Power-quality improvement in reactive power control using FC-TCR circuits

Reactive power compensation using fixed capacitor (FC) and thyristor controlled reactor (TCR) circuit is studied. The goal is the minimization of the RMS and THD values of the line current, controlling the firing angle value of the TCR branch. Some changes in the conventional architecture of the conventional FC-TCR compensator were necessary to achieve it. We show that substitution of the reactor by a switched tapped-reactor forces the thyristor-firing angle to be small, improving the power factor (PF) and the total harmonic distortion of the line current (THDI). We denote this new architecture as ´fixed capacitor-thyristor switched reactor-thyristor controlled reactor´ (FC-TSR-TCR). In the case of nonsinusoidal voltage supply, the above quantities, PF and THDI, are remarkably improved by substituting fixed capacitor by a fixed LC serial branch (FLC-TSR-TCR). These changes are also effective with nonlinear loads. For simulation purposes, FC-TSR-TCR and FLC-TSR-TCR compensator models, and linear and nonlinear loads, represented respectively by RL circuits and ideal current sources, have been considered. For several illustrative cases, an optimization algorithm is applied in each half-cycle of the voltage source, and optimum values of firing angles are obtained satisfying condition of minimum rms value of the line current. PF and THDI are calculated in the considered cases to show the performance of the FLC-TSR-TCR compensator.