A transformerless single-phase symmetrical Z-source HERIC inverter with reduced leakage currents for PV systems

Abstract

. (2018). A transformerless single-phase symmetrical Z-source HERIC inverter with reduced leakage currents for PV systems. In 2018 IEEE Applied Power Electronics Conference and Exposition (APEC) (pp. 356-361). IEEE Press. https://doi.org/10.1109/APEC.2018.8341035 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.? Users may download and print one copy of any publication from the public portal for the purpose of private study or research. ? You may not further distribute the material or use it for any profit-making activity or commercial gain ? You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access to the work immediately and investigate your claim. Abstract-A transformerless single-phase symmetric Z-source HERIC inverter featuring low leakage currents is presented in this paper. It is an attempt to utilize the Highly Efficient and Reliable Inverter Concept (HERIC) and an impedance source (Z-source) network to maintain a constant common mode voltage and thus low leakage currents in PV applications. The symmetric Z-source HERIC inverter requires two extra active switches. Nevertheless, the operation frequency of the two switches is the line frequency, leading to negligible losses. More importantly, the performance in terms of low leakage currents and harmonics is improved. Experimental tests are performed to validate the analysis and performance of the proposed system.

Transformerless Quasi-Z-Source Inverter to Reduce Leakage Current for Single-Phase Grid-Tied Applications

“…Another method is to use a decoupling circuit to disconnect the inverter from the grid [9][10][11][12][13][14][15]. The decoupling circuit technique has been described for single-phase transformerless inverter applications in [9].…”

“…Many efforts have also been made to develop transformerless inverters by applying decoupling circuits to the current source inverters [16,17]. To date, however, only a few studies [13][14][15] have been reported that apply decoupling circuits to ZS inverters. In [13], a symmetric ZS HERIC inverter was proposed.…”

“…To date, however, only a few studies [13][14][15] have been reported that apply decoupling circuits to ZS inverters. In [13], a symmetric ZS HERIC inverter was proposed. It uses an additional two power switches for maintaining the common-mode voltage constant.…”

“…It uses an additional two power switches and two power diodes for clamping the common-mode voltage. The inverters in [13][14][15] commonly have three distinct switching states, namely powering, freewheeling, and shoot-through states. During powering states, the inverter delivers the DC power into the grid.…”

“…During freewheeling states, the grid current circulates through extra power switches, which operate with the grid frequency. However, the previous inverters [13][14][15] have drawbacks such as (1) they still use the bipolar PWM for power switches in full-bridge inverter legs; and (2) they always need freewheeling states for every powering state and shoot-through state. These drawbacks increase the number of switching times for the power switches, causing high switching power losses.…”