A New Family of 1- Five-Level Transformerless Inverters for Solar PV Applications

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Abstract
This paper presents a family of 1-φ transformerless switched-capacitor based five-level inverter (TSC5LI) topologies for PV applications. The proposed family comprises 4 inverter topologies: H8, H8-UPF, H10 and H10-UPF capable of mitigating the leakage current by having continuous grid frequency voltage at PV parasitic capacitor in spite of considering switch terminal capacitances. A distinctive attribute of the TSC5LI is that 100% dc bus utilization, symmetrical operation and constant total-common-mode-voltage (TCMV) are achieved together. H8 variant of the proposed inverter family is studied extensively. The control strategy used is a simple level-shifted sine-triangle pulse width modulation (STPWM) followed by the synthesis of the gate pulses utilizing logical functions. Switching function based TCMV analysis, SC design and loss analysis are presented. Simulation and experimental results of H8 variant are presented to validate the theoretical claims. Proposed topology is also compared with the existing five-level transformerless inverters to prove its various advantages.

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