The Study On Efficiency Optimization Of Grid-connected PV Inverter

Energy and environment issues are two important issues which become a constraint for sustainable development of human society, so photovoltaic, wind power, fuel cells and other renewable energy generation systems are more and more widely appreciated. Among these renewable energy sources, PV has its unique advantages, PV inverter used as a major energy transmission device in PV system, the conversion efficiency is which is a measure of an important indicator of power generation systems.The conversion efficiency of a inverter system and the total harmonic distortion (THD) of its output current injected to the grid are interrelated, Firstly this paper turns the PV inverter main circuit to the circuit that can be calculated through equivalence. Then THDs of grid current in ideal case using three different modulations are compared based on the method proposed to figure out grid-side current of the inverter. After the impact of dead time zone on fundamental and harmonic output voltage of inverter analyzed, modulation strategies were compared in the presence of the grid current THD when employing different dead time zone to obtain an optimal modulation scheme, which is the basis for efficiency.Then loss models of power devices, filter inductors and transformer which are main loss sources of gird-connected inverter were established. The overall efficiency of the inverter was made a systematic comparison. Due to the non-sinusoidal excitation current in the filter inductor, the FEA software Ansoft Maxwell was employed to predict iron loss in the filter. The modulation scheme which can archive best overall efficiency was pick out through the caparison of loss in different parts using three different SVM schemes.Finally, the main circuit of the experimental platform was designed, and the experimental results carried out on a prototype provide verification for some of the theoretical analysis.