Research On Control Strategy Of Single Phase Grid Connected Inverter

Solar energy generation is one of the important means because of the characteristics of long-term benefit from one-time investment and the system scale without strict size restrictions.If hotovoltaic power generation is applied to family life to exert these advantages,subversive changes will be brought to the household electricity model,especially in remote mountain villages and independent houses,more choices will appear.Related standards and projects are also constantly being regulated.From a structure,a self-built household photovoltaic power generation grid-connected system generally contains four major parts,respectively a solar battery pack and its controller,storage battery,grid-connected inverter,and provides AC power for household single-phase systems.The four parts do their duties,and the grid-connected inverter is the key device connecting the power generation equipment and the point-of-use equipment and it plays a important role in converting DC power into AC power.This article mainly analyzes and studies on precise control of grid connected current,suppression of resonance peak,research and design of single-phase phase-locked loop,third harmonic of grid connected current.Firstly,aiming at the problem of precise control of grid connected current,this paper briefly describes the working principle of grid connected inverter,establishes the mathematical model,and carries out the selection of interface filter and parameter design.This paper analyzes the characteristics of traditional PR control technology,points out that PR control can not provide leading phase,and further adopts the VPI control strategy,and designs the parameters.The strategy can track the AC signal accurately and compensate the phase delay caused by the LCL interface filter by using the phase lead generated by the second-order molecules.On the basis of ensuring the stabili ty,the precise control of the grid current is realized.In this paper,the current control strategy is verified by simulation.Secondly,aiming at the problem of resonance peak suppression,this paper compares and analyzes the effect of active damping and passive damping,analyzes the influence of passive damping technology on system loss,and focuses on the influence of active damping feedback coefficient on system stability.Aiming at the problems of large calculation amount and small feasible range of p arameter selection in traditional damping coefficient selection method,a simple active damping feedback coefficient design method is proposed,which reduces the calculation amount of feedback coefficient and simplifies the design method,and the effectiveness of the design method is verified by simulation.Thirdly,aiming at the design problem of single-phase phase-locked loop,the technical difficulties caused by the lack of reference information are analyzed,and the problems of multiple coordinate transformations and poor dynamic performance existing in the traditional algorithm based on the rotating coordinate system are studied.By constructing the voltage vector and self decoupling methods of reverse synchronous rotation,the improved single-phase-locked loop algorithm is proposed to reduce the coordinate transformation times,completed the parameter design.The simulation results verify the advantages of the improved algorithm in response speed,and prove that it can obtain the angular frequency and frequency information in a shorter time.Finally,aiming at the third harmonic suppression of grid connected current,the second harmonic of DC bus voltage is obtained from the power balance relationship of two-stage system,the conduction characteristics of the second harmonic of DC bus and the third harmonic of grid connected current are studied,the influencing factors of the third harmonic of grid connected current are further analyzed,and the suppression of grid connected current 3 based on improved current control is proposed.At the same time,compared with the traditional method of increasing bus capacitance,the method proposed in this paper has obvious advantages.