JP7480562B2 - Motor control device and method for controlling sensorless synchronous motor - Google Patents

Description

The present invention relates to a motor control device and a method for controlling a sensorless synchronous motor.

Conventionally, in devices that start a motor without a sensor, the speed estimation processing unit adjusts the phase before transitioning from startup operation to steady operation. For example, a method has been proposed in which a phase adjustment section is provided when the motor is started, ensuring a transition from synchronous operation, in which the rotor position is not estimated, to vector control, in which the rotor position is estimated (see, for example, Patent Document 1). Another method has been proposed in which, if the rotor is rotating in the reverse direction due to an external force when the motor is started, the rotor is started in the reverse direction, the rotor is pulled in, and then rotated in the forward direction (see, for example, Patent Document 2).

Patent No. 6003143 Patent No. 3731105

However, in the above conventional motor control device, since it is sensorless, it is not possible to detect whether the rotating magnetic field and the rotor are synchronized, i.e., whether the motor has been successfully started. Therefore, a method capable of detecting loss of synchronism of the motor at start-up, even in a sensorless system, is desired.
The present invention has been made in response to the unresolved problems in the prior art, and aims to provide a motor control device and a control method for a sensorless synchronous motor that are capable of detecting loss of synchronism of a motor at startup.

In order to achieve the above object, a motor control device according to one aspect of the present invention is a motor control device that controls a sensorless synchronous motor, which performs synchronous operation without estimating a rotor position at start-up, and transitions to normal operation in which the rotor position is estimated after performing phase adjustment, and includes a drive unit that drives the synchronous motor in response to an input voltage command, a synchronous voltage setting unit that outputs a predetermined voltage command at start-up, and a step -out determination unit that determines step-out of the synchronous motor based on a current flowing through the synchronous motor, and the synchronous voltage setting unit determines step-out of the synchronous motor based on a current flowing through the synchronous motor during the phase adjustment, The present invention is characterized in that it comprises a calculation unit that converts the current into a current vector (Iγ, Iδ) in a γ-δ rotating coordinate system, and calculates an estimated angular velocity ωe' of a rotating magnetic field that sets the gamma component Iγ of the converted current vector to zero, and outputs a voltage proportional to the estimated angular velocity as the voltage command for the gamma component Vγ of the voltage vector (Vγ, Vδ) in the γ-δ rotating coordinate system, and the out-of-step determination unit determines that the synchronous motor is in an out-of-step state when the current flowing through the synchronous motor when the synchronous motor is driven in accordance with the voltage command for the gamma component Vγ is equal to or greater than a set threshold value .
In addition, a control method for a sensorless synchronous motor according to another aspect of the present invention is a control method for a sensorless synchronous motor in which, when starting a sensorless synchronous motor, synchronous operation is performed without estimating the rotor position , and after phase adjustment, the control method transitions to normal operation in which the rotor position is estimated , the control method comprising the steps of: converting a current in a fixed coordinate system flowing through the motor into a current vector (Iγ, Iδ) in a γ-δ rotating coordinate system; calculating an estimated angular velocity ωe' of a rotating magnetic field that makes the γ component Iγ of the current vector zero; driving the synchronous motor based on the calculated estimated angular velocity to perform the phase adjustment; detecting a motor current of the synchronous motor after the phase adjustment; and determining that the synchronous motor has lost synchronization when the motor current is equal to or greater than a threshold value set in accordance with the motor current after the phase adjustment when the synchronous motor has failed to start.

According to one aspect of the present invention, it is possible to detect loss of synchronism during start-up of a sensorless synchronous motor.

1 is a schematic configuration diagram illustrating an example of a sensorless synchronous motor control device according to an embodiment of the present invention; FIG. 11 is a block diagram showing an example of a transfer function of a phase adjustment process. 13 is an example of a U-phase current waveform when the start is successful. 13 is an example of a U-phase current waveform when a start-up fails. FIG. 11 is an explanatory diagram for explaining a method for setting a threshold voltage. FIG. 4 is a diagram illustrating an example of the relationship between the load and the rotation speed of a fan motor. 4 is a flowchart showing an example of an operation of the sensorless synchronous motor control device. 4 is a flowchart showing an example of an operation of the sensorless synchronous motor control device when determining that a step-out has occurred. 11 is a graph showing an example of changes in the rotation speed of the fan motor and the voltage V applied to the motor when start-up is successful during normal start-up. 11 is a graph showing an example of changes in the rotation speed of a fan motor and a voltage V applied to the motor when a start-up fails during normal start-up; 11 is a graph showing an example of changes in the rotation speed of the fan motor and the voltage V applied to the motor when the fan motor is successfully started from a reverse rotation state. 11 is a graph showing an example of changes in the rotation speed of the fan motor and the voltage V applied to the motor when startup fails when starting from a reverse rotation state.

In the following detailed description, certain specific configurations are described to provide a complete 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. In addition, the following embodiments do not limit the invention according to the claims, but include all combinations of the characteristic configurations described in the embodiments.

<Configuration of the motor control device>
An embodiment of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same parts are given 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 M. The fan motor M is a motor that drives an outdoor unit fan of an air conditioner, and is composed of a multi-phase, for example a three-phase, sensorless synchronous motor.

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.
The motor control device 1 is the control device described in Patent Document 1, further comprising a step-out determination unit and a rotation detection unit.
1, the motor control device 1 includes a drive unit 10, a 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 unit 70, a control unit (CPU) 80, and a rotation detection unit 81. The calculation unit 30, the voltage output unit 40, the integration unit 50, and the first conversion unit 60 correspond to a synchronous voltage setting unit.

The driving unit 10 drives the fan motor M by, for example, supplying three-phase AC signals U, V, and W to the fan motor M. The internal configuration of the driving unit 10 will be described later.
The detection unit 20 detects at least two sets of current amplitudes. Specifically, the detection unit 20 includes a U-phase/W-phase current detection circuit (hereinafter also simply referred to as a current detection circuit) 21 that detects motor currents flowing through the U-phase and W-phase stator coils of the fan motor M. The current detection circuit 21 detects the amplitude of the U-phase motor current (hereinafter also simply referred to as a U-phase current) Iu and the amplitude of the W-phase motor current (hereinafter also simply referred to as a W-phase current) Iw. The amplitudes of the U-phase current Iu and the W-phase current Iw detected by the current detection circuit 21 are input to an A/D converter 21a, and the amplitudes of the U-phase current Iu and the W-phase current Iw are AD converted and supplied to the calculation unit 30 as signals controllable by a computer.

The calculation unit 30 converts the current vector (Iu, Iw) in a fixed coordinate system (UVW coordinate system) when the drive unit 10 drives the fan motor M into a current vector (Iγ, Iδ) in a rotating coordinate system (γ-δ coordinate system). The rotating coordinate system (γ-δ coordinate system) has a δ axis and a γ axis that intersect with each other. The calculation unit 30 calculates an estimated angular velocity ωe' of the rotating magnetic field that makes the γ component Iγ of the current vector in the converted rotating coordinate system zero. Specifically, the calculation unit 30 includes a second conversion unit (three-phase to two-phase converter (UVW/γ-δ)) 31 and a speed estimation processing unit 32.

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 circuit 21. The second conversion unit 31 converts a current vector (Iu, Iw) in a fixed coordinate system (UVW coordinate system) into a current vector (Iγ, Iδ) in a rotating coordinate system (γ-δ coordinate system) by, for example, the following equations (1) and (2). Note that if the driver 12 includes a shunt resistor, the current may be detected from the shunt resistor instead of the current detection circuit 21.
Iγ
= (√2) {Iu × cos(θe' + π/6) - Iw × sin(θe')}
… (1)
Iδ
= -(√2) {Iu × sin(θe' + π/6) + Iw × cos(θe')}
… (2)

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 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, in accordance with the received γ-axis current Iγ. The speed estimation processing unit 32 supplies the calculated estimated angular velocity ωe' to the integrating unit 50 and the voltage output unit 40.

2 is a block diagram showing a transfer function of the phase adjustment process executed by the speed estimation processor 32. The speed estimation processor 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 of 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 the γ-axis also converges to zero, and the γ-δ value is substituted for the d-q value.

In the speed estimation processing unit 32, the current Iγ on the control axis γ-δ axis is PI controlled to adjust the rotation speed so that the current Iγ becomes 0 [A], and the γ-δ coordinate axis approaches the d-q coordinate axis. Specifically, the δ-axis voltage Vδ is set to a constant value, and the γ-axis current Iγ is input to the speed estimation processing unit 32 to obtain an estimated angular velocity ωe'. The estimated angular velocity ωe' is integrated by the integrator 51 to obtain an estimated rotation angle θe'. The γ-axis voltage Vγ is applied by the equation (3) in the estimated voltage output unit 42 described later, and the fan motor M converges to an appropriate operating state as an optimal synchronous operation with a rotation speed balanced by the δ-axis voltage Vδ and the load.

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, and has 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 the value to the first conversion unit 60 as a δ-axis voltage command Vδ ^* .

For example, when starting the fan motor M, 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 in consideration of load fluctuations. The motor control device 1 adjusts the angular velocity of the rotating magnetic field so that the voltage Vδ ^* that generates this torque and the load are appropriately balanced.

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 ^* .
An integrator 50 integrates the estimated angular velocity ωe' to obtain an estimated rotation angle θe'.
Specifically, the integrating unit 50 has an integrator 51. The integrator 51 integrates the estimated angular velocity ωe' of the rotating magnetic field to calculate an estimated rotation angle θe', which is an estimate of the phase angle θe of the rotating coordinate system that rotates together with the rotating magnetic field. The integrator 51 outputs the calculated estimated rotation angle θe' to the first conversion unit 60 and the calculation unit 30.

The first conversion unit 60 converts the voltage vector in 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) by, for example, the following equations (4) to (6):

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)

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

Specifically, the drive unit 10 has 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 M via the driver 12.

The driver 12 receives the PWM signal from the PWM converter 11. The driver 12 has, for example, multiple switching elements (not shown), and performs power conversion by switching the multiple switching elements at a predetermined timing according to the PWM signal, and drives the fan motor M by supplying the generated three-phase AC signals U, V, and W to the fan motor M.

As shown in FIG. 1, the out-of-step determination unit 70 includes a smoothing unit 71 and a comparator 72. The smoothing unit 71 includes a rectifier unit 71a and a low-pass filter unit (LPF) 71b. The rectifier unit 71a receives a signal representing the amplitude of, for example, the U-phase current Iu of the current detection circuit 21, performs full-wave or half-wave rectification, and outputs the signal to the low-pass filter unit 71b. The low-pass filter unit 71b receives the rectified signal from the rectifier unit 71a, performs low-pass filtering, extracts the current amplitude or effective value, and outputs the current amplitude or effective value to the comparator 72. The comparator 72 receives the amplitude signal, which is the output of the smoothing unit 71, at its positive input terminal, and a threshold voltage Vth is input to the negative input terminal of the comparator 72. A method for setting the threshold voltage (hereinafter also simply referred to as the threshold) will be described later.

The comparator 72 compares the amplitude signal with a threshold voltage Vth, and outputs the comparison result to the control unit (CPU) 80 .
The control unit 80 receives the output signal of the comparator 72 and determines that the start-up is normal when the amplitude signal is lower than the threshold voltage Vth, that is, when the output of the comparator 72 is at a LOW level, and determines that the step-out state occurs when the amplitude signal is equal to or higher than the threshold voltage Vth, that is, when the output of the comparator 72 is at a HIGH level.

When the control unit 80 determines that the synchronous operation was successful, it switches the operation mode of the fan motor M from the startup operation mode to the steady operation mode. When it determines that the synchronous operation was unsuccessful, it attempts restarting the fan motor M multiple times, and if it is not determined that the synchronous operation was successful every time even after a predetermined number of restart attempts, it determines that the fan motor M has failed and notifies the user of the failure by generating an alarm, etc.

Before starting the fan motor M, the rotation detection unit 81 detects the rotation direction of the fan motor M when it is idling (hereinafter, sometimes referred to as the "idling direction") and the rotation speed of the fan motor M when it is idling (hereinafter, sometimes referred to as the "idling rotation speed"), and outputs the detected idling direction and idling rotation speed to the control unit 80. For example, the rotation detection unit 81 detects the idling direction and idling rotation speed using the induced voltages of the U, V, and W phases of the fan motor M. For example, if the rising edge detected next to the rising edge of the induced voltage of the U phase is the rising edge of the induced voltage of the V phase, the rotation detection unit 81 determines that the idling direction is the forward direction, and if the rising edge detected next to the rising edge of the induced voltage of the U phase is the rising edge of the induced voltage of the W phase, the rotation detection unit 81 determines that the idling direction is the reverse direction. In addition, since the period of the induced voltage of the fan motor M becomes smaller as the idling speed increases, the rotation detection unit 52 detects the idling speed based on the period of the induced voltage of the U phase, for example.

Then, the control unit 80 judges whether the idling speed is within a range from a predetermined rotation speed R1 in the forward direction (hereinafter sometimes referred to as "forward rotation R1") to a predetermined rotation speed R2 in the reverse direction (hereinafter sometimes referred to as "reverse rotation R2"). For example, if the winding resistance value of the fan motor M is 60 Ω, the forward direction is positive and the reverse direction is negative, and it is preset to forward rotation R1 = 400 rpm and reverse rotation R2 = -200 rpm. If the idling speed is within the range from forward rotation R1 to reverse rotation R2, forward rotation synchronous operation is performed, and if the idling speed is not within the range from forward rotation R1 to reverse rotation R2, it is judged whether the rotation is reversed, and if the rotation is reversed, reverse rotation synchronous operation is performed.

With the above configuration, when the idling direction is the forward direction, a positioning current application process is performed to position the rotor, and then the current is reset. Then, the angular velocity ωe' of the rotating magnetic field that makes the γ-axis current Iγ zero is estimated, and a synchronous operation process is performed. As the fan motor M rotates, a signal consisting of the amplitude of the U-phase current Iu detected by the current detection circuit 21 is input to the out-of-step determination unit 70, and the amplitude signal after smoothing is compared with the threshold voltage Vth. In the control unit 80, when it is determined that the synchronous operation is successful based on the comparison result between the amplitude signal and the threshold voltage Vth, the operation mode of the fan motor M is switched from the startup operation mode to the normal operation mode. On the other hand, when it is determined that the synchronous operation has failed, a restart is attempted a predetermined number of times. Then, when the synchronous operation is not successful every time even after the predetermined number of restart attempts, a fault notification is issued. This allows the user to recognize that the fan motor M has failed.
On the other hand, when the idling direction is the reverse direction, the reverse synchronous operation is performed, and then the operation is shifted to the forward synchronous operation.

<Method of Setting Threshold Voltage Vth of Comparator 72>
Next, a method for setting the voltage value of the threshold voltage Vth of the comparator 72 will be described.
In the speed estimation processing unit 32, the current Iγ on the control axis γ-δ axis is PI controlled to adjust the rotation speed so that the current Iγ becomes 0 [A], and the phase of the γ-δ coordinate axis approaches the phase of the d-q coordinate axis. At this time, if the phase of the γ-δ coordinate axis can be brought closer to the phase of the d-q coordinate axis, as shown in the phase adjustment section T3 in FIG. 3, the U-phase current Iu advances in a direction that flows the minimum current required for the load, and the amplitude of the current gradually decreases. However, if the rotating magnetic field and the rotor cannot be synchronized and a loss of synchronism occurs, as shown in the phase adjustment section T3 in FIG. 4, the amplitude of the current does not decrease, and finally the fan motor M does not rotate. As a result, since no induced voltage is generated, the U-phase current Iu becomes Iu = (applied voltage) / (magnitude of winding resistance of the fan motor M). Therefore, by detecting the magnitude of the current after this phase adjustment, it can be determined that the motor starts normally when the current is small, and that the motor fails to start due to loss of synchronism when the current is large. 3 and 4, the horizontal axis represents elapsed time, which is divided according to the control content when the fan motor M is started.

From the above, the threshold voltage Vth can be set to a voltage value equivalent to a value between "the maximum current Iuo that would flow when the fan motor M is under maximum load when startup is successful" (normal startup level) and "the current Iux (applied voltage/magnitude of winding resistance of fan motor M) that would flow when startup fails" (out-of-step level), as shown in Figure 5, for example. In Figure 5, the voltage value equivalent to the median value between the two (Iux-Iuo)/2 is set as the threshold voltage Vth.

The relationship between the load and pre-start rotation speed in the fan motor M has the characteristics shown in FIG. 6, for example. In FIG. 6, the horizontal axis is the rotation speed [rpm] before start, and the vertical axis is the load. As shown in FIG. 6, the load is large when starting in the forward direction from a state in which the motor is rotating in reverse due to headwind, and the load is larger the higher the rotation speed during reverse rotation. Conversely, when starting from a forward rotation state, the required load is smaller the higher the rotation speed. Note that when the fan motor M is rotating at a high rotation speed due to wind, there is sufficient wind blowing onto the heat exchanger whether the motor is rotating in the forward direction or in the reverse direction, so there is no need to start the fan.

<Processing in the motor control device>
Next, an example of a processing procedure of the motor control device 1 when starting the fan motor M will be described with reference to the flowchart shown in FIG.
First, it is determined whether or not the idling rotation speed is within a range from a predetermined rotation speed R1 in the forward direction (hereinafter sometimes referred to as "forward rotation R1") to a predetermined rotation speed R2 in the reverse direction (hereinafter sometimes referred to as "reverse rotation R2") (step S1). For example, when the winding resistance value of the fan motor M is 60 Ω, the forward rotation direction is positive and the reverse rotation direction is negative, and the forward rotation R1 is preset to 400 rpm and the reverse rotation R2 is preset to -200 rpm.

If the idling speed is within the range from forward rotation R1 to reverse rotation R2, the process proceeds to step S7 without performing the processes from step S2 to step S6. On the other hand, if the idling speed is not within the range from forward rotation R1 to reverse rotation R2, the process proceeds to step S2.
In step S2, it is determined whether the idling rotation speed is within a range from reverse rotation R2 to a predetermined rotation speed R3 in the reverse direction (hereinafter also referred to as "reverse rotation R3"). However, if "reverse rotation R2>reverse rotation R3", for example, when the winding resistance value of the fan motor M is 60 Ω, reverse rotation R3 is preset to -400 rpm.

If the idling speed is not within the range from reverse rotation R2 to reverse rotation R3, the process returns to step 1. On the other hand, if the idling speed is within the range from reverse rotation R2 to reverse rotation R3, the process moves from step S2 to step S3.
In step S3, the fan motor M is synchronously operated in the reverse direction (hereinafter also referred to as "reverse synchronous operation").
Next, in step S4, the phase of the fan motor M is adjusted.
Next, the process proceeds to step S5, in which the operation mode of the fan motor M is changed from an operation mode in which the rotor position is not estimated (synchronous operation mode) to an operation mode in which the rotor position is estimated (vector control operation mode (hereinafter also referred to as vector control mode)), and the fan motor M is driven in the vector control mode.

Next, the process proceeds to step S6, where the rotation speed of the fan motor M is gradually decelerated to reverse the rotation direction of the fan motor M from the reverse direction to the forward direction, and the fan motor M is synchronously operated in the forward direction. That is, a synchronous operation (hereinafter also referred to as reverse synchronous operation) is performed in which the rotation direction of the fan motor M is reversed from the reverse direction to the forward direction.
Then, the process proceeds to step S7. When the process proceeds directly from step S6 to step S7, the synchronous operation in the forward rotation direction in step S6 is continued in step S7. When the process proceeds from step S1 to step S7, the fan motor M is synchronously operated in the forward rotation direction in step S7.

Next, in step S8, the phase of the fan motor M is adjusted, and the process proceeds to step S9 to determine whether or not the fan motor M has been successfully started. If the fan motor M has been successfully started, the process proceeds to step S10 to switch the operation mode of the fan motor M from the synchronous operation mode to the vector control mode, and the fan motor M is driven in the vector control mode.
Then, the flow proceeds to step S11, where driving in the vector control mode in step S10 is continued, and normal operation is performed in which the fan motor M is driven by vector control.

FIG. 8 is a flowchart showing an example of a processing procedure for determining out-of-step.
In the motor control device 1, first, current detection is performed (step S21). Specifically, the U-phase current Iu is detected by the current detection circuit 21, and the amplitude of the detected U-phase current Iu is full-wave rectified or half-wave rectified, and then low-pass filtered. Then, the process proceeds to step 22, where it is determined whether the amplitude signal after low-pass filtering is greater than a threshold value. If the amplitude signal is less than the threshold value, starting is deemed successful, and the process returns to FIG. 7 and proceeds to step S10.

On the other hand, if the amplitude signal is equal to or greater than the threshold value in step S22, the process proceeds to step S23, where the count number n is updated to n+1, and then the process proceeds to step S24, where the operating conditions are changed according to the count number n, and restarting is attempted. That is, if the count number n is n≦n1, the process proceeds to step S25, where the voltage at startup (e.g., acceleration voltage V ^* h) is changed. Specifically, a predetermined voltage value (ΔV) is added to the acceleration voltage V ^* h. Then, the process returns to FIG. 7 and proceeds to step S1.

Also, when the count number n is n1<n≦n2, the process proceeds to step S26, where the rotation speed at the time of starting (for example, the acceleration rotation speed ω ^* eh) is changed. Specifically, a predetermined rotation speed (Δω) is added to the acceleration rotation speed. At this time, the acceleration voltage V ^* h is returned to the voltage at the time of starting. Then, the process returns to step S1 in FIG. 7. Furthermore, when the count number n is n2<n≦n3, the process proceeds to step S27, where the voltage corresponding to the frequency (f=ω/2π) (so-called V/f characteristics) is changed. For example, the start-up voltage V ^* s, the acceleration voltage V ^* h, and the slope indicating the change in the voltage value ((V ^* h-V ^* s)/T2s (T2s is the duration of the forward rotation synchronous operation section that is set in advance)) are each increased. Then, the process returns to step S1 in FIG. 7. Furthermore, when the count number n is n3<n, the process proceeds to step S28, where the fan motor M is determined to be broken, and the user is notified of the fact that the fan motor M is broken by issuing an alarm or the like. Then, the out-of-step determination process shown in Fig. 8 is terminated, and the motor startup process shown in Fig. 7 is terminated. Note that the count number n is set to an initial value n = 0 at the start of startup. The processes from step S25 to step S27 correspond to the operating condition changing section.

<Operation when fan motor M starts from normal rotation>
<Operation when startup is successful>
Next, an example of the operation when starting the fan motor M during normal start-up, i.e., when the outdoor unit fan is not rotating in reverse, will be described with reference to Fig. 9. Fig. 9 shows the change in the number of revolutions [rad/s] and the motor applied voltage V [V] of the fan motor M from before start-up until the transition to normal operation, with the horizontal axis representing time. As shown in Fig. 9, the operation sections of the fan motor M are divided into a non-energized section T1 where the process of step S1 is performed, a forward rotation synchronous operation section T2 where the process of step S7 is performed, a phase adjustment section T3 where the process of step S8 is performed, an out-of-step determination section T3' where the process of step S9 is performed, a mode transition section T4 where the process of step S10 is performed, and a normal operation section T5 where the process of step S11 is performed.

In the de-energized section T1, the fan motor M is in a de-energized state before startup, and the rotation detector 81 detects the idling direction and idling speed. In the case of Fig. 9, the detected idling direction and idling speed match the conditions of step S1, and the operation section of the fan motor M shifts from the de-energized section T1 to the forward rotation synchronous operation section T2.
In the forward rotation synchronous operation section T2, in order to accelerate the fan motor M to a rotation speed at which sufficient induced voltage can be obtained, the rotation of the fan motor M is accelerated while increasing the motor applied voltage V and the rotation speed, and the rotation speed is increased over time.
The fan motor M is driven, for example, so that the rotation speed converges from the startup rotation speed ω ^* es to the acceleration rotation speed ω ^* eh during a time T2s, and specifically, is driven so that the rotation speed changes according to the characteristics expressed by the following equation (7).

The time T2s, the startup rotation speed ω ^* es, and the acceleration rotation speed ω ^* eh are predetermined values determined in advance by tests, etc. Furthermore, t indicates the elapsed time from the start of the forward rotation synchronous operation section T2, that is, from the start of the supply of current to the fan motor M.
Also, the fan motor M is driven, for example, so that the motor applied voltage V converges from the start-up voltage Vs ^* to the acceleration voltage Vh ^* during the time T2s, specifically so that the motor applied voltage V increases linearly.

When the fan motor M is accelerated to, for example, a target value, the phase adjustment section T3 begins.
In the phase adjustment section T3, the phase difference between the γ-δ coordinate system and the dq coordinate system is matched by adjusting the rotation speed in accordance with the current load state for the acceleration voltage value Vh ^* reached in the forward rotation synchronous operation section T2.
In other words, the fan motor M is controlled so that the rotation speed converges from the acceleration rotation speed ω ^* eh to the rotation speed ωe′ that can make the γ-axis current Iγ zero during a time T3s while the motor applied voltage ^V is maintained at the acceleration voltage Vh*. The time T3s is set to, for example, the time required for the γ-axis current Iγ to converge to zero.
In the subsequent out-of-step determination section T3', out-of-step determination is performed. Note that in the out-of-step determination section T3', the drive control of the fan motor M in the phase adjustment section T3 continues to be performed until out-of-step is determined.

When the fan motor M is started normally, the amplitude of the U-phase current Iu in the phase adjustment section T3 gradually decreases as shown in Fig. 3, so that the amplitude of the U-phase current Iu becomes smaller than the threshold value. Therefore, as a result of the out-of-step determination, it is determined that the fan motor M has started normally, and a mode transition is performed. In the mode transition section T4, the operation mode transitions from the synchronous operation mode to the vector control operation mode (hereinafter also referred to as the vector control mode), and the fan motor M is controlled to rotate at a constant rotation speed, and accordingly, the motor applied voltage V is controlled to be constant.
Then, in the subsequent normal operation section T5, the fan motor M is driven in vector control mode by speed and torque control based on the mechanical angular velocity command value ωm_ref input from outside the motor control device 1.

<Action when startup fails>
On the other hand, when the fan motor M is not started normally, the amplitude of the U-phase current Iu in the phase adjustment section T3 does not decrease, as shown in Fig. 4. Therefore, as shown in Fig. 10, in the out-of-step determination section T3', the amplitude of the U-phase current is equal to or greater than the threshold value, and it is determined that the fan motor M has failed to start. Since the fan motor M has failed to start, its drive is stopped, and both the motor applied voltage V and the rotation speed converge to zero, and the fan motor M moves to the non-energization section T1.

Then, since startup has failed, the startup conditions are changed and restart is attempted, the non-energized section T1 is shifted to the normal rotation synchronous operation section T2, and synchronous operation is started in the same manner as above.
Then, when the motor shifts from the forward rotation synchronous operation section T2 to the phase adjustment section T3 and restart fails in the out-of-step determination section T3', restart is attempted with the start-up conditions changed. If start-up fails even after driving with the start-up conditions changed a predetermined number of times, a fault notification is issued indicating that the fan motor M has broken down. This allows the user to recognize that the fan motor M has broken down.

<Operation when fan motor M starts from reverse synchronous operation>
<Operation when startup is successful>
Next, an example of the operation when the outdoor unit fan starts the fan motor M from a reverse rotation state will be described with reference to Fig. 11. Fig. 11 shows the change in the number of revolutions [rad/s] and the motor applied voltage V [V] of the fan motor M from before starting to the transition to normal operation, with the horizontal axis representing time. As shown in Fig. 11, the operation sections of the fan motor M are divided into a non-energized section T11 where the processes of steps S1 and S2 are performed, a reverse rotation synchronous operation section T12 where the process of step S3 is performed, a phase adjustment section T13 where the process of step S4 is performed, a mode transition section T14 where the process of step S5 is performed, a reverse rotation synchronous operation section T15 where the process of step S6 is performed, a forward rotation synchronous operation section T16 where the process of step S7 is performed, a phase adjustment section T17 where the process of step S8 is performed, a step-out determination section T17' where the process of step S9 is performed, a mode transition section T18 where the process of step S10 is performed, and a normal operation section T19 where the process of step S11 is performed. Further, the inverted synchronized operation section T15 includes a deceleration operation section T15a and a transition synchronized operation section T15b.

In the de-energized section T11, the fan motor M is in a de-energized state before startup, and the rotation detection unit 81 detects the idling direction and idling speed. In this case, the detected idling direction and idling speed match the conditions in step S2, and the operation section of the fan motor M shifts from the de-energized section T11 to the reverse synchronous operation section T12.
In the reverse synchronous operation section T12, the fan motor M is driven, for example, during time T2g, so that the rotation speed converges from the start rotation speed ω ^* ges during reverse rotation to the acceleration rotation speed ω ^* geh, and more specifically, is driven so that it changes according to the characteristics expressed by the following equation (8).

The time T2g, the start rotation speed ω ^* ges during reverse rotation, and the acceleration rotation speed ω ^* geh are predetermined values determined in advance by tests, etc. Furthermore, t indicates the elapsed time from the start of the reverse rotation synchronous operation section T12, that is, from the start of the supply of current to the fan motor M.
In addition, the fan motor M is driven, for example, so that the motor applied voltage V converges from the start voltage Vgs ^* at the time of reverse rotation to the acceleration voltage V ^* gh during the time T2g, specifically, so as to decrease linearly.
When the fan motor M is accelerated to, for example, a target value, the phase adjustment section T13 begins.

In the phase adjustment section T13, similar to the phase adjustment section T3 when starting from forward rotation, the phase difference between the γ-δ coordinate system and the d-q coordinate system is matched by adjusting the rotation speed in accordance with the current load condition for the acceleration voltage value V ^* gh reached in the synchronous operation section during reverse rotation.
In other words, the fan motor M is controlled so that the rotation speed converges from the acceleration rotation speed ω ^* gh to the rotation speed ωe′ that can make the γ-axis current Iγ zero during a time T13s while the motor applied voltage V is maintained at the acceleration voltage V ^* gh. The time T13s is set to, for example, the time required for the γ-axis current Iγ to converge to zero.
In the following mode transition section T14, the operation mode transitions from the synchronous operation mode to the vector control operation mode, and the fan motor M is controlled to rotate at a constant rotation speed, and accordingly the motor applied voltage V is also controlled to be constant.

Then, in the subsequent reverse synchronous operation section T15, for example, in the deceleration operation section T15a, when the rotation speed of the fan motor M at the time when the mode transition section T14 ends is the synchronous start start rotation speed ω ^* gd, the rotation speed is driven so as to converge from the synchronous start start rotation speed ω ^* gd to the deceleration rotation speed ω ^* geg. Also, when the voltage of the d-axis at the time when the mode transition section T14 ends is the synchronous start start voltage V ^* gd, the motor applied voltage V is driven so as to decelerate from the synchronous start start voltage V ^* gd to the deceleration voltage V ^* geg. In the subsequent transition synchronous operation section T15b, the fan motor M is driven so that the rotation speed of the fan motor M converges from the deceleration rotation speed ω ^* geg to the start start rotation speed ω ^* ses during time T5g'. Also, the motor applied voltage V is driven so as to converge from the deceleration voltage V ^* geg to the start start voltage V ^* sh during time T5g'. At this time, in the deceleration operation section T15a, the motor is driven so that the rotation speed converges from the synchronous start-up rotation speed ω ^* gd to the start-up rotation speed ω ^* ses during time T5g, and converges from the deceleration rotation speed ω ^* geg to the start-up rotation speed ω ^* ses during time T5g'. Similarly, in the deceleration operation section T15a, the motor applied voltage V converges from the synchronous start-up voltage V ^* gd to the start-up voltage V ^* sh during time T5g, and converges from the deceleration voltage V ^* geg to the start-up voltage V ^* sh during time T5g'.

The subsequent forward rotation synchronized operation section T16 is controlled in the same manner as the forward rotation synchronized operation section T2 when started from forward rotation, and thereafter, the phase adjustment section T17, out-of-step determination section T17', mode transition section T18, and normal operation section T19 are controlled in the same manner as the phase adjustment section T3, out-of-step determination section T3', mode transition section T4, and normal operation section T5, respectively, when started from forward rotation.
In other words, in the case of FIG. 11, after the transition to forward rotation, the start of the fan motor M is successful, so in the out-of-step determination section T17', it is determined that the start is successful, and then a mode transition occurs, and operation is performed in the vector control mode.

<Action when startup fails>
On the other hand, when the fan motor M is not started normally, the amplitude of the U-phase current Iu in the phase adjustment section T17 shown in Fig. 12 does not decrease as shown in Fig. 4. Therefore, in the out-of-step determination section T17', the amplitude of the U-phase current is equal to or greater than the threshold value, and it is determined that the fan motor M has failed to start. Since the fan motor M has failed to start, its drive is stopped, and both the motor applied voltage V and the rotation speed become zero, entering the non-energization section T11.
Since the start-up has failed, the fan motor M is restarted from reverse synchronous operation. If the start-up has failed every time the start-up conditions are changed a predetermined number of times, a notification is issued that the fan motor M has broken down. This allows the user to recognize that the fan motor M has broken down.

＜Effects＞
As described above, the motor control device 1 performs a step-out determination at start-up, and performs this step-out determination based on the current waveform of the U-phase, which is one of the phase currents supplied to the fan motor M after phase adjustment. Therefore, it is possible to determine whether the rotating magnetic field and the rotor are synchronized without providing a sensor that detects the rotor position of the fan motor M. Therefore, even when a sensorless synchronous motor is used, the fan motor M can be started more reliably.
In addition, when it is determined that the start-up of the fan motor M has failed, restart is attempted multiple times with different start-up conditions, thereby increasing the probability of successful start-up, and when start-up fails even after multiple attempts with different start-up conditions, it is determined that the fan motor M has failed, so that failure of the fan motor M can be detected by software.
In addition, by stopping the driving of the fan motor M when it is determined that the fan motor M has failed, it is possible to stop the fan motor M at an earlier stage than when the failure of the fan motor M is detected using hardware.

<Modification>
In the above embodiment, the case where the out-of-step determination is performed only by the phase adjustment after the forward rotation synchronous operation has been described, but the present invention is not limited to this, and the out-of-step determination may also be performed in the phase adjustment after the reverse rotation synchronous operation. Specifically, the out-of-step determination may be performed in the phase adjustment section T13.
In addition, in the above embodiment, when it is determined that startup has failed, one of the conditions, the startup voltage V ^* s, the startup rotation speed ω ^* es, and the voltage rise slope VF, is changed depending on the number of failures. However, it is also possible to change more than one of these.
In the above embodiment, the case has been described where the drive control is performed so that the rotation speed and the motor applied voltage V change at the time of start-up as shown in Figures 9 to 12. However, the present invention is not limited to this, and any drive method in which phase adjustment is performed when starting the fan motor M can be applied.

Although the embodiments of the present invention have been described above, the above embodiments are merely examples of devices and methods for embodying the technical ideas of the present invention, and the technical ideas of the present invention do not specify the materials, shapes, structures, arrangements, etc. of the components. The technical ideas of the present invention can be modified in various ways within the technical scope defined by the claims.

REFERENCE SIGNS LIST 1 Sensorless synchronous motor control device 10 Drive unit 20 Detection unit 30 Calculation unit 40 Voltage output unit 50 Integration unit 60 First conversion unit 70 Step-out determination unit 80 Control unit 81 Rotation detection unit

Claims (5)

A motor control device for controlling a sensorless synchronous motor , which performs synchronous operation without estimating a rotor position at start-up, performs phase adjustment, and then transitions to normal operation in which the rotor position is estimated,
a drive unit that drives the synchronous motor in response to an input voltage command;
a synchronous voltage setting unit that outputs a predetermined voltage command at the time of startup;
a step-out determination unit that determines step-out of the synchronous motor based on a current flowing through the synchronous motor;
Equipped with
The synchronization voltage setting unit is
A calculation unit is provided for converting the current in a fixed coordinate system into a current vector (Iγ, Iδ) in a γ-δ rotating coordinate system in the phase adjustment, and calculating an estimated angular velocity ωe′ of a rotating magnetic field that makes the γ component Iγ of the converted current vector zero;
A voltage proportional to the estimated angular velocity is output as the voltage command for a γ component Vγ of a voltage vector (Vγ, Vδ) in the γ-δ rotating coordinate system;
The motor control device is characterized in that the out-of-step determination unit determines that the synchronous motor is in an out-of-step state when a current flowing through the synchronous motor when the synchronous motor is driven in accordance with the voltage command for the gamma component Vγ is equal to or greater than a set threshold value. The synchronous motor has a multi-phase stator coil,
2. The motor control device according to claim 1 , wherein the out-of-step determination unit determines the out-of-step of the synchronous motor based on a current flowing through the stator coil in at least one of the plurality of phases. an operating condition changing unit that changes the predetermined voltage command when the out-of-step determining unit determines that out-of-step has occurred,
The synchronous voltage setting unit outputs the voltage command based on the operating conditions changed by the operating condition changing unit to the drive unit,
3. The motor control device according to claim 1 , wherein the drive unit attempts to restart the synchronous motor in response to the voltage command based on the changed operating condition. 4. The motor control device according to claim 3, wherein the step-out determination unit determines that the synchronous motor has failed when the step-out determination unit determines that the synchronous motor has failed every time the operating conditions are changed a predetermined number of times. A method for controlling a sensorless synchronous motor, in which, when starting a sensorless synchronous motor, a synchronous operation is performed without estimating a rotor position , and then a phase adjustment is performed, after which a transition is made to a normal operation in which a rotor position is estimated , the method comprising the steps of:
A current in a fixed coordinate system flowing through the synchronous motor is converted into a current vector (Iγ, Iδ) in a γ-δ rotating coordinate system, and an estimated angular velocity ωe′ of a rotating magnetic field that makes the γ component Iγ of the current vector zero is calculated;
performing the phase adjustment by driving the synchronous motor based on the calculated estimated angular velocity;
Detecting a motor current of the synchronous motor after the phase adjustment;
A method for controlling a sensorless synchronous motor, comprising the steps of: determining that the synchronous motor is out of step when the motor current is equal to or greater than a threshold value set according to the motor current after the phase adjustment when the synchronous motor fails to start.

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