阅读说明：本技术 同步电动机控制装置 (Synchronous motor control device ) 是由 高野裕理 大桥敬典 高田英人 梁田哲男 藤泽劝也 于 2019-07-03 设计创作，主要内容包括：本发明提供一种同步电动机控制装置(10),其电流限值生成处理部(27)基于同步电动机(50)的速度检测值,表示d轴电压的限值的d轴电压限值(vd_lim_in),和表示用于导出q轴电流指令值的运算乘数值的电流指令限值运算增益(iq_lim_ca1_gain),导出限制同步电动机(50)的电压饱和的q轴电流指令值限值(iq_lim_out)。电流指令限制处理部(28)基于电流限值生成处理部(27)导出的q轴电流指令值限值(iq_lim_out),限制q轴电流指令值。由此,即使在同步电动机控制装置的电源电压降低的情况下,也不会在高速域中过度降低输出转矩,能够抑制同步电动机的急剧的输出转矩降低。(A current limit generation processing unit (27) of a synchronous motor control device (10) derives a q-axis current command value limit (iq _ lim _ out) that limits voltage saturation of a synchronous motor (50), based on a speed detection value of the synchronous motor (50), a d-axis voltage limit (vd _ lim _ in) that indicates a limit value of a d-axis voltage, and a current command limit calculation gain (iq _ lim _ ca1_ gain) that indicates a calculation multiplier value for deriving a q-axis current command value. A current command limiting processing unit (28) limits the q-axis current command value on the basis of the q-axis current command value limit (iq _ lim _ out) derived by the current limit value generation processing unit (27). Thus, even when the power supply voltage of the synchronous motor control device is reduced, the output torque is not excessively reduced in the high-speed range, and a sudden output torque reduction of the synchronous motor can be suppressed.)

1. A synchronous motor control device is characterized by comprising:

an inverter circuit to which a direct-current voltage from a converter circuit that outputs the direct-current voltage using a three-phase power supply as an input power supply is applied and that applies a three-phase voltage command to a synchronous motor;

a speed control unit that calculates a q-axis current command value based on a difference between a speed command value that sets the rotational speed of the synchronous motor and a speed detection value that indicates the rotational speed of the synchronous motor;

a current limit value generation processing unit that outputs a current command limit value for limiting voltage saturation of the synchronous motor;

a current command limit processing unit that generates a q-axis current limit command value for suppressing the q-axis current command value calculated by the speed control unit, based on the current command limit value output from the current limit value generation processing unit;

a d-axis current command generating unit that generates a d-axis current command value at an arbitrary magnetomotive force phase difference angle based on the q-axis current limit command value generated by the current command limit processing unit;

a q-axis current control unit that generates a q-axis voltage command value based on the q-axis current limit command value generated by the current command limit processing unit;

a d-axis current control unit that generates a d-axis voltage command value based on the d-axis current command value generated by the d-axis current command generation unit; and

a three-phase conversion unit that converts the q-axis voltage command value generated by the q-axis current control unit and the d-axis voltage command value generated by the d-axis current control unit into three-phase command values,

the current limit generation processing unit derives the current command limit corresponding to a load variation of the synchronous motor using parameters including: a speed detection value of the synchronous motor; a d-axis voltage limit value representing a limit value of the d-axis voltage; and a current command limit calculation gain representing a calculation multiplier value for deriving a q-axis current command limit,

the current command limitation processing unit limits the q-axis current command value based on the current command limit derived by the current limit generation processing unit.

2. The synchronous motor control device according to claim 1, characterized in that:

the d-axis voltage limit and the current command limit calculation gain input to the current limit generation processing unit are input from the outside.

3. A synchronous motor control device is characterized by comprising:

an inverter circuit to which a direct-current voltage from a converter circuit that outputs the direct-current voltage using a three-phase power supply as an input power supply is applied and that applies a three-phase voltage command to a synchronous motor;

a speed control unit that calculates a q-axis current command value based on a difference between a speed command value that sets a rotational speed of the synchronous motor and a speed detection value that indicates a speed of the synchronous motor;

a current limit value generation processing unit that outputs a current command limit value for suppressing voltage saturation of the synchronous motor;

a current command limit processing unit that generates a q-axis current limit command value for limiting the q-axis current command value calculated by the speed control unit, based on the current command limit value output from the current limit value generation processing unit;

a d-axis current command generating unit that generates a d-axis current command value at an arbitrary magnetomotive force phase difference angle based on the q-axis current limit command value generated by the current command limit processing unit;

a q-axis current control unit that generates a q-axis voltage command value based on the q-axis current limit command value generated by the current command limit processing unit;

a d-axis current control unit that generates a d-axis voltage command value based on the d-axis current command value generated by the d-axis current command generation unit; and

a three-phase conversion unit that converts the q-axis voltage command value generated by the q-axis current control unit and the d-axis voltage command value generated by the d-axis current control unit into three-phase command values,

the current limit value generation processing unit derives the current command limit value corresponding to a change in the dc voltage supplied to the inverter circuit using parameters including: a speed detection value of the synchronous motor; the dc voltage supplied to the inverter circuit; a d-axis voltage limit calculation gain representing a calculation multiplier for deriving a d-axis voltage limit; a d-axis voltage limit calculation offset representing an offset value for deriving a d-axis voltage limit; and a q-axis current command value limit calculation gain representing a calculation multiplier value for deriving a q-axis current command limit,

the current command limitation processing unit limits the q-axis current command value based on the current command limit derived by the current limit generation processing unit.

4. The synchronous motor control device according to claim 3, characterized in that:

the d-axis voltage limit calculation gain, the d-axis voltage limit calculation offset, and the q-axis current command value limit calculation gain input to the current limit generation processing unit are input from the outside.

5. A synchronous motor control device is characterized by comprising:

an inverter circuit to which a direct-current voltage from a converter circuit that outputs the direct-current voltage using a three-phase power supply as an input power supply is applied and that applies a three-phase voltage command to a synchronous motor;

a speed control unit that calculates a q-axis current command value based on a difference between a speed command value that sets a rotational speed of the synchronous motor and a speed detection value that indicates a speed of the synchronous motor;

a current limit value generation processing unit that outputs a current command limit value for suppressing voltage saturation of the synchronous motor;

a current command limit processing unit that generates a q-axis current limit command value for limiting the q-axis current command value calculated by the speed control unit, based on the current command limit value output from the current limit value generation processing unit;

a d-axis current command generating unit that generates a d-axis current command value at an arbitrary magnetomotive force phase difference angle based on the q-axis current limit command value generated by the current command limit processing unit;

a q-axis current control unit that generates a q-axis voltage command value based on the q-axis current limit command value generated by the current command limit processing unit;

a d-axis current control unit that generates a d-axis voltage command value based on the d-axis current command value generated by the d-axis current command generation unit; and

a three-phase conversion unit that converts the q-axis voltage command value generated by the q-axis current control unit and the d-axis voltage command value generated by the d-axis current control unit into three-phase command values,

the current limit value generation processing unit derives the current command limit value corresponding to a change in the dc voltage supplied to the inverter circuit and a rotation speed of the synchronous motor using parameters including: a speed detection value of the synchronous motor; the dc voltage supplied to the inverter circuit; a d-axis voltage limit calculation gain representing a calculation multiplier for deriving a d-axis voltage limit; a d-axis voltage limit calculation offset representing an offset value for deriving a d-axis voltage limit; a q-axis current command value limit value indicating a maximum value of the limited q-axis current command values; a q-axis current command value limit value switching speed calculation gain indicating a calculation multiplier value for switching the q-axis current command value; and a q-axis current command limit switching speed calculation offset representing an offset value for deriving a switching speed of the q-axis current command,

the current command limitation processing unit limits the q-axis current command value based on the current command limit derived by the current limit generation processing unit.

6. The synchronous motor control device according to claim 5, characterized in that:

the d-axis voltage limit calculation gain, the d-axis voltage limit calculation offset, the q-axis current command value limit calculation gain, the q-axis current command value limit switching speed calculation gain, and the q-axis current command value limit switching speed calculation offset, which are input to the current limit generation processing unit, are input from the outside.

7. The synchronous motor control device according to claim 6, characterized in that:

the current limit value generation processing unit includes a first order lag filter that performs a first order lag filtering process on the current command limit value.

Technical Field

The present invention relates to a synchronous motor control device, and more particularly to a technique capable of effectively reducing a torque drop of a synchronous motor due to a saturation voltage.

Background

As a method for controlling a synchronous motor, for example, vector control, current control, or the like is known. Vector control is to independently adjust and control currents flowing to a d-axis oriented in a magnetic pole direction of a motor and a q-axis orthogonal thereto. The current control is, for example, a control of a current by a Proportional Integral (PI) method.

In a synchronous motor using reluctance torque, inductance varies with respect to a current applied by a synchronous motor control device. Therefore, the drive voltage has a nonlinear characteristic with respect to the speed of the synchronous motor.

In this case, when the power supply voltage of the synchronous motor control device decreases, the output torque of the synchronous motor abruptly decreases due to voltage saturation. Further, when the voltage saturation occurs, the current control characteristics of the synchronous motor deteriorate, and there is a problem that a rapid decrease in the rotation speed or torque ripple occurs.

As a technique for solving such a decrease in output torque of the synchronous motor, the following techniques are known: even when the power supply voltage of the synchronous motor control device is reduced, the current command value is subjected to current limiting processing so that voltage saturation does not occur with the power supply voltage (see, for example, patent document 1).

Disclosure of Invention

Technical problem to be solved by the invention

In the technique of patent document 1, for example, when a current limiting process is performed on a current command value so that voltage saturation does not occur, a current limit value is derived as a linear function with respect to the speed of the synchronous motor.

However, the relationship between the power supply voltage and the current limit that becomes the voltage saturation limit is not a linear function. Therefore, although voltage saturation does not occur by setting the current limit value by a linear function, the current command value is limited to a value more than necessary by the speed of the synchronous motor, and as a result, the output torque may be limited.

An object of the present invention is to provide a technique for suppressing a rapid decrease in output torque of a synchronous motor without excessively decreasing the output torque in a high-speed range even when the power supply voltage of a synchronous motor control device is decreased.

The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

Means for solving the problems

The outline of a representative one of the embodiments disclosed in the present application will be briefly described as follows.

That is, a typical synchronous motor control device includes an inverter circuit, a speed control unit, a current limit value generation processing unit, a current command limitation processing unit, a d-axis current command generation unit, a q-axis current control unit, a d-axis current control unit, and a three-phase conversion unit.

The inverter circuit generates a three-phase voltage command from the DC voltage, and applies the generated three-phase voltage command to the synchronous motor. The speed control unit calculates a q-axis current command value based on a difference between a speed command value for setting the rotational speed of the synchronous motor and a speed detection value indicating the rotational speed of the synchronous motor.

The current limit value generation processing unit outputs a current command limit value for suppressing voltage saturation of the synchronous motor. The current command limiting processing unit generates a q-axis current limiting command value for limiting the q-axis current command value calculated by the speed control unit, based on the current command limit value output from the current limit value generating processing unit.

The d-axis current command generating unit generates a d-axis current command value at an arbitrary magnetomotive force phase difference angle based on the q-axis current limit command value generated by the current command limit processing unit. The q-axis current control unit generates a q-axis voltage command value based on the q-axis current limit command value generated by the current command limit processing unit.

The d-axis current control unit generates a d-axis voltage command value based on the d-axis current command value generated by the d-axis current command generation unit. The three-phase conversion unit converts the q-axis voltage command value generated by the q-axis current control unit and the d-axis voltage command value generated by the d-axis current control unit into three-phase command values.

The current limit value generation processing unit derives a current command limit value corresponding to a load change of the synchronous motor, using as parameters a speed detection value of the synchronous motor, a d-axis voltage limit value indicating a limit value of a d-axis voltage, and a current command limit value calculation gain indicating a calculation multiplier value for deriving a q-axis current command limit value. The current command limiting processing unit limits the q-axis current command value based on the current command limit derived by the current limit generation processing unit.

Effects of the invention

The effects obtained by typical ones of the technical solutions disclosed in the present application will be briefly described below.

(1) Abrupt torque fluctuations of the synchronous motor can be reduced.

(2) The operation of the synchronous motor can be stabilized by the above (1).

Drawings

Fig. 1 is a block diagram showing an example of the configuration of a synchronous motor control device according to embodiment 1.

Fig. 2 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor controlled by the synchronous motor control device of fig. 1.

Fig. 3 is an explanatory diagram showing voltage vectors of the d-axis voltage vd and the q-axis voltage vq of the synchronous motor control device of fig. 1.

Fig. 4 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor.

Fig. 5 is an explanatory diagram for explaining a voltage saturation phenomenon.

Fig. 6 is a block diagram showing an example of the structure of a synchronous motor control device according to embodiment 2.

Fig. 7 is an explanatory diagram showing an example of the configuration of a current limit value generation processing unit included in the synchronous motor control device of fig. 6.

Fig. 8 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor according to embodiment 2.

Fig. 9 is an explanatory diagram of an example of the structure of the synchronous motor control device according to embodiment 3.

Fig. 10 is an explanatory diagram showing an example of the configuration of a current limit value generation processing unit included in the synchronous motor control device of fig. 9.

Fig. 11 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor according to embodiment 3.

Description of reference numerals

10 synchronous motor control device

21 inverter circuit

23 converter circuit

24 speed detection arithmetic unit

25 subtracter

26 speed control part

27 Current Limit Generation processing Unit

28 Current instruction limiting processing section

29 d-axis current command generating unit

30 q-axis current control unit

31 d-axis current control unit

32 three-phase conversion part

35 d-axis voltage limit value generation processing unit

36 q-axis current limit value generation processing unit

37 q-axis current limit value switching speed generation processing unit

38 q-axis current limit value switching processing unit

39 first order lag filter

50 synchronous motor

51 position detector.

Detailed Description

In all the drawings for explaining the embodiments, the same reference numerals are attached to the same members in principle, and the overlapping description thereof will be omitted.

(embodiment mode 1)

The following describes embodiments in detail.

Example of Structure of synchronous Motor control apparatus

Fig. 1 is a block diagram showing an example of the configuration of a synchronous motor control device 10 according to embodiment 1.

The synchronous motor control device 10 controls the rotation operation of the synchronous motor 50. The synchronous motor 50 is constituted by a servo motor or the like, for example. A position detector 51 is connected to the synchronous motor 50. The position detector 51 detects a rotor position θ m of the synchronous motor 50.

As shown in fig. 1, the synchronous motor control device 10 is configured by an inverter circuit 21, a converter circuit 23, a speed detection arithmetic unit 24, a subtractor 25, a speed control unit 26, a current limit value generation processing unit 27, a current command limitation processing unit 28, a d-axis current command generation unit 29, a q-axis current control unit 30, a d-axis current control unit 31, a three-phase conversion unit 32, and the like.

Note that, although the example of fig. 1 shows an example in which the converter circuit 23 is provided in the synchronous motor control device 10, the converter circuit 23 may be provided outside the synchronous motor control device 10.

The inverter circuit 21 applies three-phase voltage commands vu, vv, vw to the synchronous motor 50. The converter circuit 23 converts the three-phase power source VF into a dc voltage Vdc and supplies the dc voltage Vdc to the inverter circuit 21. The three-phase power source VF is a three-phase ac power source.

The speed detection computing unit 24 computes a speed detection value Nm, which is the number of revolutions of the synchronous motor 50, based on the rotor position θ m detected by the position detector 51. The subtractor 25 calculates the difference between the speed command value Nref and the speed detection value Nm calculated by the speed detection calculating unit 24.

The speed reference value Nref is input from an upper control device provided outside. For example, when the synchronous motor 50 is used for a press machine or the like, the higher-level control device is a control device or the like that is responsible for controlling the press machine, and outputs a rotation speed command value to the synchronous motor that drives the press machine.

The speed control unit 26 calculates a q-axis current command value iqref for controlling the q-axis current based on the calculation result of the subtractor 25. The current limit generation processing unit 27 generates and outputs a q-axis current command limit iq _1im _ out based on the speed detection value Nm output from the speed detection computing unit 24, the d-axis voltage limit vd _1im _ in as a parameter, and the computing gain iq _ lim _ ca1_ gain.

The d-axis voltage limit vd _ lim _ in represents a limit of the d-axis voltage. The operational gain iq _ lim _ cal _ gain represents an operational multiplier value for deriving the q-axis current command value.

These parameters such as the d-axis voltage limit vd _ lim _ in and the calculation gain iq _ lim _ ca1_ gain are set by, for example, a personal computer or the like externally connected to the synchronous motor control device 10. Alternatively, setting parameters such as dip switches may be used.

The current command limitation processing unit 28 outputs a q-axis current command value iqref _ out obtained by limiting the q-axis current command value iqref calculated by the speed control unit 26, based on the q-axis current command limit value iq _ lim _ out generated by the current limit value generation processing unit 27.

The d-axis current command generating unit 29 outputs a d-axis current command value idref _ out in accordance with a magnetomotive force difference angle β, which is a difference angle between the d-axis (magnetic field component) and the armature magnetomotive force center, based on the q-axis current command value iqref _ out output from the current command limiting processing unit 28.

The q-axis current control unit 30 calculates a q-axis voltage reference value vqref based on the q-axis current reference value iqref _ out output from the current reference limit processing unit 28. The d-axis current control unit 31 calculates a d-axis voltage command value vdref based on the q-axis current command value iqref _ out.

The three-phase conversion unit 32 converts the q-axis voltage reference value vqref output from the q-axis current control unit 30 and the d-axis voltage reference value vdref output from the d-axis current control unit 31 into three-phase reference values vuref, vvref, vwref, and supplies the three-phase reference values vuref, vvref, vwref to the inverter circuit 21.

Next, the operation of the current limit value generation processing unit 27 included in the synchronous motor control device 10 will be described in detail.

Fig. 2 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor 50 controlled by the synchronous motor control device 10 of fig. 1.

The chain line of fig. 2 shows the torque-speed characteristic in the design of the synchronous motor 50 using reluctance torque. Here, the reduction of the dc voltage Vdc output from the converter circuit 23 is not considered, and the dc voltage Vdc is, for example, about 270V.

As shown in fig. 2, when the load torque is increased at the maximum speed Nmax of the synchronous motor 50, the speed decreases with a characteristic close to a linear characteristic from a certain torque. The dc voltage Vdc (270V) at this time is referred to as a reference voltage.

However, when the dc voltage Vdc decreases (Vdc < 270V), the synchronous motor 50 is saturated with voltage by a current command from the q-axis current control unit 30 or the d-axis current control unit 31, and the speed decreases from the voltage saturation starting point by the nonlinear characteristic as shown by the solid line in fig. 2.

The voltage saturation phenomenon, which is a cause of the speed reduction, will be described with reference to fig. 3.

Fig. 3 is an explanatory diagram showing voltage vectors of the d-axis voltage vd and the q-axis voltage vq of the synchronous motor control device 10 of fig. 1.

When the maximum value of the d-axis voltage vd is set to the voltage vd _ max and the maximum value of the q-axis (torque component) voltage vq is set to the voltage vq _ max, the maximum value of the voltage that can be output by the inverter circuit 21 becomes a circular shape as shown in fig. 3.

If the length of the voltage vector is within the circle, no voltage saturation occurs. Conversely, when outside the circle, as in voltage vector B, voltage saturation occurs. In order to suppress the voltage saturation, it is necessary to suppress the length of the vector so as to converge within the circle, as in the voltage vector a shown in fig. 3.

Therefore, in the synchronous motor control device 10, the current limit value generation processing unit 27 derives the limit value of the current command in which the voltage saturation does not occur, that is, the q-axis current limit value, from the current command of the q-axis current control unit 30 or the d-axis current control unit 31.

The current limit generation processing unit 27 derives the q-axis current limit described above according to the following principle.

The current limit generation processing unit 27 derives a q-axis current limit in accordance with the d-axis voltage limit vd _ lim _ in and the motor speed Nm. Specifically, it is derived from the disturbance term of the d-axis voltage equation of the synchronous motor.

In general, the voltage equation of the synchronous motor expressed in dq coordinates is shown in the following equation (1). In the voltage equation of the synchronous motor of equation (1), the disturbance term is expressed by equation (2), and the disturbance term of the d-axis voltage equation is vod.

In equations (1) and (2), vd is a d-axis voltage, vq is a q-axis voltage, vod is a d-axis interference voltage, voq is a q-axis interference voltage, id is a d-axis current, iq is a q-axis current, R is a winding resistance value of the synchronous motor, Ld is an inductance value of the d-axis of the synchronous motor, Lq is an inductance value of the q-axis of the synchronous motor, ω is an electrical angular velocity of the synchronous motor, and Ψ a is a flux linkage of the synchronous motor.

Next, a method of deriving a specific q-axis current command limit iq _ lim _ out by the current limit generation processing unit 27 will be described using an equation.

The current limit generation processing unit 27 derives a q-axis current command limit iq _ lim _ out in accordance with the motor speed Nm using the following expression (3). In addition, when the value of the q-axis current command limit iq _ lim _ out is a negative value, the q-axis current command indicatesThe limit iq _ lim _ out is set to 0. Here, the unit of motor speed Nm is assumed to be [ min ]^-1]. Pp in the formula (3) is the pole pair number of the synchronous motor.

Vdlim _ in expression (3) is derived in advance as follows.

iq_lim_out＝(vdlim_in×iqlim_cal_gain)/(Nm×(2π/60)×Pp)…(3)

The vod is derived by substituting the current values id and iq applied when the synchronous motor is driven at the highest rotation speed (electrical angular velocity) into the interference term (expression (2)) of the d-axis voltage equation of the synchronous motor, and the vod at this time is vdlim _ in.

According to the equation (2), the value of vod changes with the rotation speed (electrical angular velocity) ω of the synchronous motor, but the equation (3) is simplified by substituting the rotation speed ω as the maximum rotation speed (electrical angular velocity) [ fixed value ] as described above. This reduces the load on the calculation process of the synchronous motor control device 10.

The q-axis current command value limit calculation gain iqlim _ cal _ gain is derived in advance by equation (4).

iqlim_cal_gain＝1/Lq…(4)

As described above, by performing the limiting process of limiting the current command according to the q-axis current command limit iq _ lim _ out derived by the current limit generation processing unit 27, it is possible to suppress the occurrence of voltage saturation due to the current command from the q-axis current control unit 30 or the d-axis current control unit 31 even when the load of the synchronous motor 50 is excessively large.

Fig. 4 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor.

In fig. 4, a torque-speed characteristic C shown by a chain line is a torque-speed characteristic that the synchronous motor can output. The torque-speed characteristic D shown by a broken line is a torque-speed characteristic when the current limit value is derived as a linear function with respect to the speed of the synchronous motor described as a countermeasure against voltage saturation in the technical problem. The torque-speed characteristic E shown by the solid line is a torque-speed characteristic when the q-axis current command limit iq _ lim _ out, which is the limit of the current command derived by the current limit generation processing unit 27 and in which voltage saturation does not occur, is used.

The q-axis current command limit iq _ lim _ out is derived from the d-axis voltage equation, and therefore can be a value at a critical level at which voltage saturation does not occur. That is, it is possible to suppress a sudden decrease in the output torque of the synchronous motor without excessively decreasing the output torque in the high speed range as in the torque-speed characteristic E shown by the solid line in fig. 4.

This makes it possible to provide the synchronous motor control device 10 that can stably operate the synchronous motor 50.

(embodiment mode 2)

In embodiment 1, the q-axis current limit value is derived on the premise that the dc voltage Vdc output from the converter circuit 23 is a substantially constant value, but in embodiment 2, an example will be described in which the q-axis current limit value is derived in consideration of the voltage drop amount when the voltage of the dc voltage Vdc output from the converter circuit 23 is reduced.

Fig. 6 is a block diagram showing an example of the configuration of the synchronous motor control device 10 according to embodiment 2.

The synchronous motor control device 10 shown in fig. 6 is different from the synchronous motor control device 10 shown in fig. 1 of embodiment 1 described above in that parameters are input from the outside. In the synchronous motor control device 10 shown in fig. 6, two parameters, i.e., a d-axis voltage limit calculation gain vd _ lim _ cal _ gain and a d-axis voltage limit calculation offset vd _ lim _ ca1_ ofst, are input to the current limit generation processing unit 27 again instead of the parameter of the d-axis voltage limit vd _ lim _ in. The present invention is also different from the synchronous motor control device 10 shown in fig. 1 in that the dc voltage Vdc is input to the current limit value generation processing unit 27.

The d-axis voltage limit calculation gain vd _ lim _ cal _ gain represents a calculation multiplier value for deriving the d-axis voltage limit. The d-axis voltage limit calculation offset vd _ lim _ ca1_ ofst represents an offset value for deriving a limit of the d-axis voltage. Since the other connection structures are the same as those in fig. 1, the description thereof is omitted.

The current limit generation processing unit 27 generates and outputs a q-axis current command value limit iq _ lim _ out based on the speed detection value Nm output from the speed detection computing unit 24, the dc voltage Vdc output from the converter circuit 23, the d-axis voltage limit computing gain vd _ lim _ ca1_ gain as a parameter for generating the current limit, the d-axis voltage limit computing offset vd _ lim _ cal _ ofst, and the q-axis current command value limit computing gain iq _ lim _ cal _ gain.

Next, a relationship between the dc voltage Vdc and the voltage saturation phenomenon will be described.

Fig. 5 is an explanatory diagram for explaining a voltage saturation phenomenon.

Fig. 5 shows voltage vectors of the d-axis voltage vd and the q-axis voltage vq. In fig. 5, when the dc voltage Vdc is a reference voltage, namely, vd _ lim _ in _ Vdc _ base, the maximum values of the d-axis voltage vd and the q-axis voltage vq are the voltage vd _ max1 and the voltage vq _ max1, respectively, and the maximum value of the voltage that can be output by the inverter circuit 21 in fig. 6 is circular as shown by the maximum value C1 of the inverter circuit output voltage shown in fig. 5.

At this time, if the length of the voltage vector is within the circle, voltage saturation does not occur. Conversely, as shown by the voltage vector B1, when the length of the voltage vector is in the outer region of the circle (the region shown by hatching in fig. 6), voltage saturation occurs. In order to suppress the voltage saturation, the length of the suppression vector as shown by the voltage vector a1 needs to be such that it converges within the circle.

When the dc voltage Vdc is the lowest voltage value, that is, vd _ lim _ in _ Vdc _ min (< vd _ lim _ in _ Vdc _ base), the maximum values of the d-axis voltage vd and the q-axis voltage vq are voltage vd _ max2 and voltage vq _ max2, respectively, and the maximum value of the voltage that can be output by the inverter circuit 21 is a circular shape shown as the inverter circuit output voltage maximum value C2 in fig. 5.

Similarly to the case where the dc voltage Vdc is vd _ lim _ in _ Vdc _ base, in order to suppress the voltage saturation, it is necessary to suppress the length of the vector so as to converge within the circle as indicated by a voltage vector a2 in fig. 5.

As in the magnitude relation of the dc voltage Vdc, the length of the voltage vector is expressed by equation (5).

An | voltage vector A2 | an | voltage vector A1 | … (5)

Therefore, when the dc voltage Vdc varies as described above, it is necessary to suppress the maximum voltage vector length in accordance with the dc voltage Vdc in order to suppress the voltage saturation phenomenon.

Fig. 7 is an explanatory diagram showing an example of the configuration of the current limit value generation processing unit 27 included in the synchronous motor control device 10 of fig. 6.

As shown in fig. 7, the current limit value generation processing unit 27 is composed of a d-axis voltage limit value generation processing unit 35 and a q-axis current limit value generation processing unit 36. The d-axis voltage limit generation processing unit 35 is input with the dc voltage Vdc, a d-axis voltage limit calculation gain vd _ lim _ ca1_ gain as a parameter, and a d-axis voltage limit calculation offset vd _ lim _ cal _ ofst as a parameter.

Next, the d-axis voltage limit generation processing unit 35 calculates and outputs a d-axis voltage limit vd _ lim _ cal based on the dc voltage Vdc, the d-axis voltage limit calculation gain vd _ lim _ ca1_ gain, and the d-axis voltage limit calculation offset vd _ lim _ ca1_ ofst.

The speed detection value Nm, the d-axis voltage limit vd _ lim _ cal output from the d-axis voltage limit generation processing unit 35, and the q-axis current command value limit calculation gain iq _ lim _ ca1_ gain as parameters are input to the q-axis current limit generation processing unit 36.

Next, the q-axis current limit generation processing unit 36 calculates and outputs a q-axis current command value limit iq _1im _ out based on the input speed detection value Nm, the d-axis voltage limit vd _ lim _ ca1, and the q-axis current command value limit calculation gain iq _ lim _ cal _ gain.

The current limit value generation processing unit 27 derives a q-axis current limit value, which is a limit value of a current command in which voltage saturation does not occur in the q-axis current control unit 30 or the d-axis current control unit 31, in consideration of the dc voltage Vdc.

The current limit generation processing unit 27 derives the q-axis current limit according to the following principle. Specifically, the d-axis voltage equation of the synchronous motor 50 is derived from the disturbance term in consideration of the dc voltage Vdc.

Next, a method of deriving a specific q-axis current command limit iq _ lim _ out by the current limit generation processing unit 27 will be described using an equation.

First, the d-axis voltage limit generation processing unit 35 derives a calculated value, i.e., a d-axis voltage limit vd _ lim _ cal, by using the following expression (6). Vdc _ base is a reference voltage of the dc voltage Vdc supplied from the converter circuit 23, and Vdc _ min is the lowest voltage of the dc voltage Vdc supplied from the converter circuit 23.

vd_lim_ca1＝Vdc×vd_lim_cal_gain+vd_1im_cal_ofst…(6)

The d-axis voltage limit calculation gain vd _ lim _ cal _ gain is derived in advance by substituting a d-axis voltage limit (reference) vd _ lim _ in _ Vdc _ base, a d-axis voltage limit vd _ lim _ in _ Vdc _ min, a reference voltage Vdc _ base of a direct current voltage, and a lowest voltage Vdc _ min of a direct current voltage by equation (7).

vd_lim_cal_gain＝(vd_lim_in_vdc_base－vd_lim_in_vdc_min)/(Vdc_base－Vdc_min)…(7)

The d-axis voltage limit calculation offset amount vd _ lim _ ca1_ ofst is also derived in advance by substituting a d-axis voltage limit calculation gain vd _ lim _ cal _ gain, a d-axis voltage limit vd _ lim _ in _ Vdc _ base, and a reference voltage Vdc _ base of a dc voltage by equation (8).

vd_lim_ca1_ofst＝vd_lim_in_vdc_base－(vd_lim_cal_gain×Vdc_base)…(8)

vd _ lim _ in _ Vdc _ base, when the dc voltage Vdc is Vdc _ base, vod is derived by substituting current values id and iq applied when the synchronous motor is driven at the highest rotation speed (electrical angular velocity) into an interference term (expression (2)) of a d-axis voltage equation of the synchronous motor. The vod at this time is set in advance as vd _ lim _ in _ vdc _ base.

Furthermore, vd _ lim _ in _ Vdc _ min is derived by substituting current values id and iq applied when the synchronous motor is driven at the highest rotation speed (electrical angular velocity) into an interference term (expression (2)) of a d-axis voltage equation of the synchronous motor when the dc voltage Vdc is Vdc _ min. The vod at this time is set to vd _ lim _ in _ vdc _ min in advance.

The q-axis current limit generation processing unit 36 derives a q-axis current command limit iq _ lim _ out by using equation (9) in accordance with the speed detection value Nm. When the value of the q-axis current command limit iq _ lim _ out is a negative value, iq _ lim _ out is 0. Here, the unit of the speed detection value Nm is assumed to be [ min-1 ]. Pp is the pole pair number of the synchronous motor.

iq_lim_out＝(vd_1im_ca1×iqlim_ca1_gain)/(Nm×(2π/60)×Pp)…(9)

The q-axis current command value limit calculation gain iqlim _ ca1_ gain is derived in advance by the above equation (4).

As described above, by performing the current command limiting process in accordance with the q-axis current command limit iq _ lim _ out derived by the current limit generation processing unit 27, it is possible to suppress the occurrence of voltage saturation when the load of the synchronous motor 50 is excessively large even when the dc voltage Vdc fluctuates.

Fig. 8 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor according to embodiment 2.

In fig. 8, a torque-speed characteristic a3 shown by a broken line is a torque-speed characteristic that can be output by the synchronous motor when the dc voltage Vdc is the d-axis voltage limit value vd _ lim _ in _ Vdc _ base. The torque-speed characteristic a4 shown by the dashed-dotted line represents the torque-speed characteristic that the synchronous motor can output when the dc voltage Vdc is the d-axis voltage limit value vd _ lim _ in _ Vdc _ min.

The torque-speed characteristic C1 shown by the thick solid line is a torque-speed characteristic when the q-axis current command limit iq _ lim _ out, which is a limit of a current command in which voltage saturation does not occur, is used when the dc voltage Vdc is the d-axis voltage limit vd _ lim _ in _ Vdc _ min.

The torque-speed characteristic C2 shown by the thin solid line is a torque-speed characteristic when the q-axis current command limit iq _ lim _ out, which is a limit of a current command in which voltage saturation does not occur, is used when the dc voltage Vdc is the d-axis voltage limit vd _ lim _ in _ Vdc _ base.

As described above, the q-axis current command limit iq _ lim _ out is derived from the d-axis voltage equation, and therefore can be a value at a critical level at which voltage saturation does not occur. That is, as shown in the torque-speed characteristics C1 and C2 of fig. 8, the output torque is not excessively reduced in the high-speed rotation region of the synchronous motor 50, and a sudden reduction in the output torque of the synchronous motor 50 can be suppressed.

As can be seen from the above, the synchronous motor control device 10 that can operate the synchronous motor 50 more stably can be provided.

(embodiment mode 3)

In embodiment 2 described above, when the voltage of the dc voltage vdc output from the converter circuit 23 decreases, the q-axis current limit value is derived in consideration of the voltage drop amount. Both the d-axis voltage limit (reference) vd _ lim _ in _ vdc _ base and the d-axis voltage limit (lowest) vd _ lim _ in _ vdc _ min, which are references for deriving the q-axis current limit, are values when the synchronous motor 50 is operated at the highest speed.

Therefore, in the low speed range, the q-axis current limit value becomes smaller than the axis current value that can be applied when the voltage is not saturated, and the output torque may become smaller than the torque that can be output by the synchronous motor 50.

Therefore, in embodiment 3, an example will be described in which, even when the dc voltage Vdc output from the converter circuit 23 is reduced, the q-axis current limit value at which the synchronous motor 50 can effectively output torque is derived in consideration of the voltage drop amount and the speed of the synchronous motor 50.

Fig. 9 is an explanatory diagram showing an example of the configuration of the synchronous motor control device 10 according to embodiment 3.

The synchronous motor control device 10 shown in fig. 9 is different from the synchronous motor control device 10 shown in fig. 6 of the above-described embodiment 2 in that a parameter is input to the current limit value generation processing unit 27.

In the synchronous motor control device 10 of fig. 9, in addition to the q-axis current command value limit calculation gain iq _ lim _ ca1_ gain and the d-axis voltage limit calculation offset vd _ lim _ cal _ ofst input to the current limit generation processing unit 27 of fig. 6, a configuration is adopted in which a q-axis current command value limit iq _ lim _ max, a q-axis current command value limit switching speed calculation gain N _ chg _ cal _ gain, and a q-axis current command value switching limit speed calculation offset N _ chg _ ca1_ ofst are input as parameters for newly generating a current limit. The q-axis current command value limit iq _1im _ max is the maximum value of the q-axis current command value limit.

The current limit generation processing unit 27 generates and outputs a q-axis current command limit iq _ lim _ out based on these input parameters. Since the other connection structure is the same as that of the synchronous motor control device 10 of fig. 6, the description thereof is omitted.

Fig. 10 is an explanatory diagram showing an example of the configuration of the current limit value generation processing unit 27 included in the synchronous motor control device 10 of fig. 9.

As shown in fig. 10, the current limit value generation processing unit 27 is composed of a d-axis voltage limit value generation processing unit 35, a q-axis current limit value generation processing unit 36, a q-axis current limit value switching speed generation processing unit 37, a q-axis current limit value switching processing unit 38, and a first-order lag filter 39.

The d-axis voltage limit generation processing unit 35 generates and outputs a d-axis voltage limit vd _ lim _ ca1 based on the dc voltage Vdc output from the converter circuit 23, the d-axis voltage limit calculation gain vd _ lim _ cal _ gain, and the d-axis voltage limit calculation offset vd _ lim _ ca1_ ofst.

The q-axis current limit generation processing unit 36 generates and outputs a q-axis current command value limit iq _ lim _ cal based on the speed detection value Nm output from the speed detection computing unit 24, the d-axis voltage limit vd _ lim _ cal output from the d-axis voltage limit generation processing unit 35, and the q-axis current command value limit computation gain iq _ lim _ cal _ gain as a parameter.

The q-axis current limit switching speed generation processing unit 37 generates and outputs a q-axis current command value limit switching speed N _ chg _ lvl for switching the q-axis current command value, based on the dc voltage Vdc, the q-axis current command value limit switching speed calculation gain N _ chg _ ca1_ gain as a parameter, and the q-axis current command value limit switching speed calculation offset N _ chg _ cal _ ofst.

The q-axis current limit switching processing unit 38 generates and outputs a q-axis current command value limit iq _ lim _ set based on the speed detection value Nm, the q-axis current command value limit iq _ lim _ ca1 output from the q-axis current limit generation processing unit 36, the q-axis current command value limit switching speed N _ chg _1v1 output from the q-axis current limit switching speed generation processing unit 37, and the q-axis current command value limit (maximum) iq _ lim _ max as a parameter.

The first order lag filter 39 is configured by, for example, a low pass filter or the like, and performs a first order lag filtering process on the q-axis current command value limit iq _ lim _ set output from the q-axis current limit switching processing unit 38 to output a q-axis current command limit iq _ lim _ out.

In this way, the current limit value generation processing unit 27 derives the limit value of the current command, i.e., the q-axis current limit value, so as not to cause voltage saturation by using the q-axis current control unit 30 or the d-axis current control unit 31 in consideration of the level of the dc voltage Vdc.

The current limit generation processing unit 27 derives the q-axis current limit according to the following principle. Specifically, the q-axis current limit is derived from the disturbance term of the d-axis voltage equation of the synchronous motor 50 in consideration of the dc voltage Vdc. The derived result is switched to the q-axis current command value limit (maximum) iq _ lim _ max based on the speed detection value Nm.

Next, a method of deriving a specific q-axis current command limit iq _ lim _ out by the current limit generation processing unit 27 will be described using an equation.

First, the d-axis voltage limit generation processing unit 35 derives the d-axis voltage limit vd _ lim _ cal by using the above-described equations (6) to (8). Then, the q-axis current limit generation processing unit 36 derives a q-axis current limit iq _ lim _ ca1 from equation (10) in accordance with the speed detection value Nm.

When the q-axis current limit iq _ lim _ ca1 has a negative value, iq _ lim _ ca1 is set to 0. Here, the unit of the speed detection value Nm is assumed to be [ min-1 ]. Pp is the pole pair number of the synchronous motor.

iq_lim_cal＝(vd_lim_cal×iqlim_cal_gain)/(Nm×(2π/60)×Pp)…(10)

In equation (7), vd _ lim _ in _ Vdc _ base is derived by substituting current values id and iq applied when the synchronous motor 50 is driven at the highest rotation speed (electrical angular velocity) into an interference term (equation (2)) of a d-axis voltage equation of the synchronous motor 50 when the dc voltage Vdc output from the converter circuit 23 is Vdc _ base, and then the vod at this time is set in advance to vd _ lim _ in _ Vdc _ base.

In addition, vd _ lim _ in _ Vdc _ min in equation (7), when the dc voltage Vdc is Vdc _ min, the vod is derived by substituting the current values id and iq applied when the synchronous motor 50 is driven at the highest rotation speed (electrical angular velocity) into the interference term (equation (2)) of the d-axis voltage equation of the synchronous motor 50, and the vod at this time is set to vd _ lim _ in _ Vdc _ min in advance.

The q-axis current command value limit calculation gain iqlim _ cal _ gain is derived in advance from the above equation (4).

The q-axis current limit switching speed generation processing unit 37 derives the d-axis voltage limit N _ chg _ lv1 using equation (11).

N_chg_lvl＝Vdc×N_chg_cal_gain+N_chg_cal_ofst…(11)

The q-axis current command value limit switching speed calculation gain N _ chg _ ca1_ gain is derived in advance using equation (12). Here, N _ chg _ lvl _ base in equation (12) is a switching point of the q-axis current command value limit value of the synchronous motor 50 when the dc voltage Vdc is the reference voltage. Similarly, N _ chg _ lvl _ min in equation (12) represents a switching point of the q-axis current command value limit value when the dc voltage Vdc is the lowest voltage.

N_chg_cal_gain＝(N_chg_lvl_base－N_chg_1vl_min)/(Vdc_base－Vdc_min)…(12)

The q-axis current command value limit switching speed calculation offset N _ chg _ ca1_ ofst is derived in advance using equation (13).

N_chg_cal_ofst＝N_chg_lv1_base－(N_chg_cal_gain×Vdc_base)…(13)

In addition, in the q-axis current limit switching processing unit 38, the q-axis current command value limit iq _ lim _ set is derived by equation (14).

iq _ lim _ set ═ iq _1im _ cal: nm is greater than or equal to N _ chg _ lvl

Iq _ lim _ max: nm < N _ chg _ lvl case … (14)

In order to reduce the switching shock of the synchronous motor 50 that occurs when the q-axis current command value limit iq _ lim _ set is switched, the q-axis current limit switching processing unit 38 performs first-order lag filtering on the q-axis current command value limit iq _ lim _ set by the first-order lag filter 39 and then outputs the q-axis current command limit iq _ lim _ out.

In this way, the current value supplied to the synchronous motor 50 can be smoothly changed by performing the filtering process of the first-order lag filter 39, and therefore, a rapid rotational change of the synchronous motor 50 can be prevented.

As described above, by performing the current command limiting process in accordance with the q-axis current command limit iq _1im _ out derived by the current limit generation processing unit 27, even when the dc voltage Vdc varies with time, it is possible to suppress the occurrence of voltage saturation in the q-axis current control unit 30 or the d-axis current control unit 31 when the load of the synchronous motor 50 is excessively large.

The q-axis current command limit iq _ lim _ out is derived from the d-axis voltage equation, and therefore can be a value at a level at which voltage saturation does not occur. Further, by monitoring the speed of the synchronous motor 50 and switching the q-axis current command value limit to the q-axis current command value limit (maximum) iq _ lim _ max, the q-axis current limit can be reduced in a low speed range without being excessively reduced.

Fig. 11 is an explanatory diagram showing an example of torque-speed characteristics of the synchronous motor 50 when the dc voltage Vdc varies.

In fig. 11, the torque-speed characteristic a3 shown by a broken line is a torque-speed characteristic that can be output by the synchronous motor when the dc voltage Vdc is the d-axis voltage limit value vd _ lim _ in _ Vdc _ base.

The torque-speed characteristic a6 shown by the dashed-dotted line is a torque-speed characteristic that can be output by the synchronous motor when the dc voltage Vdc is the d-axis voltage limit value vd _ lim _ in _ Vdc _ min.

The torque-speed characteristic C3 shown by the thick solid line is a torque-speed characteristic when the q-axis current command limit iq _ lim _ out, which is a limit of a current command in which voltage saturation does not occur, is used when the dc voltage Vdc is the d-axis voltage limit vd _ lim _ in _ Vdc _ base.

The torque-speed characteristic C4 shown by the thin solid line is a torque-speed characteristic when the q-axis current command limit iq _ lim _ out, which is a limit of a current command in which voltage saturation does not occur, is used when the dc voltage Vdc is the d-axis voltage limit vd _ lim _ in _ Vdc _ min.

As described above, even if the voltage of the dc voltage Vdc decreases, the q-axis current limit value is switched to the q-axis current command value limit (maximum) iq _ lim _ max in consideration of the speed of the synchronous motor 50, so that the output torque is not excessively decreased in the low speed region and the high speed region of the synchronous motor 50 as shown in the torque-speed characteristics C3 and C4 of fig. 11, and a sudden decrease in the output torque of the synchronous motor 50 can be suppressed.

Thus, even when the voltage of the dc voltage Vdc is reduced, the torque of the synchronous motor 50 can be efficiently output in consideration of the voltage drop amount and the speed of the synchronous motor 50.

Therefore, the synchronous motor 50 can be operated more stably.

The invention made by the present inventors has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited to the above embodiments, and various modifications can be made within a range not departing from the gist thereof.

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments are the ones described in detail to explain the present invention easily and understandably, and are not necessarily limited to having all the configurations described above.

Note that a part of the structure of one embodiment may be replaced with the structure of another embodiment, or the structure of another embodiment may be added to the structure of one embodiment. Further, a part of the configuration of each embodiment may be added, deleted, or replaced with another configuration.