Leakage current reduction in a Three-phase Transformerless photovoltaic inverter using the single-vector and double-vector model predictive control systems along with improved THD and switching Frequency

Nowadays the demand for photovoltaic (PV) systems has greatly increased due to their various advantages. In many applications for the purposes of reducing losses, increasing the efficiency and having the lower size and weight the transformer has been removed from the grid connected PV systems. In such situations, due to the absence of the galvanic isolation, the common mode voltage becomes unstable leading to flow of leakage current through the parasitic capacitor. The leakage current increases losses, deteriorates the quality of injected currents, causes the electromagnetic interference and finally presents personal safety problems. Therefore, it should be reduced to statutory limits which is defined by the VDE0126-1-1 standard. In the present paper attemps have been made to do so, using the single-vecror and double-vector model predictive control (MPCs) systems. In this approach, without using any extra hardware not only the leakage current is reduced, but the switching frequency and the THD index are also simultaneously minimized. The simulation results confirm the superior performance of the proposed method over other valuable methods.