Dual Delta Bank TCR for Harmonic Reduction in Three-Phase Static Var Controllers

The conventional “Delta” connected thyristor-controlled reactor (TCR) bank used for static var compensation and other applications is proposed to be split into two identical “Delta” banks each having kvar capacity half of the total TCR capacity. The study presented shows that such combination of two identical “Delta” connected reactor banks, one with phase switching by thyristors and the other with line switching thyristor arrangement can effectively reduce the harmonic generation of the TCR. Since both the three-phase banks are connected in delta, the zero sequence triplen harmonics generated due to phase control of thyristors remain trapped inside the delta, thus reducing the harmonic injection into the power system. Further, some other major characteristic harmonics are also minimized in the TCR line current. Thus, the proposed TCR yields a low current THD which meets the requisite harmonics standards and it can therefore be used as an economic solution for reactive power control over a reasonable range in high power grid without using any external harmonic filter or special phase shifting transformer. This paper describes in detail the modeling, analysis, and performance assessment of the proposed scheme. Simulation results are furnished to evaluate the output characteristics of the scheme under varying operating conditions. Finally, experimental results are presented, which proves the theoretical proposition.