Research And Design Of A Push-pull PV Inverter

Although the fossil energy greatly stimulates social’s development, it also causes a series of environmental problems. Being non-renewable resource, the coal and oil will be depleted in the future. For the sustainable development, new alternative energies shall be developed for substitution. Photovoltaic power generation has several advantages, such as pollution-less, convenient installation, high reliability and long life time. It will become one of the main energy sources in the future and widely applicable to a variety of fields.In this thesis, the independent structure of push-pull photovoltaic inverter is proposed, the circuit operation of the front-end and inverter are analyzed. Additionally, relevant mathematical model and control scheme are proposed with the support of computer simulation. The hardware prototype is constructed to verify the proposed design.First, this paper classifies the photovoltaic inverter system according to the power stage structures into series, series-parallel, micro-inverter, and hybrid structure. A detailed analysis in each structure is performed for the advantages and disadvantages. A micro-inverter (independent structure) is introduced and analyzed in detail, which consist of the front-end push-pull inverter and full bridge inverter. Second, small signal model is derived to analyze the topology of push-pull converter and foll bridge converter, and the controller is designed based on conventional frequency domain method, which is converted to digital version. SPWM modulation method is introduced. Moreover, simulation validation is made through PSIM circuit. Third, this thesis introduces the push-pull photovoltaic converter system’s hardware design process which is based on dsPIC controller. The design process consists of two parts, control software design and hardware production. Hardware production is composed of components selection for the main circuit, push-pull converter production, sampling circuit and driving circuit design, filter circuit design and ground reference design. The experiment results satisfy the expectations, and the push-pull photovoltaic inverter system can achieve a good sinusoidal current output. Finally, the thesis makes a summary, analyzes existing problems and issues requiring improvement, and then makes plan for future work.