JP6869130B2 - Inverter control device and control method for driving a synchronous motor - Google Patents

Description

The present invention relates to a control device and a control method for an inverter for driving a synchronous motor, and more particularly to a vector control method in a field weakening region of the synchronous motor.

Regarding the vector control method in the field weakening field of the synchronous electric motor, as a main conventional technique, a method of performing proportional calculation in a d-axis and q-axis current control system using a table-shaped d-axis current command value (Patent Document 1). , A method of proportionally and integrating the deviation between the electric motor terminal voltage obtained from each of the d-axis and q-axis voltage commands output from the current control unit and the command value of the terminal voltage to obtain a d-axis current command (Patent Document). 2), and there is a method (Patent Document 3) in which the integrated calculation value of the deviation between the output voltage and the output voltage command obtained by the voltage vector calculation unit is used as the d-axis current command value. Further, when exiting the field weakening domain, there is a method of terminating the vector control of the field weakening domain by converging the integration term of the integrated current control system to zero and stopping the integrated current control (Patent Document 4).

Japanese Unexamined Patent Publication No. 8-182398 JP-A-2002-95300 Japanese Unexamined Patent Publication No. 2006-20411 Japanese Unexamined Patent Publication No. 2002-325298

The vector control method in the prior art described above has the following problems.
A. In the technique described in Patent Document 1, since the current control is a proportional calculation method, the current according to the current command is not generated and the torque accuracy is deteriorated.
B. The technique described in Patent Document 2 tends to deteriorate the torque response because the d-axis current command is generated slowly.
C. In the technique described in Patent Document 3, since the d-axis current command accumulates the integral value by the integral calculation method, the technique of Patent Document 4 can be applied to make the integral term zero, but the voltage command is In applications where voltage limitation is applied and cases where it is not applied repeatedly, the field weakening control system may cause hunting, which reduces the stability of control.
D. Since the techniques described in Patent Documents 1 to 3 do not consider the influence of voltage fluctuation of the inverter DC power supply, the d-axis current command and the q-axis current command operate in applications where the voltage of the inverter DC power supply fluctuates. Control stability is reduced because it is not optimal for the state.

Therefore, the present invention provides a control method and a control device for realizing highly accurate, highly responsive and stable torque control of a synchronous motor even if the DC power supply of the inverter causes voltage fluctuations in the field weakening control range.

In order to solve the above problems, the inverter control device according to the present invention includes a current command generator that generates a d-axis current command and a q-axis current command from a torque command, a frequency command, and a DC power supply voltage detection value of the inverter. Based on the electrical constant and frequency command of the synchronous motor, the d-axis voltage command to make the difference between the d-axis current command and the d-axis current detection value zero, and the difference between the q-axis current command and the q-axis current detection value are zero. The output voltage command for the current control unit that calculates the q-axis voltage command and the d-axis voltage command and the output voltage command for the inverter that calculates from the q-axis voltage command is below the upper limit set according to the DC power supply voltage detection value. It is equipped with a voltage limiting unit that limits the voltage, and the current control unit calculates the d-axis voltage command using proportional / integrated control that has a frequency characteristic with a finite DC gain, and has a frequency characteristic with an infinite DC gain. It is characterized in that the q-axis voltage command is calculated using proportional / integral control.

According to the present invention, it is possible to realize highly accurate, highly responsive and stable torque control of a synchronous motor even if the DC power supply voltage of the inverter fluctuates in the field weakening control range.

FIG. 1 is a diagram showing a configuration of a control device for a synchronous motor driving inverter according to a first embodiment of the present invention. FIG. 2 is a vector diagram showing a calculation operation of the voltage limiting unit in the control device of the first embodiment. FIG. 3 is a diagram illustrating a current control unit in the control device of the first embodiment. FIG. 4 is a diagram showing a configuration of a control device for a synchronous motor driving inverter according to a second embodiment of the present invention. FIG. 5 is a diagram illustrating a field weakening command calculation unit in the control device of the second embodiment.

Hereinafter, Examples 1 and 2 will be described in detail as embodiments of the present invention with reference to the drawings. In the following description, the components common to each figure are designated by the same reference numerals, and the description of the overlapping components will be omitted.

FIG. 1 is a diagram showing a configuration of a control device for a synchronous motor driving inverter according to a first embodiment of the present invention.
The permanent magnet synchronous motor 1 (hereinafter abbreviated as “PM motor 1”) receives AC power from the inverter 2.
The inverter 2 converts the DC power of the DC power supply 21 into a three-phase AC voltage proportional to the ^{voltage commands Vu *} , Vv ^*, and Vw ^{* and outputs the voltage.}

The current detector 3 detects the phase AC currents Iu and Iw (note that the current detector 3 is not limited to the U phase and the W phase, and may be any two of the three phases).
The DC voltage detector 4 detects the DC voltage value Edc of the DC power supply 21.
The speed / phase calculation unit 5 processes the detector signal when the rotation phase / speed detector is used, and estimates the position / speed when the position / speed detector is not used. The phase command θc ^* and the frequency command ω1 ^* are calculated and output.

The coordinate conversion unit 6 outputs the current detection values Id and Iq of the d-axis and the q-axis based on the detection values of the phase AC currents Iu and Iw and the rotation phase command θc ^*.
The d-axis current command generator 7 and the q-axis current command generator 8 output the d-axis and q-axis current commands Id ^* and Iq ^{* from the torque command τ, the frequency command ω1 *, and the DC voltage detection value Edc.}

Based on the electric constant of the PM motor 1 and the frequency command ω1 ^* , the current control unit 9 sets the difference between the d-axis current command Id ^* and the d-axis current detection value Id to zero, and the q-axis current command Iq. ^* and as the difference between the q-axis current detection value Iq becomes zero (i.e., so Id approaches Id ^*, and as Iq approaches Iq ^*), calculates the voltage command Vd0 ^* and Vq0 ^* And output.

Here, the current control unit 9 is composed of a d-axis current command calculation unit 12, a q-axis current command calculation unit 13, and a voltage vector calculation unit 14, as shown in the dotted line frame at the bottom of FIG. This configuration is the same as the configuration of the second embodiment (inside the dotted line frame in FIG. 4) described later.
The d-axis current command calculation unit 12 receives the second d-axis current command Id according to the difference between ^{the first d-axis current command Id *} , which is the output of the d-axis current command generator 7, and the d-axis current detection value Id. Output ^**.
The q-axis current command calculation unit 13 has the second q-axis current command Iq according to the difference between ^{the first q-axis current command Iq *} , which is the output of the q-axis current command generator 8, and the q-axis current detection value Iq. Output ^**.
Voltage vector computation section 14, the electrical constants of the PM motor calculates the voltage command Vd0 ^* and Vq0 ^* based on the second current command ^{Id **} and ^{Iq **} and frequency command .omega.1 *.

Voltage limiting unit 10, a limit on the voltage command Vd0 ^* and Vq0 ^*. The detailed operation mode will be described later.
The coordinate conversion unit 11 outputs three-phase AC voltage commands Vu ^* , Vv ^*, and Vw ^* from the voltage-limited voltage commands Vd1 ^* and Vq1 ^* and the rotation phase command θc ^*.

Next, the operation mode of the voltage limiting unit 10 which is one of the features of the present invention will be described.
The voltage limiting unit 10 includes a polar coordinate converter 101, an upper limit limiter 102, and an inverse polar coordinate converter 103. Polar converter 101, the respective voltage command Vd0 ^* and Vq0 ^* of the dq-axis are converted into amplitude V1 ^* and the phase δ in polar coordinates. The upper limit limiter 102 limits the amplitude V1 ^* . The polar coordinate converter 103 converts the output value V1L ^* of the upper limit limiter 102 and the phase δ output by the polar coordinate converter 101 into the voltage commands Vd1 ^* and Vq1 ^{* at the} dq coordinates. Details will be described below.

Polar converter 101, an amplitude V1 ^* and the phase [delta], using a voltage command Vd0 ^* and Vq0 ^* inputted from the current controller 9, obtained by Equation (1).

^{The upper limit limiter 102 has a function of limiting the output of the amplitude V1 *} obtained by the polar coordinate converter 101 with the preset limit value V1MAX as the upper limit. This limit value V1MAX is preset according to the DC power supply voltage Edc of the inverter 2.

When the amplitude V1 ^* does not exceed the preset limit value V1MAX, the upper limit limiter 102 ^{outputs V1 *} obtained by the equation (1) as it is (V1L ^* = V1 ^* ). That is, voltage command Vd1 ^* and Vq1 inverse polar converter 103 followed outputs ^*, respectively, is equal to the voltage command Vd0 ^* and Vq0 ^* from the current controller 9.

On the other hand, when the amplitude V1 ^* exceeds the preset limit value V1MAX, the upper limit limiter 102 limits V1 ^* to V1MAX and outputs it (V1L ^* = V1MAX). The inverse polar converter 103 which received this limited output will output a different new voltage command Vd1 ^* and Vq1 ^* the voltage command Vd0 ^* and Vq0 ^* from the current controller 9.

FIG. 2 is a vector diagram showing the calculation operation of the voltage limiting unit 10. The circle drawn by the broken line in FIG. 2 is a range that limits the voltage, and the voltage command is restricted so as to be within this circle. That is, the size of the radius of this circle is equal to the size of the limit value V1MAX.
The left figure of FIG. 2 shows a case where V1 obtained by the equation (1) exceeds the limit V1MAX (V1 ^{*> V1MAX).} In this case, as shown in the right figure of FIG. 2, the amplitude is changed ^{from V1 * to V1MAX without changing the phase δ, and the voltage command Vd1 *} (= V1MAX) which is the dq axis component of the vector (V1MAX, δ).・ Cosδ) and Vq1 ^* (= V1MAX ・ sinδ) are calculated.

By limiting the amplitude of the voltage command, if the voltage applied to the motor from the inverter is insufficient with respect to the induced voltage of the motor, a negative d-axis current is generated. Since the current control unit (particularly, the d-axis current control unit) operates in an attempt to control this negative d-axis current so as to match the d-axis current command, the current control unit performs normal proportional / integral control (hereinafter, "" When "PI control" is performed, the negative d-axis current required for field weakening control does not flow.

Therefore, one of the features of the present invention is that by adjusting the gain of the current control unit, the field weakening control can be performed without providing the field weakening control unit. The operation mode will be described.

As described above, the current control unit 9 ^{so that the difference between the d-axis current command Id *} and the d-axis current detection value Id becomes zero, and the difference between the q-axis current command Iq ^* and the q-axis current detection value Iq. Is controlled to be zero (that is, Id approaches Id * and Iq ^{approaches Iq *} ), but the present invention is characterized in the control mode.
That is, as shown in FIG. 3, the present invention applies the normal PI control to the q-axis current control (characteristic shown in the lower right of FIG. 3), but applies the normal PI control to the d-axis current control. Is different, and a control having a frequency characteristic in which the DC gain (ω = 0) is finite is applied (characteristic shown in the upper right of FIG. 3).

In normal current control, PI control with an infinite DC gain is applied in order to make the steady-state error zero, so that ^{the difference between the d-axis current command Id *} and the d-axis current detection value Id becomes zero. Control. As a result, even if the voltage is limited, the negative d-axis current required for field weakening control may be insufficient. Therefore, as shown in the upper right of FIG. 3, the DC gain in the d-axis current control of the current control unit 9 is set to finite so that the steady-state deviation remains. Then, although the steady-state deviation remains, the value can be appropriately set by adjusting the value of the DC gain. As a result, the d-axis current required for field weakening control can be passed.

As described above, in order to give priority to torque control in the field weakening domain, in q-axis current control, the difference in torque current is controlled to zero by normal PI control. On the other hand, in the d-axis current control, although the deviation remains, since the DC gain is finite, the negative d-axis current required for the field weakening control flows, so that the field weakening is weakened without providing the field weakening control unit. Field control can be performed. Therefore, since the calculation time in the field weakening control unit does not occur, highly responsive control can be realized.

Next, the d-axis current command generator 7 and the q-axis current command generator 8, which are other features of the present invention, will be described. The voltage of the DC power supply 21 that supplies DC power to the inverter 2 is detected by the DC voltage detector 4, and the relationship between the detected value Edc and the output voltage V1 of the inverter 2 is expressed by the equation (2).

Therefore, when the voltage Edc of the DC power supply 21 fluctuates, the output voltage V1 of the inverter 2 changes. Therefore, in order to optimally operate the PM motor 1, the fluctuation of the voltage Edc of the DC power supply 21 during operation is taken into consideration. , D-axis current and q-axis current need to be supplied.

Therefore, in order to obtain the optimum d-axis current and q-axis current for the operating state in consideration of the fluctuation of the voltage Edc of the DC power supply 21, the d-axis current command generator 7 and the q-axis current command generator 8 are, for example, an electromagnetic field. The optimum d-axis current and q-axis current for the output torque of the PM motor are obtained by analysis, and the d-axis current and q-axis current obtained thereby are used as the torque and rotation frequency of the PM motor 1 and the voltage of the DC power supply 21. Is prepared in advance as a function with.

The d-axis current command generator 7 and the q-axis current command generator 8 use the functions prepared in this way to obtain the d-axis current and the q-axis with respect ^{to the torque command τ *} , the frequency command ω1 ^{*, and the DC power supply voltage detection value Edc.} Obtain the current, and use both as the d-axis current command and the q-axis current command. In this way, by considering the fluctuation of the DC power supply voltage that supplies DC power to the inverter, it is possible to provide the optimum d-axis current and q-axis current in the operating state of the PM motor. Therefore, highly accurate torque control can be realized.

As described above, according to the first embodiment of the present invention, even if the voltage of the DC power supply that supplies DC power to the inverter fluctuates in the field weakening control range of the permanent magnet synchronous motor (PM motor), it is highly accurate and highly accurate. Responsive and stable torque control can be realized.

In the first embodiment, by applying proportional / integral control (PI control) in which the DC gain has a finite frequency characteristic in the d-axis current control, the field weakening control is realized without providing the field weakening control unit. To do. At this time, since a steady deviation remains in the d-axis current control, the d-axis current Id and the d-axis current command Id ^* do not match, and the current cannot be generated according to the current command. Therefore, there is a possibility that the torque accuracy will be insufficient in applications where the torque accuracy is strict.

On the other hand, if the current control described in Patent Document 3 is performed, there is no steady deviation of the d-axis current control, and the current can be generated according to the current command, so that the torque accuracy does not deteriorate. However, in field weakening control, hunting may occur because the integrated value is accumulated by the integral calculation method.

On the other hand, as shown in Patent Document 4, it is conceivable to apply a means for stopping the integral control by converging the integral term of the integral control system to zero. However, when the amplitude of the voltage command is close to the voltage limit value, the amplitude of the voltage command is limited or not limited to the voltage limit value, so that the control system may not be stabilized.

Therefore, regardless of the presence or absence of voltage limitation, the control system is stabilized by continuously performing field weakening control by one means. The second embodiment of the present invention is characterized in that, as will be described next, a weakening field command calculation unit that continuously performs the field weakening control is provided, and the gain of the field weakening control is adjusted.

FIG. 4 is a diagram showing a configuration of a control device for a synchronous motor driving inverter according to a second embodiment of the present invention.
The second embodiment is characterized in that the field weakening command calculation unit based on the feedback control method employs a method in which the DC gain of proportional / integral control is finite.

In FIG. 4, 1 to 14, 21 and 101 to 103 are the same as the configuration and function of the control device for the synchronous motor driving inverter according to the first embodiment shown in FIG. However, the d-axis current command calculation unit 12 ^{detects the added value of the first d-axis current command Id * and the weakening field current command ΔId *} , which is the output of the weakening field command calculation unit 15 described later, and the d-axis current detection. The input mode is different from that of the d-axis current command calculation unit 12 of the first embodiment in that the second d-axis current command Id ^{** is output according to the difference from the value Id.}

The field weakening command calculation unit 15 calculates the field weakening current command ΔId ^{* from the difference between the output voltage command V1 *} _ref and the output voltage value V1c ^* in the field weakening region.
Output voltage calculating unit 16 calculates a voltage command Vd0 ^* and Vq0 ^* output voltage value of the inverter 2 from V1c ^*.

Next, the basic operations of voltage control and phase control in the vector control method using the field weakening command calculation unit 15, which is characterized by the second embodiment, will be described.
Output voltage calculating unit 16 uses the d-axis and q-axis voltage command Vd0 ^* and Vq0 ^*, calculates the output voltage value based on the equation (3) V1c ^*.

The field weakening command calculation unit 15 performs a field weakening current command ΔId by proportional / integration calculation so that ^{the output voltage value V1c *} of the output voltage calculation unit 16 matches the output voltage command V1 ^* _{ref in the field weakening region.} Calculate ^*. Further, the weakening field current command ΔId ^{* and the first d-axis current command Id *} output by the d-axis current command generator 7 are added to obtain a d-axis current command.

ここで、Ｒ１^＊は抵抗の設定値、Ｌｄ^＊はｄ軸インダクタンスの設定値、Ｌｑ^＊はｑ軸インダクタンスの設定値、Ｋｅ^＊は誘起電圧定数の設定値である。 The voltage vector calculation unit 14 uses the second d-axis and q-axis current commands Id ^** and Iq ^** and the motor constants, and uses the d-axis and q-axis voltage commands Vd0 ^* and the q-axis voltage commands Vd0 * based on the equation (4). Calculate Vq0 ^* .

Here, R1 ^* is a resistance set value, Ld ^* is a d-axis inductance set value, Lq ^* is a q-axis inductance set value, and Ke ^* is an induced voltage constant set value.

Further, the speed / phase calculation unit 5 processes the detector signal when the rotation phase / speed detector is used, and the position when the position / speed detector is not used, as in the first embodiment. -By estimating the speed, the rotation phase command θc ^* and the frequency command ω1 ^* are calculated and output.

Next, with reference to FIG. 5, the field weakening command calculation unit 15 by the feedback control method, which is a feature of the second embodiment of the present invention, will be described. FIG. 5 is a diagram illustrating a field weakening command calculation unit 15 in the second embodiment.

The field weakening command calculation unit 15 is composed of a proportional / integral calculation unit 151 and a limiter calculation unit 152. The proportional / integral calculator 151 has a frequency characteristic with a finite DC gain. The relationship between the gain and the frequency ω shown in the lower part of FIG. 5 is a characteristic of the gain with respect to the frequency of the input signal to the proportional / integral arithmetic unit 151. The limiter calculator 152 limits the output when the input signal is positive, as shown in the illustrated characteristics.

That is, the field weakening command calculation unit 15 is a proportional / integration calculator 151 having a frequency characteristic in which the DC gain is finite with respect to the difference between the ^{output voltage command V1 *} _ref and the output voltage value V1c ^{* in the field weakening region.} The proportional / integral calculation is performed by, and the calculated value is output as the field weakening current command ΔId ^* only when the above difference becomes negative by passing through the limiter calculator 152 (V1c ^* > V1 ^* _ref).

As shown in FIG. 5, in the second embodiment, a control having a frequency characteristic in which the DC gain (ω = 0) is finite is applied to the field weakening control, unlike the normal PI control.
In normal PI control, PI control with an infinite DC gain is applied in order to make the steady-state error zero. However, when the voltage limit is applied, the above-mentioned hunting may occur. Therefore, in the second embodiment, the DC gain in the field weakening control is set to a finite value so that the steady-state deviation remains. However, although the steady-state deviation remains, the value can be appropriately set by adjusting the value of the DC gain (ω = 0). Therefore, although the deviation remains in the field weakening control, hunting is suppressed by making the DC gain finite, and the control system can be stabilized.

As described above, according to the second embodiment, the torque control with high accuracy and high response can be obtained in the field weakening control by the control device of the synchronous motor. Further, by using the field weakening command calculation unit 15, the control system can be stabilized even if the execution and cancellation of the voltage limitation are repeated (that is, the above-mentioned concern about the occurrence of hunting). Further, since the current can be generated according to the current command, highly accurate torque control can be realized.

Here, when high torque is required during torque control operation, it is necessary to pass a large current commensurate with the torque. When high torque is required for continuous time, in the PM motor, the winding resistance value R1 inside the PM motor increases with time due to heat generation due to the energizing current. Then, since the resistance set value calculated by the voltage vector calculation unit and the actual resistance value do not match (see equation (4)), the voltage required for the motor cannot be supplied. As a result, there is a concern that the current required for torque generation does not flow and the torque becomes insufficient.

Therefore, as in Examples 1 and 2 of the present invention, by arranging the current command calculation units 12 and 13 on the upstream side of the voltage vector calculation unit 14, the output voltage is controlled so as to match the PM motor current with the current command. Will be done. As a result, it is possible to provide a control device for a synchronous motor that does not cause torque shortage from a low speed range without being affected by fluctuations in the PM motor constant.

The present invention is not limited to the above embodiments (Examples 1 and 2), and includes various modifications. For example, the above-described embodiments (Examples 1 and 2) have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. The function to be used may be a table. It is also possible to add or replace a part of the configurations of each embodiment (Examples 1 and 2) with other configurations.

Further, the method of obtaining the current command using a function is suitable for controlling the embedded magnet type PM motor because the fluctuation of the motor constant due to magnetic saturation can be taken into consideration.

Finally, the control device for the inverter for driving a synchronous motor according to the present invention has a wide range of applications such as a compressor, a spindle motor, a heating / cooling device, a conveyor, an elevator, an extruder, and a machine tool for railway vehicles and industrial use. It is a thing.

1 ... Permanent magnet synchronous motor (PM motor), 2 ... Inverter, 3 ... Current detector,
4 ... DC voltage detector, 5 ... Speed / phase calculation unit, 6 ... Coordinate conversion unit,
7 ... d-axis current command generator, 8 ... q-axis current command generator, 9 ... current control unit,
10 ... Voltage limiting unit, 11 ... Coordinate conversion unit, 12 ... d-axis current command calculation unit,
13 ... q-axis current command calculation unit, 14 ... voltage vector calculation unit, 15 ... weak field command calculation unit,
16 ... Output voltage calculation unit, 21 ... DC power supply, 101 ... Polar coordinate converter,
102 ... upper limit limiter, 103 ... inverse polar coordinate converter, 151 ... proportional / integral calculator,
152 ... Limiter calculator

Claims (6)

It is an inverter control device that drives a synchronous motor.
A current command generator that generates a d-axis current command and a q-axis current command from the torque command, frequency command, and DC power supply voltage detection value of the inverter.
Based on the electric constant of the synchronous motor and the frequency command, the d-axis voltage command for making the difference between the d-axis current command and the d-axis current detected value zero, and the q-axis current command and the q-axis current detected value. A current control unit that calculates the q-axis voltage command to make the difference between
The d-axis voltage command and the output voltage command for the inverter calculated from the q-axis voltage command are provided with a voltage limiting unit that limits the output voltage command to the upper limit value or less set according to the DC power supply voltage detection value.
The current control unit calculates the d-axis voltage command using the proportional / integral control having a frequency characteristic having a finite DC gain, and uses the proportional / integral control having a frequency characteristic having an infinite DC gain. An inverter control device for calculating the q-axis voltage command. It is an inverter control device that drives a synchronous motor.
A current command generator that generates a d-axis current command and a q-axis current command from the torque command, frequency command, and DC power supply voltage detection value of the inverter.
Based on the electric constant of the synchronous motor and the frequency command, the d-axis voltage command and the q-axis for making the difference between the added value of the d-axis current command and the field weakening current command and the d-axis current detected value zero. A current control unit that calculates the q-axis voltage command to make the difference between the current command and the q-axis current detection value zero, and
A voltage limiting unit that limits the output voltage command for the inverter calculated from the d-axis voltage command and the q-axis voltage command to or less than the upper limit set according to the DC power supply voltage detection value.
A field weakening command calculation unit that calculates the field weakening current command from the difference between the output voltage command in the field weakening region and the output voltage of the inverter calculated from the d-axis voltage command and the q-axis voltage command. Prepare,
The field weakening command calculation unit is an inverter control device that calculates the field weakening current command using proportional / integral control having a frequency characteristic in which the DC gain is finite. The inverter control device according to claim 1 or 2.
The current command generator prepares a function or table in which the torque and rotation frequency of the synchronous electric motor and the DC power supply voltage of the inverter are variables as a function or table for giving the d-axis current and the q-axis current, and prepares the function or table. An inverter control device for generating the d-axis current command and the q-axis current command with respect to the torque command, the frequency command, and the DC power supply voltage detected value of the inverter from a table. It is a control method of the inverter that drives the synchronous motor.
From the torque command, the frequency command, and the DC power supply voltage detection value of the inverter, the first step of generating the d-axis current command and the second step of generating the q-axis current command, and
A third step of calculating a d-axis voltage command for making the difference between the d-axis current command and the d-axis current detected value zero based on the electric constant of the synchronous motor and the frequency command, and the q-axis current command. The fourth step of calculating the q-axis voltage command to make the difference between and the q-axis current detection value zero, and
It has a fifth step of limiting the output voltage command to the inverter calculated from the d-axis voltage command and the q-axis voltage command to or less than the upper limit value set according to the DC power supply voltage detection value.
In the third step, the d-axis voltage command is calculated using proportional / integral control having a frequency characteristic in which the DC gain is finite.
The fourth step is a control method for an inverter, wherein the q-axis voltage command is calculated by using proportional / integral control having a frequency characteristic in which the DC gain is infinite. It is a control method of the inverter that drives the synchronous motor.
From the torque command, the frequency command, and the DC power supply voltage detection value of the inverter, the first step of generating the d-axis current command and the second step of generating the q-axis current command, and
Based on the electric constant of the synchronous motor and the frequency command, the d-axis voltage command for calculating the difference between the added value of the d-axis current command and the field weakening current command and the d-axis current detection value is calculated. The third step, the fourth step of calculating the q-axis voltage command for making the difference between the q-axis current command and the q-axis current detected value zero, and the fourth step.
The fifth step and the d-axis for calculating the weakening field current command from the difference between the output voltage command in the field-weakening region and the output voltage of the inverter calculated from the d-axis voltage command and the q-axis voltage command. The sixth step of limiting the output voltage command to the inverter calculated from the voltage command and the q-axis voltage command to the upper limit value or less set according to the DC power supply voltage detection value, and
With
Wherein in the fifth step, the inverter control method characterized that you calculating the weak field current command using a proportional-integral control with the frequency characteristic DC gain is finite. The inverter control method according to claim 4 or 5.
In the first step and the second step, as a function or table for giving the d-axis current and the q-axis current, a function or table having the torque and rotation frequency of the synchronous motor and the DC power supply voltage of the inverter as variables is used. A method for controlling an inverter, which comprises preparing, generating the torque command, the frequency command, the d-axis current command for the DC power supply voltage detection value of the inverter, and the q-axis current command from the function or the table.

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