Research On Grid-tied Series-connected Optimizer System Based On DC-Bus

The most widely used structure of grid-tied photovoltaic system is traditional series-connected centralized grid-tied system.Centralized inverter track the MPP of the series-connected array. Thus the situation will appear which PV panels in the array output different power caused by shadow or hot spot,it’s called mismatch,mean that the output voltage of PV panel deviate from the MPP,it will reduce the system efficiency.Grid-tied optimizer system mean each pv panel connect to a optimizer then series-connect to a centralized inverter.In the system optimizer track the MPP of each PV panel,thus the output voltage of the optimizer will change with situation of the total PV panels in the array changes.Optimizer has4modes:boost、buck、through and bypass The topology is H bridge.The topology of inverter is parallel buck,which has a high efficienct and low common mode leakage current and high reliability.This paper research and analysis the system of grid-tied optimizer.Also the simulation and experiment is presented.The topology of optimizer and inverter is designed same as the working mode and control strategy.We proposed a control method which use ripple compensation to reduce the THD of grid current. The system can work without communication for the special control logic designed for the systemThe first chapter is introduction,briefly introduce the current situation of power and the main construction of grid-connected system.The second chapter analyse the optimizer.The third chapter analyse the low common mode leakage current topology of invter.The forth chapter analyse the whole system of optimizer.The last chapter is summary and scope.