Research On The Interleaved Flyback-Type Photovoltaic Micro-inverter Based On Harmonic Injection Method

With the exhaustion of fossil energy and the increasingly serious environmental pollution,the global energy crisis is imminent,the development and utilization of new renewable clean energy has become the best way to solve this crisis.Due to the wide range of solar radiation,unlimited reserves,no pollution,easy to use and many other advantages,it has aroused widespread concern.Independent control of each PV Grid-connected photovoltaic Micro-inverter,therefore less affected by changes in the external environment,the utilization of photovoltaic cells is better than that of other photovoltaic power generation system structure,which has a huge market potential of PV.In this paper,the photovoltaic Micro-inverter is generally based on flyback circuit topology.However,because of the small output power,the interleaved flyback converter can improve the output power.Due to the high frequency transformer is used in the flyback circuit,the leakage energy loss of the original side is relatively large.The output of the PV module is smooth DC power,but because of the power fluctuation of the output power of two times the power frequency,there is an imbalance of the instantaneous power between the DC side and the AC side,electrolytic capacitor is required to decouple.However,the electrolytic capacitor has a large volume and a limited lifetime,which is far lower than that of the PV module,this directly affects the life and reliability of Micro-inverter system.Review of power decoupling technology at home and abroad used in photovoltaic micro inverters,and analyzes the principle of power decoupling circuit and typical circuit topology,and finally a decoupling control strategy of harmonic injection is studied,namely the three harmonic injection in the bus current,the size of the decoupling capacitor is reduced by compensating the AC side directly.Using the PSIM simulation software to build a simulation model,the simulation results verify the feasibility of the harmonic injection to reduce power ripple and the rationality of the design parameters,and developed a prototype of photovoltaic Micro-inverter 200W.Finally,the design of the inverter prototype is verified by experiments,and the experimental results verify the feasibility of the decoupling control strategy.