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

This paper proposes a 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 by using matlab Simulink software 2018a

Keywords:
Asymmetric multilevel converter topology, capacitor balancing, coupled inductor, leakage current, level doubling network (LDN), photovoltaic (PV), space vector modulation, T-neutral point clamped (TNPC)