JP2007049782A - Controller of synchronous motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To find a d-axis current idm and a q-axis current iqm by using a simple calculation for implementing a d-q conversion of an α-axis current and a β-axis current in a synchronous motor controller from an estimated magnetic pole position θ into an electric angle of 45°. <P>SOLUTION: A calculation circuit for finding the d-axis current idm and the q-axis current iqm by using a d-axis current id and a q-axis current iq outputted from a d-q converter comprises an adder 21q, a subtracter 21d, and a gain 22. The d-q converter 10 implements the d-q conversion by using the α-axis current I_alpha, the β-axis current and an estimated magnetic pole phase theta_est, and outputs the d-axis current id and the q-axis current iq. The adder 21q adds the d-axis current id and the q-axis current iq outputted from the d-q converter 10. The subtracter 21d subtracts the q-axis current iq from the d-axis current id. Outputs from the adder 21q and the subtracter 21d are multiplied by the gain 22 so as to obtain the d-axis current idm and the q-axis current iqm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an electric motor having electrical saliency.

In order to drive the synchronous motor, it is necessary to detect the magnetic pole position of the rotor with a sensor or sensorless and perform appropriate current control, but from the viewpoint of cost and reliability, the magnetic pole position by the sensorless method that does not require a sensor Due to the advantage of detection, many studies have been made on sensorless systems.
In particular, there is a method for estimating the magnetic pole position of the rotor based on the saliency of the rotor structure by superimposing a high-frequency current or voltage different from the drive frequency and superimposing the magnetic pole in the zero speed state (for example, JP 2000-102300 A). An example of such a conventional synchronous motor control method is shown in FIG.

In FIG. 2, armature currents Iu and Iw of the synchronous motor are input to the α-β converter 9 and an α-axis current i_alpha and a β-axis current i_beta are output. The dq converter 10 performs dq conversion on i_alpha and i_beta using the estimated magnetic pole position theta_est, and outputs a d-axis current id and a q-axis current iq. The low pass filter LPF 11 outputs currents id_lpf and iq_lpf from which the same frequency component as the high frequency voltage superimposed by the high frequency generator 1 is removed. The subtractor 13 outputs a deviation iq_err between iq_lpf and the iq command iq_ref. The subtracter 14 outputs a deviation id_err between id_lpf and the id command id_ref. The current controller 4 executes current control by generating and outputting voltage commands Vd_ref and Vq_ref so that the input id_err and iq_err become zero. The high frequency generator 1 generates Vinj with a high frequency voltage different from the driving frequency. The adder 15 adds the voltage command Vd_ref and the high-frequency voltage Vinj and outputs Vd_ref2. The coordinate converter 5 uses the estimated magnetic pole position theta_est to convert the voltage commands Vd_ref2 and Vq_ref on which the high-frequency voltage is superimposed into a 2-3 phase coordinate and sends the command to the PWM inverter circuit 2. The PWM inverter circuit 2 controls the synchronous motor 3 based on a command from the coordinate converter 5.
The subtractor 12 outputs a value obtained by subtracting 45 degrees (π / 4 radians) from the estimated magnetic pole position theta_est.
The dq converter 7 outputs values idm and iqm obtained by dq conversion of the α-axis current i_alpha and the β-axis current i_beta using the phase output from the subtractor 12. The band pass filter BPF 19 extracts the same frequency component as the high frequency voltage superimposed by the high frequency generator 1 from idm and iqm, and outputs idm_bpf and iqm_bpf. The outputs idm_bpf and iqm_bpf and the high-frequency voltage Vinj of the BPF 19 are input to the high-frequency impedance estimator 6, and the high-frequency impedance estimator 6 generates a high-frequency impedance Zdm at two points, a point advanced by 45 degrees in electrical angle and a point delayed from the estimated magnetic pole axis. Estimate Zqm.
For example, as shown in FIG. 3, the magnetic pole position estimator 8 includes a subtracter 16, a multiplier 17, and an integrator 18, and estimates the magnetic pole position theta_est so that the high-frequency impedances Zdm and Zqm are equal.
The subtracter 16 outputs a value obtained by subtracting Zdm from the high frequency impedance Zqm.
The multiplier 17 outputs a product obtained by multiplying the output of the subtracter 16 by a gain (Kp + Ki / s). Here, Kp is a proportional gain, and Ki is an integral gain.
The integrator 18 integrates the output of the multiplier 17 and outputs it as an estimated magnetic pole theta_est.
Thus, the conventional apparatus performs magnetic pole estimation and controls the synchronous motor.

However, if the control device is configured with the above-described conventional device configuration, the amount of calculation required for magnetic pole estimation becomes a considerable amount. For example, when the device is configured using an inexpensive CPU, the CPU calculation capability is reduced. The amount of computation may exceed. Therefore, in a situation where an inexpensive CPU must be used due to industrial necessity, it is required to reduce the amount of calculation for magnetic pole estimation as much as possible.
The present invention has been made in view of such problems, and an object of the present invention is to provide an apparatus capable of reducing the amount of calculation required for magnetic pole estimation.

In order to solve the above problem, the present invention is configured as follows.
The invention according to claim 1 relates to a control device for a synchronous motor, and is a control device for variable speed control of a permanent magnet type synchronous motor having electrical saliency by AC power from an inverter circuit, and is supplied to the synchronous motor. An α-β converter that converts the stator current for at least two phases by α-β coordinates, and a dq converter that converts the α-axis current and β-axis current output from the α-β converter by dq conversion A current controller that performs current control so that a deviation between each of the d-axis current id output from the dq converter and the current command value of the q-axis current iq is zero; and the current controller A high-frequency generator that superimposes a high-frequency voltage on the d-axis voltage command output from the coordinate generator, and a coordinate converter that converts the d-axis voltage command and the q-axis voltage command on which the high-frequency voltage is superimposed by the high-frequency generator into a 2-3 phase And synchronous power based on the output command from the coordinate converter. In a synchronous motor control device including a PWM inverter circuit for controlling a machine, the α-axis current and the q-axis current iq are output using the d-axis current id and the q-axis current iq output from the dq converter. An arithmetic circuit for obtaining a d-axis current idm and a q-axis current iqm as a result of performing a dq conversion from the estimated magnetic pole position θ to a position at an electrical angle of 45 degrees from the estimated magnetic pole position θ, and a frequency superimposed by the high-frequency generator A high-frequency extractor that extracts the same frequency component from the d-axis current idm and q-axis current iqm, which are output currents of the arithmetic circuit, and an estimated magnetic pole axis based on the current extracted by the high-frequency extractor and the high-frequency voltage A high-frequency impedance estimator for measuring high-frequency impedance at two points, a point advanced by 45 degrees and a point delayed, and estimating an impedance deviation between the two points, and a deviation between the two high-frequency impedances It is characterized with the magnetic pole position estimator which estimates a magnetic pole position such that B, in that it comprises.
According to a second aspect of the present invention, in the synchronous motor control device according to the first aspect, the arithmetic circuit is represented by the following equation:
idm = (id−iq) / 2 ^1/2 , iqm = (id + iq) / 2 ^1/2
By calculating the d-axis current idm and the q-axis current iqm from the d-axis current id and the q-axis current iq.

  With the above configuration, in the conventional calculation, it takes one cos function calculation, one sin function calculation, four multiplications, and two additions / subtractions, but with a small amount of calculation such as two additions / subtractions and two divisions. Since an equivalent result can be obtained, the amount of calculation required for magnetic pole estimation can be reduced.

ここで、図４はα-β座標のα軸電流とβ軸電流をｄ-ｑ変換したｄ軸電流idとｑ軸電流iqとの関係を説明する図である。α-β座標から推定磁極位相θの遅れた座標をｄ-ｑ座標電流とすると、α-β座標で図のような電流ベクトルｉはｄ-ｑ座標では、ｄ軸電流idとｑ軸電流iqとで表される。
一方、α軸電流とβ軸電流とを推定磁極位置θから電機角度４５度（π/４ラジアン）の位置にｄ−ｑ変換を行うと、その結果のｄ軸電流idmとｑ軸電流iqmは（２）式で示される

（２）式を展開すると、（３）式となる。

従って（１）式と（３）式から、idmとiqmはidとiqを用いて（４）式で計算することができる。

このように、（２）式で計算していたものと等価な機能を（４）式で実現できることがわかる。
演算量については、（２）式では、cos関数計算１回、sin関数計算１回、乗算４回、加減算２回かかるのに対し、（４）式では加減算２回と除算２回とより少ない演算量で等価な結果を得ることができる。
さらに、id,iqは実効値、idm,iqmは波高値で取り扱うようにすれば、（４）式は、
idm＝id−iq 、 iqm＝id＋iq
となり、加減算２回で演算可能となる。
以上のようにして演算量を低減することができることとなる。 Hereinafter, first, the principle of the present invention will be described.
When the d-q conversion is performed using the α-axis current and the β-axis current by using the estimated magnetic pole phase θ, the d-axis current id and the q-axis current iq are expressed by Expression (1).

Here, FIG. 4 is a diagram illustrating the relationship between the α-axis coordinate α-axis current and the d-axis current id obtained by dq conversion of the β-axis current and the q-axis current iq. Assuming that the coordinate delayed from the α-β coordinate by the estimated magnetic pole phase θ is the dq coordinate current, the current vector i as shown in the figure in the α-β coordinate is the d-axis current id and the q-axis current iq in the dq coordinate. It is expressed as
On the other hand, when the α-axis current and the β-axis current are subjected to dq conversion from the estimated magnetic pole position θ to the position of the electrical angle 45 degrees (π / 4 radians), the resulting d-axis current idm and q-axis current iqm are (2)

When formula (2) is expanded, formula (3) is obtained.

Therefore, from equation (1) and equation (3), idm and iqm can be calculated by equation (4) using id and iq.

Thus, it can be seen that a function equivalent to that calculated by equation (2) can be realized by equation (4).
As for the amount of calculation, in equation (2), it takes one cos function calculation, one sin function calculation, four multiplications, and two additions / subtractions, whereas in equation (4), there are fewer additions / subtractions and two divisions. Equivalent results can be obtained with the amount of computation.
Furthermore, if id and iq are handled as effective values and idm and iqm are handled as peak values, equation (4) becomes
idm = id−iq, iqm = id + iq
Thus, calculation can be performed by adding and subtracting twice.
As described above, the amount of calculation can be reduced.

An embodiment of the present invention based on the above principle will be described with reference to FIG.
FIG. 1 is a block diagram of a control apparatus for a synchronous motor according to the present invention. In FIG. 1, the same components as those in FIG. 2 are denoted by the same reference numerals, and redundant description will be omitted.
The present invention performs a d-q conversion of the α axis current i_alpha and the β axis current i_beta from the estimated magnetic pole phase to an electrical angle of 45 degrees with respect to the conventional synchronous motor control device shown in FIG. The q converter 7 is removed, and instead an arithmetic circuit 20 having an equivalent function is provided on the output side of the conventional dq converter 10 for performing dq conversion. The arithmetic circuit 20 is specifically composed of an adder 21q, a subtractor 21d, and a gain 22. Two inputs of the adder 21q and the subtractor 21d are outputs of the dq converter 10 respectively. An axial current id and a q-axis current iq are used.

As described above, the dq converter 10 d-q converts the α-axis current i_alpha and the β-axis current I_beta using the estimated magnetic pole phase theta_est as in the conventional synchronous motor, and the d-axis current id and the q-axis current iq. Is output.
The adder 21q adds id and iq output from the dq converter 10, and the subtractor 21d subtracts iq from the id output from the dq converter 10.
The outputs of the adder 21q and the subtractor 21d are respectively multiplied by a gain 22 (in this case, 1 / √2), and idm and iqm are output.
In this way, a function equivalent to the conventional one can be obtained with a smaller number of computations, and the amount of computation for magnetic pole estimation can be reduced.

  By applying the present invention, it is possible to reduce the amount of calculation for magnetic pole estimation, and it can be applied to a sensorless inverter control device using an inexpensive CPU.

It is a block diagram of the control apparatus of the synchronous motor shown based on this invention. It is a block diagram of the control apparatus of the synchronous motor which concerns on the conventional apparatus. FIG. 3 is a block diagram showing an internal configuration of a magnetic pole estimator 8 common to FIGS. 1 and 2. It is a figure showing the relationship between (alpha) -beta coordinate and dq coordinate.

Explanation of symbols

1 high frequency generator,
2 PWM inverter circuit,
3 Synchronous motor,
4 Current controller,
5 coordinate converter,
6 high frequency impedance estimator,
7 dq converter,
8 Magnetic pole position estimator,
9 α-β converter,
10 dq converter,
11 Low-pass filter (LPF),
12 Subtractor,
13 Subtractor,
14 Subtractor,
15 adder,
16 subtractor,
17 multiplier,
18 integrator,
19 Band pass filter (BPF)
20 arithmetic circuit,
21d subtractor,
21q adder,
22 gain

Claims (2)

A control device for variable speed control of a permanent magnet synchronous motor having electrical saliency with AC power from an inverter circuit, wherein α is converted to α-β coordinates of stator current for at least two phases supplied to the synchronous motor -β converter, d-q converter for dq-converting α-axis current and β-axis current output from the α-β converter, and d-axis current id output from the dq converter And a current controller that performs current control so that the deviation between each current command value of the q-axis current iq is zero, and high-frequency generation that superimposes a high-frequency voltage on the d-axis voltage command output from the current controller , A coordinate converter for converting the d-axis voltage command and the q-axis voltage command on which the high-frequency voltage is superimposed by the high-frequency generator into a 2-3 phase, and the control of the synchronous motor based on the output command from the coordinate converter Synchronous motor with PWM inverter circuit In the control device,
Using the d-axis current id and the q-axis current iq output from the dq converter, the α-axis current and the β-axis current are d-positioned from the estimated magnetic pole position θ to an electrical angle of 45 degrees. An arithmetic circuit for obtaining a d-axis current idm and a q-axis current iqm as a result of performing the -q conversion;
A high-frequency extractor that extracts the same frequency component as the frequency superimposed by the high-frequency generator from the d-axis current idm and the q-axis current iqm that are output currents of the arithmetic circuit;
Based on the current extracted by the high-frequency extractor and the high-frequency voltage, the high-frequency impedance is measured at two points, a point advanced 45 degrees from the estimated magnetic pole axis and a point delayed, and the impedance deviation between the two points is measured. A high frequency impedance estimator to estimate;
A magnetic pole position estimator for estimating a magnetic pole position such that a deviation between the two high-frequency impedances is zero;
A control apparatus for a synchronous motor, comprising: The arithmetic circuit has the following formula:
idm = (id−iq) / 2 ^1/2 , iqm = (id + iq) / 2 ^1/2
The synchronous motor control device according to claim 1, wherein the d-axis current idm and the q-axis current iqm are obtained from the d-axis current id and the q-axis current iq by calculating

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