Single-phase hybrid-H6 transformerless PV grid-tied inverter

• Published in: IET power electronics Vol. 11; no. 15; pp. 2440 - 2449
• Main Authors: Ma, Lan, Xu, Hongbing, Huang, Alex Q, Wang, Xiaodong, Zou, Jianxiao
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 18.12.2018
• Subjects: capacitors; common mode voltage fluctuation; dead time reduction; freewheeling mode; grid‐tied photovoltaic system; harmonic distortion; hybrid power systems; invertors; junction capacitance reduction; leakage current mitigation; leakage currents; modulation; modulation technique; photovoltaic power systems; power 1.0 kW; power grids; reactive power control; reactive power control capability; Research Article; safety requirement; single‐phase hybrid‐H6 transformerless PV grid‐tied inverter topologies; switch; total harmonic distortion; modulation; dead time reduction; harmonic distortion; photovoltaic power systems; modulation technique; leakage current mitigation; safety requirement; freewheeling mode; switch; leakage currents; grid-tied photovoltaic system; invertors; common mode voltage fluctuation; junction capacitance reduction; capacitors; reactive power control capability; reactive power control; power 1.0 kW; total harmonic distortion; power grids; single-phase hybrid-H6 transformerless PV grid-tied inverter topologies; hybrid power systems
• ISSN: 1755-4535; 1755-4543; 1755-4543
• DOI: 10.1049/iet-pel.2018.5009

Transformerless inverter for grid-tied photovoltaic (PV) system has been widely used due to lower cost, higher efficiency and lighter weight. Various transformerless inverter topologies have been proposed to meet the safety requirement of low leakage current and obtain the reactive power capability. To get better performance, a novel transformerless hybrid-H6 inverter with an improved modulation technique is proposed in this study. By adopting the improved modulation technique, two symmetry paths are realised to share the current during the freewheeling mode. Thus, without paralleling any additional capacitors to the switch, the inverter can reduce the influence of junction capacitance on common mode voltage naturally which results in mitigating the leakage current issue. Thanks to the dead time reduction through the improved modulation, the qualities of output waveforms are improved. Moreover, reactive power control is achieved without any modification of the inverter structure. Finally, a 1 kW prototype is simulated and tested to verify the theoretical analysis of this study. Not only the reactive power capability is obtained for the proposed inverter, but also the small common mode voltage fluctuation is achieved at the same time. In addition, the total harmonic distortion of the current is decreased by more than 1.7%.