| 摘要 |
PURPOSE:To reduce DC transmitted electric power and to shorten the AC voltage drop time of a power inverter side, by performing extremely speedy tap switching when the AC bus voltage of a power rectifier side drops. CONSTITUTION:Voltage variation of an AC system is held within a certain range under AVR controls by each generator group and reactive power control at each substation. Its variation width is assumed to be + or -3%. Then, the voltage switching width of each tap of a switch 12 is assumed to be 1%. An AC bus voltage in an initial control state has +3% variation and a tap position is set to a tap 1. In this state, if the AC voltage of an AC bus 01 varies from a +3% state to a -3% state as maximum variation, a valve-side winding voltage has a 6% voltage drop in total. A tap group selection part 11 compares it with a reference valve-side winding voltage to detect whether the deviation is greater than a prescribed value or not, thereby sending a tap group selection signal to the tap switch 12. By this signal, a switch C is closed and a switch B is opened as shown in a figure (b) ; and then a switch A is opened as shown in a figure (c). Thus, the tap position is set to a tap 4 and the switching is completed. |
