Design and test of a novel buck-boost inverter with three switching devices

A novel buck-boost inverter with three switching devices appropriate for small renewable energy applications was proposed. Operating principles, four different operating modes and pulse energy modulation (PEM) method under discontinuous inductor current conduction mode are discussed in this paper. It also describes the design of hardware, such as the power circuit, flyback transformer and control circuit, and the design of software, such as analog-to-digital converter, zero-crossing signals capturing and PEM signal generation. A 400W experimental set-up of the novel inverter system connected to the grid was constructed to verify the operation of buck-boost inverter and PEM modulation method. Experimental results conclude the buck-boost inverter can transfer the energy from dc source to ac grid efficiently. It can provide sinusoidal output current under wide range of dc input voltage.