《Integration and Operation of a Single-Phase》.pdf

5098 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 28, NO. 11, NOVEMBER 2013 Integration and Operation of a Single-Phase Bidirectional Inverter With Two Buck/Boost MPPTs for DC-Distribution Applications Tsai-Fu Wu, Senior Member, IEEE, Chia-Ling Kuo, Kun-Han Sun, Yu-Kai Chen, Yung-Ruei Chang, Member, IEEE, and Yih-Der Lee, Member, IEEE Abstract—This study is focused on integration and operation of a single-phase bidirectional inverter with two buck/boost maximum power point trackers (MPPTs) for dc-distribution applications. In a dc-distribution system, a bidirectional inverter is required to con- trol the power flow between dc bus and ac grid, and to regulate the dc bus to a certain range of voltages. A droop regulation mechanism according to the inverter inductor current levels to reduce capac- itor size, balance power flow, and accommodate load variation is proposed. Since the photovoltaic (PV) array voltage can vary from 0 to 600 V, especially with thin-film PV panels, the MPPT topology is formed with buck and boost converters to operate at the dc-bus voltage around 380 V, reducing the voltage stress of its followed inverter. Additionally, the controller can online check the input configuration of the two MPPTs, equally distribute the PV-array output current to the two MPPTs in parallel operation, and switch control laws to smooth out mode transition. A comparison between the conventional boost MPPT and the proposed buck/boost MPPT integrated with a PV inverter is also presented. Experimental re- sults obtained from a 5-kW system have verified the discussion and feasibility. Index Terms—Bidirectional inverter, buck/boost maximum Fig. 1. Configuration of a dc-distribution system. power point trackers (MPPTs), dc-distribution appl