JP3566577B2 - Induction motor control device - Google Patents

Description

により残留磁束ベクトルφ０を求めて出力する。ここで，Ｔ２は誘導電動機４の２次時定数，Ｍは相互インダクタンス，ｊは虚数単位，ｅｘｐは指数関数である。誘導電動機４の回転角周波数ω０が０に近い場合は，第２速度推定手段９においても磁束演算手段６の出力の磁束ベクトルが円弧状にならないので，ω０を求めることができないが，その場合はω０＝０およびφ０＝０を出力する。
【０００６】
運転切換器７は，第２速度推定手段９を選択した後は，通常運転制御器５を選択する。通常運転制御器５は，第１速度推定手段８または第２速度推定手段９で求められた誘導電動機４の回転角周波数ω０や残留磁束ベクトルφ０を回転角周波数や磁束の演算の初期値として使用して，誘導電動機４が所定の出力トルクや所定の速度状態となるような制御信号を出力する。
【０００７】
【発明が解決しようとする課題】
第１の問題を以下に示す。誘導電動機に直流電流ベクトルｉｘを流した時の磁束ベクトルφは，
φ＝φｘ＋（φｘ０−φｘ）・ｅｘｐ（ｊ・ω０・ｔ−ｔ／Ｔ２） ▲４▼
で表される。ここでｔは経過時間，φｘ０は直流電流ベクトルｉｘを流し始めたときの磁束，φｘは
φｘ＝Ｍ・ｉｘ／（１−ｊ・ω０・Ｔ２） ▲５▼
である。▲４▼式より磁束ベクトルφは，半径φｘ０−φｘの円弧を描き，その中心はφｘとなることが分かる。
【０００８】
従来の技術において，誘導電動機が回転している場合，第２速度推定手段９では回転角周波数ω０を求めることができるとしている。しかし，▲４▼式のφｘ０−φｘが零に近い値の場合では，磁束ベクトルφの描く円の半径が非常に小さいことになり，その円の回転角を求めることができず，回転角周波数ω０を求めることができなくなる。すると第２速度推定手段９では，ω０＝０として出力するので，通常運転制御器５においてω０は０でないにも関わらずω０＝０として制御をすることになり，正常な制御ができなくなる。
【０００９】
第２の問題を以下に示す。誘導電動機が回転している場合，第１速度推定手段８や第２速度推定手段９で用いる磁束演算手段６の出力の磁束ベクトルは円弧を描くとしているが，例えば誘導電動機の回転子のスロットがスキューされてないことにより空間高調波が大きい誘導電動機では，磁束ベクトルは前記空間高調波によって発生する高調波成分を含むようになり，磁束演算手段６の出力の磁束ベクトルは円弧に高調波が重畳されたようになる。すると円弧の中心および中心角を求める際の誤差が大きくなり，それによって求められる回転角周波数ω０や残留磁束ベクトルφ０に誤差を含むようになる。
【００１０】
第３の問題を以下に示す。第２速度推定手段９において，残留磁束ベクトルφ０を▲３▼式によって求めているが，これは▲４▼式からφｘ０＝０として導き出された式である。よって第２速度推定手段を開始した時に磁束が残っていてφｘ０が０でない場合は，残留磁束ベクトルφ０の計算を間違えてしまう。
【００１１】
第４の問題を以下に示す。第１速度推定手段８の微少時間ｔ１や第２速度推定手段９の微少時間ｔ２が固定値の場合，磁束ベクトルの円弧の中心角θは回転角周波数ω０に比例して広がる。するとω０が非常に大きな場合は，θは１８０度を越えてしまうことがあり，最初の時点の磁束ベクトルと最後の時点の磁束ベクトルと円弧の中心の情報より中心角を求めている場合は，θの計算を間違う恐れがある。
本発明は上述した点に鑑みて創案されたもので、その目的とするところは、これらの課題を解消し、始動時における誘導電動機の回転角周波数や残留磁束ベクトルがより正確により確実に把握でき，通常運転制御におけるトルクや速度の制御への移行時に，過電流になったり急加減速などの過渡現象が生じなくなる誘導電動機の制御装置を提供することにある。
【００１２】
【課題を解決するための手段】
つまり、その目的を達成するための手段は、
１．請求項１において、
前記第１の問題を解決するために，第２速度推定手段で速度が推定できなかった場合で，該第２速度推定手段の実行直後に，前記第２速度推定手段で流した電流と逆方向に直流電流を流すようにして他は前記第２速度推定手段と同じ方法で前記誘導電動機の回転角周波数と残留磁束ベクトルを推定する第３速度推定手段を具備する。
【００１３】
２．請求項２において、
前記第２の問題を解決するために，前記第１，第２または第３の速度推定手段において，前記磁束演算手段の出力の磁束ベクトルの軌跡である円弧の中心を求める際に，円弧の最初から最後までの時間を３等分して，それぞれの時間領域における円弧の平均値を計算して３点を求めて，該３点を通る円の中心を求めて前記円弧の中心とすることを特徴とする。
【００１４】
３．請求項３において、
前記第３の問題を解決するために，前記第２または第３速度推定手段において，該第２または第３速度推定手段で流す直流電流ベクトルをｉｘとし，該第２または第３速度推定手段で得られた速度に相当する角周波数をω０とし，前記誘導電動機の２次時定数をＴ２，相互インダクタンスをＭとし，虚数単位をｊで表して，前記磁束演算手段の出力の磁束ベクトルの軌跡である円弧の中心のベクトルをｆ０とし，前記第２または第３速度推定手段の最後の時点での前記磁束演算手段の出力の磁束ベクトルをｆ１として，残留磁束ベクトルφ０を，
φ０＝Ｍ・ｉｘ／（１−ｊ・ω０・Ｔ２）＋ｆ１−ｆ０ ▲６▼
により求める第２または第３速度推定手段を具備する。
【００１５】
４．請求項４において、
前記第４の問題を解決するために，前記第１速度推定手段の微少時間ｔ１，および前記第２または第３速度推定手段の微少時間ｔ２を，所定の最大時間と，前記磁束演算手段の出力の磁束ベクトルの軌跡である円弧の中心角が所定の角度になる時間との短い方の時間とすることを特徴とする。
以下、本発明の一実施例を図面に基づいて詳述する。
【００１６】
【発明の実施の形態】
本発明の実施例を図１のブロック図に示し，図１に基づいて説明する。なお、符号１〜９の説明は，従来技術で説明したので省く。
第２速度推定手段９において，回転角周波数ω０を求めることができなかった場合は，運転切換器７は，第２速度推定手段９を選択した後の所定の微少期間ｔ２の間，第３速度推定手段１０を選択する。
第３速度推定手段１０は，前記誘導電動機の入力電流が所定の直流電流ベクトルｉｘ２となるようにして，第２速度推定手段９と同様に，誘導電動機４の回転角周波数ω０と残留磁束ベクトルφ０を求めて出力する。この場合流す直流電流ベクトルの向きは第２速度推定手段９の場合の逆とする。
つまりｉｘ２＝−ｉｘ１の関係とする。第２速度推定手段９で回転角周波数を求めることができないのは，回転が停止している場合か▲４▼式のφｘ０−φｘが零に近い値の場合のどちらかである。第３速度推定手段１０においては，ｉｘ２＝−ｉｘ１とすることにより，後者の場合を除くことができるので，回転角周波数を間違いなく求めることが可能となる。
【００１７】
本実施例の第２速度推定手段９や第３速度推定手段１０において，残留磁束ベクトルφ０は，▲３▼式の代わりに▲６▼式で求められる。ここで▲６▼式のｉｘには，第２速度推定手段９の場合ｉｘ１を適用し，第３速度推定手段１０の場合ｉｘ２を適用する。▲６▼式の第１項は▲４▼式の第１項を表しており，▲６▼式のｆ１−ｆ０の項は▲４▼式の第２項のｔ＝ｔ２に相当するため，第２または第３速度推定手段を開始した時に磁束が残っていてφｘ０が０でなくても，▲６▼式では正確に残留磁束ベクトルφ０を求めることができる。
【００１８】
本実施例の第１速度推定手段８や第２速度推定手段９や第３速度推定手段１０の磁束ベクトル軌跡の円弧の中心を求める方法を図３に基づいて説明する。
微少期間ｔ１またはｔ２を３等分してそれらを時間順に期間ｔａ，ｔｂ，ｔｃとする。期間ｔａでの磁束軌跡の平均点をＰａとし，他の２つの期間の磁束軌跡の平均点をそれぞれＰｂ，Ｐｃとして求める。これらＰａ，Ｐｂ，Ｐｃの３点を通る円の中心を求める。Ｐａ点からＰｃ点までの円弧の中心角θｘを求め，それを１．５倍して▲１▼式で用いるθとする。
【００１９】
本実施例の第１速度推定手段８の微少期間ｔ１および第２速度推定手段９や第３速度推定手段１０の微少期間ｔ２は，磁束演算手段６の出力の磁束ベクトルの軌跡である円弧の中心角が所定の角度例えば１８０度を越える時間とする。
つまり各速度推定手段において随時中心角を求めておき，その中心角が例えば１８０度を越えた時点で回転角周波数ω０や残留磁束ベクトルφ０を求めて，各速度推定手段を終了するようにする。なお円弧の中心角が所定の角度を越えていない場でも所定時間例えば２０ｍｓｅｃを経過していれば，回転角周波数ω０や残留磁束ベクトルφ０を求めて，各速度推定手段を終了するようにする。
【００２０】
【発明の効果】
以上述べたように本発明によれば，始動時における誘導電動機の回転角周波数や残留磁束ベクトルがより正確により確実に把握できるため，通常運転制御におけるトルクや速度の制御への移行時に，過電流になったり急加減速などの過渡現象が生じなくなり，実用上、極めて有用性の高いものである。
【図面の簡単な説明】
【図１】本発明の１実施例を表すブロック図である。
【図２】従来の１例を表すブロック図である。
【図３】速度推定手段での磁束ベクトル軌跡の１例である。
【符号の説明】
１ 電力変換器
２ 電流ベクトル検出器
３ 電圧ベクトル検出器
４ 誘導電動機
５ 通常運転制御器
６ 磁束演算手段
７ 運転切替器
８ 第１速度推定手段
９ 第２速度推定手段
１０ 第３速度推定手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to control of an inverter that drives an AC motor, and particularly to smooth starting.
[0002]
[Prior art]
FIG. 2 shows an example of the conventional technique, and the conventional technique will be described with reference to FIG.
In the normal operation state, the operation switching unit 7 selects the normal operation controller 5 and inputs a control signal output from the normal operation controller 5 to the power converter 1. The power converter 1 supplies power to the induction motor 4 based on the input control signal.
[0003]
During a predetermined minute period t1 immediately after the power supply to the induction motor 4 is started, the operation switch 7 selects the first speed estimating means 8. The first speed estimating means 8 outputs a control signal such that the input current of the induction motor 4 becomes a DC current of zero or a value close to zero, inputs the magnetic flux vector of the output of the magnetic flux calculating means 6, and The center of the arc which is the trajectory of the magnetic flux vector in the minute period t1 is obtained, and the center angle θ of the arc is obtained to obtain ω0 = θ / t1 (1)
To obtain and output the rotational angular frequency ω0 of the induction motor 4. The first speed estimating means 8
φ0 = f1-f0 (2)
To obtain and output the residual magnetic flux vector φ0 of the induction motor 4. Here, f0 is a magnetic flux vector at the center of the arc, and f1 is a magnetic flux vector at the end of the minute period t1.
[0004]
When the rotational angular frequency ω0 of the induction motor 4 is close to 0 or the residual magnetic flux is very small, the first speed estimating means 8 does not make the magnetic flux vector output from the magnetic flux calculating means 6 circular or very small. Since it is a circular arc, the rotational angular frequency ω0 and the residual magnetic flux vector φ0 cannot be obtained. In that case, the operation switching device 7 selects the second speed estimating means 9 for a predetermined minute period t2 after selecting the first speed estimating means 8. When the rotation speed ω0 and the residual magnetic flux vector φ0 can be obtained by the first speed estimating means 8, the operation switching unit 7 selects the normal operation controller 5.
[0005]
The second speed estimating means 9 calculates and outputs the residual magnetic flux vector φ0 of the induction motor 4 in the same manner as the first speed estimating means 8 so that the input current of the induction motor becomes a predetermined DC current vector ix1. The second speed estimating means 9

To obtain and output the residual magnetic flux vector φ0. Here, T2 is a secondary time constant of the induction motor 4, M is a mutual inductance, j is an imaginary unit, and exp is an exponential function. If the rotational angular frequency ω0 of the induction motor 4 is close to 0, the second speed estimating means 9 cannot obtain ω0 because the magnetic flux vector output from the magnetic flux calculating means 6 does not have an arc shape. ω0 = 0 and φ0 = 0 are output.
[0006]
After selecting the second speed estimating means 9, the operation switching device 7 selects the normal operation controller 5. The normal operation controller 5 uses the rotation angular frequency ω0 and the residual magnetic flux vector φ0 of the induction motor 4 obtained by the first speed estimating means 8 or the second speed estimating means 9 as initial values for calculating the rotation angular frequency and the magnetic flux. Then, a control signal is output such that the induction motor 4 is set to a predetermined output torque or a predetermined speed state.
[0007]
[Problems to be solved by the invention]
The first problem is shown below. The magnetic flux vector φ when the DC current vector ix is passed through the induction motor is
φ = φx + (φx0−φx) · exp (j · ω0 · tt / T2) (4)
It is represented by Here, t is the elapsed time, φx0 is the magnetic flux when the DC current vector ix starts to flow, and φx is φx = M · ix / (1-j · ω0 · T2).
It is. From equation (4), it can be seen that the magnetic flux vector φ draws an arc with a radius φx0−φx, and the center is φx.
[0008]
According to the conventional technology, when the induction motor is rotating, the second speed estimating means 9 can determine the rotation angular frequency ω0. However, when φx0−φx in equation (4) is a value close to zero, the radius of the circle drawn by the magnetic flux vector φ is very small, and the rotation angle of the circle cannot be obtained, and the rotation angle frequency ω0 cannot be obtained. Then, since the second speed estimating means 9 outputs ω0 = 0, the normal operation controller 5 controls ω0 = 0 even though ω0 is not 0, and normal control cannot be performed.
[0009]
The second problem is described below. When the induction motor is rotating, the magnetic flux vector output from the magnetic flux calculating means 6 used in the first speed estimating means 8 and the second speed estimating means 9 is assumed to draw a circular arc. In an induction motor having large spatial harmonics because it is not skewed, the magnetic flux vector includes a harmonic component generated by the spatial harmonics, and the magnetic flux vector output from the magnetic flux calculating means 6 has the harmonics superimposed on an arc. It will be like. Then, an error in obtaining the center and the central angle of the arc increases, and the rotation angular frequency ω0 and the residual magnetic flux vector φ0 obtained by the error include errors.
[0010]
The third problem is described below. In the second velocity estimating means 9, the residual magnetic flux vector φ0 is obtained by the formula (3), which is derived from the formula (4) as φx0 = 0. Therefore, when the magnetic flux remains when the second speed estimating means is started and φx0 is not 0, the calculation of the residual magnetic flux vector φ0 is erroneously performed.
[0011]
The fourth problem is described below. When the minute time t1 of the first speed estimating means 8 and the minute time t2 of the second speed estimating means 9 are fixed values, the center angle θ of the arc of the magnetic flux vector spreads in proportion to the rotation angular frequency ω0. If ω0 is very large, θ may exceed 180 degrees. If the center angle is obtained from the information of the magnetic flux vector at the first time, the magnetic flux vector at the last time, and the center of the arc, The calculation of θ may be wrong.
The present invention has been made in view of the above points, and aims to solve these problems, and to more accurately and reliably grasp the rotational angular frequency and the residual magnetic flux vector of an induction motor at the time of starting. Another object of the present invention is to provide a control device for an induction motor in which transient phenomena such as overcurrent and rapid acceleration / deceleration do not occur when shifting to control of torque or speed in normal operation control.
[0012]
[Means for Solving the Problems]
In other words, the means to achieve that goal are:
1. In claim 1,
In order to solve the first problem, in the case where the speed cannot be estimated by the second speed estimating means, immediately after the execution of the second speed estimating means, the current flows in the opposite direction to the current flowing by the second speed estimating means. And a third speed estimating means for estimating a rotational angular frequency and a residual magnetic flux vector of the induction motor in the same manner as the second speed estimating means except that a direct current is supplied to the motor.
[0013]
2. In claim 2,
In order to solve the second problem, the first, second or third speed estimating means may determine the center of the arc which is the trajectory of the magnetic flux vector output from the magnetic flux calculating means. Dividing the time from the end to the end into three equal parts, calculating the average value of the arcs in the respective time domains, obtaining three points, obtaining the center of a circle passing through the three points, and setting the center of the arc as the center of the arc. Features.
[0014]
3. In claim 3,
In order to solve the third problem, in the second or third speed estimating means, the DC current vector flowing in the second or third speed estimating means is ix, and the second or third speed estimating means is ix. The angular frequency corresponding to the obtained speed is ω 0, the secondary time constant of the induction motor is T 2, the mutual inductance is M, the imaginary unit is j, and the trajectory of the magnetic flux vector output from the magnetic flux calculating means is Let f0 be the vector at the center of a certain arc, and let f1 be the magnetic flux vector output from the magnetic flux calculating means at the last point in time of the second or third speed estimating means.
φ0 = M · ix / (1−j · ω0 · T2) + f1−f0 (6)
And a second or third speed estimating means.
[0015]
4. In claim 4,
In order to solve the fourth problem, the minute time t1 of the first speed estimating means and the minute time t2 of the second or third speed estimating means are set to a predetermined maximum time and the output of the magnetic flux calculating means. And the time at which the center angle of the arc, which is the locus of the magnetic flux vector, becomes a predetermined angle, is the shorter time.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention is shown in the block diagram of FIG. 1 and will be described with reference to FIG. The description of reference numerals 1 to 9 is omitted because it has been described in the prior art.
If the second speed estimating means 9 cannot find the rotation angular frequency ω0, the operation switching device 7 sets the third speed estimating means 9 to the third speed during a predetermined minute period t2 after the second speed estimating means 9 is selected. The estimating means 10 is selected.
The third speed estimating means 10 controls the rotation angle frequency ω0 and the residual magnetic flux vector φ0 of the induction motor 4 in the same manner as the second speed estimating means 9 so that the input current of the induction motor becomes a predetermined DC current vector ix2. Is output. In this case, the direction of the direct current vector flowing is reverse to that of the second speed estimating means 9.
That is, a relationship of ix2 = −ix1 is set. The rotation speed cannot be determined by the second speed estimating means 9 either when the rotation is stopped or when φx0−φx in the equation (4) is a value close to zero. In the third speed estimating means 10, the latter case can be eliminated by setting ix2 = -ix1, so that the rotational angular frequency can be determined without fail.
[0017]
In the second speed estimating means 9 and the third speed estimating means 10 of the present embodiment, the residual magnetic flux vector φ0 is obtained by Expression (6) instead of Expression (3). Here, ix1 in the case of the second speed estimating means 9 and ix2 in the case of the third speed estimating means 10 are applied to ix in the equation (6). The first term of equation (6) represents the first term of equation (4), and the term f1-f0 of equation (6) corresponds to t = t2 of the second term of equation (4). Even if the magnetic flux remains when the second or third speed estimating means is started and φx0 is not 0, the residual magnetic flux vector φ0 can be accurately obtained by the equation (6).
[0018]
A method for obtaining the center of the arc of the magnetic flux vector locus of the first speed estimating means 8, the second speed estimating means 9, and the third speed estimating means 10 of this embodiment will be described with reference to FIG.
The minute period t1 or t2 is divided into three equal parts, and these are set as periods ta, tb, and tc in time order. The average point of the magnetic flux trajectory in the period ta is determined as Pa, and the average points of the magnetic flux trajectories in the other two periods are determined as Pb and Pc, respectively. The center of a circle passing through these three points Pa, Pb, and Pc is obtained. The center angle θx of the arc from the point Pa to the point Pc is obtained, multiplied by 1.5 and defined as θ used in the equation (1).
[0019]
In the present embodiment, the minute period t1 of the first speed estimating means 8 and the minute period t2 of the second speed estimating means 9 and the third speed estimating means 10 correspond to the center of the arc which is the locus of the magnetic flux vector output from the magnetic flux calculating means 6. Assume that the angle exceeds a predetermined angle, for example, 180 degrees.
In other words, the center angle is obtained as needed in each speed estimating means, and when the center angle exceeds 180 degrees, for example, the rotational angular frequency ω0 and the residual magnetic flux vector φ0 are obtained, and each speed estimating means is terminated. Even if the center angle of the circular arc does not exceed the predetermined angle, if the predetermined time, for example, 20 msec has elapsed, the rotational angular frequency ω0 and the residual magnetic flux vector φ0 are obtained, and each speed estimating means is terminated.
[0020]
【The invention's effect】
As described above, according to the present invention, the rotational angular frequency and the residual magnetic flux vector of the induction motor at the time of starting can be grasped more accurately and more reliably. No transient phenomena such as sudden acceleration or deceleration occur, which is extremely useful in practical use.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of the present invention.
FIG. 2 is a block diagram illustrating a conventional example.
FIG. 3 is an example of a magnetic flux vector locus in a speed estimating unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Power converter 2 Current vector detector 3 Voltage vector detector 4 Induction motor 5 Normal operation controller 6 Magnetic flux calculation means 7 Operation switch 8 First speed estimation means 9 Second speed estimation means 10 Third speed estimation means

Claims (4)

Magnetic flux calculating means for calculating a magnetic flux vector by time-integrating a value obtained by removing a voltage drop due to a primary resistance and a leakage inductance from an input voltage vector of the induction motor, and a predetermined minute period immediately after starting to supply power to the induction motor At t1, the input current of the induction motor is set to be a DC current of zero or a value close to zero, and the center of an arc which is the locus of a magnetic flux vector output from the magnetic flux calculating means is obtained to determine the rotation angle of the induction motor. A first speed estimating means for estimating a frequency and a residual magnetic flux vector; and a case in which the speed cannot be estimated by the first speed estimating means. The center of an arc, which is the locus of the magnetic flux vector output from the magnetic flux calculating means, is determined by setting the input current of the motor to a predetermined DC current vector. The control apparatus for an induction motor for controlling the power converter for supplying power to the induction motor and a second speed estimation means for estimating a residual magnetic flux vector and the rotation angle frequency,
In the case where the speed cannot be estimated by the second speed estimating means, the DC current is caused to flow in the opposite direction to the current passed by the second speed estimating means immediately after the execution of the second speed estimating means. A control device for an induction motor, comprising: third speed estimating means for estimating a rotational angular frequency and a residual magnetic flux vector of the induction motor in the same manner as the second speed estimating means. When the first, second or third speed estimating means finds the center of the arc which is the trajectory of the magnetic flux vector output from the magnetic flux calculating means, the time from the beginning to the end of the arc is divided into three equal parts. 2. The control of an induction motor according to claim 1, wherein an average value of the arcs in each time domain is calculated to determine three points, and a center of a circle passing through the three points is determined to be the center of the arc. apparatus. In the second or third speed estimating means, the dc current vector flowing by the second or third speed estimating means is ix, and the angular frequency corresponding to the speed obtained by the second or third speed estimating means is ω0 The secondary time constant of the induction motor is represented by T2, the mutual inductance is represented by M, the imaginary unit is represented by j, and the vector of the center of the arc which is the locus of the magnetic flux vector output from the magnetic flux computing means is represented by f0. The residual magnetic flux vector φ0 is defined as f1 as the magnetic flux vector output from the magnetic flux calculating means at the last time point of the second or third speed estimating means.
φ0 = M · ix / (1−j · ω0 · T2) + f1−f0
3. The control device for an induction motor according to claim 1, further comprising a second or third speed estimating unit obtained by the following. The minute time t1 of the first speed estimating means and the minute time t2 of the second or third speed estimating means are defined as a predetermined maximum time and a central angle of an arc which is a locus of a magnetic flux vector output from the magnetic flux calculating means. 4. The control device for an induction motor according to claim 1, wherein the time is shorter than a time at which the angle becomes a predetermined angle.

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