JP2005033911A

JP2005033911A - Three-phase ac-dc converter

Info

Publication number: JP2005033911A
Application number: JP2003195819A
Authority: JP
Inventors: Shinji Sato; 伸二佐藤
Original assignee: Sanken Electric Co Ltd
Current assignee: Sanken Electric Co Ltd
Priority date: 2003-07-11
Filing date: 2003-07-11
Publication date: 2005-02-03

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize and reduce the cost of a three-phase AC-DC power converter. <P>SOLUTION: First, second, and third power conversion circuits 2a, 2b, 2c are disposed between first, second, and third AC input terminals 1a, 1b, and 1c and first and second DC output terminals 3a and 3b. The first power conversion circuit 2a comprises a rectifying circuit 9a connected to the firsts and second AC input terminals 1a and 1b through a first inductor 1a, a switch Qa connected across AC terminals of the rectifying circuit 9a, a series circuit of a primary coil N1a and a first capacitor C1a, a series circuit of a secondary coil N2a and a second capacitor C2a, a series circuit of a diode D5a and a second inductor L2a, and a diode D6a connected between the secondary coil N2a and a common smoothing capacitor Co. The second and third power conversion circuits 2b and 2c are formed in the same way with the first power conversion circuit 2a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、スイッチング回路とトランスとを有して３相交流電力を直流電力に変換する３相交流−直流電力変換装置に関する。
【０００２】
【従来の技術】
【特許文献１】特開２００２−２３３１５５号公報
【特許文献２】特開２００２−３５４８１６号公報
通信用電源やバッテリー充電器等に使用するための絶縁型３相交流−直流電力変換装置を構成する場合に商用周波数（５０Ｈｚ又は６０Ｈｚ）側に絶縁トランスを設け、トランスの２次側に整流回路及び電圧調整用のＰＷＭスイッチング回路を設けると、トランスが大きくなる。この問題を解決するために、３相交流電源に非絶縁のＰＷＭ整流器即ち交流−直流コンバータを接続し、このコンバータの出力端子間に直流リンクコンデンサを接続し、直流リンクコンデンサの出力段に高周波絶縁トランスを有する高周波インバータを接続し、このインバータの出力段に整流平滑回路を設けることがある。この場合には、トランスとして高周波トランスを使用するので、トランスの小型化を図ることができる。
しかし、６個のスイッチから成る交流−直流コンバータ、直流リンクコンデンサ、４個のスイッチから成るインバータ、トランス、整流平滑回路が必要になるので、トランス以外の部品点数が多くなり、回路が複雑且つコスト高になる。
【０００３】
この問題を解決するための３相交流−直流電力変換装置が前記特許文献１及び前記特許文献２に開示されている。ここに開示されている３相交流−直流電力変換装置は、３相交流の各線間に接続され且つ同一のコアに巻き回された第１、第２及び第３の１次巻線と、各１次巻線に直列に接続された交流スイッチと、３相共通の２次巻線と、２次巻線に接続された整流平滑回路とから成る。
【０００４】
【発明が解決しようとする課題】
前記特許文献１及び２に記載されている３相交流−直流電力変換装置によれば、構成の大幅な簡略化を達成することができる。しかし、３相分の交流スイッチを構成するために６個のスイッチング素子が必要になる。また、トランスを３相共通に構成するために必然的にトランスが大きくなる。このため、トランスが３相個別であるにも拘らず小型且つ低コスト化を図ることができる３相交流−直流電力変換装置が要求されている。
【０００５】
そこで、本発明の目的は、上記要求を満足させることができる３相交流−直流電力変換装置を提供することにある。
【０００６】
【課題を解決するための手段】
上記課題を解決し、上記目的を達成するための本発明を図面の符号を参照して説明する。但し、特許請求の範囲及びここでの本発明の説明における参照符号は、本発明の理解を助けるためのものであって、本発明を限定するものではない。本発明は、３相交流電力を直流電力に変換するための３相交流−直流電力変換装置であって、
３相交流電圧を供給するための第１，第２及び第３の交流入力端子（１ａ，１ｂ，１ｃ）と、
負荷（３）に直流電圧を供給するための第１及び第２の直流出力端子（３ａ，３ｂ）と、
前記第１及び第２の交流入力端子（１ａ，１ｂ）に接続された第１の対の交流入力導体（５ａ，６ａ）と前記第１及び第２の直流出力端子（３ａ，３ｂ）に接続された第１の対の直流出力導体（７ａ，８ａ）とを有して前記第１の対の交流入力導体（５ａ，６ａ）間の交流電圧を直流電圧に変換する第１の電力変換回路（２ａ）と、
前記第２及び第３の交流入力端子（１ｂ，１ｃ）に接続された第２の対の交流入力導体（５ｂ，６ｂ）と前記第１及び第２の直流出力端子（３ａ，３ｂ）に接続された第２の対の直流出力導体（７ｂ，８ｂ）とを有して前記第２の対の交流入力導体（５ｂ，６ｂ）間の交流電圧を直流電圧に変換する第２の電力変換回路（２ｂ）と、
前記第３及び第１の交流入力端子（１ｃ，１ａ）に接続された第３の対の交流入力導体（５ｃ，６ｃ）と前記第１及び第２の直流出力端子（３ａ，３ｂ）に接続された第３の対の直流出力導体（７ｃ，８ｃ）とを有して前記第３の対の交流入力導体（５ｃ，６ｃ）間の交流電圧を直流電圧に変換する第３の電力変換回路（２ｃ）とを備え、
前記第１，第２及び第３の電力変換回路（２ａ，２ｂ，２ｃ）のそれぞれが、
それぞれの前記対の交流入力導体に接続された対の交流端子と、整流出力用の対の直流端子と、前記対の交流端子の一方と前記対の直流端子の一方との間に接続された第１のダイオードと、前記対の直流端子の他方と前記対の交流端子の一方との間に接続された第２のダイオードと、前記対の交流端子の他方と前記対の直流端子の一方との間に接続された第３のダイオードと、前記対の直流端子の他方と前記対の交流端子の他方との間に接続された第４のダイオードとを有する整流回路と、
前記整流回路の対の直流端子間に接続されたスイッチと、
それぞれの前記対の交流入力導体と前記スイッチとの間の交流ライン又は直流ラインに直列に接続された第１のインダクタと、
前記スイッチに並列に接続されたトランスの１次巻線と第１のコンデンサとの直列回路と、
前記１次巻線に電磁結合された２次巻線と、
前記２次巻線に直列に接続された第２のコンデンサと、
前記２次巻線と前記第２のコンデンサとの直列回路に対して並列に接続された第２のインダクタと第５のダイオードとの直列回路と、
前記第２のインダクタと前記第５のダイオードとの直列回路の一端と前記第１の直流出力端子との間に接続された第６のダイオードと、
前記スイッチを前記３相交流電圧の周波数よりも高い周波数でオン・オフ制御する制御手段と
から成ることを特徴とする３相交流−直流電力変換装置に係わるものである。
【０００７】
なお、請求項２、４及び６に示すように、第３及び第４のダイオ−ドに逆方向並列に第１及び第２のスイッチを接続することができる。なお、第３及び第４のダイオ−ドは、個別素子であってもよいし、第１及び第２のスイッチの寄生即ち内蔵ダイオ−ドであってもよい。
また、請求項３に示すように各相の他方の交流入力導体を３相交流電圧の中間電位を与える共通端子（７０）に接続することができる。
また、請求項５に示すように、第１、第２及び第３の交流入力端子（１ａ、１ｂ、１ｃ）に星形結線された第１、第２及び第３の分圧用コンデンサ（Ｃｒ、Ｃｓ、Ｃｔ）を接続し、これ等の共通接続導体（８０）に各相の他方の交流入力導体を接続することができる。
【０００８】
【発明の効果】
本発明によれば、トランスが３相個別に設けられているにも拘らず、少ない個数のスイッチによって３相交流−直流電力変換装置を構成することができ、小型化、低コスト化を図ることができる。
【０００９】
【発明の実施の形態】
次に、本発明の実施形態に従う３相交流−直流電力変換装置を説明する。
【００１０】
【実施例１】
本発明の実施例１に従う３相交流−直流電力変換装置は、図１に示すように、３相交流電源Ｅに接続される第１、第２及び第３の交流入力端子１ａ、１ｂ、１ｃと、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃと、負荷３を接続するための第１及び第２の直流出力端子３ａ、３ｂと、三相共通の平滑コンデンサＣｏと、制御回路４とを備えている。
【００１１】
３相交流電源Ｅは、例えば周波数５０Ｈｚ、２００Ｖの３相交流電圧を供給するものであり、互いに１２０度の位相差を有する第１、第２及び第３相正弦波交流電圧を供給する第１、第２及び第３相電源Ｅａ、Ｅｂ、Ｅｃでモデル化して示されている。
【００１２】
第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃは、３相の各線間電圧を直流電圧に変換して共通の第１及び第２の直流出力端子３ａ、３ｂに供給するように構成されている。
【００１３】
第１の電力変換回路２ａの第１の対の交流入力導体５ａ、６ａは第１及び第２の交流入力端子１ａ、１ｂに接続され、第１の対の直流出力導体７ａ、８ａは第１及び第２の直流出力端子３ａ、３ｂに接続されている。第２の電力変換回路２ｂの第２の対の交流入力導体５ｂ、６ｂは第２及び第３の交流入力端子１ｂ、１ｃに接続され、第２の対の直流出力導体７ｂ、８ｂは第１及び第２の直流出力端子３ａ、３ｂに接続されている。第３の電力変換回路２ｃの第３の対の交流入力導体５ｃ、６ｃは第３及び第１の交流入力端子１ｃ、１ａに接続され、第３の対の直流出力導体７ｃ、８ｃは第１及び第２の直流出力端子３ａ、３ｂに接続されている。
【００１４】
図１から明らかのように、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃの内部構成は同一であるので、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃにおいて互いに同一の機能を有する回路要素の参照符号が複数の文字で表わされ、この参照符号の最後以外の文字が同一とされ、最後の文字のみが異なる文字ａ、ｂ、ｃとされている。
第１の電力変換回路２ａは、第１、第２、第３及び第４のダイオードＤ１ａ、Ｄ２ａ、Ｄ３ａ、Ｄ４ａから成る整流回路９ａと、第５及び第６のダイオードＤ５ａ、Ｄ６ａと、スイッチＱａと、１次巻線Ｎ１ａ及び２次巻線Ｎ２ａを有する高周波トランスＴａと、第１及び第２のコンデンサＣ１ａ、Ｃ２ａと、第１及び第２のインダクタＬ１ａ、Ｌ２ａとから成る。第２の電力変換回路２ｂは、第１、第２、第３及び第４のダイオードＤ１ｂ、Ｄ２ｂ、Ｄ３ｂ、Ｄ４ｂから成る整流回路９ｂと、第５及び第６のダイオードＤ５ｂ、Ｄ６ｂと、スイッチＱｂと、１次巻線Ｎ１ｂ及び２次巻線Ｎ２ｂを有する高周波トランスＴｂと、第１及び第２のコンデンサＣ１ｂ、Ｃ２ｂと、第１及び第２のインダクタＬ１ｂ、Ｌ２ｂとから成る。第３の電力変換回路２ｃは、第１、第２、第３及び第４のダイオードＤ１ｃ、Ｄ２ｃ、Ｄ３ｃ、Ｄ４ｃから成る整流回路９ｃと、第５及び第６のダイオードＤ５ｃ、Ｄ６ｃと、スイッチＱｃと、１次巻線Ｎ１ｃ及び２次巻線Ｎ２ｃを有する高周波トランスＴｃと、第１及び第２のコンデンサＣ１ｃ、Ｃ２ｃと、第１及び第２のインダクタＬ１ｃ、Ｌ２ｃとから成る。
【００１５】
次に、第１の電力変換回路２ａを詳しく説明し、これと同一構成の第２及び第３の電力変換回路２ｂ、２ｃの詳しい説明は省略する。第１の電力変換回路２ａの整流回路９ａは第１、第２、第３及び第４のダイオードＤ１ａ、Ｄ２ａ、Ｄ３ａ、Ｄ４ａをブリッジ接続した全波整流回路である。この整流回路９ａの一方の交流端子は第１のインダクタＬ１ａ及び一方の交流入力導体５ａを介して第１の交流入力端子１ａに接続され、この他方の交流端子は他方の交流入力導体６ａを介して第２の交流入力端子１ｂに接続されている。従って、第１の電力変換回路２ａの整流回路９ａは３相交流の第１及び第２相間の線間電圧を整流する。なお、リアクトルから成る第１のインダクタＬ１ａを、他方の交流入力導体６ａに接続すること、又は２つの交流入力導体５ａ、５ｂに分けて接続すること、又は整流回路９ａとスイッチＱａとの間に接続することもできる。
【００１６】
ＩＧＢＴ（絶縁ゲートバイポーラトランジスタ）から成るスイッチＱａは整流回路９ａの対の直流端子間に接続されている。このスイッチＱａをＰＷＭ制御するための制御端子（ゲート）は制御回路４の第１の制御信号出力ライン１０ａに接続されている。第２及び第３の電力変換回路２ｂ、２ｃのスイッチＱｂ、Ｑｃの制御端子は制御回路４の第２及び第３の制御信号出力ライン１０ｂ、１０ｃに接続されている。
【００１７】
相互に電磁結合された１次巻線Ｎ１ａと２次巻線Ｎ２ａとから成る高周波トランスＴａは商用周波数（５０Ｈｚ又は６０Ｈｚ）よりも十分に高い周波数（例えば２０〜１００ｋＨｚ）に応答するものから成り、電源Ｅ側と負荷３側とを電気的に絶縁する機能を有する。この高周波トランスＴａの１次巻線Ｎ１ａと第１のコンデンサＣ１ａとの直列回路はスイッチＱａに対して並列に接続され且つ整流回路９ａの対の直流端子間に接続されている。第２のコンデンサＣ２ａは２次巻線Ｎ２ａに直列に接続されている。第１及び第２のコンデンサＣ１ａ、Ｃ２ａはエネルギ蓄積素子として機能する。第２のインダクタＬ２ａと第５のダイオードＤ５ａとの直列回路が、２次巻線Ｎ２ａと第２のコンデンサＣ２ａとの直列回路に対して並列に接続されている。また、２次巻線Ｎ２ａと第２のコンデンサＣ２ａとの直列回路及び第５のダイオードＤ５ａと第２のインダクタＬ２ａとの直列回路は、第６のダイオードＤ６ａを介して第１の対の直流出力導体７ａ、８ａにそれぞれ接続されている。
【００１８】
平滑コンデンサＣｏは第１及び第２の直流出力端子３ａ、３ｂ間に接続され、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃの出力で充電される。
【００１９】
制御回路４は、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃのスイッチＱａ、Ｑｂ、Ｑｃをオン・オフ制御する制御手段であって、前述したように第１、第２及び第３の制御信号ライン１０ａ、１０ｂ、１０ｃによって第１、第２及び第３相のスイッチＱａ、Ｑｂ、Ｑｃの制御端子に接続され、且つライン１１、１２によって第１及び第２の直流出力端子３ａ、３ｂに接続され、且つライン１３、１４、１５によって第１、第２及び第３の交流入力端子１ａ、１ｂ、１ｃに接続され、且つライン１６、１７、１８によって第１、第２及び第３の電流検出器１９、２０、２１に接続されている。第１、第２及び第３の電流検出器１９、２０、２１は第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃの第１のインダクタＬ１ａ，Ｌ１ｂ，Ｌ１ｃを通って流れる電流を検出できる位置に配置されている。
【００２０】
図２は図１の制御回路４の１例を示す。この制御回路４は商用周波数よりも高い繰返し周波数で各相のスイッチＱａ、Ｑｂ、Ｑｃをオン・オフ制御する機能と、各相の第１のインダクタＬ１ａ、Ｌ１ｂ、Ｌ１ｃを流れる電流Ｉａ、Ｉｂ、Ｉｃを正弦波に近似させるための制御機能と、直流出力電圧Ｖｏを基準電圧Ｖｏ１に追従させる制御機能を有する。
【００２１】
図２の出力電圧検出回路２２はライン１１、１２によって図１の第１及び第２の直流出力端子３ａ、３ｂに接続され、第１及び第２の直流出力端子３ａ、３ｂ間の直流出力電圧Ｖｏに比例した出力を発生する。ここでは説明を簡単にするために、出力電圧検出回路２２の入力と出力との両方をＶｏで示し、これを直流出力電圧と呼ぶことにする。
【００２２】
入力電圧検出回路２３は、ライン１３、１４、１５によって図１の第１、第２及び第３の交流入力端子１ａ、１ｂ、１ｃに接続され、正弦波の第１、第２及び第３の線間電圧Ｖｒｓ、Ｖｓｔ、Ｖｔｒをライン２４、２５、２６に送出する。第１の線間電圧Ｖｒｓは第１及び第２の交流入力端子１ａ、１ｂ間の電圧を示し、第２の線間電圧Ｖｓｔは第２及び第３の交流入力端子１ｂ、１ｃ間の電圧を示し、第３の線間電圧Ｖｔｒは第３及び第１の交流入力端子１ｃ、１ａ間の電圧を示す。
【００２３】
電流検出回路２７は、ライン１６、１７、１８によって図１の電流検出器１９、２０、２１に接続され、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃの入力電流Ｉａ、Ｉｂ、Ｉｃの検出信号を出力する。電流検出回路２７の出力はａｂｃで示されている絶対値回路２７ａ、２７ｂ、２７ｃで絶対値に変換される。図２では電流検出信号の絶対値がＩａ´、Ｉｂ´、Ｉｃ´で示されている。
【００２４】
制御回路４は、定電圧制御を実行するために基準電圧発生器２８と電圧変動検出用減算器２９と電流振幅指令演算器３０とを有している。減算器２９は基準電圧発生器２８の基準電圧Ｖｏ１から出力電圧検出回路２２の直流出力電圧Ｖｏを減算する。減算器２９の出力に基づいて電流振幅指令演算器３０は直流出力電圧Ｖｏを一定にするための電流振幅指令値Ｉｏ１を発生する。電流振幅指令演算器３０は、比例積分回路と増幅器とから成る。なお、電流振幅指令値Ｉｏ１を出力電圧制御指令値と呼ぶこともできる。この実施形態では、直流出力電圧を交流側の電流制御によって達成しているので、Ｉｏ１が電流振幅指令値と呼ばれている。
【００２５】
共通の電流振幅指令値Ｉｏ１によって第１、第２及び第３相のスイッチＱａ、Ｑｂ、Ｑｃを制御するために、第１、第２及び第３の乗算器３１、３２、３３が設けられている。第１、第２及び第３の乗算器３１、３２、３３は、ライン２４、２５、２６から供給される正弦波から成る第１、第２及び第３の線間電圧Ｖｒｓ、Ｖｓｔ、Ｖｔｒに電流振幅指令値Ｉｏ１を乗算して正弦波状の第１、第２及び第３の電流指令値Ｉｒｓ、Ｉｓｔ、Ｉｔｒを出力する。この電流指令値Ｉｒｓ、Ｉｓｔ、Ｉｔｒは、直流出力電圧Ｖｏを目標値即ち基準電圧Ｖｏ１にするための目標電流指令値に相当する３相交流信号である。第１、第２及び第３の乗算器３１，３２，３３から得られた第１、第２及び第３の電流指令値Ｉｒｓ、Ｉｓｔ、Ｉｔｒはａｂｓで示されている絶対値回路３１ａ、３１ｂ、３１ｃで絶対値に変換される。
【００２６】
第１、第２及び第３の減算器３４、３５、３６は一方の側の絶対値回路３１ａ、３２ａ、３３ａから得られた第１、第２及び第３の電流指令値Ｉｒｓ、Ｉｓｔ、Ｉｔｒの絶対値から他方の側の絶対値回路２７ａ、２７ｂ、２７ｃから得られた各相の電流検出信号の絶対値Ｉａ´、Ｉｂ´、Ｉｃ´を減算して通流率信号とも呼ぶことができる第１、第２及び第３の通電率指令信号Ｄｒｓ、Ｄｓｔ、Ｄｔｒを求めるものである。
【００２７】
第１、第２及び第３の減算器３４、３５、３６に接続された第１、第２及び第３の絶対値回路３７、３８、３９は第１、第２及び第３の通電率指令値Ｄｒｓ、Ｄｓｔ、Ｄｔｒの絶対値を出力する。ここでは説明を簡略化するために第１、第２及び第３の絶対値回路３７、３８、３９の入力と出力とを同一記号で示し、第１、第２及び第３の絶対値回路３７、３８、３９の出力を第１、第２及び第３の絶対値通電率指令値Ｄｒｓ、Ｄｓｔ、Ｄｔｒと呼ぶことにする。第１、第２及び第３の絶対値通電率指令信号Ｄｒｓ、Ｄｓｔ、Ｄｔｒは図３に示されている。
【００２８】
第１、第２及び第３の絶対値回路３７、３８、３９に接続されたＰＷＭ回路４０は、第１、第２及び第３の絶対値通電率指令信号Ｄｒｓ、Ｄｓｔ、Ｄｔｒと鋸波発生記４１から出力された鋸波電圧Ｖｔとを図３に示すように比較して図４に示す第１、第２及び第３の制御信号Ｖｇａ、Ｖｇｂ、Ｖｇｃを形成する。
【００２９】
鋸波発生器４１は比較波発生器又はキャリア発生器とも呼ぶことができるものであって、第１、第２及び第３の線間電圧Ｖｒｓ、Ｖｓｔ、Ｖｔｒの周波数よりも高い繰り返し周波数（例えば２０〜１００ｋＨｚ）で鋸波電圧Ｖｔを発生する。図３の鋸波線圧Ｖｔは立上りが傾斜し、立下りが垂直の鋸波であるが、逆に立下りが傾斜し、立上りが垂直の鋸波、又は三角波とすることもできる。
【００３０】
ＰＷＭ回路４０に含まれている各相の比較器の出力は絶対値通電率指令信号Ｄｒｓ、Ｄｓｔ、Ｄｔｒが鋸波電圧Ｖｔよりも高い時に高レベル（Ｈ）、低い時に低レベル（Ｌ）となる。従って、第１、第２及び第３の制御信号Ｖｇａ、Ｖｇｂ、Ｖｇｃの低レベルから高レベルへの転換が同時に生じ、第１、第２及び第３相のスイッチＱａ、Ｑｂ、Ｑｃが同時にオンになる。
【００３１】
ＰＷＭ回路４０の出力ライン１０ａ、１０ｂ、１０ｃの第１、第２及び第３の制御信号Ｖｇａ、Ｖｇｂ、Ｖｇｃは、図示が省略されている駆動回路を介して図１の第１、第２及び第３相のスイッチＱａ、Ｑｂ、Ｑｃの制御端子に送られる。第１、第２及び第３相のスイッチＱａ、Ｑｂ、Ｑｃは第１、第２及び第３の制御信号Ｖｇａ、Ｖｇｂ、Ｖｇｃが論理の１（Ｈレベル）の時にオン制御される。
【００３２】
第１、第２及び第３相のスイッチＱａ、Ｑｂ、Ｑｃが図４に示す第１、第２及び第３の制御信号Ｖｇａ、Ｖｇｂ、Ｖｇｃでオン・オフ制御されると、これ等のオン期間に各相の第１のインダクタＬ１ａ、Ｌ１ｂ、Ｌ１ｃ及び第２のインダクタＬ２ａ、Ｌ２ｂ、Ｌ２ｃにエネルギが蓄積され、これ等のオフ期間に平滑コンデンサＣｏ及び負荷３側にエネルギが放出される。
【００３３】
第１の交流入力端子１ａの電位が第２の交流入力端子１ｂの電位よりも高い期間に第１の電力変換回路２ａのスイッチＱａをオン・オフした時の動作を図５（Ａ）（Ｂ）（Ｃ）を参照して説明する。なお、以下の説明で電流経路を回路要素の参照符号のみで示すこともある。また、図５（Ａ）（Ｂ）（Ｃ）において、電流が流れる回路が実線で示され、電流が流れない回路が点線で示されている。
【００３４】
スイッチＱａのオン期間には、図５（Ａ）に示すように、１ａ−Ｌ１ａ−Ｄ１ａ−Ｑａ −Ｄ４ａ−１ｂの経路に電流が流れ、第１のインダクタＬ１ａにエネルギが蓄積される。第１のインダクタＬ１ａに流れる電流は第１及び第２の交流入力端子１ａ、１ｂ間の電圧の振幅に比例するので、正弦波に近似した入力電流を流すことができ、力率が改善される。スイッチＱａのオン期間には、上記の動作の他に第１のコンデンサＣ１ａが放電し、Ｃ１ａ−Ｎ１ａ−Ｑａの経路にも電流が流れる。１次巻線Ｎ１ａに図５（Ａ）において下側から上側に向って電流が流れると、２次巻線Ｎ２ａに第２のコンデンサＣ２ａを充電する向きの電流がＮ２ａ−Ｃ２ａ−Ｌ２ａ−Ｄ５ａの経路で流れ、第２のコンデンサＣ２ａが充電される。図５（Ａ）の状態では第６のダイオードＤ６ａは非導通であり、負荷３には平滑コンデンサＣｏから電力が供給される。
【００３５】
図５（Ａ）の状態においてスイッチＱａがオフに転換すると、まず図５（Ｂ）の経路に電流が流れる。即ち、１ａ−Ｌ１ａ−Ｄ１ａ−Ｎ１ａ−Ｃ１ａ−Ｄ４ａ−１ｂの経路に電流が流れ、第１のコンデンサＣ１ａが充電される。１次巻線Ｎ１ａに上から下に向う方向で電流が流れると、２次巻線Ｎ２ａに下から上に向う方向の電圧が誘起し、第６のダイオードＤ６ａが導通状態に転換し、Ｎ２ａ−Ｄ６ａ−Ｃｏ及び３−Ｃ２ａの経路で電流が流れ、第２のコンデンサＣ２ａの放電が生じる。同時に、第２のインダクタＬ２ａの蓄積エネルギの放出が生じ、Ｌ２ａ−Ｄ５ａ−Ｄ６ａ−Ｃｏ及び３の経路にも電流が流れる。
【００３６】
第２のインダクタＬ２ａの蓄積エネルギの放出が終了すると、図５（Ｃ）に示すように第５のダイオードＤ５ａが非導通となる。図５（Ｃ）において、第５のダイオードＤ５ａと第２のインダクタＬ２ａとを通る電流が零になる他は、図５（Ｂ）と同様な電流が流れる。
【００３７】
第２の交流入力端子１ｂの電位が第１の交流入力端子１ａの電位よりも低い負の半波期間には第２及び第３のダイオードＤ２ａ、Ｄ３ａが導通し、正の半波期間と同様な動作が生じる。また、第２及び第３の電力変換回路２ｂ、２ｃも第１の電力変換回路２ａと同一に構成されているので、第１の電力変換回路２ａと同様に動作する。
【００３８】
直流出力電圧Ｖｏが例えば基準電圧Ｖｏ１よりも高くなると、電圧変動検出用減算器２９の出力が低くなり、電流振幅指令値Ｉｏ１が低下し、この結果としてＰＷＭパルスの幅が狭くなり、第１、第２及び第３相のスイッチＱａ、Ｑｂ、Ｑｃのオン期間に２次側に供給される電力が低下し、直流出力電圧Ｖｏが基準電圧Ｖｏ１に戻される。直流出力電圧Ｖｏが基準電圧Ｖｏ１よりも低くなった時には、上記の高くなった時と逆の動作になる。
【００３９】
第１、第２及び第３の電流指令値Ｉｒｓ、Ｉｓｔ、Ｉｔｒは、第１、第２及び第３の線間電圧Ｖｒｓ、Ｖｓｔ、Ｖｔｒに基づいて作成された正弦波であり、３相交流に基づく周期性を有して変化する。従って、第１、第２及び第３の交流入力端子１ａ、１ｂ、１ｃにおける電流波形が正弦波に近似し、且つ力率が良くなる。
【００４０】
実施例１は次の効果を有する。
（１）この実施例の３相交流−直流電力変換装置は、従来よりも少ない３つのスイッチＱａ、Ｑｂ、Ｑｃをオン・オフ制御することによって各相の高周波トランスＴａ、Ｔｂ、Ｔｃに電力を供給できるので、高周波トランスを含む絶縁型３相交流−直流電力変換装置の小型化及び低コスト化を達成できる。
（２）力率改善及び直流出力電圧の安定化を容易に達成できる。
（３）各相の第１のコンデンサＣ１ａ、Ｃ１ｂ、Ｃ１ｃを各相の１次巻線Ｎ１ａ、Ｎ１ｂ、Ｎ１ｃに直列に接続し、各相の第２のコンデンサＣ２ａ、Ｃ２ｂ、Ｃ２ｃを各相の２次巻線Ｎ２ａ、Ｎ２ｂ、Ｎ２ｃに直列に接続したので、各相の高周波トランスＴａ、Ｔｂ、Ｔｃの励磁インダクタンスに流れる電流の増加を抑えて高周波トランスＴａ、Ｔｂ、Ｔｃの飽和を防止することができる。
【００４１】
【実施例２】
次に、図６に示す実施例２の３相交流−直流電力変換装置を説明する。但し、図６及び後述する図７及び図８において図１と実質的に同一の部分には同一の符号を付してその説明を省略する。図６の３相交流−直流電力変換装置は、図１の第１、第２及び第３の電力変換回路２ａ、２ｂ，２ｃの３つのスイッチＱａ、Ｑｂ、Ｑｃの代りに３個の第１のスイッチＱ１ａ、Ｑ１ｂ、Ｑ１ｃと３個の第２のスイッチＱ２ａ、Ｑ２ｂ、Ｑ２ｃとを設け、この他は図１と実質的に同一に形成したものである。
【００４２】
各相の第１のスイッチＱ１ａ、Ｑ１ｂ、Ｑ１ｃは各相の第３のダイオードＤ３ａ、Ｄ３ｂ、Ｄ３ｃに逆方向並列に接続され、各相の第２のスイッチＱ２ａ、Ｑ２ｂ、Ｑ２ｃは第４のダイオードＤ４ａ、Ｄ４ｂ、Ｄ４ｃに逆方向並列に接続されている。また、各相の第１のスイッチＱ１ａ、Ｑ１ｂ、Ｑ１ｃと第２のスイッチＱ２ａ、Ｑ２ｂ、Ｑ２ｃは互いに直列に接続され、且つ同一の制御信号ライン１０ａ、１０ｂ、１０ｃによって同時にオン制御される。図６では図１との対応関係を明確にするために３個の第３のダイオードＤ３ａ、Ｄ３ｂ、Ｄ３ｃ及び３個の第４のダイオードＤ４ａ、Ｄ４ｂ、Ｄ４ｃが、３個の第１のスイッチＱ１ａ、Ｑ１ｂ、Ｑ１ｃ及び３個の第２のスイッチＱ２ａ、Ｑ２ｂ、Ｑ２ｃと分離して個別部品として示されている。しかし、実際には、３個の第３のダイオードＤ３ａ、Ｄ３ｂ、Ｄ３ｃ及び３個の第４のダイオードＤ４ａ、Ｄ４ｂ、Ｄ４ｃは、それぞれがＩＧＢＴから成る３個の第１のスイッチＱ１ａ、Ｑ１ｂ、Ｑ１ｃ及び３個の第２のスイッチＱ２ａ、Ｑ２ｂ、Ｑ２ｃの寄生ダイオード即ち内蔵ダイオードである。勿論、第３のダイオードＤ３ａ、Ｄ３ｂ、Ｄ３ｃ及び第４のダイオードＤ４ａ、Ｄ４ｂ、Ｄ４ｃを個別ダイオードとすること、又はＩＧＢＴ以外の半導体スイッチの内蔵ダイオードとすることもできる。
【００４３】
図６の第１の電力変換回路２ａにおける第１及びの第２のスイッチＱ１ａ、Ｑ２ａを同時にオン制御すると、１ａ−Ｌ１ａ−Ｄ１ａ−Ｑ１ａ−１ｂの経路に電流が流れると共に、Ｃ１ａ−Ｎ１ａ−Ｑ１ａ−Ｑ２ａの経路に第１のコンデンサＣ１ａの放電電流が流れる。図６の高周波トランスＴａの２次側の動作は図１のそれと同一である。図６において第１及び第２のスイッチＱ１ａ、Ｑ２ａがオフの期間は、図５（Ｂ）及び（Ｃ）と同一の経路に電流が流れる。図６の第２及び第３の電力変換回路２ｂ、２ｃの動作は図６の第１の電力変換回路２ａの動作と同一である。
【００４４】
実施例２によっても実施例１と同一の効果を得ることができる。また、実施例２では各相において２つのスイッチが必要になるが、各相の第３及び第４のダイオードＤ３ａ、Ｄ３ｂ、Ｄ３ｃ、Ｄ４ａ、Ｄ４ｂ、Ｄ４ｃが各相の第１及び第２のスイッチＱ１ａ、Ｑ１ｂ、Ｑ１ｃ、Ｑ２ａ、Ｑ２ｂ、Ｑ２ｃの内蔵ダイオードであるので、３相交流−直流電力変換装置の全体の寸法はさほど大きくならない。また、図６において図５（Ａ）と同様な状態において、１ａ−Ｌ１ａ−Ｄ１ａ−Ｑ１ａ−１ｂの経路で電流が流れ、第４のダイオードＤ４ａに電流が流れない。従って、図６の回路によれば図１の回路で生じた第４のダイオードＤ４ａの電圧降下分が発生しなくなり、損失の低減を図ることができる。
【００４５】
【実施例３】
図７に示す実施例３に従う３相交流−直流電力変換装置は、３相交流電源Ｅと第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃとの間の接続関係を変え、この他は図１と同一に構成したものである。第１、第２及び第３相電源Ｅａ、Ｅｂ、Ｅｃの相互接続点がグランド（共通端子）に接続され、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃの一方の交流入力導体５ａ、５ｂ、５ｃは第１、第２及び第３の交流入力端子１ａ、１ｂ、１ｃに接続され、他方の交流入力導体６ａ、６ｂ、６ｃは中間電位点として機能する共通端子即ちグランド端子７０に接続されている。従って、第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃには第１、第２及び第３相電源Ｅ１、Ｅ２、Ｅ３の電圧がそのまま入力電圧として印加される。
【００４６】
図７のように電源部分の接続を変形しても実施例１と同一の効果を得ることができる。なお、図６の電源回路部分を図７と同様に変形することができる。
【００４７】
【実施例４】
図８の実施例４の３相交流−直流電力変換装置は、同一容量の第１、第２及び第３の分圧用コンデンサＣｒ、Ｃｓ、Ｃｔの一端を第１、第２及び第３の交流入力端子１ａ、１ｂ、１ｃに接続し、それぞれの他端を共通導体８０に接続し、中間電位が得られる共通導体８０に各相の他方の交流入力導体６ａ、６ｂ、６ｃを接続し、この他は図１と同一に形成したものである。図８の回路では星形結線された第１、第２及び第３の分圧用コンデンサＣｒ、Ｃｓ、Ｃｔの電圧が第１、第２及び第３の電力変換回路２ａ、２ｂ、２ｃの入力電圧となる。
【００４８】
図８の実施例４によっても実施例１と同一の効果を奏することができる。なお、図６の回路の電源部分を図８と同一に変形することができる。
【００４９】
【変形例】
本発明は上述の実施例に限定されるものでなく、例えば次の変形が可能なものである。
（１）スイッチＱａ、Ｑｂ、Ｑｃ、Ｑ１ａ、Ｑ２ａ、Ｑ１ｂ、Ｑ２ｂ、Ｑ１ｃ、Ｑ２ｃをトランジスタ、電界効果トランジスタ等の別の半導体スイッチ素子に置き換えることができる。
（２）制御回路４を前記特許文献１及び２等に記載されている別の制御回路に置き換えることができる。
（３）図１、図７及び図８の各相のスイッチＱａ、Ｑｂ、Ｑｃをそれぞれ１個で形成せずに、同時にオン・オフする複数のスイッチの直列回路で形成することができる。
（４）３相分の電圧及び電流を３相個別に検出する代わりに、２相分の電圧及び電流を個別に検出し、残りの１相分を演算で求めることができる。
【図面の簡単な説明】
【図１】本発明の実施例１の３相交流−直流電力変換装置を示す回路図である。
【図２】図１の制御回路の１例を示すブロック図である。
【図３】図２の各部の状態を示す波形図である。
【図４】図２の各部の状態を示す波形図である。
【図５】図１の第１の電力変換回路の動作を説明するための回路図である。
【図６】本発明の実施例２の３相交流−直流電力変換装置を示す回路図である。
【図７】本発明の実施例３の３相交流−直流電力変換装置を示す回路図である。
【図８】本発明の実施例４の３相交流−直流電力変換装置を示す回路図である。
【符号の説明】
１ａ、１ｂ、１ｃ第１、第２及び第３の交流入力端子
２ａ、２ｂ、２ｃ第１、第２及び第３の電力変換回路
３ａ、３ｂ第１及び第２の直流出力端子
４制御回路
５ａ、５ｂ、５ｃ一方の交流入力導体
６ａ、６ｂ、６ｃ他方の交流入力導体
７ａ、７ｂ、７ｃ一方の直流出力導体
８ａ、８ｂ、８ｃ他方の直流出力導体
９ａ、９ｂ、９ｃ整流回路
Ｑａ、Ｑｂ、Ｑｃスイッチ
Ｔａ、Ｔｂ、Ｔｃ高周波トランス
Ｌ１ａ、Ｌ１ｂ、Ｌ１ｃ第１のインダクタ
Ｌ２ａ、Ｌ２ｂ、Ｌ２ｃ第２のインダクタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a three-phase AC-DC power converter that has a switching circuit and a transformer and converts three-phase AC power into DC power.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-233155
[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-354816
When configuring an insulated three-phase AC-DC power converter for use in communication power supplies, battery chargers, etc., an insulation transformer is provided on the commercial frequency (50 Hz or 60 Hz) side, and a rectifier circuit on the secondary side of the transformer If a PWM switching circuit for voltage adjustment is provided, the transformer becomes large. In order to solve this problem, a non-insulated PWM rectifier, that is, an AC-DC converter, is connected to a three-phase AC power source, a DC link capacitor is connected between the output terminals of this converter, and a high frequency isolation is provided at the output stage of the DC link capacitor. A high frequency inverter having a transformer may be connected, and a rectifying and smoothing circuit may be provided at the output stage of the inverter. In this case, since a high frequency transformer is used as the transformer, the transformer can be reduced in size.
However, since an AC-DC converter consisting of 6 switches, a DC link capacitor, an inverter consisting of 4 switches, a transformer, and a rectifying / smoothing circuit are required, the number of parts other than the transformer increases, and the circuit is complicated and costly. Become high.
[0003]
A three-phase AC-DC power converter for solving this problem is disclosed in Patent Document 1 and Patent Document 2. The three-phase AC-DC power converter disclosed herein includes first, second, and third primary windings connected between three-phase AC lines and wound around the same core, It consists of an AC switch connected in series to the primary winding, a secondary winding common to three phases, and a rectifying and smoothing circuit connected to the secondary winding.
[0004]
[Problems to be solved by the invention]
According to the three-phase AC-DC power converter described in Patent Documents 1 and 2, the configuration can be greatly simplified. However, six switching elements are required to form an AC switch for three phases. In addition, since the transformer is configured to be common to the three phases, the transformer is necessarily enlarged. For this reason, there is a demand for a three-phase AC-DC power converter that can be reduced in size and cost even though the transformer is three-phase individual.
[0005]
Therefore, an object of the present invention is to provide a three-phase AC-DC power converter that can satisfy the above-described requirements.
[0006]
[Means for Solving the Problems]
The present invention for solving the above problems and achieving the above object will be described with reference to the drawings. However, reference signs in the claims and in the description of the invention herein are provided to help understanding of the present invention and are not intended to limit the present invention. The present invention is a three-phase AC-DC power converter for converting three-phase AC power into DC power,
First, second and third AC input terminals (1a, 1b, 1c) for supplying a three-phase AC voltage;
First and second DC output terminals (3a, 3b) for supplying a DC voltage to the load (3);
Connected to the first pair of AC input conductors (5a, 6a) connected to the first and second AC input terminals (1a, 1b) and the first and second DC output terminals (3a, 3b). And a first power conversion circuit for converting an AC voltage between the first pair of AC input conductors (5a, 6a) into a DC voltage. (2a) and
Connected to the second pair of AC input conductors (5b, 6b) connected to the second and third AC input terminals (1b, 1c) and to the first and second DC output terminals (3a, 3b). And a second power conversion circuit for converting an AC voltage between the second pair of AC input conductors (5b, 6b) into a DC voltage. (2b),
Connected to the third pair of AC input conductors (5c, 6c) connected to the third and first AC input terminals (1c, 1a) and to the first and second DC output terminals (3a, 3b). And a third power conversion circuit for converting an AC voltage between the third pair of AC input conductors (5c, 6c) into a DC voltage. (2c)
Each of the first, second and third power conversion circuits (2a, 2b, 2c)
A pair of AC terminals connected to each pair of AC input conductors, a pair of DC terminals for rectification output, and one of the pair of AC terminals and one of the pair of DC terminals connected A first diode; a second diode connected between the other of the pair of direct current terminals and one of the pair of alternating current terminals; the other of the pair of alternating current terminals and one of the pair of direct current terminals; A rectifier circuit having a third diode connected between and a fourth diode connected between the other of the pair of DC terminals and the other of the pair of AC terminals;
A switch connected between the DC terminals of the pair of rectifier circuits;
A first inductor connected in series with an AC line or a DC line between each pair of AC input conductors and the switch;
A series circuit of a primary winding of a transformer and a first capacitor connected in parallel to the switch;
A secondary winding electromagnetically coupled to the primary winding;
A second capacitor connected in series to the secondary winding;
A series circuit of a second inductor and a fifth diode connected in parallel to a series circuit of the secondary winding and the second capacitor;
A sixth diode connected between one end of a series circuit of the second inductor and the fifth diode and the first DC output terminal;
Control means for controlling on / off of the switch at a frequency higher than the frequency of the three-phase AC voltage;
The present invention relates to a three-phase AC-DC power converter characterized by comprising:
[0007]
In addition, as shown in claims 2, 4 and 6, the first and second switches can be connected in reverse direction parallel to the third and fourth diodes. The third and fourth diodes may be individual elements, or may be parasitic or built-in diodes of the first and second switches.
Further, as shown in claim 3, the other AC input conductor of each phase can be connected to a common terminal (70) for applying an intermediate potential of the three-phase AC voltage.
Further, as shown in claim 5, the first, second and third voltage dividing capacitors (Cr,) connected in a star shape to the first, second and third AC input terminals (1a, 1b, 1c). Cs, Ct) can be connected, and the other AC input conductor of each phase can be connected to these common connection conductors (80).
[0008]
【The invention's effect】
According to the present invention, a three-phase AC-DC power converter can be configured with a small number of switches even though a transformer is provided for each of the three phases, thereby achieving downsizing and cost reduction. Can do.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, a three-phase AC-DC power converter according to an embodiment of the present invention will be described.
[0010]
[Example 1]
The three-phase AC-DC power converter according to the first embodiment of the present invention includes first, second and third AC input terminals 1a, 1b, 1c connected to a three-phase AC power source E as shown in FIG. The first, second and third power conversion circuits 2a, 2b and 2c, the first and second DC output terminals 3a and 3b for connecting the load 3, and the three-phase common smoothing capacitor Co. The control circuit 4 is provided.
[0011]
The three-phase AC power source E supplies, for example, a three-phase AC voltage having a frequency of 50 Hz and 200 V, and a first phase I supply a first, second, and third-phase sine wave AC voltage having a phase difference of 120 degrees. , Modeled with second and third phase power supplies Ea 1, Eb 2, Ec 2.
[0012]
The first, second, and third power conversion circuits 2a, 2b, and 2c convert the three-phase line voltages into DC voltages and supply them to the common first and second DC output terminals 3a and 3b. It is configured.
[0013]
The first pair of AC input conductors 5a and 6a of the first power conversion circuit 2a are connected to the first and second AC input terminals 1a and 1b, and the first pair of DC output conductors 7a and 8a are the first pair. And the second DC output terminals 3a and 3b. The second pair of AC input conductors 5b and 6b of the second power conversion circuit 2b are connected to the second and third AC input terminals 1b and 1c, and the second pair of DC output conductors 7b and 8b are the first pair. And the second DC output terminals 3a and 3b. The third pair of AC input conductors 5c and 6c of the third power conversion circuit 2c are connected to the third and first AC input terminals 1c and 1a, and the third pair of DC output conductors 7c and 8c are the first pair. And the second DC output terminals 3a and 3b.
[0014]
As is apparent from FIG. 1, the first, second and third power conversion circuits 2a, 2b and 2c have the same internal configuration, so the first, second and third power conversion circuits 2a, 2b, Reference numerals of circuit elements having the same function in 2c are represented by a plurality of characters, characters other than the last character of the reference characters are the same, and only the last character is a different character a, b, c. Yes.
The first power conversion circuit 2a includes a rectifier circuit 9a including first, second, third, and fourth diodes D1a, D2a, D3a, and D4a, fifth and sixth diodes D5a and D6a, and a switch Qa. A high-frequency transformer Ta having a primary winding N1a and a secondary winding N2a, first and second capacitors C1a and C2a, and first and second inductors L1a and L2a. The second power conversion circuit 2b includes a rectifier circuit 9b including first, second, third, and fourth diodes D1b, D2b, D3b, and D4b, fifth and sixth diodes D5b and D6b, and a switch Qb. A high-frequency transformer Tb having a primary winding N1b and a secondary winding N2b, first and second capacitors C1b and C2b, and first and second inductors L1b and L2b. The third power conversion circuit 2c includes a rectifier circuit 9c including first, second, third, and fourth diodes D1c, D2c, D3c, D4c, fifth and sixth diodes D5c, D6c, and a switch Qc. And a high frequency transformer Tc having a primary winding N1c and a secondary winding N2c, first and second capacitors C1c and C2c, and first and second inductors L1c and L2c.
[0015]
Next, the first power conversion circuit 2a will be described in detail, and a detailed description of the second and third power conversion circuits 2b and 2c having the same configuration will be omitted. The rectifier circuit 9a of the first power conversion circuit 2a is a full-wave rectifier circuit in which first, second, third, and fourth diodes D1a, D2a, D3a, and D4a are bridge-connected. One AC terminal of the rectifier circuit 9a is connected to the first AC input terminal 1a via the first inductor L1a and one AC input conductor 5a, and the other AC terminal is connected to the other AC input conductor 6a. Are connected to the second AC input terminal 1b. Accordingly, the rectifier circuit 9a of the first power conversion circuit 2a rectifies the line voltage between the first and second phases of the three-phase alternating current. The first inductor L1a made of a reactor is connected to the other AC input conductor 6a, or divided into two AC input conductors 5a and 5b, or connected between the rectifier circuit 9a and the switch Qa. It can also be connected.
[0016]
A switch Qa composed of an IGBT (insulated gate bipolar transistor) is connected between the pair of DC terminals of the rectifier circuit 9a. A control terminal (gate) for PWM control of the switch Qa is connected to the first control signal output line 10a of the control circuit 4. The control terminals of the switches Qb 1 and Qc 2 of the second and third power conversion circuits 2 b and 2 c are connected to the second and third control signal output lines 10 b and 10 c of the control circuit 4.
[0017]
A high-frequency transformer Ta composed of a primary winding N1a and a secondary winding N2a that are electromagnetically coupled to each other consists of one that responds to a frequency (for example, 20 to 100 kHz) sufficiently higher than a commercial frequency (50 Hz or 60 Hz), It has a function of electrically insulating the power source E side and the load 3 side. A series circuit of the primary winding N1a of the high-frequency transformer Ta and the first capacitor C1a is connected in parallel to the switch Qa and connected between the pair of DC terminals of the rectifier circuit 9a. The second capacitor C2a is connected in series with the secondary winding N2a. The first and second capacitors C1a and C2a function as energy storage elements. A series circuit of the second inductor L2a and the fifth diode D5a is connected in parallel to the series circuit of the secondary winding N2a and the second capacitor C2a. The series circuit of the secondary winding N2a and the second capacitor C2a and the series circuit of the fifth diode D5a and the second inductor L2a are connected to the first pair of DC outputs via the sixth diode D6a. The conductors 7a and 8a are connected respectively.
[0018]
The smoothing capacitor Co is connected between the first and second DC output terminals 3a and 3b, and is charged with the outputs of the first, second and third power conversion circuits 2a, 2b and 2c.
[0019]
The control circuit 4 is a control means for controlling on / off of the switches Qa, Qb, Qc of the first, second and third power conversion circuits 2a, 2b, 2c, and as described above, the first, second, And the third control signal lines 10a, 10b, 10c are connected to the control terminals of the first, second and third phase switches Qa, Qb, Qc, and the first and second DC outputs are provided by the lines 11, 12. Connected to the terminals 3a, 3b, connected to the first, second and third AC input terminals 1a, 1b, 1c by lines 13, 14, 15 and to the first, second by lines 16, 17, 18; And the third current detectors 19, 20, and 21. The first, second, and third current detectors 19, 20, and 21 are currents that flow through the first inductors L1a, L1b, and L1c of the first, second, and third power conversion circuits 2a, 2b, and 2c. It is arrange | positioned in the position which can detect.
[0020]
FIG. 2 shows an example of the control circuit 4 of FIG. The control circuit 4 has a function of turning on / off the switches Qa 1, Qb 2, Qc of each phase at a repetition frequency higher than the commercial frequency, and currents Ia 1 Ib 1, Ib 1, L1c flowing through the first inductors L1a L1b L1c of each phase. A control function for approximating Ic to a sine wave and a control function for causing the DC output voltage Vo to follow the reference voltage Vo1 are provided.
[0021]
The output voltage detection circuit 22 in FIG. 2 is connected to the first and second DC output terminals 3a and 3b in FIG. 1 by lines 11 and 12, and the DC output voltage between the first and second DC output terminals 3a and 3b. An output proportional to Vo is generated. Here, for simplicity of explanation, both the input and output of the output voltage detection circuit 22 are denoted by Vo, and this will be referred to as a DC output voltage.
[0022]
The input voltage detection circuit 23 is connected to the first, second, and third AC input terminals 1a, 1b, and 1c of FIG. 1 by lines 13, 14, and 15, and the first, second, and third sine waves are connected. The line voltages Vrs, Vst, Vtr are sent to the lines 24, 25, 26. The first line voltage Vrs indicates the voltage between the first and second AC input terminals 1a and 1b, and the second line voltage Vst indicates the voltage between the second and third AC input terminals 1b and 1c. The third line voltage Vtr indicates the voltage between the third and first AC input terminals 1c and 1a.
[0023]
The current detection circuit 27 is connected to the current detectors 19, 20, and 21 of FIG. 1 by lines 16, 17, and 18, and the input current Ia of the first, second, and third power conversion circuits 2 a, 2 b, and 2 c, The detection signals Ib and Ic are output. The output of the current detection circuit 27 is converted into an absolute value by absolute value circuits 27a, 27b, and 27c indicated by abc. In FIG. 2, the absolute values of the current detection signals are indicated by Ia ′, Ib ′, and Ic ′.
[0024]
The control circuit 4 includes a reference voltage generator 28, a voltage fluctuation detection subtractor 29, and a current amplitude command calculator 30 in order to execute constant voltage control. The subtractor 29 subtracts the DC output voltage Vo of the output voltage detection circuit 22 from the reference voltage Vo1 of the reference voltage generator 28. Based on the output of the subtractor 29, the current amplitude command calculator 30 generates a current amplitude command value Io1 for making the DC output voltage Vo constant. The current amplitude command calculator 30 includes a proportional integration circuit and an amplifier. The current amplitude command value Io1 can also be called an output voltage control command value. In this embodiment, since the DC output voltage is achieved by current control on the AC side, Io1 is called a current amplitude command value.
[0025]
First, second, and third multipliers 31, 32, and 33 are provided to control the first, second, and third phase switches Qa, Qb, and Qc by a common current amplitude command value Io1. Yes. The first, second and third multipliers 31, 32 and 33 are connected to first, second and third line voltages Vrs, Vst and Vtr consisting of sine waves supplied from lines 24, 25 and 26. The current amplitude command value Io1 is multiplied to output sinusoidal first, second and third current command values Irs, Ist, Itr. The current command values Irs, Ist, Itr are three-phase AC signals corresponding to a target current command value for setting the DC output voltage Vo to a target value, that is, a reference voltage Vo1. The first, second and third current command values Irs, Ist and Itr obtained from the first, second and third multipliers 31, 32 and 33 are absolute value circuits 31a and 31b indicated by abs. , 31c are converted into absolute values.
[0026]
The first, second and third subtracters 34, 35 and 36 are first, second and third current command values Irs, Ist and Itr obtained from the absolute value circuits 31a, 32a and 33a on one side. The absolute values Ia ′, Ib ′, Ic ′ of the current detection signals of the respective phases obtained from the absolute value circuits 27a, 27b, 27c on the other side can be subtracted from the absolute values of the current values and can also be referred to as continuity signals. The first, second, and third energization rate command signals Drs, Dst, and Dtr are obtained.
[0027]
The first, second, and third absolute value circuits 37, 38, and 39 connected to the first, second, and third subtracters 34, 35, and 36 are first, second, and third energization rate commands. The absolute values of the values Drs, Dst, and Dtr are output. Here, in order to simplify the description, the input and output of the first, second and third absolute value circuits 37, 38 and 39 are indicated by the same symbol, and the first, second and third absolute value circuits 37 are shown. , 38 and 39 are referred to as first, second and third absolute value energization rate command values Drs, Dst and Dtr. The first, second and third absolute value energization ratio command signals Drs, Dst, Dtr are shown in FIG.
[0028]
The PWM circuit 40 connected to the first, second, and third absolute value circuits 37, 38, 39 generates sawtooth waves with the first, second, and third absolute value energization rate command signals Drs, Dst, Dtr. The first to second control signals Vga, Vgb, and Vgc shown in FIG. 4 are formed by comparing the sawtooth voltage Vt output from the above 41 with the sawtooth voltage Vt as shown in FIG.
[0029]
The sawtooth wave generator 41 can also be called a comparison wave generator or a carrier generator, and has a repetition frequency higher than the frequency of the first, second and third line voltages Vrs, Vst, Vtr (for example, The sawtooth voltage Vt is generated at 20 to 100 kHz. The sawtooth linear pressure Vt in FIG. 3 is a sawtooth wave whose rising edge is inclined and whose falling edge is vertical, but conversely, it can be a sawtooth wave or a triangular wave whose rising edge is inclined and whose rising edge is vertical.
[0030]
The output of each phase comparator included in the PWM circuit 40 is high level (H) when the absolute value energization rate command signals Drs, Dst, Dtr are higher than the sawtooth voltage Vt, and low level (L) when low. Become. Accordingly, the first, second and third control signals Vga, Vgb and Vgc are simultaneously switched from a low level to a high level, and the first, second and third phase switches Qa, Qb and Qc are simultaneously turned on. become.
[0031]
The first, second and third control signals Vga, Vgb and Vgc of the output lines 10a, 10b and 10c of the PWM circuit 40 are supplied to the first, second and third control signals in FIG. It is sent to the control terminals of the third phase switches Qa, Qb, Qc. The first, second, and third phase switches Qa, Qb, Qc are turned on when the first, second, and third control signals Vga, Vgb, Vgc are logic 1 (H level).
[0032]
When the first, second, and third phase switches Qa, Qb, Qc are controlled to be turned on / off by the first, second, and third control signals Vga, Vgb, Vgc shown in FIG. Energy is accumulated in the first inductors L1a, L1b, L1c and the second inductors L2a, L2b, L2c of each phase during the period, and energy is released to the smoothing capacitor Co 2 and the load 3 side during these off periods.
[0033]
The operation when the switch Qa of the first power conversion circuit 2a is turned on / off in a period in which the potential of the first AC input terminal 1a is higher than the potential of the second AC input terminal 1b is shown in FIGS. ) (C) will be described. In the following description, the current path may be indicated only by reference numerals of circuit elements. 5A, 5B, and 5C, a circuit through which a current flows is shown by a solid line, and a circuit through which no current flows is shown by a dotted line.
[0034]
During the ON period of the switch Qa, as shown in FIG. 5A, a current flows through the path 1a-L1a-D1a-Qa-D4a-1b, and energy is stored in the first inductor L1a. Since the current flowing through the first inductor L1a is proportional to the amplitude of the voltage between the first and second AC input terminals 1a and 1b, an input current approximating a sine wave can be passed and the power factor is improved. . During the ON period of the switch Qa, in addition to the above operation, the first capacitor C1a is discharged, and a current also flows through the path C1a-N1a-Qa. When a current flows from the lower side to the upper side in FIG. 5A in the primary winding N1a, the current in the direction to charge the second capacitor C2a in the secondary winding N2a is N2a-C2a-L2a-D5a. The second capacitor C2a is charged through the path. In the state of FIG. 5A, the sixth diode D6a is non-conductive, and power is supplied to the load 3 from the smoothing capacitor Co 2.
[0035]
When the switch Qa is turned off in the state of FIG. 5A, first, a current flows through the path of FIG. That is, a current flows through a path of 1a-L1a-D1a-N1a-C1a-D4a-1b, and the first capacitor C1a is charged. When a current flows through the primary winding N1a in the direction from the top to the bottom, a voltage in the direction from the bottom to the top is induced in the secondary winding N2a, and the sixth diode D6a changes to the conductive state, and N2a− Current flows through the path of D6a-Co and 3-C2a, and the second capacitor C2a is discharged. At the same time, the stored energy of the second inductor L2a is released, and a current also flows through the paths L2a-D5a-D6a-Co 3.
[0036]
When the discharge of the stored energy of the second inductor L2a is completed, the fifth diode D5a is turned off as shown in FIG. In FIG. 5C, the same current as in FIG. 5B flows except that the current passing through the fifth diode D5a and the second inductor L2a becomes zero.
[0037]
The second and third diodes D2a and D3a conduct in the negative half-wave period in which the potential of the second AC input terminal 1b is lower than the potential of the first AC input terminal 1a, and is the same as in the positive half-wave period. Operation occurs. Further, since the second and third power conversion circuits 2b and 2c are configured in the same manner as the first power conversion circuit 2a, they operate in the same manner as the first power conversion circuit 2a.
[0038]
When the DC output voltage Vo becomes higher than the reference voltage Vo1, for example, the output of the voltage fluctuation detection subtractor 29 decreases, the current amplitude command value Io1 decreases, and as a result, the width of the PWM pulse becomes narrower. The power supplied to the secondary side during the ON period of the second and third phase switches Qa 1, Qb 2, and Qc decreases, and the DC output voltage Vo 1 is returned to the reference voltage Vo 1. When the DC output voltage Vo is lower than the reference voltage Vo1, the operation is the reverse of the above-described increase.
[0039]
The first, second, and third current command values Irs, Ist, Itr are sine waves created based on the first, second, and third line voltages Vrs, Vst, Vtr, and are three-phase alternating current. It changes with periodicity based on. Therefore, the current waveforms at the first, second, and third AC input terminals 1a, 1b, and 1c approximate a sine wave, and the power factor is improved.
[0040]
Example 1 has the following effects.
(1) The three-phase AC-DC power converter of this embodiment supplies power to the high-frequency transformers Ta 1, Tb 2, Tc 3 of each phase by controlling on / off three switches Qa 1, Qb 2, Qc that are less than the conventional one. Since it can be supplied, it is possible to reduce the size and cost of an insulated three-phase AC-DC power converter including a high-frequency transformer.
(2) Power factor improvement and DC output voltage stabilization can be easily achieved.
(3) The first capacitors C1a, C1b, C1c of each phase are connected in series to the primary windings N1a, N1b, N1c of each phase, and the second capacitors C2a, C2b, C2c of each phase are connected to each phase. Since the secondary windings N2a, N2b, and N2c are connected in series, an increase in current flowing through the excitation inductance of each phase of the high-frequency transformers Ta, Tb, and Tc is suppressed to prevent saturation of the high-frequency transformers Ta, Tb, and Tc. Can do.
[0041]
[Example 2]
Next, the three-phase AC-DC power converter of Example 2 shown in FIG. 6 will be described. However, in FIG. 6 and FIGS. 7 and 8 to be described later, substantially the same parts as those in FIG. The three-phase AC-DC power converter shown in FIG. 6 has three first switches instead of the three switches Qa 1, Qb 2 and Qc of the first, second and third power converters 2a, 2b and 2c shown in FIG. The switches Q1a, Q1b, Q1c and three second switches Q2a, Q2b, Q2c are provided, and the others are formed substantially the same as in FIG.
[0042]
The first switches Q1a, Q1b, Q1c for each phase are connected in reverse parallel to the third diodes D3a, D3b, D3c for each phase, and the second switches Q2a, Q2b, Q2c for each phase are fourth diodes. D4a, D4b, and D4c are connected in reverse parallel. The first switches Q1a, Q1b, Q1c and the second switches Q2a, Q2b, Q2c of each phase are connected in series with each other, and are simultaneously turned on by the same control signal lines 10a, 10b, 10c. In FIG. 6, in order to clarify the correspondence with FIG. 1, three third diodes D3a, D3b, D3c and three fourth diodes D4a, D4b, D4c are three first switches Q1a. , Q1b, Q1c and three second switches Q2a, Q2b, Q2c are shown as separate components. However, in practice, the three third diodes D3a, D3b, D3c and the three fourth diodes D4a, D4b, D4c are composed of three first switches Q1a, Q1b, Q1c each made of an IGBT. And parasitic diodes of three second switches Q2a, Q2b, and Q2c, that is, built-in diodes. Of course, the third diodes D3a, D3b, D3c and the fourth diodes D4a, D4b, D4c may be individual diodes or may be built-in diodes of a semiconductor switch other than the IGBT.
[0043]
When the first and second switches Q1a and Q2a in the first power conversion circuit 2a of FIG. 6 are simultaneously turned on, a current flows through the path 1a-L1a-D1a-Q1a-1b and C1a-N1a-Q1a The discharge current of the first capacitor C1a flows through the path of -Q2a. The operation on the secondary side of the high frequency transformer Ta in FIG. 6 is the same as that in FIG. In FIG. 6, during the period when the first and second switches Q1a and Q2a are off, a current flows through the same path as in FIGS. The operations of the second and third power conversion circuits 2b and 2c in FIG. 6 are the same as the operation of the first power conversion circuit 2a in FIG.
[0044]
According to the second embodiment, the same effect as that of the first embodiment can be obtained. In the second embodiment, two switches are required for each phase. The third and fourth diodes D3a, D3b, D3c, D4a, D4b, and D4c for each phase are the first and second switches for each phase. Since it is a built-in diode of Q1a, Q1b, Q1c, Q2a, Q2b, and Q2c, the overall size of the three-phase AC-DC power converter is not so large. In FIG. 6, in the same state as in FIG. 5A, current flows through the path of 1a-L1a-D1a-Q1a-1b, and no current flows through the fourth diode D4a. Therefore, according to the circuit of FIG. 6, the voltage drop of the fourth diode D4a generated in the circuit of FIG. 1 does not occur, and the loss can be reduced.
[0045]
[Example 3]
The three-phase AC-DC power converter according to Example 3 shown in FIG. 7 changes the connection relationship between the three-phase AC power supply E and the first, second, and third power converter circuits 2a, 2b, 2c, Others are the same as those shown in FIG. The mutual connection point of the first, second and third phase power supplies Ea 1, Eb 2 and Ec is connected to the ground (common terminal), and one AC of the first, second and third power conversion circuits 2a, 2b and 2c The input conductors 5a, 5b, and 5c are connected to the first, second, and third AC input terminals 1a, 1b, and 1c, and the other AC input conductors 6a, 6b, and 6c are common terminals or grounds that function as intermediate potential points. The terminal 70 is connected. Therefore, the voltages of the first, second and third phase power supplies E1, E2 and E3 are applied as they are as input voltages to the first, second and third power conversion circuits 2a, 2b and 2c.
[0046]
Even if the connection of the power supply portion is modified as shown in FIG. 7, the same effect as in the first embodiment can be obtained. 6 can be modified in the same manner as in FIG.
[0047]
[Example 4]
In the three-phase AC-DC power converter of Example 4 in FIG. 8, one end of the first, second and third voltage dividing capacitors Cr 1, Cs 2 and Ct 3 having the same capacity is connected to the first, second and third ACs. The input terminals 1a, 1b, and 1c are connected to each other, the other ends thereof are connected to the common conductor 80, and the other AC input conductors 6a, 6b, and 6c of each phase are connected to the common conductor 80 from which an intermediate potential is obtained. Others are the same as in FIG. In the circuit of FIG. 8, the voltages of the first, second and third voltage dividing capacitors Cr 1, Cs 2 and Ct 2 connected in a star shape are the input voltages of the first, second and third power conversion circuits 2a, 2b and 2c. It becomes.
[0048]
The same effect as that of the first embodiment can be obtained by the fourth embodiment of FIG. 6 can be modified in the same manner as in FIG.
[0049]
[Modification]
The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.
(1) The switches Qa, Qb, Qc, Q1a, Q2a, Q1b, Q2b, Q1c, and Q2c can be replaced with another semiconductor switch element such as a transistor or a field effect transistor.
(2) The control circuit 4 can be replaced with another control circuit described in Patent Documents 1 and 2 and the like.
(3) Instead of forming each of the switches Qa 1, Qb 2, and Qc of each phase of FIGS. 1, 7 and 8, it can be formed by a series circuit of a plurality of switches that are simultaneously turned on / off.
(4) Instead of detecting the voltage and current for three phases individually for three phases, the voltage and current for two phases can be detected individually and the remaining one phase can be obtained by calculation.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a three-phase AC-DC power converter according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an example of the control circuit of FIG.
FIG. 3 is a waveform diagram showing the state of each part in FIG. 2;
4 is a waveform diagram showing the state of each part in FIG. 2. FIG.
FIG. 5 is a circuit diagram for explaining the operation of the first power conversion circuit of FIG. 1;
FIG. 6 is a circuit diagram showing a three-phase AC-DC power converter according to Embodiment 2 of the present invention.
FIG. 7 is a circuit diagram showing a three-phase AC-DC power converter according to Embodiment 3 of the present invention.
FIG. 8 is a circuit diagram showing a three-phase AC-DC power converter of Example 4 of the present invention.
[Explanation of symbols]
1a, 1b, 1c first, second and third AC input terminals
2a, 2b, 2c first, second and third power conversion circuits
3a, 3b first and second DC output terminals
4 Control circuit
5a, 5b, 5c One AC input conductor
6a, 6b, 6c The other AC input conductor
7a, 7b, 7c One DC output conductor
8a, 8b, 8c The other DC output conductor
9a, 9b, 9c Rectifier circuit
Qa, Qb, Qc switch
Ta, Tb, Tc high frequency transformer
L1a, L1b, L1c First inductor
L2a, L2b, L2c Second inductor

Claims

A three-phase AC-DC power converter for converting three-phase AC power to DC power,
First, second and third AC input terminals (1a, 1b, 1c) for supplying a three-phase AC voltage;
First and second DC output terminals (3a, 3b) for supplying a DC voltage to the load (3);
Connected to the first pair of AC input conductors (5a, 6a) connected to the first and second AC input terminals (1a, 1b) and the first and second DC output terminals (3a, 3b). And a first power conversion circuit for converting an AC voltage between the first pair of AC input conductors (5a, 6a) into a DC voltage. (2a) and
Connected to the second pair of AC input conductors (5b, 6b) connected to the second and third AC input terminals (1b, 1c) and to the first and second DC output terminals (3a, 3b). And a second power conversion circuit for converting an AC voltage between the second pair of AC input conductors (5b, 6b) into a DC voltage. (2b),
Connected to the third pair of AC input conductors (5c, 6c) connected to the third and first AC input terminals (1c, 1a) and to the first and second DC output terminals (3a, 3b). And a third power conversion circuit for converting an AC voltage between the third pair of AC input conductors (5c, 6c) into a DC voltage. (2c)
Each of the first, second and third power conversion circuits (2a, 2b, 2c)
A pair of AC terminals connected to each pair of AC input conductors, a pair of DC terminals for rectification output, and one of the pair of AC terminals and one of the pair of DC terminals connected A first diode; a second diode connected between the other of the pair of direct current terminals and one of the pair of alternating current terminals; the other of the pair of alternating current terminals and one of the pair of direct current terminals; A rectifier circuit having a third diode connected between and a fourth diode connected between the other of the pair of DC terminals and the other of the pair of AC terminals;
A switch connected between the DC terminals of the pair of rectifier circuits;
A first inductor connected in series with an AC line or a DC line between each pair of AC input conductors and the switch;
A series circuit of a primary winding of a transformer and a first capacitor connected in parallel to the switch;
A secondary winding electromagnetically coupled to the primary winding;
A second capacitor connected in series to the secondary winding;
A series circuit of a second inductor and a fifth diode connected in parallel to a series circuit of the secondary winding and the second capacitor;
A sixth diode connected between one end of a series circuit of the second inductor and the fifth diode and the first DC output terminal;
3. A three-phase AC-DC power converter characterized by comprising control means for controlling on / off of the switch at a frequency higher than the frequency of the three-phase AC voltage.

A three-phase AC-DC power converter for converting three-phase AC power to DC power,
First, second and third AC input terminals (1a, 1b, 1c) for supplying a three-phase AC voltage;
First and second DC output terminals (3a, 3b) for supplying a DC voltage to the load (3);
Connected to the first pair of AC input conductors (5a, 6a) connected to the first and second AC input terminals (1a, 1b) and the first and second DC output terminals (3a, 3b). And a first power conversion circuit for converting an AC voltage between the first pair of AC input conductors (5a, 6a) into a DC voltage. (2a) and
Connected to the second pair of AC input conductors (5b, 6b) connected to the second and third AC input terminals (1b, 1c) and to the first and second DC output terminals (3a, 3b). And a second power conversion circuit for converting an AC voltage between the second pair of AC input conductors (5b, 6b) into a DC voltage. (2b),
Connected to the third pair of AC input conductors (5c, 6c) connected to the third and first AC input terminals (1c, 1a) and to the first and second DC output terminals (3a, 3b). And a third power conversion circuit for converting an AC voltage between the third pair of AC input conductors (5c, 6c) into a DC voltage. (2c)
Each of the first, second and third power conversion circuits (2a, 2b, 2c) includes a pair of AC terminals connected to the pair of AC input conductors and a pair of DC terminals for rectification output. And a first diode connected between one of the pair of AC terminals and one of the pair of DC terminals, and a connection between the other of the pair of DC terminals and one of the pair of AC terminals A second diode connected between the other of the pair of alternating current terminals and one of the pair of direct current terminals, or a parasitic third diode in the first switch described later, and A rectifier circuit having a fourth diode that is parasitic between the individual second switch and the second switch, which is connected between the other of the DC terminals and the other of the pair of AC terminals;
A first switch connected in reverse parallel to the third diode;
A second switch connected in reverse parallel to the fourth diode and connected in series to the first switch;
A first inductor connected in series to an AC line or a DC line between each pair of AC input conductors and the series circuit of the first and second switches;
A series circuit of a primary winding of a transformer and a first capacitor connected in parallel to the series circuit of the first and second switches;
A secondary winding electromagnetically coupled to the primary winding;
A second capacitor connected in series to the secondary winding;
A series circuit of a second inductor and a fifth diode connected in parallel to a series circuit of the secondary winding and the second capacitor;
A sixth diode connected between one end of a series circuit of the second inductor and the fifth diode and the first DC output terminal;
3. A three-phase AC-DC power converter, comprising: control means for simultaneously controlling on / off of the first and second switches at a frequency higher than the frequency of the three-phase AC voltage.

A three-phase AC-DC power converter for converting three-phase AC power to DC power,
First, second and third AC input terminals (1a, 1b, 1c) for supplying a three-phase AC voltage;
A common terminal (70) for applying an intermediate potential of the three-phase AC voltage;
First and second DC output terminals (3a, 3b) for supplying a DC voltage to the load (3);
A first pair of AC input conductors (5a, 6a) connected to the first AC input terminal (1a) and the common terminal (70), and the first and second DC output terminals (3a, 3b). And a first pair of direct current output conductors (7a, 8a) connected to the first pair of alternating current voltages between the first pair of alternating current input conductors (5a, 6a). A power conversion circuit (2a);
A second pair of AC input conductors (5b, 6b) connected to the second AC input terminal (1b) and the common terminal (70), and the first and second DC output terminals (3a, 3b). And a second pair of DC output conductors (7b, 8b) connected to the second pair of AC input conductors (5b, 6b) for converting an AC voltage into a DC voltage. A power conversion circuit (2b);
A third pair of AC input conductors (5c, 6c) connected to the third AC input terminal (1c) and the common terminal (70), and the first and second DC output terminals (3a, 3b). And a third pair of DC output conductors (7c, 8c) connected to the third pair of AC input conductors (5c, 6c) for converting an AC voltage into a DC voltage. A power conversion circuit (2c),
Each of the first, second and third power conversion circuits (2a, 2b, 2c) includes a pair of AC terminals connected to the pair of AC input conductors and a pair of DC terminals for rectification output. And a first diode connected between one of the pair of AC terminals and one of the pair of DC terminals, and a connection between the other of the pair of DC terminals and one of the pair of AC terminals A second diode connected between the other of the pair of alternating current terminals and one of the pair of direct current terminals, the other of the pair of direct current terminals and the pair of alternating current terminals. A rectifier circuit having a fourth diode connected to the other;
A switch connected between the DC terminals of the pair of rectifier circuits;
A first inductor connected in series with an AC line or a DC line between each pair of AC input conductors and the switch;
A series circuit of a primary winding of a transformer and a first capacitor connected in parallel to the switch;
A secondary winding electromagnetically coupled to the primary winding;
A second capacitor connected in series to the secondary winding;
A series circuit of a second inductor and a fifth diode connected in parallel to a series circuit of the secondary winding and the second capacitor;
A sixth diode connected between one end of a series circuit of the second inductor and the fifth diode and the first DC output terminal;
3. A three-phase AC-DC power converter characterized by comprising control means for controlling on / off of the switch at a frequency higher than the frequency of the three-phase AC voltage.

A three-phase AC-DC power converter for converting three-phase AC power to DC power,
First, second and third AC input terminals (1a, 1b, 1c) for supplying a three-phase AC voltage;
A common terminal (70) for applying an intermediate potential of the three-phase AC voltage;
First and second DC output terminals (3a, 3b) for supplying a DC voltage to the load (3);
A first pair of AC input conductors (5a, 6a) connected to the first AC input terminal (1a) and the common terminal (70), and the first and second DC output terminals (3a, 3b). And a first pair of direct current output conductors (7a, 8a) connected to the first pair of alternating current voltages between the first pair of alternating current input conductors (5a, 6a). A power conversion circuit (2a);
A second pair of AC input conductors (5b, 6b) connected to the second AC input terminal (1b) and the common terminal (70), and the first and second DC output terminals (3a, 3b). And a second pair of DC output conductors (7b, 8b) connected to the second pair of AC input conductors (5b, 6b) for converting an AC voltage into a DC voltage. A power conversion circuit (2b);
A third pair of AC input conductors (5c, 6c) connected to the third AC input terminal (1c) and the common terminal (70), and the first and second DC output terminals (3a, 3b). And a third pair of DC output conductors (7c, 8c) connected to the third pair of AC input conductors (5c, 6c) for converting an AC voltage into a DC voltage. A power conversion circuit (2c),
Each of the first, second and third power conversion circuits (2a, 2b, 2c) includes a pair of AC terminals connected to the pair of AC input conductors and a pair of DC terminals for rectification output. And a first diode connected between one of the pair of AC terminals and one of the pair of DC terminals, and a connection between the other of the pair of DC terminals and one of the pair of AC terminals A second diode connected between the other of the pair of alternating current terminals and one of the pair of direct current terminals, or a parasitic third diode in the first switch described later, and A rectifier circuit having a fourth diode that is parasitic between the individual second switch and the second switch, which is connected between the other of the DC terminals and the other of the pair of AC terminals;
A first switch connected in reverse parallel to the third diode;
A second switch connected in reverse parallel to the fourth diode and connected in series to the first switch;
A first inductor connected in series to an AC line or a DC line between each pair of AC input conductors and the series circuit of the first and second switches;
A series circuit of a primary winding of a transformer and a first capacitor connected in parallel to the series circuit of the first and second switches;
A secondary winding electromagnetically coupled to the primary winding;
A second capacitor connected in series to the secondary winding;
A series circuit of a second inductor and a fifth diode connected in parallel to a series circuit of the secondary winding and the second capacitor;
A sixth diode connected between one end of a series circuit of the second inductor and the fifth diode and the first DC output terminal;
3. A three-phase AC-DC power converter, comprising: control means for simultaneously controlling on / off of the first and second switches at a frequency higher than the frequency of the three-phase AC voltage.

A three-phase AC-DC power converter for converting three-phase AC power to DC power,
First, second and third AC input terminals (1a, 1b, 1c) for supplying a three-phase AC voltage;
First, second and third voltage dividing capacitors (Cr, Cs, Ct) connected in a star shape and connected to the first, second and third AC input terminals (1a, 1b, 1c);
First and second DC output terminals (3a, 3b) for supplying a DC voltage to the load (3);
A first pair of AC inputs connected to the first AC input terminal (1a) and a common connection conductor (80) of the first, second and third voltage dividing capacitors (Cr, Cs, Ct). A first pair of DC output conductors (7a, 8a) connected to the conductors (5a, 6a) and the first and second DC output terminals (3a, 3b); A first power conversion circuit (2a) for converting an AC voltage between the AC input conductors (5a, 6a) into a DC voltage;
A second pair of AC input conductors (5b, 6b) connected to the second AC input terminal (1b) and the common connection conductor (80), and the first and second DC output terminals (3a, A second pair of DC output conductors (7b, 8b) connected to 3b) to convert the AC voltage between the second pair of AC input conductors (5b, 6b) into a DC voltage. Power conversion circuit (2b) of
A third pair of AC input conductors (5c, 6c) connected to the third AC input terminal (1c) and the common connection conductor (80), and the first and second DC output terminals (3a, A third pair of DC output conductors (7c, 8c) connected to 3b) for converting an AC voltage between the third pair of AC input conductors (5c, 6c) into a DC voltage. Power conversion circuit (2c),
Each of the first, second and third power conversion circuits (2a, 2b, 2c) includes a pair of AC terminals connected to the pair of AC input conductors and a pair of DC terminals for rectification output. And a first diode connected between one of the pair of AC terminals and one of the pair of DC terminals, and a connection between the other of the pair of DC terminals and one of the pair of AC terminals A second diode connected between the other of the pair of alternating current terminals and one of the pair of direct current terminals, the other of the pair of direct current terminals and the pair of alternating current terminals. A rectifier circuit having a fourth diode connected to the other;
A switch connected between the DC terminals of the pair of rectifier circuits;
A first inductor connected in series with an AC line or a DC line between each pair of AC input conductors and the switch;
A series circuit of a primary winding of a transformer and a first capacitor connected in parallel to the switch;
A secondary winding electromagnetically coupled to the primary winding;
A second capacitor connected in series to the secondary winding;
A series circuit of a second inductor and a fifth diode connected in parallel to a series circuit of the secondary winding and the second capacitor;
A sixth diode connected between one end of a series circuit of the second inductor and the fifth diode and the first DC output terminal;
3. A three-phase AC-DC power converter characterized by comprising control means for controlling on / off of the switch at a frequency higher than the frequency of the three-phase AC voltage.

A three-phase AC-DC power converter for converting three-phase AC power to DC power,
First, second and third AC input terminals (1a, 1b, 1c) for supplying a three-phase AC voltage;
First, second and third voltage dividing capacitors (Cr, Cs, Ct) connected in a star shape and connected to the first, second and third AC input terminals (1a, 1b, 1c);
First and second DC output terminals (3a, 3b) for supplying a DC voltage to the load (3);
A first pair of AC inputs connected to the first AC input terminal (1a) and a common connection conductor (80) of the first, second and third voltage dividing capacitors (Cr, Cs, Ct). A first pair of DC output conductors (7a, 8a) connected to the conductors (5a, 6a) and the first and second DC output terminals (3a, 3b); A first power conversion circuit (2a) for converting an AC voltage between the AC input conductors (5a, 6a) into a DC voltage;
A second pair of AC input conductors (5b, 6b) connected to the second AC input terminal (1b) and the common connection conductor (80), and the first and second DC output terminals (3a, A second pair of DC output conductors (7b, 8b) connected to 3b) to convert the AC voltage between the second pair of AC input conductors (5b, 6b) into a DC voltage. Power conversion circuit (2b) of
A third pair of AC input conductors (5c, 6c) connected to the third AC input terminal (1c) and the common connection conductor (80), and the first and second DC output terminals (3a, A third pair of DC output conductors (7c, 8c) connected to 3b) for converting an AC voltage between the third pair of AC input conductors (5c, 6c) into a DC voltage. Power conversion circuit (2c),
Each of the first, second and third power conversion circuits (2a, 2b, 2c) includes a pair of AC terminals connected to the pair of AC input conductors and a pair of DC terminals for rectification output. And a first diode connected between one of the pair of AC terminals and one of the pair of DC terminals, and a connection between the other of the pair of DC terminals and one of the pair of AC terminals A second diode connected between the other of the pair of alternating current terminals and one of the pair of direct current terminals, or a parasitic third diode in the first switch described later, and A rectifier circuit having a fourth diode that is parasitic between the individual second switch and the second switch, which is connected between the other of the DC terminals and the other of the pair of AC terminals;
A first switch connected in reverse parallel to the third diode;
A second switch connected in reverse parallel to the fourth diode and connected in series to the first switch;
A first inductor connected in series to an AC line or a DC line between each pair of AC input conductors and the series circuit of the first and second switches;
A series circuit of a primary winding of a transformer and a first capacitor connected in parallel to the series circuit of the first and second switches;
A secondary winding electromagnetically coupled to the primary winding;
A second capacitor connected in series to the secondary winding;
A series circuit of a second inductor and a fifth diode connected in parallel to a series circuit of the secondary winding and the second capacitor;
A sixth diode connected between one end of a series circuit of the second inductor and the fifth diode and the first DC output terminal;
3. A three-phase AC-DC power converter, comprising: control means for simultaneously controlling on / off of the first and second switches at a frequency higher than the frequency of the three-phase AC voltage.