Optimal filter design and switching loss reduction in single phase grid connected inverter system

Abstract

With the reduction of available fossil fuels, the research in the area of renewable energy system has been exponentially increased in order to find out an effective solution. Considering the case of a PV panel, it is observed that it produces a DC voltage which has to be converted to AC for grid connected applications. So a Voltage Source Inverter (VSI) with a PWM control of switching action is used for this purpose. This project presents the comparative study between unipolar and bi-polar switching scheme for single–phase grid-connected inverter system with filter design on the grid side. For that, LCL filter is considered and its performance for current ripple reduction on grid-side is compared with normal L and LC filter. It is seen that the response for LCL filter show the best results with lower current ripple as compared to L and LC Filter. Further, the obtained results show that the obtained LCL-filter can provide sufficient attenuation of current harmonics and mean while injects a sinusoidal current into the grid for maintaining power quality standard. In addition to that, the method to design the inductor is also studied. Further, the optimal design of LCL filter for grid connected inverter system is studied. For that, initially normal design is considered. Then the conduction and switching losses that are caused by the filter are calculated and are optimized considering the level of reduction of harmonics. Hence the main aim of the study is to attenuate higher order harmonics along with the reduction in switching losses to ensure sinusoidal current injection into the grid. Further, the different switching schemes for single phase unipolar full bridge inverter are studied and compared to get the switching scheme which gives lesser switching losses. The LCL filter is designed accordingly and optimal inductance and capacitance values are obtained. The complete model of the study is simulated in MATLAB-Simulink environment for feasibility of the study.