Control device for synchronous motor

Abstract

The control device of the synchronous motor can accurately estimate the winding inductance and automatically implement gain adjustment of current feedback control with high precision. A control device (1A) is provided with: an inverter (14); a current conversion means (11) for converting the three-phase current of the synchronous motor (2) into a d-axis current and a q-axis current; a current feedback control calculation means (12) for calculating a d-axis voltage command value and a q-axis voltage command value from the d-axis current and the q-axis current; and a voltage command value conversion means (13) for converting the d-axis voltage command value and the q-axis voltage command value into three-phase voltage command values, the control device outputting to the synchronous motor (2) on the basis of the three-phase voltage command values, and measuring the synchronous motor (2) in a constant rotation state by using the synchronous motor (2) as a measurement target. At the same time, the three-phase current, the three-phase voltage, and the rotational speed of the synchronous motor (2) are calculated as measurement parameters, thereby estimating the winding inductance used in current feedback control, and performing gain adjustment in the current feedback control.

Description

Technical Field

[0001] The present invention relates to a control device for a synchronous motor, and in particular to a control device for a synchronous motor having a function of automatically estimating a winding inductance which is a parameter required for current feedback control of the synchronous motor. Background Art

[0002] A synchronous motor is an electric motor that rotates at a synchronous speed determined by the frequency of an AC power supply. While the rotor is attracted by the rotating magnetic field formed by the input AC current, it rotates following the magnetic field, but is usually driven and controlled by a control system based on a control device connected to it.

[0003] Figure 3 The control system of the synchronous motor 2 is shown in a functional block diagram. In this system, a control device 1B that performs drive control of the synchronous motor 2 uses the three-phase current (i U 、i V 、i W ), or by expressing it with an axis synchronized with the estimated motor position, and converting it into a d-axis current (i d ) and q-axis current (i q ).

[0004] The current feedback control calculation unit 12 calculates the d-axis voltage command value (V dref ) and q-axis voltage command value (V qref ), so that the d-axis current (i d ) and q-axis current (i q ) are respectively related to the input d-axis current command value (i dref ) and q-axis current command value (i qref The voltage command value conversion unit 13 converts the voltage into a three-phase voltage command value (V Uref 、V Vref 、V Wref ) and controls the on / off of the switching elements of the inverter, thereby outputting the three-phase voltage command values ​​to the synchronous motor 2.

[0005] use Figure 2 A general method for measuring the winding inductance, which is a parameter required for current feedback control, in the control system of the conventional synchronous motor 2 described above is described. In this method, the winding inductance value in a stationary state is measured using an LCR meter 3 or the like, and the UV phase, VW phase, and WU phase of the synchronous motor 2 are measured, and the average of each measured value is calculated, and a value 1 / 2 times the average is used as the winding inductance of a single phase of the motor.

[0006] In addition, although the current feedback control in the above control system is expressed by the following mathematical formula, as described above, the proportional feedback gain is determined by the value of the winding inductance. [Mathematical formula 1] v d =LK A (i dref -i q ) v q =LK A (i qref -i q ) v d : d-axis voltage [V] L: motor single-phase inductance [H] v q :q-axis voltage [V] K A : Proportional feedback gain i d :d-axis current [A] i dref : d-axis current command [A] i q :q-axis current [A] i qref :q-axis current command [A]

[0007] However, since the measurement method of the winding inductance using the above-mentioned LCR meter 3 or the like is performed when the synchronous motor 2 is in a stationary state, the winding inductance value that depends on the current characteristics cannot be accurately measured, and the error is likely to become large, making it difficult to perform high-precision control in the above-mentioned current feedback control. In addition, for each change in the specification of the synchronous motor 2 as the control object, parameter measurement and adjustment operations need to be performed.

[0008] In this regard, claim 16 of International Publication No. 2009 / 144957 (Patent Document 1) proposes a method for calculating the winding inductance value of a pair of adjacent stators based on the current change rate of the three-phase AC current supplied from the three-phase inverter corresponding to each stator winding. In addition, claim 8 of International Publication No. 2011 / 024935 (Patent Document 2) proposes a method including a storage unit storing a mapping representing the relationship between the d-axis current and the q-axis current and the winding inductance, and calculating the winding inductance value based on the current command value calculated by the current command value calculation unit and the mapping of the storage unit.

[0009] However, even with the methods proposed in the above-mentioned patent documents 1 and 2, the winding inductance value of the driven synchronous motor cannot be accurately measured by the control device connected thereto. Therefore, it must be said that when the specifications of the synchronous motor are changed, it is difficult for the control device to automatically and accurately perform its current feedback control. Prior art literature Patent Literature

[0010] Patent Document 1: International Publication No. 2009 / 144957 Patent Document 2: International Publication No. 2011 / 024935 Summary of the invention Technical problem to be solved by the invention

[0011] The present invention is an invention to solve the above-mentioned problems, and its technical problem is to provide a control device for a synchronous motor that can accurately estimate the winding inductance of the synchronous motor and automatically and accurately adjust the gain in current feedback control. Technical means for solving technical problems

[0012] Therefore, the control device of the synchronous motor of the present invention includes: an inverter, which is composed of a plurality of switching elements; a current conversion unit, which converts the three-phase current of the synchronous motor detected or estimated into a d-axis current and a q-axis current; a current feedback control operation unit, which uses current feedback control to calculate a d-axis voltage command value and a q-axis voltage command value from the d-axis current and the q-axis current; and a voltage command value conversion unit, which converts the d-axis voltage command value and the q-axis voltage command value into three-phase voltage command values, and the control device of the synchronous motor performs on / off control of the switching elements based on the three-phase voltage command values, and outputs to the synchronous motor. The control device of the synchronous motor is characterized in that the winding inductance used in the current feedback control is obtained by taking the synchronous motor in a constant rotation state as a measurement object, and the three-phase current, the three-phase voltage, and the rotation speed of the synchronous motor are calculated as measurement parameters to estimate the winding inductance, and the gain adjustment in the current feedback control is automatically performed.

[0013] Thus, a method is adopted in which a synchronous motor in a constant rotation state is taken as a measurement object, and three-phase current, three-phase voltage and motor speed are calculated as measurement parameters, thereby automatically performing gain adjustment in current feedback control while estimating winding inductance. As a result, a connected control device can estimate the winding inductance of the synchronous motor in operation online, and can automatically and accurately perform gain adjustment in current feedback control.

[0014] In the present invention, the three-phase current is converted into rectangular coordinates to be displayed as d-axis current and q-axis current, the three-phase voltage is converted into rectangular coordinates to be displayed as d-axis voltage and q-axis voltage, the rotational speed of the synchronous motor is converted into mechanical angular velocity and used for each of the above operations. With this as a feature, the winding inductance in the control device can be easily and accurately estimated.

[0015] In the present invention, for the winding inductance, the following mathematical formulas (1) to (6) are used, and the mathematical formula (4) obtained by substituting the mathematical formula (2) into the mathematical formula (3) is transformed into the mathematical formula (5), [Mathematical formula 2] v d i q -v q i d …(3) i d :d-axis current [A] N r : Motor speed [rpm] R: Motor single-phase resistance value [Ω] i q :q-axis current [A] ω r : Mechanical angular velocity [rad / s] L: Motor single-phase inductance [H] v d :d-axis voltage [V] Φ m : Magnet flux [wb] v q : q-axis voltage [V] P: Number of motor poles

[0016] here, ·i d and i q are the d-axis current and the q-axis current, ·v d and v q are the d-axis voltage and the q-axis voltage, ·N r is the motor speed, which is converted into the mechanical angular velocity ω by mathematical formula (1) r , R is the single-phase resistance of the motor, L is the single-phase inductance of the motor, ·Φ m is the magnetic flux of the magnet, and is derived from equation (6), P is the number of motor poles, By taking the mechanical angular velocity (ω r ), q-axis current (i q ), d-axis current (i d ), q-axis voltage (v q )、d-axis voltage (vd ), magnetic flux (Φ m ) is substituted into mathematical formula (5) to estimate the single-phase inductance (L) of the motor. With this as a feature, the winding inductance in the above-mentioned control device can be reliably estimated and the gain adjusted. Effects of the Invention

[0017] According to the present invention, a synchronous motor in a constant rotation state is taken as a measurement object, and a control device estimates the winding inductance online while calculating the three-phase current, the three-phase voltage, and the rotational speed of the synchronous motor as measurement parameters. The winding inductance of the synchronous motor can be accurately estimated, and the gain adjustment in the current feedback control can be automatically and accurately performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a functional block diagram showing a processing state when estimating the winding inductance and automatically adjusting the gain of the synchronous motor control device according to the embodiment of the present invention. Figure 2 It is an explanatory diagram showing an outline of a conventional method for estimating the winding inductance of a synchronous motor. Figure 3 This is a functional block diagram showing an outline of a control system in a conventional synchronous motor control device. Figure 4 It is a diagram showing the derivation process of each mathematical formula of the present invention. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments for implementing the present invention will be described with reference to the accompanying drawings. In the present invention, "online" means a state in which a synchronous motor connected to a control device is being driven.

[0020] Figure 1 1 is a functional block diagram showing a characteristic portion of the control contents of the synchronous motor 2 executed by the control device 1A of the present embodiment, namely, the processing contents when estimating the winding inductance and automatically adjusting the gain. The basic structure and basic functions of the control device 1A are similar to those of FIG. Figure 3 The above-described conventional control device 1B is common.

[0021] When reference Figure 1 and Figure 3When describing the basic structure of the control device 1A of the present embodiment, the control device includes an inverter 14 composed of a plurality of switching elements, a computer 10 having a storage unit and a CPU, etc., and as a unit functionally constituted by the computer 10, it includes: a current conversion unit 11, which is used to convert the detected or estimated three-phase current of the synchronous motor 2 into a d-axis current and a q-axis current; a current feedback control calculation unit 12, which is used to calculate a d-axis voltage command value and a q-axis voltage command value based on the above-mentioned d-axis current and the above-mentioned q-axis current by using current feedback control; and a voltage command value conversion unit 13, which is used to convert the above-mentioned d-axis voltage command value and the above-mentioned q-axis voltage command value into a three-phase voltage command value. The control device turns on / off the switching elements of the inverter 14 based on the converted three-phase voltage command value, and outputs to the synchronous motor 2. The above-mentioned components are common to the control device 1B of the conventional example.

[0022] Moreover, in this embodiment, the following features are provided: the synchronous motor 2 in a constant rotation state is taken as a measurement object to obtain the winding inductance used in the above-mentioned current feedback control, and the three-phase current, three-phase voltage, and rotation speed of the synchronous motor are calculated as measurement parameters to estimate its winding inductance, and at the same time, the control device 1A performs gain adjustment in its current feedback control.

[0023] That is, the winding inductance as a parameter required for current feedback control of the synchronous motor 2 can be estimated online using the outer product of the current value and the voltage value during steady rotation, and the control device 1A can automatically and accurately adjust the gain in the current feedback control.

[0024] use Figure 1 When describing the processing details, Figure 2 As shown, conventionally, the winding inductance of the synchronous motor 2 in a stationary state is measured, but the control device 1A of the present embodiment uses the synchronous motor 2 in a constant rotation state as the measurement object through the drive control of the inverter 14 .

[0025] The measured parameter is not the winding inductance, but the three-phase current (i U ,i V ,i W )、Three-phase voltage (V U , V V , V W ) and the speed of the synchronous motor (N r ). Speed ​​of synchronous motor (N r ) is converted into mechanical angular velocity (ω) by the following mathematical formula (1) r ). [Mathematical formula 3]

[0026] By calculating these measured parameters using the computer 10 in the control device 1A, the winding inductance can be estimated and the gain adjustment in the current feedback control can be automatically performed. Figure 1 As shown, a winding inductance estimating unit 10a functionally constituted by a computer 10 automatically estimates the winding inductance, and a control gain automatic adjusting unit 10b similarly constituted automatically adjusts the gain.

[0027] Next, the principle of the above-mentioned method of measuring the winding inductance will be explained using the voltage equation and the formula of the outer product in the synchronous motor 2.

[0028] The voltage equation and outer product on the d-axis and q-axis of the synchronous motor 2 are expressed by the following mathematical formula (2) and mathematical formula (3). Here, the motor single-phase resistance (R), the motor single-phase inductance (L), the mechanical angular velocity (ω r ) and magnet flux (Φm) to describe Eq. [Mathematical formula 4] v a i q -v q i d …(3)

[0029] When deriving the single-phase inductance (L) of the motor, equation (2) which is the voltage equation of VdVq is substituted into equation (3) which is the formula of the outer product to obtain the following equation (4). [Mathematical formula 5]

[0030] Then, by transforming the motor single-phase inductance (L) to move to the left, the following mathematical formula (5) is obtained. [Mathematical formula 6]

[0031] By taking the mechanical angular velocity (ω r ), q-axis current (i q ), d-axis current (i d ), q-axis voltage (v q )、d-axis voltage (v d ) and magnet flux (Φ m ) into the mathematical formula (5), the single-phase inductance (L) of the motor can be estimated.

[0032] Figure 4 The above derivation process from equation (1) to equation (5) is shown in FIG.

[0033] In addition, the q-axis current (iq ), d-axis current (i d ) is obtained by converting the three-phase current (i U 、i V 、i W ) is converted into rectangular coordinates to display the q-axis voltage (v q ) and d-axis voltage (v d ) is obtained by dividing the three-phase voltage (V U 、V V 、V W ) is converted into rectangular coordinates. In addition, the mechanical angular velocity (ω) of the synchronous motor 2 during no-load driving can be obtained according to the following mathematical formula (6): r ) and q-axis voltage (v q ) to estimate the magnetic flux (Φ m ). [Mathematical formula 7]

[0034] In this way, the winding inductance can be estimated online taking into account the frequency and current characteristics when the synchronous motor 2 is driven, which greatly helps to improve the controllability in the current feedback control. In addition, it will not be affected by the specification changes of the synchronous motor 2, and the optimal control gain adjustment can be performed.

[0035] As described above, according to the present invention, in the control device for a synchronous motor, the winding inductance of the synchronous motor can be accurately estimated, and the gain adjustment in the current feedback control can be automatically and accurately performed. Description of symbols

[0036] 1A control device, 2 synchronous motor, 10 computer, 10a winding inductance estimation unit, 10b control gain automatic adjustment unit, 11 current conversion unit, 12 current feedback control calculation unit, 13 voltage command value conversion unit, 14 inverter.

Claims

1. A control device for a synchronous motor, comprising: An inverter, the inverter being composed of a plurality of switching elements; a current conversion unit that converts the detected or estimated three-phase current of the synchronous motor into a d-axis current and a q-axis current; a current feedback control operation unit that calculates a d-axis voltage command value and a q-axis voltage command value based on the d-axis current and the q-axis current using current feedback control; and a voltage command value conversion unit that converts the d-axis voltage command value and the q-axis voltage command value into three-phase voltage command values, The control device of the synchronous motor performs on / off control of the switching element based on the three-phase voltage command value and outputs the synchronous motor. The control device for the synchronous motor is characterized in that: The winding inductance used in the current feedback control is obtained by taking the synchronous motor in a constant rotation state as a measurement object, and the three-phase current, three-phase voltage, and rotation speed of the synchronous motor are calculated as measurement parameters to estimate the winding inductance, while automatically adjusting the gain in the current feedback control.

2. The control device for a synchronous motor according to claim 1, characterized in that: The three-phase current is converted into rectangular coordinates and displayed as d-axis current and q-axis current. The three-phase voltage is converted into rectangular coordinates and displayed as d-axis voltage and q-axis voltage. The rotation speed of the synchronous motor is converted into a mechanical angular velocity and used in each of the operations.

3. The control device for a synchronous motor according to claim 2, characterized in that: For the winding inductance, the following equations (1) to (6) are used: [Mathematical formula 1] v d i q -v q i d ···(3) i d :d-axis current [A] N r : Motor speed [rpm] R: Motor single-phase resistance value [Ω] i q :q-axis current [A]ω r : Mechanical angular velocity [rad / s] L: Motor single-phase inductance [H] v d :d-axis voltage [V]Φ m : Magnet flux [wb] v q : q-axis voltage [M] P: Number of motor poles Substituting equation (2) into equation (3) yields equation (4) which is transformed into equation (5). here, ·i d and iq are the d-axis current and q-axis current, ·v d and v q are the d-axis voltage and the q-axis voltage, ·N r is the motor speed, which is converted into the mechanical angular velocity ω by mathematical formula (1) r , R is the single-phase resistance of the motor, L is the single-phase inductance of the motor, ·Φ m is the magnetic flux of the magnet, and is derived from equation (6), P is the number of motor poles, By taking the mechanical angular velocity (ω r ), q-axis current (i q ), d-axis current (i d ), q-axis voltage (v q )、d-axis voltage (v d ), magnetic flux (Φ m ) is substituted into the above mathematical formula (5) to estimate the single-phase inductance (L) of the motor.

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