Hybrid transformerless PV converters with low leakage currents: Analysis and configuration

Abstract

This paper proposes a hybrid transformerless photovoltaic (PV) converter with simultaneous AC and DC outputs. It is specifically suitable for residential PV systems due to its high efficiency, versatility and flexibility, while maintaining lower leakage currents. The proposed converter is configured by replacing the control switch of the boost converter with a transformerless voltage‐source inverter (VSI), enabling multiple outputs. In addition, a symmetrical boost inductor is adopted to clamp the common‐mode voltage as a constant, resulting in low leakage currents. To illustrate the configuration principle, a hybrid converter with a highly efficient and reliable inverter concept (HERIC) as the VSI is exemplified. Besides, the dedicated modulation scheme for the proposed converter is detailed to achieve low leakage currents, reactive power injection and high efficiency. Furthermore, as the shoot‐through state of inverter legs is allowable for the proposed converter, i.e. no need to add dead time, the reliability and power quality of the proposed converter can be improved. Simulations and experimental tests are performed on an example hybrid converter (with an HERIC as the VSI) to validate the analysis.

Fully Symmetrical Hybrid PV Converter With Low Common-Mode Noise

“…Considering the DC-DC and DC-AC conversions during ST mode, the HERIC works in the freewheeling mode. Since S 1-6 are all ON, the grid current i AC has three flowing paths, which has been verified in [19] that it has low conduction losses compared to the traditional HERIC. Besides, there exist bidirectional current paths to support reactive power injection.…”

“…However, the dual-buck inverter has low utilization of AC inductors, leading to low power density. Another transformerless hybrid converter is introduced by adopting a symmetrical boost inductor and a symmetrical VSI to achieve low leakage currents as well as high power density in [19]. Based on it, an interlinking power converter [20] is proposed to achieve both flexible power control [21] and low leakage current.…”

Aggregate regulation strategy of distributed energy storage under power spot market in China

“…Being under the power spot market and facing with large fluctuations in real-time power prices [3], power users begin to investigate new profit models for their rich adjustable resources. This is especially true for the distributed energy storage (DES), which can use its fast adjustment characteristic to carry out real-time arbitrage for improving its own economic profits [4,5].…”