A High-Voltage Gain Transformerless Grid-Connected Inverter

Transformerless inverters are used in small and medium power photovoltaic grid-connected systems due to small-size, low-cost and high-efficiency. Transformerless inverters have problems of leakage current and low-voltage gain in applications due to the lack of electrical isolation and boost characteristics of transformers. According to these problems, this article introduces a gain unit circuit in the front-stage based on the two-stage topology of Boost converter combined with the H-bridge inverter to improve the boost capability. In addition, the rear-stage converter adopts double Buck inverter, which has the ability to prevent the short circuit of the bridge arms and improves the reliability of the system. At the same time, it is ensured that there is no high-frequency component in the parasitic capacitor voltage, and the leakage current is suppressed. In this article, the operational modes, circuit gain, devices stress and loss calculation of the proposed inverter are analyzed. Finally, an experimental platform is built to verify the effectiveness of the proposed circuit.