JP3857167B2

JP3857167B2 - Voltage fluctuation compensation device

Info

Publication number: JP3857167B2
Application number: JP2002091618A
Authority: JP
Inventors: 貢高橋; 健一小山; 博之笹尾; 明彦岩田; 昭弘鈴木; 敏之菊永; 伸彦羽田野
Original assignee: Kansai Electric Power Co Inc; Mitsubishi Electric Corp
Current assignee: Kansai Electric Power Co Inc; Mitsubishi Electric Corp
Priority date: 2002-03-28
Filing date: 2002-03-28
Publication date: 2006-12-13
Anticipated expiration: 2022-03-28
Also published as: JP2003289625A

Description

【０００１】
【発明の属する技術分野】
この発明は、負荷に供給される電力系統の電圧が瞬時的に変動した際に、それを検出して電圧変動を補償する電圧変動補償装置に関するものである。
【０００２】
【従来の技術】
雷などにより電力系統の電圧が瞬時的に低下し、工場などの精密機器などが誤作動や一時停止することにより、生産ラインで多大な被害を被ることがある。このような被害を防ぐために、電力系統の瞬時的電圧低下などの電圧変動を監視して、電圧低下を補償する電圧変動補償装置が用いられている。
例えば特開昭６１−１１６９３４号公報に記載された従来の直列接続型電圧変動補償装置は、電力系統に直列に接続し、系統電圧が低下した時に不足電圧分だけを系統電圧に重畳し負荷への供給電圧を一定に保つもので、概略構成図を図１１に示す。
図に示すように、電圧変動補償装置１は系統電圧検出部２、制御部３および補償電圧発生部４から成る。制御部３では系統電圧検出部２にて検出した系統電圧Vrと正常時の系統電圧（系統の定格電圧）を模擬する基準電圧発生部５の電圧Vsとの差異電圧、すなわち系統の不足電圧Viを検出する不足電圧検出部６と、制御信号発生部７とを備える。信号発生部７は、補償電圧発生部４が出力する補償電圧Voが不足電圧検出部６の出力である不足電圧Viになるように、補償電圧発生部４に対して補償制御信号を発生する。
【０００３】
このような電圧変動補償装置１は、電力系統の電源側８と負荷側９との間に補償電圧発生部４を直列接続し、系統の電源側８の地絡事故などで系統電圧Vrが低下すると補償電圧発生部４の出力補償電圧Voを系統電圧Vrに重畳し、（１）式に示すように負荷１０の電圧Vlを基準電圧Vsに保つ。ただし、系統インピーダンスによる電圧降下は無視した。
Vl＝Vr＋Vo＝Vr＋Vi＝Vr＋（Vs−Vr）＝Vs （１）
この結果、系統電圧が変動しても負荷に一定の電圧を供給することが出来る。
【０００４】
電力系統においては、電圧変動補償装置１の負荷側９での短絡のような事故も起こり得る。このような場合、図１２に示すように、補償電圧発生部４の負荷側９に保護遮断器１１を設置して短絡電流を遮断することにより、系統保護を行っていた。
【０００５】
【発明が解決しようとする課題】
従来の電圧変動補償装置は、以上のように構成されているため、系統の負荷側９での事故時に短絡電流のような過電流が流れる場合、以下のような問題が発生するものであった。
電圧変動補償装置１の電源側８のインピーダンスZs、負荷側９の短絡事故点までのインピーダンスZlとする。負荷側９で短絡事故が起こった瞬時では系統電圧は低下するが、未だ電圧変動補償装置１は電圧補償動作をしていない、即ち補償電圧を出力していないため、この短絡事故の発生瞬時に流れる短絡電流Ifは、（２）式となる。
If＝Vs／（Zs＋Zl）（２）
このとき、電圧変動補償装置１の系統電圧検出部２が検出する系統電圧Vrは、（３）式に示すように系統の基準電圧Vs（定格電圧）から系統電源側８のインピーダンスZsによる電圧降下分を引いた値となる。
Vr＝Vs−Zs・If （３）
【０００６】
この結果、系統電圧Vrが基準電圧Vsより低下していることが検出され、電圧変動補償装置１は電圧補償動作を開始する。すなわち系統電圧Vrの不足電圧Vi（＝Zs・If）が補償電圧Voとして系統電圧に重畳され、負荷側９の系統電圧は基準電圧Vsに保たれる。この場合の短絡電流If_ａは（４）式となる。
If_ａ＝（Vs＋Vo）／（Zs＋Zl）＞If （４）
すなわち、負荷側事故時で短絡電流のような過電流が流れる場合、電圧変動補償装置１が電圧補償動作することにより短絡電流が増加する。この短絡電流の増加により系統電圧はさらに低下し、これに伴って出力補償電圧Voも変化し、最終的には
Vo＝Zs・If_ａ
If_ａ＝Vs／Zl
となる。
このように、電圧変動補償装置１が電圧補償動作することにより負荷側事故による過電流を増大させ、過電流による被害の増加や、電圧変動補償装置１自体が過電流により破壊されるという問題点があった。また、負荷側９の系統を保護する保護遮断器１１が過電流を遮断できずに系統保護が出来なくなることもあり、新たな系統保護機器の設置など短絡電流増大対策が必要であった。
【０００７】
この発明は、上記のような問題点を解消するために成されたものであって、負荷に供給する電圧低下を補償する電圧変動補償装置において、系統の負荷側事故時に発生する過電流を増大させることなく、過電流による被害を抑制して、電力系統および電圧変動補償装置自身を保護することを目的とする。
【０００８】
【課題を解決するための手段】
この発明に係る請求項１記載の電圧変動補償装置は、電力系統における電圧低下を検出する系統電圧検出部と、該系統電圧検出部からの電圧低下検出信号を入力として電圧補償制御信号を出力する制御部と、上記電力系統に直列に接続され、上記電圧補償制御信号により補償電圧を発生させる補償電圧発生部とを備えて、系統電圧低下時に上記補償電圧発生部にて発生させた上記補償電圧を該系統電圧に重畳して、負荷に供給される電圧変動を抑える装置構成であって、上記補償電圧発生部が直列接続された上記系統に流れる過電流を検出して過電流検出信号を上記制御部に出力する過電流検出部を備え、上記制御部では、上記過電流検出信号の入力時には、上記電圧低下検出信号が入力されても上記電圧補償制御信号を出力せず、該電圧補償制御信号の替わりに過電流抑制制御信号を出力し、該過電流抑制制御信号を入力として補償電圧発生部は、上記補償電圧を発生させずに、系統電圧と逆極性の過電流抑制電圧を発生して上記系統電圧に重畳させるものである。
【０００９】
またこの発明に係る請求項２記載の電圧変動補償装置は、請求項１において、補償電圧発生部が直列接続された系統の負荷側に保護遮断器を備え、過電流検出部からの過電流検出信号を保持し、該保持した過電流検出信号により上記保護遮断器を遮断させるものである。
【００１０】
またこの発明に係る請求項３記載の電圧変動補償装置は、請求項１または２において、補償電圧発生部から発生される過電流抑制電圧は、正常な系統電圧と逆極性でほぼ同じ大きさである。
【００１１】
またこの発明に係る請求項４記載の電圧変動補償装置は、請求項１または２において、補償電圧発生部は、直流電源と、該直流電源の両側あるいは片側に配されて該直流電源を電力系統に接続し、ダイオードが逆並列に接続された自己消弧型の半導体スイッチング素子とから成り、上記直流電源に接続される上記ダイオードは、該直流電源の正極側では該ダイオードの負極が接続され、該直流電源の負極側では該ダイオードの正極が接続され、制御部から過電流抑制制御信号が入力されると、上記全ての半導体スイッチング素子をオフにして、上記直流電源の電圧を逆極性の過電流抑制電圧として上記ダイオードにより系統電圧に重畳するものである。
【００１２】
またこの発明に係る請求項５記載の電圧変動補償装置は、請求項１〜３のいずれかにおいて、系統電圧検出部にて電圧低下が検出されない正常時に補償電圧発生部をバイパスするために該補償電圧発生部に並列に接続された短絡スイッチを備え、上記短絡スイッチが閉極状態で、過電流検出信号あるいは電圧低下検出信号が制御部に入力されると、該制御部は、上記短絡スイッチに開極指令を出力し、該短絡スイッチが開極状態になった後、過電流抑制制御信号あるいは電圧補償制御信号を出力して補償電圧発生部にて電圧を発生させるものである。
【００１３】
またこの発明に係る請求項６記載の電圧変動補償装置は、請求項１〜３のいずれかにおいて、系統電圧検出部にて電圧低下が検出されない正常時に補償電圧発生部をバイパスするために、短絡スイッチを該補償電圧発生部に並列に接続して備え、上記短絡スイッチが閉極状態で、過電流検出信号が制御部に入力されると、該制御部は過電流抑制制御信号を出力せず上記短絡スイッチは閉極状態を維持し、上記短絡スイッチが閉極状態で、過電流検出信号は入力されずに電圧低下検出信号のみ制御部に入力されると、該制御部は、上記短絡スイッチに開極指令を出力して開極した後、電圧補償制御信号を出力するものである。
【００１４】
【発明の実施の形態】
実施の形態１．
以下、この発明の実施の形態１を図について説明する。
図１は、この発明の実施の形態１による電圧変動補償装置の概略構成図である。
図に示すように、電圧変動補償装置１００は系統電圧検出部２、過電流検出部１２、制御部３１および補償電圧発生部４から成る。制御部３１では系統電圧検出部２にて検出した系統電圧Vrと正常時の系統電圧（系統の定格電圧）を模擬する基準電圧発生部５の電圧Vsとの差異電圧、すなわち系統の不足電圧Viを検出する不足電圧検出部６と、制御信号発生部７とを備え、不足電圧検出部６と信号発生部７との間には信号遮断部１３を設ける。また、補償電圧発生部４は、電力系統の電源側８と負荷側９との間に直列に接続され、制御信号発生部７からの電圧補償制御信号により、補償電圧Voをその大きさが不足電圧Viとなるように出力して系統電圧Vrに重畳し、負荷１０に供給する系統電圧を基準電圧Vsに保つ。また補償電圧発生部４の負荷側９に保護遮断器１１を設置し、短絡電流などの過電流を遮断する。
【００１５】
過電流検出部１２は、補償電圧発生部４が直列接続された系統を流れる過電流を検出すると過電流検出信号を制御部３１の信号遮断部１３に出力する。信号遮断部１３は、過電流検出信号が入力されない場合は不足電圧検出部６の出力を信号発生部７に通し、過電流検出信号が入力された場合は不足電圧検出部６の出力を信号発生部７に通さないように信号路を遮断する。
従って、電源側８の地落事故等により系統電圧が低下した場合は過電流が流れないため不足電圧検出部６の検出した不足電圧Viは、電圧低下検出信号として信号遮断部１３を通り、信号発生部７で補償電圧発生部４の出力補償電圧VoをViにするよう制御する電圧補償制御信号が発生され、電圧変動補償装置１００は系統電圧を補償する。
負荷側９の短絡事故等で過電流が発生して系統電圧が低下した場合、不足電圧検出部６が不足電圧を検出しても、同時に過電流検出部１２が過電流検出信号を信号遮断部１３に送るため、信号遮断部１３は不足電圧検出部６の出力である電圧低下検出信号を遮断し信号発生部７に送らない。この結果、信号発生部７は補償電圧を発生させる電圧補償制御信号を発生しない、即ち不足電圧Vi＝０として補償電圧発生部４の出力補償電圧Voが零になるような指令を補償電圧発生部４に送り、系統電圧に補償電圧が重畳されること無く、過電流は増大しない。
このため、系統電圧の変動を抑制する電圧変動補償装置１００を設置しても、過電流を増大させることがなく、通常の保護遮断器１１以外の新たな系統保護機器の設置など短絡電流増大対策を要することなく、過電流による被害を抑制して、電力系統および電圧変動補償装置自身を保護できる。
【００１６】
実施の形態２．
上記実施の形態１では、過電流を検出した場合に不足電圧を補償電圧として系統に重畳させないものとしたが、この実施の形態２では、過電流検出時に、正常時の系統電圧（基準電圧Vs）と逆極性の電圧を過電流抑制電圧として系統電圧に重畳して過電流を抑制する。
図２に示すように、制御部３２では、図１での信号遮断部１３の替わりに信号切替部１４および反転増幅部１５を設け、信号発生部７への入力を信号切替部１４によって切り替える。信号切替部１４は２つの入力端子を持ち、不足電圧検出部６の信号あるいは基準電圧発生部５の電圧Vsを反転増幅部１５を通した信号のいずれかを、過電流検出信号の入力により選択する。
過電流検出信号が信号切替部１４に入力されない場合は、不足電圧検出部６の信号は信号切替部１４を介して信号発生部７に入力され、系統電圧低下時には信号発生部７からの電圧補償制御信号により補償電圧発生部４は不足電圧を出力して系統電圧を補償する。
【００１７】
過電流検出器１２が過電流を検出し、過電流検出信号が信号切替部１４に入力されると、信号発生部７には、反転増幅部１５から基準電圧Vsの極性を反転させた信号が信号切替部１４を介して入力される。これにより、信号発生部７は補償電圧発生部４の出力電圧を、正常時の系統電圧と絶対値が等しく極性が逆の過電流抑制電圧とするように制御する過電流抑制制御信号を発生し、補償電圧発生部４から出力される過電流抑制電圧は系統電圧に重畳される。
この時の短絡電流（過電流）If_ｂは、補償電圧発生部４の出力電圧Voを−Vsに等しいと置けば、
If_ｂ＝（Vs＋Vo）／（Zs＋Zl）＝（Vs＋（−Vs））／（Zs＋Zl）＝０（５）
となり、過電流は零に抑えられる。なお、電圧変動補償装置１の電源側８のインピーダンスZs、負荷側９の短絡事故点までのインピーダンスZlとする。
【００１８】
補償電圧発生部４が発生する過電流抑制電圧は、正常時の系統電圧と絶対値が等しく逆極性の電圧でなくとも、系統電圧と逆極性の電圧であれば、過電流を抑制する効果はある。従って、負荷側事故により系統に流れる過電流を抑制できるため、通常の保護遮断器１１以外の新たな系統保護機器の設置など短絡電流増大対策を要することなく、過電流による電力系統の損傷や事故の被害を低減でき、電圧変動補償装置１００自身の損傷も避けることができる。
なお、正常時の系統電圧と逆極性の過電流抑制電圧を重畳する方式は、補償電圧発生部４の負荷側事故に対してのみ為されるもので、電源側事故には対応できない。
【００１９】
またこの実施の形態では図２に示すように、過電流検出部１２で発生した過電流検出信号を保持し、その信号により負荷側系統９の保護遮断器１１を遮断させる構成にした。負荷側事故による過電流は電圧変動補償装置１００で抑制されるため、保護遮断器１１の過電流リレー（図示せず）が動作しなかったり動作が遅れたりすることがあるが、上述したように、保護遮断器１１を過電流検出信号で遮断させる構成にしたことにより、過電流が抑制されても確実に保護遮断器１１を遮断して事故系統を切り離せる効果を有する。
【００２０】
実施の形態３．
上記実施の形態２では、過電流検出時に、正常時の系統電圧（基準電圧Vs）と逆極性の電圧を過電流抑制電圧として系統電圧に重畳する電圧変動補償装置１００を示したが、系統電圧と逆極性の過電流抑制電圧を系統電圧に重畳する電圧変動補償装置１００の回路構成の１形態を図３に示す。図に示すように、補償電圧発生部４ａ内のコンデンサ１６などの直流電圧源を系統に直列に挿入して、系統に電圧を重畳する。コンデンサ１６を系統に接続したり、切離したりするために自己消弧型の４個のスイッチング素子Ｔ１〜Ｔ４から成るインバータが用いられる。ここでは、PWMインバータ方式を用い、系統に重畳する電圧を制御するために、制御部３３から各スイッチング素子Ｔ１〜Ｔ４のON、OFFを制御するゲート信号Ｇ１〜Ｇ４を出力して、コンデンサ１６を断続的に系統に直列に接続し、接続時間すなわち電圧パルス幅を制御して必要な電圧を重畳する。
なお、複数個のコンデンサ（図示せず）を備えて必要な電圧に応じて直列接続させるコンデンサの組合せを選択し、その出力電圧の総和を系統に重畳する方式を用いても良い。また、この例では補償電圧発生部４ａを直接系統に直列接続しているが、トランスを介して系統に接続しても良い。また高調波除去のためのフィルターは図示を省略した。
いずれの方式でも自己消弧型スイッチング素子Ｔ１〜Ｔ４には逆向きの電流を流せるように逆並列にダイオードＤ１〜Ｄ４が接続される。これは系統に繋がれている負荷１０が純抵抗の場合は直列に接続されたコンデンサ１６の極性の向き（コンデンサ１６の電圧を重畳する電圧の向き）にしか電流が流れないため必要無いが、負荷１０が純抵抗以外の場合はコンデンサ１６の電圧の向きと電流の向きとが異なる場合があるため、この電流を流すためにスイッチング素子Ｔ１〜Ｔ４には逆並列ダイオードＤ１〜Ｄ４が必要となる。
【００２１】
このように、コンデンサ１６を系統に直列に接続するスイッチング素子Ｔ１〜Ｔ４には逆並列のダイオードＤ１〜Ｄ４が接続されているため、コンデンサ１６は常にダイオードＤ１〜Ｄ４を介して系統に接続される。そしてコンデンサ１６の極性の向きと逆方向の電流を流す向きにダイオードＤ１〜Ｄ４は接続され、すなわち図に示すように、コンデンサ１６の正極はダイオードＤ１、Ｄ４の負極に接続されて系統に繋がれ、コンデンサ１６の負極はダイオードＤ２、Ｄ３の正極に接続されて系統に繋がれて、コンデンサ１６は系統電圧と逆極性になるように接続される。
【００２２】
制御部３３では、信号発生部７の出力と過電流検出部１２の出力の反転信号との論理積を判別部１７にて演算し、各スイッチング素子Ｔ１〜Ｔ４のON、OFFを制御するゲート信号Ｇ１〜Ｇ４を出力する。ここで、ゲート信号Ｇ１〜Ｇ４が「Ｈ」でスイッチング素子Ｔ１〜Ｔ４はON、「Ｌ」でスイッチング素子Ｔ１〜Ｔ４はOFFとし、過電流検出部１２の出力である過電流検出信号は、過電流を検出した場合は「Ｈ」、過電流を検出しない場合は「Ｌ」信号とする。
【００２３】
不足電圧検出部６が系統電圧の不足電圧を検出すると、補償電圧発生部４ａが不足電圧に等しい補償電圧を出力するように信号発生部７が各ゲート信号を発生する。この時に過電流検出部１２が過電流を検出していなければ、過電流検出信号は「Ｌ」であり信号発生部７からのゲート信号はそのまま補償電圧発生部４ａのスイッチング素子Ｔ１〜Ｔ４を制御し、補償電圧を発生する。
一方、過電流を検出すると過電流検出信号は「Ｈ」となり、信号発生部７からの出力が何であれ過電流検出信号の反転信号との論理積は全て「Ｌ」となり、過電流抑制制御信号としてスイッチング素子Ｔ１〜Ｔ４は全てOFFとなる。この場合、系統とコンデンサ１６はダイオードＤ１〜Ｄ４を介して繋がっているが、系統電圧の極性に拘わらず、常にコンデンサ１６が系統に挿入される電圧極性は一定であり、コンデンサ１６を充電する方向、すなわち系統電圧とは逆極性となる。
【００２４】
図４に、負荷側短絡事故時の電圧電流波形を示す。図４（ａ）は過電流抑制電圧を発生させない場合の比較例を示し、負荷側短絡事故により、大きな短絡電流が過電流として流れることが判る。図４（ｂ）はこの実施の形態による電圧変動補償装置１００により過電流抑制電圧を発生させたときの、電圧電流波形である。
以下、図４（ｂ）に基づいて、過電流の抑制動作について説明する。
系統負荷側９の短絡事故等に起因する過電流を検出してスイッチング素子Ｔ１〜Ｔ４が全てOFFになると、補償電圧発生部４ａは、コンデンサ１６のその時点の充電電圧を過電流抑制電圧としてダイオードＤ３、Ｄ４を介して出力する。コンデンサ１６は充電する向きに接続されているため、充電電流が流れるが、コンデンサ１６が充電されるに従って充電電流は減少し、系統正常電圧のピークまでコンデンサ１６が充電されると、流れる充電電流は零となり、即ち、電流は流れず過電流は抑制される。系統電圧が反転した場合は、コンデンサ１６はダイオードＤ１、Ｄ２を介して系統に接続されるが、この向きもコンデンサ１６を充電する向きであり、コンデンサ１６が既に正常電圧ピークまで充電されていれば電流は流れない。
PWMインバータで系統の電圧低下を１００％補償するには、コンデンサ１６の充電電圧はほぼ系統電圧のピーク値が必要であり、従って電流は流れないことになる。コンデンサ１６の充電電圧が系統電圧のピーク値より小さい時でも、上述したように、系統にコンデンサ１６の電圧が過電流抑制電圧として逆極性に重畳され、さらにコンデンサ１６が充電されるに従ってコンデンサ電圧は系統のピーク電圧に近づくため過電流は抑制されることになる。
【００２５】
この実施の形態では、過電流検出で発生された過電流抑制制御信号によりスイッチング素子Ｔ１〜Ｔ４を全てOFFにすることにより、コンデンサ１６の充電電圧が、スイッチング素子Ｔ１〜Ｔ４に逆並列に接続されたダイオードＤ１〜Ｄ４を介して系統電圧に逆極性となるように重畳される。即ち、コンデンサ１６の充電電圧を系統電圧と逆極性の過電流抑制電圧として用い、過電流を抑制することができる。
【００２６】
なお、この実施の形態では、補償電圧発生部４ａには、それぞれダイオードＤ１〜Ｄ４が逆並列に接続された４個の半導体スイッチング素子Ｔ１〜Ｔ４から成るフルブリッジインバータを用いたが、これに限るものではない。即ち、ダイオードが逆並列に接続された半導体スイッチング素子をコンデンサの両側あるいは片側に配してコンデンサ１６を電力系統に接続し、コンデンサに接続される上記ダイオードは、コンデンサの正極側であれば負極が、コンデンサの負極側であれば正極が接続されるようにすればよい。
【００２７】
実施の形態４．
次に、この実施の形態４による電圧変動補償装置について図５に基づいて説明する。上記実施の形態２では、過電流検出時に、正常時の系統電圧（基準電圧Vs）と逆極性の電圧を過電流抑制電圧として系統電圧に重畳する電圧変動補償装置１００を示したが、このような電圧変動補償装置１００に、図５に示すように、補償電圧発生部４と並列に接続された短絡スイッチ１８と、この短絡スイッチ１８に流れる電流を検出する電流検出部１９とを設ける。
ところで、直列接続型の電圧変動補償装置１００では、系統電圧に電圧低下が発生しない正常時にも電流を補償電圧発生部４を通すと、補償電圧を発生しなくとも（零電圧を発生）スイッチング素子やダイオードなどの複数の半導体素子を電流が通るため、常時損失が大きい。このため、補償電圧発生部４に短絡スイッチ１８を並列接続して、系統電圧が正常で補償電圧発生部４が補償電圧を発生する必要のない時は、電流を短絡スイッチ１８を介して負荷１０に送り、系統電圧が低下した時に短絡スイッチ１８を遮断し電流を補償電圧発生部４を介して（不足電圧を重畳して）負荷１０に送る。
短絡スイッチ１８として機械式スイッチを用いれば常時の損失はほとんど無く、また半導体スイッチを用いても補償電圧発生部４を通すよりは損失は少なくなる。
【００２８】
短絡スイッチ１８は入力信号によってON、OFFし、過電流検出部１２は短絡スイッチ１８の系統への接続点より外側に配置して、短絡スイッチ１８を通る電流でも補償電圧発生部４を通る電流でも系統を流れる電流を検出する。
正常時は短絡スイッチ１８はONであり、系統電流は短絡スイッチ１８を流れている。系統の負荷側９で短絡事故が発生した場合、過電流検出部１２が過電流を検出し過電流検出信号を制御部３０に送る。制御部３０では過電流検出信号により短絡スイッチ１８に開極指令を送り短絡スイッチ１８をOFFして、流れる電流を遮断する。短絡スイッチ１８の電流が遮断されると系統電流は補償電圧発生部４に転流される。また、短絡スイッチ１８に流れる電流が零になると電流検出部１９が電流零検出信号を制御部３０に送る。制御部３０では電流零検出信号を受けてから、補償電圧発生部４に過電流抑制制御信号を出力し、過電流抑制電圧を発生させるよう制御する。
【００２９】
このように、制御部３０は、短絡スイッチ１８の電流が遮断された後に、補償電圧発生部４に過電流抑制電圧を出力させるため、正常時の電圧変動補償装置１００の損失を低減させる短絡スイッチ１８を用いた場合でも、補償電圧発生部４が発生する過電流抑制電圧が短絡スイッチ１８で短絡されることなく、過大な電流が補償電圧発生部４を流れて素子を損傷させることはない。このため、信頼性良く過電流を抑制することができ、系統の被害を低減できる。
また短絡スイッチ１８として機械式スイッチを採用し、例えば特開平１１−１１１１２３号公報に示す方式で、交流自然電流零点前に強制的に遮断する場合、強制遮断可能な電流値は自然電流零点での遮断可能な電流値より小さい。過電流を検出した時、まず強制遮断を行うように短絡スイッチ１８に指令を出すが遮断電流が強制遮断領域を越えた場合は自然電流零点で遮断することになる。このような場合でも短絡スイッチ１８に流れる電流を検出し短絡スイッチ１８が電流を遮断したことを確認してから過電流抑制電圧を発生させているので、短絡スイッチ１８で過電流抑制電圧が短絡されることは無い。
なお、系統の電源側８の事故により系統電圧が低下した時にも、制御部３０は、短絡スイッチ１８を開極指令により遮断し、電流検出部１９からの電流零検出信号を受けた後、補償電圧発生部４に電圧補償制御信号を出力し、補償電圧を発生させるよう制御する。
【００３０】
実施の形態５．
上記実施の形態４を、図２で示した回路構成に適用した形態例を図６に示す。
図に示すように、この構成では信号切替部１４の出力端子と信号発生部７との間に信号遮断部１３を設け、また不足電圧検出部６の出力を入力する電圧低下検出部２０を設ける。信号遮断部１３には短絡スイッチ１８に流れる電流を検出する電流検出部１９の電流零検出信号が入力される。電流零検出信号は電流が零の時は「Ｈ」、電流が流れている時は「Ｌ」とする。電圧低下検出部２０は不足電圧が設定電圧を超えると電圧低下検出信号として「Ｈ」、電圧低下を検出しなければ「Ｌ」信号を出力する。信号遮断部１３は入力信号「Ｈ」でON、「Ｌ」でOFFとする。系統の過電流を検出する過電流検出部１２は過電流を検出すれば過電流検出信号として「Ｈ」、過電流を検出しなければ「Ｌ」信号を出力する。過電流検出部１２の出力は信号切替部１４の制御入力に入力され、信号切替部１４の出力端子は、制御入力が「Ｈ」の場合は基準電圧Vsの極性を反転させる反転増幅部１５の出力に、制御入力が「Ｌ」の場合は不足電圧検出部６の出力に繋がれる。
過電流検出部１２の出力は同時に信号合成部２１で電圧低下検出部２０の出力と論理和が取られ、信号合成部２１の出力が短絡スイッチ１８の制御入力に入力される。短絡スイッチ１８は制御信号「Ｈ」で開極、「Ｌ」で閉極とする。
【００３１】
系統電圧が正常で負荷１０に電流が流れている場合は電圧低下検出部２０の出力は「Ｌ」、過電流検出部１２の出力も「Ｌ」、電流検出部１９の出力も「Ｌ」であり、信号合成部２１の出力は「Ｌ」のため短絡スイッチ１８は閉極状態で電流は補償電圧発生部４を通らず短絡スイッチ１８を流れる。また信号遮断部１３は制御入力が「Ｌ」のためOFFであるので、信号発生部７には不足電圧が零と入力され補償電圧発生部４は電圧出力しない（零電圧出力）。また信号切替部１４への制御入力は「Ｌ」のため、出力端子は不足電圧検出部６の出力に繋がれている状態である。
系統電源側８で事故が起こり系統電圧が低下すると、電圧低下検出部２０の出力が「Ｈ」となり、信号合成部２１の出力も「Ｈ」、従って短絡スイッチ１８の制御入力が「Ｈ」になるため短絡スイッチ１８は開極し電流遮断を行う。短絡スイッチ１８の電流が遮断され電流零となると電流検出部１９の出力は「Ｈ」となり信号遮断部１３の制御入力が「Ｈ」となるため、信号遮断部１３はONとなる。過電流検出部１２の出力は「Ｌ」のままなので信号切替部１４の出力端子も不足電圧検出部６の出力に繋がれたままで、不足電圧検出部６の出力は信号発生部７に入力され、補償電圧発生部４は不足電圧を補償電圧として発生し、系統電圧が補償される。
【００３２】
一方、系統負荷側９で事故が起こり過電流と系統電圧低下とが発生すると、信号合成部２１の出力が「Ｈ」となり短絡スイッチ１８は開極して電流遮断を行うと共に、信号切替部１４の制御入力も「Ｈ」となり出力端子は基準電圧Vsの極性を反転させる反転増幅部１５の出力に繋がれる。短絡スイッチ１８の電流が遮断され零になると信号遮断部１３は制御入力が「Ｈ」となりONとなるため、信号発生部７には系統定格電圧（基準電圧Vs）に絶対値が等しく極性が逆の電圧が入力される。従って、補償電圧発生部４は系統電圧に対して逆極性の電圧を発生し過電流を抑制できる。この結果、補償電圧発生部４の発生する過電流抑制電圧は短絡スイッチ１８で短絡されることなく、即ち補償電圧発生部４に過大な電流が流れることなく過電流抑制電圧が系統に重畳されるため過電流による被害を低減できる。
【００３３】
なお、短絡スイッチ１８の電流遮断は実際に電流を検出することで確認しているが、予め短絡スイッチ１８の遮断時間を測定しておき、短絡スイッチ１８への開極指令から短絡スイッチ１８の遮断時間経過後に信号遮断部１３にON指令を出力するように構成しても良い。
【００３４】
実施の形態６．
実施の形態３の図３で示した回路構成に、短絡スイッチ１８とこの短絡スイッチ１８に流れる電流を検出する電流検出部１９とを設けたものを図７に示す。
上述したように、過電流を抑制するための過電流抑制電圧の発生は、補償電圧発生部４ａのコンデンサ１６と系統を接続しているスイッチング素子Ｔ１〜Ｔ４を全てOFFにすることで行う。系統電圧がコンデンサ１６の電圧より小さければコンデンサ１６はダイオードＤ１〜Ｄ４の働きにより系統から切離された状態であり、系統電圧がコンデンサ１６の電圧より大きくなると系統電圧と逆極性にコンデンサ１６が系統に接続される。
このような過電流抑制機能を持つ構成の電圧変動補償装置１００に常時損失低減用の短絡スイッチ１８を設けた場合、過電流検出時に短絡スイッチ１８に開極指令と全てのスイッチング素子Ｔ１〜Ｔ４に過電流抑制制御信号となるOFF指令を同時に出しても、短絡スイッチ１８が電流遮断するまでは補償電圧発生部４ａに印加される系統電圧は短絡スイッチ１８で短絡されるためほぼ零となり、コンデンサ１６は系統から切離された状態で不都合は起こらない。短絡スイッチ１８が電流遮断した後に自動的に過電流抑制電圧が系統に重畳されることになる。従って、補償電圧発生部４ａに過電流抑制電圧を発生させるための制御を短絡スイッチ１８の電流遮断に関係無く行うことができ、短絡スイッチ１８が閉極状態では過電流抑制電圧の発生が無く、短絡スイッチ１８が開極状態になると過電流抑制電圧が発生できる。
【００３５】
系統の電源側８の事故で電圧低下が発生した時は、短絡スイッチ１８の電流遮断完了後に補償電圧を重畳しなければならない。しかし、過電流検出部１２が過電流を検出した時は、短絡スイッチ１８に開極指令を出すのと同時にスイッチング素子Ｔ１〜Ｔ４を全てOFFにする指令を出して良い。信号合成部２１で過電流検出信号（過電流検出時「Ｈ」）と電圧低下検出部２０の出力（電圧低下検出時「Ｈ」）との論理和を取り、短絡スイッチ１８の制御信号とすれば良い。
補償電圧発生部４ａがコンデンサ１６とそれぞれダイオードＤ１〜Ｄ４を逆並列されたスイッチング素子Ｔ１〜Ｔ４とから構成されていれば、回路構成に関係なく、短絡スイッチ１８が開極状態になってから自動的に過電流抑制電圧が系統に重畳されることになり、補償電圧発生部４ａに過大な電流が流れることなく過電流抑制ができる。
【００３６】
実施の形態７．
上記実施の形態５、６では、短絡スイッチ１８への開極指令は電圧低下検出部２０の出力信号（電圧低下時「Ｈ」）と過電流検出部１２の出力信号（過電流検出時「Ｈ」）を信号合成部２１で論理和を取り少なくとも一方が起こった時（電圧低下、過電流）に短絡スイッチ１８を遮断するようにしたが、この実施の形態では、短絡スイッチ１８に通電されている状態では、過電流が発生しても短絡スイッチ１８を遮断しないようにするもので、図８に示すような信号合成部２１ａが用いられる。
図に示すように、過電流検出部１２の出力（過電流検出時「Ｈ」）と電圧低下検出部２０の出力（電圧低下検出時「Ｈ」）の論理積と、過電流検出部１２の出力の反転信号と電流検出部１９の出力（電流が流れてない時「Ｈ」）の論理積との論理和を出力とし、短絡スイッチ１８の制御信号とすれば良い。このようにすると、過電流を検出しない時か過電流を検出しても短絡スイッチ１８に電流が流れていない時以外は系統電圧低下を検出しても短絡スイッチ１８へは開極指令が送られない。即ち、短絡スイッチ１８に通電されている状態では、過電流が発生しても短絡スイッチ１８は閉極状態を維持し電流を遮断しないため、過電流遮断能力の無い短絡スイッチ１８でも、遮断不能を起こさずに使用することができる。
【００３７】
また短絡スイッチ１８が開極状態で過電流が流れた時は過電流抑制ができ、閉極状態で過電流が流れた場合でも、少なくとも過電流を増加させるような補償電圧を系統に重畳することは無い。
また、短絡スイッチ１８に過電流遮断能力は有るが、補償電圧発生部４の過電流耐量が小さい場合にも有効であり、以下に説明する。
短絡スイッチ１８に通電されている状態で過電流を検出したときに、短絡スイッチ１８の電流を遮断すると、その後過電流が補償電圧発生部４に転流されてから過電流抑制が始まるまでは抑制されていない過電流が補償電圧発生部４を流れ続ける。この時間は短絡スイッチ１８の遮断時間、電流検出部１９の電流零検出時間、制御部３の制御時間に依存し、短絡スイッチ１８が開極状態で過電流を検出した場合より長くなる。補償電圧発生部４の過電流耐量が小さい場合、過電流が流れる継続時間が長いと補償電圧発生部４が損傷することがある。このため、上述したように、短絡スイッチ１８に通電されている状態では、過電流が発生しても短絡スイッチ１８は閉極状態を維持し過電流を補償電圧発生部４に転流させないように制御することは補償電圧発生部４の保護に有効となる。
【００３８】
実施の形態８．
上記実施の形態７では、短絡スイッチ１８に通電されている状態で過電流が発生しても短絡スイッチ１８を閉極状態に維持させたが、この実施の形態では、過電流が発生した時は直ちに短絡スイッチ１８を閉極状態にし、過電流を補償電圧発生部４に流さないようにするもので、図９に示すような信号合成部２１ｂが用いられる。
図に示すように、電圧低下検出部２０の出力と過電流検出部１２の出力の反転信号との論理積を取り、短絡スイッチ１８の制御信号とすればよい。このように、過電流を補償電圧発生部４に流さないように制御するため、補償電圧発生部４に過電流通電能力の無い場合でも用いることができ、補償電圧発生部４を保護できる。
【００３９】
図９に示す信号合成部２１ｂを適用した電圧変動補償装置１００の構成図を図１０に示す。電源側８、負荷側９が正常な場合は、電圧が低下していないため電圧低下検出部２０の出力は「Ｌ」、過電流が流れていないため過電流検出部１２の出力は「Ｌ」、このため短絡スイッチ１８の制御信号となる信号合成部２１ｂの出力は「Ｌ」となり短絡スイッチ１８は閉極状態となる。したがって正常時には負荷側９への電力は短絡スイッチ１８を介して送られる。
電源側８で事故が発生し系統電圧が低下すると電圧低下検出部２０の出力が「Ｈ」となる。電源側８の事故のため過電流は流れていないため過電流検出部１２の出力は「Ｌ」、したがって信号合成部２１ｂの出力は「Ｈ」となり短絡スイッチ１８は開極し電流遮断を行う。短絡スイッチ１８の電流が遮断されると電流検出部１９からの出力は「Ｈ」となり、信号遮断部１３が「ON」となり不足電圧を補償電圧として系統に重畳するように補償電圧発生部４が制御される。したがって過電流が流れていない状況では系統電圧補償動作を行い負荷１０に正常な電圧を供給することができる。
【００４０】
一方、負荷側９の事故により系統電圧が低下すると電圧低下検出部２０の出力は「Ｈ」、過電流が流れるため過電流検出部１２の出力は「Ｈ」、したがって信号合成部２１ｂの出力は「Ｌ」となり、短絡スイッチ１８は閉極となる。電源側８、負荷側９が正常で短絡スイッチ１８が閉極状態の場合に負荷側９で事故が起こると短絡スイッチ１８は閉極状態を維持し、過電流は短絡スイッチ１８に流れる。
また電源側８の事故により系統電圧が低下し系統電圧補償動作中の場合に負荷側９でも事故が発生し過電流が流れると、過電流検出部１２の出力が「Ｌ」から「Ｈ」になるため短絡スイッチ１８は閉極し過電流は短絡スイッチ１８を流れる。
また短絡スイッチ１８が遮断されないため、電流検出部１９の信号により信号遮断部１３は「OFF」であり過電流を増大させる補償電圧も発生しない。即ち、過電流を検出した時は常に短絡スイッチ１８が閉極状態になるように制御されて、補償電圧発生部４を過電流から保護できる。また少なくとも過電流を増加させるような補償電圧を系統に重畳することは無い。
なお、この場合、補償電圧発生部４ａにPWMインバータを用いた例を示したが、これに限らず、他の回路構成であっても良い。
【００４１】
【発明の効果】
この発明に係る請求項１記載の電圧変動補償装置は、電力系統における電圧低下を検出する系統電圧検出部と、該系統電圧検出部からの電圧低下検出信号を入力として電圧補償制御信号を出力する制御部と、上記電力系統に直列に接続され、上記電圧補償制御信号により補償電圧を発生させる補償電圧発生部とを備えて、系統電圧低下時に上記補償電圧発生部にて発生させた上記補償電圧を該系統電圧に重畳して、負荷に供給される電圧変動を抑える装置構成であって、上記補償電圧発生部が直列接続された上記系統に流れる過電流を検出して過電流検出信号を上記制御部に出力する過電流検出部を備え、上記制御部では、上記過電流検出信号の入力時には、上記電圧低下検出信号が入力されても上記電圧補償制御信号を出力せず、該電圧補償制御信号の替わりに過電流抑制制御信号を出力し、該過電流抑制制御信号を入力として補償電圧発生部は、上記補償電圧を発生させずに、系統電圧と逆極性の過電流抑制電圧を発生して上記系統電圧に重畳させるため、過電流を抑制でき、過電流による被害が低減でき、電力系統および電圧変動補償装置自身を保護できる。また電圧変動補償装置の設置に伴い新たな系統保護機器などの短絡電流増大対策を要することなく装置構成の簡略化が図れる。
【００４２】
またこの発明に係る請求項２記載の電圧変動補償装置は、請求項１において、補償電圧発生部が直列接続された系統の負荷側に保護遮断器を備え、過電流検出部からの過電流検出信号を保持し、該保持した過電流検出信号により上記保護遮断器を遮断させるため、過電流が抑制されても確実に保護遮断器を遮断して事故系統を切り離せる。
【００４３】
またこの発明に係る請求項３記載の電圧変動補償装置は、請求項１または２において、補償電圧発生部から発生される過電流抑制電圧は、正常な系統電圧と逆極性でほぼ同じ大きさであるため、過電流を効果的に低減できてほぼ零にでき、過電流による被害をさらに低減できる。
【００４４】
またこの発明に係る請求項４記載の電圧変動補償装置は、請求項１または２において、補償電圧発生部は、直流電源と、該直流電源の両側あるいは片側に配されて該直流電源を電力系統に接続し、ダイオードが逆並列に接続された自己消弧型の半導体スイッチング素子とから成り、上記直流電源に接続される上記ダイオードは、該直流電源の正極側では該ダイオードの負極が接続され、該直流電源の負極側では該ダイオードの正極が接続され、制御部から過電流抑制制御信号が入力されると、上記全ての半導体スイッチング素子をオフにして、上記直流電源の電圧を逆極性の過電流抑制電圧として上記ダイオードにより系統電圧に重畳するため、過電流発生時に、容易で確実に正常な系統電圧と逆極性の過電流抑制電圧を安定して発生させて系統電圧に重畳でき、効果的に過電流を抑制できる。
【００４５】
またこの発明に係る請求項５記載の電圧変動補償装置は、請求項１〜３のいずれかにおいて、系統電圧検出部にて電圧低下が検出されない正常時に補償電圧発生部をバイパスするために該補償電圧発生部に並列に接続された短絡スイッチを備え、上記短絡スイッチが閉極状態で、過電流検出信号あるいは電圧低下検出信号が制御部に入力されると、該制御部は、上記短絡スイッチに開極指令を出力し、該短絡スイッチが開極状態になった後、過電流抑制制御信号あるいは電圧補償制御信号を出力して補償電圧発生部にて電圧を発生させるため、補償電圧発生部が発生する電圧が短絡スイッチで短絡されることなく、補償電圧発生部を保護できる。
【００４６】
またこの発明に係る請求項６記載の電圧変動補償装置は、請求項１〜３のいずれかにおいて、系統電圧検出部にて電圧低下が検出されない正常時に補償電圧発生部をバイパスするために、短絡スイッチを該補償電圧発生部に並列に接続して備え、上記短絡スイッチが閉極状態で、過電流検出信号が制御部に入力されると、該制御部は過電流抑制制御信号を出力せず上記短絡スイッチは閉極状態を維持し、上記短絡スイッチが閉極状態で、過電流検出信号は入力されずに電圧低下検出信号のみ制御部に入力されると、該制御部は、上記短絡スイッチに開極指令を出力して開極した後、電圧補償制御信号を出力するため、過電流遮断能力の無い短絡スイッチでも、遮断不能を起こさずに適用できる。また、過電流耐量の小さな補償電圧発生部を適用しても、確実に保護することができる。
【図面の簡単な説明】
【図１】この発明の実施の形態１による電圧変動補償装置の回路構成図である。
【図２】この発明の実施の形態２による電圧変動補償装置の回路構成図である。
【図３】この発明の実施の形態３による電圧変動補償装置の回路構成図である。
【図４】この発明の実施の形態３による系統負荷側事故時の電圧電流波形を示す図である。
【図５】この発明の実施の形態４による電圧変動補償装置の回路構成図である。
【図６】この発明の実施の形態５による電圧変動補償装置の回路構成図である。
【図７】この発明の実施の形態６による電圧変動補償装置の回路構成図である。
【図８】この発明の実施の形態７による電圧変動補償装置の信号合成部を示す図である。
【図９】この発明の実施の形態８による電圧変動補償装置の信号合成部を示す図である。
【図１０】この発明の実施の形態８による電圧変動補償装置の回路構成図である。
【図１１】従来の電圧変動補償装置の回路構成図である。
【図１２】従来の電圧変動補償装置の問題点を説明する図である。
【符号の説明】
２系統電圧検出部、４，４ａ補償電圧発生部、７信号発生部、１０負荷、
１１保護遮断器、１２過電流検出部、１３信号遮断部、１４信号切替部、
１６直流電源としてのコンデンサ、１８短絡スイッチ、１９電流検出部、
２１，２１ａ，２１ｂ信号合成部、３０，３１，３２，３３，３４，３５制御部、
１００電圧変動補償装置、Ｔ１〜Ｔ４半導体スイッチング素子、
Ｄ１〜Ｄ４ダイオード。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a voltage fluctuation compensator that detects and compensates for voltage fluctuation when the voltage of a power system supplied to a load fluctuates instantaneously.
[0002]
[Prior art]
  The voltage of the electric power system is instantaneously reduced by lightning, etc., and precision equipment such as factories malfunctions or is temporarily stopped, which can cause great damage on the production line. In order to prevent such damage, a voltage fluctuation compensator that monitors voltage fluctuation such as instantaneous voltage drop of the power system and compensates for the voltage drop is used.
  For example, a conventional series-connected voltage fluctuation compensator described in Japanese Patent Application Laid-Open No. 61-116934 is connected in series to an electric power system, and when the system voltage drops, only the insufficient voltage is superimposed on the system voltage and applied to the load. The supply voltage is kept constant, and a schematic configuration diagram is shown in FIG.
  As shown in the figure, the voltage fluctuation compensation device 1 includes a system voltage detector 2, a controller 3, and a compensation voltage generator 4. In the control unit 3, the difference voltage between the system voltage Vr detected by the system voltage detection unit 2 and the voltage Vs of the reference voltage generation unit 5 that simulates the normal system voltage (system rated voltage), that is, the system undervoltage Vi. Is provided with an undervoltage detection unit 6 and a control signal generation unit 7. The signal generator 7 generates a compensation control signal for the compensation voltage generator 4 such that the compensation voltage Vo output from the compensation voltage generator 4 becomes the undervoltage Vi output from the undervoltage detector 6.
[0003]
  In such a voltage fluctuation compensator 1, the compensation voltage generator 4 is connected in series between the power supply side 8 and the load side 9 of the power system, and the system voltage Vr decreases due to a ground fault in the power supply side 8 of the system. Then, the output compensation voltage Vo of the compensation voltage generator 4 is superimposed on the system voltage Vr, and the voltage Vl of the load 10 is maintained at the reference voltage Vs as shown in the equation (1). However, the voltage drop due to system impedance was ignored.
        Vl = Vr + Vo = Vr + Vi = Vr + (Vs−Vr) = Vs (1)
  As a result, a constant voltage can be supplied to the load even if the system voltage fluctuates.
[0004]
  In the electric power system, an accident such as a short circuit on the load side 9 of the voltage fluctuation compensating apparatus 1 may occur. In such a case, as shown in FIG. 12, system protection is performed by installing a protective circuit breaker 11 on the load side 9 of the compensation voltage generating unit 4 to interrupt a short-circuit current.
[0005]
[Problems to be solved by the invention]
  Since the conventional voltage fluctuation compensator is configured as described above, when an overcurrent such as a short-circuit current flows during an accident on the load side 9 of the system, the following problem occurs. .
  The impedance Zs on the power supply side 8 of the voltage fluctuation compensator 1 and the impedance Zl up to the short-circuit fault point on the load side 9 are used. At the instant when the short circuit accident occurs on the load side 9, the system voltage drops, but the voltage fluctuation compensator 1 has not yet performed the voltage compensation operation, that is, does not output the compensation voltage. The flowing short-circuit current If is expressed by equation (2).
        If = Vs / (Zs + Zl) (2)
  At this time, the system voltage Vr detected by the system voltage detector 2 of the voltage fluctuation compensator 1 is a voltage drop due to the impedance Zs of the system power supply side 8 from the system reference voltage Vs (rated voltage) as shown in the equation (3). The value minus the minute.
        Vr = Vs-Zs · If (3)
[0006]
  As a result, it is detected that the system voltage Vr is lower than the reference voltage Vs, and the voltage fluctuation compensator 1 starts the voltage compensation operation. That is, the undervoltage Vi (= Zs · If) of the system voltage Vr is superimposed on the system voltage as the compensation voltage Vo, and the system voltage on the load side 9 is maintained at the reference voltage Vs. Short-circuit current If in this case_aBecomes the equation (4).
        If_a= (Vs + Vo) / (Zs + Zl)> If (4)
  That is, when an overcurrent such as a short-circuit current flows at the time of a load-side accident, the short-circuit current increases as the voltage fluctuation compensator 1 performs a voltage compensation operation. As the short-circuit current increases, the system voltage further decreases, and the output compensation voltage Vo changes accordingly.
        Vo ＝ Zs ・ If_a
        If_a= Vs / Zl
It becomes.
  As described above, the voltage fluctuation compensator 1 performs the voltage compensation operation, thereby increasing the overcurrent due to the load side accident, increasing the damage due to the overcurrent, and destroying the voltage fluctuation compensator 1 itself by the overcurrent. was there. Further, the protective circuit breaker 11 that protects the system on the load side 9 may not be able to protect the system because the overcurrent cannot be interrupted, and it is necessary to take measures for increasing the short circuit current, such as installing a new system protection device.
[0007]
  The present invention has been made to solve the above-described problems, and in a voltage fluctuation compensator for compensating for a voltage drop supplied to a load, an overcurrent generated at the time of a load-side fault in a system is increased. The purpose is to protect the power system and the voltage fluctuation compensation device itself without causing damage by overcurrent.
[0008]
[Means for Solving the Problems]
  According to a first aspect of the present invention, there is provided a voltage fluctuation compensator that detects a voltage drop in a power system, and outputs a voltage compensation control signal with a voltage drop detection signal from the system voltage detector as an input. A compensation voltage generator that is connected in series to the power system and generates a compensation voltage in response to the voltage compensation control signal; Is superimposed on the system voltage to suppress voltage fluctuations supplied to the load, and the overvoltage detection unit detects the overcurrent flowing through the system in which the compensation voltage generator is connected in series. It has an overcurrent detection unit that outputs to the control unit,When the overcurrent detection signal is input, the control unit does not output the voltage compensation control signal even if the voltage drop detection signal is input, and outputs an overcurrent suppression control signal instead of the voltage compensation control signal. The compensation voltage generator receives the overcurrent suppression control signal as input and generates an overcurrent suppression voltage having a polarity opposite to that of the system voltage without generating the compensation voltage, and superimposes it on the system voltage.Is.
[0009]
  Claims related to this invention2The voltage fluctuation compensation device described in claim1, A protection circuit breaker is provided on the load side of the system in which the compensation voltage generation unit is connected in series, holds an overcurrent detection signal from the overcurrent detection unit, and shuts off the protection circuit breaker by the held overcurrent detection signal It is something to be made.
[0010]
  Claims related to this invention3The voltage fluctuation compensation device described in claim1 or 2, The overcurrent suppression voltage generated from the compensation voltage generator is approximately the same magnitude as the normal system voltage with the opposite polarity.
[0011]
  Claims related to this invention4The voltage fluctuation compensation device described in claim1 or 2The compensation voltage generator includes a DC power supply, a self-extinguishing semiconductor switching element that is arranged on both sides or one side of the DC power supply, connects the DC power supply to the power system, and has diodes connected in antiparallel. The diode connected to the DC power supply is connected to the negative electrode of the diode on the positive electrode side of the DC power supply, and connected to the positive electrode of the diode on the negative electrode side of the DC power supply. When a control signal is input, all the semiconductor switching elements are turned off, and the voltage of the DC power supply is superimposed on the system voltage by the diode as an overcurrent suppression voltage having a reverse polarity.
[0012]
  Claims related to this invention5The voltage fluctuation compensation device described in claim1-3In any of the above, a short-circuit switch connected in parallel to the compensation voltage generator is provided in order to bypass the compensation voltage generator when the voltage drop is not detected by the system voltage detector, and the short-circuit switch is in a closed state When the overcurrent detection signal or the voltage drop detection signal is input to the control unit, the control unit outputs an opening command to the shorting switch, and the overcurrent is detected after the shorting switch is opened. A suppression control signal or a voltage compensation control signal is output and a voltage is generated by the compensation voltage generator.
[0013]
  Claims related to this invention6The voltage fluctuation compensation device described in claim1-3In order to bypass the compensation voltage generator when the voltage drop is not detected by the system voltage detector, the short-circuit switch is connected in parallel to the compensation voltage generator, and the short-circuit switch is closed. In this state, when an overcurrent detection signal is input to the control unit, the control unit does not output an overcurrent suppression control signal, the shorting switch maintains a closed state, and the shorting switch is in a closed state. When only a voltage drop detection signal is input to the control unit without inputting a current detection signal, the control unit outputs a voltage opening control command to the shorting switch, and then outputs a voltage compensation control signal. It is.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
  Embodiment 1 of the present invention will be described below with reference to the drawings.
  FIG. 1 is a schematic configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 1 of the present invention.
  As shown in the figure, the voltage fluctuation compensation device 100 includes a system voltage detection unit 2, an overcurrent detection unit 12, a control unit 31, and a compensation voltage generation unit 4. In the control unit 31, the difference voltage between the system voltage Vr detected by the system voltage detection unit 2 and the voltage Vs of the reference voltage generation unit 5 that simulates the normal system voltage (system rated voltage), that is, the system undervoltage Vi. And a control signal generator 7. A signal blocking unit 13 is provided between the undervoltage detector 6 and the signal generator 7. The compensation voltage generator 4 is connected in series between the power supply side 8 and the load side 9 of the power system, and the compensation voltage Vo is insufficient in magnitude due to the voltage compensation control signal from the control signal generator 7. The voltage Vi is output and superimposed on the system voltage Vr, and the system voltage supplied to the load 10 is maintained at the reference voltage Vs. A protective circuit breaker 11 is installed on the load side 9 of the compensation voltage generator 4 to cut off overcurrent such as short circuit current.
[0015]
  When the overcurrent detection unit 12 detects an overcurrent flowing through a system in which the compensation voltage generation unit 4 is connected in series, the overcurrent detection unit 12 outputs an overcurrent detection signal to the signal cutoff unit 13 of the control unit 31. The signal cutoff unit 13 passes the output of the undervoltage detection unit 6 to the signal generation unit 7 when no overcurrent detection signal is input, and generates the output of the undervoltage detection unit 6 when the overcurrent detection signal is input. The signal path is blocked so as not to pass through the section 7.
  Accordingly, when the system voltage drops due to a ground accident or the like on the power supply side 8, no overcurrent flows, so that the undervoltage Vi detected by the undervoltage detector 6 passes through the signal blocker 13 as a voltage drop detection signal. The generator 7 generates a voltage compensation control signal for controlling the output compensation voltage Vo of the compensation voltage generator 4 to Vi, and the voltage fluctuation compensator 100 compensates the system voltage.
  When an overcurrent occurs due to a short circuit accident or the like on the load side 9 and the system voltage drops, even if the undervoltage detection unit 6 detects an undervoltage, the overcurrent detection unit 12 simultaneously sends an overcurrent detection signal to the signal cutoff unit. 13, the signal cut-off unit 13 cuts off the voltage drop detection signal that is the output of the undervoltage detection unit 6 and does not send it to the signal generation unit 7. As a result, the signal generator 7 does not generate a voltage compensation control signal for generating a compensation voltage, that is, a command for setting the output compensation voltage Vo of the compensation voltage generator 4 to zero when the undervoltage Vi = 0 is set. The overcurrent does not increase without the compensation voltage being superimposed on the system voltage.
  For this reason, even if the voltage fluctuation compensator 100 that suppresses fluctuations in the system voltage is installed, the overcurrent is not increased, and measures for increasing short-circuit current such as installation of new system protection equipment other than the normal protective circuit breaker 11 are provided. Therefore, it is possible to protect the power system and the voltage fluctuation compensation device itself by suppressing damage due to overcurrent.
[0016]
Embodiment 2. FIG.
  In the first embodiment, when an overcurrent is detected, the undervoltage is not superimposed on the system as a compensation voltage. However, in this second embodiment, when the overcurrent is detected, the normal system voltage (reference voltage Vs ) And a reverse polarity voltage are superimposed on the system voltage as an overcurrent suppression voltage to suppress overcurrent.
  As shown in FIG. 2, the control unit 32 includes a signal switching unit 14 and an inverting amplification unit 15 instead of the signal blocking unit 13 in FIG. 1, and the signal switching unit 14 switches the input to the signal generation unit 7. The signal switching unit 14 has two input terminals, and selects either the signal of the undervoltage detection unit 6 or the signal obtained by passing the voltage Vs of the reference voltage generation unit 5 through the inverting amplification unit 15 by inputting the overcurrent detection signal. To do.
  When the overcurrent detection signal is not input to the signal switching unit 14, the signal of the undervoltage detection unit 6 is input to the signal generation unit 7 through the signal switching unit 14, and voltage compensation from the signal generation unit 7 is performed when the system voltage is reduced. The compensation voltage generator 4 outputs an undervoltage according to the control signal to compensate the system voltage.
[0017]
  When the overcurrent detector 12 detects an overcurrent and an overcurrent detection signal is input to the signal switching unit 14, the signal generation unit 7 receives a signal obtained by inverting the polarity of the reference voltage Vs from the inverting amplification unit 15. It is input via the signal switching unit 14. As a result, the signal generator 7 generates an overcurrent suppression control signal for controlling the output voltage of the compensation voltage generator 4 to be an overcurrent suppression voltage having the same absolute value as that of the normal system voltage but the opposite polarity. The overcurrent suppression voltage output from the compensation voltage generator 4 is superimposed on the system voltage.
  Short-circuit current (overcurrent) If_bIf the output voltage Vo of the compensation voltage generator 4 is set equal to −Vs,
  If_b= (Vs + Vo) / (Zs + Zl) = (Vs + (− Vs)) / (Zs + Zl) = 0 (5)
Thus, the overcurrent is suppressed to zero. It is assumed that the impedance Zs on the power supply side 8 of the voltage fluctuation compensator 1 and the impedance Zl up to the short-circuit fault point on the load side 9 are used.
[0018]
  Even if the overvoltage suppression voltage generated by the compensation voltage generator 4 is not the voltage of the normal system voltage and the same polarity but of the opposite polarity, if the voltage is of the opposite polarity to the system voltage, the effect of suppressing the overcurrent is is there. Therefore, since the overcurrent flowing through the system due to the load side accident can be suppressed, there is no need to take measures to increase the short circuit current such as installing a new system protection device other than the normal protective circuit breaker 11, and the power system is damaged or accidents due to the overcurrent. Damage to the voltage fluctuation compensation device 100 itself can be avoided.
  Note that the method of superimposing the overcurrent suppression voltage of the reverse polarity with the normal system voltage is performed only for the load side accident of the compensation voltage generator 4, and cannot cope with the power supply side accident.
[0019]
  Further, in this embodiment, as shown in FIG. 2, the overcurrent detection signal generated by the overcurrent detection unit 12 is held, and the protection circuit breaker 11 of the load side system 9 is cut off by the signal. Since the overcurrent due to the load side accident is suppressed by the voltage fluctuation compensator 100, the overcurrent relay (not shown) of the protective circuit breaker 11 may not operate or the operation may be delayed. Since the protective circuit breaker 11 is configured to be interrupted by the overcurrent detection signal, the protective circuit breaker 11 can be reliably interrupted and the accident system can be disconnected even if the overcurrent is suppressed.
[0020]
Embodiment 3 FIG.
  In the second embodiment, the voltage fluctuation compensator 100 that superimposes the voltage having the opposite polarity to the normal system voltage (reference voltage Vs) on the system voltage as the overcurrent suppression voltage when the overcurrent is detected is shown. FIG. 3 shows one form of a circuit configuration of the voltage fluctuation compensator 100 that superimposes an overcurrent suppression voltage having a polarity opposite to that on the system voltage. As shown in the figure, a DC voltage source such as a capacitor 16 in the compensation voltage generator 4a is inserted in series in the system, and the voltage is superimposed on the system. In order to connect or disconnect the capacitor 16 to the system, an inverter comprising four self-extinguishing type switching elements T1 to T4 is used. Here, in order to control the voltage superimposed on the system using the PWM inverter system, the control unit 33 outputs gate signals G1 to G4 for controlling ON / OFF of the switching elements T1 to T4, and the capacitor 16 The connection is intermittently connected in series to the system, and the necessary voltage is superimposed by controlling the connection time, that is, the voltage pulse width.
  A method may be used in which a plurality of capacitors (not shown) are provided and a combination of capacitors connected in series according to a required voltage is selected and the sum of output voltages is superimposed on the system. In this example, the compensation voltage generator 4a is directly connected to the system in series, but may be connected to the system via a transformer. The filter for removing harmonics is not shown.
  In any system, diodes D1 to D4 are connected in parallel to the self-extinguishing switching elements T1 to T4 so that a reverse current can flow. This is not necessary because when the load 10 connected to the system is a pure resistor, current flows only in the direction of the polarity of the capacitor 16 connected in series (the direction of the voltage that superimposes the voltage of the capacitor 16). When the load 10 is other than a pure resistance, the direction of the voltage of the capacitor 16 and the direction of the current may be different. Therefore, the switching elements T1 to T4 need antiparallel diodes D1 to D4 to flow this current. .
[0021]
  As described above, since the anti-parallel diodes D1 to D4 are connected to the switching elements T1 to T4 that connect the capacitor 16 in series to the system, the capacitor 16 is always connected to the system via the diodes D1 to D4. . The diodes D1 to D4 are connected in such a direction that current flows in the direction opposite to the polarity direction of the capacitor 16, that is, as shown in the figure, the positive electrode of the capacitor 16 is connected to the negative electrodes of the diodes D1 and D4 and connected to the system. The negative electrode of the capacitor 16 is connected to the positive electrodes of the diodes D2 and D3 and connected to the system, and the capacitor 16 is connected so as to have a polarity opposite to that of the system voltage.
[0022]
  In the control unit 33, the determination unit 17 calculates the logical product of the output of the signal generation unit 7 and the inverted signal of the output of the overcurrent detection unit 12, and controls the ON and OFF of the switching elements T1 to T4. G1 to G4 are output. Here, when the gate signals G1 to G4 are “H”, the switching elements T1 to T4 are ON, and when the gate signals G1 to G4 are “L”, the switching elements T1 to T4 are OFF, and the overcurrent detection signal that is the output of the overcurrent detection unit 12 is When the current is detected, the signal is “H”. When the overcurrent is not detected, the signal is “L”.
[0023]
  When the undervoltage detection unit 6 detects an undervoltage of the system voltage, the signal generation unit 7 generates each gate signal so that the compensation voltage generation unit 4a outputs a compensation voltage equal to the undervoltage. If the overcurrent detection unit 12 does not detect an overcurrent at this time, the overcurrent detection signal is “L”, and the gate signal from the signal generation unit 7 directly controls the switching elements T1 to T4 of the compensation voltage generation unit 4a. And a compensation voltage is generated.
  On the other hand, when an overcurrent is detected, the overcurrent detection signal becomes “H”, and the logical product of all the outputs from the inversion signal of the overcurrent detection signal becomes “L” whatever the output from the signal generator 7, and the overcurrent suppression control signal As a result, the switching elements T1 to T4 are all turned off. In this case, the system and the capacitor 16 are connected via the diodes D1 to D4. However, regardless of the polarity of the system voltage, the voltage polarity in which the capacitor 16 is always inserted into the system is constant, and the capacitor 16 is charged. That is, the polarity is opposite to that of the system voltage.
[0024]
  FIG. 4 shows a voltage / current waveform at the time of a load-side short circuit accident. FIG. 4A shows a comparative example when no overcurrent suppression voltage is generated, and it can be seen that a large short-circuit current flows as an overcurrent due to a load-side short circuit accident. FIG. 4B shows a voltage / current waveform when an overcurrent suppression voltage is generated by the voltage fluctuation compensator 100 according to this embodiment.
  Hereinafter, the overcurrent suppressing operation will be described with reference to FIG.
  When an overcurrent caused by a short circuit accident or the like on the system load side 9 is detected and all of the switching elements T1 to T4 are turned off, the compensation voltage generator 4a uses the charging voltage at that time of the capacitor 16 as an overcurrent suppression voltage to turn the diode Output via D3 and D4. Since the capacitor 16 is connected in the charging direction, a charging current flows. However, as the capacitor 16 is charged, the charging current decreases. When the capacitor 16 is charged to the peak of the system normal voltage, the flowing charging current is It becomes zero, that is, no current flows and overcurrent is suppressed. When the system voltage is inverted, the capacitor 16 is connected to the system via the diodes D1 and D2. This direction is also the direction to charge the capacitor 16, and the capacitor 16 has already been charged to the normal voltage peak. No current flows.
  In order to compensate 100% of the voltage drop of the system with the PWM inverter, the charging voltage of the capacitor 16 requires a peak value of the system voltage, and therefore no current flows. Even when the charging voltage of the capacitor 16 is smaller than the peak value of the system voltage, as described above, the voltage of the capacitor 16 is superimposed on the system in the reverse polarity as the overcurrent suppression voltage, and the capacitor voltage is further charged as the capacitor 16 is charged. Since it approaches the peak voltage of the system, the overcurrent is suppressed.
[0025]
  In this embodiment, all the switching elements T1 to T4 are turned OFF by the overcurrent suppression control signal generated by the overcurrent detection, whereby the charging voltage of the capacitor 16 is connected in antiparallel to the switching elements T1 to T4. It is superimposed on the system voltage via the diodes D1 to D4 so as to have a reverse polarity. In other words, the overcurrent can be suppressed by using the charging voltage of the capacitor 16 as the overcurrent suppression voltage having the opposite polarity to the system voltage.
[0026]
  In this embodiment, a full-bridge inverter composed of four semiconductor switching elements T1 to T4 each having diodes D1 to D4 connected in antiparallel is used as the compensation voltage generator 4a. However, the present invention is not limited to this. It is not a thing. That is, a semiconductor switching element having a diode connected in antiparallel is arranged on both sides or one side of a capacitor, and the capacitor 16 is connected to the power system. The diode connected to the capacitor has a negative polarity if it is on the positive side of the capacitor. If it is the negative electrode side of the capacitor, the positive electrode may be connected.
[0027]
Embodiment 4 FIG.
  Next, a voltage fluctuation compensating apparatus according to Embodiment 4 will be described with reference to FIG. In the second embodiment, the voltage fluctuation compensator 100 that superimposes a voltage having a polarity opposite to that of the normal system voltage (reference voltage Vs) on the system voltage as an overcurrent suppression voltage when the overcurrent is detected has been described. As shown in FIG. 5, the voltage fluctuation compensator 100 is provided with a short-circuit switch 18 connected in parallel with the compensation voltage generator 4 and a current detector 19 that detects a current flowing through the short-circuit switch 18.
  By the way, in the series connection type voltage fluctuation compensator 100, if the current is passed through the compensation voltage generator 4 even when the voltage drop does not occur in the system voltage, the switching element does not generate the compensation voltage (generates zero voltage). Since current flows through a plurality of semiconductor elements such as a diode and a diode, the loss is always large. For this reason, when the short-circuit switch 18 is connected in parallel to the compensation voltage generator 4 and the system voltage is normal and the compensation voltage generator 4 does not need to generate the compensation voltage, the current is supplied to the load 10 via the short-circuit switch 18. When the system voltage drops, the short-circuit switch 18 is cut off, and the current is sent to the load 10 via the compensation voltage generator 4 (with insufficient voltage superimposed).
  If a mechanical switch is used as the short-circuit switch 18, there is almost no loss at all times, and even if a semiconductor switch is used, the loss is smaller than when the compensation voltage generator 4 is passed.
[0028]
  The short-circuit switch 18 is turned ON / OFF according to the input signal, and the overcurrent detection unit 12 is arranged outside the connection point of the short-circuit switch 18 to the system so that the current passing through the short-circuit switch 18 or the current passing through the compensation voltage generation unit 4 Detect current flowing through the grid.
  When normal, the short-circuit switch 18 is ON, and the system current flows through the short-circuit switch 18. When a short circuit accident occurs on the load side 9 of the system, the overcurrent detection unit 12 detects an overcurrent and sends an overcurrent detection signal to the control unit 30. The controller 30 sends an opening command to the short-circuit switch 18 by the overcurrent detection signal to turn off the short-circuit switch 18 and cut off the flowing current. When the current of the short-circuit switch 18 is cut off, the system current is commutated to the compensation voltage generator 4. When the current flowing through the short-circuit switch 18 becomes zero, the current detection unit 19 sends a zero current detection signal to the control unit 30. After receiving the zero current detection signal, the control unit 30 outputs an overcurrent suppression control signal to the compensation voltage generation unit 4 so as to generate an overcurrent suppression voltage.
[0029]
  As described above, the control unit 30 causes the compensation voltage generation unit 4 to output the overcurrent suppression voltage after the current of the short-circuit switch 18 is interrupted, and thus the short-circuit switch that reduces the loss of the voltage fluctuation compensator 100 at the normal time. Even when 18 is used, the overcurrent suppression voltage generated by the compensation voltage generator 4 is not short-circuited by the short-circuit switch 18, and an excessive current does not flow through the compensation voltage generator 4 and damage the element. For this reason, overcurrent can be suppressed with high reliability, and damage to the system can be reduced.
  Further, when a mechanical switch is employed as the short-circuit switch 18 and forcibly cut off before the AC natural current zero point, for example, in the method shown in Japanese Patent Laid-Open No. 11-111123, the current value that can be forcibly cut off is the value at the natural current zero point. Less than the current value that can be cut off. When an overcurrent is detected, a command is issued to the short-circuit switch 18 so as to perform forcible interruption first. However, when the interruption current exceeds the forcible interruption region, interruption is performed at a natural current zero point. Even in such a case, since the overcurrent suppression voltage is generated after detecting the current flowing through the short-circuit switch 18 and confirming that the short-circuit switch 18 has cut off the current, the overcurrent suppression voltage is short-circuited by the short-circuit switch 18. There is nothing to do.
  Even when the system voltage drops due to an accident on the power supply side 8 of the system, the control unit 30 shuts off the short-circuit switch 18 by the opening command and receives the current zero detection signal from the current detection unit 19 and compensates for it. A voltage compensation control signal is output to the voltage generator 4 to control to generate a compensation voltage.
[0030]
Embodiment 5. FIG.
  FIG. 6 shows an example in which the fourth embodiment is applied to the circuit configuration shown in FIG.
  As shown in the figure, in this configuration, a signal blocking unit 13 is provided between the output terminal of the signal switching unit 14 and the signal generating unit 7, and a voltage drop detection unit 20 for inputting the output of the undervoltage detection unit 6 is provided. . A zero current detection signal from a current detection unit 19 that detects a current flowing through the short-circuit switch 18 is input to the signal cutoff unit 13. The zero current detection signal is “H” when the current is zero and “L” when the current is flowing. The voltage drop detection unit 20 outputs “H” as a voltage drop detection signal when the undervoltage exceeds the set voltage, and outputs an “L” signal if no voltage drop is detected. The signal blocking unit 13 is turned on when the input signal is “H” and turned off when the signal is “L”. The overcurrent detection unit 12 that detects an overcurrent of the system outputs an “H” signal as an overcurrent detection signal if an overcurrent is detected, and outputs an “L” signal if no overcurrent is detected. The output of the overcurrent detection unit 12 is input to the control input of the signal switching unit 14, and the output terminal of the signal switching unit 14 of the inverting amplification unit 15 that inverts the polarity of the reference voltage Vs when the control input is “H”. When the control input is “L”, the output is connected to the output of the undervoltage detector 6.
  The output of the overcurrent detection unit 12 is logically summed with the output of the voltage drop detection unit 20 at the same time by the signal synthesis unit 21, and the output of the signal synthesis unit 21 is input to the control input of the short-circuit switch 18. The short-circuit switch 18 is opened by the control signal “H” and closed by “L”.
[0031]
  When the system voltage is normal and current flows through the load 10, the output of the voltage drop detection unit 20 is “L”, the output of the overcurrent detection unit 12 is “L”, and the output of the current detection unit 19 is “L”. In addition, since the output of the signal synthesis unit 21 is “L”, the short circuit switch 18 is in a closed state, and the current flows through the short circuit switch 18 without passing through the compensation voltage generation unit 4. Since the signal cut-off unit 13 is OFF because the control input is “L”, the undervoltage is input to the signal generation unit 7 as zero, and the compensation voltage generation unit 4 does not output a voltage (zero voltage output). Since the control input to the signal switching unit 14 is “L”, the output terminal is connected to the output of the undervoltage detection unit 6.
  When an accident occurs on the system power supply side 8 and the system voltage drops, the output of the voltage drop detection unit 20 becomes “H”, the output of the signal synthesis unit 21 also becomes “H”, and therefore the control input of the short-circuit switch 18 becomes “H”. Therefore, the short-circuit switch 18 is opened to cut off the current. When the current of the short-circuit switch 18 is interrupted and the current becomes zero, the output of the current detector 19 becomes “H” and the control input of the signal interrupter 13 becomes “H”, so that the signal interrupter 13 is turned on. Since the output of the overcurrent detection unit 12 remains “L”, the output terminal of the signal switching unit 14 is also connected to the output of the undervoltage detection unit 6, and the output of the undervoltage detection unit 6 is input to the signal generation unit 7. The compensation voltage generator 4 generates an undervoltage as a compensation voltage to compensate the system voltage.
[0032]
  On the other hand, when an accident occurs on the system load side 9 and an overcurrent and a system voltage drop occur, the output of the signal synthesizer 21 becomes “H”, the short-circuit switch 18 opens to cut off the current, and the signal switching unit 14 The control input becomes “H”, and the output terminal is connected to the output of the inverting amplifier 15 for inverting the polarity of the reference voltage Vs. When the current of the short-circuit switch 18 is cut off and becomes zero, the control input of the signal cut-off unit 13 becomes “H” and is turned on. Therefore, the signal generator 7 has the same absolute value as the system rated voltage (reference voltage Vs) and the opposite polarity. Is input. Accordingly, the compensation voltage generator 4 generates a voltage having a reverse polarity with respect to the system voltage and can suppress overcurrent. As a result, the overcurrent suppression voltage generated by the compensation voltage generator 4 is not short-circuited by the short-circuit switch 18, that is, the overcurrent suppression voltage is superimposed on the system without excessive current flowing through the compensation voltage generator 4. Therefore, damage due to overcurrent can be reduced.
[0033]
  Although the current interruption of the short-circuit switch 18 is confirmed by actually detecting the current, the interruption time of the short-circuit switch 18 is measured in advance, and the short-circuit switch 18 is interrupted from the opening command to the short-circuit switch 18. You may comprise so that ON instruction | command may be output to the signal interruption | blocking part 13 after progress.
[0034]
Embodiment 6 FIG.
  FIG. 7 shows a circuit configuration shown in FIG. 3 of the third embodiment, in which a shorting switch 18 and a current detection unit 19 for detecting a current flowing through the shorting switch 18 are provided.
  As described above, the generation of the overcurrent suppression voltage for suppressing the overcurrent is performed by turning off all the switching elements T1 to T4 connecting the capacitor 16 of the compensation voltage generation unit 4a and the system. If the system voltage is smaller than the voltage of the capacitor 16, the capacitor 16 is disconnected from the system by the action of the diodes D1 to D4. When the system voltage becomes larger than the voltage of the capacitor 16, the capacitor 16 has a polarity opposite to that of the system voltage. Connected to.
  When the voltage fluctuation compensator 100 having such an overcurrent suppressing function is provided with the short-circuit switch 18 for reducing loss at all times, an open command is sent to the short-circuit switch 18 and all the switching elements T1 to T4 are detected when an overcurrent is detected. Even when an OFF command serving as an overcurrent suppression control signal is issued at the same time, the system voltage applied to the compensation voltage generator 4a is short-circuited by the short-circuit switch 18 until the short-circuit switch 18 cuts off the current. Will not cause any inconvenience when disconnected from the grid. After the short circuit switch 18 cuts off the current, the overcurrent suppression voltage is automatically superimposed on the system. Therefore, the control for generating the overcurrent suppression voltage in the compensation voltage generator 4a can be performed regardless of the current interruption of the short-circuit switch 18, and no overcurrent suppression voltage is generated when the short-circuit switch 18 is in a closed state. When the short-circuit switch 18 is in an open state, an overcurrent suppression voltage can be generated.
[0035]
  When a voltage drop occurs due to an accident on the power supply side 8 of the system, a compensation voltage must be superimposed after completion of current interruption of the short-circuit switch 18. However, when the overcurrent detection unit 12 detects an overcurrent, it may issue a command to turn off all the switching elements T1 to T4 at the same time as issuing a contact opening command to the short-circuit switch 18. The signal synthesizer 21 takes the logical sum of the overcurrent detection signal (“H” at the time of overcurrent detection) and the output of the voltage drop detection unit 20 (“H” at the time of voltage drop detection) to obtain the control signal for the short-circuit switch 18. It ’s fine.
  If the compensation voltage generator 4a is composed of the capacitor 16 and the switching elements T1 to T4 in which the diodes D1 to D4 are antiparallel, respectively, the automatic operation after the short-circuit switch 18 is opened regardless of the circuit configuration. Thus, the overcurrent suppression voltage is superimposed on the system, and the overcurrent suppression can be performed without an excessive current flowing through the compensation voltage generator 4a.
[0036]
Embodiment 7 FIG.
  In the fifth and sixth embodiments, the opening command to the short-circuit switch 18 is the output signal of the voltage drop detection unit 20 (“H” when the voltage is lowered) and the output signal of the overcurrent detection unit 12 (“H” when the overcurrent is detected). ") Is ORed by the signal synthesizer 21 to cut off the short-circuit switch 18 when at least one occurs (voltage drop, overcurrent). In this embodiment, the short-circuit switch 18 is energized. In such a state, even if an overcurrent occurs, the short-circuit switch 18 is not cut off, and a signal synthesis unit 21a as shown in FIG. 8 is used.
  As shown in the figure, the logical product of the output of the overcurrent detection unit 12 (“H” at the time of overcurrent detection) and the output of the voltage drop detection unit 20 (“H” at the time of voltage drop detection) and the overcurrent detection unit 12 The logical sum of the inverted signal of the output and the output of the current detector 19 (“H” when no current is flowing) may be used as the output and used as the control signal for the short-circuit switch 18. In this way, a contact opening command is sent to the short-circuit switch 18 even if a system voltage drop is detected except when no overcurrent is detected or when no current is flowing through the short-circuit switch 18 even if an overcurrent is detected. Absent. That is, in the state where the short-circuit switch 18 is energized, even if an overcurrent occurs, the short-circuit switch 18 maintains a closed state and does not cut off the current. Can be used without waking up.
[0037]
  Also, overcurrent can be suppressed when the short-circuit switch 18 is open and an overcurrent flows, and even when an overcurrent flows in a closed state, a compensation voltage that at least increases the overcurrent is superimposed on the system. There is no.
  Further, although the short-circuit switch 18 has an overcurrent cutoff capability, it is also effective when the overcurrent tolerance of the compensation voltage generator 4 is small, and will be described below.
  When an overcurrent is detected while the short-circuit switch 18 is energized, if the current of the short-circuit switch 18 is interrupted, the overcurrent is suppressed until the overcurrent suppression starts after the overcurrent is commutated to the compensation voltage generator 4. The overcurrent that has not been performed continues to flow through the compensation voltage generator 4. This time depends on the interruption time of the short-circuit switch 18, the current zero detection time of the current detection unit 19, and the control time of the control unit 3, and becomes longer than when the short-circuit switch 18 detects an overcurrent in the open state. When the overcurrent tolerance of the compensation voltage generation unit 4 is small, the compensation voltage generation unit 4 may be damaged if the duration of the overcurrent flow is long. For this reason, as described above, in a state where the short-circuit switch 18 is energized, even if an overcurrent occurs, the short-circuit switch 18 maintains a closed state so that the overcurrent is not commutated to the compensation voltage generator 4. Control is effective in protecting the compensation voltage generator 4.
[0038]
Embodiment 8 FIG.
  In the seventh embodiment, the short-circuit switch 18 is maintained in a closed state even when an overcurrent occurs while the short-circuit switch 18 is energized. However, in this embodiment, when an overcurrent occurs, The short circuit switch 18 is immediately closed to prevent the overcurrent from flowing through the compensation voltage generator 4, and a signal synthesizer 21b as shown in FIG. 9 is used.
  As shown in the figure, the logical product of the output of the voltage drop detection unit 20 and the inverted signal of the output of the overcurrent detection unit 12 may be taken as a control signal for the short-circuit switch 18. As described above, since control is performed so that no overcurrent flows through the compensation voltage generation unit 4, the compensation voltage generation unit 4 can be used even when the compensation voltage generation unit 4 does not have overcurrent conduction capability, and the compensation voltage generation unit 4 can be protected.
[0039]
  FIG. 10 shows a configuration diagram of the voltage fluctuation compensating apparatus 100 to which the signal synthesis unit 21b shown in FIG. 9 is applied. When the power supply side 8 and the load side 9 are normal, the voltage is not lowered, so the output of the voltage drop detection unit 20 is “L”, and the overcurrent is not flowing, the output of the overcurrent detection unit 12 is “L”. Therefore, the output of the signal synthesis unit 21b, which is a control signal for the short circuit switch 18, becomes "L", and the short circuit switch 18 is in a closed state. Therefore, the power to the load side 9 is sent via the short-circuit switch 18 at the normal time.
  When an accident occurs on the power supply side 8 and the system voltage drops, the output of the voltage drop detection unit 20 becomes “H”. Since an overcurrent does not flow due to an accident on the power supply side 8, the output of the overcurrent detection unit 12 is “L”, so the output of the signal synthesis unit 21b is “H”, and the short-circuit switch 18 is opened to cut off the current. When the current of the short-circuit switch 18 is cut off, the output from the current detection unit 19 becomes “H”, the signal cut-off unit 13 becomes “ON”, and the compensation voltage generation unit 4 causes the undervoltage to be superimposed on the system as a compensation voltage. Be controlled. Therefore, in a situation where no overcurrent flows, a system voltage compensation operation can be performed to supply a normal voltage to the load 10.
[0040]
  On the other hand, when the system voltage decreases due to an accident on the load side 9, the output of the voltage drop detection unit 20 is “H”, and since the overcurrent flows, the output of the overcurrent detection unit 12 is “H”, and therefore the output of the signal synthesis unit 21b is “L”, and the short-circuit switch 18 is closed. When the power supply side 8 and the load side 9 are normal and the short-circuit switch 18 is in a closed state, if an accident occurs on the load side 9, the short-circuit switch 18 maintains the closed state, and an overcurrent flows to the short-circuit switch 18.
  Further, when the system voltage decreases due to an accident on the power supply side 8 and the system voltage compensation operation is being performed, if an accident occurs on the load side 9 and an overcurrent flows, the output of the overcurrent detection unit 12 changes from “L” to “H”. Therefore, the short-circuit switch 18 is closed, and an overcurrent flows through the short-circuit switch 18.
  Further, since the short-circuit switch 18 is not cut off, the signal cut-off unit 13 is “OFF” by the signal of the current detection unit 19 and no compensation voltage for increasing the overcurrent is generated. That is, when the overcurrent is detected, the short-circuit switch 18 is always controlled to be in a closed state, so that the compensation voltage generator 4 can be protected from the overcurrent. Further, at least a compensation voltage that increases the overcurrent is not superimposed on the system.
  In this case, an example in which a PWM inverter is used for the compensation voltage generation unit 4a has been described. However, the present invention is not limited to this, and other circuit configurations may be used.
[0041]
【The invention's effect】
  According to a first aspect of the present invention, there is provided a voltage fluctuation compensator that detects a voltage drop in a power system, and outputs a voltage compensation control signal with a voltage drop detection signal from the system voltage detector as an input. A compensation voltage generator that is connected in series to the power system and generates a compensation voltage in response to the voltage compensation control signal; Is superimposed on the system voltage to suppress voltage fluctuations supplied to the load, and the overvoltage detection unit detects the overcurrent flowing through the system in which the compensation voltage generator is connected in series. It has an overcurrent detection unit that outputs to the control unit,When the overcurrent detection signal is input, the control unit does not output the voltage compensation control signal even if the voltage drop detection signal is input, and outputs an overcurrent suppression control signal instead of the voltage compensation control signal. The compensation voltage generator receives the overcurrent suppression control signal as input and generates an overcurrent suppression voltage having a polarity opposite to that of the system voltage without generating the compensation voltage, and superimposes it on the system voltage.For,Overcurrent can be suppressed, damage due to overcurrent can be reduced,The power system and the voltage fluctuation compensation device itself can be protected. Further, with the installation of the voltage fluctuation compensation device, the device configuration can be simplified without requiring a countermeasure for increasing the short circuit current such as a new system protection device.
[0042]
  Claims related to this invention2The voltage fluctuation compensation device described in claim1, A protection circuit breaker is provided on the load side of the system in which the compensation voltage generation unit is connected in series, holds an overcurrent detection signal from the overcurrent detection unit, and shuts off the protection circuit breaker by the held overcurrent detection signal Therefore, even if the overcurrent is suppressed, the protective circuit breaker can be reliably cut off and the accident system can be disconnected.
[0043]
  Claims related to this invention3The voltage fluctuation compensation device described in claim1 or 2In this case, the overcurrent suppression voltage generated from the compensation voltage generator is almost the same magnitude as the reverse polarity of the normal system voltage, so the overcurrent can be effectively reduced to almost zero, and the damage caused by the overcurrent Can be further reduced.
[0044]
  Claims related to this invention4The voltage fluctuation compensation device described in claim1 or 2The compensation voltage generator includes a DC power supply, a self-extinguishing semiconductor switching element that is arranged on both sides or one side of the DC power supply, connects the DC power supply to the power system, and has diodes connected in antiparallel. The diode connected to the DC power supply is connected to the negative electrode of the diode on the positive electrode side of the DC power supply, and connected to the positive electrode of the diode on the negative electrode side of the DC power supply. When a control signal is input, all the semiconductor switching elements are turned off, and the voltage of the DC power supply is superimposed on the system voltage by the diode as an overcurrent suppression voltage having a reverse polarity. A normal system voltage and an overcurrent suppression voltage having a reverse polarity can be reliably generated and superimposed on the system voltage, and the overcurrent can be effectively suppressed.
[0045]
  Claims related to this invention5The voltage fluctuation compensation device described in claim1-3In any of the above, a short-circuit switch connected in parallel to the compensation voltage generator is provided in order to bypass the compensation voltage generator when the voltage drop is not detected by the system voltage detector, and the short-circuit switch is in a closed state When the overcurrent detection signal or the voltage drop detection signal is input to the control unit, the control unit outputs an opening command to the shorting switch, and the overcurrent is detected after the shorting switch is opened. Since the suppression control signal or the voltage compensation control signal is output and the voltage is generated by the compensation voltage generator, the compensation voltage generator can be protected without the voltage generated by the compensation voltage generator being short-circuited by the short-circuit switch.
[0046]
  Claims related to this invention6The voltage fluctuation compensation device described in claim1-3In order to bypass the compensation voltage generator when the voltage drop is not detected by the system voltage detector, the short-circuit switch is connected in parallel to the compensation voltage generator, and the short-circuit switch is closed. In this state, when an overcurrent detection signal is input to the control unit, the control unit does not output an overcurrent suppression control signal, the shorting switch maintains a closed state, and the shorting switch is in a closed state. When only the voltage drop detection signal is input to the control unit without inputting the current detection signal, the control unit outputs a voltage compensation control signal after opening the circuit by outputting an opening command to the shorting switch. Even a short-circuit switch without an overcurrent cutoff capability can be applied without causing inability to shut down. Further, even if a compensation voltage generator having a small overcurrent withstand capability is applied, it can be reliably protected.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a circuit configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 2 of the present invention.
FIG. 3 is a circuit configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 3 of the present invention.
FIG. 4 is a diagram showing a voltage-current waveform at the time of a system load side accident according to Embodiment 3 of the present invention.
FIG. 5 is a circuit configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 4 of the present invention.
FIG. 6 is a circuit configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 5 of the present invention.
FIG. 7 is a circuit configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 6 of the present invention.
FIG. 8 is a diagram showing a signal combining unit of a voltage fluctuation compensating apparatus according to Embodiment 7 of the present invention.
FIG. 9 is a diagram showing a signal combining unit of a voltage fluctuation compensating apparatus according to Embodiment 8 of the present invention.
FIG. 10 is a circuit configuration diagram of a voltage fluctuation compensator according to an eighth embodiment of the present invention.
FIG. 11 is a circuit configuration diagram of a conventional voltage fluctuation compensator.
FIG. 12 is a diagram illustrating a problem of a conventional voltage fluctuation compensation device.
[Explanation of symbols]
  2 system voltage detector, 4, 4a compensation voltage generator, 7 signal generator, 10 load,
11 Protection circuit breaker, 12 Overcurrent detection part, 13 Signal interruption part, 14 Signal switching part,
16 Capacitor as a DC power source, 18 Short-circuit switch, 19 Current detection unit,
21, 21 a, 21 b Signal synthesis unit, 30, 31, 32, 33, 34, 35 control unit,
100 voltage fluctuation compensator, T1-T4 semiconductor switching element,
D1-D4 diode.

Claims

A system voltage detection unit that detects a voltage drop in the power system, a control unit that outputs a voltage compensation control signal with the voltage drop detection signal from the system voltage detection unit as an input, and is connected in series to the power system, the voltage A compensation voltage generator for generating a compensation voltage by a compensation control signal, and the voltage supplied to the load by superimposing the compensation voltage generated by the compensation voltage generator when the system voltage drops on the system voltage In the voltage fluctuation compensator for suppressing fluctuation, the voltage fluctuation compensator includes an overcurrent detection unit that detects an overcurrent flowing through the system in which the compensation voltage generation unit is connected in series and outputs an overcurrent detection signal to the control unit,
When the overcurrent detection signal is input, the control unit does not output the voltage compensation control signal even if the voltage drop detection signal is input, and outputs an overcurrent suppression control signal instead of the voltage compensation control signal. The compensation voltage generator receives the overcurrent suppression control signal as an input, generates an overcurrent suppression voltage having a polarity opposite to that of the system voltage without generating the compensation voltage, and superimposes the overcurrent suppression voltage on the system voltage. Voltage fluctuation compensation device.

A protective circuit breaker is provided on the load side of the system in which the compensation voltage generation unit is connected in series, holds an overcurrent detection signal from the overcurrent detection unit, and interrupts the protective circuit breaker by the held overcurrent detection signal. The voltage fluctuation compensator according to claim 1 .

3. The voltage fluctuation compensator according to claim 1, wherein the overcurrent suppression voltage generated from the compensation voltage generator is substantially the same in magnitude and opposite in polarity to a normal system voltage.

The compensation voltage generator is composed of a DC power supply and a self-extinguishing semiconductor switching element which is arranged on both sides or one side of the DC power supply, connects the DC power supply to the power system, and has diodes connected in antiparallel. The diode connected to the DC power supply is connected to the negative electrode of the diode on the positive electrode side of the DC power supply, and connected to the positive electrode of the diode on the negative electrode side of the DC power supply. When is inputted, turn off all of the above semiconductor switching element, according to claim 1 or 2, wherein the superimposed on the system voltage by the diode voltage of the DC power supply as a polarity opposite overcurrent suppression voltage Voltage fluctuation compensation device.

In order to bypass the compensation voltage generator when the voltage drop is not detected by the system voltage detector, a short-circuit switch connected in parallel to the compensation voltage generator is provided. When the signal or the voltage drop detection signal is input to the control unit, the control unit outputs an opening command to the shorting switch, and after the shorting switch is opened, the overcurrent suppression control signal or voltage 4. The voltage fluctuation compensation device according to claim 1, wherein a compensation control signal is output and a voltage is generated by a compensation voltage generator.

In order to bypass the compensation voltage generator when the voltage drop is not detected by the system voltage detector, a short-circuit switch is connected in parallel to the compensation voltage generator. When a detection signal is input to the control unit, the control unit does not output an overcurrent suppression control signal, the short-circuit switch maintains a closed state, the short-circuit switch is in a closed state, and an overcurrent detection signal is input. If only the voltage drop detection signal is input to the control unit without being output, the control unit outputs a voltage compensation control signal after outputting a contact opening command to the shorting switch and opening the contact. Item 4. The voltage fluctuation compensation device according to any one of Items 1 to 3 .