Effect of Semiconductor Parasitic Capacitances on Ground Leakage Current in Three-Phase Current Source Inverters

Giovanni Migliazza,Giampaolo Buticchi,Fabio Immovilli,Emilio Carfagna,Emilio Lorenzani

doi:10.3390/en14217364

Abstract

This paper investigates the influence of power semiconductor parasitic components on the ground leakage current in the three-phase Current Source Inverter topology, in the literature called H7 or CSI7. This topology allows reducing converter conduction losses with respect to the classic CSI, but at the same time makes the topology more susceptible to the parasitic capacitances of the semiconductors devices. In the present work, a grid-connected converter for photovoltaic power systems is considered as a case study, to investigate the equivalent circuit for ground leakage current. The same analysis can be extended to applications regarding electric drives, since the HF model of electric machines is characterized by stray capacitance between windings and the stator slots/motor frame. Simulation results proved the correctness of the proposed simplified common-mode circuit and highlighted the need of an additional common-mode inductor filter in case of resonance frequencies of the common-mode circuit close to harmonics of the power converter switching frequency. Experimental results are in agreement with the theoretical analysis.

Highlights

The exploitation of photovoltaic energy has been a key topic of industrial and academic research in the past decade
In this work the effect of the power device parasitic capacitances on ground leakage current was investigated in case of the CSI7 topology
Simulations and experiments show that the effect of device parasitic capacitances have a great impact on the behavior of Current Source Inverters (CSI) topologies that ideally present a separation between the DC source and the AC grid during the zero vector application

Summary

Introduction

The exploitation of photovoltaic energy has been a key topic of industrial and academic research in the past decade. The need for a DC/AC conversion for the grid interface has spurred the researchers to investigate the subject from multiple points of view: energy source, power electronics, controls, etc. Plants ranging from hundreds of Watts to MW are installed. In this framework, the research for optimized power electronics for small-scale photovoltaic installation has been active [1]. The most widely adopted topology for the DC/AC converters for photovoltaic system is the voltage source inverter (VSI), due to the good efficiency, low component count and the ease of control. The presence of electrolytic capacitors which limit the lifetime, the absence of boost capability and short-circuit resilience, has pushed the investigators to study different topologies, including the impedance source converters and the Current Source Inverters (CSI) [2]

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Conclusion