A Double Reduced Order Generalized Integrator based Algorithm for Control of Four-leg Converter to Enhance Power Quality

This paper presents an implementation of four-leg converter using a double reduced order generalized integrator (DROGI) control algorithm to alleviate the power quality problems caused by unbalanced RL loads in a three phase four wire utility grid. The DROGI based control serves multi-functionalities such as load balancing, power factor correction, and DC side voltage regulation of capacitor-fed four-leg converter. First, the unbalanced load currents are decomposed into respective fundamental frequency component for the estimation of the reference compensation currents by employing one ROGI. Then, the converter currents are decoupled for DC link voltage regulation and unbalanced loads compensation with the help of the other ROGI. As a result, the rectification mode and compensation mode of converter can be controlled separately. A detailed description of the proposed control algorithm is presented in this paper and it has been validated by simulation and experiment results.