In this paper, a new topology for grid-connected solar PV inverter is proposed. The proposed topology employs an LLC resonant converter with high frequency isolation transformer in the DC-DC stage. The DC-DC converter stage is controlled to generate a rectified sine wave voltage and current at the line frequency. An unfolder inverter interfaces between this DC stage and the grid. Both phase-shift and frequency control methods are used to control the LLC resonant converter. The switching frequency is determined depending on the phase-shift angle to extend the zero-voltage switching (ZVS) region. The transformer leakage and magnetization inductances are also properly designed to provide ZVS for wide operation area. The LLC converter operates in the ZVS region except the narrow band around the zero-crossings of the inverter output current. Since the LLC resonant converter has a high frequency transformer, the line frequency transformer requirement is eliminated, and thus more compact and efficient design is obtained. The proposed topology is validated by the simulation and experimental results.
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A Multiport Bidirectional LLC Resonant Converter for Grid-Tied Photovoltaic-Battery Hybrid System
Distributed power generation plants with combined photovoltaic (PV) systems and integrated energy storage for grid-connected applications have seen an increase in research interest in recent years. However, the combination of multiple energy sources requires numerous DC-DC converters and thus becomes more complex. To address this issue, a multiport bidirectional DC-DC LLC resonant converter for grid connected applications is presented in this research. In order to minimize the control complexity of the proposed system, a zone based controller approach with an integrated modified maximum power point tracking (MMPPT) method, which is based on the incremental conductance method, is also developed. This proposed controller is able to regulate the converter voltage and power flow while either delivering or taking power from the utility grid. The converter presented in this study contains a bidirectional buck-boost converter and an LLC resonant converter in addition to a voltage source grid-tied inverter which are interfacing the PV, the battery and the utility. Extensive simulation analyses through MATLAB/Simulink have proved the operations of the proposed topology.
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- Award ID(s):
- 1939124
- NSF-PAR ID:
- 10221381
- Date Published:
- Journal Name:
- International Journal of Renewable Energy Research
- Volume:
- 10
- Issue:
- 2
- ISSN:
- 1309-0127
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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