Research On Photovoltaic Grid-connected Micro-inverter With Power Decoupling Circuit

The instantaneous power on the DC side of the photovoltaic micro-inverter will produce a double-frequency power pulsation when it runs in grid-connected mode,which increases the reactive power loss on the DC side of the micro-inverter,the utility model reduces the utilization rate of the photovoltaic module output energy.In order to eliminate the double-frequency power pulsation of the micro-inverter,the traditional solution is to connect the electrolytic capacitors with large capacity at both ends of the photovoltaic module to eliminate the double-frequency power pulsation at the DC side,however,the service life of electrolytic capacitors is far less than that of photovoltaic modules,which limits the overall life of the micro-inverter system.In order to solve the double-frequency pulsating power problem of grid-connected photovoltaic micro-inverter,the power decoupling scheme and control strategy of photovoltaic micro-inverter are studied in this paper.Firstly,several different power decoupling schemes are compared and analyzed,and a new power decoupling photovoltaic grid-connected micro-inverter is proposed.Based on the new power decoupling topology,the Operation States of the two modes are analyzed,and it is proved theoretically that the new topology can realize the instantaneous power balance of the AC/DC side of the micro-inverter,the aim of eliminating the double frequency pulsation power on the DC side is achieved.Secondly,according to the proposed power decoupling circuit,the control strategy of the DC link in the front stage and the inverter link in the back stage is studied.The former DC link controls by comparing the decoupling port current initial value and the reference value to determine the operation mode of the circuit,the latter inverter control adopts the current inner loop,voltage outer loop double-loop control strategy.The New Power Decoupling Circuit,the calculation of the parameters of the main components,the DSP control circuit,the sampling circuit and the driving circuit are designed.Finally,a micro-inverter simulation model with a new power decoupling circuit is built on the MATLAB/Simulink simulation platform,and the simulation results show that the proposed topology can balance the instantaneous power of the micro-inverter on the AC/DC side,and can have the obvious suppression function to the DC side ripple current.A 100 W micro-inverter experimental platform has been built in the laboratory,and the experimental results are basically consistent with the simulation results.Figure [52] Table [2] Reference [80]...