Synchronous motor control device and control method for a 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 Art]

[0002] As a control method for synchronous motors, there is vector control, which independently adjusts and controls currents flowing through a d-axis set along the magnetic pole direction of the motor and a q-axis orthogonal to the d-axis. In addition, current control is generally performed by a proportional-integral method.

[0003] In a synchronous motor that utilizes reluctance torque, the inductance changes in response to the current applied by the synchronous motor control device, so the drive voltage versus the rotational speed of the synchronous motor exhibits non-linear characteristics.

[0004] In this case, when the power supply voltage of the synchronous motor control device drops, for example, voltage saturation causes the output torque to decrease sharply as shown in the torque-speed characteristic curve of the synchronous motor in Fig. 4. Furthermore, when voltage saturation occurs, the current control characteristic of the synchronous motor deteriorates, leading to problems such as a sharp drop in the rotational speed of the motor and the occurrence of torque ripple.

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

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

[0007] [Patent Document 1] Japanese Patent Laid-Open No. 2015-35923 [Summary of the Invention] [Problems that the invention aims to solve]

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

[0009] However, since the relationship between the power supply voltage and the current limit value that represents the voltage saturation limit is not linear, setting this current limit value using a linear function will not cause voltage saturation, but depending on the speed of the synchronous motor, it may unnecessarily restrict the current command value.

[0010] Therefore, as shown in Figure 6, the output torque may be unnecessarily limited compared to the maximum torque that a synchronous motor can output.

[0011] In particular, when synchronous motors operate at high speeds, the output torque is often unnecessarily limited. Furthermore, the large number of parameters to adjust can increase the adjustment time.

[0012] Therefore, the problem that the present invention aims to solve is to provide a synchronous motor control device that reduces the abrupt 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 decreases. [Means for solving the problem]

[0013] The above problem is solved by a synchronous motor control device comprising: an inverter circuit that receives a DC voltage from a converter circuit that takes a three-phase power supply as input and outputs a DC voltage, and applies the DC voltage to a synchronous motor and applies a three-phase voltage command; and a speed control unit that generates a q-axis current command value according to the difference between a speed command value that sets the rotational speed of the synchronous motor and a speed detection value that indicates the speed of the synchronous motor, wherein the synchronous motor control device comprises 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 which is a limit value of the q-axis current applied to the synchronous motor, The problem is 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 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 the input to the inverter circuit, wherein the q-axis current command limit processing unit limits the q-axis current command value based on the q-axis current command limit value. [Effects of the Invention]

[0014] Even if the power supply voltage of the synchronous motor control device drops, 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. [Brief explanation of the drawing]

[0015] [Figure 1] This is a block diagram of a synchronous motor control device in Embodiment 1 of the present invention. [Figure 2] This is a block diagram of the q-axis current limit value generation processing unit in Embodiment 1 of the present invention. [Figure 3] This flowchart shows the processing of the q-axis current limit value generation processing unit in Embodiment 1 of the present invention. [Figure 4] This is an example of the operation of the q-axis current limit value generation processing unit in Embodiment 1 of the present invention. [Figure 5] This is an example of the torque-speed characteristics of a synchronous motor. [Figure 6] This is an example of torque-speed characteristics of a synchronous motor when countermeasures against a sudden drop in output torque caused by voltage saturation are implemented by current limiting using a linear function. [Figure 7] This is an explanatory example of the sudden output torque drop phenomenon caused by voltage saturation. [Figure 8] This is an example of torque-speed characteristics of a synchronous motor when countermeasures against a sudden drop in output torque caused by voltage saturation are implemented according to Embodiment 1. [Figure 9] This is a second example of the q-axis current limit value generation processing unit according to Embodiment 1. [Figure 10] This is an example of a current limit value table in Embodiment 2 of the present invention. [Figure 11] This is an example of the q-axis current limit value generation processing unit in Embodiment 2 of the present invention. [Figure 12] This is another example of the q-axis current limit value generation processing unit in Embodiment 2 of the present invention. [Figure 13] This is an example of a current limit value table storing current limit values for each of a plurality of synchronous motors.

Mode for Carrying Out the Invention

Examples

[0016] Hereinafter, examples of the present invention will be described with reference to the drawings. The examples are exemplifications for explaining the present invention, and are appropriately omitted and simplified for clarifying the description. The present invention can also be implemented in various other forms.

[0017] Unless otherwise particularly limited, 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] Examples of various types of information may be described using terms such as "table," "list," and "queue," but these types of information may also be represented by other data structures. For example, various types of information such as "XX table," "XX list," and "XX queue" may be referred to as "XX information." When describing identification information, terms such as "identification information," "identifier," "name," "ID," and "number" are used, and these terms are interchangeable.

[0020] When there are multiple components with the same or similar function, they may be described using the same symbol but with different subscripts. Furthermore, when it is not necessary to distinguish between these multiple components, the subscripts may be omitted in the description.

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

[0022] Therefore, the entity that performs the processing by executing the program may be a processor. Similarly, the entity that performs the processing by executing the program may be a controller, device, system, computer, or node having a processor. The entity that performs the processing by executing the program may be an arithmetic unit, and may include dedicated circuits that perform specific processing.

[0023] Here, "dedicated circuitry" refers to, for example, FPGAs (Field Programmable Gate Arrays), ASICs (Application Specific Integrated Circuits), and CPLDs (Complex Programmable Logic Devices).

[0024] The program may be installed on the computer from its program source. The program source may be, for example, a program distribution server or a storage medium readable by the computer.

[0025] If the program source is a program distribution server, the program distribution server includes a processor and memory resources to store the program to be distributed, and the processor of the program distribution server may distribute the program to other computers.

[0026] Furthermore, in the embodiment, two or more programs may be implemented as one program, or one program may be implemented as two or more programs.

[0027] Figure 1 is a block diagram showing the basic configuration of a synchronous motor control device, which is a first embodiment of the present invention.

[0028] The synchronous motor control device includes a synchronous motor 1, a position detector 2 for detecting the rotor position θm of the synchronous motor 1, an inverter circuit 3 for applying 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 takes the three-phase power supply as input and applies a DC voltage Vdc to the inverter circuit 3.

[0029] Furthermore, the q-axis current limit value generation processing unit 9 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 the q-axis current command value iqref based on the output of the subtractor 7. The q-axis current limit value generation processing unit 9 takes the speed detection value Nm and the DC voltage Vdc from the speed detection calculation unit 6 as inputs and outputs the q-axis current limit value iq_lim_out.

[0030] Furthermore, the system includes a current command limit processing unit 10 that limits the q-axis current command value iqref, which is the output of the speed control unit 8, by 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 generation unit 11 that outputs the d-axis current command value idref_out according to 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 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, which are inputs to the inverter circuit 3.

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

[0033] Figure 5 shows the torque-speed characteristics. In Figure 5, the dashed line shows the design torque-speed characteristics of the synchronous motor 1 that utilizes reluctance torque, when the decrease in the DC voltage Vdc output by the converter circuit 5 is not considered (here, Vdc is fixed at 270[V]).

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

[0035] However, when the DC voltage Vdc becomes low (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 in a nonlinear manner from the voltage saturation starting point, as shown by the solid line in Figure 5.

[0036] The voltage saturation phenomenon, which is the cause of this speed reduction, will be explained using Figure 7.

[0037] Figure 7 shows the voltage vector diagrams 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 voltage that the inverter circuit can output is represented by the dotted circle.

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

[0039] To reduce voltage saturation, it is necessary to control the length of the voltage vector so that it stays within this circle, as shown by voltage vector A.

[0040] Therefore, the q-axis current limit value generation processing unit 9 determines the limit value of the current command (q-axis current limit value) based on the maximum outputtable magnetic flux, and controls the voltage vector so that its length fits 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 instruct the q-axis current command limit processing unit using the following method.

[0042] In the q-axis current limit value generation processing unit 9, the maximum magnetic flux φ1max is derived using the DC voltage Vdc applied to the inverter circuit and the speed detection value of the synchronous motor as parameters, and the q-axis current limit value iq_lim_out is derived 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 relationship (2). In equation (2) below, 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] The waveform of f(φ1max) is as shown in Figure 4.

[0047] Next, the 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 explained using Figures 2 and 3.

[0048] In the q-axis current limit value generation processing unit 9, the effective voltage Vdcr is obtained by multiplying the DC voltage Vdc by a coefficient 91 (S1), the electrical angular velocity ωe is obtained by multiplying the motor speed detection value Nm by a coefficient 92 (S2), and the maximum magnetic flux (φ1max) is obtained by dividing the effective voltage Vdcr by the electrical angular velocity ωe in the divider 93 (S3). This result φ1max is input to the 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 being driven, for example, if the unit of the speed detection value Nm is [min -1 If ] then the electric angle ωe[rad / s] is, ωe[rad / s]=K×Nm[min -1 ], K = number of poles × (2π / 60), and number of poles = 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 to make voltage saturation less likely to occur by providing a voltage margin Vx, as shown in Figure 9.

[0051] Specifically, the effective voltage Vdcr is obtained by multiplying the DC voltage Vdc by a coefficient 91, (Vdcr-Vx) is obtained by subtracting the voltage margin Vx from Vdcr, the electrical angular velocity ωe is obtained by multiplying the motor speed detection value Nm by a coefficient 92, and φ1max (=(Vdcr-Vx) / ωe) is obtained using the divider 93.

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

[0053]

number

[0054] As described above, by performing current command limit processing according to the q-axis current limit value iq_lim_out derived by the q-axis current limit value generation processing unit 9, voltage saturation will 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] In other words, as shown by the solid line in the torque-speed characteristic of Figure 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 Example 1, 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 complex, and there is a challenge in that the calculation is too complex for the microcontrollers (microprocessors) used in actual devices, making it difficult to implement without using high-performance microcontrollers.

[0058] To solve this problem, as shown in Figure 10, the storage unit may be equipped with a current limit value table in table format, which is a two-dimensional array representation data (maximum magnetic flux-q-axis current map data 96) that has been precalculated to show the relationship between the maximum magnetic flux (φ1max) calculated from the DC voltage value (Vdc) and the driving electrical angular velocity of the synchronous motor and the q-axis current limit value. By having the q-axis current limit value generation unit equipped with a current limit value table, the computational load can be reduced.

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

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

[0061] Alternatively, the system may be configured as shown in Figure 11 to calculate the maximum magnetic flux (φ1max) from the DC voltage value (Vdc) and the speed detection value (Nm), and then use the obtained maximum magnetic flux (φ1max) to refer to the maximum magnetic flux-q axis current map data 96 and determine the q axis current limit value iq_lim_out.

[0062] The relationship between the q-axis current limit value and the 2D array representation data (maximum magnetic flux-q-axis current map data 96), which is calculated in advance, must be set for each synchronous motor under control. The current limit value table may also have 2D array representation data for each synchronous motor that the control device controls. 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 value for each synchronous motor from synchronous motor 1 to synchronous motor m.

[0063] Here, as shown in Figure 12, the maximum magnetic flux-q axis current map data 96 may be modified (downloaded) using a PC 15 connected to the synchronous motor control device via a network. This configuration allows for remote updating of the two-dimensional array representation data, improving maintainability.

[0064] Furthermore, by connecting the PC15 to the synchronous motor control device installed at the site and modifying 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, by providing a memory slot in the synchronous motor control device for reading the maximum magnetic flux-q axis current map data 96, it becomes possible to update the maximum magnetic flux-q axis current map data 96 without using the PC 15.

[0066] The maximum magnetic flux-q-axis current map data 96 for each controlled synchronous motor stored on PC15 can be downloaded to the synchronous motor control device as is, but the storage capacity can be reduced by downloading only the map data corresponding to the controlled synchronous motor being driven at any given time.

[0067] Furthermore, by providing a memory chip containing only the maximum magnetic flux-q-axis current map data 96, and replacing only that memory chip when the motor being controlled changes, it is possible to obtain a q-axis current limit value suitable for the motor being controlled. [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 unit, 91, 92 Coefficients, 93 Divider, 94 Function, 95 Adder, 96 Maximum magnetic flux-Q-axis current map data, 10 Current command limit 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 converter circuit that takes a three-phase power supply as input and outputs a DC voltage applies the DC voltage to an inverter circuit that applies a three-phase voltage command to a synchronous motor. A synchronous motor control device comprising: a speed control unit that generates a q-axis current command value according to the difference between a speed command value that sets the rotational speed of the synchronous motor and a speed detection value that indicates the 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, which is a limit value of the q-axis current applied to the synchronous motor. A d-axis current command generation unit generates a d-axis current command value from the q-axis current limiting command value and the 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, The system includes 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 which is the input to the inverter circuit. The q-axis current command limit processing unit limits the q-axis current command value based on the q-axis current limit value. A synchronous motor control device 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 defined as φ1max (= (Vdcr - Vx) / ωe), where Lq is the q-axis inductance, Ld is the d-axis inductance, and Ke is the induced voltage coefficient.

2. In the synchronous motor control device of 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, The q-axis current limit value generation unit 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 uses the maximum magnetic flux to obtain the q-axis current limit value. A synchronous motor control device characterized by limiting the q-axis current command value in the q-axis current command limit processing unit using the obtained q-axis current limit value.

3. In the synchronous motor control device of claim 2, A synchronous motor control device characterized in that the current limit value table used in the q-axis current limit value generation unit can be rewritten by an externally connected device.

4. In the synchronous motor control device according to claim 1, The system receives the current limit value table corresponding to the synchronous motor to be controlled from a server that stores multiple current limit value tables corresponding to the maximum magnetic flux of multiple synchronous motors. It includes a storage unit that stores the received current limit value table, The q-axis current limit value generation unit 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. A synchronous motor control device characterized by limiting the q-axis current command value in the q-axis current command limit processing unit using the obtained q-axis current limit value.

5. In the synchronous motor control device according to claim 1, It includes a memory unit that stores multiple current limit value tables corresponding to the maximum magnetic flux of multiple synchronous motors, The q-axis current limit value generation unit 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. A synchronous motor control device characterized by limiting the q-axis current command value in the q-axis current command limit processing unit using the obtained q-axis current limit value.

6. A converter circuit that takes a three-phase power supply as input and outputs a DC voltage applies the DC voltage to an inverter circuit that applies a three-phase voltage command to a synchronous motor. A speed command value that sets the rotational speed of the synchronous motor and a speed indicator that shows the speed of the synchronous motor. A control method for a synchronous motor control device comprising a speed control unit that generates a q-axis current command value according to the difference from the output value, The 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 the q-axis current limit value, which is the limit value of the q-axis current applied to the synchronous motor. The d-axis current command generation unit generates a d-axis current command value from the q-axis current limit command value and the magnetomotive force phase difference angle. The q-axis current control unit generates a q-axis voltage command value based on the q-axis current limit command value. The d-axis current control unit generates a d-axis voltage command value based on the d-axis current command value. The 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 the input to the inverter circuit. A control method for a synchronous motor control device, characterized in that the q-axis current command limit processing unit limits the q-axis current command value based on the q-axis current limit value, and the q-axis current limit value iq_lim_out is obtained by the following formula. Here the magnetic flux φ1 is φ1max is defined as φ1max (= (Vdcr - Vx) / ωe), where Lq is the q-axis inductance, Ld is the d-axis inductance, and Ke is the induced voltage coefficient.

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