چكيده به لاتين
In photovoltaic microinverters, the most vulnerable parts are electrolytic capacitors, which reduce the microinverter lifetime. To overcome this problem, power decoupling methods have been proposed in which electrolytic capacitors with high capacitance are replaced by thin-film capacitors with low capacitance and thereby the lifetime of the microinverter increases. Based on the location of the decoupling capacitor, the power decoupling techniques are divided into three types: PV-side decoupling, DC-link decoupling, and AC-side decoupling. In this Thesis, a variety of structures related to these techniques have been studied and compared and finally, based on the comparison, a technique has been selected wich has the best performance and the highest efficiency. According to the selected technique, the grid-connected single-phase microinverter has been designed so that to reduce the size of power decoupling capacitor, injected current THD to the grid, and improve the transient response, and make it possible to use thin-film capacitors with longer lifetimes instead of electrolytic capacitors. The proposed microinverter is connected to the grid (220V, 50Hz). It has a very small 20µF bus capacitor. The bus voltage has negligible overshoot and undershoot in response to a 200W input power jump. THD of the injected current to the grid is 0.44% at 250W output power. The proposed method is validated by simulation results in Matlab-Simulink software.
Keywords: lifetime, microinverter, photovoltaic (PV), power decoupling, electrolytic capacitor, thin film capacitor.
