DSOGI_PLL Technique for Improving the Power Quality of an Unbalanced-Distorted Grid Connected PV System Based on Quasi-Z-Source Cascade Multilevel Inverter

As it is well known, having a low Total Harmonic Distortion (THD) is a crucial characteristic in electrical systems, as in international standards such as IEC 61000-3-2 and IEEE-519 which have set limits on harmonics in currents in various classes of electrical equipment that are connected to an unbalanced-distorted three-phase grid. In this context a DSOGI_PLL technique applied on Photovoltaic (PV) system supplying a quasi-Z-source cascade multi-level inverter (QZS_CMLI) connected to an unbalanced distorted grid is presented. The QZSI is coupled between the DC input source (PV system with maximum power point tracking control (MPPT)) and the H-bridge (HBI) module, it provides desired output DC voltage, without requiring any intermediate circuit elements, thanks to the network impedance in its structure. As the DSOGI_PLL technique is employed to control and optimize the energy quality, it has been proven to provide better performance for controlling the energy's quality according to the obtained (THD) measure, leading to lower peak currents, and higher efficiency.