JP2024122514A - Control device - Google Patents

Abstract

[Problem] To improve the accuracy of determining whether or not a step-out has occurred in a motor control device. [Solution] A control device 1 is configured to include a current value converter 7 that converts the current flowing through a motor M into a γ-axis current value and a δ-axis current value, a γ-δ current command value output unit 11 that outputs a γ-axis current command value and a δ-axis current command value, a γ-δ voltage command value calculator that calculates a γ-axis voltage command value based on the γ-axis current value and the γ-axis current command value and calculates a δ-axis voltage command value based on the δ-axis current value and the δ-axis current command value, a drive signal output unit that converts the γ-axis voltage command value and the δ-axis voltage command value into drive signals and outputs them to an inverter 2, and a step-out determination unit 16 that estimates a δ-axis interference term using the δ-axis voltage command value, the δ-axis current value, and motor parameters, and determines that the motor M has stepped out if the δ-axis interference term is equal to or greater than a threshold value. [Selected Figure] Figure 1

Description

The present invention relates to a motor control device.

There is a motor control device that, when the resultant magnetic flux of the motor's γ-axis magnetic flux and δ-axis magnetic flux, which is estimated using the rotation speed command value, γ-axis voltage value, δ-axis voltage value, γ-axis voltage command value, δ-axis voltage command value, γ-axis current value, δ-axis current value, motor resistance component, motor d-axis inductance component, and motor q-axis inductance component, changes significantly, it determines that the deviation between the estimated value of the motor's rotor position (electrical angle) and the actual position is relatively large, making it difficult to control the motor, in other words, that the motor is out of step. Related technology is disclosed in Patent Document 1.

However, when the motor is actually out of step, the deviation between the rotation speed command value and the true value becomes relatively large, and the errors contained in the γ-axis magnetic flux and the δ-axis magnetic flux become relatively large.

As a result, the above control device uses the rotation speed command value when determining whether or not the motor has lost synchronism. If the motor has actually lost synchronism, the accuracy of estimating the γ-axis magnetic flux and the δ-axis magnetic flux decreases, and there is a risk of erroneously determining that the motor has not lost synchronism.

In addition, the above control device has a relatively large number of parameters for estimating the γ-axis magnetic flux and the δ-axis magnetic flux, and the error contained in each parameter has a large effect on the estimation of the γ-axis magnetic flux and the δ-axis magnetic flux, which may reduce the accuracy of determining whether or not a step-out has occurred.

JP 2008-092787 A

The object of one aspect of the present invention is to improve the accuracy of determining step-out in a motor control device.

A control device according to one embodiment of the present invention is a control device that generates a drive signal to control an inverter that drives a motor, and includes a current value conversion unit that converts a current flowing through the motor into a γ-axis current value and a δ-axis current value, a γ-δ current command value output unit that outputs a γ-axis current command value and a δ-axis current command value, a γ-δ voltage command value calculation unit that calculates a γ-axis voltage command value based on the γ-axis current value and the γ-axis current command value and calculates a δ-axis voltage command value based on the δ-axis current value and the δ-axis current command value, a drive signal output unit that converts the γ-axis voltage command value and the δ-axis voltage command value into the drive signal and outputs it to the inverter, and a step-out determination unit that estimates a δ-axis interference term using the δ-axis voltage command value, the δ-axis current value, and motor parameters, and determines that the motor is out of step if the estimated δ-axis interference term is equal to or greater than a threshold value.

For example, if the rotation speed of the rotor of the motor is ω, the q-axis inductance component of the motor is Lq, the γ-axis current value is Iγ, the induced voltage constant is K _E , and the error between the q-axis position and the δ-axis position of the rotor is Δθ, the δ-axis interference term can be expressed as ω{-LqIγ-K _E cos(Δθ)}, and it can be seen that the δ-axis interference term increases as Δθ increases. Therefore, by setting the δ-axis interference term corresponding to Δθ when the motor is out of step as a threshold, it is possible to determine that the motor is out of step when the δ-axis interference term is equal to or greater than the threshold. In addition, according to a control device as one embodiment of the present invention, since the rotation speed command value is not included as a parameter for estimating the δ-axis interference term, it is possible to improve the accuracy of determining whether or not the motor is out of step, compared to a configuration in which the rotation speed command value is used to determine whether or not the motor is out of step.

Furthermore, when the δ-axis interference term is Vδ ^dec ^, the δ-axis voltage command value is Vδ*, the δ-axis current value is Iδ, the resistance component of the motor is R^, the q-axis inductance component of the motor is Lq^, and a differential operator is s, the out-of-step determination unit may be configured to estimate the δ-axis interference term by calculating the following formula 1.

Vδ ^dec ^=-Vδ*+(R^+Lq^s) Iδ...Formula 1

The out-of-step determination unit may be configured to set a first estimated value of the δ-axis interference term that is greater than the true value of the δ-axis interference term as the threshold value when the δ-axis current value is a negative value, and to set a second estimated value of the δ-axis interference term that is smaller than the true value of the δ-axis interference term as the threshold value when the δ-axis current value is a positive value.

The motor may also be a non-salient motor.

The present invention makes it possible to improve the accuracy of detecting motor out-of-step in a motor control device.

FIG. 2 is a diagram illustrating an example of a control device according to an embodiment. FIG. 13 is a diagram showing the relationship between the error between the d-axis position and the γ-axis position, and the δ-axis interference term. FIG. 13 is a diagram for explaining a method of estimating a δ-axis interference term. FIG. 13 is a diagram showing the relationship between a true value of a δ-axis interference term, an estimated value of the δ-axis interference term, and a δ-axis current value.

The following describes the embodiment in detail with reference to the drawings.

Figure 1 shows an example of a control device in an embodiment.

The control device 1 shown in FIG. 1 controls the operation of a motor M mounted on a vehicle such as an electric forklift or a plug-in hybrid vehicle, and includes an inverter 2 and a control circuit 3. The motor M is, for example, a surface magnet synchronous motor or an embedded magnet synchronous motor.

The inverter 2 drives the motor M with power supplied from the power source P, and includes a capacitor C, switching elements SW1 to SW6 (e.g., IGBTs (Insulated Gate Bipolar Transistors)), and current sensors Se1 to Se3. That is, one terminal of the capacitor C is connected to the positive terminal of the power source P and the collector terminals of the switching elements SW1, SW3, and SW5, and the other terminal of the capacitor C is connected to the negative terminal of the power source P and the emitter terminals of the switching elements SW2, SW4, and SW6. The connection point between the emitter terminal of the switching element SW1 and the collector terminal of the switching element SW2 is connected to the U-phase input terminal of the motor M via the current sensor Se1. The connection point between the emitter terminal of the switching element SW3 and the collector terminal of the switching element SW4 is connected to the V-phase input terminal of the motor M via the current sensor Se2. The connection point between the emitter terminal of switching element SW5 and the collector terminal of switching element SW6 is connected to the W-phase input terminal of motor M via current sensor Se3.

Capacitor C smoothes the voltage output from power supply P and input to inverter 2.

The switching element SW1 is turned on or off based on the drive signal S1 output from the control circuit 3. The switching element SW2 is turned on or off based on the drive signal S2 output from the control circuit 3. The switching element SW3 is turned on or off based on the drive signal S3 output from the control circuit 3. The switching element SW4 is turned on or off based on the drive signal S4 output from the control circuit 3. The switching element SW5 is turned on or off based on the drive signal S5 output from the control circuit 3. The switching element SW6 is turned on or off based on the drive signal S6 output from the control circuit 3. By turning on or off the switching elements SW1 to SW6, respectively, the DC voltage output from the power source P is converted into three AC voltages whose phases differ from each other by 120 degrees, and these AC voltages are applied to the input terminals of the U phase, V phase, and W phase of the motor M, causing the rotor of the motor M to rotate.

Current sensor Se1 is composed of a Hall element, a shunt resistor, etc., and detects a U-phase current value Iu flowing through the U-phase of motor M and outputs it to the control circuit 3. Current sensor Se2 is composed of a Hall element, a shunt resistor, etc., and detects a V-phase current value Iv flowing through the V-phase of motor M and outputs it to the control circuit 3. Current sensor Se3 is composed of a Hall element, a shunt resistor, etc., and detects a W-phase current value Iw flowing through the W-phase of motor M and outputs it to the control circuit 3. Note that although three current sensors Se1 to Se3 are provided in this embodiment, a configuration in which any two of the three are provided may also be provided instead of three.

The control circuit 3 includes a memory unit 4, a drive circuit 5, and a calculation unit 6. The control circuit 3 drives the motor M by controlling the inverter 2.

The memory unit 4 is configured with a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores the threshold value Vδth, which will be described later.

The drive circuit 5 is composed of an IC (Integrated Circuit) and compares the voltage value of the carrier wave (triangular wave, sawtooth wave, inverse sawtooth wave, etc.) with the U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw* output from the calculation unit 6, and outputs drive signals S1 to S6 according to the comparison results to the gate terminals of the switching elements SW1 to SW6.

For example, when the U-phase voltage command value Vu* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S1 and a low-level drive signal S2. When the U-phase voltage command value Vu* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S1 and a high-level drive signal S2. When the V-phase voltage command value Vv* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S3 and a low-level drive signal S4. When the V-phase voltage command value Vv* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S3 and a high-level drive signal S4. When the W-phase voltage command value Vw* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S5 and a low-level drive signal S6. When the W-phase voltage command value Vw* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S5 and a high-level drive signal S6.

The calculation unit 6 is configured by a microcomputer and includes a current value conversion unit 7, an estimation unit 8, a subtraction unit 9, a torque command value calculation unit 10, a gamma-delta current command value output unit 11, a subtraction unit 12, a subtraction unit 13, a voltage command value calculation unit 14, a voltage command value conversion unit 15, and a step-out determination unit 16. For example, the current value conversion unit 7, the estimation unit 8, the subtraction unit 9, the torque command value calculation unit 10, the gamma-delta current command value output unit 11, the subtraction unit 12, the subtraction unit 13, the voltage command value calculation unit 14, the voltage command value conversion unit 15, and the step-out determination unit 16 are configured by the microcomputer executing a program stored in the storage unit 4.

The current value converter 7 converts the U-phase current value _Iu , the V-phase current value _Iv , and the W-phase current value Iw into a γ-axis current value Iγ and a δ-axis current value _Iδ using the estimated rotor position (electrical angle) θ^ estimated by the estimator 8. That is, the current value converter 7 converts the current flowing through the motor M into a γ-axis current value Iγ and a δ-axis current value Iδ. The current value converter 7 may have a function of receiving current values of two phases out of the U-phase current value _Iu , the V-phase current value _Iv , and the W-phase current value _Iw , and calculating the current value of the remaining phase from the received current values of the two phases.

The γ-δ coordinate system is an estimated rotating coordinate system used in position sensorless control, with the γ axis corresponding to the d-axis of the d-q coordinate system and the δ axis corresponding to the q-axis. The d-q coordinate system is a rotating coordinate system with the d-axis oriented in the direction of the north pole of the magnet of motor M and the q-axis perpendicular to the d-axis.

The estimated position θ^ is an estimate of the rotor position θ of the motor M.

Note that in the notation "θ^", the "^" is located to the upper right of the "θ", but in this specification, the symbol "^" means an estimated value.

For example, the current value converter 7 converts the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw into the γ-axis current value Iγ and the δ-axis current value Iδ using the conversion matrix C1 shown in the following formula 2.

The estimator 8 has a function of calculating an estimated rotation speed ω^ and an estimated position θ^. The method by which the estimator 8 calculates the estimated rotation speed ω^ and the estimated position θ^ is a known method, and the calculations are performed from the γ-axis current value Iγ, the δ-axis current value Iδ, and motor parameters that can be estimated in advance (resistance component R^, d-axis inductance component Ld^, and q-axis inductance component Lq^ ₎ . The resistance component R^, the d-axis inductance component Ld^, and the q-axis inductance component Lq^ are estimated values of the motor parameters of the motor M to be controlled, and are estimated in advance by measurements using the motor M, etc. The motor parameters of the motor M are estimated values rather than actual values because the motor parameters vary depending on the current flowing through the motor M and the temperature.

The subtraction unit 9 calculates the rotation speed difference Δω between the estimated rotation speed ω^ estimated by the estimation unit 8 and the rotation speed command value ω* input from the outside.

The torque command value calculation unit 10 calculates the torque command value T* using the rotation speed difference Δω output from the subtraction unit 9. For example, the torque command value calculation unit 10 refers to information (not shown) stored in the memory unit 4 that associates the rotation speed (angular velocity) of the rotor of the motor M with the torque of the motor M, and determines the torque corresponding to the rotation speed equivalent to the rotation speed difference Δω as the torque command value T*.

The γ-δ current command value output unit 11 uses the torque command value T* to output the γ-axis current command value Iγ* and the δ-axis current command value Iδ*. For example, the γ-δ current command value output unit 11 refers to information (not shown) stored in the memory unit 4 in which the torque of the motor M is associated with the γ-axis current command value Iγ* and the δ-axis current command value Iδ*, and determines the γ-axis current command value Iγ* and the δ-axis current command value Iδ* that correspond to the torque command value T*.

The subtraction unit 12 calculates the differential γ-axis current command value ΔIγ, which is the difference between the γ-axis current command value Iγ* output from the γ-δ current command value output unit 11 and the γ-axis current value Iγ output from the current value conversion unit 7.

The subtraction unit 13 calculates the differential δ-axis current command value ΔIδ, which is the difference between the δ-axis current command value Iδ* output from the γ-δ current command value output unit 11 and the δ-axis current value Iδ output from the current value conversion unit 7.

The voltage command value calculation unit 14 converts the differential γ-axis current command value ΔIγ output from the subtraction unit 12 and the differential δ-axis current command value ΔIδ output from the subtraction unit 13 into a γ-axis voltage command value Vγ* and a δ-axis voltage command value Vδ*. For example, the voltage command value calculation unit 14 calculates the γ-axis voltage command value Vγ* by calculating the following formula 3, and calculates the δ-axis voltage command value Vδ* by calculating the following formula 4. Note that Kp is a constant for the proportional term of the PI control, Ki is a constant for the integral term of the PI control, and ω^ is the rotation speed estimated by the estimation unit 8.

Vγ*=KpΔIγ+∫(KiΔIγ)-ω^Lq^Iq...Formula 3
Vδ*=KpΔIδ+∫(KiΔIδ)+ω＾Ld＾Iδ+ω＾K _E... Formula 4

That is, the subtraction units 12 and 13 and the voltage command value calculation unit 14 function as a γ-δ voltage command value calculation unit that calculates the γ-axis voltage command value Vγ* based on the γ-axis current value Iγ and the γ-axis current command value Iγ*, and calculates the δ-axis voltage command value Vδ* based on the δ-axis current value Iδ and the δ-axis current command value Iδ*.

The voltage command value converter 15 converts the γ-axis voltage command value Vγ* and the δ-axis voltage command value Vδ* into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* using the estimated position θ^ estimated by the estimator 8. For example, the voltage command value converter 15 converts the γ-axis voltage command value Vγ* and the δ-axis voltage command value Vδ* into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* using a conversion matrix C2 shown in the following formula 5. The voltage command value converter 15 then outputs the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* to the drive circuit 5. In other words, the voltage command value converter 15 and the drive circuit 5 function as a drive signal output unit that converts the γ-axis voltage command value Vγ* and the δ-axis voltage command value Vδ* into drive signals and outputs them to the inverter 2.

The out-of-step determination unit 16 estimates a δ-axis interference term Vδ ^dec using the δ-axis voltage command value Vδ*, the δ-axis current value Iδ, and motor parameters that can be estimated in advance, and determines that the motor M is out of step when the estimated δ-axis interference term Vδ ^dec ^ is equal to or greater than a threshold value Vδth. The out-of-step determination in the out-of-step determination unit 16 is performed, for example, every control period of the motor M, every operation clock of the calculation unit 6, or every sampling period. The calculation unit 6 may be configured to stop the motor M by setting each of the γ-axis current command value Iγ*, the δ-axis current command value Iδ*, the γ-axis voltage command value Vγ*, and the δ-axis voltage command value Vδ* to zero when the out-of-step determination unit 16 determines that the motor M is out of step.

For example, the δ-axis interference term Vδ ^dec can be expressed as the following equation 7 using the following equation 6. Note that Vd ^dec is the d-axis interference term, Vq ^dec is the q-axis interference term, and Δθ is the error between the rotor position θ on the d-axis and the rotor position θ on the γ-axis as a reference, or the error between the rotor position θ on the q-axis and the rotor position θ on the δ-axis as a reference.

Ｖδ^ｄｅｃ＝－（－Ｖｄ^ｄｅｃｓｉｎ（－Δθ）＋Ｖｑ^ｄｅｃｃｏｓ（－Δθ））・・・式７

Vδ ^dec =-(-Vd ^dec sin(-Δθ)+Vq ^dec cos(-Δθ))...Formula 7

Furthermore, when the d-axis interference term Vd ^dec is defined as in the following formula 8, and the q-axis interference term Vq ^dec is defined as in the following formula 9, the above formula 7 can be transformed into the following formula 10. Here, ω is the rotation speed of the rotor.

Vd ^dec = -ωLqIq...Formula 8
Vq ^dec = ω(LdId+K _E )...Formula 9
Vδ ^dec =ω{-LqIqsin(-Δθ)-LdIdcos(-Δθ)-K _E cos(-Δθ)}...Formula 10

In addition, if the motor M is a surface magnet type synchronous motor, the d-axis inductance component Ld can be replaced with the q-axis inductance component Lq, so that the above formula 10 can be transformed into the following formula 11.

Vδ ^dec =ω{Lq(-Iqsin(-Δθ)-Idcos(-Δθ))-K _E cos(-Δθ)}...Formula 11

Furthermore, using the following formula 12, the above formula 11 can be transformed into the following formula 13.

Ｖδ^ｄｅｃ＝ω｛－ＬｑＩγ－Ｋ_Ｅｃｏｓ（Δθ）}・・・式１３

Vδ ^dec =ω{-LqIγ-K _E cos(Δθ)}...Formula 13

When the motor M is an embedded magnet synchronous motor, the d-axis inductance component Ld can be replaced with k times the q-axis inductance component Lq, so that the above formula 10 can be modified as shown in the following formula 14.

Vδ ^dec =ω{-LqIqsin(-Δθ)-LqIdcos(-Δθ))-(k-1)LqIdcos(-Δθ))-K _E cos(-Δθ)}...Formula 14

Furthermore, using the above formula 12, the above formula 14 can be transformed into the following formula 15.

Vδ ^dec =ω^{Lq^Iγ+(k-1)Lq^Idcos(Δθ))+K _E cos(Δθ)}...Formula 15

As shown in the above formula 13 or 15, since the term cos(Δθ) exists in the formula expressing the δ-axis interference term Vδ ^dec , it can be seen that the δ-axis interference term Vδ ^dec increases as Δθ increases.

Here, FIG. 2 is a diagram showing the relationship between Δθ and the δ-axis interference term Vδ ^dec . The horizontal axis of the two-dimensional coordinate system shown in FIG. 2 indicates Δθ [rad], and the vertical axis indicates the δ-axis interference term Vδ ^dec [V]. The solid line shown in FIG. 2 indicates the relationship between Δθ and the δ-axis interference term Vδ ^dec when the rotor rotation speed ω is the rotation speed ω1, the dashed line shown in FIG. 2 indicates the relationship between Δθ and the δ-axis interference term Vδ ^dec when the rotor rotation speed ω is the rotation speed ω2, and the dashed line shown in FIG. 2 indicates the relationship between Δθ and the δ-axis interference term Vδ ^dec when the rotor rotation speed ω is the rotation speed ω3. The rotation speed ω1<the rotation speed ω2<the rotation speed ω3. Also, -V3<-V2<-V1<0<+V1<+V2<+V3.

When the rotation speed ω is ω1, while Δθ increases from zero to π/2, the δ-axis interference term Vδ ^dec increases from −V1 to zero, and while Δθ increases from π/2 to π, the δ-axis interference term Vδ ^dec increases from zero to +V1.

When the rotation speed ω is ω2, while Δθ increases from zero to π/2, the δ-axis interference term Vδ ^dec increases from −V2 to zero, and while Δθ increases from π/2 to π, the δ-axis interference term Vδ ^dec increases from zero to +V2.

When the rotation speed ω is ω3, while Δθ increases from zero to π/2, the δ-axis interference term Vδ ^dec increases from −V3 to zero, and while Δθ increases from π/2 to π, the δ-axis interference term Vδ ^dec increases from zero to +V3.

That is, the larger Δθ becomes, the larger the δ-axis interference term Vδ ^dec becomes, regardless of the magnitude of the rotation speed ω. Also, the larger the rotation speed ω becomes, the larger the increase in the δ-axis interference term Vδ ^dec becomes.

In the case where the motor M having such characteristics is defined as being out of synchronism when Δθ is equal to or greater than π/2, it is possible to determine whether the motor M is out of synchronism by setting the threshold value Vδth to zero. That is, the out-of-synchronization determination unit 16 determines that the motor M is out of synchronism when the δ-axis interference term ^Vδdec is equal to or greater than zero.

Next, a method for estimating the δ-axis interference term Vδ ^dec will be described.

Figure 3(a) shows a typical block diagram of motor M on the q axis.

First, in conversion block 20, the δ-axis voltage command value Vδ* is converted to the q-axis voltage command value Vq* by Δθ.

Next, in an adder 21, the q-axis interference term Vq ^dec is added to the q-axis voltage command value Vq*, and a corrected q-axis voltage command value Vq*' is output.

Next, in the motor model 22, the corrected q-axis voltage command value Vq*' is multiplied by 1/(R^+Lq^s) to output the q-axis current value Iq.

Then, in conversion block 23, the q-axis current value Iq is converted to the δ-axis current value Iδ by Δθ.

Also, by moving the adder 21 before the conversion block 20, the block diagram shown in FIG. 3(a) can be transformed into the block diagram shown in FIG. 3(b).

First, in an adder 21, the δ-axis interference term Vδ ^dec is added to the δ-axis voltage command value Vδ*, and a corrected δ-axis voltage command value Vδ*' is output.

Next, in conversion block 20, the corrected δ-axis voltage command value Vδ*' is converted to a corrected q-axis voltage command value Vq*' by Δθ.

Next, in the motor model 22, the corrected q-axis voltage command value Vq*' is multiplied by 1/(R^+Lq^s) to output the q-axis current value Iq.

Then, in conversion block 23, the q-axis current value Iq is converted to the δ-axis current value Iδ by Δθ.

In addition, conversion block 20 converts the δ-axis voltage command value Vδ* to the q-axis voltage command value Vq* using Δθ, while conversion block 23 converts the q-axis current value Iq to the δ-axis current value Iδ using θ. Therefore, conversion blocks 20 and 23 can be omitted, and the block diagram shown in FIG. 3(b) can be transformed into the block diagram shown in FIG. 3(c).

First, in an adder 21, the δ-axis interference term Vδ ^dec is added to the δ-axis voltage command value Vδ*, and a corrected δ-axis voltage command value Vδ*' is output.

Then, in the motor model 22, the corrected δ-axis voltage command value Vδ*' is multiplied by 1/(R^+Lq^s) to output the δ-axis current value Iδ.

Moreover, by modifying the block diagram shown in FIG. 3(c) so as to output the δ-axis interference term Vδ ^dec , it is possible to construct an observer (a mechanism for estimating the δ-axis interference term) shown in FIG. 3(d).

First, in the motor model 22', the δ-axis current value Iδ is multiplied by (R^+Lq^s) to output the corrected δ-axis voltage command value Vδ*'.

Then, an adder 21' divides the corrected δ-axis voltage command value Vδ* by the δ-axis voltage command value Vδ*' to output the δ-axis interference term Vδ ^dec .

That is, the following formula 16, which corresponds to the block diagram shown in FIG. 3(c), can be transformed into the following formula 1, which corresponds to the observer shown in FIG. 3(d).

Iδ=(Vδ*+Vδ ^dec )×1/(R^+Lq^s)...Formula 16
Vδ ^dec ^=-Vδ*+(R^+Lq^s) Iδ...Formula 1

In this manner, the δ-axis interference term Vδ ^dec can be estimated using the δ-axis voltage command value Vδ*, the δ-axis current value Iδ, the resistance component R^, and the q-axis inductance component Lq^.

That is, the out-of-step determination unit 16 estimates the δ-axis interference term Vδ ^dec by calculating the above formula 1, and determines that the motor M is out of step when the δ-axis interference term Vδ ^dec ^, which is the estimated value of the δ-axis interference term Vδ ^dec , is equal to or greater than the threshold value Vδth. Note that the threshold value Vδth may be changed to a smaller value in consideration of errors contained in the δ-axis voltage command value Vδ*, the δ-axis current value Iδ, and the motor parameters (resistance component R^, q-axis inductance component Lq^).

In this manner, the control device 1 of the embodiment is configured to determine whether or not the motor M has stepped out by using the δ-axis interference term Vδ ^dec ^ estimated from the δ-axis voltage command value Vδ*, the δ-axis current value Iδ, and the motor parameters of the motor M (resistance component R^, q-axis inductance component Lq^). Since the rotation speed command value ω* is not included as a parameter for estimating the δ-axis interference term Vδ ^dec ^, the control device 1 can improve the accuracy of determining whether or not the motor M has stepped out by using the rotation speed command value ω*.

Furthermore, the control device 1 of the embodiment is configured to determine whether or not the motor M has stepped out using the δ-axis interference term Vδ ^dec ^ estimated from four parameters, namely, the δ-axis voltage command value Vδ*, the δ-axis current value Iδ, the resistance component R, and the q-axis inductance component Lq. This reduces the effect that errors contained in each parameter have on the accuracy of determining whether or not the motor M has stepped out, compared to a configuration in which five or more parameters are used to determine whether or not the motor M has stepped out.

In addition, in the case of a position sensorless non-salient motor M (for example, a surface magnet type synchronous motor or an embedded magnet type synchronous motor with a salient pole ratio close to 1), the position estimation accuracy is relatively low when the motor is driven at low speeds, making it easy for the motor to lose synchronism. According to the control device 1 of the embodiment, it is possible to accurately determine whether the motor M has lost synchronism not only when the motor M is driven at medium to high speeds, but also when the motor is driven at low speeds, making it particularly effective for position sensorless non-salient motors M.

The present invention is not limited to the above embodiments, and various improvements and modifications are possible without departing from the spirit of the present invention.

<Modification>
Fig. 4(a) is a diagram showing a schematic change in the δ-axis current value Iδ over time, and Fig. 4(b) is a diagram showing a schematic change in the δ-axis interference term Vδ ^dec ^ over time. The horizontal axis of the two-dimensional coordinate system shown in Fig. 4(a) indicates time, and the vertical axis indicates current. The solid line shown in Fig. 4(a) indicates the δ-axis current value Iδ. The horizontal axis of the two-dimensional coordinate system shown in Fig. 4(b) indicates time, and the vertical axis indicates voltage. The solid line shown in Fig. 4(b) indicates the true value of the δ-axis interference term Vδ ^dec ^, and the dashed line shown in Fig. 4(b) indicates the δ-axis interference term Vδ ^dec ^. Times t0, t1, and t2 in Fig. 4(a) coincide with times t0, t1, and t2 in Fig. 4(b). The true value of the δ-axis interference term ^Vδdec ^ is, for example, the δ-axis interference term Vδdec^ estimated when no error is contained in the parameters of the δ-axis voltage command value Vδ ^* , the δ-axis current value Iδ, the resistance component R, and the q-axis inductance component Lq.

As shown in FIGS. 4A and 4B, when the δ-axis current value Iδ is a negative value, the δ-axis interference term Vδ ^dec ^ becomes a first estimated value that is larger than the true value of the δ-axis interference term Vδ ^dec ^.

Furthermore, when the δ-axis current value Iδ is a positive value, the δ-axis interference term Vδ ^dec ^ becomes a second estimated value that is smaller than the true value of the δ-axis interference term Vδ ^dec ^.

In the motor M having such characteristics, the out-of-step determination unit 16 may be configured to set, as the threshold value Vδth, a first estimated value of the δ-axis interference term Vδ ^dec ^ that is larger than the true value of the δ-axis interference term Vδ ^dec when the δ-axis current value Iδ is a negative value, and to set, as the threshold value Vδth, a second estimated value of the δ-axis interference term Vδ ^dec ^ that is smaller than the true value of the δ-axis interference term Vδ ^dec when the δ-axis current value Iδ is a positive value.

In this way, in the motor M having the characteristic that the δ-axis interference term Vδ ^dec ^ changes in response to a change in the sign (positive or negative) of the δ-axis current value Iδ, the accuracy of determining whether or not a step-out has occurred can be further improved by changing the threshold value Vδth in response to a change in the sign of the δ-axis current value Iδ.

REFERENCE SIGNS LIST 1 Control device 2 Inverter 3 Control circuit 4 Memory unit 5 Drive circuit 6 Calculation unit 7 Current value conversion unit 8 Estimation unit 9 Subtraction unit 10 Torque command value calculation unit 11 γ-δ current command value output unit 12 Subtraction unit 13 Subtraction unit 14 Voltage command value calculation unit 15 Voltage command value conversion unit 16 Loss of synchronism determination unit P Power supply C Capacitor Se1 Current sensor Se2 Current sensor Se3 Current sensor

Claims (4)

A control device that generates a drive signal to control an inverter that drives a motor,
a current value converter for converting a current flowing through the motor into a γ-axis current value and a δ-axis current value;
a γ-δ current command value output unit that outputs a γ-axis current command value and a δ-axis current command value;
a γ-δ voltage command value calculation unit that calculates a γ-axis voltage command value based on the γ-axis current value and the γ-axis current command value, and calculates a δ-axis voltage command value based on the δ-axis current value and the δ-axis current command value;
a drive signal output unit that converts the γ-axis voltage command value and the δ-axis voltage command value into the drive signals and outputs the drive signals to the inverter;
a step-out determination unit that estimates a δ-axis interference term by using the δ-axis voltage command value, the δ-axis current value, and motor parameters, and determines that the motor is out of step when the estimated δ-axis interference term is equal to or greater than a threshold value;
A control device comprising: The control device according to claim 1 ,
When the δ-axis interference term is Vδ ^dec ^, the δ-axis voltage command value is Vδ*, the δ-axis current value is Iδ, the resistance component of the motor is R^, the q-axis inductance component of the motor is Lq^, and a differential operator is s, the out-of-step determination unit estimates the δ-axis interference term by calculating the following formula 1: Vδ ^dec ^=-Vδ*+(R^+Lq^s)Iδ... formula 1
A control device comprising: The control device according to claim 2,
The out-of-step determination unit is
when the δ-axis current value is a negative value, a first estimated value of the δ-axis interference term that is greater than a true value of the δ-axis interference term is set as the threshold value;
a second estimated value of the δ-axis interference term that is smaller than a true value of the δ-axis interference term is set as the threshold value when the δ-axis current value is a positive value. The control device according to any one of claims 1 to 3,
The control device according to claim 1, wherein the motor is a non-salient motor.

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