A Common Ground Four Quadrant Buck Converter for DC-AC Conversion

Abstract

With the increasing stand-alone and grid integrated low power renewable energy generation, the use of non-isolated DC-AC converters has increased multifold. However, the non-isolated power conversion with conventional DC-AC converters can cause high leakage currents due to parasitic capacitances. To resolve this problem, research on common ground converter topologies is gaining significance. This paper presents a novel single-phase DC-AC converter with common ground for the input and output terminals. There are only minor modifications required in comparison to the topology of the commonly used conventional H-bridge inverter for DC-AC conversion. In addition, the basic components and their counts remain the same. The gain ratio of the proposed inverter is such that it reduces the effect of switching delays. The availability of common ground for DC input and AC output sides provides the advantage of zero common-mode voltage and avoids leakage currents due to parasitic capacitances. The voltage gain ratio of the proposed converter is superior compared to the H-bridge inverter. Further, the switch stresses, switch utilization ratio and ratings of the constituent components have been derived for an accurate design of the converter. The proposed converter is observed to be more preferable when compared with other converters and modulation techniques for leakage current elimination based on the number of components and complexity of the circuit and control. The simulation and experimental results for different loads and load changes are presented to verify the theoretical claims. It is capable of supporting real and reactive power while operating competently under sudden changes in load. Therefore, the proposed common ground DC-AC converter can replace the H-bridge by modifying its circuit or replacing it with readily available half-bridge modules to obtain zero common-mode voltage and leakage currents. Hence, it is particularly attractive for low-power renewable generation and energy storage system applications.