JP4328544B2

JP4328544B2 - Power converter

Info

Publication number: JP4328544B2
Application number: JP2003034684A
Authority: JP
Inventors: 秀幸高岡
Original assignee: Toshiba Mitsubishi Electric Industrial Systems Corp
Current assignee: Toshiba Mitsubishi Electric Industrial Systems Corp
Priority date: 2003-02-13
Filing date: 2003-02-13
Publication date: 2009-09-09
Anticipated expiration: 2023-02-13
Also published as: JP2004248389A

Description

【０００１】
【発明の属する技術分野】
本発明は、電力変換装置に係り、特に各相間の電圧不均衡を補正するようにした単位インバータ方式の電力変換装置に関する。
【０００２】
【従来の技術】
三相電力を出力する電力変換装置において、電力変換装置の大容量化、高電圧化を目的とし、また、出力波形を改善するために、例えば特許文献１に示すような電力変換装置が知られている。この電力変換装置は、三相電源から２次側に複数の巻線を持った変圧器を介して三相交流電力を複数台の単位インバータへ供給する。単位インバータは３グループに分割され、各グループの単位インバータの出力は夫々直列に接続され、そのグループ同志の一方を中性点として接続し、その他方を夫々３相の交流電動機の各相に接続することにより、交流電動機に三相交流電力を供給している。
【０００３】
尚、前述の単位インバータの主回路は、変圧器の２次巻線からの電力を整流回路及び直流平滑コンデンサで直流電力に変換し、単相インバータ回路で任意の周波数、電圧を持った電力に変換するよう構成されている。
【０００４】
このような単位インバータ方式の電力変換装置において、整流回路側だけを直列多重接続し、単位インバータは単一の大容量の単相インバータとした構成とすることも考えられる（例えば特許文献２参照。）。この場合、単相インバータは高圧インバータとなることが多いが、近年のパワーデバイス技術の進歩により、高圧インバータは比較的容易に実現できるようになってきている。
【０００５】
【特許文献１】
特開平１１−１２２９４３号公報（第１４頁、図１）
【０００６】
【特許文献２】
特許第３１７１５５１号公報（第８−９頁、図１）
【０００７】
【発明が解決しようとする課題】
上述したように、整流回路側だけを直列多重接続し、単位インバータは大容量の単相インバータ３台を用いた電力変換装置を使用する場合、多重直列接続した整流回路の素子の一部が損傷した時などに生じる単相インバータ間の直流電圧不均衡により、直流電圧の不均衡がそのまま変換装置出力の相電圧不均衡となって現れてしまうという問題点があった。
【０００８】
このような相電圧の不均衡は、負荷となる交流電動機に不均衡電流を生じ、損失の増大やトルク脈動の増大を招く恐れがある。
【０００９】
本発明は上記問題を解決するためになされたもので、単相インバータ間の直流電圧不均衡発生時にインバータ装置の出力相電圧の不均衡を抑制することが可能な電力変換装置を提供する事を目的とする。
【００１０】
【課題を解決するための手段】
上記目的を達成するために、本発明は、２次巻線を複数個有する入力変圧器と、前記２次巻線に１対１で接続される単位整流器を複数台直列接続して成る３組の整流回路と、前記整流回路の夫々の直流出力電圧を交流電圧に変換し、各相を構成する３台の単相インバータをＹ接続して成る３相インバータ装置と、前記夫々の単相インバータの出力電圧を制御する制御回路とから構成され、前記制御回路は、前記単相インバータの直流電圧の不均衡に起因する前記３相インバータ装置の相電圧の不均衡を夫々抑制する補正手段を有し、前記補正手段は、前記３台の単相インバータに供給される直流出力電圧を夫々検出する直流電圧検出手段と、この検出された直流出力電圧の最大値を選択する最大値選択手段と、この最大値を前記直流電圧検出手段の出力で除して夫々係数を演算する係数演算手段と、この係数演算手段の出力と各相の電圧指令値を乗じて前記各単相インバータへの補正電圧指令値を夫々出力する補正値出力手段とを備えたことを特徴とする。
また、本発明は、２次巻線を複数個有する入力変圧器と、前記２次巻線に１対１で接続される単位整流器を複数台直列接続して成る３組の整流回路と、前記整流回路の夫々の直流出力電圧を交流電圧に変換し、各相を構成する３台の単相インバータをＹ接続して成る３相インバータ装置と、前記夫々の単相インバータの出力電圧を制御する制御回路とから構成され、前記制御回路は、前記単相インバータの直流電圧の不均衡に起因する前記３相インバータ装置の相電圧の不均衡を夫々抑制する補正手段を有し、前記補正手段は、前記３台の単相インバータに供給される直流出力電圧を夫々検出する直流電圧検出手段と、この直流電圧検出手段の出力に含まれる高周波数成分を夫々除去する高周波成分除去手段と、この高周波成分除去手段の出力の最大値を選択する最大値選択手段と、この最大値選択手段の出力を前記高周波成分除去手段の出力で除して夫々係数を演算する係数演算手段と、この係数演算手段の出力の上限値を夫々制限する上限値制限手段と、この上限値制限手段の出力と各相の電圧指令値を乗じて前記各単相インバータへの補正電圧指令値を夫々出力する補正値出力手段とを備えたことを特徴とする。
また、本発明は、２次巻線を複数個有する入力変圧器と、前記２次巻線に１対１で接続される単位整流器を複数台直列接続して成る３組の中性点を有する３レベル整流回路と、この３レベル整流回路の夫々の直流出力電圧を交流電圧に変換し、各相を構成する３台の単相３レベルインバータをＹ接続して成る３相インバータ装置と、前記単相３レベルインバータの出力電圧を夫々制御する制御回路とから構成され、前記制御回路は、前記単相３レベルインバータの正側及び負側の直流電圧の不均衡に起因する前記３相インバータ装置の出力電圧の不均衡を夫々抑制する補正手段を有し、前記補正手段は、前記３レベルインバータに供給される正側及び負側直流電圧を夫々検出する直流電圧検出手段と、この直流電圧検出手段の出力の最大値を選択する最大値選択手段と、この最大値選択手段の出力を前記直流電圧検出手段の出力で除して夫々係数を演算する係数演算手段と、各相の電圧指令値の正値を抽出する正値抽出手段と、各相の電圧指令値の負値を抽出する負値抽出手段と、前記係数演算手段の出力と前記正値抽出手段の出力の積、及び前記係数演算手段の出力と前記負値抽出手段の出力の積を加算して前記各３レベル単相インバータへの補正電圧指令値を夫々出力する補正値出力手段とを備えたことを特徴とする。
さらに、本発明は、２次巻線を複数個有する入力変圧器と、前記２次巻線に１対１で接続される単位整流器を複数台直列接続して成る３組の中性点を有する３レベル整流回路と、この３レベル整流回路の夫々の直流出力電圧を交流電圧に変換し、各相を構成する３台の単相３レベルインバータをＹ接続して成る３相インバータ装置と、前記単相３レベルインバータの出力電圧を夫々制御する制御回路とから構成され、前記制御回路は、前記単相３レベルインバータの正側及び負側の直流電圧の不均衡に起因する前記３相インバータ装置の出力電圧の不均衡を夫々抑制する補正手段を有し、前記補正手段は、前記３レベルインバータに供給される正側及び負側直流電圧を夫々検出する直流電圧検出手段と、この直流電圧検出手段の出力の高周波数成分を夫々除去する高周波成分除去手段と、この高周波成分除去手段の出力の最大値を選択する最大値選択手段と、この最大値選択手段の出力を前記高周波成分除去手段の出力で除して夫々係数を演算する係数演算手段と、この係数演算手段の出力の上限値を制限する上限値制限手段と、各相の電圧指令値の正値を抽出する正値抽出手段と、各相の電圧指令値の負値を抽出する負値抽出手段と、前記係数演算手段の出力と前記正値抽出手段の出力の積、及び前記係数演算手段の出力と前記負値抽出手段の出力の積を加算して前記各３レベルインバータへの補正電圧指令値を夫々出力する補正値出力手段とを備えたことを特徴とする。
【００１２】
本発明によれば、単相インバータ間の直流電圧不均衡発生時にインバータ装置の出力相電圧の不均衡を抑制することが可能な電力変換装置を提供することができる。
【００１３】
【発明の実施の形態】
（第１の実施の形態）
以下に、本発明による電力変換装置の第１の実施の形態を図１を用いて説明する。図１は本発明の第１の実施の形態に係る電力変換装置の構成図である。
【００１４】
入力変圧器１は複数個の２次巻線を有し、夫々の２次巻線はヒューズFを介して整流器Rに接続されている。これら複数台の整流器Rは３グループに分割され、各グループに属する複数台の整流器Rの直流出力は夫々直列に接続され、整流回路２ａ、２ｂ及び２ｃを形成している。整流回路２ａ、２ｂ及び２ｃの直流出力は単相インバータ４ａ、４ｂ及び４ｃに夫々接続され、所望の周波数、電圧の交流を得ている。これらの単相インバータ４ａ、４ｂ及び４ｃの出力はＹ接続され、中性点を持つ３相インバータ装置を形成すると共に、リアクトルLを介して交流電動機Ｍに３相電力を供給している。
【００１５】
以上が図１の主回路構成である。以下制御回路の構成について説明する。尚、図１では、本発明に直接関係する電圧制御回路部分を中心に描いてあり、その他の制御回路は省略されている。
【００１６】
整流回路２ａ、２ｂ及び２ｃの直流出力は、直流出力線路間に接続した直流電圧検出回路３ａ、３ｂ及び３ｃで夫々検出される。この検出値は最大値検出回路５に入力され、最大値を得る。この得られた最大値を係数演算器６ａ、６ｂ及び６ｃに入力し、この係数演算器６ａ、６ｂ及び６ｃでは、この最大値を前述の直流電圧検出回路３ａ、３ｂ及び３ｃの検出値で夫々除算する。更に、これらの演算で得られた値を乗算器７ａ、７ｂ及び７ｃに入力し、単相インバータ４ａ、４ｂ及び４ｃの電圧指令値Ｖ*u、Ｖ*v及びＶ*wと夫々乗算される。このようにして得られた各補正電圧指令値をＰＷＭ制御器８ａ、８ｂ及び８ｃに入力し、単相インバータ４ａ、４ｂ及び４ｃの主回路デバイスのゲート制御信号に変換する。
【００１７】
次に、以上の構成における図１の動作について説明する。
【００１８】
入力変圧器１の複数個の２次巻線から得られる交流を整流器Rで整流し、これを直列に接続した整流回路２ａ、２ｂ及び２ｃの各直流出力電圧は、通常時には同一となる様になっている。すなわち、各単相インバータ４ａ、４ｂ及び４ｃの直流電圧が全て同一値Ｖ０で平衡状態が保たれている場合は、係数演算器６ａ、６ｂ及び６ｃの出力は１となり、この時の補正電圧指令値は各相の電圧指令値と等しくなる。
【００１９】
この状態から、例えば、Ｕ相用単相インバータ４ａの直流電圧のみがＶ１まで低下した事象を想定すると、最大値選択回路５の出力はＶ０、係数演算器６ａ、６ｂ及び６ｃの出力は夫々、６ａがＶ０／Ｖ１、６ｂ及び６ｃが１となる。これらの出力が各相の電圧指令値Ｖ*u、Ｖ*v及びＶ*wに夫々乗じられる結果、最終的な補正電圧指令値はＵ相用だけが直流電圧の逆比で補正され、ＰＷＭ制御器８ａにより単相インバータ４ａの出力をＶ０／Ｖ１倍するようなゲートパルスがＵ相用単相インバータ４ａに与えられ、この結果３相出力電圧は平衡化される。
【００２０】
このようにして、単相インバータ間の直流電圧不均衡発生時にインバータ装置の出力相電圧の不均衡を抑制することが可能な電力変換装置を提供することができる。
【００２１】
（第２の実施の形態）
図２は本発明の第２の実施の形態に係る電力変換装置の構成図である。この第２の実施の形態の各部について、図１の第1の実施の形態に係る電力変換装置の各部と同一部分は同一符号で示し、その説明を省略する。この第2の実施の形態が、第1の実施の形態と異なる点は、直流電圧検出回路３ａ、３ｂ及び３ｃの出力にローパスフィルタ１０ａ、１０ｂ及び１０ｃを夫々挿入している点、及び係数演算器６ａ、６ｂ及び６ｃの出力にリミッタ９ａ、９ｂ及び９ｃを夫々挿入している点である。
【００２２】
直流電圧には電源周波数の６倍調波及び単相インバータ出力周波数の４倍調波の高周波リプル電圧が重畳されるため、ローパスフィルタ１０ａ、１０ｂ及び１０ｃの挿入により前記リプル電圧は除去される。このように構成することにより最大値選択回路５並びに係数演算器６ａ、６ｂ及び６ｃの動作精度を向上させることができる。
【００２３】
また不平衡が増大した際に、補正電圧指令値が単相インバータ４ａ、４ｂ及び４ｃの電圧制御範囲を逸脱しないようにリミッタ９ａ、９ｂ及び９ｃによって上限値を設けたので、電力変換装置に安定した動作を行なわせることができる。
【００２４】
このようにすれば、単相インバータ間の直流電圧不均衡発生時にインバータ出力相電圧の不均衡を抑制することが可能な安定度の高い電力変換装置を提供することができる。
【００２５】
（第３の実施の形態）
図３は本発明の第３の実施の形態に係る電力変換装置の構成図である。この第３の実施の形態の各部について、図１の第1の実施の形態に係る電力変換装置の各部と同一部分は同一符号で示し、その説明を省略する。この第３の実施の形態が、第1の実施の形態と異なる点は、単相インバータ４ａ、４ｂ及び４ｃが、直流中性点電圧を利用した３レベル方式となっている点である。この図３に示したように、整流回路２ａ、２ｂ及び２ｃ側に中性点を設けない場合には、図１の第１の実施の形態と同様の電圧制御回路の構成を適用することができる。
【００２６】
このようにして、３レベル単相インバータ間の直流電圧不均衡発生時にインバータ装置の出力相電圧の不均衡を抑制することが可能な電力変換装置を提供することができる。
【００２７】
（第４の実施の形態）
図４は本発明の第４の実施の形態に係る電力変換装置の構成図である。この第４の実施の形態の各部について、図２の第２の実施の形態に係る電力変換装置の各部と同一部分は同一符号で示し、その説明を省略する。この第４の実施の形態が、第２の実施の形態と異なる点は、単相インバータ４ａ、４ｂ及び４ｃが、直流中性点電圧を利用した３レベル方式となっている点である。
【００２８】
このようにすれば、第２の実施の形態と同様、ローパスフィルタ１０ａ、１０ｂ及び１０ｃにより、高周波成分を除去し、且つリミッタ９ａ、９ｂ及び９ｃにより電圧制御の安定性を確保しているので、３レベル単相インバータ間の直流電圧不均衡発生時にインバータ装置の出力相電圧の不均衡を抑制することが可能な安定度の高い電力変換装置を提供することができる。
【００２９】
（第５の実施の形態）
図５は本発明の第５の実施の形態に係る電力変換装置の構成図である。この第５の実施の形態の各部について、図３の第３の実施の形態に係る電力変換装置の各部と同一部分は同一符号で示し、その説明を省略する。この第５の実施の形態が、第３の実施の形態と異なる点は、整流回路２ａ、２ｂ及び２ｃの夫々の中性点と単相インバータ４ａ、４ｂ及び４ｃの中性点が接続されている点、また直流電圧検出器３ａ、３ｂ、３ｃ、３ｄ、３ｅ及び３ｆと、係数演算器６ａ、６ｂ、６ｃ、６ｄ、６ｅ及び６ｆと、乗算器７ａ、７ｂ、７ｃ、７ｄ、７ｅ及び７ｆとを単相インバータ４ａ、４ｂ及び４ｃの正側直流及び負側直流用に独立に備えている点、更に３相電圧指令Ｖ*u、Ｖ*v及びＶ*wを正側と負側に分離するための正値通過フィルタ１１ａ、１１ｂ及び１１ｃ、並びに負値通過フィルタ１２ａ、１２ｂ及び１２ｃを備えている点である。
【００３０】
このように、整流器Ｒと３レベル単相インバータ４ａ、４ｂ及び４ｃの中性点が接続されている場合、単相インバータ４ａ、４ｂ及び４ｃの正側直流電圧と負側直流電圧の不平衡も補正対象とし、相電圧基準の正側と負側に独立の係数を乗じる構成として３相インバータ装置の出力電圧を平衡化することが可能となる。
【００３１】
このようにすれば、３レベル単相インバータ間の直流電圧不均衡発生時にインバータ装置の出力相電圧の不均衡を正側と負側を独立に抑制することが可能な電力変換装置を提供することができる。
【００３２】
（第６の実施の形態）
図６は本発明の第６の実施の形態に係る電力変換装置の構成図である。この第６の実施の形態の各部について、図５の第５の実施の形態に係る電力変換装置の各部と同一部分は同一符号で示し、その説明を省略する。この第６の実施の形態が、第５の実施の形態と異なる点は、直流電圧検出回路３ａ、３ｂ、３ｃ、３ｄ、３ｅ及び３ｆの出力にローパスフィルタ１０ａ、１０ｂ、１０ｃ、１０ｄ、１０ｅ及び１０ｆを夫々挿入した点、また係数演算器６ａ、６ｂ、６ｃ、６ｄ、６ｅ及び６ｆの出力にリミッタ９ａ、９ｂ、９ｃ、９ｄ、９ｅ及び９ｃを夫々挿入した点である。
【００３３】
直流電圧には電源周波数の６倍調波及び単相インバータ出力周波数の４倍調波のリプル電圧が重畳されるため、第２の実施の形態と同様に、ローパスフィルタ１０ａ、１０ｂ、１０ｃ、１０ｄ、１０ｅ及び１０ｆの挿入により前記リプル電圧を除去する。このように構成すれば最大値選択回路５あるいは係数演算器６ａ、６ｂ及び６ｃの動作精度を向上させることができる。
【００３４】
また不平衡が増大した際に補正出力が単相インバータ４ａ、４ｂ及び４ｃの電圧制御範囲を逸脱しないようリミッタ９ａ、９ｂ、９ｃ、９ｄ、９ｅ及び９ｆにより上限値を設けることにより電力変換装置の安定動作を得ることができる。
【００３５】
異常の実施の形態によれば、３レベル単相インバータ間の直流電圧不均衡発生時にインバータ装置の出力相電圧の不均衡を正側と負側を独立に抑制することが可能な安定度の高い電力変換装置を提供することができる。
【００３６】
尚、以上の説明では、インバータ装置の出力電圧と出力周波数の関連については言及していないが、本発明の電力変換装置は、通常のいわゆるＶ／Ｆ一定制御、また励磁電流とトルク電流を独立して制御するベクトル制御やセンサレスベクトル制御にも適用可能であることは勿論である。
【００３７】
【発明の効果】
以上述べたように、本発明によれば単相インバータ間の直流電圧不均衡発生時にインバータ出力相電圧の不均衡を抑制することが可能な電力変換装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の第1の実施の形態に係る電力変換装置の構成図。
【図２】本発明の第２の実施の形態に係る電力変換装置の構成図。
【図３】本発明の第３の実施の形態に係る電力変換装置の構成図。
【図４】本発明の第４の実施の形態に係る電力変換装置の構成図。
【図５】本発明の第５の実施の形態に係る電力変換装置の構成図。
【図６】本発明の第６の実施の形態に係る電力変換装置の構成図。
【符号の説明】
１入力変圧器
２ａ、２ｂ、２ｃ整流回路
３ａ、３ｂ、３ｃ、３ｄ、３ｅ、３ｆ直流電圧検出回路
４ａ、４ｂ、４ｃインバータ
５最大値選択回路
６ａ、６ｂ、６ｃ、６ｄ、６ｅ、６ｆ係数演算器
７ａ、７ｂ、７ｃ、７ｄ、７ｅ、７ｆ乗算器
８ａ、８ｂ、８ｃＰＷＭ制御器
９ａ、９ｂ、９ｃ、９ｄ、９ｅ、９ｆリミッタ
１０ａ、１０ｂ、１０ｃ、１０ｄ、１０ｅ、１０ｆローパスフィルタ
１１ａ、１１ｂ、１１ｃ正値通過フィルタ
１２ａ、１２ｂ、１２ｃ負値通過フィルタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power conversion device, and more particularly to a unit inverter type power conversion device that corrects voltage imbalance between phases.
[0002]
[Prior art]
In order to increase the capacity and voltage of a power conversion device in a power conversion device that outputs three-phase power, and to improve the output waveform, for example, a power conversion device as shown in Patent Document 1 is known. ing. This power converter supplies three-phase AC power to a plurality of unit inverters via a transformer having a plurality of windings on the secondary side from a three-phase power source. The unit inverter is divided into three groups, and the output of the unit inverter of each group is connected in series, one of the groups is connected as a neutral point, and the other is connected to each phase of the three-phase AC motor By doing so, three-phase AC power is supplied to the AC motor.
[0003]
The main circuit of the unit inverter described above converts the power from the secondary winding of the transformer into DC power by a rectifier circuit and a DC smoothing capacitor, and converts it to power having an arbitrary frequency and voltage by a single-phase inverter circuit. Is configured to convert.
[0004]
In such a unit inverter type power converter, it is also conceivable that only the rectifier circuit side is connected in series and the unit inverter is configured as a single large-capacity single-phase inverter (see, for example, Patent Document 2). ). In this case, the single-phase inverter is often a high-voltage inverter, but with the recent advancement of power device technology, the high-voltage inverter can be realized relatively easily.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-122943 (page 14, FIG. 1)
[0006]
[Patent Document 2]
Japanese Patent No. 3171551 (page 8-9, FIG. 1)
[0007]
[Problems to be solved by the invention]
As described above, when only the rectifier circuit side is connected in series and a power converter using three large-capacity single-phase inverters is used as a unit inverter, some elements of the rectifier circuit connected in multiple series are damaged. Due to the DC voltage imbalance between the single-phase inverters that occurs during the operation, the DC voltage imbalance appears as it is as the phase voltage imbalance of the converter output.
[0008]
Such an imbalance in phase voltage may cause an unbalanced current in the AC motor serving as a load, leading to an increase in loss and an increase in torque pulsation.
[0009]
The present invention has been made to solve the above problem, and provides a power converter that can suppress an imbalance in output phase voltage of an inverter device when a DC voltage imbalance between single-phase inverters occurs. Objective.
[0010]
[Means for Solving the Problems]
To achieve the above object, the present onset Ming, an input transformer with a plurality of secondary windings, comprising a unit rectifier is connected in one-to-one to the secondary winding and multiple series 3 A pair of rectifier circuits, a three-phase inverter device formed by converting each DC output voltage of the rectifier circuit into an AC voltage, and Y-connecting three single-phase inverters constituting each phase; A control circuit for controlling the output voltage of the inverter, and the control circuit includes correction means for respectively suppressing the phase voltage imbalance of the three-phase inverter device caused by the DC voltage imbalance of the single-phase inverter. Yes, and the correction means includes a DC voltage detecting means for respectively detecting the DC output voltage supplied to the three single-phase inverters, the maximum value selecting means for selecting the maximum value of the detected DC output voltage This maximum value is detected by the DC voltage Coefficient calculation means for calculating the coefficient by dividing by the output of the stage, and a correction value for multiplying the output of the coefficient calculation means and the voltage command value for each phase to output the correction voltage command value for each single-phase inverter, respectively Output means .
The present invention also provides an input transformer having a plurality of secondary windings, three sets of rectifier circuits formed by connecting a plurality of unit rectifiers connected in a one-to-one relationship to the secondary windings, Each DC output voltage of the rectifier circuit is converted into an AC voltage, and a three-phase inverter device formed by Y-connecting three single-phase inverters constituting each phase, and the output voltage of each of the single-phase inverters are controlled. A control circuit, and the control circuit includes a correction unit that suppresses a phase voltage imbalance of the three-phase inverter device caused by a DC voltage imbalance of the single-phase inverter, respectively. DC voltage detecting means for detecting DC output voltages supplied to the three single-phase inverters, high frequency component removing means for removing high frequency components included in the output of the DC voltage detecting means, and the high frequency Component removal means Maximum value selecting means for selecting the maximum value of the output, coefficient calculating means for calculating the coefficient by dividing the output of the maximum value selecting means by the output of the high frequency component removing means, and the upper limit value of the output of the coefficient calculating means Upper limit value limiting means, and correction value output means for multiplying the output of the upper limit value limiting means and the voltage command value of each phase and outputting the corrected voltage command value to each single-phase inverter, respectively. It is characterized by that .
Further, the present invention has three sets of neutral points formed by serially connecting an input transformer having a plurality of secondary windings and a plurality of unit rectifiers connected to the secondary windings on a one-to-one basis. A three-level rectifier circuit, a three-phase inverter device formed by converting each DC output voltage of the three-level rectifier circuit into an AC voltage and Y-connecting three single-phase three-level inverters constituting each phase; And a control circuit that controls the output voltage of the single-phase three-level inverter, respectively, and the control circuit includes the three-phase inverter device caused by an imbalance between the positive and negative DC voltages of the single-phase three-level inverter. Correction means for respectively suppressing the imbalance in output voltage of the output voltage, the correction means detecting DC voltage detection means for detecting positive and negative DC voltages supplied to the three-level inverter, and DC voltage detection The maximum output of the means A maximum value selection means for selecting, a coefficient calculation means for calculating the coefficient by dividing the output of the maximum value selection means by the output of the DC voltage detection means, and a positive value for extracting the positive value of the voltage command value of each phase. A value extraction means, a negative value extraction means for extracting a negative value of the voltage command value of each phase, a product of an output of the coefficient calculation means and an output of the positive value extraction means, and an output of the coefficient calculation means and the negative Correction value output means for adding the products of the outputs of the value extraction means and outputting correction voltage command values to each of the three-level single-phase inverters .
Furthermore, the present invention has three sets of neutral points formed by connecting in series a plurality of unit rectifiers connected to the secondary winding in a one-to-one relationship with a plurality of secondary transformers. A three-level rectifier circuit, a three-phase inverter device formed by converting each DC output voltage of the three-level rectifier circuit into an AC voltage and Y-connecting three single-phase three-level inverters constituting each phase; And a control circuit that controls the output voltage of the single-phase three-level inverter, respectively, and the control circuit includes the three-phase inverter device caused by an imbalance between the positive and negative DC voltages of the single-phase three-level inverter. Correction means for respectively suppressing the imbalance in output voltage of the output voltage, the correction means detecting DC voltage detection means for detecting positive and negative DC voltages supplied to the three-level inverter, and DC voltage detection Means output high frequency A high frequency component removing means for removing each component, a maximum value selecting means for selecting the maximum value of the output of the high frequency component removing means, and an output of the maximum value selecting means divided by the output of the high frequency component removing means, respectively. Coefficient calculation means for calculating a coefficient, upper limit value limiting means for limiting the upper limit value of the output of the coefficient calculation means, positive value extraction means for extracting the positive value of the voltage command value for each phase, and voltage command for each phase A negative value extracting means for extracting a negative value of the value; a product of the output of the coefficient calculating means and the output of the positive value extracting means; and a product of the output of the coefficient calculating means and the output of the negative value extracting means. And correction value output means for outputting a correction voltage command value to each of the three-level inverters .
[0012]
ADVANTAGE OF THE INVENTION According to this invention, the power converter device which can suppress the imbalance of the output phase voltage of an inverter apparatus at the time of DC voltage imbalance generation between single phase inverters can be provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of a power converter according to the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of a power conversion device according to a first embodiment of the present invention.
[0014]
The input transformer 1 has a plurality of secondary windings, and each secondary winding is connected to a rectifier R via a fuse F. The plurality of rectifiers R are divided into three groups, and the DC outputs of the plurality of rectifiers R belonging to each group are connected in series to form rectifier circuits 2a, 2b and 2c. The direct current outputs of the rectifier circuits 2a, 2b, and 2c are connected to the single-phase inverters 4a, 4b, and 4c, respectively, to obtain alternating current with a desired frequency and voltage. The outputs of these single-phase inverters 4a, 4b, and 4c are Y-connected to form a three-phase inverter device having a neutral point, and three-phase power is supplied to the AC motor M via the reactor L.
[0015]
The above is the main circuit configuration of FIG. The configuration of the control circuit will be described below. In FIG. 1, the voltage control circuit portion directly related to the present invention is mainly shown, and other control circuits are omitted.
[0016]
The DC outputs of the rectifier circuits 2a, 2b and 2c are detected by DC voltage detection circuits 3a, 3b and 3c connected between the DC output lines, respectively. This detection value is input to the maximum value detection circuit 5 to obtain the maximum value. The obtained maximum value is input to the coefficient calculators 6a, 6b and 6c. In the coefficient calculators 6a, 6b and 6c, the maximum values are respectively detected by the detected values of the DC voltage detection circuits 3a, 3b and 3c. Divide. Further, the values obtained by these operations are input to the multipliers 7a, 7b and 7c and multiplied by the voltage command values V * u, V * v and V * w of the single-phase inverters 4a, 4b and 4c, respectively. . The correction voltage command values thus obtained are input to the PWM controllers 8a, 8b and 8c, and converted into gate control signals for the main circuit devices of the single-phase inverters 4a, 4b and 4c.
[0017]
Next, the operation of FIG. 1 in the above configuration will be described.
[0018]
The AC output obtained from the plurality of secondary windings of the input transformer 1 is rectified by the rectifier R, and the DC output voltages of the rectifier circuits 2a, 2b and 2c, which are connected in series, are normally the same. It has become. That is, when the DC voltages of the single-phase inverters 4a, 4b and 4c are all the same value V0 and the balanced state is maintained, the outputs of the coefficient calculators 6a, 6b and 6c are 1, and the correction voltage command at this time The value is equal to the voltage command value for each phase.
[0019]
From this state, for example, assuming an event in which only the DC voltage of the U-phase single-phase inverter 4a drops to V1, the output of the maximum value selection circuit 5 is V0, and the outputs of the coefficient calculators 6a, 6b, and 6c are respectively 6a becomes V0 / V1, 6b and 6c become 1. These outputs are multiplied by the voltage command values V * u, V * v and V * w of each phase, respectively. As a result, the final corrected voltage command value is corrected by the inverse ratio of the DC voltage only for the U phase. The controller 8a gives a gate pulse for multiplying the output of the single-phase inverter 4a by V0 / V1 to the U-phase single-phase inverter 4a. As a result, the three-phase output voltage is balanced.
[0020]
In this way, it is possible to provide a power conversion device that can suppress an imbalance in output phase voltage of an inverter device when a DC voltage imbalance occurs between single-phase inverters.
[0021]
(Second Embodiment)
FIG. 2 is a configuration diagram of a power conversion device according to the second embodiment of the present invention. About each part of this 2nd Embodiment, the part same as each part of the power converter device which concerns on 1st Embodiment of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The second embodiment differs from the first embodiment in that low-pass filters 10a, 10b, and 10c are inserted into the outputs of the DC voltage detection circuits 3a, 3b, and 3c, respectively, and coefficient calculation. Limiters 9a, 9b and 9c are inserted into the outputs of the devices 6a, 6b and 6c, respectively.
[0022]
Since the high frequency ripple voltage of the 6th harmonic of the power supply frequency and the 4th harmonic of the single-phase inverter output frequency is superimposed on the DC voltage, the ripple voltage is removed by inserting the low-pass filters 10a, 10b and 10c. With this configuration, the operation accuracy of the maximum value selection circuit 5 and the coefficient calculators 6a, 6b, and 6c can be improved.
[0023]
In addition, when the unbalance increases, an upper limit value is provided by the limiters 9a, 9b, and 9c so that the correction voltage command value does not deviate from the voltage control range of the single-phase inverters 4a, 4b, and 4c. Operation can be performed.
[0024]
In this way, it is possible to provide a highly stable power conversion device that can suppress an imbalance in inverter output phase voltage when a DC voltage imbalance occurs between single-phase inverters.
[0025]
(Third embodiment)
FIG. 3 is a configuration diagram of a power conversion device according to the third embodiment of the present invention. About each part of this 3rd Embodiment, the part same as each part of the power converter device which concerns on 1st Embodiment of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The third embodiment is different from the first embodiment in that the single-phase inverters 4a, 4b, and 4c are a three-level system that uses a DC neutral point voltage. As shown in FIG. 3, when a neutral point is not provided on the rectifier circuits 2a, 2b, and 2c side, the configuration of the voltage control circuit similar to that of the first embodiment of FIG. 1 can be applied. it can.
[0026]
In this way, it is possible to provide a power conversion device that can suppress an imbalance in output phase voltage of an inverter device when a DC voltage imbalance between three-level single-phase inverters occurs.
[0027]
(Fourth embodiment)
FIG. 4 is a configuration diagram of a power conversion device according to the fourth embodiment of the present invention. About each part of this 4th Embodiment, the part same as each part of the power converter device which concerns on 2nd Embodiment of FIG. 2 is shown with the same code | symbol, and the description is abbreviate | omitted. The fourth embodiment is different from the second embodiment in that the single-phase inverters 4a, 4b, and 4c are a three-level system that uses a DC neutral point voltage.
[0028]
In this way, as in the second embodiment, high-frequency components are removed by the low-pass filters 10a, 10b and 10c, and stability of the voltage control is ensured by the limiters 9a, 9b and 9c. It is possible to provide a highly stable power conversion device that can suppress an imbalance in output phase voltage of an inverter device when a DC voltage imbalance between three-level single-phase inverters occurs.
[0029]
(Fifth embodiment)
FIG. 5 is a configuration diagram of a power conversion apparatus according to the fifth embodiment of the present invention. About each part of this 5th Embodiment, the same part as each part of the power converter device which concerns on 3rd Embodiment of FIG. 3 is shown with the same code | symbol, and the description is abbreviate | omitted. The fifth embodiment differs from the third embodiment in that the neutral points of the rectifier circuits 2a, 2b and 2c and the neutral points of the single-phase inverters 4a, 4b and 4c are connected. DC voltage detectors 3a, 3b, 3c, 3d, 3e and 3f, coefficient calculators 6a, 6b, 6c, 6d, 6e and 6f, and multipliers 7a, 7b, 7c, 7d, 7e and 7f Are separately provided for the positive and negative DCs of the single-phase inverters 4a, 4b and 4c, and the three-phase voltage commands V * u, V * v and V * w are set to the positive and negative sides. The point is that positive value passing filters 11a, 11b and 11c for separation and negative value passing filters 12a, 12b and 12c are provided.
[0030]
In this way, when the rectifier R and the neutral point of the three-level single-phase inverters 4a, 4b, and 4c are connected, the positive DC voltage and the negative DC voltage of the single-phase inverters 4a, 4b, and 4c are also unbalanced. It is possible to balance the output voltage of the three-phase inverter device as a configuration to be corrected and to multiply the positive and negative sides of the phase voltage reference by independent coefficients.
[0031]
In this way, it is possible to provide a power conversion device capable of independently suppressing the positive side and the negative side of the output phase voltage imbalance of the inverter device when the DC voltage imbalance between the three-level single-phase inverters occurs. Can do.
[0032]
(Sixth embodiment)
FIG. 6 is a configuration diagram of a power conversion apparatus according to the sixth embodiment of the present invention. About each part of this 6th Embodiment, the same part as each part of the power converter device which concerns on 5th Embodiment of FIG. 5 is shown with the same code | symbol, and the description is abbreviate | omitted. The sixth embodiment is different from the fifth embodiment in that the outputs of the DC voltage detection circuits 3a, 3b, 3c, 3d, 3e and 3f are low-pass filters 10a, 10b, 10c, 10d, 10e and 10f is inserted, and limiters 9a, 9b, 9c, 9d, 9e, and 9c are inserted into the outputs of the coefficient calculators 6a, 6b, 6c, 6d, 6e, and 6f, respectively.
[0033]
Since the ripple voltage of the 6th harmonic of the power supply frequency and the 4th harmonic of the single-phase inverter output frequency is superimposed on the DC voltage, the low pass filters 10a, 10b, 10c, and 10d are the same as in the second embodiment. The ripple voltage is removed by inserting 10e and 10f. With this configuration, it is possible to improve the operation accuracy of the maximum value selection circuit 5 or the coefficient calculators 6a, 6b and 6c.
[0034]
Further, when the unbalance increases, the upper limit value is provided by the limiters 9a, 9b, 9c, 9d, 9e and 9f so that the correction output does not deviate from the voltage control range of the single-phase inverters 4a, 4b and 4c. Stable operation can be obtained.
[0035]
According to the embodiment of the abnormality, when DC voltage imbalance between three-level single-phase inverters occurs, the output phase voltage imbalance of the inverter device can be suppressed independently on the positive side and the negative side with high stability A power converter can be provided.
[0036]
In the above description, the relation between the output voltage and the output frequency of the inverter device is not mentioned. However, the power conversion device of the present invention can perform normal so-called V / F constant control, independent excitation current and torque current. Of course, the present invention can also be applied to vector control and sensorless vector control.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a power conversion device that can suppress an imbalance in inverter output phase voltage when a DC voltage imbalance occurs between single-phase inverters.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a power conversion device according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a power conversion device according to a second embodiment of the present invention.
FIG. 3 is a configuration diagram of a power conversion device according to a third embodiment of the present invention.
FIG. 4 is a configuration diagram of a power conversion device according to a fourth embodiment of the present invention.
FIG. 5 is a configuration diagram of a power conversion device according to a fifth embodiment of the present invention.
FIG. 6 is a configuration diagram of a power conversion device according to a sixth embodiment of the present invention.
[Explanation of symbols]
1 Input transformer 2a, 2b, 2c Rectifier circuit 3a, 3b, 3c, 3d, 3e, 3f DC voltage detection circuit 4a, 4b, 4c Inverter 5 Maximum value selection circuit 6a, 6b, 6c, 6d, 6e, 6f Coefficient calculation 7a, 7b, 7c, 7d, 7e, 7f Multipliers 8a, 8b, 8c PWM controllers 9a, 9b, 9c, 9d, 9e, 9f Limiters 10a, 10b, 10c, 10d, 10e, 10f Low pass filters 11a, 11b 11c Positive value pass filters 12a, 12b, 12c Negative value pass filters

Claims

An input transformer having a plurality of secondary windings;
Three sets of rectifier circuits formed by connecting a plurality of unit rectifiers connected to the secondary winding in a one-to-one relationship;
A three-phase inverter device formed by converting each DC output voltage of the rectifier circuit into an AC voltage and Y-connecting three single-phase inverters constituting each phase;
A control circuit that controls the output voltage of each of the single-phase inverters,
Wherein the control circuit have a respective inhibit correcting means imbalance of the phase voltage of the three-phase inverter device due to an imbalance of the DC voltage of the single-phase inverter,
The correction means includes
DC voltage detection means for detecting each DC output voltage supplied to the three single-phase inverters;
Maximum value selection means for selecting the maximum value of the detected DC output voltage;
Coefficient computing means for computing the coefficient by dividing the maximum value by the output of the DC voltage detecting means;
A power conversion apparatus comprising correction value output means for multiplying the output of the coefficient calculation means by the voltage command value of each phase and outputting a correction voltage command value to each single-phase inverter .

An input transformer having a plurality of secondary windings;
Three sets of rectifier circuits formed by connecting a plurality of unit rectifiers connected to the secondary winding in a one-to-one relationship;
A three-phase inverter device formed by converting each DC output voltage of the rectifier circuit into an AC voltage and Y-connecting three single-phase inverters constituting each phase;
A control circuit that controls the output voltage of each of the single-phase inverters,
The control circuit has correction means for respectively suppressing the phase voltage imbalance of the three-phase inverter device due to the DC voltage imbalance of the single-phase inverter,
The correction means includes
DC voltage detection means for detecting each DC output voltage supplied to the three single-phase inverters;
High frequency component removing means for removing high frequency components included in the output of the DC voltage detecting means, respectively;
Maximum value selecting means for selecting the maximum value of the output of the high frequency component removing means,
Coefficient calculating means for calculating the coefficient by dividing the output of the maximum value selecting means by the output of the high frequency component removing means;
Upper limit limiting means for limiting the upper limit of the output of the coefficient calculating means,
A power conversion apparatus comprising : a correction value output means for multiplying the output of the upper limit value limiting means and the voltage command value of each phase to output a correction voltage command value to each single-phase inverter .

The power converter according to claim 1, wherein the single-phase inverter is a three-level system having a neutral point .

An input transformer having a plurality of secondary windings;
A three-level rectifier circuit having three sets of neutral points formed by connecting a plurality of unit rectifiers connected in a one-to-one relationship to the secondary winding in series;
A three-phase inverter device configured by converting each DC output voltage of the three-level rectifier circuit into an AC voltage and Y-connecting three single-phase three-level inverters constituting each phase;
A control circuit for controlling the output voltage of the single-phase three-level inverter,
The control circuit has correction means for respectively suppressing imbalances in the output voltages of the three-phase inverter device caused by imbalances in positive and negative DC voltages of the single-phase three-level inverter;
The correction means includes
DC voltage detecting means for respectively detecting positive and negative DC voltages supplied to the three-level inverter;
Maximum value selection means for selecting the maximum value of the output of the DC voltage detection means;
Coefficient calculating means for calculating the coefficient by dividing the output of the maximum value selecting means by the output of the DC voltage detecting means;
A positive value extracting means for extracting a positive value of the voltage command value of each phase;
Negative value extraction means for extracting the negative value of the voltage command value of each phase;
The product of the output of the coefficient calculation means and the output of the positive value extraction means, and the product of the output of the coefficient calculation means and the output of the negative value extraction means are added to correct the voltage command to each of the three-level single-phase inverters. A power conversion apparatus comprising correction value output means for outputting values .

An input transformer having a plurality of secondary windings;
A three-level rectifier circuit having three sets of neutral points formed by connecting a plurality of unit rectifiers connected in a one-to-one relationship to the secondary winding in series;
A three-phase inverter device configured by converting each DC output voltage of the three-level rectifier circuit into an AC voltage and Y-connecting three single-phase three-level inverters constituting each phase;
A control circuit for controlling the output voltage of the single-phase three-level inverter,
The control circuit has correction means for respectively suppressing imbalances in the output voltages of the three-phase inverter device caused by imbalances in positive and negative DC voltages of the single-phase three-level inverter;
The correction means includes
DC voltage detecting means for respectively detecting positive and negative DC voltages supplied to the three-level inverter;
High frequency component removing means for removing high frequency components of the output of the DC voltage detecting means, respectively;
Maximum value selecting means for selecting the maximum value of the output of the high frequency component removing means,
Coefficient calculating means for calculating the coefficient by dividing the output of the maximum value selecting means by the output of the high frequency component removing means;
Upper limit limiting means for limiting the upper limit of the output of the coefficient calculating means;
A positive value extracting means for extracting a positive value of the voltage command value of each phase;
Negative value extraction means for extracting the negative value of the voltage command value of each phase;
The product of the output of the coefficient calculation means and the output of the positive value extraction means, and the product of the output of the coefficient calculation means and the output of the negative value extraction means are added to obtain a corrected voltage command value for each of the three-level inverters. A power conversion device comprising correction value output means for outputting each .