A Study On Single-phase Grid-connected Inverter Under Harmonic Grid Conditions

Nowadays,researches on distributed generations has gained a great popularity due to the shortage of traditional fossil energy and the increase of global energy consumption.As a core interface device of distributed generation system and the power grid,grid-connected inverter is gradually playing an important role.A phase-locked loop(PLL)is used as a popular synchronization strategy,which is responsible for the smooth connection of the converter to the utility grid and monitoring the grid condition.In order to ensure that the grid-connected inverter is synchronized under non-ideal grid conditions,a PLL is required with good performance.In this paper,a single-phase grid-connected with LCL filter is selected as the subject of research.Aiming at providing grid information used for different monitoring and control purposes under a non-ideal grid condition with harmonic distortion,a PLL with moving average filter(MAF)based prefiltering stage is proposed in this paper.The main research contents of this paper are as follows:The grid-connected inverter system is synoptically introduced at the first stage.The SPWM modulation technology and the filter type are introduced in detail.Based on the mathematical model of the single-phase grid-connected inverter,the inverter control strategies of PI and PR are presented.Then,the proposed PLL structure is introduced.A simulation model is built to verify the performance of the proposed PLL structure under harmonically distorted grid condition.At last,an experimental hardware of the single-phase grid-connected inverter is built,and experiment results proves the efficiency of the proposed structure.