Voltage Control Scheme for Multilevel Interfacing PV Application: Real-Time MRAC-Based Approach

Cascaded H-bridge multilevel inverters (CHB-MLIs) have a proper structure and significant advantages like filter-less topology due to their desired output voltage levels and being suitable for employing isolated DC voltage sources that have been utilized in multi-sources applications such as photovoltaic (PV) power generation. However, unbalanced DC voltage sources of the DC/DC output section or fast voltage variations can decrease the output voltage quality and make some undesired fluctuations and harmonics, affecting the load behavior in different applications. To overcome these problems, a new real-time voltage control technique has been proposed to regulate the output voltage magnitude properly. This aim can be obtained by employing the model reference adaptive control (MRAC) technique for voltage regulation to improve total harmonic distortion (THD), and to decrease some harmonic orders (HOs) magnitude, especially lower harmonics (3rd, 5th, and 7th). Therefore, the proposed solution is designed to stabilize the dynamic error originating from the DC side. At the same time, the DC voltage sources are interfaced with variations, where they do not have equal magnitudes with each other. The effectiveness of the proposed control technique has been verified by simulation in MATLAB/Simulink.