Research On Photovoltaic Grid-Connected Micro-inverter

The21st century, the energy and the environment problems become two problems restricting thesustainable development of human society. Therefore, more attention is given to the efficient use ofgreen renewable energy such as solar, wind and fuel cell. Solar energy is a clean, non-polluting energy,with features like wide distribution and infinite stock. It’s evolving from alternative energy into basicenergy increasingly. Photovoltaic power generation is an important component of distributedgeneration. It will develop rapidly.There are two development directions of development of photovoltaic power generation. One islarge-scale megawatts photovoltaic power plant. The other is residential photovoltaic power supplyless than5kW. PV grid-connected micro-inverter is less than500W. A PV panel is equipped with onemicro-inverter, to ensure that each panel can operate at the maximum power point, thus improving theutilization of solar power generation system in the cloudy weather conditions.The quality of a photovoltaic micro-inverter depends highly on its efficiency. In this paper, anactive clamp flyback converter that works alternatively in continuous conduction mode (CCM) ordiscontinuous conduction mode (DCM) is researched. The main switch and the auxiliary switch aredriven non-complementarily. With the proposed control method, the energy in the leakage inductorcan be fully transferred to the secondary side. The voltage spikes are effectively limited when themain switch of the flyback converter is turn-off so that voltage stress of the switch can be lower. Thusthe efficiency of the inverter can be greatly optimized. The operation principle of the converter ispresented. The main factors which affect efficiency are analyzed. The design reference of keyparameters is presented. Theory and simulation analysis of power loss are dicussed. Model isestablished for closed-loop control design. The prototype is tested. Experiment results are shown toverify the effectiveness of the proposed control strategy and the high efficiency of the converter.Detailed design of the entire micro-inverter system hardware and software part is presented. Onthis basis, a220W PV grid-connected micro-inverter experimental platform based on the DSP2812isdesigned. Basic functions such as grid-connecting, maximum power point tracking and anti-islandingare realized.