A Wide-Range TCR With Low-Current THD by Optimized Combination of Coupled Reactors and Thyristor Switching and Control

A 3-phase 3-wire thyristor controlled reactor topology is presented comprising of two banks, involving thyristor switched and controlled coupled reactors (TSCCR), one bank of which is “Δ” connected and the other being “Y” connected. Each TSCCR comprises of a reactor with two well coupled identical sections, two main thyristor back-to-back switches and an auxiliary thyristor switch such that the two sections can be either connected in parallel or in series. The ratio of the effective reactor values between the “Δ” bank phase and that of the “Y” bank, as well as the condition when and which switch shall be used for phase control, are selected from an optimization process. Such an arrangement prevents the triplen harmonics from entering into the supply system and some major characteristic harmonics are also eliminated from the source current. Thus, without using any additional filters or phase shifting transformer or oversized reactors, this scheme enables reactive power control with a low current total harmonic distortion over a wide range of kVAr control. Simplicity in construction and operational requirements of the proposed topology makes it a viable and cost effective solution. Its modeling, analysis, and performance assessment are presented, supported by simulation and experimental results.