The Research And Design Of Solar Grid-connected Micro-inverter With Interleaved Flyback Topology

The Micro-inverter is connected between PV modules and utility grid,which plays a key role in the distributed photovoltaic generation system.Not only it controls and converts the energy from PV modules to the utility grid,but also obtains to get the maximum energy from PV modules.It also observes system and environment parameters and so on.In this paper we have launched a design of grid-connect micro-inverter based on the interleaved active clamp flyback topology,which is beneficial for dealing with spike voltage,leakage energy loss,power limit and high current ripple.The proposed micro-inverter is mainly consisted of two stages: interleaved active clamp flyback circuit and the full bridge circuit.The active clamp circuit is adopted to protect switches from the leakage energy which may result in voltage spike in the switch off interval,and it is beneficial for the efficiency of system due to recycling leakage energy.In order to deal with the power constrained problem and reduce the current ripple,we have proposed the interleaved flyback topology.Two flyback circuits work alternately and it reduces the volume of filter and can extend the life of decoupling capacitor and increase the stability of the system.In order to improve the stability and anti-interference performance of the system,this paper have proposed a double loop control method,which include external voltage loop and internal current loop.On the one hand,the internal current loop tracks the phase the voltage of utility grid and control the flyback and active clamp circuit with the PLL and PI.On the other hand,the internal current loop controls the load balance of interleaved flyback circuit.The external voltage loop can track the voltage of the PV panel and utility grid in real time which can improve the anti-interference and stability of the system.Finally,we have made a prototype based on the proposed topology.And we have tested the grid-connected function and converter efficiency under different power conditions according to 《 Technical Requirement and Test Method of Grid-connected PV Micro inverter》CGC/GF 027:2013 and《Technical specification for China efficiency of grid connected PV inverters》CGC/CF 035:2013.Testing results have proved that the interleaved active clamp flyback circuits can protect the switches,recycle the leakage energy and decrease the current ripple.And the weighted efficiency can achieve 89.51%,which verified the feasibility and efficiency of the system,and the expected goal is achieved.