Transformerless inverters have become an important integration of the modern photovoltaic (PV) grid-tied systems. Unfortunately, it has a general safety problem regarding the earth leakage current that must be less than the recommended standards. Lately, the H7 transformerless inverter, which is a three-phase inverter with an additional switch on the DC side, is introduced to mitigate the earth leakage current. Different modulation techniques and controllers are proposed to optimize its performance. This paper proposed the application of model predictive control (MPC) to grid-connected H7 transformerless inverter supplied by the PV power system. In modeling the system, the grid inductance has been taken into consideration. The inverter is linked with the PV through a boost converter. It is found that the boost converter inductance value has a great effect on the leakage current. Matlab's simulations for the proposed system are carried out. The performance of the proposed system controlled by MPC is compared to that controlled by the proportional-integral (PI) controller. The results show that the MPC gives the system greater benefits than the PI controller. The effects of the boost-converter inductance on the earth leakage current are studied. Also, the design of the boost-converter inductance is introduced.

Photovoltaic; 3-φ transformerless inverter; H7; boost converter; model predictive control; earth leakage current; common-mode voltage