Power Electronic Hybrid System for Load Balancing Compensation and Frequency-Selective Harmonic Suppression

The proposed power electronic hybrid system which consists of a thyristor-controlled reactor (TCR) and a resonant-impedance-type hybrid active power filter (RITHAPF) is used for compensating reactive power and harmonic current. From the point of the nature of load balancing compensation, the calculation of balancing controlled susceptance based on voltage vector transformation is proposed for the TCR to exactly compensate negative-sequence current caused by asymmetrical loads in industrial field. Because the impedance of a filter inductor, a matching transformer, and passive power filters according to the harmonic current is inductive, the phase of the RITHAPF compensating current through them would be shifted. A π-aimed Smith predictor is established based on the fact that there is a π delay between the compensating current and the sum of harmonic currents of loads and the TCR. In terms of the proposed predictor and generalized integrators, a frequency-selective predictive current controller is designed for perfectly eliminating the impact of phase shift on the RITHAPF filtering performance. The simulation and industrial application results validate the theoretical analysis.