Photovoltaic power conversion circuit using a symmetric boost converter for low-voltage distribution systems

This paper proposes a new high-efficiency and low-cost dc-to-ac power conversion circuit for installation on a low-voltage distribution system in which the s-phase terminal is grounded. The circuit consists of two half-bridge PWM inverters and a symmetric boost converter. The symmetric boost converter uses four IGBTs as the switching devices, and can independently boost the dc-link voltage up and control its positive and negative terminal potential against the ground level. As a result, two of the four phase legs need to be operated in PWM operation for controlling the output grid current, and the other devices can be kept at on- or off-state. This makes it possible to reduce the switching power loss significantly. Experimental results obtained by the proposed circuit using low-cost IGBTs demonstrates 2% improvement in power conversion efficiency compared with a conventional circuit.