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.