報告書番号

T96035

タイトル（和文）

自励式変換装置の制御・保護方式の開発（その２）－系統事故時の過電流・過電圧抑制方式－

タイトル（英文）

DEVELOPMENT OF CONTROL FOR SELF-COMMUTATED CONVERTER(PART 2)-CONTROL SCHEME OF OVERCURRENT AND OVERVOLTAGE AT SYSTEM FAULT CONDITION-

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究では，自励式変換器を用いた直流送電系統を対象に，各種の交流系および直流系事故時の過電流・過電圧の発生要因を分析し，これらの抑制制御を組み込んだ新たな制御・保護方式を開発した。各種交流事故に対して，変換器過電流を１．５ｐｕ程度以下に抑制しつつ運転継続を行うためには，交換器制御の応答速度（サンプリング時間）とＰＷＭパルス数を適切に選定した上で，電流指令値絞り制御や逆相分補償回路を採用することが有効である。直流線路の地絡事故に対しては，中性線の接地回路定数の適切な選定と変換器ゲートブロックの採用により，中性線の電圧上昇と変換器過電流の双方を抑制できる。また，変換器ゲートブロック後，直流■断器により事故電流（定格直流電流程度）を■断し再起動を行うことで，他励式とほぼ同等の高速停止－再起動が可能となる。

概要 （英文）

TO USE SELF-COMMUTATED CONVERTERS EXTENSIVELY IN FUTURE TRUNK POWER SYSTEMS,IT IS IMPORTANT TO DEVELOP STABLE OPERATION AT SYSTEM FAULTS AS WELL AS TO PURSUE COST REDUCTION THROUGH RATIONALIZED CONVERTER AND SYSTEM DESIGN.THIS REPORT DISCUSSES THE CAUSE OF CONVERTER OVERCURRENT AND HVDC SYSTEM OVERVOLTAGE AT VARIOUS AC AND DC SYSTEM FAULTS.CONVERTER CONTROL AND PROTECTION SCHEMES WITH COORDINATEDCONTROL OF OVERCURRENT AND OVERVOLTAGE WERE DEVELOPED BY AC･DC POWER SYSTEM SIMULATOR TESTS AND EMTP ANALYSIS. (1)DEVELOPMENT OF CONTROL AND PROTECTION AT AC SYSTEM FAULT CONVERTER OVERCURRENTS AT AC SYSTEM FAULTS ARE CAUSED BY (1)CONTROL IMPOSSIBILITY AT PWM SWITCHING INTERVAL JUSTAFTER BALANCED AC LINE FAULT,AND (2)CONVERTER CURRENT CONTROL DELAY INCOMPENSATING NEGATIVE-SEQUENCE CURRENT AT UNBALANCED FAULT.TO ACHIEVE CONTINUOUS OPERATION WITH SUPPRESSION OF CONVERTER OVERCURRENT BELOW ABOUT 1.5 PU,EFFECTIVE CONTROLS WERE DEVELOPED BY ADDING A CONVERTER CURRENT ORDER LIMIT AND/OR NEGATIVE-SEQUENCE COMPENSATION TO THE CONVERTER CONTROL,WHICH HAS SUFFICIENT SAMPLING CONTROL SPEED AND PWM PULSE NUMBER. (2)DEVELOPMENT OF CONTROL AND PROTECTION AT DC SYSTEM FAULT COORDINATED CONTROL OF CONVERTER OVERCURRENT AND DC LINE OVERVOLTAGE CAN BE ACHIEVED BY A COMBINATION OF (1)SELECTION OF ADEQUATE RESISTANCE AND CAPACITANCE IN NEUTRAL LINE GROUNDING,AND (2)ADOPTION OF CONVERTER GATE BLOCK BY DETECTING DC LINE VOLTAGE DROP.A CONTROL AND PROTECTION SEQUENCE USING A CONVERTER GATE BLOCK FOLLOWED BY DC CIRCUIT BREAKER OPENING(TO RESTORE DC LINE INSULATION BY EXTINGUISH FAULT CURRENT)AND RECLOSING,ENSURES HIGH-SPEED STOP-RESTART OPERATION AS A LINE-COMMUTATED HVDC SYSTEM.

報告者

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