Research On AC-side Pan Buck-Boost Power Decoupling Technology Of Photovoltaic Microinverter

With the popularization of photovoltaic power generation systems,photovoltaic microinverters have received more and more attention due to their characteristics of large power generation,high reliability,and guaranteed maximum power point tracking,and they have gradually become the development trend of distributed photovoltaic systems in the future.The imbalance of input and output instantaneous power is the main research problem of microinverters.The transmission of double-frequency AC components on the grid side to the input will reduce the life of the micro-inverter and interfere with the tracking effect of the maximum power point.Aiming at the double-frequency power disturbance problem of micro-inverters,this paper proposes an AC-side pan-buck-boost power decoupling technology.The four decoupling circuits designed to realize bidirectional energy flow are all connected in parallel on the AC side of the inverter.Different topologies can work equivalently in Buck,Boost or Buck-boost mode.The four decoupling circuits designed are analyzed from the aspects of topology,working mode and decoupling performance,as well as the ability of each topology to suppress the second harmonic,and the calculation method of pulse energy buffer is discussed.The basic principle of AC-side power decoupling is introduced,and the circuit structure and working mode of the designed AC-side power electronic power coupling circuit are explained.Study and understand the small signal model of the coupling circuit,discuss the calculation method of the pulse energy,and use the pulse modulation strategy for the power decoupling circuit.Using Matlab / Simulink 2014 a software,the simulation of traditional two-stage microinverter and the simulation of two-stage micro-inverter based on four kinds of power decoupling circuits are respectively established for comparison and simulation.At the same time,the four topologies were decoupled from the decoupling capacity and capacitors based on the simulation results.The voltage is compared,and the four decoupling topologies are compared to conclude that the single-mode six-switch Buck-Boost decoupling circuit has advantages in terms of performance.Simulation results show that the three-mode six-switch Buck-boost power decoupling circuit has the best effect on suppressing the second harmonic of the voltage,and the single-mode six-switch Buck-boost power decoupling circuit has the best effect on suppressing the second harmonic of the current.Pan Buck-boost power decoupling technology can greatly reduce the decoupling capacitor capacitance without relying on the large voltage of the bus,realize no electrolytic capacitor and extend the life of the system.A two-stage micro-inverter experimental platform based on a power decoupling circuit is set up,and a power decoupling circuit is tested.The experimental results verify the correctness of the theory and topology.The traditional large electrolytic capacitor can be replaced with a thin film capacitor with a longer life and a smaller capacity,and an electrolytic capacitor is realized.