Transformerless grid tied inverter using neutral point clamped full bridge topologies and hybrid filter for THD reduction

In photovoltaic applications, it is possible to remove the transformer in the inverter to reduce losses, costs, and size. Galvanic connection of the grid and the dc sources in transformer less systems can introduce additional ground currents due to the ground parasitic capacitance. The leakage current has to be tackled carefully for such type of inverter topologies. Neutral point clamped (NPC) topology is an effective way to eliminate the leakage current. A universal prototype for these three NPC-type topologies is built to evaluate the topologies at conversion efficiency and the leakage current characteristic. The PN-NPC topology exhibits similar leakage current with the FB-DCBP, which is lower than that of the oH5 topology, and features higher efficiency than both the oH5 and the FB-DCBP topologies. Total harmonic distortion of NPC topologies will get better with Hybrid filters.