Research Of Single-phase Inverter And Grid Connected Technology

In recent years,new energy power generation equipment in the power system is becoming more and more prevalent,but it is difficult for researchers to control and use distributed power equipment.In the future energy system,the application of power electronic equipment will be more and more extensive with the gradual increase of the proportion of new energy.Especially for the research of new energy grid connected converter,it will be a research hotspot in the future.This paper mainly focuses on the research of single-phase grid connected inverter and its grid connected technology.The main contents are as follows:1.The basic structure of the single-phase inverter is selected.Through the comparison of the LC filter and the LCL filter,it is no doubt that the LCL filter can better filter out the high-frequency components of the grid connected current.Therefore,the LCL single-phase inverter structure is adopted and the topological modeling is carried out.2.The LCL inverter system has a high resonance peak at the resonant frequency,which can make the system become instability and enable the current become distortion.The control strategy of the inner loop of grid current and the outer loop of the capacitor current is usually adopted,which can effectively restrain the system resonance and realize the high-quality power grid connection.In order to improve the practicability of the control strategy,this paper presents a practical control strategy of indirectly calculating the capacitor current through the grid-connected current and grid voltage,which can reduce the cost of one current transformer.In addition,this enhances the reliability of the system reliability because of reducing detection of an electrical amount.At the same time,in order to eliminate the impact of grid voltage fluctuation,this paper adds the grid voltage feedback to increase the stability of inverter control.3.Phase-locked loop is a pivotal technology of grid-connected inverter.Phase-locked loops based on second-order generalized integrator(SOGI)cannot rectify because of its harmonic frequency is fixed,so it cannot realize the tracking of grid voltage phase in the case of grid voltage and frequency are fluctuating.Therefore,based on the SOGI phase-locked loop,this paper introduces a frequency-locked loop(FLL),which can accurately estimate the voltage frequency of the power grid and adjust the resonant frequency of the SOGI structure.4.This paper designs a 10kW LCL single-phase grid inverter experimental platform and carries out deeply study for system hardware and the software program.Eventually,the new control strategy of capacitor current feedback and phase-locked loop structure are verified by experiments in this paper.