Common-Ground-Type Five-Level Transformerless Inverter Topology With Full DC-Bus Utilizaton

Abstract

Transformerless inverters (TIs) are widespread in photovoltaic (PV) applications due to their low cost and high efficiency. However, TIs suffer due to leakage current as a consequence of PV parasitic capacitance, and high-frequency common-mode voltage, which has resulted in the emergence of several topological and control scheme modifications. In this article, a switched-capacitor (SC) based inverter capable of synthesizing a five-level voltage is proposed. In the devised structure, the negative pole of the dc bus is directly connected to the grid neutral, thereby resulting in zero leakage current. In addition, industrial standard half-bridge modules can be employed directly for implementing the proposed inverter without modifications, making it more practically feasible. The proposed topology has the capability of self-voltage balancing of SC, reactive power processing, and full dc-bus utilization as opposed to half-bridge topologies. The principle of operation and a simple logic-gate-based pulse generation scheme is presented in detail. Simulation and experimental results confirming the practical viability of the proposed topology are presented. Finally, the superior features and the merits of the proposed topology are shown through a detailed comparison against state-of-the-art topologies.