JP2004312902A

JP2004312902A - Three-level power converter

Info

Publication number: JP2004312902A
Application number: JP2003104453A
Authority: JP
Inventors: Makoto Kuraki; 誠椋木
Original assignee: Toshiba Mitsubishi Electric Industrial Systems Corp
Current assignee: Toshiba Mitsubishi Electric Industrial Systems Corp
Priority date: 2003-04-08
Filing date: 2003-04-08
Publication date: 2004-11-04
Anticipated expiration: 2023-04-08
Also published as: JP4314050B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-level power converter hardly causing the problem that an overvoltage destroys a flywheel diode by transiently applying a P-N DC voltage (2E(V)) to the flywheel diode of an intermediate potential C side self-extinguishing semiconductor device in blocking a gate. <P>SOLUTION: In the three-level power converter in which the self-extinguishing semiconductor devices 2a to 2h which include the flywheel diode as the power conversion element are used, junction capacitance of the flywheel diodes 3b, 3c, 3f, 3g undergoing a voltage which is higher than the intermediate potential makes equivalently larger than the junction capacitance of the other flywheel diodes 3a, 3d, 3e, 3h in blocking the gate of each self-extinguishing semiconductor device, thus the flywheel diode undergoing a voltage which is higher than the intermediate potential does not undergo a voltage which is higher than the intermediate potential. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、電力変換素子として、例えばゲ−ト転流型タ−ンオフサイリスタ、絶縁型ゲ−トバイポ−ラトランジスタ等の自己消孤型半導体素子を使用した３レベル電力変換装置に関するものである。
【０００２】
【従来の技術】
３レベル電力変換装置は、周知のように、３つの電位、即ち電位Ｐ、電位Ｎ、及びこれら電位Ｐ，Ｎの中間の電位Ｃを有する直流電圧回路と、前記電位Ｐ、電位Ｃ、もしくは電位Ｎを出力することができる３レベル電力変換器とを有する電力変換装置である。
【０００３】
このような３レベル電力変換装置は、例えば特開２０００−１５２６４６号公報（特許文献１）に示されているように、前記３レベル電力変換器を構成する電力変換素子として、ゲ−ト転流型タ−ンオフサイリスタ、絶縁型ゲ−トバイポ−ラトランジスタ等の自己消孤型半導体素子を使用し、装置効率を向上するため臨界電圧上昇率を抑制する為のスナバ回路を使用しない３レベル電力変換装置とする傾向がある。
【０００４】
ところで、このような電力変換素子として自己消孤型半導体素子を使用した３レベル電力変換装置において、直流電圧回路は商用電源（交流）を直流に変換して直流電圧を得る場合が多く、例えば商用電源側の異常などによる過電圧等により直流電圧回路の出力が直流過電圧となることが有り得る。
【０００５】
もし異常な直流過電圧が発生した場合、３レベル電力変換装置を停止するため、自己消孤型半導体素子を一斉に点弧状態からオフ状態（以下ゲ−トブロックと記す）とした際、負荷電流は、自己消孤型半導体素子に並列接続されたフライホイ−ルダイオ−ドを還流し、直流電圧と系統電源もしくはモ−タ誘起電圧の和とケ−ブルインダクタンスや系統電源もしくはモ−タの漏れインダクタンス等で決まる緩やかな電流減少率で電流零に向かう。電流零後、フライホイ−ルダイオ−ドの逆電流がピ−クに達した付近から、フライホイ−ルダイオ−ドはその内部の空乏層が広がりオフ状態を迎え、フライホイ−ルダイオ−ドに直流電圧が印加されることになる。
【０００６】
ここで、前記３レベル電力変換器は、自相の複数のフライホイ−ルダイオ−ドと他相の複数のフライホイ−ルダイオ−ドの直列接続の回路における各フライホイ−ルダイオ−ドで電位Ｐ−Ｎ間の直流電圧を分担することになるが、最も早く空乏層が広がりオフ状態を迎えるフライホイ−ルダイオ−ドに過渡的に前記Ｐ−Ｎ間の直流電圧が印加され、当該フライホイ−ルダイオ−ドが耐圧破壊する恐れがあるということを見出した。
【０００７】
前述の事象を、図６及び図７により具体的に説明する。図６（Ａ）は単相電力変換器におけるゲ−トブロック後の負荷電流の還流ル−プの一例を一点鎖線の矢印で示す図、図６（Ｂ）はゲ−トブロック時のフライホイ−ルダイオ−ドに流れる負荷電流を示す図、図６（Ｃ）は負荷電流還流ル−プの等価回路を示す図、図７（Ａ）はフライホイ−ルダイオ−ド３ａ（中間電位Ｃ側の自己消孤型半導体素子ではない他の自己消孤型半導体素子のフライホイ−ルダイオ−ド）の電圧クランプル−プを示す図、図７（Ｂ）はフライホイ−ルダイオ−ド３ｂ（中間電位Ｃ側の自己消孤型半導体素子のフライホイ−ルダイオ−ド）の電圧クランプル−プを示す図である。
【０００８】
以下、構成を簡略的に説明し、その後、動作について詳述する。
【０００９】
先ず、３レベル電力変換装置の構成は、その代表的な一例として図６（Ａ）に示されているように、電位Ｐ、電位Ｎ、及びこれら電位Ｐ，Ｎの中間の電位Ｃを有する直流電圧回路１と、ゲ−ト転流型タ−ンオフサイリスタ、絶縁型ゲ−トバイポ−ラトランジスタ等の自己消孤型半導体素子２ａ〜２ｈと、フライホイ−ルダイオ−ド３ａ〜３ｈと、アノ−ドリアクトル４ａ〜４ｄと、リセットダイオ−ド５ａ〜５ｄと、リセット抵抗６ａ〜６ｄと、クランプコンデンサ７ａ〜７ｄと、クランプダイオ−ド８ａ〜８ｄと、出力端子ＯＵＴとを有した構成となっており、３レベル電力変換装置の実運用状態では、例えば、前記出力端子ＯＵＴに、系統電源もしくはモ−タ誘起電圧１３と、ケ−ブルインダクタンスや系統電源もしくはモ−タの漏れインダクタンス等のインダクタンス１４とが接続された状態となる。
【００１０】
次いで、動作を説明する。説明の便宜上、自己消孤型半導体素子２ａ〜２ｄ側を自相、自己消孤型半導体素子２ｅ〜２ｈ側を他相と呼ぶことにし、定常運転時の動作は周知の通りであり、その説明は割愛し、前記ゲ−トブロック（例えば商用電源側の異常などによる過電圧等により直流電圧回路の出力が直流過電圧との場合、３レベル電力変換装置を停止するため、自己消孤型半導体素子を一斉に点弧状態からオフ状態とする）場合の動作について説明する。
【００１１】
前記ゲ−トブロック時のフライホイ−ルダイオ−ド３ａ〜３ｈに流れる負荷電流は図６（Ｂ）示すように変化する。図６（Ｂ）に示すように、前記ゲ−トブロック時点から、例えば図６（Ａ）に一点鎖線の矢印で示す自相のフライホイ−ルダイオ−ド３ｂ，３ａ及び他相のフライホイ−ルダイオ−ド３ｈ，３ｇに負荷電流還流電流が流れ、直流電圧回路１の直流電圧と系統電源もしくはモ−タ誘起電圧１３の和とケ−ブルインダクタンスや系統電源もしくはモ−タの漏れインダクタンス等のインダクタンス１４で決まる緩やかな電流減少率で、図６（Ｂ）に示すように電流零に向かい、更にフライホイ−ルダイオ−ド３ｂ，３ａ，３ｈ，３ｇの逆電流がピ−クに達した付近から、フライホイ−ルダイオ−ド３ｂ，３ａ，３ｈ，３ｇ内の空乏層が広がり（等価的にコンデンサ状態となり）、オフ状態を迎え、フライホイ−ルダイオ−ド３ｂ，３ａ，３ｈ，３ｇに直流電圧回路１の直流電圧が印加されることになる。
【００１２】
ここで、図６（Ａ）に一点鎖線の矢印で示す負荷電流還流ル−プの等価回路を図６（Ｃ）に示す。前記ゲ−トブロック時の負荷電流の還流ル−プにおいて、自相のフライホイ−ルダイオ−ド３ａ，３ｂと、他相のフライホイ−ルダイオ−ド３ｇ，３ｈとの直列接続となるため、フライホイ−ルダイオ−ド３ａ，３ｂ，３ｇ，３ｈの中で前記等価的なコンデンサ容量（以下、接合容量という）が最も小さいフライホイ−ルダイオ−ドが存在する場合、当該フライホイ−ルダイオ−ドに、過渡的に直流電圧回路１のＰ−Ｎ間の直流電圧が印加されることになる。
【００１３】
そこで、自相のフライホイ−ルダイオ−ド３ａ，３ｂ及び他相のフライホイ−ルダイオ−ド３ｇ，３ｈの中で、例えば、自相のフライホイ−ルダイオ−ド３ａの接合容量が最も小さい場合、前述のように、直流電圧回路１のＰ−Ｎ間の直流電圧（２Ｅ（Ｖ））が過渡的に当該フライホイ−ルダイオ−ド３ａに印加されることになるが、図７（Ａ）のフライホイ−ルダイオ−ド３ａの電圧クランプル−プに示されているように、フライホイ−ルダイオ−ド３ａのカソ−ド側→リセットダイオ−ド５ａ→リセット抵抗６ａによりＰ−Ｃ間直流電圧（Ｅ（Ｖ））に固定されたクランプコンデンサ７ａ→クランプダイオ−ド８ａ→フライホイ−ルダイオ−ド３ａのアノ−ド側のル−プで、電圧がクランプされる為、フライホイ−ルダイオ−ド３ａには、過渡的にＰ−Ｃ間直流電圧（Ｅ（Ｖ））しか印加されず、Ｃ−Ｎ間直流電圧（Ｅ（Ｖ））は、自相のフライホイ−ルダイオ−ド３ｂと他相のフライホイ−ルダイオ−ド３ｇ，３ｈとで分圧することになる。
【００１４】
従って、自相のフライホイ−ルダイオ−ド３ａ，３ｂ及び他相のフライホイ−ルダイオ−ド３ｇ，３ｈの中で、自相のフライホイ−ルダイオ−ド３ａの接合容量が最も小さい場合は、自相のフライホイ−ルダイオ−ド３ａ，３ｂ及び他相のフライホイ−ルダイオ−ド３ｇ，３ｈの何れも、過電圧破壊される恐れは無い。
【００１５】
ところが、自相のフライホイ−ルダイオ−ド３ａ，３ｂ及び他相のフライホイ−ルダイオ−ド３ｇ，３ｈの中で、自相のフライホイ−ルダイオ−ド３ｂ（中間電位Ｃ側の自己消孤型半導体素子２ｂのフライホイ−ルダイオ−ド）の接合容量が最も小さい場合は、図７（Ｂ）のフライホイ−ルダイオ−ド３ｂの電圧クランプル−プに示されているように、フライホイ−ルダイオ−ド３ｂのカソ−ド側→フライホイ−ルダイオ−ド３ａ→リセットダイオ−ド５ａ→リセット抵抗６ａによりＰ−Ｃ間直流電圧（Ｅ（Ｖ））に固定されたクランプコンデンサ７ａ→リセット抵抗６ｂによりＣ−Ｎ間直流電圧（Ｅ（Ｖ））に固定されたクランプコンデンサ７ｂ→リセットダイオ−ド５ｂ→フライホイ−ルダイオ−ド３ｄ→フライホイ−ルダイオ−ド３ｃ→フライホイ−ルダイオ−ド３ｂのアノ−ド側のル−プで、電圧がクランプされる為、フライホイ−ルダイオ−ド３ｂには、過渡的にＰ−Ｎ間直流電圧（２Ｅ（Ｖ））が印加され、フライホイ−ルダイオ−ド３ｂが過電圧破壊される恐れがある。
【００１６】
【特許文献１】
特開２０００−１５２６４６号公報（図１、段落番号０００５〜０００６）
【００１７】
【発明が解決しようとする課題】
従来の３レベル電力変換装置においては、前述のように、中間電位Ｃ側の自己消孤型半導体素子のフライホイ−ルダイオ−ドの接合容量が最も小さい場合には、前記ゲ−トブロック時に、当該フライホイ−ルダイオ−ドに、過渡的にＰ−Ｎ間直流電圧（２Ｅ（Ｖ））が印加され、当該フライホイ−ルダイオ−ドが過電圧破壊される恐れがあり、また、各フライホイ−ルダイオ−ドの耐電圧、電流容量等を同一のものとしても、各フライホイ−ルダイオ−ドの接合容量は必ずしも同一ではないため、中間電位Ｃ側の自己消孤型半導体素子のフライホイ−ルダイオ−ドの接合容量が最も小さい場合が生じ得ることを見出した。なお、前述と同様に、中間電位側の他の自己消孤型半導体素子のフライホイ−ルダイオ−ド３ｃ，３ｆ，３ｇも、接合容量が最も小さい場合には、前記ゲ−トブロック時に、当該フライホイ−ルダイオ−ドが過電圧破壊される恐れがある。なお、前述の単相電力変換装置の場合と同様に多相電力変換装置も、前記ゲ−トブロック時に、フライホイ−ルダイオ−ドが過電圧破壊される恐れがある。
【００１８】
この発明は、前述のような従来の実情に鑑みてなされたもので、電力変換素子として自己消孤型半導体素子を使用した３レベル電力変換装置において、前記ゲ−トブロック時に、中間電位側の自己消孤型半導体素子のフライホイ−ルダイオ−ドが過電圧破壊されないようにすることを目的とするものである。
【００１９】
【課題を解決するための手段】
この発明に係る３レベル電力変換装置は、電力変換素子としてフライホイ−ルダイオ−ドを有する自己消孤型半導体素子を使用した３レベル電力変換装置において、各自己消孤型半導体素子のゲ−トブロック時に中間電位より高い電圧がかかるフライホイ−ルダイオ−ドの接合容量を、他のフライホイ−ルダイオ−ドの接合容量より、等価的に大きくし、前記中間電位より高い電圧がかかるフライホイ−ルダイオ−ドに前記中間電位より高い電圧がかからないようにしたものである。
【００２０】
また、この発明に係る３レベル電力変換装置は、電力変換素子としてフライホイ−ルダイオ−ドを有する自己消孤型半導体素子を使用した３レベル電力変換装置において、中間電位より高い電圧がかかるフライホイ−ルダイオ−ドの接合容量を、他のフライホイ−ルダイオ−ドの接合容量より、大きくしたものである。
【００２１】
また、この発明に係る３レベル電力変換装置は、電力変換素子としてフライホイ−ルダイオ−ドを有する自己消孤型半導体素子を使用した３レベル電力変換装置において、ゲ−トブロック時に中間電位より高い電圧がかかるフライホイ−ルダイオ−ドと対を成す自己消孤型半導体素子のゲ−トブロックを、他の自己消孤型半導体素子のゲ−トブロック後の負荷電流を遮断する遮断器の動作後に行うように、各自己消孤型半導体素子のゲ−ト制御を行い、ゲ−トブロック時に中間電位より高い電圧がかかるフライホイ−ルダイオ−ドに中間電位より高い電圧がかからないようにしたものである。
【００２２】
【発明の実施の形態】
実施の形態１．
以下、この発明の実施の形態１を、３レベル単相電力変換装置の主回路の一例を示す図１に基づいて説明する。初めに構成を説明し、その後、動作を説明する。
【００２３】
先ず、以下に構成を説明する。
【００２４】
３レベル単相電力変換装置の構成は、その代表的な一例として図１に示されているように、高電位Ｐ、低電位Ｎ、及びこれら電位Ｐ，Ｎの中間の中間電位Ｃを有する直流電圧回路１と、ゲ−ト転流型タ−ンオフサイリスタ、絶縁型ゲ−トバイポ−ラトランジスタ等の自己消孤型半導体素子２ａ〜２ｈと、フライホイ−ルダイオ−ド３ａ〜３ｈと、アノ−ドリアクトル４ａ〜４ｄと、リセットダイオ−ド５ａ〜５ｄと、リセット抵抗６ａ〜６ｄと、クランプコンデンサ７ａ〜７ｄと、クランプダイオ−ド８ａ〜８ｄと、分圧コンデンサ９ａ〜９ｄと、出力端子ＯＵＴとを有した構成となっており、３レベル電力変換装置の実運用状態では、例えば、前記出力端子ＯＵＴに、系統電源もしくはモ−タ誘起電圧１３と、ケ−ブルインダクタンスや系統電源もしくはモ−タの漏れインダクタンス等のインダクタンス１４とが接続された状態となる。
【００２５】
説明の便宜上、自己消孤型半導体素子２ａ〜２ｄ側を自相、自己消孤型半導体素子２ｅ〜２ｈ側を他相と呼ぶこととする。
【００２６】
前記自相の側は、自己消孤型半導体素子２ａ〜２ｄと、フライホイ−ルダイオ−ド３ａ〜３ｄと、アノ−ドリアクトル４ａ〜４ｂと、リセットダイオ−ド５ａ〜５ｂと、リセット抵抗６ａ〜６ｂと、クランプコンデンサ７ａ〜７ｂと、クランプダイオ−ド８ａ〜８ｂと、分圧コンデンサ９ａ〜９ｂとで構成され、前記他相の側は、自己消孤型半導体素子２ｅ〜２ｈと、フライホイ−ルダイオ−ド３ｅ〜３ｈと、アノ−ドリアクトル４ｃ〜４ｄと、リセットダイオ−ド５ｃ〜５ｄと、リセット抵抗６ｃ〜６ｄと、クランプコンデンサ７ｃ〜７ｄと、クランプダイオ−ド８ｃ〜８ｄと、分圧コンデンサ９ｃ〜９ｄとで構成されている。
【００２７】
前記直流電圧回路１は、例えば商用交流電源を電力変換して直流を得る回路であり、例えば商用交流電源側の事故等の異常により、その直流側の出力電圧は直流過電圧となる場合がある。
【００２８】
前記自己消孤型半導体素子２ｅ〜２ｈは、何れも、例えば臨界電圧上昇率が規定されない、或いは具体的に１ｋＶ／μｓを超える臨界電圧上昇率を有し、スナバ回路を必要としないものである。このような自己消孤型半導体素子は、具体的には、例えば、ゲ−ト転流型タ−ンオフサイリスタ、絶縁型ゲ−トバイポ−ラトランジスタ等が該当する。
【００２９】
前記フライホイ−ルダイオ−ド３ａ〜３ｈは、対を成す対応自己消孤型半導体素子２ａ〜２ｈに逆並列に接続されている。即ち、前記フライホイ−ルダイオ−ド３ａは対を成す対応自己消孤型半導体素子２ａに、前記フライホイ−ルダイオ−ド３ｂは対を成す対応自己消孤型半導体素子２ｂに、それぞれ逆並列に接続され、以下同様に３ｃは２ｃに、３ｄは２ｄに、３ｅは２ｅに、３ｆは２ｆに、３ｇは２ｇに、３ｈは２ｈに、それぞれ逆並列に接続されている。
【００３０】
前記アノ−ドリアクトル４ａは、それぞれ直列接続された前記自己消孤型半導体素子２ａ〜２ｄにおける自己消孤型半導体素子２ａのアノ−ドと前記直流電圧回路１の高電位Ｐの端子との間に直列接続されている。
【００３１】
前記アノ−ドリアクトル４ｂは、それぞれ直列接続された前記自己消孤型半導体素子２ａ〜２ｄにおける自己消孤型半導体素子２ｄのカソ−ドと前記直流電圧回路１の低電位Ｎの端子との間に直列接続されている。
【００３２】
前記アノ−ドリアクトル４ｃは、それぞれ直列接続された前記自己消孤型半導体素子２ｅ〜２ｈにおける自己消孤型半導体素子２ｅのアノ−ドと前記直流電圧回路１の高電位Ｐの端子との間に直列接続されている。
【００３３】
前記アノ−ドリアクトル４ｄは、それぞれ直列接続された前記自己消孤型半導体素子２ｅ〜２ｈにおける自己消孤型半導体素子２ｈのカソ−ドと前記直流電圧回路１の低電位Ｎの端子との間に直列接続されている。
【００３４】
前記自相側の前記リセットダイオ−ド５ａと前記クランプコンデンサ７ａと前記クランプコンデンサ７ｂと前記リセットダイオ−ド５ｂとの直列回路は、前記自己消孤型半導体素子２ａ〜２ｄの直列回路に、前記リセットダイオ−ド５ａ，５ｂが前記自己消孤型半導体素子２ａ〜２ｄと導極性になるように、並列接続されている。また、前記リセットダイオ−ド５ａと前記クランプコンデンサ７ａと前記クランプコンデンサ７ｂと前記リセットダイオ−ド５ｂとの直列回路における前記クランプコンデンサ７ａ，７ｂの直列接続点は、前記直流電圧回路１の中間電位Ｃの端子に接続されている。
【００３５】
前記他相側の前記リセットダイオ−ド５ｃと前記クランプコンデンサ７ｃと前記クランプコンデンサ７ｄと前記リセットダイオ−ド５ｄとの直列回路は、前記自己消孤型半導体素子２ｅ〜２ｈの直列回路に、前記リセットダイオ−ド５ｃ，５ｄが前記自己消孤型半導体素子２ｅ〜２ｈと導極性になるように、並列接続されている。また、前記リセットダイオ−ド５ｃと前記クランプコンデンサ７ｃと前記クランプコンデンサ７ｄと前記リセットダイオ−ド５ｄとの直列回路における前記クランプコンデンサ７ｃ，７ｄの直列接続点は、前記直流電圧回路１の中間電位Ｃの端子に接続されている。
【００３６】
前記自相側の前記リセット抵抗６ａは、前記リセットダイオ−ド５ａと前記クランプコンデンサ７ａとの直列接続点と、前記アノ−ドリアクトル４ａの前記直流電圧回路１の高電位Ｐの端子側との間に接続されている。
【００３７】
前記自相側の前記リセット抵抗６ｂは、前記リセットダイオ−ド５ｂと前記クランプコンデンサ７ｂとの直列接続点と、前記アノ−ドリアクトル４ｂの前記直流電圧回路１の低電位Ｎの端子側との間に接続されている。
【００３８】
前記他相側の前記リセット抵抗６ｃは、前記リセットダイオ−ド５ｃと前記クランプコンデンサ７ｃとの直列接続点と、前記アノ−ドリアクトル４ｃの前記直流電圧回路１の高電位Ｐの端子側との間に接続されている。
【００３９】
前記他相側の前記リセット抵抗６ｄは、前記リセットダイオ−ド５ｄと前記クランプコンデンサ７ｄとの直列接続点と、前記アノ−ドリアクトル４ｄの前記直流電圧回路１の低電位Ｎの端子側との間に接続されている。
【００４０】
前記自相側の前記クランプダイオ−ド８ａ，８ｂの直列回路は、中間電位Ｃ側の前記自己消孤型半導体素子２ｂ，２ｃの直列回路に逆並列に接続されている。また、前記クランプダイオ−ド８ａ，８ｂの直列接続点は、前記直流電圧回路１の中間電位Ｃの端子に接続されている。
【００４１】
前記他相側の前記クランプダイオ−ド８ｃ，８ｄの直列回路は、中間電位Ｃ側の前記自己消孤型半導体素子２ｆ，２ｇの直列回路に逆並列に接続されている。また、前記クランプダイオ−ド８ｃ，８ｄの直列接続点は、前記直流電圧回路１の中間電位Ｃの端子に接続されている。
【００４２】
前記自相側の前記分圧コンデンサ９ａは、前記中間電位Ｃ側の前記自己消孤型半導体素子２ｂと前記フライホイ−ルダイオ−ド３ｂとの逆並列回路に並列に接続されている。換言すれば、前記分圧コンデンサ９ａは、前記フライホイ−ルダイオ−ド３ｂに並列に接続されている。
【００４３】
前記自相側の前記分圧コンデンサ９ｂは、前記中間電位Ｃ側の前記自己消孤型半導体素子２ｃと前記フライホイ−ルダイオ−ド３ｃとの逆並列回路に並列に接続されている。換言すれば、前記分圧コンデンサ９ｂは、前記フライホイ−ルダイオ−ド３ｃに並列に接続されている。
【００４４】
前記他相側の前記分圧コンデンサ９ｃは、前記中間電位Ｃ側の前記自己消孤型半導体素子２ｆと前記フライホイ−ルダイオ−ド３ｆとの逆並列回路に並列に接続されている。換言すれば、前記分圧コンデンサ９ｃは、前記フライホイ−ルダイオ−ド３ｆに並列に接続されている。
【００４５】
前記他相側の前記分圧コンデンサ９ｄは、前記中間電位Ｃ側の前記自己消孤型半導体素子２ｇと前記フライホイ−ルダイオ−ド３ｇとの逆並列回路に並列に接続されている。換言すれば、前記分圧コンデンサ９ｄは、前記フライホイ−ルダイオ−ド３ｇに並列に接続されている。
【００４６】
なお、前記クランプコンデンサ７ａ〜７ｄの各コンデンサ容量は、同じにしてある。また、前記分圧コンデンサ９ａ〜９ｄの各コンデンサ容量は、同じにしてある。更に、前述のようにフライホイ−ルダイオ−ド３ｂとフライホイ−ルダイオ−ド３ｃに並列に分圧コンデンサ９ａ，９ｂを接続することにより、フライホイ−ルダイオ−ド３ａとフライホイ−ルダイオ−ド３ｄの接合容量に対して、フライホイ−ルダイオ−ド３ｂとフライホイ−ルダイオ−ド３ｃの接合容量が等価的に大きくしてある。
【００４７】
次に作用・動作について説明する。
【００４８】
前述の図１の構成において、例えば、直流電圧回路１の交流側における系統事故、故障、等の交流側異常等によって異常な直流過電圧が発生した場合、３レベル電力変換装置を停止するために、自己消孤型半導体素子２ａ〜２ｈを一斉に点弧状態からオフ状態（ゲ−トブロック）とするが、その場合、３レベル電力変換装置内には、例えば、フライホイ−ルダイオ−ド３ａ，３ｂ，３ｇ，３ｈの導通により、矢印一点鎖線で示すように、還流負荷電流が、自相の出力端子ＯＵＴ→自相のフライホイ−ルダイオ−ド３ｂ→自相のフライホイ−ルダイオ−ド３ａ→直流電圧回路１の高電位Ｐの端子→中間電位Ｃ→低電位Ｎの端子→他相のフライホイ−ルダイオ−ド３ｈ→他相のフライホイ−ルダイオ−ド３ｇ→他相の出力端子ＯＵＴの還流ル−トで流れる。
【００４９】
ゲ−トブロック時にこのような還流ル−トで還流負荷電流が流れその逆電流が零に向かうことによりフライホイ−ルダイオ−ド３ａ，３ｂ，３ｈ，３ｇがオフ状態を迎えた場合、等価的に接合容量が小さいフライホイ−ルダイオ−ド３ａに電圧が印加されるが、フライホイ−ルダイオ−ド３ａのカソ−ド側→リセットダイオ−ド５ａ→リセット抵抗６ａにより高圧電位Ｐ−中間電位Ｃ間の直流電圧（Ｅ（Ｖ））に固定されたクランプコンデンサ７ａ→クランプダイオ−ド８ａ→フライホイ−ルダイオ−ド３ａのアノ−ド側のル−プでクランプされる為、フライホイ−ルダイオ−ド３ａには、過渡的に高圧電位Ｐ−中間電位Ｃ間の直流電圧（Ｅ（Ｖ））しか印加されず、残りの中間電位Ｃ−低電位Ｎ間の直流電圧（Ｅ（Ｖ））を、自相の等価的に接合容量が大きい（並列の分圧コンデンサ９ａを有する）フライホイ−ルダイオ−ド３ｂと、他相のフライホイ−ルダイオ−ド３ｈと、他相の等価的に接合容量が大きい（並列の分圧コンデンサ９ｄを有する）フライホイ−ルダイオ−ド３ｇとで分圧することになる。
【００５０】
ここで、もし、中間電位Ｃ側のフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに等価的に接合容量を大きくする分圧コンデンサ９ａ，９ｂ，９ｃ，９ｄを設けなかった場合は、前述の従来の技術のように、自相のフライホイ−ルダイオ−ド３ａ，３ｂ及び他相のフライホイ−ルダイオ−ド３ｇ，３ｈの中で、自相のフライホイ−ルダイオ−ド３ｂ（中間電位Ｃ側の自己消孤型半導体素子２ｂのフライホイ−ルダイオ−ド）の接合容量が最も小さい場合は、前述の図７（Ｂ）のフライホイ−ルダイオ−ド３ｂの電圧クランプル−プにも示されているように、フライホイ−ルダイオ−ド３ｂのカソ−ド側→フライホイ−ルダイオ−ド３ａ→リセットダイオ−ド５ａ→リセット抵抗６ａによりＰ−Ｃ間直流電圧（Ｅ（Ｖ））に固定されたクランプコンデンサ７ａ→リセット抵抗６ｂによりＣ−Ｎ間直流電圧（Ｅ（Ｖ））に固定されたクランプコンデンサ７ｂ→リセットダイオ−ド５ｂ→フライホイ−ルダイオ−ド３ｄ→フライホイ−ルダイオ−ドフライホイ−ルダイオ−ド３ｃ→フライホイ−ルダイオ−ド３ｂのアノ−ド側のル−プで、電圧がクランプされる為、フライホイ−ルダイオ−ド３ｂには、過渡的にＰ−Ｎ間直流電圧（２Ｅ（Ｖ））が印加され、フライホイ−ルダイオ−ド３ｂが過電圧破壊される恐れがあるが、中間電位Ｃ側のフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに等価的に接合容量を大きくする分圧コンデンサ９ａ，９ｂ，９ｃ，９ｄを設けることにより、フライホイ−ルダイオ−ド３ｂ自体の接合容量が最も小さい場合であっても、フライホイ−ルダイオ−ド３ｂには、過渡的にＰ−Ｎ間直流電圧（２Ｅ（Ｖ））が印加されることは無くなる。また、中間電位Ｃ側の他のフライホイ−ルダイオ−ド３ｃ，３ｆ，３ｇの何れかの接合容量が最も小さい場合でも同様である。
【００５１】
このように、分圧コンデンサ９ａ，９ｂ，９ｃ，９ｄを設けなければ、各自己消孤型半導体素子のゲ−トブロック時に、中間電位より高い電圧（２Ｅ）がかかるフライホイ−ルダイオ−ド（中間電位側のフライホイ−ルダイオ−ド）３ｂ，３ｃ，３ｆ，３ｇの接合容量を、分圧コンデンサ９ａ，９ｂ，９ｃ，９ｄを設けることにより、他のフライホイ−ルダイオ−ド３ａ，３ｄ，３ｅ，３ｈの接合容量より、等価的に大きくし、前記分圧コンデンサ９ａ，９ｂ，９ｃ，９ｄを設けなければ中間電位より高い電圧がかかるフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに、前記中間電位より高い電圧がかからないようにしたので、分圧コンデンサ９ａ，９ｂ，９ｃ，９ｄを設けなければ、ゲ−トブロック時に中間電位より高い電圧（２Ｅ）がかかるフライホイ−ルダイオ−ド（中間電位側のフライホイ−ルダイオ−ド）３ｂ，３ｃ，３ｆ，３ｇが過電圧破壊される恐れがなくなる。つまり、ゲ−トブロック時にフライホイ−ルダイオ−ドが過電圧破壊されるようなことのない信頼性の高い安価な３レベル電力変換装置を得ることができる。
【００５２】
なお、前述のこの発明の実施の形態１は、電位Ｐ，Ｎと中間電位Ｃの３つの電位を有する直流電圧回路１と、前記各電位Ｐ，Ｎ，Ｃを出力することができる３レベル変換器を有する電力変換装置であって、前記３レベル変換器は第１〜第４の自己消孤型半導体素子２ａ〜２ｄと、前記各自己消孤型半導体素子２ａ〜２ｄに逆並列接続された第１〜第４のフライホイ−ルダイオ−ド３ａ〜３ｄと、前記直流電圧回路１の電位Ｃの端子と前記第２の自己消孤型半導体素子２ｂのアノ−ド端子との間に接続された第１のクランプダイオ−ド８ａと、前記第３の自己消孤型半導体素子２ｃのカソ−ド端子と前記前記直流電圧回路１の電位Ｃの端子との間に接続された第２のクランプダイオ−ド８ｂと、前記直流電圧回路１の電位Ｐの端子と前記第１の自己消孤型半導体素子２ａのアノ−ド端子との間に接続された第１のアノ−ドリアクトル４ａと、この第１のアノ−ドリアクトル４ａに並列接続された第１のリセットダイオ−ド５ａと第１のリセット抵抗６ａから構成される第１の直列接続体と、前記第１のリセットダイオ−ド５ａと前記第１のリセット抵抗６ａとの接続点と前記直流電圧回路１の電位Ｃの端子との間に接続され前記第１のリセット抵抗６ａを介してのみ前記直流電圧回路１へ放電できる第１のクランプコンデンサ７ａと、前記第４の自己消孤型半導体素子２ｄのカソ−ド端子と前記直流電圧回路１の電位Ｎの端子との間に接続された第２のアノ−ドリアクトル４ｂと、この第２のアノ−ドリアクトル４ｂに並列接続された第２のリセットダイオ−ド５ｂと第２のリセット抵抗６ｂから構成される第２の直列接続体と、前記第２のリセットダイオ−ド５ｂと前記第２のリセット抵抗６ｂとの接続点と前記直流電圧回路１の電位Ｎの端子との間に接続され前記第２のリセット抵抗６ｂを介してのみ前記直流電圧回路１へ放電できる第２のクランプコンデンサ７ｂと、前記第２の自己消孤型半導体素子２ｂと前記第３の自己消孤型半導体素子２ｃとの接続点に設けられた出力端子ＯＵＴとを有するブリッジ回路により構成されるものにおいて、前記各自己消孤型半導体素子２ａ〜２ｄは臨界電圧上昇率が規定されない或いは具体的に１ｋＶ／μｓを超える臨界電圧上昇率を有しスナバ回路を必要とせず、前記第１のフライホイ−ルダイオ−ド３ａの容量成分に対し、前記第２のフライホイ−ルダイオ−ド３ｂの容量成分を大きくすること、及び前記第４のフライホイ−ルダイオ−ド３ｄの容量成分に対し、前記第３のフライホイ−ルダイオ−ド３ｃの容量成分を大きくした３レベル電力変換装置でもある。
【００５３】
なお、前記電位Ｐ，Ｎの各端子間に直流電源を接続し、前記自相側の出力端子ＯＵＴと前記他相側の出力端子ＯＵＴとの間に交流負荷を接続すれば３レベルインバ−タ装置となり、前記電位Ｐ，Ｎの各端子間に直流負荷を接続し、前記自相側の出力端子ＯＵＴと前記他相側の出力端子ＯＵＴとの間に交流電源を接続すれば３レベルコンバ−タ装置となる。
【００５４】
実施の形態２．
この発明の実施の形態２を、３レベル単相電力変換装置の主回路の一例を示す図２に基づいて説明する。
【００５５】
前述のこの発明の実施の形態１では、フライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに並列に分圧コンデンサ９ａ〜９ｄを接続した場合を例示したが、この発明の実施の形態２では、フライホイ−ルダイオ−ド３ａ，３ｄ，３ｅ，３ｈにも、図２に示すように、分圧コンデンサ１０ａ，１０ｂ，１０ｃ，１０ｄを接続した事例を示すものである。
【００５６】
ここで、前記分圧コンデンサ９ａ〜９ｄの各コンデンサ容量は同じにしてある。前記分圧コンデンサ１０ａ〜１０ｄの各コンデンサ容量は同じにしてある。更に、前記分圧コンデンサ９ａ〜９ｄの各コンデンサ容量は、前記分圧コンデンサ１０ａ〜１０ｄの各コンデンサ容量より大きなものにしてある。
【００５７】
この発明の実施の形態２においては、前記分圧コンデンサ９ａ〜９ｄを、前記分圧コンデンサ１０ａ〜１０ｄより、コンデンサ容量が大きなものとすることにより、フライホイ−ルダイオ−ド３ａ〜３ｈ自体の接合容量特性に因らず、フライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇの等価的な接合容量を、フライホイ−ルダイオ−ド３ａ，３ｄ，３ｅ，３ｈの等価的な接合容量より、確実に大きくでき、前述のこの発明の実施の形態１と同様にして、フライホイ−ルダイオ−ド３ａ，３ｅ，もしくは３ｄ，３ｈに、高電位Ｐ−中間電位Ｃ間の直流電圧（Ｅ（Ｖ））もしくは中間電位Ｃ−低電位Ｎ間の直流電圧（Ｅ（Ｖ））が印加され、残りの直流電圧（Ｅ（Ｖ））を、自相のフライホイ−ルダイオ−ド３ｂ及び他相のフライホイ−ルダイオ−ド３ｇ，３ｈの各等価的接合容量、もしくは自相のフライホイ−ルダイオ−ド３ｃ及び他相のフライホイ−ルダイオ−ド３ｅ，３ｆの各等価的接合容量、で分圧するので、若し分圧コンデンサ分圧コンデンサ９ａ〜９ｄ，１０ａ〜１０ｄを設けなかったら直流過電圧が印加され破壊される可能性のある（中間電位側の）フライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇの耐圧破壊を防止でき、信頼性の高い安価な３レベル電力変換装置を得ることができる。
【００５８】
実施の形態３．
この発明の実施の形態３を、３レベル単相電力変換装置の主回路の一例を示す図３に基づいて説明する。
【００５９】
前述のこの発明の実施の形態１では、フライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに並列に分圧コンデンサ９ａ〜９ｄを接続した場合を例示したが、この発明の実施の形態３では、図３に示すように、分圧コンデンサ９ａ〜９ｄの各々に直列に且つフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに並列に、抵抗１１ａ，１１ｂ，１１ｃ，１１ｄを接続した事例を示すものである。
【００６０】
前述のこの発明の実施の形態１のように、分圧コンデンサ９ａ〜９ｄの各々に直列に且つフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに並列に接続された抵抗１１ａ，１１ｂ，１１ｃ，１１ｄを設けてない場合には、自己消孤型半導体素子２ｂ，２ｃ，２ｆ，２ｇのタ−ンオン動作時に分圧コンデンサ９ａ〜９ｄが放電を行うので、自己消孤型半導体素子２ｂ，２ｃ，２ｆ，２ｇのタ−ンオン損失が増加することになるが、前述のこの発明の実施の形態３のように、分圧コンデンサ９ａ〜９ｄの各々に直列に且つフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに並列に接続された抵抗１１ａ，１１ｂ，１１ｃ，１１ｄを設けることにより、前記分圧コンデンサ９ａ〜９ｄの放電電流を当該抵抗１１ａ，１１ｂ，１１ｃ，１１ｄで限流し、前記自己消孤型半導体素子２ｂ，２ｃ，２ｆ，２ｇのタ−ンオン損失を抑制でき、信頼性の高い３レベル電力変換装置を得ることができる。
【００６１】
実施の形態４．
図示してないが、前述のこの発明の実施の形態２（図２）における分圧コンデンサ９ａ〜９ｄ，１０ａ〜１０ｄの各々に直列に且つ対応フライホイ−ルダイオ−ド３ａ〜３ｈに並列に抵抗を接続すれば、前述のこの発明の実施の形態３（図３）と同様にして、前述のこの発明の実施の形態２（図２）における自己消孤型半導体素子２ａ〜２ｈの各タ−ンオン損失を抑制でき、前述のこの発明の実施の形態２（図２）より信頼性の高い３レベル電力変換装置を得ることができる。
【００６２】
実施の形態５．
この発明の実施の形態５を、３レベル単相電力変換装置の主回路の一例を示す図４に基づいて説明する。
【００６３】
前述のこの発明の実施の形態２では、フライホイ−ルダイオ−ド３ａ〜３ｈの各々に並列に分圧コンデンサ９ａ、９ｂ、９ｃ、９ｄ、１０あ、１０ｂ、１０ｃ，１０ｄを設けた場合を例示したが、この発明の実施の形態５では、図４に示すように、前述のこの発明の実施の形態２における分圧コンデンサ９ａ、９ｂ、９ｃ、９ｄ、１０ａ、１０ｂ、１０ｃ，１０ｄを設けずに、フライホイ−ルダイオ−ド３ａ，３ｂの組み合わせ１２ａ、フライホイ−ルダイオ−ド３ｃ，３ｄの組み合わせ１２ｂ、フライホイ−ルダイオ−ド３ｅ，３ｆの組み合わせ１２ｃ、及びフライホイ−ルダイオ−ド３ｇ，３ｈの組み合わせ１２ｄで、当該組み合わせの中においてフライホイ−ルダイオ−ドの接合容量の特性を選別してある。
【００６４】
具体的には、前記組み合わせ１２ａでは、フライホイ−ルダイオ−ド３ｂはフライホイ−ルダイオ−ド３ａより接合容量の大きなものを選別して接続してある。同様に、前記組み合わせ１２ｂでは、フライホイ−ルダイオ−ド３ｃはフライホイ−ルダイオ−ド３ｄより接合容量の大きなものを、前記組み合わせ１２ｃでは、フライホイ−ルダイオ−ド３ｆはフライホイ−ルダイオ−ド３ｅより接合容量の大きなものを、前記組み合わせ１２ｄでは、フライホイ−ルダイオ−ド３ｇはフライホイ−ルダイオ−ド３ｈより接合容量の大きなものを、それぞれ選別して接続してある。
【００６５】
なお、前記フライホイ−ルダイオ−ドの選別の仕方として、前記中間電位側のフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇは夫々実質的に同じ接合容量のものを選別して使用し、前記中間電位側ではない他のフライホイ−ルダイオ−ド３ａ，３ｄ，３ｅ，３ｈは夫々実質的に同じ接合容量のものを選別して使用し、更に、前記中間電位側のフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇは前記中間電位側ではない他のフライホイ−ルダイオ−ド３ａ，３ｄ，３ｅ，３ｈより接合容量が大きなものを選別して使用してもよい。
【００６６】
前述のように、この発明の実施の形態５では、前記接合容量の選別使用をしなければ、各自己消孤型半導体素子のゲ−トブロック時に、中間電位より高い電圧（２Ｅ）がかかるフライホイ−ルダイオ−ド（中間電位側のフライホイ−ルダイオ−ド）３ｂ，３ｃ，３ｆ，３ｇの接合容量が、３ｂについては他のフライホイ−ルダイオ−ド３ａより、３ｃについては他のフライホイ−ルダイオ−ド３ｄより、３ｆについては他のフライホイ−ルダイオ−ド３ｅより、３ｇについては他のフライホイ−ルダイオ−ド３ｈより、それぞれ大きなものを選別して使用し、このような選別使用しなければ中間電位より高い電圧がかかるフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに、前記中間電位より高い電圧がかからないようにしたので、このような選別使用しなければ、ゲ−トブロック時に中間電位より高い電圧（２Ｅ）がかかるフライホイ−ルダイオ−ド（中間電位側のフライホイ−ルダイオ−ド）３ｂ，３ｃ，３ｆ，３ｇが過電圧破壊されるような恐れがなくなる。つまり、前述のこの発明の実施形態１〜４のような分圧コンデンサや抵抗のような付加部品使用することなく、少ない部品点数で信頼性の高い安価な３レベル電力変換装置を得ることができる。
【００６７】
実施の形態６．
この発明の実施の形態６を図５に基づいて説明する。図５（Ａ）は３レベル単相電力変換装置の主回路の一例を示す図、図５（Ｂ）は制御ロジックを自己消孤型半導体素子（以下ＧＣＴと略記する）のスイッチング動作とゲ−トブロックと遮断器の開放時間との関係で示す図である。なお、図５（Ａ）において、前述の図１〜４と同一または相当部分には同一符号を付し、前述の図１〜４と同一構成、同一動作、同一機能については、それらの説明は省略する。また、図５（Ａ）は、その回路構成が前述の図４と同じであるので、動作説明のみを以下に記載する。
【００６８】
ＧＣＴ（自己消孤型半導体素子）２ａ〜２ｈのゲ−トブロック動作において、図５（Ｂ）に示すように、ＧＣＴ２ａ，２ｅとＧＣＴ２ｄ，２ｈとを同時にゲ−トブロック（ゲ−トブロック１と呼称する）すると、一例として図５（Ａ）に矢印一点鎖線で示すように負荷電流経路が形成される。ＧＣＴ２ａ，２ｅ，２ｄ，２ｈはゲ−トブロックである為、フライホイ−ルダイオ−ド３ａ，３ｅが高電位Ｐ−中間電位Ｃ間の直流電圧（Ｅ（Ｖ））を負担し、フライホイ−ルダイオ−ド３ｄ，３ｈが中間電位Ｃ−低電位Ｎ間の直流電圧（Ｅ（Ｖ））を負担する。フライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇの電圧は、それらと対を成すＧＣＴ２ｂ，２ｃ，２ｆ，２ｇが導通状態である為、零となる。
【００６９】
図５（Ｂ）に示すように、ゲ−トブロック１と同期して前記負荷電流を遮断器１５で遮断し、その後、遮断器開放時間以上後（負荷電流が零になった後）に、ＧＣＴ２ｂ，２ｃ，とＧＣＴ２ｆ，２ｇとを同時にゲ−トブロック（ゲ−トブロック２と呼称する）する。前記ゲ−トブロック２の時点では、負荷電流は遮断器１５で遮断され零であるため電圧分担状態は変わらない。
【００７０】
前述の制御ロジックが組み込まれた制御装置１６と遮断器１５とにより、前述のように、中間電位Ｃ側のフライホイ−ルダイオ−ド３ｂ，３ｃ，３ｆ，３ｇに過電圧２Ｅ（Ｖ）が印加されることはなくなり、信頼性の高い３レベル電力変換装置を得ることができる。
【００７１】
なお、前述のこの発明の実施の形態６は、電位Ｐ，Ｎと中間電位Ｃの３つの電位を有する直流電圧回路１と、前記各電位Ｐ，Ｎ，Ｃを出力することができる３レベル変換器を有する電力変換装置であって、前記３レベル変換器は第１〜第４の自己消孤型半導体素子２ａ〜２ｄと、前記各自己消孤型半導体素子２ａ〜２ｄに逆並列接続された第１〜第４のフライホイ−ルダイオ−ド３ａ〜３ｄと、前記直流電圧回路１の電位Ｃの端子と前記第２の自己消孤型半導体素子２ｂのアノ−ド端子との間に接続された第１のクランプダイオ−ド８ａと、前記第３の自己消孤型半導体素子２ｃのカソ−ド端子と前記前記直流電圧回路１の電位Ｃの端子との間に接続された第２のクランプダイオ−ド８ｂと、前記直流電圧回路１の電位Ｐの端子と前記第１の自己消孤型半導体素子２ａのアノ−ド端子との間に接続された第１のアノ−ドリアクトル４ａと、この第１のアノ−ドリアクトル４ａに並列接続された第１のリセットダイオ−ド５ａと第１のリセット抵抗６ａから構成される第１の直列接続体と、前記第１のリセットダイオ−ド５ａと前記第１のリセット抵抗６ａとの接続点と前記直流電圧回路１の電位Ｃの端子との間に接続され前記第１のリセット抵抗６ａを介してのみ前記直流電圧回路１へ放電できる第１のクランプコンデンサ７ａと、前記第４の自己消孤型半導体素子２ｄのカソ−ド端子と前記直流電圧回路１の電位Ｎの端子との間に接続された第２のアノ−ドリアクトル４ｂと、この第２のアノ−ドリアクトル４ｂに並列接続された第２のリセットダイオ−ド５ｂと第２のリセット抵抗６ｂから構成される第２の直列接続体と、前記第２のリセットダイオ−ド５ｂと前記第２のリセット抵抗６ｂとの接続点と前記直流電圧回路１の電位Ｎの端子との間に接続され前記第２のリセット抵抗６ｂを介してのみ前記直流電圧回路１へ放電できる第２のクランプコンデンサ７ｂと、前記第２の自己消孤型半導体素子２ｂと前記第３の自己消孤型半導体素子２ｃとの接続点に設けられた出力端子ＯＵＴとを有するブリッジ回路により構成されるものにおいて、前記各自己消孤型半導体素子２ａ〜２ｄは臨界電圧上昇率が規定されない或いは具体的に１ｋＶ／μｓを超える臨界電圧上昇率を有しスナバ回路を必要とせず、変換器出力端子ＯＵＴと系統電源もしくはモ−タ誘起電圧１３との間に遮断器１５を有し、故障停止時のゲ−トブロック時に、第１及び第４の自己消孤型半導体素子２ａ，２ｄが同時にゲ−トブロックした後、遮断器開放時間以上後（負荷電流が零になった後）に、第２及び第３の自己消孤型半導体素子２ｂ，２ｃをゲ−トブロックする制御装置１６を有している３レベル電力変換装置でもある。
【００７２】
【発明の効果】
前述のように、この発明は、電力変換素子としてフライホイ−ルダイオ−ドを有する自己消孤型半導体素子を使用した３レベル電力変換装置において、各自己消孤型半導体素子のゲ−トブロック時に中間電位より高い電圧がかかるフライホイ−ルダイオ−ドの接合容量を、他のフライホイ−ルダイオ−ドの接合容量より、等価的に大きくし、前記中間電位より高い電圧がかかるフライホイ−ルダイオ−ドに前記中間電位より高い電圧がかからないようにしたので、ゲ−トブロック時にフライホイ−ルダイオ−ドが過電圧破壊されることのない信頼性の高い３レベル電力変換装置を得ることができる効果がある。
【００７３】
また、この発明は、電力変換素子としてフライホイ−ルダイオ−ドを有する自己消孤型半導体素子を使用した３レベル電力変換装置において、中間電位より高い電圧がかかるフライホイ−ルダイオ−ドの接合容量を、他のフライホイ−ルダイオ−ドの接合容量より、大きくしたので、ゲ−トブロック時にフライホイ−ルダイオ−ドが過電圧破壊されることのない信頼性の高い３レベル電力変換装置を、部品点数の少ない安価なものとすることができる効果がある。
【００７４】
また、この発明は、電力変換素子としてフライホイ−ルダイオ−ドを有する自己消孤型半導体素子を使用した３レベル電力変換装置において、ゲ−トブロック時に中間電位より高い電圧がかかるフライホイ−ルダイオ−ドと対を成す自己消孤型半導体素子のゲ−トブロックを、他の自己消孤型半導体素子のゲ−トブロック後の負荷電流を遮断する遮断器の動作後に行うように、各自己消孤型半導体素子のゲ−ト制御を行い、ゲ−トブロック時に中間電位より高い電圧がかかるフライホイ−ルダイオ−ドに中間電位より高い電圧がかからないようにしたので、ゲ−トブロック時にフライホイ−ルダイオ−ドが過電圧破壊されることのない信頼性の高い３レベル電力変換装置を得ることができる効果がある。
【図面の簡単な説明】
【図１】この発明の実施の形態１を示す図で、３レベル単相電力変換装置の主回路の一例を示す図である。
【図２】この発明の実施の形態２を示す図で、３レベル単相電力変換装置の主回路の一例を示す図である。
【図３】この発明の実施の形態３を示す図で、３レベル単相電力変換装置の主回路の一例を示す図である。
【図４】この発明の実施の形態５を示す図で、３レベル単相電力変換装置の主回路の一例を示す図である。
【図５】この発明の実施の形態６を示す図で、（Ａ）は３レベル単相電力変換装置の主回路の一例を示す図、（Ｂ）は制御ロジックを自己消孤型半導体素子（ＧＣＴ）のスイッチング動作とゲ−トブロックと遮断器の開放時間との関係で示す図である。
【図６】従来の３レベル電力変換装置に関する図で、（Ａ）は単相電力変換器におけるゲ−トブロック後の負荷電流の還流ル−プの一例を一点鎖線の矢印で示す図、（Ｂ）はゲ−トブロック時のフライホイ−ルダイオ−ドに流れる負荷電流を示す図、（Ｃ）は負荷電流還流ル−プの等価回路を示す図である。
【図７】従来の３レベル電力変換装置に関する図で、（Ａ）はフライホイ−ルダイオ−ド３ａ（中間電位Ｃ側の自己消孤型半導体素子ではない他の自己消孤型半導体素子のフライホイ−ルダイオ−ド）の電圧クランプル−プを示す図、（Ｂ）はフライホイ−ルダイオ−ド３ｂ（中間電位Ｃ側の自己消孤型半導体素子のフライホイ−ルダイオ−ド）の電圧クランプル−プを示す図である。
【符号の説明】
１直流電圧回路、
２ａ〜２ｄ自己消孤型半導体素子（ゲ−ト転流型タ−ンオフサイリスタ）、
３ａ〜３ｈフライホイ−ルダイオ−ド、
４ａ，４ｂ，４ｃ，４ｄアノ−ドリアクトル、
５ａ，５ｂ，５ｃ、５ｄリセットダイオ−ド、
６ａ，６ｂ，６ｃ，６ｄリセット抵抗、
７ａ，７ｂ，７ｃ，７ｄクランプコンデンサ、
８ａ，８ｂ，８ｃ，８ｄクランプダイオ−ド、
９ａ，９ｂ，９ｃ，９ｄ，１０ａ，１０ｂ，１０ｃ，１０ｄ分圧コンデンサ、
１１ａ，１１ｂ，１１ｃ，１１ｄ抵抗、
１２ａ，１２ｂ，１２ｃ，１２ｄフライホイ−ルダイオ−ドの組み合わせ、
１３系統電源もしくはモ−タ誘起電圧、
１４ケ−ブルインダクタンスや系統電源もしくはモ−タの漏れインダクタンス等のインダクタンス、
１５遮断器、
１６制御装置、
Ｐ，Ｃ，Ｎ直流電圧回路の各端子電圧、
ＯＵＴ出力端子。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a three-level power conversion device using a self-extinguishing semiconductor device such as a gate commutation type turn-off thyristor or an insulated gate bipolar transistor as a power conversion device. .
[0002]
[Prior art]
As is well known, the three-level power converter includes a DC voltage circuit having three potentials, namely, a potential P, a potential N, and a potential C intermediate between the potentials P and N, and the potential P, the potential C, or the potential. And a three-level power converter capable of outputting N.
[0003]
Such a three-level power converter is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-152646 (Patent Document 1), in which a gate commutation is used as a power conversion element constituting the three-level power converter. -Level power that uses self-extinguishing semiconductor devices such as die turn-off thyristors and insulated gate bipolar transistors, and does not use a snubber circuit to suppress the critical voltage rise rate in order to improve device efficiency They tend to be conversion devices.
[0004]
In a three-level power converter using a self-extinguishing semiconductor device as such a power converter, a DC voltage circuit often converts a commercial power supply (AC) to DC to obtain a DC voltage. The output of the DC voltage circuit may become a DC overvoltage due to an overvoltage due to an abnormality on the power supply side or the like.
[0005]
If an abnormal DC overvoltage occurs, the three-level power converter is stopped. When the self-extinguishing semiconductor elements are simultaneously turned off from the ignition state (hereinafter referred to as a gate block), the load current is reduced. Circulates a flywheel diode connected in parallel with the self-extinguishing semiconductor device, and sums the DC voltage and the system power supply or motor induced voltage with cable inductance, system power supply or motor leakage inductance, etc. The current goes to zero at a gradual current decrease rate determined by. When the reverse current of the flywheel diode reaches a peak after zero current, the flywheel diode expands its depletion layer to the off state, and a DC voltage is applied to the flywheel diode. Will be done.
[0006]
Here, the three-level power converter is connected between a potential PN at each flywheel diode in a series connection circuit of a plurality of flywheel diodes of the own phase and a plurality of flywheel diodes of another phase. The PN voltage is transiently applied to the flywheel diode in which the depletion layer expands and enters the off state earliest, and the flywheel diode withstands the breakdown voltage. I found that it could be destroyed.
[0007]
The above-described event will be described more specifically with reference to FIGS. FIG. 6A is a diagram showing an example of a return loop of the load current after the gate block in the single-phase power converter by a chain line arrow, and FIG. 6B is a flywheel diode at the time of the gate block. FIG. 6C is a diagram showing an equivalent circuit of a load current return loop, and FIG. 7A is a diagram showing a flywheel diode 3a (self-extinguishing type on the intermediate potential C side). FIG. 7B shows a voltage clamp loop of a flywheel diode of another self-extinguishing semiconductor device other than a semiconductor device, and FIG. 7B shows a flywheel diode 3b (self-extinguishing type on the intermediate potential C side). FIG. 4 is a diagram showing a voltage clamp loop of a flywheel diode (semiconductor element).
[0008]
Hereinafter, the configuration will be briefly described, and then the operation will be described in detail.
[0009]
First, as a typical example of the configuration of the three-level power converter, as shown in FIG. 6A, a direct current having a potential P, a potential N, and a potential C intermediate between the potentials P and N is used. A voltage circuit 1, self-extinguishing semiconductor elements 2a to 2h such as a gate commutation type turn-off thyristor and an insulated gate bipolar transistor, flywheel diodes 3a to 3h, and an anode. It has a configuration including reactors 4a to 4d, reset diodes 5a to 5d, reset resistors 6a to 6d, clamp capacitors 7a to 7d, clamp diodes 8a to 8d, and an output terminal OUT. In an actual operation state of the three-level power converter, for example, a system power supply or a motor induced voltage 13 and a cable inductance, a system power supply or a motor leakage motor are connected to the output terminal OUT. A state in which the inductance 14 are connected, such as conductance.
[0010]
Next, the operation will be described. For convenience of explanation, the self-extinguishing type semiconductor elements 2a to 2d side will be referred to as a self-phase and the self-extinguishing type semiconductor elements 2e to 2h side will be referred to as other phases, and the operation at the time of steady operation is well known. The gate block (for example, when the output of the DC voltage circuit is a DC overvoltage due to an overvoltage or the like due to an abnormality in the commercial power supply or the like, the three-level power converter is stopped, so that the self-extinguishing type semiconductor elements are simultaneously removed. The operation in the case where the ignition state is changed to the off state will be described.
[0011]
The load current flowing through the flywheel diodes 3a to 3h during the gate block changes as shown in FIG. As shown in FIG. 6B, from the time of the gate block, the flywheel diodes 3b and 3a of the self-phase and the flywheel diodes of the other phase, which are indicated by dashed-dotted arrows in FIG. 6A, for example. The load current return current flows through 3h and 3g, and the sum of the DC voltage of the DC voltage circuit 1 and the system power supply or motor induced voltage 13 and the inductance 14 such as the cable inductance and the system power supply or motor leakage inductance are used. At the determined gradual current reduction rate, as shown in FIG. 6 (B), the current approaches zero, and from the vicinity where the reverse current of the flywheel diodes 3b, 3a, 3h, 3g reaches the peak, the flywheel decreases. The depletion layers in the diodes 3b, 3a, 3h, and 3g expand (equivalently to a capacitor state) and turn off, and the flywheel diodes 3b, 3a, 3h, and 3g are turned off. So that the DC voltage of the DC voltage circuit 1 is applied.
[0012]
Here, FIG. 6C shows an equivalent circuit of a load current return loop indicated by a dashed line arrow in FIG. In the return loop of the load current at the time of the gate block, the flywheel diodes 3a, 3b of the own phase and the flywheel diodes 3g, 3h of the other phases are connected in series, so that the flywheel diodes are connected. If there is a flywheel diode having the smallest equivalent capacitor capacitance (hereinafter referred to as junction capacitance) among the diodes 3a, 3b, 3g, and 3h, the flywheel diode is transiently connected to the flywheel diode. A DC voltage between PN of the voltage circuit 1 is applied.
[0013]
Thus, for example, when the junction capacity of the self-phase flywheel diode 3a is the smallest among the self-phase flywheel diodes 3a and 3b and the other phase flywheel diodes 3g and 3h, As described above, the DC voltage (2E (V)) between PN of the DC voltage circuit 1 is transiently applied to the flywheel diode 3a, but the flywheel diode shown in FIG. As shown in the voltage clamp loop of the diode 3a, the cathode side of the flywheel diode 3a → the reset diode 5a → the DC resistance (E (V)) between the PCs by the reset resistor 6a. Since the voltage is clamped by the clamp on the anode side of the clamp capacitor 7a, the clamp diode 8a, and the flywheel diode 3a fixed to the flywheel diode 3a, the flywheel diode 3a has Only the DC voltage (E (V)) is transiently applied, and the DC voltage (E (V)) between the CN is changed by the flywheel diode 3b of the own phase and the flywheel diode of the other phase. 3g and 3h.
[0014]
Accordingly, when the junction capacity of the self-phase flywheel diode 3a is the smallest of the self-phase flywheel diodes 3a and 3b and the other phase flywheel diodes 3g and 3h, The flywheel diodes 3a and 3b and the other phases of the flywheel diodes 3g and 3h are not likely to be damaged by overvoltage.
[0015]
However, among the self-phase flywheel diodes 3a and 3b and the other-phase flywheel diodes 3g and 3h, the self-phase flywheel diode 3b (the self-isolating semiconductor element at the intermediate potential C side) is used. When the junction capacitance of the flywheel diode 2b is the smallest, as shown in the voltage clamp loop of the flywheel diode 3b in FIG. 7B, the cathode of the flywheel diode 3b − Side → flywheel diode 3a → reset diode 5a → clamp capacitor 7a fixed to DC voltage (E (V)) between PC by reset resistor 6a → DC current between CN by reset resistor 6b Clamp capacitor 7b fixed at voltage (E (V)) → reset diode 5b → flywheel diode 3d → flywheel diode 3c Since the voltage is clamped by the loop on the anode side of the flywheel diode 3b, the PN DC voltage (2E (V)) is transiently applied to the flywheel diode 3b. As a result, the flywheel diode 3b may be damaged by overvoltage.
[0016]
[Patent Document 1]
JP 2000-152646 A (FIG. 1, paragraphs 0005 to 0006)
[0017]
[Problems to be solved by the invention]
In the conventional three-level power conversion device, as described above, when the junction capacitance of the flywheel diode of the self-extinguishing semiconductor element on the intermediate potential C side is the smallest, the flywheel is disabled during the gate block. -A PN DC voltage (2E (V)) is transiently applied to the flywheel diode, and the flywheel diode may be damaged by overvoltage, and the resistance of each flywheel diode may be reduced. Even if the voltage, current capacity, and the like are the same, the junction capacitance of each flywheel diode is not always the same, so that the junction capacitance of the flywheel diode of the self-extinguishing semiconductor device at the intermediate potential C is the most. It has been found that small cases can occur. As described above, the flywheel diodes 3c, 3f, and 3g of the other self-extinguishing semiconductor elements on the intermediate potential side also have the smallest junction capacitance when the flywheel is connected to the gate block. The diode may be destroyed by overvoltage. As in the case of the above-described single-phase power converter, the multi-phase power converter also has a possibility that the flywheel diode may be damaged by overvoltage during the gate block.
[0018]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and in a three-level power conversion device using a self-extinguishing semiconductor device as a power conversion device, a self-container on the intermediate potential side during the gate block. It is an object of the present invention to prevent a flywheel diode of an isolated semiconductor device from being damaged by overvoltage.
[0019]
[Means for Solving the Problems]
A three-level power converter according to the present invention is a three-level power converter using a self-extinguishing semiconductor device having a flywheel diode as a power converting device. The junction capacitance of a flywheel diode to which a voltage higher than the intermediate potential is applied is made equivalently larger than the junction capacitance of another flywheel diode, and the flywheel diode to which a voltage higher than the intermediate potential is applied is connected to the flywheel diode. A voltage higher than the intermediate potential is not applied.
[0020]
Further, the three-level power converter according to the present invention is a three-level power converter using a self-extinguishing semiconductor device having a flywheel diode as a power conversion device. In this case, the junction capacitance of the flywheel is made larger than that of the other flywheel diodes.
[0021]
In the three-level power converter according to the present invention, in a three-level power converter using a self-extinguishing semiconductor element having a flywheel diode as a power conversion element, a voltage higher than the intermediate potential at the time of gate block is applied. A gate block of a self-extinguishing semiconductor device paired with such a flywheel diode is performed after an operation of a circuit breaker for interrupting a load current after a gate block of another self-extinguishing semiconductor device. Gate control of each self-extinguishing semiconductor device is performed so that a voltage higher than the intermediate potential is not applied to a flywheel diode to which a voltage higher than the intermediate potential is applied at the time of gate blocking.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. 1 showing an example of a main circuit of a three-level single-phase power converter. The configuration will be described first, and then the operation will be described.
[0023]
First, the configuration will be described below.
[0024]
As shown in FIG. 1 as a typical example, the configuration of the three-level single-phase power converter has a direct current having a high potential P, a low potential N, and an intermediate potential C intermediate between these potentials P and N. A voltage circuit 1, self-extinguishing semiconductor elements 2a to 2h such as a gate commutation type turn-off thyristor and an insulated gate bipolar transistor, flywheel diodes 3a to 3h, and an anode. Reactors 4a to 4d, reset diodes 5a to 5d, reset resistors 6a to 6d, clamp capacitors 7a to 7d, clamp diodes 8a to 8d, voltage dividing capacitors 9a to 9d, and an output terminal OUT. In the actual operation state of the three-level power converter, for example, a system power supply or a motor induced voltage 13 and a cable inductance or system Power source or motor - a state of the inductance 14 is connected in the leakage inductance or the like of the motor.
[0025]
For convenience of explanation, the self-extinguishing semiconductor elements 2a to 2d side will be referred to as a self-phase and the self-extinguishing semiconductor elements 2e to 2h side will be referred to as other phases.
[0026]
The self-phase side includes self-extinguishing semiconductor devices 2a to 2d, flywheel diodes 3a to 3d, anode reactors 4a to 4b, reset diodes 5a to 5b, and reset resistors 6a to 6b. 6b, clamp capacitors 7a to 7b, clamp diodes 8a to 8b, and voltage dividing capacitors 9a to 9b, and the other phase side includes self-extinguishing semiconductor elements 2e to 2h, and a flywheel. The diodes 3e to 3h, the anode reactors 4c to 4d, the reset diodes 5c to 5d, the reset resistors 6c to 6d, the clamp capacitors 7c to 7d, and the clamp diodes 8c to 8d. It comprises pressure capacitors 9c to 9d.
[0027]
The DC voltage circuit 1 is, for example, a circuit that obtains DC by converting the power of a commercial AC power supply. For example, due to an abnormality such as an accident on the commercial AC power supply side, the output voltage on the DC side may be a DC overvoltage.
[0028]
Each of the self-extinguishing semiconductor elements 2e to 2h does not require a snubber circuit, for example, the critical voltage rise rate is not specified, or more specifically, has a critical voltage rise rate exceeding 1 kV / μs. . Specifically, such a self-extinguishing semiconductor device corresponds to, for example, a gate commutation type turn-off thyristor, an insulating type gate bipolar transistor or the like.
[0029]
The flywheel diodes 3a to 3h are connected in antiparallel to corresponding self-isolating semiconductor elements 2a to 2h forming a pair. That is, the flywheel diode 3a is connected in antiparallel to the corresponding self-isolating semiconductor element 2a forming a pair, and the flywheel diode 3b is connected in antiparallel to the corresponding self-isolating semiconductor element 2b forming a pair. Similarly, 3c is connected to 2c, 3d is connected to 2d, 3e is connected to 2e, 3f is connected to 2f, 3g is connected to 2g, and 3h is connected to 2h in anti-parallel.
[0030]
The anode reactor 4a is connected between the anode of the self-extinguishing semiconductor device 2a in the self-isolating semiconductor devices 2a to 2d connected in series and the high potential P terminal of the DC voltage circuit 1 respectively. Are connected in series.
[0031]
The anodized reactor 4b is connected between the cathode of the self-extinguishing semiconductor element 2d of the self-extinguishing semiconductor elements 2a to 2d connected in series and the low potential N terminal of the DC voltage circuit 1 respectively. Are connected in series.
[0032]
The anodic reactor 4c is connected between the anode of the self-extinguishing semiconductor element 2e in the series-connected self-isolating semiconductor elements 2e to 2h and the high potential P terminal of the DC voltage circuit 1. Are connected in series.
[0033]
The anodic reactor 4d is connected between the cathode of the self-extinguishing semiconductor device 2h and the low potential N terminal of the DC voltage circuit 1 in the self-extinguishing semiconductor devices 2e to 2h connected in series. Are connected in series.
[0034]
The series circuit of the reset diode 5a, the clamp capacitor 7a, the clamp capacitor 7b, and the reset diode 5b on the self-phase side is similar to the series circuit of the self-extinguishing semiconductor elements 2a to 2d. The reset diodes 5a and 5b are connected in parallel with the self-extinguishing semiconductor elements 2a to 2d so as to be conductive. The series connection point of the clamp capacitors 7a and 7b in the series circuit of the reset diode 5a, the clamp capacitor 7a, the clamp capacitor 7b, and the reset diode 5b is connected to the intermediate potential of the DC voltage circuit 1. It is connected to the C terminal.
[0035]
The series circuit of the reset diode 5c, the clamp capacitor 7c, the clamp capacitor 7d, and the reset diode 5d on the other phase side is the same as the series circuit of the self-extinguishing semiconductor elements 2e to 2h. The reset diodes 5c and 5d are connected in parallel with the self-extinguishing semiconductor elements 2e to 2h so as to be conductive. The series connection point of the clamp capacitors 7c and 7d in the series circuit of the reset diode 5c, the clamp capacitor 7c, the clamp capacitor 7d, and the reset diode 5d is connected to the intermediate potential of the DC voltage circuit 1. It is connected to the C terminal.
[0036]
The reset resistor 6a on the self-phase side is connected between a series connection point of the reset diode 5a and the clamp capacitor 7a and a terminal on the high potential P of the DC voltage circuit 1 of the anode reactor 4a. Connected between them.
[0037]
The reset resistor 6b on the self-phase side is connected between a series connection point of the reset diode 5b and the clamp capacitor 7b and a low potential N terminal side of the DC voltage circuit 1 of the anode reactor 4b. Connected between them.
[0038]
The reset resistor 6c on the other phase side is connected between a series connection point of the reset diode 5c and the clamp capacitor 7c and a terminal of the anodically reactor 4c at the high potential P terminal of the DC voltage circuit 1. Connected between them.
[0039]
The reset resistor 6d on the other phase side is connected between a series connection point of the reset diode 5d and the clamp capacitor 7d and a terminal of the anodized reactor 4d at the low potential N terminal of the DC voltage circuit 1. Connected between them.
[0040]
The series circuit of the clamp diodes 8a and 8b on the self-phase side is connected in anti-parallel to the series circuit of the self-extinguishing semiconductor elements 2b and 2c on the intermediate potential C side. A series connection point of the clamp diodes 8a and 8b is connected to a terminal of the intermediate potential C of the DC voltage circuit 1.
[0041]
The series circuit of the clamp diodes 8c and 8d on the other phase is connected in anti-parallel to the series circuit of the self-extinguishing semiconductor elements 2f and 2g on the intermediate potential C side. The series connection point of the clamp diodes 8c and 8d is connected to the terminal of the intermediate potential C of the DC voltage circuit 1.
[0042]
The voltage dividing capacitor 9a on the self-phase side is connected in parallel to an anti-parallel circuit of the self-extinguishing semiconductor element 2b and the flywheel diode 3b on the intermediate potential C side. In other words, the voltage dividing capacitor 9a is connected in parallel to the flywheel diode 3b.
[0043]
The voltage dividing capacitor 9b on the self-phase side is connected in parallel to an anti-parallel circuit of the self-extinguishing semiconductor element 2c and the flywheel diode 3c on the intermediate potential C side. In other words, the voltage dividing capacitor 9b is connected in parallel to the flywheel diode 3c.
[0044]
The voltage dividing capacitor 9c on the other phase is connected in parallel to an anti-parallel circuit of the self-extinguishing semiconductor element 2f and the flywheel diode 3f on the intermediate potential C side. In other words, the voltage dividing capacitor 9c is connected in parallel to the flywheel diode 3f.
[0045]
The voltage dividing capacitor 9d on the other phase is connected in parallel to an anti-parallel circuit of the self-extinguishing semiconductor element 2g and the flywheel diode 3g on the intermediate potential C side. In other words, the voltage dividing capacitor 9d is connected in parallel to the flywheel diode 3g.
[0046]
The capacitances of the clamp capacitors 7a to 7d are the same. The capacitances of the voltage dividing capacitors 9a to 9d are the same. Further, by connecting the voltage dividing capacitors 9a and 9b in parallel with the flywheel diode 3b and the flywheel diode 3c as described above, the junction capacitance of the flywheel diode 3a and the flywheel diode 3d is established. On the other hand, the junction capacitance between the flywheel diode 3b and the flywheel diode 3c is equivalently increased.
[0047]
Next, the operation and operation will be described.
[0048]
In the configuration of FIG. 1 described above, for example, if an abnormal DC overvoltage occurs due to an AC-side abnormality such as a system fault or a failure on the AC side of the DC voltage circuit 1, in order to stop the three-level power converter, The self-extinguishing type semiconductor elements 2a to 2h are simultaneously turned from the ignition state to the off state (gate block). In this case, the three-level power converter includes, for example, flywheel diodes 3a, 3b, Due to the conduction of 3g and 3h, the return load current is changed from the output terminal OUT of the own phase → the flywheel diode 3b of the own phase → the flywheel diode 3a of the own phase → DC voltage circuit as shown by the dashed line in FIG. 1 high potential P terminal → intermediate potential C → low potential N terminal → other phase flywheel diode 3h → other phase flywheel diode 3g → other phase output terminal OUT return route It flows.
[0049]
When the flywheel diodes 3a, 3b, 3h and 3g are turned off due to the return load current flowing through the return route and the reverse current going to zero during the gate block, the junction is equivalently performed. Although a voltage is applied to the flywheel diode 3a having a small capacity, the direct current voltage between the high potential P and the intermediate potential C is controlled by the cathode side of the flywheel diode 3a → the reset diode 5a → the reset resistor 6a. (E (V)) clamp clamp 7a → clamp diode 8a → clamp by the loop on the anode side of flywheel diode 3a, so flywheel diode 3a has: Only the DC voltage (E (V)) between the high potential P and the intermediate potential C is transiently applied, and the remaining DC voltage (E (V)) between the intermediate potential C and the low potential N is converted to the equivalent of the own phase. Target A flywheel diode 3b having a large junction capacitance (having a parallel voltage dividing capacitor 9a), a flywheel diode 3h of another phase, and an equivalently large junction capacitance of the other phase (parallel voltage dividing capacitor 9d) And 3 g of flywheel diode.
[0050]
Here, if the flywheel diodes 3b, 3c, 3f, 3g on the intermediate potential C side are not provided with the voltage dividing capacitors 9a, 9b, 9c, 9d equivalently increasing the junction capacitance, As in the prior art, the flywheel diodes 3a, 3b of the self-phase and the flywheel diodes 3g, 3h of the other phase are among the flywheel diodes 3b of the self-phase (the self-phase of the intermediate potential C side). When the junction capacitance of the flywheel diode of the isolated semiconductor element 2b is the smallest, as shown in the voltage clamp loop of the flywheel diode 3b of FIG. The cathode side of flywheel diode 3b → flywheel diode 3a → reset diode 5a → clamp fixed to PC DC voltage (E (V)) by reset resistor 6a Capacitor 7a → Clamp capacitor 7b fixed to CN DC voltage (E (V)) by reset resistor 6b → Reset diode 5b → Fly wheel diode 3d → Fly wheel diode Fly wheel diode 3c → Because the voltage is clamped by the loop on the anode side of the flywheel diode 3b, the flywheel diode 3b transiently receives a PN DC voltage (2E (V)). When applied, the flywheel diode 3b may be destroyed by overvoltage, but the voltage dividing capacitors 9a, 9b, which increase the junction capacitance equivalently to the flywheel diodes 3b, 3c, 3f, 3g on the intermediate potential C side. By providing 9b, 9c, 9d, even if the junction capacity of flywheel diode 3b itself is the smallest, flywheel diode 3b can be used. - The de 3b, eliminates the transiently P-N between the DC voltage (2E (V)) is applied. The same applies to the case where the junction capacitance of any of the other flywheel diodes 3c, 3f, 3g on the intermediate potential C side is the smallest.
[0051]
As described above, if the voltage dividing capacitors 9a, 9b, 9c, 9d are not provided, a flywheel diode (intermediate potential) to which a voltage (2E) higher than the intermediate potential is applied at the time of gate blocking of each self-extinguishing semiconductor device. The flywheel diodes (3b, 3c, 3f, 3g) are connected to the other flywheel diodes 3a, 3d, 3e, 3h by providing voltage dividing capacitors 9a, 9b, 9c, 9d. The flywheel diodes 3b, 3c, 3f, and 3g, which are equivalently larger than the junction capacitance and receive a higher voltage than the intermediate potential unless the voltage dividing capacitors 9a, 9b, 9c, and 9d are provided, Since a high voltage is not applied, unless the voltage dividing capacitors 9a, 9b, 9c and 9d are provided, a voltage (2E) higher than the intermediate potential at the time of gate blocking. Such flywheel - Rudaio - de (intermediate potential side flywheel - Rudaio - de) 3b, 3c, 3f, is a risk that 3g is overvoltage breakdown eliminated. That is, it is possible to obtain a highly reliable and inexpensive three-level power converter that does not cause overvoltage breakdown of the flywheel diode during the gate block.
[0052]
In the first embodiment of the present invention, the DC voltage circuit 1 having three potentials P and N and the intermediate potential C, and a three-level converter capable of outputting the potentials P, N and C are provided. A three-level converter connected in anti-parallel to first to fourth self-extinguishing semiconductor devices 2a to 2d and each of the self-extinguishing semiconductor devices 2a to 2d. The first to fourth flywheel diodes 3a to 3d are connected between a terminal of the potential C of the DC voltage circuit 1 and an anode terminal of the second self-extinguishing semiconductor device 2b. A first clamp diode 8a, a second clamp diode connected between the cathode terminal of the third self-extinguishing semiconductor device 2c and the terminal of the potential C of the DC voltage circuit 1; And the terminal of the potential P of the DC voltage circuit 1 and the first A first anode reactor 4a connected between the anode terminal of the self-isolating semiconductor device 2a and a first reset diode connected in parallel to the first anode reactor 4a. 5a and a first series connection composed of a first reset resistor 6a, a connection point between the first reset diode 5a and the first reset resistor 6a, and a potential C of the DC voltage circuit 1. And a cathode of the fourth self-extinguishing semiconductor element 2d, which can be discharged to the DC voltage circuit 1 only through the first reset resistor 6a. A second anode reactor 4b connected between the terminal and the terminal of the potential N of the DC voltage circuit 1, and a second reset diode connected in parallel to the second anode reactor 4b. 5b and second reset A second series connection composed of a resistor 6b, a connection point between the second reset diode 5b and the second reset resistor 6b, and a terminal of the potential N of the DC voltage circuit 1 A second clamp capacitor 7b that is connected and can be discharged to the DC voltage circuit 1 only through the second reset resistor 6b, the second self-extinguishing semiconductor device 2b, and the third self-extinguishing semiconductor Each of the self-extinguishing semiconductor devices 2a to 2d has a critical voltage rising rate that is not specified or specifically 1 kV / A critical voltage rising rate exceeding .mu.s, a snubber circuit is not required, and a capacitance component of the second flywheel diode 3b is compared with a capacitance component of the first flywheel diode 3a. It is increased, and the fourth flywheel - Rudaio - to the capacitive component of the de 3d, the third flywheel - Rudaio - is also a three-level power converter to increase the capacitance component of de 3c.
[0053]
If a DC power supply is connected between the terminals of the potentials P and N, and an AC load is connected between the output terminal OUT on the self-phase side and the output terminal OUT on the other phase side, a three-level inverter is provided. If a DC load is connected between the terminals of the potentials P and N and an AC power supply is connected between the output terminal OUT on the self-phase side and the output terminal OUT on the other phase, a three-level converter is obtained. Data device.
[0054]
Embodiment 2 FIG.
Embodiment 2 of the present invention will be described based on FIG. 2 showing an example of a main circuit of a three-level single-phase power converter.
[0055]
In the above-described first embodiment of the present invention, the case where the voltage dividing capacitors 9a to 9d are connected in parallel to the flywheel diodes 3b, 3c, 3f and 3g has been exemplified. However, in the second embodiment of the present invention, As shown in FIG. 2, the flywheel diodes 3a, 3d, 3e, 3h are also connected to voltage dividing capacitors 10a, 10b, 10c, 10d as shown in FIG.
[0056]
Here, the capacitances of the voltage dividing capacitors 9a to 9d are the same. The capacitors of the voltage dividing capacitors 10a to 10d have the same capacitance. Further, the capacity of each of the voltage dividing capacitors 9a to 9d is larger than the capacity of each of the voltage dividing capacitors 10a to 10d.
[0057]
In the second embodiment of the present invention, the junction capacitors of the flywheel diodes 3a to 3h themselves are formed by making the voltage dividing capacitors 9a to 9d larger in capacitance than the voltage dividing capacitors 10a to 10d. Irrespective of the characteristics, the equivalent junction capacitance of the flywheel diodes 3b, 3c, 3f, 3g can be surely made larger than the equivalent junction capacitance of the flywheel diodes 3a, 3d, 3e, 3h. In the same manner as in the first embodiment of the present invention, a flywheel diode 3a, 3e or 3d, 3h is supplied with a DC voltage (E (V)) between the high potential P and the intermediate potential C or an intermediate potential. A DC voltage (E (V)) between C and low potential N is applied, and the remaining DC voltage (E (V)) is converted to the flywheel diode 3b of its own phase and the flywheel diode of the other phase. Since the voltage is divided by the equivalent junction capacitances of the gates 3g and 3h, or the equivalent junction capacitances of the flywheel diode 3c of the own phase and the flywheel diodes 3e and 3f of the other phase, If the voltage dividing capacitors 9a to 9d and 10a to 10d are not provided, a DC overvoltage is applied and the flywheel diodes 3b, 3c, 3f, and 3g (at the intermediate potential side) may be destroyed. A highly reliable and inexpensive three-level power converter can be obtained.
[0058]
Embodiment 3 FIG.
Third Embodiment A third embodiment of the present invention will be described with reference to FIG. 3 showing an example of a main circuit of a three-level single-phase power converter.
[0059]
In the above-described first embodiment of the present invention, the case where the voltage dividing capacitors 9a to 9d are connected in parallel to the flywheel diodes 3b, 3c, 3f and 3g has been exemplified. However, in the third embodiment of the present invention, As shown in FIG. 3, there is shown an example in which resistors 11a, 11b, 11c and 11d are connected in series with each of the voltage dividing capacitors 9a to 9d and in parallel with the flywheel diodes 3b, 3c, 3f and 3g. It is.
[0060]
As in the first embodiment of the present invention, the resistors 11a, 11b, 11c, connected in series with the voltage dividing capacitors 9a to 9d and in parallel with the flywheel diodes 3b, 3c, 3f, 3g, respectively. In the case where the self-extinguishing semiconductor elements 2b, 2c, 2c, 2f, 2g are not turned on, the voltage dividing capacitors 9a to 9d discharge when the self-isolating semiconductor elements 2b, 2c, 2f, 2g are turned on. Although the turn-on losses of 2f and 2g increase, as in the third embodiment of the present invention, the flywheel diodes 3b, 3c, are connected in series with each of the voltage dividing capacitors 9a to 9d. By providing resistors 11a, 11b, 11c and 11d connected in parallel to 3f and 3g, the discharge current of the voltage dividing capacitors 9a to 9d is limited by the resistors 11a, 11b, 11c and 11d. And, said self arc extinguishing type semiconductor elements 2b, 2c, 2f, 2 g of motor - can be suppressed N'on loss, it is possible to obtain a highly reliable three-level power converter.
[0061]
Embodiment 4 FIG.
Although not shown, a resistor is connected in series with each of the voltage dividing capacitors 9a to 9d and 10a to 10d and in parallel with the corresponding flywheel diodes 3a to 3h in the second embodiment (FIG. 2) of the present invention. Once connected, each turn-on of self-extinguishing semiconductor elements 2a to 2h in the above-described second embodiment (FIG. 2) of the present invention is performed in the same manner as in the above-described third embodiment (FIG. 3). Loss can be suppressed, and a more reliable three-level power converter can be obtained than in the above-described second embodiment (FIG. 2) of the present invention.
[0062]
Embodiment 5 FIG.
Embodiment 5 of the present invention will be described with reference to FIG. 4 showing an example of a main circuit of a three-level single-phase power converter.
[0063]
In the above-described second embodiment of the present invention, the case where the voltage dividing capacitors 9a, 9b, 9c, 9d, 10a, 10b, 10c, and 10d are provided in parallel with the flywheel diodes 3a to 3h, respectively, has been exemplified. However, in the fifth embodiment of the present invention, as shown in FIG. 4, the voltage dividing capacitors 9a, 9b, 9c, 9d, 10a, 10b, 10c, and 10d in the above-described second embodiment of the present invention are not provided. The combination 12a of the flywheel diodes 3a and 3b, the combination 12b of the flywheel diodes 3c and 3d, the combination 12c of the flywheel diodes 3e and 3f, and the combination 12d of the flywheel diodes 3g and 3h. The characteristics of the junction capacitance of the flywheel diode are selected among the combinations.
[0064]
More specifically, in the combination 12a, the flywheel diode 3b is selectively connected to one having a larger junction capacity than the flywheel diode 3a. Similarly, in the combination 12b, the flywheel diode 3c has a larger junction capacity than the flywheel diode 3d, and in the combination 12c, the flywheel diode 3f has a larger junction capacity than the flywheel diode 3e. In the combination 12d, the flywheel diode 3g is selected and connected to each having a larger junction capacity than the flywheel diode 3h.
[0065]
As a method of selecting the flywheel diodes, the flywheel diodes 3b, 3c, 3f, and 3g on the intermediate potential side select and use those having substantially the same junction capacitance. The other flywheel diodes 3a, 3d, 3e and 3h which are not on the potential side are selected from those having substantially the same junction capacity, and the flywheel diodes 3b and 3c on the intermediate potential side are used. , 3f and 3g may be selected from those having a larger junction capacity than other flywheel diodes 3a, 3d, 3e and 3h which are not on the intermediate potential side.
[0066]
As described above, in the fifth embodiment of the present invention, when the selection and use of the junction capacitance is not performed, a flywheel which receives a voltage (2E) higher than the intermediate potential is applied when the gate of each self-extinguishing semiconductor element is blocked. The junction capacitance of the flywheel (the flywheel diode on the intermediate potential side) 3b, 3c, 3f, 3g is 3b, the other flywheel diode is 3a, and 3c is the other flywheel diode 3d. From 3f, a flywheel diode 3e larger than the other flywheel diode 3e is used for 3g, and a flywheel diode 3h larger than the other flywheel diode 3h is used. A voltage higher than the intermediate potential is not applied to the flywheel diodes 3b, 3c, 3f, 3g to which a voltage is applied. If not used, the flywheel diodes (flywheel diodes on the intermediate potential side) 3b, 3c, 3f and 3g, which receive a voltage (2E) higher than the intermediate potential during gate blocking, are destroyed by overvoltage. Fear is gone. That is, it is possible to obtain an inexpensive three-level power converter with a small number of components and a high reliability without using additional components such as voltage dividing capacitors and resistors as in the first to fourth embodiments of the present invention. .
[0067]
Embodiment 6 FIG.
Embodiment 6 of the present invention will be described with reference to FIG. FIG. 5A is a diagram showing an example of a main circuit of a three-level single-phase power converter, and FIG. 5B is a diagram showing control logic for switching operation and gain of a self-extinguishing semiconductor device (hereinafter abbreviated as GCT). FIG. 5 is a diagram showing a relationship between a lock and an open time of a circuit breaker. In FIG. 5A, the same or corresponding parts as those in FIGS. 1 to 4 are denoted by the same reference numerals, and the same configuration, operation, and function as those in FIGS. Omitted. Also, FIG. 5A has the same circuit configuration as that of FIG. 4 described above, and therefore only the operation description will be described below.
[0068]
In the gate block operation of the GCTs (self-extinguishing semiconductor elements) 2a to 2h, as shown in FIG. 5B, GCTs 2a and 2e and GCTs 2d and 2h are simultaneously referred to as a gate block (gate block 1). Then, as an example, a load current path is formed as shown by the dashed line in FIG. 5A. Since the GCTs 2a, 2e, 2d and 2h are gate blocks, the flywheel diodes 3a and 3e bear the DC voltage (E (V)) between the high potential P and the intermediate potential C, and the flywheel diodes are used. 3d and 3h bear the DC voltage (E (V)) between the intermediate potential C and the low potential N. The voltages of the flywheel diodes 3b, 3c, 3f, 3g become zero because the GCTs 2b, 2c, 2f, 2g forming a pair with them are in a conductive state.
[0069]
As shown in FIG. 5B, the load current is cut off by the circuit breaker 15 in synchronization with the gate block 1, and thereafter, after the circuit breaker opening time (after the load current becomes zero), the GCT 2b , 2c, and GCTs 2f, 2g are simultaneously gate-blocked (referred to as gate-block 2). At the time of the gate block 2, the load current is interrupted by the circuit breaker 15 and is zero, so that the voltage sharing state does not change.
[0070]
As described above, the overvoltage 2E (V) is applied to the flywheel diodes 3b, 3c, 3f, and 3g on the intermediate potential C side by the control device 16 and the circuit breaker 15 in which the above-described control logic is incorporated. No problem occurs, and a highly reliable three-level power converter can be obtained.
[0071]
In the sixth embodiment of the present invention, the DC voltage circuit 1 having three potentials P, N and the intermediate potential C, and a three-level converter capable of outputting the potentials P, N, C are provided. A three-level converter connected in anti-parallel to first to fourth self-extinguishing semiconductor devices 2a to 2d and each of the self-extinguishing semiconductor devices 2a to 2d. The first to fourth flywheel diodes 3a to 3d are connected between a terminal of the potential C of the DC voltage circuit 1 and an anode terminal of the second self-extinguishing semiconductor device 2b. A first clamp diode 8a, a second clamp diode connected between the cathode terminal of the third self-extinguishing semiconductor device 2c and the terminal of the potential C of the DC voltage circuit 1; And the terminal of the potential P of the DC voltage circuit 1 and the first A first anode reactor 4a connected between the anode terminal of the self-isolating semiconductor device 2a and a first reset diode connected in parallel to the first anode reactor 4a. 5a and a first series connection composed of a first reset resistor 6a, a connection point between the first reset diode 5a and the first reset resistor 6a, and a potential C of the DC voltage circuit 1. And a cathode of the fourth self-extinguishing semiconductor element 2d, which can be discharged to the DC voltage circuit 1 only through the first reset resistor 6a. A second anode reactor 4b connected between the terminal and the terminal of the potential N of the DC voltage circuit 1, and a second reset diode connected in parallel to the second anode reactor 4b. 5b and second reset A second series connection composed of a resistor 6b, a connection point between the second reset diode 5b and the second reset resistor 6b, and a terminal of the potential N of the DC voltage circuit 1 A second clamp capacitor 7b that is connected and can be discharged to the DC voltage circuit 1 only through the second reset resistor 6b, the second self-extinguishing semiconductor device 2b, and the third self-extinguishing semiconductor Each of the self-extinguishing semiconductor elements 2a to 2d has a critical voltage rising rate that is not specified or specifically 1 kV / .sup.2, which is constituted by a bridge circuit having an output terminal OUT provided at a connection point with the element 2c. It has a critical voltage rising rate exceeding .mu.s, does not require a snubber circuit, has a circuit breaker 15 between the converter output terminal OUT and the system power supply or the motor induced voltage 13, and has a gate blower at the time of failure stop. After the gates of the first and fourth self-extinguishing semiconductor elements 2a and 2d have been simultaneously gated, the second and third self-extinguishing semiconductor elements 2a and 2d must be opened more than the breaker open time (after the load current has become zero). It is also a three-level power converter having a controller 16 for gate-blocking the self-extinguishing semiconductor elements 2b, 2c.
[0072]
【The invention's effect】
As described above, the present invention relates to a three-level power converter using a self-extinguishing semiconductor device having a flywheel diode as a power converting device. The junction capacitance of a flywheel diode to which a higher voltage is applied is equivalently larger than the junction capacitance of another flywheel diode, and the flywheel diode to which a voltage higher than the intermediate potential is applied has the intermediate potential. Since a higher voltage is prevented from being applied, there is an effect that a highly reliable three-level power converter can be obtained in which the flywheel diode is not overvoltage-destructed during the gate block.
[0073]
Also, the present invention provides a three-level power conversion device using a self-extinguishing semiconductor device having a flywheel diode as a power conversion device, wherein the junction capacitance of the flywheel diode to which a voltage higher than the intermediate potential is applied is as follows: Since the junction capacity of the other flywheel diodes is larger than that of the other flywheel diodes, a highly reliable three-level power converter that does not cause overvoltage breakdown of the flywheel diodes during the gate block can be provided at a low cost with a small number of parts. There is an effect that can be made.
[0074]
Further, the present invention provides a three-level power conversion device using a self-extinguishing semiconductor device having a flywheel diode as a power conversion device, wherein a flywheel diode to which a voltage higher than an intermediate potential is applied at the time of gate blocking. Each self-extinguishing semiconductor device is configured such that a gate block of a self-isolating semiconductor device forming a pair is performed after an operation of a circuit breaker that interrupts a load current after a gate block of another self-isolating semiconductor device. Of the flywheel diode, which is applied with a voltage higher than the intermediate potential at the time of gate blocking, so that a voltage higher than the intermediate potential is not applied to the flywheel diode. There is an effect that a highly reliable three-level power conversion device that does not need to be obtained can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a first embodiment of the present invention and is a diagram illustrating an example of a main circuit of a three-level single-phase power converter.
FIG. 2 is a diagram illustrating a second embodiment of the present invention and is a diagram illustrating an example of a main circuit of a three-level single-phase power converter.
FIG. 3 is a diagram illustrating a third embodiment of the present invention and is a diagram illustrating an example of a main circuit of a three-level single-phase power converter.
FIG. 4 is a diagram illustrating a fifth embodiment of the present invention, and illustrating an example of a main circuit of a three-level single-phase power converter.
FIGS. 5A and 5B are diagrams showing a sixth embodiment of the present invention, in which FIG. 5A shows an example of a main circuit of a three-level single-phase power converter, and FIG. FIG. 4 is a diagram showing a relationship between a switching operation of GCT), a gate block, and an open time of a circuit breaker.
FIG. 6 is a diagram related to a conventional three-level power converter, in which (A) shows an example of a return loop of the load current after the gate block in the single-phase power converter by a dashed line arrow, and (B). () Shows the load current flowing through the flywheel diode at the time of gate blocking, and (C) shows the equivalent circuit of the load current return loop.
FIG. 7 is a diagram relating to a conventional three-level power conversion device, in which (A) is a flywheel diode 3a (a flywheel of a self-extinguishing semiconductor device other than the self-extinguishing semiconductor device at the intermediate potential C side). (B) is a diagram showing a voltage clamp loop of a flywheel diode 3B (a flywheel diode of a self-extinguishing semiconductor device at the intermediate potential C side). It is.
[Explanation of symbols]
1 DC voltage circuit,
2a to 2d self-extinguishing semiconductor devices (gate commutation type turn-off thyristors),
3a to 3h flywheel diodes,
4a, 4b, 4c, 4d anodreactor,
5a, 5b, 5c, 5d reset diodes,
6a, 6b, 6c, 6d reset resistor,
7a, 7b, 7c, 7d Clamp capacitors,
8a, 8b, 8c, 8d Clamp diode,
9a, 9b, 9c, 9d, 10a, 10b, 10c, 10d voltage dividing capacitors,
11a, 11b, 11c, 11d resistance,
12a, 12b, 12c, 12d Combination of flywheel diodes,
13 System power supply or motor induced voltage,
14 Inductance such as cable inductance, system power supply or motor leakage inductance,
15 breaker,
16 control devices,
P, C, N Terminal voltage of DC voltage circuit,
OUT Output terminal.

Claims

In a three-level power conversion device using a self-extinguishing semiconductor device having a flywheel diode as a power conversion device, a flywheel diode to which a voltage higher than an intermediate potential is applied when each self-extinguishing semiconductor device is gate-blocked. The junction capacitance of the flywheel diode is equivalently larger than the junction capacitance of another flywheel diode so that a flywheel diode to which a voltage higher than the intermediate potential is applied does not receive a voltage higher than the intermediate potential. A three-level power conversion device characterized by the above-mentioned.

In a three-level power conversion device using a self-extinguishing semiconductor device having a flywheel diode as a power conversion device, the junction capacitance of the flywheel diode of the self-extinguishing semiconductor device on the intermediate potential side is reduced. The flywheel diode of the self-extinguishing semiconductor element on the potential side is equivalently larger than the junction capacitance of the flywheel diode, and a voltage higher than the intermediate potential is applied to the flywheel diode of the self-isolating semiconductor element on the intermediate potential side. A three-level power conversion device, characterized in that the power is not applied.

3. A three-level power converter according to claim 1, wherein a voltage dividing capacitor is connected in parallel to a flywheel diode to which a voltage higher than the intermediate potential is applied, so that a flywheel diode to which a voltage higher than the intermediate potential is applied. The junction capacitance of the negative electrode is made equivalently larger than the junction capacitance of the other flywheel diodes, so that a voltage higher than the intermediate potential is not applied to a flywheel diode to which a voltage higher than the intermediate potential is applied. A three-level power converter, comprising:

3. A three-level power converter according to claim 1, wherein a voltage dividing capacitor is connected in parallel to each flywheel diode, and the voltage dividing capacitor of the flywheel diode to which a voltage higher than the intermediate potential is applied. By making the capacitance larger than the capacitance of the voltage dividing capacitor of the other flywheel diode, the junction capacitance of the flywheel diode to which a voltage higher than the intermediate potential is applied can be made larger than the junction capacitance of the other flywheel diode. A three-level power conversion device, wherein a flywheel diode to which a voltage higher than the intermediate potential is applied does not receive a voltage higher than the intermediate potential.

3. A three-level power converter according to claim 1, wherein a resistor and a voltage dividing capacitor connected in series to each other are connected in parallel to a flywheel diode to which a voltage higher than the intermediate potential is applied. The junction capacitance of a flywheel diode to which a higher voltage is applied is equivalently larger than the junction capacitance of another flywheel diode, and the flywheel diode to which a voltage higher than the intermediate potential is applied has the intermediate potential. A three-level power converter, wherein higher voltage is not applied.

In a three-level power conversion device using a self-extinguishing semiconductor device having a flywheel diode as a power conversion device, the junction capacitance of a flywheel diode to which a voltage higher than the intermediate potential is applied can be reduced by using another flywheel diode. 3. A three-level power converter, wherein the junction capacitance of the flywheel diode is larger than the junction potential of the flywheel diode so that a flywheel diode to which a voltage higher than the intermediate potential is applied does not receive a voltage higher than the intermediate potential.

In a three-level power converter using a self-extinguishing semiconductor device having a flywheel diode as a power conversion element, three-level power using a self-extinguishing semiconductor device having a flywheel diode as a power conversion element In the converter, a gate block of a self-extinguishing semiconductor device paired with a flywheel diode to which a voltage higher than the intermediate potential is applied at the time of gate blocking is replaced with a gate block of another self-extinguishing semiconductor device after the gate block. Gate control of each self-extinguishing type semiconductor element is performed as in the case of the operation of the circuit breaker for interrupting the load current, and the flywheel diode, which receives a voltage higher than the intermediate potential during gate blocking, is higher than the intermediate potential. A three-level power converter, wherein no voltage is applied.