JP4038343B2

JP4038343B2 - Distributed power supply

Info

Publication number: JP4038343B2
Application number: JP2001054341A
Authority: JP
Inventors: 啓宇川崎; 英彦杉本
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2001-02-28
Filing date: 2001-02-28
Publication date: 2008-01-23
Anticipated expiration: 2021-02-28
Also published as: JP2002262464A

Description

【０００１】
【発明の属する技術分野】
この発明は、太陽光発電や燃料電池発電などの発電手段からの発電電力を交流電力に変換し、交流電力系統に系統連系させることにより、交流電力系統に接続された負荷に交流電力を供給するための分散型電源装置に関し、特に単独運転状態を素早く且つ確実に検出して連系点からの切り離し処置を可能にした分散型電源装置に関するものである。
【０００２】
【従来の技術】
従来、一般家庭や工場などに交流電力を供給するいわゆる商用電源の配線系統（交流電力系統）においては、遮断器よりも下流側に任意数の分散型電源装置が連系され、交流電力系統に接続された負荷に対して、連系点を介して交流電力を供給するようになっている。
【０００３】
この種の交流電力系統においては、変圧器などを含む負荷側の保守点検が必要となるが、このような保守点検は、交流電力系統の上流側に設置された遮断器を開放し、発電所からの電力供給を遮断することにより、いわゆる停電状態にして実施される。
【０００４】
このとき、遮断器よりも下流側の系統に連系された分散型電源装置が遮断後も運転を続けている状態（一般に、「単独運転」と呼ばれる）は、作業員が保守点検を行うときに危険なので、保守点検時には単独運転を素早く且つ確実に検出して分散型電源装置の運転を停止させる必要がある。
【０００５】
一般に、負荷電力と分散型電源装置からの出力電力との差が大きいときには、単独運転発生時の連系点の電圧値や位相が大きく変化するので、従来の単独運転の検出方法としては、連系点の電圧値や位相の変化を捕捉する受動方式がよく知られている。
【０００６】
また、他の単独運転の検出を可能にする方法として、負荷電力と分散型電源装置からの出力電力とが均衡している場合においても、系統分散型電源装置の運転周波数を、連系点の周波数に対して常に微小バイアスを加えた値とし、この微小バイアスが連系点の周波数変化に与える影響度を検出する周波数シフト方式などの能動方式も知られている。
【０００７】
しかしながら、上記周波数シフト方式においても、分散型電源装置が力率一定で制御されている場合に、負荷状態によっては、力率一定制御と周波数シフト運転とが干渉しあってしまい、連系点の周波数に対する微小バイアスの影響が出なくなる場合がある。
【０００８】
たとえば、交流電力が供給される負荷が容量性負荷である場合には、系統点電圧のゼロクロス点が電流のゼロクロスよりも遅れて発生するので、微小バイアスをプラス方向にシフトし、連系点電圧の周波数よりも高い運転周波数で単独運転状態を検出しようとしても、連系点電圧の周波数（電圧ゼロクロス周期の逆数）が高くならず、単独運転を検出することはできない。
【０００９】
そこで、上記のような不具合を解消するための従来方法として、たとえば特開平１１−４１８１９号公報に参照されるように、電流目標値の周波数に加えられる微小バイアスの方向をプラスとマイナスとに振る方法も提案されている。
【００１０】
しかしながら、上記公報に記載の方法においては、同一フィーダに複数台の分散型電源装置が連系された場合に、分散型電源装置の出力同士が互いに周波数の微小バイアス分をキャンセルし合ってしまい、交流電力系統に停電が発生しても連系点の電圧周波数に周波数シフト分が現れず、単独運転の検出が不可能になるおそれがある。
【００１１】
【発明が解決しようとする課題】
従来の分散型電源装置は以上のように、負荷特性の違いによる不具合を回避した方法（特開平１１−４１８１９号公報参照）を用いても、同一フィーダに複数台の分散型電源装置が連系された場合には、系統停電発生時に連系点電圧に周波数シフト分が現れず、確実に単独運転を検出することができないという問題点があった。
【００１２】
この発明は上記のような問題点を解決するためになされたもので、負荷特性や同一フィーダへの接続台数などに係わらず、単独運転を素早く且つ確実に検出して連系点からの切り離し処置を施すことのできる分散型電源装置を得ることを目的とする。
【００１３】
【課題を解決するための手段】
この発明の請求項１に係る分散型電源装置は、連系点を介して交流電力系統と連系され、連系点に接続された負荷に交流電力を供給するための分散型電源装置であって、発電電力を生成する発電手段と、発電電力を交流電力に変換する電力変換手段と、連系点の電圧位相を検出する電圧位相検出手段と、電圧位相に基づいて連系点の電圧周期情報を計測する周期計測手段と、電圧位相および電圧周期情報に基づいて電力変換手段の出力電流目標値を生成する電流基準発生手段と、出力電流目標値に応じて電力変換手段を制御する電流制御手段と、電圧周期情報に基づいて分散型電源装置による単独運転の可能性を検出する単独運転検出手段と、連系点の電圧および電圧位相に基づいて分散型電源装置による単独運転状態を確定し、分散型電源装置の連系状態を禁止するための単独運転確定手段とを備え、電流基準発生手段は、出力電流目標値の電流周期情報を、連系点の電圧周期情報に対して微小バイアスを加えた値に設定し、分散型電源装置が交流電力系統と連系された通常時には、出力電流目標値の電流位相を連系点の電圧位相に合わせてリセットし、単独運転検出手段により単独運転の可能性が検出された後は、電圧位相に合わせた電流位相のリセット処理を中止するものである。
【００１４】
また、この発明の請求項２に係る分散型電源装置は、請求項１において、周期計測手段は、連系点の電圧の正期間および負期間を計測し、単独運転検出手段は、正期間と負期間とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するものである。
【００１５】
また、この発明の請求項３に係る分散型電源装置は、請求項１において、周期計測手段は、出力電流目標値の位相がリセットされる直前またはリセットされた直後の連系点の第１の電圧周期情報とそれ以降の第２の電圧周期情報とを計測し、単独運転検出手段は、第１の電圧周期情報と第２の電圧周期情報とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するものである。
【００１６】
また、この発明の請求項４に係る分散型電源装置は、連系点を介して交流電力系統と連系され、連系点に接続された負荷に交流電力を供給するための分散型電源装置であって、発電電力を生成する発電手段と、発電電力を交流電力に変換する電力変換手段と、連系点の電圧位相を検出する電圧位相検出手段と、電圧位相に基づいて連系点の電圧周期情報を計測する周期計測手段と、電圧位相および電圧周期情報に基づいて電力変換手段の出力電流目標値を生成する電流基準発生手段と、出力電流目標値に応じて電力変換手段を制御する電流制御手段と、電圧周期情報に基づいて分散型電源装置による単独運転の可能性を検出する単独運転検出手段と、連系点の電圧および電圧位相に基づいて分散型電源装置による単独運転状態を確定し、分散型電源装置の連系状態を禁止するための単独運転確定手段とを備え、電流基準発生手段は、出力電流目標値の電流周期情報を、連系点の電圧周期情報に対して微小バイアスを加えた値に設定し、分散型電源装置が交流電力系統と連系された通常時には、出力電流目標値の電流位相を連系点の電圧位相に合わせてリセットし、周期計測手段は、連系点の電圧の正期間および負期間を計測し、単独運転検出手段は、正期間と負期間とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するものである。
【００１７】
また、この発明の請求項５に係る分散型電源装置は、請求項４において、出力電流目標値の電流周期情報は、連系点の電圧周期情報に対して一方向に微小バイアスを加えた値に設定されたものである。
【００１８】
また、この発明の請求項６に係る分散型電源装置は、連系点を介して交流電力系統と連系され、連系点に接続された負荷に交流電力を供給するための分散型電源装置であって、発電電力を生成する発電手段と、発電電力を交流電力に変換する電力変換手段と、連系点の電圧位相を検出する電圧位相検出手段と、電圧位相に基づいて連系点の電圧周期情報を計測する周期計測手段と、電圧位相および電圧周期情報に基づいて電力変換手段の出力電流目標値を生成する電流基準発生手段と、出力電流目標値に応じて電力変換手段を制御する電流制御手段と、電圧周期情報に基づいて分散型電源装置による単独運転の可能性を検出する単独運転検出手段と、連系点の電圧および電圧位相に基づいて分散型電源装置による単独運転状態を確定し、分散型電源装置の連系状態を禁止するための単独運転確定手段とを備え、電流基準発生手段は、出力電流目標値の電流周期情報を、連系点の電圧周期情報に対して微小バイアスを加えた値に設定し、分散型電源装置が交流電力系統と連系された通常時には、出力電流目標値の電流位相を連系点の電圧位相に合わせてリセットし、周期計測手段は、出力電流目標値の位相がリセットされる直前またはリセットされた直後の連系点の第１の電圧周期情報とそれ以降の第２の電圧周期情報とを計測し、単独運転検出手段は、第１の電圧周期情報と第２の電圧周期情報とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するものである。
【００１９】
また、この発明の請求項７に係る分散型電源装置は、請求項６において、出力電流目標値の電流周期情報は、連系点の電圧周期情報に対して一方向に微小バイアスを加えた値に設定されたものである。
【００２０】
【発明の実施の形態】
実施の形態１．
以下、図面を参照しながら、この発明の実施の形態１について詳細に説明する。
【００２１】
図１はこの発明の実施の形態１を示すブロック構成図であり、分散型電源装置を交流電力系統に連系した状態を示している。
また、ここでは、代表的に１台の分散型電源装置を示されているが、任意数の分散型電源装置が連系され得る。
【００２２】
図１において、１は商用交流電力を出力する交流発電設備、２は交流発電設備１の出力側に挿入された遮断器、３は遮断器２を介して交流発電設備１に接続された変圧器、４は変圧器３の二次側（出力側）に接続された系統負荷であり、これらは交流電力系統５を構成している。
【００２３】
交流電力系統５内の系統負荷４は、一般家庭で使用される電気機器などを含んでいる。
６は交流電力系統５の連系点であり、図１中の連系点６よりも交流発電設備１側の回路系統は、交流電力系統５と総称される。
【００２４】
７は連系点６に接続された自家負荷、８は分散型電源装置である。
分散型電源装置８は、連系点６を介して交流電力系統５および自家負荷７に接続されている。
【００２５】
分散型電源装置８は、太陽電池などの発電手段９と、発電手段９からの発電電力（この場合、直流電力）を交流電力に変換する電力変換手段１０と、電力変換手段１０の出力側に挿入された連系用開閉手段１１と、連系点６の電圧Ｖから電圧位相φＶを検出する電圧位相検出手段１２とを備えている。
【００２６】
また、分散型電源装置８は、周期計測手段１３、電流位相確定手段１４、電流周期確定手段１５、電流基準確定手段１６、電流制御手段１７、単独運転検出手段１８および単独運転確定手段１９を備えている。
【００２７】
周期計測手段１３は、電圧位相φＶから連系点電圧Ｖの正の半周期と負の半周期および１周期（または周波数）とを電圧周期情報として計測する。
電流位相確定手段１４は、電圧位相φＶから電流目標値ｉｏの電流位相φｉを決定する。
【００２８】
電流周期確定手段１５は、電流目標値ｉｏの電流周期情報に付加される微小バイアスＢを出力する微小バイアス生成手段１５ａと、周期計測手段１３からの電圧周期情報と微小バイアスＢとを加算する加算手段１５ｂとを備え、周期計測手段１３からの電圧周期情報に微小バイアスＢを加えて電流目標値ｉｏの周期（または周波数）を決定する。
【００２９】
電流基準確定手段１６は、電流位相確定手段１４からの電流位相φｉと、電流周期確定手段１５からの出力信号（電流周期）とに基づいて、電力変換手段１０から出力されるべき電流目標値ｉｏを電流基準として決定する。
【００３０】
電流位相確定手段１４、電流周期確定手段１５および電流基準確定手段１６は、電圧位相φＶおよび電圧周期情報に基づいて電力変換手段１０の出力電流目標値ｉｏを生成する電流基準発生手段を構成している。
【００３１】
電流制御手段１７は、電力変換手段１０の出力電流ｉを検出する変流器１７ａと、電流目標値ｉｏと出力電流ｉとの電流偏差（＝ｉｏ−ｉ）を算出する減算器１７ｂと、電流偏差に基づいて電力変換手段１０をフィードバック制御する制御部１７ｃとを備え、電流基準確定手段１６からの電流目標値ｉｏに基づいて電力変換手段１０を制御して出力電流ｉを調整する。
【００３２】
単独運転検出手段１８は、周期計測手段１３からの電圧周期情報に基づいて、分散型電源装置８による単独運転の可能性を検出し、検出結果を電流位相確定手段１４に入力する。
【００３３】
単独運転確定手段１９は、連系点６の電圧Ｖと、電流位相検出手段１２からの電圧位相φＶと、周期計測手段１３からの電圧周期情報とに基づいて、分散型電源装置８が単独運転状態であることを確定し、電力変換手段１０の停止および連系用開閉手段１１の開放を行うための駆動信号を出力する。
【００３４】
電流基準発生手段を構成する電流位相確定手段１４は、分散型電源装置８が交流電力系統５と連系された通常時には、出力電流目標値ｉｏの電流位相φｉを連系点６の電圧位相φＶに合わせてリセットし、単独運転検出手段１８により単独運転の可能性が検出された後は、電圧位相φＶに合わせた電流位相φｉのリセット処理（力率一定制御）を中止するようになっている。
【００３５】
次に、図１に示したこの発明の実施の形態１による具体的な動作について説明する。
まず、遮断器２が投入されている通常時において、分散型電源装置８内の電力変換機１０は、発電手段９の発電電力を交流電力に変換し、連系用開閉手段１１を介して自家負荷７に交流電力を供給する。
【００３６】
このとき、自家負荷７の容量が発電電力よりも小さい場合には、分散型電源装置８からの過剰な交流電力は、交流電力系統５へと逆潮流される。
また、電力変換手段１０からの出力電流ｉの位相は、力率一定とするために連系点６の電圧位相φＶと同期がとられる。
【００３７】
すなわち、分散型電源装置８内の電流位相確定手段１４は、連系点電圧Ｖがゼロクロスするときに出力電流ｉがゼロクロスするように、電流目標値ｉｏの電流位相φｉを決定する。
【００３８】
また、電流周期確定手段１５は、出力電流ｉの電流周期情報（周期または周波数）として、連系点６の電圧周期（または、周波数ｆＶ）に微小バイアスＢを加えた周期（または、周波数ｆｉｏ）を決定する。
【００３９】
なお、この発明の主旨とは無関係であるが、出力電流ｉの振幅は、一般的には発電手段９の最大能力を引き出すように、電流基準確定手段１６によって決定される。
【００４０】
また、前述のように、周波数は周期の逆数として置き換えられるので、以降は周期情報を代表的に周波数として説明する。
【００４１】
図２はこの発明の実施の形態１による位相同期関係を示す波形図であり、連系点６から検出される連系点電圧Ｖ（二点鎖線参照）と、電力変換手段１０を制御する電流目標値ｉｏ（実線参照）とを関連付けて示している。
【００４２】
図２において、横軸は時間ｔ、縦軸は電流目標値ｉｏ［Ａ］および連系点電圧Ｖ［Ｖ］であり、目標電流ｉｏおよび連系点電圧Ｖの時間変化が示されている。
【００４３】
連系点電圧Ｖ（二点鎖線）は、連系点６から直接検出され、電流目標値ｉｏ（実線）は、電力変換手段１０の出力電流ｉの目標値として電流基準確定手段１６から出力される。
【００４４】
電流目標値ｉｏの周波数ｆｉｏは、連系点電圧Ｖの周波数ｆＶよりも微小バイアスＢ分だけ高い（電流目標値ｉｏの周期は連系点電圧Ｖの周期よりも短い）が、連系点電圧Ｖのゼロクロス点（図２内の１．０１６７秒、１．０３３３秒）に合わせて、１周期毎にリセットされる。
【００４５】
また、電力変換手段１０からの出力電流ｉは、電流目標値ｉｏにほぼ追従して流れる。
【００４６】
しかし、周知のように、交流電力系統５のインピーダンスは分散型電源装置８の内部インピーダンスよりもかなり小さいので、出力電流ｉの周波数ｆｉｏへの微小バイアスＢ分の影響は、連系点電圧Ｖ（二点鎖線）にはほとんど現れない。
【００４７】
したがって、単独運転検出手段１８に入力される連系点電圧Ｖの周波数ｆＶや連系点電圧Ｖの正の半周期および負の半周期には、特段の変化が現れないので、単独運転検出手段１８は、単独運転の可能性はなしと判断し、通常の連系状態が継続される。
【００４８】
つまり、遮断器２が開放されていない（停電時でない）状態において、分散型電源装置８による単独運転状態を誤検出することはない。
【００４９】
次に、遮断器２が開放された（実際に単独運転が発生した）場合の動作について説明する。
遮断器２の開放後（単独運転）においては、遮断器２が開放される前に比べて、連系点６から見た交流電力系統５のインピーダンスが格段に大きくなるので、連系点６の電圧周波数ｆＶへの微小バイアスＢの影響は現れ易い。
【００５０】
しかし、前述のように、自家負荷７と系統負荷４および変圧器４や配線のインピーダンスとを合成した負荷状態によっては、電圧ゼロクロスと電流ゼロクロスとを合わせる力率一定制御と、上記周波数シフト運転とが干渉しあうので、連系点電圧Ｖの周波数ｆＶへの微小バイアスＢの影響が現れなくなる場合がある。
【００５１】
たとえば、運転周波数（図２参照）の微小バイアスＢの極性が正の場合には、前述の容量性負荷において上記条件が成立する。
【００５２】
しかしながら、上記容量性負荷の場合や逆の誘導性負荷の場合には、周波数に微小バイアスＢを加え、各周期毎に電圧のゼロクロスに電流のゼロクロスを揃えるようにリセットをかけているので、過渡現象としてリセット直後の半周期と次の半周期との間に周期差が現れることになる。
【００５３】
そこで、この発明による単独運転検出手段１８は、上記周期差を利用して、連系点電圧Ｖの正の期間と負の期間との差が所定値を超えた場合に、単独運転検出の可能性が有ると判断する。
【００５４】
なお、負荷状態が純抵抗に近い場合には、電流のゼロクロスリセットによる過渡現象が現れにくくなるが、周波数として微小バイアスＢ分が現れるので、単独運転検出手段１８は、周波数の変化で単独運転の可能性が有ると判断することができる。
【００５５】
次に、電圧位相確定手段１４は、単独運転検出手段１８からの検出結果に応答して、本当に単独運転状態であるか否かを確定するために、電圧のゼロクロスに電流のゼロクロスを揃えるリセット処理を中止する。
【００５６】
これにより、連系点電圧Ｖの周波数ｆＶは、１周期毎にほぼ微小バイアスＢ分だけ増加していくように変化するので、単独運転確定手段１９は、１周期毎の周波数変化を捕捉することにより、単独運転状態にあることを確定し、連系用開閉手段１１を開放して分散型電源装置８を連系点６から切り離す。
【００５７】
図３はこの発明の実施の形態１による単独運転発生時刻ｔｄからの周波数変化を示す説明図であり、電流目標値ｉｏの周波数ｆｉｏ（実線参照）と、連系点電圧Ｖの周波数ｆＶ（破線参照）との各時間変化を関連付けて示している。
図３において、横軸は時間ｔ［秒］、縦軸は周波数［Ｈｚ］を示す。
【００５８】
ここでは、時刻ｔｄ（＝７秒）において単独運転が発生した場合を示し、単独運転発生後に、各周波数ｆｉｏおよびｆＶは微小バイアスＢ分ずつ増加している。
【００５９】
以上のように、周期情報（周期または周波数）の微小バイアスの方向を一方向（プラス方向のみ）に設定することにより、同一フィーダに複数台の分散型電源装置８を連系しても、各出力同士で周波数シフトの微小バイアスＢ分がキャンセルされることはなく、単独運転の可能性を迅速に且つ確実に検出することができる。
【００６０】
また、連系点電圧Ｖの正の半周期と負の半周期との差に基づいて単独運転の可能性を検出することにより、負荷状態とは無関係に単独運転の可能性を検出することができる。
【００６１】
さらに、電圧のゼロクロスに電流のゼロクロスを揃えるリセット処理（力率一定制御）を中止することにより、図３のように、連系点６の電圧周波数ｆＶを確実に発散させることができる。したがって、単独運転確定手段１９において、最終的に単独運転状態か否かを高い信頼性で確定することができる。
【００６２】
実施の形態２．
なお、上記実施の形態１では、図２のように、電流目標値ｉｏのゼロクロスリセット処理を１周期毎に行うようにしたが、複数周期毎に行うようにしてもよく、たとえば２周期に１回だけリセット処理を行うようにしてもよい。
【００６３】
この場合、周期計測手段１３は、電流目標値ｉｏの電流位相φｉがリセットされた直後の連系点６の周波数ｆＶ１とそれ以降の周波数ｆＶ２とを計測し、単独運転検出手段１８は、各周波数ｆＶ１、ｆＶ２のずれ量が所定値を超えた場合に、分散型電源装置８による単独運転の可能性有りと判断する。
【００６４】
すなわち、電流位相確定手段１４は、２周期毎にリセット処理を行い、周期計測手段１３は、リセット直後の１周期と次の１周期に現れる連系点電圧Ｖの周波数変化の過渡現象による周期差を検出する。
【００６５】
このように、複数周期毎に電流周波数ｆｉのゼロクロスリセットを行い、リセット直後の１周期と次の１周期との周波数差（周期差）から単独運転の可能性を検出することにより、連系点電圧Ｖを検出する電圧検出装置に直流オフセットが発生しても誤動作することがなく、単独運転の可能性を高い信頼性で検出することができる。
【００６６】
また、上記実施の形態１では、単独運転の可能性有りと判断された場合に電流目標値ｉｏのリセット処理（力率一定制御）を中止することと、連系点電圧Ｖの正負期間のずれ量から単独運転の可能性を判断することと、電流目標値ｉｏの周波数ｆｉに一方向（正方向）のみの微小バイアスＢを加えることとを組み合わせて説明したが、個別の特徴のみによっても作用効果を奏する。
【００６７】
たとえば、連系点電圧Ｖの正負期間のずれ量から単独運転の可能性を判断することのみによっても、単独運転の可能性を高い信頼性で検出することができる。同様に、上記実施の形態２の特徴のみによっても、単独運転の可能性を高い信頼性で検出することができる。
【００６８】
さらに、上記実施の形態１では、周期計測手段１３において、電流目標値ｉｏの電流位相φｉがリセットされた直後の連系点６の周波数ｆＶ１とそれ以降の周波数ｆＶ２とを計測したが、電流位相φｉがリセットされる直前の連系点６の周波数とそれ以降の周波数ｆＶ２とを計測してもよい。
【００６９】
【発明の効果】
以上のように、この発明の請求項１によれば、連系点を介して交流電力系統と連系され、連系点に接続された負荷に交流電力を供給するための分散型電源装置であって、発電電力を生成する発電手段と、発電電力を交流電力に変換する電力変換手段と、連系点の電圧位相を検出する電圧位相検出手段と、電圧位相に基づいて連系点の電圧周期情報を計測する周期計測手段と、電圧位相および電圧周期情報に基づいて電力変換手段の出力電流目標値を生成する電流基準発生手段と、出力電流目標値に応じて電力変換手段を制御する電流制御手段と、電圧周期情報に基づいて分散型電源装置による単独運転の可能性を検出する単独運転検出手段と、連系点の電圧および電圧位相に基づいて分散型電源装置による単独運転状態を確定し、分散型電源装置の連系状態を禁止するための単独運転確定手段とを備え、電流基準発生手段は、出力電流目標値の電流周期情報を、連系点の電圧周期情報に対して微小バイアスを加えた値に設定し、分散型電源装置が交流電力系統と連系された通常時には、出力電流目標値の電流位相を連系点の電圧位相に合わせてリセットし、単独運転検出手段により単独運転の可能性が検出された後は、電圧位相に合わせた電流位相のリセット処理を中止するようにしたので、負荷特性や同一フィーダへの接続台数などに係わらず、単独運転を素早く且つ確実に検出して連系点からの切り離し処置を施すことのできる分散型電源装置が得られる効果がある。
【００７０】
また、この発明の請求項２によれば、請求項１において、周期計測手段は、連系点の電圧の正期間および負期間を計測し、単独運転検出手段は、正期間と負期間とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するようにしたので、負荷特性や同一フィーダへの接続台数などに係わらず、単独運転の可能性を高い信頼性で検出することのできる分散型電源装置が得られる効果がある。
【００７１】
また、この発明の請求項３によれば、請求項１において、周期計測手段は、出力電流目標値の位相がリセットされる直前またはリセットされた直後の連系点の第１の電圧周期情報とそれ以降の第２の電圧周期情報とを計測し、単独運転検出手段は、第１の電圧周期情報と第２の電圧周期情報とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するようにしたので、負荷特性や同一フィーダへの接続台数などに係わらず、単独運転の可能性を高い信頼性で検出することのできる分散型電源装置が得られる効果がある。
【００７２】
また、この発明の請求項４によれば、連系点を介して交流電力系統と連系され、連系点に接続された負荷に交流電力を供給するための分散型電源装置であって、発電電力を生成する発電手段と、発電電力を交流電力に変換する電力変換手段と、連系点の電圧位相を検出する電圧位相検出手段と、電圧位相に基づいて連系点の電圧周期情報を計測する周期計測手段と、電圧位相および電圧周期情報に基づいて電力変換手段の出力電流目標値を生成する電流基準発生手段と、出力電流目標値に応じて電力変換手段を制御する電流制御手段と、電圧周期情報に基づいて分散型電源装置による単独運転の可能性を検出する単独運転検出手段と、連系点の電圧および電圧位相に基づいて分散型電源装置による単独運転状態を確定し、分散型電源装置の連系状態を禁止するための単独運転確定手段とを備え、電流基準発生手段は、出力電流目標値の電流周期情報を、連系点の電圧周期情報に対して微小バイアスを加えた値に設定し、分散型電源装置が交流電力系統と連系された通常時には、出力電流目標値の電流位相を連系点の電圧位相に合わせてリセットし、周期計測手段は、連系点の電圧の正期間および負期間を計測し、単独運転検出手段は、正期間と負期間とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するようにしたので、負荷特性や同一フィーダへの接続台数などに係わらず、単独運転の可能性を高い信頼性で検出することのできる分散型電源装置が得られる効果がある。
【００７３】
また、この発明の請求項５によれば、請求項４において、出力電流目標値の電流周期情報は、連系点の電圧周期情報に対して一方向に微小バイアスを加えた値に設定されたので、同一フィーダへの接続台数などに係わらず、単独運転の可能性を高い信頼性で検出することのできる分散型電源装置が得られる効果がある。
【００７４】
また、この発明の請求項６によれば、連系点を介して交流電力系統と連系され、連系点に接続された負荷に交流電力を供給するための分散型電源装置であって、発電電力を生成する発電手段と、発電電力を交流電力に変換する電力変換手段と、連系点の電圧位相を検出する電圧位相検出手段と、電圧位相に基づいて連系点の電圧周期情報を計測する周期計測手段と、電圧位相および電圧周期情報に基づいて電力変換手段の出力電流目標値を生成する電流基準発生手段と、出力電流目標値に応じて電力変換手段を制御する電流制御手段と、電圧周期情報に基づいて分散型電源装置による単独運転の可能性を検出する単独運転検出手段と、連系点の電圧および電圧位相に基づいて分散型電源装置による単独運転状態を確定し、分散型電源装置の連系状態を禁止するための単独運転確定手段とを備え、電流基準発生手段は、出力電流目標値の電流周期情報を、連系点の電圧周期情報に対して微小バイアスを加えた値に設定し、分散型電源装置が交流電力系統と連系された通常時には、出力電流目標値の電流位相を連系点の電圧位相に合わせてリセットし、周期計測手段は、出力電流目標値の位相がリセットされる直前またはリセットされた直後の連系点の第１の電圧周期情報とそれ以降の第２の電圧周期情報とを計測し、単独運転検出手段は、第１の電圧周期情報と第２の電圧周期情報とのずれ量が所定値を超えた場合に、分散型電源装置による単独運転の可能性有りと判断するようにしたので、負荷特性や同一フィーダへの接続台数などに係わらず、単独運転の可能性を高い信頼性で検出することのできる分散型電源装置が得られる効果がある。
【００７５】
また、この発明の請求項７によれば、請求項６において、出力電流目標値の電流周期情報は、連系点の電圧周期情報に対して一方向に微小バイアスを加えた値に設定されたので、同一フィーダへの接続台数などに係わらず、単独運転の可能性を高い信頼性で検出することのできる分散型電源装置が得られる効果がある。
【図面の簡単な説明】
【図１】この発明の実施の形態１を交流電力系統と関連付けて示すブロック構成図である。
【図２】この発明の実施の形態１により検出される連系点電圧および制御される電流目標値を示す波形図である。
【図３】この発明の実施の形態１による連系点電圧および電流目標値の周波数変化を示す説明図である。
【符号の説明】
１交流発電設備、２遮断器、４系統負荷、５交流電力系統、６連系点、７自家負荷、８分散型電源装置、９発電手段、１０電力変換手段、１１連系用開閉手段、１２電圧位相検出手段、１３周期計測手段、１４電流位相確定手段、１５電流周期確定手段、１５ａ微小バイアス生成手段、１６電流基準確定手段、１７電流制御手段、１８単独運転検出手段、１９単独運転確定手段、Ｂ微小バイアス、ｆｉ電流目標値の周波数（電流周期情報）、ｆＶ連系点電圧の周波数（電圧周期情報）、ｉｏ電流目標値、Ｖ連系点電圧、φｉ電流位相、φＶ電圧位相。[0001]
BACKGROUND OF THE INVENTION
The present invention supplies AC power to a load connected to an AC power system by converting the generated power from a power generation means such as solar power generation or fuel cell power generation into AC power and interconnecting the AC power system. More particularly, the present invention relates to a distributed power supply apparatus that can quickly and reliably detect an isolated operation state and can perform a disconnection process from a connection point.
[0002]
[Prior art]
Conventionally, in a so-called commercial power supply wiring system (AC power system) that supplies AC power to ordinary homes and factories, an arbitrary number of distributed power supply devices are connected downstream of the circuit breaker, and the AC power system AC power is supplied to the connected load via a connection point.
[0003]
In this type of AC power system, maintenance on the load side, including transformers, etc. is required. Such maintenance and inspection involves opening the circuit breaker installed upstream of the AC power system and This is performed in a so-called power failure state by cutting off the power supply from the power source.
[0004]
At this time, the state where the distributed power supply unit connected to the system downstream of the circuit breaker continues to operate after being shut off (generally referred to as “single operation”). Therefore, it is necessary to stop the operation of the distributed power supply by detecting the isolated operation quickly and reliably at the time of maintenance and inspection.
[0005]
In general, when the difference between the load power and the output power from the distributed power supply device is large, the voltage value and phase at the interconnection point at the time of isolated operation change greatly. Passive systems that capture changes in the voltage value and phase of a system point are well known.
[0006]
As another method for enabling detection of isolated operation, even when the load power and the output power from the distributed power supply are balanced, the operation frequency of the system distributed power supply is There is also known an active method such as a frequency shift method in which a value obtained by always adding a minute bias to the frequency and detecting the influence of the minute bias on the frequency change at the interconnection point.
[0007]
However, even in the above frequency shift method, when the distributed power supply is controlled at a constant power factor, depending on the load condition, the power factor constant control and the frequency shift operation interfere with each other, and the connection point In some cases, the influence of the minute bias on the frequency does not appear.
[0008]
For example, if the load to which AC power is supplied is a capacitive load, the zero cross point of the grid point voltage occurs later than the zero cross of the current, so the minute bias is shifted in the positive direction and the grid point voltage is Even if an attempt is made to detect an isolated operation state at an operation frequency higher than the frequency, the frequency of the interconnection point voltage (the reciprocal of the voltage zero-cross cycle) does not increase, and an isolated operation cannot be detected.
[0009]
Therefore, as a conventional method for solving the above problems, for example, as referred to in Japanese Patent Application Laid-Open No. 11-41819, the direction of the minute bias applied to the frequency of the current target value is changed between plus and minus. A method has also been proposed.
[0010]
However, in the method described in the above publication, when a plurality of distributed power supply devices are connected to the same feeder, the outputs of the distributed power supply devices cancel each other with a minute frequency bias. Even if a power failure occurs in the AC power system, the frequency shift does not appear in the voltage frequency at the connection point, and it may be impossible to detect an isolated operation.
[0011]
[Problems to be solved by the invention]
As described above, even when a conventional distributed power supply apparatus uses a method (see Japanese Patent Application Laid-Open No. 11-41819) that avoids problems due to differences in load characteristics, a plurality of distributed power supply apparatuses are connected to the same feeder. In such a case, there is a problem that the frequency shift does not appear in the connection point voltage when a system power failure occurs, and the isolated operation cannot be detected reliably.
[0012]
The present invention has been made to solve the above-described problems, and it is possible to quickly and surely detect an isolated operation regardless of load characteristics or the number of units connected to the same feeder, and to perform disconnection from the interconnection point. It is an object of the present invention to obtain a distributed power supply device that can be applied.
[0013]
[Means for Solving the Problems]
A distributed power supply apparatus according to claim 1 of the present invention is a distributed power supply apparatus that is connected to an AC power system via a connection point and supplies AC power to a load connected to the connection point. A power generation means for generating generated power, a power conversion means for converting the generated power into AC power, a voltage phase detection means for detecting a voltage phase at the connection point, and a voltage cycle at the connection point based on the voltage phase. Period measuring means for measuring information, current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and voltage period information, and current control for controlling the power conversion means in accordance with the output current target value And an isolated operation detecting means for detecting the possibility of isolated operation by the distributed power supply based on the voltage cycle information, and the isolated operation state by the distributed power supply is determined based on the voltage and voltage phase of the interconnection point. Distributed power supply An independent operation determining means for prohibiting the connected state of the device, and the current reference generating means is a value obtained by adding a minute bias to the current period information of the output current target value to the voltage period information of the connection point. When the distributed power supply is normally connected to the AC power system, the current phase of the output current target value is reset according to the voltage phase of the connection point, and the possibility of isolated operation is possible by the isolated operation detection means Is detected, the current phase reset process in accordance with the voltage phase is stopped.
[0014]
According to a second aspect of the present invention, in the distributed power supply device according to the first aspect, the period measuring means measures the positive period and the negative period of the voltage at the interconnection point, and the isolated operation detecting means is the positive period. When the amount of deviation from the negative period exceeds a predetermined value, it is determined that there is a possibility of isolated operation by the distributed power supply device.
[0015]
According to a third aspect of the present invention, there is provided the distributed power supply device according to the first aspect, wherein the period measuring means is the first of the interconnection points immediately before or just after the phase of the output current target value is reset. The voltage cycle information and the second voltage cycle information after that are measured, and the isolated operation detecting means, when the deviation amount between the first voltage cycle information and the second voltage cycle information exceeds a predetermined value, It is determined that there is a possibility of isolated operation by the distributed power supply.
[0016]
According to a fourth aspect of the present invention, there is provided a distributed power supply apparatus for supplying AC power to a load connected to an AC power system via a connection point and connected to the connection point. The power generation means for generating the generated power, the power conversion means for converting the generated power into AC power, the voltage phase detection means for detecting the voltage phase of the connection point, and the connection point based on the voltage phase A period measuring means for measuring voltage period information; a current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and voltage period information; and controlling the power conversion means in accordance with the output current target value Current control means, isolated operation detecting means for detecting the possibility of isolated operation by the distributed power supply device based on the voltage cycle information, and isolated operation state by the distributed power supply device based on the voltage and voltage phase of the interconnection point Confirm and distribute An independent operation determining means for prohibiting the interconnection state of the power supply device, and the current reference generating means applies a minute bias to the current period information of the output current target value to the voltage period information of the interconnection point When the distributed power supply is normally connected to the AC power system, the current phase of the output current target value is reset in accordance with the voltage phase of the connection point. Measures the positive and negative periods of the voltage, and the isolated operation detection means determines that there is a possibility of isolated operation by the distributed power supply when the deviation between the positive and negative periods exceeds a predetermined value It is.
[0017]
According to claim 5 of the present invention, in the distributed power supply according to claim 4, the current cycle information of the output current target value is a value obtained by adding a minute bias in one direction to the voltage cycle information of the interconnection point. Is set.
[0018]
According to a sixth aspect of the present invention, there is provided a distributed power supply apparatus for supplying AC power to a load connected to an AC power system via a connection point and connected to the connection point. The power generation means for generating the generated power, the power conversion means for converting the generated power into AC power, the voltage phase detection means for detecting the voltage phase of the connection point, and the connection point based on the voltage phase A period measuring means for measuring voltage period information; a current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and voltage period information; and controlling the power conversion means in accordance with the output current target value Current control means, isolated operation detecting means for detecting the possibility of isolated operation by the distributed power supply device based on the voltage cycle information, and isolated operation state by the distributed power supply device based on the voltage and voltage phase of the interconnection point Confirm and distribute An independent operation determining means for prohibiting the interconnection state of the power supply device, and the current reference generating means applies a minute bias to the current period information of the output current target value to the voltage period information of the interconnection point When the distributed power supply unit is normally connected to the AC power system, the current phase of the output current target value is reset according to the voltage phase of the connection point, and the period measuring means sets the output current target value. The first voltage cycle information at the interconnection point immediately before the phase of the first phase is reset or the second voltage cycle information after that is reset, and the islanding operation detecting means detects the first voltage cycle information. And the second voltage cycle information exceed the predetermined value, it is determined that there is a possibility of independent operation by the distributed power supply device.
[0019]
According to claim 7 of the present invention, in the distributed power supply according to claim 6, the current cycle information of the output current target value is a value obtained by adding a minute bias in one direction to the voltage cycle information of the interconnection point. Is set.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 is a block diagram showing a first embodiment of the present invention, and shows a state where a distributed power supply apparatus is linked to an AC power system.
In addition, here, one distributed power supply device is shown as a representative, but any number of distributed power supply devices can be interconnected.
[0022]
In FIG. 1, 1 is an AC power generation facility that outputs commercial AC power, 2 is a circuit breaker inserted on the output side of the AC power generation facility 1, and 3 is a transformer connected to the AC power generation facility 1 via the circuit breaker 2. Reference numeral 4 denotes a system load connected to the secondary side (output side) of the transformer 3, and these constitute an AC power system 5.
[0023]
The system load 4 in the AC power system 5 includes electrical equipment used in general households.
Reference numeral 6 denotes a connection point of the AC power system 5, and circuit systems closer to the AC power generation equipment 1 than the connection point 6 in FIG. 1 are collectively referred to as an AC power system 5.
[0024]
7 is a private load connected to the interconnection point 6, and 8 is a distributed power supply.
The distributed power supply device 8 is connected to the AC power system 5 and the private load 7 via the interconnection point 6.
[0025]
The distributed power supply 8 includes a power generation unit 9 such as a solar cell, a power conversion unit 10 that converts power generated from the power generation unit 9 (DC power in this case) into AC power, and an output side of the power conversion unit 10. The connected open / close means 11 and the voltage phase detection means 12 for detecting the voltage phase φV from the voltage V at the connection point 6 are provided.
[0026]
The distributed power supply device 8 includes a cycle measuring unit 13, a current phase determining unit 14, a current cycle determining unit 15, a current reference determining unit 16, a current control unit 17, an isolated operation detecting unit 18, and an isolated operation determining unit 19. ing.
[0027]
The cycle measuring means 13 measures the positive half cycle, the negative half cycle and one cycle (or frequency) of the interconnection point voltage V from the voltage phase φV as voltage cycle information.
The current phase determination means 14 determines the current phase φi of the current target value io from the voltage phase φV.
[0028]
The current cycle determining unit 15 outputs a minute bias B added to the current cycle information of the current target value io, and an addition for adding the voltage cycle information from the cycle measuring unit 13 and the minute bias B. Means 15b, and the period (or frequency) of the current target value io is determined by adding a minute bias B to the voltage period information from the period measuring means 13.
[0029]
The current reference determination means 16 is based on the current phase φi from the current phase determination means 14 and the output signal (current cycle) from the current cycle determination means 15, and the current target value io to be output from the power conversion means 10. Is determined as a current reference.
[0030]
The current phase determination unit 14, the current cycle determination unit 15 and the current reference determination unit 16 constitute a current reference generation unit that generates the output current target value io of the power conversion unit 10 based on the voltage phase φV and the voltage cycle information. Yes.
[0031]
The current control means 17 includes a current transformer 17a that detects the output current i of the power conversion means 10, a subtractor 17b that calculates a current deviation (= io−i) between the current target value io and the output current i, And a control unit 17c that feedback-controls the power conversion unit 10 based on the deviation, and controls the power conversion unit 10 based on the current target value io from the current reference determination unit 16 to adjust the output current i.
[0032]
The isolated operation detection means 18 detects the possibility of isolated operation by the distributed power supply device 8 based on the voltage cycle information from the period measurement means 13 and inputs the detection result to the current phase determination means 14.
[0033]
The isolated operation determining means 19 is configured so that the distributed power supply device 8 operates independently based on the voltage V at the interconnection point 6, the voltage phase φV from the current phase detecting means 12, and the voltage period information from the period measuring means 13. The state is determined, and a drive signal for stopping the power conversion means 10 and opening the connection opening / closing means 11 is output.
[0034]
The current phase determination means 14 constituting the current reference generation means converts the current phase φi of the output current target value io to the voltage phase φV of the connection point 6 when the distributed power supply 8 is normally connected to the AC power system 5. The reset processing (power factor constant control) of the current phase φi matched with the voltage phase φV is stopped after the possibility of isolated operation is detected by the isolated operation detection means 18. .
[0035]
Next, a specific operation according to the first embodiment of the present invention shown in FIG. 1 will be described.
First, in a normal time when the circuit breaker 2 is turned on, the power converter 10 in the distributed power supply device 8 converts the power generated by the power generation means 9 into alternating current power, and uses the open / close means 11 for connection to the home. AC power is supplied to the load 7.
[0036]
At this time, when the capacity of the private load 7 is smaller than the generated power, the excess AC power from the distributed power supply device 8 is reversely flowed to the AC power system 5.
Further, the phase of the output current i from the power conversion means 10 is synchronized with the voltage phase φV of the interconnection point 6 in order to make the power factor constant.
[0037]
That is, the current phase determination means 14 in the distributed power supply device 8 determines the current phase φi of the current target value io so that the output current i zero-crosses when the interconnection point voltage V crosses zero.
[0038]
Further, the current cycle determining means 15 uses a cycle (or frequency fio) obtained by adding a minute bias B to the voltage cycle (or frequency fV) of the interconnection point 6 as current cycle information (cycle or frequency) of the output current i. To decide.
[0039]
Although not related to the gist of the present invention, the amplitude of the output current i is generally determined by the current reference determining means 16 so as to bring out the maximum capacity of the power generating means 9.
[0040]
As described above, since the frequency is replaced as the reciprocal of the period, the period information will be described as a representative frequency hereinafter.
[0041]
FIG. 2 is a waveform diagram showing the phase synchronization relationship according to the first embodiment of the present invention. The connection point voltage V (see the two-dot chain line) detected from the connection point 6 and the current for controlling the power conversion means 10 are shown. The target value io (see solid line) is shown in association with it.
[0042]
In FIG. 2, the horizontal axis represents time t, the vertical axis represents the current target value io [A] and the connection point voltage V [V], and the time change of the target current io and the connection point voltage V is shown.
[0043]
The connection point voltage V (two-dot chain line) is directly detected from the connection point 6, and the current target value io (solid line) is output from the current reference determination unit 16 as the target value of the output current i of the power conversion unit 10. The
[0044]
The frequency fio of the current target value io is higher by the minute bias B than the frequency fV of the connection point voltage V (the period of the current target value io is shorter than the period of the connection point voltage V), but the connection point voltage It is reset every cycle in accordance with the zero cross point of V (1.0167 seconds and 1.0333 seconds in FIG. 2).
[0045]
Further, the output current i from the power conversion means 10 flows almost following the target current value io.
[0046]
However, as is well known, since the impedance of the AC power system 5 is considerably smaller than the internal impedance of the distributed power supply device 8, the influence of the minute bias B on the frequency fio of the output current i is affected by the interconnection point voltage V ( Almost no two-dot chain line) appears.
[0047]
Therefore, since no particular change appears in the frequency fV of the interconnection point voltage V input to the isolated operation detection means 18 and the positive half cycle and the negative half cycle of the interconnection point voltage V, the isolated operation detection means. No. 18 determines that there is no possibility of an independent operation, and the normal interconnection state is continued.
[0048]
That is, in the state where the circuit breaker 2 is not opened (not during a power failure), the single operation state by the distributed power supply device 8 is not erroneously detected.
[0049]
Next, an operation when the circuit breaker 2 is opened (actual operation has actually occurred) will be described.
After the circuit breaker 2 is opened (single operation), the impedance of the AC power system 5 viewed from the connection point 6 is significantly higher than before the circuit breaker 2 is opened. The influence of the minute bias B on the voltage frequency fV tends to appear.
[0050]
However, as described above, depending on the load state obtained by combining the private load 7, the system load 4, the transformer 4 and the impedance of the wiring, the power factor constant control for combining the voltage zero cross and the current zero cross, and the frequency shift operation described above. May interfere with each other, so that the influence of the minute bias B on the frequency fV of the interconnection point voltage V may not appear.
[0051]
For example, when the polarity of the minute bias B at the operating frequency (see FIG. 2) is positive, the above condition is satisfied in the above-described capacitive load.
[0052]
However, in the case of the above capacitive load or in the opposite inductive load, a minute bias B is applied to the frequency, and the reset is performed so that the current zero cross is aligned with the voltage zero cross every cycle. As a phenomenon, a period difference appears between the half cycle immediately after the reset and the next half cycle.
[0053]
Therefore, the isolated operation detecting means 18 according to the present invention can detect the isolated operation when the difference between the positive period and the negative period of the interconnection point voltage V exceeds a predetermined value by using the period difference. Judge that there is sex.
[0054]
When the load state is close to a pure resistance, a transient phenomenon due to the zero cross reset of the current is less likely to appear, but since a minute bias B appears as a frequency, the isolated operation detecting means 18 performs the isolated operation by changing the frequency. It can be determined that there is a possibility.
[0055]
Next, in response to the detection result from the isolated operation detecting means 18, the voltage phase determining means 14 performs a reset process for aligning the current zero cross with the voltage zero cross in order to determine whether or not the actual operation is in the isolated state. Cancel.
[0056]
As a result, the frequency fV of the interconnection point voltage V changes so as to increase by almost a minute bias B for each cycle, so that the independent operation determination means 19 captures the frequency change for each cycle. Thus, it is determined that the vehicle is in the single operation state, the connection open / close means 11 is opened, and the distributed power supply device 8 is disconnected from the connection point 6.
[0057]
FIG. 3 is an explanatory diagram showing changes in frequency from the isolated operation occurrence time td according to Embodiment 1 of the present invention. The frequency fio (see the solid line) of the current target value io and the frequency fV of the interconnection point voltage V (broken line) Each time change with reference).
In FIG. 3, the horizontal axis represents time t [seconds], and the vertical axis represents frequency [Hz].
[0058]
Here, a case where an isolated operation occurs at time td (= 7 seconds) is shown, and after the occurrence of the isolated operation, the frequencies fio and fV increase by a minute bias B.
[0059]
As described above, by setting the direction of the minute bias of the period information (period or frequency) to one direction (only in the plus direction), even if a plurality of distributed power supply devices 8 are connected to the same feeder, The minute shift B of the frequency shift is not canceled between outputs, and the possibility of isolated operation can be detected quickly and reliably.
[0060]
Further, by detecting the possibility of isolated operation based on the difference between the positive half cycle and the negative half cycle of the interconnection point voltage V, it is possible to detect the possibility of isolated operation regardless of the load state. it can.
[0061]
Furthermore, by canceling the reset process (power factor constant control) that aligns the zero cross of the current with the zero cross of the voltage, the voltage frequency fV of the interconnection point 6 can be reliably diverged as shown in FIG. Therefore, it is possible to determine with high reliability whether or not the islanding operation determination unit 19 is finally in the islanding operation state.
[0062]
Embodiment 2. FIG.
In the first embodiment, the zero cross reset process of the current target value io is performed every cycle as shown in FIG. 2, but it may be performed every plural cycles, for example, 1 every 2 cycles. The reset process may be performed only once.
[0063]
In this case, the cycle measuring means 13 measures the frequency fV1 of the interconnection point 6 immediately after the current phase φi of the current target value io is reset and the frequency fV2 after that, and the isolated operation detecting means 18 When the amount of deviation between fV1 and fV2 exceeds a predetermined value, it is determined that there is a possibility of isolated operation by the distributed power supply device 8.
[0064]
That is, the current phase determination means 14 performs a reset process every two periods, and the period measurement means 13 determines the period difference due to the transient phenomenon of the frequency change of the connection point voltage V appearing in one period immediately after the reset and the next one period. Is detected.
[0065]
In this way, the zero cross reset of the current frequency fi is performed every plural cycles, and the possibility of isolated operation is detected from the frequency difference (cycle difference) between one cycle immediately after the reset and the next one cycle. Even if a DC offset occurs in the voltage detection device that detects the voltage V, no malfunction occurs, and the possibility of isolated operation can be detected with high reliability.
[0066]
Further, in the first embodiment, when it is determined that there is a possibility of isolated operation, the reset processing (power factor constant control) of the current target value io is stopped, and the difference between the positive and negative periods of the connection point voltage V The combination of determining the possibility of isolated operation from the amount and adding a minute bias B only in one direction (positive direction) to the frequency fi of the current target value io has been described. There is an effect.
[0067]
For example, the possibility of isolated operation can be detected with high reliability only by determining the possibility of isolated operation from the amount of deviation of the connection point voltage V between the positive and negative periods. Similarly, the possibility of isolated operation can be detected with high reliability only by the feature of the second embodiment.
[0068]
Further, in the first embodiment, the period measuring unit 13 measures the frequency fV1 of the interconnection point 6 immediately after the current phase φi of the current target value io is reset and the frequency fV2 after that, but the current phase The frequency of the interconnection point 6 immediately before φi is reset and the subsequent frequency fV2 may be measured.
[0069]
【The invention's effect】
As described above, according to claim 1 of the present invention, there is provided a distributed power supply device for supplying AC power to a load connected to an AC power system via a connection point and connected to the connection point. A power generation means for generating generated power, a power conversion means for converting the generated power into AC power, a voltage phase detection means for detecting a voltage phase at the connection point, and a voltage at the connection point based on the voltage phase. Period measurement means for measuring period information, current reference generation means for generating an output current target value of the power conversion means based on the voltage phase and voltage period information, and current for controlling the power conversion means in accordance with the output current target value Control unit, islanding detection means for detecting the possibility of islanding operation by the distributed power supply device based on the voltage cycle information, and islanding operation state by the distributed power supply device are determined based on the voltage and voltage phase of the interconnection point And distributed power supply An independent operation determining means for prohibiting the connected state of the device, and the current reference generating means is a value obtained by adding a minute bias to the current period information of the output current target value to the voltage period information of the connection point. When the distributed power supply is normally connected to the AC power system, the current phase of the output current target value is reset according to the voltage phase of the connection point, and the possibility of isolated operation is possible by the isolated operation detection means Since the reset process of the current phase in accordance with the voltage phase is stopped after the detection of the fault, independent operation can be detected quickly and reliably regardless of the load characteristics or the number of units connected to the same feeder. There is an effect of obtaining a distributed power supply device that can be separated from the system point.
[0070]
According to a second aspect of the present invention, in the first aspect, the period measuring means measures the positive period and the negative period of the voltage at the connection point, and the isolated operation detecting means is provided with a positive period and a negative period. When the deviation exceeds the specified value, it is judged that there is a possibility of isolated operation by the distributed power supply.Therefore, regardless of load characteristics and the number of units connected to the same feeder, There is an effect that a distributed power supply device that can be detected with high reliability can be obtained.
[0071]
According to a third aspect of the present invention, in the first aspect, the period measuring means includes the first voltage period information of the interconnection point immediately before or after the phase of the output current target value is reset. The subsequent second voltage cycle information is measured, and the isolated operation detecting means is a distributed power supply device when a deviation amount between the first voltage cycle information and the second voltage cycle information exceeds a predetermined value. Therefore, a distributed power supply that can detect the possibility of islanding with high reliability regardless of the load characteristics and the number of units connected to the same feeder is obtained. There is an effect.
[0072]
According to claim 4 of the present invention, there is provided a distributed power supply device for supplying AC power to a load connected to an AC power system via an interconnection point and connected to the interconnection point, Power generation means for generating generated power, power conversion means for converting the generated power into AC power, voltage phase detection means for detecting the voltage phase of the connection point, and voltage cycle information of the connection point based on the voltage phase A period measuring means for measuring, a current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and voltage period information, and a current control means for controlling the power conversion means in accordance with the output current target value Independent operation detection means for detecting the possibility of isolated operation by the distributed power supply device based on the voltage cycle information, and the isolated operation state by the distributed power supply device is determined based on the voltage and voltage phase at the interconnection point, and distributed Type power supply An independent operation confirmation means for prohibiting the state, the current reference generating means sets the current cycle information of the output current target value to a value obtained by adding a minute bias to the voltage cycle information of the interconnection point, When the distributed power supply is normally connected to the AC power system, the current phase of the output current target value is reset in accordance with the voltage phase of the connection point. Since the negative period is measured and the isolated operation detection means determines that there is a possibility of isolated operation by the distributed power supply when the deviation between the positive period and the negative period exceeds a predetermined value, the load Regardless of the characteristics and the number of units connected to the same feeder, there is an effect of obtaining a distributed power supply device that can detect the possibility of isolated operation with high reliability.
[0073]
According to claim 5 of the present invention, in claim 4, the current cycle information of the output current target value is set to a value obtained by adding a minute bias in one direction to the voltage cycle information of the interconnection point. Therefore, there is an effect of obtaining a distributed power supply device that can detect the possibility of isolated operation with high reliability regardless of the number of units connected to the same feeder.
[0074]
According to claim 6 of the present invention, there is provided a distributed power supply device for supplying AC power to a load connected to an AC power system through an interconnection point and connected to the interconnection point, Power generation means for generating generated power, power conversion means for converting the generated power into AC power, voltage phase detection means for detecting the voltage phase of the connection point, and voltage cycle information of the connection point based on the voltage phase A period measuring means for measuring, a current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and voltage period information, and a current control means for controlling the power conversion means in accordance with the output current target value Independent operation detection means for detecting the possibility of isolated operation by the distributed power supply device based on the voltage cycle information, and the isolated operation state by the distributed power supply device is determined based on the voltage and voltage phase at the interconnection point, and distributed Type power supply An independent operation confirmation means for prohibiting the state, the current reference generating means sets the current cycle information of the output current target value to a value obtained by adding a minute bias to the voltage cycle information of the interconnection point, At the normal time when the distributed power supply is connected to the AC power system, the current phase of the output current target value is reset according to the voltage phase of the connection point, and the period measuring means resets the phase of the output current target value. The first voltage cycle information of the interconnection point immediately after resetting or immediately after being reset and the second voltage cycle information after that are measured, and the isolated operation detecting means detects the first voltage cycle information and the second voltage. When the amount of deviation from the cycle information exceeds the specified value, it is judged that there is a possibility of isolated operation by the distributed power supply unit, so independent operation is possible regardless of load characteristics and the number of units connected to the same feeder. With high reliability Distributed power supply has an effect obtained that can be.
[0075]
According to claim 7 of the present invention, in claim 6, the current cycle information of the output current target value is set to a value obtained by adding a minute bias in one direction to the voltage cycle information of the interconnection point. Therefore, there is an effect of obtaining a distributed power supply device that can detect the possibility of isolated operation with high reliability regardless of the number of units connected to the same feeder.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram illustrating Embodiment 1 of the present invention in association with an AC power system.
FIG. 2 is a waveform diagram showing an interconnection point voltage detected by a first embodiment of the present invention and a current target value to be controlled.
FIG. 3 is an explanatory diagram showing changes in frequency of interconnection point voltage and current target value according to Embodiment 1 of the present invention;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power generation equipment, 2 Circuit breaker, 4 system load, 5 AC power system, 6 connection point, 7 Self load, 8 Distributed power supply device, 9 Power generation means, 10 Power conversion means, 11 Opening / closing means for connection system, 12 Voltage phase detection means, 13 period measurement means, 14 current phase determination means, 15 current cycle determination means, 15a minute bias generation means, 16 current reference determination means, 17 current control means, 18 isolated operation detection means, 19 isolated operation determination means , B Minute bias, fi Current target value frequency (current period information), fV interconnection point voltage frequency (voltage period information), io current target value, V interconnection point voltage, φi current phase, φV voltage phase.

Claims

A distributed power supply device that is connected to an AC power system via a connection point and supplies AC power to a load connected to the connection point,
Power generation means for generating generated power;
Power conversion means for converting the generated power into the AC power;
Voltage phase detection means for detecting the voltage phase of the interconnection point;
Period measuring means for measuring voltage period information of the interconnection point based on the voltage phase;
Current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and the voltage cycle information;
Current control means for controlling the power conversion means in accordance with the output current target value;
Islanding detection means for detecting the possibility of islanding by the distributed power supply based on the voltage cycle information;
An isolated operation determining means for determining the isolated operation state by the distributed power supply device based on the voltage of the interconnection point and the voltage phase, and prohibiting the connected state of the distributed power supply device;
The current reference generating means is
Set the current cycle information of the output current target value to a value obtained by adding a minute bias to the voltage cycle information of the interconnection point,
When the distributed power supply device is normally connected to the AC power system, the current phase of the output current target value is reset in accordance with the voltage phase of the connection point,
The distributed power supply apparatus, wherein after the possibility of the isolated operation is detected by the isolated operation detecting means, the reset process of the current phase in accordance with the voltage phase is stopped.

The period measuring means measures a positive period and a negative period of the voltage at the interconnection point,
2. The isolated operation detecting means determines that there is a possibility of isolated operation by the distributed power supply device when a deviation amount between the positive period and the negative period exceeds a predetermined value. The distributed power supply device according to 1.

The period measuring means measures the first voltage period information of the interconnection point immediately after the phase of the output current target value is reset or immediately after the reset, and the second voltage period information after that.
The isolated operation detecting means determines that there is a possibility of isolated operation by the distributed power supply device when the amount of deviation between the first voltage cycle information and the second voltage cycle information exceeds a predetermined value. The distributed power supply device according to claim 1.

A distributed power supply device that is connected to an AC power system via a connection point and supplies AC power to a load connected to the connection point,
Power generation means for generating generated power;
Power conversion means for converting the generated power into the AC power;
Voltage phase detection means for detecting the voltage phase of the interconnection point;
Period measuring means for measuring voltage period information of the interconnection point based on the voltage phase;
Current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and the voltage cycle information;
Current control means for controlling the power conversion means in accordance with the output current target value;
Islanding detection means for detecting the possibility of islanding by the distributed power supply based on the voltage cycle information;
An isolated operation determining means for determining the isolated operation state by the distributed power supply device based on the voltage of the interconnection point and the voltage phase, and prohibiting the connected state of the distributed power supply device;
The current reference generating means is
Set the current cycle information of the output current target value to a value obtained by adding a minute bias to the voltage cycle information of the interconnection point,
When the distributed power supply device is normally connected to the AC power system, the current phase of the output current target value is reset in accordance with the voltage phase of the connection point,
The period measuring means measures a positive period and a negative period of the voltage at the interconnection point,
The isolated operation detecting means determines that there is a possibility of isolated operation by the distributed power supply device when a deviation amount between the positive period and the negative period exceeds a predetermined value. apparatus.

5. The distributed power supply device according to claim 4, wherein the current cycle information of the output current target value is set to a value obtained by applying a minute bias in one direction to the voltage cycle information of the interconnection point. .

A distributed power supply device that is connected to an AC power system via a connection point and supplies AC power to a load connected to the connection point,
Power generation means for generating generated power;
Power conversion means for converting the generated power into the AC power;
Voltage phase detection means for detecting the voltage phase of the interconnection point;
Period measuring means for measuring voltage period information of the interconnection point based on the voltage phase;
Current reference generating means for generating an output current target value of the power conversion means based on the voltage phase and the voltage cycle information;
Current control means for controlling the power conversion means in accordance with the output current target value;
Islanding detection means for detecting the possibility of islanding by the distributed power supply based on the voltage cycle information;
An isolated operation determining means for determining the isolated operation state by the distributed power supply device based on the voltage of the interconnection point and the voltage phase, and prohibiting the connected state of the distributed power supply device;
The current reference generating means is
Set the current cycle information of the output current target value to a value obtained by adding a minute bias to the voltage cycle information of the interconnection point,
When the distributed power supply device is normally connected to the AC power system, the current phase of the output current target value is reset in accordance with the voltage phase of the connection point,
The period measuring means measures the first voltage period information of the interconnection point immediately after the phase of the output current target value is reset or immediately after the reset, and the second voltage period information after that.
The isolated operation detecting means determines that there is a possibility of isolated operation by the distributed power supply device when the amount of deviation between the first voltage cycle information and the second voltage cycle information exceeds a predetermined value. A distributed power supply device.

7. The distributed power supply device according to claim 6, wherein the current cycle information of the output current target value is set to a value obtained by applying a minute bias in one direction to the voltage cycle information of the interconnection point. .