JP4407151B2

JP4407151B2 - Sensorless control method and control apparatus for AC motor

Info

Publication number: JP4407151B2
Application number: JP2003121733A
Authority: JP
Inventors: 英昭井浦; 賢志末島; 勝志寺園; 光次郎沢村
Original assignee: Yaskawa Electric Corp
Current assignee: Yaskawa Electric Corp
Priority date: 2003-04-25
Filing date: 2003-04-25
Publication date: 2010-02-03
Anticipated expiration: 2023-04-25
Also published as: JP2004328920A

Description

【０００１】
【発明の属する技術分野】
本発明は交流電動機を始動する場合に、フリーラン状態の交流電動機の速度を推定して、推定した速度で運転することにより、スムーズに交流電動機を始動することを特徴とする交流電動機のセンサレス制御方法及び装置に関する。
【０００２】
【従来の技術】
特開２００１−１６１０９４では、交流電動機へ電力を出力する電力変換器を有し、電流指令信号と電力変換器の出力電流検出信号の偏差信号に基づいて、電力変換器の出力電流を制御する電流制御部を備え、速度検出器と電圧検出器を持たない交流電動機の制御方法において、前記交流電動機がフリーラン状態にある場合に、前記交流電動機の電流をゼロにするように強制的に前記電流指令信号をゼロとして電流制御し、この時の前記電流制御部出力を用いて、演算する出力電圧指令信号を基に、前記交流電動機の残留電圧の大きさと位相および角速度を求めることにより、フリーラン状態の前記交流電動機の回転方向及び速度を推定することによりフリーラン状態の前記交流電動機をスムーズに始動する制御方法が開示されている。しかしながら、電流制御器部の応答が悪い場合には、前記交流電動機の電流をゼロにすることが困難となり、前記電力変換器が過電流状態となり、スムーズに始動することができない。また、前記電流指令信号をゼロとして電流制御した時の前記電流制御部出力を用いて、演算する出力電圧指令信号が任意に設定した電圧レベルよりも低い場合には、電流制御することをやめ、任意の方向に任意の大きさの直流電流指令を設定された時間印加し、その後前記直流電圧の指令方向と180°位相を変えた方向に任意の大きさの電流指令を与え、設定された時間再び電流制御し、電流検出値に表れる周波数成分とその位相関係を検出し、この周波数成分を交流電動機の速度と推定して、位相関係からその回転方向を推定する制御方法が開示されている。しかし、前記交流電動機が高速でフリーランしている場合には、電流検出値に現れる周波数の検出分解能が粗くなったり、電流検出値に現れる周波数成分の信号の振幅が小さくなり、周波数を検出できなくなってしまう。
【０００３】
【特許文献１】
特開２００１−１６１０９４号公報
【０００４】
【発明が解決しようとする課題】
本発明は上記問題点に鑑みてなされたものであり、その目的は以下の交流電動のセンサレス制御方法及び装置を提供することを目的とする。（１）前記交流電動機の電流をゼロにするように強制的に前記電流指令信号をゼロとして電流制御する場合に、電流制御器の応答を高め、前記電力変換器が過電流状態とならないようにし、スムーズに運転継続できるようにする。（２）交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時にも、前記交流電動機が高速でフリーランしている場合、周波数検出の精度を向上する。（３）交流電動機が高速でフリーランしている場合でもスムーズに運転継続する。
【０００５】
【課題を解決するための手段】
上記課題を解決するため請求項1記載の発明では、交流電動機へ電力を出力する電力変換器を有し、電流指令信号と電力変換器の出力電流検出信号の偏差信号に基づいて電力変換器の出力電流を制御する電流制御部を備え、前記交流電動機がフリーラン状態にある場合に、前記交流電動機の電流をゼロにするように強制的に前記電流指令信号をゼロとして電流制御し、この時の前記電流制御部出力を用いて、演算する出力電圧指令信号を基に、前記交流電動機の残留電圧の大きさと位相および角速度を求めることにより、フリーラン状態の前記交流電動機の回転方向及び速度を推定する速度検出器と電圧検出器の両方の検出器を備えない交流電動機のセンサレス制御方法において、前記交流電動機の電流をゼロにする処理を行う時は、通常制御時よりも電流制御の処理のスキャン時間を短くすることを特徴とするものである。
【０００６】
また請求項２記載の発明では、前記交流電動機の電流をゼロにする処理を行う時は、通常制御時よりも電流制御の処理のスキャン時間を短くすると同時に、電力変換器のキャリア周波数を高くすることを特徴とする請求項1記載の交流電動機のセンサレス制御方法である。
【０００７】
また請求項３記載の発明では、交流電動機へ電力を出力する電力変換器を有し、電流指令信号と電力変換器の出力電流検出信号の偏差信号に基づいて、電力変換器の出力電流を制御する電流制御部を備え、前記交流電動機がフリーラン状態にある場合に、前記交流電動機の電流をゼロにするように強制的に前記電流指令信号をゼロとして電流制御し、この時の前記電流制御部出力を用いて、演算する出力電圧指令信号を基に、前記交流電動機の残留電圧の大きさと位相および角速度を求めることにより、フリーラン状態の前記交流電動機の回転方向及び速度を推定する速度検出器と電圧検出器の両方の検出器を備えない交流電動機のセンサレス制御装置において、前記交流電動機の電流をゼロにする処理を行う時、通常制御時よりも電流制御の処理のスキャン時間を短くする手段を備えたことを特徴とする交流電動機のセンサレス制御装置である。
【０００８】
また請求項４記載の発明は、前記交流電動機の電流をゼロにする処理を行う時、通常制御時よりも電流制御の処理のスキャン時間を短くすると同時に、電力変換器のキャリア周波数を高くする手段を備えたことを特徴とする請求項３記載の交流電動機のセンサレス制御装置である。
【０００９】
また請求項５記載の発明は、交流電動機へ電力を出力する電力変換器を有し、電流指令信号と電力変換器の出力電流検出信号の偏差信号に基づいて、電力変換器の出力電流を制御する電流制御部を備え、前記交流電動機がフリーラン状態にある場合に、前記交流電動機の電流をゼロにするように強制的に前記電流指令信号をゼロとして電流制御すると共にこの時の前記電流制御部出力を用いて、演算する出力電圧指令信号が任意に設定した電圧レベルよりも低い場合には、電流制御することをやめ、任意の方向に任意の大きさの直流電流指令を設定された時間印加し、その後前記直流電圧の指令方向と180°位相を変えた方向に任意の大きさの電流指令を与え、設定された時間再び電流制御し、速度推定回路が電流検出値に表れる周波数成分とその位相関係を検出し、この周波数成分を交流電動機の速度と推定して、位相関係からその回転方向を推定する速度検出器と電圧検出器の両方の検出器を備えない交流電動機のセンサレス制御方法において、前記交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時、通常制御時よりも電流制御の処理のスキャン時間を短くすることを特徴とする交流電動機のセンサレス制御方法である。
【００１０】
また請求項６記載の発明は、前記交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時は、通常制御時よりも電流制御の処理のスキャン時間を短くすると同時に、電力変換器のキャリア周波数を高くすることを特徴とする請求項５記載の交流電動機のセンサレス制御方法である。
【００１１】
また請求項７記載の発明は、前記交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時、通常制御時よりも電流制御の処理のスキャン時間を短くすると同時に、通常制御時とは別の小さな電流も検出できるような感度の高い電流検出器を用いることを特徴とする請求項５または６記載の交流電動機のセンサレス制御方法である。
【００１２】
また請求項８記載の発明は、交流電動機へ電力を出力する電力変換器を有し、電流指令信号と電力変換器の出力電流検出信号の偏差信号に基づいて、電力変換器の出力電流を制御する電流制御部を備え、前記交流電動機がフリーラン状態にある場合に、前記交流電動機の電流をゼロにするように強制的に前記電流指令信号をゼロとして電流制御すると共にこの時の前記電流制御部出力を用いて、演算する出力電圧指令信号が任意に設定した電圧レベルよりも低い場合には、電流制御することをやめ、任意の方向に任意の大きさの直流電流指令を設定された時間印加し、その後前記直流電圧の指令方向と180°位相を変えた方向に任意の大きさの電流指令を与え、設定された時間再び電流制御する。このとき、速度推定回路が電流検出値に表れる周波数成分とその位相関係を検出し、この周波数成分を交流電動機の速度と推定して、位相関係からその回転方向を推定する速度検出器と電圧検出器の両方の検出器を備えない交流電動機のセンサレス制御装置において、前記交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時は、通常制御時よりも電流制御の処理のスキャン時間を短くする手段を備えたことを特徴とする交流電動機のセンサレス制御装置である。
【００１３】
また請求項９記載の発明は、前記交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時、通常制御時よりも電流制御の処理のスキャン時間を短くすると同時に、電力変換器のキャリア周波数を高くする手段を備えたことを特徴とする請求項８記載の交流電動機のセンサレス制御装置である。
【００１４】
また請求項１０記載の発明は、前記交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時、通常制御時よりも電流制御の処理のスキャン時間を短くすると同時に、通常制御時とは別の小さな電流も検出できる感度の高い電流検出器を備えたことを特徴とする請求項８または９記載の交流電動機のセンサレス制御装置である。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態について、図面に基づいて説明する。図１は本発明における交流電動機のセンサレス制御装置の第１の実施形態の構成を示すブロック図である。
本実施形態における交流電動機のセンサレス制御装置は、電力変換器１、交流電動機２、電流検出器３、電流座標変換回路４、トルク電流制御回路５、励磁電流制御回路６、位相演算回路７、Ｖ／ｆ変換回路８、出力電圧演算回路９、スイッチングパターン発生回路１０、速度推定回路１１、加算器１２を備えている。電力変換器１は、パワー素子により三相交流を変換した直流電圧をＰＷＭ制御方式により任意の周波数と電圧の交流に変換し、交流電動機２に供給する。
電流検出器３は、前記交流電動機２に供給される電流を検出し、その電流検出信号を電流座標変換回路４へ入力する。
電流座標変換回路４は、前記電流検出器３で検出された電流をトルク電流検出値i_qfbと励磁電流検出値i_dfbに分離し、分離したトルク電流検出値i_qfbをトルク電流制御回路５へ入力し、分離した励磁電流検出値i_dfbを励磁電流制御回路６へ入力する。トルク電流制御回路５は、与えられたトルク電流指令値i_qrefと前記トルク電流検出値i_qfbとが一致するように第１のｑ軸電圧指令値V'_qrefを演算する。
励磁電流制御回路６は、与えられた励磁電流指令値i_drefと前記励磁電流検出値i_dfbとが一致するようにｄ軸電圧指令値V_drefを演算する。
位相演算回路７は、入力された周波数f₁を積分することにより、位相θを演算し、位相θを電流座標変換回路４と加算器１２へ入力する。
Ｖ／ｆ変換回路８は、入力された周波数f₁から、交流電動機の誘起電圧に相当する電圧E_refを演算する。この電圧E_refはE_ref／f₁＝一定値になるように予め設定している。
出力電圧演算回路９は、前記トルク電流制御回路５の出力である第１のｑ軸電圧指令値V'_qrefと前記Ｖ／ｆ変換回路８の出力である電圧E_refを加算し、第２のｑ軸電圧指令値V_qrefを演算し、前記第２のｑ軸電圧指令値と前記ｄ軸電圧指令値とから、出力電圧指令値V_1refとその電圧位相θ_Vを出力する。
V_1ref＝[(V_dref)²+(V_qref)²]^1/2・・・（１）
θ_V＝ｔａｎ^-1（V_qref／V_dref）・・・（２）
スイッチングパターン発生回路１０は、前記出力電圧指令値V_1ref及び前記電圧位相θ_Vと前記位相θを加算した電力変換器出力位相θ_degから、電力変換器１のスイッチングパターンを決定する。
速度推定回路１１は、前記電圧位相θ_Vの単位時間当りの変化から、フリーラン状態の交流電動機２の速度f_rとその回転方向を推定する回路である。
【００１６】
次に、フリーラン状態になった交流電動機を再始動する場合の動作について詳細に説明する。前記交流電動機２がフリーラン状態の場合、図１の３つのスイッチ１３、１４、１５がＡ側の通常運転状態から、Ｂ側のフリーラン始動状態になる。これにより、トルク電流指令値i_qref＝０及び励磁電流指令値i_dref＝０となる。また、通常制御中は出力周波数に応じて、積算される位相も前記交流電動機がフリーランしているので、基準となる位相がないため、ゼロに固定した状態で、前記交流電動機に流れる電流をゼロに制御する。ここで、前記交流電動機がフリーラン状態の場合、回転速度に応じた誘起電圧を発生する。前記誘起電圧は前記交流電動機２の回転速度で回転するため、前記交流電動機２の回転速度や誘起電圧の大きさと無関係に前記電力変換器１を運転し始めると、前記交流電動機２と前記電力変換器１との間に電流が流れてしまう。前記トルク電流制御回路５及び前記励磁電流制御回路６により、電流をゼロに制御すれば、前記交流電動機２の誘起電圧と前記電力変換器の出力電圧の大きさ、位相、周波数が一致することになる。このように前記交流電動機に流れる電流をゼロに制御することを零電流制御と呼ぶ。
【００１７】
零電流制御時のトルク電流制御回路５、励磁電流制御回路６の出力である第１のｑ軸電圧指令値V'_qref、ｄ軸電圧指令値V_drefは、前記交流電動機２の回転速度に一致した周波数の正弦波状の電圧指令値となる。出力電圧演算回路９は、前記第１のｑ軸電圧指令値V'_qrefと前記ｄ軸電圧指令値V_drefを入力とし、出力電圧指令値V_1refとその電圧位相θ_Vを出力する。前記出力電圧指令値V_1refは前記交流電動機の誘起電圧の大きさを表し、前記電圧位相θ_Vは誘起電圧の位相を表す。このため、この誘起電圧の位相の時間変化を、一定時間毎に測定することで、前記速度推定回路１１は誘起電圧の周波数を測定する。前記誘起電圧の周波数は、これまでの説明からわかるように、前記交流電動機２の回転速度に一致する。このため、フリーラン状態の前記交流電動機２の回転速度を推定することができる。前記交流電動機が逆転している場合には、位相の変化率が負になるので、フリーラン状態の交流電動機が正転しているか逆転しているかも推定することができる。このように零電流制御により、前記交流電動機の誘起電圧を観測すれば、交流電動機の回転方向を含めて、回転速度を推定できる。
【００１８】
次に、零電流制御を止め通常制御に切り替わる場合における、推定した回転方向及び速度を前記電力変換器に設定方法について説明する。
零電流制御状態から通常運転に移行する場合に、周波数だけ一致させて前記電力変換器１を始動しても、前記交流電動機には過大な電流が流れたりして、スムーズな始動ができない可能性がある。これを防止するためには、零電流制御中の誘起電圧の大きさと位相が通常制御に移行する瞬間にも連続しなければならない。このため、電力変換器の出力電圧指令値V_1ref及び電力変換器出力位相θ_deg及び出力周波数f₁に初期値を設定しなければならない。具体的には、通常運転状態では、前記電力変換器出力位相θ_degは前記交流電動機２の磁束の位相を基準にして制御するが、零電流制御中は、前記交流電動機２の誘起電圧と一致するような位相を出力している。このため、零電流制御中においては、通常制御の位相に対して、正転の場合には９０°位相が進んでいて、逆転の場合には９０°位相が遅れている。従って、前記電力変換器出力位相θ_degの初期値は、零電流制御の最後の位相から回転方向に応じて９０°位相を修正した後、前記速度推定回路１１が出力する交流電動機２の回転速度の推定値f_rを位相に換算して加えて補正した値を設定する。こうすることにより位相の連続性が保たれる。
また、零電流制御中に出力していた出力電圧指令値V_1refを誘起電圧に設定すれば、出力電圧の連続性が保たれる。このようにして、零電流制御から通常制御にスムーズに移行することができる。
前記交流電動機の誘起電圧を二次回路時定数に従って少しずつ上昇していき、正規のＶ／ｆレベルに一致できた時点でフリーラン状態の交流電動機を正常に始動できたと判断して、３つのスイッチがＡ側に切り替わる。
【００１９】
次に本発明である零電流制御中の電流応答を向上するための方法について説明する。フリーラン状態の前記交流電動機の速度を推定するためには、零電流制御時のトルク電流制御回路５、励磁電流制御回路６の出力である第１のｑ軸電圧指令値V'_qref、ｄ軸電圧指令値V_drefが、前記交流電動機の誘起電圧と一致しなければならない。
ここで、トルク電流制御回路５、励磁電流制御回路６が十分な能力を発揮し、前記交流電動機に流れる電流をゼロに制御できる場合には問題とならないが、トルク電流制御回路５、励磁電流制御回路６のゲインが大きくできない場合や前記交流電動機が高速で回転している場合には、大きな誘起電圧が発生しているため、前記電力変換器を始動した直後に過大な電流が流れ、前記電力変換器がトリップしてスムーズな始動ができないことがある。これを防止するためには、トルク電流制御回路５、励磁電流制御回路６の応答を向上しなければならない。電流制御を処理するスキャン時間が短ければ、その分だけ遅れがなくなるため、指令通りに電流を制御することができる。このため、零電流制御中はその他の演算を省略すれば、通常制御に対して、電流制御するためのスキャン時間を短くできるので、電流制御応答は向上できる。また、零電流制御時に電流制御のスキャン時間を短くしても、電力変換器のスイッチングパターンの作成が遅ければ、電流制御のスキャン時間を短くした効果が半減してしまう。そこで、零電流制御を実施する場合は、電力変換器も高速に動作できるように、その基準となるキャリア周波数を高くすることにより、電流制御応答を向上できる。
このように通常制御時に対して、零電流制御中の電流制御のスキャン時間を短くしたり、電力変換器のキャリア周波数を高くすることで、電流制御応答を向上することができ、零電流制御中に過大な電流が流れ、前記電力変換器がトリップするのを防止して、前記交流電動機をスムーズ再始動することを特徴としている。
【００２０】
次に、本発明における交流電動機のセンサレス制御装置の第２の実施形態の構成を示すブロック図である図２について説明する。
本実施形態における電動機の制御装置は、電力変換器１、交流電動機２、電流検出器３、電流座標変換回路４、トルク電流制御回路５、励磁電流制御回路６、位相演算回路７、Ｖ／ｆ変換回路８、出力電圧演算回路９、スイッチングパターン発生回路１０、速度推定回路１１Ｂを備えている。速度推定回路１１Ｂ以外は共通であるので、説明を省略する。
速度推定回路１１Ｂは、直流電流印加時のトルク電流検出値i_qfbと励磁電流検出値i_dfbより、フリーラン状態の交流電動機２の速度及び回転方向を推定する回路である。
【００２１】
次に、フリーラン状態になった交流電動機を再始動する場合の動作について詳細に説明する。第１の実施形態において、零電流制御中に前記出力電圧演算回路９から出力される出力電圧指令値値V_1refが、設定された任意のレベルよりも低い場合には、フリーラン状態の交流電動機がほぼ停止しているためか、二次回路時定数が短いため残留電圧がなくなってしまったか判断できない。そこで、このような状態になった場合には、第１の実施形態での運転を停止して、第２の実施形態での運転に切り替える。
【００２２】
図２の３つのスイッチ（１３，１５，１６）がＡ側の通常運転状態から、Ｂ側のフリーラン始動状態になる。これにより、トルク電流指令値i_qref＝０となる。また、通常制御中は出力周波数に応じて、積算される位相も前記交流電動機がフリーランしているので、基準となる位相がないため、ゼロに固定した状態で、前記交流電動機に流れる電流を制御する。また、前記交流電動機のフリーラン状態のトルク電流検出値i_qfbを用いて、前記交流電動機の速度及び回転方向を推定するため、第２のｑ軸電圧指令値V_qrefは、ゼロにする。
前記交流電動機を励磁するため、励磁電流指令値i_drefはある設定した値を与え、励磁電流制御回路６で励磁電流検出値i_dfbを励磁電流指令値i_drefに一致させるように設定された時間だけ制御する。その後、励磁電流指令値i_drefの符号と大きさを変更して、設定された時間だけ制御する。
このときフリーラン中の前記交流電動機には、直流電流が印加されたことにより、磁束が発生する。この際に過度的に前記交流電動機のロータに流れる二次電流をトルク電流検出値i_qfbにより検出するものである。このトルク電流検出値i_qfbの周波数及び直流電流印加時の位相情報を検出して、前記交流電動機の速度及び回転方向を推定するものである。
【００２３】
前記交流電動機２が正転で回転している場合には、トルク電流検出値i_qfbは図３（ａ）のように変化する。励磁電流検出値i_dfbの符号が負の場合には、トルク電流検出値i_qfbは位相が０°から始まる正弦波に変化し、励磁電流検出値i_dfbの符号が正の場合にはトルク電流検出値i_qfbは位相が１８０°から始まる正弦波に変化する。このトルク電流検出値i_qfbの正弦波の周波数はフリーラン中の交流電動機２の速度と一致するので、トルク電流検出値i_qfbの周波数を計測することにより、前記交流電動機２の速度を検出できる。また、前記交流電動機が逆転している場合には、図３（ｂ）のように変化し、励磁電流検出値i_dfbの符号が負の場合には、トルク電流検出値i_qfbは位相が１８０°から始まる正弦波に変化し、励磁電流検出値i_dfbの符号が正の場合には、トルク電流検出値i_qfbは位相が０°から始まる正弦波に変化する。
このように前記交流電動機に直流電流を印加した場合の励磁電流検出値i_dfb及びトルク電流検出値i_qfbの位相関係とトルク電流検出値i_qfbの周波数を検出することにより速度及び回転方向を推定できる。
【００２４】
次に、任意の時間経過後直流電流印加状態から通常制御に切り替わる場合における、推定した回転方向及び速度を前記電力変換器に設定方法について説明する。
この場合、第１の実施形態とは異なり、前記交流電動機に誘起電圧がほとんど残ってないため、磁束を改めて作ればよいので、回転方向と周波数を一致させて前記電力変換器１を始動すればよい。前記交流電動機の誘起電圧を二次回路時定数に従って少しずつ上昇していき、正規のＶ／ｆレベルに一致できた時点でフリーラン状態の交流電動機を正常に始動できたと判断して、３つのスイッチがＡ側に切り替わる。
【００２５】
次に本発明である直流電流印加中のトルク電流検出値i_qfbの周波数を検出することにより速度を推定する場合の精度を向上する方法について説明する。
前記交流電動機が高速でフリーランしている場合には、図３のトルク電流検出値i_qfbの周波数が高くなる。トルク電流検出値i_qfbの周波数の一測定方法として、正側のピークと負側のピークの周期または零クロスポイント間の周期を測定する方法がある。正側のピークと負側のピークの周期または零クロスポイント間の周期を測定する際に、電流制御のスキャンが遅いと周期の測定精度が荒くなるため、周波数の検出精度も荒くなってしまう。また、高速でフリーランすると、直流電流に対して、前記交流電動機の周波数の差が大きくなるため、この周波数の差のためにインピーダンスが大きくなり、ロータ側に流れる電流は小さくなってしまう。このため、トルク電流検出値i_qfbが小さくなり、トルク電流検出値i_qfbの正側のピークと負側のピークの周期または零クロスポイント間の周期を測定が困難となる。
【００２６】
このため、直流電流印加中はその他の演算を省略すれば、通常制御に対して、電流制御するためのスキャン時間を短くできるので、正側のピークと負側のピークの周期または零クロスポイント間の周期を測定分解能が高くなるため、周波数検出精度が向上できる。また、直流電流を印加中に電流制御のスキャン時間を短くしたり、電力変換器のキャリア周波数を高くすることにより、電流制御応答が向上できるため、励磁電流検出値i_dfbを矩形波状に制御できるので、トルク電流検出値i_qfbに前記交流電動機の二次電流がすべて表れる。また、フリーラン状態の交流電動機の速度が高ければ高いほど、トルク電流検出値i_qfbが小さくなるため、通常の電流検出方法では検出が困難となるので、直流電流印加時には、電流検出回路の検出感度を数倍にして、小さな電流も検出できるようにすれば、高速でフリーランしている場合でも、正側のピークと負側のピークの周期または零クロスポイント間の周期を測定できるようになる。
【００２７】
このように通常制御時に対して、直流電流印加中の電流制御のスキャン時間を短くしたり、電力変換器のキャリア周波数を高くすることで、電流制御応答を向上することができるのと、トルク電流検出値i_qfbの正側のピークと負側のピークの周期または零クロスポイント間の周期の測定分解能が高くなることから、フリーラン中の交流電動機の速度を正確に測定でき、通常制御時に対して、直流電流印加中の電流検出回路の検出感度を高くすることにより、拘束にフリーランしている場合でも速度検出できるようにすることで、前記交流電動機をスムーズ再始動することを特徴としている。
また、上記実施例では、交流電動機２に流れる電流をトルク電流と励磁電流に分離して、それぞれ独立に制御するベクトル制御を行う電力変換装置として説明したが、Ｖ／ｆ一定制御を行う電力変換装置においても、フリーラン始動時に交流電動機に流れる電流をトルク電流と励磁電流に分離して、をそれぞれ独立に制御する電流制御回路を付加すれば、全く同様の処理で本発明を実施することができる。
【００２８】
【発明の効果】
本発明によれば、以下の効果がある。
（１）前記交流電動機の電流をゼロにするように強制的に前記電流指令信号をゼロとして電流制御する場合に、電流制御器の応答を高め、前記電力変換器が過電流状態とならないようにし、スムーズに運転継続できる。
（２）交流電動機に直流電流指令を与え、前記交流電動機の速度及び回転方向を推定している時にも、前記交流電動機が高速でフリーランしている場合、周波数検出の精度を向上する。
（３）交流電動機が高速でフリーランしている場合でもスムーズに運転継続できる。
【図面の簡単な説明】
【図１】本発明における交流電動機のセンサレス制御装置の第１の実施形態の構成を表すブロック図
【図２】本発明における交流電動機のセンサレス制御装置の第２の実施形態の構成を表すブロック図
【図３】交流電動機がフリーラン中に直流電流を与えた場合の励磁電流検出値及びトルク電流検出値
【符号の説明】
１電力変換器
２交流電動機
３電流検出器
４電流座標変換回路
５トルク電流制御回路
６励磁電流制御回路
７位相演算回路
８Ｖ／ｆ変換回路
９出力電圧演算回路
１０スイッチングパターン発生回路
１１速度推定回路（第１の形態）
１１Ｂ速度推定回路（第２の形態）
１２加算器
１３スイッチ１
１４スイッチ２
１５スイッチ３
１６スイッチ４[0001]
BACKGROUND OF THE INVENTION
According to the present invention, when starting an AC motor, the speed of the AC motor in a free-run state is estimated, and the AC motor is started smoothly by operating at the estimated speed. The present invention relates to a method and an apparatus.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 2001-161094 has a power converter that outputs power to an AC motor, and controls the output current of the power converter based on a deviation signal between the current command signal and the output current detection signal of the power converter. In the control method of an AC motor having a control unit and not having a speed detector and a voltage detector, the current is forcibly set to zero when the AC motor is in a free-run state. Current control is performed with the command signal set to zero, and the residual voltage of the AC motor is calculated based on the output voltage command signal to be calculated using the current control unit output at this time. A control method for smoothly starting the AC motor in a free-run state by estimating the rotation direction and speed of the AC motor in a state Disclosure Has been. However, when the response of the current controller section is poor, it becomes difficult to make the current of the AC motor zero, and the power converter becomes overcurrent and cannot be started smoothly. Further, when the output voltage command signal to be calculated is lower than the arbitrarily set voltage level by using the current control unit output when the current control is performed with the current command signal set to zero, the current control is stopped, Apply a direct current command of any magnitude in any direction for a set time, then give a current command of any magnitude in a direction that is 180 ° out of phase with the DC voltage command direction, and set the time There is a control method in which current control is performed again, the frequency component appearing in the current detection value and its phase relationship are detected, the frequency component is estimated as the speed of the AC motor, and the rotational direction is estimated from the phase relationship. Disclosure Has been. However, when the AC motor is free-running at high speed, the detection resolution of the frequency appearing in the current detection value becomes coarse, the amplitude of the frequency component signal appearing in the current detection value becomes small, and the frequency can be detected. It will disappear.
[0003]
[Patent Document 1]
JP 2001-161094 A
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and an object of the present invention is to provide the following AC electric sensorless control method and apparatus. (1) When the current command signal is forcibly set to zero so that the current of the AC motor is zero, the response of the current controller is enhanced so that the power converter does not enter an overcurrent state. , So that you can continue driving smoothly. (2) Even when a DC current command is given to the AC motor and the speed and direction of rotation of the AC motor are estimated, the accuracy of frequency detection is improved when the AC motor is free running at high speed. (3) Continue operation smoothly even when the AC motor is free running at high speed.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 has a power converter that outputs power to the AC motor, and the power converter is configured based on a deviation signal between the current command signal and the output current detection signal of the power converter. A current control unit for controlling an output current, and when the AC motor is in a free-run state, the current command signal is forcibly set to zero so that the current of the AC motor is zero; Based on the output voltage command signal to be calculated using the output of the current control unit, the magnitude, phase, and angular velocity of the residual voltage of the AC motor are obtained, whereby the rotational direction and speed of the AC motor in the free-run state are determined. In the sensorless control method of an AC motor that does not include both the speed detector and the voltage detector to be estimated, normal control is performed when the process of making the current of the AC motor zero is performed. This is characterized in that the scan time of the current control process is made shorter than the time.
[0006]
According to a second aspect of the present invention, when performing the process of reducing the current of the AC motor to zero, the scan time of the current control process is shortened and the carrier frequency of the power converter is increased at the same time as in the normal control. 2. The sensorless control method for an AC motor according to claim 1, wherein:
[0007]
According to a third aspect of the present invention, the power converter for outputting power to the AC motor is provided, and the output current of the power converter is controlled based on the deviation signal between the current command signal and the output current detection signal of the power converter. A current control unit that controls the current command signal to be zero so that the current of the AC motor is zero when the AC motor is in a free-run state, and the current control at this time Speed detection that estimates the rotational direction and speed of the AC motor in a free-run state by determining the magnitude, phase, and angular speed of the residual voltage of the AC motor based on the output voltage command signal to be calculated using the part output In a sensorless control device for an AC motor that does not include both a detector and a voltage detector, when performing the process of reducing the current of the AC motor to zero, the current control is performed more than during normal control. A sensorless control apparatus of an AC motor, characterized in that it comprises means for shortening the scan time of the processing.
[0008]
According to a fourth aspect of the present invention, when performing the process of reducing the current of the AC motor to zero, the means for increasing the carrier frequency of the power converter at the same time as shortening the scan time of the current control process than during normal control. The sensorless control device for an AC motor according to claim 3, comprising:
[0009]
The invention according to claim 5 has a power converter that outputs power to the AC motor, and controls the output current of the power converter based on a deviation signal between the current command signal and the output current detection signal of the power converter. A current control unit for controlling the current command signal to be zero so that the current of the AC motor is zero when the AC motor is in a free-run state, and the current control at this time If the output voltage command signal to be calculated using the part output is lower than the arbitrarily set voltage level, stop the current control and set the DC current command of any magnitude in any direction. After that, a current command of an arbitrary magnitude is given in a direction in which the phase of the DC voltage is changed by 180 ° and the current is controlled again for a set time, and the frequency component that the speed estimation circuit appears in the current detection value A sensorless control method for an AC motor that does not include both a speed detector and a voltage detector that estimates the rotational direction from the phase relationship by detecting the phase relationship of the motor and estimating the frequency component as the speed of the AC motor In the AC motor, a DC current command is given to the AC motor, and when the speed and direction of rotation of the AC motor are estimated, the scan time of the current control process is made shorter than that during normal control. This is a sensorless control method.
[0010]
In the invention according to claim 6, when a DC current command is given to the AC motor and the speed and rotation direction of the AC motor are estimated, the scan time of the current control process is made shorter than that during the normal control. 6. The sensorless control method for an AC motor according to claim 5, wherein the carrier frequency of the power converter is increased at the same time.
[0011]
According to a seventh aspect of the present invention, when a direct current command is given to the alternating current motor and the speed and rotation direction of the alternating current motor are estimated, the scan time of the current control process is shortened compared with the normal control time. 7. The sensorless control method for an AC motor according to claim 5, wherein a current detector having high sensitivity capable of detecting a small current different from that during normal control is used.
[0012]
The invention according to claim 8 has a power converter that outputs power to the AC motor, and controls the output current of the power converter based on a deviation signal between the current command signal and the output current detection signal of the power converter. A current control unit for controlling the current command signal to be zero so that the current of the AC motor is zero when the AC motor is in a free-run state, and the current control at this time If the output voltage command signal to be calculated using the part output is lower than the arbitrarily set voltage level, stop the current control and set the DC current command of any magnitude in any direction. After that, a current command of an arbitrary magnitude is given in the direction in which the phase of the DC voltage is changed by 180 ° and the current is controlled again for a set time. At this time, the speed estimation circuit detects the frequency component appearing in the current detection value and its phase relationship, estimates this frequency component as the speed of the AC motor, and estimates the rotational direction from the phase relationship and voltage detection. In a sensorless control device for an AC motor that does not include both detectors, when a DC current command is given to the AC motor and the speed and rotation direction of the AC motor are estimated, current control is performed more than in normal control. This is a sensorless control device for an AC motor, characterized by comprising means for shortening the scan time of the process.
[0013]
According to the ninth aspect of the present invention, when a direct current command is given to the alternating current motor and the speed and rotation direction of the alternating current motor are estimated, the scan time of the current control process is shortened as compared with the normal control time. The sensorless control device for an AC motor according to claim 8, further comprising means for increasing the carrier frequency of the power converter.
[0014]
According to the invention of claim 10, when a direct current command is given to the alternating current motor and the speed and rotation direction of the alternating current motor are estimated, the scan time of the current control process is made shorter than that during the normal control. 10. The sensorless control device for an AC motor according to claim 8, further comprising a highly sensitive current detector capable of detecting a small current different from that during normal control.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a first embodiment of a sensorless control device for an AC motor according to the present invention.
The sensorless control device for an AC motor in the present embodiment includes a power converter 1, an AC motor 2, a current detector 3, a current coordinate conversion circuit 4, a torque current control circuit 5, an excitation current control circuit 6, a phase calculation circuit 7, and a V A / f conversion circuit 8, an output voltage calculation circuit 9, a switching pattern generation circuit 10, a speed estimation circuit 11, and an adder 12 are provided. The power converter 1 converts a DC voltage obtained by converting a three-phase AC by a power element into an AC having an arbitrary frequency and voltage by a PWM control method, and supplies the AC voltage to the AC motor 2.
The current detector 3 detects the current supplied to the AC motor 2 and inputs the current detection signal to the current coordinate conversion circuit 4.
The current coordinate conversion circuit 4 converts the current detected by the current detector 3 into a torque current detection value i. _qfb And excitation current detection value i _dfb Torque current detection value i separated into _qfb Is input to the torque current control circuit 5 and the separated excitation current detection value i is input. _dfb Is input to the excitation current control circuit 6. The torque current control circuit 5 receives the given torque current command value i. _qref And the torque current detection value i _qfb To match the first q-axis voltage command value V ′ _qref Is calculated.
The exciting current control circuit 6 receives the given exciting current command value i. _dref And the excitation current detection value i _dfb D-axis voltage command value V so that _dref Is calculated.
The phase calculation circuit 7 receives the input frequency f ₁ Is calculated, and the phase θ is input to the current coordinate conversion circuit 4 and the adder 12.
The V / f conversion circuit 8 receives the input frequency f ₁ To the voltage E corresponding to the induced voltage of the AC motor. _ref Is calculated. This voltage E _ref Is E _ref / F ₁ = It is set in advance so as to be a constant value.
The output voltage calculation circuit 9 outputs a first q-axis voltage command value V ′ that is an output of the torque current control circuit 5. _qref And the voltage E which is the output of the V / f conversion circuit 8 _ref To the second q-axis voltage command value V _qref And the output voltage command value V is calculated from the second q-axis voltage command value and the d-axis voltage command value. _1ref And its voltage phase θ _V Is output.
V _1ref = [(V _dref ) ² + (V _qref ) ² ] ^1/2 ... (1)
θ _V = Tan ^-1 (V _qref / V _dref (2)
The switching pattern generation circuit 10 outputs the output voltage command value V _1ref And the voltage phase θ _V And the power converter output phase θ _deg From the above, the switching pattern of the power converter 1 is determined.
The speed estimation circuit 11 is configured to output the voltage phase θ _V From the change per unit time, the speed f of the AC motor 2 in the free-run state _r And a circuit for estimating the rotation direction.
[0016]
Next, the operation when restarting the AC motor in the free-run state will be described in detail. When the AC motor 2 is in a free-running state, the three switches 13, 14, and 15 in FIG. 1 change from a normal operation state on the A side to a free-run starting state on the B side. As a result, the torque current command value i _qref = 0 and excitation current command value i _dref = 0. In addition, during normal control, the AC motor is free-running in accordance with the output frequency, so there is no reference phase, so the current flowing through the AC motor is fixed to zero. Control to zero. Here, when the AC motor is in a free-running state, an induced voltage corresponding to the rotational speed is generated. Since the induced voltage rotates at the rotational speed of the AC motor 2, when the power converter 1 is started regardless of the rotational speed of the AC motor 2 or the magnitude of the induced voltage, the AC motor 2 and the power conversion are started. A current flows between the device 1 and the container 1. If the torque current control circuit 5 and the excitation current control circuit 6 control the current to zero, the induced voltage of the AC motor 2 and the output voltage of the power converter match in magnitude, phase and frequency. Become. Controlling the current flowing through the AC motor to zero in this way is called zero current control.
[0017]
The first q-axis voltage command value V ′ that is the output of the torque current control circuit 5 and the excitation current control circuit 6 during zero current control. _qref D-axis voltage command value V _dref Is a sinusoidal voltage command value having a frequency matching the rotational speed of the AC motor 2. The output voltage calculation circuit 9 is configured to output the first q-axis voltage command value V ′. _qref And the d-axis voltage command value V _dref As input, and output voltage command value V _1ref And its voltage phase θ _V Is output. Output voltage command value V _1ref Represents the magnitude of the induced voltage of the AC motor, and the voltage phase θ _V Represents the phase of the induced voltage. For this reason, the speed estimation circuit 11 measures the frequency of the induced voltage by measuring the time change of the phase of the induced voltage at regular intervals. The frequency of the induced voltage matches the rotational speed of the AC motor 2 as can be seen from the above description. For this reason, the rotational speed of the AC motor 2 in a free-running state can be estimated. When the AC motor is rotating in reverse, the phase change rate becomes negative, so it can be estimated whether the AC motor in the free-running state is rotating forward or reverse. Thus, by observing the induced voltage of the AC motor by zero current control, the rotational speed including the rotation direction of the AC motor can be estimated.
[0018]
Next, a method for setting the estimated rotation direction and speed in the power converter when the zero current control is stopped and the control is switched to the normal control will be described.
When shifting from the zero current control state to the normal operation, even if the power converter 1 is started with the same frequency, an excessive current may flow through the AC motor and a smooth start may not be possible. There is. In order to prevent this, the magnitude and phase of the induced voltage during zero current control must be continued at the moment when the control shifts to normal control. For this reason, the output voltage command value V of the power converter _1ref And power converter output phase θ _deg And output frequency f ₁ Must be set to an initial value. Specifically, in the normal operation state, the power converter output phase θ _deg Is controlled based on the phase of the magnetic flux of the AC motor 2, but during zero current control, a phase that matches the induced voltage of the AC motor 2 is output. For this reason, during zero current control, the 90 ° phase is advanced in the case of normal rotation and the 90 ° phase is delayed in the case of reverse rotation with respect to the phase of normal control. Therefore, the power converter output phase θ _deg Is an estimated value f of the rotational speed of the AC motor 2 output from the speed estimation circuit 11 after correcting the 90 ° phase according to the rotational direction from the last phase of the zero current control. _r Is converted into a phase and added to set a corrected value. By doing so, the continuity of the phase is maintained.
Also, the output voltage command value V output during zero current control _1ref If is set to the induced voltage, the continuity of the output voltage is maintained. In this way, it is possible to smoothly shift from zero current control to normal control.
The induced voltage of the AC motor is gradually increased according to the secondary circuit time constant, and when it can be matched with the normal V / f level, it is determined that the free-run AC motor has been started normally. The switch switches to the A side.
[0019]
Next, a method for improving the current response during zero current control according to the present invention will be described. In order to estimate the speed of the AC motor in the free-running state, the first q-axis voltage command value V ′ that is the output of the torque current control circuit 5 and the excitation current control circuit 6 at the time of zero current control is used. _qref D-axis voltage command value V _dref Must match the induced voltage of the AC motor.
Here, there is no problem when the torque current control circuit 5 and the excitation current control circuit 6 exhibit sufficient capability and the current flowing through the AC motor can be controlled to zero, but the torque current control circuit 5 and the excitation current control When the gain of the circuit 6 cannot be increased or when the AC motor is rotating at a high speed, a large induced voltage is generated. Therefore, an excessive current flows immediately after starting the power converter, and the power The converter may trip and not start smoothly. In order to prevent this, the response of the torque current control circuit 5 and the excitation current control circuit 6 must be improved. If the scan time for processing the current control is short, there will be no delay by that amount, so the current can be controlled as directed. For this reason, if other calculations are omitted during zero current control, the scan time for current control can be shortened with respect to normal control, so that the current control response can be improved. Even if the current control scan time is shortened during zero current control, the effect of shortening the current control scan time is halved if the creation of the switching pattern of the power converter is slow. Thus, when zero current control is performed, the current control response can be improved by increasing the reference carrier frequency so that the power converter can also operate at high speed.
In this way, the current control response can be improved by shortening the scan time of current control during zero current control or increasing the carrier frequency of the power converter, compared with normal control. An excessive current flows through the power converter to prevent the power converter from tripping, and the AC motor is smoothly restarted.
[0020]
Next, FIG. 2 which is a block diagram showing the configuration of the second embodiment of the sensorless control device for an AC motor according to the present invention will be described.
The motor control apparatus in this embodiment includes a power converter 1, an AC motor 2, a current detector 3, a current coordinate conversion circuit 4, a torque current control circuit 5, an excitation current control circuit 6, a phase calculation circuit 7, and a V / f. A conversion circuit 8, an output voltage calculation circuit 9, a switching pattern generation circuit 10, and a speed estimation circuit 11B are provided. Since the components other than the speed estimation circuit 11B are common, the description is omitted.
The speed estimation circuit 11B calculates a torque current detection value i when a direct current is applied. _qfb And excitation current detection value i _dfb Thus, this is a circuit for estimating the speed and rotation direction of the AC motor 2 in a free-running state.
[0021]
Next, the operation when restarting the AC motor in the free-run state will be described in detail. In the first embodiment, the output voltage command value V output from the output voltage calculation circuit 9 during zero current control. _1ref However, if it is lower than the set arbitrary level, it cannot be determined whether the AC motor in the free-run state is almost stopped or whether the residual voltage has disappeared because the secondary circuit time constant is short. Therefore, in such a state, the operation in the first embodiment is stopped and the operation is switched to the operation in the second embodiment.
[0022]
The three switches (13, 15, 16) in FIG. 2 change from the normal operation state on the A side to the free run start state on the B side. As a result, the torque current command value i _qref = 0. In addition, during normal control, the AC motor is free-running in accordance with the output frequency, so there is no reference phase, so the current flowing through the AC motor is fixed to zero. Control. Also, the torque motor detected value i in a free-run state of the AC motor _qfb To estimate the speed and rotation direction of the AC motor, the second q-axis voltage command value V _qref Is zero.
In order to excite the AC motor, the excitation current command value i _dref Gives a certain set value and the excitation current control circuit 6 determines the excitation current detection value i. _dfb Excitation current command value i _dref Control for the time set to match. Then, excitation current command value i _dref Change the sign and size of and control for the set time.
At this time, a magnetic flux is generated by applying a direct current to the AC motor during free running. At this time, the secondary current flowing excessively in the rotor of the AC motor is converted to a torque current detection value i. _qfb Is detected by This torque current detection value i _qfb The frequency and the phase information when the DC current is applied are detected to estimate the speed and rotation direction of the AC motor.
[0023]
When the AC motor 2 is rotating forward, the torque current detection value i _qfb Changes as shown in FIG. Excitation current detection value i _dfb When the sign of is negative, the torque current detection value i _qfb Changes to a sine wave whose phase starts from 0 °, and the excitation current detection value i _dfb When the sign of is positive, the torque current detection value i _qfb Changes to a sine wave whose phase starts at 180 °. This torque current detection value i _qfb Since the frequency of the sine wave coincides with the speed of the AC motor 2 during free running, the torque current detection value i _qfb The speed of the AC motor 2 can be detected by measuring the frequency. Further, when the AC motor is rotating in reverse, it changes as shown in FIG. _dfb When the sign of is negative, the torque current detection value i _qfb Changes to a sine wave whose phase starts from 180 °, and the excitation current detection value i _dfb When the sign of is positive, the detected torque current value i _qfb Changes to a sine wave whose phase starts at 0 °.
Thus, the excitation current detection value i when a DC current is applied to the AC motor _dfb And torque current detection value i _qfb Phase relationship and torque current detection value i _qfb By detecting the frequency, the speed and direction of rotation can be estimated.
[0024]
Next, a method of setting the estimated rotation direction and speed in the power converter when the direct current application state is switched to the normal control after an arbitrary time has elapsed will be described.
In this case, unlike the first embodiment, since almost no induced voltage remains in the AC motor, it is sufficient to create a new magnetic flux. Therefore, if the power converter 1 is started with the rotational direction and the frequency matched. Good. The induced voltage of the AC motor is gradually increased according to the secondary circuit time constant, and when it can be matched with the normal V / f level, it is determined that the free-run AC motor has been started normally. The switch switches to the A side.
[0025]
Next, torque current detection value i during DC current application according to the present invention _qfb A method for improving the accuracy when the speed is estimated by detecting the frequency will be described.
When the AC motor is free running at high speed, the torque current detection value i in FIG. _qfb The frequency of becomes higher. Torque current detection value i _qfb As one method of measuring the frequency, there is a method of measuring a period between a positive peak and a negative peak or a period between zero cross points. When measuring the cycle of the positive peak and the negative peak or the cycle between the zero cross points, if the current control scan is slow, the cycle measurement accuracy becomes rough, and the frequency detection accuracy also becomes rough. In addition, when free running at high speed, the difference in frequency of the AC motor with respect to the direct current increases, so the impedance increases due to the difference in frequency, and the current flowing to the rotor side decreases. Therefore, the torque current detection value i _qfb Becomes smaller and the detected torque current value i _qfb It becomes difficult to measure the period between the positive peak and the negative peak or the period between zero cross points.
[0026]
For this reason, if other calculations are omitted during DC current application, the scan time for current control can be shortened compared to normal control, so the period between the positive peak and the negative peak or the zero cross point can be reduced. Since the measurement resolution becomes high, the frequency detection accuracy can be improved. Also, since the current control response can be improved by shortening the current control scan time or increasing the carrier frequency of the power converter while applying DC current, the excitation current detection value i _dfb Can be controlled in a rectangular wave shape, so the torque current detection value i _qfb All the secondary currents of the AC motor appear. In addition, the higher the speed of the AC motor in the free-run state, the higher the torque current detection value i _qfb Therefore, when a direct current is applied, the detection sensitivity of the current detection circuit is increased several times to enable detection of small currents. Even in this case, the period between the positive peak and the negative peak or the period between zero cross points can be measured.
[0027]
In this way, the current control response can be improved by shortening the scan time of current control during DC current application or increasing the carrier frequency of the power converter, compared to the normal control, and the torque current Detection value i _qfb Because the measurement resolution of the period between the positive and negative peaks of the AC or the period between the zero cross points is high, the speed of the AC motor during free run can be measured accurately. The AC motor is smoothly restarted by increasing the detection sensitivity of the current detection circuit that is being applied so that the speed can be detected even when the engine is free running.
Moreover, although the said Example demonstrated as a power converter device which performs the vector control which isolate | separates the electric current which flows into the alternating current motor 2 into a torque current and an excitation current, and controls each independently, power conversion which performs V / f constant control Even in the device, the present invention can be implemented with exactly the same processing by adding a current control circuit that separates the current flowing through the AC motor at the time of free-run starting into torque current and excitation current and independently controls them. it can.
[0028]
【The invention's effect】
The present invention has the following effects.
(1) When the current command signal is forcibly set to zero so that the current of the AC motor is zero, the response of the current controller is enhanced so that the power converter does not enter an overcurrent state. Smooth operation can be continued.
(2) Even when a DC current command is given to the AC motor and the speed and direction of rotation of the AC motor are estimated, the accuracy of frequency detection is improved when the AC motor is free running at high speed.
(3) Even when the AC motor is free running at high speed, the operation can be continued smoothly.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a first embodiment of a sensorless control device for an AC motor according to the present invention.
FIG. 2 is a block diagram showing a configuration of a second embodiment of a sensorless control device for an AC motor according to the present invention.
[Fig. 3] Exciting current detection value and torque current detection value when an AC motor gives a DC current during free run
[Explanation of symbols]
1 Power converter
2 AC motor
3 Current detector
4 Current coordinate conversion circuit
5 Torque current control circuit
6 Excitation current control circuit
7 Phase calculation circuit
8 V / f conversion circuit
9 Output voltage calculation circuit
10 Switching pattern generator
11 Speed estimation circuit (first form)
11B Speed estimation circuit (second form)
12 Adder
13 Switch 1
14 Switch 2
15 Switch 3
16 Switch 4

Claims

A power converter that outputs power to the AC motor, and a current control unit that controls an output current of the power converter based on a deviation signal between a current command signal and an output current detection signal of the power converter, the AC motor Is in a free-run state, the current command signal is forcibly controlled to zero so that the current of the AC motor is zero, and the output voltage to be calculated using the current control unit output at this time Both a speed detector and a voltage detector for estimating the rotational direction and speed of the AC motor in a free-run state by obtaining the magnitude, phase and angular velocity of the residual voltage of the AC motor based on the command signal In a sensorless control method of an AC motor not equipped with
When performing a zero current control for controlling the current flowing through the AC motor to zero when in a free-run state, a calculation time other than the zero current control is omitted, and the scan time of the current control process is greater than that during the normal control. A sensorless control method for an AC motor, characterized in that

2. The process for reducing the current of the AC motor to zero is characterized by shortening the scan time of the current control process and increasing the carrier frequency of the power converter at the same time as during normal control. Sensorless control method for AC motors.

A power converter that outputs power to the AC motor, and a current control unit that controls an output current of the power converter based on a deviation signal between a current command signal and an output current detection signal of the power converter; When the motor is in a free-run state,
The AC motor is forcibly controlled so that the current of the AC motor is zero, and the AC motor is controlled based on the output voltage command signal calculated using the current control unit output at this time. A sensorless control device for an AC motor that does not include both a speed detector and a voltage detector that estimate the rotational direction and speed of the AC motor in a free-run state by determining the magnitude, phase, and angular velocity of the residual voltage of the motor In
When performing a zero current control for controlling the current flowing through the AC motor to zero when in a free-run state, a calculation time other than the zero current control is omitted, and the scan time of the current control process is greater than that during the normal control. A sensorless control device for an AC motor, characterized by comprising means for shortening the length of the AC motor.

When performing the process of making the current of the AC motor zero, it is provided with means for shortening the scan time of the current control process and increasing the carrier frequency of the power converter as compared with the normal control time. Item 4. A sensorless control device for an AC motor according to Item 3.

A power converter that outputs power to the AC motor, and a current control unit that controls an output current of the power converter based on a deviation signal between a current command signal and an output current detection signal of the power converter; When the motor is in a free-run state, the current command signal is forcibly set to zero so that the current of the AC motor is zero, and the output is calculated using the current control unit output at this time When the voltage command signal is lower than the arbitrarily set voltage level, the current control is stopped, a DC current command of an arbitrary magnitude is applied in an arbitrary direction for a set time, and then the DC current command Give a current command of arbitrary magnitude in the direction changed from the command direction and 180 ° phase, control the current again for the set time, the speed estimation circuit detects the frequency component appearing in the current detection value and its phase relationship, Estimates the frequency component as the speed of the alternating current motor, the sensorless control method of the speed detector and the voltage detector AC motor without a both detectors to estimate the rotational direction from the phase relationship,
When in a free-run state, a DC current command is given to the AC motor, and when estimating the speed and rotation direction of the AC motor , calculations other than the estimation are omitted, and current control is performed more than in normal control. A sensorless control method for an AC motor, characterized in that the processing scan time is shortened.

When a DC current command is given to the AC motor and the speed and direction of rotation of the AC motor are estimated, the scan time of the current control process is made shorter than that during normal control, and the carrier frequency of the power converter is set at the same time. The sensorless control method for an AC motor according to claim 5, wherein the sensorless control method is increased.

When a DC current command is given to the AC motor and the speed and direction of rotation of the AC motor are estimated, the current control processing scan time is shortened compared to that during normal control, and at the same time smaller than that during normal control. 7. The sensorless control method for an AC motor according to claim 5, wherein a current detector having a high sensitivity capable of detecting a current is used.

A power converter that outputs power to the AC motor, and a current control unit that controls an output current of the power converter based on a deviation signal between a current command signal and an output current detection signal of the power converter; When the motor is in a free-run state, the current command signal is forcibly set to zero so that the current of the AC motor is zero, and the output is calculated using the current control unit output at this time When the voltage command signal is lower than the arbitrarily set voltage level, the current control is stopped, a DC current command of an arbitrary magnitude is applied in an arbitrary direction for a set time, and then the DC current command giving a current command of any size in the direction of changing the command direction and 180 ° phase, set time again current control, this time, the frequency component velocity estimation circuit appears in the current detection value and the phase relationship Detecting, the frequency component is estimated the speed of the AC motor, the sensorless control apparatus of an AC motor without a both detectors velocity detector and a voltage detector for estimating a direction of rotation from the phase relationship,
When in a free-run state, when a DC current command is given to the AC motor and the speed and direction of rotation of the AC motor are estimated, calculations other than the estimation are omitted, and current control is performed more than during normal control. A sensorless control device for an AC motor, characterized by comprising means for shortening the scan time of the process.

When a DC current command is given to the AC motor and the speed and direction of rotation of the AC motor are estimated, the current control processing scan time is shortened and the carrier frequency of the power converter is increased as compared with normal control. 9. A sensorless control device for an AC motor according to claim 8, further comprising means for performing the operation.

When a DC current command is given to the AC motor and the speed and direction of rotation of the AC motor are estimated, the current control processing scan time is shortened compared to that during normal control, and at the same time smaller than that during normal control. The sensorless control device for an AC motor according to claim 8 or 9, further comprising a current detector with high sensitivity capable of detecting a current.