JP3676946B2

JP3676946B2 - Induction motor control device

Info

Publication number: JP3676946B2
Application number: JP16912799A
Authority: JP
Inventors: 智寿亀山
Original assignee: Okuma Corp
Current assignee: Okuma Corp
Priority date: 1999-06-16
Filing date: 1999-06-16
Publication date: 2005-07-27
Anticipated expiration: 2019-06-16
Also published as: JP2001008500A

Description

【０００１】
【発明の属する技術分野】
本発明は工作機械の主軸駆動などに利用され、誘導電動機の出力トルクを任意に制御する誘導電動機の制御装置に関するものである。
【０００２】
【従来の技術】
工作機械の主軸駆動などの用途には、すべり周波数型ベクトル制御によって駆動される誘導電動機が多く用いられている。
図４に従来の誘導電動機の制御装置の一例を示す。この制御装置に対して外部から回転速度指令ω*が入力される。演算器１は、回転速度指令ω*から磁束密度指令φ*を演算する磁束密度指令演算器である。演算器４は、下式（１）、（２）に基づき励磁電流指令id*より磁束密度推定値φ^を演算する磁束密度推定器である。
【数１】
φ^＝Ｍ・id*／（１＋ＴＳ）・・・（１）
【数２】
Ｔ＝Ｍ／ｒ2 ・・・（２）
ここで、Ｍは励磁インダクタンス、ｒ2は二次抵抗であり、Ｔは式（２）で表すことのできる電気的時定数である。
減算器２は、回転速度指令ω*と誘導電動機の回転速度ωmから速度の偏差を算出する。演算器３は、前記減算器２の出力からトルク指令Ｔ*を算出するトルク指令演算器である。演算器５bは、磁束密度指令φ*と磁束密度推定値φ^とトルク指令Ｔ*を入力とし、励磁電流指令id*とトルク電流指令iq*を出力する電流指令演算器である。dq軸電圧指令算出部９は、励磁電流指令id*と励磁電流検出値idおよびトルク電流指令iq*とトルク電流検出値iqから下式（３）、（４）に基づき励磁電流同相電圧指令ｅd*，トルク電流同相電圧指令ｅq*を演算する。
【数３】
ｅd*＝Ｇd・(id*−id)−ωＬσ・iq*＋ｒ1・id* ・・・（３）
【数４】
ｅq*＝ωＬσ・id*＋Ｇq・(iq*−iq)＋ｒ1・iq*＋ω・φ^ ・・・（４）
ここで、ｒ1は一次巻線抵抗、Ｌσは漏れインダクタンスである。また、Ｇd,Ｇqは十分に大きなゲインであり、ｐi演算増幅器などを用いて実現する。
【０００３】
ｄｑ軸電圧指令算出部９の出力した励磁電流同相電圧指令ｅd*，トルク電流同相電圧指令ｅq*は、三相電圧指令発生手段を構成する二相三相変換器１０によって三相の交流電圧指令ｅu*，ｅv*，ｅw*に変換され、インバータ１５に入力される。インバータ１５は直流電源１４をエネルギー源として、この三相の交流電圧指令ｅu*，ｅv*，ｅw*に応じた電圧を誘導電動機１７に印加することによって三相交流電流iu，iv，iwが流れる。この三相交流電流iu，iv，iwは電流検出器１６a，１６b，１６cによって検出され、三相二相変換器１２によって励磁電流検出値idおよびトルク電流検出値iqに変換される。なお、二相三相変換器１２と三相二相変換器１０とが座標変換に使用する信号sinωｔ，cosωｔは、角周波数指令ωを基に二相正弦波発生器１１によって出力される。この角周波数指令ωは、位置検出器１９によって検出された誘導電動機１７の回転位置を微分器１８で微分することによって得た回転速度ωmに、滑り周波数演算器７によりトルク電流指令iq*と磁束密度推定値φ^および二次抵抗ｒ2から演算したすべり角周波数ωsを加算する角周波数指令算出手段８によって得られる。切換器２０は、誘導電動機の巻線を切換る巻線切換器である。
【０００４】
電流指令演算器５bの詳細図を図３に示す。磁束密度指令φ*と磁束密度推定値φ^の差を減算器２１で算出する。演算器２２は、下式（５）に基づき減算器２１の出力より励磁電流指令値id*'を演算する。
【数５】
id*'＝Ｇφ（φ*−φ^）・・・（５）
ここで、Ｇφは十分に大きなゲインであり、ｐi演算増幅器などを用いて実現する。
リミット器２４は、励磁電流指令値id*'を任意の励磁電流指令制限値id*limで制限し励磁電流指令id*を出力する。励磁電流指令制限値id*limは、下記数式（６）で表される範囲以内の値である。
【数６】
｜id*lim｜ ≦ ｜i1max｜・・・（６）
ここで｜｜は絶対値を示しｉ1maxは誘導電動機に流すことの可能な一次電流の最大値である。
演算器２７は、下式（７）に基づきトルク電流制限値iq*limを演算する。
【数７】
iq*lim ＝ √（i1max~2ーid*~2）・・・（７）
ここで、~2は二乗を示す。
除算器２６は、トルク指令Ｔ*を磁束密度推定値φ^で除算しトルク電流指令値iq*'を演算する。リミット器２５は、トルク電流指令値iq*'をトルク電流制限値iq*limで制限し、トルク電流指令iq*を出力する。
【０００５】
【発明が解決しようとする課題】
図６に、従来技術における各指令等を示したタイムチャートを示す。T0、T1、T2、T3は時間を示し、T0で停止している誘導電動機に誘導電動機の最高回転数ωmaxの回転速度指令ω*が与えられた場合について各指令および検出値について説明する。T1は磁束密度推定値φ^が磁束密度指令φ*に一致する時点であり、T2は誘導電動機の回転速度ωmが基底回転数に到達した時点であり、T3は誘導電動機の回転速度ωmが最高回転速度に到達した時点である。T0-T1間は、誘導電動機内部の磁束を確立するための磁束フォーシング期間であり、T0-T1間の励磁電流指令id*は、式（６）に基づき一次電流制限値i1maxの値となる。また、トルク電流指令iq*は、式（７）に基づきフォーシング期間中はiq*＝0となり、T0-T1間では、式（３）、（４）は下記の様に表すことができる。
【数８】
ｅd*＝Ｇd・(id*−id)＋ｒ1・id* ・・・（８）
【数９】
ｅq*＝ωＬσ・id*＋ω・φ^ ・・・（９）
T1での一次電圧指令ｅ1*は、励磁電流同相電圧指令ｅd*，トルク電流同相電圧指令ｅq*のベクトル合成演算によって算出するため、下式（１０）に示す様に表すことができる。
【数１０】
ｅ1*＝√（ｅd*~2＋ｅq*~2）・・・（１０）
漏れインダクタンスＬσが大きな誘導電動機等においては、T1時点でトルク電流同相電圧指令ｅq*がインバータの出力飽和電圧ｅsatを越え、T1-T2間の一次電圧指令ｅ1*がインバータの出力飽和電圧ｅsatを越える場合があり、指令通りの一次電圧を誘導電動機に印加することができない。この様な場合、T1の直前およびT1-T2間でid*≠id，iq*≠iqとなり、電流制御が不安定となる現象が発生する。また、T1時点において一次電圧指令ｅ1*がインバータの出力飽和電圧ｅsatを越えているにもかかわらず、磁束フォーシングを行なっており無駄なエネルギーを消費していた。
【０００６】
【課題を解決するための手段】
上述した課題を解決するために本発明にかかる誘導電動機の制御装置は、直流電源をエネルギー源として直流電流からインバータにより変換した三相交流電流によって駆動する誘導電動機の制御装置であって、トルク指令と磁束密度指令の二相指令を前記誘導電動機の１次電流を制御するための三相の一次電圧指令に変換し、前記誘導電動機の三相の１次電流検出値をトルク電流検出値と励磁電流検出値の二相の検出値に変換し、フィードバック制御を行う誘導電動機の制御装置において、前記磁束密度推定値と前記直流電源の直流電圧検出値と漏れインダクタンスと角周波数指令とに基づき、一次電圧指令がインバータの飽和電圧を超えない励磁電流制限値を演算する手段と、前記磁束密度指令と磁束密度推定値の差に基づいて演算した値を、前記励磁電流制限値に基づいて制限して励磁電流指令を出力する励磁電流指令演算手段と、前記励磁電流指令に基づき前記磁束密度推定値を演算する磁束密度演算手段と、前記励磁電流指令と前記励磁電流検出値に基づき励磁電流誤差を算出し、該励磁電流誤差に基づき、励磁電流と同相の励磁電流同相電圧指令を算出するｄ軸電圧指令算出手段と、前記トルク指令と前記磁束密度推定値と前記励磁電流指令に基づきトルク電流指令を算出するトルク電流指令発生手段と、前記トルク電流指令と前記トルク電流検出値に基づきトルク電流誤差を算出し、該トルク電流誤差に基づき、トルク電流と同相のトルク電流同相電圧指令を算出するｑ軸電圧指令算出手段と、前記励磁電流同相電圧指令もしくは前記トルク電流同相電圧指令に基づき誘導電動機に印加する三相の一次電圧指令を算出する三相電圧指令発生手段と、を有することを特徴とする。
本発明は次の特徴をもつ誘導電動機の制御装置であってもよい。すなわち、直流電源をエネルギー源として直流電流からインバータにより変換した三相交流電流によって駆動する誘導電動機の制御装置であって、トルク指令と磁束密度指令の二相指令を前記誘導電動機の１次電流を制御するための三相の一次電圧指令に変換し、前記誘導電動機の三相の１次電流検出値をトルク電流検出値と励磁電流検出値の二相の検出値に変換し、フィードバック制御を行う誘導電動機の制御装置において、前記磁束密度推定値と前記誘導電動機の一次電圧指令または一次電圧制限値と漏れインダクタンスと角周波数指令とに基づき、一次電圧指令がインバータの飽和電圧を超えない励磁電流制限値を演算する手段と、前記磁束密度指令と磁束密度推定値の差に基づいて演算した値を、前記励磁電流制限値に基づいて制限して励磁電流指令を出力する励磁電流指令演算手段と、前記励磁電流指令に基づき前記磁束密度推定値を演算する磁束密度演算手段と、前記励磁電流指令と前記励磁電流検出値に基づき励磁電流誤差を算出し、該励磁電流誤差に基づき、励磁電流と同相の励磁電流同相電圧指令を算出するｄ軸電圧指令算出手段と、前記トルク指令と前記磁束密度推定値と前記励磁電流指令に基づきトルク電流指令を算出するトルク電流指令発生手段と、前記トルク電流指令と前記トルク電流検出値に基づきトルク電流誤差を算出し、該トルク電流誤差に基づき、トルク電流と同相のトルク電流同相電圧指令を算出するｑ軸電圧指令算出手段と、前記励磁電流同相電圧指令および前記トルク電流同相電圧指令に基づき誘導電動機に印加する三相電圧指令を算出する三相電圧指令発生手段と、を有する。
【０００７】
また、本発明の誘導電動機の制御装置においては、前記励磁電流制限値を演算する手段は、前記直流電圧検出値もしくは前記誘導電動機の一次電圧指令または前記一次電圧制限値を前記角周波数指令で除算する演算器と、該演算器の出力から前記磁束密度推定値を減算する減算器とを有し、これらを用いて前記励磁電流制限値を演算し、前記励磁電流指令演算手段は、リミット器を有し、これを用いて前記励磁電流制限値に基づく制限を行うものであってもよい。
【０００８】
本発明による誘導電動機の制御装置によれば、磁束フォーシング中の励磁電流指令を直流電圧検出値と回転速度指令と漏れインダクタンスに基づいてリミット処理することにより、一次電圧指令がインバータの飽和電圧を越えないように制御を行なうことができる。また、一次電圧指令がインバータの飽和電圧を越えない範囲で電流制御するため、励磁電流指令とトルク電流指令に対して常に適切な電流分配が可能となる。
【０００９】
【発明の実施の形態】
図２は本発明に係る誘導電動機の制御装置の一実施形態のブロック図である。図４に示す従来の誘導電動機の制御装置と同じ構成要素は同一符号で示してあり、その説明は重複するので省略する。
図２中の５は、直流電圧検出値Ｖdcと回転速度指令ω*と磁束密度指令φ*と磁束密度推定値φ^とトルク指令Ｔ*とを入力とし、励磁電流指令id*とトルク電流指令iq*を出力する電流指令演算器である。電流指令演算器５の詳細図を図１に示す。磁束密度指令φ*と磁束密度推定値φ^の差を減算器２１で算出する。演算器２２は、式（５）に基づき減算器２１の出力より励磁電流指令値id*'を演算する。演算器２３は、直流電圧検出値Ｖdcと回転速度指令ω*と磁束密度推定値φ^に基づき励磁電流指令制限値id*limを演算する。リミット器２４は、演算器２３の出力である励磁電流制限値id*limに基づき前記励磁電流指令値id*'を制限し励磁電流指令id*として出力する。演算器２６は、トルク指令Ｔ*を磁束密度推定値φ^で除算することでトルク電流指令値iq*'を演算する。演算器２７は、式（７）に基づき励磁電流指令式よりトルク電流制限値iq*limを演算する。リミット器２５は、演算器２７の出力であるトルク電流制限値iq*limに基づき前記トルク電流指令値iq*'を制限し、トルク電流指令iq*として出力する。
【００１０】
前記演算器２３による励磁電流指令制限値id*limの演算方法に関する例を説明する。
式（８）においてフィードフォワード補償が適切であるとするとid*−id＝０となり、第１項を無視することができるため、式（８）は下式（１１）となる。
【数１１】
ｅd*＝ｒ1・id* ・・・（１１）
式（１０）は、式（９）、（１１）を用いて表すと、下式（１２）となる。
【数１２】
ｅ1*＝√[（ｒ1・id*）~2＋（ωＬσ・id*＋ω・φ^）~2］・・・（１２）
式（１２）の第１項は第２項と比較し十分小さいので無視し、電流が安定に制御できるのは一次電圧指令ｅ1*がインバータの飽和電圧ｅsat以下のときであるため、式（１２）は、下式（１３）となる。
【数１３】
ｅ1*＝ωＬσ・id*＋ω・φ^≦ｅsat ・・・（１３）
インバータの飽和電圧は、直流電圧値Ｖdcに等しいので、式（１３）より励磁電流指令の範囲を求めると下式（１４）の様になる。
【数１４】
id*≦ （Ｖdc／ω−φ^）／Ｌσ ・・・（１４）
正の励磁電流指令制限値id*Plimは式（１４）および式（６）より下式（１５）、（１６）の様に表すことができる。
【数１５】
（Ｖdc／ω−φ^）／Ｌσ ＞ i1max の場合
id*Plim ＝ i1max ・・・（１５）
【数１６】
（Ｖdc／ω−φ^）／Ｌσ ≦ i1max の場合
id*Plim ＝（Ｖdc／ω−φ^）／Ｌσ ・・・（１６）
励磁電流指令id*が負の場合、常にｅ1*≦Ｖdcであるので、負の励磁電流制限値は下式（１７）の様に表すことができる。
【数１７】
id*Nlim ＝ -i1max ・・・（１７）
図１中の演算器２３は、前式（１５）、（１６）、（１７）に基づき励磁電流制限値id*limを出力する。
【００１１】
また、一次電圧指令値ｅ1*がインバータの飽和電圧を越えないように一次電圧指令値に制限値ｅ1*limを設けている制御装置の場合、図１中の演算器２３の演算において、直流電圧検出値の代わりに一次電圧指令ｅ1*の制限値ｅ1*limを用いて演算してもよい。
【００１２】
図５に、本発明における各指令等を示したタイムチャートを示す。図６で説明した内容は、重複するので省略する。励磁電流指令制限値id*limが式（１５）から式（１６）に切り替わった時点をT4で示す。T4-T1間では、式（１６）に基づき励磁電流制限値id*limによって励磁電流指令がリミット処理されているため、T4-T2間で電圧指令ｅ1*がインバータの出力飽和電圧ｅsatを越えない。さらに、また、T4-T1間で式（１６）に基づき励磁電流を制限した分、式（７）に基づきトルク電流指令iq*が指令されている。
【００１３】
【発明の効果】
以上、説明したように本発明による誘導電動機の制御装置によれば、磁束フォーシング中の励磁電流指令を回転速度指令と漏れインダクタンスと直流電圧検出値または一次電圧指令制限値とに基づいてリミット処理することにより、一次電圧指令がインバータの飽和電圧を越えないように制御を行うことができる。その結果、常に安定した電流フィードバック制御ができ、電流制御が不安定となる現象が発生しない。また、一次電圧指令がインバータの飽和電圧を越えない様に電流指令をすることにより、励磁電流指令とトルク電流指令に対して常に適切な電流指令分配が可能であり無駄なエネルギーを消費しないので誘導電動機の加速時における立ち上がり時間が最短となる。
【図面の簡単な説明】
【図１】本発明による誘導電動機の制御装置の電流指令制限値演算器の一実施形態のブロック図である。
【図２】本発明による誘導電動機の制御装置の一実施形態のブロック図である。
【図３】従来の誘導電動機の制御装置の電流指令制限値演算器のブロック図である。
【図４】従来の誘導電動機の制御装置のブロック図である。
【図５】図２に示す誘導電動機の制御装置の各指令および検出値の波形図である。
【図６】図４に示す誘導電動機の制御装置の各指令および検出値の波形図である。
【符号の説明】
１、３、４、５、７、２２、２３、２６、２７演算器
２、２１減算器
２４、２５リミット器
８加算器
９ｄｑ軸電圧指令算出部
１０二相三相変換器
１１二相正弦波発生器
１２三相二相変換器
１４直流電源
１５インバータ
１６電流検出器
１７誘導電動機
１８微分器
１９位置検出器
２０巻線切替器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an induction motor that is used for driving a spindle of a machine tool and arbitrarily controls an output torque of the induction motor.
[0002]
[Prior art]
Induction motors driven by slip frequency vector control are often used for applications such as spindle driving of machine tools.
FIG. 4 shows an example of a conventional induction motor control device. A rotational speed command ω * is input from the outside to this control device. The calculator 1 is a magnetic flux density command calculator that calculates a magnetic flux density command φ * from the rotational speed command ω *. The calculator 4 is a magnetic flux density estimator that calculates a magnetic flux density estimated value φ ^ from the excitation current command id * based on the following equations (1) and (2).
[Expression 1]
φ ^ = M · id * / (1 + TS) (1)
[Expression 2]
T = M / r2 (2)
Here, M is an excitation inductance, r2 is a secondary resistance, and T is an electrical time constant that can be expressed by equation (2).
The subtracter 2 calculates a speed deviation from the rotational speed command ω * and the rotational speed ωm of the induction motor. The calculator 3 is a torque command calculator that calculates a torque command T * from the output of the subtractor 2. The computing unit 5b is a current command computing unit that receives the magnetic flux density command φ *, the magnetic flux density estimated value φ ^, and the torque command T * and outputs the excitation current command id * and the torque current command iq *. The dq axis voltage command calculation unit 9 calculates the excitation current common mode voltage command ed from the excitation current command id *, the excitation current detection value id, the torque current command iq *, and the torque current detection value iq based on the following equations (3) and (4). * Calculates the torque current common-mode voltage command eq *.
[Equation 3]
ed * = Gd · (id * −id) −ωLσ · iq * + r1 · id * (3)
[Expression 4]
eq * = ωLσ · id * + Gq · (iq * −iq) + r1 · iq * + ω · φ ^ (4)
Here, r1 is the primary winding resistance and Lσ is the leakage inductance. Gd and Gq are sufficiently large gains, and are realized using a pi operational amplifier or the like.
[0003]
The excitation current common-mode voltage command ed * and torque current common-mode voltage command eq * output from the dq-axis voltage command calculation unit 9 are converted into a three-phase AC voltage command by the two-phase three-phase converter 10 constituting the three-phase voltage command generation means. It is converted into eu *, ev *, ew * and input to the inverter 15. The inverter 15 uses the DC power supply 14 as an energy source, and applies a voltage corresponding to the three-phase AC voltage commands eu *, ev *, and ew * to the induction motor 17 so that three-phase AC currents iu, iv, and iw flow. . The three-phase alternating currents iu, iv, iw are detected by the current detectors 16a, 16b, 16c, and converted into the excitation current detection value id and the torque current detection value iq by the three-phase two-phase converter 12. The signals sinωt and cosωt used for coordinate conversion by the two-phase three-phase converter 12 and the three-phase two-phase converter 10 are output by the two-phase sine wave generator 11 based on the angular frequency command ω. This angular frequency command ω is converted into a rotational speed ωm obtained by differentiating the rotational position of the induction motor 17 detected by the position detector 19 with a differentiator 18, and a torque current command iq * and a magnetic flux by a slip frequency calculator 7. It is obtained by the angular frequency command calculating means 8 for adding the slip angular frequency ωs calculated from the density estimated value φ ^ and the secondary resistance r2. The switcher 20 is a winding switcher that switches the windings of the induction motor.
[0004]
A detailed view of the current command calculator 5b is shown in FIG. The subtractor 21 calculates the difference between the magnetic flux density command φ * and the magnetic flux density estimated value φ ^. The calculator 22 calculates the excitation current command value id * ′ from the output of the subtractor 21 based on the following equation (5).
[Equation 5]
id * '= Gφ (φ * −φ ^) (5)
Here, Gφ is a sufficiently large gain, and is realized using a pi operational amplifier or the like.
The limit device 24 limits the excitation current command value id * ′ with an arbitrary excitation current command limit value id * lim and outputs the excitation current command id *. The excitation current command limit value id * lim is a value within the range represented by the following mathematical formula (6).
[Formula 6]
｜ id * lim ｜ ≦ ｜ i1max ｜ (6)
Here, || represents an absolute value, and i1max represents the maximum value of the primary current that can be passed through the induction motor.
The calculator 27 calculates the torque current limit value iq * lim based on the following equation (7).
[Expression 7]
iq * lim = √ (i1max ~ 2 ー id * ~ 2) (7)
Here, ~ 2 represents a square.
The divider 26 divides the torque command T * by the estimated magnetic flux density value φ ^ to calculate the torque current command value iq * ′. The limit device 25 limits the torque current command value iq * ′ with the torque current limit value iq * lim and outputs the torque current command iq *.
[0005]
[Problems to be solved by the invention]
FIG. 6 shows a time chart showing each command in the prior art. T0, T1, T2, and T3 indicate time, and each command and detection value will be described when the rotation speed command ω * of the maximum rotation speed ωmax of the induction motor is given to the induction motor stopped at T0. T1 is the time when the estimated magnetic flux density φ ^ coincides with the magnetic flux density command φ *, T2 is the time when the rotational speed ωm of the induction motor reaches the base rotational speed, and T3 is the maximum speed ωm of the induction motor. This is the point when the rotational speed is reached. Between T0 and T1 is a magnetic flux forcing period for establishing the magnetic flux inside the induction motor, and the excitation current command id * between T0 and T1 becomes the value of the primary current limit value i1max based on the equation (6). . The torque current command iq * is iq * = 0 during the forcing period based on the equation (7), and the equations (3) and (4) can be expressed as follows between T0 and T1.
[Equation 8]
ed * = Gd · (id * −id) + r1 · id * (8)
[Equation 9]
eq * = ωLσ · id * + ω · φ ^ (9)
Since the primary voltage command e1 * at T1 is calculated by the vector synthesis operation of the excitation current common-mode voltage command ed * and the torque current common-mode voltage command eq *, it can be expressed as shown in the following equation (10).
[Expression 10]
e1 * = √ (ed * ~ 2 +＋ eq * ~ 2) (10)
In induction motors with large leakage inductance Lσ, the torque current common-mode voltage command eq * exceeds the inverter output saturation voltage esat at time T1, and the primary voltage command e1 * between T1 and T2 exceeds the inverter output saturation voltage esat. In some cases, the primary voltage as commanded cannot be applied to the induction motor. In such a case, id * ≠ id and iq * ≠ iq immediately before T1 and between T1 and T2, and a phenomenon that current control becomes unstable occurs. Further, even though the primary voltage command e1 * exceeds the output saturation voltage esat of the inverter at time T1, magnetic flux forcing is performed and wasteful energy is consumed.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, an induction motor control device according to the present invention is a control device for an induction motor that is driven by a three-phase AC current converted from a DC current by an inverter using a DC power source as an energy source, and a torque command Is converted into a three-phase primary voltage command for controlling the primary current of the induction motor, and the three-phase primary current detection value of the induction motor is converted into a torque current detection value and an excitation. converting the detected values of the two-phase current detection value, the control apparatus for an induction motor which performs feedback control, before being leaked Ki磁 flux density estimates and the DC voltage detection value of the DC power supply to the inductance and the angular frequency command and based, means for calculating an exciting current limit primary voltage command does not exceed the saturation voltage of the inverter, the magnetic flux density command value calculated based on the difference of the magnetic flux density estimates The excitation current command calculation means for outputting the excitation current command limit based on the excitation current limit value, the magnetic flux density calculating means for calculating a magnetic flux density estimates based on the excitation current command, and the exciting current command An excitation current error is calculated based on the excitation current detection value, a d-axis voltage command calculation means for calculating an excitation current common-mode voltage command in phase with the excitation current based on the excitation current error, the torque command and the magnetic flux density estimation Torque current command generating means for calculating a torque current command based on the value and the excitation current command; calculating a torque current error based on the torque current command and the torque current detection value; Based on the q-axis voltage command calculating means for calculating the torque current common-mode voltage command and the excitation current common-mode voltage command or the torque current common-mode voltage command. A three-phase voltage command generating means for calculating a primary voltage command of the three-phase to be applied to the guide motor, and having a.
The present invention may be an induction motor control device having the following characteristics. That is, a control device for an induction motor driven by a three-phase alternating current converted from a direct current by an inverter using a direct current power source as an energy source, wherein a two-phase command of a torque command and a magnetic flux density command is used as a primary current of the induction motor. It converts into a three-phase primary voltage command for control, converts the three-phase primary current detection value of the induction motor into a two-phase detection value of a torque current detection value and an excitation current detection value, and performs feedback control In the induction motor control device, based on the estimated magnetic flux density value, the primary voltage command or primary voltage limit value of the induction motor, the leakage inductance, and the angular frequency command, the excitation voltage limit is such that the primary voltage command does not exceed the saturation voltage of the inverter. A means for calculating a value, and a value calculated based on a difference between the magnetic flux density command and the magnetic flux density estimated value is limited based on the excitation current limit value. Excitation current command calculation means for outputting an excitation current command, magnetic flux density calculation means for calculating the magnetic flux density estimated value based on the excitation current command, and excitation current error based on the excitation current command and the excitation current detection value. D-axis voltage command calculating means for calculating an excitation current in-phase voltage command in phase with the excitation current based on the excitation current error, and a torque current command based on the torque command, the magnetic flux density estimated value, and the excitation current command. A torque current command generating means for calculating the torque current, a torque current error based on the torque current command and the detected torque current value, and a torque current common-mode voltage command in phase with the torque current based on the torque current error q A three-phase voltage command to be applied to the induction motor is calculated based on the shaft voltage command calculation means and the excitation current common-mode voltage command and the torque current common-mode voltage command. Has a three-phase voltage command generating means that, the.
[0007]
In the induction motor control apparatus of the present invention , the means for calculating the excitation current limit value divides the DC voltage detection value or the primary voltage command of the induction motor or the primary voltage limit value by the angular frequency command. And a subtractor for subtracting the magnetic flux density estimated value from the output of the calculator, the excitation current limit value is calculated using these, and the excitation current command calculation means includes a limiter Yes, and it may perform the restriction based on the excitation current limit value by using this.
[0008]
According to the induction motor control device of the present invention, the primary voltage command determines the saturation voltage of the inverter by limiting the excitation current command during magnetic flux forcing based on the detected DC voltage value, the rotational speed command, and the leakage inductance. Control can be performed so as not to exceed. In addition, since current control is performed in a range where the primary voltage command does not exceed the saturation voltage of the inverter, appropriate current distribution can always be performed for the excitation current command and the torque current command.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a block diagram of an embodiment of the control apparatus for an induction motor according to the present invention. The same components as those of the conventional induction motor control device shown in FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted because it is duplicated.
2 in FIG. 2 receives the DC voltage detection value Vdc, the rotational speed command ω *, the magnetic flux density command φ *, the magnetic flux density estimated value φ ^, and the torque command T * as input, and the excitation current command id * and the torque current command. This is a current command calculator that outputs iq *. A detailed view of the current command calculator 5 is shown in FIG. The subtractor 21 calculates the difference between the magnetic flux density command φ * and the magnetic flux density estimated value φ ^. The calculator 22 calculates the excitation current command value id * ′ from the output of the subtractor 21 based on the equation (5). The calculator 23 calculates the excitation current command limit value id * lim based on the DC voltage detection value Vdc, the rotation speed command ω *, and the magnetic flux density estimated value φ ^. The limiter 24 limits the excitation current command value id * ′ based on the excitation current limit value id * lim that is the output of the calculator 23 and outputs the limit as the excitation current command id *. The calculator 26 calculates the torque current command value iq * ′ by dividing the torque command T * by the estimated magnetic flux density value φ ^. The calculator 27 calculates the torque current limit value iq * lim from the excitation current command formula based on the formula (7). The limiter 25 limits the torque current command value iq * ′ based on the torque current limit value iq * lim that is the output of the computing unit 27, and outputs it as the torque current command iq *.
[0010]
An example relating to a method of calculating the excitation current command limit value id * lim by the calculator 23 will be described.
If feedforward compensation is appropriate in equation (8), id * −id = 0, and the first term can be ignored, so equation (8) becomes equation (11) below.
[Expression 11]
ed * = r1 · id * (11)
When expression (10) is expressed using expressions (9) and (11), the following expression (12) is obtained.
[Expression 12]
e1 * = √ [(r1 · id *) ~ 2 + (ωLσ · id * + ω · φ ^) ~ 2] (12)
The first term of equation (12) is sufficiently smaller than the second term and is ignored, and the current can be stably controlled when the primary voltage command e1 * is equal to or lower than the saturation voltage esat of the inverter. ) Becomes the following expression (13).
[Formula 13]
e1 * = ωLσ · id * + ω · φ ^ ≦ esat (13)
Since the saturation voltage of the inverter is equal to the DC voltage value Vdc, when the range of the excitation current command is obtained from the equation (13), the following equation (14) is obtained.
[Expression 14]
id * ≦ (Vdc / ω−φ ^) / Lσ (14)
The positive excitation current command limit value id * Plim can be expressed by the following equations (15) and (16) from the equations (14) and (6).
[Expression 15]
When (Vdc / ω-φ ^) / Lσ> i1max
id * Plim = i1max (15)
[Expression 16]
(Vdc / ω-φ ^) / Lσ ≤ i1max
id * Plim = (Vdc / ω-φ ^) / Lσ (16)
When the excitation current command id * is negative, e1 * ≦ Vdc is always satisfied, and thus the negative excitation current limit value can be expressed as in the following equation (17).
[Expression 17]
id * Nlim = -i1max (17)
The calculator 23 in FIG. 1 outputs the excitation current limit value id * lim based on the previous equations (15), (16), and (17).
[0011]
In the case of a control device in which the primary voltage command value e1 * is provided with a limit value e1 * lim so that the primary voltage command value e1 * does not exceed the saturation voltage of the inverter, in the calculation of the calculator 23 in FIG. The calculation may be performed using the limit value e1 * lim of the primary voltage command e1 * instead of the detected value.
[0012]
FIG. 5 is a time chart showing each command in the present invention. The contents described in FIG. 6 are omitted because they overlap. A point in time when the excitation current command limit value id * lim is switched from Expression (15) to Expression (16) is indicated by T4. Between T4 and T1, the excitation current command is limited by the excitation current limit value id * lim based on equation (16), so the voltage command e1 * does not exceed the inverter output saturation voltage esat between T4 and T2. . Further, the torque current command iq * is commanded based on the equation (7) by the amount that the excitation current is limited based on the equation (16) between T4 and T1.
[0013]
【The invention's effect】
As described above, according to the induction motor control apparatus of the present invention, the excitation current command during the magnetic flux forcing is subjected to limit processing based on the rotation speed command, the leakage inductance, the DC voltage detection value, or the primary voltage command limit value. By doing so, control can be performed so that the primary voltage command does not exceed the saturation voltage of the inverter. As a result, stable current feedback control can always be performed, and the phenomenon that current control becomes unstable does not occur. In addition, by giving a current command so that the primary voltage command does not exceed the saturation voltage of the inverter, appropriate current command distribution is always possible for the excitation current command and torque current command, and wasteful energy is not consumed. The rise time during acceleration of the motor is the shortest.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of a current command limit value calculator of a control device for an induction motor according to the present invention.
FIG. 2 is a block diagram of an embodiment of a control device for an induction motor according to the present invention.
FIG. 3 is a block diagram of a current command limit value calculator of a conventional induction motor control device.
FIG. 4 is a block diagram of a conventional control device for an induction motor.
FIG. 5 is a waveform diagram of each command and detected value of the control device for the induction motor shown in FIG. 2;
6 is a waveform diagram of each command and detected value of the control device for the induction motor shown in FIG. 4; FIG.
[Explanation of symbols]
1, 3, 4, 5, 7, 22, 23, 26, 27 Calculator 2, 21 Subtractor 24, 25 Limiter 8 Adder 9 dq-axis voltage command calculator 10 Two-phase three-phase converter 11 Two-phase sine Wave generator 12 Three-phase two-phase converter 14 DC power supply 15 Inverter 16 Current detector 17 Induction motor 18 Differentiator 19 Position detector 20 Winding switch

Claims

A control device for an induction motor driven by a three-phase AC current converted from a DC current by an inverter using a DC power source as an energy source, and controlling a primary current of the induction motor with a two-phase command of a torque command and a magnetic flux density command An induction motor that performs feedback control by converting a three-phase primary current command value of the induction motor into a two-phase detection value of a torque current detection value and an excitation current detection value In the control device of
Based ago Ki磁 flux density estimates and the DC voltage detection value of the DC power supply leakage inductance and the angular frequency command and, means for calculating an exciting current limit primary voltage command does not exceed the saturation voltage of the inverter,
Excitation current command calculation means for limiting the value calculated based on the difference between the magnetic flux density command and the estimated magnetic flux density value based on the excitation current limit value and outputting the excitation current command;
Magnetic flux density calculating means for calculating the magnetic flux density estimated value based on the excitation current command;
D-axis voltage command calculation means for calculating an excitation current error based on the excitation current command and the excitation current detection value, and calculating an excitation current in-phase voltage command in phase with the excitation current based on the excitation current error;
Torque current command generating means for calculating a torque current command based on the torque command, the magnetic flux density estimated value, and the excitation current command;
Q-axis voltage command calculation means for calculating a torque current error based on the torque current command and the detected torque current value, and calculating a torque current common-mode voltage command in phase with the torque current based on the torque current error;
Three-phase voltage command generating means for calculating a three-phase primary voltage command to be applied to the induction motor based on the excitation current common-mode voltage command and the torque current common-mode voltage command;
An induction motor control device comprising:

A control device for an induction motor driven by a three-phase AC current converted from a DC current by an inverter using a DC power source as an energy source, and controlling a primary current of the induction motor with a two-phase command of a torque command and a magnetic flux density command An induction motor that performs feedback control by converting a three-phase primary current command value of the induction motor into a two-phase detection value of a torque current detection value and an excitation current detection value In the control device of
Based prior to the primary voltage command or primary voltage limit Ki磁 flux density estimates and said induction motor and the leakage inductance and the angular frequency command and means for calculating an exciting current limit primary voltage command does not exceed the saturation voltage of the inverter When,
Excitation current command calculation means for limiting the value calculated based on the difference between the magnetic flux density command and the estimated magnetic flux density value based on the excitation current limit value and outputting the excitation current command;
Magnetic flux density calculating means for calculating the magnetic flux density estimated value based on the excitation current command;
D-axis voltage command calculation means for calculating an excitation current error based on the excitation current command and the excitation current detection value, and calculating an excitation current in-phase voltage command in phase with the excitation current based on the excitation current error;
Torque current command generating means for calculating a torque current command based on the torque command, the magnetic flux density estimated value, and the excitation current command;
Q-axis voltage command calculation means for calculating a torque current error based on the torque current command and the detected torque current value, and calculating a torque current common-mode voltage command in phase with the torque current based on the torque current error;
Three-phase voltage command generating means for calculating a three-phase voltage command to be applied to the induction motor based on the excitation current common-mode voltage command and the torque current common-mode voltage command;
An induction motor control device comprising:

A control device for an induction motor according to claim 1 or 2,
The means for calculating the excitation current limit value includes a calculator that divides the DC voltage detection value or the primary voltage command of the induction motor or the primary voltage limit value by the angular frequency command, and outputs the magnetic flux from the output of the calculator. A subtractor for subtracting the density estimation value, using these to calculate the excitation current limit value,
The excitation current command calculating means, have a limit device, the control device of an induction motor, characterized in that, perform restriction based on the excitation current limit value by using this.