Voltage ripple analysis of simplified active power compensator for negative sequence and reactive power compensation

As for the compensation of unbalanced load, a simplified active power quality compensator (SAPC) was discussed, which consists of a three-phase two-leg inverter and a voltage-balance circuit. According to the principle of power balance, the analytical expression of 2nd ripple in dc-link voltage is derived, and it can be used by the control system of SAPC to avoid 3rd harmonic output. According to the structure characteristic of SAPC, the odd ripples in dc-link voltage is analysed mathematically, and the analytical expression of odd ripples is derived in this study, which can give a clear picture about the link between the output current of SAPC and the ripples essentially. Then an integrated control method is proposed for SAPC, which can associate the merits of feedback control and feedforward control, and it can effectively improve the response performance. Finally, simulation and experimental results have verified the analysis and control method correctly.