A Reactive Power Compensation Scheme for Unbalanced Four-Wire System Using Virtual Y-TCR Model

A modified scheme for reactive power compensation using static VAr compensators (SVCs) has been proposed in this paper for unbalanced four-wire system. The conventional SVC-based scheme requires both delta (Δ )and star (Y)-connected SVCs for the same purpose. The proposed scheme uses a single-equivalent delta-connected thyristor controlled reactor (TCR) along with a combination of Yand Δ-connected thyristor switched capacitors for this purpose. The single-equivalent Δ-TCR in the present scheme is the result of a virtual Y-TCR and the conventional Δ-TCR. This can reduces effective number of switching devices, cost, complexity, and space requirement compared to the conventional SVC-based schemes. Moreover, the proposed scheme can have various advantageous features compared to newly used DSTATCOM. The proposed scheme can also prevent injection of triplen harmonics in to the line, which is injected by Y-TCR in the conventional scheme. An optimized switching function is adopted in the proposed scheme for reduction of additional injected harmonics by TCR. The optimized switching angles are computed offline using gravitational search algorithm and stored in the processor memory for online application. The viability of the proposed scheme is simulated using MATLAB/Simulink and verified by suitable experimental results on a practical system.