Research On Grid-tied Control Strategy Based On Combined Inverter

In the new energy field, Our country has made breakthrough progress,but there are problems of poor portability and Expansion difficulties for small and medium-grid system. To solve these problems problems,a flexible and reliable control scheme of combined grid-connected inverter is represented in this paper.We research the key technologies of combined grid-connected inverter based on photovoltaic inverter, which unit capacity is 2KVA.The technologies include the current-sharing control methods of the parallel combination inverter, control theme of grid, design of inverter filter, genlock, MPPT and prevention of islanding effect of combined grid-connected inverter.There are two working states of combined inverter, including the parallel and cascade ways. Multi-inverter operating in parallel way can realize redundant power supply and improve the stability and reliability of system. In the process of building the whole system, we compare the common current flow control strategy and establish a model of multi-inverter parallel system, then suppress circulation by using the instantaneous average current control method.And cascade grid-connected way can effectively inhibit the influence of the whole system caused by load imbalance.There exist some differences between Single Inverter and combined grid-connected inverter.So we use active frequency shift method with a positive feedback to prevent islanding effect.Finally, we selected device by calculating the key parameters of whole system. After the simulation of MATLAB, the simulation results demonstrate that the system is feasible.we use TMS320LF2407 as the core controller, then set up a test platform in accordance with the selected method and setted parameters. The preliminary datas of experiment show that the system has a good performance.