Design of an AC Voltage Regulator Using a Harmonic Free TCR

Abstract

In this work, a T-connected phase voltage-controlling scheme is presented. The mid branch of the T-configuration is a pure susceptance controlled smoothly in inductive and capacitive operating modes. This susceptance is built of a TCR shunted by a filtering circuit, which is designed to suppress the three significant odd harmonics released by the TCR. The left hand branch is a pure inductive impedance, while the right hand one is a pure capacitive impedance equal in magnitude to the left hand one. If the input phase voltage is below its rated value VLrated, then the controlling susceptance is capacitive and its value is set such that it can raise the load voltage to its desired rated value. If the input voltage is above its rated value, then the susceptance is inductive causing the load voltage reduce to its desired rated value. The regulator is harmonic free and capable of keeping its output voltage within its rated value even though its input voltage is varying in the range of (0.75-1.25)VLrated. Once a voltage disturbance occurs, the regulator approaches its steady state response within five cycles of the input phase voltage. The regulator is capable of supplying 220 V, 50 Hz, 3 kVA loads.