Power Inverters For Grid-connected Fuel Cells

Renewable and green energy sources are currently exploited for sustainable development due to the world energy crisis and environmental deterioration. Distributed generation (DG) is not only an important supplement to current energy consumption, but also a potential main energy source in the future. As DG becomes more and more popular, the grid-connected power inverter system attracts much attention.This paper studies the control strategy for a dual-mode power inverter for fuel cells. The inverter can be grid-connected or stand-alone, This kind of inverter has the properties of good reliability and higher utilization ratio of renewable energy. First, the single polarity SPWM control method is selected to generate control signals of inverter in this paper after comparing various control methods. Then different control strategies are applied with different modes:In the grid-connected mode, the load voltage is determined by the grid. The output current is directly controlled by double current closed-loop control strategy; In the stand-alone mode, the voltage is controlled by current-voltage closed-loop control strategy. Finally, single-phase inverters working under the two modes are simulated in MATLAB/Simulink.When the dual-mode inverter switches between the two modes, it will probably cause surge and interference to loads, electrical network and power sources, so it is necessary to reduce this influence by adopting some effective control strategy. The switching processes between modes of stand-alone and grid-connected with different switching sequence are studied in detail in this paper. A bumpless switching scheme between the two modes is presented. Simulation results for the switching process of single-phase inverters between the two modes using this strategy show its effectiveness.