Synchronous motor control device and method for controlling synchronous motor control device

Abstract

Provided is a synchronous motor control device that suppresses a rapid decrease in the output torque of a synchronous motor without output voltage saturation. The synchronous motor control device includes a speed control unit for generating a q-axis current command value in accordance with the difference between a speed command value for setting the rotation speed of a synchronous motor and a speed detection value indicating the speed of the synchronous motor. The synchronous motor control device includes: a q-axis current command limit processing unit for generating a q-axis current limit command value for limiting the q-axis current command value on the basis of a q-axis current limit value limiting the q-axis current applied to the synchronous motor; a d-axis current command generation unit for generating a d-axis current command value from the q-axis current limit command value and a magnetomotive force phase difference angle; a q-axis current control unit for generating a q-axis voltage command value on the basis of the q-axis current limit command value; a d-axis current control unit for generating a d-axis voltage command value on the basis of the d-axis current command value; and a three-phase conversion unit for converting a two-phase command voltage of the q-axis voltage command value and the d-axis voltage command value into a three-phase command value that is an input to an inverter circuit. The q-axis current command limit processing unit limits the q-axis current command value on the basis of the q-axis current limit value.

Description

Synchronous motor control device and control method for synchronous motor control device

[0001] The present invention relates to a synchronous motor control device and a control method for a synchronous motor control device.

[0002] One method of controlling a synchronous motor is vector control, which independently adjusts the current flowing in the d-axis, which is taken along the magnetic pole direction of the motor, and the q-axis, which is perpendicular to this. Current control is generally performed using a proportional-integral method.

[0003] In a synchronous motor that utilizes reluctance torque, the inductance changes with the current applied by the synchronous motor control device, so the drive voltage relative to the speed of the synchronous motor exhibits nonlinear characteristics.

[0004] At this time, if the power supply voltage of the synchronous motor control device drops, the output torque drops sharply due to voltage saturation, as shown in the torque-speed characteristics of the synchronous motor shown in Figure 4. Furthermore, when voltage saturation occurs, the current control characteristics of the synchronous motor deteriorate, causing problems such as a sudden drop in the rotation speed of the motor and torque ripple.

[0005] As background art in this technical field, there is Japanese Patent Application Laid-Open No. 2015-35923 (Patent Document 1).

[0006] In this publication, as a solution to the problem of a decrease in output torque of a synchronous motor due to voltage saturation, a current limiting process is performed on the current command value in accordance with the power supply voltage so that voltage saturation does not occur even when the power supply voltage of the synchronous motor control device drops.

[0007] JP 2015-35923 A

[0008] Generally, when current limiting processing is performed on a current command value so as to prevent voltage saturation, the current limit value is derived as a linear function of the speed of the synchronous motor.

[0009] However, since the relationship between the power supply voltage and the current limit value that becomes the voltage saturation limit is not a linear function, setting this current limit value as a linear function will not cause voltage saturation, but depending on the speed of the synchronous motor, the current command value may be excessively restricted.

[0010] Therefore, as shown in FIG. 6, there are cases where the output torque is restricted more than the maximum torque that the synchronous motor can output.

[0011] In particular, when the speed of the synchronous motor is high, the output torque is often restricted excessively. Also, since there are many parameters to be adjusted, the number of adjustment steps may increase.

[0012] Therefore, the problem that the present invention aims to solve is to provide a synchronous motor control device that reduces the sudden decrease in output torque of a synchronous motor without excessively reducing the output torque in the high-speed range, even when the power supply voltage of the synchronous motor control device drops.

[0013] The above problem is solved by a synchronous motor control device including an inverter circuit that receives a DC voltage from a converter circuit that receives an input of a three-phase power supply and outputs a DC voltage, and that applies a three-phase voltage command to a synchronous motor, and a speed control unit that generates a q-axis current command value in accordance with a difference between a speed command value that sets the rotation speed of the synchronous motor and a speed detection value that indicates the speed of the synchronous motor, the synchronous motor control device including a q-axis current limit command value generation unit that generates a q-axis current limit command value that limits the q-axis current command value based on a q-axis current limit value that is a limit value of the q-axis current applied to the synchronous motor; The aforementioned problems are solved by a synchronous motor control device comprising: a d-axis current command generation unit that generates a d-axis current command value from a q-axis current limit command value and a magnetomotive force phase difference angle; a q-axis current control unit that generates a q-axis voltage command value based on the q-axis current limit command value; a d-axis current control unit that generates a d-axis voltage command value based on the d-axis current command value; and a three-phase conversion unit that converts two-phase command voltages of the q-axis voltage command value and the d-axis voltage command value into three-phase command values ​​that are input to the inverter circuit, and the q-axis current command value is limited by the q-axis current command limit value in a q-axis current command limit processing unit.

[0014] Even if the power supply voltage of the synchronous motor control device drops, the output torque is not excessively reduced in the high speed range, and a sudden drop in the output torque of the synchronous motor can be prevented.

[0015] FIG. 1 is a block diagram of a synchronous motor control device according to a first embodiment of the present invention. FIG. 2 is a block diagram of a q-axis current limit value generation processor according to the first embodiment of the present invention. FIG. 3 is a flowchart showing the processing of the q-axis current limit value generation processor according to the first embodiment of the present invention. FIG. 4 is an example of the operation of the q-axis current limit value generation processor according to the first embodiment of the present invention. FIG. 5 is an example of the torque-speed characteristics of a synchronous motor. FIG. 6 is an example of the torque-speed characteristics of a synchronous motor when a countermeasure against a sudden drop in output torque due to voltage saturation is implemented by current limiting using a linear function. FIG. 7 is an explanatory example of the phenomenon of a sudden drop in output torque due to voltage saturation. FIG. 8 is an example of the torque-speed characteristics of a synchronous motor when a countermeasure against a sudden drop in output torque due to voltage saturation is implemented according to the first embodiment. FIG. 9 is a second example of a q-axis current limit value generation processor according to the first embodiment. FIG. 10 is an example of a current limit value table according to a second embodiment of the present invention. FIG. 11 is an example of a q-axis current limit value generation processor according to the second embodiment of the present invention. FIG. 12 is an example of a current limit value table containing current limit values ​​for each of a plurality of synchronous motors.

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments are merely examples for explaining the present invention, and some details have been omitted or simplified for clarity of explanation. The present invention can be implemented in various other forms.

[0017] Unless otherwise specified, each component may be singular or plural. The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention.

[0018] Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0019] Although various types of information may be described using expressions such as "table," "list," and "queue" as examples, the various types of information may also be expressed using data structures other than these. For example, various types of information such as "XX table," "XX list," and "XX queue" may also be expressed as "XX information." When describing identification information, expressions such as "identification information," "identifier," "name," "ID," and "number" are used, but these are interchangeable.

[0020] When there are multiple components with the same or similar functions, they may be described using the same reference numeral with different subscripts. When there is no need to distinguish between these multiple components, the subscripts may be omitted.

[0021] In the examples, there may be described processes performed by executing a program. Here, a computer executes the program using a processor (e.g., a CPU or a GPU), and performs the processes defined by the program using storage resources (e.g., memory), interface devices (e.g., communication ports), etc.

[0022] Therefore, the entity that executes the program and performs the processing may be a processor. Similarly, the entity that executes the program and performs the processing may be a controller, device, system, computer, or node that has a processor. The entity that executes the program and performs the processing may be any computing unit, and may include a dedicated circuit that performs a specific process.

[0023] Here, the dedicated circuit is, for example, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a complex programmable logic device (CPLD), or the like.

[0024] The program may be installed in the computer from a program source, which may be, for example, a program distribution server or a computer-readable storage medium.

[0025] When the program source is a program distribution server, the program distribution server may include a processor and a storage resource for storing the program to be distributed, and the processor of the program distribution server may distribute the program to be distributed to other computers.

[0026] In addition, in the embodiments, two or more programs may be realized as one program, or one program may be realized as two or more programs.

[0027] FIG. 1 is a block diagram showing the basic configuration of a synchronous motor control device according to a first embodiment of the present invention.

[0028] The synchronous motor control device includes a synchronous motor 1, a position detector 2 that detects the rotor position θm of the synchronous motor 1, an inverter circuit 3 that applies three-phase voltage commands vu, vv, and vw to the synchronous motor 1, a three-phase power supply 4, and a converter circuit 5 that receives the three-phase power supply as an input and applies a DC voltage Vdc to the inverter circuit 3.

[0029] The system further includes a speed detection calculation unit 6 that calculates a speed detection value Nm from the rotor position θm, a subtractor 7 that calculates the deviation between the speed command value Nref and the speed detection value Nm, and a speed control unit 8 that calculates a q-axis current command value iqref based on the output of the subtractor 7, and a q-axis current limit value generation processing unit 9 that receives the speed detection value Nm of the speed detection calculation unit 6 and the DC voltage Vdc as input and outputs a q-axis current limit value iq_lim_out.

[0030] The motor also includes a current command limiting unit 10 that limits the q-axis current command value iqref, which is the output of the speed control unit 8, using the aforementioned q-axis current limit value iq_lim_out and outputs the q-axis current command value iqref_out, and a d-axis current command generating unit 11 that outputs a d-axis current command value idref_out based on the q-axis current command value iqref_out in accordance with the magnetomotive force phase difference angle β.

[0031] The inverter circuit 3 includes a q-axis current control unit 12 that calculates a q-axis voltage command value vqref based on the q-axis current command value iqref_out, a d-axis current control unit 13 that calculates a d-axis voltage command value vdref based on the d-axis current command value idref_out, and a three-phase conversion unit 14 that converts the two-phase command voltages vqref and vdref output by the q-axis current control unit 12 and the d-axis current control unit 13 into three-phase command values ​​vuref, vvref, and vwref that are input to the inverter circuit 3.

[0032] Here, the q-axis current limit value generating unit 9 will be described in detail.

[0033] 5 shows torque-speed characteristics, where the dashed dotted line indicates the designed torque-speed characteristics of the synchronous motor 1 that utilizes reluctance torque when a decrease in the DC voltage Vdc output by the converter circuit 5 is not taken into consideration (here, Vdc is fixed at 270 V).

[0034] When the load torque is increased at the maximum speed Nmax, the speed decreases from a certain torque with a characteristic that is close to a clean linear characteristic. The DC voltage Vdc (= 270 [V]) at this time will be called the reference voltage.

[0035] However, when the DC voltage Vdc becomes low (when Vdc<270 V), voltage saturation occurs in the q-axis current control unit 12 or the d-axis current control unit 13, and the speed decreases nonlinearly from the point where voltage saturation begins, as shown by the solid line in Figure 5.

[0036] The voltage saturation phenomenon that causes this speed reduction will be explained with reference to FIG.

[0037] 7 is a voltage vector diagram of vd and vq in a synchronous motor control device. The maximum values ​​of vd and vq are vd_max and vq_max, respectively, and the maximum value of the voltage that the inverter circuit can output is shown by the circle indicated by the dotted line.

[0038] If the length of the voltage vector is within this circle, voltage saturation will not occur. Conversely, if it is outside the circle, voltage saturation will occur.

[0039] In order to reduce voltage saturation, it is necessary to control the length of the vector so that it fits within this circle, like voltage vector A.

[0040] Therefore, the q-axis current limit value generation processing unit 9 calculates the limit value of the current command (q-axis current limit value) based on the maximum magnetic flux that can be output, and controls the length of the voltage vector so that it falls within the circle, thereby preventing voltage saturation from occurring in the q-axis current control unit 12 or the d-axis current control unit 13.

[0041] Specifically, the q-axis current limit value generation processing unit 9 calculates the q-axis current limit value iq_lim_out to be instructed to the q-axis current command limit processing unit by the following method.

[0042] The q-axis current limit value generation processing unit 9 derives the maximum magnetic flux φ1max using the DC voltage Vdc applied to the inverter circuit and the detected speed value of the synchronous motor as parameters, and derives the q-axis current limit value iq_lim_out according to the function f(φ1max) using this maximum magnetic flux as an argument, as shown in equation (1).

[0043]

[0044] Here, f(φ1max) can be derived from, for example, the following relational expression (2): In the following expression (2), φ1 is the magnetic flux, Lq is the q-axis inductance, Ld is the d-axis inductance, and Ke is the induced voltage coefficient.

[0045]

[0046] f(φ1max) has a waveform as shown in FIG.

[0047] Next, a specific method for deriving the q-axis current limit value iq_lim_out in the q-axis current limit value generation processing unit 9 will be described with reference to FIGS. 2 and 3. FIG.

[0048] The q-axis current limit value generation processor 9 multiplies the DC voltage Vdc by a coefficient 91 to obtain an effective voltage Vdcr (S1), multiplies the detected speed value Nm of the motor by a coefficient 92 to obtain an electrical angular velocity ωe (S2), and then divides the effective voltage Vdcr by the electrical angular velocity ωe using a divider 93 to obtain a maximum magnetic flux (φ1max) (S3). The resulting φ1max is input to a function 94 to obtain the q-axis current limit value iq_lim_out (S4).

[0049] The coefficient 92 is determined by the number of poles of the motor to be driven. For example, if the unit of the speed detection value Nm is [min －１ ], the electrical angle ωe [rad / s] is －１ ], K = number of pole pairs × (2π / 60), number of pole pairs = number of poles / 2.

[0050] Furthermore, the q-axis current limit value generation processing unit 9 can also adjust the q-axis current limit value iq_lim_out so that voltage saturation is less likely to occur by providing a voltage margin Vx as shown in FIG.

[0051] Specifically, the effective voltage Vdcr is calculated by multiplying the DC voltage Vdc by a coefficient 91, a voltage margin Vx is subtracted from Vdvr to calculate (Vdcr-Vx), the detected speed value Nm of the motor is multiplied by a coefficient 92 to calculate the electrical angular velocity ωe, and a divider 93 calculates φ1max (=(Vdcr-Vx) / ωe).

[0052] The resulting φ1max is input to a function 94 that performs the calculation shown in equation (3) to determine the q-axis current limit value iq_lim_out.

[0053]

[0054] As described above, by performing current command limit processing in accordance with the q-axis current limit value iq_lim_out derived by the q-axis current limit value generation processing unit 9, voltage saturation does not occur in the q-axis current control unit 12 or the d-axis current control unit 13 even when the load on the synchronous motor becomes excessive.

[0055] That is, as shown by the solid line of the torque-speed characteristic in FIG. 8, the output torque is not excessively reduced in the high speed range, and a sudden drop in the output torque of the synchronous motor can be prevented.

[0056] In the first embodiment, the q-axis current limit value generation processing unit 9 derives the maximum magnetic flux φ1max using the DC voltage Vdc applied to the inverter circuit and the detected speed value of the synchronous motor as parameters, and derives the q-axis current limit value iq_lim_out according to the function f(φ1max) using this maximum magnetic flux as an argument.

[0057] However, the calculation of the function f(φ1max) is complicated, and the calculation is too complicated for a microcomputer (microprocessor) used in an actual device, making it difficult to realize unless a high-performance microcomputer is used.

[0058] To solve this problem, the storage unit may be provided with a current limit value table, which is a table of two-dimensional array expression data (maximum magnetic flux-q-axis current map data 96) that pre-calculates the relationship between the maximum magnetic flux (φ1max) calculated from the DC voltage value (Vdc) and the drive electrical angular velocity of the synchronous motor and the q-axis current limit value, as shown in Figure 10. By providing the current limit value table in the q-axis current limit value generation unit, the calculation load can be reduced.

[0059] By referring to the current limit value table stored in the storage unit, the q-axis current limit value corresponding to the maximum magnetic flux can be found without performing any calculation.

[0060] By storing the data once in the storage unit of the synchronous motor control device in this way, it becomes possible to control the synchronous motor without delay.

[0061] A configuration as shown in FIG. 11 may be used in which the maximum magnetic flux (φ1max) is calculated from the DC voltage value (Vdc) and the detected speed value (Nm), and the obtained maximum magnetic flux (φ1max) is used to refer to maximum magnetic flux-q-axis current map data 96 to determine the q-axis current limit value iq_lim_out.

[0062] Two-dimensional array representation data (maximum magnetic flux-q-axis current map data 96) that pre-calculates the relationship between the q-axis current limit value must be set for each synchronous motor to be controlled. The current limit value table may have two-dimensional array representation data for each synchronous motor to be controlled by the control device. This configuration is expected to improve the compatibility of synchronous motors. Figure 13 shows an example of a current limit value table that stores the maximum magnetic flux current values ​​for each synchronous motor, from synchronous motor 1 to synchronous motor m.

[0063] 12, the maximum magnetic flux-q-axis current map data 96 may be changed (downloaded) by a PC 15 connected to the synchronous motor control device via a network. This configuration allows the two-dimensional array representation data to be updated remotely, improving maintainability.

[0064] Furthermore, by connecting a PC 15 to the synchronous motor control device installed at the site and changing the maximum magnetic flux-q-axis current map data 96, it is possible to provide maximum magnetic flux-q-axis current map data 96 specific to the synchronous motor control device installed at the site.

[0065] Furthermore, if a memory slot for reading the maximum magnetic flux-q axis current map data 96 is provided in the synchronous motor control device, the maximum magnetic flux-q axis current map data 96 can be updated without using the PC 15 .

[0066] All of the maximum magnetic flux-q-axis current map data 96 for each synchronous motor to be controlled, which is stored in the PC 15, may be downloaded to the synchronous motor control device. However, if only the map data corresponding to the synchronous motor to be driven at that time is downloaded, the capacity of the storage unit can be reduced.

[0067] In addition, by preparing a memory chip that stores only the maximum magnetic flux-q-axis current map data 96, and replacing only the memory chip when the motor to be controlled is changed, it is possible to obtain a q-axis current limit value that is suitable for the motor to be controlled.

[0068] 1: Synchronous motor 2: Position detector 3: Inverter circuit 4: Three-phase power supply 5: Converter circuit 6: Speed ​​detection calculation unit 7: Subtractor 8: Speed ​​control unit 9: Q-axis current limit value generation processing unit 91, 92: Coefficient 93: Divider 94: Function 95: Adder 96: Maximum magnetic flux - Q-axis current map data 10: Current command limit processing unit 11: D-axis current command generation unit 12: Q-axis current control unit 13: D-axis current control unit 14: Three-phase conversion unit 15: PC

Claims

1. A synchronous motor control device comprising: an inverter circuit which receives a DC voltage from a converter circuit which receives an input of a three-phase power source and outputs a DC voltage, and which applies a three-phase voltage command to a synchronous motor; and a speed control section which generates a q-axis current command value in accordance with a difference between a speed command value which sets the rotation speed of the synchronous motor and a speed detection value which indicates the speed of the synchronous motor; a q-axis current command limit processing section which generates a q-axis current limit command value which limits the q-axis current command value based on a q-axis current limit value which is a limit value of the q-axis current applied to the synchronous motor; a d-axis current command generating section which generates a d-axis current command value from the q-axis current limit command value and a magnetomotive force phase difference angle; a q-axis current control section which generates a q-axis voltage command value based on the q-axis current limit command value; a d-axis current control section which generates a d-axis voltage command value based on the d-axis current command value; and a three-phase conversion section which converts a two-phase command voltage of the q-axis voltage command value and the d-axis voltage command value into a three-phase command value which is an input to the inverter circuit, The synchronous motor control device, wherein the q-axis current command limit processing unit limits the q-axis current command value based on the q-axis current limit value.

2. A synchronous motor control device according to claim 1, comprising: a memory section storing a current limit value table in which the DC voltage, maximum magnetic flux and the q-axis current limit value are associated; and a q-axis current limit value generating section which determines the maximum magnetic flux from the DC voltage and the driving electrical angular velocity of the synchronous motor, refers to the current limit value table stored in the memory section, and obtains the q-axis current limit value using the maximum magnetic flux, and wherein the q-axis current command value is limited in the q-axis current command limit processing section using the obtained q-axis current limit value.

3. A synchronous motor control device according to claim 2, wherein the current limit value table used in the q-axis current limit value generating section is rewritable by an externally connected device.

4. The synchronous motor control device according to claim 1, wherein the q-axis current limit value iq_lim_out is calculated by the following formula: Here, the magnetic flux φ1 is φ1max is φ1max (=(Vdcr-Vx) / ωe), Lq is the q-axis inductance, Ld is the d-axis inductance, and Ke is the induced voltage coefficient.

5. A synchronous motor control device as described in claim 1, comprising: a memory unit which receives a current limit value table corresponding to a synchronous motor to be controlled from a server which stores a plurality of current limit value tables corresponding to maximum magnetic fluxes of a plurality of synchronous motors; and a q-axis current limit value generation unit which determines a maximum magnetic flux from the DC voltage and the driving electrical angular velocity of the synchronous motor, refers to the current limit value table stored in the memory unit, and obtains the q-axis current limit value using the maximum magnetic flux; and a q-axis current command limit processing unit which uses the obtained q-axis current limit value to limit the q-axis current command value.

6. A synchronous motor control device as claimed in claim 1, characterized in that it comprises a q-axis current limit value generating unit which generates the q-axis current limit value which is a limit value of the q-axis current applied to the synchronous motor, and generates the q-axis current limit value based on a maximum magnetic flux calculated from the DC voltage and the driving electrical angular velocity of the synchronous motor, and the q-axis current command limit processing unit limits the q-axis current command value based on the q-axis current limit value.

7. A synchronous motor control device as claimed in claim 1, further comprising: a memory unit storing a plurality of current limit value tables corresponding to maximum magnetic fluxes of a plurality of synchronous motors; a q-axis current limit value generating unit which determines the maximum magnetic flux from the DC voltage and the driving electrical angular velocity of the synchronous motor, refers to the current limit value table stored in the memory unit, and obtains the q-axis current limit value using the maximum magnetic flux; and a q-axis current command limit processing unit which limits the q-axis current command value using the obtained q-axis current limit value.

8. A control method for a synchronous motor control device comprising: an inverter circuit which receives a DC voltage from a converter circuit which receives an input of a three-phase power source and outputs a DC voltage, and which applies a three-phase voltage command to a synchronous motor; and a speed control section which generates a q-axis current command value according to a difference between a speed command value which sets the rotation speed of the synchronous motor and a speed detection value which indicates the speed of the synchronous motor, wherein a q-axis current command limit processing section generates a q-axis current limit command value which limits the q-axis current command value based on a q-axis current limit value which is a limit value of the q-axis current applied to the synchronous motor; a d-axis current command generating section generates a d-axis current command value from the q-axis current limit command value and a magnetomotive force phase difference angle; a q-axis current control section generates a q-axis voltage command value based on the q-axis current limit command value; a d-axis current control section generates a d-axis voltage command value based on the d-axis current command value; a three-phase conversion section converts a two-phase command voltage of the q-axis voltage command value and the d-axis voltage command value into a three-phase command value which is an input to the inverter circuit; The control method for a synchronous motor control device, wherein the q-axis current command limit processing unit limits the q-axis current command value based on the q-axis current limit value.

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