A Transformerless Single-Phase Current Source Inverter Topology and Control for Photovoltaic Applications

Abstract

Low power grid-tied photovoltaic (PV) generation systems increasingly use transformerless inverters. The elimination of the transformer allows smaller, lighter and cheaper systems, and improves the total efficiency. However, a leakage current may appear, flowing from the grid to the PV panels through the existing parasitic capacitance between them, since there is no galvanic isolation. As a result, electromagnetic interferences and security issues arise. This paper presents a novel transformerless single-phase Current Source Inverter (CSI) topology with a reduced inductor, compared to conventional CSIs. This topology directly connects the neutral line of the grid to the negative terminal of the PV system, referred as common mode configuration, eliminating this way, theoretically, the possibility of any leakage current through this terminal. The switches control is based on a hysteresis current controller together with a combinational logic circuitry and it is implemented in a digital platform based on National Instruments Technology. Results that validate the proposal, based on both simulations and tests of a low voltage low power prototype, are presented.

Overview of Recent Advanced Topologies for Transformerless Dual-Grounded Inverters

“…Five-Switch [64] 2. Seven-Switch [65] Chopper Circuits Semi-Z source Iverter H-Bridge Single DC Source…”

A Novel Single-Phase Five-Level Current-Source Inverter Topology

“…A SiC-based implementation of this inverter is then presented in [45], wherein system reliability is analysed in light of load overvoltage. Another transformerless single-phase three-level topology is introduced in [46] for PV systems. The proposed CSI mitigates leakage current by coupling the grid neutral line to the negative terminal of the PV panel.…”