Motor control system and motor control method

Abstract

To achieve smooth acceleration by estimating a rotor phase of a motor in a stop state regardless of presence or absence of saliency and starting inverter control based on the rotor phase.SOLUTION: A motor control system includes: a current sensor configured to detect a current of a motor; an inverter connected to the motor; an inverter control unit configured to control an output voltage of the inverter; and a phase estimation unit configured to estimate a rotor phase of the motor. The inverter control unit controls the inverter to apply an output voltage in a state in which the motor is stopped, rotates the motor back and forth by switching an output voltage between positive and negative, and generates an induced voltage of the motor by this rotation. The phase estimation unit estimates the rotor phase based on a detection value of a current flowing by the induced voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a motor control system and a motor control method. [Background technology]

[0002] In motor control systems, the inverter output voltage is determined based on the motor rotor phase, requiring detection or estimation of the rotor phase. From a cost reduction perspective, it is desirable to estimate the rotor phase from motor current, inverter output voltage, etc., without using an encoder. Controlling a motor using such estimation is called "position sensorless control."

[0003] Regarding position sensorless control, a technique for estimating the rotor phase when the motor is stopped is disclosed in Patent Document 1.

[0004] Patent Document 1 discloses a configuration for estimating the magnetic pole position of a synchronous motor with high accuracy, comprising a synchronous motor 1, a current detector 4, a power converter 7, a magnetic pole position estimation means 8, and an axis and polarity discrimination unit 16 or a polarity discrimination unit 16a, with the magnetic pole position estimation means 8 utilizing a part of the motor control device that controls the synchronous motor 1, and for estimating the magnetic pole position at startup, an estimation d-axis current command id1*, which is a sinusoidal command having a predetermined frequency, is output to the current control unit 3a at startup from a stopped state (initial startup), and the q'-axis current iq' generated by applying the estimation d-axis current command id1* is fed back via the current detector 4 and the dq conversion unit 5a to estimate the magnetic pole position θ. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-143894 [Overview of the project] [Problems that the invention aims to solve]

[0006] The magnetic pole position estimation means described in Patent Document 1 utilizes the salient polarity of the motor, i.e., the difference between the d-axis and q-axis inductances. Therefore, if the d-axis and q-axis inductances are equivalent, the rotor phase cannot be estimated. Consequently, for example, in a surface magnet type motor, since the d-axis and q-axis inductances are the same, the rotor phase cannot be estimated even using the technology described in Patent Document 1.

[0007] Furthermore, if a motor used in a fan, for example, rotates in reverse, it will cease to function as a fan. Therefore, even when position sensors are not used, it is necessary to prevent motors from rotating in reverse.

[0008] The purpose of this disclosure is to estimate the rotor phase of a motor in a stopped state, regardless of whether it has saliency or not, and to start inverter control based on this rotor phase to achieve smooth acceleration. [Means for solving the problem]

[0009] The motor control system of this disclosure comprises a current sensor for detecting motor current, an inverter connected to the motor, an inverter control unit for controlling the output voltage of the inverter, and a phase estimation unit for estimating the rotor phase of the motor. The inverter control unit controls the inverter to apply an output voltage when the motor is stopped, and rotates the motor back and forth by switching the output voltage between positive and negative, thereby generating an induced voltage in the motor. The phase estimation unit estimates the rotor phase based on the detected value of the current flowing due to the induced voltage. The inverter control unit calculates an orthogonal component from the vector of the current flowing due to the induced voltage, which is a component orthogonal to the same direction as the phase direction of the output voltage. The phase of the output voltage is changed until the absolute value of this orthogonal component is less than or equal to a predetermined value, and the phase estimation unit repeats the phase estimation. It is characterized by the following: [Effects of the Invention]

[0010] According to this disclosure, regardless of whether or not there is saliency, smooth acceleration can be achieved by estimating the rotor phase of a motor in a stopped state and initiating inverter control based on this rotor phase. [Brief explanation of the drawing]

[0011] [Figure 1] This is a configuration diagram showing the motor control system of Example 1. [Figure 2] This graph shows the voltage and current waveforms when the rotor phase θd is 30 degrees while the motor is stopped. [Figure 3] This graph shows the voltage and current waveforms when the rotor phase θd is 0 degrees while the motor is stopped. [Figure 4] This graph shows the voltage and current waveforms when the rotor phase θd is -30 degrees while the motor is stopped. [Figure 5] This is a vector diagram relating to magnetic flux, voltage, and current of a magnet. [Figure 6A] This graph shows the correlation between the position on the d-axis and the sign of the current before the phase estimate is updated. [Figure 6B] This graph shows the correlation between the position on the d-axis and the sign of the current after updating the phase estimate. [Figure 7A] This graph shows the correlation between the position on the d axis and the sign of the current when a voltage is applied to the d axis. [Figure 7B] This graph shows the correlation between the position on the d axis and the sign of the current when a voltage is applied to the qc axis. [Figure 8] This graph shows the changes in voltage, current, and phase over time during polarity determination. [Figure 9] This is a diagram showing the inverter control unit, which constitutes part of the motor control system of Example 2. [Figure 10] This is a diagram showing the inverter control unit, which constitutes part of the motor control system of Example 3. [Figure 11A] This graph shows the time-dependent changes in the induced voltages and their phases of the three-phase system during motor rotation. [Figure 11B] This graph shows the time-dependent changes in the induced voltage and its phase of the three-phase system when the motor is stopped. [Figure 12] This is a diagram showing the motor control system of Example 4. [Modes for carrying out the invention]

[0012] This disclosure relates to a technique for estimating the rotor phase in a motor control system.

[0013] Hereinafter, embodiments will be described with reference to the drawings.

Embodiment

[0014] FIG. 1 is a configuration diagram showing the motor control system of Embodiment 1.

[0015] In this figure, the motor 1 is connected to the inverter 2. The inverter 2 receives the DC voltage V v and outputs the U-phase, V-phase, and W-phase voltages v u v v v w As a result, the U-phase, V-phase, and W-phase currents i u i v i w flow through the motor 1. These currents are detected by the current sensor 3.

[0016] The inverter control unit 4 controls the upper and lower gate signals s u s v s w of the U-phase, V-phase, and W-phase of the inverter 2 according to i up s un s vp s vn s wp s wn and as a result, controls v u v v v w <00**********><00**********><00**********>The inverter control unit 4 includes a rectangular wave voltage calculation unit 4a, a two-phase / three-phase conversion unit 4b, a PWM control unit 4c, a three-phase / two-phase conversion unit 4d, and a phase estimation unit 4e. <00**********><00**********><00**********>The rectangular wave voltage calculation unit 4a calculates the dc-axis and qc-axis voltage commands v dc * v qc * ​Set one of the following to a square wave. The two-phase / three-phase conversion unit 4b is v dc * , v qc * v u * , v v * , v w * Converts to v u * , v v * , v w * According to pulse width modulation, s up , s un , s vp , s vn , s wp , s wn Converts to i. u i v i w DC axis and QC axis current i dc i qc Convert to i dc i qc Based on the rotor phase θ of motor 1 d The rotor phase estimate θ is an estimated value of dc Outputs.

[0019] The phase estimation unit 4e includes a phase correction amount calculation unit 4e1 and a delay element calculation unit 4e2.

[0020] The phase correction amount calculation unit 4e1 is i dc i qc Based on θ dc Phase correction amount θ step The delay element calculation unit 4e2 calculates θ dc Past value θ dc-old Outputs.

[0021] And then, θ dc-old θ step By adding θ, dc The value is updated and used as the output value of the phase estimation unit 4e. dc This data is transmitted to the two-phase / three-phase conversion unit 4b and the three-phase / two-phase conversion unit 4d, and serves as the reference during coordinate transformation.

[0022] By including a phase estimation unit 4e, and in particular a phase correction amount calculation unit 4e1, θ can be calculated without an encoder. dc This makes it possible to estimate the position. Therefore, this type of control is called "position sensorless control."

[0023] Here, we will explain the challenges of position sensorless control.

[0024] As shown in Patent Document 1, the d-axis and q-axis inductance L of the motor d , L q If there is a difference, v dc * , v qc * Keeping θ constant d When you change i dc i qc This also changes. By formulating this relationship mathematically or in a table, i dc i qc From θ d It becomes possible to estimate L. However, this phenomenon is L d , L q This applies only when there is a difference. When designing a motor with an emphasis on quietness, L d , L q There are cases where they are equal, in which case θ d It is impossible to estimate this. This is a challenge of position sensorless control.

[0025] In the method of Patent Document 1, the L of the motor d , L q It can be said that this utilizes the position dependence of the motor. Other motor parameters include the resistance value R and the induced voltage coefficient Ke. R is not position dependent, while Ke is. In the stopped state, the motor's rotational speed ω is zero, so the induced voltage (ωKe) is zero, and its effect is i dc i qc It doesn't show up.

[0026] Therefore, in this disclosure, the rectangular wave voltage calculation unit 4a calculates v dc* Alternatively, v qc * is switched between positive and negative to rotate the motor 1 forward and backward, and θ is estimated based on the induced voltage generated at that time. d is estimated.

[0027] The operating principle will be described below.

[0028] Figures 2 to 4 respectively show the voltage and current waveforms when θ d is different. [[ID=第十七条]]

[0029] Figure 2 is a graph showing the voltage and current waveforms when the rotor phase θ d is 30 deg in the stopped state of the motor.

[0030] [[ID=第二十五条]] Figure 3 is a graph showing the voltage and current waveforms when the rotor phase θ d is 0 deg in the stopped state of the motor.

[0031] Figure 4 is a graph showing the voltage and current waveforms when the rotor phase θ d is -30 deg in the stopped state of the motor.

[0032] In any of the figures, the horizontal axis represents time t (s), and the vertical axis represents voltage V (V) and current I (A).

[0033] In these figures, the qc-axis voltage command v qc * is kept constant, and the dc-axis voltage command v dc * is a positive and negative rectangular wave. In response to this change over time, the dc-axis and qc-axis currents i dc and i qc change.

[0034] In any of the cases of Figures 2 to 4, the change over time of i dc is the same, but the change over time of i qc differs depending on whether θ d is positive, zero, or negative. In these figures, iqc The time point corresponding to the extreme value of the curve showing the change over time is shown as t1.

[0035] Thus θ d i qc The reason for this change will be explained next.

[0036] Figure 5 is a vector diagram relating to magnetic flux, voltage, and current of a magnet. In the figure, the horizontal axis is the DC axis, the vertical axis is the QC axis, and the d axis represents the direction of the magnet.

[0037] As shown in this figure, initially, the magnetic flux of the magnet is represented by a vector Φ, and the qc axis component is Φ qc That is the case.

[0038] DC axis voltage command v dc * When set to positive, the d-axis is attracted to the dc-axis, and the magnetic flux changes from Φ to Φ'. At this time, the qc-axis component of the magnetic flux is Φ qc From Φ qc It decreases to '. Therefore, the qc axis current i to counteract this. qc It flows in the positive direction.

[0039] On the other hand, if the d-axis is in a position symmetrical to the position shown in Figure 5 with respect to the dc-axis, then i qc It flows negatively by a similar principle.

[0040] Also, if the dc axis and d axis coincide, i qc This becomes zero. This is θ d i qc This is the reason for the change.

[0041] Figure 6A summarizes the above information and is a graph showing the correlation between the position on the d axis and the sign of the current before the phase estimate is updated. In the figure, the horizontal axis is the dc axis and the vertical axis is the qc axis. In the first and third quadrants, i qc >0, and in the second and fourth quadrants, i qc <0. Δθ' indicates the phase of the d-axis with respect to the dc-axis.

[0042] Here, v dc * or v qc * The reason for changing v between positive and negative is that if we use a square wave that is either positive or negative in only one direction, the motor will continue to rotate in one direction, and the d-axis will shift to another quadrant in the graph shown in Figure 6A. Therefore, v dc * or v qc * The motor is returned to its original position by changing the value between positive and negative.

[0043] Next, i qc The principle of generation will be explained from the perspective of the voltage equation of motor 1, which is represented by the following equation (1).

[0044]

number

[0045] However, v d d-axis voltage [V], v q is the q-axis voltage [V], i d d-axis current [A], i q is the q-axis current [A], p is the differential operator, and R is the resistance value.

[0046] In equation (1) above, if the rotational speed of motor 1 is low, then R >> ωL d , R>>ωL q Therefore, equation (2) below holds true.

[0047]

number

[0048] Here, L d ≒L q Assuming dω / dt ≈ 0, and performing a coordinate transformation from the dq coordinate system to the dc-qc coordinate system, we obtain equation (3) below.

[0049]

number

[0050] However, Δθ is the phase [rad] of the dc axis with respect to the d axis.

[0051] v qc Since = 0, from the second row of equation (3) above, equation (4) below holds true.

[0052]

number

[0053] If τ0 is the maximum torque generated when the dc axis and d axis are orthogonal, then the following equation (5) holds from the equation of motion.

[0054]

number

[0055] However, T d is v dc * The application time is [s], τ is the motor torque [Nm], and J is the motor inertia [kg·m]. 2 ]

[0056] From equations (4) and (5) above, equation (6) below holds true.

[0057]

number

[0058] However, Δθ' is the d-axis phase [rad] (Δθ'=-Δθ) with respect to the dc axis.

[0059] Focusing on cosΔθ'sinΔθ' in equation (6) above, i qc It can be seen that the sign of is as shown in Figure 6A.

[0060] In the transformation from equation (2) to equation (3) above, L d ≒L q We assumed that L d =L q The same conclusion is reached in this case as well. Therefore, the i shown in Figure 6A qc The sign is guaranteed even if motor 1 does not have salient polarity.

[0061] The phase correction amount calculation unit 4e1 is θ d and θ dc The difference between i converges to zero. qc θ step Perform the calculation.

[0062] Figure 6B shows that the d-axis is in the first quadrant, as shown in Figure 6A. qc This example shows the correlation between the d-axis position and the sign of the current after updating the phase estimate, with >0 being a positive value.

[0063] As shown in Figure 6B, θ step By setting this to positive, the dc axis advances to the dc' axis and approaches the d axis due to the update of the phase estimate value by the delay element calculation unit 4e2. Consequently, the qc axis in Figure 6A also moves to the qc' axis.

[0064] The above describes the operating principle of this disclosure, and its features can be summarized as follows:

[0065] (1) The rectangular wave voltage calculation unit 4a rotates the motor 1 back and forth by switching the output voltage of the inverter 2 to positive and negative while the motor 1 is stopped, and generates an induced voltage in the motor 1 by this rotation.

[0066] (2) The phase estimation unit 4e estimates the rotor phase of the motor 1 based on the detected value of the current flowing due to the induced voltage.

[0067] Next, we will explain the means to enhance the added value of the above-mentioned features.

[0068] (1) The inverter control unit 4 calculates the orthogonal component i from the current vector that flows due to the induced voltage, which is an orthogonal component that is in the same direction as the phase direction of the output voltage. qc The orthogonal component is calculated, and the phase of the output voltage is changed until the absolute value of this orthogonal component falls below a predetermined value.

[0069] (2) The phase estimation unit 4e repeats the phase estimation.

[0070] This improves the accuracy of phase estimation. The θ used in the two-phase / three-phase conversion unit 4b is used each time the phase estimation is updated. dc Because this is changed, the output voltage phase of inverter 2 will change with each phase estimation.

[0071] In changing (updating) the phase estimation, θ step θ can also be a variable value; for example, it increases as the number of updates increases. step You may reduce i qc Not only the sign of i qc θ depends on the absolute value of step You may change it, for example i qc θ according to the magnitude of the absolute value step You may increase or decrease θ. step By making this variable, high phase estimation accuracy can be obtained with fewer updates.

[0072] When the phase estimation is repeatedly updated, the dc' axis in Figure 6B converges to the d axis.

[0073] Here, we will explain the behavior when the d-axis is virtually fixed and the d-axis changes.

[0074] Figure 7A shows the position of the d axis and the current i when a voltage is applied to the d axis. qc This graph shows the correlation with the sign of . In the figure, the horizontal axis is the dc axis and the vertical axis is the qc axis. In the first and third quadrants, i qc >0, and in the second and fourth quadrants, i qc < 0

[0075] For example, if the d-axis is in the first quadrant, the d-axis will converge to the dc-axis along the path shown by arrow A1. In addition to the dc-axis, there are four other directions in which the d-axis can converge: the -dc-axis, the qc-axis, and the -qc-axis. Regarding the ±qc-axis directions, unless the initial d-axis exactly coincides with either the ±qc-axis or the d-axis, the d-axis will move away from the ±qc-axis along the path shown by arrows A1 to A4, and will not remain on the ±qc-axis.

[0076] On the other hand, with respect to the ±dc axis direction, arrows A1 and A4, and arrows A2 and A3 are opposite each other, so the d axis can potentially stagnate in either direction of the ±dc axis. Here, we will refer to the d axes when they converge in the ±dc axis direction as the d1 axis and the d2 axis, respectively. Whether the d axis is the d1 axis or the d2 axis is determined by i qc It is not possible to distinguish them by this alone. Physically, it is a state where it is not possible to determine whether the magnetic flux of the magnet is the north pole or the south pole, and the process of determining this is called "polarity determination."

[0077] In updating the phase estimate, i qc If the absolute value of becomes less than or equal to a predetermined value, the rectangular wave voltage calculation unit 4a calculates a positive value of v qc * Set (v dc * (is zero). And i dc If it is positive, the dc axis direction is determined to be the N pole, i dc If the value is negative, the direction in the dc axis direction is determined to be the south pole.

[0078] Figure 7B shows the positive v calculated by the rectangular wave voltage calculation unit 4a. qc * This shows a specific example of the settings, and the position of the d axis and current i when the qc axis voltage is applied. dc This graph shows the correlation with the sign of . In the figure, the horizontal axis is the dc axis and the vertical axis is the qc axis. In the first and third quadrants, i dc >0, and in the second and fourth quadrants, i dc < 0

[0079] The reason why polarity can be determined in this way will be explained next.

[0080] positive v qc * When this is set, both the d1 and d2 axes move in the qc direction, and as shown in Figure 5, the change in magnetic flux affects i dc It plays. dc The sign of i depends on whether the d-axis is the d1 axis or the d2 axis. dc If this is positive, then the d1 axis is the true d axis, which means that the dc axis direction is the direction of the north pole. dc If it is negative, then conversely, the direction of the dc axis is the direction of the south pole. In the above, positive v qc * We have explained the case where the setting is negative v qc * Polarity can be determined in the same way even when this setting is enabled.

[0081] After polarity determination, if the dc axis direction is the south pole, the phase correction amount calculation unit 4e1 calculates θ step Set θ to a range of 0 to 180 degrees. dc By offsetting the value, the motor 1 is prevented from reversing.

[0082] Next, I will explain why it is possible to prevent a reversal.

[0083] At the point when polarity determination is complete, the d2 axis is in the second quadrant, i.e., the phase range of 90-180 degrees, and v qc * It is rotating in the opposite direction, i.e., in the qc axis direction. To output a positive torque to stop the reverse rotation, v qc * The phase of should be advanced by 0 to 90 degrees relative to the d2 axis. In other words, v qc * The desired phase range is 90-270 degrees, as shown in Figure 7B. qc * Inversion can be prevented by offsetting the phase within the range of 0 to 180 degrees, using a phase of 90 degrees as the reference.

[0084] Next, we will explain polarity discrimination and phase offset correction.

[0085] Figure 8 is a graph showing the time-dependent changes in voltage, current, and phase during polarity discrimination. In the figure, the horizontal axis represents time, and the vertical axes represent voltage, current, and phase. For voltage, v dc * Use a solid line, v qc * This is shown with a dashed line. Regarding the current, i dc Use a solid line, i qc This is shown by a dashed line. Regarding the phase, θ d Let θ be the solid line. dc This is indicated by a dashed line.

[0086] As shown in this figure, at time t0, θ d θ is -180 degrees, dc It is 0 degrees. Polarity determination starts at time t1. At time t1, v qc * Set to a predetermined positive value. Accordingly, θ d This will be 180 degrees.

[0087] In this figure, i at time t2 dc As shown at point P1, the value became smaller than the predetermined value, so the polarity is determined to be the south pole. Then, at time t2, as shown at point P2, θ dc This is corrected with a 90-degree offset. d The reversal (decrease) stops at the time indicated by point P3, and from there it rotates forward. The time lag between time t2 and the time indicated by point P3 is due to the inertia of motor 1.

[0088] In this diagram, motor 1 is accelerating from time t3 onwards; this will be explained later.

[0089] The characteristics of polarity discrimination and phase offset correction are as follows:

[0090] (1) In updating the phase estimate i qc If the absolute value of becomes less than or equal to a predetermined value, the rectangular wave voltage calculation unit 4a calculates a positive or negative v qc* Set the v used in the phase estimation update. dc * Compared to that, the phase of the output voltage is advanced by 90 degrees either clockwise or counterclockwise.

[0091] (2)i dc Based on the sign, polarity determination is performed, and if the determination result is the south pole, the phase correction amount calculation unit 4e1 calculates θ step Set θ to a range of 0 to 180 degrees. dc Apply offset correction.

[0092] In other words, the inverter control unit 4 controls the orthogonal component i of the current. qc If the absolute value falls below a predetermined value, the phase of the output voltage is advanced by 90 degrees either clockwise or counterclockwise. The phase estimation unit 4e then performs polarity determination of the motor based on the current detection value after the phase change of the output voltage. If the result of the polarity determination is the south pole, the rotor phase estimate, which is the estimated value of the rotor phase, is offset and corrected within the range of 0 to 180 degrees.

[0093] As described above, according to Example 1, the L of motor 1 d and L q Even when these conditions are equal, position sensorless control can be performed. [Examples]

[0094] Figure 9 is a configuration diagram showing the inverter control unit, which constitutes a part of the motor control system of Embodiment 2. However, parts that are the same as those in Figure 1 are omitted. That is, Figure 9 shows only the configuration of the inverter control unit 4.

[0095] In this figure, the inverter control unit 4, as in Figure 1, includes a rectangular wave voltage calculation unit 4a, a two-phase to three-phase conversion unit 4b, a PWM control unit 4c, a three-phase to two-phase conversion unit 4d, and a phase estimation unit 4e. In Figure 9, the inverter control unit 4 includes d-axis and q-axis current commands i d * i q * More vdc * , v qc * It has a motor model calculation unit 4f that calculates the voltage. A switch 4g is provided between the rectangular wave voltage calculation unit 4a and the two-phase / three-phase conversion unit 4b to switch between the rectangular wave voltage calculation unit 4a and the motor model calculation unit 4f.

[0096] Furthermore, in this figure, the phase estimation unit 4e has a phase correction amount calculation unit 4e1 and a delay element calculation unit 4e2, similar to Figure 1. And in Figure 9, the phase estimation unit 4e is θ d and θ dc The estimated value of Δθ, which is the difference from Δθ. est A phase difference estimation unit 4e3 calculates the phase difference, a PLL-type phase correction amount calculation unit 4e4 calculates the phase difference, and the PLL-type phase correction amount θ is the output of the PLL-type phase correction amount calculation unit 4e4. PLL and θ step It has a switch 4e5 to switch between and . Here, PLL is an abbreviation for Phase Locked Loop, and is also called a "phase-locked circuit".

[0097] The phase difference estimation unit 4e3 is an observer based on the induced voltage of the motor 1, and during operation when an induced voltage is generated, position sensorless control can be performed using only the phase difference estimation unit 4e3. On the other hand, when stopped, the induced voltage is zero, so position sensorless control cannot be performed using only the phase difference estimation unit 4e3.

[0098] In the PLL-type phase correction amount calculation unit 4e4, for example, θ PLL This is calculated using the following formula (7).

[0099]

number

[0100] However, ω * This is the speed command for motor 1 [rad / s], K PLL T is the PLL gain. s This is the delay time [s] of the delay element calculation unit 4e2.

[0101] The ability of these configurations to accelerate the motor 1 from a stationary state will be explained next.

[0102] In Figure 8, motor 1 begins accelerating at time t3.

[0103] At time t3, the input source of switch 4g is switched from the rectangular wave voltage calculation unit 4a to the motor model calculation unit 4f (Figure 9), which is shown by points P4 and P5 in Figure 8. qc * , v dc * These are i q * i d * It is calculated based on this. This ensures that the voltage necessary for accelerating motor 1 is secured. Also, at the same time, the input source of switch 4e5 is set to θ step From θ PLL Switch to (Figure 9). In that case, as shown in Figure 9, θ dc The following equation (8) holds true for .

[0104]

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[0105] Considering the delay element calculated by the delay element calculation unit 4e2 and equation (7) above, the following equation (9) holds true.

[0106]

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[0107] Differentiating equation (9) above yields equation (10) below.

[0108]

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[0109] K PLLSince is positive, equation (10) above is θ dc It is a stable equation with respect to θ, dc is θ d It converges to θ. dc and θ d Synchronizing these two is called "PLL control". dc =θ d Substituting this into equation (10) above, we obtain equation (11) below.

[0110]

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[0111] From equation (11) above, the rotational speed of motor 1 is ω * Therefore, θ in Figure 8 dc and θ d The slope is ω * It increases until it reaches [value]. This is the principle of accelerating motor 1. Note that θ dc From time t3, indicated by point P6, increases according to equation (9) or (10) above.

[0112] As described above, according to Example 2, acceleration of the motor 1 can be performed. Its features are as follows:

[0113] (1) After the phase estimation is completed by the phase correction amount calculation unit 4e1, the motor model equation calculation unit 4f calculates v dc * , v qc * Perform the calculation.

[0114] (2) After the phase estimation is completed by the phase correction amount calculation unit 4e1, the phase difference estimation unit 4e3 and the PLL type phase correction amount calculation unit 4e4 control the θ dc Perform the calculation.

[0115] In other words, after the inverter control unit 4 completes the estimation of the rotor phase when the motor 1 is stopped, it calculates the output voltage based on the motor model, and the phase estimation unit 4e updates the rotor phase estimate by PLL control based on the difference between the rotor phase and the rotor phase estimate. [Examples]

[0116] Figure 10 is a diagram showing the inverter control unit, which constitutes a part of the motor control system of Embodiment 3. However, parts that are the same as those in Figure 1 have been omitted.

[0117] In Figure 10, the motor control system includes a voltage sensor 5 that detects the induced voltage of motor 1, and the induced voltage phase θ. v The induced voltage phase calculation unit 4e6 calculates the induced voltage amplitude a v The induced voltage amplitude calculation unit 4e7 calculates a v Based on θ dc and θ v The system includes a switch 4e8 to switch between and θ. In this embodiment, for illustrative purposes, the phase selected by switch 4e8 is set to θ dc θ as dc To distinguish it from that.

[0118] With these configurations, even when motor 1 is rotating, θ d The following explains how we can estimate this.

[0119] Figure 11A is a graph showing the time-dependent changes in the three-phase induced voltages and their phases during motor rotation.

[0120] Figure 11B is a graph showing the time-dependent changes in the three-phase induced voltage and its phase when the motor is stopped.

[0121] When motor 1 is rotating, an induced voltage is generated as shown in Figure 11A, and its phase θ v is θ d It is synchronized with a v If the value is greater than or equal to a predetermined value, switch 4e8 is set to θ vBy switching to this, θ is determined based on the induced voltage. d It is possible to estimate this.

[0122] On the other hand, when motor 1 is stopped, the induced voltage is zero as shown in Figure 11B, so a v If the value is less than the predetermined value, switch 4e8 is set to θ dc By switching to this, θ according to Example 1 d It is possible to estimate this.

[0123] In summary, the motor control system further includes a voltage sensor 5 that detects the induced voltage of the motor 1, and the phase estimation unit 4e estimates the rotor phase based on the detected induced voltage if the detected induced voltage is above a certain value, and estimates the rotor phase based on the detected current if the detected induced voltage is below a certain value.

[0124] As described above, according to Embodiment 3, regardless of whether the motor 1 is rotating or stopped, θ d It is possible to estimate this. [Examples]

[0125] Figure 12 is a diagram showing the motor control system of Embodiment 4. However, parts that are the same as those in Figure 1 have been omitted.

[0126] In Figure 12, motor 1 is configured as the power source for fan 6. The inverter control unit 4 has an abnormality detection unit 4h that detects abnormalities in fan 6 and a gate signal cutoff unit 4i. The abnormality detection unit 4h is θ dc i when changed qc The abnormality detection unit 4h determines θ dc Regardless of i qc If the absolute value of is less than or equal to a predetermined value, an abnormal signal F indicates that fan 6 is locked. s It outputs the following. The gate signal cutoff unit 4i is F s If this is output, the gate signal output from the PWM control unit 4c is blocked.

[0127] In summary, the motor control system further comprises a mechanism powered by motor 1 and an abnormality detection unit 4h that detects abnormalities in the mechanism. The abnormality detection unit 4h outputs an abnormality signal indicating that the mechanism is locked if the absolute value of the detected current is less than or equal to a predetermined value, regardless of the phase of the output voltage.

[0128] These configurations allow fan 6 to be driven safely.

[0129] The reason is explained below.

[0130] If a foreign object gets stuck in fan 6 and it locks up, the rotation speed of motor 1 will be fixed at zero. In this case, the phase change of Φ shown in Figure 5 will not occur, i qc is any θ d , θ dc It becomes zero for this.

[0131] Even if it is not locked, as shown in Figure 6A, i qc It is possible that it will be zero, but multiple θ dc against i qc The case where is zero is only when locked. Therefore, θ dc i when changed qc Determine θ dc Regardless of i qc If the absolute value of is less than or equal to a predetermined value, it can be determined that the fan 6 is locked. If the inverter 2 continues to operate while locked, problems such as damage to the fan 6 and burnout of the motor 1 may occur.

[0132] Therefore, when locked, the gate signal is blocked by the gate signal blocking unit 4i, and the operation of the inverter 2 is stopped to ensure safety.

[0133] The Fan 6 can also be similarly configured to any mechanism that uses the Motor 1 as a driving source, such as a pump, automobile, or railway vehicle. Therefore, according to Embodiment 4, the safety of the mechanism that uses the Motor 1 as a driving source can be ensured.

[0134] According to the control described herein, smooth acceleration can be achieved by estimating the rotor phase in the motor-stopped state without using an encoder and initiating inverter control based on this rotor phase. [Explanation of Symbols]

[0135] 1: Motor, 2: Inverter, 3: Current sensor, 4: Inverter control unit, 4a: Square wave voltage calculation unit, 4b: Two-phase to three-phase conversion unit, 4c: PWM control unit, 4d: Three-phase to two-phase conversion unit, 4e: Phase estimation unit, 4e1: Phase correction amount calculation unit, 4e2: Delay element calculation unit, 4e3: Phase difference estimation unit, 4e4: PLL type phase correction amount calculation unit, 4e5: Switch, 4e6: Induced voltage phase calculation unit, 4e7: Induced voltage amplitude calculation unit, 4e8: Switch, 4f: Motor model equation calculation unit, 4g: Switch, 4h: Anomaly detection unit, 4i: Gate signal cutoff unit, 5: Voltage sensor, 6: Fan.

Claims

1. A current sensor that detects the motor current, The inverter connected to the motor, An inverter control unit that controls the output voltage of the inverter, A motor control system comprising a phase estimation unit for estimating the rotor phase of the motor, The inverter control unit controls the inverter to apply the output voltage while the motor is stopped, and by switching the output voltage between positive and negative, rotates the motor back and forth, and generates an induced voltage in the motor through this rotation. The phase estimation unit estimates the rotor phase based on the detected value of the current flowing due to the induced voltage. The inverter control unit calculates an orthogonal component from the current vector flowing due to the induced voltage, which is a component orthogonal to the same direction as the phase direction of the output voltage, and changes the phase of the output voltage until the absolute value of this orthogonal component is less than or equal to a predetermined value. The motor control system is characterized in that the phase estimation unit repeatedly performs phase estimation.

2. In the motor control system according to claim 1, When the absolute value of the orthogonal component of the current falls below a predetermined value, the inverter control unit advances the phase of the output voltage by 90 degrees in either the clockwise or counterclockwise direction. The motor control system is characterized in that the phase estimation unit performs polarity determination of the motor based on the detected value of the current after the phase change of the output voltage, and if the result of the polarity determination is the south pole, it offsets and corrects the rotor phase estimate, which is the estimated value of the rotor phase, within the range of 0 to 180 degrees.

3. In the motor control system according to claim 2, After the inverter control unit has completed estimating the rotor phase when the motor is stopped, it calculates the output voltage based on the motor model. The motor control system is characterized in that the phase estimation unit updates the rotor phase estimate by PLL control based on the difference between the rotor phase and the rotor phase estimate.

4. In the motor control system according to claim 1, The system further includes a voltage sensor for detecting the induced voltage of the motor, The motor control system is characterized in that the phase estimation unit estimates the rotor phase based on the detected value of the induced voltage if the detected value of the induced voltage is above a certain value, and estimates the rotor phase based on the detected value of the current if the detected value of the induced voltage is below a certain value.

5. In the motor control system according to claim 1, The system further comprises a mechanism powered by the aforementioned motor and an abnormality detection unit for detecting abnormalities in the aforementioned mechanism, The motor control system is characterized in that the abnormality detection unit outputs an abnormality signal indicating that the mechanism is locked when the absolute value of the detected current is less than or equal to a predetermined value, regardless of the phase of the output voltage.

6. A method for controlling a motor using a current sensor for detecting the motor's current, an inverter connected to the motor, an inverter control unit for controlling the output voltage of the inverter, and a phase estimation unit for estimating the rotor phase of the motor, The inverter control unit controls the inverter to apply the output voltage while the motor is stopped, and by switching the output voltage between positive and negative, the motor rotates back and forth, and this rotation generates an induced voltage in the motor. The phase estimation unit estimates the rotor phase based on the detected value of the current flowing due to the induced voltage. The inverter control unit calculates an orthogonal component from the vector of the current flowing due to the induced voltage, which is a component orthogonal to the same direction as the phase direction of the output voltage, and changes the phase of the output voltage until the absolute value of this orthogonal component is less than or equal to a predetermined value. A motor control method characterized in that the phase estimation unit repeatedly performs phase estimation.

7. In the motor control method according to claim 6, If the absolute value of the orthogonal component of the current falls below a predetermined value, the inverter control unit advances the phase of the output voltage by 90 degrees in either the clockwise or counterclockwise direction. A motor control method characterized in that the phase estimation unit performs polarity determination of the motor based on the detected value of the current after the phase change of the output voltage, and if the result of the polarity determination is the south pole, it offsets and corrects the rotor phase estimate, which is the estimated value of the rotor phase, within the range of 0 to 180 degrees.

8. In the motor control method according to claim 7, After completing the estimation of the rotor phase while the motor is stopped, the inverter control unit calculates the output voltage based on the motor model. A motor control method characterized in that the phase estimation unit updates the rotor phase estimate by PLL control based on the difference between the rotor phase and the rotor phase estimate.

9. In the motor control method according to claim 6, A motor control method characterized in that the phase estimation unit estimates the rotor phase based on the detected value of the induced voltage of the motor detected by the voltage sensor if the detected value of the induced voltage is above a certain value, and estimates the rotor phase based on the detected value of the current if the detected value of the induced voltage is below a certain value.

10. In the motor control method according to claim 6, A motor control method characterized in that an abnormality detection unit, which detects an abnormality in a mechanism powered by the motor, outputs an abnormality signal indicating that the mechanism is locked when the absolute value of the detected current is less than or equal to a predetermined value, regardless of the phase of the output voltage.

11. A current sensor for detecting the motor current, A voltage sensor for detecting the induced voltage of the motor, The inverter connected to the motor, An inverter control unit that controls the output voltage of the inverter, A motor control system comprising a phase estimation unit for estimating the rotor phase of the motor, The inverter control unit controls the inverter to apply the output voltage while the motor is stopped, and by switching the output voltage between positive and negative, rotates the motor back and forth, and generates the induced voltage of the motor through this rotation. The motor control system is characterized in that the phase estimation unit estimates the rotor phase based on the detected value of the induced voltage if the detected value of the induced voltage is above a certain value, and estimates the rotor phase based on the detected value of the current flowing due to the induced voltage if the detected value of the induced voltage is below a certain value.

12. A method for controlling a motor using a current sensor for detecting the motor current, a voltage sensor for detecting the induced voltage of the motor, an inverter connected to the motor, an inverter control unit for controlling the output voltage of the inverter, and a phase estimation unit for estimating the rotor phase of the motor, The inverter control unit controls the inverter to apply the output voltage while the motor is stopped, and by switching the output voltage between positive and negative, the motor rotates back and forth, and this rotation generates an induced voltage in the motor. A motor control method characterized in that the phase estimation unit estimates the rotor phase based on the detected value of the induced voltage of the motor detected by the voltage sensor if the detected value of the induced voltage is greater than or equal to a certain value, and estimates the rotor phase based on the detected value of the current flowing due to the induced voltage if the detected value of the induced voltage is less than a certain value.

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