Modified double hysteresis current control method for unified power quality controller

Summary The conventional double hysteresis control method for unified power quality controller (UPQC) is used to get the optimal voltage that can control the error of phase current quickly according to the distribution of reference voltage, the location of current error and whether the current error is beyond the limits. Although this method can provide fast current response and decrease high-order harmonics and switching frequency, it decreases the compensation accuracy because when the current error is in the inner loop, the inverter does no actions. In this paper, a modified double hysteresis current control method is proposed to improve the performance of UPQC, the active disturbance rejection controller (ADRC) is innovatively introduced to the inner control of double hysteresis current control for UPQC, both inner uncertainty and external uncertainty are treated as unified unknown disturbances that are estimated by the extended state observer and are compensated by the nonlinear state error feedback control law, and the algorithm of particle swarm optimization (PSO) is used to optimize the ADRC parameters. Therefore, the proposed method offers the following additional benefits: the complicated calculation is avoided; the accurate measurement of harmonics is not required; the utilization ratio of voltage is improved; and the adaptability of control system is strong. The simulation results show that the proposed method has good static/dynamic performance and strong robustness. Copyright © 2014 John Wiley & Sons, Ltd.