JP3766348B2 - Electric motor torque control apparatus, electric motor torque control method, hermetic compressor, and refrigeration cycle apparatus - Google Patents

Description

【００８６】
ここで、ｆ（ｎ）はＩｑ＿ＡＣの各値であり、ＮはストックしたＩｑ＿ＡＣの標本点数である。また、ｅｘｐは指数関数を表す。（１）式よりＦ（１）、すなわちＩｑ＿ＡＣの基本波実軸成分ｒ＿ｄａｔ１と虚軸成分ｉ＿ｄａｔ１を得る。
【００８７】
次に、（２）式のアークサインの計算によりＩｑ＿ＡＣの基本波成分の位相スペクトルを演算する。
【００８８】
【数２】

【００８９】
算出法は、アークコサイン、アークタンジェントを用いても良い。
【００９０】
この位相スペクトルの演算値θｍは、ｑ軸電流Ｉｑの最大値が現れるポイントであり、仮の基準位置θ０から見たときの位相差である。
【００９１】
ｑ軸電流Ｉｑと負荷トルク変動には相関があり、θｍは負荷トルクが最小になるポイントとして近似できる。周期的な負荷トルク変動を有する負荷要素を駆動する電動機においては、周期的な位置関係は常に１対１に維持されるので、θｍは常に負荷トルクが最小になるポイントとおける。
【００９２】
原理的には、θｍの算出は電動機の起動時に１回行えば良い。ただし、定常運転中にトルク制御を行う前に、必要に応じて再度θｍの算出を行っても良い。特殊な負荷状態での運転の際にも回転子位置検出が再度行えるので、回転子位置検出誤差が大きくなることなく、より高精度にトルク制御を行うことが出来る。
【００９３】
起動時は特に、ｑ軸電流Ｉｑの電流リプルが表れにくいため検出精度が落ちる。そのため、起動時から所定の回転数ωαまで加速した後、Ｉｑ＿ＡＣの基本波成分の振幅スペクトルｓｐｃ１を（３）式のように常時計算し、スレッショルドレベルＩαを超えたところで基準位置の演算を行うことで、検出精度の向上が行える。また、振動が大きくなる前に回転子位置を検出でき、トルク制御を迅速に行えるため、制御安定までの時間が少なくて済む。
【００９４】
【数３】

【００９５】
また、起動時から所定の回転数ωαまで加速した後、所定時間経過した時点で、基準位置の演算を行うようにしてもよい。
【００９６】
さらに、起動時から所定の回転数ωαまで加速した後、所定時間経過し、かつスレッショルドレベルＩαを超えたところで基準位置の演算を行うようにしてもよい。
【００９７】
ここで図７に示すように、負荷トルクが最小となるポイントθｍより電動機１の負荷が１回転中の負荷トルク平均値よりも重くなり始めるポイントＳＴＰＴとの位相差を位相補正量Δθとすると、ＳＴＰＴは（４）式のようになる。ここで、ＳＴＰＴの位相範囲は０〜２πの繰り返しとする。位相補正量Δθは事前に試験を実施し、データとして振動が小さくなるような値を記憶させておく。
【００９８】
【数４】

【００９９】
位相補正量Δθは、Ｉｑ＿ＡＣの基本波成分の振幅スペクトルｓｐｃ１に対して図１１の例のような特性を持つ場合がある。振幅スペクトルｓｐｃ１の値に応じてΔθが異なる時、この特性例に合わせて位相補正量Δθを最適化し、電動機１の負荷が１回転中の負荷トルク平均値よりも重くなり始めるポイントＳＴＰＴを算出することで精度向上が行える。
【０１００】
また、電動機１の負荷が１回転中の負荷トルク平均値よりも軽くなり始めるポイントＷＫＰＴは、（５）式のようにおける。ＷＫＰＴの位相範囲も０〜２πの繰り返しとする。
【０１０１】
【数５】

【０１０２】
位相補正量Δθを、負荷トルクが最小となるポイントθｍより電動機１の負荷が１回転中の負荷トルク平均値よりも重くなり始めるポイントＳＴＰＴとの位相差とすることを説明したが、電動機１の負荷が１回転中の負荷トルク平均値よりも軽くなり始めるポイントＷＫＰＴとの位相差としてもよい。この場合は、補正のかけ方を逆にすればよい。
【０１０３】
ｄ軸電流の基点は、負荷トルクの平均値より負荷が変化し始める点としたが、ｄ軸電流の基点は、トルク制御を行わない状態で出力トルクと負荷トルクが同一になる点（この点から後、大きくなり始める点、あるいは小さくなり始める点）の意味である。
【０１０４】
ｑ軸電流の基本波成分の電流リプルレベルによって周期的に変化させるｄ軸電流の基点までの位相差を制御することにより、負荷状態による検出誤差が少なくて済む。また１次及び高調波ノイズによらず周期的に変化させるｄ軸電流の基点までの位相差を制御することにより、より高精度にトルク制御を行うことができる。
【０１０５】
次にトルク制御手段について説明する。
トルク制御を行わない際、ｄ軸電流指令値Ｉｄ^*が、電動機１の回転速度指令ω^*に対して、例えば図１２のようになっている場合を例として取り上げる。トルク制御を行わない場合、回転速度指令ω１に対して、ｄ軸電流指令値Ｉｄ^*がＩｄ１の時、ｄ軸電流指令値の最終出力Ｉｄ^**は、Ｉｄ１がそのまま出力される。つまりトルク制御を行わない時は、（６）式のように指令値Ｉｄ^*がそのまま指令値Ｉｄ^**として設定される。
【０１０６】
【数６】

【０１０７】
回転速度指令ω１に対して、ｄ軸電流指令値Ｉｄ^*がＩｄ１である時、トルク制御を行うには以下のようにする。図７（ｄ）において、１回転中の平均負荷トルクよりも負荷が重い領域を負荷トルク大領域とすると、この領域ではｄ軸電流指令値の最終出力Ｉｄ^**には補正量Ｋｍを（７）式のように加算して出力する。
【０１０８】
【数７】

【０１０９】
１回転中の平均負荷トルクよりも負荷が軽い領域を負荷トルク小領域とすると、この領域ではｄ軸電流指令値の最終出力Ｉｄ^**には補正量Ｋｍを（８）式のように減算して出力する。
【０１１０】
【数８】

【０１１１】
ｄ軸電流指令値の最終出力Ｉｄ^**を負荷トルク大の区間（半周期）で強めて、負荷トルク小の区間（半周期）で弱めることでトルク制御を行う。これにより、不特定の高調波ノイズを発生することなく、安定したトルク制御を簡易に行うことができる。
【０１１２】
上記のように、Ｋｍは１周期中の負荷大および負荷小の各領域において補正量を変化させるか、または周期性のある関数（正弦波、余弦波等）によって（９）式のように変化させる。
【０１１３】
【数９】

【０１１４】
ここで、ｆ（θ）は周期性のある関数を表す。
【０１１５】
周期性のある関数によって、周期的に変化させるｄ軸電流の変化幅または変化値を変えることにより、不特定の高調波ノイズを発生することなく、安定したトルク制御を自由度高く行うことができる。
【０１１６】
ｄ軸電流指令値Ｉｄ^**の補正量Ｋｍは、回転速度指令ω^*により変化させることで、より精度良くトルク制御が行える。適切でない励磁電流の印可により安定な運転を阻害することなく、回転速度によってきめ細かく、かつ自由度高くトルク制御を行うことができる。
【０１１７】
１周期中の負荷大及び負荷小の各領域においてｄ軸電流指令値Ｉｄ^**の補正量Ｋｍを変化させる場合は、Ｋｍは回転速度指令ω^*により図１３のように記憶しておく。それにより、適切でない励磁電流の印可により安定な運転を阻害することなく、回転速度によってきめ細かく、かつ信頼性高くトルク制御を行うことができる。
【０１１８】
周期性のある関数によってｄ軸電流指令値Ｉｄ^**の補正量Ｋｍを変化させる場合は、回転速度指令ω^*を含めた関数を用い、（１０）式により変化させる。
【０１１９】
【数１０】

【０１２０】
ここで、ｆ（θ，ω^*）は回転速度指令ω^*に依存した周期性のある関数を表す。
【０１２１】
以上よりインバータ２にて電動機の負荷トルクと出力トルクの偏差を最小化するような電流波形を発生し、振動を抑制する（図７（ｅ）参照）。また、電流量を用いて位置推定を行うので、誘起電圧ゼロクロスを検出する装置が必要なく、回転子位置を検出できる。また、ｑ軸電流の変動が負荷トルク変動に起因する周期性を有することより電動機の回転子位置を検出するので、１次及び高次のノイズに対して強く、検出精度が高い。また、誘起電圧ゼロクロスを検出するための非通電区間が不要なため、トルク制御を行う際の電流脈動が少なくて済む。
【０１２２】
本発明の電動機のトルク制御装置を、密閉形圧縮機の電動機に用いれば、新たな装置を付加することなく、振動を抑制できる。
【０１２３】
また、上記密閉形圧縮機を冷凍サイクル装置に搭載すれば、新たな装置を付加することなく、振動を抑制できる。
【０１２４】
【発明の効果】
この発明の請求項１に係る電動機のトルク制御装置は、ｑ軸電流から算出した機械的な回転子位置情報を用いて、記憶された補正量により周期的にｄ軸電流を変化させてトルク制御を行うので、電圧量の検出や振動の検出に新たな装置を付加することなく、振動を抑制することができる。また、ｑ軸電流の変動が負荷トルク変動に起因する周期性を有することを利用して電動機の回転子位置を検出するので、１次及び高次のノイズに対して強く、検出の精度が高い。また、誘起電圧ゼロクロスを検出するための非通電区間が不要なため、トルク制御を行う際電流脈動が少なくて済む。
【０１２５】
また、この発明の請求項２に係る電動機のトルク制御装置は、ｄ軸電流とｑ軸電流を求める手段は、電動機に流れる少なくとも１相分の電流を検出して、各相に流れる電流を算出する相電流演算手段と、各相に流れる電流からｄ軸電流とｑ軸電流を算出する３相２相変換手段とを備えたことにより、電流量を用いて位置推定を行うので、誘起電圧ゼロクロスを検出する装置が必要なく、回転子位置を検出できる。また、誘起電圧ゼロクロスを検出するための非通電区間が不要なため、トルク制御を行う際電流脈動が少なくて済む。
【０１２６】
また、この発明の請求項３に係る電動機のトルク制御装置は、相電流演算手段は、各相電流は１２０度ずつ位相がずれることにより、他の相の電流値を求めることにより、各相ごとに電流を検出するセンサーを取り付ける必要がなく、安価かつ正確に電流検出が行える。
【０１２７】
また、この発明の請求項４に係る電動機のトルク制御装置は、インバータは、外部より与えられる前記電動機の回転速度指令と、算出したｄ軸電流とｑ軸電流と、次に与えるｄ軸電流の指令値に基づいてＰＷＭ信号を作成する駆動信号生成部と、ＰＷＭ信号を発生させるＰＷＭ信号発生手段と、電動機を駆動するインバータ主回路とを備えたことにより、電流量を用いて位置推定を行うので、誘起電圧ゼロクロスを検出する装置が必要なく、回転子位置を検出できる。また、誘起電圧ゼロクロスを検出するための非通電区間が不要なため、トルク制御を行う際電流脈動が少なくて済む。
【０１２８】
また、この発明の請求項５に係る電動機のトルク制御装置は、駆動信号生成部は、ｄ軸電圧とｑ軸電圧を演算する電圧指令演算手段と、ｄ軸電圧とｑ軸電圧から３相分の出力電圧を求める２相３相変換手段と、３相分の出力電圧が得られるようにＰＷＭ信号を作成するＰＷＭ信号作成部とを備えたことにより、電流量を用いて位置推定を行うので、誘起電圧ゼロクロスを検出する装置が必要なく、回転子位置を検出できる。また、誘起電圧ゼロクロスを検出するための非通電区間が不要なため、トルク制御を行う際電流脈動が少なくて済む。
【０１２９】
また、この発明の請求項６に係る電動機のトルク制御装置は、電動機の回転子位置を検出する手段は、ｑ軸電流から電動機の負荷トルクが１回転中で最小または最大になるポイントを検出することにより、ｑ軸電流と電動機の負荷トルクの相関関係から位置推定を行うので、位置検出のための新たな装置を設けることなく、回転子位置を検出できる。
【０１３０】
また、この発明の請求項７に係る電動機のトルク制御装置は、トルク制御手段は、外部より与えられる電動機の回転速度指令と、回転子位置を検出する手段で検出される電動機の負荷トルクが１回転中で最小または最大になるポイント、電動機の負荷が１回転中の負荷トルク平均値より重くなり始めるポイント、電動機の負荷が１回転中の負荷トルク平均値より軽くなり始めるポイントの情報から、次に与えるｄ軸電流の指令値を補正して出力することにより、回転速度によって振動をより簡易且つ緻密に抑制できる。
【０１３１】
また、この発明の請求項８に係る電動機のトルク制御装置は、トルク制御手段は、外部より与えられる電動機の回転速度指令と、回転子位置を検出する手段で検出される電動機の負荷トルクが１回転中で最小または最大になるポイント、１回転中を等間隔で負荷トルク大小の２区間に分けた際、負荷トルク大区間の始点、負荷トルク小区間の始点の情報から、次に与えるｄ軸電流の指令値を補正して出力することにより、回転速度によって振動をより簡易且つ緻密に抑制できる。
【０１３２】
また、この発明の請求項９に係る電動機のトルク制御装置は、ｑ軸電流に発生する負荷トルクと出力トルクの偏差に応じた電流リプルを利用して、トルク制御の際に使用する電動機の負荷が１回転中の負荷トルク平均値より重くなり始めるポイント、電動機の負荷が１回転中の負荷トルク平均値より軽くなり始めるポイントを算出することにより、ｑ軸電流と電動機の負荷トルクの相関関係から位置推定を行うので、位置検出のための新たな装置を設けることなく、回転子位置を検出できる。
【０１３３】
また、この発明の請求項１０に係る電動機のトルク制御装置は、ｑ軸電流に発生する負荷トルクと出力トルクの偏差に応じた電流リプルを利用して、１回転中を等間隔で負荷トルク大小の２区間に分けた際、負荷トルク大区間の始点、負荷トルク小区間の始点の情報を算出することにより、ｑ軸電流と電動機の負荷トルクの相関関係から位置推定を行うので、位置検出のための新たな装置を設けることなく、回転子位置を検出できる。
【０１３４】
また、この発明の請求項１１に係る電動機のトルク制御装置は、電動機においてトルク制御を行っていない状態からトルク制御を行う状態に移行する前に、電動機の回転子位置を検出し直す手段を備えたことにより、特殊な負荷状態での運転の際にも回転子位置検出誤差が大きくなることはなく、より精度よく振動を抑制できる。
【０１３５】
また、この発明の請求項１２に係る電動機のトルク制御装置は、電動機を起動する際、特定の周波数まで加速させた後、ｑ軸電流の基本波成分の電流リプルレベルが所定の値以上になった時点で電動機の回転子位置を検出する手段を作動させることにより、起動時の電流リプル不足に起因する位置推定誤差を抑えることができる。また、ｑ軸電流の瞬時値ではなく、基本波成分の電流リプルレベルを見ているので、１次及び高次のノイズ成分に対して強い。また振動が大きくなる前に回転子位置を早く検出できトルク制御が行えるため、制御安定までの時間が短く、より高い信頼性が得られる。
【０１３６】
また、この発明の請求項１３に係る電動機のトルク制御装置は、電動機を起動する際、特定の周波数まで加速させた後、所定時間経過した時点で電動機の回転子位置を検出する手段を作動させることにより、起動時の電流リプル不足に起因する位置推定誤差を抑えることができる。
【０１３７】
また、この発明の請求項１４に係る電動機のトルク制御装置は、電動機を起動する際、特定の周波数まで加速させた後、所定時間経過し、かつｑ軸電流の基本波成分の電流リプルレベルが所定の値以上になった時点で電動機の回転子位置を検出する手段を作動させることにより、起動時の電流リプル不足に起因する位置推定誤差を抑えることができる。
【０１３８】
また、この発明の請求項１５に係る電動機のトルク制御装置は、電動機の回転子位置を検出する際、ｑ軸電流の基本波成分の電流リプルレベルにより回転子基準位置から周期的に変化させるｄ軸電流の基点までの位相差を決める手段を備えたことにより、負荷状態による検出誤差が少なくて済む。また、１次及び高調波ノイズによらず周期的に変化させるｄ軸電流の基点までの位相を制御できるので、精度よく振動を抑制できる。
【０１３９】
また、この発明の請求項１６に係る電動機のトルク制御装置は、ｄ軸電流の基点は、トルク制御を行わない状態で負荷トルクと出力トルクの偏差がほぼ０になる点（この点から後、正になり始める点、あるいは負になり始める点）としたことにより、負荷状態による検出誤差が少なくて済む。
【０１４０】
また、この発明の請求項１７に係る電動機のトルク制御装置は、ｄ軸電流の基点は、負荷トルクの平均値より負荷が変化し始める点としたことにより、負荷状態による検出誤差が少なくて済む。
【０１４１】
また、この発明の請求項１８に係る電動機のトルク制御装置は、ｄ軸電流の基点は、１回転中を等間隔で負荷トルク大小の２区間に分けた際の負荷トルク大区間の始点、あるいは負荷トルク小区間の始点としたことにより、負荷状態による検出誤差が少なくて済む。
【０１４２】
また、この発明の請求項１９に係る電動機のトルク制御装置は、位相差は、事前に試験を実施し、データとして振動が小さくなるような値を記憶させておくことにより、環境条件、負荷条件、運転条件、電動機の固体ばらつきによらず、精度よくトルク制御を行える。
【０１４３】
また、この発明の請求項２０に係る電動機のトルク制御装置は、位相区間により周期的に変化させるｄ軸電流の変化幅または変化値を変える手段を備えたことにより、不特定の高調波ノイズを発生することなく、簡易且つ精度よく振動を抑制することができる。
【０１４４】
また、この発明の請求項２１に係る電動機のトルク制御装置は、ｄ軸電流指令値の最終出力を負荷トルク大の区間で強めて、負荷トルク小の区間で弱めることでトルク制御を行うことにより、不特定の高調波ノイズを発生することなく、簡易且つ精度よく振動を抑制することができる。
【０１４５】
また、この発明の請求項２２に係る電動機のトルク制御装置は、周期性のある関数によって周期的に変化させるｄ軸電流の変化幅または変化値を変える手段を備えたことにより、不特定の高調波ノイズを発生することなく、自由度高く且つ精度よく振動を抑制することができる。
【０１４６】
また、この発明の請求項２３に係る電動機のトルク制御装置は、正弦波関数または余弦波関数によりｄ軸電流の変化幅または変化値を変えることにより、位相区間の変わり目で急峻にモータ電流位相を変化させることがないので急峻なノイズを発生することなく、トルク制御が行える。
【０１４７】
また、この発明の請求項２４に係る電動機のトルク制御装置は、電動機の回転速度によって周期的に変化させるｄ軸電流の変化幅または変化値を事前に記憶しておく手段を備えたことにより、回転速度によって振動をより簡易かつ緻密に抑制できる。
【０１４８】
また、この発明の請求項２５に係る電動機のトルク制御装置は、電動機の回転速度によって周期的に変化させるｄ軸電流の変化幅または変化値を変える手段を備えたことにより、自由度高く且つ緻密に振動を抑制できる。
【０１４９】
この発明の請求項２６に係る密閉形圧縮機は、請求項１〜２５の何れかに記載の電動機のトルク制御装置により、圧縮機用電動機を制御することにより、新たな装置を付加することなく、振動を抑制できる。
【０１５０】
この発明の請求項２７に係る冷凍サイクル装置は、請求項２６記載の密閉形圧縮機を冷凍サイクルに搭載したことにより、新たな装置を付加することなく、振動を抑制できる。
【０１５１】
この発明の請求項２８に係る電動機のトルク制御方法は、ｑ軸電流Ｉｑから算出した機械的な回転子位置情報を用いて、記憶された補正量により周期的にｄ軸電流Ｉｄを変化させてトルク制御を行うので、電圧量の検出や振動の検出に新たな装置を付加することなく、振動を抑制することができる。また、ｑ軸電流の変動が負荷トルク変動に起因する周期性を有することを利用して電動機の回転子位置を検出するので、１次及び高次のノイズに対して強く、検出の精度が高い。また、トルク制御を行う際の電流脈動が少なくて済む。
【０１５２】
また、この発明の請求項２９に係る電動機のトルク制御方法は、電動機に流れる少なくとも１相分の電流を検出して、各相に流れる電流を算出し、各相に流れる電流からｄ軸電流とｑ軸電流を算出することにより、誘起電圧ゼロクロスを検出する装置が必要なく、回転子位置を検出できる。また、誘起電圧ゼロクロスを検出するための非通電区間が不要なため、トルク制御を行う際電流脈動が少なくて済む。
【０１５３】
また、この発明の請求項３０に係る電動機のトルク制御方法は、各相電流は１２０度ずつ位相がずれることにより、他の相の電流値を求めることにより、各相ごとに電流を検出するセンサーを取り付ける必要がなく、安価かつ正確に電流検出が行える。
【０１５４】
また、この発明の請求項３１に係る電動機のトルク制御方法は、インバータは、外部より与えられる電動機の回転速度指令と、算出したｄ軸電流とｑ軸電流と、次に与える励磁電流成分の指令値に基づいてＰＷＭ信号を作成し、ＰＷＭ信号を発生させて、インバータ主回路により電動機を駆動することにより、電流量を用いて位置推定を行うので、誘起電圧ゼロクロスを検出する装置が必要なく、回転子位置を検出できる。また、誘起電圧ゼロクロスを検出するための非通電区間が不要なため、トルク制御を行う際電流脈動が少なくて済む。
【０１５５】
また、この発明の請求項３２に係る電動機のトルク制御方法は、ｑ軸電流から電動機の負荷トルクが１回転中で最小または最大になるポイントを検出することにより、電動機の回転子位置を検出することにより、ｑ軸電流と電動機の負荷トルクの相関関係から位置推定を行うので、位置検出のための新たな装置を設けることなく、回転子位置を検出できる。
【０１５６】
また、この発明の請求項３３に係る電動機のトルク制御方法は、外部より与えられる電動機の回転速度指令と、回転子位置を検出する手段で検出される電動機の負荷トルクが１回転中で最小または最大になるポイント、電動機の負荷が１回転中の負荷トルク平均値より重くなり始めるポイント、電動機の負荷が１回転中の負荷トルク平均値より軽くなり始めるポイントの情報から、次に与えるｄ軸電流の指令値を補正して出力し、電動機のトルク制御を行うことにより、回転速度によって振動をより簡易且つ緻密に抑制できる。
【０１５７】
また、この発明の請求項３４に係る電動機のトルク制御方法は、外部より与えられる電動機の回転速度指令と、回転子位置を検出する手段で検出される電動機の負荷トルクが１回転中で最小または最大になるポイント、１回転中を等間隔で負荷トルク大小の２区間に分けた際、負荷トルク大区間の始点、負荷トルク小区間の始点の情報から、次に与えるｄ軸電流の指令値を補正して出力することにより、回転速度によって振動をより簡易且つ緻密に抑制できる。
【０１５８】
また、この発明の請求項３５に係る電動機のトルク制御方法は、ｑ軸電流に発生する負荷トルクと出力トルクの偏差に応じた電流リプルを利用して、トルク制御の際に使用する電動機の負荷が１回転中の負荷トルク平均値より重くなり始めるポイント、電動機の負荷が１回転中の負荷トルク平均値より軽くなり始めるポイントを算出することにより、ｑ軸電流と電動機の負荷トルクの相関関係から位置推定を行うので、位置検出のための新たな装置を設けることなく、回転子位置を検出できる。
【０１５９】
また、この発明の請求項３６に係る電動機のトルク制御方法は、ｑ軸電流に発生する負荷トルクと出力トルクの偏差に応じた電流リプルを利用して、１回転中を等間隔で負荷トルク大小の２区間に分けた際、負荷トルク大区間の始点、負荷トルク小区間の始点の情報を算出することにより、ｑ軸電流と電動機の負荷トルクの相関関係から位置推定を行うので、位置検出のための新たな装置を設けることなく、回転子位置を検出できる。
【０１６０】
また、この発明の請求項３７に係る電動機のトルク制御方法は、電動機においてトルク制御を行っていない状態からトルク制御を行う状態に移行する前に、電動機の回転子位置を検出し直すことにより、特殊な負荷状態での運転の際にも回転子位置検出誤差が大きくなることはなく、より精度よく振動を抑制できる。
【０１６１】
また、この発明の請求項３８に係る電動機のトルク制御方法は、電動機を起動する際、特定の周波数まで加速させた後、ｑ軸電流の基本波成分の電流リプルレベルが所定の値以上になった時点で電動機の回転子位置を検出する工程を作動させることにより、起動時の電流リプル不足に起因する位置推定誤差を抑えることができる。また、ｑ軸電流の瞬時値ではなく、基本波成分の電流リプルレベルを見ているので、１次及び高次のノイズ成分に対して強い。また振動が大きくなる前に回転子位置を早く検出できトルク制御が行えるため、制御安定までの時間が短く、より高い信頼性が得られる。
【０１６２】
また、この発明の請求項３９に係る電動機のトルク制御方法は、電動機を起動する際、特定の周波数まで加速させた後、所定時間経過した時点で電動機の回転子位置を検出する工程を作動させることにより、起動時の電流リプル不足に起因する位置推定誤差を抑えることができる。
【０１６３】
また、この発明の請求項４０に係る電動機のトルク制御方法は、電動機を起動する際、特定の周波数まで加速させた後、所定時間経過し、かつｑ軸電流の基本波成分の電流リプルレベルが所定の値以上になった時点で電動機の回転子位置を検出する工程を作動させることにより、起動時の電流リプル不足に起因する位置推定誤差を抑えることができる。
【０１６４】
また、この発明の請求項４１に係る電動機のトルク制御方法は、電動機の回転子位置を検出する際、ｑ軸電流の基本波成分の電流リプルレベルにより回転子基準位置から周期的に変化させるｄ軸電流の基点までの位相差を決めることにより、負荷状態による検出誤差が少なくて済む。また、１次及び高調波ノイズによらず周期的に変化させるｄ軸電流の基点までの位相を制御できるので、精度よく振動を抑制できる。
【０１６５】
また、この発明の請求項４２に係る電動機のトルク制御方法は、ｄ軸電流の基点は、トルク制御を行わない状態で負荷トルクと出力トルクの偏差がほぼ０になる点（この点から後、正になり始める点、あるいは負になり始める点）としたことにより、負荷状態による検出誤差が少なくて済む。
【０１６６】
また、この発明の請求項４３に係る電動機のトルク制御方法は、ｄ軸電流の基点は、負荷トルクの平均値より負荷が変化し始める点としたことにより、負荷状態による検出誤差が少なくて済む。
【０１６７】
また、この発明の請求項４４に係る電動機のトルク制御方法は、ｄ軸電流の基点は、１回転中を等間隔で負荷トルク大小の２区間に分けた際の負荷トルク大区間の始点、あるいは負荷トルク小区間の始点としたことにより、負荷状態による検出誤差が少なくて済む。
【０１６８】
また、この発明の請求項４５に係る電動機のトルク制御方法は、位相差は、事前に試験を実施し、データとして振動が小さくなるような値を記憶させておくことにより、環境条件、負荷条件、運転条件、電動機の固体ばらつきによらず、精度よくトルク制御を行える。
【０１６９】
また、この発明の請求項４６に係る電動機のトルク制御方法は、位相区間により周期的に変化させるｄ軸電流の変化幅または変化値を変えることにより、不特定の高調波ノイズを発生することなく、簡易且つ精度よく振動を抑制することができる。
【０１７０】
また、この発明の請求項４７に係る電動機のトルク制御方法は、ｄ軸電流指令値の最終出力を負荷トルク大の区間で強めて、負荷トルク小の区間で弱めることでトルク制御を行うことにより、不特定の高調波ノイズを発生することなく、簡易且つ精度よく振動を抑制することができる。
【０１７１】
また、この発明の請求項４８に係る電動機のトルク制御方法は、周期性のある関数によって周期的に変化させるｄ軸電流の変化幅または変化値を変えることにより、不特定の高調波ノイズを発生することなく、自由度高く且つ精度よく振動を抑制することができる。
【０１７２】
また、この発明の請求項４９に係る電動機のトルク制御方法は、正弦波関数または余弦波関数によりｄ軸電流の変化幅または変化値を変えることにより、位相区間の変わり目で急峻にモータ電流位相を変化させることがないので急峻なノイズを発生することなく、トルク制御が行える。
【０１７３】
また、この発明の請求項５０に係る電動機のトルク制御方法は、電動機の回転速度によって周期的に変化させるｄ軸電流の変化幅または変化値を事前に記憶しておくことにより、回転速度によって振動をより簡易かつ緻密に抑制できる。
【０１７４】
また、この発明の請求項５１に係る電動機のトルク制御方法は、電動機の回転速度によって周期的に変化させるｄ軸電流の変化幅または変化値を変えることにより、自由度高く且つ緻密に振動を抑制できる。
【図面の簡単な説明】
【図１】 実施の形態１を示す図で、電動機のトルク制御装置の構成図である。
【図２】 実施の形態１を示す図で、電動機を駆動するインバータ部の内部構成図である。
【図３】 実施の形態１を示す図で、電動機を駆動するインバータスイッチング素子のＰＷＭ駆動信号及びＵＶＷ各相の端子電圧波形図である。
【図４】 実施の形態１を示す図で、電動機巻線に流れる電流より励磁電流成分（ｄ軸電流Ｉｄ）とトルク電流成分（ｑ軸電流Ｉｑ）を求める手段の内部構成図である。
【図５】 実施の形態１を示す図で、電動機のトルク制御装置において、トルク制御を行わない時のｄ軸電流指令値Ｉｄ^**及びｑ軸電流Ｉｑと相電流Ｉｕと電動機の負荷トルク変動と振動を示す図である。
【図６】 実施の形態１を示す図で、電動機のトルク制御装置において、負荷要素がシングルロータリ圧縮機である場合の機械的位置と負荷トルクの関係を示す図である。
【図７】 実施の形態１を示す図で、電動機のトルク制御装置において、トルク制御を行なっている時のｄ軸電流指令値Ｉｄ^**及びｑ軸電流Ｉｑと相電流Ｉｕと電動機の負荷トルクと振動を示す図である。
【図８】 実施の形態１を示す図で、電動機のトルク制御装置の相電流波形の例を示す図である。
【図９】 実施の形態１を示す図で、電動機のトルク制御装置において、電動機１の負荷が１回転中の負荷トルク平均値よりも重くなり始めるポイントＳＴＰＴ・電動機１の負荷が１回転中の負荷トルク平均値よりも軽くなり始めるポイントＷＫＰＴ（または１回転を等間隔で負荷トルク大小の２区間に分けた際の負荷トルク大区間の始点ＳＴＰＴ、負荷トルク小区間の始点ＷＫＰＴ）を演算するフローチャート図である。
【図１０】 実施の形態１を示す図で、電動機のトルク制御装置において、ｑ軸電流の交流成分データをストックする過程を示した図である。
【図１１】 実施の形態１を示す図で、電動機のトルク制御装置において、Ｉｑ＿ＡＣの基本波成分の振幅スペクトルｓｐｃ１と位相補正量Δθの特性例を示した図である。
【図１２】 実施の形態１を示す図で、電動機のトルク制御装置において、回転周波数指令ω^*とｄ軸電流指令Ｉｄ^*の特性例を示す図である。
【図１３】 実施の形態１を示す図で、電動機のトルク制御装置において、回転周波数指令ω^*とトルク補正量Ｋｍの特性例を示す図である。
【図１４】 従来の圧縮機用電動機の制御装置の構成図である。
【図１５】 従来の圧縮機用電動機の制御装置のトルクパターン記憶手段の記憶データを示す図である。
【図１６】 従来の圧縮機用電動機の制御装置のＰＷＭ信号を示す図である。
【図１７】 従来の圧縮機用電動機の制御装置のインバータのＵ相端子電圧波形を示す図である。
【図１８】 従来の圧縮機用電動機の制御装置のトルク制御における相電流波形図である。
【符号の説明】
１ 電動機、２ インバータ、３ 電流検出手段、４ 励磁電流成分（ｄ軸電流）とトルク電流成分（ｑ軸電流）を求める手段、５ 回転子位置検出手段、６トルク制御手段、７ 電動機のトルク制御装置、８ インバータ主回路、９ 駆動信号生成手段、１０ａ〜１０ｆ スイッチング素子、１１ａ〜１１ｆ 還流ダイオード、１２ ＰＷＭ信号発生手段、１３ ＰＷＭ信号作成部、１４ ２相３相変換手段、１５ 電圧指令演算手段、１６ 相電流演算手段、１７ ３相２相変換手段、１８ 電圧検出手段、１９ 圧縮機、２０ 速度制御手段、２１ 負荷トルクパターン記憶部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor torque control apparatus and an electric motor torque control method for controlling torque of an electric motor that drives a load element having a periodic load torque fluctuation such as a compressor used in an air conditioner.
[0002]
[Prior art]
In recent years, inverters have been used for variable speed control of electric motors that drive load elements with load fluctuations. A compressor or the like used in an air conditioner is a representative example of the load element. In a hermetic compressor used for an air conditioner, it is known that a change in refrigerant gas pressure in each stroke of suction, compression, and discharge acts on a load torque. It is also known that the load torque due to the gas pressure fluctuates in synchronization with the rotation of the compressor, and accordingly, the rotation speed of the compressor fluctuates periodically to cause vibration of the compressor itself. As means for suppressing the vibration, there has been proposed a method (hereinafter referred to as torque control) in which the output torque of the electric motor is changed in synchronization with the load torque of the compressor to suppress the rotational speed fluctuation.
[0003]
Conventionally, as a method for controlling an electric motor that drives a load element having a periodic load torque variation such as the compressor, a control device as shown in FIG. 14 has been proposed. This is a control device provided with torque control means for generating electric motor output torque corresponding to load torque so as to suppress vibration of the compressor.
[0004]
The motor torque control device 7 shown in FIG. 14 includes an inverter 2 that drives the motor 1 without using a position sensor for detecting the rotor position, and terminal voltages U, V, and W of the armature winding of the motor 1. Voltage detecting means 18 for detecting the rotor, rotor position detecting means 5 for calculating the position of the rotor of the electric motor 1, and a pulsation pattern of load torque in one rotation cycle of the electric motor 1 built in the compressor 19 (see FIG. 15). Load torque pattern storage unit 21 for storing (shown).
[0005]
The inverter 2 includes an inverter main circuit 8 that switches a DC power source to apply a voltage to the electric motor 1 in the compressor 19 and an operating frequency command f given from the outside. ^* Speed control means 20 for determining an average output voltage command based on the above, and average voltage command value V output from the speed control means 20 ^* A three-phase voltage command is created based on the rotor position signal output from the rotor position detecting means 5 and information obtained from the load torque pattern storage unit 21, and the six switch elements 10a in the inverter are generated from the voltage command. Drive signal generating means 9 for generating six control signals for PWM driving of each of .about.10f, and PWM signal generating means 12 for converting the control signals into voltages capable of driving the switching elements 10a to 10f in the inverter main circuit 8. Is done.
[0006]
The drive signal generation means 9 includes a torque control means 6 for outputting a correction amount of the output voltage corresponding to the load torque fluctuation of the compressor 19 depending on the rotation angle phase in the compressor, a speed control means 20 and a torque control means. 6 is configured by a PWM signal generating unit 13 that receives the output of 6 and generates a PWM signal.
[0007]
Next, the operation of a conventional compressor motor control device will be described. The rotational frequency command f of the compressor 19 to the speed control means 20 ^* Is given, the inverter output voltage command value V corresponding to the rotation speed ^* And a signal as shown in FIG. 16 is output from the PWM signal section. The PWM signal generator 13 changes the pulse width of the chopping switch (for example, Sup, Svp, Swp) at each time based on the given voltage command, and the PWM signal generator 12 outputs the PWM signal.
[0008]
When the voltage from the inverter 2 is applied, the electric motor 1 starts rotating in synchronization with the voltage frequency. At this time, the control signals Sup and Sun of the U-phase switches 10a and 10d and the U-phase voltage waveforms are as shown in FIGS. 17 (a) to 17 (c). The rotor position detecting means 5 extracts only the induced voltage zero-cross information from this waveform, and uses this as a trigger to create and output the rotational position information.
[0009]
The torque control outputs a correction voltage value that makes the motor output torque τm substantially equal to τ1 based on the current load torque value τ1 read from the load torque pattern storage unit 21. Further, the PWM signal generator 13 is configured to output the voltage command value V ^* Then, a PWM control signal for each phase is created based on the correction voltage value and the rotational position information. As a result, a current waveform (see FIG. 18) corresponding to the load torque pulsation of the compressor is generated, and the difference between the load torque and the motor output torque is minimized to suppress the rotational speed fluctuation and vibration.
[0010]
As described above, in a control device equipped with torque control that generates motor output torque according to load torque so as to suppress vibration of the compressor, an inverter system that drives the motor at a conduction angle of 120 degrees for each of the three phases. As an example in which torque control is performed, as shown in, for example, Japanese Patent Laid-Open No. 10-148184, a pulsation torque pattern for storing data on the pulsation of load torque per one rotation of the compressor and motor output torque There is a method of correcting the current or voltage so as to reduce the difference between the data in the storage unit and the load torque and output torque data in the current rotational phase.
[0011]
[Problems to be solved by the invention]
The conventional control device that performs torque control on an electric motor that drives a load element having a periodic load torque fluctuation such as a compressor is configured as described above. Therefore, the method of driving the electric motor detects an induced voltage zero cross. Therefore, it was driven by energizing each of the three phases by 120 degrees. Therefore, torque control in the non-energized section could not be performed.
[0012]
Further, since there is a non-energized section, the current pulsation in the section where torque control is performed is large.
[0013]
Further, in the case of torque control according to the conventional method, there is a problem that control is difficult to stabilize when the compressor is started, and vibration and noise increase during the time until the control is stabilized.
[0014]
Also, with respect to load fluctuations, the output torque of the inverter fluctuates, making it difficult to quickly stabilize the control.
[0015]
Also, when sampling physical quantities required for torque control such as detection position, detection speed, detection acceleration, detection speed difference, etc., the amount of information includes a primary noise component, so the detection accuracy is not very high, Accurate torque control was difficult.
[0016]
In addition, when torque control is performed by the conventional method, disturbance of harmonic component (higher order noise component) is included in the detected position / detected speed / detected acceleration / detected speed difference information, so torque control is unstable It was.
[0017]
The present invention has been made to solve the above-described problems, and an object thereof is to provide an electric motor torque control device and an electric motor torque control method that can suppress vibration without adding a new device. And
[0018]
[Means for Solving the Problems]
A torque control apparatus for an electric motor according to the present invention drives an electric motor that drives a load element having periodic load torque fluctuations, and the electric motor 180 degree conduction method An inverter, a means for detecting a current flowing through the motor and obtaining a d-axis current that is an exciting current component and a q-axis current that is a torque current component, and a periodicity in which fluctuations in the q-axis current are caused by load torque fluctuations. Of having an electric motor mechanical Using means for detecting rotor position and rotor position information Depending on the stored correction amount Torque control means for performing torque control by periodically changing the d-axis current.
[0019]
In the motor torque control apparatus according to the present invention, the means for obtaining the d-axis current and the q-axis current detects a current for at least one phase flowing in the motor and calculates a current flowing in each phase. And three-phase to two-phase conversion means for calculating a d-axis current and a q-axis current from the current flowing in each phase.
[0020]
In addition, the torque control apparatus for an electric motor according to the present invention is characterized in that the phase current calculation means obtains a current value of another phase by shifting the phase of each phase current by 120 degrees.
[0021]
In the motor torque control apparatus according to the present invention, the inverter is based on the rotation speed command of the motor given from the outside, the calculated d-axis current and q-axis current, and the command value of the d-axis current given next. And a drive signal generator for generating a PWM signal, PWM signal generating means for generating a PWM signal, and an inverter main circuit for driving the electric motor.
[0022]
In the motor torque control apparatus according to the present invention, the drive signal generation unit includes voltage command calculation means for calculating the d-axis voltage and the q-axis voltage, and an output voltage for three phases from the d-axis voltage and the q-axis voltage. It comprises a two-phase / three-phase conversion means to be obtained and a PWM signal creation section for creating a PWM signal so as to obtain an output voltage for three phases.
[0023]
The motor torque control apparatus according to the present invention is characterized in that the means for detecting the rotor position of the motor detects a point at which the load torque of the motor becomes minimum or maximum during one rotation from the q-axis current. To do.
[0024]
In the torque control apparatus for an electric motor according to the present invention, the torque control means includes a motor rotation speed command given from the outside, and a load torque of the electric motor detected by the means for detecting the rotor position is minimum during one rotation. Or, the d axis given next from the information of the point at which the load becomes maximum, the point at which the motor load begins to become heavier than the average load torque value during one rotation, and the point at which the motor load begins to become lighter than the average load torque value during one rotation. The current command value is corrected and output.
[0025]
In the torque control apparatus for an electric motor according to the present invention, the torque control means includes a motor rotation speed command given from the outside, and a load torque of the electric motor detected by the means for detecting the rotor position is minimum during one rotation. Or, when the point of maximum rotation is divided into two sections of load torque large and small at equal intervals, the command value of the d-axis current to be given next is determined from the information of the start point of the large load torque section and the start point of the small load torque section. Is output after correction.
[0026]
In addition, the torque control apparatus for an electric motor according to the present invention uses a current ripple corresponding to the deviation between the load torque generated in the q-axis current and the output torque, and the load of the electric motor used for torque control is rotating once. And calculating a point at which the load of the motor starts to become lighter than the load torque average value during one rotation.
[0027]
In addition, the torque control apparatus for an electric motor according to the present invention uses a current ripple according to the deviation between the load torque generated in the q-axis current and the output torque to make the load torque large and small at equal intervals during one rotation. When divided, information on the start point of the large load torque section and the start point of the small load torque section is calculated.
[0028]
In addition, the torque control apparatus for an electric motor according to the present invention includes means for redetecting the rotor position of the electric motor before shifting from a state where the electric motor is not performing torque control to a state where torque control is performed. And
[0029]
The torque control device for an electric motor according to the present invention is such that when starting up the electric motor, the motor is accelerated to a specific frequency and then the current ripple level of the fundamental wave component of the q-axis current becomes equal to or higher than a predetermined value. The means for detecting the rotor position is activated.
[0030]
The torque control apparatus for an electric motor according to the present invention is characterized in that when starting up the electric motor, after accelerating to a specific frequency, a means for detecting the rotor position of the electric motor is activated when a predetermined time has elapsed. To do.
[0031]
In addition, the torque control device for an electric motor according to the present invention is such that when starting up the electric motor, after accelerating to a specific frequency, a predetermined time has elapsed, and the current ripple level of the fundamental component of the q-axis current is equal to or higher than a predetermined value At this time, the means for detecting the rotor position of the electric motor is operated.
[0032]
In addition, when detecting the rotor position of the motor, the torque control device for the motor according to the present invention is based on the d-axis current that is periodically changed from the rotor reference position by the current ripple level of the fundamental component of the q-axis current. Means for determining the phase difference up to is provided.
[0033]
In the motor torque control apparatus according to the present invention, the d-axis current base point is a point at which the deviation between the load torque and the output torque becomes almost zero in a state where torque control is not performed (after this point, it starts to become positive. Point, or a point that starts to become negative).
[0034]
The torque control apparatus for an electric motor according to the present invention is characterized in that the base point of the d-axis current is a point at which the load starts to change from an average value of the load torque.
[0035]
In the motor torque control apparatus according to the present invention, the d-axis current base point is the start point of the large load torque section or the small load torque section when the load torque is divided into two sections of large and small load torque at equal intervals. It is characterized by being the starting point of.
[0036]
In addition, the torque control apparatus for an electric motor according to the present invention is characterized in that the phase difference is subjected to a test in advance and is stored as a value that reduces vibration as data.
[0037]
In addition, the torque control apparatus for an electric motor according to the present invention includes means for changing a change width or a change value of the d-axis current that is periodically changed according to a phase interval.
[0038]
The torque control apparatus for an electric motor according to the present invention is characterized in that torque control is performed by strengthening a final output of a d-axis current command value in a section with a large load torque and weakening in a section with a small load torque.
[0039]
In addition, the torque control apparatus for an electric motor according to the present invention includes means for changing a change width or a change value of the d-axis current that is periodically changed by a function having periodicity.
[0040]
The torque control apparatus for an electric motor according to the present invention is characterized in that the change width or change value of the d-axis current is changed by a sine wave function or a cosine wave function.
[0041]
In addition, the torque control apparatus for an electric motor according to the present invention is characterized by comprising means for previously storing a change width or a change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor.
[0042]
In addition, the torque control apparatus for an electric motor according to the present invention is characterized by comprising means for changing a change width or a change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor.
[0043]
The hermetic compressor according to the present invention is characterized in that the motor for a compressor is controlled by the torque control device for an electric motor according to any one of claims 1 to 25.
[0044]
A refrigeration cycle apparatus according to the present invention is characterized in that the hermetic compressor according to claim 26 is mounted in a refrigeration cycle.
[0045]
A torque control method for an electric motor according to the present invention includes an electric motor for driving a load element having periodic load torque fluctuations. 180 degree conduction method In a torque control method for an electric motor when driven by an inverter, a step of detecting a current flowing through the electric motor to obtain a d-axis current that is an excitation current component and a q-axis current that is a torque current component, and fluctuations in the q-axis current Using the periodicity caused by load torque fluctuations mechanical Using the rotor position information and the process of detecting the rotor position Depending on the stored correction amount And a step of performing torque control by periodically changing the d-axis current.
[0046]
In addition, the torque control method for an electric motor according to the present invention detects current for at least one phase flowing through the electric motor, calculates current flowing through each phase, and calculates d-axis current and q-axis current from the current flowing through each phase. It is characterized by calculating.
[0047]
In addition, the torque control method for an electric motor according to the present invention is characterized in that current values of other phases are obtained by shifting the phase of each phase current by 120 degrees.
[0048]
Also, in the motor torque control method according to the present invention, the inverter is based on the motor rotational speed command given from the outside, the calculated d-axis current and q-axis current, and the command value of the excitation current component to be given next. A PWM signal is generated, a PWM signal is generated, and an electric motor is driven by an inverter main circuit.
[0049]
Further, the torque control method for an electric motor according to the present invention is characterized in that the rotor position of the electric motor is detected by detecting a point at which the load torque of the electric motor is minimum or maximum during one rotation from the q-axis current. To do.
[0050]
In addition, the motor torque control method according to the present invention is a point at which the motor rotational speed command given from the outside and the load torque of the motor detected by the means for detecting the rotor position are minimized or maximized during one rotation. From the information of the point where the load of the motor begins to become heavier than the average value of the load torque during one rotation and the point where the load of the motor begins to become lighter than the average value of the load torque during one rotation, the command value of the d-axis current to be given next The output is corrected and output, and torque control of the electric motor is performed.
[0051]
In addition, the motor torque control method according to the present invention is a point at which the motor rotational speed command given from the outside and the load torque of the motor detected by the means for detecting the rotor position are minimized or maximized during one rotation. When one rotation is divided into two sections with large and small load torque at equal intervals, the command value of the d-axis current to be given next is corrected and output from information on the starting point of the large load torque section and the starting point of the small load torque section It is characterized by doing.
[0052]
In addition, the motor torque control method according to the present invention uses a current ripple according to the deviation between the load torque generated in the q-axis current and the output torque, and the load of the motor used for torque control is one rotation. And calculating a point at which the load of the motor starts to become lighter than the load torque average value during one rotation.
[0053]
In addition, the torque control method for an electric motor according to the present invention uses a current ripple according to the deviation between the load torque generated in the q-axis current and the output torque to make the load torque large and small at equal intervals during one rotation. When divided, information on the start point of the large load torque section and the start point of the small load torque section is calculated.
[0054]
The electric motor torque control method according to the present invention is characterized in that the rotor position of the electric motor is re-detected before shifting from a state where torque control is not performed in the electric motor to a state where torque control is performed.
[0055]
Also, the torque control method for an electric motor according to the present invention is such that when the electric motor is started up, after accelerating to a specific frequency, when the current ripple level of the fundamental wave component of the q-axis current becomes equal to or higher than a predetermined value. The step of detecting the rotor position is activated.
[0056]
The torque control method for an electric motor according to the present invention is characterized in that, when starting up the electric motor, after accelerating to a specific frequency, the step of detecting the rotor position of the electric motor is activated when a predetermined time has elapsed. To do.
[0057]
Further, in the torque control method for an electric motor according to the present invention, when starting the electric motor, a predetermined time elapses after acceleration to a specific frequency, and the current ripple level of the fundamental component of the q-axis current is equal to or higher than a predetermined value. At this point, the step of detecting the rotor position of the electric motor is activated.
[0058]
The torque control method for an electric motor according to the present invention provides a d-axis current base point that is periodically changed from the rotor reference position by the current ripple level of the fundamental component of the q-axis current when detecting the rotor position of the electric motor. It is characterized in that the phase difference is determined.
[0059]
In the torque control method for an electric motor according to the present invention, the base point of the d-axis current is a point at which the deviation between the load torque and the output torque becomes almost zero without torque control (after this point, it starts to become positive. Point, or a point that starts to become negative).
[0060]
The torque control method for an electric motor according to the present invention is characterized in that the base point of the d-axis current is a point at which the load starts to change from the average value of the load torque.
[0061]
Also, in the torque control method for an electric motor according to the present invention, the d-axis current base point is the starting point of the large load torque section or the small load torque section when the load torque is divided into two sections of large and small load torque at equal intervals. It is characterized by being the starting point of.
[0062]
Also, the torque control method for an electric motor according to the present invention is characterized in that the phase difference is tested in advance and a value that reduces vibration as data is stored.
[0063]
In addition, the torque control method for an electric motor according to the present invention is characterized in that the change width or change value of the d-axis current that is periodically changed according to the phase interval is changed.
[0064]
The torque control method for an electric motor according to the present invention is characterized in that torque control is performed by increasing the final output of the d-axis current command value in a section with a large load torque and weakening in a section with a small load torque.
[0065]
In addition, the torque control method for an electric motor according to the present invention is characterized in that a change width or a change value of the d-axis current that is periodically changed by a periodic function is changed.
[0066]
The torque control method for an electric motor according to the present invention is characterized in that the change width or change value of the d-axis current is changed by a sine wave function or a cosine wave function.
[0067]
In addition, the torque control method for an electric motor according to the present invention is characterized in that a change width or a change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor is stored in advance.
[0068]
In addition, the torque control method for an electric motor according to the present invention is characterized in that the change width or change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor is changed.
[0069]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
1 to 13 are diagrams showing Embodiment 1, FIG. 1 is a configuration diagram of a torque control device for an electric motor, FIG. 2 is an internal configuration diagram of an inverter unit for driving the electric motor, and FIG. 3 is an inverter switching element for driving the electric motor. FIG. 4 is an internal configuration diagram of a means for obtaining an excitation current component (d-axis current Id) and a torque current component (q-axis current Iq) from the current flowing in the motor winding. FIG. 5 shows a d-axis current command value Id when torque control is not performed in the motor torque control device. ^** FIG. 6 is a graph showing q-axis current Iq, phase current Iu, motor load torque fluctuation and vibration, and FIG. 6 shows the relationship between mechanical position and load torque when the load element is a single rotary compressor in the motor torque control device. FIG. 7 shows a d-axis current command value Id when torque control is performed in the motor torque control device. ^** FIG. 8 is a diagram showing an example of a phase current waveform of a torque control device for a motor, FIG. 9 is a diagram showing an example of a phase current waveform of a motor torque control device, and FIG. Point STPT at which the load begins to become heavier than the average value of the load torque during one rotation, and point WKPT at which the load of the motor begins to become lighter than the average value of the load torque during one rotation (or 2 of the load torque large and small at equal intervals) FIG. 10 shows a process of stocking the AC component data of the q-axis current in the torque control device of the motor. FIG. 10 is a flowchart for calculating the start point STPT of the large load torque section and the start point WKPT of the small load torque section. FIG. 11 shows a characteristic example of the amplitude spectrum spc1 of the fundamental wave component of Iq_AC and the phase correction amount Δθ in the torque control device for the motor. FIG. 12 shows a rotation frequency command ω in the torque control device for an electric motor. ^* And d-axis current command Id ^* FIG. 13 is a diagram showing an example of characteristics of the motor, and FIG. ^* It is a figure which shows the example of a characteristic of torque correction amount Km.
[0070]
The motor torque control device 7 shown in FIG. 1 includes an inverter 2 that drives the motor 1, a current detection unit 3 that detects a current for at least one phase flowing through the motor 1, and a current obtained by the current detection unit 3. Means 4 for obtaining the excitation current component (d-axis current Id) and torque current component (q-axis current Iq), means 5 for detecting the rotor position of the motor 1 using the q-axis current Iq, and rotor position information And a control means 6 that performs torque control by periodically changing the d-axis current Id.
[0071]
As shown in FIG. 2, in the inverter 2, the rotational speed command ω of the electric motor 1 given from the outside. ^* Calculated d-axis current Id, q-axis current Iq, and command value Id of d-axis current to be given next ^** The PWM signal is generated by the drive signal generator 9 based on the above, the PWM signal is generated by the PWM signal generator 12, and the motor is driven by the inverter main circuit 8.
[0072]
The drive signal generation unit 9 is divided into a voltage command calculation unit 15, a two-phase / three-phase conversion unit 14, and a PWM signal creation unit 13. In the voltage command calculation means 15, the d-axis voltage Vd ^* And q-axis voltage Vq ^* And the output voltage V for three phases in the two-phase / three-phase conversion means 14 ^* (Vu, Vv, Vw) is obtained. The PWM signal generator 13 outputs the output voltage V ^* A PWM signal is created so that (Vu, Vv, Vw) is obtained. The inverter main circuit 8 is composed of switching elements 10a to 10f and freewheeling diodes 11a to 11f. The inverter main circuit 8 receives a signal generated by the PWM signal generating means 12 and changes and outputs the conduction width of the switching elements 10a to 10f at each time.
[0073]
The PWM signal is generated in the PWM signal generating means 12. Signals as shown in FIGS. 3A to 3F are output from the inverter main circuit section 8. Here, Sup is a signal generated from the U-phase upper arm switching element, Sun is a signal generated from the U-phase lower arm switching element, Svp is a signal generated from the V-phase upper arm switching element, and Svn is V A signal generated from the lower arm switching element of the phase, Swp represents a signal generated from the upper arm switching element of the W phase, and Swn represents a signal generated from the lower arm switching element of the W phase. At this time, the terminal voltage waveform of each phase is as shown in FIGS.
[0074]
In the block of the means 4 for obtaining the excitation current component (d-axis current Id) and the torque current component (q-axis current Iq) shown in FIG. 4, from the current for at least one phase flowing in the electric motor 1 detected by the current detection means 3. The phase current calculation means 16 calculates the amount of current flowing in each phase of the UVW, and the three-phase two-phase conversion means 17 determines the d-axis current value Id and the q-axis current value Iq.
[0075]
The rotor position detecting means 5 detects a point θm at which the load torque of the electric motor 1 is minimum during one rotation from the q-axis current. The point of θm is a point indicated by the rotation angle in FIG.
However, the rotor position detecting means 5 may detect the point at which the load torque of the electric motor 1 becomes maximum during one rotation from the q-axis current.
[0076]
For example, when the load element having periodic load torque fluctuation is a single rotary compressor, θm corresponds to a mechanical position where the piston passes through the top dead center as shown in FIG. 6 (a) or (d). . This position corresponds to the point where the load torque is minimized. The rotor position corresponding to θm is set as a reference position in torque control.
[0077]
From θm, a point STPT where the load of the electric motor 1 starts to become heavier than the average load torque value during one rotation and a point WKPT where the load of the electric motor 1 starts to become lighter than the average load torque value during one rotation are calculated. In STPT and WKPT, when one rotation is divided into two sections with large and small load torque at equal intervals, the start point of the large load torque section may be STPT and the start point of the small load torque section may be WKPT. The points of STPT and WKPT are points indicated by the rotation angle in FIG.
[0078]
In the torque control means 6, the rotational speed command ω of the electric motor 1 ^* The point θm at which the load torque of the electric motor 1 detected by the rotor position detecting means 5 is minimized during one rotation, the point STPT at which the load of the electric motor 1 starts to become heavier than the average load torque during one rotation, and the electric motor 1 Point WKPT (or starting point STPT of large load torque section when one rotation is divided into two sections of large and small load torque at equal intervals, starting point of small load torque section Command value Id of d-axis current to be given next ^* To correct Id ^** Output as. Id obtained by adding a correction amount to FIG. ^** The state of is shown.
[0079]
Next, the operation will be described. The current detection means 3 detects the current value of at least one phase of the phase current waveform as shown in FIG. 8 obtained by being output from the inverter main circuit unit 8. The phase current calculation means 16 obtains the current values of the other phases by shifting the phase of each phase current by 120 degrees. The phase current signal for three phases obtained by the phase current calculation means 16 is coordinate-converted into an excitation current component (d-axis current) and a torque current component (q-axis current) by the three-phase two-phase conversion means 17.
[0080]
Here, when the load torque fluctuates as shown in FIG. 5D, a current ripple corresponding to the deviation between the load torque and the output torque is generated in the q-axis current Iq as shown in FIG. 5B. Using this current ripple, the point STPT at which the load of the electric motor 1 used for torque control starts to become heavier than the average value of load torque during one rotation. The load of the electric motor 1 is lighter than the average value of load torque during one rotation. A starting point WKPT (or a starting point STPT of a large load torque section and a starting point WKPT of a small load torque section when one rotation is divided into two sections of large and small load torque at equal intervals) is calculated.
[0081]
Point STPT at which the load of the electric motor 1 used for torque control begins to become heavier than the average load torque value during one rotation, and the point WKPT (or one rotation) at which the load of the electric motor 1 begins to become lighter than the average load torque value during one rotation FIG. 9 shows a flowchart for calculating the start point STPT of the large load torque section and the start point WKPT of the small load torque section when the load torque is divided into two sections of large and small load torque at equal intervals.
[0082]
First, as shown in FIG. 10A, one cycle of the q-axis current Iq is divided into n and the q-axis current Iq position is labeled. Here, the first q-axis current Iq capture position is set to a temporary reference position θ0 = 0 ° for position detection.
[0083]
Thereafter, as shown in FIG. 10B, the DC component Iq_fil of the q-axis current Iq is subtracted to obtain Iq_AC by the AC component detection means 11 that detects only the AC component. Next, data for one cycle of Iq_AC is stocked.
[0084]
The data to be stocked may be an average value of m cycles (m ≧ 2). Further, in order to remove noise, a filtering process such as comparison with the previous data may be performed to such an extent that it does not cause a problem in the following Fourier analysis. These data are subjected to the discrete Fourier transform of equation (1).
[0085]
[Expression 1]

[0086]
Here, f (n) is each value of Iq_AC, and N is the number of sampled Iq_AC samples. Exp represents an exponential function. From equation (1), F (1), that is, the fundamental wave real axis component r_dat1 and the imaginary axis component i_dat1 of Iq_AC are obtained.
[0087]
Next, the phase spectrum of the fundamental wave component of Iq_AC is calculated by calculating the arc sine of equation (2).
[0088]
[Expression 2]

[0089]
As a calculation method, arc cosine or arc tangent may be used.
[0090]
The calculated value θm of the phase spectrum is a point at which the maximum value of the q-axis current Iq appears, and is a phase difference when viewed from the temporary reference position θ0.
[0091]
There is a correlation between the q-axis current Iq and the load torque fluctuation, and θm can be approximated as a point at which the load torque is minimized. In an electric motor that drives a load element having a periodic load torque fluctuation, the periodic positional relationship is always maintained in a one-to-one relationship, so that θm is always the point at which the load torque is minimized.
[0092]
In principle, θm may be calculated once when the motor is started. However, before performing torque control during steady operation, θm may be calculated again as necessary. Since the rotor position can be detected again during operation in a special load state, torque control can be performed with higher accuracy without increasing the rotor position detection error.
[0093]
Especially at the time of start-up, since the current ripple of the q-axis current Iq hardly appears, the detection accuracy is lowered. Therefore, after accelerating to a predetermined rotational speed ωα from the time of startup, the amplitude spectrum spc1 of the fundamental wave component of Iq_AC is always calculated as in equation (3), and the reference position is calculated when the threshold level Iα is exceeded. Thus, the detection accuracy can be improved. Further, since the rotor position can be detected before the vibration becomes large and the torque control can be performed quickly, the time until the control is stabilized can be reduced.
[0094]
[Equation 3]

[0095]
Alternatively, the reference position may be calculated when a predetermined time elapses after acceleration to a predetermined rotational speed ωα from the start.
[0096]
Further, the reference position may be calculated when a predetermined time elapses and the threshold level Iα is exceeded after acceleration to a predetermined rotational speed ωα from the time of activation.
[0097]
Here, as shown in FIG. 7, when the phase difference from the point STPT at which the load of the electric motor 1 starts to become heavier than the average value of the load torque during one rotation from the point θm at which the load torque is minimum is defined as a phase correction amount Δθ. STPT is expressed by equation (4). Here, the phase range of the STPT is a repetition of 0 to 2π. For the phase correction amount Δθ, a test is performed in advance, and a value that reduces vibration is stored as data.
[0098]
[Expression 4]

[0099]
The phase correction amount Δθ may have characteristics as in the example of FIG. 11 with respect to the amplitude spectrum spc1 of the fundamental wave component of Iq_AC. When Δθ varies according to the value of the amplitude spectrum spc1, the phase correction amount Δθ is optimized according to this characteristic example, and the point STPT at which the load of the electric motor 1 starts to become heavier than the load torque average value during one rotation is calculated. The accuracy can be improved.
[0100]
Further, the point WKPT at which the load of the electric motor 1 starts to become lighter than the average value of the load torque during one rotation is expressed by the equation (5). The phase range of WKPT is also repeated from 0 to 2π.
[0101]
[Equation 5]

[0102]
It has been described that the phase correction amount Δθ is a phase difference from the point STPT at which the load of the electric motor 1 starts to become heavier than the average value of the load torque during one rotation from the point θm at which the load torque becomes minimum. The phase difference from the point WKPT at which the load starts to become lighter than the average load torque value during one rotation may be used. In this case, the correction may be reversed.
[0103]
The d-axis current base point is the point at which the load begins to change from the average value of the load torque, but the d-axis current base point is the point where the output torque and load torque are the same without torque control (this point After that, it means that it starts to increase, or starts to decrease).
[0104]
By controlling the phase difference to the base point of the d-axis current that is periodically changed according to the current ripple level of the fundamental wave component of the q-axis current, detection errors due to the load state can be reduced. In addition, torque control can be performed with higher accuracy by controlling the phase difference up to the base point of the d-axis current that periodically changes regardless of the primary and harmonic noise.
[0105]
Next, the torque control means will be described.
When torque control is not performed, the d-axis current command value Id ^* Is the rotational speed command ω of the electric motor 1 ^* On the other hand, the case where it becomes like FIG. 12, for example is taken up as an example. When torque control is not performed, the d-axis current command value Id with respect to the rotational speed command ω1 ^* When Id1, the final output Id of the d-axis current command value ^** Id1 is output as it is. In other words, when torque control is not performed, the command value Id ^* Is the command value Id as it is ^** Set as
[0106]
[Formula 6]

[0107]
For the rotational speed command ω1, the d-axis current command value Id ^* When is Id1, torque control is performed as follows. In FIG. 7D, if a region where the load is heavier than the average load torque during one rotation is defined as a large load torque region, the final output Id of the d-axis current command value is obtained in this region. ^** The correction amount Km is added as shown in the equation (7) and output.
[0108]
[Expression 7]

[0109]
If a region where the load is lighter than the average load torque during one rotation is defined as a small load torque region, the final output Id of the d-axis current command value in this region. ^** Is output by subtracting the correction amount Km as shown in equation (8).
[0110]
[Equation 8]

[0111]
Final output Id of d-axis current command value ^** Is increased in the section with a large load torque (half cycle) and is weakened in the section with a small load torque (half cycle). Thereby, stable torque control can be easily performed without generating unspecified harmonic noise.
[0112]
As described above, Km changes as shown in the equation (9) by changing the correction amount in each region of large load and small load in one cycle, or by a periodic function (sine wave, cosine wave, etc.). Let
[0113]
[Equation 9]

[0114]
Here, f (θ) represents a function having periodicity.
[0115]
By changing the change width or change value of the d-axis current that is periodically changed by a function having periodicity, stable torque control can be performed with a high degree of freedom without generating unspecified harmonic noise. .
[0116]
d-axis current command value Id ^** The correction amount Km of the rotation speed command ω ^* Thus, torque control can be performed with higher accuracy. Torque control can be performed finely and with a high degree of freedom without obstructing stable operation by improper application of excitation current.
[0117]
D-axis current command value Id in each region of large load and small load during one cycle ^** When the correction amount Km is changed, Km is the rotational speed command ω ^* Is stored as shown in FIG. Thereby, torque control can be performed finely and with high reliability by the rotation speed without impeding stable operation due to improper excitation current application.
[0118]
D-axis current command value Id by a periodic function ^** When changing the correction amount Km of the rotation speed command ω ^* Using the function including, change according to equation (10).
[0119]
[Expression 10]

[0120]
Where f (θ, ω ^* ) Is the rotation speed command ω ^* Represents a function with periodicity depending on.
[0121]
As described above, the inverter 2 generates a current waveform that minimizes the deviation between the load torque and the output torque of the motor, and suppresses vibration (see FIG. 7E). Moreover, since position estimation is performed using the amount of current, a rotor position can be detected without the need for a device for detecting the induced voltage zero cross. In addition, since the rotor position of the motor is detected because the fluctuation of the q-axis current has periodicity due to the load torque fluctuation, it is strong against primary and high-order noise and has high detection accuracy. In addition, since a non-energized section for detecting the induced voltage zero cross is not required, current pulsation during torque control can be reduced.
[0122]
If the torque control device for an electric motor of the present invention is used for an electric motor of a hermetic compressor, vibration can be suppressed without adding a new device.
[0123]
Further, if the hermetic compressor is mounted on a refrigeration cycle apparatus, vibration can be suppressed without adding a new apparatus.
[0124]
【The invention's effect】
The torque control apparatus for an electric motor according to claim 1 of the present invention is calculated from the q-axis current. mechanical Using rotor position information Depending on the stored correction amount Since the torque control is performed by periodically changing the d-axis current, the vibration can be suppressed without adding a new device for detecting the voltage amount or detecting the vibration. In addition, since the rotor position of the motor is detected by utilizing the fact that the fluctuation of the q-axis current has periodicity due to the load torque fluctuation, it is strong against primary and high-order noise and has high detection accuracy. . In addition, since a non-energized section for detecting the induced voltage zero cross is not required, current pulsation can be reduced when performing torque control.
[0125]
In the motor torque control apparatus according to claim 2 of the present invention, the means for obtaining the d-axis current and the q-axis current detects the current for at least one phase flowing through the motor and calculates the current flowing through each phase. Phase current calculation means and three-phase two-phase conversion means for calculating the d-axis current and the q-axis current from the current flowing in each phase, so that the position is estimated using the amount of current. The position of the rotor can be detected without the need for a device for detecting In addition, since a non-energized section for detecting the induced voltage zero cross is not required, current pulsation can be reduced when performing torque control.
[0126]
According to a third aspect of the present invention, there is provided the torque control apparatus for an electric motor, wherein the phase current calculation means obtains the current value of the other phase by shifting the phase of each phase current by 120 degrees, thereby obtaining the current value of each phase. It is not necessary to attach a sensor for detecting current to the sensor, and current detection can be performed accurately at low cost.
[0127]
According to a fourth aspect of the present invention, there is provided a torque control apparatus for an electric motor, wherein the inverter includes: a rotation speed command for the electric motor given from outside; a calculated d-axis current and a q-axis current; The position estimation is performed using the amount of current by including a drive signal generation unit that generates a PWM signal based on the command value, a PWM signal generation unit that generates the PWM signal, and an inverter main circuit that drives the motor. Therefore, a device for detecting the induced voltage zero cross is not necessary, and the rotor position can be detected. In addition, since a non-energized section for detecting the induced voltage zero cross is not required, current pulsation can be reduced when performing torque control.
[0128]
In the torque control apparatus for an electric motor according to claim 5 of the present invention, the drive signal generation unit includes voltage command calculation means for calculating the d-axis voltage and the q-axis voltage, and a three-phase component from the d-axis voltage and the q-axis voltage. Since a two-phase / three-phase conversion means for obtaining the output voltage and a PWM signal creation unit for creating a PWM signal so that an output voltage for three phases can be obtained, position estimation is performed using a current amount. The rotor position can be detected without a device for detecting the induced voltage zero cross. In addition, since a non-energized section for detecting the induced voltage zero cross is not required, current pulsation can be reduced when performing torque control.
[0129]
In the motor torque control apparatus according to claim 6 of the present invention, the means for detecting the rotor position of the motor detects the point at which the load torque of the motor becomes minimum or maximum during one rotation from the q-axis current. Thus, since the position is estimated from the correlation between the q-axis current and the load torque of the electric motor, the rotor position can be detected without providing a new device for position detection.
[0130]
According to a seventh aspect of the present invention, there is provided a torque control device for an electric motor, wherein the torque control means has a motor rotational speed command given from outside and a load torque of the electric motor detected by the means for detecting the rotor position is 1. From the information of the point at which the motor load begins to become heavier than the average load torque value during one rotation, the point at which the motor load begins to become lighter than the average load torque value during one rotation, By correcting and outputting the command value of the d-axis current applied to the vibration, vibration can be more easily and precisely controlled by the rotational speed.
[0131]
In the motor torque control apparatus according to claim 8 of the present invention, the torque control means is configured such that the motor rotation speed command given from the outside and the load torque of the motor detected by the means for detecting the rotor position are 1 The d-axis to be given next from the information of the starting point of the large load torque section and the starting point of the small load torque section when dividing the minimum or maximum point during the rotation into two sections of the load torque large and small at equal intervals By correcting and outputting the current command value, vibration can be more easily and precisely controlled by the rotational speed.
[0132]
According to a ninth aspect of the present invention, there is provided a torque control apparatus for an electric motor that uses a current ripple corresponding to a deviation between a load torque generated in a q-axis current and an output torque, and that is used for torque control. From the correlation between the q-axis current and the load torque of the motor, by calculating the point at which the load begins to become heavier than the load torque average value during one rotation and the point at which the motor load begins to become lighter than the load torque average value during one rotation Since the position is estimated, the rotor position can be detected without providing a new device for position detection.
[0133]
According to a tenth aspect of the present invention, there is provided a torque control apparatus for an electric motor that uses a current ripple according to a deviation between a load torque generated in a q-axis current and an output torque, and the load torque is increased or decreased at equal intervals during one rotation. When the position is estimated from the correlation between the q-axis current and the load torque of the motor by calculating the information of the start point of the large load torque section and the start point of the small load torque section, the position detection The rotor position can be detected without providing a new device.
[0134]
According to an eleventh aspect of the present invention, there is provided a torque control apparatus for an electric motor comprising means for redetecting the rotor position of the electric motor before shifting from a state where the electric motor is not performing torque control to a state where torque control is performed. As a result, the rotor position detection error does not increase even during operation in a special load state, and vibration can be suppressed more accurately.
[0135]
In the motor torque control apparatus according to claim 12 of the present invention, when starting up the motor, the current ripple level of the fundamental wave component of the q-axis current becomes equal to or higher than a predetermined value after acceleration to a specific frequency. By actuating the means for detecting the rotor position of the electric motor at this time, it is possible to suppress a position estimation error due to insufficient current ripple at startup. In addition, since the current ripple level of the fundamental wave component is seen instead of the instantaneous value of the q-axis current, it is strong against the first-order and higher-order noise components. In addition, since the rotor position can be detected early before the vibration becomes large and torque control can be performed, the time until the control is stabilized is short and higher reliability can be obtained.
[0136]
According to a thirteenth aspect of the present invention, the torque control apparatus for an electric motor activates a means for detecting the rotor position of the electric motor when a predetermined time has elapsed after the acceleration to a specific frequency when starting the electric motor. Thus, it is possible to suppress a position estimation error due to insufficient current ripple at the time of startup.
[0137]
According to a fourteenth aspect of the present invention, there is provided a torque control apparatus for an electric motor according to a fourteenth aspect of the present invention, in which a predetermined time elapses after the acceleration to a specific frequency when starting the electric motor, and the current ripple level of the fundamental wave component of the q-axis current is By activating the means for detecting the rotor position of the electric motor when it becomes a predetermined value or more, it is possible to suppress a position estimation error due to insufficient current ripple at the time of startup.
[0138]
According to a fifteenth aspect of the present invention, when the rotor position of the motor is detected, the motor torque control apparatus periodically changes from the rotor reference position by the current ripple level of the fundamental component of the q-axis current. By providing means for determining the phase difference up to the base point of the axial current, detection errors due to the load state can be reduced. In addition, since the phase up to the base point of the d-axis current that changes periodically regardless of the primary and harmonic noises can be controlled, vibration can be suppressed with high accuracy.
[0139]
In the torque control apparatus for an electric motor according to the sixteenth aspect of the present invention, the d-axis current base point is a point at which the deviation between the load torque and the output torque becomes almost zero when torque control is not performed (after this point, The point that starts to become positive or the point that starts to become negative) makes it possible to reduce detection errors due to load conditions.
[0140]
In the torque control apparatus for an electric motor according to claim 17 of the present invention, since the base point of the d-axis current is a point at which the load starts to change from the average value of the load torque, the detection error due to the load state can be reduced. .
[0141]
In the torque control apparatus for an electric motor according to claim 18 of the present invention, the d-axis current base point is the starting point of the large load torque section when one rotation is divided into two sections of large and small load torque at equal intervals, or By using the starting point of the small load torque section, detection errors due to the load state can be reduced.
[0142]
According to a nineteenth aspect of the present invention, there is provided the torque control apparatus for an electric motor by performing a test in advance and storing a value that reduces vibration as data, so that environmental conditions and load conditions are stored. Torque control can be performed with high accuracy regardless of operating conditions and variations in individual motors.
[0143]
According to a twentieth aspect of the present invention, the torque control apparatus for an electric motor includes means for changing a change width or a change value of the d-axis current that is periodically changed in accordance with the phase section, so that unspecified harmonic noise is generated. Vibration can be suppressed easily and accurately without occurrence.
[0144]
According to a twenty-first aspect of the present invention, there is provided a torque control apparatus for an electric motor by performing torque control by strengthening a final output of a d-axis current command value in a section with a large load torque and weakening in a section with a small load torque. The vibration can be easily and accurately suppressed without generating unspecified harmonic noise.
[0145]
According to a twenty-second aspect of the present invention, there is provided a torque control apparatus for an electric motor comprising means for changing a change width or a change value of a d-axis current that is periodically changed by a periodic function. Vibration can be suppressed with high degree of freedom and accuracy without generating wave noise.
[0146]
According to a twenty-third aspect of the present invention, there is provided a torque control apparatus for an electric motor, wherein a motor current phase is sharply changed at a change of a phase interval by changing a change width or a change value of a d-axis current by a sine wave function or a cosine wave function. Since it is not changed, torque control can be performed without generating steep noise.
[0147]
In addition, the torque control apparatus for an electric motor according to claim 24 of the present invention includes means for storing in advance a change width or a change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor. Vibration can be more easily and precisely controlled by the rotation speed.
[0148]
According to a twenty-fifth aspect of the present invention, the torque control apparatus for an electric motor includes a means for changing a change width or a change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor. Vibration can be suppressed.
[0149]
According to a twenty-sixth aspect of the present invention, there is provided a hermetic compressor according to any one of the first to twenty-fifth aspects, wherein a motor for a compressor is controlled by the torque control device for a motor without adding a new device. , Vibration can be suppressed.
[0150]
The refrigeration cycle apparatus according to claim 27 of the present invention can suppress vibration without adding a new apparatus by mounting the hermetic compressor according to claim 26 in the refrigeration cycle.
[0151]
A torque control method for an electric motor according to claim 28 of the present invention is calculated from q-axis current Iq. mechanical Using rotor position information Depending on the stored correction amount Since the torque control is performed by periodically changing the d-axis current Id, the vibration can be suppressed without adding a new device for detecting the voltage amount or detecting the vibration. In addition, since the rotor position of the motor is detected by utilizing the fact that the fluctuation of the q-axis current has periodicity due to the load torque fluctuation, it is strong against primary and high-order noise and has high detection accuracy. . In addition, current pulsation during torque control can be reduced.
[0152]
According to a twenty-ninth aspect of the present invention, there is provided a torque control method for an electric motor that detects a current for at least one phase flowing in the electric motor, calculates a current flowing in each phase, and calculates a d-axis current from the current flowing in each phase. By calculating the q-axis current, a rotor position can be detected without a device for detecting the induced voltage zero cross. In addition, since a non-energized section for detecting the induced voltage zero cross is not required, current pulsation can be reduced when performing torque control.
[0153]
According to a thirty-third aspect of the present invention, there is provided a torque control method for an electric motor in which a current is detected for each phase by obtaining a current value of another phase by shifting a phase of each phase current by 120 degrees. It is not necessary to attach a current sensor, and current detection can be performed accurately at low cost.
[0154]
In the motor torque control method according to the thirty-first aspect of the present invention, the inverter includes a motor rotation speed command given from the outside, a calculated d-axis current and q-axis current, and a command of an excitation current component to be given next. By creating a PWM signal based on the value, generating the PWM signal, and driving the motor by the inverter main circuit, position estimation is performed using the amount of current, so there is no need for a device that detects the induced voltage zero crossing, The rotor position can be detected. In addition, since a non-energized section for detecting the induced voltage zero cross is not required, current pulsation can be reduced when performing torque control.
[0155]
According to a thirty-second aspect of the torque control method for an electric motor of the present invention, the rotor position of the electric motor is detected by detecting a point at which the load torque of the electric motor is minimum or maximum in one rotation from the q-axis current. Thus, since the position is estimated from the correlation between the q-axis current and the load torque of the electric motor, the rotor position can be detected without providing a new device for position detection.
[0156]
According to a thirty-third aspect of the present invention, there is provided a torque control method for an electric motor wherein the motor rotational speed command given from the outside and the motor load torque detected by the means for detecting the rotor position are minimized or The d-axis current to be given next is determined based on the maximum point, the point at which the motor load begins to be heavier than the average load torque value during one rotation, and the point at which the motor load begins to become lighter than the average load torque value during one rotation. By correcting and outputting the command value and performing torque control of the electric motor, vibration can be suppressed more easily and precisely by the rotational speed.
[0157]
According to a thirty-fourth aspect of the present invention, there is provided a torque control method for an electric motor wherein the motor rotational speed command given from the outside and the motor load torque detected by the means for detecting the rotor position are minimized or When the maximum point and one rotation are divided into two sections with large and small load torque at equal intervals, the command value of the d-axis current to be given next is determined from the information of the starting point of the large load torque section and the starting point of the small load torque section. By correcting and outputting, vibration can be more easily and precisely controlled by the rotation speed.
[0158]
According to a thirty-fifth aspect of the present invention, there is provided a torque control method for an electric motor that uses a current ripple according to a deviation between a load torque generated in a q-axis current and an output torque to control the load of the electric motor used for torque control. From the correlation between the q-axis current and the load torque of the motor, by calculating the point at which the load begins to become heavier than the load torque average value during one rotation and the point at which the motor load begins to become lighter than the load torque average value during one rotation Since the position is estimated, the rotor position can be detected without providing a new device for position detection.
[0159]
According to a thirty-sixth aspect of the present invention, there is provided a torque control method for an electric motor using a current ripple according to a deviation between a load torque generated in a q-axis current and an output torque, and the magnitude of the load torque at regular intervals during one rotation. When the position is estimated from the correlation between the q-axis current and the load torque of the motor by calculating the information of the start point of the large load torque section and the start point of the small load torque section, the position detection The rotor position can be detected without providing a new device.
[0160]
Further, in the torque control method for an electric motor according to claim 37 of the present invention, by re-detecting the rotor position of the electric motor before shifting from the state where torque control is not performed in the electric motor to the state where torque control is performed, The rotor position detection error does not increase even during operation in a special load state, and vibration can be suppressed more accurately.
[0161]
In the torque control method for an electric motor according to claim 38 of the present invention, the current ripple level of the fundamental wave component of the q-axis current becomes equal to or higher than a predetermined value after acceleration to a specific frequency when starting the electric motor. By operating the step of detecting the rotor position of the electric motor at this time, it is possible to suppress position estimation errors caused by insufficient current ripple at the time of startup. In addition, since the current ripple level of the fundamental wave component is seen instead of the instantaneous value of the q-axis current, it is strong against the first-order and higher-order noise components. In addition, since the rotor position can be detected early before the vibration becomes large and torque control can be performed, the time until the control is stabilized is short and higher reliability can be obtained.
[0162]
According to a thirty-ninth aspect of the present invention, the torque control method for an electric motor activates a step of detecting the rotor position of the electric motor when a predetermined time has elapsed after accelerating to a specific frequency when starting the electric motor. Thus, it is possible to suppress a position estimation error due to insufficient current ripple at the time of startup.
[0163]
According to a 40th aspect of the present invention, there is provided a torque control method for an electric motor in which a predetermined time elapses after the acceleration to a specific frequency when starting the electric motor, and the current ripple level of the fundamental wave component of the q-axis current is By activating the step of detecting the rotor position of the electric motor when the predetermined value or more is reached, it is possible to suppress position estimation errors caused by insufficient current ripple at the time of startup.
[0164]
According to a 41st aspect of the present invention, in the torque control method for an electric motor, when detecting the rotor position of the electric motor, d is periodically changed from the rotor reference position by the current ripple level of the fundamental wave component of the q-axis current. By determining the phase difference up to the base point of the shaft current, detection errors due to load conditions can be reduced. In addition, since the phase up to the base point of the d-axis current that changes periodically regardless of the primary and harmonic noises can be controlled, vibration can be suppressed with high accuracy.
[0165]
Further, in the torque control method for an electric motor according to claim 42 of the present invention, the d-axis current base point is a point at which the deviation between the load torque and the output torque becomes almost zero in a state where the torque control is not performed (after this point, The point that starts to become positive or the point that starts to become negative) makes it possible to reduce detection errors due to load conditions.
[0166]
In the torque control method for an electric motor according to claim 43 of the present invention, since the base point of the d-axis current is a point at which the load starts to change from the average value of the load torque, the detection error due to the load state can be reduced. .
[0167]
In the motor torque control method according to claim 44 of the present invention, the d-axis current base point is the starting point of the large load torque section when one rotation is divided into two sections of large and small load torque at equal intervals, or By using the starting point of the small load torque section, detection errors due to the load state can be reduced.
[0168]
In addition, in the torque control method for an electric motor according to claim 45 of the present invention, the phase difference is tested in advance, and a value that reduces vibration as data is stored. Torque control can be performed with high accuracy regardless of operating conditions and variations in individual motors.
[0169]
According to a 46th aspect of the present invention, there is provided a torque control method for an electric motor without generating unspecified harmonic noise by changing a change width or a change value of a d-axis current that is periodically changed according to a phase interval. The vibration can be suppressed easily and accurately.
[0170]
According to a 47th aspect of the present invention, there is provided a torque control method for an electric motor by performing torque control by increasing a final output of a d-axis current command value in a section with a large load torque and weakening in a section with a small load torque. The vibration can be easily and accurately suppressed without generating unspecified harmonic noise.
[0171]
According to a 48th aspect of the present invention, there is provided a torque control method for an electric motor that generates unspecified harmonic noise by changing a change width or a change value of a d-axis current that is periodically changed by a periodic function. Therefore, vibration can be suppressed with high degree of freedom and accuracy.
[0172]
According to a 49th aspect of the present invention, there is provided a torque control method for an electric motor in which a motor current phase is sharply changed at a phase interval by changing a change width or a change value of a d-axis current by a sine wave function or a cosine wave function. Since it is not changed, torque control can be performed without generating steep noise.
[0173]
According to a 50th aspect of the present invention, there is provided a torque control method for an electric motor that stores in advance a change width or a change value of a d-axis current that is periodically changed according to the rotation speed of the electric motor, and thereby vibrates depending on the rotation speed. Can be more easily and precisely controlled.
[0174]
In addition, the torque control method for an electric motor according to claim 51 of the present invention suppresses vibration with high degree of freedom and precision by changing the change width or change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor. it can.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment and is a configuration diagram of a torque control device for an electric motor.
FIG. 2 is a diagram showing the first embodiment, and is an internal configuration diagram of an inverter unit that drives an electric motor.
FIG. 3 is a diagram showing the first embodiment, and is a PWM drive signal of an inverter switching element for driving an electric motor and terminal voltage waveform diagrams of each phase of UVW.
FIG. 4 is a diagram showing the first embodiment, and is an internal configuration diagram of a means for obtaining an excitation current component (d-axis current Id) and a torque current component (q-axis current Iq) from a current flowing in a motor winding.
FIG. 5 shows the first embodiment, and shows a d-axis current command value Id when torque control is not performed in the torque control device for an electric motor. ^** FIG. 5 is a diagram showing q-axis current Iq, phase current Iu, load torque fluctuation and vibration of the motor.
FIG. 6 is a diagram showing the first embodiment, and is a diagram showing a relationship between a mechanical position and a load torque when the load element is a single rotary compressor in the torque control apparatus for an electric motor.
7 shows the first embodiment, and shows a d-axis current command value Id when torque control is performed in the torque control device of the motor. FIG. ^** FIG. 5 is a diagram showing q-axis current Iq, phase current Iu, load torque and vibration of the motor.
FIG. 8 is a diagram showing the first embodiment and showing an example of a phase current waveform of a torque control device for an electric motor.
FIG. 9 shows the first embodiment. In the motor torque control device, the point STPT at which the load of the motor 1 starts to become heavier than the average load torque during one rotation. The load of the motor 1 is during one rotation. A flowchart for calculating a point WKPT that starts to become lighter than the average load torque value (or a start point STPT of a large load torque section and a start point WKPT of a small load torque section when one rotation is divided into two sections of large and small load torque at equal intervals). FIG.
FIG. 10 is a diagram illustrating the first embodiment, and is a diagram illustrating a process of stocking AC component data of a q-axis current in a torque control device for an electric motor.
FIG. 11 is a diagram illustrating the first embodiment and is a diagram illustrating a characteristic example of the amplitude spectrum spc1 of the fundamental wave component of Iq_AC and the phase correction amount Δθ in the torque control device of the motor.
FIG. 12 shows the first embodiment, and shows a rotational frequency command ω in a torque control device for an electric motor. ^* And d-axis current command Id ^* It is a figure which shows the example of a characteristic.
FIG. 13 is a diagram illustrating the first embodiment, and illustrates a rotational frequency command ω in a torque control device for an electric motor. ^* It is a figure which shows the example of a characteristic of torque correction amount Km.
FIG. 14 is a configuration diagram of a conventional compressor motor control device.
FIG. 15 is a diagram showing data stored in torque pattern storage means of a conventional compressor motor control device.
FIG. 16 is a diagram showing a PWM signal of a conventional compressor motor control device.
FIG. 17 is a diagram showing a U-phase terminal voltage waveform of an inverter of a conventional compressor motor control device.
FIG. 18 is a phase current waveform diagram in torque control of a conventional compressor motor control device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric motor 2 Inverter 3 Current detection means 4 Excitation current component (d-axis current) and torque current component (q-axis current) means 5 Rotor position detection means 6 Torque control means 7 Motor torque control Device, 8 inverter main circuit, 9 drive signal generating means, 10a to 10f switching element, 11a to 11f freewheeling diode, 12 PWM signal generating means, 13 PWM signal generating section, 14 two-phase three-phase converting means, 15 voltage command calculating means , 16-phase current calculation means, 17 3-phase 2-phase conversion means, 18 voltage detection means, 19 compressor, 20 speed control means, 21 load torque pattern storage unit.

Claims (51)

An electric motor for driving a load element having periodic load torque fluctuations;
An inverter of a 180-degree energization method for driving the electric motor;
Means for detecting a current flowing through the electric motor to obtain a d-axis current as an exciting current component and a q-axis current as a torque current component;
Means for detecting a mechanical rotor position of the electric motor by utilizing the fact that the fluctuation of the q-axis current has periodicity due to the load torque fluctuation;
Using the rotor position information, torque control means for performing torque control by periodically changing the d-axis current according to a stored correction amount ;
A torque control device for an electric motor, comprising: The means for obtaining the d-axis current and the q-axis current detects a current for at least one phase flowing through the electric motor, calculates a current flowing through each phase, and calculates the current flowing through each phase from the current flowing through each phase. The torque control device for an electric motor according to claim 1, further comprising three-phase to two-phase conversion means for calculating a shaft current and a q-axis current. 3. The torque control apparatus for an electric motor according to claim 2, wherein the phase current calculation unit obtains a current value of another phase by shifting the phase of each phase current by 120 degrees. 4. The inverter includes a drive signal generation unit that creates a PWM signal based on a rotation speed command of the motor given from the outside, a calculated d-axis current and a q-axis current, and a command value of the d-axis current to be given next, 2. The motor torque control device according to claim 1, further comprising: a PWM signal generating means for generating the PWM signal; and an inverter main circuit for driving the motor. The drive signal generation unit includes a voltage command calculation unit that calculates a d-axis voltage and a q-axis voltage, a two-phase / three-phase conversion unit that determines an output voltage for three phases from the d-axis voltage and the q-axis voltage, and the three-phase The motor torque control device according to claim 4, further comprising: a PWM signal generation unit that generates a PWM signal so that an output voltage of a minute can be obtained. 2. The motor torque according to claim 1, wherein the means for detecting the rotor position of the motor detects a point at which the load torque of the motor becomes minimum or maximum during one rotation from the q-axis current. Control device. The torque control means is a point at which the rotation speed command of the motor given from the outside and the load torque of the motor detected by the means for detecting the rotor position become minimum or maximum in one rotation, and the load of the motor is 1. Correct and output the d-axis current command value to be given next, based on the information of the point where the load torque starts to become heavier than the average value during rotation and the point where the motor load begins to become lighter than the average value of load torque during one rotation. The torque control device for an electric motor according to claim 1. The torque control means is a point at which the rotation speed command of the electric motor given from the outside and the load torque of the electric motor detected by the means for detecting the rotor position become minimum or maximum in one rotation, during one rotation, etc. When divided into two sections with large and small load torque at intervals, the command value of the d-axis current to be given next is corrected and output from the information of the start point of the large load torque section and the start point of the small load torque section. The torque control device for an electric motor according to claim 1. When a current ripple according to the deviation between the load torque generated in the q-axis current and the output torque is used to divide one rotation into two sections of large and small load torque at equal intervals, the starting point of the load torque large section, the load Information of the starting point of the torque subsection The point where the load of the motor used for torque control begins to become heavier than the average value of the load torque during one rotation, and the point where the load of the motor begins to become lighter than the average value of the load torque during one rotation The torque control device for an electric motor according to claim 7, wherein the torque control device is calculated. When a current ripple according to the deviation between the load torque generated in the q-axis current and the output torque is used to divide one rotation into two sections of large and small load torque at equal intervals, the starting point of the load torque large section, the load 2. The torque control apparatus for an electric motor according to claim 1, wherein information on a starting point of the small torque section is calculated. The torque of the electric motor according to claim 1, further comprising means for redetecting a rotor position of the electric motor before shifting from a state in which the electric motor does not perform torque control to a state in which torque control is performed. Control device. When starting up the electric motor, after accelerating to a specific frequency, the means for detecting the rotor position of the electric motor is activated when the current ripple level of the fundamental wave component of the q-axis current exceeds a predetermined value. The torque control apparatus for an electric motor according to claim 1, wherein: 2. The motor torque control according to claim 1, wherein when the electric motor is started, a means for detecting a rotor position of the electric motor is activated when a predetermined time elapses after acceleration to a specific frequency. apparatus. When starting up the electric motor, after accelerating to a specific frequency, when a predetermined time elapses and the current ripple level of the fundamental component of the q-axis current exceeds a predetermined value, the rotor position of the electric motor 2. The torque control apparatus for an electric motor according to claim 1, wherein means for detecting the motor is operated. When detecting the rotor position of the motor, there is provided means for determining a phase difference from the rotor reference position to the base point of the d-axis current that is periodically changed based on the current ripple level of the fundamental wave component of the q-axis current. The torque control apparatus for an electric motor according to claim 1, wherein the torque control apparatus is an electric motor. The base point of the d-axis current is a point where the deviation between the load torque and the output torque becomes almost zero (a point at which starting to become positive or starting to become negative after this point) without performing torque control. The torque control apparatus for an electric motor according to claim 15. The torque control device for an electric motor according to claim 15, wherein a base point of the d-axis current is a point at which the load starts to change from an average value of the load torque. 16. The base point of the d-axis current is a start point of a large load torque section or a start point of a small load torque section when one rotation is divided into two sections of large and small load torque at equal intervals. The torque control apparatus for the electric motor according to 1. 16. The torque control apparatus for an electric motor according to claim 15, wherein the phase difference is subjected to a test in advance and is stored as a value such that vibration is reduced. The torque control apparatus for an electric motor according to claim 1, further comprising means for changing a change width or a change value of the d-axis current that is periodically changed according to the phase section. 21. The torque control apparatus for an electric motor according to claim 20, wherein torque control is performed by strengthening a final output of the d-axis current command value in a section with a large load torque and weakening in a section with a small load torque. The torque control apparatus for an electric motor according to claim 1, further comprising means for changing a change width or a change value of the d-axis current that is periodically changed by a function having periodicity. 23. The torque control apparatus for an electric motor according to claim 22, wherein a change width or a change value of the d-axis current is changed by a sine wave function or a cosine wave function. 2. The motor torque control apparatus according to claim 1, further comprising means for previously storing a change width or a change value of a d-axis current that is periodically changed according to a rotation speed of the electric motor. 2. The torque control apparatus for an electric motor according to claim 1, further comprising means for changing a change width or a change value of the d-axis current that is periodically changed according to a rotation speed of the electric motor. 26. A hermetic compressor, wherein a motor for a compressor is controlled by the torque control device for an electric motor according to any one of claims 1 to 25. 27. A refrigeration cycle apparatus comprising the hermetic compressor according to claim 26 mounted in a refrigeration cycle. In the torque control method of an electric motor in the case of driving an electric motor that drives a load element having a periodic load torque fluctuation with an inverter of a 180-degree energization method ,
Detecting a current flowing through the electric motor to obtain a d-axis current as an exciting current component and a q-axis current as a torque current component;
Detecting the mechanical rotor position of the electric motor using the fact that the fluctuation of the q-axis current has periodicity due to the load torque fluctuation;
Using the rotor position information to perform torque control by periodically changing the d-axis current according to a stored correction amount ;
An electric motor torque control method comprising: 29. The current of at least one phase flowing through the motor is detected, the current flowing through each phase is calculated, and the d-axis current and the q-axis current are calculated from the current flowing through each phase. The torque control method of the electric motor described. 30. The torque control method for an electric motor according to claim 29, wherein the current values of the other phases are obtained by shifting the phase of each phase current by 120 degrees. The inverter creates a PWM signal based on the rotation speed command of the motor given from the outside, the calculated d-axis current and q-axis current, and the command value of the excitation current component to be given next, and generates the PWM signal 29. The torque control method for an electric motor according to claim 28, wherein the electric motor is driven by an inverter main circuit. 29. The motor torque according to claim 28, wherein a rotor position of the motor is detected by detecting a point at which the load torque of the motor is minimum or maximum in one rotation from the q-axis current. Control method. The motor rotation speed command given from the outside, the point at which the load torque of the motor detected by the means for detecting the rotor position becomes the minimum or maximum during one rotation, and the load torque average when the motor load is one rotation From the information of the point that starts to become heavier than the value and the point that the load of the motor starts to become lighter than the load torque average value during one rotation, the command value of the d-axis current to be applied next is corrected and output to control the torque of the motor The torque control method for an electric motor according to claim 28. The motor rotation speed command given from the outside and the point at which the load torque of the motor detected by the means for detecting the rotor position becomes the minimum or maximum during one rotation. 29. The command value of the d-axis current to be applied next is corrected and output from information on the start point of the large load torque section and the start point of the small load torque section when divided into two sections. Torque control method for an electric motor. A point where the load of the motor used for torque control starts to become heavier than the average value of the load torque during one rotation by using a current ripple according to the deviation between the load torque generated in the q-axis current and the output torque; 34. The torque control method for an electric motor according to claim 33, wherein a point at which the load begins to become lighter than an average load torque value during one rotation is calculated. When a current ripple according to the deviation between the load torque generated in the q-axis current and the output torque is used to divide one rotation into two sections of large and small load torque at equal intervals, the starting point of the load torque large section, the load 29. The torque control method for an electric motor according to claim 28, wherein information on a starting point of the small torque section is calculated. 29. The torque control method for an electric motor according to claim 28, wherein the rotor position of the electric motor is re-detected before shifting from a state where torque control is not performed in the electric motor to a state where torque control is performed. When starting up the electric motor, after accelerating to a specific frequency, operating a step of detecting the rotor position of the electric motor when the current ripple level of the fundamental component of the q-axis current exceeds a predetermined value The torque control method for an electric motor according to claim 28, wherein: 29. The torque control of the electric motor according to claim 28, wherein when starting the electric motor, the step of detecting the rotor position of the electric motor is activated when a predetermined time has elapsed after accelerating to a specific frequency. Method. When starting up the electric motor, after accelerating to a specific frequency, when a predetermined time elapses and the current ripple level of the fundamental component of the q-axis current exceeds a predetermined value, the rotor position of the electric motor 29. The method for controlling torque of an electric motor according to claim 28, wherein the step of detecting the motor is activated. The phase difference from the rotor reference position to the d-axis current base point that is periodically changed is determined by the current ripple level of the fundamental wave component of the q-axis current when detecting the rotor position of the motor. Item 29. The torque control method for an electric motor according to Item 28. The base point of the d-axis current is a point where the deviation between the load torque and the output torque becomes almost zero (a point at which starting to become positive or starting to become negative after this point) without performing torque control. The torque control method for an electric motor according to claim 41, wherein: 42. The torque control method for an electric motor according to claim 41, wherein a base point of the d-axis current is a point at which a load starts to change from an average value of load torque. The base point of the d-axis current is a starting point of a large load torque section or a starting point of a small load torque section when one rotation is divided into two sections of large and small load torque at equal intervals. A torque control method for an electric motor according to claim 1. 42. The torque control method for an electric motor according to claim 41, wherein the phase difference is subjected to a test in advance and is stored as a data such that vibration is reduced. 29. The torque control method for an electric motor according to claim 28, wherein a change width or a change value of the d-axis current that is periodically changed according to the phase section is changed. 47. The torque control method for an electric motor according to claim 46, wherein torque control is performed by strengthening a final output of the d-axis current command value in a section with a large load torque and weakening in a section with a small load torque. 29. The torque control method for an electric motor according to claim 28, wherein a change width or a change value of the d-axis current that is periodically changed by a function having periodicity is changed. 49. The torque control method for an electric motor according to claim 48, wherein a change width or a change value of the d-axis current is changed by a sine wave function or a cosine wave function. 29. The torque control method for an electric motor according to claim 28, wherein a change width or a change value of the d-axis current that is periodically changed according to the rotation speed of the electric motor is stored in advance. 29. The torque control method for an electric motor according to claim 28, wherein a change width or a change value of the d-axis current that is periodically changed according to a rotation speed of the electric motor is changed.

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