A soft-switched highly reliable grid-tied inverter for PV applications

This paper introduces a soft-switched high-frequency-link inverter for grid-tied PV systems. This single-stage inverter can perform the step-up/down operation and also has the ability to effectively harvest the highest possible power from the PV array. The high-frequency link is formed by an ac inductor and a small ac capacitor without the use of bulky short-life electrolytic capacitors. The link inductor is responsible for transferring the PV power to the grid while the link capacitor facilitates zero-voltage switching for the power devices. Galvanic isolation can be realized by replacing the link inductor with an air-gapped high-frequency transformer. This novel topology has seven total switches, making it suitable for low and medium power PV applications. Furthermore, the converter has a high power density and reliability due to the minimization of passive component sizes and the requisite number of power switches. The proposed PV inverter's control scheme and operating algorithm are presented, followed by a detailed design analysis. Experimental results are also provided to demonstrate the effectiveness of the proposed topology under different operating conditions.