| 摘要 |
PURPOSE:To prevent commutation failure due to deficiency of commutation margin angle caused by abrupt variation of current due to disturbance of DC voltage at the time of restarting from BPP state by providing a BPP phase selecting circuit for determining the BPP (bias pair) phase of an AC/DC converter, a BPP phase decision circuit for deciding the phase, and a BPP phase converting circuit. CONSTITUTION:A monitor signal 9 for confirming the conducting state of thyristor valves 2U-2Z is fed to a pulse generator 4. A BPP state decision circuit 11 decides which valve phase is in BPP state based on the signal 9 and notifies the decision result to controllers 5A, 5B. The controllers 5A, 5B deliver signals to BPP phase modifying circuits 10A, 10B and BPP phase selecting circuits 7A, 7B modify thus selected BPP phase. According to the invention, commutation failure due to deficiency of commutation margin angle caused by abrupt variation of current due to disturbance of DC voltage is prevented at the time of restarting from BPP state. |
