JP3796657B2

JP3796657B2 - Distributed power system interconnection protection system

Info

Publication number: JP3796657B2
Application number: JP2001227211A
Authority: JP
Inventors: 倫行内山; 康則大野; 浩有田; 幹祐樋口
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2001-07-27
Filing date: 2001-07-27
Publication date: 2006-07-12
Anticipated expiration: 2021-07-27
Also published as: JP2003047156A

Description

【０００１】
【発明の属する技術分野】
本発明は、分散型電源設備の連系保護システムに係り、特に、瞬時電圧低下と単独運転を検出して分散型電源設備や負荷を保護するに好適な分散型電源設備の連系保護システムに関する。
【０００２】
【従来の技術】
工場や大規模ビルなどの需要家の電力設備においては、電力系統側の給電停止時のバックアップ対策や不足電力を補うために、あるいはコージェネレーションシステムのように電熱併給システムとして総合エネルギー費用を削減する目的で、分散型電源を自家発電用電源として設置し、電力系統と分散型電源とを連系して運用する構成が増加している。
【０００３】
従来の分散型電源設備の連系保護システムは、分散型電源を持たない受電設備と同様に、保護の目的に応じて個別に設置された専用の保護装置を協調制御して運用されている。例えば、落雷などによる電力系統側の短時間故障により生じる瞬時電圧低下に対しては、例えば、特開平１０−３３６８７８号公報に記載されているように、電力系統と分散型電源設備との間に配置されて半導体スイッチにより構成された遮断装置により、電力系統から需要家の分散型電源設備と重要負荷を高速に解列（通常、２０ｍｓ以内）することで、電圧低下による被害を軽減させる瞬時電圧低下防止装置が提案されている。
【０００４】
また、系統給電停止時の保護上の対策（感電などの防止）として、必要な分散型電源の単独運転防止に対しては、電力会社の変電所と分散型電源を持つ需要家との間で通信を行う転送遮断装置や、分散型電源側で単独運転を検出する専用の検出装置が設置されている。ここで、単独運転とは、電力系統側の電源が喪失したときに、分散型電源が電力系統から解列されないままになり、局所的に分散型電源から他の一般需要家に電力を供給している状態を言う。
【０００５】
単独運転状態になると、本来無電圧であるべき系統が分散型電源によって充電されるため、そのままでは安全上に問題を生じることになる。さらに、分散型電源から系統が充電された状態で系統が自動的に再閉路されると、非同期投入によって機器などが損傷する問題が生じる。このため、このような問題点が生ずるのを防止するために、連系ガイドラインにより、需要家には単独運転を検出するための装置を設けるとともに、単独運転時に系統と分散型電源とを解列する解列手段を設置することが義務付けられている。
【０００６】
分散型電源設備の連系保護システムにおいて、瞬時電圧低下などの異常を検出するに際しては、例えば、各相の電圧の平均値を算出して基準値と比較する方法や、各相の電圧および電流の瞬時値（絶対値、時間変化率など）を基準値と比較する方法の他、特開平６−８２４９９号公報に記載されているように、三相の電圧の自乗和を用いる方法や、特開平５−２９７０３０号公報に記載されているように、三相／二相変換による合成電圧ベクトルを用いる方法が提案されているとともに、単独運転を検出する方法として、特開平１０−２３４１３６号公報に記載されているように、系統側の電圧と分散電源側の電圧とを検出し、各検出電圧の波形から両者の位相差と周波数差および電力方向を求め、これらの値が一定値を超えたときの組合わせから単独運転を検出する方法が提案されている。
【０００７】
【発明が解決しようとする課題】
従来の連系保護システムにおいては、保護の目的ごとに専用の装置を個別に設置しているため、需要家の設備投資が増加するとともに、各装置を協調して運用するための保護システムの構成が複雑化し、システム全体の制御の応答性／信頼性が低下するという問題点がある。そこで、単一の制御装置に複数の保護機能を持たせて集中制御することも考えられるが、単一の制御装置に単に複数の保護機能を持たせても、１つの演算処理装置で処理する演算量が増加するだけで演算処理を円滑に行うことができない。
【０００８】
また、従来の連系保護システムにおいて異常を検出するに際して、瞬時電圧低下の検出を行うにも、電圧の平均値を用いる方法では、積分処理を行うために、原理的に検出に時間がかかるという問題点がある。また各相ごとの電圧・電流の瞬時値を用いる方法では、検出時間は短いが、系統のわずかな擾乱（波形歪み、周波数変動など）に対しても動作する可能性がある。また各相の電圧の自乗和や三層／二相変換による合成ベクトルを用いる方法では、各相の電圧低下の割合にばらつきがあるような場合には、電圧低下の小さい、あるいは遅い相に影響されて検出時間が長くなり、検出不能になる恐れがある。
【０００９】
本発明の課題は、演算処理を円滑に行うことができ、かつ瞬時電圧検出を高速に、高精度に行うことができる分散型電源設備の連系保護システムを提供することにある。
【００１０】
本発明の他の課題は、瞬時電圧検出を高速に且つ高精度に行うことができる分散型電源設備の連系保護システムを提供することにある。
【００１１】
【課題を解決するための手段】
前記課題を解決するために、本発明の分散型電源設備の連系保護システムは、三相の電力系統と分散型電源の母線を連絡する連絡母線に設けられた遮断器と、前記電力系統側の母線電圧を検出する系統側電圧検出器と、前記分散型電源側の母線電圧を検出する分散電源側電圧検出器と、前記連絡母線の電流を検出する電流検出器と、前記系統側電圧検出器と前記分散電源側電圧検出器及び前記電流検出器の検出出力を基に前記電力系統の異常の有無を判定し、この判定結果に従って前記遮断器を制御する制御手段とを備え、前記制御手段は、前記系統側電圧検出器の検出電圧と前記電流検出器の検出電流を演算処理して瞬時電圧低下を検出する瞬時電圧低下検出手段と、前記分散型電源側電圧検出器の検出電圧の周波数変化率から単独運転を検出する単独運転検出手段と、前記瞬時電圧低下検出手段の検出出力又は前記単独運転検出手段の検出出力に応答して前記遮断器の遮断指令を出力する遮断指令出力手段とを含んで構成されてなることを前提構成とする。
【００１２】
前記分散型電源設備の連系保護システムを構成するに際しては、以下の要素を付加することができる。
【００１３】
（１）前記制御手段は、前記系統側電圧検出器の検出電圧と前記分散電源側電圧検出器の検出電圧との位相差を検出する位相差検出手段と、前記位相差検出手段の検出出力により同期タイミングを判定する同期判定手段と、前記同期判定手段から同期タイミングであるとの判定結果が出力されたときに前記遮断器に対して投入指令を出力する投入指令出力手段とを含んで構成されてなる。
【００１４】
（２）前記制御手段は、前記分散型電源の運転状態を制御する分散型電源制御手段を含んで構成されてなる。
【００１５】
（３）前記瞬時電圧低下検出手段は、前記系統側電圧検出器の検出出力を三相／二相変換して合成電圧ベクトルの絶対値を算出する絶対値算出手段と、前記絶対値算出手段の算出による絶対値と異常判定のしきい値とを比較して瞬時電圧低下の発生の有無を判定する瞬時電圧低下判定手段と、前記電流検出器の検出による各相の電流を演算処理して異常を検出する電流異常検出手段と、前記電流異常検出手段の検出出力により前記異常判定のしきい値を補正する補正手段とから構成されてなる。
【００１６】
（４）前記瞬時電圧低下検出手段は、前記系統側電圧検出器の検出出力を三相／二相変換して合成電圧ベクトルの絶対値を算出する絶対値算出手段と、前記絶対値算出手段の算出による絶対値と異常判定のしきい値とを比較して瞬時電圧低下の発生の有無を判定する瞬時電圧低下判定手段と、前記系統側電圧検出器の検出による各相の電圧を演算処理して異常を検出する電圧異常検出手段と、前記電圧異常検出手段の検出出力により前記異常判定のしきい値を補正する補正手段とから構成されてなる。
【００１７】
（５）前記瞬時電圧低下検出手段は、前記系統側電圧検出器の検出出力を三相／二相変換して合成電圧ベクトルの絶対値を算出する絶対値算出手段と、前記絶対値算出手段の算出による絶対値と異常判定のしきい値とを比較して瞬時電圧低下の発生の有無を判定する瞬時電圧低下判定手段と、前記系統側電圧検出器の検出による各相の電圧を演算処理して異常を検出する電圧異常検出手段と、前記電流検出器の検出による各相の電流を演算処理して異常を検出する電流異常検出手段と、前記電流異常検出手段の検出出力または前記電圧異常検出手段の検出出力により前記異常判定のしきい値を補正する補正手段とから構成されてなる。
【００１８】
（６）前記電流異常検出手段は、前記電流検出器の検出による各相の電流の時間変化率のうちいずれかの時間変化率が変化率判定値を超えたときに異常を検出してなる。
【００１９】
（７）前記電流異常検出手段は、前記電流検出器の検出による各相の電流の絶対値のうちいずれかの絶対値が絶対値判定値を超えたときに異常を検出してなる。
【００２０】
（８）前記電圧異常検出手段は、前記系統側電圧検出器の検出による各相の電圧降下量のうちいずれかの電圧降下量が電圧判定値以下になったときに異常を検出してなる。
【００２１】
前記した手段によれば、単一の制御手段により、瞬時電圧低下および単独運転を検出し、この検出結果にしたがって母線連絡用遮断器を遮断する制御を行い、瞬時電圧低下のための演算処理と単独運転検出のための演算処理の共有化を図るようにしたため、演算量を低減することができ、演算処理を円滑に行うことができる。
【００２２】
また、瞬時電圧低下を検出するに際して、系統側電圧検出器の検出出力を三相／二相変換して合成電圧ベクトルの絶対値を算出し、この絶対値と異常判定のしきい値とを比較して瞬時電圧低下の発生の有無を判定するときに、電圧異常検出手段または電流異常検出手段の検出出力により異常判定のしきい値を補正し、例えば、異常判定のしきい値を大きくして検出感度を上げるようにしているため、ノイズ処理、故障継続性判定などの複雑な処理を加えることなく、外乱に強く且つ所定の時間内で瞬時電圧低下を高精度に検出することができる。
【００２３】
【発明の実施の形態】
以下、本発明の一実施形態を図面に基づいて説明する。図１は本発明の一実施形態を示す分散型電源設備の連系保護システムの単線結線図である。図１に示す需要家の主回路は、電力系統４に接続された負荷２を含む系と、分散型電源となる発電装置５１とこれに接続された負荷３を含む系を母線１６で連系する方式であって、分散型電源を保有する需要家が電力系統４と連系する場合に一般的に用いられる回路構成である。
【００２４】
図１において、三相の電力系統４から電力を受ける受電点には遮断器６が設置されており、この遮断器６は受電用変圧器１０、遮断器８を介して負荷２に接続されている。受電用変圧器１０と遮断器８との接続点には母線１６が接続されている。
【００２５】
一方、自家発電設備となる分散型電源設備５は分散型電源としての発電装置５１、制御装置５２を備えて構成されており、発電装置５１は遮断器７、９を介して負荷３に接続されている。そして遮断器７と遮断器９との接続点に母線１６が接続されている。制御装置５２は連系保護システム１の制御装置１１から電圧変動指令を受け、この指令にしたがって発電装置５１の出力電圧を制御するように構成されている。負荷３は負荷２よりも高い電力品質が要求されており、通常短時間の停電も許容されないもので構成されている。
【００２６】
連系保護システム１は、系統側の系と分散電源側の系とを結ぶ母線１６の途中に挿入されて配置された母線連絡用遮断器１２、母線の通過電流Ｉを検出する電流検出器１３、遮断器１２より電力系統側の母線電圧Ｖｓを検出する系統側電圧検出器１４、遮断器１２より分散電源側の母線電圧Ｖｇを検出する分散電源側電圧検出器１５、電流検出器１３の検出電流、電圧検出器１４、１５の検出電圧を基に電力系統４の異常の有無を判定し、この判定結果にしたがった遮断器１２の遮断・投入を制御する制御手段としての制御装置１１を備えて構成されている。
【００２７】
本実施形態による連系保護システム１では、母線連絡用遮断器１２として、高速動作可能な真空遮断器あるいは半導体式の遮断器が採用されている。また制御装置１１は、電圧検出器１４の検出電圧と電流検出器１３の検出電流を演算処理して瞬時電圧低下を検出する瞬時電圧低下検出手段と、電圧検出器１５の検出電圧の周波数変化率から単独運転を検出する単独運転検出手段と、各検出手段の検出出力に応答して遮断器１２に対して遮断指令を出力する遮断指令出力手段としての機能を備えて構成されている。さらに、制御装置１１は、電圧検出器１４の検出電圧と電圧検出器１５の検出電圧との位相差を検出する位相差検出手段と、位相差検出手段の検出出力により同期タイミングを判定する同期判定手段と、この同期判定手段から同期タイミングであるとの判定結果が出力されたときに遮断器１２に対して投入指令を出力する投入指令出力手段としての機能を備えて構成されている。以下、制御装置１１の具体的制御アルゴリズムを図２ないし図５を用いて詳細に説明する。
【００２８】
制御装置１１は、図２に示すように、電流検出器１３、電圧検出器１４、１５の検出出力（アナログ量の信号）をディジタル信号に変換するＡ／Ｄ変換部１１０、電流情報演算部１１１、比較部１１２、電圧情報演算部１１４、比較部１１５、前処理判定部１１７、三相ベクトル処理部１１８、単独運転検出部１２０、同期検出部１２１などを備えて構成されている。
【００２９】
上記構成による制御装置１１において瞬時電圧低下の検出を行うに際しては、検出器１３の検出による各相の電流Ｉｕ、Ｉｖ、Ｉｗ、電圧検出器１４の検出による各相の電圧Ｖｓｕ、Ｖｓｖ、Ｖｓｗ、電圧検出器１５の検出による各相の電圧Ｖｇｕ、Ｖｇｖ、ＶｇｗをそれぞれＡ／Ｄ変換部１１０で指定のサンプリング周波数にしたがってサンプリングするとともにホールドし、電圧情報演算部１１４で各相の電圧Ｖｓｕ、Ｖｓｖ、ＶｓｗおよびＶｇｕ、Ｖｇｖ、Ｖｇｗの瞬時値を用いて各相の電圧低下量ΔＶの計算を行う。
【００３０】
次に、比較部１１５で電圧情報演算部１４で算出された各相の電圧低下量ΔＶと判定値ε１とを比較し、いずれかの相の電圧低下量ΔＶが判定値ε１よりも下回っているときには、いずれかの相の電圧に異常があるとして異常検出信号を前処理判定部１１７に出力する。すなわち電圧情報演算部１１４、比較部１１５は電圧異常検出手段として構成されている。このとき同時に、各相の電流Ｉｕ、Ｉｖ、Ｉｗの瞬時値を用いて電流情報演算部１１１において各相の電流の絶対値あるいは時間変化率の算出が行われ、この算出結果と判定値ε２とが比較部１１２において行われ、いずれかの算出結果が判定値ε２を超えているときには電流に異常が生じたとして異常検出信号を前処理判定部１１７に出力する。すなわち、電流情報演算部１１１、比較部１１２は電流異常検出手段として構成されている。
【００３１】
次に、前処理判定部１１７において、比較部１１２または比較部１１５から異常検出信号が入力されたとき、すなわち、いずれか一方の比較部から、入力信号が基準値を逸脱しているとの比較結果が出力されたときには、所定のゲインａ（＞１）を出力する。これにより異常判定のしきい値ε３にゲインａが乗算され、異常判定のしきい値ε３を大きくして検出感度を高めるための補正が行われる。すなわち前処理判定部１１７は異常判定のしきい値を補正する補正手段として構成されている。
【００３２】
一方、三相ベクトル処理部１１８では、以下のような処理が行われる。Ａ／Ｄ変換部１１０でサンプリングされた電力系統４側の電圧Ｖｓｕ、Ｖｓｖ、Ｖｓｗを用いて三相／二相変換部１１８１で、次の（１）式および（２）式により合成電圧ベクトルＶα、Ｖβを求め、これらを絶対値計算部１１８２でベクトル合成して絶対値｜Ｖαβ｜（一定の直流分となる電圧値）を算出する。
【００３３】
【数１】

【００３４】
【数２】

このあと、絶対値計算部１１８２の算出による絶対値と異常判定のしきい値とを瞬時電圧低下判定部１１８３で比較し、この比較により瞬時電圧低下の有無を判定し、瞬時電圧低下が発生したときには瞬時電圧低下判定部１１８３から遮断器１２に対して遮断指令が出力され、遮断器１２が遮断されるようになっている。すなわち、三相／二相変換部１１８１、絶対値計算部１１８２は絶対値算出手段として、瞬時電圧低下判定部１１８３は瞬時電圧低下判定手段および遮断指令出力手段として構成されている。
【００３５】
ここで、本実施形態においては、合成ベクトルの絶対値｜Ｖαβ｜に対する判定値（異常判定のしきい値）ε３に、各相の電圧、電流の瞬時値による前処理判定部１１７から出力される所定のゲインａ（＞１）を乗じるに際して、いずれかの相の電圧・電流に異常を検出したときのみ絶対値｜Ｖαβ｜に対する判定値ε３を大きくして検出感度を上げるようにしている。このようにすることで、検出時間は短いが、波形歪み、周波数変動などで誤検出しやすい各相ごとの瞬時値による検出と、外乱には強いが故障の様相によっては検出に時間を要する三相の合成ベクトル処理による検出の短所を補いながら、互いの長所を活かすことができる。結果として、本実施形態による補正処理を行うことで、ノイズ処理、故障継続性判定処理などの複雑な処理を加えることなく、外乱に強く且つ所定の時間内で瞬時電圧低下を高精度に検出することができる。
【００３６】
次に、瞬時電圧低下の具体的な検出動作を図３にしたがって説明する。まず、電力系統４で一線地絡故障が発生したときのように、三相電圧低下の割合にばらつきがある場合の例について説明する。図３（ａ）に示すように、Ｖ相で一線地絡故障が発生した場合、（ｂ）に示すように、電力系統４側の電圧Ｖｓｕ、Ｖｓｖ、Ｖｓｗの波形のうち、Ｖ相の電圧が低下し、Ｖ相の電圧低下率が最も早く大きくなる。すなわち、Ｖ相の電圧が低下すると、次の（３）式で定義されるＶ相の電圧の瞬時値の低下率ΔＶｓｖｉは、（ｂ）に示すように、急激に低下する。
【００３７】
【数３】

ここで、添字ｉはＡ／Ｄ変換部１１０によるサンプリング時刻、ｎは一周期のサンプリング点数である。（３）式のΔＶｓｖｉと判定値ε１とを比較部１１５で比較し、（ｂ）に示すように、所定のサンプリング回数以上連続してΔＶｓｖｉ＜ε１が成立したときには、Ｖ相の電圧低下の可能性が有りとする比較結果、すなわち、異常検出信号が前処理判定部１１７に出力される。比較部１１５の比較演算により電圧低下の可能性があるとの判定結果が得られたときには、（ｃ）に示すように、三相／二相変換部１１８１および絶対値計算部１１８２の演算で得られた合成電圧ベクトルの絶対値｜Ｖαβ｜に対する判定値ε３に対してゲインａ（＞１）を乗算し、この判定値ε３を大きくして検出感度を上げるための補正が行われる。
【００３８】
このような補正処理を行うことで、三相の電圧低下のばらつきのために、絶対値｜Ｖαβ｜が脈動し、且つ電圧低下量を検出するのに十分でない場合においても、従来の三相／二相変換のみによる検出方法に比べて、検出時間を短縮することができる。また、各相の瞬時値と合成電圧ベクトルの組合わせによるもので、各相ごとの瞬時値のみを用いた検出時に起こり得る誤検出の問題を回避することもできる。
【００３９】
次に、瞬時電圧低下を検出するに際して、電流情報演算部１１１、電圧情報演算部１１４、比較部１１２、１１５における具体的な処理内容を図４にしたがって説明する。まず、瞬時電圧低下の各相ごとの瞬時値処理を行うに際して、電圧低下率によって瞬時電圧低下を検出するに際しては、（ａ）に示すように、電力系統４側および分散型電源５側の電圧の瞬時値Ｖｓｕｉ、Ｖｓｖｉ、ＶｓｗｉおよびＶｇｕｉ、Ｖｇｖｉ、Ｖｇｗｉを用いて電圧情報演算部１１４において各相の電圧低下率を求め、各算出値をそれぞれ判定値ε１と比較し、電力系統４側および分散型電源５側の少なくとも１つの相に関する電圧低下率が同時に所定のサンプリング回数以上連続して判定値ε１を下回ったときには、電圧異常が生じたとして異常検出信号が比較部１１５から前処理判定部１１７に出力される。すなわち電圧情報演算部１１４、比較部１１５は各相の電圧降下量（電圧低下率）のうちいずれかの相の電圧降下量が電圧判定値（判定値ε１）以下になったときに異常を検出する電圧異常検出手段として構成されている。
【００４０】
次に、瞬時電圧低下を電流の絶対値によって検出する場合には、（ｂ）に示すように、各相の電流の瞬時値Ｉｕｉ、Ｉｖｉ、Ｉｗｉから電流情報演算部１１１でそれぞれの絶対値を算出し、各算出値と判定値ε２とをそれぞれ比較し、少なくとも１つの相の算出値が所定のサンプリング回数以上連続して判定値ε２を超えていると比較部１１２において判定されたときには、比較部１１２から前処理判定部１１７に対して電流の異常が生じたとして異常検出信号が出力される。すなわち電流情報演算部１１１、比較部１１２は電流異常検出手段として構成されている。
【００４１】
また、電流の時間変化により瞬時電圧低下を検出する場合には、（ｃ）に示すように、各相の電流の瞬時値Ｉｕｉ、Ｉｖｉ、Ｉｗｉを用いて電流情報演算部１１１でそれぞれの時間変化率を算出し、各算出値と判定値ε２とをそれぞれ比較し、少なくとも１つの算出値が所定のサンプリング回数以上連続して判定値ε２を超えているときには、電流に異常が生じたとして、異常検出信号が比較部１１２から前処理判定部１１７に出力される。すなわち、電流情報演算部１１１、比較部１１２は電流異常検出手段として構成されている。
【００４２】
なお、瞬時電圧低下を検出するに際しては、前処理判定に用いる各相の瞬時値による処理として、図４（ａ）の電圧低下量の演算処理と（ｂ）あるいは（ｃ）の電流の演算処理とを併用しても良いし、（ａ）の電圧低下量の演算処理だけでも良い。
【００４３】
次に、単独運転を検出するに際しては、図２に示す受動方式の単独運転検出部１２０が用いられる。単独運転検出部１２０は周波数変化率演算部１２０１、単独運転判定部１２０２を備えて構成されている。周波数変化率演算部１２０１では、まず、電圧情報演算部１１４において、上述したように、各相の瞬時電圧低下の検出に必要な各相の電圧低下量を検出する過程で検出しておいた、分散型電源５側の電圧Ｖｇの波形の零クロス点の時刻ｔｇｕ、ｔｇｖ、ｔｇｗを用いて周波数を算出する。次に、（４）式で定義される周波数変化率Δｆを計算する。
【００４４】
【数４】

ここで、ｆ（Ｈｚ）基準周波数で、例えば現在のサンプリング時刻から０．５〜１ｓ前の時間区間の平均値とする。ｆ１（Ｈｚ）は現在の時刻における周波数で、例えば、現在のサンプリング時刻から３サイクル前の時間区間平均値とする。
【００４５】
（４）式の周波数変化率Δｆを各相ごとに算出し、この算出結果と判定値ε４とを判定部１２０２でそれぞれ比較し、少なくとも１つの算出値が判定値ε４を超えているときには、単独運転と判定し、遮断器１２に対して遮断指令を出力し遮断器１２を開放する。すなわち単独運転検出部１２０は単独運転検出手段とともに遮断指令出力手段として構成されている。
【００４６】
単独運転を検出するに際しては、受動方式による単独運転検出部１２０とともに、図５に示すように、能動方式による単独運転検出部１２２を用いることができる。この能動方式による単独運転検出部１２２においては、発電設備の制御系や外部の回路などにより、常時何らかの変動を与えておき、単独運転時に顕著になるこの変動を利用して単独運転を検出する方式が採用されている。
【００４７】
図５において、電圧変動信号発生部１２２４は、常時所定の変動信号Ｖｃｎｔを分散型電源５の制御装置５２へ送り続ける。周波数変化率演算部１２２１では、受動方式のときと同様に、分散型電源５側の電圧Ｖｇの波形の零クロス点の時刻ｔｇｕ、ｔｇｖ、ｔｇｗを用いて周波数を算出したあと、（４）式を用いて各相の周波数変化率Δｆを算出する。判定部１２２２では、各相の周波数変化率Δｆと２つの判定値ε４、ε５とをそれぞれ比較する。まず、各相の周波数変化率Δｆのうち少なくとも１つがε４＜Δｆ＜ε５を満たすならばゲインｂを出力する。このゲインｂは電圧変動信号発生器１２２４から送られる変動信号に乗算され、分散型電源５の制御装置５２への変動指令値を大きくする。また、少なくとも、１つの相に関する算出値がε５＜Δｆを満たすときには、母線連絡用遮断器１２に対して遮断指令を出力する。
【００４８】
このように、単独運転の検出に、周波数変化率を用いれば、太陽電池、燃料電池、マイクロガスタービンのように、インバータを介して連系される分散型電源にも、回転機系の分散型電源にも適用可能である。なお、本実施形態では、単独運転の検出を図２に示す受動方式と図５に示す能動方式について述べたが、これらに限定されるものではなく、他の方法を採用することもできる。
【００４９】
また、遮断器１２を遮断したあと同期投入するに際しては、同期検出部１２１によって同期検出が行われる。この同期検出部１２１は位相差演算部１２１１、同期判定部１２１２を備えて構成されており、遮断器１２の投入に必要な系統側電圧Ｖｓと分散型電源側の電圧Ｖｇの同期検出が行われる。まず位相差演算部１２１１においては、各相の電圧情報演算部１１４で求められた各相の系統側電圧Ｖｓの波形の零クロス点と、分散型電源側電圧Ｖｇの波形の零クロス点の時間差から位相差｜Δθ｜を計算する。同期判定部１２１では、位相差演算部１２１１の算出による位相差｜Δθ｜と判定値ε６とを比較し、｜Δθ｜＜ε６を満たしているときには、同期と判定し、遮断器１２に対して投入指令を出力する。
【００５０】
このように、本実施形態においては、連系保護システムの制御アルゴリズムをマイコンなどの演算処理装置にプログラミングし、これを電源、Ａ／Ｄ変換器、メモリとともに単一のプリント基板に設置して制御基板を構成し、この制御基板を制御装置１１に組み込むこととしている。
【００５１】
次に、本発明の他の実施形態を図６にしたがって説明する。本実施形態は、分散型電源設備の制御装置５２に瞬時電圧低下および単独運転を検出する機能を付加するとともに、分散型電源の運転状態を制御する分散型電源制御手段としての機能を付加して連系保護システムを構成したものであり、他の構成は図１のものと同様である。
【００５２】
分散型電源の制御装置５２は、電源制御部５２１と連系保護制御部５２２を備えて構成されており、連系保護制御部５２２には、前記実施形態で用いた制御アルゴリズムに関する情報を搭載した制御基板が採用されている。電源制御部５２１は、連系保護制御部５２２から出力される電圧変動指令にしたがって発電装置５１による運転状態を制御するように構成されている。
【００５３】
本実施形態においては、連系保護制御部５２２に前記実施形態と同様な機能を持たせているため、前記実施形態と同様な効果を得ることができる。
【００５４】
なお、電源制御部５２１の制御基板内に、図２の制御アルゴリズムをプログラミングし、且つこの制御基板に電流検出器１３、電圧検出器１４、１５の入力部を追加して、電源制御部５２１に連系保護制御部５２２の機能を組み込むことも可能である。
【００５５】
上述したように、前記各実施形態によれば、瞬時電圧低下および単独運転の検出に伴う演算処理の共有化を図ることで、単一の制御装置１１、５２に上記の機能を集約することが可能となるため、専用の瞬時電圧低下検出装置や単独運転検出装置および転送遮断装置を設置する必要がなくなる。したがって、設備投資を増加することなく、また保護システムの構成や制御を複雑化することなく、従来と同様な保護機能を得ることができる。また保護装置間の通信線を削減できるため、制御の応答性／信頼性も向上する。
【００５６】
さらに、瞬時電圧低下の検出方法においては、各相の電圧、電流の瞬時値による検出と、三相／二相変化による合成電圧ベクトルを用いた検出を併用し、且つ瞬時値による検出結果を用いて合成電圧ベクトルのための異常判定値を補正するようにしているため、波形歪み、周波数変動などの擾乱の影響を受けずに、且つ検出時間を増加させることなく信頼性を向上させることができる。
【００５７】
【発明の効果】
以上説明したように、本発明によれば、単一の制御手段により、瞬時電圧低下および単独運転を検出し、この検出結果にしたがって母線連絡用遮断器を遮断する制御を行い、瞬時電圧低下のための演算処理と単独運転検出のための演算処理の共有化を図るようにしたため、演算量を低減することができ、演算処理を円滑に行うことができる。また、本発明によれば、系統側電圧検出器の検出出力を三相／二相変換して合成電圧ベクトルの絶対値を算出し、この絶対値と異常判定のしきい値とを比較して瞬時電圧低下の発生の有無を判定するときに、電圧異常検出手段または電流異常検出手段の検出出力により異常判定のしきい値を補正するようにしているため、ノイズ処理、故障継続性判定などの複雑な処理を加えることなく、外乱に強く且つ所定の時間内で瞬時電圧低下を高精度に検出することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示す分散型電源設備の連系保護システムのブロック構成図である。
【図２】瞬時電圧低下化と単独運転を検出するアルゴリズムを説明するためのブロック構成図である。
【図３】瞬時電圧低下の検出方法を説明するための波形図である。
【図４】瞬時電圧低下の具体的アルゴリズムを説明するためのブロック構成図である。
【図５】能動方式による単独運転検出方法を説明するためのブロック構成図である。
【図６】本発明の他の実施形態を示す連系保護システムのブロック構成図である。
【符号の説明】
１連系保護システム
２、３負荷
４電力系統
５分散型電源設備
６、７、８、９遮断器
１０受電用変圧器
１１制御装置
１１０Ａ／Ｄ変換部
１１１電流情報演算部
１１２電圧情報演算部
１１３三相ベクトル処理部
１１４電圧情報演算部
１１５単独運転検出部
１１７前処理判定部
１２母線連絡用遮断器
１３電力検出器
１４、１５電圧検出器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an interconnection protection system for distributed power supply equipment, and more particularly to an interconnection protection system for distributed power supply equipment suitable for protecting a distributed power supply equipment and a load by detecting instantaneous voltage drop and isolated operation. .
[0002]
[Prior art]
For power facilities of customers such as factories and large-scale buildings, reduce the total energy cost as a backup measure at the time of stopping power supply on the power system side or to compensate for insufficient power, or as a cogeneration system like a cogeneration system For this purpose, a configuration in which a distributed power source is installed as a power source for private power generation and the power system and the distributed power source are connected to operate is increasing.
[0003]
A conventional distributed protection system for a distributed power supply facility is operated by cooperative control of dedicated protection devices individually installed according to the purpose of protection, similarly to a power receiving facility that does not have a distributed power supply. For example, an instantaneous voltage drop caused by a short-time failure on the power system side due to a lightning strike or the like, for example, as described in JP-A-10-336878, between the power system and the distributed power supply facility Instantaneous voltage that reduces damage caused by voltage drop by disconnecting the distributed power supply equipment and important loads of customers from the power system at high speed (usually within 20 ms) by the interrupting device that is arranged and composed of semiconductor switches. A fall prevention device has been proposed.
[0004]
In addition, as a protective measure (prevention of electric shock, etc.) at the time of system power supply stoppage, for the prevention of isolated operation of the required distributed power source, between the substation of the power company and the customer with the distributed power source A transfer interruption device that performs communication and a dedicated detection device that detects isolated operation on the distributed power supply side are installed. Here, isolated operation means that when the power supply on the power system side is lost, the distributed power supply remains unseparated from the power system, and power is locally supplied from the distributed power supply to other general consumers. Say that state.
[0005]
In a single operation state, a system that should originally be non-voltage is charged by the distributed power source, and as a result, a safety problem occurs. Furthermore, if the system is automatically reclosed while the system is charged from the distributed power source, there is a problem that equipment and the like are damaged by asynchronous charging. For this reason, in order to prevent such problems from occurring, according to the interconnection guidelines, the customer is provided with a device for detecting isolated operation, and the system and the distributed power supply are disconnected during isolated operation. It is obliged to install a means of disconnection.
[0006]
When detecting abnormalities such as instantaneous voltage drop in a distributed power system interconnection protection system, for example, a method of calculating the average value of the voltage of each phase and comparing it with a reference value, or the voltage and current of each phase In addition to the method of comparing the instantaneous value (absolute value, rate of change of time, etc.) of the reference value with the reference value, as described in JP-A-6-82499, a method using the sum of squares of three-phase voltages, As described in Japanese Laid-Open Patent Publication No. 5-297030, a method using a synthesized voltage vector by three-phase / two-phase conversion has been proposed, and as a method for detecting an isolated operation, Japanese Patent Laid-Open No. 10-234136 discloses. As described, the voltage on the system side and the voltage on the distributed power source side are detected, and the phase difference, frequency difference, and power direction of both are obtained from the waveform of each detected voltage, and these values exceed a certain value. The union of time Method of detecting is proposed islanding from.
[0007]
[Problems to be solved by the invention]
In the conventional interconnection protection system, dedicated equipment is installed for each purpose of protection, so the capital investment of consumers increases and the configuration of the protection system to operate each equipment in a coordinated manner However, there is a problem that the response / reliability of control of the entire system is lowered. Therefore, it is conceivable that a single control device is provided with a plurality of protection functions for centralized control, but even if a single control device is simply provided with a plurality of protection functions, processing is performed by a single arithmetic processing unit. Arithmetic processing cannot be performed smoothly only by increasing the amount of computation.
[0008]
In addition, when detecting an abnormality in the conventional interconnection protection system, the method using the average value of the voltage is also used to detect the instantaneous voltage drop. There is a problem. Further, in the method using the instantaneous value of voltage / current for each phase, the detection time is short, but there is a possibility of operating even for slight disturbances of the system (waveform distortion, frequency fluctuation, etc.). Also, in the method using the sum of squares of the voltage of each phase or the composite vector by the three-layer / two-phase conversion, if the rate of voltage drop of each phase varies, it affects the phase with small or slow voltage drop. As a result, the detection time becomes longer and the detection may become impossible.
[0009]
An object of the present invention is to perform arithmetic processing smoothly.In addition, instantaneous voltage detection can be performed at high speed and with high accuracy.It is to provide an interconnection protection system for distributed power supply facilities.
[0010]
Another object of the present invention is to provide an interconnection protection system for a distributed power supply facility capable of performing instantaneous voltage detection at high speed and with high accuracy.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present inventionInterconnection protection system for distributed power facilitiesIs a three-phase power system and distributed power supplyA circuit breaker provided on the communication bus that communicates with the other bus;A system side voltage detector for detecting the bus voltage on the power system side;Said minutesA distributed power supply side voltage detector for detecting the bus voltage on the distributed power supply side;Current of the connecting busA current detector for detecting the system side voltage detector and the distributed power source side voltage detectoras well asControl means for determining the presence or absence of abnormality of the power system based on the detection output of the current detector, and controlling the circuit breaker according to the determination result, the control means detecting the system side voltage detector An instantaneous voltage drop detecting means for calculating an instantaneous voltage drop by calculating a voltage and a detected current of the current detector, and an isolated operation for detecting an isolated operation from a frequency change rate of a detection voltage of the distributed power supply side voltage detector Detection means and detection output of the instantaneous voltage drop detection meansOrAnd an interruption command output means for outputting an interruption command for the circuit breaker in response to the detection output of the isolated operation detection means.This is the premise configuration.
[0012]
In configuring the interconnection protection system for the distributed power supply facility, the following elements can be added.
[0013]
(1) The control means includes a phase difference detection means for detecting a phase difference between a detection voltage of the system side voltage detector and a detection voltage of the distributed power supply side voltage detector, and a detection output of the phase difference detection means. Synchronization determination means for determining the synchronization timing; and a closing instruction output means for outputting a closing instruction to the circuit breaker when a determination result indicating that the synchronization timing is reached is output from the synchronization determination means. It becomes.
[0014]
(2) The control means includes a distributed power supply control means for controlling the operating state of the distributed power supply.
[0015]
(3) The instantaneous voltage drop detecting means includes: an absolute value calculating means for calculating the absolute value of the combined voltage vector by performing three-phase / two-phase conversion on the detection output of the system side voltage detector; and the absolute value calculating means Comparing the absolute value calculated and the threshold value for abnormality determination to determine whether or not an instantaneous voltage drop has occurred, instantaneous voltage drop determination means for calculating the abnormality of each phase current detected by the current detector Current abnormality detecting means for detecting the abnormality, and correcting means for correcting the threshold value for abnormality determination by the detection output of the current abnormality detecting means.
[0016]
(4) The instantaneous voltage drop detection means includes: an absolute value calculation means for calculating the absolute value of the combined voltage vector by performing three-phase / two-phase conversion on the detection output of the system side voltage detector; and the absolute value calculation means Comparing the absolute value calculated and the threshold for abnormality determination, the instantaneous voltage drop determination means for determining whether or not an instantaneous voltage drop has occurred, and the voltage of each phase detected by the system side voltage detector are processed. Voltage abnormality detecting means for detecting abnormality and correction means for correcting the threshold value for abnormality determination by the detection output of the voltage abnormality detecting means.
[0017]
(5) The instantaneous voltage drop detection means includes: an absolute value calculation means for calculating the absolute value of the combined voltage vector by performing three-phase / two-phase conversion on the detection output of the system side voltage detector; and the absolute value calculation means Comparing the absolute value calculated and the threshold for abnormality determination, the instantaneous voltage drop determination means for determining whether or not an instantaneous voltage drop has occurred, and the voltage of each phase detected by the system side voltage detector are processed. Voltage abnormality detection means for detecting abnormality, current abnormality detection means for detecting abnormality by calculating current of each phase detected by the current detector, detection output of the current abnormality detection means or voltage abnormality detection And a correcting means for correcting the threshold value of the abnormality determination based on the detection output of the means.
[0018]
(6) The current abnormality detection means detects an abnormality when any of the time change rates of the current of each phase detected by the current detector exceeds a change rate determination value.
[0019]
(7) The current abnormality detection means detects an abnormality when any one of the absolute values of the currents of the respective phases detected by the current detector exceeds an absolute value determination value.
[0020]
(8) The voltage abnormality detection means detects an abnormality when one of the voltage drop amounts of each phase detected by the system-side voltage detector is equal to or less than a voltage determination value.
[0021]
According to the above-described means, the single control means detects the instantaneous voltage drop and the single operation, and performs control for shutting off the bus bar breaker according to the detection result, and the arithmetic processing for instantaneous voltage drop Since the calculation process for the isolated operation detection is shared, the calculation amount can be reduced and the calculation process can be performed smoothly.
[0022]
Also, when detecting an instantaneous voltage drop, the absolute value of the combined voltage vector is calculated by three-phase / two-phase conversion of the detection output of the system side voltage detector, and this absolute value is compared with the threshold value for abnormality determination. When determining whether or not an instantaneous voltage drop has occurred, the abnormality determination threshold is corrected by the detection output of the voltage abnormality detection means or current abnormality detection means, for example, the abnormality determination threshold is increased. Since the detection sensitivity is increased, an instantaneous voltage drop can be detected with high accuracy against a disturbance and within a predetermined time without adding complicated processing such as noise processing and failure continuity determination.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a single-line connection diagram of an interconnection protection system for a distributed power supply facility showing an embodiment of the present invention. The customer's main circuit shown in FIG. 1 is connected to a system including a load 2 connected to an electric power system 4 and a system including a power generator 51 serving as a distributed power source and a load 3 connected thereto with a bus 16. This is a circuit configuration generally used when a consumer having a distributed power source is linked to the power system 4.
[0024]
In FIG. 1, a circuit breaker 6 is installed at a power receiving point that receives power from a three-phase power system 4, and this circuit breaker 6 is connected to a load 2 via a power receiving transformer 10 and a circuit breaker 8. Yes. A bus 16 is connected to a connection point between the power receiving transformer 10 and the circuit breaker 8.
[0025]
On the other hand, the distributed power supply facility 5 serving as a private power generation facility is configured to include a power generation device 51 and a control device 52 as a distributed power supply, and the power generation device 51 is connected to the load 3 via the circuit breakers 7 and 9. ing. A bus 16 is connected to a connection point between the circuit breaker 7 and the circuit breaker 9. The control device 52 is configured to receive a voltage variation command from the control device 11 of the interconnection protection system 1 and to control the output voltage of the power generation device 51 in accordance with this command. The load 3 is required to have higher power quality than the load 2 and is normally configured such that a short-time power failure is not allowed.
[0026]
The interconnection protection system 1 includes a busbar connection breaker 12 that is inserted and arranged in the middle of a busbar 16 that connects a system on the system side and a system on the distributed power source side, and a current detector 13 that detects a passing current I of the busbar. , A system side voltage detector 14 for detecting the bus voltage Vs on the power system side from the circuit breaker 12, a distributed power source side voltage detector 15 for detecting the bus voltage Vg on the distributed power source side from the circuit breaker 12, and a detection by the current detector 13. A control device 11 is provided as a control means for determining the presence / absence of an abnormality in the power system 4 based on the detected voltages of the current and voltage detectors 14 and 15 and controlling the breaking / closing of the breaker 12 according to the determination result. Configured.
[0027]
In the interconnection protection system 1 according to the present embodiment, a vacuum circuit breaker capable of high speed operation or a semiconductor circuit breaker is employed as the busbar communication circuit breaker 12. In addition, the control device 11 performs an arithmetic process on the detection voltage of the voltage detector 14 and the detection current of the current detector 13 to detect an instantaneous voltage drop, and a frequency change rate of the detection voltage of the voltage detector 15. Are provided with functions as an isolated operation detecting means for detecting isolated operation and an interruption command output means for outputting an interruption command to the circuit breaker 12 in response to detection outputs of the respective detecting means. Further, the control device 11 detects the phase difference between the detection voltage of the voltage detector 14 and the detection voltage of the voltage detector 15, and the synchronization determination for determining the synchronization timing based on the detection output of the phase difference detection means. And a function as an input command output means for outputting an input command to the circuit breaker 12 when a determination result indicating that it is a synchronization timing is output from the synchronization determination means. Hereinafter, a specific control algorithm of the control device 11 will be described in detail with reference to FIGS.
[0028]
As shown in FIG. 2, the control device 11 includes an A / D conversion unit 110 that converts detection outputs (analog amount signals) of the current detector 13 and the voltage detectors 14 and 15 into a digital signal, and a current information calculation unit 111. , A comparison unit 112, a voltage information calculation unit 114, a comparison unit 115, a preprocessing determination unit 117, a three-phase vector processing unit 118, an isolated operation detection unit 120, a synchronization detection unit 121, and the like.
[0029]
When detecting the instantaneous voltage drop in the control device 11 having the above configuration, the currents Iu, Iv, Iw of each phase detected by the detector 13 and the voltages Vsu, Vsv, Vsw of each phase detected by the voltage detector 14 are detected. The voltages Vgu, Vgv, and Vgw detected by the voltage detector 15 are sampled and held by the A / D converter 110 according to the specified sampling frequency, and the voltages Vsu and Vsv of each phase are detected by the voltage information calculator 114. , Vsw and the instantaneous value of Vgu, Vgv, Vgw are used to calculate the voltage drop amount ΔV of each phase.
[0030]
Next, the comparison unit 115 compares the voltage drop amount ΔV of each phase calculated by the voltage information calculation unit 14 with the determination value ε1, and the voltage decrease amount ΔV of any phase is less than the determination value ε1. In some cases, an abnormality detection signal is output to the preprocessing determination unit 117, assuming that the voltage of any phase is abnormal. That is, the voltage information calculation unit 114 and the comparison unit 115 are configured as voltage abnormality detection means. At the same time, using the instantaneous values of the currents Iu, Iv, and Iw of each phase, the current information calculation unit 111 calculates the absolute value or time change rate of the current of each phase, and the calculation result and the determination value ε2 Is performed in the comparison unit 112, and when any calculation result exceeds the determination value ε2, an abnormality detection signal is output to the preprocessing determination unit 117 as an abnormality has occurred in the current. That is, the current information calculation unit 111 and the comparison unit 112 are configured as current abnormality detection means.
[0031]
Next, in the preprocessing determination unit 117, when an abnormality detection signal is input from the comparison unit 112 or the comparison unit 115, that is, from one of the comparison units, a comparison that the input signal deviates from the reference value. When the result is output, a predetermined gain a (> 1) is output. As a result, the threshold value ε3 for abnormality determination is multiplied by the gain a, and correction for increasing the detection sensitivity by increasing the threshold value ε3 for abnormality determination is performed. That is, the pre-processing determination unit 117 is configured as a correction unit that corrects the abnormality determination threshold value.
[0032]
On the other hand, in the three-phase vector processing unit 118, the following processing is performed. The three-phase / two-phase converter 1181 uses the voltages Vsu, Vsv, and Vsw on the power system 4 sampled by the A / D converter 110 to generate a combined voltage vector Vα according to the following equations (1) and (2). , Vβ are obtained, and these are vector-combined by an absolute value calculation unit 1182 to calculate an absolute value | Vαβ | (a voltage value that is a constant DC component).
[0033]
[Expression 1]

[0034]
[Expression 2]

After that, the absolute value calculated by the absolute value calculation unit 1182 and the threshold value for abnormality determination are compared by the instantaneous voltage drop determination unit 1183, and the presence or absence of the instantaneous voltage drop is determined by this comparison, and the instantaneous voltage drop occurs. Sometimes the instantaneous voltage drop determination unit 1183 outputs a break command to the breaker 12 so that the breaker 12 is broken. That is, the three-phase / two-phase conversion unit 1181 and the absolute value calculation unit 1182 are configured as absolute value calculation means, and the instantaneous voltage drop determination unit 1183 is configured as instantaneous voltage drop determination means and cutoff command output means.
[0035]
Here, in this embodiment, the determination value (abnormality determination threshold value) ε3 for the absolute value | Vαβ | of the combined vector is output from the preprocessing determination unit 117 based on the instantaneous value of the voltage and current of each phase. When multiplying a predetermined gain a (> 1), only when an abnormality is detected in the voltage / current of any phase, the detection value ε3 for the absolute value | Vαβ | is increased to increase the detection sensitivity. In this way, although the detection time is short, detection based on instantaneous values for each phase, which are easy to detect erroneously due to waveform distortion, frequency fluctuations, etc. It is possible to take advantage of each other's advantages while compensating for the disadvantages of detection by the combined vector processing of phases. As a result, by performing the correction process according to the present embodiment, it is resistant to disturbance and accurately detects an instantaneous voltage drop within a predetermined time without adding complicated processes such as noise processing and failure continuity determination processing. be able to.
[0036]
Next, a specific detection operation of the instantaneous voltage drop will be described with reference to FIG. First, an example will be described in which there is a variation in the rate of three-phase voltage drop, such as when a one-line ground fault occurs in the power system 4. As shown in FIG. 3A, when a one-line ground fault occurs in the V phase, as shown in FIG. 3B, the voltage of the V phase among the waveforms of the voltages Vsu, Vsv, and Vsw on the power system 4 side is shown. Decreases, and the V-phase voltage decrease rate increases most quickly. That is, when the V-phase voltage decreases, the rate of decrease ΔVsvi of the instantaneous value of the V-phase voltage defined by the following equation (3) rapidly decreases as shown in (b).
[0037]
[Equation 3]

Here, the subscript i is the sampling time by the A / D converter 110, and n is the number of sampling points in one cycle. The ΔVsvi in the expression (3) is compared with the determination value ε1 by the comparison unit 115. As shown in (b), when ΔVsvi <ε1 is established continuously for a predetermined number of times or more, a V-phase voltage drop is possible. A comparison result indicating that there is a possibility, that is, an abnormality detection signal is output to the preprocessing determination unit 117. When it is determined by the comparison calculation of the comparison unit 115 that there is a possibility of a voltage drop, as shown in (c), it is obtained by the calculation of the three-phase / two-phase conversion unit 1181 and the absolute value calculation unit 1182. The determination value ε3 for the absolute value | Vαβ | of the combined voltage vector thus obtained is multiplied by a gain a (> 1), and the determination value ε3 is increased to correct the detection sensitivity.
[0038]
By performing such correction processing, even when the absolute value | Vαβ | pulsates due to variations in voltage drop of the three phases and is not sufficient for detecting the voltage drop amount, the conventional three-phase / Compared to the detection method using only two-phase conversion, the detection time can be shortened. Further, it is based on the combination of the instantaneous value of each phase and the combined voltage vector, and it is possible to avoid the problem of false detection that may occur at the time of detection using only the instantaneous value for each phase.
[0039]
Next, specific processing contents in the current information calculation unit 111, the voltage information calculation unit 114, and the

comparison units

112 and 115 when detecting the instantaneous voltage drop will be described with reference to FIG. First, when performing instantaneous value processing for each phase of instantaneous voltage drop, when detecting the instantaneous voltage drop by the voltage drop rate, as shown in (a), the voltages on the power system 4 side and the distributed power source 5 side are shown. The voltage information calculation unit 114 obtains the voltage drop rate of each phase using the instantaneous values Vsui, Vsvi, Vswi, and Vgui, Vgvi, Vgwi, and compares each calculated value with the determination value ε1, respectively. When the voltage drop rate for at least one phase on the mold power supply 5 side simultaneously falls below the determination value ε1 for a predetermined number of samplings, an abnormality detection signal is output from the comparison unit 115 to the preprocessing determination unit 117 as a voltage abnormality has occurred. Is output. That is, the voltage information calculation unit 114 and the comparison unit 115 detect an abnormality when the voltage drop amount of any phase out of the voltage drop amount (voltage drop rate) of each phase is equal to or less than the voltage determination value (determination value ε1). This is configured as a voltage abnormality detection means.
[0040]
Next, when the instantaneous voltage drop is detected by the absolute value of the current, as shown in (b), the current information calculation unit 111 calculates the absolute value of each phase from the instantaneous values Iui, Ivi, and Iwi of each phase. Each of the calculated values is compared with the determination value ε2, and when the comparison unit 112 determines that the calculated value of at least one phase exceeds the determination value ε2 continuously for a predetermined number of sampling times, the comparison is performed. The abnormality detection signal is output from the unit 112 to the preprocessing determination unit 117 that an abnormality of the current has occurred. That is, the current information calculation unit 111 and the comparison unit 112 are configured as current abnormality detection means.
[0041]
Further, in the case where an instantaneous voltage drop is detected by a time change of current, as shown in (c), the current information calculation unit 111 uses the instantaneous values Iui, Ivi, and Iwi of each phase to change each time. The rate is calculated, each calculated value is compared with the determination value ε2, and if at least one calculated value continuously exceeds the determination value ε2 for a predetermined number of sampling times, it is determined that an abnormality has occurred in the current. A detection signal is output from the comparison unit 112 to the preprocessing determination unit 117. That is, the current information calculation unit 111 and the comparison unit 112 are configured as current abnormality detection means.
[0042]
When detecting the instantaneous voltage drop, the voltage drop amount calculation process in FIG. 4A and the current calculation process in FIG. 4B or FIG. May be used in combination, or only the voltage drop amount calculation process of (a) may be performed.
[0043]
Next, when detecting an isolated operation, a passive isolated operation detection unit 120 shown in FIG. 2 is used. The isolated operation detection unit 120 includes a frequency change rate calculation unit 1201 and an isolated operation determination unit 1202. In the frequency change rate calculation unit 1201, first, the voltage information calculation unit 114 detects in the process of detecting the voltage drop amount of each phase necessary for detecting the instantaneous voltage drop of each phase, as described above. The frequency is calculated using the times tgu, tgv, and tgw of the zero cross point of the waveform of the voltage Vg on the distributed power source 5 side. Next, the frequency change rate Δf defined by the equation (4) is calculated.
[0044]
[Expression 4]

Here, it is assumed that the average value of the time interval 0.5 to 1 s before the current sampling time is used at the f (Hz) reference frequency. f1 (Hz) is a frequency at the current time, and is, for example, a time interval average value three cycles before the current sampling time.
[0045]
The frequency change rate Δf of the equation (4) is calculated for each phase, and the calculation result and the determination value ε4 are respectively compared by the determination unit 1202. When at least one calculated value exceeds the determination value ε4, the frequency change rate Δf It determines with driving | running | working, outputs the interruption | blocking command with respect to the circuit breaker 12, and opens the circuit breaker 12. FIG. That is, the isolated operation detection unit 120 is configured as a shutoff command output means together with the isolated operation detection means.
[0046]
When detecting an isolated operation, an isolated operation detection unit 122 using an active method can be used together with an isolated operation detection unit 120 using a passive method, as shown in FIG. In the isolated operation detection unit 122 by this active method, a certain variation is always given by the control system of the power generation facility, an external circuit, etc., and the isolated operation is detected by using this variation that becomes remarkable during the isolated operation. Is adopted.
[0047]
In FIG. 5, the voltage fluctuation signal generator 1224 always sends a predetermined fluctuation signal Vcnt to the control device 52 of the distributed power source 5. In the frequency change rate calculation unit 1221, the frequency is calculated using the times tgu, tgv, and tgw of the zero cross point of the waveform of the voltage Vg on the distributed power source 5 side as in the passive method, and then the equation (4) Is used to calculate the frequency change rate Δf of each phase. The determination unit 1222 compares the frequency change rate Δf of each phase with the two determination values ε4 and ε5. First, if at least one of the frequency change rates Δf of each phase satisfies ε4 <Δf <ε5, the gain b is output. This gain b is multiplied by the fluctuation signal sent from the voltage fluctuation signal generator 1224 to increase the fluctuation command value to the control device 52 of the distributed power source 5. Further, at least when the calculated value for one phase satisfies ε5 <Δf, a cutoff command is output to the busbar breaker 12.
[0048]
In this way, if the frequency change rate is used for the detection of an isolated operation, a distributed power source connected via an inverter such as a solar cell, a fuel cell, and a micro gas turbine can also be used for a distributed type rotating machine. Applicable to power supply. In the present embodiment, the detection of the isolated operation is described with respect to the passive method shown in FIG. 2 and the active method shown in FIG. 5, but the present invention is not limited to these, and other methods can be adopted.
[0049]
In addition, when the circuit breaker 12 is disconnected and then synchronized, the synchronization detection unit 121 performs synchronization detection. The synchronization detection unit 121 includes a phase difference calculation unit 1211 and a synchronization determination unit 1212. The synchronization detection of the system side voltage Vs necessary for turning on the circuit breaker 12 and the voltage Vg on the distributed power source side is performed. . First, in the phase difference calculation unit 1211, the time difference between the zero cross point of the waveform of the system side voltage Vs of each phase obtained by the voltage information calculation unit 114 of each phase and the zero cross point of the waveform of the distributed power supply side voltage Vg. From this, the phase difference | Δθ | is calculated. The synchronization determination unit 121 compares the phase difference | Δθ | calculated by the phase difference calculation unit 1211 with the determination value ε6. When | Δθ | <ε6 is satisfied, the synchronization determination unit 121 determines that synchronization is performed and Output the input command.
[0050]
As described above, in this embodiment, the control algorithm of the interconnection protection system is programmed in an arithmetic processing unit such as a microcomputer, and this is installed on the single printed circuit board together with the power supply, the A / D converter, and the memory. A board is configured, and this control board is incorporated into the control device 11.
[0051]
Next, another embodiment of the present invention will be described with reference to FIG. In the present embodiment, a function for detecting an instantaneous voltage drop and an isolated operation is added to the control device 52 of the distributed power supply facility, and a function as a distributed power control means for controlling the operation state of the distributed power supply is added. The interconnection protection system is configured, and other configurations are the same as those in FIG.
[0052]
The distributed power supply control device 52 includes a power supply control unit 521 and an interconnection protection control unit 522, and the interconnection protection control unit 522 is loaded with information on the control algorithm used in the embodiment. A control board is adopted. The power supply control unit 521 is configured to control the operation state of the power generation device 51 in accordance with the voltage fluctuation command output from the interconnection protection control unit 522.
[0053]
In the present embodiment, since the interconnection protection control unit 522 has the same function as that of the above embodiment, the same effect as that of the above embodiment can be obtained.
[0054]
In addition, the control algorithm of FIG. 2 is programmed in the control board of the power supply control unit 521, and the input units of the current detector 13 and the voltage detectors 14 and 15 are added to the control board, so that the power supply control unit 521 It is also possible to incorporate the function of the interconnection protection control unit 522.
[0055]
As described above, according to each of the above embodiments, the above functions can be integrated into a

single control device

11, 52 by sharing the arithmetic processing associated with the detection of instantaneous voltage drop and isolated operation. Therefore, it becomes unnecessary to install a dedicated instantaneous voltage drop detection device, an isolated operation detection device, and a transfer interruption device. Therefore, the same protection function as the conventional one can be obtained without increasing the capital investment and without complicating the configuration and control of the protection system. In addition, since communication lines between the protective devices can be reduced, control response / reliability is also improved.
[0056]
Furthermore, in the detection method of the instantaneous voltage drop, the detection by the instantaneous value of the voltage and current of each phase is combined with the detection using the composite voltage vector by the three-phase / two-phase change, and the detection result by the instantaneous value is used. Thus, the abnormality determination value for the composite voltage vector is corrected, so that the reliability can be improved without being affected by disturbances such as waveform distortion and frequency fluctuation and without increasing the detection time. .
[0057]
【The invention's effect】
As described above, according to the present invention, instantaneous voltage drop and islanding operation are detected by a single control means, and the control for shutting off the bus contact circuit breaker is performed in accordance with the detection result. Therefore, the calculation amount can be reduced, and the calculation process can be performed smoothly. Further, according to the present invention, the absolute value of the combined voltage vector is calculated by three-phase / two-phase conversion of the detection output of the system side voltage detector, and the absolute value is compared with the threshold value for abnormality determination. When determining whether or not an instantaneous voltage drop has occurred, the threshold value for abnormality determination is corrected by the detection output of the voltage abnormality detection means or current abnormality detection means, so noise processing, failure continuity determination, etc. Without adding complicated processing, it is possible to detect an instantaneous voltage drop with high accuracy against a disturbance and within a predetermined time.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram of an interconnection protection system for a distributed power supply facility according to an embodiment of the present invention.
FIG. 2 is a block diagram for explaining an algorithm for detecting instantaneous voltage drop and isolated operation.
FIG. 3 is a waveform diagram for explaining a method of detecting an instantaneous voltage drop.
FIG. 4 is a block configuration diagram for explaining a specific algorithm for instantaneous voltage drop;
FIG. 5 is a block diagram for explaining an isolated operation detection method by an active method.
FIG. 6 is a block configuration diagram of an interconnection protection system showing another embodiment of the present invention.
[Explanation of symbols]
1 Interconnection protection system
2, 3 load
4 Power system
5 Distributed power supply facilities
6, 7, 8, 9 Circuit breaker
10 Power receiving transformer
11 Control device
110 A / D converter
111 Current information calculator
112 Voltage information calculation unit
113 Three-phase vector processing unit
114 Voltage information calculation unit
115 Independent operation detector
117 Pre-processing determination unit
12 Busbar circuit breaker
13 Power detector
14, 15 Voltage detector

Claims

A circuit breaker provided on a communication bus that connects a three-phase power system and a distributed power source bus, a system voltage detector that detects a bus voltage on the power system side, and a bus voltage on the distributed power source side. The power based on the distributed power supply side voltage detector to detect, the current detector to detect the current of the connecting bus, the system side voltage detector, the distributed power source side voltage detector, and the detection output of the current detector It is determined whether there is a system abnormality, and includes a control means for controlling the circuit breaker according to the determination result,
The control means includes an instantaneous voltage drop detection means for calculating an instantaneous voltage drop by calculating a detection voltage of the system side voltage detector and a detection current of the current detector, and detection of the distributed power supply side voltage detector. An isolated operation detecting means for detecting an isolated operation from a voltage frequency change rate, and an interruption command for outputting an interruption command of the circuit breaker in response to a detection output of the instantaneous voltage drop detecting means or a detection output of the isolated operation detection means And output means,
The instantaneous voltage drop detection means includes an absolute value calculation means for calculating an absolute value of a combined voltage vector by performing three-phase / two-phase conversion on a detection output of the system side voltage detector, and an absolute value calculated by the absolute value calculation means. An instantaneous voltage drop determination means for comparing the value and the threshold value for abnormality determination to determine whether or not an instantaneous voltage drop has occurred, and an abnormality is detected by computing the current of each phase detected by the current detector current abnormality detecting means and said current abnormality detecting means and the abnormality judgment interconnection protection system Do that distributed-type power supply equipment is composed of a correcting means for correcting the threshold value of the detection output of.

A circuit breaker provided on a communication bus that connects a three-phase power system and a distributed power source bus, a system voltage detector that detects a bus voltage on the power system side, and a bus voltage on the distributed power source side. The power based on the distributed power supply side voltage detector to detect, the current detector to detect the current of the connecting bus, the system side voltage detector, the distributed power source side voltage detector, and the detection output of the current detector It is determined whether there is a system abnormality, and includes a control means for controlling the circuit breaker according to the determination result,
The control means includes an instantaneous voltage drop detection means for calculating an instantaneous voltage drop by calculating a detection voltage of the system side voltage detector and a detection current of the current detector, and detection of the distributed power supply side voltage detector. An isolated operation detecting means for detecting an isolated operation from a voltage frequency change rate, and an interruption command for outputting an interruption command of the circuit breaker in response to a detection output of the instantaneous voltage drop detecting means or a detection output of the isolated operation detection means And output means,
The instantaneous voltage drop detection means includes an absolute value calculation means for calculating an absolute value of a combined voltage vector by performing three-phase / two-phase conversion on a detection output of the system side voltage detector, and an absolute value calculated by the absolute value calculation means. An instantaneous voltage drop determination means for comparing the value and the threshold value of the abnormality determination to determine whether or not an instantaneous voltage drop has occurred, and calculating and processing the voltage of each phase detected by the system side voltage detector. abnormal voltage detecting apparatus and the abnormal voltage detecting means and the abnormality judgment interconnection protection system Do that distributed-type power supply equipment is composed of a correcting means for correcting the threshold value of the detection output of the detecting.

A circuit breaker provided on a communication bus that connects a three-phase power system and a distributed power source bus, a system voltage detector that detects a bus voltage on the power system side, and a bus voltage on the distributed power source side. The power based on the distributed power supply side voltage detector to detect, the current detector to detect the current of the connecting bus, the system side voltage detector, the distributed power source side voltage detector, and the detection output of the current detector It is determined whether there is a system abnormality, and includes a control means for controlling the circuit breaker according to the determination result,
The control means includes an instantaneous voltage drop detection means for calculating an instantaneous voltage drop by calculating a detection voltage of the system side voltage detector and a detection current of the current detector, and detection of the distributed power supply side voltage detector. An isolated operation detecting means for detecting an isolated operation from a voltage frequency change rate, and an interruption command for outputting an interruption command of the circuit breaker in response to a detection output of the instantaneous voltage drop detecting means or a detection output of the isolated operation detection means And output means,
The instantaneous voltage drop detection means includes an absolute value calculation means for calculating an absolute value of a combined voltage vector by performing three-phase / two-phase conversion on a detection output of the system side voltage detector, and an absolute value calculated by the absolute value calculation means. An instantaneous voltage drop determination means for comparing the value and the threshold value of the abnormality determination to determine whether or not an instantaneous voltage drop has occurred, and calculating and processing the voltage of each phase detected by the system side voltage detector. A voltage abnormality detection means for detecting, a current abnormality detection means for detecting an abnormality by calculating the current of each phase detected by the current detector, and a detection output of the current abnormality detection means or a detection of the voltage abnormality detection means the abnormality determination interconnection protection system Do that distributed-type power supply equipment is composed of a correcting means for correcting the threshold value of the output.

4. The distributed power system interconnection protection system according to claim 1 or 3 , wherein the current abnormality detection means has a time change rate of any time change rate of current of each phase detected by the current detector. A distributed protection system for a distributed power facility, characterized by detecting an abnormality when a change rate judgment value is exceeded.

4. The distributed power system interconnection protection system according to claim 1 or 3 , wherein the current abnormality detection means is configured such that one of the absolute values of the current of each phase detected by the current detector is an absolute value. An interconnection protection system for a distributed power facility, wherein an abnormality is detected when a judgment value is exceeded.

4. The distributed power supply system interconnection protection system according to claim 2 or 3 , wherein the voltage abnormality detection means has a voltage drop amount of any voltage drop amount of each phase detected by the system side voltage detector. An interconnection protection system for a distributed power supply system, wherein an abnormality is detected when a voltage judgment value or less is detected.

4. The distributed power system interconnection protection system according to claim 1 , wherein the control unit is configured to determine a level between a detection voltage of the system side voltage detector and a detection voltage of the distributed power source side voltage detector. A phase difference detection means for detecting a phase difference; a synchronization determination means for determining a synchronization timing based on a detection output of the phase difference detection means; and the interruption when a determination result indicating the synchronization timing is output from the synchronization determination means A distributed power system interconnection protection system, comprising: a charging command output means for outputting a charging command to the device.

4. The distributed power system interconnection protection system according to claim 1 , wherein the control means includes a distributed power control means for controlling an operating state of the distributed power supply. An integrated protection system for distributed power facilities.