Motor Control Device

Abstract

To provide a control device of a sensorless brushless motor capable of performing power swing determination easily, regardless of presence / absence of a counter electromotive voltage detector.SOLUTION: A motor control device 1 switches a fan motor 100 including a stator around which motor windings of a plurality of phases are wound and a rotator holding a permanent magnet, from a synchronous operation of controlling current flowing through the motor windings without estimating a position of the rotator at a starting time of a synchronous motor to a sensorless vector control operation of controlling the current flowing through the motor windings based on the position of the rotator. The motor control device has a current detecting part 20 detecting the current flowing through the motor windings and power swing determination means 70 determining power swing of the fan motor 100 at the starting time based on a change of an amplitude of the current detected by the current detecting part 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a brushless motor that does not have a position sensor that detects the position of the rotor of the motor. [Background technology]

[0002] In a control device for a brushless motor (sensorless brushless motor) that does not have a position sensor to detect the position of the motor rotor, it is not possible to detect whether the motor's rotation speed recognized by the control device does not match the actual motor rotation speed at motor startup (out-of-step), i.e., whether the motor startup was successful. Therefore, there has been a demand for a method that can detect motor out-of-step at startup, even in a sensorless system.

[0003] Therefore, as a detection means for detecting loss of synchronism in a sensorless brushless motor at startup, Patent Document 1 discloses a brushless motor drive device that includes a multi-phase motor drive coil, a plurality of drive transistors provided in the drive coil, an energization switching circuit that sequentially transmits an energization switching signal for the drive coil to the drive transistors, and a back EMF detector that detects the back EMF generated in the drive coil, and is configured so that an output signal based on the back EMF detected by the back EMF detector is input to the energization switching circuit, and so that loss of synchronism is determined to have occurred when the change rate of the output signal from the back EMF detector is equal to or greater than a first predetermined value or equal to or less than a second predetermined value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-170781 Summary of the Invention [Problem to be solved by the invention]

[0005] In the sensorless brushless motor drive device disclosed in Patent Document 1, loss of synchronization is determined by detecting the rate of change of the output signal (back electromotive force waveform) from a back electromotive force detector. Detecting the rate of change of the back electromotive force waveform makes it possible to detect abnormally fast or slow motor rotation, thereby enabling loss of synchronization to be determined. This method requires detecting the rotor state (speed), which requires a detector (back electromotive force detector), resulting in increased costs.

[0006] An object of the present invention is to provide a control device for a sensorless brushless motor that can easily determine step-out, regardless of whether a back electromotive force detector is included, as a drive device for the sensorless brushless motor. [Means for solving the problem]

[0007] One aspect of the present invention is a motor control device that switches, when starting a synchronous motor including a stator around which motor windings of multiple phases are wound and a rotor holding a permanent magnet, from synchronous operation, in which current flowing through the motor windings is controlled without estimating the position of the rotor, to vector control operation, in which current flowing through the motor windings is controlled based on the position of the rotor, and the motor control device includes a current detection unit that detects the current flowing through the motor windings. and, A step-out determination means for determining step-out of the synchronous motor at start-up based on a change in the amplitude of the current flowing through the motor windings detected by the current detection unit. and, Equipped with The step-out determination means determines step-out of the synchronous motor based on a gradient representing a tendency of a temporal change in the amplitude of the current flowing through the motor winding and a set first threshold value. This is a motor control device. Also, This motor control device switches, at start-up, from synchronous operation, which controls the current flowing through the motor windings without estimating the rotor position, to vector control operation, which controls the current flowing through the motor windings based on the rotor position, for a synchronous motor including a stator wound with multi-phase motor windings and a rotor holding a permanent magnet. The motor control device includes: a current detection unit that detects the current flowing through the motor windings; out-of-step determination means that determines out-of-step of the synchronous motor at start-up based on changes in the amplitude of the current flowing through the motor windings detected by the current detection unit; a drive unit that drives the synchronous motor in accordance with an input voltage command; and a synchronous voltage setting unit that outputs a predetermined voltage command at start-up. The synchronous voltage setting unit includes a calculation unit that converts a current vector in a fixed coordinate system when the synchronous motor is driven by the drive unit into a current vector (Iγ, Iδ) in a γ-δ coordinate system, and calculates an estimated angular velocity ωe′ of the rotating magnetic field that sets the γ component Iγ of the converted current vector to zero, and the motor control device sets a voltage proportional to the estimated angular velocity as a voltage command for the γ component Vγ of the voltage vector (Vγ, Vδ) in the γ-δ coordinate system. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to easily determine whether a motor is out of step, regardless of whether a back electromotive force detector is present or not. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a configuration of a sensorless synchronous motor control device according to an embodiment of the present invention; [Figure 2] FIG. 10 is a block diagram showing an example of a transfer function of the phase adjustment process. [Figure 3] 10 is an example of a U-phase current waveform when the start-up is successful. [Figure 4] 10 is an example of a U-phase current waveform when a start-up failure occurs. [Figure 5] 3 is a flowchart illustrating an example of the operation of the sensorless synchronous motor control device. [Figure 6] 10 is a flowchart illustrating an example of an operation of the sensorless synchronous motor control device when a step-out is determined. [Figure 7] 10 is a flowchart of correlation filter processing when determining loss of synchronism. [Figure 8] 10 is a flowchart of a regression line calculation when a step-out is determined. [Figure 9] FIG. 10 is a diagram showing the slope of a regression line. [Figure 10] FIG. 10 is a block diagram showing a configuration of a sensorless synchronous motor control device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following detailed description, certain specific configurations are described to provide a thorough understanding of the embodiments of the present invention. However, it is clear that other embodiments can be implemented without being limited to such specific configurations. Furthermore, the following embodiments do not limit the invention according to the claims, and include all combinations of the characteristic configurations described in the embodiments.

[0011] <Motor control device configuration> An embodiment of the present invention will be described below with reference to the drawings. In the following description of the drawings, identical parts are designated by the same reference numerals. Here, a case will be described in which a motor control device according to the present invention is applied to a sensorless synchronous motor control device for a fan motor. The fan motor 100 is a motor that drives an outdoor unit fan of an air conditioner, and is made up of a sensorless synchronous motor equipped with a multi-phase (for example, three-phase) stator (not shown) wound with motor windings, and a rotor (not shown) that holds a permanent magnet.

[0012] FIG. 1 is a configuration diagram showing an example of a sensorless synchronous motor control device (hereinafter also simply referred to as a motor control device) 1 according to an embodiment of the present invention. As shown in FIG. 1, the motor control device 1 includes a drive unit 10, a current detection unit 20, a calculation unit 30, a voltage output unit 40, an integration unit 50, a first conversion unit 60, a step-out determination means 70, and a control unit (CPU) 80. The calculation unit 30, the voltage output unit 40, the integration unit 50, the first conversion unit 60, and the step-out determination means 70 constitute a control unit 80. The calculation unit 30, the voltage output unit 40, the integration unit 50, and the first conversion unit 60 correspond to a synchronization voltage setting unit.

[0013] The driving unit 10 drives the fan motor 100 by supplying, for example, three-phase AC signals U, V, and W to the fan motor 100. The internal configuration of the driving unit 10 will be described later. The current detection unit 20 detects the amplitude of at least two sets of currents. Specifically, the current detection unit 20 detects the amplitude of the motor currents flowing through the U-phase and W-phase stator coils (motor windings) of the fan motor 100. The amplitude of the U-phase current Iu and the amplitude of the W-phase current Iw detected by the current detection unit 20 are supplied to the calculation unit 30.

[0014] The calculation unit 30 converts a current vector (Iu, Iw) in a fixed coordinate system (UVW coordinate system) used when the fan motor 100 is driven by the drive unit 10 into a current vector (Iγ, Iδ) in a rotating coordinate system (γ-δ coordinate system). The d-axis of the motor's rotating coordinate system (dq coordinate system) is the direction of the magnetic flux generated by the magnetic poles, and the q-axis is a direction orthogonal to the d-axis electrically and magnetically. In contrast, the rotating coordinate system (γ-δ coordinate system) for control has a δ-axis and a γ-axis corresponding to the d-axis and q-axis, respectively. The calculation unit 30 calculates an estimated angular velocity ωe′ of the rotating magnetic field that zeros the γ-component Iγ of the current vector in the converted rotating coordinate system. Specifically, the calculation unit 30 includes a second conversion unit (a three-phase-to-two-phase converter (UVW / γ-δ)) 31 and a speed estimation processing unit 32.

[0015] The second conversion unit 31 receives the detected value of the amplitude of the U-phase current Iu and the detected value of the amplitude of the W-phase current Iw from the current detection unit 20. The second conversion unit 31 converts the current vector (Iu, Iw) in the fixed coordinate system (UVW coordinate system) into a current vector (Iγ, Iδ) in the rotating coordinate system (γ-δ coordinate system) using, for example, the following equations (1) and (2): Iγ =(√2){Iu×cos(θe′+π / 6)-Iw×sin(θe′)} ……(1) Iδ =-(√2){Iu×sin(θe′+π / 6)+Iw×cos(θe′)} ……(2)

[0016] The second conversion unit 31 outputs the γ component of the current vector in the converted rotating coordinate system (γ-δ coordinate system), i.e., the γ-axis current Iγ, to the speed estimation processing unit 32, and outputs the δ component of the current vector, i.e., the δ-axis current Iδ, to the voltage output unit 40. The speed estimation processing unit 32 receives the γ-axis current Iγ from the second conversion unit 31. The speed estimation processing unit 32 calculates, in accordance with the received γ-axis current Iγ, an estimated angular velocity ωe′, which is an estimate of the angular velocity ωe of the rotating magnetic field that makes the γ-axis current Iγ zero. The speed estimation processing unit 32 supplies the calculated estimated angular velocity ωe′ to the integrating unit 50 and the voltage output unit 40.

[0017] 2 is a block diagram showing a transfer function of the phase adjustment processing executed by the speed estimation processing unit 32. The speed estimation processing unit 32 multiplies the γ-axis current Iγ by coefficients Ki and Kp in a multiplier 32a and a multiplier 32b, respectively, integrates the output of the multiplier 32a in an integrator 32c, and adds the output of the integrator 32c and the output of the multiplier 32b in an adder 32d to calculate an estimated angular velocity ωe′. At this time, in order to converge the estimated angular velocity ωe′, Vd (=Vγ) is calculated using the estimated angular velocity ωe′. An appropriate value for the γ-axis voltage Vγ is given by the following equation (3). Vγ=-ωe′·Lq·Iδ ……(3) In equation (3), Lq is the q-axis inductance value, and Iδ is a substitute value. In other words, when the estimated angular velocity ωe′ converges, the phase difference between the d-axis and γ-axis also converges to zero, and the γ-δ value is substituted for the dq value.

[0018] The speed estimation processor 32 adjusts the rotation speed by PI control so that the current Iγ on the control axes γ-δ is 0 [A], thereby bringing the γ-δ coordinate axes closer to the dq coordinate axes. Specifically, the δ-axis voltage Vδ is kept constant, and the γ-axis current Iγ is input to the speed estimation processor 32 to calculate an estimated angular velocity ωe′. The integrator 51 integrates the estimated angular velocity ωe′ to calculate an estimated rotation angle θe′. The estimated voltage output unit 42, described below, provides the γ-axis voltage Vγ using equation (3). This causes the fan motor 100 to converge to an appropriate operating state for optimal synchronous operation at a rotation speed at which the δ-axis voltage Vδ has a value corresponding to the load. The speed estimation processor 32 also outputs the estimated angular velocity ωe′ to the out-of-step determination means 70.

[0019] The voltage output unit 40 estimates the γ component Vγ of the voltage vector on the rotating coordinate system (γ-δ coordinate system) based on the estimated angular velocity ωe′ calculated by the calculation unit 30. At the same time, the voltage output unit 40 sets the δ component Vδ of the voltage vector on the rotating coordinate system (γ-δ coordinate system) to a predetermined value. Specifically, the voltage output unit 40 receives the motor applied voltage V as input, and includes a fixed voltage output unit 41 and an estimated voltage output unit 42. The fixed voltage output unit 41 sets Vδ to a predetermined value (for example, a fixed value), and outputs this value to the first conversion unit 60 as a δ-axis voltage command Vδ*.

[0020] For example, when starting the fan motor 100, the voltage output unit 40 starts driving with a starting voltage of Vγ*=0 and Vδ*=a predetermined value (e.g., a fixed value). The starting voltage Vδ* preset in the fixed voltage output unit 41 is set to a value that creates a high overvoltage state, taking into account fluctuations in the load. The motor control device 1 adjusts the angular velocity of the rotating magnetic field so that the voltage Vδ* that generates this torque is a value that corresponds to the load.

[0021] The estimated voltage output unit 42 receives the estimated angular velocity ωe′ from the velocity estimation processing unit 32, and receives the δ-axis current Iδ from the second conversion unit 31 of the calculation unit 30. The estimated voltage output unit 42 estimates a γ-component Vγ of the voltage vector using the estimated angular velocity ωe′ and the δ-axis current Iδ, and outputs the estimated value to the first conversion unit 60 as a γ-axis voltage command Vγ*. The integrator 50 integrates the estimated angular velocity ωe' to obtain the estimated rotation angle θe'. Specifically, the integrating unit 50 has an integrator 51. The integrator 51 integrates the estimated angular velocity ω′ of the rotating magnetic field to calculate an estimated rotation angle θ′, which is an estimate of the phase angle θ of the rotating coordinate system that rotates together with the rotating magnetic field. The integrator 51 outputs the calculated estimated rotation angle θ′ to the first converting unit 60 and the calculating unit 30.

[0022] The first conversion unit 60 converts the voltage vector on the rotating coordinate system (γ-δ coordinate system) estimated by the voltage output unit 40 into a voltage vector in a fixed coordinate system (UVW coordinate system) using the estimated rotation angle θe′ obtained by the integration unit 50. Specifically, the first conversion unit 60 has a two-phase to three-phase converter (γ-δ / UVW) 61. The two-phase to three-phase converter 61 receives a γ-axis voltage command Vγ* and a δ-axis voltage command Vδ*, i.e., a voltage vector (Vγ, Vδ) in a rotating coordinate system (γ-δ coordinate system) from the voltage output unit 40. The two-phase to three-phase converter 61 receives an estimated rotation angle θe′ from the integration unit 50. The two-phase to three-phase converter 61 converts the voltage vector (Vγ, Vδ) in the rotating coordinate system (γ-δ coordinate system) into a voltage vector (Vu, Vv, Vw) in a fixed coordinate system (UVW coordinate system) using, for example, the following equations (4) to (6):

[0023] Vu =(√(2 / 3)){Vγ×cos(θe′)-Vδ×sin(θe′)} ……(4) Vv =(√(1 / 2)×Vγ+√(1 / 6)×Vδ)×sin(θe′) +(√(1 / 2)×Vδ-√(1 / 6)×Vγ)×cos(θe′) ……(5) Vw =(√(1 / 6)×Vδ-√(1 / 2)×Vγ)×sin(θe′) -(√(1 / 6)×Vγ+√(1 / 2)×vδ)×cos(θe′)……(6)

[0024] The two-phase-to-three-phase converter 61 outputs the voltage vectors (Vu, Vv, Vw) in the fixed coordinate system (UVW coordinate system) in the converted rotating coordinate system (γ-δ coordinate system) to the driver 10. Note that although equations (4) to (6) are equations for three-phase modulation, the two-phase-to-three-phase converter 61 may perform two-phase modulation to increase the voltage utilization rate. The driving unit 10 drives the fan motor 100 so that the fan motor M operates at a voltage corresponding to the voltage vector converted by the first conversion unit 60.

[0025] Specifically, the drive unit 10 includes a PWM converter 11 and a driver 12. The PWM converter 11 receives voltage vectors (Vu, Vv, Vw) in a fixed coordinate system (UVW coordinate system), i.e., a U-phase voltage command Vu*, a V-phase voltage command Vv*, and a W-phase voltage command Vw*, from a first conversion unit 60. The PWM converter 11 converts the U-phase voltage command Vu*, the V-phase voltage command Vv*, and the W-phase voltage command Vw* into PWM signals and supplies them to the driver 12. In this way, the PWM converter 11 drives the fan motor 100 via the driver 12.

[0026] The driver 12 includes a shunt resistor 25 and receives the PWM signal from the PWM converter 11. The driver 12 has, for example, a plurality of switching elements (not shown), and performs power conversion by switching the plurality of switching elements at predetermined timings in accordance with the PWM signal, and supplies the generated three-phase AC signals U, V, and W to the fan motor M, thereby driving the fan motor 100.

[0027] Next, the loss of synchronization state at startup will be described using Figures 3 and 4. Figures 3 and 4 are graphs showing the temporal transition of the current waveform flowing through the motor windings from startup. As shown in the startup procedure of the motor control device 1, which will be described later, the fan motor 100 is driven in the following order: synchronous operation, phase adjustment, mode transition, and vector control operation. The horizontal axis represents elapsed time, which is divided according to the control content at startup of the fan motor 100.

[0028] The speed estimation processor 32 adjusts the rotation speed by applying PI control so that the current Iγ on the control axis γ-δ axes approaches 0 [A], thereby bringing the phase of the γ-δ coordinate axes closer to the phase of the dq coordinate axes. If the phase of the γ-δ coordinate axes approaches the phase of the dq coordinate axes, the fan motor 100 rotates efficiently. Therefore, as shown in the phase adjustment section T3 in FIG. 3, the U-phase current Iu flows in a direction that minimizes the current required for the load, and the current amplitude gradually decreases. However, if the rotating magnetic field and the rotor (rotor) are not synchronized and a loss of synchronization occurs, the current amplitude does not decrease, and the fan motor 100 rotates inefficiently, as shown in the phase adjustment section T3 in FIG. 4. Therefore, an attempt to accelerate to the normal rotation speed results in an overcurrent error and a stop. Therefore, by detecting the current during this phase adjustment section and examining the change in current amplitude, it is possible to determine whether the fan motor 100 starts normally when the current amplitude is decreasing, or whether a start-up failure due to loss of synchronization is occurring when the current amplitude does not decrease.

[0029] Next, the procedure for starting up the motor control device 1, including the step-out determination process, will be described with reference to the flowcharts shown in FIGS. The out-of-step determination process is performed by out-of-step determination means 70 provided in the control unit 80 shown in Fig. 1. The out-of-step determination means 70 includes a correlation filter 71. Here, the correlation filter 71 is a filter that performs Fourier series expansion (filtering) on ​​the current, and will be described in detail later. The out-of-step determination means 70 performs out-of-step determination process based on the amplitude of either the U-phase current Iu or the W-phase current Iw detected by the current detection unit 20 used to drive the fan motor 100. In this embodiment, the out-of-step determination process performed based on the amplitude of the U-phase current Iu will be described.

[0030] The fan motor 100 is started in synchronous operation (S1), where current is passed through the motor windings without estimating the rotor position, and the frequency of the current is gradually increased to accelerate the rotation of the fan motor 100. Next, the phase of the fan motor 100 is adjusted, i.e., the phase of the γ-δ coordinate axes is brought closer to the phase of the dq coordinate axes (S2). After the phase adjustment begins, a step-out determination is made to determine whether or not the fan motor 100 has lost synchronism (S3) using the step-out determination means 70 of the present invention. That is, it is determined whether or not the fan motor 100 has successfully started. If step-out is not detected (NO in S3), a mode transition is performed to switch the operation of the fan motor 100 from synchronous operation to vector control operation, which estimates the rotor position, and the fan motor 100 is driven in vector control operation (S4). Here, the mode transition is a period in which the motor rotation speed is maintained without increasing until the current flowing through the motor windings stabilizes. This prevents excessive current from flowing through the motor windings when vector control operation begins. If the out-of-step determination determines that an out-of-step has occurred (YES in S3), operation is stopped (S6) and synchronous operation is restarted (S1). Note that synchronous operation (S1) corresponds to the synchronous operation section T2 in Figures 3 and 4, and similarly, phase adjustment (S2) corresponds to the phase adjustment section T3, mode transition (S4) corresponds to the mode transition section T4, and vector control operation (S5) corresponds to the vector control operation section T5. Out-of-step determination (S3) is performed in the phase adjustment section T3.

[0031] Next, a specific procedure for determining out-of-step is explained. Out-of-step determination is performed by calculating the trend in the amplitude change of the U-phase current Iu during the transition period from the synchronous operation period to the vector control operation period, more specifically, during the phase adjustment period, from the start of the phase adjustment process until a predetermined number of current periods (current periods) have elapsed. The length (in seconds) of one current period depends on the estimated angular velocity ωe′ and is the reciprocal of the value obtained by dividing this by 2π. Furthermore, the shorter the period set as the predetermined period, the fewer data points are acquired, which can lead to insufficient detection of current amplitude changes due to noise, making it more likely that an out-of-step detection will occur. On the other hand, the longer the period set as the predetermined period, the longer the startup time. Taking these factors into consideration, an appropriate value is determined for the predetermined period. If the amplitude tends to decrease over time, it is determined that no out-of-step has occurred. Conversely, if the amplitude increases or remains unchanged over time, it is determined that an out-of-step has occurred. The change in amplitude is confirmed by the change in the correlation value obtained by filtering using a correlation filter 71 (described later) within the out-of-step determination means 70, which removes the effects of noise. By calculating the slope of the linear approximation of the correlation value, the slope indicates the trend of the amplitude change over time. Therefore, by comparing the slope with a threshold value (hereinafter referred to as the first threshold value) that is the first threshold value of the present invention, a loss of synchronization is determined. In this embodiment, the trend of change in the amplitude of the U-phase current Iu from the start of the phase adjustment process is calculated to determine whether a loss of synchronization has occurred. However, the trend of change in the amplitude of the U-phase current Iu in the middle of the phase adjustment period, rather than from the start of the phase adjustment process, may be calculated to determine whether a loss of synchronization has occurred. However, because the amplitude of the U-phase current Iu changes significantly in the early stages of the phase adjustment period, it is preferable to calculate the trend of change in the amplitude of the U-phase current Iu from the start of the phase adjustment process, i.e., in the early stages of the phase adjustment period, to determine whether a loss of synchronization has occurred.

[0032] The detailed procedure will be explained using the flowchart shown in FIG. First, a timer is started (S10). The timer value measures the time until the correlation value is calculated and is used when calculating the linear approximation line, which will be described later. Next, the frequency of the Fourier series expansion of the correlation filter 71 is determined (S11). Because the angular velocity of the rotating magnetic field that drives the motor differs for each current period, the frequency of the Fourier series expansion must be determined for each current period. The flow for determining the frequency of the Fourier series expansion will be described later using the flowchart in Figure 7. Next, filtering is performed using the correlation filter 71 with the determined frequency (S12), and the frequency determination and filtering are repeated n times (S13). Here, the frequency determination and filtering are performed for each current period, where n is determined based on the predetermined number of current periods (e.g., 10 times). After that, a regression line is calculated using the least squares method as a linear approximation line (S14). Next, the presence or absence of step-out is determined from the slope of the regression line obtained (S15). Here, the regression line is a line that represents the central distribution tendency of two sets of data (time and correlation value in this embodiment). A negative slope of the regression line indicates that the amplitude of the U-phase current Iu is decreasing. On the other hand, a positive slope or zero indicates that the amplitude of the U-phase current Iu is increasing or is unchanged. Therefore, the presence or absence of a loss of synchronism is determined by comparing the slope of the regression line with a first threshold value.

[0033] Next, the determination of the frequency of the Fourier series expansion of the correlation filter 71 (S11) will be described with reference to the flowchart shown in FIG. 7(a). To determine the frequency of the Fourier series expansion, first, the estimated angular velocity ωe' calculated during phase adjustment is obtained (S20), the phase θt is calculated using the estimated angular velocity ωe' (S21), and the frequencies sin(θt) and cos(θt) are determined (S22). The phase θt is calculated using the following equation (7). Note that the initial value of θt is 0 rad, and Δt represents the control period. θt=θt-1+ωe´×Δt (7)

[0034] Next, the execution of the filtering process by the correlation filter 71 (S12) will be described with reference to the flowchart shown in FIG. 7(b). First, the U-phase current Iu(t) at time t detected by the current detection unit 20 is obtained (S30), and then the U-phase current Iu(t) is multiplied by sin(θt)×(ωe′×Δt) and cos(θt)×(ωe′×Δt) (S31). Next, the sums sin_sum and cos_sum of the products of Iu(t) and sin(θt)×(ωe′×Δt) and Iu(t) and cos(θt)×(ωe′×Δt) are calculated within the range of 0≦θt<2π. First, it is determined whether θt is greater than or equal to 2π (S32). If θt is less than 2π (S32: No), that is, if 0≦θt<2π, the sums sin_sum and cos_sum are updated, and the process returns to S20 (S37). By returning to the previous step and repeating the process of S37, the sums sin_sum and cos_sum can be calculated within the range of 0≦θt<2π. The sum sin_sum can be expressed by the following equation (8), and the sum cos_sum can be expressed by the following equation (9).

[0035]

number

[0036] If θt is greater than or equal to 2π (S32: Yes), that is, if θt increases over time and becomes greater than or equal to 2π, θt is reset by subtracting 2π from θt (S33), and the sums sin_sum and cos_sum are obtained (S34). Next, sin_sum and cos_sum are divided by 2π and normalized by the L2 norm to obtain the correlation value soukan, and the time soukanTime from the start of phase adjustment to the calculation of the correlation value is obtained (S35). soukan is calculated using the following equation (10):

[0037]

number

[0038] As described above, the frequency determination process (S11) shown in FIG. 7(a) and the filter process (S12) shown in FIG. 7(b) are repeated n times, so the correlation value soukan and the time until calculation soukanTime are obtained n times. Next, the sums sin_sum and cos_sum are reset (S36), that is, sin_sum=0, cos_sum=0.

[0039] Next, calculation of a linear approximation line representing the tendency of the correlation value using the least squares method will be described with reference to FIG. By performing the filtering process using the correlation filter 71, the following n correlation values ​​and the time required for calculation are obtained. (soukanTime1, soukan1), (soukanTime2, soukan2), ..., (soukanTime n, soukan n) A regression line is calculated using the least squares method from n pieces of x-axis (time axis) data and y-axis (execution axis) data. A regression line is a linear line that represents the relationship between x and y when a large number of data pairs (xi, yi) are given. When the regression line is y=ax+b, the slope a and intercept b can be calculated using the following formula.

[0040]

number

[0041] The items in each formula are shown below.

[0042]

number

[0043] First, the execution axis data (y-axis) and time axis data (x-axis) are obtained (S40). Next, the variance of the x-axis data is calculated (S41). Next, the covariance of the x-axis data and the y-axis data is calculated (S41). Then, the slope a of the regression line is calculated (S43).

[0044] Next, the relationship between the regression line calculated using the least squares method based on the U-phase current Iu and the amplitude and correlation value of the U-phase current Iu will be explained using Figure 9. Figure 9 shows the waveform, correlation value, and regression line of the U-phase current Iu in the phase adjustment section during the transition from the synchronous operation section to the vector control operation section. Figure 9(a) shows the case where the transition from synchronous operation to vector control operation was successful without loss of synchronism, and Figure 9(b) shows the case where loss of synchronism occurred. The horizontal axis represents time in seconds. The vertical axis (left axis) represents the current value in amperes, and the vertical axis (right axis) represents the correlation value. The current waveform is shown with a thin line, the correlation value is shown with a circle, and the regression line is shown with a thick line.

[0045] When vector control operation was successfully initiated without a loss of synchronism, the slope of the regression line (shown in bold in Figure 9(a)) was a negative value, downward sloping to the right. In this embodiment, the slope a was -0.169. On the other hand, when a loss of synchronism occurred and vector control operation was not initiated, the slope a of the regression line (shown in bold in Figure 9(b)) was -0.0028. In this case, the slope a was a negative value indicating a decreasing trend, but the absolute value of the slope a was sufficiently small (approximately 1% in this embodiment) relative to the initial value of the correlation value (0.270 in this embodiment), and the current amplitude hardly decreased. Therefore, when the slope a is negative and the absolute value of the slope a is not sufficiently small relative to the initial value of the correlation value (e.g., greater than 10%), it can be determined that the current amplitude has decreased and no loss of synchronism has occurred. For example, a loss of synchronism can be determined by setting the slope a of the regression line to -0.027 as the first threshold for determining loss of synchronism. In this embodiment, a regression line is calculated using the least squares method based on the U-phase current Iu, and if the slope a of the regression line is smaller than the first threshold value of -0.027, it is determined that a transition from synchronous operation to vector control operation will occur without loss of synchronism, and if the slope a of the regression line is equal to or greater than the first threshold value of -0.027, it is determined that a transition from synchronous operation to vector control operation will occur with loss of synchronism.

[0046] Synchronous operation is an operation in which the rotor is forcibly rotated by passing current through the motor windings without estimating the rotor position, i.e., ignoring the rotor position. On the other hand, vector control operation is an operation in which the rotor position is estimated and the current is controlled in accordance with the rotor position to rotate the rotor. Since synchronous operation is less efficient than vector control operation, the current flowing through the motor windings is larger in synchronous operation than in vector control operation. Focusing on this point, the present invention determines loss of synchronization based on the slope that represents the change in the amplitude of the current flowing through the motor windings.

[0047] In this embodiment, out-of-step determination is performed based on the amplitude of the U-phase current Iu out of the amplitudes of the U-phase current Iu and the W-phase current Iw detected by the current detection unit 20. However, out-of-step determination may also be performed based on the amplitudes of two or more currents detected by the current detection unit 20. Performing out-of-step determination based on the amplitudes of two or more currents has the effect of preventing erroneous determination due to an abnormal value even if an abnormality occurs in the current detection unit 20 or the fan motor 100 and the detected current indicates an abnormal value. Here, possible abnormalities include, for example, a failure of the current transformer when a current transformer is used as the current detection unit 20, demagnetization of the rotor of the fan motor 100, or a layer short in the stator winding.

[0048] For example, out-of-step determination means 70 performs out-of-step determination processing based on the amplitudes of U-phase current Iu and W-phase current Iw of the three-phase motor windings. Slopes representing temporal changes in the amplitude of U-phase current Iu (hereinafter referred to as the slope of U-phase current Iu) and W-phase current Iw (hereinafter referred to as the slope of W-phase current Iw) are calculated, and if both the slopes of U-phase current Iu and W-phase current Iw are equal to or greater than a first threshold, it is determined that fan motor 100, which is a synchronous motor, is out of step. If either the slope of U-phase current Iu or the slope of W-phase current Iw is less than the first threshold and the other slope of U-phase current Iu or the slope of W-phase current Iw is equal to or greater than the first threshold, it is determined that there is an abnormality in current detection unit 20 or fan motor 100. If both the gradient of the U-phase current Iu and the gradient of the W-phase current Iw are less than the first threshold value, it is determined that the fan motor 100 has not lost synchronism.

[0049] In the above description, out-of-step determination is performed based on the amplitude of the currents flowing through two of the three-phase motor windings, the U-phase current Iu and the W-phase current Iw. However, out-of-step determination (determination based on multiple current values) may be performed based on the amplitude of the currents flowing through all phases of the motor windings. In this case, the out-of-step determination means 70 determines that the fan motor 100 has out-of-step if the gradients of the currents flowing through all phases used for determination are equal to or greater than a first threshold value. If there is a mixture of phases with current gradients less than the first threshold value and phases with current gradients equal to or greater than the first threshold value, it determines that there is an abnormality in the current detection unit 20 or the fan motor 100. If the gradients of the currents flowing through all phases are less than the first threshold value, it determines that the fan motor 100 has not out-of-step. This enables detection of an abnormality in the current detection unit 20 or the fan motor 100, thereby avoiding erroneous determinations due to abnormal values ​​of the detected currents and enabling accurate out-of-step determination.

[0050] Furthermore, to more accurately determine out-of-step, the following procedure may be adopted. First, out-of-step determination means 70 calculates the slopes of, for example, U-phase current Iu and W-phase current Iw of the three-phase motor windings, and determines that fan motor 100, which is a synchronous motor, has lost synchronism if both the slopes of U-phase current Iu and W-phase current Iw are equal to or greater than a first threshold value. Next, it calculates the absolute value of the difference between the slopes of U-phase current Iu and W-phase current Iw, and determines that there is an abnormality in current detection unit 20 or fan motor 100 (determination based on the difference between multiple current values) if the absolute value of the difference between the slopes of U-phase current Iu and W-phase current Iw is greater than a second threshold value. This allows for more accurate detection of an abnormality and determination of out-of-step.

[0051] In the judgment based on the difference between the multiple current values ​​described above, when the out-of-step judgment means 70 determines that the fan motor 100 has out-of-step, it calculates the absolute value of the difference between the slope of the U-phase current Iu and the slope of the W-phase current Iw, and if this absolute value exceeds a second threshold value, it determines that there is an abnormality in the current detection unit 20 or the fan motor 100.However, when the out-of-step judgment means 70 determines that the fan motor 100 has not out-of-step, it may also calculate the absolute value of the difference between the slope of the U-phase current Iu and the slope of the W-phase current Iw, and if this absolute value exceeds a second threshold value, it may determine that there is an abnormality in the current detection unit 20 or the fan motor 100.

[0052] Although the above describes the determination based on multiple current values ​​and the determination based on the difference between multiple current values ​​separately, it is also possible to perform out-of-step determination by combining the determination based on multiple current values ​​and the determination based on the difference between multiple current values. In this way, it is possible to more accurately detect abnormalities and perform out-of-step determination.

[0053] In the above-described embodiment, the current detection unit 20 detects the current flowing in the U-phase current Iu of the fan motor 100 and performs the process of determining whether or not a step-out has occurred based on the amplitude of the U-phase current Iu. However, other embodiments may be used. The other embodiments will be described with reference to FIG. 10. The only difference from the above-described embodiment is the method of detecting the current of each phase by the current detection unit 20; the other configurations are the same.

[0054] A shunt resistor 25 is connected to the driver 12, and a current detection unit 20 detects the current of each phase from the current flowing through the shunt resistor 25 based on the PWM signal to drive the fan motor 100, while a step-out determination means 70 determines step-out based on a change in the amplitude of the current of at least one of the phases detected by the current detection unit 20. The method of determining step-out is omitted as it is the same as in the above embodiment.

[0055] The motor control device 1 of the present invention performs the process of determining out-of-step based on the amplitude of the current flowing through the motor windings detected by the current detection unit 20 used to drive the fan motor 100, and therefore does not require the addition of a new circuit for determining out-of-step, thereby reducing the cost of manufacturing the motor control device 1. Furthermore, because the process of determining out-of-step is performed based on the amplitude of the current flowing through the motor windings detected by the current detection unit 20 used to drive the fan motor 100, out-of-step determination can be performed regardless of the presence or absence of a back-EMF voltage detector.

[0056] In the above embodiment, the fan motor 100 is driven in the order of synchronous operation, phase adjustment, mode transition, and vector control operation, and loss of synchronism determination is performed during the phase adjustment process, but this is not necessarily limited to this. For example, in operation without phase adjustment during the drive of the fan motor 100, loss of synchronism determination may be performed during the mode transition section between synchronous operation and vector control operation. This is because during the mode transition section, the current driving the fan motor 100 attenuates, making it possible to determine loss of synchronism. That is, the determination of a loss of synchronism may be performed during the transition period from synchronous operation to vector control operation. When the determination of a loss of synchronism is performed during the transition period from synchronous operation to vector control operation, it is desirable to determine whether or not a loss of synchronism has occurred during the initial stage of the transition period, because the amplitude of each phase current changes significantly during the initial stage of the transition period.

[0057] In the above embodiment, a regression line was found using the least squares method based on the current detected by the current detection unit 20 used to drive the fan motor 100, and a step-out detection was performed based on the slope a of the regression line, but it is not necessary to find the regression line using the least squares method. For example, a slope representing a change in the amplitude of the current flowing through the motor windings may be found from the peak values ​​of the current in two different current cycles, and step-out detection may be performed based on that slope.

[0058] Although the present invention has been described above with reference to a limited number of embodiments, the scope of the invention is not limited thereto, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art. [Explanation of symbols]

[0059] 1...motor control device, 10...drive unit, 20...current detection unit, 30...calculation unit, 40...voltage output unit, 50...integration unit, 60...first conversion unit, 70...step-out determination means, 71...correlation filter, 80...control unit, 100...fan motor (synchronous motor)

Claims

1. A motor control device for a synchronous motor including a stator around which motor windings of multiple phases are wound and a rotor holding a permanent magnet, the motor control device switching from a synchronous operation in which a current flowing through the motor windings is controlled without estimating a position of the rotor to a vector control operation in which a current flowing through the motor windings is controlled based on a position of the rotor, at the start of the synchronous motor, a current detection unit that detects a current flowing through the motor winding; a step-out determination means for determining step-out of the synchronous motor at the time of start-up based on a change in amplitude of the current flowing through the motor winding detected by the current detection unit, The motor control device is characterized in that the out-of-step determination means determines out-of-step of the synchronous motor based on a slope representing the tendency of time-dependent change in the amplitude of the current flowing through the motor windings and a set first threshold value.

2. the first threshold value is a negative value indicating that the amplitude of the current flowing through the motor winding is decreasing, 2. The motor control device according to claim 1, wherein the step-out determining means determines that the synchronous motor is out of step when the gradient is equal to or greater than the first threshold value.

3. the slope is a slope of a regression line that represents a central distribution tendency of a set of data of time and correlation value in a predetermined period of a current flowing through the motor winding, the correlation value is calculated by performing a filtering process on a current flowing through the motor winding using a correlation filter; a frequency of a Fourier series expansion in the correlation filter is determined using an estimated angular velocity of a rotating magnetic field that drives the synchronous motor; The frequency determination and the filtering are performed every current period.

3. The motor control device according to claim 1 or 2.

4. 4. The motor control device according to claim 1, wherein the out-of-step determination means determines out-of-step of the synchronous motor based on a change in amplitude of a current flowing through at least one of the motor windings of the multiple phases.

5. A transition section is provided during switching from the synchronous operation to the vector control operation, 5. The motor control device according to claim 1, wherein the step-out determination means determines the step-out of the synchronous motor in the transition section.

6. 6. The motor control device according to claim 5, wherein the step-out determining means determines step-out of the synchronous motor based on a change in amplitude of a current flowing through the motor windings in an initial stage of the transition section.

7. the step-out determination means determines step-out of the synchronous motor based on a change in amplitude of a current flowing through two or more motor windings among the motor windings of the multiple phases; determining that the synchronous motor is out of step when the gradients of all phases used for the determination are equal to or greater than the first threshold value; 7. The motor control device according to claim 1, wherein when there is a mixture of a phase in which the slope is less than the first threshold value and a phase in which the slope is equal to or greater than the first threshold value, it is determined that there is an abnormality in the current detection unit or the synchronous motor.

8. The step-out determination means determines an absolute value of a difference between the slopes of any two of the plurality of phases.

8. The motor control device according to claim 1, wherein when the current detection unit detects a current exceeding a second threshold value, it is determined that an abnormality exists in the current detection unit or the synchronous motor.

9. A motor control device for a synchronous motor including a stator around which multiple phase motor windings are wound and a rotor holding a permanent magnet, which switches from a synchronous operation in which a current flowing through the motor windings is controlled without estimating a position of the rotor to a vector control operation in which a current flowing through the motor windings is controlled based on the position of the rotor at the time of start-up of the synchronous motor, a current detection unit that detects a current flowing through the motor winding; a step-out determination means for determining step-out of the synchronous motor at the time of start-up based on a change in amplitude of the current flowing through the motor winding detected by the current detection unit; a drive unit that drives the synchronous motor in response to an input voltage command, and a synchronous voltage setting unit that outputs a predetermined voltage command at the time of startup, the synchronous voltage setting unit includes a calculation unit that converts a current vector in a fixed coordinate system when the synchronous motor is driven by the drive unit into a current vector (Iγ, Iδ) in a γ-δ coordinate system, and calculates an estimated angular velocity ωe′ of a rotating magnetic field that makes the γ component Iγ of the converted current vector zero; A motor control device comprising: a voltage proportional to the estimated angular velocity as a voltage command for a γ component Vγ of a voltage vector (Vγ, Vδ) in the γ-δ coordinate system.

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