JP4156767B2

JP4156767B2 - Power converter

Info

Publication number: JP4156767B2
Application number: JP2000041147A
Authority: JP
Inventors: 孝雄六藤; 久博矢部
Original assignee: Shizuki Electric Co Inc
Current assignee: Shizuki Electric Co Inc
Priority date: 2000-02-18
Filing date: 2000-02-18
Publication date: 2008-09-24
Anticipated expiration: 2020-02-18
Also published as: JP2001231166A

Description

【０００１】
【発明の属する技術分野】
この発明は、交流電源に接続された負荷と並列に接続され、交流電源が正常な給電時は、高調波補償電流を出力して負荷から交流電源への高調波電流の流出を防止し、交流電源の停電時は負荷に交流電力を供給する電力変換装置に関するものである。
【０００２】
【従来の技術】
電力半導体を使用したインバータやコンバータ等の負荷装置からは有害な高調波電流が発生し、この高調波電流の交流電源への流出が問題となるが、この対策として、高調波補償電流を出力して高調波電流の交流電源への流出を防止する、いわゆるアクティブフィルタ装置が実用化されている。
一方、運転継続性の要請が高いコンピュータ関連機器等の負荷装置にあっては、交流電源の突発的な停電発生時、これに替わって上記負荷装置に交流電力を供給して負荷への電力供給の継続性を保障する、いわゆるＵＰＳ（無停電電源装置）も実用化されている。
【０００３】
更に、最近では、上述した両装置の機能を兼ね具えた装置が開発されている。例えば、特開平８−５１７３５号公報に開示された電源装置は、制御系として電流制御系と電圧制御系の両制御系を備え、交流電源が正常な給電時は、この電流制御系を動作させ高調波補償電流を出力して高調波電流を抑制するアクティブフィルタとして機能する。また、交流電源が途絶えて停電になると、制御系を電流制御系から電圧制御系に切り替え、負荷に交流電力を供給するＵＰＳとして機能する。
【０００４】
そして、同公報の装置では、負荷に電力を供給するときの電流と電圧の継続性を保つため、電流制御系と電圧制御系のそれぞれを二重系で構成し、一方を実制御に他方を待機動作に保つ冗長システムを採用している。即ち、給電中は電流制御系が実動し、この間、電圧制御系は負荷変動に応じて電圧指令を補正する待機動作をなす。また、停電中は電圧制御系が実動し、この間電流制御系は負荷変動に応じて電流指令を補正する待機動作をなす。
【０００５】
【発明が解決しようとする課題】
高調波抑制のためのアクティブフィルタ装置とＵＰＳとの機能を併せもつ従来の電力変換装置は以上のように、制御系として電流制御系と電圧制御系とを備えた複雑な構成となる。更に、交流電源の停電発生時、またその復電時に、電流制御系から電圧制御系に、またその逆に、電圧制御系から電流制御系に切り替える必要があり、この制御系の切り替えに伴う異常現象が発生する可能性がある。
特に、電流制御系から電圧制御系に切り替える場合、元の電源電圧値と新たに印加する電圧値との継続性を保つ必要から装置の出力電流値が切り替えの前後で不連続に変化して異常電圧を発生させる可能性が高い。
【０００６】
この発明は以上のような従来の問題点を解消するためになされたもので、電流制御系と電圧制御系との切り替えを行うことなく、給電時の高調波補償電流出力動作と停電時の交流電力出力動作とを円滑に切り替えることができる電力変換装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
この発明に係る電力変換装置は、直流電源およびこの直流電源の電力を交流に変換して負荷に供給する電力変換手段を備え、開閉手段を介して上記負荷を交流電源に接続し、上記交流電源が正常な給電時は、上記開閉手段を閉路して上記交流電源から上記負荷に電力を供給するとともに上記電力変換手段から上記負荷の高調波電流を補償する高調波補償電流を出力し、上記交流電源の停電時は、上記開閉手段を開路して上記電力変換手段から上記負荷に交流電力を供給する電力変換装置において、
上記負荷の電流を検出する負荷電流検出手段、この負荷電流検出手段の出力からその基本波成分を抽出し入力喪失後も所定時間継続出力可能な形態の基本波パターンを作成する基本波パターン作成手段、上記負荷電流検出手段の出力から上記高調波補償電流である高調波パターンを作成する高調波パターン作成手段、および給電時は上記高調波パターンを入力しこれを電流指令として上記電力変換手段の出力電流を制御し停電時は上記基本波パターンを入力しこれを電流指令として上記電力変換手段の出力電流を制御する電流制御手段を備えたものである。
【０００８】
この発明に係る電力変換装置は、直流電源およびこの直流電源の電力を交流に変換して負荷に供給する電力変換手段を備え、開閉手段を介して上記負荷を交流電源に接続し、上記交流電源が正常な給電時は、上記開閉手段を閉路して上記交流電源から上記負荷に電力を供給するとともに上記電力変換手段から上記負荷の高調波電流を補償する高調波補償電流を出力し、上記交流電源の停電時は、上記開閉手段を開路して上記電力変換手段から上記負荷に交流電力を供給する電力変換装置において、
上記負荷の電流を検出する負荷電流検出手段、この負荷電流検出手段の出力からその基本波成分を抽出し入力喪失後も所定時間継続出力可能な形態の基本波パターンを作成する基本波パターン作成手段、上記負荷電流検出手段の出力から上記高調波補償電流を求め入力喪失後も所定時間継続出力可能な形態の高調波パターンを作成する高調波パターン作成手段、および給電時は上記高調波パターンを入力しこれを電流指令として上記電力変換手段の出力電流を制御し停電時は上記基本波パターンと高調波パターンとを入力しこれらの加算値を電流指令として上記電力変換手段の出力電流を制御する電流制御手段を備えたものである。
【０００９】
この発明に係る電力変換装置の高調波パターン作成手段は、負荷電流検出手段の出力から高調波補償電流を作成する高調波補償電流作成手段、およびこの作成した高調波補償電流を所定時間保持するサンプルホールド手段を備えたものである。
【００１０】
この発明に係る電力変換装置の基本波パターン作成手段は、負荷電流検出手段の出力からその基本波成分を抽出するＬＣ帯域フィルタを備えたものである。
【００１１】
この発明に係る電力変換装置の基本波パターン作成手段は、負荷電流検出手段の出力からその基本波成分を抽出する基本波抽出手段、およびこの抽出した基本波成分を所定時間保持するサンプルホールド手段を備えたものである。
【００１２】
この発明に係る電力変換装置は、その基本波パターン作成手段に負荷電流検出手段の出力から抽出した基本波成分を補正して基本波パターンとして出力するための乗算手段を設けるとともに、交流電源の電圧基準値を設定する基準電圧設定手段、負荷の電圧を検出する負荷電圧検出手段、および上記電圧基準値と負荷電圧検出値との偏差を入力しこの偏差が零となるよう上記乗算手段の補正乗算係数を作成する電圧補正手段を備えたものである。
【００１３】
この発明に係る電力変換装置は、その交流電源の電圧を検出しこの検出値を所定時間保持するサンプルホールド手段を備え、そのサンプルホールド値を基準電圧設定手段の電圧基準値としたものである。
【００１４】
この発明に係る電力変換装置の高調波パターン作成手段は、負荷電流検出手段の出力から基本波パターン作成手段で抽出された基本波成分を減算して高調波補償電流を作成するものである。
【００１５】
この発明に係る電力変換装置は、その直流電源を、電気二重層コンデンサおよびまたは二次蓄電池と電解コンデンサとの並列接続体で構成し、給電時、交流電源から電力変換手段を介して上記並列接続体を充電するようにしたものである。
【００１６】
【発明の実施の形態】
実施の形態１．
図１はこの発明の実施の形態１における電力変換装置を示す構成図である。図において、１は３相商用周波数の交流電源、２は開閉手段としての開閉器３を介して交流電源１に接続された負荷装置で、ここでは、既述した通り高調波を発生するコンバータやインバータ等の負荷装置を想定している。また、開閉器３は、ここでは、サイリスタ等のスイッチング素子を使用したいわゆる無接点型の開閉器を採用している。４はＩＧＢＴ等のスイッチング素子とこれに逆並列接続されたダイオードとからなる単位アームを３相ブリッジ構成に接続してなる電力変換器で、コンデンサＣからなる直流電源５の電力を交流に変換して出力する。
【００１７】
６は交流電源１の電圧を検出する電圧検出器で、７はこの電圧検出器６の検出値に基づき交流電源１の給電、停電の判別を行う停電検知回路である。８は負荷装置２の電圧を検出する負荷電圧検出器、９は負荷装置２の電流を検出する負荷電流検出器、１０は電力変換器４の出力電流を検出する出力電流検出器、１１は電力変換器４の後述するＰＷＭ制御に基づき発生するキャリア周波数の成分を取り除くためのフィルタである。
１２は電力変換器４の制御装置で、停電検知回路７、負荷電圧検出器８、負荷電流検出器９、出力電流検出器１０からの信号を入力し、以下で詳述する高調波パターン１３および基本波パターン１４を作成し、交流電源１の給電時は高調波パターン１３を指令値として、また交流電源１の停電時は基本波パターン１４を指令値として電力変換器４の出力電流を制御するＰＷＭ制御部１５を備えている。
【００１８】
図２は図１の制御装置１２の詳細構成を示す図である。図２において、１６は負荷電流検出器９からの負荷検知電流ＩＬからその基本波成分を抽出するＬＣ帯域フィルタ、１７は負荷検知電流ＩＬからＬＣ帯域フィルタ１６の出力である基本波成分を減算して負荷検知電流ＩＬの高調波成分を出力する加算器で、その出力から高調波補償電流の高調波パターン１３が作成される。なお、高調波補償電流は負荷装置２から交流電源１に流出しようとする高調波電流を、電力変換器４から交流電源１へ送り出す当該高調波補償電流により相殺するものであるので、負荷検知電流ＩＬを今、負荷装置２に流入する向きにその極性を設定し、電力変換器４の出力電流を流出する向きにその極性を設定したとすると、ここで高調波パターン１３として設定する高調波補償電流は、加算器１７からの高調波成分と同極性の信号とすればよい。即ち、この発明では、負荷装置２の高調波電流は交流電源１から負荷装置２へ流入するものととらえ、交流電源１から負荷装置２へのルートに替って、電力変換器４から上記高調波電流と同極性の高調波補償電流を負荷装置２に送り込むことで高調波電流の補償を行う訳である。結果としては、従来からの現象と全く同一の高調波補償動作が得られる。
１８はＬＣ帯域フィルタ１６からの基本波成分信号に後述する補正乗算係数を乗算して基本波パターン１４として出力する乗算器である。１９は負荷装置２に供給すべき電圧値である基準電圧ＶＳと負荷電圧検出器８からの負荷検知電圧ＶＬとの偏差を出力する加算器、２０は加算器１９からの偏差出力が零となるよう乗算器１８の補正乗算係数を作成するＰＩ制御器である。２１は停電検知回路７からの信号に応じて指令パターンを切り替えるパターン切替器である。
【００１９】
次に動作について説明する。先ず、負荷検知電流ＩＬの一例を図３に示す。図において、実線の波形が負荷電流検出器９で検出される負荷検知電流ＩＬ、一点鎖線の波形がその基本波成分、点線の波形がその高調波成分である。
図２に示すＬＣ帯域フィルタ１６は、図３で示す負荷検知電流ＩＬからその基本波成分を抽出するフィルタであるが、交流電源１の商用周波数、即ち、基本周波数で共振するインダクタンスＬおよびコンデンサＣから構成されているので、これらの定数に基づく時定数に応じて出力持続能力を有している。この現象を図４に基づいて説明する。
【００２０】
図４は、ＬＣ帯域フィルタ１６単体の入力／出力特性を示すもので、基本周波数の入力が時間０．１０ＳＥＣまで与えられ、この時点で零となり、その後時間０．１５ＳＥＣから再び印加されている。
これに対し、ＬＣ帯域フィルタ１６の出力は、時間０．１０ＳＥＣまでは、入力に等しい基本周波数を出力し、この時点で入力が途絶えると、その出力は振幅値は次第に低減するが、同じ基本周波数の出力が少なくとも２〜３周期分継続する。そして、時間０．１５ＳＥＣで入力が再開すると、出力は再び上昇を始め、入力＝出力の定常状態に向かう。
【００２１】
以上のように、ＬＣ帯域フィルタ１６はその構成原理から、入力喪失後も所定時間継続出力が得られるという特性を有している。本願発明は、この特性を効果的に利用したもので、以下、これを予備知識として電力変換装置としての動作を詳細に説明する。
【００２２】
図１に戻り、先ず、交流電源１が正常な給電時の動作から説明する。この場合、停電検知回路７の給電判別出力により開閉器３は閉路され負荷装置２は交流電源１に接続されてその給電を受ける。図２において、パターン切替器２１は同じく停電検知回路７の給電判別出力によりＡ側を選択しており、即ち、加算器１７の出力から得られる高調波補償電流である高調波パターン１３を電流指令として、ＰＷＭ制御部１５は出力電流検出器１０からの出力電流検出値が上記電流指令に一致するよう電力変換器４の各スイッチング素子にゲート信号を送出する。
以上のように、図３に示す負荷電流の高調波成分から求めた高調波補償電流が電力変換器４から出力されるので、負荷装置２への高調波電流が交流電源１に替ってこの電力変換器４からの高調波補償電流によって供給されるので、交流電源１からの高調波電流の流入が防止される、即ち、高調波電流の補償動作が達成される。
【００２３】
図５は、各部の電流波形を示すもので、交流電源１の給電時はその時間０．１０ＳＥＣまでの状態が相当する。即ち、同図（ａ）に示すように、高調波を含む負荷電流（点線）に対し、電力変換器４は高調波パターン１３に基づき高調波補償電流である出力電流（実線）を出力し、同図（ｂ）に示すように、電源電流（一点鎖線）は高調波成分を含まない基本周波数の正弦波形となっている。
【００２４】
ここで、送電系統の事故等により、交流電源１からの給電が停止、即ち、停電が発生すると、停電検知回路７の停電判別出力により開閉器３は直ちに開路され負荷装置２と交流電源１との接続が断たれる。同時に、制御装置１２のパターン切替器２１がＢ側に切り替わる。
停電発生により、負荷検知電流ＩＬは瞬間零になるが、図４で説明した通り、ＬＣ帯域フィルタ１６はその出力を継続し従って基本波パターン１４は給電時から作成されていた状態を維持している。従って、ＰＷＭ制御部１５はこの基本波パターン１４を電流指令として出力電流検出器１０からの出力電流検出値が上記電流指令に一致するよう電力変換器４の各スイッチング素子にゲート信号を送出する。
なお、現実の回路では電流指令パターンの切り替えは停電発生後瞬時になされるので、ＬＣ帯域フィルタ１６の出力、従って、基本波パターン１４は停電発生直前までの波形をその振幅を変えることなく維持し、結果として、給電時の負荷電流の基本波成分が停電後、そのまま、電力変換器４から負荷装置２に供給されることになる。
【００２５】
図５の時間０．１０〜０．１５ＳＥＣが、停電時に相当する。即ち、同図（ａ）に示すように、電力変換器４から出力電流＝負荷電流が負荷装置２に供給され、同図（ｂ）に示すように、当然ながら、電源電流は零となっている。
【００２６】
なお、図５の時間０．１５ＳＥＣ以降は交流電源１が復電した以降の状態を示している。即ち、停電検知回路７が復電を検知すると、直ちに開閉器３が閉路して交流電源１から負荷装置２への給電が再開し、ＰＷＭ制御部１５は再び高調波パターン１３を電流指令として高調波補償電流を出力する。
【００２７】
以上のように、この発明の実施の形態１では、停電発生また復電に際し、電流指令パターンの切り替えは行うが、電力変換器４の動作形態を決定する電流制御系自体は常に維持しているので、従来装置の電流制御系と電圧制御系との切り替えによる弊害は生じず、図５にも示すように、停電、復電時に有害な過渡現象が発生しない。
【００２８】
なお、本願発明は、既述したように、ＬＣ帯域フィルタ１６の、入力喪失後の出力持続能力を利用し、停電発生後その持続指令パターンに基づき電流を出力し、その出力電流の検出値から指令パターンを作成して動作を続けていく、いわば自己発振形の制御動作を行うものである。
従って、停電時間が比較的長時間継続したり、各検出手段の誤差や制御系各部の定数等によっては、停電時間の経過に従って、電力変換器４からの出力電流が次第に上昇または下降していく可能性がある。
【００２９】
図２の乗算器１８はこの弊害を防止するものである。即ち、停電時、電力変換器４からの出力電流に基づく負荷装置２の電圧を検出し、この負荷検知電圧ＶＬと基準電圧ＶＳとの偏差が零となるよう、ＬＣ帯域フィルタ１６で抽出した基本波成分に補正乗算係数を乗算して基本波パターン１４の振幅値を補正する構成としている。
【００３０】
なお、この基準電圧ＶＳの値としては、負荷装置２に供給すべき値として、例えば、回路の定格公称電圧値に設定してもよいが、例えば、電圧検出器６で検出する交流電源１の電圧値を所定時間保持するサンプルホールド手段を備えておき、このホールド値を基準電圧ＶＳとしてもよい。この場合、停電発生直前に負荷装置２に供給されていた電圧が、停電発生後も継続して負荷装置２に供給されるので、停電発生が負荷装置２に及ぼす影響をより低減させることができる利点がある。
【００３１】
なお、起こり得る停電時間が極めて短い等、想定される停電発生条件等によっては、乗算器１８による補正手段は省略してもよいことは勿論である。
【００３２】
また以上では、入力喪失後も所定時間継続出力可能な、負荷検知電流ＩＬの基本波成分抽出手段としてＬＣ帯域フィルタ１６を使用した場合について説明したが、これに限られるものではない。即ち、例えば負荷検知電流ＩＬをＡ／Ｄ変換し、これから所定の論理演算で基本波成分を求め、これを所定時間保持するサンプルホールド手段を経て基本波パターン１４を作成するようにしてもよく、この場合も上述したと同等の効果を得ることができることは言うまでもない。
また、以上では、負荷検知電流ＩＬの高調波成分を、負荷検知電流ＩＬからＬＣ帯域フィルタ１６で抽出した基本波成分を減算することにより求めたが、例えば、ＬＣバンドパスフィルタの組み合わせ等を使用して負荷検知電流ＩＬから直接、高調波成分を抽出するようにしてもよい。
【００３３】
次に、図１の直流電源５を構成するコンデンサについて説明する。図６はこの直流電源５の一構成例で、ここでは、電解コンデンサ５１と電気二重層コンデンサ５２との並列接続体としている。それぞれの点線枠内にコンデンサの等価回路を示すように、電解コンデンサ５１と電気二重層コンデンサ５２との時定数、Ｒｓ１×Ｃ１とＲｓ２×Ｃ２とを比較した場合、前者が小さい（後者の約１／１００倍）。従って、給電時高調波補償電流を出力する場合は、時定数の小さい、即ち、周波数応答の速い電解コンデンサ５１が適している。
一方、停電時に負荷装置２へ基本周波数の有効電力を供給する場合は、速い周波数応答は不要であるが、大きな蓄電量が要求され、電気二重層コンデンサ５２が適している。
図６は、この両タイプのコンデンサの特性を生かしたもので、主として高調波補償電流の出力のための比較的小容量の電解コンデンサ５１と、基本波電流の出力のための比較的大容量の電気二重層コンデンサ５２とを並列に接続している。
【００３４】
図７は、直流電源５の他の構成例で、電解コンデンサ５１と二次蓄電池５３とを並列に接続している。二次蓄電池５３はその電荷の移動が化学反応を伴うためその充放電特性は、電気二重層コンデンサよりも更に緩慢となる。しかし、大容量の蓄電手段としては優れているので、図６の場合と同様、電解コンデンサ５１と組み合わせることによって、本願発明の電力変換装置に使用する直流電源５として有用である。
【００３５】
なお、これらコンデンサを充電する手段は公知であるので詳細な説明は省略するが、例えば、コンデンサの電圧を検出する手段を備え、この検出値と所定の電圧設定値との偏差に基づく直流電圧指令成分を作成し、これを本来の電流指令に加算して制御することにより、給電時に交流電源１から電力変換器４を介してコンデンサを所定の設定値に充電することができる。
【００３６】
また、図示は省略するが、直流電源５の構成例としては、電解コンデンサ５１、電気二重層コンデンサ５２、二次蓄電池５３の３者の並列接続体としてもよく、また、例えば、電気二重層コンデンサではあるが、その内部構造の改良等により周波数応答が改善されたものであれば、直流電源５を電気二重層コンデンサ５２のみで構成してもよい。更に、補償すべき高調波の次数が比較的低次の範囲に限定できる場合等には、コンデンサとして特に速い周波数応答が要求されないので、同様に、大容量の構成が比較的容易安価に実現できる電気二重層コンデンサ５２や二次蓄電池５３を使用するようにしてもよい。
【００３７】
実施の形態２．
次にこの発明の実施の形態２における電力変換装置について説明する。図８はその要部を示す構成図で、その他の部分は先の形態１と全く同様である。この形態２においては、図８に示すように、加算器１７からの出力に基づく高調波補償電流を、入力喪失後も所定時間継続出力可能なサンプルホールド回路２２を経てこの出力により高調波パターン１３を作成する。更に、高調波パターン１３と基本波パターン１４とを加算する加算器２３を設け、パターン切替器２１により、ＰＷＭ制御部１５に送出する電流指令パターンを、給電時は高調波パターン１３、停電時は高調波パターン１３＋基本波パターン１４とする。
【００３８】
従って、給電時の動作は、所定時間、例えば、基本周波の１周期分ホールドした高調波補償電流からなる高調波パターン１３を使用する点を除いて形態１の場合と同様の動作となるが、停電時は、この高調波パターン１３に基本波パターン１４を加えたパターンにより電流制御を行う動作に変わる。このように、この形態２においては停電時、負荷装置２に対し、基本波電流だけでなく、停電直前まで出力していた高調波補償電流も継続して出力するので、即ち、基本波成分と高調波成分とを含む、正常な給電時と同じ波形の負荷電流を負荷装置２に供給することになるので、結果として、停電時における負荷装置２の電圧波形が、形態１の場合と比較して正弦波状に改善されることになり、停電時の代替供給電力の質が向上する訳である。
【００３９】
なお、図８では、加算器１７により負荷検知電流ＩＬからＬＣ帯域フィルタ１６の出力を減算し、この出力をサンプルホールド回路２２でホールドする構成としたが、想定される高調波各次数毎のＬＣバンドパスフィルタを備え、その出力合成値から直接高調波パターン１３を作成するようにしてもよい。これらＬＣバンドパスフィルタ自体が図４で示したと同様の、入力喪失後の出力継続能力を有しているため、特別のサンプルホールド手段を必要としないからである。
【００４０】
以上のように、この実施の形態２においても、電流制御系を変えることなく、給電、停電時の切り替えを行うので、安定した連続的な切り替え動作が可能となる。更に、停電時の負荷電圧の歪みも低減する。
【００４１】
【発明の効果】
以上のように、この発明に係る電力変換装置は、直流電源およびこの直流電源の電力を交流に変換して負荷に供給する電力変換手段を備え、開閉手段を介して上記負荷を交流電源に接続し、上記交流電源が正常な給電時は、上記開閉手段を閉路して上記交流電源から上記負荷に電力を供給するとともに上記電力変換手段から上記負荷の高調波電流を補償する高調波補償電流を出力し、上記交流電源の停電時は、上記開閉手段を開路して上記電力変換手段から上記負荷に交流電力を供給する電力変換装置において、
上記負荷の電流を検出する負荷電流検出手段、この負荷電流検出手段の出力からその基本波成分を抽出し入力喪失後も所定時間継続出力可能な形態の基本波パターンを作成する基本波パターン作成手段、上記負荷電流検出手段の出力から上記高調波補償電流である高調波パターンを作成する高調波パターン作成手段、および給電時は上記高調波パターンを入力しこれを電流指令として上記電力変換手段の出力電流を制御し停電時は上記基本波パターンを入力しこれを電流指令として上記電力変換手段の出力電流を制御する電流制御手段を備えたので、電流制御系を維持したまま、給電時の高調波補償電流の出力動作から停電時の負荷への電力供給動作、またその逆向きの動作の切り替えが可能となり、制御に係る構成が簡便で切り替え時の動作も安定する。
【００４２】
また、この発明に係る電力変換装置は、直流電源およびこの直流電源の電力を交流に変換して負荷に供給する電力変換手段を備え、開閉手段を介して上記負荷を交流電源に接続し、上記交流電源が正常な給電時は、上記開閉手段を閉路して上記交流電源から上記負荷に電力を供給するとともに上記電力変換手段から上記負荷の高調波電流を補償する高調波補償電流を出力し、上記交流電源の停電時は、上記開閉手段を開路して上記電力変換手段から上記負荷に交流電力を供給する電力変換装置において、
上記負荷の電流を検出する負荷電流検出手段、この負荷電流検出手段の出力からその基本波成分を抽出し入力喪失後も所定時間継続出力可能な形態の基本波パターンを作成する基本波パターン作成手段、上記負荷電流検出手段の出力から上記高調波補償電流を求め入力喪失後も所定時間継続出力可能な形態の高調波パターンを作成する高調波パターン作成手段、および給電時は上記高調波パターンを入力しこれを電流指令として上記電力変換手段の出力電流を制御し停電時は上記基本波パターンと高調波パターンとを入力しこれらの加算値を電流指令として上記電力変換手段の出力電流を制御する電流制御手段を備えたので、電流制御系を維持したまま、給電時の高調波補償電流の出力動作から停電時の負荷への電力供給動作、またその逆向きの動作の切り替えが可能となり、制御に係る構成が簡便で切り替え時の動作も安定する。更に、停電時の負荷電圧の歪みも低減する。
【００４３】
また、この発明に係る電力変換装置の高調波パターン作成手段は、負荷電流検出手段の出力から高調波補償電流を作成する高調波補償電流作成手段、およびこの作成した高調波補償電流を所定時間保持するサンプルホールド手段を備えたので、停電発生後も高調波補償電流が確実に出力される電流制御系が形成される。
【００４４】
また、この発明に係る電力変換装置の基本波パターン作成手段は、負荷電流検出手段の出力からその基本波成分を抽出するＬＣ帯域フィルタを備えたので、簡便な構成で、停電発生後、基本波電流が確実に出力される電流制御系が形成される。
【００４５】
また、この発明に係る電力変換装置の基本波パターン作成手段は、負荷電流検出手段の出力からその基本波成分を抽出する基本波抽出手段、およびこの抽出した基本波成分を所定時間保持するサンプルホールド手段を備えたので、停電発生後、基本波電流が確実に出力される電流制御系が形成される。
【００４６】
また、この発明に係る電力変換装置は、その基本波パターン作成手段に負荷電流検出手段の出力から抽出した基本波成分を補正して基本波パターンとして出力するための乗算手段を設けるとともに、交流電源の電圧基準値を設定する基準電圧設定手段、負荷の電圧を検出する負荷電圧検出手段、および上記電圧基準値と負荷電圧検出値との偏差を入力しこの偏差が零となるよう上記乗算手段の補正乗算係数を作成する電圧補正手段を備えたので、停電発生後、負荷電圧を所望の基準値に維持することができる。
【００４７】
また、この発明に係る電力変換装置は、その交流電源の電圧を検出しこの検出値を所定時間保持するサンプルホールド手段を備え、そのサンプルホールド値を基準電圧設定手段の電圧基準値としたので、停電発生後、負荷電圧を停電発生直前の値に維持することができ、停電発生前後の負荷状態の変化を一層小さくすることができる。
【００４８】
また、この発明に係る電力変換装置の高調波パターン作成手段は、負荷電流検出手段の出力から基本波パターン作成手段で抽出された基本波成分を減算して高調波補償電流を作成するので、高調波パターンを作成するための回路構成が簡便となる。
【００４９】
また、この発明に係る電力変換装置は、その直流電源を、電気二重層コンデンサおよびまたは二次蓄電池と電解コンデンサとの並列接続体で構成し、給電時、交流電源から電力変換手段を介して上記並列接続体を充電するようにしたので、比較的小容量の高調波補償電流の出力と、比較的大容量の基本波電流の出力とを、共に無理なく、コンデンサとして経済的合理的な構成で実現することができる。
【図面の簡単な説明】
【図１】この発明の実施の形態１における電力変換装置を示す構成図である。
【図２】図１の制御装置１２の詳細を示す構成図である。
【図３】負荷電流の高調波成分と基本波成分の一例を示す波形図である。
【図４】ＬＣ帯域フィルタ１６の特性を示す波形図である。
【図５】電力変換装置の出力波形等を示す図である。
【図６】直流電源５の一構成例を示す図である。
【図７】直流電源５の他の構成例を示す図である。
【図８】この発明の実施の形態２における電力変換装置の要部を示す構成図である。
【符号の説明】
１交流電源、２負荷装置、３開閉器、４電力変換器、５直流電源、６電圧検出器、７停電検知回路、８負荷電圧検出器、
９負荷電流検出器、１０出力電流検出器、１２制御装置、
１３高調波パターン、１４基本波パターン、１５ＰＷＭ制御部、
１６ＬＣ帯域フィルタ、１７，１９，２３加算器、１８乗算器、
２０ＰＩ制御器、２１パターン切替器、２２サンプルホールド回路、
５１電解コンデンサ、５２電気二重層コンデンサ、５３二次蓄電池。[0001]
BACKGROUND OF THE INVENTION
This invention is connected in parallel with a load connected to an AC power supply, and when the AC power supply is normal, the harmonic compensation current is output to prevent the harmonic current from flowing from the load to the AC power supply. The present invention relates to a power conversion device that supplies AC power to a load during a power failure.
[0002]
[Prior art]
Harmful harmonic currents are generated from load devices such as inverters and converters that use power semiconductors, and the leakage of this harmonic current to the AC power supply becomes a problem. As a countermeasure, harmonic compensation current is output. So-called active filter devices that prevent the outflow of harmonic current to an AC power source have been put into practical use.
On the other hand, in the case of a load device such as a computer-related device that has a high demand for continuity of operation, in the event of a sudden power failure of the AC power supply, instead of this, AC power is supplied to the load device to supply power to the load. A so-called UPS (uninterruptible power supply) that ensures the continuity of the system has been put into practical use.
[0003]
Furthermore, recently, a device having the functions of both devices described above has been developed. For example, a power supply device disclosed in Japanese Patent Application Laid-Open No. 8-51735 has both a current control system and a voltage control system as control systems, and operates this current control system when the AC power supply is normal. It functions as an active filter that outputs harmonic compensation current and suppresses harmonic current. When the AC power supply is interrupted and a power failure occurs, the control system is switched from the current control system to the voltage control system, and functions as a UPS that supplies AC power to the load.
[0004]
And in the device of the publication, in order to maintain the continuity of the current and voltage when supplying power to the load, each of the current control system and the voltage control system is configured as a dual system, and one is used for actual control. A redundant system that maintains standby operation is adopted. That is, the current control system actually operates during power feeding, and during this time, the voltage control system performs a standby operation for correcting the voltage command according to the load fluctuation. In addition, during a power failure, the voltage control system operates, and during this time, the current control system performs a standby operation for correcting the current command in accordance with the load fluctuation.
[0005]
[Problems to be solved by the invention]
As described above, the conventional power conversion device having the functions of the active filter device for suppressing harmonics and the UPS has a complicated configuration including a current control system and a voltage control system as a control system. Furthermore, it is necessary to switch from the current control system to the voltage control system and vice versa when a power failure occurs in the AC power supply or when the power is restored. The phenomenon may occur.
In particular, when switching from the current control system to the voltage control system, it is necessary to maintain the continuity between the original power supply voltage value and the newly applied voltage value. There is a high possibility of generating a voltage.
[0006]
The present invention has been made to solve the above-described conventional problems, and without switching between the current control system and the voltage control system, the harmonic compensation current output operation during power feeding and the alternating current during a power failure. An object of the present invention is to provide a power converter that can smoothly switch between power output operations.
[0007]
[Means for Solving the Problems]
The power conversion device according to the present invention comprises a DC power supply and power conversion means for converting the power of the DC power supply into AC and supplying the load to the load, connecting the load to the AC power supply via an opening / closing means, and the AC power supply. When the power supply is normal, the switching means is closed to supply power from the AC power source to the load, and the power conversion means outputs a harmonic compensation current that compensates for the harmonic current of the load. At the time of a power failure, in the power conversion device that opens the switching means and supplies AC power from the power conversion means to the load,
Load current detection means for detecting the load current, and a fundamental wave pattern creation means for extracting a fundamental wave component from the output of the load current detection means and creating a fundamental wave pattern that can be output continuously for a predetermined time after the loss of input. A harmonic pattern creating means for creating a harmonic pattern which is the harmonic compensation current from the output of the load current detecting means, and the harmonic pattern is inputted at the time of power feeding, and this is used as a current command to output the power converting means. The current control means is provided with a current control means for controlling the output current of the power conversion means by inputting the fundamental wave pattern at the time of a power failure and using this as a current command.
[0008]
The power conversion device according to the present invention comprises a DC power supply and power conversion means for converting the power of the DC power supply into AC and supplying the load to the load, connecting the load to the AC power supply via an opening / closing means, and the AC power supply. When the power supply is normal, the switching means is closed to supply power from the AC power source to the load, and the power conversion means outputs a harmonic compensation current that compensates for the harmonic current of the load. At the time of a power failure, in the power conversion device that opens the switching means and supplies AC power from the power conversion means to the load,
Load current detection means for detecting the load current, and a fundamental wave pattern creation means for extracting a fundamental wave component from the output of the load current detection means and creating a fundamental wave pattern that can be output continuously for a predetermined time after the loss of input. A harmonic pattern creating means for obtaining the harmonic compensation current from the output of the load current detecting means to create a harmonic pattern in a form that can be continuously output for a predetermined time after the input is lost, and the harmonic pattern is input at the time of power feeding This is used as a current command to control the output current of the power conversion means, and in the event of a power failure, the fundamental wave pattern and the harmonic pattern are input, and these added values are used as current commands to control the output current of the power conversion means. Control means are provided.
[0009]
The harmonic pattern creating means of the power conversion device according to the present invention includes a harmonic compensation current creating means for creating a harmonic compensation current from the output of the load current detecting means, and a sample for holding the created harmonic compensation current for a predetermined time A holding means is provided.
[0010]
The fundamental wave pattern creating means of the power converter according to the present invention comprises an LC band filter for extracting the fundamental wave component from the output of the load current detecting means.
[0011]
The fundamental wave pattern creating means of the power converter according to the present invention comprises fundamental wave extracting means for extracting the fundamental wave component from the output of the load current detecting means, and sample hold means for holding the extracted fundamental wave component for a predetermined time. It is provided.
[0012]
In the power converter according to the present invention, the fundamental wave pattern creating means is provided with multiplication means for correcting the fundamental wave component extracted from the output of the load current detecting means and outputting it as a fundamental wave pattern, and the voltage of the AC power supply Reference voltage setting means for setting a reference value, load voltage detection means for detecting the voltage of the load, and correction multiplication of the multiplication means so that a deviation between the voltage reference value and the load voltage detection value is inputted and this deviation becomes zero A voltage correction means for creating a coefficient is provided.
[0013]
The power conversion device according to the present invention includes sample hold means for detecting the voltage of the AC power source and holding the detected value for a predetermined time, and the sample hold value is used as a voltage reference value of the reference voltage setting means.
[0014]
The harmonic pattern creating means of the power conversion device according to the present invention creates a harmonic compensation current by subtracting the fundamental wave component extracted by the fundamental wave pattern creating means from the output of the load current detecting means.
[0015]
In the power conversion device according to the present invention, the DC power supply is constituted by a parallel connection body of an electric double layer capacitor and / or a secondary storage battery and an electrolytic capacitor, and the power supply means is connected in parallel through the power conversion means during power feeding. It is designed to charge the body.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a block diagram showing a power conversion apparatus according to Embodiment 1 of the present invention. In the figure, 1 is a three-phase commercial frequency AC power source, 2 is a load device connected to the AC power source 1 via a switch 3 as a switching means, and here, as described above, a converter that generates harmonics, A load device such as an inverter is assumed. The switch 3 is a so-called contactless switch using a switching element such as a thyristor. 4 is a power converter in which a unit arm composed of a switching element such as an IGBT and a diode connected in reverse parallel thereto is connected in a three-phase bridge configuration, which converts the power of the DC power source 5 composed of a capacitor C into an alternating current. Output.
[0017]
Reference numeral 6 denotes a voltage detector that detects the voltage of the AC power supply 1, and reference numeral 7 denotes a power failure detection circuit that performs power feeding of the AC power source 1 and discrimination of power failure based on the detection value of the voltage detector 6. 8 is a load voltage detector that detects the voltage of the load device 2, 9 is a load current detector that detects the current of the load device 2, 10 is an output current detector that detects the output current of the power converter 4, and 11 is power. This is a filter for removing a carrier frequency component generated based on PWM control of the converter 4 to be described later.
12 is a control device for the power converter 4, which receives signals from the power failure detection circuit 7, the load voltage detector 8, the load current detector 9, and the output current detector 10. A fundamental wave pattern 14 is created, and the output current of the power converter 4 is controlled using the harmonic pattern 13 as a command value when the AC power supply 1 is fed, and using the fundamental wave pattern 14 as a command value during a power failure of the AC power supply 1. A PWM control unit 15 is provided.
[0018]
FIG. 2 is a diagram showing a detailed configuration of the control device 12 of FIG. In FIG. 2, 16 is an LC band filter for extracting the fundamental wave component from the load detection current IL from the load current detector 9, and 17 is a subtraction of the fundamental wave component which is the output of the LC band filter 16 from the load detection current IL. The adder that outputs the harmonic component of the load detection current IL generates the harmonic pattern 13 of the harmonic compensation current from the output. The harmonic compensation current cancels out the harmonic current that is about to flow from the load device 2 to the AC power supply 1 by the harmonic compensation current that is sent from the power converter 4 to the AC power supply 1. Assuming that the polarity of IL is set in the direction of flowing into the load device 2 and the polarity of the output current of the power converter 4 is set in the direction of flowing out, the harmonic compensation set as the harmonic pattern 13 here. The current may be a signal having the same polarity as the harmonic component from the adder 17. That is, in the present invention, the harmonic current of the load device 2 is regarded as flowing into the load device 2 from the AC power source 1, and instead of the route from the AC power source 1 to the load device 2, the above harmonics from the power converter 4. The harmonic current is compensated by sending a harmonic compensation current having the same polarity as the wave current to the load device 2. As a result, the same harmonic compensation operation as the conventional phenomenon can be obtained.
A multiplier 18 multiplies the fundamental wave component signal from the LC band filter 16 by a correction multiplication coefficient, which will be described later, and outputs the result as a fundamental wave pattern 14. 19 is an adder that outputs a deviation between the reference voltage VS, which is a voltage value to be supplied to the load device 2, and the load detection voltage VL from the load voltage detector 8, and 20 is a deviation output from the adder 19. It is a PI controller that creates a corrected multiplication coefficient for the multiplier 18. Reference numeral 21 denotes a pattern changer that switches a command pattern in accordance with a signal from the power failure detection circuit 7.
[0019]
Next, the operation will be described. First, an example of the load detection current IL is shown in FIG. In the figure, the solid line waveform is the load detection current IL detected by the load current detector 9, the alternate long and short dash line waveform is the fundamental wave component, and the dotted line waveform is the harmonic component.
The LC band filter 16 shown in FIG. 2 is a filter that extracts the fundamental wave component from the load detection current IL shown in FIG. 3, but the inductance L and the capacitor C that resonate at the commercial frequency of the AC power source 1, that is, the fundamental frequency. Therefore, it has the output sustaining ability according to the time constant based on these constants. This phenomenon will be described with reference to FIG.
[0020]
FIG. 4 shows the input / output characteristics of the LC band filter 16 alone. The input of the fundamental frequency is given until time 0.10 SEC, becomes zero at this point, and is applied again after time 0.15 SEC.
In contrast, the output of the LC band filter 16 outputs a fundamental frequency equal to the input until the time 0.10 SEC, and when the input is interrupted at this time, the output gradually decreases in amplitude value, but the same fundamental frequency. Output continues for at least 2-3 cycles. When the input resumes at time 0.15 SEC, the output starts to rise again and goes to the steady state of input = output.
[0021]
As described above, the LC band filter 16 has a characteristic that a continuous output can be obtained for a predetermined time even after the input is lost due to its configuration principle. The present invention effectively utilizes this characteristic, and hereinafter, the operation as a power conversion apparatus will be described in detail with this knowledge as prior knowledge.
[0022]
Returning to FIG. 1, first, the operation when the AC power supply 1 is normally fed will be described. In this case, the switch 3 is closed by the power supply discrimination output of the power failure detection circuit 7, and the load device 2 is connected to the AC power source 1 and receives the power supply. In FIG. 2, the pattern switching unit 21 similarly selects the A side based on the power feeding discrimination output of the power failure detection circuit 7, i.e., the harmonic pattern 13 which is a harmonic compensation current obtained from the output of the adder 17. As a result, the PWM control unit 15 sends a gate signal to each switching element of the power converter 4 so that the output current detection value from the output current detector 10 matches the current command.
As described above, since the harmonic compensation current obtained from the harmonic component of the load current shown in FIG. 3 is output from the power converter 4, the harmonic current to the load device 2 is replaced by the AC power source 1. Since it is supplied by the harmonic compensation current from the power converter 4, the inflow of the harmonic current from the AC power supply 1 is prevented, that is, the harmonic current compensation operation is achieved.
[0023]
FIG. 5 shows current waveforms of each part, and corresponds to the state up to 0.10 SEC at the time when the AC power supply 1 is fed. That is, as shown in FIG. 5A, the power converter 4 outputs an output current (solid line) that is a harmonic compensation current based on the harmonic pattern 13 with respect to a load current (dotted line) including harmonics, As shown in FIG. 2B, the power source current (one-dot chain line) is a sine waveform having a fundamental frequency not including a harmonic component.
[0024]
Here, when power supply from the AC power supply 1 is stopped due to a power transmission system failure or the like, that is, when a power failure occurs, the switch 3 is immediately opened by the power failure determination output of the power failure detection circuit 7 and the load device 2 and the AC power source 1 are connected. Is disconnected. At the same time, the pattern switch 21 of the control device 12 is switched to the B side.
Due to the occurrence of a power failure, the load detection current IL becomes zero instantaneously. However, as described with reference to FIG. 4, the LC band filter 16 continues its output, and thus the fundamental wave pattern 14 maintains the state created from the time of power supply. Yes. Therefore, the PWM control unit 15 sends the gate signal to each switching element of the power converter 4 so that the output current detection value from the output current detector 10 matches the current command using the fundamental wave pattern 14 as a current command.
In an actual circuit, since the current command pattern is switched instantaneously after the occurrence of a power failure, the output of the LC band filter 16, and thus the fundamental wave pattern 14 maintains the waveform up to immediately before the occurrence of the power failure without changing its amplitude. As a result, the fundamental wave component of the load current at the time of power feeding is supplied from the power converter 4 to the load device 2 as it is after the power failure.
[0025]
The time 0.10 to 0.15 SEC in FIG. 5 corresponds to a power failure. That is, as shown in FIG. 9A, output current = load current is supplied from the power converter 4 to the load device 2, and as shown in FIG. Yes.
[0026]
In addition, after time 0.15SEC of FIG. 5, the state after AC power supply 1 has recovered is shown. That is, when the power failure detection circuit 7 detects power recovery, the switch 3 is immediately closed, and the power supply from the AC power source 1 to the load device 2 is resumed, and the PWM control unit 15 again uses the harmonic pattern 13 as a current command. Outputs wave compensation current.
[0027]
As described above, in the first embodiment of the present invention, when a power failure occurs or power is restored, the current command pattern is switched, but the current control system itself that determines the operation mode of the power converter 4 is always maintained. Therefore, no adverse effect due to switching between the current control system and the voltage control system of the conventional apparatus occurs, and no harmful transient phenomenon occurs at the time of power failure and power recovery as shown in FIG.
[0028]
As described above, the present invention uses the output sustainability after the loss of input of the LC band filter 16 and outputs a current based on the sustain command pattern after the occurrence of a power failure. From the detected value of the output current, A command pattern is created and the operation is continued, that is, a self-oscillation type control operation is performed.
Therefore, the power outage time continues for a relatively long time, or the output current from the power converter 4 gradually increases or decreases as the power outage time elapses depending on the error of each detecting means, the constants of each part of the control system, or the like. there is a possibility.
[0029]
The multiplier 18 shown in FIG. 2 prevents this problem. In other words, at the time of a power failure, the voltage of the load device 2 based on the output current from the power converter 4 is detected, and the basic value extracted by the LC band filter 16 so that the deviation between the load detection voltage VL and the reference voltage VS becomes zero. The wave component is multiplied by a correction multiplication coefficient to correct the amplitude value of the fundamental wave pattern 14.
[0030]
As the value of the reference voltage VS, for example, the rated nominal voltage value of the circuit may be set as the value to be supplied to the load device 2, but for example, the value of the AC power source 1 detected by the voltage detector 6 is used. Sample hold means for holding the voltage value for a predetermined time may be provided, and this hold value may be used as the reference voltage VS. In this case, since the voltage supplied to the load device 2 immediately before the occurrence of the power failure is continuously supplied to the load device 2 after the occurrence of the power failure, the influence of the occurrence of the power failure on the load device 2 can be further reduced. There are advantages.
[0031]
Of course, the correction means by the multiplier 18 may be omitted depending on the assumed power outage occurrence condition such as a possible power outage time being extremely short.
[0032]
In the above description, the case where the LC band filter 16 is used as the fundamental wave component extraction unit of the load detection current IL that can be continuously output for a predetermined time after the loss of input has been described. However, the present invention is not limited to this. That is, for example, the load detection current IL may be A / D converted, a fundamental wave component may be obtained from this by a predetermined logical operation, and the fundamental wave pattern 14 may be generated through a sample-and-hold unit that holds the fundamental wave component for a predetermined time. It goes without saying that the same effect as described above can also be obtained in this case.
In the above description, the harmonic component of the load detection current IL is obtained by subtracting the fundamental wave component extracted by the LC band filter 16 from the load detection current IL. For example, a combination of LC bandpass filters is used. Then, the harmonic component may be extracted directly from the load detection current IL.
[0033]
Next, a capacitor constituting the DC power supply 5 of FIG. 1 will be described. FIG. 6 shows an example of the configuration of the DC power supply 5. Here, a parallel connection body of an electrolytic capacitor 51 and an electric double layer capacitor 52 is shown. When the time constants of the electrolytic capacitor 51 and the electric double layer capacitor 52, Rs1 × C1 and Rs2 × C2, are compared, the former is small (about 1 of the latter), as shown in each dotted line frame. / 100 times). Therefore, when outputting the harmonic compensation current at the time of feeding, the electrolytic capacitor 51 having a small time constant, that is, a fast frequency response is suitable.
On the other hand, when supplying active power of the fundamental frequency to the load device 2 at the time of a power failure, a fast frequency response is not required, but a large amount of power storage is required, and the electric double layer capacitor 52 is suitable.
FIG. 6 makes use of the characteristics of both types of capacitors. The electrolytic capacitor 51 has a relatively small capacity for mainly outputting harmonic compensation current, and the relatively large capacity has a relatively large capacity for outputting fundamental current. An electric double layer capacitor 52 is connected in parallel.
[0034]
FIG. 7 shows another configuration example of the DC power supply 5 in which an electrolytic capacitor 51 and a secondary storage battery 53 are connected in parallel. The secondary storage battery 53 has a slower charge / discharge characteristic than the electric double layer capacitor because the movement of the charge is accompanied by a chemical reaction. However, since it is excellent as a large-capacity power storage means, it is useful as the DC power source 5 used in the power conversion device of the present invention by combining with the electrolytic capacitor 51 as in the case of FIG.
[0035]
The means for charging these capacitors is well known and will not be described in detail. For example, a means for detecting the voltage of the capacitor is provided, and a DC voltage command based on a deviation between the detected value and a predetermined voltage setting value is provided. By creating a component and controlling it by adding it to the original current command, the capacitor can be charged to a predetermined set value from the AC power supply 1 via the power converter 4 during power feeding.
[0036]
Although not shown, the DC power supply 5 may be configured as a three-way parallel connection of an electrolytic capacitor 51, an electric double layer capacitor 52, and a secondary storage battery 53. For example, an electric double layer capacitor may be used. However, if the frequency response is improved by improving the internal structure or the like, the DC power supply 5 may be constituted by only the electric double layer capacitor 52. Furthermore, when the order of the harmonics to be compensated can be limited to a relatively low range, a particularly fast frequency response is not required as a capacitor, and thus a large-capacity configuration can be realized relatively easily and inexpensively. An electric double layer capacitor 52 or a secondary storage battery 53 may be used.
[0037]
Embodiment 2. FIG.
Next, a power conversion device according to Embodiment 2 of the present invention will be described. FIG. 8 is a block diagram showing the main part, and the other parts are exactly the same as in the first embodiment. In the second embodiment, as shown in FIG. 8, the harmonic compensation current based on the output from the adder 17 passes through a sample hold circuit 22 that can continuously output a predetermined time after the input is lost. Create Further, an adder 23 for adding the harmonic pattern 13 and the fundamental wave pattern 14 is provided, and a current command pattern to be sent to the PWM control unit 15 by the pattern switcher 21 is set to the harmonic pattern 13 at the time of power supply and at the time of power failure. It is assumed that the harmonic pattern 13 + the fundamental wave pattern 14.
[0038]
Therefore, the operation at the time of power supply is the same as that in the case of the form 1 except that the harmonic pattern 13 composed of the harmonic compensation current held for a predetermined time, for example, one period of the fundamental frequency, is used. At the time of a power failure, the operation is changed to an operation for performing current control by a pattern obtained by adding the fundamental wave pattern 14 to the harmonic pattern 13. In this way, in this mode 2, at the time of a power failure, not only the fundamental wave current but also the harmonic compensation current output until immediately before the power failure is continuously output to the load device 2, that is, the fundamental wave component and As a result, the voltage waveform of the load device 2 at the time of a power failure is compared with that in the first mode. As a result, the quality of the alternative supply power at the time of a power failure is improved.
[0039]
In FIG. 8, the adder 17 subtracts the output of the LC band filter 16 from the load detection current IL and holds the output by the sample hold circuit 22. However, the LC for each assumed harmonic order is used. A band pass filter may be provided, and the harmonic pattern 13 may be created directly from the output composite value. This is because these LC bandpass filters themselves have the output continuation capability after the loss of input, similar to that shown in FIG. 4, and therefore no special sample hold means is required.
[0040]
As described above, also in the second embodiment, since the power supply and the power failure are switched without changing the current control system, a stable and continuous switching operation is possible. Furthermore, load voltage distortion during a power failure is also reduced.
[0041]
【The invention's effect】
As described above, the power conversion device according to the present invention includes a DC power supply and power conversion means that converts the power of the DC power supply into AC and supplies the load to the load, and connects the load to the AC power supply via the switching means. When the AC power supply is normally fed, the switching means is closed to supply power from the AC power supply to the load, and a harmonic compensation current for compensating the harmonic current of the load is supplied from the power conversion means. In the power converter that outputs the AC power to the load when the AC power supply is interrupted and opens the switching means to supply AC power from the power conversion means,
Load current detection means for detecting the load current, and a fundamental wave pattern creation means for extracting a fundamental wave component from the output of the load current detection means and creating a fundamental wave pattern that can be output continuously for a predetermined time after the loss of input. A harmonic pattern creating means for creating a harmonic pattern which is the harmonic compensation current from the output of the load current detecting means, and the harmonic pattern is inputted at the time of power feeding, and this is used as a current command to output the power converting means. Since current control is provided and current control means for controlling the output current of the power conversion means using the fundamental wave pattern as a current command in the event of a power failure, the harmonics during power supply are maintained while maintaining the current control system. It is possible to switch from the compensation current output operation to the power supply operation to the load at the time of a power failure and vice versa. Also stabilized.
[0042]
Moreover, the power conversion device according to the present invention includes a DC power supply and power conversion means for converting the power of the DC power supply into AC and supplying the load to the load, and connects the load to the AC power supply through an opening / closing means. When the AC power supply is normally fed, the switching means is closed and power is supplied from the AC power supply to the load and a harmonic compensation current for compensating the harmonic current of the load is output from the power conversion means. At the time of a power failure of the AC power supply, in the power conversion device that opens the switching means and supplies AC power from the power conversion means to the load
Load current detection means for detecting the load current, and a fundamental wave pattern creation means for extracting a fundamental wave component from the output of the load current detection means and creating a fundamental wave pattern that can be output continuously for a predetermined time after the loss of input. A harmonic pattern creating means for obtaining the harmonic compensation current from the output of the load current detecting means to create a harmonic pattern in a form that can be continuously output for a predetermined time after the input is lost, and the harmonic pattern is input at the time of power feeding This is used as a current command to control the output current of the power conversion means, and in the event of a power failure, the fundamental wave pattern and the harmonic pattern are input, and these added values are used as current commands to control the output current of the power conversion means. Since the control means is provided, while maintaining the current control system, the harmonic compensation current output operation during power feeding to the power supply operation to the load during a power failure, and vice versa Enables switching of the operation, construction of the control is also stable operation at the time convenient switching. Furthermore, load voltage distortion during a power failure is also reduced.
[0043]
Further, the harmonic pattern creating means of the power conversion device according to the present invention includes a harmonic compensation current creating means for creating a harmonic compensation current from the output of the load current detecting means, and the created harmonic compensation current for a predetermined time. Since the sample-and-hold means is provided, a current control system in which the harmonic compensation current is reliably output even after a power failure occurs is formed.
[0044]
In addition, the fundamental wave pattern creating means of the power conversion device according to the present invention includes an LC band filter for extracting the fundamental wave component from the output of the load current detecting means. A current control system in which current is reliably output is formed.
[0045]
Further, the fundamental wave pattern creating means of the power conversion device according to the present invention comprises a fundamental wave extracting means for extracting the fundamental wave component from the output of the load current detecting means, and a sample hold for holding the extracted fundamental wave component for a predetermined time. Since the means is provided, a current control system in which the fundamental wave current is reliably output after the occurrence of a power failure is formed.
[0046]
In addition, the power conversion device according to the present invention is provided with a multiplying means for correcting the fundamental wave component extracted from the output of the load current detecting means and outputting it as a fundamental wave pattern in the fundamental wave pattern creating means, and an AC power source The reference voltage setting means for setting the voltage reference value, the load voltage detection means for detecting the voltage of the load, and the multiplication means for inputting the deviation between the voltage reference value and the load voltage detection value so that the deviation becomes zero. Since the voltage correction means for generating the correction multiplication coefficient is provided, the load voltage can be maintained at a desired reference value after the occurrence of a power failure.
[0047]
In addition, the power conversion device according to the present invention includes sample hold means for detecting the voltage of the AC power supply and holding the detected value for a predetermined time, and the sample hold value is used as the voltage reference value of the reference voltage setting means. After the occurrence of a power failure, the load voltage can be maintained at the value immediately before the occurrence of the power failure, and the change in the load state before and after the occurrence of the power failure can be further reduced.
[0048]
Further, the harmonic pattern creating means of the power converter according to the present invention creates the harmonic compensation current by subtracting the fundamental wave component extracted by the fundamental wave pattern creating means from the output of the load current detecting means. The circuit configuration for creating the wave pattern becomes simple.
[0049]
Further, the power conversion device according to the present invention is configured such that the DC power source is an electric double layer capacitor and / or a parallel connection body of a secondary storage battery and an electrolytic capacitor, and the above power supply is supplied from the AC power source via the power conversion means during power feeding. Since the parallel connection is charged, both the output of the relatively small-capacitance harmonic compensation current and the output of the relatively large-capacitance fundamental current can be easily and economically configured as a capacitor. Can be realized.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a power conversion device according to Embodiment 1 of the present invention.
FIG. 2 is a configuration diagram showing details of the control device 12 of FIG. 1;
FIG. 3 is a waveform diagram showing an example of a harmonic component and a fundamental component of a load current.
4 is a waveform diagram showing characteristics of the LC band filter 16. FIG.
FIG. 5 is a diagram showing an output waveform and the like of the power converter.
6 is a diagram showing an example of the configuration of a DC power supply 5. FIG.
7 is a diagram showing another configuration example of the DC power supply 5. FIG.
FIG. 8 is a configuration diagram showing a main part of a power conversion device according to Embodiment 2 of the present invention.
[Explanation of symbols]
1 AC power supply, 2 load device, 3 switch, 4 power converter, 5 DC power supply, 6 voltage detector, 7 power failure detection circuit, 8 load voltage detector,
9 Load current detector, 10 Output current detector, 12 Control device,
13 harmonic pattern, 14 fundamental wave pattern, 15 PWM controller,
16 LC band filter, 17, 19, 23 adder, 18 multiplier,
20 PI controller, 21 pattern switcher, 22 sample hold circuit,
51 electrolytic capacitor, 52 electric double layer capacitor, 53 secondary storage battery.

Claims

A DC power supply and power conversion means for converting the power of the DC power supply into alternating current and supplying the load to the load, and connecting the load to the AC power supply via the opening / closing means. The circuit is closed to supply power from the AC power source to the load, and the power conversion unit outputs a harmonic compensation current that compensates for the harmonic current of the load. In the power conversion device that opens the circuit and supplies AC power from the power conversion means to the load,
Load current detection means for detecting the load current, and a fundamental wave pattern creation means for extracting a fundamental wave component from the output of the load current detection means and creating a fundamental wave pattern that can be output continuously for a predetermined time after the loss of input. A harmonic pattern creating means for creating a harmonic pattern which is the harmonic compensation current from the output of the load current detecting means, and the harmonic pattern is inputted at the time of power feeding, and this is used as a current command to output the power converting means. A power conversion device comprising: current control means for controlling current and inputting the fundamental wave pattern at the time of a power failure, and controlling the output current of the power conversion means using this as a current command.

A DC power supply and power conversion means for converting the power of the DC power supply into alternating current and supplying the load to the load, and connecting the load to the AC power supply via the opening / closing means. The circuit is closed to supply power from the AC power source to the load, and the power conversion unit outputs a harmonic compensation current that compensates for the harmonic current of the load. In the power conversion device that opens the circuit and supplies AC power from the power conversion means to the load,
Load current detection means for detecting the load current, and a fundamental wave pattern creation means for extracting a fundamental wave component from the output of the load current detection means and creating a fundamental wave pattern that can be output continuously for a predetermined time after the loss of input. A harmonic pattern creating means for obtaining the harmonic compensation current from the output of the load current detecting means to create a harmonic pattern in a form that can be continuously output for a predetermined time after the input is lost, and the harmonic pattern is input at the time of power feeding This is used as a current command to control the output current of the power conversion means, and in the event of a power failure, the fundamental wave pattern and the harmonic pattern are input, and these added values are used as current commands to control the output current of the power conversion means. A power converter comprising a control means.

The harmonic pattern creation means includes a harmonic compensation current creation means for creating a harmonic compensation current from the output of the load current detection means, and a sample hold means for holding the created harmonic compensation current for a predetermined time. The power conversion device according to claim 2.

4. The power conversion device according to claim 1, wherein the fundamental wave pattern creating means includes an LC band filter for extracting a fundamental wave component from the output of the load current detecting means.

The fundamental wave pattern creating means includes a fundamental wave extracting means for extracting the fundamental wave component from the output of the load current detecting means, and a sample hold means for holding the extracted fundamental wave component for a predetermined time. Item 4. The power conversion device according to any one of Items 1 to 3.

A fundamental voltage pattern creating means is provided with multiplication means for correcting the fundamental wave component extracted from the output of the load current detecting means and outputting it as a fundamental wave pattern, and a reference voltage setting means for setting a voltage reference value of the AC power supply, Load voltage detecting means for detecting the voltage of the load, and voltage correcting means for inputting a deviation between the voltage reference value and the load voltage detected value and creating a correction multiplication coefficient of the multiplying means so that the deviation becomes zero. The power conversion device according to claim 1, wherein the power conversion device is a power conversion device.

7. The power converter according to claim 6, further comprising sample hold means for detecting a voltage of the AC power source and holding the detected value for a predetermined time, and using the sample hold value as a voltage reference value for the reference voltage setting means.

The harmonic pattern creating means creates a harmonic compensation current by subtracting the fundamental wave component extracted by the fundamental wave pattern creating means from the output of the load current detecting means. The power converter device described in 1.

The DC power supply is constituted by a parallel connection body of an electric double layer capacitor and / or a secondary storage battery and an electrolytic capacitor, and the parallel connection body is charged from the AC power supply via the power conversion means during power feeding. The power converter according to any one of claims 1 to 8.