Model Predictive Control of PVGCI for Reducing Common Mode Voltage and Switching Frequency

In this study, the common mode voltage (CMV) of photovoltaic grid-connected inverter (PVGCI) is reduced due to minimal switching constraints and lower PVGCI input dc voltage during low power injection. In the absence of a transformer at the grid side, a high-frequency CMV in PVGCI can cause electromagnetic interference, magnetic saturation, and circulating currents among other things. In the literature on reducing CMV, various topologies, control algorithms, and filter components have been used. The design recommended in the article uses a two-level four-leg inverter with 14 switching states to reduce CMV. The grid current total harmonic distortion (THD) increases as the number of switching states evaluated decreases; however, the approach suggested minimizes the grid current THD by decreasing the dc voltage during low-power flow from PVGCI, and the CMV amplitude is determined by PVGCI input dc voltage, which decreases during low-power injection. A cost function of average switching frequency is considered for decreasing the switching frequency of PVGCI. The suggested approach is simulated in MATLAB simulation, and a hardware experiment is performed in hardware laboratory to demonstrate its superiority over existing models.