SERIES COMPENSATING DEVICE AND SWITCHING ELEMENT CONTROLLING DEVICE

摘要

PROBLEM TO BE SOLVED: To enable a switching element to operate properly at the time of a system failure and the elimination of the failure. SOLUTION: The phase difference between a synchronizing pulse signal Sn that is synchronized with the current of a system and a reference pulse signal Ss is detected by a phase difference detecting circuit 44. This phase difference Δθ is amplified by a calculating and amplifying circuit 46 to obtain a control voltage Ec and to generate a pulse signal of an oscillating frequency in proportion to the control voltage Ec by a voltage controlling and oscillating circuit 56. The frequency of this pulse signal is divided by a frequency divider circuit 58 to generate a reference pulse signal Ss. Based on this signal, a firing pulse signal for igniting each thyristor is generated. If a failure occurred in the system, a pulse signal is generated of the oscillating frequency based on the control voltage Ec' that has been stored in a phase memory circuit 54 prior to the occurrence of the failure. Then, the frequency of this pulse signal is divided by the frequency divider circuit 58 to generate the reference pulse signal Ss.