Sequence filters for determining the symmetrical components of multiphase AC power systems.

摘要

Sequence filters to find out positive sequence or negative sequence components of a three phase AC system employ one to three operational amplifiers and a single reactive element to generate the required sequence voltage of a three phase AC power system by producing two line-to-line voltages, phase shifting one of them to bring them into phase and summing the resultant signals. The phase shifting circuit includes a potentiometer, one end of which serves as the imput to the circuit and the other end of which is connected to the inverting input of an operational amplifier. A capacitor is connected between the tap point of the potentiometer and ground an the values of the components are selected so that the tap point of the potentiometer can be positioned to compensate for variations in the capacitive reactance of the capacitor without affecting the magnitude of the phase shifted signal.