DC capacitor energization and voltage regulation of a single-phase hybrid filter

This paper presents a study about the charging process of the DC capacitor of a single-phase shunt hybrid filter. The control algorithm is based on an adaptation of the instantaneous power theory for single-phase circuits. Two controllers are used to generate the reference current to control the hybrid filter. When the DC capacitor is discharged, the hybrid filter AC current leads the voltage of common coupling point by π/2 rad, implying a capacitive characteristic for the filter. During this period the instantaneous reactive power signal is used to energize the DC capacitor. On the other hand, after the DC capacitor is charged, the instantaneous active power signal is used as reference signal to regulate the DC voltage of the hybrid filter. Simulation results are presented in order to validate the proposed methodology and theoretical analysis.