Synchronous motor control device, control method of synchronous motor control device

Abstract

To provide a control device that reduces output torque reduction of a synchronous motor, without saturating an output voltage.SOLUTION: A synchronous motor control device comprises s speed control part 8 for generating a q-axis current command value according to a difference between a speed command value of setting a rotary speed of a synchronous motor 1 and a speed detection value of a motor speed. A q-axis current command limit processing part limits the q-axis current command value based on a q-axis current limit value by comprising: the q-axis current command limit processing part 10 that generates a q-axis current limitation command value for limiting the q-axis current command value, based on the q-axis current limit value for limiting a q-axis current applied to a motor; a d-axis current command generation part 11 for generating a d-axis current command value from the q-axis current limitation command value and a magnetomotive force phase difference angle; a q-axis current control part 12 for generating a q-axis voltage command value, based on the q-axis current limitation command value; a d-axis current control part 13 for generating a d-axis voltage command value, based on the d-axis current command value; and a three-phase conversion part 14 for converting a two-phase command voltage between the q-axis voltage command value and the d-axis voltage command value.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] In a synchronous motor that utilizes reluctance torque, the inductance varies with the current applied by a synchronous motor control device, so the drive voltage with respect to the speed of the synchronous motor has 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 characteristic 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 Publication No. 2015-35923 (Patent Document 1).

[0006] In this publication, as a solution to the reduction in output torque of a synchronous motor due to voltage saturation, a current limiting process is applied to 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. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-35923 A Summary of the Invention [Problem to be solved by the invention]

[0008] In general, when current limiting processing is performed on a current command value so as to prevent voltage saturation, the current limiting 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 will result in excessive restriction of the current command value depending on the speed of the synchronous motor.

[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 reducing the output torque too much in the high-speed range, even when the power supply voltage of the synchronous motor control device drops. [Means for solving the problem]

[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 source 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 according to a difference between a speed command value that sets a 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 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 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 input to the inverter circuit, and is characterized in that the q-axis current command value is limited by the q-axis current command limit value in the q-axis current command limit processing unit. Effect of the Invention

[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. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram of a synchronous motor control device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram of a q-axis current limit value generating processor in the first embodiment of the present invention. [Diagram 3] 5 is a flowchart showing a process of a q-axis current limit value generation processor in the first embodiment of the present invention. [Figure 4] 4 is an example of the operation of a q-axis current limit value generation processing unit in the first embodiment of the present invention. [Diagram 5] This is an example of the torque-speed characteristics of a synchronous motor. [Figure 6] 13 is an example of the torque-speed characteristic 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. [Figure 7] 1 is an explanatory example of a phenomenon in which the output torque drops suddenly due to voltage saturation. [Figure 8] 4 is an example of torque-speed characteristics of a synchronous motor when measures against a sudden drop in output torque due to voltage saturation are implemented according to the first embodiment. [Figure 9] 13 is a second example of the q-axis current limit value generation processing unit in the first embodiment. [Figure 10] 13 is an example of a current limit value table in the second embodiment of the present invention. [Figure 11] 13 is an example of a q-axis current limit value generating processor in the second embodiment of the present invention. [Figure 12] 13 is an example of a q-axis current limit value generating processor in the second embodiment of the present invention. [Figure 13] 13 is an example of a current limit value table that stores current limit values ​​for each of a plurality of synchronous motors. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment is an example for explaining the present invention, and for the sake of clarity, some details have been omitted or simplified. The present invention can be embodied 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] As examples of various information, the various information may be described using expressions such as "table," "list," and "queue," but the various information may be expressed using data structures other than these. For example, various information such as "XX table," "XX list," and "XX queue" may be expressed as "XX information." When describing identification information, expressions such as "identification information," "identifier," "name," "ID," and "number" are used, but these are mutually interchangeable.

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

[0021] In the embodiments, there may be cases where a process is performed by executing a program. Here, a computer executes the program using a processor (e.g., a CPU or a GPU), and performs the process defined by the program while using storage resources (e.g., a memory) and interface devices (e.g., a communication port), etc.

[0022] Therefore, the subject of the processing performed by executing the program may be a processor. Similarly, the subject of the processing performed by executing the program may be a controller, device, system, computer, or node having a processor. The subject of the processing performed by executing the program may be a calculation unit, and may include a dedicated circuit for performing 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] Furthermore, in the embodiments, two or more programs may be realized as one program, and 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] It 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 receives the speed detection value Nm of the speed detection calculation unit 6 and the DC voltage Vdc as input and outputs the q-axis current limit value iq_lim_out.

[0030] The inverter also includes a current command limiting processing unit 10 which limits the q-axis current command value iqref, which is the output of the speed control unit 8, by the above-mentioned 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 which outputs a d-axis current command value idref_out in accordance with the magnetomotive force phase difference angle β based on the q-axis current command value iqref_out.

[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, 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, vwref which are input to the inverter circuit 3.

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

[0033] Fig. 5 shows torque-speed characteristics. In Fig. 5, the dashed dotted line shows the torque-speed characteristics of the synchronous motor 1 using reluctance torque in the design when the decrease in the DC voltage Vdc output by the converter circuit 5 is not taken into consideration (here, Vdc=270[V] is fixed).

[0034] When the load torque is increased at the maximum speed Nmax, the speed decreases from a certain torque with a characteristic close to a clean linear characteristic. The DC voltage Vdc (=270[V]) at this time is 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 with nonlinear characteristics from the point where voltage saturation starts, 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 the circle indicated by the dotted line.

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

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

[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 to fall 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 determines 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 speed detection 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]

number

[0044] Here, f(φ1max) can be derived, for example, from 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]

number

[0046] f(φ1max) has a waveform as shown in Figure 4.

[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 FIG. 2 and FIG.

[0048] In the q-axis current limit value generation processor 9, the effective voltage Vdcr is obtained by multiplying the DC voltage Vdc by a coefficient 91 (S1), the motor speed detection value Nm is multiplied by a coefficient 92 to obtain an electrical angular velocity ωe (S2), and a divider 93 divides the effective voltage Vdcr by the electrical angular velocity ωe 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 factor 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 ωe [rad / s] = K × Nm [min -1 ], K = number of pole pairs × (2π / 60), number of pole pairs = number of poles / 2.

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

[0051] Specifically, the effective voltage Vdcr is obtained by multiplying the DC voltage Vdc by a coefficient 91, a voltage margin Vx is subtracted from this Vdvr to obtain (Vdcr-Vx), the detected speed value Nm of the motor is multiplied by a coefficient 92 to obtain the electrical angular velocity ωe, and a divider 93 is used to obtain 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]

number

[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, it is possible to prevent a sudden drop in the output torque of the synchronous motor without excessively reducing the output torque in the high speed range. EXAMPLES

[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 speed detection 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 calculations are too complicated for the microcomputer (microprocessor) used in the actual device, making it difficult to realize without using a high-performance microcomputer.

[0058] To solve this problem, the storage unit may be provided with a current limit value table in the form of 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 Fig. 10. By providing the q-axis current limit value generation unit with the current limit value table, 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 obtained without performing any calculation.

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

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

[0062] Two-dimensional array representation data (maximum magnetic flux-q-axis current map data 96) in which the relationship of the q-axis current limit value is calculated in advance 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. Fig. 13 shows an example of a current limit value table that stores the maximum magnetic flux current value for each synchronous motor from synchronous motor 1 to synchronous motor m.

[0063] Here, as shown in Fig. 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. By adopting such a configuration, it becomes possible to update the two-dimensional array expression data remotely, improving maintainability.

[0064] Furthermore, by connecting the 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 the 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 controlled that is driven at any given 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 that memory chip when the motor to be controlled is changed, the q-axis current limit value suitable for the motor to be controlled can be obtained. [Explanation of symbols]

[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. an inverter circuit to which a DC voltage is applied from a converter circuit that receives a three-phase power supply as an input and outputs a DC voltage, and which applies a three-phase voltage command to a synchronous motor; a speed control unit that generates a q-axis current command value according to a difference between a speed command value that sets a rotation speed of the synchronous motor and a speed detection value that indicates a speed of the synchronous motor, a q-axis current command limit processing 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; a d-axis current command generating unit that generates a d-axis current command value based on the 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; a three-phase conversion unit that converts the two-phase command voltages 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 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. 2. The synchronous motor control device according to claim 1, a storage unit that stores a current limit value table that associates the DC voltage, the maximum magnetic flux, and the q-axis current limit value; a q-axis current limit value generating unit that obtains a maximum magnetic flux from the DC voltage and the drive electrical angular velocity of the synchronous motor, refers to the current limit value table stored in the storage unit, and obtains the q-axis current limit value using the maximum magnetic flux; a q-axis current command limit processor using the obtained q-axis current limit value to limit the q-axis current command value.

3. 3. The synchronous motor control device according to claim 2, 13. A synchronous motor control device, comprising: a synchronous motor control section for controlling a synchronous motor according to claim 12, wherein the current limit value table used in the q-axis current limit value generating section is rewritable by an externally connected device.

4. 2. The synchronous motor control device according to claim 1, The synchronous motor control device is characterized in that 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. 2. The synchronous motor control device according to claim 1, receiving a current limit value table corresponding to a synchronous motor to be controlled from a server storing a plurality of current limit value tables corresponding to maximum magnetic fluxes of a plurality of synchronous motors; a storage unit that stores the received current limit value table; a q-axis current limit value generating unit that obtains a maximum magnetic flux from the DC voltage and a drive electrical angular velocity of the synchronous motor, refers to the current limit value table stored in the storage unit, and obtains the q-axis current limit value using the maximum magnetic flux; a q-axis current command limit processor using the obtained q-axis current limit value to limit the q-axis current command value.

6. 2. The synchronous motor control device according to claim 1, generating a q-axis current limit value that is a limit value of a q-axis current applied to the synchronous motor, and generating the q-axis current limit value based on a maximum magnetic flux calculated from the DC voltage and a drive electrical angular velocity of the synchronous motor; The q-axis current command limit processing unit limits the q-axis current command value based on the q-axis current limit value.

7. 2. The synchronous motor control device according to claim 1, a storage unit that stores 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 that obtains a maximum magnetic flux from the DC voltage and a drive electrical angular velocity of the synchronous motor, refers to the current limit value table stored in the storage unit, and obtains the q-axis current limit value using the maximum magnetic flux; a q-axis current command limit processor using the obtained q-axis current limit value to limit the q-axis current command value.

8. an inverter circuit which receives a DC voltage from a converter circuit which receives a three-phase power supply as an input and outputs a DC voltage, and applies a three-phase voltage command to a synchronous motor; a speed control unit that generates a q-axis current command value according to a difference between a speed command value that sets a rotation speed of the synchronous motor and a speed detection value that indicates a speed of the synchronous motor, a q-axis current command limit processing unit 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; a d-axis current command generating unit generating a d-axis current command value from the q-axis current limit command value and the magnetomotive force phase difference angle; a q-axis current control unit generating a q-axis voltage command value based on the q-axis current limit command value; a d-axis current control unit generating a d-axis voltage command value based on the d-axis current command value; a three-phase conversion unit converts the two-phase command voltages 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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