Analysis and Control of a Single-Inductor-QAB-Based Modular PV Inverter Considering Effects of Parasitic Circuits

In this article, a quad-active-bridge (QAB) converter with one single inductor is presented for the modular photovoltaic inverter, which is able to achieve ac/dc power decoupling in magnetic paths without increasing the size of the power transformer, thus reducing the bus capacitance. The single inductor QAB structure simplifies the circuit design of the QAB. In addition, a detailed analysis was conducted on the influencing factors of the double-line frequency voltage ripple for the presented topology, revealing that the parasitic circuits have a very significant impact on its performance, which makes it impractical for real-world applications. Therefore, a control strategy based on the power balancing and phase-shifting principles is proposed to suppress the voltage ripple caused by the inevitable parasitic circuit resistance and leakage inductance. The effectiveness of the analysis and the control strategy is validated by simulation and experimental results.