Multi-Input Single-Stage Bi-Directional Grid-Connected Inverter

The objective of this dissertation is to propose a multi-input single-stage bi-directional grid-connected inverter (MSBG-inverter). The proposed MSBG -inverter is composed of multiple buck-boost type dc-dc converters (BBCs) and a dc-ac unfolder. Because there is only one switch operating at high frequency, single-stage conversion with circuit simplicity and higher efficiency can be achieved. For photovoltaic (PV) system application, the MSBG-inverters can eliminate the shading effect while fulfill the functions of dc-ac conversing and the distributed maximum power point tracking (DMPPT). For battery energy storage system application, the MSBG-inverters can realize individual power-handling capability while fulfill the functions of battery charging and discharging. Moreover, based on the developed equations, the power flow of the BBCs can be controlled without the need of input current sensor. Also, with the interleaved operation between BBCs, the current ripple of the output inductor can be reduced too. Finally, the computer simulations and hardware experimental results are shown to verify the performance of the proposed MSBG-inverter for the PV system and the battery energy storage system.