Two-Stage Three-Phase Transformerless Hybrid Multilevel Inverter for Solar PV Application

The proposed inverter topology is emerged from the multiple level-doubling-network (LDN) based topology for grid-connected solar photovoltaic (PV) system, where dc buses of three phases could not be merged without electrical isolation. Three-phase T-neutral point clamped (TNPC) is used to merge all the three phases without transformer. Due to LDN operation, balancing the capacitors of TNPC (main bridge) is a major challenge. A dc–dc converter is customized in this work, which is normally required for two-stage operation of solar PV inverter. This converter topology reduces the size and losses of filter inductors due to high-resolution inverter output voltage in addition to restricting the leakage current well below the relevant standards. To validate the concept, experiments are carried out using hardware prototype and those matched well with simulation result.