0042] According to a particular feature, the predetermined angle is determined as a function of the torque stored in a look-up table.

[0043] Therefore, accurate MTPA conditions can be met in states that deviate from nominal conditions, improving the efficiency of the DFVC controller at low speeds and at rest. For example, the table can be obtained using an MTPA tracking algorithm that is available at high speeds.

[0044] According to a particular feature, the predetermined angle is determined based on the current to torque reference ratio observed at different sizes of the predetermined angle and different sizes of the torque reference, and the optimal angle is determined as the angle that minimizes the current to torque reference ratio observed for the determined torque reference.

[0045] Therefore, the precise MTPA conditions can be met at deviating conditions from the nominal conditions, improving the efficiency of the DFVC controller at low speeds and at rest. The controller can acquire the table at rest without having to perform MTPA acquisition at high speeds.

[0046] According to a particular feature, the estimated magnetic flux level is estimated by multiplying the current projected onto the axis of the estimated magnetic flux by a fixed ratio.

[0047] Therefore, even at low speeds, the flux estimate is easily determined. The linearity assumption has considerable error, but correctly reflects the monotonicity of the dependence of the flux level on the current level. In other words, the estimated flux may tend to have estimation errors in norm and / or direction (e.g. due to saturation and / or saliency), but the estimation error is locally stable. Even in the low speed / stationary operating region where the back EMF due to rotation is difficult to detect, DFVC can effectively control the flux estimate with errors to be close to the reference flux reference.

[0048] According to one particular feature, the fixed ratio is determined according to the nameplate characteristics of the motor.

[0049] Therefore, the estimated flux is estimated without error at the nominal operating point of the machine. At this point, the proposed control method operates at MTPA conditions, i.e., the current level required to achieve the desired torque level is minimized. At other torque conditions, the control method operates without greatly deviating from the true MTPA conditions and the resulting increase in copper losses is kept small. The sensorless control method operates near the true MTPA conditions at low speeds.

[0050] According to a specific feature, the high-frequency injection signal is parallel to the estimated magnetic flux vector, and the angle of the magnetic flux vector is estimated in such a way that the high-frequency response of the current vector becomes parallel to the current.

[0051] Thus, despite the lack of knowledge of the exact inductive conditions of the machine, the angle of the flux vector is estimated. The proposed control method operates in the complete absence of a look-up table. Since the HF flux injection is proportional to the flux, changes in the current level orthogonal to the current direction are easily detected, causing it to become zero.

[0052] According to a specific feature, the high frequency injection is perpendicular to the estimated magnetic flux vector, and the angle of the magnetic flux vector is estimated in such a way that the high frequency response of the current vector becomes perpendicular to the current vector.

[0053] Thus, despite the lack of knowledge of the exact inductive conditions of the machine, the angle of the flux vector is estimated. The proposed control method operates in the complete absence of a look-up table. Since the HF flux injection is perpendicular to the flux, the iron losses due to HF injection are minimized.

[0054] The features of the present invention will become more apparent from a reading of the following description of embodiments, which is made with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1A first example of a direct flux vector controller of a motor using a constant current angle locus (CCAL) according to the present invention is shown.

[0056] Figure 2 An example of a block diagram of a high-frequency injection module according to the present invention is shown.

[0057] Figure 3 An example of a block diagram of a magnetic flux estimation module according to the present invention is shown.

[0058] Figure 4 An example of a block diagram of a module for estimating a magnetic flux level of a current perpendicular to an estimated direction of the magnetic flux according to the present invention is shown.

[0059] Figure 5 An example of a block diagram of a direct flux vector control module according to the present invention is shown.

[0060] Figure 6 An example of a torque estimation module according to the present invention is shown.

[0061] Figure 7 Shows a motor frame used in the present invention.

[0062] Figure 8 An example of a frame conversion module that uses the estimated direction of the magnetic flux vector The reference voltage v in the fτ frame * fτ Convert to the reference voltage v in the αβ frame ** αβ .

[0063] Fig. 9 An example of an algorithm for controlling a motor according to the present invention is shown.

[0064] Fig.10a Results from measurements at different angles compared to an ideal MTPA system are shown.

[0065] Fig.10b Results from measurements at different angles compared to an ideal MTPA system are shown.

[0066] Fig.11 A second example of a direct flux vector controller for a motor using a constant current angle trajectory according to the present invention is shown. DETAILED DESCRIPTION

[0067] Figure 1 A first example of a direct flux vector controller for a motor using a constant current angle trajectory according to the present invention is shown.

[0068] Figure 1The direct flux vector controller of the electric motor using the constant current angle trajectory shown includes: a current-flux angle determination module 100; a constant current angle trajectory module 101; a direct flux vector control module 102; an HF injection module 103; a frame conversion module 104; an inverter 105a, which is connected to the electric motor 105b; a current measurement module 107; a flux angle estimation module 108; an estimation module 109, which is an estimation module of the flux level and the current perpendicular to the estimated direction of the flux; and a torque reference determination module 110.

[0069] For linear machines, MTPA operation is for a 45° dq frame (i.e., I d =I q ) of the current emission angle For non-linear machines, ideal MTPA operation is achieved for higher current angles, which may deviate from the nominal point by, for example, 55°.

[0070] When considering a typical synchronous reluctance machine with a typical saliency ratio of 2-4, this gives a corresponding flux emission angle of 15-25° on the d-axis.

[0071] The current flux angle determination module 100 determines the angle of the current vector in the fτ frame, that is, the predetermined angle γ λ , which is equal to the difference between the current emission angle and the magnetic flux emission angle. λ It is set within the range of 30-45°.

[0072] In the first variation of the present invention, the predetermined angle γ λ is in accordance with And it is determined that, and is the nominal inductance estimated from the motor's nameplate characteristics, and e.g.

[0073] In a preferred embodiment of the present invention, since the sensorless control is operated away from the low incremental salient pole region, the predetermined angle is preferably reduced by, for example, 5° (for example, using ), thereby maintaining the stability margin of sensorless control.

[0074] In another variation of the present invention, the predetermined angle γ λ is determined as a function of torque stored in a lookup table. For example, the MTPA trajectory can be acquired at high speed together with the inductance data. From this data, a function that correlates torque with the optimal predetermined angle γ can be constructed. λ At low speed, the predetermined angle γ is set according to the determined torque level. λ .

[0075] In another variation of the present invention, at different angles γ λ The current to torque reference ratio is observed and stored for different magnitudes of torque. The optimal angle is determined as the angle that minimizes the current to torque reference ratio of the torque reference determined by the torque reference determination module 110 .

[0076] The constant current angle trajectory module 101 is based on the torque reference T * and angle γ λ * The flux reference level λ is determined * and the current reference level i τ * .

[0077] The constant current angle trajectory module 101 stores the nominal parameters of the motor and adjusts the flux reference level λ according to the first function. * The first function is calculated by multiplying the nominal parameters of the motor by the torque reference divided by the angle γ λ * The square root of the value obtained by taking the tangent of .

[0078] The constant current angle trajectory module 101 calculates the current reference level i according to the second function τ * The second function is calculated by multiplying the nominal parameters of the motor 105 by the product torque reference by the angle γ λ * The square root of the value obtained by taking the tangent of .

[0079] In a preferred embodiment of the present invention, the first function is And the second function is Among them, λ n is the nominal magnetic flux of the motor 105b, I n is the nominal current of the motor 105b, sin(φ n ) is based on the nominal power factor cos(φ n ) is determined, and p is the number of electrode pairs of the motor 105b.

[0080] Torque is usually expressed as:

[0081]

[0082] where ‖λ‖ is the norm of the magnetic flux vector, and i τ is the projection of the current vector perpendicular to the magnetic flux vector.

[0083] At the nominal operating point, ‖λ‖=λ n And i τ =In sin(φ n ),therefore I n , n ,φ n 、T n and p are the nominal conditions of the motor 105b, which can be accessed through the data sheet or the motor.

[0084] Using the linear flux inference model, we get

[0085] Considering that the current vector forms the required angle γ with the magnetic flux vector λ * , we get i τ =‖I‖sin(γ λ * ),i f = ‖I‖cos(γ λ * ),thus, Thus, the expression for the current amplitude becomes

[0086] According to the present invention, the formulas for the reference torque and current levels are given as follows:

[0087]

[0088] refer to Figure 5 A direct flux vector control module 102 is disclosed.

[0089] Figure 5 An example of a block diagram of a direct flux vector control module according to the present invention is shown.

[0090] The direct flux vector control module 102 includes two subtraction modules 500 and 502 and proportional integral filters 501 and 503 .

[0091] The subtraction module 500 is derived from the flux reference level λ * Subtract the estimated flux vector from Norm.

[0092] The output of the subtraction module 500 is provided to a proportional-integral filter 501, which provides a voltage reference V on the f-axis. f * .

[0093] As a result of PI control, the voltage vector V f * Driving is performed so that the estimated magnetic flux norm is equal to the reference magnetic flux norm.

[0094] The subtraction module 502 obtains the current reference level i τ * Subtract the estimated current from

[0095] The output of the subtraction module 502 is provided to the proportional-integral filter 503, which provides the voltage reference V on the τ axis. τ * .

[0096] As a result of PI control, the voltage vector V τ * Driving is performed so that the estimated current is equal to the reference current level.

[0097] According to the predetermined controller bandwidth ω DFVC And set the coefficients of the PI filter:

[0098] k p,f =2ω f

[0099] k i,f =(ω f ) 2

[0100] k p,τ =2L τ ω τ

[0101] k i,τ =(ω τ ) 2 ·L τ

[0102] For example, ω f =2πf f rad / s,ω τ =2πf τ rad / s, where f f and f τ Falls into [50..500]Hz. L τ represents the inductance of the machine on the v-axis and can be estimated from the machine's nameplate characteristics. DFVC control frequency f DFVC The choice of is related to the desired dynamics of the control, i.e., the ability to bring the estimated flux and current close to the reference flux and current within a given time window. In a variant, the DFVC module may also add feedforward terms (determined according to current level and speed) and / or decoupling terms.

[0103] The high frequency injection module 103 injects the high frequency signal (-1) n V hf Superimposed on the voltage reference V fτ* .

[0104] Figure 2 A high frequency injection module 103 is disclosed.

[0105] Figure 2 An example of a block diagram of a high-frequency injection module according to the present invention is shown.

[0106] The high frequency injection module 103 is composed of a conversion module 211 and a summing module 212 .

[0107] The conversion module 211 executes Transformation, where J is a matrix And θ inj represents the angle of HF injection in the stator flux reference frame. For example, θ inj =0 or Π / 2.

[0108] In other words, the high-frequency injection signal is parallel to the estimated flux vector at this time, and the direction of the flux angle is estimated in such a way that the high-frequency response of the current vector becomes parallel to the current, or the high-frequency injection becomes perpendicular to the estimated flux vector. The direction of the flux angle is estimated in such a way that the high-frequency response of the current vector becomes perpendicular to the current vector.

[0109] The output of the conversion module 211 is added to the voltage reference V determined by the DFVC module 102. fτ * Then, the frame conversion module 104 converts V fτ ** The results are converted to the αβ framework.

[0110] For example, a high frequency signal is a sine wave.

[0111] For example, a high frequency signal (-1) n V hf It has a fixed amplitude in the range of 5V to 100V and changes polarity at the activation frequency of the DFVC controller. For example, the activation frequency of the DFVC controller is equal to the switching frequency of the inverter 105a or twice the switching frequency of the inverter 105a. The switching frequency falls within [1..50]kHz.

[0112] Figure 8 An example of the frame conversion module 104 is given.

[0113] The frame conversion module 104 uses the estimated magnetic flux direction implement Transformation, where J is a matrix And V αβ * It is then used to drive the electric motor 105b via the voltage source inverter 105a.

[0114] The measurement module 107 measures the motor current vector i in the three-phase abc abc The motor current i measured in the three-phase abc is abc Converted to the motor current vector i measured in the αβ frame αβ .

[0115] The motor current vector i αβ It is provided to the module 108 for estimating the magnetic flux angle, the module 109 for estimating the magnetic flux level and the current perpendicular to the estimated direction of the magnetic flux.

[0116] refer to Figure 3 An example of the flux angle estimation module 108 is disclosed.

[0117] Figure 3 An example of a block diagram of a magnetic flux estimation module according to the present invention is shown.

[0118] The magnetic flux angle estimation module 108 is composed of two filters 311 and 321 , an angle detection module 312 , a frame conversion module 313 , two multipliers 322 and 323 , a proportional-integral filter 324 , and an integrator 325 .

[0119] The filter 311 converts the current vector i αβ The sampling and current vector i αβ The previous samples are added.

[0120] The angle detection module 312 determines the angle γ of the current vector projected onto the α-axis. α , and provides the angle of the current vector on the α-axis to the frame conversion module 313.

[0121] The frame conversion module 313 executes Rotation conversion, where J is the current vector i αβ The matrix

[0122] Only orthogonal to (γ α +θ inj The converted current vector projected by a rotation angle (on the +π / 2 axis) is provided to the filter 321.

[0123] Filter 321 converts the current vector Sampling and current vector The previous samples are added.

[0124] The output of the filter 321 is multiplied by (-1) by the multiplier 322. n-1, i.e., using the polarity of the HF voltage injected at the previous activation of the high frequency injection module 103. The function of the multiplier 322 is similar to a simplified heterodyne demodulation applied to a square wave. The invention can be equally applied to other injection types where the multiplier 322 can be replaced by a heterodyne demodulator.

[0125] The output of the multiplier 322 is multiplied by 1 / i0 by the multiplier 323 .

[0126] Therefore, the HF response current is first heterodyned and then the proportional-integral filter 324 makes the output of the heterodyne demodulation zero. The output of the proportional-integral filter 324 estimates the speed of the motor. Integration by integrator 325 provides an estimated direction of the magnetic flux

[0127] According to the proportional-integral filter bandwidth ω δ And set the coefficients of the integrating filter 324:

[0128] k p,δ =2ω δ

[0129] k i,δ =(ω δ ) 2

[0130] For example, ω δ =15rad / s. Proportional integral filter bandwidth ω δ Related to the expected dynamics of tracking various changes in speed.

[0131] The gain of the result of the integrating filter is given by:

[0132]

[0133] V hf is the injection level, T s is the period between successive activations of the controller, l d and l q is the added inductance of the motor 105b on the d-axis and q-axis. For example, the activation frequency of the proportional-integral filter is 1 kHz, and T s =1ms.

[0134] In a preferred embodiment, the nameplate characteristics (T n : Nominal torque, i n : Nominal current, P n : Nominal power, ω n : Nominal electrical speed, PF = cos(φ n): nominal power factor, p: number of electrode pairs) derived l d and l q Approximate value of .

[0135] Considering the current emission angle ψ ~ 55° under nominal conditions, the nominal torque is From this we get:

[0136]

[0137] Based on the power factor at the nominal operating point, assuming unity efficiency of the drive, the reactive power is expressed as Therefore, we get the inductance level at the nominal operating point as follows:

[0138]

[0139] Finally, assuming the machine is magnetically linear, we obtain:

[0140]

[0141] The output of the flux angle estimation module 108 is provided to a module 109 estimating the flux level and the current perpendicular to the estimated direction of the flux, and to the frame conversion module 104 .

[0142] refer to Figure 4 An example of an estimation module 109 for a magnetic flux level and a current perpendicular to an estimated direction of the magnetic flux is disclosed.

[0143] Figure 4 An example of a block diagram of a module for estimating a magnetic flux level and a current perpendicular to the estimated direction of the magnetic flux according to the present invention.

[0144] The module 109 for estimating the magnetic flux level and the current perpendicular to the estimated direction of the magnetic flux comprises a frame conversion module 400 and a multiplier 401 .

[0145] Using the estimated direction of magnetic flux The current vector i αβ Convert to flux frame to determine The amount Multiply According to the component of the current corresponding to the magnetic flux The norm of the magnetic flux is determined by

[0146] According to the invention, it is assumed that the norm of the flux vector is linearly related to the current on the flux axis and that, according to the nominal operating conditions I which can be obtained from the nameplate characteristics of the machine, n , n ,φ n Determine the norm of the magnetic flux vector:

[0147]

[0148] Then, the estimated magnetic flux level is estimated from the current projected onto the axis of the estimated magnetic flux using a fixed ratio determined based on the nameplate characteristics of the motor.

[0149] The presumption to be determined and Provided to DFVC module 102.

[0150] refer to Figure 6 An example of a torque reference estimation module 110 is disclosed.

[0151] Figure 6 An example of a torque reference estimating module according to the present invention is shown.

[0152] The torque reference estimation module includes a subtraction module 600 and a proportional-integral filter 601 .

[0153] Subtraction module 600 obtains the speed reference ω from * Subtract the estimated speed The output of the subtraction module is provided to the proportional-integral filter 601 .

[0154] As a result of the proportional-integral filter 601, the torque reference T * Drive so that the estimated speed Equal to the reference speed level ω * .

[0155] According to the bandwidth ω of the proportional-integral filter 601 speed Set the coefficients of proportional-integral filter 601:

[0156] k p,ω =2Jω speed

[0157] k i,ω = J(ω speed ) 2

[0158] where J is the mechanical inertia of the system. For example, ω speed =2πf speed rad / s, where f speed Falls within [1..20] Hz. Speed ​​control frequency f speed The choice of is related to the expected dynamics of the proportional-integral filter, ie, its ability to bring the estimated speed close to the reference speed within a given time window.

[0159] Figure 7 Shows a motor frame used in the present invention.

[0160] The stator (αβ) frame is fixed. The current stator (ij) frame is rotated by an angle (γ) relative to (αβ). α ) frame, the angle is defined by the current vector i aligned with the i axis. The flux stator (fτ) frame is rotated by an angle (δ) relative to (αβ) α ) frame, the angle is defined by the flux vector λ aligned with the f-axis.

[0161] According to the present invention, the CCAL module is configured to make the angle between the i vector and the λ vector equal to the reference γ λ * The formula for determining the reference amplitude of the magnetic flux ‖λ‖ according to the torque reference * and the reference current level i τ * .

[0162] According to the present invention, the HF injection module 103 is oriented in the direction θ relative to the axis of the estimated stator flux frame. inj Inject HF flux. The flux angle estimation module determines the estimated value of the angle of the stator flux frame The estimated value makes the HF response of the current vector i form the same angle θ with respect to the i-axis of the estimated stator current frame. inj .

[0163] These formulas use scaling rules based on the machine's nameplate characteristics to relate the estimated level of magnetic flux to the current i observed on the f-axis. f level is associated with.

[0164] Figure 10 shows the measurement results of a commercial synchronous reluctance motor at different angles compared to an ideal MTPA system.

[0165] Fig.10a The horizontal axis of shows the current on the d-axis expressed in amperes.

[0166] Fig.10a The vertical axis shows the current on the q-axis expressed in amperes.

[0167] Fig.10b The horizontal axis shows the torque expressed in Nm.

[0168] The vertical axis of FIG. 10 q shows the absolute value of the current in the dq frame expressed in amperes.

[0169] The ideal MTPA trajectory is shown by the curves marked 10a and 10b. According to the present invention, two different fixed angles γ λ The actual trajectories of are shown by curves 11a, 11b, 12a and 12b.

[0170] Without properly choosing the angle γ λ, for example, when 15° is selected, as shown in curves 12a and 12b, the current trajectory deviates seriously from the ideal trajectory, resulting in higher current levels for a given torque and, therefore, losses.

[0171] According to the invention, the angle γ is appropriately selected. λ For example, when 30° is selected, the current trajectory as shown in curves 11a and 11b also deviates from the ideal trajectory, but the current level is maintained similar to the current in the MTPA as shown in curves 10a and 10b.

[0172] Fig. 9 An example of an algorithm for controlling a motor according to the present invention is shown.

[0173] The algorithm is disclosed in an example where it is executed by a processor 1100 of a direct flux vector controller of an electric motor.

[0174] In step S90, the processor 1100 performs the Figure 1 or Figure 6 The torque reference T is determined as disclosed in * .

[0175] In step S91, the processor 1100 obtains a predetermined angle γ λ * .

[0176] Predetermined angle γ λ * is the angle of the current vector in the fτ frame, which is equal to the difference between the current emission angle and the flux emission angle.

[0177] In the first variation of the present invention, the predetermined angle γ λ It is set within the range of 30-45°.

[0178] Predetermined angle γ λ is in accordance with And it is determined that, and is the nominal inductance estimated from the motor's nameplate characteristics, and for example γ d =55°.

[0179] In a preferred embodiment of the present invention, since the sensorless control is operated in a state deviating from the low incremental salient pole region, the predetermined angle is preferably reduced by, for example, 5° (for example, using γ d =50°), thereby maintaining the stability margin of sensorless control.

[0180] In another variation of the present invention, the predetermined angle γ λis determined as a function of torque stored in a lookup table. For example, the MTPA trajectory can be acquired at high speed along with inductance data. From these data, a function that correlates torque with the optimal predetermined angle γ can be constructed. λ At low speed, the predetermined angle γ is set according to the determined torque level. λ .

[0181] In another variation of the present invention, at different angles γ λ The current to torque reference ratio is observed and stored for torque references of different magnitudes. The optimum angle is determined as the angle that minimizes the current to torque reference ratio measured for the torque reference determined in step S90.

[0182] In step S92, the processor 1100 determines a flux reference and a current reference according to a torque reference and a predetermined angle.

[0183] The flux reference is determined using a first function that is the nominal parameters of the motor multiplied by the square root of the value obtained by multiplying the torque product divided by the tangent of the reference angle, and the current reference is determined using a second function that is the nominal parameters of the motor multiplied by the square root of the value obtained by multiplying the product torque reference multiplied by the tangent of the reference angle.

[0184] The first function is And the second function is Among them, λ n is the nominal magnetic flux of the motor, I n is the nominal current of the motor, sin(φ n ) is based on the nominal power factor of the motor cos(φ n ) is determined by, p is the number of electrode pairs of the motor.

[0185] Determine the flux reference λ according to the following formula * and the current reference i τ * :

[0186]

[0187] Among them, λ n is the nominal magnetic flux of the motor, I n is the nominal current of the motor, sin(φ n ) is based on the nominal power factor of the motor cos(φ n ), p is the number of electrode pairs of the motor, T * is the torque reference and γ λ * is a predetermined angle.

[0188] In step S93, the processor 1100 performs the Figure 1 The DFVC 102 performs processing in a similar manner to determine the reference voltage provided to the motor.

[0189] In step S94, the processor 1100 performs the Figure 1 The high frequency signal injection 103 is performed in a similar manner to the injection of the signal to inject the high frequency signal into the reference voltage.

[0190] In step S95, the processor 1100 performs the Figure 1 The current measurement module 107 performs the measurement of the current in a similar manner to obtain the motor current vector measurement value.

[0191] In step S96, the processor 1100 performs the Figure 1 In a similar manner to the processing performed by the flux angle estimation module 108 , an estimate of the direction of the motor's magnetic flux is determined based on the motor current vector.

[0192] In step S97, the processor 1100 performs the Figure 1 The estimated value of the magnetic flux and the estimated value of the current perpendicular to the estimated direction of the magnetic flux are determined based on the estimated value of the direction of the magnetic flux in a manner similar to the parameters determined by the estimation module 109.

[0193] In step S98, processor 1100 provides the estimated value of the magnetic flux and the estimated value of the current perpendicular to the estimated direction of the magnetic flux to direct flux vector control step S92.

[0194] Fig.11 A second example of a direct flux vector controller for a motor using a constant current angle trajectory according to the present invention is shown.

[0195] The direct flux vector controller 11 of the electric motor using the constant current angle trajectory has, for example, a configuration based on components connected by a bus 1101 and by Fig. 9 The architecture of the processor 1100 is controlled by the program disclosed in the disclosure.

[0196] The bus 1101 connects the processor 1100 to a read-only memory ROM 1102 , a random access memory RAM 1103 , and an input / output I / O IF interface 1105 .

[0197] The input-output I / O IF interface 1105 enables the device direct flux vector controller 110 to sense a signal representative of the current flowing through the motor 105b.

[0198] The memory 1103 includes registers for receiving and Fig. 9 The variables and instructions of the program related to the algorithm disclosed in.

[0199] Read-only memory, or possibly flash memory 1102, contains the Fig. 9 The instructions of the program related to the algorithm disclosed in the , are loaded into the random access memory 1103 when the power of the device 11 is turned on. Alternatively, the program can also be executed directly from the ROM memory 1102.

[0200] The calculations performed by device 11 can be implemented in the form of software by a programmable computer, such as a PC (personal computer), a DSP (digital signal processor) or a microcontroller executing a series of instructions or a program group, or in the form of hardware by a machine or dedicated component, such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0201] In other words, the device 11 includes circuitry or a device including circuitry that enables the device 11 to perform the same operations as those described in the example of FIG. Fig. 9 Programs related to the algorithms disclosed in .

Claims

1. A method for controlling a motor using a direct flux vector control module and a constant current angle trajectory module, It is characterized in that The method comprises the following steps: Determine the torque reference; Determining a flux reference and a current reference by the constant current angle trajectory module according to the torque reference and a predetermined angle; providing the flux reference and the current reference to the direct flux vector control module to obtain a reference voltage provided to the motor; injecting a high frequency signal into the reference voltage; determining an estimate of the direction of the magnetic flux of the motor based on the motor current vector; determining an estimated value of a norm of the magnetic flux and an estimated value of a current flowing perpendicularly to the estimated direction of the magnetic flux based on the estimated value of the direction of the magnetic flux; and The estimated value of the norm of the magnetic flux and the estimated value of the current flowing perpendicular to the estimated direction of the magnetic flux are provided to the direct flux vector control module.

2. The method according to claim 1, characterized in that The flux reference is determined using a first function, which is the square root of a value obtained by multiplying the product of the torque and the tangent of a reference angle by the nominal parameters of the motor, and the current reference is determined using a second function, which is the square root of a value obtained by multiplying the product of the torque reference and the tangent of the reference angle by the nominal parameters of the motor.

3. The method according to claim 2, characterized in that The first function is And the second function is Among them, λ n is the nominal magnetic flux of the motor, I n is the nominal current of the motor, sin(φ n ) is based on the nominal power factor cos(φ n ) is determined, and p is the number of electrode pairs of the motor.

4. The method according to claim 1, characterized in that: The flux reference λ is determined according to the following formula * and the current reference i τ * : Among them, λ n is the nominal magnetic flux of the motor, I n is the nominal current of the motor, sin(φ n ) is based on the nominal power factor cos(φ n ), p is the number of electrode pairs of the motor, T * is the torque reference and γ λ * is the predetermined angle.

5. The method according to any one of claims 1 to 4, characterized in that The predetermined angle falls between 30° and 45°.

6. The method according to any one of claims 1 to 4, characterized in that The predetermined angle is based on And it is determined that, and is the nominal inductance estimated from the nameplate characteristics of the motor, and γ d =55°.

7. The method according to any one of claims 1 to 4, characterized in that The predetermined angle is determined as a function of the torque stored in a lookup table.

8. The method according to any one of claims 1 to 4, characterized in that The predetermined angle is determined based on current to torque reference ratios observed at different magnitudes of the predetermined angle and different magnitudes of torque references, and the optimal angle is determined as the angle that minimizes the current to torque reference ratio observed for the determined torque reference.

9. The method according to any one of claims 1 to 8, characterized in that The estimated magnetic flux level is estimated by multiplying the current projected onto the axis of the estimated magnetic flux by a fixed ratio.

10. The method according to claim 9, characterized in that The fixed ratio is determined based on the nameplate characteristics of the motor.

11. The method according to any one of claims 1 to 10, characterized in that The high-frequency injection signal is parallel to the estimated magnetic flux vector, and the angle of the magnetic flux vector is estimated so that the high-frequency response of the current vector becomes parallel to the current.

12. The method according to any one of claims 1 to 10, characterized in that The high frequency injection is perpendicular to the estimated magnetic flux vector, and the angle of the magnetic flux vector is estimated so that the high frequency response of the current vector becomes perpendicular to the current vector.

13. A device for controlling an electric motor using a direct flux vector control module and a constant current angle trajectory module, It is characterized in that The device comprises means for performing the following processes: Determine the torque reference; Determining a flux reference and a current reference by the constant current angle trajectory module according to the torque reference and a predetermined angle; providing the flux reference and the current reference to the direct flux vector control module to obtain a reference voltage provided to the motor; injecting a high frequency signal into the reference voltage; determining an estimate of the direction of the magnetic flux of the motor based on the motor current vector; determining an estimated value of a norm of the magnetic flux and an estimated value of a current flowing perpendicularly to the estimated direction of the magnetic flux based on the estimated value of the direction of the magnetic flux; as well as The estimated value of the norm of the magnetic flux and the estimated value of the current flowing perpendicular to the estimated direction of the magnetic flux are provided to the direct flux vector control module.

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