Study Of Dual Mode Microgrid Inverter Controller Based On Improved Droop Control

Distributed power has obvious environmental and social benefits. With the development of smart grid, micro-grid has gained more and more attention from domestic and foreign scholars. The operation mode of the microgrid consists of grid-connected and off-grid. If smooth switching in these two modes can be achieved, and without shutting down the inverter,like " Hot plug", then the distributed power flexible operating mode can be better used. The inverter of micro-grid has become one of the key technologies of smart grid in the future. The control strategy of microgrid determines its operation in the grid-connected and off-grid patterns, and affects the smoothness when the operation mode switches. Therefore, determining dual mode micro-grid controller is the important issues to achieve the stable of micro-grid’s operation. The droop method is a good method for the inverter controller on the dual mode operation and seamless switching of the two modes.In this paper, the Common distributed power including fuel cell, photovoltaic cell, wind turbine and diesel generator is introduced. And then the concept of micro grid and control technology is simply introduced. And the current research of switching of microgrid operation mode is analyzedIn this paper, based on micro-grid modeling and simulation, firstly, By analyzing the micro-grid inverter model and its decoupling principle, and starting from the traditional principle of droop control, droop control model was built by piece.Combined with the properties of grid-connected and off-grid, and discovers that droop control policy which is applied in dual mode operation and seamless switching of the two mode has obvious advantages for other control strategy. and its problems have been discussed from the point of view of the dual mode operation. SOGI have presents inductive at 50 Hz, and can suppress the input signal noise. According that, the virtual impedance of SOGI can improve output impedance of the droop controller and harmonic the suppression. Learn from the advantages of conventional generators, virtual inertia has been added to the droop control to inhibit the sudden change in process of grid-connected and off-grid. And simulation system has been built, by comparation, discovers that, The introduction of virtual impedance based on SOGI and virtual inertia, improved the characteristics of the micro power, the inertia and tracking control of the controller, making it more seamless, and achieving the goal of design of dual mode controller which could make smooth swiching of grid-connected and off-grid of Micro-grid.Finally, a typical micro-grid simulation platform which consists of several parallel-connected inverters and load composition is built in the matlab environment by using the simulink. Hybrid simulation with different styles of micro-powers, which breaks the traditional of two parallel-connected micro-powers, to get closer to the actual results. The micro-power inverter is dual-mode controller as the articles proposed, which introducdes virtual impedance based SOGI and virtual inertia. The simulation results show that the designe of impoved droop controller is effective on dual mode and smooth switching of grid-connected and off-grid of micro-grid.